DSS help

[CapturingTheNight (Greg)]

Hello,

I'm new to this astrophotography game and I was wondering if anyone had any thoughts on what appear to be bubbles around my stars after stacking in Deep Sky Stacker. I have attached a before frame which is a 1:1 crop of one of the sub exposures. The after frame is of the same section of the picture after stacking. The 'bubbles' are not really noticible in the full frame view (3rd attachment). I'm certain that all the subs are identical (I checked them all....twice) with no focus shift during the exposures. I'm convinced that it is something to do with the stacking process. Is there a setting I am missing or a setting I should uncheck??? Any thoughts would be greatly appreciated.

Thanks

Greg

Canon EOS 1000D
Baader Coma Corrector
10 inch (25cm) F/4 Newtonian Reflector Telescope
NEQ6 PRO Computerised Goto Mount
Orion 80mm ShortTube Guide Scope
Synguider Autoguider
21 X 120 seconds exposures
ISO 400
Images stacked and alligned in Deep Sky Stacker
Final processing in Photoshop Elements 8.0

[apaulo (Paul)]

Hi Greg

I don't think it is a dss problem, i reckon after looking at your second image, Focus maybe the issue. The donut looking stars give it away.
Try and use a bathinos mask if you have one.
I too had the same problem and the bubbles went once good focus was achieved.
Regards Paul.

[jjjnettie (Jeanette)]

In your Stacking Parameters, under Cosmetic, I think you might have "Detect and clean remaining Hot Pixels" and "Detect and clean remaining Cold Pixels"
selected.
Untick the boxes, then try again.

[CapturingTheNight (Greg)]

Originally Posted by apaulo

Hi Greg

I don't think it is a dss problem, i reckon after looking at your second image, Focus maybe the issue. The donut looking stars give it away.
Try and use a bathinos mask if you have one.
I too had the same problem and the bubbles went once good focus was achieved.
Regards Paul.

Thank you for your thoughts on it Paul. I didn't think it was focus because none of the subs have stars as big as what they turn into after stacking. It looked like they were expanded into bubbles or donuts during the stacking process. But I guess if you had the same problem then it must be focus. I've just been focusing using magnified live view on the DSLR (getting the diffraction spikes around a bright star as clear as possible) so yes it may be slightly out. I'll investigate one of those masks.
Cheers

Originally Posted by jjjnettie

In your Stacking Parameters, under Cosmetic, I think you might have "Detect and clean remaining Hot Pixels" and "Detect and clean remaining Cold Pixels"
selected.
Untick the boxes, then try again.

Thank you for the advice jjjnettie I'll try stacking them again this afternoon (unless the weather finally clears up, inwhich case i'll be setting up the scope) with those settings off. I can't remember what settings I used. I really should keep a log of what I do use for future reference. Rookie mistake. I'll let you know if it makes any difference.
Thanks again.

[cybereye (Mario)]

Greg,

The good news is I've had this problem with dss and managed to solve it. The bad news is that I can't remember what I did!! Try JJJ's advice and if that doesn't work try one of the simpler stacking algorithms. However the more I think about the more JJJ's tip sounds familiar!

Oh if only I hadn't had that last scotch and dry back in '81 then I'd be able to remember!!!

Cheers,
Mario

[CapturingTheNight (Greg)]

Originally Posted by cybereye

Greg,

The good news is I've had this problem with dss and managed to solve it. The bad news is that I can't remember what I did!! Try JJJ's advice and if that doesn't work try one of the simpler stacking algorithms. However the more I think about the more JJJ's tip sounds familiar!

Oh if only I hadn't had that last scotch and dry back in '81 then I'd be able to remember!!!

Cheers,
Mario

Thanks for the good news that it is solvable Mario I'll keep you all posted on how it goes.

[CapturingTheNight (Greg)]

So I just restacked the Carina Nebula frames with the cold/hot pixel detection boxes unchecked.

The donut/bubbles have gone. Wahoo!!! The focus of the subs might still be a fraction out but i'm well pleased with how this turned out, considering it was only my second attempt at a proper astrophoto through my telescope.
Thank You very much jjjnettie for the advice. I really appreciate it. Thanks again to Paul and Mario for your thoughts on my problem as well.

[jjjnettie (Jeanette)]

glad to be of service.

[apaulo (Paul)]

Pleased to hear its worked out.
Learn something everyday, thanks Jen for the hint.
Regards Paul.
Ps Mario watch your focus after a couple of scotches Mate.

[CapturingTheNight (Greg)]

Originally Posted by apaulo

Pleased to hear its worked out.
Learn something everyday, thanks Jen for the hint.
Regards Paul.
Ps Mario watch your focus after a couple of scotches Mate.

Thanks Paul,
I'm sure my focus is not as good as it could be, as you suggested, so I've got a focus mask on order.
Cheers
Greg

[apaulo (Paul)]

Hi Greg
Glad to hear you have solved the problem. I have two Bathinos masks, one for the 8" astrograph and for the ed80. Makes life so much easier.
Can I suggest when you use the mask take a image for say 20 seconds and check the focus cross hairs. I tighten the screws only when I am happy.

Look forward to viewing your images.

Regards Paul.

[CapturingTheNight (Greg)]

Originally Posted by apaulo

Hi Greg
Glad to hear you have solved the problem. I have two Bathinos masks, one for the 8" astrograph and for the ed80. Makes life so much easier.
Can I suggest when you use the mask take a image for say 20 seconds and check the focus cross hairs. I tighten the screws only when I am happy.

Look forward to viewing your images.

Regards Paul.

Thanks for the tip Paul. Itching to get the scope out again but the weather has not been kind for the last 2-3 weeks. Tomorrow night is looking somewhat promissing. *fingers crossed*