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Televue eyepiece adapter

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#1 Garbagecan

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Posted 22 February 2018 - 01:08 PM

I bought a Televue eyepiece adapter for my older field model scope so that I can use other 1 1/4 eyepieces that I have.  Here's the link:

 

https://www.amazon.c...adapter questar

 

But, I've run into a problem.  The Televue adapter will not lower my eyepieces close enough to the scope body for the finder to be in focus.

 

When looking through the scope of course, there is no problem because of the main scope focus knob.   The original Brandon and its finder focus work fine.

 

I do have a single eyepiece that works.  It is an old ortho eyepiece of uncertain origin.  The only Televue eyepiece I have is a 2 inch (with 1 1/4 adapter) 16mm, and it is too far

away from the scope to have the finder come into focus.

 

So the question is whether others have had similar problems with the Televue adapter, or does the adapter only work with Televue eyepieces?

 

Wayne



#2 Mattimac

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Posted 22 February 2018 - 01:48 PM

Here is a link to the Tele Vue page that explains which TV eyepieces will come to focus in the finder and the telescope.  I'd put my money on the Delos.  Good luck!

 

http://www.televue.c...id=60&Tab=_Q3.5


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#3 Garbagecan

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Posted 22 February 2018 - 01:58 PM

Here is a link to the Tele Vue page that explains which TV eyepieces will come to focus in the finder and the telescope.  I'd put my money on the Delos.  Good luck!

 

http://www.televue.c...id=60&Tab=_Q3.5

Fantastic link.  I'm in the market for a new eyepiece or two and this gives an excellent assist in choosing.

 

Thanks

Wayne



#4 DAVIDG

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Posted 22 February 2018 - 02:51 PM

 I machined my down by about 1/16" so almost all the eyepieces in my collection especially a 25mm Clave will now come to focus with the finder.

 

                  - Dave 


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#5 Optics Patent

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Posted 22 February 2018 - 04:32 PM

Does this have anything to do with the outer threads just below the shoulder on Questar eyepieces preventing full insertion?


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#6 JimK

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Posted 22 February 2018 - 04:41 PM

... So the question is whether others have had similar problems with the Televue adapter, or does the adapter only work with Televue eyepieces?

 

Wayne

The Questar finder mode is really using another "telescope" (an f/6.6, 4x16 or 7x16 monocular; my old post on this ==> https://www.cloudyni...al-information/ ), however the depth of focus, or ability to reach focus on "other" eyepieces, is very limited.

 

Another old post of mine (here: https://www.cloudyni...randon-oculars/ ) identified how some (then) relatively common eyepieces behaved with the finder (although it related to the "Questar finder", the "Televue finder" is very similar) -- others may have more comprehensive information.



#7 Garbagecan

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Posted 22 February 2018 - 05:00 PM

Does this have anything to do with the outer threads just below the shoulder on Questar eyepieces preventing full insertion?

My particular eyepieces all insert fully, but need to be a bit lower for finder focus.

However, with the adapter full screwed down, most of my eyepieces will not fully insert if a filter is screwed in the bottom.



#8 DAVIDG

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Posted 22 February 2018 - 05:03 PM

 The issue I had was that I couldn't have the finder in focus  when using the adapter  and  flip the mirror in place so the object was in focus when main optics was used. That is not too big of an issue when you use the scope at night but I do crazy things like observe the planets and bright stars in the daytime. So the finder must be perfectly in focus to see even Venus in it during the day. So by machining the  adapter down now I was able to have the finder in focus and the telescope in focus at the same time with many of my eyepieces, just like the original eyepieces work. 

 

                - Dave 


Edited by DAVIDG, 22 February 2018 - 05:21 PM.

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#9 Garbagecan

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Posted 22 February 2018 - 05:11 PM

I have been using a "workaround" to avoid the finder focus problem.

 

For astronomy, I use a Custom Brackets gimbal.  I've put together a bracket that clamps to the gimbal and clamps onto a Samsung S7 phone.

 

I pull up an app called SkEye on the phone and go into the indirect mode.  That allows the view to be offset from being directly perpendicular to the phone.

 

After sighting a known star in the Questar, I align the SkEye app to show the same star in the crosshairs on the phone screen..

 

From then on, I can search for any object and get a directional arrow from the app.

