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New RKE Collection

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#1 BillP

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Posted 05 November 2020 - 04:51 PM

It has been a long time since I re-assembled an eyepiece line that I used to have.  I usually do not.  But decided that I really want a classic minimum glass design that is also only single coated as these usually excel on planetary and double stars.  Recently tested out an RKE in the planetary role with Mars and it was quite impressive, even next to the likes of my ZAO and XO.  So that sealed it for me.  But there is more too that makes the RKEs a little more special for me.  I grew up in south Jersey and when a young kid would often have my brother drive me to the Edmund Scientific showroom in Barrington, NJ.  That place was an absolute playground of science stuff and they had a huge surplus room filled with old optics and odds and ends.  Could stay there for hours it was so much fun.  Plus I got several of my first telescopes from there as well.  So have a lot of history with that brand.

 

Today just received the last focal length I have been waiting for.  I already had the 28 RKE and I have 2 for binoviewing.  The 15mm I recently got used as this focal length is now discontinued.  The rest I purchased new from Edmund Optical.  These will now become part of my primary observing eyepieces that I keep in my small grab case.  I replaced the anodized aluminum barrels they came with with nice chromed brass ones.  These give the little RKEs a lot nicer heft, plus looks good as well.  The 28 RKE is the only one where the field stop is part of the barrel, so for that one I got a rubber o-ring from Home Depot and cut it to fit and works perfectly as a field stop; the seam is very difficult to notice and you have to search for it.

 

To round out the two ends of the focal length range I placed a Celestron 30mm Pre-Ultima and then a classic single coated Celestron 6mm Ortho that is an amazing performer as well (had to go thru a number of these classic Abbes to find an exceptional one).  Btw, the AFOV on the RKEs, even though the data table says is 45 degrees, is really 51 degrees, so not so constraining of a view smile.gif  They are pictured below on the new 2nd edition of the S&T Jumbo Pocket Atlas that just arrived yesterday!  Can't wait for Orion to make its appearance now laugh.gif

 

Full Set (web).jpg

 

EP Case - Current.jpg

 


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#2 John Carlini

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Posted 05 November 2020 - 05:18 PM

Nice collection! I purchased a lot of stuff from Edmund Scientific in the 70s. Never made it to the showroom. It was just as well since I would have spent all my cash on gizmos and gear...


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#3 Tropobob

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Posted 05 November 2020 - 05:28 PM

Hi Bill,

 

These days, I place a premium on EPs which are parfocal with each other.  Are Your Pentax and RKE close to being parfocal?

 

I only had a used range of RKEs.  I thought the 8mm was outstanding. I can not recall why I parted with it.  However, I thought the 15, 21 & 28mms were only average. In fact, for reasons unknown, their EP lens developed cracks in both the 15 & 21mm.  I wondered if they did not like the tropics or had a rough life before I purchased them.  

 

I ponder buying a 12mm, and maybe another 8mm, but would need to know if it was parfocal with any of my existing Tak & Vixen EPs.  The only Pentax that I owned (28mm XL) was parfocal with these. 



#4 Thomas_M44

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Posted 05 November 2020 - 05:45 PM

The chrome barrels you added Bill, they really do look nice.

 

I think it'd be fantastic if the RKE would be rediscovered by contemporary amateur astronomers as being the superb planetary eyepiece that it is.

 

The novelty/notoriety of the fabled "floating in space" view produced by the 28mm RKE I believe unfortunately draws attention away from the fact that this is a very capable series of eyepieces.

 

The Edmund RKE's are currently being produced to a high level of quality, give splendid planetary performance, carry a current price of only $85 USD price *and* are made in USA --there is a lot to appreciate here.

 

These EP's also work very well with Barlows. 

 

I look forward to hear more of your contemporary RKE experimentation and comparisons Bill.

 

I'm wondering in particular how your new set will perform with binary star viewing.

 

Keep us posted !   ;-)


Edited by Thomas_M44, 05 November 2020 - 05:48 PM.

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#5 BillP

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Posted 05 November 2020 - 07:27 PM

These days, I place a premium on EPs which are parfocal with each other.  Are Your Pentax and RKE close to being parfocal?

I have not done a critical examination yet of that, but my impressions from using them the past few weeks is that they are more precisely parfocal than any I have tried!  So even when I have one in focus under Barlow at very high magnification, when I put another in there is zero need to refocus.  So seems they meticulously ensured the field stops were very accurately placed.

