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What's New in SkyView?

This document describes changes in SkyView and news items of interest to its users.

Note: Over time some links may no longer be valid. We apologize for any resulting inconvenience. Please contact us if you have any questions.

13 March 2007
Over the past couple of days we experienced problems retrieving data from the remote machine that provides Second Generation Digitized Sky Survey and VLA FIRST Survey data due to system outage. The remote machine is now back to normal. We apologize for any inconvenience.
9 October 2006
The latest release (DR5) of the Sloan Digital Sky Survey (SDSS) covering over 8,000 square degrees of the sky in the optical wavelength is now available through SkyView. More information can be found on our survey documents page or at the SDSS site
27 September 2006
Due to hardware upgrade SkyView web servers was intermittently unavailable for a couple of hours on Wednesday September 27 starting at 10:00am. We apologize for the inconvenience.
17 July 2006
Due to a re-engineering of the HEASARC network, access to remote services is not available. Attempts to access the DSS2, NEAT, 2MASS and FIRST surveys may fail or hang unless the request is in a region already cached at our SkyView server. We anticipate restoring full access later this week.
6 June 2006
SkyView will be unavailable from 6:00-9:00 pm EST on Thursday June 8, 2006 as a system upgrade is being performed. We apologize for the inconvenience.
31 May 2006
Corrections have been made to the SkyView Java Applet Interface that should resolve applet loading errors. If you have had problems in the past, please try the interface and let us know if there are still problems.

This interface is only minimally maintained. We recommend using the SkyView in a Jar application as an alterative to the web-based interfaces.

10 May 2006
Recently the ST ScI has upgraded the astrometry released with DSS2 image headers. To get this more accurate astrometry all DSS2 images cached at SkyView have been deleted. DSS2 downloads may seem to take a little longer as the cache is rebuilt.

A few errors have been noted where the new headers were incorrect. Users looking at DSS2 images in regions they are not familiar with can check by comparing with the DSS image of the same region.

14 April 2006
We recently discovered a mistake in the FITS header of the SkyView CO survey data file. SkyView images generated from this data have been shifted by one pixel. The bug has been fixed and CO survey images are now correct. We apologize for this error.
27 March 2006
Version 2.0 of the SkyView-in-a-Jar standalone application is now available with support for GIF and JPEG images, interactive image analysis using ImageJ, grid and catalog overlays and much more. Please see the SkyView-in-a-Jar information page for more information. V2.0 also updates the survey descriptions for the DSS surveys to accommodate changes in the ST ScI Web services.

A substantial amount of 2MASS survey data have been unavailable over the last week due to connection problems with the remote system used to transfer data. This has now been fixed and all-sky 2MASS survey data should again be available. We apologize for any inconvenience.

12 October 2005
SkyView in a Jar, a new Java-based version of SkyView that can be downloaded and run from your machine, is now available. See the SkyView in a Jar Information Page for documentation and download instructions.
10 August 2005
Please try our Java-based version of SkyView. This new version provides a more efficient and robust geometry engine for image generation and new resampling and image processing capabilities. Not all surveys and advanced options are included at this time but they will be made available over the next several weeks.
13 June 2005
The COBE DIRBE/Annual Average Maps (AAM) and COBE DIRBE/Zodi-Subtracted Mission Average (ZSMA) have been added to SkyView. More information on these infrared surveys can be found on our survey documents page .
25 January 2005
SkyView previously would appear to accept coordinate strings beginning with quotes, but treat the hours of right ascension as 0. Coordinate strings beginning with quotes now fail with an appropriate error message.
12 July 2004
The Maki link has been removed from the SkyView results page. Maki is now a standalone product. More information can be found at the Maki web site
28 June 2004
The main SkyView server skyview.gsfc.nasa.gov became available after being down over the past weekend for hardware maintenance. There were still problems with the alternate server skys.gsfc.nasa.gov until about midday. We apologize for the inconvenience.
25 June 2004
Due to a major hardware maintenance project SkyView web servers were be unavailable from Friday June 25 6:00pm until Monday June 28 6:00am. We apologize for the inconvenience.
24 June 2004
SkyView has been updated to include the full public release of VLA FIRST data. This map shows the current coverage.
20 April 2004
Due to recent system problems caused by numerous simultaneous SkyView requests originating from one or two users we will now limit the number of simultaneous requests from each host. We apologize for any inconvenience and hope that this will enable SkyView to provide more reliable service.
19 April 2004
The GRANAT/SIGMA survey of hard X-ray sky (40-100 keV), is now available. See the survey documentation page for images and more information.
22 March 2004
The RXTE/PCA All Sky Slew Survey (XSS), a mission primarily designed to study the variability of X-ray sources on time scales from sub-milliseconds to years, is now available. See the survey documentation page for images and more information.
September 18, 2003
SkyView will most likely be offline starting around 12:00pm EST on Thursday September 18 in anticipation of bad storms caused by Hurricane Isabel. The systems should be back up sometime on Friday September 19. We apologize for any inconvenience.
September 15, 2003
An error in the handling of the CROTA keywords has been fixed. 2MASS images may have had position errors of typically ~1" near the poles (e.g., +/- 85) with substantially smaller errors elsewhere in the image. No other survey should be affected.
July 23, 2003
SkyView was unavailable overnight due to system problems but is now back online. We apologize for any inconvenience.
July 7, 2003
The Two Micron All Sky Survey (2MASS) All-Sky Data Release is now available through SkyView. More information can be found on our survey documents page or at the 2MASS site.
July 1, 2003
This morning we experienced problems with NED, one of the remote systems that SkyView uses to resolve object names to sky coordinates. It looks like the NED system is back to normal. We apologize for any inconvenience.
13 February 2003
The H-alpha Full-Sky map, a composite of the Virginia Tech Spectral line Survey (VTSS) and the Southern H-Alpha Sky Survey Atlas (SHASSA), has been added to the SkyView Optical survey list. See the survey documentation page for images and more information.
11 February 2003
SkyView was unavailable overnight due to system problems. Everything appears to be back to normal. We apologize for any inconvenience.
4 February 2003
A new disk was added to cache survey data files that are FTP'd from remote systems resulting in reduced generation times for frequently requested images from these surveys.
8 January 2003
Added a SkyView Usage page with figures from SkyView: A Decade with the Virtual Telescope, a paper recently presented at the American Astronomical Society meeting. Figures show how and how much SkyView is used.
25 November 2002
The Southern H-Alpha Sky Survey Atlas (SHASSA) is now available. This atlas is the product of a wide-angle digital imaging survey of the H-alpha emission from the warm ionized interstellar gas of our Galaxy. It covers the southern hemisphere sky (declinations less than +15 degrees). See our Survey page for more information.
19 October 2002
SkyView was unavailable on Saturday, October 19 10:00am -6:00pm EST due to a network upgrade at the NASA Goddard Space Flight Center facility. We apologize for any inconvenience.
10 October 2002
SkyView was not able to display images for some named objects because the remote SIMBAD name resolver system and its US mirror were unavailable. We are sorry for any inconvenience.
9 July 2002
Two new infrared surveys are now available. New survey data include a full sky 100 micron map (SFD 100 micron), a reprocessed composite of the COBE/DIRBE and IRAS/ISSA maps, and a full sky map proportional to dust column density (SFD Dust Map) calculated using the new 100 micron data and data from 240 microns. More Information
4 June 2002
Skyview has been named one of 50 top sites in the Scientific American.com Sci/Tech Web Awards. Look for us in the Astronomy & Astrophysics category.
21 May 2002
Over 100 new 4x4 degree mosaics from the Sydney University Molonglo Sky Survey (SUMSS) are now available through SkyView. SUMSS data currently covers a 1500 square degree area of the sky south of declination -30 degrees. See the updated High Resolution Radio Survey Coverage map.
6 May 2002
A catalog overlay section listing 10 popular and/or interesting catalogs was added to the Basic Interface. Objects from selected catalogs will be marked on SkyView Images.
22 April 2002
Three large catalogs provided by Centre de Données astronomiques de Strasbourg (CDS) VizieR Catalog Service are now available. Look for VizieR: GSC 2.2 Catalog (STScI, 2001), VizieR: The 2MASS Database (IPAC/UMass, 2000) and VizieR: USNO A2 Catalog (Monet) in the Catalog Overlays list on the SkyView Advanced Interface.
1 April 2002
We fixed a bug that caused no image to display if contour overlay was selected and the resolution of the contour survey data was significantly different than that of base image survey.
22 March 2002
The transition to new server hardware is complete for both SkyView systems skyview.gsfc.nasa.gov and skys.gsfc.nasa.gov. The new hardware provides faster image display and improved system stability. As always, please let us know if you have questions or problems.
20 March 2002
The backup SkyView server (skys.gsfc.nasa.gov) will be unavailable for a short period of time over the next couple of days as we update hardware and software. This down time will affect web and batch access. We apologize for any inconvenience. The alternate SkyView server (skyview.gsfc.nasa.gov) will be available during this time.
15 March 2002
The link to Maki: The Astro-E/Multi-Mission Observation Visualizer was removed from the page that displays SkyView images. Although Maki is not supported at this time it is still functional and we have included a link to it on the Other Interfaces Using SkyView page.
14 March 2002
The Second Generation Digitized Sky Survey (DSS2) is now available in SkyView. This optical survey provides high-resolution all-sky images in two colors. More information can be found in our Survey Document.
12 February 2002
skyview.gsfc.nasa.gov now accesses the new SkyView server. Please let us know if you have any comments or questions. The old SkyView server and back-up will still be available for the next month or so.
29 January 2002
The new SkyView system skys4.gsfc.nasa.gov is once again available for testing. If all goes well this new system will become the default SkyView system next week. Please let us know if you have any problems.
23 January 2002
Due to a problem with the NED name resolver this morning incorrect coordinates were associated with object names entered on the SkyView interfaces and incorrect images were displayed. We notified IPAC and the problem was quickly resolved.
23 January 2002
The new SkyView system should be back up for testing within the next couple of days. A major data loss occurred last week and data restoration has been a slow and painful process.
14 January 2002
A major data loss on the new SkyView system has occurred and the system has been taken offline for data restoration. The current SkyView systems (this page and the backup SkyView server) are available.
10 December 2001
The new SkyView system is available for testing. We would appreciate any feedback.

