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Friday, August 13, 2010


Putting Comet 2P/Encke in Stellarium

Comet 2P/Encke is within a binocular field of Mercury on the 17th, 18th and 19th of August. Shown here is the view on the 18th. The comet is fainter than magnitude 6, so you will only see it in binoculars (and even then as a fuzzy dot).

In about a weeks time Comet 2P/Encke will be visible in the southern hemisphere in western skies, sadly it will be binocular visible only, but it does come close to Mercury. As I've mentioned several times before, you can add new objects, such as comets and asteroids, to Celestia and Stellarium. If you want to follow 2P/Encke in stellarium or Celestia. I've made up a Stellarium add-on and a Celestia .ssc file for 2P Encke. (scroll down to the bottom of the second image for the add-on.)

The approximate view seen through a pair of 10x50 binoculars on 18th August, centred on Mercury. ENcke might a a discernible tail, depending on how dark the sky is where you are.

2P/Encke orbital data from JPL Horizons.

JPL/HORIZONS 2P/Encke 2010-Aug-10 03:10:25
Rec #:900092          Soln.date: 2010-Jan-28_17:27:03   # obs: 1718 (1996-2009)

FK5/J2000.0 helio. ecliptic osc. elements (AU, DAYS, DEG, period=Julian yrs):

EPOCH= 2455044.5 != 2009-Aug-01.0000000 (CT) Residual RMS= .65962
EC= .8479456370992317 QR= .3369758246572427 TP= 2455415.077574995
OM= 334.5696032945518 W= 186.4988142344296 IN= 11.78284902989807
A= 2.216153606043881 MA= 249.29087442532 ADIST= 4.095331387430519
PER= 3.2991950396685 N= .298747504 ANGMOM= .013574549
DAN= 3.95366 DDN= .33797 L= 160.9326132
B= -1.3243517 TP= 2010-Aug-06.5775750
The stellarium file for Encke (works in versions 10.x and 9.x); just copy and paste the section below at the end of the system.ini file. When you run Stellarium, you will have to turn planet hints on in the configuration menu if they are not already on. you will also have to adjust the magnitude slider so the circle will appear in Version 10.x. For Celestia the .ssc file goes into the extras folder. Note that the albedo and diamtere are wrong in the Stellarium add-on, but it doesn't give me the right magnitude if I use the real values.

name = 2P/Encke
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 = 2455415.077574995
orbit_PericenterDistance = 0.3369758246572427
orbit_Eccentricity = 0.8479456370992317
orbit_ArgOfPericenter = 186.4988142344296
orbit_AscendingNode = 334.5696032945518
orbit_Inclination = 11.78284902989807
lighting = false
albedo = 1
sidereal_period = 365.25

"2P-Encke" "Sol"
Class "comet"
Mesh "roughsphere.cms"
Texture "asteroid.jpg"

EllipticalOrbit # elements for epoch 2009-Aug-01.0000000
Epoch 2455415.077574995
Period 3.302403
PericenterDistance 0.3369758246572427
Eccentricity 0.8479456370992317
Inclination 11.78284902989807
AscendingNode 334.5696032945518
ArgOfPericenter 186.4988142344296
MeanAnomaly 0.0

InfoURL "http://www.astrobgs.dyndns.org/astro/cmt2005/__2P.htm"
Radius 3.100000
Orientation [ 90 0 0 1 ] # random value
RotationPeriod 15.080000 # http://www.ifa.hawaii.edu/~meech/rot.html
Obliquity 22.193060 # random value
EquatorAscendingNode 228.225959 # random value
Albedo 0.04

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