Cartes du Ciel / Sky Charts
RealSky® is a set of CDs distributed by the ASP (Astronomical Society of the Pacific), based on The Digitized Sky Survey (DSS).
The Digitized Sky Survey is a collection of scanned photographic images
from the Palomar Schmidt plates and the UK Schmidt plates. These digital
images were used by the Space Telescope Science Institute to create the
Hubble Guide Star Catalog (GSC).
RealSky is a more compressed version of the same data. CDs numbered 1-8 contain images from the Palomar Sky Survey (the entire northern hemisphere, down to about 12 degrees south declination). CDs numbered 9-18 contain images from the UK Schmidt Telescope (UKST) (The entire southern hemisphere up to about 3 degrees north declination.)
"Cartes du Ciel", Sky Charts use a library developed by Bill Gray of
Pluto and the Windows DLL is based on a version by Chris Marriott of
Change were made to the original DLL code and it was renamed GETDSS.DLL
to avoid confusion with the Skymap version.