SkyView has been ported to new machines that should provide significantly faster image display. We plan to run the new and old systems in parallel for a while before taking down the older systems. A consequence of this change will be that the X-Windows Interface which we have been phasing out over the last couple of years will no longer be available. All web, Java and batch interfaces will continue to be available. Please let us know if this adversely affects anyone and, if so, in what way.

28 September 2001
The remote server that SkyView uses to resolve object names was down resulting in a long wait for some SkyView images. There was no problem if coordinates were used instead of object names when filling out the SkyView query form. Image display times were back to normal when the server came back online.
20 July 2001
Numerous nearly simultaneous image requests have caused system problems over the last couple of weeks. We will be installing monitoring software soon to limit the number of requests that can be submitted. We apologize for any inconvenience.
05 June 2001
Maintenance operations on SkyView disk drives were performed over the last 2 days. We switched over to our backup disks so that all survey data would be available while the primary disks were off-line.
29 May 2001
The main SkyView server experienced problems over the holiday weekend. We apologize for any inconvenience. The SkyView backup system ( http://skys.gsfc.nasa.gov) was up and running during this interruption. In the event that our main site in not available please check our backup site.
08 May 2001
Our disk problems have been fixed and all SkyView survey data are available once again. Thank you for your patience.
27 April 2001
The disk on which most of the SkyView data are stored failed overnight. We were able to switch over to our old disks however some data may not be complete. The problem is being worked on and hopefully we will be back up to full service soon. We sincerely apologize for the inconvenience.
24 April 2001
The remote FIRST survey FTP server was inaccessible for approximately 24 hours and FIRST data was not available through SkyView. We apologize for any inconvenience.
24 January 2001
2MASS infrared data is currently not available. For the time being, 2MASS images can be accessed from their Image Server. We apologize for any inconvenience.
7 November 2000
The SkyView geometry engine has been updated to use Besselian coordinates for all epochs prior to 1975. Previously Julian coordinates had been used for all epochs. The differences between Besselian and Julian coordinates are a few tenths of an arc-second or less (at the typical 1950 epoch).
While this difference was generally small compared to the pixel sizes used in SkyView surveys, it introduces errors in catalog positions for high precision catalogs. With many of the newer surveys having pixel sizes getting closer to 1" the shifts in image data have also begun to become significant.
24 October 2000
A more complete set of the Faint Images of the Radio Sky at Twenty-cm (FIRST) survey data is now available through SkyView. FIRST is a project designed to produce the radio equivalent of the Palomar Observatory Sky Survey over 10,000 square degrees of the North Galactic Cap.
3 October 2000
New higher resolution galactic CO data is now available. The 115 GHz radio survey now consists of 488,000 spectra that Nyquist or beamwidth (1/8-degree) sample the entire Galactic plane over a strip 4 - 10 degrees wide in latitude, and beamwidth or 1/4-degree sample nearly all large local clouds at higher latitudes.
14 August 2000
An error in the representation of catalog overlay information in SkyView image FITS files has been fixed. The ASCII table extension header and data are now correct. We apologize for any inconvenience this error may have caused.
26 July 2000
The Sydney University Molonglo Sky Survey (SUMSS) is now available! SUMSS is a deep radio survey at 843 MHz that will eventually cover the entire sky south of declination -30 degrees. 35% of the survey has been completed.
10 July 2000
Several bugs were fixed relating to the tiling of large images and handling of data outside of the standard projection region (for finite projections such as the Aitoff or Orthographic). These sometimes caused image creation to fail and occasionally caused Aitoff projections with data repeated outside the normal Aitoff ellipse.
7 July 2000
The Catalog Overlay function has been updated to provide better messages for the cases where the catalog query times out, returns no sources or returns too many sources to list.
8 June 2000
A link to a list of the names of data files used to generate a SkyView image has been added below each image. Although not useful for all images this information can provide extra survey details such as the plate names for the Digitized Sky Survey and tile and subimage numbers for the 2MASS Survey.
15 May 2000
Information about the color table, scaling method and range of image values has been added to the information below each generated SkyView image.
4 May 2000
Data used to generate ROSAT All-Sky Survey images are now on disks local to the SkyView system and are no longer FTP'd from the Max-Planck Institute in Germany. As a result, ROSAT All-Sky Survey images will be displayed more quickly.
4 May 2000
Quick SkyView Image Information: A feature to allow users to generate a Quick SkyView Image without having to select a SkyView interface was added to the main SkyView page. Just enter an object or set of Equatorial coordinates and then select one of the 5 most frequently selected surveys. The 5 surveys include an optical survey, Digitized Sky Survey (DSS), two xray surveys, ROSAT All-Sky Survey (RASS 3) and HEAO 1 A-2 (HEAO), an infrared survey, IRAS 100 micron (IRAS), and a radio survey 0408 MHz (0408MHz). The size of the generated image in degrees will be the default size for the selected survey. The size in pixels will be 300 x 300. The image will be in J2000 Equatorial coordinates and Gnomonic projection.
4 May 2000
The main SkyView server experienced problems due to low system swap space last night from approximately 09:10PM EST to this morning at 8:15AM EST. We apologize for any inconvenience. The SkyView backup system ( http://skys.gsfc.nasa.gov) was up and running during this interruption. In the event that our main site in not available please check our backup site.
14 April 2000
Data from the latest release of The Two Micron All Sky Survey (2MASS) is now available. Coverage is now 19,600 deg2 of the northern and southern infrared sky.
10 April 2000
SkyView was not able to display images for some named objects at times today because the US mirror of the SIMBAD name resolver was unavailable. We are sorry for any inconvenience. We have made changes so that in the future SkyView will try the SIMBAD server in France if the US site is not available.
10 April 2000
The ROSAT All-Sky Survey from the Max-Planck Institute for Extraterrestrial Physics is now available! This survey covers the entire x-ray sky in the frequency range of 0.1-2.0 KeV. SkyView retrieves the survey data from MPE via FTP.
22 March 2000
The FITS file headers for CARTESIAN projection images were changed. The reference position indicated by the CRVAL keywords is now set to 0,0 and the CRPIX keywords have been changed accordingly. This change was made to make SkyView FITS headers more in line with the WCS FITS standard.
21 March 2000
Yesterday evening the Advanced and Basic interface on the main SkyView server were not displaying surveys and catalogs after some files were moved to comply with new security policies. We sincerely apologize for any inconvenience. This problem did not affect the SkyView backup system ( http://skys.gsfc.nasa.gov). In the event that there are problems at the main site please check our backup site.
11 February 2000
Yesterday, a network reconfiguration temporarily disabled access to the SkyView main server from outside of Goddard Space Flight Center. We apologize for any inconvenience. The SkyView backup system ( http://skys.gsfc.nasa.gov) was up and running during this interruption. In the event that our main site in not available please check our backup site.
19 January 2000
Because the SIMBAD name resolver was unavailable SkyView was not able to display images for some named objects. The SIMBAD system is now back up and running. We are sorry for any inconvenience.
17 January 2000
The main SkyView server experienced system problems this past weekend from approximately 1/15/00 02:50AM EST to 1/17/00 10:14AM EST. We apologize for any inconvenience. The SkyView backup system ( http://skys.gsfc.nasa.gov) was up and running during this interruption. In the event that our main site in not available please check our backup site.
16 December 1999
As part of NASA's Y2K policy, the SkyView computers will be shut down for the new year rollover sometime on the afternoon of December 30. We anticipate that the systems will be back up and running sometime early on January 3, 2000. We apologize for any inconvenience this may cause.
19 November 1999
Due to a new security policy, the Telnet access interface is considered a potential security risk and has been removed from SkyView. This interface allowed the SkyView X-Windows interface to be accessed in a telnet environment. Although the telnet capability is no longer available the X-Windows interface can be directly accessed from our main page.
28 October 1999
All local survey data have been moved to the new disk farm. This should resolve some of our recent problems with data being unavailable due to the decreasing reliability of our older disks. An image size option of 2 degrees was added to the Non-Astronomer and Basic Interfaces.
14 October 1999
The Java Interface on the main SkyView server has not been working correctly outside the SkyView LAN since Wednesday July 29. At that time a network reconfiguration was performed. We apologize for any inconvenience. The Java interface on the backup server http://skys.gsfc.nasa.gov was unaffected by the problem.
13 October 1999
The list of HEASARC catalogs on the Advanced Interface page are now updated daily using an automated database query. Prior to this change the file containing the list was manually updated and did not always reflect the actual number of catalogs available.
12 October 1999
Extra Submit buttons have been added to the Advanced Interface page for convenience. Users no longer have to scroll back to the top of the page to submit the Skyview request.
7 October 1999
We are in the process of moving survey data to a new, more dependable disk farm. All Digitized Sky Survey data has now been moved. Some of the DSS data was located on a disk that has been problematic for the last couple of months.
10 September 1999
Due to a disk problem, a portion of the sky was unavailable for some time for the Digitized Sky Survey. The problem was resolved this morning. We apologize for any inconvenience.
2 September 1999
The EGRET survey has been updated to include data from the beginning of the mission (4/21/91) through 10/3/95.
27 August 1999
The main SkyView server experienced system problems this morning (8/27/99) from approximately 2:25 AM to 8:40 AM EST. We apologize for any inconvenience. The SkyView backup system ( http://skys.gsfc.nasa.gov) was up and running during this interruption. In the event that our main site in not available please check our backup site.
11 August 1999
The current release of the Two Micron All Sky Survey 2MASS is now available! This release covers 2,483 deg2 of the northern infrared sky.
29 July 1999
A network reconfiguration made SkyView's primary web server inaccessible to computers outside its LAN from 1630-2300 on Wednesday July 29. Router tables have been updated so that SkyView should once again be fully visible. The backup server http://skys.gsfc.nasa.gov and the non-Web based interface were unaffected by the problem.
28 July, 1999
A bug that prevented image generation using the SkyView Java interface was fixed.

Sample multi-wavelength SkyView images of selected objects have been added to the General Help page.

26 July, 1999
A second optical survey has been added to SkyView! Images from the Near-Earth Asteroid Tracking (NEAT/SkyMorph) project which covers approximately 30% of the sky are now available.
7 July, 1999
The Advanced Interface of Skyview has been changed to more clearly catagorize our surveys. Surveys are now grouped together by spectral regime.
22 June, 1999
The Westerbork Northern Sky Survey (WENSS) has been added to SkyView. WENSS is a low-frequency radio survey that covers the whole sky north of delta=30 degree at a wavelength of 92 cm to a limiting flux density of approximately 18 mJy (5 sigma).
17 June, 1999
The US Naval Observatory A2 catalog of more than 500 million objects is now available as a catalog overlay through the HEASARC. Please do not use this catalog for fields larger than a few tenths of a degree on a side.
09 June, 1999
The links to the HEASARC W3Browse site which provides information on catalog overlays were changed to accommodate a change to the URL syntax.
01 June, 1999
SkyView experienced system problems on Sunday 5/30/99 and Monday 5/31/99 when the error logs and disk space filled due to a problem retrieving catalog data. We apologize for any inconvenience.
24 May, 1999
The names of GIF and FITS files were changed to include the system time to ensure that all file names are unique.

