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1.25" Thread-on Eyepiece Holders for Classic Refractors

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#26 Pete W

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Posted 25 August 2020 - 04:56 PM

Good point Chuck.   My bigger 1.25" eyepieces are in 18"'s eyepiece case so I won't be tempted to push the limits of the step-up rings. 

 

Do they make brass step-ups?  Just curious.


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#27 Chuck Hards

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Posted 25 August 2020 - 06:04 PM

Do they make brass step-ups?  Just curious.

 

They most definitely used to, but honestly I can't say if they are still available in brass.  

 

Edit:  A quick search turned up brass rings at B&H, so it looks like they are still available. 

 


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#28 Terra Nova

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Posted 25 August 2020 - 06:23 PM

That 1.25” Tak adapter looks right at home on the AVA Swift! I might need to get one of those for my Model 839. I currently have one of my Vixen adapters in my Swift kit but the Tak mimics the original 0.965” twist compression v.b.


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#29 Chuck Hards

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Posted 25 August 2020 - 06:58 PM

The Tak adapter has been out of stock everywhere, all summer long.  Hopefully someone gets a shipment one of these days.


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#30 ccwemyss

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Posted 26 August 2020 - 11:16 AM

Just to document this somewhere, as it's related:

 

The classic Pentax refractors of the late 70's and early 80's have an unusual 38mm ID tailpiece that holds their standard 0.965 prism. I found that this is also the diameter of the camera port on Nikon microscopes, and that there are thus 38mm to T-thread adapters available on E-bay and elsewhere. A Baader low-profile 1.25" eyepiece holder from their T2 system fits it nicely, enabling use of a 1.25" diagonal. It does, however, increase back-focus, so that some eyepieces don't get enough in-focus with the limited travel of the focuser.

 

Pentax Adapter - 1.jpeg

 

Pentax also made a 1.25" prism diagonal with a 38mm nosepiece, although these are hard to find. They do shorten the optical path so that more eyepieces come to focus. 

 

In addition, the back of these refractors consists of two pieces. There is the focus tube with the rack gear, and into that is inserted a reducer that brings the diameter down to 38mm. The reducer is held on by a threaded ring. The threads on the end of the focus tube are 50mm, and appear to be metric thread. I found a no-name 2" mirror diagonal that threads onto it all the way, with its nosepiece removed. That enables use of 2" eyepieces with these scopes, with no vignetting. 

 

Unfortunately, the threads are not quite the same as the 2" SCT rear cell threads. Those only go on about 1.5 to 3 turns before jamming. For example, a GSO 2" diagonal only goes on about 2 turns. So the Baader lock ring for their 2" SCT thread diagonals won't go on and then be usable to control the angle of a diagonal. That leaves the diagonal pointing in whatever direction the threads bottom out (straight down in the first case, up in the case of the GSO). I need to see if I can find a 50mm metric ring, maybe a filter thread adapter, that could be used instead. It would also be nice to find a better quality diagonal that has the 50mm threads (the no-name gives rather mediocre views).

 

Chip W. 


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#31 Chuck Hards

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Posted 31 August 2020 - 04:48 PM

Similar to BB’s solution, I’ve used camera filter step-up rings that thread onto to pullout draw tube of my Sears 6339a and Tasco 10 TE.  This then allows a 1.25” male T2 visual back to thread onto the draw tube.  This approach was first mentioned by Catboat a few years ago.

 

I dug out my step ring collection and put together this setup, only to find that it won't fit.  

 

I tried it on two Royal Astro Tasco 10TE's, only threaded-on about one half turn.  It wouldn't even start threading on a Meade 80mm Tasco.  I did not attempt to force it once the threads started to bind-up.  

 

I tried two different 30.5mm step rings, neither would thread onto the three sliders I tried.

 

I have several other Royal Astro scopes to check (when the stars align and I have the time to pull them out of storage) but the fact that the 30.5mm step ring is not fitting the three OTA's I have handy, tells me that we have a similar situation to the slight thread mismatch between 36.4mm and 36.25 sizes.  It fits some, not all.

