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Kowa TE-11WZ zoom on astro telescope? (1 Viewer)

A

Albert P

Beginner Birder
Hello!

Has anyone heard of a way to use the Kowa TE-11WZ zoom on the astro telescope?

I am asking, because I am thinking about buying a telescope and I might want to try this combo.

I've noticed two self made adapters on cloudynights, but I have no possibility to make such thing on my own.
 
Albert,

I have just read the link posted by Joachim and done some measurements on my TE-11WZ eyepiece.
To adapt to 2" you will need a 2" diameter (50,8 mm or perhaps 50,7 mm?) cylinder of aluminium or delrin (POM, the same material used for kitchen knife grips). The overall length should be a minimum of 23 mm.
It should be bored out to an internal diameter of 38,5 mm and the last 5 mm of the bore should be enlarged to 42 mm to clear the O-ring seal of the Kowa ocular.
If using aluminium you could use an Edding marker to blacken the telescope end of the adapter
You will need one or two grub screws in the middle of the adapter to fix it to the TE-11WZ. It would perhaps be a good idea to place a small plastic plug under the grub screws to avoid damage to the ocular barrel.
I'm sure all of this would be a very easy job for anyone with a lathe.

John
 
Thanks for the input! I think I'll try that to save some money on astro eyepieces once I finally have the funds for my telescope.

Albert
 
As a quick alternative, I’ve used the astronomy adapters for the Leica 25-50 zoom eyepiece. APM in Germany makes a 2 inch and a 1.25 adapter both of which I’ve used with the Kowa zoom to fit the Kowa into a Televue 85. APM is very reputable, ships to the USA and Marcus Ludes is fluent in English as well as German.

They’ve recently open an outpost in the US, Outdoor Sports Optics, But I don’t know if the US store carries the Leica adapters.

No, I don’t work for Marcus or get a commission on every sale - just a very satisfied customer.

Best and good luck, the Kowa is great in my astronomical scopes,
Jerry
 
Hey Jerry,

So Kowa eyepiece sits tight in this Leica adapter? That would be some very good news! But I'm guessing the 1kg weight must be a mistake :)

Albert
 
The weight of the adapter is only 0.10 kg. (3.5 oz).

The APM adapter isn't made to be a tight fit with the bayonet mount of the eyepiece. There are three grub screws (visible in the photo) which tighten against the eyepiece barrel to hold the adapter in place. I've bought a few sets of grub screws of different lengths to accommodate different eyepieces.

If it matters to you the tips of the screws are likely to penetrate the surface of the eyepiece barrel and leave little bright dig marks.
 
Last edited:
Hello Joachim and Albert,

I can confirm Tringa45 measurements. If I were simply printing an adapter then I’d make it a little less complex than Tringa’s excellent suggestions for a quality machined product. If printing you could make a cylinder with length of 23mm, OD of 50.8mm and ID of 41.8mm.

The O ring in the eyepiece is compressible and a friction fit should be sufficient to center the eyepiece in the adapter and hold it securely. You could also use nylon grub screws at 0, 120, 240 for extra grip if my suggestion is a little too quick and dirty for your taste.

The APM adapter does a pretty good job of holding the Kowa in place. There are nylon grub screws which are sufficient if you’re careful but I use a little trimmed rubber sheeting around the eyepiece just to be sure. I’ve been able to use the 1.25 as well as the 2 inch Leica adapters, but using the 1.25 means you must take special care to purchase a telescope with adequate in-travel. Using the 2 inch is a snap. Actual weight is about 50 grams but APM uses really heavy boxes for shipping :>)

Best,
Jerry
 
Hi Joachim,

jring said:
Or maybe I could try to print sth according to the measures taken by Tringa45... shoud be easy enough to design in openscad...
Click to expand...

Didn't mean to derive you of the fun experience, but when I saw John's post with measurements, I just stopped reading and fired up OpenSCAD before I got to your post:

Eyepiece Telescope Adapter.png

Code attached below. I don't know how to arrange the grub screws, and which size they normally are. It probably would be a good idea not to bore through entirely but to leave the plastic (if you print it in plastic) thinly in place to protect the eyepiece barrel, but that would look odd in the picture :)

Regards,

Henning

Code: 
$fn = 128;

epsilon = 0.01;

difference ()
{
    cylinder (d = 2 * 25.4, h = 23);
    
    translate ([0, 0, -epsilon])
        cylinder (d = 38.5, h = 23 + 2 * epsilon);
    
    translate ([0, 0, -epsilon])
        cylinder (d = 42, h = 5);
    
    l_grub = (2 * 25.4 - 38.5)/2 + 2;
    for (i = [0:120:240])
        rotate ([0, 0, i])
            translate ([0, 38.5/2 + l_grub - 1, 23/2])
                rotate ([90, 0, 0])
                    cylinder (d = 5.5, h = l_grub);
}
 
Hauksen said:
Didn't mean to derive you of the fun experience, but when I saw John's post with measurements, I just stopped reading and fired up OpenSCAD before I got to your post:
Click to expand...

Hi,

no worries, this way I can learn from sb with way more experience than me... so far my endeavours with openscad and my 3d printer are limited to lens caps and solar filter holders...

I could actually print this and deliver it to Albert in person as I need to go near Fulda in the next month or so anyways... So please let me know if you'd like that, Albert.

Joachim
 
JerryLogan said:
I can confirm Tringa45 measurements. If I were simply printing an adapter then I’d make it a little less complex than Tringa’s excellent suggestions for a quality machined product. If printing you could make a cylinder with length of 23mm, OD of 50.8mm and ID of 41.8mm.

