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Adapting 0.965" Scopes for 1.25" Oculars

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#1 Joe Cepleur

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Posted 17 January 2013 - 08:02 PM

I just answered a private message asking me how to convert a 0.965" Jason 313 to use 1.25" oculars. It occurs to me that this is better on the public forum, where others might find it.

This method will work for many scopes, but not all. Some have problems reaching focus with the longer diagonal and the extra inch or so of back focus required by the adapter. Sorry; I'm no expert on that. I've heard about it, but have not yet had the problem myself. But -- for those for whom this will work:

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Blue Fireball 0.965"-to-1.25" adapter has a compression ring to protect your oculars, and extra strong aluminum, allowing a thin tube to prevent vignetting:

http://agenaastro.co...ce-adapter.html


Celestron prism diagonal -- yes, prism! At long focal lengths, there is good argument for prisms over mirrors. 100% internal reflection, no trouble with chromatic fringes, no coatings to break down over time, easier to clean. This one should be exactly like mine, with an oddly unadvertised anti-reflective coating on the prism. Astronmics could confirm that:

http://www.astronomi...onal_p3601.aspx


If you need low-cost eyepieces, get 40mm, 25mm, 15mm, and 2x Barlow discounted set:

http://www.owlastron...superplossl.htm


One problem using modern oculars with their bigger diagonals, and a trick: They are far heavier than the 0.965" originals, so the scope won't balance. Go to the hardware store and buy a 3' length of lightweight chain and some S-hooks to attach to each end. Cover the end of the S-hook with electrical tape so it won't scratch the dew shield, and hang it there. Adjust where the scope sits in the mount until it balances. The chain will also absorb vibration, so the scope will settle faster.

Always a pleasure helping a classic scope and its astronomer!

#2 David E

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Posted 17 January 2013 - 08:50 PM

If your refractor has a combination drawtube/r&p then focus will not be a problem with an adapter. Since many simple R&P's will not have enough in-focus to accommodate the extra length of the adapter, a hybrid diagonal such as this one on EBay might be a better solution. Bear in mind that you are still working with a .965" focuser, so long focal length 1.25" eyepieces, such as a 32mm Plossl, will be vignetted in the field of view.

#3 tecmage

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Posted 17 January 2013 - 09:47 PM

Joe,
Does the Vixen 3720 work as well? I'm thinking about buying one of these because it screws into the drawtube.

#4 TheMadHatter

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Posted 17 January 2013 - 10:04 PM

David, that one works very well for the jason model 311, it still seems a bit out of focus that could be due to collimation issues on the scope itself.

Never really thought about doing it this way, since i found the hybrid diangle, very interesting. It may help focus the object better.

#5 Joe Cepleur

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Posted 17 January 2013 - 10:29 PM

I don't know whether the Vixen 3720 works in the Jason 313, nor do I have one to test. I'll measure the openings, and then guess at the threads. I'd swap my current rig for that in a heartbeat if it would work. Stay tuned...

#6 Jon Isaacs

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Posted 17 January 2013 - 11:52 PM

If your refractor has a combination drawtube/r&p then focus will not be a problem with an adapter. Since many simple R&P's will not have enough in-focus to accommodate the extra length of the adapter, a hybrid diagonal such as this one on EBay might be a better solution. Bear in mind that you are still working with a .965" focuser, so long focal length 1.25" eyepieces, such as a 32mm Plossl, will be vignetted in the field of view.


:waytogo:

Ideally, one's scope has a full sized drawtube and only needs an adapter like the Vixen to use 1.25 inch eyepieces without vignetting. But some telescopes have a small diameter drawtube that can only use a hybrid diagonal or something like the Blue Fireball. Some though don't have enough back focus to focus with even a hybrid diagonal. Each scope is an individual challenge.

My old Asahi-Pentax is a case in point. It has the full sized drawtube and the diameter is right for the Vixen adapter but the thread pitch is wrong. :( Scrounging through my parts boxes I discovered that the eyepiece end of the 1.25 inch diagonal that came with a Burgess Optical 102F/6 was a perfect fit. :) When I saw another diagonal available on Astromart I bought it just to be prepared and sure enough, one day another Asahi-Pentax showed up on Craigslist and I was already prepared.

