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Binoviewer conundrum, could use some advice

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#1 CrazyPanda

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Posted 06 August 2019 - 12:29 PM


That combo of optics has given me some wonderful views, but I am craving more magnification.

 

The fundamental problem is that the BVer does not have individually adjustable diopters, only the eyepieces themselves do. As I prefer observing without glasses, I *need* individual diopter adjustment of some kind. I've tried pulling an eyepiece out part way, and the reality is it's just too finicky to do that accurately (holding it, tightening down the locking collar etc), so proper diopter adjustment is a must-have.

 

Given the BVer doesn't have diopter adjustments, my options are a bit limited as I have to stick with the Zeiss eyepieces I currently have and then use different barlows to change magnification, but a 4x powermate is a bit too much power for my skies. I would need something between 2.5x and 3x. And ideally something I can use the quick bayonet mount to switch between.

 

An alternative is to sell the BVer and go with something like a Denk which does have individual diopter adjustment as well as a powerswitch. But that's going to be more costly, and I've heard it doesn't hold collimation quite as well as the Zeiss-based BVer I currently have.

 

Any thoughts?


Edited by CrazyPanda, 06 August 2019 - 12:30 PM.


#2 ngc7319_20

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Posted 06 August 2019 - 01:08 PM

Could one or both eyepiece holders be swapped out for one of these focusing units from Baader?  Thats what I've done on my Zeiss Mk 4.

https://www.highpoin...older-eyehold-2

 

Another approach is to make a variable 3x - 4x by using one of these cheap Chinese 2" Barlow lenses.  They have standard 48mm (2" filter threads) on both ends so can be threaded on the front end of the bino.  At least for my setup it gives about 3x when threaded directly to the bino.  And then you can add some 48mm extension tubes to move the Barlow lens farther out and increase the power to around 4x.

 

The lens unit can be unthreaded from the Barlow assembly, and threaded directly to the bino, assuming it takes standard 48mm / 2" filters.  Probably the same 2" Barlow is sold by many vendors:

https://www.highpoin...apter-zhue006-1

 

And then you can get more power by adding these 48mm x 1" long threaded extension tubes:

http://www.scopestuff.com/ss_epe2.htm

 

If the bino does not accept 2" filters on the input end, you might need a part like this T2-16 to make the T2 to 48mm connection:

http://www.alpineast....htm#Nosepieces

 

BTW I have not had good luck with the TeleVue 4x PowerMate.  I find a very large spherical aberration when used around F/4.2 in my scopes. Apparently is does not like having the focal plane so far back as the light path through the bino.


Edited by ngc7319_20, 06 August 2019 - 01:44 PM.


#3 CrazyPanda

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Posted 06 August 2019 - 01:22 PM

Could one or both eyepiece holders be swapped out for one of these focusing units from Baader?  Thats what I've done on my Zeiss Mk 4.

https://www.highpoin...holder-eyehold-

I think the eyepiece holders are mounted with male threads, so the female thread of that focuser you linked to might not be compatible. I'd have to take a closer look.



#4 ngc7319_20

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Posted 06 August 2019 - 01:42 PM

I think the eyepiece holders are mounted with male threads, so the female thread of that focuser you linked to might not be compatible. I'd have to take a closer look.

Yes those focusing holders have female T2-threads. 

 

Maybe you can use a gender changing ring like this T2-26.  It has male T2-threads on both ends:

http://www.alpineast...eaded Couplings

I guess it will depend on what threads the bino has on the output end.  Maybe Dennis can help you also.


Edited by ngc7319_20, 06 August 2019 - 01:45 PM.


#5 Eddgie

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Posted 06 August 2019 - 02:06 PM

 

 

Any thoughts?

 

Get an inexpensive pair of parfocalizing rings.  Pull out the eyepeice(s) to the proper distance then lock down the parfocalizing rings.

 

Now, is all you have to do is insert the eyepieces.

