Celestia Forums

Hmm this is an odd problem. I added Wolf 359 to my data, and it appears properly (though with abnormaly small radius), but when I put in its variable designation CN Leonis, it will show up on the stars name, but will not allow me to search for it. I can find it via its "fake" HIP number and the name Wolf 359, but CN Leonis wont work, neither will UV Ceti. Are these protected names or what?

Cheers.

Apollo7 wrote:... but when I put in its variable designation CN Leonis, it will show up on the stars name, but will not allow me to search for it. I can find it via its "fake" HIP number and the name Wolf 359, but CN Leonis wont work, neither will UV Ceti. Are these protected names or what?

Odd indeed. My own Wolf 359 has the alternative name "CN Leo", and that's searchable. Here's the text I added to starnames.dat:

But if I just add in those three letters "nis", the name seems to drop out of searchability, despite, as you say, appearing in the name list for the object. Meanwhile, "Gliese 406" remains searchable.

Grant

If I am not mistaken, CN Leonis and UV Ceti are variable star designations. They are not Bayer or Flamsteed designations. Perhaps when Celestia sees the constellation name it assumes the latter, so the search fails.

- Hank

After looking at the code for a few minutes I see what the problem is . . . The star name lookup code checks for a constellation name (either the abbreviation or the genitive form), and if it finds one, it canonicalizes the name before searching. So, CN Leonis gets converted to CN Leo, which doesn't match anything in the star names database. Any star name that includes a constellation name (Bayer, Flamsteed, etc. designations) should use the standard three letter abbreviation for the constellation. If you do this, the canonicalization step assures that a user will be able to lookup the star using any form of the constellation name (e.g. CN Leo or CN Leonis). At first I thought this was a bug, but I actually think it's a very reasonable restriction on how star names should appear in the names file.

Right now, I'm working on letting star names appear in .stc files. I'm also trying to come up with ways to make it easy to add catalog cross-references. For example, it'd be nice to include a file mapping numbers from one catalog to some sort of standardized star number (currently, the HIP or Tycho number):



as an alternative to adding Gliese names for every star in a catalog. The HD catalog could be implemented this way instead of storing an HD number for every single star (extremely wasteful in the 2 million+ star Tycho catalog, where the vast majority of stars don't even have an HD number.)

--Chris

Keep in mind that not all star catalogs use a simple prefix/sequence number format. For example:

NASA's NStars database (http://nstars.arc.nasa.gov/index.cfm) of nearby stars (currently including 2633 objects in 2029 systems within 25 parsecs) uses a format which encodes the RA and Dec. of the object, e.g.:

NS 1103+3558
NS 2305-3551

(Companion stars use the RA and Dec. of the brightest component, plus a letter suffix: A,B,C.)

The Bonner Durchmusterung, Cordoba Durchmusterung, and Cape Photographic Durchmusterung (BD, CD or CPD respectively) use a signed zone number (Dec.) plus sequence number (and possibly a letter suffix), e.g.:

CD-36 15693
BD+04 3561a

In the last example the letter suffix indicates a supplement entry, not a companion star.

Here are a couple of technical references:

IAU specs for nomenclature http://vizier.u-strasbg.fr/Dic/iau-spec.htx
Descriptions of formats http://vizier.u-strasbg.fr/Dic/formats.htx


- Hank