Thursday, March 17, 2011

Comet 2010 X1 Elenin for Celestia and Stellarium

Comet 2010 X1 Elenin visualised in Stellarium on 16 October, 2010 (click to embiggen).

As a follow up to the previous posts on 2010 X1 Elenin, I present to you these data files for Celestia and Stellarium so you can simulate the comet in these programs.

For Celestia, copy the data between the lines into a file called 2010X1.ssc (or Elenin.ssc or whatever you like), and copy that file into the Celestia extras folder. The data for Elenin is fairly old in the Celestia file, obtained here. For some reason the newest data, that works perfectly in Stellarium, results in Elenin just sitting in front of the Beehive cluster.

======cut 8<==================2010X1.ssc========================
"Elenin:2010X1" "Sol"
{
Class "comet" # Just copying the data for Halley
Mesh "halley.cmod"
Texture "asteroid.jpg"
Radius 4 # best guess at maximum semi-axis
MeshCenter [ -0.338 1.303 0.230 ]

# No idea why any of this works.
# These are old orbital elements, but replacing them with
# more recent elements, the ones that work perfectly for Stellarium and
# SkyMap, causes the comet to sit in front of the Beehive cluster
# and not move. I’ve been driven to frustration by this

EllipticalOrbit
{
Epoch 2455578.5 #2011-Jan-17.0
Period 3457004.12
SemiMajorAxis 22862.71468671387
Eccentricity 0.9999788963233883
Inclination 1.840276249645969
AscendingNode 323.2462306600872
ArgOfPericenter 343.7899811826415
MeanAnomaly 359.9999325013102
}

#Again, this data is copied straight from the ssc files for Halleys’ Comet
# chaotic rotation, imperfectly defined:
# this version from "The New Solar System", 4th Edition; Eds.
# JK Beatty, CC Petersen, A Chaikin
PrecessingRotation
{
Period 170 # 7.1 day axial rotation period
Inclination 66
PrecessionPeriod 3457004.12 # 3.7 day precession period
}

Albedo 0.8
}
==========8<=====cut================================================

For Stellarium 0.10.5 and older, make a backup copy of your Stellarium.ini file, then add the following lines to the end of the INI file. The radius is wrong, but it’s the only way I know of to get the magnitude right (there is a way to specify magnitude in Stellarium, add these lines
absolute_magnitude = 8.0
slope_parameter = 4
but it makes the comet too dim)
Stellarium 0.10.6 has just been released, which has a plugin which will allow you to add comets and asteroids directly, but the above method will still work.

[Elenin]
name = 2010X1/Elenin
parent = Sun
radius = 24
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 = 2455815.22816
orbit_PericenterDistance = 0.482473
orbit_Eccentricity = 1.000016
orbit_ArgOfPericenter = 343.8071
orbit_AscendingNode = 323.2259c
orbit_Inclination = 1.8392
lighting = false
albedo = 1
sidereal_period = 365.25

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