The name of the Astro-E/Multi-Mission Observation Visualizer has been changed from WASABI to MAKI. MAKI is a tool that accepts an image file from SkyView and plots it, along with when that target is visible during the current year. A link to MAKI appears in the SkyView results window. More info.
16 May, 1999
SkyView experienced system problems on Sunday 5/16/99 for approximately 24 hours. We apologize for any inconvenience. The SkyView backup system ( http://skys.gsfc.nasa.gov) was up and running during this interruption. In the event that our main site in not available please check our backup site.
06 May, 1999
Radio CO surveys maps were added. 3D CO maps will be installed soon.
27 April, 1999
The Overlay section on the Advanced Form was changed. Catalogs under the Catalogs: (Local) heading were removed. These catalogs were copied to the system several years ago and have not been maintained. The quality of these catalogs is not known and errors were recently found so they have been removed from the system. Most of these catalogs can be found under the Catalogs: (HEASARC) heading. SkyView users are encouraged to let us know if this change causes any problems.
5 April, 1999
The system suffered from two hardware glitches over the Easter weekend. The first caused all requests to hang for several hours on the main server. The second made a portion of the sky unavailable for the DSS survey. The system is now fully recovered.
30 March, 1999
The SkyView server's disk filled up yesterday (3/29) afternoon causing requests not to be fulfilled. The problem has been identified and corrected.
19 March, 1999
Due to the recent web server upgrade, the compressed FITS button returned a file not found error. This has been fixed.
16 March, 1999
The SkyView web server was upgraded. This should allow WebTV and AOL browsers to work (some users had reported that SkyView did not work with the previous web server configuration).
3 March, 1999
The operating system on the SkyView server was upgraded in compliance with Y2K standards. With this upgrade, SkyView is completely Y2K compliant.
3 Februaray, 1999
An error in the HEASARC HST Guide Star Catalog (HGSC) had been rounding positions to the nearest 1/1000th of a degree. This has been fixed to give positions to the nearest 1/10,0000th of a degree. The nominal error in the HGSC is typically about an arcsecond (roughly one pixel in a default sized Digitized Sky Survey SkyView image which is comparable to the rounding error).
9 January, 1999
A bug in the contour overlays has been fixed.
11 November, 1998
A small bug in the tiling code caused image requests between 300 x 300 pixels and 600 x 600 pixels to display incorrectly (black regions around a 300 x 300 image). This has been fixed.
10 November, 1998
WASABI has been included in SkyView. WASABI is a tool that accepts an image file from SkyView and plots it, along with when that target is visible during the selected year. You may then place different satellite fields of view on top of the image, to plan out your observation. You can also view the sun angle visibility limits for several missions, as well as add phase constraints and also see what the total overlapping window of opportunity is for your selections. In order to run WASABI, you will need to download the HEARSARC TCL/TK plug-in (currently, only UNIX machines are supported, though a MS Windows version is coming soon).

The Java interface was temporarily broken with the release of the large image support. The problem has been fixed (and should be accessible to all Java 1.0 and 1.1 compatable browsers).

9 November, 1998
The large image support is now in the released version of SkyView.
1 October, 1998
The SkyView disk server was rebooted to re-enable access to a disk containing about 15% of the DSS data.
4 September, 1998
More memory was added to the server to better serve requests.
14 August, 1998
Four more surveys have been added in the UltraViolet range (UV Total, UV Galactic, UV Stellar, and UV SolSys).
10 August, 1998
There is new and improved large image support in SkyView! Previously, requested images larger than 1000 x 1000 did not always work due to memory limits. We have changed things to allow images up to 2400 x 2400 pixels. The change is currently in the Test version's Advanced interface. We appreciate any comments, suggestions, or problems you may have.

A couple of notes: this does not change the limit on pixels obtained from a given survey (i.e. you cannot get images larger than 4.5 x 4.5 degrees from the Digitized Sky Survey). Also, making a series of large image requests still places a high burden on the SkyView, and we ask you to not to make several simultaneous requests but to spread them out.

27 July, 1998
The main HEASARC catalog suffered a disk crash that made SkyView catalog queries inoperable for a few days. We've switched to a backup catalog server, and things appear to be working normally. Thanks to everyone who brought this to our attention.
27 May, 1998
The main SkyView was down temporarily. We took the opportunity to switch over a faster network connection. If you have any problems, please send e-mail to scollick@skys.gsfc.nasa.gov.
11 May, 1998
The main SkyView server was down for about a day due to some technical difficulties. They have been resolved, and things are working normally again.
20 April, 1998
The HEASARC catalogs have been updated adding three new catalogs.
1 April, 1998
Both SkyView servers played a cruel April fool's joke as both web servers stop responding. The problem has been fixed.
20 March, 1998
A problem with the local network caused SkyView requests to return as garbled characters for a few hours. The problem has been fixed. While we don't expect this to happen again, the "old" server was unaffected and was up during the above problem.
9 March, 1998
SkyView is now checking that required fields have been specified before sending requests. This should eliminate the annoying wait before SkyView indicates that there is an error. Instead you will immediately get a pop-up message indicating the error. The current version simply checks that values have been entered. Future versions will perform some syntax checking.

This new feature uses JavaScript but if your browser does not support JavaScript, or you have turned it off, then you should see the old behavior (see the March 4 entry for specific web browser information). The SkyView version on skys.gsfc.nasa.gov does not currently incorporate this change so you can use that system if you are experiencing problems. We very much encourage you to report any issues since we will put this change in both versions of SkyView unless we hear of problems from our users.

4 March, 1998
Added to the forms pages of the Test version is JavaScript validation. This will provide quick feedback when a form is submitted without all the required information specified. The advantage is that a connection with the SkyView server is not needed before the error is caught. Currently, the validation checks for a survey (or catalog if it is a catalog only request on the Advanced page) and a value entered in the Coordinate Value box. Further (more complex) error checking of the pages is likely down the road.

Browser note: The current implementation of the JavaScript code works with Netscape 2, 3, and 4 as well as Microsoft Internet Explorer 4 or emulators of these browsers. The only notable exception is for the Non-Astronomer page where Netscape 2 does not work. Microsoft Internet Explorer 3 and earlier is NOT compatable! For browsers not running JavaScript (i.e. Lynx, Mosaic, etc.), SkyView will run as before.

If you encounter any problems, please send e-mail to scollick@skys.gsfc.nasa.gov .

2 March, 1998
The HEASARC catalogs have been updated in the Advanced Page.
24 February, 1998
The SkyView primary machine was brought down last night to add additional swap space. Unfortunately it did not reboot properly and was not available till this morning.
23 February, 1998
The HEASARC catalog server was down for part of this morning (2/23 until ~11:30 a.m. EST). The server has been reset and the HEASARC catalogs are working.

The SkyView server was unaccessible for a day or two over this past weekend. The problem has been fixed. As a reminder, if a problem does occur, our backup server at http://skys.gsfc.nasa.gov/ is accessible.

