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Filters size for imaging camera

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#1 TareqPhoto

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Posted 30 May 2017 - 07:31 PM

Hi,

 

If i get one of those mono camera for imaging, and using a filter wheel, what size of filters should i get?

 

Does the size of filter depends on the wheel or the scope or the camera?

 

I am not sure which wheel i may get, are they all accommodating the same size of filters?



#2 mistateo

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Posted 30 May 2017 - 07:53 PM

There are tons of threads that go over filter/sensors/filter wheels in depth.  Generally speaking minimum filter size is directly related to the size of the ccd/cmos sensor and how far they are located from the sensor (for instance 1.25" filters will work up to a certain point and they are pretty much maxed out on the ASI 1600mm at f4/f5 YMMV located about 10-13mm from the sensor).  Larger sensors, or ones located further away need larger filters, like 36mm or 2" etc.  Filters are expensive as well, so if you upgrade to a larger camera, it is likely you will want to get appropriate sized filters to avoid vignetting.  1.25 inch filters are definitely not suitable for DSLR sized sensors, in my opinion.  You can do it, but with more unnecessary processing.  So you want to choose your camera first, then ensure your filter wheel will work in your optical train (can be tricky with some focal reducers etc), and keep potential camera upgrades in mind, otherwise you will buy a whole new set eventually.


Edited by mistateo, 30 May 2017 - 07:54 PM.


#3 TareqPhoto

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Posted 30 May 2017 - 09:23 PM

There are tons of threads that go over filter/sensors/filter wheels in depth.  Generally speaking minimum filter size is directly related to the size of the ccd/cmos sensor and how far they are located from the sensor (for instance 1.25" filters will work up to a certain point and they are pretty much maxed out on the ASI 1600mm at f4/f5 YMMV located about 10-13mm from the sensor).  Larger sensors, or ones located further away need larger filters, like 36mm or 2" etc.  Filters are expensive as well, so if you upgrade to a larger camera, it is likely you will want to get appropriate sized filters to avoid vignetting.  1.25 inch filters are definitely not suitable for DSLR sized sensors, in my opinion.  You can do it, but with more unnecessary processing.  So you want to choose your camera first, then ensure your filter wheel will work in your optical train (can be tricky with some focal reducers etc), and keep potential camera upgrades in mind, otherwise you will buy a whole new set eventually.

I said one of those mono dedicated cameras, so no DSLR, and most likely i am planning or aiming at ASI1600mm cool, so what do you say for this particular camera as filter size?



#4 mistateo

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Posted 30 May 2017 - 09:36 PM

 

There are tons of threads that go over filter/sensors/filter wheels in depth.  Generally speaking minimum filter size is directly related to the size of the ccd/cmos sensor and how far they are located from the sensor (for instance 1.25" filters will work up to a certain point and they are pretty much maxed out on the ASI 1600mm at f4/f5 YMMV located about 10-13mm from the sensor).  Larger sensors, or ones located further away need larger filters, like 36mm or 2" etc.  Filters are expensive as well, so if you upgrade to a larger camera, it is likely you will want to get appropriate sized filters to avoid vignetting.  1.25 inch filters are definitely not suitable for DSLR sized sensors, in my opinion.  You can do it, but with more unnecessary processing.  So you want to choose your camera first, then ensure your filter wheel will work in your optical train (can be tricky with some focal reducers etc), and keep potential camera upgrades in mind, otherwise you will buy a whole new set eventually.

I said one of those mono dedicated cameras, so no DSLR, and most likely i am planning or aiming at ASI1600mm cool, so what do you say for this particular camera as filter size?

 

Many have had success as fast as f4/f5 as stated above using 1.25" filters with the ASI 1600MM.  If you think you will use this camera forever, or never plan to go with faster f-ratios, 1.25 should work.  If you ever plan on a larger sensor, or a faster scope, you would be better off buying 36mm or even 2" filters up front depending on your budget constraints and imaging train requirements.

 

Here are a few threads that have hammered out this exact topic:

 

https://www.cloudyni...ther-questions/

 

https://www.cloudyni...s-with-asi1600/

 

https://www.cloudyni...-filter-advice/



#5 baron555

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Posted 31 May 2017 - 07:11 AM

I bought the 36mm filters just to have some headroom later on.



#6 TareqPhoto

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Posted 31 May 2017 - 08:50 AM

So it is like better to have bigger one to be in safe side?

 

I am not sure if the filter wheel can accept bigger, it means i should buy the filter wheel that can take bigger ones.

 

Thank you very much!



#7 TareqPhoto

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Posted 31 May 2017 - 09:15 AM

One last thing, when i look at filters option i do read something like that "unmounted", "Round", what does that mean? and which one i should get?



#8 TareqPhoto

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Posted 31 May 2017 - 09:23 AM

Sorry, the previous isn't the last, i apologize.

 

In the site where i read about the filter wheel description, it says:

 

"The distance between the filter and sensor is around 10mm when you connect it to ASI1600. So 1.25″ filters won’t have vignetting up to F5 focal ratio scope and 31mm filter won’t have vignetting up to F2 lens. Our new RGBL filters are recommended to work with ASI1600, it will offer nearly 1:1:1 RGB color balance."

 

I think i will never go for faster than F4, or maximum F2 if i am rich enough, so does that mean if i use 31mm i will be fine? and what is the difference between 1.25" and 31mm anyway?



#9 Stelios

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Posted 31 May 2017 - 10:03 AM

Unmounted means the filter is just a piece of glass. You attach it with three small screws (and likely smudge it in the process...).

