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Filter Placement

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#1 vidrazor

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Posted 14 August 2019 - 02:31 AM

I have an AT60ED with it's flat field corrector. Is it be possible to place a filter between them? Are filter mounts readily available to do exactly this? How much of an aperture effect will this have?

Thanks.

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#2 sg6

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Posted 14 August 2019 - 03:12 AM

Assuming the AT and the WO are the same at the "narrow" end there are internal threads and the filter would screw into those. Appears to be a 2" fitting.

 

Not overly deep so I would say only 1 filter at a time.

 

Effect in transmission will depend on the filter. An OIII filter chops out 95% of the spectrum and passes only the OIII band area - if UHC then often OIII and Hb. Whereas an IR/UV cut will have little effect.

 

Other effect will be focus/distance. Thjat will change by approximately 1/3 the filter glass thickness. So a nice solid 3mm glass substrate will make a difference of 1mm.



#3 vidrazor

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Posted 14 August 2019 - 09:12 PM

Assuming the AT and the WO are the same at the "narrow" end there are internal threads and the filter would screw into those. Appears to be a 2" fitting.

 

Not overly deep so I would say only 1 filter at a time.

 

Effect in transmission will depend on the filter. An OIII filter chops out 95% of the spectrum and passes only the OIII band area - if UHC then often OIII and Hb. Whereas an IR/UV cut will have little effect.

 

Other effect will be focus/distance. Thjat will change by approximately 1/3 the filter glass thickness. So a nice solid 3mm glass substrate will make a difference of 1mm.

It measures what appears to be 52mm, as you can see below, but my 52mm filters "fall" in. Are there drop-in filter attachments that can be placed here?

What I meant by aperture is the consequence of narrowing the light passage at the reduction in diameter opening to accommodate the filter, unless of course the glass goes to the edge and the filter neatly screws on to the scope, and the corrector neatly screws on to the filter.

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  • 52mm.jpg


#4 the Elf

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Posted 15 August 2019 - 01:01 PM

What kind of camera do you use? How to you attach it? In case of a canon DSLR you can use the Baader protective T-ring that offers a special compartment for threaded and glass only 2'' filters. If you have a dedicated astro camera a filter drawer or a manual filter wheel might be a better option.



#5 vidrazor

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Posted 16 August 2019 - 10:06 PM

What kind of camera do you use? How to you attach it? In case of a canon DSLR you can use the Baader protective T-ring that offers a special compartment for threaded and glass only 2'' filters. If you have a dedicated astro camera a filter drawer or a manual filter wheel might be a better option.

At the moment I'm using an Olympus E-M10 Mk II M4/3  body with an adapter for Nikon optics. I also have full frame, APS-C, and 1-inch Nikon bodies. The AT60FF has a 48mm Nikon mount on it.

The problem I see with placing filter behind the corrector is that you need to maintain the proper distance to the focal plane for the corrector. Right now everything just happens to line up with the recommended 55mm distance. Hence my wanting to place filtration between the scope and the corrector, if this is possible.



#6 the Elf

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Posted 17 August 2019 - 02:05 AM

Understand. I agree to your conclusion, in front of the reducer seems the best solution. I'm using this thing to place my reducer inside the drawtube while everything is threaded:

https://www.teleskop...ussadapter.html

Inner diameter is 48mm = 2'' filter. There is a female to one side and a male to the other side. It will take a 2'' filter. Outer diameter is M68 and M63, see drawing:

 

riccardi.png

 

I was able to attach this to the draw tube end using a female-female ring plus more adapter. You see only the thin knurled outer ring here, marked by an arrow. The next ring to the right is the OAG front plate, the wider knurled ring to the left is the female-female and alas I needed some PTFE plumbing tape to match another male male ring inside to screw onto the drawtube.

 

riccardi2.JPG

 

Maybe this ring and some sort of adapters can help you to place the filter where you want it. Good luck!

 

BTW: the T-ring is the Baader with the filter compartment inside, but this is available for Canon only and wont help you.


Edited by the Elf, 17 August 2019 - 02:07 AM.



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