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Old Monday 11th April 2016, 21:00   #1
billb9430
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Adapting 1.25" Astronomy Eyepieces to the Nikon ED50

Owners of the little Nikon ED50 spotting scope who want wider fields than zoom eyepieces provide and do not have a full assortment of the hard-to-find Nikon wide field fixed focal length eyepieces may want to adapt astronomy eyepieces to their scope. An excellent post suggesting this was made by “mayoayo” on Dec. 2, 2013. It is the 8th post in this thread: http://www.birdforum.net/showthread.php?t=260667
“mayoayo” also mentioned this in the 4th post in this current thread: http://www.birdforum.net/showthread.php?t=322210

I recently bought a new Nikon ED50a (body only) and have had some success using “mayoayo’s” ideas with SWA (Super Wide Angle) and Flat Field 1.25” eyepieces. Though “mayoayo” was able to adapt one eyepiece having optics in the lower barrel, all of mine have the lenses attached only in the upper barrel. To use these eyepieces, just remove the lower 1.25” OD barrel and thread on an adapter that allows you to attach the upper barrel directly to the Nikon ED50 eyepiece port.

Here’s a listing of six relatively wide field, low cost ($45-$69 U.S. New, often about 2/3 that cost if purchased used) astronomy eyepieces that work well when adapted like this. Also listed for each is its magnification, apparent field of view (Afov), true field, and exit pupil when used in the Nikon ED50a.

20 mm SWA 70˚Afov ----------- 14x w/ 5.0˚ true field - - - - - 3.6 mm
19 mm Flat Field 65˚Afov ---- 15x w/ 4.4˚ true field - - - - - 3.3 mm
16 mm Flat Field 60˚Afov ---- 18x w/ 3.4˚ true field - - - - - 2.8 mm
15 mm SWA 70˚Afov ---------- 19x w/ 3.8˚ true field - - - - - 2.6 mm
12 mm Flat Field 60˚Afov------ 23x w/ 2.6˚ true field - - - - - 2.2 mm
8 mm Flat Field 60˚Afov------- 35x w/ 1.7˚ true field - - - - - 1.4 mm

The 20 mm SWA at 14x is exceptional for wide field scanning with its amazing 5˚ field (262 ft @1000 yds.) while the 12, 15, and 16 mm oculars are nice for general viewing. I tried a 10 mm SWA eyepiece, but found its eye relief is uncomfortably short AND it is the only one I’ve found with upper barrel threading too small in diameter to screw securely into the anodized barrel adapter described below. Higher power views begin to get dim with the little 50 mm objective once below 2 mm exit pupil, though the 8 mm Flat Field producing 35x can sometimes be used on sunny days so long as there is not too much wavy refraction from nonuniformly heated air near the ground.

See photo #1: Nikon ED50a, 20 SWA on scope. L to R : 19, 16, 15, 12, and 8 mm eyepieces.

Use caution when first unscrewing the lower 1.25” barrel from the 20 mm SWA eyepiece. That lower barrel screws onto a short extension of an externally threaded retaining ring that ALSO threads into the upper barrel and serves to keep the eyepiece lenses in place. If that ring unscrews from the upper rather than lower barrel, it could allow the eyepiece lenses in the upper barrel to tumble out with possible damage. To avoid this problem, invert the eyepiece and unscrew with the “bottom” 1.25” barrel facing UP. You may want to apply a drop of “lite” thread-locking compound to the upper part of the retaining ring threads if your upper barrel threading is loose.

See photo #2: Inverted 20 mm eyepiece with 1.25” barrel removed to show threaded ring

For my first attempt at turning an adapter, I used a piece of aluminum rod, boring and threading it on a lathe 0.60 mm pitch inside to accept the eyepiece threading and 0.75 mm pitch outside to fit the eyepiece port in the Nikon ED50. This worked well, but was tedious to do. Some have used the technique of wrapping tape or some other material around the eyepiece retaining ring threads to fit it to the scope eyepiece socket by friction, but this provides less security, might allow misalignment of the eyepiece, and makes changing eyepieces in the field more difficult.

