What Is This Shadow In The Image? - Forums

Topic starter

Nov 26, 2024 · Edited: Nov 26, 2024

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

Nov 26, 2024

Those are clouds.

Bill Meador

Nov 26, 2024

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

Topic starter

Nov 26, 2024 · Edited: Nov 26, 2024

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

Nov 27, 2024

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

Nov 27, 2024 · Edited: Nov 27, 2024

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

Nov 27, 2024

Remark to SkyHoinar
In this case the darks (= calibration frames) are already included in the sub- .fits saved in S50 storage.

Ken Mascola

Nov 28, 2024

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

Frequent contributor

Nov 28, 2024

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

Topic starter

Nov 28, 2024 · Edited: Nov 28, 2024

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.