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Sunday, February 22, 2009


Adding Lulin to Stellarium and Celestia

Almost everyone knows that you can add new objects, such as comets and asteroids, to Celestia. It is less widely known that you can add new comets and asteroids to Stellarium. See this Ice in Space thread and this one at Astronomy Log for more details.

For Stellarium, you have to add the comet details to the ssystem.ini file in the data folder (always make a backup of this file okay). When you run Stellarium, you will have to turn planet hints on in the configuration menu. Otherwise you won't be able to see Lulin (comets don't render correctly in the current version of Stellarium, but that is supposed to be fixed in the next version (which is just about to be released)).

Here the Lulin data I used, taken from Astronomy Log.
name = Lulin
parent = Sun
radius = 1000
oblateness = 0.0
halo = true
color = 1.0,1.0,1.0
tex_halo = star16×16.png
tex_map = nomap.png
coord_func = comet_orbit
orbit_TimeAtPericenter = 2454842.1414
orbit_PericenterDistance = 1.212289
orbit_Eccentricity = 0.999987
orbit_ArgOfPericenter = 136.8614
orbit_AscendingNode = 338.5353
orbit_Inclination = 178.3730
lighting = false
albedo = 1
sidereal_period =

If you want to make your own files for comets in the future, you can use the data sources I linked to in my post Making SSC Files for Celestia. Here is the data for a Lulin SSC file for Celestia. Note that it is slightly different from the Stellarium file in some items as I've used slighly different data sources.

======= 8< cut here 8< ==========================
# C/2007 N3 Lulin
"N3-Lulin" "Sol"
Class "comet"
Mesh "roughsphere.cms"
Texture "asteroid.jpg"

EllipticalOrbit # elements for epoch 2009
Epoch 2454842.115631206611 #January 14.35 2009
# Epoch is actually the Julian date of perihelion
Period 28250000 #wild guess, but it works
PericenterDistance 1.212289
Eccentricity 0.999987
Inclination 178.373
AscendingNode 338.5353
ArgOfPericenter 136.8614
MeanAnomaly 0.0

InfoURL "http://cometography.com/lcomets/2007n3.html"
Radius 10.45 # Hn=12.50 Hn=14.10-2.5*log(Albedo)-5*log(Radius) Albedo=0.04
Orientation [ 90 0 0 1 ] # random value
RotationPeriod 15.613880 # random value
Obliquity 77.387310 # random value
EquatorAscendingNode 239.190649 # random value
Albedo 0.04

=========== 8 < cut here 8< =============================

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Thanks for posting this--came in handy.
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