How to image Comet Hartley?

[OzDave]

Hi,

I'm planning to head to my dark(-ish) site on the weekend, where I plan to try my hand at imaging Comet Hartley.

I'm wondering what would be the best approach?

I'm planning on using my ED80 with 450D and flattener at prime focus. I've read in various Astro mags that short subs would be the way to go, like say 25 secs max.

But I'm wondering if I setup my guide cam and used the Comet nucleus to guide with, would that allow longer subs, and would this make the result better?

If the guiding doesn't work out, I think I'll try take a pile of 20sec subs and then stack them and see how it comes out.

Does this (these) approaches sound ok? I've never imaged a comet before and so I'd like to roughly know what I'm doing once I get to site on the weekend.

Cheers,

David

[FraserClarke]

A few weeks ago, this comet was moving at ~0.5" per minute, so you can take exposures up to a couple of minutes without worrying about blurring. ED80 is quite short focal length isn't it? So you might not even notice the comet moving in ~5 minutes or so...

The usual way to take comet images (see some of the great examples by NickH in the "imaging - comets" section) is to track on a star, and the the shift and combine the subs afterwards, aligning on the comet. This gives you a nice fixed comet with long star trails.

Guiding on the nucleus would be tough I think. If you want to do this 'offset guiding' you usually guide on a star, and get the software to apply a pre-calculated offset so that the guide star 'drags' the telescope in the right direction to follow the comet. MaximDL can certainly do this, I don't know about others.

[Dave-Ryan]

It would be intersting to see how you get on, OzDave, as I have never imaged a comet before either and was thinking of giving Hartley a go with my ED80.

I've just checked the weather forecast and it looks like rain for at least the next five days so not sure when I'll get a chance.

Please post any pics you get OzDave, I'd love to see what I'm missing.

[OzDave]

Ok, I think I'll follow TeaDwarf's advice.

Since the ED80 is only 500mm FL, I may try my luck with a 2x Barlow if I can figure out how to attach it with my field flattener etc...If not, I might try my Mak 127 instead although it's ~f/12 so not ideal. Maybe the flattener isn't essential for this, but would be nice...guess I can try various combos.

Fortunately I'm in Greece and my dark site is on an island, and I usually get clear dark skies at this time of year. So I'm pretty excited about this weekend! Will post anything I get.

Cheers,

Dave