 

I suspect that 30.5mm is not the true thread for the sliding tubes, or because they were all cut by hand (as opposed to CNC for most modern machining), there is lots of individual variation.  


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#32 Defenderslideguitar

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Posted 31 August 2020 - 06:49 PM

possibly another source ? 21,99   free shipping

 

 

https://www.ebay.com...353.m2749.l2649



#33 Pete W

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Posted 31 August 2020 - 07:19 PM

Don’t know if this is correct...but get‘em while they last?

https://www.opticspl...m-to-1-1-4.html



#34 Jon Isaacs

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Posted 31 August 2020 - 07:51 PM

My story:

 

My 60mm x 800mm Asahi-Pentax had a full sized draw tube and an 0.965" adapter that was the same diameter as the Vixen but the thread pitch was different.

 

I looked through my parts box and was lucky enough to find that the eyepiece holder of a certain Burgess Optical 1.25 inch diagonal was a perfect fit. Later I acquired a second 60mm x 800mm and was lucky enough to find a second diagonal on Astromart.  This a photo with a 16 mm type 2 Nagler.

 

4758229-Pentax in front of fireplace.jpg
 
The diagonal itself is very rare. It was a temporary replacement 1.25" diagonal  for a promised 2 inch diagonal that was part of the 102 mm F/6 Burguss Optical debacle. 
 
Some years ago, I gave both scope to members of the forum..
 
Now I'm back looking for another one. I recently purchased my third 60 mm x 800mm A-P from Chuck, I'm waiting on whether I'll ever be able to pick it up on the way to visit our sons family in Montana or to ship it.
 
It's looking more and more like shipping.
 
Using 1.25 inch eyepieces really makes these scopes come alive. The 4.8 mm Nagler provided 167x, some very nice planetary and double star views.
 
I'm not sure what I'm going to do. I'll start with a hybrid diagonal.
 
Jon

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#35 clamchip

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Posted 31 August 2020 - 07:59 PM

This is not a thread on adapter but it works so well I thought I would

show it off.

If you use the eyepiece end of the pictured Edmund barlow it's a push

fit on my Astro Optical focuser drawtube. Clean and simple.

Robert

 

post-50896-0-56784300-1549851495.jpg

post-50896-0-23221000-1549851550.jpg


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#36 MisterDan

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Posted 31 August 2020 - 08:41 PM

A couple months ago, I was hunting for another Vixen visual back, but there was no way I was willing to pay $50 (or more). They're getting harder to find, so this discussion is both timely and valuable.  I opted for this...

Double helical

 

Svbony calls this a "double helical focuser," and there are a few versions, depending on scope-side interface (SCT, M31, 2-inch, and "M36"). The "M36" version fits both my 999VR and Carton refractors perfectly. This focuser may be a good option for several classic f/5 refractors, such as the Meade 227, Towa T-300, the Tasco "VR" siblings (9, 99, 999, & 10), Celestron/Vixen SS80. It *may* be a straight swap with the collar on the old C6 sled focuser, but someone who owns or is familiar with that focuser would have to verify.

 

Svbony also markets this...

focuser adapter

 

This "universal focuser adapter" utilizes a T-thread (female) scope-side interface and a 3-thumbscrew 1.25-inch eyepiece collar. The eyepiece collar separates (unscrews) from the M42 back, and that interior thread interface is, conveniently enough, another "M36" (though obviously much "deeper").  This adapter has a shorter profile than the helical focuser, but only if it seats deeply enough in the drawtube.

 

Them's my two pennies.

Best wishes, everyone.


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#37 Don W

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Posted 31 August 2020 - 09:16 PM

Got one for my Selsi from Agena (I think).