Making a nice adapter became much simpler when I discovered that Surplus Shed in Fleetwood, PA, USA sells black anodized aluminum barrels for 1.25” eyepieces that are ALREADY threaded the requisite diameter and 0.60 mm pitch inside. (Surplus Shed was sold out of these for some time, so I delayed writing this until they got a new supply on Mar 24, 2016.) These barrels are 30 mm long (though listed as 1 1/8”), are item No. M2104, and sell for $4.00 each. Find them here: http://www.surplusshed.com/pages/item/m2104.html

The Surplus Shed barrel still needs to be threaded on the outside to screw into the ED50 eyepiece port. The barrel can be held internally in a lathe 3-jaw chuck and outside threaded with a pitch of 0.75 mm. The anodized barrel is slightly too small in OD for correct fit with a full depth thread, but works well if threaded to a depth of .013” or .33 mm. (That’s .015” or .38 mm on the compound feed at 30˚.) If you do remove all the anodizing while threading to form sharp thread crests, the adapter will still work, but will fit loosely until the eyepiece base is tightened against the scope flange. You’ll need to take light passes removing only .002” or so each time when doing this threading, since you are gripping the piece with chuck jaws expanded against the internal threading and must be careful not to over tighten and damage those threads.

See photo #3: 1.25” barrel in lathe being threaded .75 mm pitch on outside – note some anodizing left between thread cuts because threads are not full depth

Once threaded, leave the little 30 mm long barrel in the lathe and use a narrow parting tool to slice off adapter rings 6 mm long. This length will give you about four turns to conveniently secure the eyepiece (with adapter screwed all the way onto the eyepiece retaining ring) in the ED50 eyepiece socket. You should be able to get 3 or possibly 4 of these from each barrel, depending on the thickness of your cutoff tool. The very top threads of each adapter do not engage in the eyepiece port, so if you grind a narrow threading bit, you can even use the ring closest to the chuck face that you could not thread all the way to the top. You’ll want to smooth the bottom cut edges of these rings with a fine file followed by 0000 grade steel wool. Clean the swarf from the threads after this treatment and then wipe with a lightly oiled cloth to allow the rings to turn easily into the ED50 eyepiece port. It is best to do the file and steel wool treatment before you cut off each ring so you can spin the barrel in the lathe as you smooth. Attach the adapter ring to the eyepiece with the smoothed end to the bottom, so it will go into the eyepiece port of the ED50.

You may also want to cut two notches 180˚ apart in the other (upper) edge of the ring, once cut off, so that you can remove it from the Nikon eyepiece socket with a ring spanner in the unlikely event your eyepiece unscrews from the adapter as you remove it from the scope. These notches can be cut with a screw slotting file or a Dremel tool emery disk. You can make a ring spanner wrench sized to fit this ring from a used disposable utility knife blade. See the fifth post in the following thread for more detailed information on making this type of wrench. http://www.birdforum.net/showthread.php?t=249576

See Photo #4: L to R: 1.25 barrel before threading, threaded barrel, barrel sectioned into rings, spanner made from utility knife blade, adapter ring on eyepiece, plastic bolt case for eyepiece

This adaptation is very easy to do, provided you have a lathe capable of cutting metric threads and know how to do that. These machines are likely in common use everywhere except in the USA. For USA folks, transposing gears are available that enable you to cut metric threads on an inch standard lathe. I use those. You also may be able to find a local machine shop that has a metric lathe and is willing to do this small threading and parting job for a reasonable fee. (You should bring them a couple of the Surplus Shed 1.25” anodized barrels since this will speed the work and so reduce your cost.)

