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Saturday, April 11, 2009

 

C/2009 G1 in Stellarium (and Celestia, sort of)

UPDATE: Thanks to Dimitry, (see comments) I've fixed up the elements for Celestia. Looks like I will have to update my "how to make" instructions for Celestia (here) and Stellarium (here).

I've put together the orbital elements for C/2009 G1 as files for Stellarium and Celestia. For Stellarium, add the section to the end of your ssytem.ini file (always back up). For Celestia, add the file to the extras folder. The only problem is that Celestia puts the comet nowhere near where it should go. I have no idea why and will try and fix this (fixed via Dimitri). If you want elements to add to a planetarium program like SkyMap, see this link to the MPC elements for planetarium programs.

Stellarium elements:
[Ruan]
name = C/2009G1
parent = Sun
radius = 100
oblateness = 0.0
halo = true
color = 1.0,1.0,1.0
tex_halo = star16x16.png
tex_map = nomap.png
coord_func = comet_orbit
orbit_TimeAtPericenter = 2454936.73194
orbit_PericenterDistance = 1.12993
orbit_Eccentricity = 1.0000
orbit_ArgOfPericenter = 173.823
orbit_AscendingNode = 120.657
orbit_Inclination = 108.091
lighting = false
albedo = 1
sidereal_period = 365.25

Celestia
===========2009G1.ssc=======================
# C/2009 G1 Ruan
"C/2009 G1 Ruan" "Sol"
{
Class "comet"
Mesh "roughsphere.cms"
Texture "asteroid.jpg"

EllipticalOrbit # elements for epoch 2008 11 30
{
Epoch 2454936.5 # 2009-April-15.0930000
Period 1000000 37981954.4996 #P=(q/(1-e))^1.5
PericenterDistance 1.12993
Eccentricity 1.0000 0.99999 #no idea why this works, it just does
Inclination 108.091
AscendingNode 120.657
ArgOfPericenter 173.823
#MeanAnomaly 0.0
}

InfoURL "http://astroblogger.blogspot.com/2009/04/comet-c2009-g1-congratulations-jiangao.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
}
===================================================
The celestia file now works thanks to Dimitry (see comments)

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Comments:
Ian,

For Celestia, try to use value 0.99999 for eccentricity and calculate a period from this formula: P=(q/(1-e))^1.5

I use such method to introduce any long-period into Celestia, and it works.
 
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