Jon

#7 grendel

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Posted 18 January 2013 - 04:41 AM

I have several methods I use on my various scopes, one has the correct thread for the vixen adaptor, another with the long drawtube I use either a hybrid prism diagonal, or a straight through .965 - 1.25" adaptor I have (you need about 1.25" extra in focus, but if the scope originally came with a diagonal this should work straight through (might not work if you then try and use a 1.25" diagonal)
I even have a hybrid erecting prism diagonal too, so where there is a will there is a way.
Grendel

#8 Grava T

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Posted 18 January 2013 - 07:15 AM

If your refractor has a combination drawtube/r&p then focus will not be a problem with an adapter. Since many simple R&P's will not have enough in-focus to accommodate the extra length of the adapter, a hybrid diagonal such as this one on EBay might be a better solution. Bear in mind that you are still working with a .965" focuser, so long focal length 1.25" eyepieces, such as a 32mm Plossl, will be vignetted in the field of view.


:waytogo:

Ideally, one's scope has a full sized drawtube and only needs an adapter like the Vixen to use 1.25 inch eyepieces without vignetting. But some telescopes have a small diameter drawtube that can only use a hybrid diagonal or something like the Blue Fireball. Some though don't have enough back focus to focus with even a hybrid diagonal. Each scope is an individual challenge.

My old Asahi-Pentax is a case in point. It has the full sized drawtube and the diameter is right for the Vixen adapter but the thread pitch is wrong. :( Scrounging through my parts boxes I discovered that the eyepiece end of the 1.25 inch diagonal that came with a Burgess Optical 102F/6 was a perfect fit. :) When I saw another diagonal available on Astromart I bought it just to be prepared and sure enough, one day another Asahi-Pentax showed up on Craigslist and I was already prepared.

Jon


Jon, I use the .965"-1.25" adapter on my Asahi Jupiter and it works just fine but a 1.25" visual back would be better. I discovered, like you, that the Vixen adapter threads are not quite right for the drawtube unfortunately. I will try the eyepiece end from one of my diagonals...thanks for the tip.

#9 Ducky62

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Posted 23 February 2013 - 05:19 PM

Somebody else test this hybrid diagonal out and report back :question:


GSO .965/1.25" 99% Dielectric Hybrid Diagonal w/ Compression Ring

#10 BarabinoSr

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Posted 23 February 2013 - 06:33 PM

This question came up recently in the Yahoo 60mm forum and I addressed it as follows.It does depend on the in to out focus travel of the focusers on the scopes in question whether you'll need the adapter or the hybrid . Some of the 60mm TOWA scopes in my group such as the TASCO 9TE-5 , the Jason #311 Constellation, the TASCO 50mm 6TE-5 Cosmic and certain other 60mms have about 2.5 " of in to out focus travel, so the hybrids should work fine. They will not allow an adapter in the configuration so you dont need one if your scope has this type of focuser. All other 60mms can take the adapter, like the Jason #313 Discoverer,the TASCO 7TE and 7TE-5 or the Bushnell Sky Chief. Gary(G:cool:)

#11 OneGear

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Posted 26 February 2013 - 07:44 PM

I replaced the entire focuser on my Tasco. It's not "classic" in the valuable sense so I happily modified it.

The focuser from a Meade NG60 fits nicely and is better in every way. It would probably fit most 60mm scopes that use three screws through the tube to fasten the focuser.

#12 Roger64

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Posted 27 February 2013 - 06:31 AM

PM sent.

#13 labmand

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Posted 11 March 2013 - 11:00 PM

OneGear, Is the Meade NG60 plastic? Any metal 60mm focusers availabe new today?
BaraBinoSr, Do I understand this correctly
I should be able to get a vintage Jason #313 Discoverer,the TASCO 7TE and 7TE-5 or the Bushnell Sky Chief, remove the
drawtube/focuser and mount it on my Vintage Sears Discoverer?

