SkyView is now using the DR7 release of the Sloan Digital Sky Survey (SDSS) surveys. It doesn’t appear that there is a big difference for SkyView between the DR6 and DR7 releases but there is a bit more coverage in a few areas.
Posts Tagged ‘SDSS’
SDSS DR7 now available
Monday, October 5th, 2009SkyView SDSS and 2MASS data availability
Friday, November 21st, 2008The SDSS server connection problems that were reported earlier this week have been resolved. However again due to connection problems with the remote system that provides the data, 2MASS survey data are unavailable via SkyView. We have been in touch with personnel at IPAC and hope to have the connection issues resolved soon. We apologize for the inconvenience.
SkyView SDSS data are unavailable
Tuesday, November 18th, 2008Sloan Digitized Sky Survey images are not available at this time due to problems connecting to the remote server that hosts the SDSS data. We are investigating the problem and apologize for any inconvenience.
SkyView LogLog scaling
Friday, October 24th, 2008
SDSS Image of 3c273 with standard log scaling.
SDSS Image of 3C273 with new LogLog scaling.
If you compare an SDSS image versus one for another optical survey like the DSS, there usually appears to be a lot less there. However this is mostly an artifact of the scaling of images. The SDSS images are derived from CCDs rather than photographic plates. You can get something much closer to the plate images if you do a log(log(b)) scaling of the image. Our test version of SkyView now has a loglog scaling option.
We first multiply the each pixel so that that smallest positive value has the value 1.01. Then we take the log of each pixel in that image, Finally we take the log of that result. The ImageJ log function that we use returns a value of 0 for inputs of 0 or less, so those values all end up at 0.
If you want to really bring out detail in the image you’ll soon be able to try scaling=loglog. The two images that start the post show the difference between Log and LogLog scaling. In the loglog image, the jet is plainly visible while it’s completly missing in the first image.