SharpCap Forums

No Robin. It was not my case.
It mess up from the beginning, without changing nothing.

Hi Robin,

Thanks for continuing to think about this.

I am fairly sure that I reset the stack after turning background/gradient correction on or off, but I will need a clear night to verify that did (or didn't) fix the jumping histogram. Right now, we have solid clouds for a few more days.

Is there any way that this could be related to the camera's driver? I noticed that Tiago appears to be using ZWO cameras, as are we. Is there anything the driver could be doing that might cause this behavior with certain cameras but not others? I have certainly upgraded drivers at least once in the past year. Just a thought. (We use a ZWO ASI 071MC Pro.)

--david

Hi,

I think it is unlikely to be the camera driver - if it was coming through at that level then you would see the background image brightness jump around from frame to frame when not stacking and we would have heard all about an issue like that!

Going back to the symptoms and 'jumping around'. Does the peak actually move around (as in randomly moves left and right), or is it more a gradual drift in one direction or the other?

cheers,

Robin

With me, usually start gradually (with large moves, not small) to the right and then starts moving left and right like crazy and if i adjust it moves again and again.
One day i even reinstalled the camera drivers, sharpcap, everything but it didn't change the behavior.
With the old background removal it even changed the background color to pink, green, and happened the same, when restarting the software, sometimes it didn't fix it when i started without the feature and i've restarted again. It's weird and the reason i never touch it again was because after happening it was hard to come back to "normal" again and made me loose time and gave me stress.
294MC camera, RAW16, Darks, short exposures.

Robin,

For me, it also jumps to the right, as if the mean is changing significantly.
I can't swear that it never jumps left, but I am sure it jumps to the right.

The jump is almost always enough to "spoil" the current stretch (i.e., you have to significantly move the black and midpoint to recover a viewable image.)
My recollection is that eventually it stops moving so much, and converges (?) on a stable shaped histogram.
But by then, the viewers are left with a disorienting process of watching the image look good, then bad, then good, then...

I don't use darks, and sometimes don't use flats. Makes no difference.
Happens with both stacking modes.
No subframe filters or sharpening or any other non-vanilla livestack setting is used.
Gain is usually pretty high - around 200 to 250 (ZWO ASI 071MC pro).
Cooling is on.
Connected via Alpaca to a Maestro telescope controller, and via ASCOM to a Moonlite focuser.
Windows 11
(This weekend is probably going to be clear - will attempt to get screenshots and/or movie)
(If I remember, I will save a set of subframes too.)

When it happens (rarely): shifting mid level always to the right.
Don't use darks or gradient removal.
Happens when high veil clouds.

This is getting weird. It just happened to me again and i had no gradient removal on. I had to restart sharpcap and took off the usb cable and reconnect the camera and it cleaned everything. Otherwise even the regular image without stacking was now weird, messed up.
It could really be that Roelb, and the gradient or background features for some reason boost that and trigger the issue.
I can't see any clouds but they may be there. Thin and invisible to me because during the day there were thin clouds all day. At night they became invisible to me. I was live stacking now with the 12" dob at f/3.75 and using ROI which turns all brighter. Much brighter.
I will not give up yet because i remember to also use the gradient removal and nothing happened, absolutely nothing.
My guess is that in a good seeing night may work. I will try it again with perfect seeing.
A solution to confirm could be connect also my allsky camera which can detect thin clouds.

Hi folks,

more useful info - varying thin cloud could possibly be the cause as if it starts to get a little thicker then the sky background will brighten and that will slowly pull the histogram peak to the right.

I will have a go myself the next time we get some clear skies, but if someone has the chance to capture a sequence of raw frame from live stacking that show the issue then I will happily investigate them.

cheers,

Robin

Hi Robin,

I captured some images last night that demonstrate the "jumping histogram" problem. I have ~10 fits files (31MB each) that when processed using the v4 "folder camera" should demonstrate the problem. How can I best share these fits files with you? Can you accept Dropbox links? If so, where should I post them?

I have a few ideas based on last night's imaging. It seems like the jumping is highly dependent on the strength of the signal. When I use very short exposures or low gain, and the target is faint, the jumping is much worse. On longer exposures with higher gain and brighter targets, the jumping goes away completely.

Nonetheless, the fits I mentioned above should demonstrate the behavior. I'll be happy to share them if you tell me how!

--david

Hi David,

yes, dropbox links are fine - you can post the link here or send it to me via the private message system here on the forums.

Thanks for taking the time to test

cheers,

Robin