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Edmund RKE, Pre RKE myth, more RKE

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#1 apfever

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Posted 13 October 2021 - 03:32 PM

I spent some time rounding up everything I could find RKE. 
All the containers should be RKE. At least two of the early black bodies on the right are RKE.

This should be 15 or 16 RKE so far plus the barlow. I have no idea what focal lengths. I sure hope I have at least one of each. I sold a couple of complete sets including a full collector set in original container. Some more have probably come in since the sales. 

 

A recent interaction has prompted me to go through these and see what's here. I've had these apart several times before and maybe this will be the last go through so I can thin and get to a keeper set. I might find more later. There might be one in a scope or with an 'original' package scope purchase. I did a decent walk around to minimize potential stragglers. 

 

I'll also open some of the 1-1/8" focal length eyepieces in the black bodies. These look identical to the early black body RKE, but they are NOT a 'pre' RKE. The 1-1/8" eyepieces are a different optical design and the parts will not exchange. The interior of the bodies are different. 

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#2 petert913

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Posted 13 October 2021 - 03:54 PM

Sorry if I missed it, but what's the point of this endeavor?


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#3 fftulip

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Posted 13 October 2021 - 04:28 PM

I've opened up one of my 1 1/8" pre RKE in the all black Al body and it's definitely a 4 element Plossl configuration.  However, there is supposed to be more than one version - what I heard is when they ran out of the surplus military lenses, they reconfigured the design using then available lenses (but I believe the configuration is basically the same).  And no, I don't know how to tell the difference, possiblly the body is slightly different sized.


Edited by fftulip, 13 October 2021 - 04:29 PM.

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#4 Bomber Bob

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Posted 13 October 2021 - 04:35 PM

Sorry if I missed it, but what's the point of this endeavor?

Hopefully, to sort, categorize, date, etc. Edscorp's RKE Series of eyepieces & accessories...

 

Bust some Myths, and maybe support the Legends...


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#5 apfever

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Posted 13 October 2021 - 04:56 PM

um wow. OK so it takes me a while to process pictures, reducing and all and hoping something shows up. 

 

Simplicity in the body. It's two parts, lower and upper barrel, both serve to hold the lens assemblies. I prefer it. Two issues. It's the easiest to undo by human nature and end up dumping out a scramble in lens' and spacer. Second and most important is it's the easiest to tighten and clam chip. All of these have (and should) unscrewed fine since I always back off the barrels for a rattle. 

 

RKE on the left, SAE on the far right. RKE has a thicker wall lower barrel for a smaller field lens. Distinct optical difference. RKE is a singlet eye lens, the SAE is two doublets.

 

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#6 apfever

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Posted 13 October 2021 - 05:07 PM

Here's the red band by comparison the same optical assembly as the black barrel version. The SAE has a step in the barrel and a smaller eye lens. There are other differences that won't let the assemblies swap. 

 

The clam chip and it's the red band. I'll pull a Robert and keep that one with some blackening. I'll never know the difference. I tried to make is gastly as I could. 

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#7 apfever

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Posted 13 October 2021 - 05:14 PM

Sorry if I missed it, but what's the point of this endeavor?

I have a pm with inquiry about the RKE. I have the answers to some of that so multi purpose to going through them. It's been a project laid out on part of a table for a while. Some think the SAE version is a "pre" RKE because the barrels are identical on the outside (except for the engraved print).  I guess the black versions with "RKE" engraved could be considered the 'pre' version of the red band. All the same to me. Also, I haven't opened all the boxes yet so ...it'll be fun and get it done. 



#8 apfever

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Posted 13 October 2021 - 05:22 PM

Final pic for a few minutes, need to flip that James Taylor.  Putting all the SAE away as they are not the subject. Look for all the 28mm. Look at them all for that eh? Hope there is still a full set. Now I'm curious about the smaller SAE of the same series with close f number to the RKE. See how they compare. I'm thinking the SAE preceeded. 