 

Mounted means it's in a filter cage, just like almost all the filters you see advertised for visual use. The mounted filter just screws into the EFW.

 

I bought the 31mm *unmounted* filters with the EFW8. If I were doing it again, I would have bought the 1.25" filters, as the fastest I'm likely to ever get is F5.6 if I use an .8FR with my 115/805. 

 

It's silly to future-proof something like this, or way overthink it. I'd say if you are using fast scopes (F/4 or reduced to that) then get the EFW7 + 36mm filters. If you're using F6 and up, get the EFW8 + 1.25" mounted. 



#10 TareqPhoto

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Posted 31 May 2017 - 10:10 AM

Unmounted means the filter is just a piece of glass. You attach it with three small screws (and likely smudge it in the process...).

 

Mounted means it's in a filter cage, just like almost all the filters you see advertised for visual use. The mounted filter just screws into the EFW.

 

I bought the 31mm *unmounted* filters with the EFW8. If I were doing it again, I would have bought the 1.25" filters, as the fastest I'm likely to ever get is F5.6 if I use an .8FR with my 115/805. 

 

It's silly to future-proof something like this, or way overthink it. I'd say if you are using fast scopes (F/4 or reduced to that) then get the EFW7 + 36mm filters. If you're using F6 and up, get the EFW8 + 1.25" mounted. 

I am buying F5 scope sooner or later, and also i am planning to use my Canon lenses, mostly they have fast aperture, not sure if that is same as in the scopes, but i can go anywhere from F2 up to whatever, but if wide open then from F2 up to F5.6.

 

And because of what you said, i should be sure i won't go for faster than F6, but i can't see that coming at any time, if not this year then next year, if not next year then definitely in 2019, but if i am planning to spend a lot then getting a scope of F5 is just a matter of time, but let's say if i will force myself to stay with F5 only [or if i will use a reducer to put the scope nearly at F4] should i go with 36mm? Also how much that 31mm may cause issues with F5 or faster scopes?



#11 TareqPhoto

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Posted 31 May 2017 - 10:21 AM

So the only issue going with smaller will be the vignetting?

 

Can't we solve this problem by process?

 

Also if i take subs including flats and bias, aren't those giving nice results and eliminate vignetting too?

 

How bad it will be if i use smaller filters with faster scopes?



#12 Stelios

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Posted 31 May 2017 - 03:21 PM

"only"? Vignetting is an issue, and no, you can't fully solve it by process. Bias compensates for shutter noise. Flats do reduce vignetting, and of course you can always crop. But you won't be taking full advantage of your equipment. 

 

If you want to be as prepared for "anything" with the ASI1600MM-Cool, then get the EFW7 with 36mm filters. It only costs you $200 over the 1.25" mounted and only $100 over the 31mm unmounted. 


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#13 TareqPhoto

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Posted 31 May 2017 - 04:36 PM

"only"? Vignetting is an issue, and no, you can't fully solve it by process. Bias compensates for shutter noise. Flats do reduce vignetting, and of course you can always crop. But you won't be taking full advantage of your equipment. 

 

If you want to be as prepared for "anything" with the ASI1600MM-Cool, then get the EFW7 with 36mm filters. It only costs you $200 over the 1.25" mounted and only $100 over the 31mm unmounted. 

Ok, will consider it then, thanks.



#14 Marcelofig

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Posted 31 May 2017 - 10:30 PM

Of course, keep in mind that a 36mm LRGB/Narrowband filter set can be very expensive if you want a upgrade.



#15 mistateo

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Posted 01 June 2017 - 02:12 AM

What he said is true!  I still kick myself for not jumping on that ASI1600MM-C Gen 3 with efw and 36mm Baader LRGB + HA, OIII, SII set on here for $1500 recently.  That was truly a steal of a deal.



#16 TareqPhoto

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Posted 01 June 2017 - 07:47 AM

That is really a big investment, but after all i must go that route one day or another [sooner or later].

 

I will add the filters one by one, i will start with Ha then LRGB, O and S can wait.



#17 Ethanwyh

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Posted 18 September 2019 - 10:03 PM

Hi all, Was wondering if a spacing between the sensor and filter is at around 30-40mm, will it cause any vignetting?

 

Most diagrams usually show the MINIMUM backfocus distance from filter to sensor but will it really hurt/impact much if one were to palce the filter slightly further than the stated amount?



#18 plouto

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Posted 24 March 2021 - 03:33 PM

Unmounted means the filter is just a piece of glass. You attach it with three small screws (and likely smudge it in the process...).

 

Mounted means it's in a filter cage, just like almost all the filters you see advertised for visual use. The mounted filter just screws into the EFW.

 

I bought the 31mm *unmounted* filters with the EFW8. If I were doing it again, I would have bought the 1.25" filters, as the fastest I'm likely to ever get is F5.6 if I use an .8FR with my 115/805. 

 

It's silly to future-proof something like this, or way overthink it. I'd say if you are using fast scopes (F/4 or reduced to that) then get the EFW7 + 36mm filters. If you're using F6 and up, get the EFW8 + 1.25" mounted. 

Hi ,

 

I have the zwo ASI294mm pro camera with the new 1.25" Zwo filter set and the zwo EFW. I am thinking of getting the TS 150/750 Newtonian scope for galaxy season, with a x0.95 coma corrector which will drop the f ration down to 4.75 and the focal length to 717mm. Do you think I might experience vignetting with that setup?

 

I did some calculations. The clear aperture of the new ZWO filters is 26mm.I also measured them myself. With the astronomy tools site calculation with that scope and the 23.2mm image sensor of the 294MM i get a suggested filter aperture of 25mm. 

 

Thanks




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