 

If you have several pairs of eyepieces, you would need a pair of rings for each but Parfocalizing rings are $10 apiece.

 

Another example of why I recommend power switch systems for dobs.  One pair of eyepieces, three powers. 


Edited by Eddgie, 06 August 2019 - 02:11 PM.


#6 Eddgie

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Posted 06 August 2019 - 02:16 PM

 

  • I've heard it doesn't hold collimation quite as well as the Zeiss-based BVer I currently have.

 

Any thoughts?

 

I have owned two pairs of Denks and one Binotron.  I never had any problem with them holding collimation.  I am not saying what you heard is not true, what I am saying is that it may overstate the problem.   All of the Denks I have owned had good collimation.

 

The collimation on the B27 is very easily adjusted by the customer, and the only tool needed is supplied with the binoviewer if you should ever feel the need to change collimation. 



#7 beatlejuice

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Posted 09 August 2019 - 01:45 PM

Never had a collimation problem with the Binotrons in the 5 years I've had them.

 

Eric



#8 Kunama

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Posted 09 August 2019 - 11:36 PM

Contact Rafael at Raf Camera, he has some adapters I designed to allow the T2 Baader eyepiece holders to fit the M38x1 thread of the binoviewer.

Screw the adapters into the Baader eyepiece clamps then remove the blue collars and screw the Baader clamps onto the binoviewers....

 

See here:  Kunama M38>T2 adapter  https://www.rafcamer...x1f-to-t2m-flat


Edited by Kunama, 09 August 2019 - 11:40 PM.


#9 noisejammer

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Posted 11 August 2019 - 09:00 PM

That looks like a Zeiss binoviewer - you could look for a thread in its mounting ring and perhaps install a Baader GPC (Glass Path Compensator). These are available in a number of magnifications. Denis will be familiar with them.

 

A second option would be a pair of zoom eyepieces - the Baader 8-24 Mk 4 is frequently recommended (although I only have experience of the Mk 2).

 

As for dioptre correction, there's a Baader click-lock version of the piece linked to above. These tolerate undercuts really well.



#10 CrazyPanda

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Posted 11 August 2019 - 09:43 PM

That looks like a Zeiss binoviewer - you could look for a thread in its mounting ring and perhaps install a Baader GPC (Glass Path Compensator). These are available in a number of magnifications. Denis will be familiar with them.

 

A second option would be a pair of zoom eyepieces - the Baader 8-24 Mk 4 is frequently recommended (although I only have experience of the Mk 2).

 

As for dioptre correction, there's a Baader click-lock version of the piece linked to above. These tolerate undercuts really well.

That looks awesome. I wonder if the male adapter threads that Kunama linked to would work for that.

 

Regarding the GPC, how does this fare compared to a Powermate? I keep stealing the 2x Powermate from my BVer for high power monoviewing, and have been thinking about getting a dedicated barlow so I can leave the Powermate in the BVer, but I could just replace the Powermate in the BVer with something else and use the Powermate for mono.


Edited by CrazyPanda, 11 August 2019 - 09:43 PM.


#11 noisejammer

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Posted 11 August 2019 - 09:53 PM

That looks awesome. I wonder if the male adapter threads that Kunama linked to would work for that.

 

Regarding the GPC, how does this fare compared to a Powermate? I keep stealing the 2x Powermate from my BVer for high power monoviewing, and have been thinking about getting a dedicated barlow so I can leave the Powermate in the BVer, but I could just replace the Powermate in the BVer with something else and use the Powermate for mono.

It has the same T2(f) thread (42x0.75mm) so what works for one will work for the other.

 

On the GPC - If your binoviewer has the thread, it replaces a Barlow but they do shorten the effective optical length slightly. This might compensate for the clicklocks lengthening it. If memory serves, Baader also offers a 2x corrector for use with Newtonians that should fit all 2" drawtubes. You should discuss it with Denis because he knows your binoviewers better than I do.




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