What Is This Shadow In The Image?

ZWO Seestar S50 Artifacts Help Needed
11 replies•436 views
Szijártó Áron avatar
Szijártó Áron avatar
I was attempting to process the Witch Head Nebula image with my SeeStar at dawn when I noticed an unusual shadow that appeared despite the enhancement. I'm not sure what is causing it. Is it something in the field of view, or could it be related to a calibration frame in the SeeStar processing? What could this strange shadow be below? Can anyone help me identify what might be causing this?
Well written Engaging
BigArtimon avatar
BigArtimon avatar
Those are clouds.
Bill Meador avatar
Bill Meador avatar
Looks like dispersed high altitude aircraft contrails or cloud bands………..had several pass over day before yesterday and a couple while I was imagining night before last.  Got luck and none ended up in my stack.
Szijártó Áron avatar
Szijártó Áron avatar
Bill Meador:
Looks like dispersed high altitude aircraft contrails or cloud bands...........had several pass over day before yesterday and a couple while I was imagining night before last.  Got luck and none ended up in my stack.

Is there a way to avoid that or remove it? Or there isn't?
And all I can do with that is just remove those frames.
Ralph avatar
Ralph avatar
Hello, the lighter parts seems to be for me as well high clouds. You may control the sub frames. I recommend to take more pictures with clear sky and stack the .fits with siril. For me it is the normal workforce with a siril Skript (can be found in the German forum astrotreff.de). I use the newest version 8c with recent sirik version - so more than 2048 images can be stacked. You will need some disc space but if everything works it is an almost fully automated process.
The fine tuning can be done im any photo software (I use luminar or gimp). To get rid of gradients that may come from the clouds you can use graxpert with AI model (very easy to use as well).
Good luck, with greetings from Goettingen - Ralph
SkyHoinar avatar
SkyHoinar avatar
It looks like clouds to me. I had that a couple of times, when the sky looked reasonably ok for the naked eye, but it was actually covered by very thin dispersed clouds or a kind of haze.
I don't know if there is an efective way to remove that; I doubt it. I prefer to simply remove the frames from stacking. I actually review manually all the frames before stacking. Not only the ligths, but also the calibration ones (it happened to me to get some weird artefacts in the stacked image due to a bad calibration frame).
Helpful
Ralph avatar
Ralph avatar
Remark to SkyHoinar
In this case the darks (= calibration frames) are already included in the sub- .fits saved in S50 storage.
Ken Mascola avatar
Ken Mascola avatar
agree with others. I have seen similar patterns and my scope was relatively low (~ 20 deg )  hard to detect cloud banding.  probably shows in most of your subs. you didnt include the date / time and coordinates of the image but if it was lower then thats what i would say.  also if the moon was up or about to come up or just set then moonlight reflecting off the upper cloud layers may account for this.
Tony Gondola avatar
Tony Gondola avatar
The bad frames do need to be removed from your stack. In Siril there would be a number of ways to do that, both manual and automatic. Frame culling is a very common thing to do. If not for coulds the maybe for guiding or just a few moments of really bad seeing. I almost never use 100% of the sub-frames I collect.
Szijártó Áron avatar
Szijártó Áron avatar
Ken Mascola:
Agree with others. I have seen similar patterns and my scope was relatively low (~ 20 deg )  hard to detect cloud banding.  probably shows in most of your subs. you didnt include the date / time and coordinates of the image but if it was lower then thats what i would say.  also if the moon was up or about to come up or just set then moonlight reflecting off the upper cloud layers may account for this.

The time when I tried to do that was during dawn its pretty much central European time, around 4 am and 5 am but wanted to do that during the night after 8 pm, but there was so something else too that I wanted to take frames as well, which only can, be seen around these times.  Also, the moon is currently about to enter its new moon phase as well it was at the waning crescent.
Seldom avatar
Seldom avatar
I see similar patterns when my scope is low. In my case it is tree branches.  Auto focus sharpens the branches right up.
ScottF avatar
ScottF avatar
Clouds is my guess—no way to fix it either, other than taking more frames. Deleting them is what I do.
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