19 replies to this topic

[hornjs]

I have this weird blooming artifact in my entire afternoon run of animation images.  Not sure what is causing it or how to fix it.  

Equipment:  Omni 120xlt, quark chromosphere, player one erf, zwo 432

Skies were clear with average to above average seeing.  

Didn't do anything different than usual other than 8bit capture rather than 16.  
gain was 205 and exp 6.5s, again usual Ha settings for me

Other images from this setup look fine (surface features etc)

I did take flats right before this and the flats calibrated nicely on surface detail.  (I know lesson from before is calibrate flats separately from capture but i didn't listen did I).  

 

Edited by hornjs, 28 May 2024 - 01:33 AM.

[rigel123]

I get a similar effect at times particularly when trying to manipulate the images with portions treated as positive and others as inverted and I often wonder if there are some high, interfering cirrus clouds that aren’t obvious before that mess with the background sky.  We are stretching the image tremendously to highlight the proms and much less so on the surface so the effect is all on the background of the sky.  

[C0rs4ir_]

This is why 12 bit imaging makes sense sometimes. You are running out of dynamic range here.

Edited by C0rs4ir_, 28 May 2024 - 08:11 AM.

[hornjs]

I could see it on the preview on sharpcap if I move the histogram slider to the left.  It didn't change with time.  Same pattern.  Wasn't sure if it was going to be in the final images but sure enough it was.

 

I get a similar effect at times particularly when trying to manipulate the images with portions treated as positive and others as inverted and I often wonder if there are some high, interfering cirrus clouds that aren’t obvious before that mess with the background sky.  We are stretching the image tremendously to highlight the proms and much less so on the surface so the effect is all on the background of the sky.  

[rigel123]

I could see it on the preview on sharpcap if I move the histogram slider to the left.  It didn't change with time.  Same pattern.  Wasn't sure if it was going to be in the final images but sure enough it was.

Interesting, I’ll have to watch for that

This is why 12 bit imaging makes sense sometimes. You are running out of dynamic range here.

Wouldn’t the same pattern still be there just a bit smoother?

[C0rs4ir_]

Interesting, I’ll have to watch for that

Wouldn’t the same pattern still be there just a bit smoother?

If its clouds or reflections yes.

[rigel123]

If its clouds or reflections yes.

I am guessing it may be some sort of reflection since it seems to stay static as he describes.

[hornjs]

As it was happening it seemed like an area that was somehow over exposed.  My suspicion is flat related.  When I take flats on the 120xlt, i do it on the center on the sun to take them

so manybe as I am viewing on the limb and area that was being corrected is adjusting what is supposed to be pure black into an overexposed area.

It is weird though because I have taken animations with the same flat process before with this not happening.  I suppose that for limb animations I should skip the flat process? 

 

I am guessing it may be some sort of reflection since it seems to stay static as he describes.

[ch-viladrich]

Did you use AutoStakker ? With local or global choice ?

[SgrB2]

Look at the camera sensor optical window just to make sure

it's clean.

[hornjs]

Did you use AutoStakker ? With local or global choice ?

Good question I will double check.  Again I was seeing this in sharpcap before the autostakkert step but will double check this setting

Look at the camera sensor optical window just to make sure

it's clean.

I took the rig apart last night and double checked all surfaces for smudges or fogging etc.  Didn't see any on the quark surfaces, erf, or camera sensor window.  

[ch-viladrich]

Sorry, I've read too fast. You've already said you had the problem during acquistion.

So maybe an issue with the flat and/or the use of flat in Sharpcap ?

[hornjs]

So just set up again today with same equipment train.  It was a flat problem.  But not entirely.  The 8bit messed things up too.

Looks like when I switched to 8bit, it automatically converted me to AVI capture.

So today, while in 8 bit, if I turned off flats the problem went away, but still had uneveness due to etalon (quark)

When I switched back to 16bit (and back into SER capture) the flat worked great without affecting the background.  

Thanks for all your help. 

 

Now if I could only figure out how to salvage 6hrs of files from yesterday 

 

Sorry, I've read too fast. You've already said you had the problem during acquistion.

So maybe an issue with the flat and/or the use of flat in Sharpcap ?

Edited by hornjs, 28 May 2024 - 03:01 PM.

[T~Stew]

I see this a lot, when trying to stretch things to the limit. Have not tested 8 bit vs full to see if it makes a difference. I figured it might have to do with the quality of the Quark... sure it looks clean on each end but if you look through it open (no eyepiece) at the sun I can usually see all sorts of optical imperfections in it. 

