Thanks John for forwarding that link. This is the crucial paragraph:
"
*New UCAC-3 designation scheme: *UCAC-3 had two designation schemes, but
a third has been settled upon: '3UC', followed by a zone number from 1
(stars between declinations -90 to -89.5) to 360 (stars between decs
+89.5 to +90), followed by a six-digit number giving the order of that
star within that declination zone. For example, '3UC314-159265' would be
the 159265th star in zone 314 (the zone covering declinations +66.5 to +67).
'3UC' was used because '3U' had been taken by another astronomical
catalogue.
"
It doesn't really say who settled this. It would be nice to see a
confirmation from the USNO especially because it's not consistent with
UCAC2.
Sander
John Mahony wrote:
>
>
> 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
> <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] <mailto:pch%40ap-i.net>>
> >
> > 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
> <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
> <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
> >
> >
> >
>
>