 

Over the coming weeks/months I am going to put these thru the paces on multiple targets then write up a review on the line.


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#6 BillP

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Posted 05 November 2020 - 07:35 PM

...I think it'd be fantastic if the RKE would be rediscovered by contemporary amateur astronomers as being the superb planetary eyepiece that it is.

 

The novelty/notoriety of the fabled "floating in space" view produced by the 28mm RKE I believe unfortunately draws attention away from the fact that this is a very capable series of eyepieces.

 

The Edmund RKE's are currently being produced to a high level of quality, give splendid planetary performance, carry a current price of only $85 USD price *and* are made in USA --there is a lot to appreciate here. ...

 

I'm wondering in particular how your new set will perform with binary star viewing.

They are indeed fantastic planetary eyepieces when mated with a good Barlow.  They have very much impressed me on Mars when compared to the uber-premiums no longer made.

 

I agree about the 28mm novelty kind of overshadowing the rest of the line.  Unfortunate as that is probably the weakest of the bunch with a poorer off-axis and difficult exit pupil, which the others are not like that at all.

 

In decades past when I had the whole set, they were my got eyepiece for Trap E & F as they showed it more reliably than any other eyepiece I had.  So looking forward to when Orion hits the scene again.  Was out last evening looking at some faint stars in clusters and they again surprised me that they were showing the dimmest stars more cleanly and authoritatively then my current day multicoated eyepieces.  Very odd, but in the end I do not care why, just that they do so I can capitalize on that in the field.  But I need to do a lot more testing on that point, and especially with stars that are adverted vision only and those that are just on the edge of being visible direct vision.  Am going to have a fun winter with the RKEs grin.gif


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#7 Daniel Mounsey

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Posted 05 November 2020 - 08:00 PM

It has been a long time since I re-assembled an eyepiece line that I used to have.  I usually do not.  But decided that I really want a classic minimum glass design that is also only single coated as these usually excel on planetary and double stars.  Recently tested out an RKE in the planetary role with Mars and it was quite impressive, even next to the likes of my ZAO and XO.  So that sealed it for me.  But there is more too that makes the RKEs a little more special for me.  I grew up in south Jersey and when a young kid would often have my brother drive me to the Edmund Scientific showroom in Barrington, NJ.  That place was an absolute playground of science stuff and they had a huge surplus room filled with old optics and odds and ends.  Could stay there for hours it was so much fun.  Plus I got several of my first telescopes from there as well.  So have a lot of history with that brand.

 

Today just received the last focal length I have been waiting for.  I already had the 28 RKE and I have 2 for binoviewing.  The 15mm I recently got used as this focal length is now discontinued.  The rest I purchased new from Edmund Optical.  These will now become part of my primary observing eyepieces that I keep in my small grab case.  I replaced the anodized aluminum barrels they came with with nice chromed brass ones.  These give the little RKEs a lot nicer heft, plus looks good as well.  The 28 RKE is the only one where the field stop is part of the barrel, so for that one I got a rubber o-ring from Home Depot and cut it to fit and works perfectly as a field stop; the seam is very difficult to notice and you have to search for it.

 

To round out the two ends of the focal length range I placed a Celestron 30mm Pre-Ultima and then a classic single coated Celestron 6mm Ortho that is an amazing performer as well (had to go thru a number of these classic Abbes to find an exceptional one).  Btw, the AFOV on the RKEs, even though the data table says is 45 degrees, is really 51 degrees, so not so constraining of a view smile.gif  They are pictured below on the new 2nd edition of the S&T Jumbo Pocket Atlas that just arrived yesterday!  Can't wait for Orion to make its appearance now laugh.gif

 

attachicon.gifFull Set (web).jpg

 

Awesome!



#8 bulletdodger

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Posted 05 November 2020 - 08:18 PM

I also have had the RKE eyepieces and let them go for newer and wider models. I kept the 28mm for the famous spacewalk experience. I have some regrets with my decision as they were a bit brighter on planets than my plossls. Not much brighter
but when viewing planets like Jupiter with a lot of detail every photon counts.
My Edmunds 28mm plossl is a better performer than my 28mm RKE, but the RKE gets more telescope time, especially when I am introducing someone to the hobby.
I have benefited greatly from your extensive and detailed posts, Bill and will use this post to thank you for being such a bright light on this website. 💫

Bob
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#9 SandyHouTex

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Posted 05 November 2020 - 08:43 PM