#14 BarabinoSr

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Posted 12 March 2013 - 12:39 AM

Hi Dave! The TASCO 7TE-5 or 7TE focuser will not fit your Sears Discoverer because they were made by an old Japanese firm called Royal Astro Optical and they thread into a ring mounted on the tube.Sears used to market a 3-inch made by Royal Astro. The scopes made by TOWA- Sears Discoverer, Bushnell Sky Chief III and the Jason Model #313 Discoverer (depending on the year of construction) all have the same or similar focusers. Gary

#15 bremms

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Posted 12 March 2013 - 08:12 AM

Could machine an adapter to put a feathertouch or AP focuser on there .. Just being funny I held an AP focuser up to my Sears 6339 and Laughed. It weighs more than the whole OTA

#16 bremms

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Posted 12 March 2013 - 08:15 AM

Thing is, It wouldn't be hard to retrofit a different focuser on the Sears Royal Astro. but the drawtube is so long, you would need an extension of some kind. Then the scope looses it's charm without that long slender bright chrome drawtube.

#17 labmand

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Posted 12 March 2013 - 10:17 AM

Thanks BarabinoSr/ Gary
I have a Jason 313 SYW Yamamoto 60mm
I was able to screw an adapter from one of my other scopes
on the Jason draw tube for 1.25 use. works great. Was hoping to find a similar large drawtube focuser to place on the Sears main tube, to replace the .96 focuser. The Jason 313 like mine are not something you see everyday, Was hoping to get a list of large drawtube/focuser telescopes that would work with just an adapter for 1.25 use. Something
that I would be able to find easely. Thanks for any help

#18 bremms

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Posted 12 March 2013 - 11:26 AM

My swift Aerolite has the Vixen thread. It is a Carton scope.

#19 labmand

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Posted 12 March 2013 - 02:16 PM

Thanks Bremms, have not seen to many swift or Cartons
out there, Sure would be nice to be able to pickup a
decent metal focuser for these 60mm vintage scopes,
anyone have any idea's
An Please forgive me if I'm highjacking this thread

#20 moynihan

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Posted 15 March 2013 - 06:38 AM

Ther is always the option of getting a Crawmach crayford focuser...

#21 t.r.

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Posted 15 March 2013 - 07:33 AM

You have to be careful though. The longer draw tubes are not standard on the Crawmach and one would come up short on focal point. I've heard that Crawmach can make a custom one though for these pull-out drawtube scopes of long focal length.

#22 xavier

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Posted 15 March 2013 - 12:14 PM

This is a long time discussion and search. Hereby a photo of the different Polarex draw tubes with standard and custom solutions. The Polarex draw tubes don't have the Vixen thread. Most of the Vixen adapters are glued in the draw tubes. It works. Sometimes it's hard to get into focus with modern diagonals and eyepieces.

Attached Files



#23 TahoeNoob

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Posted 08 June 2013 - 04:30 PM

I have three classic scopes that take 0.965" eyepieces. I'd like to be able to use 1.25" eyepieces in them. Two of them have male threads on the focus assembly, and one of them has female threads.

I believe I can use THIS adapter on the female threaded focus assembly. Does anybody know where I can find an adapter to use on the male focus assemblies? (I'm thinking that I'll be using diagonals on these, if that makes any difference, and obviously I'll need to be able to focus when I have the adapter installed.)

From left to right: Sears 6335; Scope 2531; Sans & Streiffe 618
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#24 sgorton99

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Posted 08 June 2013 - 05:28 PM

I have one of these that Danny Crawford made for my Unitron scopes.

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#25 TahoeNoob

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Posted 28 June 2013 - 04:01 PM

Not sure why those images are no longer showing. I don't think I moved or deleted them.

Ok, so I ordered a Vixen adapter ©, so I'd be able to use 1.25" eyepieces. The problem is that the adapter doesn't fit the end of my drawtube (B). Instead it fits onto the back of my focuser. (E)

I'm flummoxed! If anybody knows what adapter I need, I'm all ears!

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