12 February, 1998
SkyView is now running off the new, faster server. As of noon today (2/12) the URLs http://skyview.gsfc.nasa.gov and http://skview.gsfc.nasa.gov point to the new machine. Unfortunately, the change cannot be instantaneous for everyone. Hopefully, by Friday 2/13, the change will take effect globally. If you continue to point to the old server, please contact your system administrator.

The "old" server will continue to operate as well and can be accessed via http://skys.gsfc.nasa.gov. If you have any questions, please contact scollick@skys.gsfc.nasa.gov.
26 January, 1998
SkyView Frequently Asked Questions have been added.
5 January, 1998
The contour bug fix is now part of the released version of SkyView.
2 January, 1998
An error was discovered that caused incorrect results to occur when contouring an image on top of another image. This error only happens when the contouring image and display image are of differing default scales, and when the "Image size" is set to "Default". The fix has been placed in the Test interface.
29 December, 1997
A bug was introduced in v3.1 that caused some surveys to return blank. This has been fixed.
15 December, 1997
The VLA FIRST survey is now in the final released version of SkyView.
26 November, 1997
The VLA FIRST survey is back in the test version. The total number of images has nearly doubled.
25 November, 1997
The SkyView Java interface has been upgraded to version 1.1! Please see the Release Notes for changes and updates.
24 November, 1997
The SkyView geometry engine has been updated to version 3.1. Most notable among the changes, the triangular decomposition routines have been altered for improved efficiency.
21 November, 1997
The NRAO is currently re-organizing their FTP site, and it has been necessary to put the FIRST data off-line temporarily.
17 November, 1997
The NVSS data has been updated in the release version of SkyView.
13 November, 1997
Updated VLA NVSS data has been placed in the Test Version . The recent update comprised complete coverage above a declination of 40°.
10 November, 1997
SkyView Java version 1.1 (beta4) has been released. The new version is now compatable with both v1.0.x and v1.1.x Java Virtual Machines.
10 November, 1997
The ROSAT PSPC survey data has been completely restored.
7 November, 1997
A small problem introduced during the switch to the U.S. SIMBAD name resolver has been corrected. Note: we are currently seeing slow response in accesses to the NED name resolver.
5 November, 1997
We discovered an error was introduced into the routine to transform from galactic to ecliptic coordinates. This error would only effect the COBE and HEAO data (and only when the returned image was requested in galactic coordinates). The fix to this problem has solved the problems seen in the COBE data.
5 November, 1997
Sprint and NSI will be working to upgrade network services for NASA Goddard this weekend on Sunday, November 9th, from 9am until 5pm EST. All network traffic will be affected by this outage.
4 November, 1997
The ROSAT PSPC surveys are back in the Test Version. After more testing, they will be included in the Final Version by the end of this week or early next week.
27 October, 1997
SkyView now uses a US SIMBAD mirror site for name resolving which shortens the retrieval time by a few seconds.
21 October, 1997
The SkyView Advanced page now supports catalog only overlays. Choosing catalogs without an image survey will create the overlay (note: image scaling must be explicitly entered -- default will return an error).
17 October, 1997
There is a planned power outage this weekend in the building of the SkyView server. We have been assured that this will not affect SkyView, but we are providing a warning just in case things do not go according to plan.
10 October, 1997
The HEAO 1 A-2 data has been updated to fix a procession error.
7 October, 1997
A serious error has been found in a number of the archival ROSAT events files which were used to construct the ROSAT PSPC mosaic surveys. The FITS headers for these observations give incorrect orientation information leading to the creation of images flipped in the north/south direction. At least several hundred (out of ~4500) images are involved. The HEASARC is correcting these data and we are reprocessing all of the SkyView Rosat mosaic surveys. The older ROSAT PSPC survey had used an earlier data product which did not have this error.

In the interim we have made the newer SkyView ROSAT mosaics unavailable for use. Correcting this error will take several weeks. We deeply regret any problems we have caused and apologize to any affected users. We would like to thank Dr. Manfred Pakull for bringing this problem to our attention.

Unfortunately, there is no obvious marker for incorrect data. Since only event data is affected and not the exposure data, spurious spokes may appear at the positions of the ribs but this is often subtle. The most serious errors may occur at positions where there are overlapping images in both the correct and flipped orientation. The resulting summed images will have both valid and invalid targets.

The problem observations are those derived from ROSAT observations which have not yet been reprocessed to the latest software level (Rev 2). A preliminary list of affected observations and centroids is included is available. A more complete list will be available shortly.

6 October, 1997
A problem has been detected with the ROSAT PSPC surveys (not including the OLD PSPC survey). Returned data in some regions appears to be flipped along the horizontal axis. We are looking into the problem and hope to have a fix soon. The OLD PSPC survey is not affected by this problem.
3 October, 1997
Currently in the Test Version, catalog overaly only requests (i.e. catalog requests without selecting an image survey) have been added as a new feature. This can be accomplished only through the Advanced Page at the moment, though we anticapte adding a dedicated page to just catalog overlays in the near future. Please send all questions and feedback to scollick@skys.gsfc.nasa.gov.
1 September, 1997
SkyView was down briefly to complete the software maintenance. For a few hours after the machine was back up, the Digitized Sky Survey was not working. This problem has been fixed. If you notice any problems, please send e-mail to scollick@skys.gsfc.nasa.gov.
24 August, 1997
SkyView was down for a day to perform software maintenance.
12 August, 1997
A problem with catalog overlays with the Java Interface (beta) has been detected and fixed.
8 August, 1997
A new beta version of the SkyView Java interface has been released. The new version corrects problems with the Netscape Communicator Just-In-Time compiler, threads with MACs, and display problems with Microsoft IE4.0 beta (problems still exist with IE3.0). If you have any problems please contact scollick@skys.gsfc.nasa.gov.
31 July, 1997
Three new surveys have been added to SkyView. The ROSAT Diffuse All-Sky Survey at 0.25KeV, 0.75KeV, and 1.5Kev.
28 July, 1997
The SkyView server took longer to get back up than originally anticipated. Things should be working normally. If you have any problems please let us know.
25 July, 1997
A bug was discovered in the W3Browse facility that prevented catalog requests from working in the Java interface. This bug did not effect requests from the Advanced or X-windows interfaces.
15 July, 1997
The COBE DIRBE data has been updated with Band pass 3.
8 July, 1997
The FITS file header for Digitized Sky Survey contained a stray that may cause problems with some FITS readers. This has been fixed.
27 May, 1997
In the process of upgrading the SkyView web pages, the previous batch file (skvbatch.pl) no longer works. If you have had problems with batch requests please download the latest copy of skvbatch.pl. The file webquery.pl has not changed.
19 May, 1997
The forms pages have been altered such that Microsoft Internet Explorer users no longer have to deselect unwanted items defaulted by the browser. This should make it much easier to use the forms pages.
19 May, 1997
The SkyView web pages have been revamped! If you encounter any problems please e-mail scollick@skys.gsfc.nasa.gov.
12 May, 1997
Starting next Monday (5/19), the SkyView web pages will undergo a re-organization. The effect is to make getting information quicker and easier. For a sneak preview check out http://skys.gsfc.nasa.gov:2000/ . One quick note, the Java interfaces may or may not work with all web browsers until next Monday (it depends on web browser security).
5 May, 1997
In the process of changing one of the local network servers, SkyView experienced unforseen problems. I have done my best over the course of the day to undo all of the system dependencies on that server such that SkyView can work normally again. To the best of my knowledge, things are working as before, yet there maybe some hidden bugs as a result of the earlier patching. If you experience a problem please send details to me at scollick@skys.gsfc.nasa.gov. We apologize for the problems, but we have taken steps such that this will not happen again.
24 April, 1997
A local network server machine was rebooted that had the inadvertent effect of preventing SkyView from running normally.
21 April, 1997
The ROSAT PSPC data has been overhauled. When a PSPC image request returns, a table is provided to get counts, exposure, and other intesity maps (not directly obtainable from the forms page) for the given region. Several different PSPC surveys are available using information out to different maximum radii from the center of the observation: 2°, 1°, and 0.6°. For more information regarding the process of the PSPC map generation, please refer to the ROSAT PSPC Generation Document.