It is possible to get by with just one adapter ring for your ED50, since it could be moved from eyepiece to eyepiece as you change to different oculars. However, since a single Surplus Shed anodized barrel will provide 3 or 4 adapter rings, I find it more convenient to just keep a ring on every ocular I plan to use. You’ll probably want to keep the original 1.25” barrel from each eyepiece in a safe place – so you can return them to astronomy use if you like. When using the adapted eyepieces with your spotter, it’s handy to keep them in small bolt cases rather than using lens caps. These provide excellent protection even if the eyepiece is sometimes carried in a pocket. Plastic bolt cases (as well as all the eyepieces listed) are available from Agena Astroproducts. The adapted 8 mm Flat Field and the SWA eyepieces fit in the 37 x 60 mm size bolt cases while the 12, 16, and 19 mm Flat Field oculars require the slightly larger 42x60 mm case. (The Agena SWA and BST Flat Field eyepieces currently come with a free bolt case if ordered new from Agena.)

I enjoy the views provided by these adapted eyepieces in my Nikon ED50a and hope you will, too. Special thanks and acknowledgement to “mayoayo” for the initial post and developing this idea! - Bill
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Old Tuesday 12th April 2016, 00:24   #2
mooreorless
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Hi Bill,

Thanks for posting this, a great alternative to Nikon Fieldscope eyepieces, esp. with these eyepieces being hard to find and expensive. I really like your great pictures! BTW I will be trying out the adapter.

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Old Tuesday 12th April 2016, 01:50   #3
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What a great post! Thanks for your very specific and very useful information.

Very best,
Jerry
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Old Tuesday 12th April 2016, 02:36   #4
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I now have 4 eye pieces for my Pentax. I use two, they are actually identical Vixen zooms. So, while it seems good to have expanded choices, I just don't use the extra two in the field. Too much trouble. My smallest is 20x or so and i sometimes wish I had 15x, it's not such a big deal. ( I have a cheap one that does that but the field of view is not much more than my zoom at 20x).

If you are used to using the wide angle eye pieces, that is another matter.

Also, as you travel, it may be of advantage to have a small scope and the eye pieces, but even there zoom would be handy. Less to go wrong while traveling (drop eye piece in mud etc.)

With the 50-65mm scopes the limit is really the high power where dimness finally beats any gain in power.
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Old Tuesday 12th April 2016, 17:56   #5
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Wow..excellent post ,great job..thanks a lot for sharing all the info..I need to get one of these surplus shed 1 1/4 barrels shipped to Spain..or maybe I can buy one if i visit the states this summer(likely)...do they only sell this in the 0.60 pitch...?..
The BST explorer i have now,is the one with elements in the barrel..The diameter of the threads are different to the Flat field ones
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Old Thursday 14th April 2016, 17:36   #6
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Easily adapted VERY low cost 28X eyepiece for Nikon ED50

The Vite Aspheric 10 mm eyepiece has an Afov of 62˚ and is one of a series of three focal lengths (23, 10, and 4 mm) that inspired a 400 post thread on the Cloudy Nights Astronomy site beginning last June, 2015. See here: http://www.cloudynights.com/topic/50...-23m-aspheric/
Discussed in 400 posts with quite a bit of enthusiasm, these are worth a look for use with spotters. While the 23 mm aspheric may be useful for spotting scopes that use 1.25” barrel diameter eyepieces, the 4 mm provides far too much magnification for most spotting scopes and has lenses in its lower barrel. The 10 mm, giving 28x, is the only one of the three adaptable to the Nikon ED50 scope using the same threaded ring described in the first post of this thread. In CN posts, it is claimed that these Chinese made 3 element eyepieces have one aspheric plastic lens inside, where it is not subject to abrasion.

Despite having only 3 lens elements, this eyepiece delivers a nice view except at the very edge of the field. In the little Nikon ED50, it gives a high power 28x with a true field of 2.2˚, exit pupil of 1.8 mm, and adequate eye relief for non-eyeglass users. By far the biggest surprise for this eyepiece, however, is the price. It is available on Ebay for the princely sum of $9.69 US including shipping from China to the USA! Here’s one of several sellers:
http://www.ebay.com/itm/361453329703...%3AMEBIDX%3AIT
The eyepiece body and .60 mm pitch threaded extension section are made of plastic, so the ocular is very light weight, but still works well. The metal threaded lower 1.25” barrel must be unscrewed and set aside, just like the previous eyepiece adaptations.

