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 Post subject: Clever Design?
 Post Posted: Wed Oct 18, 2017 10:59 am 
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Joined: Thu Jun 02, 2016 10:17 am
Posts: 20
I have bought the Nikon to asi 1600 adapter. "Nikon-T2 Adapter suitable for all ASI cameras"
It has variable length and can take a filter inside.
However, when I put an IR cut filter inside I had to increase the length to the point where the adapter is too long for a Nikon lens to focus to infinity.
What can I do?

.....who thought of such a "clever" design??

Ross.


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 Post subject: Re: Clever Design?
 Post Posted: Fri Oct 20, 2017 1:25 am 
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Joined: Thu Feb 21, 2013 2:51 am
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you can add T2 spacer

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 Post subject: Re: Clever Design?
 Post Posted: Fri Oct 20, 2017 10:45 am 
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Adding a T2 spacer will only make the problem worse!
With a filter enclosed the adapter is already too long to allow the Nikon lens to focus on infinity.


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 Post subject: Re: Clever Design?
 Post Posted: Wed Oct 25, 2017 6:32 am 
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add a filter usually increase the focal distance
so you need some spacer to make it focus

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 Post subject: Re: Clever Design?
 Post Posted: Tue Oct 31, 2017 10:37 am 
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I do not understand how adding a spacer will bring the lens to focus when the filter has already made the adapter too long.
Adding a T spacer would only make the problem worse.

Ross.


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 Post subject: Re: Clever Design?
 Post Posted: Wed Nov 01, 2017 1:48 am 
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Ross G wrote:
I do not understand how adding a spacer will bring the lens to focus when the filter has already made the adapter too long.
Adding a T spacer would only make the problem worse.

Ross.


adding one filter make the focus distance longer
and it depends on the filter thickness
it will increase about 1mm if the filter is 3mm thick
so you need to add one 1mm spacer to reach focus

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 Post subject: Re: Clever Design?
 Post Posted: Fri Nov 24, 2017 10:12 am 
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With a filter in the Nikon T2 adapter, the adapter is too long so the Nikon lens cannot focus to infinity.
Adding T extensions will make the situation worse.
You do not seem to understand the problem!

Ross.


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 Post subject: Re: Clever Design?
 Post Posted: Mon Nov 27, 2017 1:14 am 
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Joined: Mon Nov 27, 2017 1:08 am
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When you add a filter, you should compensate by adding a spacer/washer for about 1/3rd of the filter's thickness. Remember, a filter slightly bends the light path, so the back focus length is effectively decreased.

So for a Nikon lens, where you need 46.5mm back focus, you should set the adapter thickness to 46.5mm + 1/3rd filter thickness. Like Sam mentioned many popular filters are 3mm thick, so you should add 1mm to compensate. Hope this helps.


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 Post subject: Re: Clever Design?
 Post Posted: Mon Nov 27, 2017 11:45 am 
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Hello,

Thank you for trying to help but I think you miss the point as well.
I do understand that you have to compensate for the thickness of the filters.
However, my problem is that I have too much thickness.
I cannot get the lens to focus to infinity because the adapter is too long.
The ASI Nikon adapter I have is the variable length one.
When you insert a 2" filter in the middle of it, you are forced to extend it to its longest length to accommodate the inserted filter.
This length combined with the 17.5mm nosepiece to chip distance of the ASI 1600, results in a distance far greater than the 46.5mm back focus of a Nikon lens.
I therefore cannot focus a Nikon lens to infinity.....nothing to do with the thickness of the filter.

I have just noticed on their website that ZWO have changed the design of their Nikon T2 adapter.....maybe they understand my problem more than they make out!

Lets see.....is that version 3 of the Nikon T2 adapter? Nearly catching up to the ASI 1600MM which is now at Version 4!

"Clever Design" seems to be the motto of this company!

Ross.


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 Post subject: Re: Clever Design?
 Post Posted: Mon Nov 27, 2017 7:28 pm 
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Ross, thanks for the detailed explanation. It makes sense to me now. You're right, I misunderstood your point.

I have the same adapter you mentioned - the adjustable one. I wanted to use it with my ASI071 which has 17.5mm sensor distance as well. I was able to set the adapter length to 30mm, and including my 3mm thick filter inside, the effective length was 46.5mm. I was able to focus to infinity without any problems. But I did have bad tilting issue, so I stopped using it.


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