M81/M82 and how to know if data is good?

Questions and answers about processing in StarTools and how to accomplish certain tasks.

M81/M82 and how to know if data is good?

Postby khobar95 » Fri Mar 23, 2018 7:54 pm


I've been trying to improve my result of M81 and M82. I'm using DSS for stacking, an 80mm ExploreScientific triplet APO and a Nikon D5100, ISO400, 2,4, and 5 minutes exposures, flats, bias, and darks. I've tried various Star Tools approaches and some of what I'm seeing is getting interesting, but I don't know if my data is as good as it could be.

Could some kind soul take a look at the .fts spit out from DSS and tell me if it's good/bad?
I've not used Google drive to share anything, so hopefully this will work.
I've uploaded the .fts file: https://drive.google.com/file/d/1gf9iYU ... sp=sharing

Thanks very much.

This is where I'm at with it:
where I'm at with it.
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Re: M81/M82 and how to know if data is good?

Postby almcl » Sat Mar 24, 2018 9:00 pm

I think that looks quite nice (not that I'm any sort of expert, or anything) there's some nice detail in M82.

I do notice a little bit of 'walking noise' which you might be able to reduce if you dither between frames. The yellow streaks running Northeast/Southwest:
walking noise.jpg
walking noise.jpg (33.66 KiB) Viewed 1065 times

There are also a couple of artefacts towards the top of the frame, not a problem, they can be cropped out, but it might be worth trying to find what's causing them?
artefacts.jpg (140.89 KiB) Viewed 1065 times

Finally, there appears to be some vignetting, although your flats should have taken this out, not sure what the remedy for that is.
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Re: M81/M82 and how to know if data is good?

Postby khobar95 » Sat Apr 14, 2018 7:05 pm

Sorry for the delay.

Thank you for the reply. I've now tested my rig with "dithering" enabled and the results are really quite nice. Unfortunately, until the parts arrive for my serial shutter control I'm stuck with 30s exposures. Parts are due Monday, so I'm anxiously waiting.

The weird artifact is present in all my shots lately. I suspect it's dirt or grime of some kind - does not come off with canned air.

Vignetting should be fixable with better flats I think.

Anyway, thanks for the input. I'm not focused on M51 as I have more time with it. But if my M81/82 data is okay then that's what I needed to know. Thanks!
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