RGB filter reflections from bright stars - Forums

Topic starter

Nov 26, 2020

Hi - I just started processing some of my RGB data captured over the past few weeks using the ZWO RGB "optimized for ASI 1600" filters.

As I researched, I now understand I may be dealing with expected performance with very low cost filters, but though I'd share my experience here for others. I'm open to advice if others have seen this and resolved it.

I've attached 2 items for reference:
- First is a processed M45 where you can see the red/green flares / reflections pretty easily below.
- I've also linked to a PixInsight Blink video of 60 raw (registered & stretched) photos so you can see the glare / reflection moving along with the scope throughout the evening.

I haven't used these filters too much yet, but I didn't have any issues with them on M31/M33.

Am I missing something obvious or is it safe to assume these filters aren't suitable for directly capturing bright stars?

Thank you,
John

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Aaron Hakala

Nov 26, 2020

So I could not see the video (I could not get it to play?) If the reflections change positions across the frames. That seems like a nearby light shining into your telescope? I have never seen a reflection like that before from any filter.

John Mart

Topic starter

Nov 27, 2020

Thanks for the feedback Aaron. I replaced the video of the BLINK mentioned above with a GIF below. should be faster to load and easier to see.

The gif below contains calibrated & auto STF data (not registered). The glare spots seem to move slightly as the telescope dithers over the 1hr of images below.

appreciate if anyone else has seen anything like this before. The usual glare spots from filters from other posts seem to be circles over the bright light source. This is quite different to me, but not unlike a sun-flare spot with a typical DSLR camera..

Thank you for looking,
John

Aaron Hakala

Nov 27, 2020

That reflection does not look like it’s from the stars. Sure seems like stray light getting into image train from somewhere. I can see (what I call normal reflections) around the bright stars, I also have the ASI1600 and get the same kind of reflection pattern around bright stars. The additional reflection obviously moves as the mount moves changing position relative to the stars. Good luck finding out source of the reflection!

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Elmiko

Nov 27, 2020

I agree with Aaron. If it was glare from the stars then it would follow the stars. Looking like you are getting light intrusion on your main objective. Or perhaps, some light leaking in somewhere on the optical train.

Lars Stephan

Nov 27, 2020 · Edited: Nov 27, 2020

I think:
reflection area 1 is from Alkyone
reflektion area 2 is from Merope
reflektion area 3 is from Maja

When you draw a line from the reflektion to the star, then all lines will cross in one point.The further a star is from the intersection in the center, the further its reflection is from the center.

And there are always two reflections on the lines - a smaller and a larger spot.

CS Lars

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