Televue Nagler 9T1 questions

[pavel_s]

Hi guys, I have just ordered second-hand Nagler 9mm type 1 (not sure whether made in Japan or Taiwan).

From the photos I already have, it seems there are no threads on the outer 2'' barrel, so I could not attach the EBX-2120 barrel extension. I'm curious whether the eyepiece will require focuser outtravel when used in 2'' mode?

Is it possible to swap the 2'' barrel with some other, that has threads?

Could you share some more photos of the bottom of your 9T1?

Edited December 12, 2023 by pavel_s

[John]

The T1 Nagler 9mm's seem to come in a number of designs depending on the production run. The very early ones (Japan made) were smooth sided with no eye cup and later ones (Japan first then Taiwan I think) had rubber grips and eyecups added. The barrel fitting has always been the hybrid 2 inch - 1.25 inch type but there were detail changes through the production runs.

The one thing that they all have in common is that the hybrid barrel (2 inch and 1.25 inch parts) houses the lower set of lenses so cannot be removed or replaced.

I can't find any data on their focal plane / field stop position although the Tele Vue specs page does have some information on these discontinued models at the bottom:

Tele Vue Optics: Tele Vue Eyepiece Specifications

Here are a Japan made 9mm T1 and a Taiwan made one (neither are mine) from the bottom to compare their barrel design. The Taiwan one (right) seems to have a threaded 2 inch skirt whereas on the Japan one (left) it's unthreaded. Sounds like yours is one of the earlier Japanese ones.

 

Edited December 12, 2023 by John

[pavel_s]

Thank you John for your explanation and link to specification. That helped me a lot about what to expect.

Additionaly, I have found the following picture on the web. It shows N9T1 with an adapter, that makes it exclusively a 2'' eyepiece. Is this thing available to buy or is it rather a DIY thing?

Edited December 12, 2023 by pavel_s

[globular]

If you want to make it 2" exclusive and have 48mm threads too, you could use one of these...

https://www.firstlightoptics.com/adapters/baader-low-profile-eyepiece-adapter-for-steeltrack.html

[John]

17 minutes ago, pavel_s said:

Thank you John for your explanation and link to specification. That helped me a lot about what to expect.

Additionaly, I have found the following picture on the web. It shows N9T1 with an adapter, that makes it exclusively a 2'' eyepiece. Is this thing available to buy or is it rather a DIY thing?

That looks like a DIY thing coupled with a 2 inch par-focalisation ring on the 2 inch section of the barrel. 

The disadvantage is that the DIY adapter does not enable the use of 2 inch filters whereas adapters such as the one that @globular links to above, to give you a 2 inch filter thread.

 

[pavel_s]

23 minutes ago, globular said:

If you want to make it 2" exclusive and have 48mm threads too, you could use one of these...

https://www.firstlightoptics.com/adapters/baader-low-profile-eyepiece-adapter-for-steeltrack.html

Thanks, but the problem with such adapter is it does not create a smooth continuation of the 2'' main section, while the diy thing does.

I do not expect to use filters at this eyepiece, I have Baader UFC filter changer.

Edited December 12, 2023 by pavel_s

[Louis D]

16 hours ago, pavel_s said:

I do not expect to use filters at this eyepiece, I have Baader UFC filter changer.

Okay, but supposing you did want to directly use 2" filters with it, you could use this 1.25" to 2" Step Up Ring attached to the 1.25" filter thread.

[pavel_s]

1 hour ago, Louis D said:

Okay, but supposing you did want to directly use 2" filters with it, you could use this 1.25" to 2" Step Up Ring attached to the 1.25" filter thread.

Thanks, but I cannot imagine using this thing in real world. It's the best way to break the filter.

[Louis D]

3 hours ago, pavel_s said:

Thanks, but I cannot imagine using this thing in real world. It's the best way to break the filter.

How so?

I'd say the best way to break a 2" filter would be to screw it onto the bottom of a 2" to 1.25" eyepiece adapter and then insert a long barreled 1.25" eyepiece into the adapter.

[Don Pensack]

Simply use a 2" barrel extender threaded to the skirt and you have a 2" eyepiece.

If the 2" skirt is not threaded to accept barrel extenders, then an attached adapter works.

The eyepiece is usable as 2" in base form, but it takes 1.25" filters.

[pavel_s]

A very interesting article about Naglers.

https://www.cloudynights.com/documents/naglers.pdf

[John]

43 minutes ago, pavel_s said:

A very interesting article about Naglers.

https://www.cloudynights.com/documents/naglers.pdf

Tom Trusock wrote a couple of other good peices on Naglers as well as that one:

CN Report: The Nagler Eyepieces, Part 1 - T1's, T2's, and the Nagler Zooms - Eyepiece Reports - Articles - Articles - Cloudy Nights

CN Report: The Nagler Eyepieces, Part II - The Type 4's - Eyepiece Reports - Articles - Articles - Cloudy Nights

I've owned Nagler T1's T4's, T5's and T6's over the years. No T2's. I only have the 31mm T5 now. I enjoyed the Naglers that I've owned in the past though 🙂

Edited December 16, 2023 by John

[pavel_s]

Finally, it has arrived after long journey from US to EU

I had already a short session with it on Jupyter and optically it's excellent!

But practically, when used in two inches mode and fully inserted, it required significant focuser outtravel as I expected. As is, it will be impossible to parfocalise it with the rest of my EPs collections.

I will try to visit local metal machinery company, whether they could machine a skirt extension from a block of aluminium.

[John]

A Tele Vue Hi-Hat 1.25 inch - 2 inch adapter would do the job:

You might be able to get something less expensive made for you though or there maybe a less expensive adapter of similar design ?

[Don Pensack]

I was just going to recommend the Hi-Hat adapter, but John beat me to it.