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Etaloning effect with 2600MC and dual band filters

Artifacts Help Needed
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Dylan avatar
Dylan avatar

Hello all,

I’ve been trying to work out the cause of what seems to be an issue with an etaloning effect in my images recently. I’ve only been imaging for a little over a month now but this is the first time I’ve seen this. Doing some research, I’ve read that this is more common with with the 294 and similar cameras but haven’t seen others having this issue with the 2600. I’m currently working on a mosaic of Orion and don’t have this issue in earlier frames taken. The only difference I can think of is the moon has gotten closer since I started the project and is somehow contributing to this effect.

Any thoughts or advice would be greatly appreciated.

Here are two examples from two different days with two separate filters.
https://app.astrobin.com/i/hjv2m5

https://app.astrobin.com/i/ujoddp

imaging train used:
WO Redcat 91
ZWO OAG
Antlia 3nm duoband filters, HaO3 and S2O3 in a ZWO filter wheel
2600mc pro

bigCatAstro avatar
bigCatAstro avatar

How close to the Moon were you when taking those tests? It does appear that you’re getting Moon glow interference and/or light leakage.

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Dylan avatar
Dylan avatar

The Moon would have be right above or right below Pleiades on the two nights for my linked photos

bigCatAstro avatar
bigCatAstro avatar

Dylan · Jan 5, 2026 at 12:30 AM

The Moon would have be right above or right below Pleiades on the two nights for my linked photos

I see, alright. So, would you say that the area in the sky you were test shooting in was in that same region—either above or below the Pleiades?

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Dylan avatar
Dylan avatar

Oh sorry, I wasn’t clear in the original post. These images are of M78 and the other one is just adjacent to it

bigCatAstro avatar
bigCatAstro avatar

Dylan · Jan 5, 2026 at 02:16 AM

Oh sorry, I wasn’t clear in the original post. These images are of M78 and the other one is just adjacent to it

Got it, were you testing during the full Moon on 01/03 and, if so, at what time? I took a look at Stellarium during the 01/03 time frame and the Moon, though not too close, it’s still close enough to cause a problem throughout the night. That’s even with narrowband filters, at least in my experience. I try to shoot targets that are on the complete opposite side of the sky of the Moon if I’m going to try to image.

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Dylan avatar
Dylan avatar

Close too it, These two stacks were taken on 12/30 and 1/1 both between 8pm and 3am. I expected to get some extra glow from the moon, but the Etaloning took me by surprise and I just wasn’t sure what to blame it on.

bigCatAstro avatar
bigCatAstro avatar

Dylan · Jan 5, 2026 at 02:27 AM

Close too it, These two stacks were taken on 12/30 and 1/1 both between 8pm and 3am. I expected to get some extra glow from the moon, but the Etaloning took me by surprise and I just wasn’t sure what to blame it on.

Based on my review in Stellarium, my educated guess would be that the Moon is the likely culprit. Your other photos were taken with the same set-up, right?

Dylan avatar
Dylan avatar

Yeah, all my equipment is identical in my all my photos other than the galaxies being shot without a filter. But, that was the answer I was hoping to hear.

When I get a chance I kinda want to pick two targets in a night, one close to the moon and one far, and shoot them for an hour or two each and see if its more prominent with the object closer to the moon.

I really appreciate your input!

bigCatAstro avatar
bigCatAstro avatar

Dylan · Jan 5, 2026 at 03:21 AM

Yeah, all my equipment is identical in my all my photos other than the galaxies being shot without a filter. But, that was the answer I was hoping to hear.

When I get a chance I kinda want to pick two targets in a night, one close to the moon and one far, and shoot them for an hour or two each and see if its more prominent with the object closer to the moon.

I really appreciate your input!

Yeah, that’s a good idea to test and experiment with.

I go by the old advice and also avoid imaging when the Moon is at 50% or greater in illumination. It creates all sorts of weird gradients, it can expose all the imperfections with your imaging train, and really washout narrowband DSOs.

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andrea tasselli avatar
andrea tasselli avatar
Well, well, well. I reckon the old advice is to shoot no closer than 3 hours from the Moon, regardless of filters.
bigCatAstro avatar
bigCatAstro avatar

andrea tasselli · Jan 5, 2026 at 09:56 AM

Well, well, well. I reckon the old advice is to shoot no closer than 3 hours from the Moon, regardless of filters.

😆 Yes, you’re right!