DSS Subs rejection problem

[Nico13 (Ken)]

Hi all,

Well finally been getting a few clearer nights and have been collecting more data on NGC253 to add to some earlier subs.
I had only about a half hr of subs originally and now had another hr to add to it, total subs 26 made up of 9 and 17 from the two lots.

Problem arises when the initial lot of 9 subs is not included in the stack for some reason.
These are all shot on my DSLR in raw and the only difference I can see is that the frame alignment is slightly different from the second set but not much and the seeing conditions were not as good for the first set.

Any ideas on why DSS would reject the first set,

[AstroJason (Jason)]

Hi Ken, I am by no means experienced with DSS, I have only started using it. However, check the Register Settings menu. I believe here is where you can force DSS to select 100% of the images rather than DSS selecting a percentage of the best images to stack.

I have been watching this guys tutorials on youtube and they have helped me a lot. http://www.youtube.com/watch?v=UWWaKkCUm6c

Beware though, he sounds a hell of a lot like Michael Caine

[Nico13 (Ken)]

Thanks Jason,
Yes I did have 100% of images selected but it still rejected those earlier subs.
Will have a look at the tutes.

Cheers

[naskies (Dave)]

A couple of thoughts...

* You may need to click on the option to re-align subs that have already been aligned.

* Your star alignment threshold might be okay for your second set of 17 subs, but not right for the first set of 9. One way to check would be to see how many stars get detected for one of the frames for your first set versus the second set - if it's substantially different, then that may be a problem. I've found that there's a sweet spot for the threshold - too high/low runs into alignment problems.

* This is obvious... but have you checked that all 26 subs have check boxes next to them (i.e. that they're all included in the stack)?

* Are you using dark/flats/bias calibration frames? It's important that these are generated properly... I've run into countless problems with alignment when they've been problematic. Poor flats has been my biggest problem - sometimes it stacks better without the flats included.

* Worst case scenario, you could stack the first set of 9 subs together, and split your second set of 17 into two separate sets of 9 frames. Stack the three sets of 9 separately, and then stack the three output TIFFs together to get your final result.

Hope that helps!