Adapting 1.25" Astronomy Eyepieces to the Nikon ED50 (1 Viewer)

[Zeroforhire]

Messaged the op

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[billb9430]

The ring adapters I made in Feb of 2017 and mentioned in post 14 of this thread are all claimed, so I will no longer be able to fill requests to send one. I hope those who received the little rings have been able to put them to good use adapting astronomy eyepieces to the ED50 - Bill.

 

[justabirdwatcher]

I realize this is a very old thread now, but I wanted to provide an update with my experience using astronomy eyepieces on the ED50.

First of all, I want to thank Bill for offering to send me two of the threaded barrel adapters so I could use astronomy eyepieces on my scope. I started out with the 13-30 Nikon eyepiece, and that was fine, but I was intrigued by the idea of being able to use fixed-power eyepieces with a wider field of view.

My first eyepiece was the 20mm SWA recommended by Bill. I could quickly see why this was his favorite. Although only providing about 12x magnification, the huge field of view and bright, sharp image was just so pleasing to the eye!

My next eyepiece was a 15mm SWA, and that was also excellent. It was very small and provided a very good image. Comparing it to my 13-30x Nikon, the image quality was nearly as good as that eyepiece at 19x, but the field of view was quite a bit better.

Both of the eyepieces above were essentially "plug and play," needing only to unscrew the 1.25" barrel and fit the threaded collar provided by Bill. It couldn't have been much easier.

Recently, I wanted a little better quality eyepiece so I took a chance and ordered the Pentax 12mm, not knowing for certain whether it could be fitted to the scope with Bill's adapter rings. When I received the eyepiece, I was immediately struck by the quality and robust build. Compared the the less expensive 15 and 20 SWA's, the Pentax is in another class. Unfortunately, it was not "plug and play" because I could not easily remove the 1.25" barrel like I could on the SWA eyepieces. Nothing I tried would get it to unscrew... Until...

I happen to have the tools to do some amateur gunsmithing, and one of those tools is a barrel vise. As a last resort, I put the barrel of the Pentax eyepiece in my barrel vise (Yikes!), wrapped the top portion of the eyepiece in tape, and got out the pipe wrench (double Yikes!). I was either going to get the barrel off or break the eyepiece trying. After some effort and a few four-letter words, the barrel finally relented and unscrewed from the body of the eyepiece. The damage done was minor and mostly cosmetic. Nothing that couldn't be touched up with a black sharpie.

Upon removing the 1.25 barrel from the body, I realized that unlike the hollow barrels on the 15 and 20mm SWA's, the Pentax barrel has a lens inside of it! At that point, I wasn't sure if the eyepiece would even work, but I muddled on anyway with the hopes that I could salvage something out of this mess I had gotten myself into...

From there, fitting the Pentax body to the ED50 was fairly straightforward because (fortunately for me) the outside thread on Bill's adapter fit both the ED50 scope threads and the inside of the Pentax eyepiece body. Finally something went right!

Unfortunately, I wasn't done yet. The eyepiece was a thing of beauty and functioned perfectly, except that it wouldn't focus to infinity (Grrrrrr...). What to do, what to do... It was awfully close though, and I knew that if I could just reduce the distance from the eyepiece to the body of the ED50, I could get infinity focus. So out came the metal file! (Triple Yikes!!!). And I filed off about 1/16" from the bottom of the eyepiece body so when it was screwed into the scope, I could achieve infinity focus. AND IT WORKED!!!!!

So here's the final result. Infinity focus is just before the focuser limit is achieved. What that also means is that this scope/eyepiece combination will now focus to just about 10 feet as well! I'm not sure the situations that I'll need such close focus, but I'm sure I will find one.

I have no idea what the resulting magnification is, or how to measure it, but I don't think it's the 23x estimated by Bill at the top of the thread. I'm sure that's due to removing one lens that stayed with the 1.25" barrel I removed. However, the image quality is just SUPERB, and I estimate the final magnification to be something around 15-17x, which is really good for my needs, as I tend to prefer the brighter images that lower magnifications provide anyway. With just a 50mm objective lens, anything over 20x will be too dim to be useful in my opinion, especially at those "magic hours" of dawn and dusk.

At the end of the day, I'm rather thrilled with how this experiment worked out. I was comparing this ED50/Pentax 12mm combo to a Leica 62 spotter the other day, and the little ED50 more than held it's own against the Leica at 16x. Truth be told, I preferred the image from the ED50/Pentax combo a fair amount more. It was at least as sharp, if not sharper, it was considerably brighter, and the field of view was much better. As far as I'm concerned, I have found my eyepiece for this lovely little spotter! If you're brave enough to try this, and have the tools to remove the barrel from the Pentax 12mm, you will end up with an amazing eyepiece for your ED50.

 

[6chen]

I'd like to add my bricks to this thread.
The WA 17 and UF 10 also work well with the adapter.
WA 17 is a good compromise for 15mm+20mm combination, if you only want to bring one eyepiece with you.
UF 10 has a 16mm EP and is very comfortable with eyeglasses.
I usually have SWA 20 always on my ED50, throw UF 10 in my pocket for extra magnification when I go out. The bulky WMC 40x now stays in the dry box most of the time.

I also tried to adapt the svbony 7-21mm zoom, but its barrel is too long and too big to fit in. Even if I could make an adapter, the long focal length makes it impossible to focus. However, I am able to adapt it to my daughter's Vixen Aroma 52A which has a collapsable objective and get good focus.

 

[Binastro]

I have a couple of Opticron MM2s that seem to be the same as the Vixen Aroma 52A.

They have slightly different threads for eyepieces but have collapsing front barrels.

Presumably these scopes have little trouble with using any eyepiece with a suitable adapter.

There may be some vignetting.