 

Vixen adapter.jpg


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#38 JoeInMN

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Posted 31 August 2020 - 09:46 PM

Earlier this year I got a better 60mm objective and a nice hefty focuser to fit the tube of my Tasco. The focuser has a drawtube big enough to take 1.25" eyepiece barrels, and I was looking into somehow getting a visual back to make that happen, and discovered that I already had two of them... The eyepiece holder from an old Meade Starfinder focuser, and one from an unidentified long drawtube that I must have gotten from one surplus store or another long ago, both threaded perfectly onto the focuser's drawtube. I used the one from the orphaned drawtube; nothing could have worked any better. Pics of the frankenscope's original back end, the 1.25" upgrade, and my two options:

 

vis_back_965_700.jpg

vis_back_125_700.jpg

vis_back_options_700.jpg

 


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#39 MisterDan

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Posted 31 August 2020 - 11:24 PM

Just to document this somewhere, as it's related:

 

The classic Pentax refractors of the late 70's and early 80's have an unusual 38mm ID tailpiece that holds their standard 0.965 prism. I found that this is also the diameter of the camera port on Nikon microscopes, and that there are thus 38mm to T-thread adapters available on E-bay and elsewhere. A Baader low-profile 1.25" eyepiece holder from their T2 system fits it nicely, enabling use of a 1.25" diagonal. It does, however, increase back-focus, so that some eyepieces don't get enough in-focus with the limited travel of the focuser.

 

attachicon.gifPentax Adapter - 1.jpeg

 

Pentax also made a 1.25" prism diagonal with a 38mm nosepiece, although these are hard to find. They do shorten the optical path so that more eyepieces come to focus. 

 

In addition, the back of these refractors consists of two pieces. There is the focus tube with the rack gear, and into that is inserted a reducer that brings the diameter down to 38mm. The reducer is held on by a threaded ring. The threads on the end of the focus tube are 50mm, and appear to be metric thread. I found a no-name 2" mirror diagonal that threads onto it all the way, with its nosepiece removed. That enables use of 2" eyepieces with these scopes, with no vignetting. 

 

Unfortunately, the threads are not quite the same as the 2" SCT rear cell threads. Those only go on about 1.5 to 3 turns before jamming. For example, a GSO 2" diagonal only goes on about 2 turns. So the Baader lock ring for their 2" SCT thread diagonals won't go on and then be usable to control the angle of a diagonal. That leaves the diagonal pointing in whatever direction the threads bottom out (straight down in the first case, up in the case of the GSO). I need to see if I can find a 50mm metric ring, maybe a filter thread adapter, that could be used instead. It would also be nice to find a better quality diagonal that has the 50mm threads (the no-name gives rather mediocre views).

 

Chip W. 

Very cool, Chip.  I may fashion one of those, myself. waytogo.gif

 

I ended up making my own 38mm and 60mm adapters for my Pentax 75 (plus a custom 38mm adapter from S&S Optika... I sure miss that wonderful shop). With the myriad photo tube and imaging formats in the microscope world, many oddball ports can be adapted to T-threaded visual backs with minimal hassle.

 

Best wishes.

Dan



#40 Chuck Hards

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Posted 01 September 2020 - 10:35 AM

Earlier this year I got a better 60mm objective and a nice hefty focuser to fit the tube of my Tasco. The focuser has a drawtube big enough to take 1.25" eyepiece barrels, and I was looking into somehow getting a visual back to make that happen, and discovered that I already had two of them... The eyepiece holder from an old Meade Starfinder focuser, and one from an unidentified long drawtube that I must have gotten from one surplus store or another long ago, both threaded perfectly onto the focuser's drawtube. I used the one from the orphaned drawtube; nothing could have worked any better. Pics of the frankenscope's original back end, the 1.25" upgrade, and my two options:

 

Joe, the one from the long drawtube is the exact same one I posted here:  LINK

 

Only my black anodizing has long worn-off.  Be careful with this one, it is too sloppy on most of the focusers I tried it on.  


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#41 JoeInMN

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Posted 01 September 2020 - 02:41 PM

Joe, the one from the long drawtube is the exact same one I posted here:  LINK

 

Only my black anodizing has long worn-off.  Be careful with this one, it is too sloppy on most of the focusers I tried it on.  

