Need to troubleshoot 120mc stacking issue

firstc8

I have run into this issue. Try to use either DSS or Regstax to stack frames and Photoshop to process. Not able to remove noise with one dark using Registax, and with 5 darks/15biases using DSS, the stacked image is not clean, has diagonal line noise.

I have attached two processed images, one stacked with DSS, the other Regstax. Sharpcap 100 lights, 5 darks (only one loaded in Regstax), and 15 biases (not loaded in Regstax), all 23 secs and 100 gain. I tried low gain longer exposure the other day the results were similar.

Trying to find out if there are additional noises from the camera I could not remove, or something else? As you can see if the noises are properly removed, the final DSS image would have been great.

Thank you!

riklaunim

Single dark frame will always add more noise than help. You need good master darks/flats and sometimes master bias frames as well. If the exposure was short I would do a master dark from ~100 frames or more, and 500-1000 frames for master flat and master bias.

firstc8

Thanks for the quick response.

When I used Registax 6 I could only load one dark, no bias. I did try to load a master dark the result was similar.

I regularly see people using small number of darks with good results, so I limited the number of darks to save time.

In the DSS image, I could load all my darks and biases. The stacked image did show thermal noises successfully removed, just not sure what are the diagonal line noise. I doubt biases will help because I don't see any diagonal lines in biases, or in darks/lights. Where did they come from?

BTW, during my very first astrophoto session I also did the Dumbell (image posted here before) with 100 lights and 20 darks, no biases, after DSS there was no diagonal lines. Don't know what has changed.

betacapricorni

Hi, it seems that something work bad, i have the same diagonal line with my Sxv- h9 when make wrong bias file. You say that bias frame have not that lines, even the master bias? Which is bias time expositions? 0 sec?

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riklaunim

In registax select all dark frames and stack them as dark frame (there is an option somewhere in the top menu). that creates a master dark frame. The same thing for flat frame.

I don't use DSS or Regisax for DS processing, I prefer Nebulosity, where every step is explicit and you can control it (dark/bias/flat, stacking etc.).

landbo

Hi.

Try and stack in Regim instead if possible. ;) http://www.andreasroerig.de/regim/regim_e.htm

Regards Leif.

firstc8

One thing I added this time was a light pollution filter, don't know if it had any impact? The images have a heavy blue base tone, making adjustment difficult.

betacapricorni

The blu/green base tone are normal with light pollution filters but you can normalize in photoshop. How long the bias exposure?

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firstc8

I think bias was .0064ms, shortest for 120mc.

I played number of stars to detect in DSS. It used to say 400+ stars, I then realized there were not so many, only 10 to 15. So adjusted the % to get to around 10 to 15 stars. The end result was a little better but not a cure.

I used the LP filter because of severe sky glow that night, so maybe seeing was shot anyway. But Sharpcap live screen looked fine.

betacapricorni

Is the camera cooled? Which sensor T° had when taking all the frame? it changed a lot?

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firstc8

Camera is not cooled. Temp has been stable, +- 0.5C and calm.

Until last night! When I tried to set up again, I noticed my AVX mount can't handle light wind. Worse, the peg on the mount slipped during polar alignment, I could not get good polar anymore. As I turned the two knobs against the peg, I could hear clicking sound and the base of the mount moved in steps, not smoothly.

Another good seeing night wasted. Did I over tighten the mount and tripod? What caused the mount to slip?

betacapricorni

Have you cheched the thread of the screw who lock the tripod to the mount? if you over tight making some damage have to check that in my opinion

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firstc8

Gave it another try tonight, 439 lights, 100 darks and 453 biases, 8s and 100 gain. Probably the best the 120MC can do?

betacapricorni

I like a lot! Try to cool them!

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firstc8

I used similar exposure settings (400 lights, 100darks and 400 biases) to make an attempt at M33, again diagonal noises. In fact the same noises were also in the above Dumbbell image, but the image was bright enough to clip the noise, in doing so some details were lost.

This one simply could not get rid of the diagonal line noise. Wonder if this is camera specific? The 120mc does have a lot of noise and is not very sensitive.

betacapricorni

In my opinion the problem are the bias. A bias file MUST be done at 0 secs. Please try to elaborate the same but without bias

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firstc8

Will try without biases.

Here is M1 image at F6.3, similar exposure settings. I think if the object is bright enough I can clip the diagonal noise.

firstc8

You may be on to something! This one stacked without biases.

I will have to restack all of them to find out.

firstc8

Stacking without biases does allow a little more detail brought out since there is little diagonal line noise to cover.