The O ring in the eyepiece is compressible and a friction fit should be sufficient to center the eyepiece in the adapter and hold it securely. You could also use nylon grub screws at 0, 120, 240 for extra grip if my suggestion is a little too quick and dirty for your taste.
Click to expand...

Jerry & Albert,

As the 41,8 mm diameter is only a 5 mm long step in the mount holding the O-ring, it would be better to stick with the 38,5 mm bore if one wants to simplify things. Then the adapter will stand 5 mm proud of the external section of the eyepiece but should not cause any problems with in-focus.

Many astro adapters have a single grub screw. The Kowa adapter for astro eyepieces has two placed at 90°. Two or three might help to prevent the eyepiece rotating in the adapter when using the zoom function.

Just a thought, but would the TE-11WZ work as well on an astro scope as it does on the 883/884? They at f/5,6 are very fast scopes and the TE-11WZ corrects their field curvature almost to perfection. I have played around with various astro eyepieces on my birding scopes and none of them achieve anywhere near the edge correction of the original eyepieces.

John
 
jring said:
I could actually print this and deliver it to Albert in person as I need to go near Fulda in the next month or so anyways... So please let me know if you'd like that, Albert.
Click to expand...

That would be awesome! My only problem is that the nearest possibility for me to test the adapter would be around Christmas... or when I buy my own telescope. This however is, you know, wife-dependent :)

Tringa45 said:
Just a thought, but would the TE-11WZ work as well on an astro scope as it does on the 883/884? They at f/5,6 are very fast scopes and the TE-11WZ corrects their field curvature almost to perfection. I have played around with various astro eyepieces on my birding scopes and none of them achieve anywhere near the edge correction of the original eyepieces.
Click to expand...

I've read on cloudynights, that TE-11WZ does pretty well on astro scopes. Both of the adapters, I've read about, caused however some vignetting when zooming in. I would expect this to be be the case also with this printed adapter. But who knows...
 
Albert P said:
Both of the adapters, I've read about, caused however some vignetting when zooming in. I would expect this to be be the case also with this printed adapter. But who knows...
Click to expand...

With a 1 1/4" adapter perhaps, but I can't see how this could happen with the 2" adapter.

John
 
Albert P said:
That would be awesome! My only problem is that the nearest possibility for me to test the adapter would be around Christmas... or when I buy my own telescope.
Click to expand...

I can bring a small astro scope and mount too to test... SW 100 ED maybe?

Joachim
 
The performance of the eyepiece may depend on what type of astro telescope is purchased.

A Maksutov or SCT will have a longer focal ratio of say f/14 to f/10. The smaller ones may only have 1.25 inch eyepiece tubes.

With a short focus refractor or Newtonian the eyepiece may or may not be as suitable.
These may range from f/4 to f/7 although planetary Newtonians may be f/9 and long focus refractors f/15.

One cannot be sure how any eyepiece will match an astro scope as there are many different types.
It depends really on what type of observations one makes.
 
Hi,

yeah, that's correct, but since the Kowa spotter it was designed for is a fairly fast refractor at f5.5, it should be fine with slow scopes like Mak, SCT or my 100 ED, reasonably fast reflectors like an 8" f6 dobs and also fast refractors.

Very fast reflectors in the f5 and below range must be tested of course - I don't have one...

Joachim
 
Tringa45 said:
With a 1 1/4" adapter perhaps, but I can't see how this could happen with the 2" adapter.
Click to expand...

Unfortunately both adapters were 2". They both were vignetting at higher mag.
https://www.cloudynights.com/topic/569030-kowa-te-11wz-the-plot-thickens/
https://www.cloudynights.com/topic/581215-kowa-zoom-impressions/

jring said:
I can bring a small astro scope and mount too to test... SW 100 ED maybe?
Click to expand...

If it's not a problem for you then sure it would be great. I might have very limited time though as I am more and more intensively preparing myself to be a father and I will have to be there for my wife also.

Also both topics on cloudynights stated that Kowa is really good. In one of them TE-11WZ was checked in f4.9 reflector and still it was really nice. Seems like the only problem with the eyepiece was vignetting.
 
Albert P said:
Unfortunately both adapters were 2". They both were vignetting at higher mag.
https://www.cloudynights.com/topic/569030-kowa-te-11wz-the-plot-thickens/
https://www.cloudynights.com/topic/581215-kowa-zoom-impressions/



If it's not a problem for you then sure it would be great. I might have very limited time though as I am more and more intensively preparing myself to be a father and I will have to be there for my wife also.

Also both topics on cloudynights stated that Kowa is really good. In one of them TE-11WZ was checked in f4.9 reflector and still it was really nice. Seems like the only problem with the eyepiece was vignetting.
Click to expand...

Hi,

from the 2nd thread on CN it looks like the first tester might have been mistaken with the vignetting - if there really was vignetting, the light cone would be blocked by sth far before the focal point, for example an overly long focuser tube or a too small secondary mirror. In this case some light loss at the edge of the field will be visible, but only at low magnification. It will also be visible as a fuzzy field stop in these low mag EPs even if they normally have a sharp field stop.

But in that 2nd thread, the poster sees different field stops at or close to focus (and thus inside the eyepiece) at higher magnifications - this is not classic vignetting and I think the effect should be cosmetic only (ie. the edge of the image is not nice and sharp at high mag).

If you can spare half an hour or so to try this, I can put a scope and tripod in the trunk when I go to Bischofsheim. I'll shoot you a pm when I know when.

Joachim
 
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