Hmm.. Thanks for the headsup. If I remember right, it fits my focuser about as well as it did its original tube, and takes four or five turns to screw on. I'm at work at the moment, though, so I'll have to check it when I get home.



#42 JoeInMN

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Posted 01 September 2020 - 07:03 PM

Actually it takes about three and a half turns. Screwing it in, I can feel that it does have a wee bit smaller diameter thread than the original .965" unit, but not enough for me to foresee it ever stripping or falling out.

 

I found that an eyepiece holder from yet another focuser (I believe it's from a Vixen scope of some sort) fits well enough to possibly fool the unwary, but I can screw that one halfway in and then, if I do it right, wiggle it out again without unscrewing it, so I obviously won't be using that one. I definitely can't do that with the one I'm using. I'll keep half an eye out for another one anyway, as I eventually might want to use that drawtube for something else.



#43 Kasmos

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Posted 02 September 2020 - 03:37 PM

Nobody has mentioned the Celestron VB Unitron trick

Tried it and it appears to work.

 

Uni-Celest-VB-1.jpg

Remove thumbscrew to unscrew and remove the ring

 

Uni-Celest-VB-2.jpg

Flip and the small threads fit the Unitron Pull Tube.

 

Uni-Celest-VB-3.jpg

The thumbscrew's position is further forward than normal but it still grabs the diagonal's tube.

 

ScopeStuff also has a nice Unitron 1.25"adaptor, plus they have another for Tasco and other .965"telescopes with 35.5mm threads 

http://scopestuff.com/ss_utea.htm


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#44 Kasmos

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Posted 02 September 2020 - 03:45 PM

Good News. It appears you can still get a Vixen adaptor (last one), on ebay for only $15.76 with free shipping.

 

https://www.ebay.com...675.c100623.m-1


Edited by Kasmos, 02 September 2020 - 10:07 PM.


#45 RichA

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Posted 02 September 2020 - 10:29 PM

ScopeStuff sells a 1.25" adapter listed with a 36.25mm thread.  Because the older imported scopes were machined by hand, there is often enough slop in the focuser thread to accommodate the slightly different adapter thread.

 

It does NOT fit on all scopes.  

 

I like it for it's low profile.  Adds the least amount of additional drawtube length.  Too bad it's not a true 36.4mm thread.

 

attachicon.gif012.jpg  

 

attachicon.gif013.jpg

Better  than the other two. Cheaper and it fits more with the looks of the older scopes and it doesn't alter the focus distance much.


Edited by RichA, 02 September 2020 - 10:30 PM.


#46 Senex Bibax

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Posted 06 September 2020 - 06:24 AM

A couple months ago, I was hunting for another Vixen visual back, but there was no way I was willing to pay $50 (or more). They're getting harder to find, so this discussion is both timely and valuable.  I opted for this...

 

 

Svbony calls this a "double helical focuser," and there are a few versions, depending on scope-side interface (SCT, M31, 2-inch, and "M36"). The "M36" version fits both my 999VR and Carton refractors perfectly. This focuser may be a good option for several classic f/5 refractors, such as the Meade 227, Towa T-300, the Tasco "VR" siblings (9, 99, 999, & 10), Celestron/Vixen SS80. It *may* be a straight swap with the collar on the old C6 sled focuser, but someone who owns or is familiar with that focuser would have to verify.

 

Svbony also markets this...

 

 

This "universal focuser adapter" utilizes a T-thread (female) scope-side interface and a 3-thumbscrew 1.25-inch eyepiece collar. The eyepiece collar separates (unscrews) from the M42 back, and that interior thread interface is, conveniently enough, another "M36" (though obviously much "deeper").  This adapter has a shorter profile than the helical focuser, but only if it seats deeply enough in the drawtube.

 

Them's my two pennies.

Best wishes, everyone.

