Clever Design?

ross g

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.

Sam@ZWO

you can add T2 spacer

ross g

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.

Sam@ZWO

add a filter usually increase the focal distance

so you need some spacer to make it focus

ross g

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.

Sam@ZWO

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

ross g

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.

premk19

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.

ross g

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.

premk19

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.

Sam@ZWO

premk19 wrote:
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.

Is the adapter cause tilting issue?

we sold hundreds of this adapter and it must can reach focus with Nikon lens

premk19

Sam wrote:
premk19 wrote: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.

Is the adapter cause tilting issue?

we sold hundreds of this adapter and it must can reach focus with Nikon lens

Yes it must be the adapter. I can reach focus no problem, but stars in corners are bad and are slightly out of focus. I do not get this issue with the same lens on my D5300 dslr.

Sam@ZWO

premk19 wrote:
Sam wrote:
premk19 wrote: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.

Is the adapter cause tilting issue?

we sold hundreds of this adapter and it must can reach focus with Nikon lens

Yes it must be the adapter. I can reach focus no problem, but stars in corners are bad and are slightly out of focus. I do not get this issue with the same lens on my D5300 dslr.

maybe camera?

usually adaper should not have such issue

premk19

Very unlikely. I have used the camera on two other refractors and it works fine. No tilting visible. I think the weak point in the adapter is where the lens connects. It never felt as secure as it does on my Nikon DSLR.

ross g

Hello Premk19,

You are lucky that you can achieve focus. Maybe your filter is physically thinner than my standard 2" filters.

The tilt maybe because you are not screwing the front part of the adapter fully into the back part of the adapter because of the thickness of the filter.

The solution is to extend the adapter more. This will solve the tilt problem but then you may have my problem of the adapter being too long.

A temporary solution is to use a 1.25" filter screwed into the nosepiece of the ASI 1600 thereby not requiring a 2" filter in the Nikon T adapter.

Good luck.

Ross.