The SA catalog is a very specialized catalog not intended for general charting purposes. It was designed for amateur asteroid hunters back when the typical hard drive was only a couple GB. The full USNO-A catalog is about 6 GB. The "SA" catalog is a subset with about 1/10 of the stars, but with the stars chosen specifically to give a reasonably uniform distribution by area. It is used for "solving" astrometric plates, where the stars in an image (which hopefully contains an asteroid) are "matched" to reference stars, so that the RA/dec of any object in the image can be determined to very high precision. Asteroid hunters needed a set of reference stars dense enough so that there would be enough reference stars in any given image to give a reliable and accurate "match" for accurate measurements. But they didn't have room on their computers for a 6GB catalog. If you can get the catalog to display properly, it will look very unnatural, with the stars forming a very rough "grid". That's because the stars were chosen specifically for uniform spatial distribution. The sky was divided into squares about 2.5' on a side, and one star was chosen out of each square. But these stars represent only a small fraction of the total stars down to that magnitude.
So do you really want to use this catalog? -John --- Mike <[EMAIL PROTECTED]> wrote: > > Happy turkey day world. > > Have downloaded the USNO 600meg file on CD-ROM. Which file should > this be loaded and linked inside Cartes? > __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ------------------------ Yahoo! Groups Sponsor --------------------~--> $9.95 domain names from Yahoo!. Register anything. http://us.click.yahoo.com/J8kdrA/y20IAA/yQLSAA/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/