Also, the intensity, counts, and exposure maps are available through the current Java Interface (beta version).
25 March, 1997
Attention all comet watchers. Unfortunately, SkyView is not intended for solar system objects (entering them will return an error). But, you can get the latest updates on Comet Hale-Bopp from http://comet.hq.nasa.gov (including daily uploaded pictures).
11 March, 1997
The SkyView Java Inteface v1.1(beta2) is now available. The new beta adds zooming to the PC browsers (via the "z" key) and gridding to all Java implementations. Plus, several bugs have been fixed with, unfortunately, some new ones introduced. Please read the beta release notes for the latest changes and known bugs.
25 February, 1997
The VLA First Survey has been added to the SkyView database. The First Survey is the first remote survey to be added to SkyView. The actual data is retrieved from the NRAO FTP area (though files are cached by SkyView).
25 February, 1997
The SkyView Java Inteface v1.1(beta) is now available. The beta release adds a new, self-contained help facility along with smooth, zoom, and several other new options. Please read the beta release notes for the latest changes and known bugs.
28 January, 1997
The algorithm for projecting data into the Digital Sky Survey plate projections has been refined. This fixes a problem which made it impossible to see data at the North pole and will slightly shift pixels in the image, typically by of order 0.1 arc-second. For nearest neighbor resampling, the default, this means that most pixel values are unaffected but occasional pixels will now have values that in the previous image were in a neighboring pixel. If an interpolation technique is used, all pixels values will likely change by some fraction of the difference between the pixel and it's neighbors. Please let us know if you have any questions or problems.
27 January, 1997
The SkyView server has encountered some hardware problems that has caused SkyView service to be unattainable since Jan. 25. We think that everything is back and running normally. Sorry, for any inconvenience this may have caused.
21 January, 1997
SkyView has been selected as five star Platinum site by NetGuide magazine.
15 January, 1997
SkyView has been updated to version 3.0. The biggest addition is the release of the Java interface. If you experience any problems as a result of this upgrade please let us know.
8 January, 1997
The VLA NVSS survey has been updated to include the latest images available. Here is the current coverage.
17 December, 1996
An error was discovered in the images of the 4850 MHz survey. Positions requested below the equatorial equator were wrongly labelled as J2000 instead of B1950 causing all requests from this region to be improperly precessed. This has been fixed. Thanks to Tom Oosterloo and Vincent McIntyre for bringing this to our attention.
6 December, 1996
The planned installation of a new uninterruptable power supply has been postponed for this weekend. SkyView will stay up all weekend.
6 Decemeber, 1996
SkyView will be unavailable from 10:00 p.m. EST on Friday Dec. 6 to approximately 3:00 p.m. EST Saturday Dec. 7 to install a new uninterruptable power supply.
25 November, 1996
A bug was discovered in the interpolation resampling routine. This caused images to be offset by one-half the default scaling per pixel. Thanks to Klaus Hodapp for pointing this out to us. The error has been fixed.
15 November, 1996
The SkyView Batch page has been updated. The file skvbatch.pl has been altered to now allow the retrieval of GIF files. The use of the keyword RETURN='gif' with the batch file will retrieve the GIF instead of the FITS file.
13 November, 1996
Some cosmetic changes were made to aid in getting the survey documents to download faster. Also, a new button has been added to the image return page that allows the transfer of compressed FITS file using the GNU zip (gzip) format.
1 November, 1996
The beta release of verion 1.0 of the SkyView Java Interface is now available.
31 October, 1996
Ghostly spirits invaded our system that prevented SkyView from working for about an hour. The apparitions were exorcised, and everything is working normally again.
15 October, 1996
SkyView had a temporary disk failure that prevented several key executables from running. The disk is up and running again, and things appear to be running normally.
9 October, 1996
A small glich resulted in SkyView not working for a small period of time (i.e. requests returned blank screens). The problem has been fixed, and we apologize for any inconvenience.
3 October, 1996
An nH 21 cm map has been added to the list of surveys.
26 September, 1996
In the Test Version, we have added a Java interface with some basic functionality. We are curious to get your input and suggestions. We hope to have a more fully featured interface ready by the middle of October. What is currently on the interface should work (with a known bug of returning positions on the image when the Rectangular and Hammer-Aitoff map projection is selected).

A small bug was found with the Digitized Sky Survey that caused a blank screen to return instead of an image. This occurred most often near the center of a DSS plate. This has been fixed.
21 August, 1996
It was noticed that the flat fielding of mosaicked Digitized Sky Survey was not working properly. This has been fixed, and the plate boundries on these images should have a vast improvement.
15 August, 1996
SkyView has now added a new interface geared towards the non-professional astronomer. It is our hope to make SkyView accessible to anyone and everyone interested in getting pictures of the sky. Your feedback is important to us to make this possible.
24 July, 1996
An error was discovered that caused certain small areas of the IRAS survey not to load properly leaving blank regions in the returned image. This problem was a result of a change within the past two months and should not have affected most image retrievals. If you experience any continued problems, please let us know.
12 June 1996
Over night, SkyView was bombarded with dummy requests that prevented people from accessing the web forms. The offending processes have been removed, and things appear to be working normally once again.
3 June 1996
The NRAO VLA Sky Survey (NVSS) has been added to SkyView's list of surveys. This is a radio survey with a frequency of 1.4 GHz. Currently, the coverage is incomplete but new data will be included as it becomes available.
31 May 1996
As of May 31, 1996, there will be no restrictions on the Digitized Sky Survey. Up until this point, the FITS files of the Northern sky were of reduced intensity resolution. This restriction is no longer in place.
15 May 1996
SkyView is now connected to the Internet via a fiber optic link. This should improve SkyView's speed, though it is difficult to say by how much (there are other limiting factors). For a brief time accessing SkyView with the address skyview.gsfc.nasa.gov may have caused problems, but this has been resolved.
2 May 1996
A new feature has been added for Netscape users, and anyone else whose browser supports the TARGET feature. SkyView images will now appear in a separate window to keep the submission form and final image in easy view, simultaneously. All output images will be sent to the new window, thereby keeping a record of all your images retrieved from SkyView. Your feedback is important as to whether you like this new feature or not.
1 May 1996
The HEASARC catalog service is now working normally.
30 April 1996
Due to changes by the HEASARC for their remote catalog service, the HEASARC catalogs are not working in SkyView. They have been notified of the problem and should have a fix relatively soon. Sorry, for any inconvenience this may cause.
29 April 1996
The Skyview code for version 2.3 is now available. This includes all the IDL procedures and Perl scripts used to create and run SkyView. The code is available from