 

When I get time I'll post pictures of the gimbal and special bracket.



#10 Garbagecan

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Posted 22 February 2018 - 05:14 PM

 I machined my down by about 1/16" so almost all the eyepieces in my collection especially a 25mm Clave will now come to focus with the finder.

 

                  - Dave 

I had considered that but would have to send it out to get the work done.

I'm in the mood for a new eyepiece, so that's probably the route I'll take.



#11 RobertPettengill

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Posted 23 February 2018 - 09:16 AM

The Questar design favors eyepieces with a focal plane that is very low.  This is not an issue with the main telescope focus because of the large range of adjustment.  The finder telescope has a much smaller range of focus provided by the diopter adapter.

 

Questar makes a diopter adapter that accommodates both Questar eyepieces with the screw in Brandon thread and smooth 1.25" barrels.  I believe that the TeleVue adapter does not have the Brandon thread and may also sit the eyepiece slightly higher than the Questar adapter.  As a result there will be differences in the finder focus.

 

Observers who use the eyepiece focusing to achieve vision correction further complicate the compatibility with eyepiece focus.  The limited focussing range of the diopter adapter must accommodate both normal focussing range and any offset introduced by the users non-perfect vision.

 

I've summarized eyepiece compatibility reports from a number of sources in a table:
http://astronomy.rob...inderFocus.html

 

;rob


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#12 Garbagecan

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Posted 23 February 2018 - 12:27 PM

The Questar design favors eyepieces with a focal plane that is very low.  This is not an issue with the main telescope focus because of the large range of adjustment.  The finder telescope has a much smaller range of focus provided by the diopter adapter.

 

Questar makes a diopter adapter that accommodates both Questar eyepieces with the screw in Brandon thread and smooth 1.25" barrels.  I believe that the TeleVue adapter does not have the Brandon thread and may also sit the eyepiece slightly higher than the Questar adapter.  As a result there will be differences in the finder focus.

 

Observers who use the eyepiece focusing to achieve vision correction further complicate the compatibility with eyepiece focus.  The limited focussing range of the diopter adapter must accommodate both normal focussing range and any offset introduced by the users non-perfect vision.

 

I've summarized eyepiece compatibility reports from a number of sources in a table:
http://astronomy.rob...inderFocus.html

 

;rob

Thanks Robert. I'm new to the Q world with my older field scope.  Originally I thought the old scope was the problem, but I have one ortho eyepiece that works perfectly.

 

  I can confirm in your table that my Televue 16mm Nagler 2 doesn't have finder focus.   Same with my Celestron silver top 26mm plossl.

 

Wayne Price


Edited by Garbagecan, 23 February 2018 - 12:27 PM.


#13 JamesMStephens

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Posted 24 February 2018 - 09:24 PM

The current Questar adapter accepts standard 1.25" eyepieces so there is really no reason to get the Televue version.


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#14 Billydee

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Posted 24 February 2018 - 11:09 PM

James,

 

The Questar Diopter Corrector for Finder Focus and the Diopter Adapter was changed in late 1995 to accommodate all 1.25" EPs.  This does not change the problem with various non-Brandon EPs failing to coming into focus.  I think the Questar unit is better than the TV unit but it does cost more.

 

Bill



#15 JamesMStephens

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Posted 25 February 2018 - 01:08 AM

James,

 

The Questar Diopter Corrector for Finder Focus and the Diopter Adapter was changed in late 1995 to accommodate all 1.25" EPs.  This does not change the problem with various non-Brandon EPs failing to coming into focus.  I think the Questar unit is better than the TV unit but it does cost more.

 

Bill

Yep, I know that.  Correct.   Bearing this in mind why would anyone ever replace a current Questar unit with the TeleVue?  I did in the eighties when I decided that I didn't like the threaded eyepieces and wanted to replace my Questar Brandons with standard Brandons and also use other e/ps with the Questar.  If my original Questar adapter had worked with standard eyepieces I wouldn't have had any need for an after market replacement.  I've since replaced my TV adapter with a new Questar e/p adapter, it looks better and is built better.  And it's Questar!


Edited by JamesMStephens, 25 February 2018 - 01:11 AM.

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#16 Billydee

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Posted 25 February 2018 - 01:53 PM

James,

 

You are right on in every point.

 

Bill




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