I took a series of photos of Lulin early saturday morning and made this video of its movement:
[ame="http://www.vimeo.com/3139918"]Comet Lulin - 2/7/09 on Vimeo[/ame]
And here's a stacked still image:
Could it not be done in an Add-on in the same way that exhaust textures can be changed via addons (not sure how far into the Direct3D layer you can get via the orbiter APIs to start spawning single-point-polys)