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M31 with ASI1600MM

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This image was captured with an ASI1600MM (Lx179@60and30s_RGBx20ea@60)

It clearly needs more data but it was fun comparing this to the results I got with my OSC camera (QHY8)

There isn't a huge difference - but there will be when I add Ha to this :-)

Zoom in and you'll see black flecks across the image - not sure what's going on there as it appears on all subs (processed Flat/Bias - no need for darks - tested that)

David

 

 

M31_161005_65_ASI1600_Lx76@60and30s_RGBx20@60s.png

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I see the "flecks" of which you speak---strange.  Could it be related to a high gain?  There seems to be a pattern in them--at least on the left side of the image they appear as pairs.  Are they in the raw subs?  If they are--maybe gain?  If they are not, maybe an alignment setting, or a integration (stacking) setting.  Are they in other subs/images you have taken with the camera?

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23 minutes ago, Rodd said:

I see the "flecks" of which you speak---strange.  Could it be related to a high gain?  There seems to be a pattern in them--at least on the left side of the image they appear as pairs.  Are they in the raw subs?  If they are--maybe gain?  If they are not, maybe an alignment setting, or a integration (stacking) setting.  Are they in other subs/images you have taken with the camera?

The gain is rather high - I use unity gain which is 139 on this camera but I haven't seen similar artifacts in other peoples work with it

You're absolutely right - the do appear in pairs leading me to think they're some sort of guiding or registration issue - but the error isn't appearing in the photons captured so I'm a bit confused.

I just checked an individual sub in the blue channel and each has small black dots on them when stretched - so I think you might be right about the gain and I just need more subs

David

 

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28 minutes ago, David_L said:

The gain is rather high - I use unity gain which is 139 on this camera but I haven't seen similar artifacts in other peoples work with it

You're absolutely right - the do appear in pairs leading me to think they're some sort of guiding or registration issue - but the error isn't appearing in the photons captured so I'm a bit confused.

I just checked an individual sub in the blue channel and each has small black dots on them when stretched - so I think you might be right about the gain and I just need more subs

David

 

Are they in the dark frames?  I know you did not calibrate using darks--but did you make a Master Dark and inspect it?  Maybe  a master dark made from dark frames using eth same gain would help.  It would be interesting to shoot a target using several different gains and compare subs.  

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Good thinking - I checked the darks and have processed a different image using them and I still had the flecks - so I think I can count that out

 

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OK putting together what i can see.

1. The background (possibly all the image) is skewed into the red so this is amplifying the red star halo. 

2. The field does not appear to be flat.  If you check lower right to the top centre you can see the red fleck on satr edges moves position and gets more exaggerated as it goes to top right.  Red is likely bloated more than lum so seeing that effect exaggerated (flattening field is obvious answer but a colour calibration and some colour noise reduction may help).

3. The black flecks - can't comment on gain on this camera but it does look like bad calibration data at first glance.  Even if the error is on lights matching calibration should remove.  I would try a new set taken very diligently and min 25 darks and flats (100+ bias, i run 500 bias and 50 each of others as a min) also ensure you have some sort of averaging stack selected (don't know which software you are using for calibration) if not averaged it will add the issue up making it worse rather than better.

All that said there is some good detail in there and galaxy colour is closer than the background colour so good start, get past the teething issues and will be kicking out some solid data/images in no time.

Paddy    

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lovely Start to your image. look farward to seeing the finished article and hearing how you solved you're issue. :)

 

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Looking at this the day after processing it is clearly purple lol!

I use PixInsight and sint use colour calibration as the histogram looked ok - but normally I always do - it's now clear ro me the histogram won't help me establish colour balance - I'll rework it with the great advice you guys have provided and post mark II later in the week

Thanks again 

David

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