Both the USNO-A2.0 and -B1.0 catalogs are scanned versions of the Palomar Sky Surveys. The first was done in the 1950's, the second in the mid-70's. Because they are based on scans of glass plates, the position accuracy is at best ~0.25 arcsec for the epoch they were taken.
The surveys were done in both red and blue light. For the A catalog, an object was considered "real" if it appeared in both colors. The epoch time is late 1950's though, and since it's a single epoch many extreme red or blue stars are overlooked. For the B catalogs, detections of very red or blue objects were included if they showed up in both epochs. That's why the B catalog has almost twice the number of stars than the A. There's also some basic photometry and proper motions associated with the B catalog, which is why the dataset is so much bigger than the A. There is documentation on the file formats, etc. that should have come down the pipe with the rest of the data when you downloaded the catalog. I highly recommend that you digest this stuff first before pinging Dave for answers. He does answer his email...when he gets around to it...and his somewhat acerbic tone should not be taken as any kind of personal swipe. He's just "that way". Cheers, Geoff --- In [email protected], Sander Pool <[EMAIL PROTECTED]> wrote: > > > Geoff, > > I was able to download the files and build the catalogs for CdC. I'm now > trying to convert the tycho-2 catalog that comes with winoccult for use > with CdC. I sent Dave an email with some questions about the format. > Hopefully I'll have a conversion program ready soon. > > Sander > > starryeyeguy wrote: > > > > Sander: > > > > Unfortunately we've been out of the UCAC2 CD's for a couple of years > > now. You might try the ADC or ViZier servers, which have the catalog > > online. > > > > FWIW USNO has compiled a sort of "Frankenstein" catalog, the NOMAD, > > available from ADC, ViZier, and our Flagstaff Station > > (www.nofs.navy.mil). NOMAD consists of a "merge" of the current best > > available catalogs for various magnitude ranges, giving complete > > astrometric sky coverage to 20th magnitude with some limited > > photometry and proper motions as well. > > > > The older 2.76 version of CdC could interface with ViZier to read the > > USNO-B1.0 catalog, and hopefully as Patrick continues development of > > CdC 3 he'll include the capability to do so for the NOMAD dataset. > > > > Right now the only way to get a "hard copy" of NOMAD is to send a > > ~200Gb external HDD to the folks at Flagstaff, so the servers are > > probably the best way to go right now. > > > > Cheers, > > > > Geoff > > > > --- In [email protected] > > <mailto:skychart-discussion%40yahoogroups.com>, Sander Pool <sander@> > > wrote: > > > > > > > > > Yes, I saw that catalog but it doesn't appear to be available for > > > download anywhere. Some sites hold information files and code but no > > > data. If you know of a location please let me know. > > > > > > I requested a CD set. > > > > > > Sander > > > > > > starryeyeguy wrote: > > > > > > > > UCAC-2 covers the south pole to about +30 dec from 8th to 16th > > > > magnitude. There is a supplement for the brighter stars derived from > > > > Tycho-2. The complete catalog should be available next year. > > > > > > > > Cheers, > > > > > > > > Geoff Chester > > > > > > > > --- In [email protected] > > <mailto:skychart-discussion%40yahoogroups.com> > > > > <mailto:skychart-discussion%40yahoogroups.com>, Sander Pool <sander@> > > > > wrote: > > > > > > > > > > > > > > > I'm seeing more stars in my C11 than the Tycho-2 catalog contains. > > > > There > > > > > is the GSC-ACT catalog but its homepage on projectpluto says it's > > > > > obsolete. USNO is nice but huge and I don't need mag-20 (I wish :). > > > > > UCAC-2 sounds promising and contains the range of stars I care > > > > about. If > > > > > I'm reading http://ad.usno.navy.mil/ucac/ > > <http://ad.usno.navy.mil/ucac/> > > > > <http://ad.usno.navy.mil/ucac/ <http://ad.usno.navy.mil/ucac/>> > > correctly it's mostly geared > > > > > towards the Southern hemisphere though, right? > > > > > > > > > > So, which catalog do you recommend for dim stars in CdC? > > > > > > > > > > Thanks, > > > > > > > > > > Sander > > > > > > > > > > > > > > > > > > > > > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/skychart-discussion/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/skychart-discussion/join (Yahoo! ID required) <*> To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] <*> 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/
