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Bloated stars & DSS

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Just a couple of quick questions on long exposure subs.

The other night I was experimenting with a few crazy sub lenghts on M42 to see how far QHY5/PHD would go before cracking up.

Using the 2" Barlow & Skywatcher LPF, I took a series of 10 minute subs @ ISO 800, one of which I will attach below. In the end it felt like time wasted with 10 min @ ISO800... its tracked reasonably well, but god those stars are a bit bloated.

Anyway, I took a series of 4 and 2 min subs (also @ ISO800) to mix it up a bit - but when I put them through DSS, it didnt stack them - it only seemed to stack the long exposure pics (it registered 16 but only stacked 6). Its not the first time thats happened.

So my first question is:

Is there a way to reduce bloating on the stars? I was thinking of setting a limit of no more than 4 or 5 min for any light sub... maybe 10min was a bit too OTT. ;) The only catch is the filter, yes its cheap but I cant operate above 2min without it here due to LP, trouble is that is seems to block a bit too much and the stars lose their nice diffraction spikes - forcing me to go for longer exposures.

My second query is about making DSS stack everything i give it when using a mix of long & short exposures - Ive set it to use 100% of subs / Mosaic mode, but that still doesnt work. Am I missing something, or should I try other software?

Here is one of the 10min subs (unprocessed, coverted from RAW to JPG), not sure what the patches are in the corners... maybe I should make a longer dew shield to block unwanted lights.


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I think that's just the way the camera is blooming the light source on the longer exposure. I'm not sure there's much you can do about it, but there are actions available to reduce the effect... I think Peter Shah released some on here.

In respect of the differing sub lengths in DSS... you could try Entropy weighted stacking, it's designed to be used on subs that combine into a much higher dynamic range, i.e. you've got subs of different lengths. Otherwise, stack them separately, and combine them afterwards.

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Thanks man ;) will try that. Hopefully I can now use more of the data I collect.

I think you made a reference to PS (actions), im going to take another look at it later but from what I remember its not exactly friendly for the beginner...lol.

Will post any improvements I make, cheers!

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I dont know much about guiding etc, but the patches in the corners are camera light leaks, which darks will get rid of.

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