24.5mm fit eyepieces also fit most scopes.
Or 23.2mm fit microscope eyepieces.

Regards,
B.

 

[Astrospotter]

The ring adapters I made in Feb of 2017 and mentioned in post 14 of this thread are all claimed, so I will no longer be able to fill requests to send one. I hope those who received the little rings have been able to put them to good use adapting astronomy eyepieces to the ED50 - Bill.

 

[Astroguy2000]

Drew a M32x0.75 to M28.5x0.6 adapter and printed in PLA.
Works surprisingly well
I have a few other eyepieces coming that I want to use on my ED82 as well.

let me know if you want the file for the SWA eyepieces.

 

[Engineer117]

High Power Adaptable Eyepiece – On Sale!

While I enjoy carrying the featherweight Nikon ED50 while hiking and normally keep the wide field, low power 20mm SWA eyepiece on the scope, occasionally views and conditions along the trail call for the maximum power possible in this small spotter. As detailed in the above posts, the nice 8mm BST flat field eyepiece giving 35x was formerly the highest power easily attainable with low cost adaptable eyepieces. The problems with shorter FL eyepieces previously investigated were the very short eye relief of orthoscopic types and the presence of a negative “Smythe” type field lens in the bottom barrel of others that precluded removing the bottom 1.25” barrel and attaching an adapter ring to fit into the ED50 eyepiece port.

Several weeks ago, a post in the Cloudy Nights site “Eyepiece” forum showed a photo of the relatively new Explore Scientific 5.5mm 62˚ afov eyepiece with the bottom barrel removed. While the bottom lens DOES protrude a bit below the eyepiece shoulder, it is NOT attached to the removable 1.25” lower barrel, so the adapter rings described earlier in this thread WILL attach nicely to this eyepiece. As a fortunate coincidence, Explore Scientific eyepieces, including this one, are on sale thru the end of December, 2017 for 20% off! The price until the end of December is $79.99. While that is certainly more than the cost of a bargain 20mm SWA, it is much less than the $200 street price for many of the Nikon eyepieces for this scope.

My new ES 5.5mm 62˚ eyepiece arrived today and I’ve done some preliminary testing in the ED50 angled scope. The eyepiece provides a calculated 51x with about 1.2˚ true field of view. It gives a 1 mm exit pupil – though small, it is still usable when there is good illumination. Smaller exit pupils than that may show image deterioration due to diffraction limitations of the small opening. With the 5.5mm held in an adapter ring in the ED50, the close focus is 11 feet and when focused at infinity the focus knob still has 1.25 turns of “in” focus to accommodate nearsighted observers who wish to view without their glasses. So the eyepiece is very compatible with the focus range of the ED50. I can see the whole 62˚ apparent field with my eye glasses on, but of course this may vary with glasses of different design. The listed eye relief is 12.9 mm and that agrees closely with the result of 13 mm obtained by focusing on a ground glass slide and measuring with a dial caliper. The view through this eyepiece with the ED50 is very sharp, but does show just a little bit of what I believe is angular magnification distortion.

Last spring I offered to send a free (including free shipping) adapter ring to USA Birdforum members who requested one, so long as my supply of extras lasted. The response was underwhelming. With so few requesting them, two packages with three rings each were sent to folks in Europe willing to pay for the $13.50 international shipping. I STILL have 9 of those original rings left and will send one free to USA folks who send me a request via Birdforum P.M. until the rings are gone. Perhaps you already have the excellent Nikon eyepieces and so do not need adapted ones, but I find their light weight, small form and low cost make these modified eyepieces ideal for “along the trail” use. With a clear 55mm filter over the objective and one of these low cost but nice viewing eyepieces in the ED50’s eyepiece port, there should be minimal worries about finger prints on the expensive lens when novices or small children want to view a bird, bear, or moose through the little spotter.

For those seeking wide field, the ES24mm 68˚ eyepiece mentioned in a post above is also on sale. Unfortunately, based on a photo sent to me by a friend, the bottom 1.25" barrel on THAT eyepiece has outside threading that screws into an inside threaded opening in the ocular upper barrel bottom, so the quick adaptation with the little ring that works with all the other eyepieces listed here will NOT work with the ES24mm 68˚.

Attached is a photo of the Explore Scientific 5.5mm 62˚afov eyepiece with lower barrel removed & adapter ring attached and also a spreadsheet listing the power, field of view, and exit pupil for various fixed FL eyepieces that work well with the Nikon ED50. – Bill

Hello Bill! I can't find a 5.5mm eyepiece for sale. But there are many 3mm options.
Will I have enough focusing range on the ED50?

https://aliexpress.ru/item/1005006125451421.html?sku_id=12000035867360593&spm=a2g2w.productlist.search_results.16.7a5c2447ph0Sji

 

[billb9430]

Hello Engineer117. With the Nikon ED50's small 50 mm objective, a 3 mm FL eyepiece (site says "diameter" is 3 mm rather than focal length?) would give around 93 x, but a very small 0.53 mm exit pupil. I find even the longer FL 5.5 mm at 51 x appropriate only for bright scenes with its small 1 mm exit pupil. The 3 mm information also says it is "ultra wide angle", but 52˚ is hardly that. (The 5.5 is 62˚ AFOV and the 20 mm SWA has a 70˚ AFOV and 5˚ true field of view at 14 x with a bright 3.6 mm exit pupil.)
I have not tried the eyepiece you mention, so do not know if it will reach focus in the ED50. Please post your findings if you try it. - Bill

 

[mayoayo]

Drew a M32x0.75 to M28.5x0.6 adapter and printed in PLA.
Works surprisingly well
I have a few other eyepieces coming that I want to use on my ED82 as well.

let me know if you want the file for the SWA eyepieces.

View attachment 1549818


View attachment 1549819

Yes..I want the file!!