Position of Ring Nebula in Celestia?

[fsgregs]

Hi. I got this e-mail yesterday from Mauro D'Antonio, a user of the educational activities, which include a copy of the ring nebula add-on.

Some days ago I was looking with my telescope at the Ring Nebula (M57). Then I thought that I saw it also in Celestia and so I ran Celestia with Ring Nebula add-on. Immediately I realized that in Celestia its position is wrong! The real position for the Ring Nebula is roughly halfway between Sheliak and Sulafat (Beta and Gamma Lyra respectively), RA: 18h53m46.37s DE:+33°02'21.6".

I do not know where the fault is but maybe you better than me can correct or ask to the original author to do it.

Is this correct? Should we edit the coordinates for the ring?

Frank

[granthutchison]

Which Ring Nebula add-on?
Where is your correspondent seeing the Ring Nebula in Celestia?

Grant

[selden]

Frank,

Which activity is involved?
Which Ring Nebula addon does it use?
What are the contents of its DSC catalog file?

Without actually seeing the DSC file, my guess is that whoever created the Ring Nebula's DSC catalog file might have used the wrong units when placing it on the sky. RA in DSC catalogs must be in units of fractional hours, while RA in STC catalogs must be in units of fractional degrees.

Here are the coordinates that I used for M57 in my Messier-All Addon. The RA and Dec values in the one you use should be close to what is shown below. The exact numbers will depend on the size and orientation of the model that's included.

Code: Select all

# Ring Nebula = NGC 6720
Nebula "M57"
{
   Mesh "m57.3ds"
Axis       [-0.0761426 -0.954784 -0.287383] Angle 169.996

   RA   18.89275
   Dec  33.028
   Distance   2300

   Radius 1.18
   InfoURL "http://simbad.u-strasbg.fr/sim-id.pl?Ident=M+57"
}

[DaveMc]

The M57addon I'm using had the Declination in the DSC file as 3.33333 while it should be, as Selden points out, something like 33.0333. I don't know whose addon it is. There is an associated STC file for Aria and Meteraum should be modified as well.

Dave

[TERRIER]

I'm currently running a NGC 6720 add-on contributed by astroboy, and the dsc settings are;

Code: Select all

Nebula "Ring Nebula NGC6720"
{
   Mesh "ngc6720.3ds"
   Radius    0.93
   RA    18.8933333
   Dec    33.0333333
   Distance 2300
}

which seems OK, yes ?

[DaveMc]

That should be OK. I'm not sure but I believe the addon I'm using is from Rassilon, here's the corrected DSC settings:

Code: Select all

# M57 - Ring Nebula
Nebula "M57"
{
   Mesh "m57.3ds"
   Radius 5
   RA 18.8933
   Dec 33.033    # ORIGINALLY WAS 3.33333
   Distance 2300            
}

Dave