1 1/4" Eyepiece Adapter for Kowa TSN-883 or884 (1 Viewer)

1 1/4" or 2" Eyepiece Adapter for Kowa TSN-883 or 884 wanted

Hi. Does any one know of a source or is willing to build me an adapter enabling the use of 1.25" or 2" astronomical eyepieces on my 883 scope? Internet search indicates it's been done privately in plastic. Thanks.

delrin is often a good material for this type of work, having enough in focus is often a problem though (esp with the larger taller 2" epos)

Malcolm,

You should estimate the diameter of the "window" in the scope body under the eyepiece.
There would be no point in using eyepieces with a larger field stop than this as they would vignette.
As a guide see this link: http://www.televue.com/engine/TV3b_page.asp?id=214&plain=TRUE#.U4cCXHauOFA
As dannat pointed out, long barrels (dimension "B" in the chart) may prevent you from achieving infinity focus.

John

I understand the prism system's small size limits perfect performance to very short focal length eyepieces. My worry is not being able to reach focus, but many eyepieces I have just hand held in place seen to focus. I just want to put my existing collection to use, instead of having to purchase more glass that can only fit one scope. The EP mounting area on the Kowa seems closer to 2" and it can be stepped down with an astro 1.250" reducer if it doesn't screw up the light path length.

It would be nice if some manufacturer offered an adapter. I guess it would not behoove Kowa to do so.

Malcolm,

I have used three different astro adapters on Zeiss Diascope and a Swarovski ATM scopes, so I think you have some options, even if you are going to have to get something made.

A Kowa equivalent of this Baader Diascope adapter http://www.baader-planetarium.de/zeiss_diascope/zeiss/diascope-start.htm (last illustration) would involve complex machining of the bayonet flanges.

The original Zeiss adapter is a lot simpler: http://www.zeiss.de/sports-optics/de_de/natur/spektive/spektiv-zubehoer.html (penultimate illustration, not Astro-Adapter). It consists of a sleeve of 31,8 mm (1 1/4") ID and 41 mm OD and is 21 mm long. It has a grub screw to secure the astro eyepiece. OD and length would of course differ for the Kowa.

The Diascopes have a short 45 mm male thead on the scope body and a locking ring with female thread is used to secure the astro-adapter. If the Kowa does not have a thread on the scope body (the black ring is just the eyepiece retention catch?) you could machine a groove on the outside of the sleeve and use an O-ring for a friction fit. This, of course would involve some caution near the zenith!

John

I though I remembered an old thread about a home made 1.25" adapter for the Kowa 883. A little searching turned it up.

http://www.birdforum.net/showthread.php?t=105037&highlight=Kowa+eyepiece+adapter

The thread below mentions a pre-product astro adapter for Kowa. I wish I knew the manufacturer so I could place a pre-order.

http://www.birdforum.net/showthread.php?t=284292

malcolm64 said:

Hi. Does any one know of a source or is willing to build me an adapter enabling the use of 1.25" or 2" astronomical eyepieces on my 883 scope? Internet search indicates it's been done privately in plastic. Thanks.

Click to expand...

Hi .... I also have a Kowa 883. After reading the post/review that "binomania" posted here on June 3 2014, in which Kowa had a prototype that had a positive review but never came to be available to the public .... Has really bugged me ! Do they think their own eyepiece sales would go down ? I guess Kowa must think it's not in the company's best interest to do so. After studying the eye mounting area of my 883, I decided to purchase a used 25x long eye relief eyepiece, the one that is designed for the 77/883 series. I was able to find a used one at a very cheap price, so I am going to breakdown/take out the guts just to see if the remaining shell can be modified to be used as a adapter for 1.25"/2" astro eyepieces. This eyepiece seemed to be the perfect match due to its outside diameter(is much larger than 1.25") & the fact the male end of the eyepiece already is machined to lock in place. I have a friend who is a retired machinist take a look at my good 25x eyepiece I use & without taking it apart ,thinks making modifications won't be the issue. The only thing in question will be the small exit opening in the existing shell, where the last lens is located. How much modifications(enlarging it) if any with out destroying the part that locks the eyepiece into the scope body. Now many are probably asking why possibly take the risk of wrecking a good useable eyepiece ? ...... for one thing the price I paid for the eyepiece will not keep me up at night if it gets tossed, so why not ? Why screw around with pvc or some other plastic tubing when ...... the eyepiece shell already fits the scope perfectly(large enough to house a 1.25" eyepiece & maybe a 2") & no special tooling has to be made for the locking end since its already there. What, if any eyepiece will focus ?, my Pentax XW20 does now when hand held in place. If my friend can make this happen with what machines/tooling equipment he has & my Pentax still works, I am going to a metal fabrication shop to see what the cost would be to have some professionally made out of aluminum. I should have the used eyepiece next week. Then we will remove all the glass & go from there .... gwen

malcolm64 said:

Hi. Does any one know of a source or is willing to build me an adapter enabling the use of 1.25" or 2" astronomical eyepieces on my 883 scope? Internet search indicates it's been done privately in plastic. Thanks.