Since this is the 7th astronomical eyepiece mentioned and adapted in this thread, I should probably make it clear that no one would want to carry ALL these oculars in the field for their Nikon ED50 scope. They are listed here simply as “ones that work” so folks who do astronomy may be able to adapt eyepieces they already have rather than buying new. I generally carry just three, - with the 20 mm wide field in the scope and a medium and high power in bolt cases. While my “kit” in the past has been the 20, 12, and 8 mm eyepieces, that may change to the 20 SWA, 16 Flat Field, and 10 Aspheric now, for greater utility. By the way, I find the Nikon-supplied scope case nearly useless and so carry the scope and two bolt-contained eyepieces in a nicely padded full zip “pistol rug” 14 inches long that provides great protection, quick access, and fits in my daypack. These are available for the bargain price of $4 or $5 at a local gun show! Take your ED50 along to insure good fit and look for tables loaded with a variety of cases. You may get some strange looks from other birders in the field when you first pull the case out of your daypack to watch birds, however! - Bill

Photo 7: Adapted 10 mm 62˚ Aspheric w/ threaded ring and unmodified 23 mm 62˚ Aspheric. While the original eyepieces were labeled “Vite” the ones I received in January only have focal length, Afov, and “Aspheric Eyepiece” on the gold label band.

Photo 8: Nikon ED50a w/3 adapted fixed focal length eyepieces in padded “pistol rug” scope case.

Photo 9: Case closed
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Old Friday 15th April 2016, 15:01   #7
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Bill, I bought the 10mm eye piece. Will use it as is, as I have a Pentax 65mm scope. It will be fun to use in some stationary sports where we stay a while in a wetland area and I just pan mostly, no need to zoom so much.
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Old Tuesday 26th April 2016, 22:35   #8
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OK, it's here. The 10mm gives about the same view as my 12mm Pentax XF-12. The eye relief is much less than the Pentax, so I have to take my glasses off. Field of view is about the same.

If I could find a cheap astronomy scope that takes the 1.25 inch eye piece, I could set up an extra scope for a guest.
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Old Thursday 7th July 2016, 17:52   #9
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I have a Pentax 65mm and use it with XW 14 and XW 10. I'm looking to add another scope in 80-90mm range but would like to use XW 14,10,7. While Kowa 883 and Swaro 90mm best in class scopes, I am looking for something which can handle XW EP's. Can someone point me where to buy Nikon Fieldscope to 1.25" adapter. I could buy another Pentax 80ED but have read on the forums that Pentax scopes are inferior to Alphas, Kowa and Nikon.
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Old Thursday 7th July 2016, 20:08   #10
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Hi,

I suspect you won't have luck with using your XWs on Nikon Fieldscopes since they seem to have a negative element in the barrel. All adaptions mentioned above involve removing the 1.25" barrel of the EP since the diameter of the Nikons eyepiece mount is too small to take an 1.25" barrel (BF user mayoayo has adapted one EP with an element in the barrel but he needed to make an adapter which has to hold the element removed from the barrel).

Some of the current big alpha scopes seem to have wide angle zooms with a large enough diameter of the EP mount for using 1.25" EPs. The big Kowa is known to be very good even at higher magnifications.

Joachim
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Old Thursday 7th July 2016, 20:33   #11
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Hi,

I suspect you won't have luck with using your XWs on Nikon Fieldscopes since they seem to have a negative element in the barrel. All adaptions mentioned above involve removing the 1.25" barrel of the EP since the diameter of the Nikons eyepiece mount is too small to take an 1.25" barrel (BF user mayoayo has adapted one EP with an element in the barrel but he needed to make an adapter which has to hold the element removed from the barrel).

Some of the current big alpha scopes seem to have wide angle zooms with a large enough diameter of the EP mount for using 1.25" EPs. The big Kowa is known to be very good even at higher magnifications.

