DSS stacking and histogram problems

[Rocket Stars]

Hi! 

Finally my rig is up and running. (now, time to climb over the next hindrance) Did som astrophotography some years ago, with a unmodded DSLR. But didn't do much else than tweaked them in PS. 

Now I have a set of galaxy images. ready to process. Did try stacking, but got all assorted weird results. Probably due to my beginner status in this matter. Images got fairly ok stacked. But the histogram was strange. Exept RGB Chanels was ofset to a certen degree. But mostly notcible was red Chanel. It was just a extremely short spike to de left edge of the histogram. Made it impossible to stretch it and get a somewhat color balance . 

Had som weird stacking results too. Anything from cropped out galaxy, to extremely overexposure result. Level cracked pixel/screaming cyan ect.  Have not a matching set of flats, darks ect. But a bunch from both Sharpcap and NINA. I was hoping I would get something out of the captured fits files. Oh, the captures are between 15 sec to 3 min. Did assortment of capture sets. Testing different exposure times and gain settings. 

Didn't use guiding, but it tracked quite well. Up to 3 min exposures seemed to work well. Little elongated stars at som of the 3 min exposures. 

About 100 frames in total. 15 to 3 min exposures at f2 with a edge 8hd. 

Have checked YouTube ect on DSS settings. did maby 50 different stacking efforts. But no (except monochrome) came out decent to get color balance and som detail in PS. 

 

Some  hints would be greatly appreciated!  

 

Edit/ i realize that this post maby fits better int the beginner/get started section. Moderators, feel free to move the post if it more appropriate.

 

 

Edited March 23, 2020 by Rocket Stars

[Rocket Stars]

stacking trial and error, in progress!

Ok, there is something going on with my bias/offcet files. Have tried one from NINA, wish give me extremely overexposures. 

Sharpcap bias/offcet calibrates out everything! Get a pretty much black image.. 🤣 

Flats give me a very faint image, darks.. Who knows 😆

[happy-kat]

Are you using a modded camera?

Also red bias could be local light pollution.

[Rocket Stars]

Hi, Im using 178color (non cooled) . Im under lightpolution. Have a IDAS LPS D2 filter. I was just realizing that it is also IR cut. And I also have a IR cut just infront of the sensor. 

Can not for my life, find out why my frames is being white/overexposured after stacking in DSS.. Another 6hrs not getting anywhere.. 

 

 

[Rocket Stars]

Her is a image how my DSS stack, looks like. 

And a result of a little ps work. A overly white picture, is harder to balance colors, brightness ect. Than a darker. The result in ps suffers quite a bit. But it is my first (almost, past years docent count) image!! 

Data is about 1 hr, stacked so many different times. I have lost track.. Sky wasn't great. Very few stars visible with the naked eye. 

 

 

[happy-kat]

That light image doesn't phase me. If you stack without calibration files that will only effect noise and vignetting.

[happy-kat]

I don't judge an image output potential from the DSS preview

[Rocket Stars]

Ty for you're reply!

 The white is also how it looks in ps.  But Im pretty sure my calibration files is wrong some how. 

There is about 20 darks, flats, dark flats in this stack. tried making flats both in NINA and Sharpcap. Must have got it wrong. 

With bias, I got crazy results! 

What bothers me, is that is I stack the 10 short 15sec subs, with same calibration files. I get darker green images. As in the turitorials I have looked at. 

If I take the same amount of 1min subs, or longer. I get this white stacked image.  Have not found any info about that. 

[happy-kat]

I would check each of the light frames by hand to make sure there is not a rogue one in there.

Look at the DSS register results, do any light frames have a bad score or high FWHM if so exclude them.

Pick your highest scoring light frame as your reference file (likely to have one of the smallest FWHM values as well)

[Rocket Stars]

Ok. Here is another shot at ps processing. Didn't bother about stars. But tried to enchange the galaxy features. 

There is defenetly need of better imaging data. Were very few stars visible on the night. Streetlamp derby ect. Tryed to take new flats, ect. did improv the stacking a bit. But still not happy. 

 

[Rocket Stars]

Ok, Trying to learn about the camera a bit more. 

So I did several sensor analysis in SharpCap. Cam is AA GPCAM3 178C. 

Im not getting my head around those numbers. Where is unity gain, or best gain to read noise setting in this camera? 

Adding data for both 8bit raw and 14raw. 

Also found out today, that calibrating bias should be avoided on cmos cameras. Especial with short exposures. Interesting, intresting.

 

Edited March 27, 2020 by Rocket Stars
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