 

Its very apparent in this animation https://www.astrobin.com/eoimgq/ if its like yours. That was my first animation.  I really stretched the curves a lot there to bring out all the faint plasma surges. it moves around since the scope tracking was not perfect but the software stabilized on the sun.

Edited by T~Stew, 29 May 2024 - 09:48 AM.

[hornjs]

Great video Stewie.  Were you using flats?  Were you in 8bit mode?  That was what did it for me was going back to 16

I see this a lot, when trying to stretch things to the limit. Have not tested 8 bit vs full to see if it makes a difference. I figured it might have to do with the quality of the Quark... sure it looks clean on each end but if you look through it open (no eyepiece) at the sun I can usually see all sorts of optical imperfections in it. 

 

Its very apparent in this animation https://www.astrobin.com/eoimgq/ if its like yours. That was my first animation.  I really stretched the curves a lot there to bring out all the faint plasma surges. it moves around since the scope tracking was not perfect but the software stabilized on the sun.

[T~Stew]

Great video Stewie.  Were you using flats?  Were you in 8bit mode?  That was what did it for me was going back to 16

Flats - yes, my Quark is quite poor without flats, I consider them essential.

8 bit - yes, else my frame rate took a big hit with the ASI432. With the 533 I wasn't noticing much of a hit and often do 16 bit there but I can't recall seeing a difference. 

 

So you are saying using flats was a major factor in the uneven background, thats kind of a requirement for me. But I'm confused whether you found 8 or 16 also to cause issue?

 

From my prior linked recording (a single capture)...

FireCapture v2.7.10 Settings
------------------------------------
Camera=ZWO ASI432MM
Filter=Halpha
Profile=Sun
Filename=Sun_100825.ser
Date=120423
Start=100802.676
Mid=100825.178
End=100847.681
Start(UT)=140802.676
Mid(UT)=140825.178
End(UT)=140847.681
Duration=45.005s
Date_format=ddMMyy
Time_format=HHmmss
LT=UT -4h
Frames captured=5400
FPS (avg.)=119
File type=SER
Binning=1x1
Data=Mono
ROI=1608x1104
ROI(Offset)=0x0
Shutter=8.000ms
Gain=270 (77%)
AutoExposure=off
AutoGain=off
Brightness=1
USBTraffic=80
Histogramm(min)=0
Histogramm(max)=118
Histogramm=46%
Noise(avg.deviation)=n/a
Limit=45 Seconds
Sensor temperature=43.1°C
Flat=ZWOASI432MM_1608x1104__8bit_Exp=10.00ms_Gain=270_T=39°C_Frames=50_2023-12-04_100330.flat

[hornjs]

Yeah Stewie the problem was the combination of 8bit AND flats (and maybe AVI as capture mode).  

With flat captured and ticked in the preprocessing section of sharpcap....

Background was blotchy due to some sort of correction problem?  I assume.

If I turned flats off the blotchy went away (I am viewing the image with histogram slider pushed left to see limb activity).

If I turned it back to 16 bit SER capture, flats did NOT affect the background at all.  It was nice to watch the experiment in real time. 

[T~Stew]

Yeah Stewie the problem was the combination of 8bit AND flats (and maybe AVI as capture mode).  

With flat captured and ticked in the preprocessing section of sharpcap....

Background was blotchy due to some sort of correction problem?  I assume.

If I turned flats off the blotchy went away (I am viewing the image with histogram slider pushed left to see limb activity).

If I turned it back to 16 bit SER capture, flats did NOT affect the background at all.  It was nice to watch the experiment in real time. 

I'll have to experiment. My usually hi-res setup switching to 16 bit drops me from 120fps to ~80 iirc. And not using flats looks kind of crappy. But if it makes that background gradient go away it might be worth it, at least with proms over the limb shots with dark background. Thanks for this info!

[hornjs]

No problem!  I haven't found a huge problem on my zwo432 by using 16 bit.  I usually don't do an ROI for an animation as I will crop it later.

As an example I am doing an animation right now and using 5ms and have an fps around 90.  Fine for the 500 frames every 20sec.  

If you do ROI then it will of course be faster.  

I'll have to experiment. My usually hi-res setup switching to 16 bit drops me from 120fps to ~80 iirc. And not using flats looks kind of crappy. But if it makes that background gradient go away it might be worth it, at least with proms over the limb shots with dark background. Thanks for this info!

[astroflak88]

That means you lost some data and the image you are trying to manipulate is too compressed file size wise due to loss of data.