You don't want USNO-SA. It a catalog extracted from USNO-A, intended for use as an astrometric reference catalog by amatuer asteroid hunters back when hard drives were much smaller than they are now.
Here's a description from the USNO: "USNO-SA2.0 is a subset of USNO-A2.0 which is a lot easier to handle on a small computer because it contains only a tenth as many stars as the parent catalog (54,787,624 stars in all). The goal in creating this smaller catalog was to provide a spatially uniform distribution of stars in an intermediate range of magnitudes which would be useful as a ``reference grid'' for astrometric analysis." The details of how the stars were chosen is at <ftp://ftp.nofs.navy.mil/usnosa/readmesa.v10>, but to sum it up, one star was chosen for each 2.5' square area on the sky, so this is not a realistic view of the sky down to a certain magnitude, but rather gives an unnatural, somewhat irregular square grid distribution of stars. All the stars are real, but they are only a small subset of all (USNO-A) stars down to that magnitude. -John --- jamesdixon80 <[EMAIL PROTECTED]> wrote: > > Why the GSC-ACT? > > Is there an advantage of it over the USNO SA2.0? The SA2.0 is larger > but not greatly so, you need a CD or broadband access for both. > > Jim Dixon > > --- In [email protected], "Len Philpot" <[EMAIL PROTECTED]> > wrote: > > I realize this subject has been covered (in a manner of speaking) > > over the past few months, but it was rather sporadic. I'm wondering > > > if there's a reasonably concise "howto" someone that tells where to > > > get the GSC and how to get it working with CdC in four easy steps > or > > less... ? :-) > > > > Thanks. > > > > -- > > Len Philpot ><> > > [EMAIL PROTECTED] http://philpot.org/ > > > > > > ------------------------ Yahoo! Groups Sponsor > --------------------~--> > What would our lives be like without music, dance, and theater? > Donate or volunteer in the arts today at Network for Good! > http://us.click.yahoo.com/TzSHvD/SOnJAA/79vVAA/1.XolB/TM > --------------------------------------------------------------------~-> > > > To Post a message, send it to: [email protected] > > To Unsubscribe, send a blank message to: > [EMAIL PROTECTED] > Yahoo! Groups Links > > > > > > > > __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ------------------------ Yahoo! Groups Sponsor --------------------~--> In low income neighborhoods, 84% do not own computers. At Network for Good, help bridge the Digital Divide! http://us.click.yahoo.com/EA3HyD/3MnJAA/79vVAA/1.XolB/TM --------------------------------------------------------------------~-> To Post a message, send it to: [email protected] To Unsubscribe, send a blank message to: [EMAIL PROTECTED] Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/skychart-discussion/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
