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Antlia Quad Band AWFUL Halos help. Set up issue or bad filter?

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#1 LiquidMan

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Posted 26 February 2024 - 11:37 PM

Hey everyone, I hope you're doing well today!

 

I was gifted the Antlia Quad Band for Christmas. I was very excited to get out and use it after months of terrible weather, only to find it produces some of the NASTIEST halos I've ever seen...

 

I double checked filter orientation was correct following Antlia's instructions. My other filters do not exhibit the same issues. I've seen it recommended to flip the filter regardless of the side the anti reflection coating is on, but I'm not too sure how accurate that is. Unfortunately, I am unable to flip the filter inside my filter wheel due to its thickness. I am also unable to flip the filter wheel as I have a thin adapter currently stuck on one side, which prevents me from attaching  to my gear scope side, so I have not tested it flipped around.

 

Here's an example of the Horsehead at 30s exposures. One ~3hr integration and one individual sub. The massive halo around Alnitak is very faint in the individual subs, I did not notice it until after stacking. Any ideas on if I just got a bum filter, or do we think there's something else going on? I understand most filters will have halos around Alnitak, but this doesn't look normal to me when compared to others with the same filter, or any other filter in general!

 

Horsehead
Horsehead halo 30s exposure

Edited by LiquidMan, 26 February 2024 - 11:57 PM.


#2 sharkmelley

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Posted 27 February 2024 - 01:05 AM

The "halo" around Alnitak is pretty typical of microlens diffraction, probably within the sensor itself.


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#3 LiquidMan

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Posted 27 February 2024 - 01:08 AM

The "halo" around Alnitak is pretty typical of microlens diffraction within the camera.


Now that I’m looking at it a little closer, I do see a pattern in there…

Is there anything I can do to help reduce microlensing?

Edited by LiquidMan, 27 February 2024 - 01:13 AM.


#4 Tapio

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Posted 27 February 2024 - 01:26 AM

Now that I’m looking at it a little closer, I do see a pattern in there…

Is there anything I can do to help reduce microlensing?

Not really. It happends in bright stars. Your camera is one of the victims.

The pricey solution is to get a new camera...

 

Edit: one thing to minimize the effect is to remove stars before stretching the image. It seems that you haven't used it here.

StarXTerminator is a good tool for that.


Edited by Tapio, 27 February 2024 - 01:36 AM.

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#5 sharkmelley

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Posted 27 February 2024 - 01:27 AM

Unfortunately I don't know of anything that will help. Microlens diffraction is something you just have to live with on bright stars.


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#6 LiquidMan

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Posted 27 February 2024 - 01:38 AM

Well that sucks… I just found this thread on Astrobin when googling “ASI294MC Microlensing” where users speculate that it’s being caused by the fact that the Quad Band passes near infrared.

 

https://www.astrobin...e-halos/?page=1

 

The OP seems to have the same problem specifically with the Quad Band while none of their other filters cause this issue. None of my other filters, or old filters I no longer have, ever caused microlensing, so I’m thinking the Astrobin thread theory may have some weight to it. Shame, it’s a very nice filter besides this. The Crab Nebula on my Astrobin account was shot with the quad band, the only issue there was one small halo which was able to be mostly removed with my novice halo removal skills.


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#7 bobzeq25

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Posted 27 February 2024 - 01:46 AM

The filter is not known as being particularly bad with regard to halos.  It's certainly not _just_ the filter.  Other factors.

 

Processing.  For one thing,the data is stretched very hard, probably in an effort to get more dim detail.  Too hard, I think.  A tipoff is how good star color in the single sub changed to bad star color in the final image.

 

The camera is more a suspect than the filter.

 

The Horsehead is not a good target for judging halo propensity, it's pretty much a worst case scenario for halos.  How is the filter working on other targets?



#8 bobzeq25

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Posted 27 February 2024 - 01:50 AM

Well that sucks… I just found this thread on Astrobin when googling “ASI294MC Microlensing” where users speculate that it’s being caused by the fact that the Quad Band passes near infrared.

 

https://www.astrobin...e-halos/?page=1

 

The OP seems to have the same problem specifically with the Quad Band while none of their other filters cause this issue. None of my other filters, or old filters I no longer have, ever caused microlensing, so I’m thinking the Astrobin thread theory may have some weight to it. Shame, it’s a very nice filter besides this. The Crab Nebula on my Astrobin account was shot with the quad band, the only issue there was one small halo which was able to be mostly removed with my novice halo removal skills.

