We have updated SkyView to use the DR8 release of the Sloan Digital Sky Survey (SDSS). The DR8 includes substantially greater sky coverage and is a major reprocessing of all data in the SDSS. There are a fair number of changes both in the content and internal formats. The changes are summarized by the SDSS team in their differences page. A key change is that the new data are sky subtracted so that individual pixel values are very different between the DR7 and DR8. While the loglog scaling was often helpful is showing features in the DR7, the default log scaling generally does fine with the DR8.
Internally the data provided to SkyView has changed substantially. Data are now compressed using the BZIP2 compression technique and getting efficient support for decompressing these data was one of the reasons it took us so long to update.
Since the DR7 and DR8 differ significantly SkyView will support both for a transition period. The SDSSx survey names will point to the DR8 while the SDSSDR7x surveys will point to the DR7. The servers for the DR8 and entirely different from the DR7. Last week there was some problem with the DR8’s servers’ hardware. If such problems recur you can use the DR7 surveys as a backup. The DR7 surveys are listed at the bottom of the menu in which the DR8 surveys are found.
Since the SDSS data are retrieved from a remote source, SkyView needs to download the data into its cache before processing. SkyView only downloads files once, but SDSS requests may take a little longer than users are used to since we’d already filled the DR7 cache with many of the popular target areas. We’ll phase out DR7 support if and as usage of the DR7 surveys drops off.