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#9 Terra Nova

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Posted 13 October 2021 - 08:12 PM

I had the one with the black anodized metal body one that was marked 1 1/8. I sold it because I had a lighter weight, blacker red band version marked 28mm RKE at the same time and in side by side examination in several different telescopes, I liked the red band version better. I like it to this day. In fact I used it just last Sunday night in my Vixen ED102SS. It really does give that floating in space feeling. To me, it’s the classic Edmund RKE that everyone should have in the tool kit.


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#10 apfever

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Posted 13 October 2021 - 08:59 PM

 

Hopefully, to sort, categorize, date, etc. Edscorp's RKE Series of eyepieces & accessories...

 

Bust some Myths, and maybe support the Legends...

Thanks Bob, but not this time. I'm not sure of dates at all, more going after mechanics and some test viewing. Sorting, catagorize, open each focal length to look at the design, check out things like Terra's comment since I have all those out, that sort of thing.  Now what scope to use for quick checks, preferably and Edmund, super simple quick grab n go with some decent aperture, more aperture than a small grab frac...hmmmm ideas?

 

I had the one with the black anodized metal body one that was marked 1 1/8. I sold it because I had a lighter weight, blacker red band version marked 28mm RKE at the same time and in side by side examination in several different telescopes, I liked the red band version better. I like it to this day. In fact I used it just last Sunday night in my Vixen ED102SS. It really does give that floating in space feeling. To me, it’s the classic Edmund RKE that everyone should have in the tool kit.

The 1-1/8" is very similar to a Plossl. The RKE is similar to a Konig.  Different eyepieces. 

 

Some notes in passing. Any chips (clams) were all in the field facing surface that contacts the lower barrel. Two blackenings shown in the photo, the small one didn't need to be done. With this number of eyepieces at one time, it became obvious that the field surface shows the most 'wear' for lack of a better word. This is the surface that would take rotational contact from the lower barrel. I don't see any concern from it. The chips are from being too tight.  The two assembled units on the Right had some small spots in the same edge I blackened. 

 

One of the eye lens in a 1-1/8" was flipped.  All the 1-1/8" are done and out of the picture. I did a swap comparison and definitely prefer the RKE in an Astroscan. The SAE has a larger AFOV by way of no field stop control. The RKE has a sharp edge of field, the SAE is a rotten blur. 

 

From the left:

An empty body I found with no optics.

The orange band had to come apart for cleaning. It was locked tight and took two strap wrenches, no damage to the glass or threads. 

The next three are the red band with the big black clam and two early black body, all previously shown.

The last two are 28 RKE that were nice enough to not take apart for any reason till I found the lens assemblies both scrambled order eggs. 

The big clam still makes an excellent eyepiece. The clam is shallow and that edge is hardly visible from the eye end compared to looking at it directly from the back. The thicker barrel covers it too.   

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Edited by apfever, 14 October 2021 - 11:52 AM.

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#11 Bomber Bob

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Posted 13 October 2021 - 09:14 PM

Thanks Bob, but not this time.

 

I think... it'll be a group effort -- you don't have to do it all yourself.  It's enough with the CSNs to get the ball rolling...



#12 Terra Nova

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Posted 13 October 2021 - 09:25 PM

Did anyone ever figure out what makes the red band 28mm RKE unique in making that ‘floating in space’ feeling? Neil, you say it’s similar to a König but my 27mm Questar globe eyepiece (which is a König) doesn’t produce it? (And that is a very nice sharp eyepiece.) My late 1940s 32mm Brandon doesn’t either, nor did the 1 1/8” Edmund. I do have another rather unique eyepiece that does it (the ‘floating in space’ thing). It was that heavy brass 30mm anti-aircraft gunsight that Edmund offered in the 1960s. It also produces a peculiar, almost vertigo-like, beyond-immersive effect while looking through it. 


