Comet McNaught #3 (Prime Focus)

[2020BC (Bill Christie)]

Camera: Canon 350D unmod
Scope: Orion 80ED
Exposure: 15x8 secs ISO 800 Noise Reduc on
Process: Aligned MaxDSLR, composited in Photoshop

Anyone know what the straight dark line behind the nucleus is? Is it the comet's shadow?

[sheeny (Al)]

That's a nice image Bill! I don't know if it's a shadow or not, but it sounds plausible!

Al.

[DobDobDob (Ron)]

Assuming it's not an artifact, it could be what we call a 'slip stream' as in the traditional sense when riding/driving behind a larger vehicle in front.

This is all guesswork, but seeing the head of the comet is pushing space out of its way setting up a wave that wraps around behind, the most central part takes longest to fill in, creating this 'empty' space.

[fringe_dweller]

awesome collection Bill, been admiring all your shots

the dark lane you can see is called a .. 'dark lane' lol, actually its an visible extension of the parabolic hood. you only get these with proper 'dusty' comets, which as you know arent very common. altho not extremely rare, Comet 2000 WM1 (LINEAR) and, i'm not sure, but i thought i remember seeing some pics that showed Comet 2004 F4 Bradfield display this feature, briefly?, hmmm, cant seem to find that shot now? might be thinking of the ion tail thru the guts?

here's a widefield pic of wm1 that we took showing same feature

http://southern-x.org/g-wm1/gallery-pic3.html

you might of seen it described as the 'shadow of the nucleus' but that is just a very old classical term/description. as was pointed out during height of mcnaught mania, a shadow cant bend (many shots show it bending further up), and its not in the anti-solar direction proper anyway.

its the results of jet(s) at either side or one or may at the front of nucleus, that dont quite meet up, leaving the resulting gap in spewing material, pushed along by solar wind of course, but still tending towards orbital wake/trail