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fwm891

ASI 294MC Pro users - Dark frames?

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I'm really liking my ASI294MC Pro but having headaches trying to get dark frames that work.

I capture at -20°C with a gain setting of 122 and offset of 15 which seems to suit my DSO's (I'm not a planetary or lunar guy).

What sort of settings are other 294MC users using?

At what stage during processing are you applying your darks?

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1 hour ago, david_taurus83 said:

What do you mean your trying to get them to work? How are you applying them in your workflow?

My Workflow with ASI294MC Pro

Generate Bias – circa 50 subs

Generate Darks – circa 20 subs (use subs at same duration and temp as lights)

Generate flats – circa 25 subs

No Flat darks (must try these)

Above masters are generated as per Warren Keller’s notes in ‘Inside PixInsight’.

1,  Blink (assess images to weed out aircraft trails etc)

2, Image Calibration – apply bias, Darks and flat masters

3, Cosmetic Correction

4, Debayer (RGGB)

5, Star Alignment

6, Image Integration

7, Crop as required

8, Background (ABE or DBE)

9, Background Neutralisation

10 Colour Calibration

Then various transformations, SCNR, TGVD, Colour saturation… (as I think is needed)

I'm open to suggested modifications to this....

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Don't use bias in regular workflow - you don't need them and they can cause issues (maybe even issues that you are seeing).

Since you did not take flat darks (or dark flats - whichever way you prefer) - use bias that you captured instead of those.

Btw offset of only 15 looks suspiciously low. Since you have bias subs - you can check if offset 15 is indeed adequate. Could you do following:

Make a stack of bias subs only but use simple minimum stacking method, then run stats on it (min,max, average, stddev and such) and histogram and post those?

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3 hours ago, david_taurus83 said:

How are the darks not working?

An STF on the dark master and same on a single sub...

_300s_15_C294MC_DARK_RGB_VNG.jpg

ngc 7331_300sec_1x1_OSC-ngc7331_frame4_c_cc_d_r.jpg

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On 04/09/2019 at 16:12, fwm891 said:

My Workflow with ASI294MC Pro

 

Generate Bias – circa 50 subs

 

Generate Darks – circa 20 subs (use subs at same duration and temp as lights)

 

Generate flats – circa 25 subs

 

No Flat darks (must try these)

 

Above masters are generated as per Warren Keller’s notes in ‘Inside PixInsight’.

 

1,  Blink (assess images to weed out aircraft trails etc)

 

2, Image Calibration – apply bias, Darks and flat masters

 

3, Cosmetic Correction

 

4, Debayer (RGGB)

 

5, Star Alignment

 

6, Image Integration

 

7, Crop as required

 

8, Background (ABE or DBE)

 

9, Background Neutralisation

 

10 Colour Calibration

 

Then various transformations, SCNR, TGVD, Colour saturation… (as I think is needed)

I'm open to suggested modifications to this....

Assuming 'image integration' is your stacking, I wouldn't apply any cosmetic correction before stacking (unless it's automated hot pixel removal and the like).

Also consider sigma clipping or auto-adaptive averaging to get rid of aircraft and satellites rather than just dumping those frames.

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I had some good experiences with the ASI294MC-Pro and agree with vlaiv - ditch the bias frames and take dark-flats and you should have no problem completely getting rid of the amp glow in the finished image.

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21 hours ago, fwm891 said:

An STF on the dark master and same on a single sub...

_300s_15_C294MC_DARK_RGB_VNG.jpg

ngc 7331_300sec_1x1_OSC-ngc7331_frame4_c_cc_d_r.jpg

Yes, there is residual amp glow.

Could you upload this light and set of darks that you used to calibrate it for inspection?

There might be something that is causing this that could be solved?

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Well I've been trying many different processing options and found (I think) my problem lies in the Image Calibration stage when Master dark Calibrate and Optimise are checked I get amp glow, with these un checked amp glow disappears. Also tried with one or the other checked and turns out that it's the Optimisation that's causes the amp glow to show.

The images below are tight crops from the area of worse amp glow in my images (full frame also included).

Now this is strange because previously I have been following Warren Keller's routine and in that he says to check calibrate and optimise but to set the optimise level at zero? Does this mean that something is happening even when setting optimise to zero?

NoCalNoOpt.jpg

WithCalNoOpt.jpg

WithCalwithOpt.jpg

Opt-Cal.jpg

NoCalNoOpt_FullImage.jpg

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Yes, for dark optimization to work - you need to have proper bias, and CMOS sensors don't have proper bias, so it's best to avoid dark optimization as it will cause issues - like you've shown.

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Hi Francis,

I am no expert here but I follow the processing of calibration images which is posted on the Light Vortex website. https://www.lightvortexastronomy.com/tutorial-pre-processing-calibrating-and-stacking-images-in-pixinsight.html#Section2 .Just scan read Warren's book on calibration frames and there are subtle differences between his workflow and that described on Light Vortex. 

During my brief spell astro imaging I have used the ASI294MC and always taken dark flats opposed to bias frames and followed the Light Vortex workflow with no major issues.

Might be worth a look.

John

Edited by Hughsie
typo
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Could the amp glow on both sides be due to a meridian flip performed during imaging session?

By the way I also have the ASI294MC Pro, and ever since I got it I have never managed satisfactory flats with it. When I stack images, the result with flats always appears to be worse than the result without any flats applied. Can I ask you what your method is for capturing flats? I am using a DIY panel as per in this thread:

https://stargazerslounge.com/topic/325457-flatstub-a-rough-ready-diy-flats-solution/

 

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