Edited by Terra Nova, 13 October 2021 - 09:26 PM.

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#13 apfever

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Posted 13 October 2021 - 09:36 PM

Terra,  

 

Sorry but I have to say this. Your heavy brass aircraft gunsight creates that floating in space feeling due to the extensive radiation blasting your brain from thorium impregnated glass. 

Take heart, the RKE is totally cool with how it does it. 


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#14 Terra Nova

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Posted 13 October 2021 - 09:51 PM

Ha ha Neil! I well remember those huge, heavy erfle gun-sight eyepieces with the army green painted bodies and the tea-brown thoriated glass. Actually my 30mm is in a brass housing, weighs less (tho it still weighs around 12 oz?), and has very clear glass with no hint of coatings.

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#15 Jaimo!

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Posted 13 October 2021 - 09:53 PM

Here's some more data to cloud the waters, something I started writing up a few years ago and never finished...

 

RKE and Pre RKE.jpg

 

The 28mm Edmund RKE has become a legendary but inexpensive astronomical eyepiece due to its ability to disappear when viewing, meaning the focal plane of the image is high enough that the body of the eyepiece when the image is viewed, is obstructed.  Many claims that other eyepieces also experience this phenomenon, but not to the extent of the 28mm RKE.  Edmunds and other astronomy vendors began selling Military Surplus eyepieces in the 1950’s typically with a focal length of 1 1/8”, these eyepieces were originally used in the M4 Sherman Tank Gun Sight M70 telescope, manufactured by Bell and Howell, which was also sold my Edmunds.  According to Chris Lord in his article “Comparison Test of Three Plössl Eyepiece Types Brandon, Televue, GSO Revelation” The only readily procurable "Plössl" eyepieces were war surplus Symmetrical eyepieces removed from sighting or predictor 'scopes. Edmund Scientific in the 50’s & 60’s bought thousands of war surplus M-70 tank telescopes, and stripped out their 32mm Brandon eyepiece which they fitted into a 1 1/4-inch adaptor, and sold for $5.95 as a “Type III Kellner [Plössl]”.

 

Edmunds Ad 1956 - M70.jpg   M70 Tank Telescope.jpg


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#16 Jaimo!

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Posted 13 October 2021 - 09:55 PM

More...

 

The 28mm, or 1” to 1 ¼” where 1 1/8” seems to be most common, war surplus eyepiece from these gun sight telescope were also sold by Edmunds, as well as other supplies, such as Edscorp (see the first photo) and American Science Center between 1956 and 1980 with a price ranging between $5.95 and $24.75.  These war surplus eyepieces were a traditional asymmetrical Plössl design, but you can see in the Edmunds ad below they call it a Kellner type 3.  I find it amazing, that this eyepiece from WWII is still influencing amateur astronomy to this day.

 

Edmunds Ad 1956 - Eyepiece.jpg   Edmunds Pre-RKE Ad.jpg

 

ASC Plossl - Dec. Sky and Telescope 1980 Ad..jpg

 

 

 

 


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#17 Jaimo!

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Posted 13 October 2021 - 09:57 PM

and more...

 

RKE - Astronomy News Vol 16 No 2.jpg


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#18 Jaimo!

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Posted 13 October 2021 - 10:07 PM

My basic thought (AND THIS IS JUST THEORY) is Edmund sold the war surplus "Pre-RKE's" for years and years.  They realized the value to the amateur astronomer and the profits that they were reaping.  As the surplus of eyepieces from WWII began to dry up, Edmund must have seen a niche market for this eyepiece.   They then designed a economical replacement for the war surplus eyepieces with the RKE, the housings are remarkable similar, and the disappearing view of the war surplus EP is retained in the RKE.  Edmunds then marketed them in the 1980's with all of the glitz and glam associated with that decade, and none of the other RKE focal lengths are nearly as captivation as the 28mm.  This was at the same time TV was releasing their first line of eyepieces, the smoothie Plössls.

