There's been much discussion on MPML about UCAC3, and I recall specifically a discussion about some confusion about ID numbers. Unfortunately since the yahoogroups message search feature has been broken for over 6 months now, I can't seem to find it, but I'll keep looking. I did find one paragraph that might be useful, however:
--------------------------------------------------------------------------- "A final bit of information that is appropriate to share, as it is not something most will have expected. The raw UCAC data at USNO is sorted entirely by declination. RA is not used in any way in the sort, so that sequentially numbered stars can have RA's differing by up to +/-12hrs in RA. The MPOS number (field 37 of the UCAC3 record) is the sequential number allocated to the stars in the raw data on the basis of this sort (and there are about 140 million stars in this dataset, compared to the 100 million in UCAC3). The data is placed into the declination bands and sorted by RA _solely_ for the purpose of creating the public catalogue." --------------------------------------------- But I don't think that was part of the specific discussion about ID numbers. Also, Bill Grey (Project Pluto/ Guide8) has some source code available for accessing the catalog: <http://www.projectpluto.com/ucac3.htm> I'm not a programmer so I didn't look very close there at first, but now I see he also has some info on the designation confusion (see the last few paragraphs). -John ----- Original Message ---- > From: Patrick Chevalley <[email protected]> > > From what I understand I already found tree different way to identify an > UCAC3 > star :-( > We need to clarify this point before to build a search index. > > From the UCAC3 readme 3i) : http://ad.usno.navy.mil/ucac/readme_u3.html > 1- the last 4 bytes of the zone files contain the MPOS number. This number > spans > the range of 3 to 140051297 > 2- ID = n0 + running star number in zone z "3UCAC100200300". n0 is the > largest > star ID number of the previous zone. The star ID number runs from 000000001 > to > 100766420. > > From Vizier Note (1): http://cdsarc.u-strasbg.fr/viz-bin/Cat?I/315#sRM3.1 > 3- 3UC"zzz-nnnnnnn", where zzz is the zone number and nnnnnn a 6-digit > running > number in the zone. "3UC180-000007" > > Can someone with better english can clarify the UCAC3 readme 3i). it is quite > confuse for me. > > Also, do anyone know which identifier will be used the most frequently by > people > using UCAC2 now? by IOTA? for SN chart? > > Patrick > > > > ------------------------------------ > > Yahoo! Groups Links > > >
