M51 Image - Not sure what am i doing wrong in my settings

[Nittany]

My System: CGEM Mount Edge HD8 OTA, Celestron Focus Motor (Connected to laptop via USB and USB hub), ASI678MC (Connected to laptop via USB3.0 and USB hub)
Workflow: I use Skyportal app on Samsung tablet and Star Sense to sky align and polar align (Tablet is connected to the mount via Celestron Skyportal Wifi Module)
Primary Imaging Software: Sharpcap Pro Beta 4.1 (latest copy as of 03/20/2023) --> Save Exactly as seen
Laptop: 32 GB ram and 1TB HD (Plenty space available)
Image controls: Exposure 5s and Gain = 300; I use auto color balance from histogram peak (thunderbolt icon)
Location: Chandler AZ, Bortle 8
Celestron Edge HD8 Mount: CGEM Celestron Focus Motor - Sharpcap controls
Backfocus 108mm (i need to be at 105mm); 0.7x reducer, ASI678MC (not exactly a DSO camera),

See pics below - 1) Why my color balance is off 2) Why am i not getting a decent picture? I am pretty new to DSO. (Not sure what i am doing...)

Can somebody point me in the right direction?
Regards
Nittany

[admin]

Hi,

a couple of things to check

* Did you have a display stretch set up as well as the stretch in live stacking? The combination of the two can often lead to weird effects like this, particularly if the display stretch is quite a strong one

* Check processing options (dark subtraction, background subtraction, flat correction) are either off or set to reasonable values. Incorrect darks/flats/etc can cause issues.

My guess from the look of it though is a display stretch SharpCap 4.1 now has an otpion (in the live stacking options) to automatically turn off display stretch when live stacking is enabled for just this reason.

cheers,

Robin

[Nittany]

Thanks Robin for the response.

So this is definitely not turned ON -
* Check processing options (dark subtraction, background subtraction, flat correction) are either off or set to reasonable values. Incorrect darks/flats/etc can cause issues.
Background Subtraction=Off
Planet/Disk Stabilization=Off
Banding Threshold=10
Banding Suppression=0
Apply Flat=None
Hot Pixel Sensitivity=5
Subtract Dark=None
DisplayStretchEnable=1
NegativeDisplay=0
Display Black Point=0.03125
Display MidTone Point=0.0400833509412767
Display White Point=0.058837890625

Do any of these Display values adding to the picture?

* Did you have a display stretch set up as well as the stretch in live stacking? The combination of the two can often lead to weird effects like this, particularly if the display stretch is quite a strong one

See attached picture - are these the controls you are referring to? And are you saying that i check the box in Live stacking option so to turn off display stretch when live stacking is enabled? But leave the "Display Histogram Strech" to the right/above the scope controls - ON?

[admin]

Hi,

yes, those are the controls - it certainly looks like you have the display stretch off, but since the on/off button is brand new in the beta, I would try turning it back on and then using the reset button to put the display stretch black/mid/white levels back to the defaults (0, 0.5, 1.0). It's possible that there is a bug with turning it off under some circumstances that I haven't worked out yet.

It still looks very much like an over-stretched image, so I would reset all the stretches (live stack and display) and see if that helps, then work from there.

cheers,

Robin

[Nittany]

Thanks. I think at 1 time, i had it on but then switched it off because i am not sure what i was doing - In all that it has been ON/OFF a few times and i think i messed it up.

I will reset both the stretches. When i read your first reply, i immediately fired up SC and was looking for the setting in Live Stacking. I was using the test camera and i was playing around with the stretch in live stacking and i did hit the reset on it and it cleared up the image. The image i replied with completely cleared up - so i think resetting both the stretches might be the way to go.

Thanks

[Nittany]

Thanks Robin. All worked out well with resetting the stretches and adjusting a few other things.

[oopfan]

Darned good guiding!

Not a bad result for only 21 minutes in Bortle 8 skies.

Brian

[Nittany]

Yep.....Really not bad result. Again thank you for all the help on this forum.

[admin]

Hi,

yes, a nice M51 for such a short exposure - good work

I would suggest looking at dark subtraction and slightly longer exposures (15s to 30s) as the next steps. 5s is quite short for the long focal length of an SCT, and dark frame might help reduce the slightly grainy look to the background that is often the result of slightly warm/cool pixels being smeared out in lines by drift as the stack builds up.

cheers,

[Nittany]

Thank you for the recommendation. Will need to read on dark subtraction, extending the exposure is easy win.