 

And "Pre-RKE" is just an easy term to refer to the war surplus eyepieces sold before the marketing of the RKE's, nothing more.


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#19 apfever

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Posted 13 October 2021 - 10:23 PM

Well, I have a small problem.  Two assembled 28mm RKE had totally scrambled lens assemblies. The field lens doublet is easy to get right. The eye lens is symetrical as far as I can tell. Direct examination of the eye lens looks symetrical to me, and I've looked at several from several ways each. 

 

I compared two in my Astroscan. I then flipped the eye lens in one of the eyepieces but not the other. I could not see any difference in performance. The two eyepieces compared exactly the same from edge to edge of the field of view. By the way, edge performance was very good with the Astroscan.

 

I did some web search to no avail. This might even be tough for this forum. Can anybody confirm the symetry of the eye lens, and a way to determine which side is which if not perfectly symetrical?  Since my two assembled reference eyepieces were bass ackwards, I'm now not sure of any of them. It would be nice to know something before putting these all together. 

 

Thanks.



#20 EJN

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Posted 13 October 2021 - 11:22 PM

post-32845-0-88144300-1634180045.jpg

I bought that eyepiece in the ad from them sometime in the mid 1980's. No longer have it though.

 

I lived about 8 miles from American Science Center, my dad would take me there when I was a kid. When I was a bit older I would ride my bike there, and eventually drive there on my own. I still have some of the old Edmund books I bought there.

 

They actually still exist as American Science and Surplus at a different location.

https://www.sciplus.com/

 

asc1.jpg

 

asc2.jpg


Edited by EJN, 13 October 2021 - 11:32 PM.

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#21 highfnum

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Posted 14 October 2021 - 08:04 AM

these are my 3 eyepiece comparison to RKE 28mm

the Sherman tank eyepiece comes closest to RKE 28mm for float effect

but RKE has better edge definition

older Edmund Kellner does not have this effect

the other eyepiece (not shown) that comes close is a Jeager 28mm 

but again RKE had better edge definition 

scope used was 80mm triplet APO  F6

 

3eyes.jpg

IMHO RKE 28 still king of the "field float"


Edited by highfnum, 14 October 2021 - 08:11 AM.

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#22 apfever

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Posted 14 October 2021 - 11:08 AM

The test bench. There was enough room to squish everything over without something falling in the sink. I took this as an omen. The eye lens of the 28mm RKE is symetrical. That's my story and going with it.

 

The micro lightbulb filament is focused on the distant triangle white screen.  Small movements of the lens create a big change in the screen focus. Rotation of an assymetrical lens should create a big change in focus due to the shift in surface location. A symetrical lens won't do diddly.

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Edited by apfever, 14 October 2021 - 11:11 AM.

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#23 apfever

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Posted 14 October 2021 - 11:17 AM

Here is the filament of the micro bulb from a few different lens and rotations. Anything showing the winding in the filament is within a very narrow band of lens location. Less than 1mm of movement between the bulb and screen blurs this out. Rotating a lens moves the surfaces a lot more.  For those that just want to see, that's it for the oooohhhh and aahhhh. 

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#24 apfever

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Posted 14 October 2021 - 11:29 AM

Here's the fun end.  It was easy to mark the lens edge, nice glass edge. It was easy to move and align without disturbing anything except the lens. Moving forwards or backwards on the marks by a small fraction of the width blurs the image. Rotation moves each face a full lens thickness. It was easy to do another one - I'm satisfied, I didn't do them all.  Each lens had to be well centered on the same marks when rotated. Every lens uses the exact same mark, one mark for all of them in any rotation. It's Tiddley Wink time. You could play (jersey gloves) and put them back random. 

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#25 Mitrovarr

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Posted 14 October 2021 - 11:39 AM

Are you going to blacken the lens edges while you have them all apart? Or keeping them original?
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