Click to expand...

A local machine can do a pretty good job on the basic shape, though
cutting a thread is an extra thing to get right. The key is to use the
right jargon for the shape. A thick tube section with a shelf on top is
a "flange bushing". It's fairly easy to make with a lathe if you ask
for an easily-machined material. Brass is the easiest and most precise,
then Aluminum 6061-T6, then nylon, maybe. Steel is tough to work.
Most plastics are fussy.

Delrin is now becoming common in 3D-printer machine shops, though.

You sort have what you have with telescope eyepieces. They may or may
not be in range of the focusing and the stopping might work or not.
Long telescope focusers are far more forgiving than spotting scope focusers.
Might be worth it to get a minimal offset and a longer tube.

I adapted some Plossl and Plossl-plus (field lens) binocular eyepieces
to a Swift spoteer that had 2 orthos (the improve FOV). It took some
hand-fiddling to understand the ideal length for each one, and I did a
trick with wax and epoxy putty to use the protector-cap threads
(so I didn't have to stick a lathe in the garage). The proper plane
is way off between Ortho and Plossl.
I guess the upshot is....fiddle a bit with hand-holding before you have
things made. It's tweaky with spotters. The ultimate dream adaptor
would have adjustable sleeving length.

OPTIC_NUT said:

A local machine can do a pretty good job on the basic shape, though
cutting a thread is an extra thing to get right. The key is to use the
right jargon for the shape. A thick tube section with a shelf on top is
a "flange bushing". It's fairly easy to make with a lathe if you ask
for an easily-machined material. Brass is the easiest and most precise,
then Aluminum 6061-T6, then nylon, maybe. Steel is tough to work.
Most plastics are fussy.

Delrin is now becoming common in 3D-printer machine shops, though.

You sort have what you have with telescope eyepieces. They may or may
not be in range of the focusing and the stopping might work or not.
Long telescope focusers are far more forgiving than spotting scope focusers.
Might be worth it to get a minimal offset and a longer tube.

I adapted some Plossl and Plossl-plus (field lens) binocular eyepieces
to a Swift spoteer that had 2 orthos (the improve FOV). It took some
hand-fiddling to understand the ideal length for each one, and I did a
trick with wax and epoxy putty to use the protector-cap threads
(so I didn't have to stick a lathe in the garage). The proper plane
is way off between Ortho and Plossl.
I guess the upshot is....fiddle a bit with hand-holding before you have
things made. It's tweaky with spotters. The ultimate dream adaptor
would have adjustable sleeving length.

Click to expand...

Thanks for the advice. I just received a Russell Optics Super Wide 19mm Konig Eyepiece which is made out of Delrin. Delrin looks & feels like it would be the ideal material to work with. Their Web Site says they also do custom work, maybe if this gets to that stage I will contact them to see what they would be willing to do & the cost involved. .... gwen

If you need to build a couple to get the price down I could take one. Hopefully the price will be $50-100. Hopefully the focal distance will work for the different eyepiece designs out there. I have some Pentax too, so working with just that one would be fine too. Malcolm

Awesome idea, a buyer's pool.
Might give them incentive to include the work for low or free if you increase your pool size
(in buyers or EPs).

there is long time after the last time of log on.

Actually I did build one with thread, that will use with1.25 EPs. the question is that it just can be focusable in a certain number of EPs, and I have also gotten TE10Z 20-60, so I lost some interest.

If anybody are still interest, I can help to build some or give you thread spec, you can make it if you have resources.

Can you post a picture of it here or somewhere else? There is a provision to lock down on the eyepiece, hopefully non marring? thanks

malcolm64 said:

Can you post a picture of it here or somewhere else? There is a provision to lock down on the eyepiece, hopefully non marring? thanks

Click to expand...

it is locked down by a screw as picture shows,

malcolm64 said:

Can you post a picture of it here or somewhere else? There is a provision to lock down on the eyepiece, hopefully non marring? thanks

Click to expand...