ftp://skys.gsfc.nasa.gov/software/skyview_v2.3.tar.gz

and is gzipped tar file. IDL v3.6.1 or higher and Perl v4.036 or higher are needed to run SkyView from this distribution.
12 April 1996
We have now added a batch execution page that includes two Perl scripts designed to run SkyView from your computer to retrieve FITS files. These scripts have only been tested on UNIX machines and would require modification to work on other platforms.
10 April 1996
Data from the Compton Gamma-Ray CompTel instrument have been added to SkyView. CompTel data ranges in energies from 1 to 30 MeV. CompTel is available either as a two dimensional image (at 3-10 MeV) from either web interface or as a three dimensional image using the Advanced page.
9 April 1996
COBE DIRBE data (1.25 to 240 microns) has been added to SkyView. COBE data can be accessed either as a two dimensional image (at 100 microns) from either web page or as a three dimensional image using the Advanced page.
2 April 1996
A potential bug for some FITS readers was corrected. If 3-D images were selected with the size of the third dimension being one [i.e. (x,y,1)], the FITS writer was incorrectly labelling the NAXIS keyword as being two instead of three. Note: only some FITS readers were having a problem reading this, but it has been corrected.
25 March 1996
An error was discovered in the CRPIX1 keywork for FITS files written using an Aitoff map projection. The CRPIX1 value should be the negative of the value given. Thanks to Dr. Julian Daniels for pointing this out.
4 March 1996
As a result of the upgrade to v2.3, the 4850 MHz survey was no longer loading properly. This has been fixed.
28 February 1996
The following catalogs were discovered to be incorrectly processed by the HEASARC catalog service: Compton GRO Observations, EXOSAT CMA images/lightcurves, EXOSAT CMA central 6, ROSAT Catalog PSPC 1WGA Sources, and XTE Master Catalog. Requests using these catalogs would incorrectly return null results. HEASARC has fixed this problem, and these catalogs are working properly.
27 February 1996
SkyView has been upgraded to version 2.3. This version is the same as the test version with the exception that the UV data has been removed. For a list of new features and/or bug fixes please see the Feb. 16 entry. If you have any problems with version 2.3 please let us know.
22 February 1996
Due to changes in the HEASARC W3Browse program, the link to the HEASARC remote catalogs is not currently working. HEASARC catalogs can still be retrieved, but the link to get further information is no longer valid. We expect a fix within a day or two. Sorry, for any inconvenience this may cause.

