SkyView Blog

GALEX UV survey GR4 images may not be available at this time due to hardware failure at the remote MAST site.  The most recent notice on the MAST website indicates data will not be available until the week of 8/25/08 at the earliest.

SkyView saves images from remote survey queries so GALEX image generation at many positions may still be possible.

SkyView operations were interrupted Monday afternoon August 18, 2008 due to a local network problem. The website was unavailable from approximately 4:00-8:00pm EST. We apologize for the inconvenience.

We have completed changes to SkyView to accommodate FIRST data changes at the MAST archive. FIRST data file names have changed and files for additional coverage have been added. Both the SkyView web site and SkyView-in-a-Jar file have been updated.

The latest version of SkyView has a new capability for drawing overlays on SkyView images. One major use of this will be to allow us to provide templates of the fields of view of various telescopes. E.g., in the image below we’ve overlaid information on the fields of view of two of the instruments of the Swift observatory on a simple DSS image of the region around 3c273. The X-ray Telescope (XRT) field of view has calibration sources (C1-4) marked in the corners, while the UltraViolet-Optical Telescope (UVOT) has a large rotation (and small offset) with respect to the satellite’s nominal pointing.

The overlays use simple ‘Draw’ files that describe the fields of view. E.g., the draw file for the XRT part of the overlay above is just:

reset
scale 2.36"

thick 2
color cyan

-300 -301
300 -301
300 301
-300 301
-300 -301

text 0 270 0 XRT FOV
text 0 -290 0 XRT FOV
text 290 0 90 XRT FOV
text -270 0 90 XRT FOV

thick 1
color pink
circle -265 269 47
circle 273 260 48
circle -264 -274 47
circle 276 -281 44

text -265 269 0 C0
text 273 260 0 C1
text -264 -274 0 C2
text 276 -281 0 C3

SkyView gets the underlying data for the FIRST data from the MAST archive. They have recently changed how they provide the data a little. The data used to be gzip-compressed but is now uncompressed. There’s a little bit of extra data too — coverage is extended over an additional 22 square degrees. The change shouldn’t affect many users of the Web page. Most of the FIRST data is already cached here at SkyView. It can cause problems for SkyView-in-a-Jar users since the current jar is trying to access the URLs using the old names.

We’ll be putting out an updated jar in the next couple of days. 99% of what we need to do is to just get rid of the .gz suffixes in the FIRST survey description which is very easy, but we also need to index the new files which will take a little longer.

The bug that caused the incorrect values of FITS CRVAL keywords for fixed projections (described in the previous post) has been fixed.

SkyView is currently putting incorrect values in the FITS CRVAL keywords of the fixed projections. The CRVAL keywords should be the center of the projection which in fixed projections is not necessarily the center of the image. For CAR, SFL and AIT projections the fixed center is 0,0 while it is 0,90 for the TOAST projection. SkyView is currently giving the center of the image — so that all-sky images, for which these projections are often used, are fine.

The image data themselves are unaffected.

We’ll be installing a patch shortly.

The current SkyView JAR files were compiled using Java 1.5. We’re likely to move to 1.6 in the next release unless we hear an outcry from our users. It should be a little faster but if you just download the JAR file and use it on your machine you will need to have 1.6 installed. We’ll add a link to a 1.5 version, but we’ll likely stop updating that in a release or two.

There was an error in the VO Simple Image Access (SIA) server for the SkyMorph/NEAT database.  It had an error in its error handling. When an SIA call results in an error the service is supposed to return a specified XML format which describes the error. In this case the server call failed before finishing the table. This should now be fixed. While this service is located on the SkyView server (at http://skyview.gsfc.nasa.gov/vo/sia_skm.pl) there was no error in actual SkyView code.