Hello Malcolm,

I've made good progress on this front recently. On the Kowa 883, 884 there is a ring which surrounds the eyepiece mount. If you remove the eyepiece then it's possible to unscrew the black ring from the telescope body. This exposes a ring of male threads. Ideally, we'd like an eyepiece holder that screws directly onto those threads.

I haven't found something that simple, but I have found something fairly inexpensive that gets very close to the ideal. The scope's thread is M54.75 which happens to match the top of old Baader clickstop zoom eyepieces. Baader makes an adapter to take the M54 male to a T2 male and they also make an inexpensive T2 eyepiece holder. So, screw the Hyperion SP54/T2 adapter to the scope and screw the T-2i eyepiece clamp to the SP 54 adapter and there you are! It looks pretty much just like Jerry Fangs drawing above.

Except (isn't there always an exception?) for the particular eyepiece I wanted to use, the eyepiece holder was too tall. So I had to engage in a little amputation to get the top down to about 5mm above the T2 threads. Now I can use a Televue 32mm Plossl for 15x views.

Got the two Baader pieces from Alpine Astro for $27 each. It's also possible to order a custom made adapter from Precise Parts that is really nice, but costs 2 to 3x the Baader solution.

Best to you, let me know if you need any additional information.

PS. Beware the really nice (and expensive) Baader T2 eyepiece clamps. They're very good and the helical focusing looks like it would be perfect, but they've been to tall for any eyepieces I've tried and, unlike the inexpensive clamp, they can't be cut down to size.

The custom made adapter from Precise Parts will not work. They insist to have 0.736 in of effect length when making the adapter so that the adapter is simply way too tall for most if not all eyepieces on market today. I have tried TeleVue/Pentax/Nikon/Brandon/Takahashi/TMB and none can reach focus. So you basically need to cut most of the adapter off by yourself. In that case, Jerry's solution is much cheaper.

Another expensive alternative is to use the Kowa TSN-PZ Digital SLR Photo Adapter. You attach it to Kowa 883/884 and then attach a Baader 1.25" clocklock eyepiece adapter to the photo adapter. This will make the effective focal length of the spotting scope to be between 680mm and 1000mm. Someone on Cloudy Nights has tried this route and he can use Ethos 3.7 to get a 270x view and the result is still good.

That didn't occur to me. I have one of those already. The PZ is basically a barlow lense I think, so it is pushing the focal plane further out. Then Baader clicklock also has T2 threads and 1.25" barrel acceptance on the other end?

http://agenaastro.com/baader-1-25-click-lock-eyepiece-adapter-visual-back-t-2-thread-t208.html is the correct part?

Is there any way to get 2" eyepieces working? I can't find a T2 to 2" barrel adapter. I know it will vignette a little, but I have so many 2" eyepieces.

Thanks for the good idea.

Just a quick note for Malcolm and CW. If you want to use this approach then you don't need to buy a PZ. You can mount T2 eyepiece holders to any 770, 880 lens using the DA10 digiscoping adapter.

Best
Jerry

I've also had very good luck using the EC2 adapter to mount the full size Precise Parts holder inside the 883. Let me know if there's any interest in this. Virtue is that high quality, low mag views are possible since I'm only using a single eyepiece and objective lens.

malcolm64 said:

That didn't occur to me. I have one of those already. The PZ is basically a barlow lense I think, so it is pushing the focal plane further out. Then Baader clicklock also has T2 threads and 1.25" barrel acceptance on the other end?

http://agenaastro.com/baader-1-25-click-lock-eyepiece-adapter-visual-back-t-2-thread-t208.html is the correct part?

Is there any way to get 2" eyepieces working? I can't find a T2 to 2" barrel adapter. I know it will vignette a little, but I have so many 2" eyepieces.

Thanks for the good idea.

Click to expand...

Malcolm,

That eyepiece holder will work (I think) but I'm using the cheaper focusing eyepiece clamp.
http://agenaastro.com/baader-1-25-t2-eyepiece-holder-helical-microfocuser.html

If you're following up on CWs suggestion then you probably want to be sure to get a focusing holder. You could work with a basic holder and T2 extensions but the built in focusing is a lot easier. Basic holder is about $27, focusing about $56.

I think Blue Fireball made a 2 inch T2 at one time - I'll check but it's not the T2 that will limit your fov so much as the fact that the scopes themselves are designed around an eyepiece smaller than 2 inches. So even if you manage to mount a 2 inch eyepiece you're still going to get a 1-1/4 like view.

Best,
Jerry