The fix is now in place (10:10 EST) -- KAS

16 February 1996
Starting today, we are providing access to a SkyView Test Version. The test version includes new features and improvements that will be released with version 2.3 of SkyView. Changes include: The test version has been tested to be devoid of obvious bugs, but subtle errors probably still exist (usually occurring when using a wide combination of features). We welcome any feedback as to the changes and/or errors in the test version , as well as comments of what you would like to see included in SkyView. Though it is our hope to have the test version up constantly and consistently, there maybe times when it will unvailable to make changes.
15 December 1995
A bug report indicated that catalog searches that returned a null value were failing in version 2.2. This has been corrected.
12 December 1995
A significant error in the astrometry for approximately 25% of the northern sky plates was brought to our attention by Brian Skiff. For 126 plates in the northern sky a term in the plate solution that SkyView had assumed to be nil was non-zero. The positions of these plates are given here. The magnitude of the error grows with distance from the center of the plate. Errors can be as large as tenths of an arc-minute. We have corrected this error in all released versions of the system. User's who require accurate astrometry in the northern sky may wish to regenerate their maps.
11 December 1995
Two minor bugs were reported concerning the gridding of points with negative declination and with the erroneous error messages displayed when certain HEASARC catalogs are selected. These have been fixed.
4 December 1995
At the request of the University of Minnesota, there is a size request on all APS catalog searches. The maximum radius for a search is 15 arc minutes. Also, SkyView now limits the total number of catalogs to 10 catalogs per search.
30 November 1995
SkyView has been updated to version 2.2. This upgrade offers a variety of new features and speed enhancements. Changes to SkyView include:
2 November 1995
Over the course of the evening of Nov. 1, several network configuration tasks were performed. As a result, SkyView was not reachable until about noon this afternoon. Also, the numeric IP address has changed to 128.183.126.105.
23 October 1995
The computer network that SkyView is connected to was broken into on Oct. 20. This action forced the closing of the network to the outside world for the weekend until the extent of the break-in was determined. As of noon EDT Oct. 23, the network has been re-opened, and SkyView should be operating normally again.
15 September 1995
There has been a change to the Basic and Advanced interfaces such that the surveys are all displayed at once instead of in a scroll box. We are fairly confident that this will work with all web browsers, but if you have a problem please let us know.
14 September 1995
Images obtained of the southern hemisphere from the Digitized Sky Survey are now distributed at full resolution. The northern hemisphere is still distributed at reduced resolution.
14 September 1995
The 4850Mhz data has been updated and expanded. Coverage of this data now extends from -88 to +75 degrees in declination with gaps at -9 to 0 and -27 to -39 degrees. These gaps can be filled using the 4850Mhz (OLD) survey, but this survey is recommended only for these regions.
10 September 1995
The HEASARC catalog list have been updated to reflect the current list of available catalogs. Please note that the HST Guide Star Catalog is now listed just as the Guide Star Catalog.
31 August 1995
On August 30, SkyView experienced hardware problems that kept it down for the better part of the day. It has been fixed, and things appear to be running normally. Please let us know if you experience any problems.
22 August 1995
A error was discovered in the BSCALE keyword in FITS files created with the Digitized Sky Survey that caused the value to be the inverse of the real value. This error has been fixed. All FITS files now created with the DSS survey have a COMMENT notifying that the BSCALE is now correct.
27 June 1995
An error was discovered in catalog searches using the HEARSARC catalog service. This was due to an unexpected changed on their part but has been fixed. Sorry for any inconvience this may have caused.
22 June 1995
The images of EUVE surveys have been updated. The image resolution has been changed from 0.5 degree to approx. 2 arcminutes. This means that the default image size will now return images 7.5 x 7.5 degrees. If you encounter any problems, please let us know.
19 May 1995
As of 2:00 p.m. EST May 19, without rigorous testing, we believe that all of SkyView's functionality is in place and operating normally. Again, we regret any inconvience this may have caused. If you have any problems please e-mail scollick@skyview.gsfc.nasa.gov.
18 May 1995
SkyView crashed during a thunderstorm on 17 May. When we tried to reboot the system we encountered serious problems with one of the disks. We had been planning on moving SkyView to a new machine at the end of the month and decided to take this opportunity to accelerate the process. The new numerical IP address is 128.183.8.26. The new address is bound to the old name skyview.gsfc.nasa.gov . If you use the numerical address of SkyView, e.g., in an /etc/hosts file, then please update to the new address. The system has come up fairly quickly after the move but we anticipate that there will be some glitches. Currently our access to the SIMBAD name-resolver seems to be down so users must specify explicit locations.
12 May 1995
A bug introduced in the May 5th update has been corrected. This bug caused catalog searches using the HEASARC catalogs to hang the system. Sorry, for any inconvience this may have caused.
11 May 1995
Over the evening, there was a power outage and SkyView was down for several hours. Everything is back and should be operating normally.
5 May 1995
Several minor bugs are now in place. The more important ones include a timing out of catalog searches after an hour. This will prevent the unneccessary filling of the disk that caused the problems a couple of days ago. The CRPIX2 keyword has been fixed when FITS files are created of non-square regions. A wrap-around problem using the Rectangular projection in certain cases has been fixed.
1 May 1995
We had a recurrence of the problem of 3 April where the cron job used to clean up old files crashed. As a result the SkyView disks filled up and users were returned blank images since no new images could be stored. We apologize for the inconvenience. Note that application of Murphy's law in that both times this has occured over the weekend. We are working on ensuring that the system will fail more gracefully in the future.
3 April 1995
Over the weekend, the hard disk that is used to store the images generating by SkyView was filled. As a result, several requests could have returned blank images instead of the proper image. This has been fixed and we regret any inconvenience this may have caused.
23 March 1995