Joachim
I'll have to scratch Nikon FS ED 82 from the list. Thanks for the quick response.
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Old Thursday 15th September 2016, 19:56   #12
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Small Update to Original Post:

Last spring the optics company Explore Scientific had a sale and offered some of their eyepieces at discounted prices. I bought a 16 mm FL eyepiece of their 68˚Afov type. It has a 1.25" barrel. I bought it for astronomical use, but just today noticed that if the lower barrel, containing no optics is removed, the protruding threaded section is the same as the other eyepieces adapted and fits the Surplus Shed No. M2104 barrel perfectly. Thus the adapter, when outside threaded and cut off as above, allows use of this additional eyepiece in the Nikon ED50 scopes. It provides a magnification of 18x, just like the FF16mm, but because its Afov is 68˚ rather then 60˚, gives a true field that is 3.9˚, about half a degree larger than when using the Flat Field 16 mm eyepiece. Unfortunately, the ES16 mm eyepiece is heavier and currently costs $149. (The spring sale at $99 each has ended.)

I'd suggest that no one who has the FF16 go out and buy this larger and more expensive eyepiece for such marginal improvement, but if you already have the eyepiece or find one at a good price on the used market, this is another viable alternative for the little Nikon scopes. Since this is the only Explore Scientific 1.25" barrel diameter eyepiece I own, I cannot tell whether other focal lengths of this brand will also be adaptable - perhaps others who own them will chime in.

Just two additional comments: My favorite non-Nikon adapted eyepiece in the Nikon ED50 scope is still the low cost 20 mm SWA at 14X and 5˚ true field. Also, Surplus Shed is once again sold out of the No. M2104 threaded barrels needed to make these adapters - hopefully they will get more in soon. - Bill
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Old Thursday 15th September 2016, 21:31   #13
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Hi,

actually I own the ES 16mm 68 deg and like it a lot - on my Kowa it gives 26x though and I have a Kowa 30x EP, so it's not really sth new. My other ES EPs are 2" so no dice.

If you are looking for rich field, there's the 24mm from the same series - even bigger and it's often called the poor mans Panoptic 24. I'm looking to get this used or with the next sale. Your ED50 would give 5.7 degrees at 12x - my Kowa 3.9 deg at 17.5x....

Joachim
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Old Monday 6th February 2017, 20:57   #14
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Special offer while they last - Eyepiece adapters as described in post 1.

My wife and I used the little Nikon ED50 scope while hiking in the Rockies last summer and remain enthusiastic about the adapted eyepieces as described in this thread. The Surplus Shed 1.25” anodized barrels to make the astro-eyepiece-to-Nikon ED50 adapters are back in stock now, but having made enough for personal use, I had 6 left over and used those to make 24 more little adapters to give away to friends on Birdforum.

I recently managed to snag a new Nikon DS 16/24/30 (4.5˚ field at 16x) eyepiece on ebay for just $100. While it gives an amazing view – sharp all the way to the field edge - its extra weight, bulk, and exposed eye lens cause me to still prefer the smaller, cheaper, and slightly wider field of the adapted 20 mm SWA (14x, 4.75˚ field) for general “along the trail” use when other hikers will be enjoying views with the scope, too. A nice combination is to have that eyepiece on the scope with BST Flat Field eyepieces of 12mm (23x) and 8mm (35x) in the scope case for higher power use. The 20mm SWA would also be a good low cost wide field addition for those who use a Nikon Zoom as their choice for higher power viewing.

If you would like to try one of the little ring adapters to fit your astro-eyepiece on the Nikon ED50 (see post 1 for eyepieces that will work), just send me a Birdforum Private Message with your (USA) mailing address and I will send them out in a couple of weeks on a first come first served basis. I will post here when (or if) the 24 adapters are all claimed. Because metric threading lathes are not common in the USA, (and postage is reasonable compared to international shipping) this offer is limited to mailing addresses in the USA only. The little adapter fits nicely in a small padded mailing envelope, so I will cover the shipping cost. -Bill
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Old Wednesday 8th February 2017, 11:41   #15
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Quote:
Originally Posted by bdg1 View Post
I have a Pentax 65mm and use it with XW 14 and XW 10. I'm looking to add another scope in 80-90mm range but would like to use XW 14,10,7. While Kowa 883 and Swaro 90mm best in class scopes, I am looking for something which can handle XW EP's. Can someone point me where to buy Nikon Fieldscope to 1.25" adapter. I could buy another Pentax 80ED but have read on the forums that Pentax scopes are inferior to Alphas, Kowa and Nikon.
Be aware that astro eyepieces won't always come to focus in all spotting scopes because a lot of scopes won't have enough focus travel compared to a telescope which may have 4-5 inches of travel.