A carefully chosen IR cut filter may reduce the problem, while keeping most of the good qualities of the Quad.

 

The OP you refer to did a 300 second exposure.  That's pretty long, no doubt makes the problem worse.

 

Bottom line.  The halos can likely be significantly reduced.  IR cut filter.  Shorter subs.  Less agressive processing.

 

Camera replacement.  <smile>  Something with an integral UV/IR cut would be good.


Edited by bobzeq25, 27 February 2024 - 01:54 AM.

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#9 sharkmelley

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Posted 27 February 2024 - 01:51 AM

Yes, definitely you should cut out all IR light since it's a major cause of microlens diffraction. This is because the anti-reflection coating on the sensor cover slip are not designed for IR.

 

Sorry, I was unfamiliar with Antlia's quad-band filter and never imagined that it deliberately allowed IR to pass through..


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#10 LiquidMan

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Posted 27 February 2024 - 02:01 AM

The filter is not known as being particularly bad with regard to halos.  It's certainly not _just_ the filter.  Other factors.

 

Processing.  For one thing,the data is stretched very hard, probably in an effort to get more dim detail.  Too hard, I think.  A tipoff is how good star color in the single sub changed to bad star color in the final image.

 

The camera is more a suspect than the filter.

 

The Horsehead is not a good target for judging halo propensity, it's pretty much a worst case scenario for halos.  How is the filter working on other targets?

Seeing as I've never seen halos with any other filters I've used, my money is on the Quad Band being at least a bigger part of the problem in my set up. I've used the L-eNhance, IDAS LPS P2 and ALP-T on both scopes in my signature and none produced halos except the Quad Band.

 

It's definitely stretched pretty hard. I never had any intention on sharing the image once I saw the microlensing effect, so I stretched the crap out of it just to see what was able to be captured in the time I had on it.

 

In terms of other targets, I've only had the opportunity to shoot the Crab Nebula as well. The apparently typical problem star near it does produce a halo, but it honestly isn't terrible. Keep in mind, the crab was auto stretched with no other processing:

 
M1 Crab

 

 

Yes, definitely you should cut out all IR light since it's a major cause of microlens diffraction. This is because the anti-reflection coating on the sensor cover slip are not designed for IR.

 

Sorry, I was unfamiliar with Antlia's quad-band filter and never imagined that it deliberately allowed IR to pass through..

 

The strange thing is Antlia advertises the NIR pass as beneficial and recommends using it with cameras like the ASI294MC without integrated IR cut filters to take advantage of it... That's a pretty misleading statement from them.. The new IDAS GNB does the same thing. I don't particularly want to add an additional piece of glass to my image train, but I might try out the Quad Band with a good IR cut addition.


Edited by LiquidMan, 27 February 2024 - 02:09 AM.


#11 sharkmelley

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Posted 27 February 2024 - 02:09 AM

Personally I can't think of any good reason for wanting the IR.  It will wash out out the colour in your emission nebulae, reducing the signal-to-noise ratio.



#12 LiquidMan

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Posted 27 February 2024 - 02:19 AM

Personally I can't think of any good reason for wanting the IR.  It will wash out out the colour in your emission nebulae, reducing the signal-to-noise ratio.

I'll have to see if my family is able to get in contact with Agena Astro and see if we can set up an exchange for an Antlia Tri Band or similar at this point. That filter doesn't pass NIR and still offers the three most important band passes. I doubt it will be possible to exchange this far out from purchase, but might as well check.

 

Thank you for your help, I'd been googling haloing issues and what might cause them for a week or so. I would have never realized that was microlensing without your input!


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#13 bobzeq25

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Posted 27 February 2024 - 02:28 AM

Personally I can't think of any good reason for wanting the IR.  It will wash out out the colour in your emission nebulae, reducing the signal-to-noise ratio.

The NIR band is not for emission nebulae, there are essentially no emission lines there.  The theory is that things like galaxies emit some in the NIR, while there is little light pollution there.

 

And you know how big I am about theory.  (Ducks and runs for cover <smile>  )

 

More seriously I don't like so-called "light pollution" filters on galaxies in general.  They cut out a lot of the galaxy signal.


