Antlia Triband RGB Ultra Filter - Forums

Topic starter

Sep 30, 2023

I just purchased this filter the Antlia Triband RGB Ultra Filter for use with my setup which includes a Canon 60D unmodded camera, Sky-Watcher 82ED Evolux and a 12" Meade Lx200 SCT. My question is;
I used the filter for the first time last night on the Double Cluster. I acquired 45sec subs with my Canon and my 82ED with the Antlia Triband RGB Ultra Filter. As each sub was coming in I noticed a blue cast to each image. I didn't think too much about it although it make me pause. Not knowing what to do to handle it I kept going and figured it would be fixed in post. I stacked the images in Siril and then went about processing the image in PixInsight. I've done the DBE, ImageSolver, and then SPCC, but I am noticing a blue halo which is very pronounced around each and every star. The Evolux is a doublet APO, but this filter made my image look as though it had been shot through a dime store Achromatic refractor. I'm at a loss as to what might be causing the issue and how to rectify it. I'm not sure if I was supposed to set a custom white balance, I use daylight all the time. Or just what the problem is. I was able to use SPCC in PI with the Canon and Antlia Triband RGB Ultra Filter selection for the RGB channels, but that didn't do anything for the blue halos around all my stars. My capture was around 3hr 45mins total. I'm not finding any info anywhere on how to shoot with this filter, if I need to do anything different, focus different or just what's going on. I can fix the star halos in Photoshop using the defringe tool in camera raw, but because the halo is so big it removes the blue but then makes the stars look extremely bloated. I've reached out to a couple of guys on here that have shot with it with OSC, but no answers yet. So I'm reaching out to the entire community here. I've posted my results here. Oh and I did use a batonov mask to focus the scope, with the filter in place. I did a focus the scope without the filter on the camera, and when I put the filter on and remounted the camera I did have to refocus it, maybe that was my mistake, I'm just not sure. The stars do look out of focus and maybe that's the issue, so if that's the case how would I focus the camera using the filter, or without. Just have no idea.

Here is after DBE, SPCC, BXT before stretching or any fixes.

Horrible background I know, but this is autostretched.
Anybody got any ideas I'd sure love to know them, because I'm at a loss.

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Zak Jones

Sep 30, 2023

Hi Anthony,

What telescope did you use for this photo?

I have heard that doublet telescopes can cause chromatic aberrations like this, but since the Evolux 82ED has one ED element theoretically it should help reduce this.

My Radian 61 has this same issue too, which I only recently discovered after owning it for nearly 3 years. It's a triplet as well, but regardless, I will not be using it ever again for broadband imaging due to this, but when I use it for narrowband imaging there are no issues except for the occasional halo on some stars.

I don't think that the Antlia Triband RGB filter would be causing this, but I could be wrong. I have one but haven't had the chance to test it yet, but once I do I will definitely be reporting my findings.

Zak

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Anthony (Tony) Johnson

Topic starter

Sep 30, 2023

Zak Jones:
Hi Anthony,

What telescope did you use for this photo?

I have heard that doublet telescopes can cause chromatic aberrations like this, but since the Evolux 82ED has one ED element theoretically it should help reduce this.

My Radian 61 has this same issue too, which I only recently discovered after owning it for nearly 3 years. It's a triplet as well, but regardless, I will not be using it ever again for broadband imaging due to this, but when I use it for narrowband imaging there are no issues except for the occasional halo on some stars.

I don't think that the Antlia Triband RGB filter would be causing this, but I could be wrong. I have one but haven't had the chance to test it yet, but once I do I will definitely be reporting my findings.

Zak

I’ve taken numerous images with the scope and just a a few small halos once in a while but nothing to this extent. It’s the sky-watcher 82ED evolux. No reducer flattener was used. Yeah in looking at the shot closer I’m thinking the focus may have been off even though I used a bahtinov mask.

Zak Jones

Sep 30, 2023

Zak Jones:
Hi Anthony,

What telescope did you use for this photo?

I have heard that doublet telescopes can cause chromatic aberrations like this, but since the Evolux 82ED has one ED element theoretically it should help reduce this.

My Radian 61 has this same issue too, which I only recently discovered after owning it for nearly 3 years. It's a triplet as well, but regardless, I will not be using it ever again for broadband imaging due to this, but when I use it for narrowband imaging there are no issues except for the occasional halo on some stars.

I don't think that the Antlia Triband RGB filter would be causing this, but I could be wrong. I have one but haven't had the chance to test it yet, but once I do I will definitely be reporting my findings.

Zak

I’ve taken numerous images with the scope and just a a few small halos once in a while but nothing to this extent. It’s the sky-watcher 82ED evolux. No reducer flattener was used. Yeah in looking at the shot closer I’m thinking the focus may have been off even though I used a bahtinov mask.

Hmm it's a tough one! It does look like your focus is spot on though.

Do you own the reducer for the Evolux 82ED? It helps flatten out the field of view and corrects for field curvature up to APS-C sized sensors. It is usually recommended that with those types of telescopes that you use the telescope's paired reducer to further reduce these effects.

If you do own it, I suggest you use it and try the same thing. If it's not the reducer/telescope it could well be the filter. I have heard on the very rare occasion that the Triband RGB filter can cause halos around bright stars, but not to the extent of other branded filters.

Zak

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Anthony (Tony) Johnson

Topic starter

Sep 30, 2023

Zak Jones:
Zak Jones:
Hi Anthony,

What telescope did you use for this photo?

I have heard that doublet telescopes can cause chromatic aberrations like this, but since the Evolux 82ED has one ED element theoretically it should help reduce this.

My Radian 61 has this same issue too, which I only recently discovered after owning it for nearly 3 years. It's a triplet as well, but regardless, I will not be using it ever again for broadband imaging due to this, but when I use it for narrowband imaging there are no issues except for the occasional halo on some stars.

I don't think that the Antlia Triband RGB filter would be causing this, but I could be wrong. I have one but haven't had the chance to test it yet, but once I do I will definitely be reporting my findings.

Zak

I’ve taken numerous images with the scope and just a a few small halos once in a while but nothing to this extent. It’s the sky-watcher 82ED evolux. No reducer flattener was used. Yeah in looking at the shot closer I’m thinking the focus may have been off even though I used a bahtinov mask.

Hmm it's a tough one! It does look like your focus is spot on though.

Do you own the reducer for the Evolux 82ED? It helps flatten out the field of view and corrects for field curvature up to APS-C sized sensors. It is usually recommended that with those types of telescopes that you use the telescope's paired reducer to further reduce these effects.

If you do own it, I suggest you use it and try the same thing. If it's not the reducer/telescope it could well be the filter. I have heard on the very rare occasion that the Triband RGB filter can cause halos around bright stars, but not to the extent of other branded filters.

Zak

I don’t own it but have given thought to buying it. I’d be hard pressed to think that would fix this problem, but it would only be a positive addition to my astrophotography kit. I may try this filter tomorrow night with my 12” SCT and see what it does. Just very perplexing.