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Is a Filter Wheel really practical with DSLR Astrophotography?

DSLR Equipment Imaging
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#1 Young Padawan

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Posted 02 October 2022 - 11:02 AM

Greetings,

 

Newbie questions. 

 

I'm trying to find out whether or not using a Filter Wheel with a DSLR will produce better image results (after post processing). The reason I'm asking because I remember watching a YouTube video that said using a filter wheel with like HA, Oxygen, Sulfur, or Light Pollution filters, is pointless. I can't find the video for the life of me now, but that was the gist. 

 

Question 1 - Does anyone have any knowledge on this topic? 

 

Questions 2 - Alternatively, are there any filters for a non-modified DSLR that will improve my results?

 

 

Clear Skies!

  


Edited by Young Padawan, 02 October 2022 - 11:03 AM.


#2 hollo

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Posted 02 October 2022 - 11:20 AM

Filter wheels are usually used by people shooting with mono cameras to change between Red/Green/Blue, or between narrowband filters. With a colour DSLR camera you're unlikely to be wanting to change filters often enough for a filter wheel to be useful. Also for many scopes it will be impossible to get the focus (back focus in particular) lengths correct with a filter wheel taking up space between your DSLR and your scope (dedicated astro cameras have the sensor much closer to the front which gives space to get this in).

 

I think the most likely filter you're going to want for a DSLR would be a dual-band filter. This is a narrowband filter that lets Ha and Oii through, and allows you to do narrowband imaging reasonable efficiently with your colour camera. People seem to disagree on light pollution filters - I watched a YouTube by NebulaPhotos where he compared different ones, and I concluded the difference in the final images was too marginal to be worth the hassle! Others may have different opinions. I suspect it depends a lot on whether your local light pollution is mainly old sodium lights, or LEDs. If LEDs then don't bother.

 

I don't think there are other particularly useful filters for a DSLR, but am not an expert.

 

[edited to clarify it was me that decided LP filters not worth it, not NebulaPhotos]


Edited by hollo, 02 October 2022 - 11:21 AM.

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#3 bbasiaga

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Posted 02 October 2022 - 11:28 AM

On am unmodified DSLR you may no want to go narrower than a light pollution filter, or maybe OIII.  Not sure how much red sensitivity is left on an unmodded DSLR, so a dual hand may effectively cut you off there.  You could research the pass bands of each and see what makes sense. 

 

I have a Ha/Baader modded DSLR and just got a dual band filter.  The optolong L-enhance.  So far it's great.  Kills a ton of light pollution but gives a strong red signal still. 

 

Butaswas said, the R G B or multiple narrow band filters are for mono cameras.  The big advantage of color cameras is not having to use them!  Of course, there are drawbacks too.  But can still get good results with a dslr. 

 

Brian 


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#4 james7ca

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Posted 02 October 2022 - 11:29 AM

You might have some success in using one of the narrow, multi-band filters on your one-shot-color DSLR. But, that would work better on a sensor-modified camera that allows greater sensitivity in the red (for H-alpha emissions). The most common multi-band filters pass both Ha (red) and OIII (blue-green). But, these filters tend to be pretty expensive.

 

However, it's possible that you will NOT be able to use a filter wheel since most scopes have a limit on the available spacing between the rear of the scope and their point of focus (sometimes called backfocus). So, if you add a fitler wheel between the scope and camera you may not have enough inward travel on the focuser to reach infinity focus (a common problem with DSLRs since they tend to have a "lot" of space between their lens mount and the sensor itself, usually around 45mm or so, at least with a single lens reflex camera, much less with a mirrorless camera).


Edited by james7ca, 02 October 2022 - 11:32 AM.

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#5 17.5Dob

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Posted 02 October 2022 - 02:37 PM

There is no sense, and in all practicality, no way to use a filter wheel with a dSLR. From the start, there is no way to maintain your backspacing with a dSLR if you have a flattener, reducer, or coma corrector in your optical chain. You "might" be able to use one if you are imaging with a Petzval type refractor as long as you have enough focus travel. "Light Pollution" filters are generally a waste. They do not work for galaxies, clusters, or reflection/dark nebula because they block the same amount of light from your target as the actual LP and also cause moderate to very severe color shifts. You "might" see some slight improvement for emission nebula, but without a modded cam, it will be even "slighter".

The only filter worth using on a dSLR is a duoband filter, and to make use of them your camera needs to be modded, first.
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#6 bbasiaga

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Posted 02 October 2022 - 03:28 PM

There is no sense, and in all practicality, no way to use a filter wheel with a dSLR. From the start, there is no way to maintain your backspacing with a dSLR if you have a flattener, reducer, or coma corrector in your optical chain. You "might" be able to use one if you are imaging with a Petzval type refractor as long as you have enough focus travel. "Light Pollution" filters are generally a waste. They do not work for galaxies, clusters, or reflection/dark nebula because they block the same amount of light from your target as the actual LP and also cause moderate to very severe color shifts. You "might" see some slight improvement for emission nebula, but without a modded cam, it will be even "slighter".

The only filter worth using on a dSLR is a duoband filter, and to make use of them your camera needs to be modded, first.


I have an IDAS light pollution filter that doesn't have a bad color shift (or really any shift). I can't really image without it in my suburban skies. Bit the advice is good...beware not all LPR filters are created equal.
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