30 mins tracked on c/2012 K5 LINEAR

rogerg (Roger) · #1 15-01-2013, 01:33 AM

Hi all,

Another clear night! amazing.

This is 30 minutes (180 seconds x 10) of comet C/2012 K5 (LINEAR) tracking at the comet's rate (TheSkyX+PME). It's the first time I've tried tracking at comet rate to this depth.

I'm very happy with the results even though there are some squiggles in the star trails.

At the top of the page is the 180s x 10 exposure. Below that is a standard 60 x 10 for comparison with previous nights (part of my standard script). I will be photographing them north-up from now (see older ones which are rotated).

http://rogergroom.com/astro-photogra...012-k5-linear/

It's a beautiful comet. I wish I had a focal length of about 1200mm to fit it in nicely.

I did try photographing the comet through the Megrez 90 with 7D but it's 30c here right now so the noise combined with short focal length just didn't work.

Regards,
Roger.

naskies (Dave) · #2 15-01-2013, 02:09 AM

Looking pretty good, Roger!

Have you tried stacking them in "comet mode" to keep both the stars and comet sharp and untrailed?

iceman (Mike) · #3 15-01-2013, 04:29 AM

Very nice Roger!

rogerg (Roger) · #4 15-01-2013, 10:56 AM

Quote:

Originally Posted by naskies

Looking pretty good, Roger!

Have you tried stacking them in "comet mode" to keep both the stars and comet sharp and untrailed?

Interesting! what program provides that functionality? I can think how I might do it in PS but would be time expensive.

Quote:

Originally Posted by iceman

Very nice Roger!

Thanks Mike

Astroman (Andrew Wall) · #5 15-01-2013, 11:12 AM

Deep Sky Stacker has this feature.

Great image too, despite the squiggly lines its a great shot.

naskies (Dave) · #6 15-01-2013, 11:54 AM

Quote:

Originally Posted by rogerg

Interesting! what program provides that functionality? I can think how I might do it in PS but would be time expensive.

As Andrew says, Deep Sky Stacker:

http://deepskystacker.free.fr/englis...#cometstacking

I think you're currently doing the equivalent of "comet stacking" mode, but "comet and stars stacking" would be even better

It basically creates two separate stacks - one for the comet, one for the stars - subtracts out the alternative during stack, and then pastes them back together at the end.

Look forward to seeing how it goes

jjjnettie (Jeanette) · #7 15-01-2013, 02:51 PM

A lovely image Roger.
A wider FOV would be awesome. Show us the rest of that tail.

rogerg (Roger) · #8 15-01-2013, 03:14 PM

Quote:

Originally Posted by Astroman

Deep Sky Stacker has this feature.

Great image too, despite the squiggly lines its a great shot.

Thanks

Quote:

Originally Posted by naskies

As Andrew says, Deep Sky Stacker:

http://deepskystacker.free.fr/englis...#cometstacking

I think you're currently doing the equivalent of "comet stacking" mode, but "comet and stars stacking" would be even better

It basically creates two separate stacks - one for the comet, one for the stars - subtracts out the alternative during stack, and then pastes them back together at the end.

Look forward to seeing how it goes

I didn't realise DSS had comet functionality, I"ll check it out tonight. I wonder how it locks on to the comet or does it allow centroid selection?

Quote:

Originally Posted by jjjnettie

A lovely image Roger.
A wider FOV would be awesome. Show us the rest of that tail.

Thanks JJJ

Yes, larger FOV would be great

Oh well, need to buy another telescope

Astroman (Andrew Wall) · #9 15-01-2013, 04:23 PM

SOmetimes it can select the comet quite easy, especially if the comet has a bright nucleus, other times you may need to select it manually by holding down the shift key while clicking on the comet head. It should be all in the help of DSS...

rogerg (Roger) · #10 15-01-2013, 05:11 PM

Quote:

Originally Posted by Astroman

SOmetimes it can select the comet quite easy, especially if the comet has a bright nucleus, other times you may need to select it manually by holding down the shift key while clicking on the comet head. It should be all in the help of DSS...

Thanks

rogerg (Roger) · #11 18-01-2013, 12:05 AM

DSS doesn't seem able to detect enough stars in the images to align. I've tried various settings with no success

I'll see if I can work out how to do it manually. In other software I will be able to align stars and comet in to two separate files, so then it's a case of working out what needs to be subtracted from what.

naskies (Dave) · #12 18-01-2013, 12:31 AM

I would have thought there would be plenty of stars, seeing your comet-stacked version? Have you tried adjusting the star detection threshold? I find that setting very important for getting the subs to stack properly.

rogerg (Roger) · #13 18-01-2013, 12:59 AM

Quote:

Originally Posted by naskies

I would have thought there would be plenty of stars, seeing your comet-stacked version? Have you tried adjusting the star detection threshold? I find that setting very important for getting the subs to stack properly.

Yes ... seems to have no impact (at either extreme) which is odd. I will keep playing to see what's going on. I have just tried with my DSLR shots from tonight and it's only choosing 6/10 with the same effect that altering the detection shreshold isn't altering the situation.