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Question about filter sizes

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9 replies to this topic

#1 vidrazor

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Posted 13 November 2019 - 12:15 AM

I see ads for astrophotography filters that you can get in "2-inch" size. I'm not exactly sure what that means. Its that a literal size at 50.8mm, or is it something else?

The reason I asked is because I've been eyeing this for a while, and wondering if "2-inch" would fit in this, as it would make my astrophography life a bit easier.

 

Thanks.



#2 Obi-Wan Kenewbie

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Posted 13 November 2019 - 02:39 AM

 I own a deo tech owl adapter myself for my old nikon lenses with a7s and i use both 48mm and 52mm filters with it. I guess you ll be alright with both sizes.

 

I think that 2" filter stands for m48 but i am not sure.


Edited by Obi-Wan Kenewbie, 13 November 2019 - 02:45 AM.


#3 Benach

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Posted 13 November 2019 - 03:32 AM

A 2" filter has a thread of M48x0.5. That is all to it. These filter drawers are too big for conventional astronomical filters. That could be solved with an adapter ring but I am not sure, have to measure it yourself, if they still fit in the drawer. However, there is a 2" filter (M48x0.5) filter drawer system on the market that doesn't require an adapter. Details can be found here: https://www.gerdneum...den-system.html



#4 DubbelDerp

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Posted 14 November 2019 - 08:53 AM

Not to nitpick, but I believe that the standard 2" filter is M48x0.75 pitch.



#5 the Elf

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Posted 14 November 2019 - 10:56 AM

All sorts of pitch are used. Here is a compatibility table. The text is German but Google helps...

http://www.svenwiens...atstabelle.html

Baader also made a long research to find something that matches most eyepieces.

More to transgoogle:

http://www.rudolf-re...tergewinde.html


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#6 vidrazor

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Posted 14 November 2019 - 06:00 PM

Thanks for your replies. Unless the thread is non-standard, a 52-48mm filter adapter should do the trick.

That filter drawer system appears to be for telescopes, the adapter I'm looking at allows me to use my Nikkors, as well as my Nikon-adapted AT60ED scope with my Micro 4/3rds cameras, without adding excessive weight and bulk.

#7 DubbelDerp

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Posted 14 November 2019 - 06:19 PM

I use a 52-48 step down ring to mount 2” astro filters to the front of my DSLR lenses. Then I use a step down ring specific to the lens objective to get it to 52mm. Works fine. The couple filters I have are both m48x.75, same pitch as most lens filter threads. The back of the AT60ED is also threaded for an m48x.75 filter thread, so it should work fine with that as well.

 

Which specific filter are you looking at getting? Mine are optolong, and both have this thread size. 



#8 vidrazor

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Posted 14 November 2019 - 09:45 PM

I use a 52-48 step down ring to mount 2” astro filters to the front of my DSLR lenses. Then I use a step down ring specific to the lens objective to get it to 52mm. Works fine. The couple filters I have are both m48x.75, same pitch as most lens filter threads. The back of the AT60ED is also threaded for an m48x.75 filter thread, so it should work fine with that as well.

Which specific filter are you looking at getting? Mine are optolong, and both have this thread size.

Thanks. I'm thinking hydrogen and oxygen. Don't really know which specific ones. It'll be for unmodded cameras for now.

Didn't think about the AT60ED, I can put it ahead of the flat field corrector and maintain my sensor distance.

The nice thing about the adapter is that the filter closer to the m4/3 sensor.

Edited by vidrazor, 14 November 2019 - 09:49 PM.


#9 DubbelDerp

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Posted 14 November 2019 - 10:04 PM

I went with the optolong l-enhance dual band, and am happy with it. Lots of others make essentially the same filter with slightly different band passes. Works really well with my modded canon DSLR. Only issue is that it blocks a lot of light, so it can be tricky to find a target at longer focal lengths. 
 

When I said the back of the AT60ED is threaded for a filter, I meant to say the back of the FLATTENER is threaded for it. It goes between the flattener and sensor, but doesn’t add any length. There’s a separate thread for it inside the nosepiece. 



#10 vidrazor

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Posted 15 November 2019 - 06:08 PM

Well, then it would be more practical to use the AT60ED via DEO-Tech OWL because I can preserve the distance to sensor. I can also just swap lenses as needed and maintain proper sensor distance. The filter to sensor distance should (hopefully) avoid any vignetting.

Good point about focus. Although I would ultimately focus through it, I can remove the filter for a preliminary focus setting.


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