When I tried the Pentax XW's on my Zeiss 85mm Diascope, I couldn't focus to infinity - infact i couldn't focus on anything beyond about 300m as I hit the end of the focus stop on the spotter...

cheers
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Old Wednesday 26th April 2017, 09:30   #16
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My ED50 with adapted eyepieces

A while ago, I bought myself the angled version of the ED50. To keep things on a low budget, I decided to go for the adapted astronomy eyepieces as described by mayomayo and Bill (see top post).
Bill was so kind to send me three of the threaded adapters he made.

So now I have an ED50 with two eyepieces.

The first eyepiece is a 10mm flat field 60˚Afov eyepiece I purchase on ebay for about 15 euro (about the same in US dollars). This eyepiece had a perfect fit in the adapter made by bill and was easy to attach to the ED to.

The second eyepiece is a 12mm BST explorer eyepiece that mayomayo described in a thread. This issue with this eyepiece is that it's outer threading is too big to fit the adapter ring I received. Furthermore this eyepiece has a lens inside the astronomy barrel which make adaptation more tricky. After several hours or careful filing the outside threading of the eyepiece and filing the inside threading of the adapter ring, I was able to press-fit the adapter ring onto the eyepiece. Then I glued the field lens which was inside the astronomy barrel onto the bottom of this configuration. The end result now nicely fits onto the ED50.

Evaluation of the quality : The 12mm eyepiece (which costs about 60$) is clearly superior to the 10mm eyepiece. Although the 10mm eyepiece brings a little bit extra magnification, the details are less clear. So I always use the 12mm eyepiece (which also is a bit bulkier than then 10mm one).

I still need to purchase a 20 mm SWA 70˚eyepiece for my little scope. I heard from bill that the performance of this little thing is really very good albeit with a smaller magnification.

many thanks to bill for helping me through the process and a shoutout to mayomayo for the very nice idea.
Jan
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Old Wednesday 23rd August 2017, 11:17   #17
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Originally Posted by JanKindt View Post
The second eyepiece is a 12mm BST explorer eyepiece that mayomayo described in a thread. This issue with this eyepiece is that it's outer threading is too big to fit the adapter ring I received. Furthermore this eyepiece has a lens inside the astronomy barrel which make adaptation more tricky. After several hours or careful filing the outside threading of the eyepiece and filing the inside threading of the adapter ring, I was able to press-fit the adapter ring onto the eyepiece. Then I glued the field lens which was inside the astronomy barrel onto the bottom of this configuration. The end result now nicely fits onto the ED50.
Hello Jan!
Inspired by everyone's suggestions I've decided to try the BST 12mm dual ED on my ED50. I recieved the lens from Sky is the limit yesterday.

How did you manage to get the field lens out of the astronomy barrel? There are notches at each side of the lens that you can use to grab it, but when i tried to use them to unscrew it I couldn't get it to move. There is a drop of something clear and hard where the lens meets the barrel, I am afraid that that is glue. Was it the same on your specimen?
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Old Wednesday 23rd August 2017, 12:49   #18
JanKindt
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Hi Geastru,

In my case, the field lens was not glued into the barrel. I did have to make a dedicated tooling that fitted both notches as I was unable to unscrew the lens without applying force to both notches at the same time. I filed a piece of aluminum so that it tightly fitted into both notches and used pliers to unscrew the lens.

I hope that will work for you too..

regards,
Jan
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Old Wednesday 23rd August 2017, 20:07   #19
geastrum
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Many thanks, Jan. I will try something similar, it always helps knowing how someone else solved a problem.
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