[vsnet-chat 732] Re: USNO-A

[Taichi Kato <tkato>]

Arne Henden wrote:

> I've noticed several stars designated on this net in the format:
>       USNO 1425.0988332
> Which I presume is the 1425 declination zone and a running index into
> that zone.  Now this subject has probably been discussed before, and if
> so I apologize for bringing it up again, but as far as I know, there is
> no guarantee that USNO-A 2.0 or USNO-B will have the same number of
> detected objects/zone or will keep the same ordering.  While giving the
> star a USNO designation is free advertisement for what is probably the
> best stellar catalog currently available, I'm a little concerned that
> you are not using a more generic designation.
>   I'd suggest something like an IAU naming convention.  For example,
>        USNOJ 1438015+293944
> would refer to an object from the USNO-A catalog at J2000 coordinates
> 14:38:01.5 +29:39:44 (that is, to about the nearest arcsec).  This is
> a little more cumbersome but might make more sense.

   Our naming convention using USNO-A stems from the famous dwarf nova,
USNO 1425.09823278, which designation was given in IAUC (enough to convince
us the naming had been approved by the IAU Committee).  After checking
this PMM-ID is consistently used in ESO/ST-ECF and SIMBAD PMM catalogue
servers, I have understood this neming convention is the "standard" in
referring to USNO A star.  While the position-based naming is far more
convenient for us (at least I can reduce my HDD content by 35%), it might
be hard to reconcile with that the same star from the same catalog is called
as USNO 1425.09823278 in IAUC and as USNO J1927116+541752 in other places.
Will future IAUCs use the latter designation?

   However, I have noticed the same problem you have mentioned arising from
the zone+PMM-ID numbering, and would like to know how future versions of
USNO catalogs will treat this problem.  I suspected we should use
USNOA1.0 1425.09823278 instead..  The latent problem of position-based
designation may be the revised position would give a different name.  This
is already a problem in uniquely specifying the IRAS PSC object (some of
coordinates have been siginificantly improved since PSC 1.0, giving different
source names).

   The same problem, though lesser in degree, already existed in GSC.
I wondered why GSC J.... designations were/are not preferred rather than
the current zone+number designation.  Improvements in positions of objects
near the zonal border may result in that either some stars having a certain
zonal number may not be in the zone specified, or some zones may contain stars
outside their coordinate-grid border.  This kind of "border transgression"
(though I have confirmed none in USNO A1.0) would certainly make search-tool
programming more difficult.

Regards,
Taichi Kato

VSNET Home Page

Return to Daisaku Nogami

---

vsnet-adm@kusastro.kyoto-u.ac.jp