By Carton refractors, do you mean the older ones (1950s - 1960s) with threaded diagonals that screw into the focuser tube?



#47 MisterDan

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Posted 06 September 2020 - 02:15 PM

By Carton refractors, do you mean the older ones (1950s - 1960s) with threaded diagonals that screw into the focuser tube?

My particular '60s-era Carton does not utilize a threaded diagonal. In my own case, it's this Carton 60mm Equatorial model (link from another CN thread):

 

https://www.cloudyni...e/#entry8398159

Scroll up to see pics of the scope's label.

Posting #15 of that thread includes an Archive.com "Wayback Machine" link to a copy of the Carton manual.

 

Other brands which marketed "siblings" to this particular Carton included Monolux and Hilkin, both of whom marketed other scopes from multiple makers.  Monolux offerings included models from H.O.C., Royal Astro, and APL (perhaps others). Hilkin offered models from Carton and Eikow, at least (they are less common, stateside, so I'm not sure).

 

Typical U.S. models were labeled "C.O.C" (within a stylized placard/badge) with "ASTRONOMICAL TELESCOPE" below badge (as shown in linked pic).  Later versions of the Carton models included the T-633 and T-635.  Accessories and design details varied over the years (compression or set-screw eyepiece/diagonal collars, tripod leg clamps, focuser knob materiel, other details).

 

I believe all variants of this Carton refractor utilized drawtubes with an M36 (or M36.4) female thread interface.  The compression ring "eyepiece holder" (seen in the linked pics and manual) has a 0.965 format, as does the porro prism assembly.  Each threads directly into the drawtube.  My Carton's drawtube also accepts the Vixen 1.25-inch visual back, a Tanzutzu 0.965 visual back, the Svbony helical focuser, and (likely, but not personally confirmed) the other Svbony adapter.

 

I'm overdue for taking the Carton out for a spin (did some tripod leg repairs, last month), so I may share some pics of my set-up, soon.  (Scope is currently stored away, and my back's been a bit "tricky" of late. I need to take care of it, first.)gramps.gif  Last time I tested the Carton was maybe a dozen years ago.  If I recall correctly, it showed me some minor astigmatism, but it may not have been "in the glass."  It may have been tilt-induced astigmatism (hence my need to get behind the wheel and "drive" it!).

 

If you do a Forums search for "carton refractor" and/or "hilkin," you'll find many more pics and discussions.

Best wishes and kind regards.

Dan


Edited by MisterDan, 06 September 2020 - 02:31 PM.


#48 Senex Bibax

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Posted 06 September 2020 - 06:06 PM

My acquisition from yesterday is a "Polaroscope" refreactor from the late 1950s, but the metal cover on the bottom of the focuser has the diamond symbol with "COC" , so I presume the focuser at least is by Carton. Since I have a bunch of Meade 1.25" plössl eyepieces, looks like I need to get me one of those Vixen or Svbony thread-in adapters.



#49 MisterDan

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Posted 06 September 2020 - 06:57 PM

-Said Polaroscope being the 76x1200 in your signature?!...

If so, that's a nice ol' vintage three-incher. Congratulations.

-Just don't tell us you paid $25 for it... praying.gifjawdrop.gif

Cheers!



#50 Senex Bibax

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Posted 07 September 2020 - 08:10 AM

-Said Polaroscope being the 76x1200 in your signature?!...

If so, that's a nice ol' vintage three-incher. Congratulations.

-Just don't tell us you paid $25 for it... praying.gifjawdrop.gif

Cheers!

No, it's not in my signature yet but thanks for reminding me. The 76x1200 is a Sears 6309 with RAO objective, a definite keeper. I bought it last October complete with original EQ mount and tripod, plus a bonus Sears 6309 60x700 scope. Including a hideous brushed-on orange and white paint job, all for $80.00 CAD.

 

I bought the Polaroscope two days ago, it is 60x910, complete with original case, mount, tripod, accessories and tobacco stains for $90.00 CAD


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