Hello folks,

For some time now (since version 0.8 days) I've found that Stellarium displays
many "unnamed" stars, i.e., stars which it can plot and show both position
(eg, RA/DE, Az/Alt) and magnitude/color ( Mag and B-V) data, but can't
identify (i.e., won't show a catalog number).

From what I could learn from the user guide, that seems to happen because
Stellarium uses Hipparcos catalog numbers, and these stars aren't in
Hipparcos. Is that correct? If so, what would be the difficulty of adding a
more comprehensive catalog ID (e.g, TYCHO-2) for Stellarium stars?

Below is an Stellarium 0.10.4 screenshot to illustrate my point: the star
marked with a red arrow is TYC 9005-3928-1 (according to the excellent sky-
map.org site at http://my.sky-
map.org/starview?object_type=1&object_id=2387805) and has no Hipparcos ID;
apart from the position relative to Hadar the data Stellarium shows for that
star (on the upper left corner of the screenshot) agrees with Sky-map.org data
with very little variation (why the variation?), so it's probably the same
star.

Cheers,

Durval.

Hi

For information on the star catalogues look at the readme.rtf file that comes
with Stellarium.
The Hipparcos stars that are used by stellarium have designations. The stars
from the Tyco 2 and NOMAD catalogues do not have any designation in the files
we are able to use. It is a pity but it is a limitation at the moment

Barry

.

Hello,

First of all, thanks for the prompt response.

For information on the star catalogues look at the readme.rtf file that
comes with Stellarium.

I searched but could not find a readme.rtf, neither in my Ubuntu-installed
package (/usr/share/doc/stellarium) nor inside the source tarball. I managed
to locate a README text contained mostly superficial information regarding
catalogs, but pointed me to http://cdsweb.u-strasbg.fr/ftp/cats/I/259 for TYCHO-2 catalog data.

The Hipparcos stars that are
used by stellarium have designations. The stars from the Tyco 2 and NOMAD
catalogues do not have any designation in
the files we are able to use. It is a pity but it is a limitation at the
moment

On the TYCHO-2 ReadMe file found above, it's listed (among other things) the
catalog's structure, and reading it I found the following (copied verbatim):

==============================================================================
=[
Byte-by-byte Description of file: tyc2.dat

Bytes Format Units Label Explanations

1- 4 I4 --- TYC1 += TYC1 from TYC or GSC (1)
6- 10 I5 --- TYC2 TYC2 from TYC or GSC (1)
12 I1 --- TYC3 TYC3 from TYC (1)
==============================================================================
=]

So, begging for your pardon in advance if I'm being dense, aren't these three
fields the exact 3 numeric components of the TYCHO-2 designation (i.e., TYC
XXXX-XXXX-X)?

If yes, I see that there's RA/DEC positioning data on the same record:

==============================================================================
=[
16- 27 F12.8 deg RAmdeg ? Mean Right Asc, ICRS, epoch=J2000 (3)
29- 40 F12.8 deg DEmdeg ? Mean Decl, ICRS, at epoch=J2000 (3)
==============================================================================
=]

If all the above checks, I had the following idea: how about a plugin that,
when invoked on an "unindentified" star, would take its RA/DEC and then search
the above TYCHO-2 records for the nearest (position-speaking) star, and then
print its TYCHO-2 designation? Wouldn't that be a easy/"cheap" way to find any
star TYCHO-2 designation? know that it's not so simple (I imagine for example
that there would have to be some pretty sofisticated indexing for that to be
feasible given the large number of records and the inexact nature of the
search, and also I have no idea of how Stellarium plugins are supposed to
work), but shouldn't it work in principle?

Cheers,

Durval Menezes.

Yes. It would be nice to use all that data in the star files. However the
files we use for the larger star catalogues have been reduced to the bare
essentials to keep them at a reasonable size. The main aim of the stellarium
display is to use as many stars as possible to make the sky look real for a
real time planetarium display.

Please feel free to write a suitable plugin to display the stars with
designations. I am sure we could use it.

Barry

Hello,

I am also constantly bumping into these non-named stars, like TYC 5288-491-1
(HD 16269). Writing a plugin sounds also interesting.

I understand that the internal catalogue format:
[http://www.stellarium.org/wiki/index.php/Star_Catalogue_Format
does not contain anything but the HIP designations.

Does stars have a sort of "internal name" (zone-index, or file-zone-index)?

Do you have a mapping from that internal name to TYC codes?

(And thank you for this wonderful piece of software!)](http://www.stellarium.o
rg/wiki/index.php/Star_Catalogue_Format%0D%3Cbr/%3Edoes%20not%20contain%20anyt
hing%20but%20the%20HIP%20designations.%0D%3Cbr/%3E%0D%3Cbr/%3EDoes%20stars%20h
ave%20a%20sort%20of%20%22internal%20name%22%20%28zone-index%2C%20or%20file-
zone-index%29?%0D%3Cbr/%3E%0D%3Cbr/%3EDo%20you%20have%20a%20mapping%20from%20t
hat%20internal%20name%20to%20TYC%20codes?%0D%3Cbr/%3E%0D%3Cbr/%3E%28And%20than
k%20you%20for%20this%20wonderful%20piece%20of%20software%21%29)

(and how do I edit my post!)