Edited by bobzeq25, 27 February 2024 - 02:30 AM.

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#14 LiquidMan

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Posted 27 February 2024 - 02:34 AM

The NIR band is not for emission nebulae, there are essentially no emission lines there.  The theory is that things like galaxies emit some in the NIR, while there is little light pollution there.

 

And you know how big I am about theory.  (Ducks and runs for cover <smile>  )

 

More seriously I don't like so-called "light pollution" filters on galaxies in general.  They cut out a lot of the galaxy signal.

I completely agree about using filters on galaxies. I can visibly spot the difference in images that were shot with vs. without a light pollution filter. Without usually looks more crisp imo. After your advice very early on, I only shoot galaxies with my UV/IR cut filter.


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#15 bbasiaga

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Posted 27 February 2024 - 09:54 AM

Seeing as I've never seen halos with any other filters I've used, my money is on the Quad Band being at least a bigger part of the problem in my set up. I've used the L-eNhance, IDAS LPS P2 and ALP-T on both scopes in my signature and none produced halos except the Quad Band.

 

It's definitely stretched pretty hard. I never had any intention on sharing the image once I saw the microlensing effect, so I stretched the crap out of it just to see what was able to be captured in the time I had on it.

 

In terms of other targets, I've only had the opportunity to shoot the Crab Nebula as well. The apparently typical problem star near it does produce a halo, but it honestly isn't terrible. Keep in mind, the crab was auto stretched with no other processing:

 
 

 

 

 

The strange thing is Antlia advertises the NIR pass as beneficial and recommends using it with cameras like the ASI294MC without integrated IR cut filters to take advantage of it... That's a pretty misleading statement from them.. The new IDAS GNB does the same thing. I don't particularly want to add an additional piece of glass to my image train, but I might try out the Quad Band with a good IR cut addition.

Its sort of a chicken/egg question.  None of your other filters let through the NIR.  Now that this one does, we see an interaction with the camera sensor and NIR light causing the halo/lensing.  So is it the filter's fault, or the camera's?  

 

Brian


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#16 LiquidMan

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Posted 27 February 2024 - 11:09 AM

Its sort of a chicken/egg question.  None of your other filters let through the NIR.  Now that this one does, we see an interaction with the camera sensor and NIR light causing the halo/lensing.  So is it the filter's fault, or the camera's?  

 

Brian

I see what you're saying. It seems this filter is just a poor pairing with my camera. Oh well!


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#17 Cryhavoc38

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Posted 27 February 2024 - 07:03 PM

So I also do quite a bit of imaging using the Antlia Tri Band RGB Pro filter, using the 294mc pro

The only object that gives me fits is the horsehead with Alnitak blooming out big time.

 

Not sure the issue is with your Quad Band.

I just think personally, that the Antlia's don't do well with that darn star in certain environmental conditions such as high humidity.

 

I've no real proof other than whenever I've imaged IC434 and its really humid outside, I get bloom

 

Here is an example..antlia tri band, 294mc pro, humidity 90%.

I was doing some initial setup imaging with the new scope to see where my back focus is.

this was comprised of 30 sec exposures.

 

gallery_440823_23717_2156643.jpg

 

 

And this is the stacked file, auto stretched and graxpert ai bge applied.

no other processing done

you can see bloooom

 

gallery_440823_25678_13668091.jpg


Edited by Cryhavoc38, 27 February 2024 - 07:13 PM.


#18 kgb

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Posted 27 February 2024 - 08:27 PM

I get microlensing on really bright stars too and that is why I only use the Antlia Quad band on galaxies from my SQM 18.9 site. The NIR pass enables me to capture details that I couldn't if I used an UV/IR alone. If I am shooting emission nebula with a bright star in the field, I will usually reach for a tri-band or duo. The Antlia Quad is great if you are in moderate to heavy light polluted skies and need that NIR pass to capture galaxies, but there is a reason why Agena Astro says that they will not accept returns for halos.

#19 sharkmelley

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Posted 28 February 2024 - 01:34 AM

So is it the filter's fault, or the camera's?

Brian

The filter is acting as designed. The camera is behaving in a way that was probably not intentional i.e. I don't think the camera designer decided they wanted to produce "pretty" diffraction patterns around stars.

Edited by sharkmelley, 28 February 2024 - 01:46 AM.



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