A bug was discovered in the retrieval of ROSAT PSPC data in which data would be improperly returned as blank images. This has been fixed. Thanks to Bob Huron at U. Chicago for pointing this out. This bug affects only v2.1.
21 March 1995
SkyView v2.1 is released. Changes include the inclusion of the northern sky (with a few gaps that will be added in the next couple of weeks) in the Digitized Sky Survey, the addition of the Zenith Equal Area map projection, the ability for SkyView to work with different web browsers, e.g., lynx and the prodigy server, and internal changes to make request processing faster.
13 March 1995
The appearance of the Basic Form was modified slightly to more clearly indicate the required fields. All of the Southern Sky Survey should once again be available.
9 March 1995
Due to the transfer of hardware from one building to another, there will be regions of the Southern Sky Survey unavailable for retrieval. We are unsure as to the exact regions missing but it should cover no more than a few degrees. The transfer should be complete by early next week. Sorry, for any inconvenience this may cause.
10 February 1995
As of noon today, the Southern Sky Survey and the IRAS 12 and 100 micron surveys will be accessed via local hard disk which should decrease the time required for a request. If there are any problems let us know.
2 February 1995
The HTTP server has been changed to incorporate a subtle change that will soon allow batch operations. If there are any problems please let us know.
31 January 1995
On the Basic and Advanced Web interfaces, there is now a size limit for the retrieval of images. The limit is different for each survey (i.e. for the Southern Sky Survey the limit is 4.5 square degrees, for ROSAT it is roughly 45 square degrees). This is done to shorten the time to retrieve images. The interactive interface is not bound by this constraint.
6 January 1995
On the 5th, several catalogs and surveys were moved onto a new local hard drive. This move accidentally caused the Southern Sky Survey data to be inaccessible. This has been fixed.
4 January 1995
SkyView has added a 2 GB hard drive which should quicken access times to some of the smaller surveys as well as the local catalogs. In the near future, the length of time files created by SkyView are retained will increase to eight hours.
29 December 1994
The SkyView User's Guide and Survey Documentation have been updated and corrected. If you find any errors please let us know.
13 December 1994
A bug in Feedback was discovered due to a recent upgrade to Perl v5.0. This should have caused a server error anytime the submit button was pressed on the Feedback page. This error has been fixed, and Feedback is working again.
5 December 1994
An automatic purging of files generated on the Web interface was instituted. Files over two hours old are deleted. When a replacement is received for the disk which failed in October, files will be left on-line much longer.
2 December 1994
SkyView was down temporarily for software maintainance.
29 November 1994
FITS files created from the Radio surveys did not include some comment information that explained the survey's properties as well as certain other keywords. This has been fixed.
23 November 1994
A bug was discovered in the FITS writing routine. When saving data sets in Galatic Coordinates, the GLON and GLAT values were interchanged. It has been fixed.
16 November 1994
The HEAO A1 survey data was replaced with a new more refined dataset produced at the HEASARC. This dataset interpolates over data gaps to provide a cleaner image than the older dataset. Many other all-sky images are available through the HEASARC, including data with the gaps showing, and data from other epochs of the HEAO 1 mission.
7 November 1994
On Nov. 8, the ROSAT survey was replaced with a higher resolution dataset containing data at 15 arcseconds resolution. This new data also includes all observations made public before September 1994.
A bug was found in the execution of the SIMBAD name resolver. Any request to the name resolver that included a space was done incorrectly. The bug has been fixed.
20 October 1994
A bug was discovered in our implemenation of the SIMBAD name resolver. All name resolver requests that had to be precessed from an equinox of 2000.0 were incorrectly done. The bug has been fixed. This affects only images retrieved since the crash on 3 October.
19 October 1994
SkyView should be fully operational once again for the first time since the disk failure on October 3. All interfaces are working, all surveys and catalogs are available, and full help is restored. Please let us know if you note anything amiss. Local disk space is still very restricted so user data will be deleted within a few hours of creation. Please copy your files back to your home institution quickly. We apologize for any inconvenience our down time has caused.
19 October 1994
Marc Postman of the Space Telescope Science Institute has noted that when SSS data are retrieved in SkyView , images of individual objects may be distorted if the chosen resolution is comparable the intrinsic pixel resolution. For example, the typical SSS image has a slight rotation with regard to the nominal coordinate system (~0.5 degrees) and so when SkyView samples a row it will periodically jump from one row in the original image to the one above or below it. Users who need to worry about such glitches may want to retrieve data at significantly higher resolution than the 1.7" intrinsic resolution. The output will then clearly show the original pixel structure. This problem is not restricted to the SSS data, it can happen wherever the data is not sufficiently well sampled. The EUVE datasets for example are also poorly sampled.
17 October 1994
Goddard-wide power hits brought down SkyView for several hours on the afternoon of October 17. Some problems with remounting the jukebox have necessitated occasional interruptions in service to particular catalogs.
7 October 1994.
The disk used to store all SkyView code, HTML documents, user data files, and many of the smaller surveys had an irrecoverable failure on Monday, October 3. The SkyView code and surveys were backed up and the system was up for limited service by the evening of Wednesday. However, some HTML forms and documents were lost and have had to be regenerated. Additionally, the space available for users to generate images was much reduced and all surveys are now retrieved from an optical disk jukebox. While we anticipate having full service available by the middle of next week, response may be slightly degraded due to more frequent use of the jukebox and the use of an NFS mounted disk to provide space for users.

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SkyView has been developed with generous support from the NASA AISR and ADP programs (P.I. Thomas A. McGlynn) under the auspices of the High Energy Astrophysics Science Archive Research Center (HEASARC) at the NASA/GSFC Astrophysics Science Division.

We gratefully acknowledge the support of NASA and contributors of SkyView surveys.