It has been a long time since I re-assembled an eyepiece line that I used to have.  I usually do not.  But decided that I really want a classic minimum glass design that is also only single coated as these usually excel on planetary and double stars.  Recently tested out an RKE in the planetary role with Mars and it was quite impressive, even next to the likes of my ZAO and XO.  So that sealed it for me.  But there is more too that makes the RKEs a little more special for me.  I grew up in south Jersey and when a young kid would often have my brother drive me to the Edmund Scientific showroom in Barrington, NJ.  That place was an absolute playground of science stuff and they had a huge surplus room filled with old optics and odds and ends.  Could stay there for hours it was so much fun.  Plus I got several of my first telescopes from there as well.  So have a lot of history with that brand.

 

Today just received the last focal length I have been waiting for.  I already had the 28 RKE and I have 2 for binoviewing.  The 15mm I recently got used as this focal length is now discontinued.  The rest I purchased new from Edmund Optical.  These will now become part of my primary observing eyepieces that I keep in my small grab case.  I replaced the anodized aluminum barrels they came with with nice chromed brass ones.  These give the little RKEs a lot nicer heft, plus looks good as well.  The 28 RKE is the only one where the field stop is part of the barrel, so for that one I got a rubber o-ring from Home Depot and cut it to fit and works perfectly as a field stop; the seam is very difficult to notice and you have to search for it.

 

To round out the two ends of the focal length range I placed a Celestron 30mm Pre-Ultima and then a classic single coated Celestron 6mm Ortho that is an amazing performer as well (had to go thru a number of these classic Abbes to find an exceptional one).  Btw, the AFOV on the RKEs, even though the data table says is 45 degrees, is really 51 degrees, so not so constraining of a view smile.gif  They are pictured below on the new 2nd edition of the S&T Jumbo Pocket Atlas that just arrived yesterday!  Can't wait for Orion to make its appearance now laugh.gif

 

attachicon.gifFull Set (web).jpg

 

That is quite a set.



#10 Thomas_M44

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Posted 05 November 2020 - 10:57 PM

BillP Quote: "Btw, the AFOV on the RKEs, even though the data table says is 45 degrees, is really 51 degrees, so not so constraining of a view. "

 

You know, I wonder if Edmund very conservatively claimed a 45-degrees AFOV for the RKE  *perhaps* because the orthoscopic FOV may actually about 45-degrees when the eyepieces are used with an f/4.5 telescope.

 

I believe it was CN member Lyler who stated he was informed by Edmund that f/4.5 was the f-ratio the RKE series was originally designed to accommodate.

 

The above I present only as a conjecture. This would be interesting however, to investigate further.


Edited by Thomas_M44, 05 November 2020 - 10:59 PM.


#11 BillP

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Posted 05 November 2020 - 11:59 PM

I just gave them a check in my f/7.7 Vixen 81S.  They have enough RD that I would not call them orthoscopic, even at the 45 deg mark.  Traditional Abbes have very little, but still some.  I think the Tak LEs have about the least I have seen, all but the 10 LE which is more a typical level of RD.  Given how large the AFOV is of the XWs, they have only a very small amount in the furthest off-axis.  So LEs and XWs are very well controlled as far as RD is concerned.


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#12 greenjuice

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Posted 06 November 2020 - 01:03 AM

Beautiful set you have assembled there Bill, all you need is a Tak TOA 4mm and it would be perfect.

I loved Edmunds catalog in the early seventies. I would spend hours pouring over it.


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#13 luxo II

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Posted 06 November 2020 - 01:08 AM

Sigh... I had a full set, early '80 when they were first released, their assemblies were fairly rough, frankly. Then came Vixen with the LV's and side-by-side figured the LV were a tad better and gave the RKE set to a worthy cause. Maybe Edmunds production quality has improved since.

 

Fond memories though of the 21mm which was my favourite RKE. The 28 was always a party trick for those who hadn't encountered it, and the 15 was OK. Personally I found the 12 and especially the 8mm a bit tough, with very short eye-relief.


Edited by luxo II, 06 November 2020 - 01:10 AM.

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#14 Thomas_M44

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Posted 06 November 2020 - 01:15 AM

I just gave them a check in my f/7.7 Vixen 81S.  They have enough RD that I would not call them orthoscopic, even at the 45 deg mark.  Traditional Abbes have very little, but still some.  I think the Tak LEs have about the least I have seen, all but the 10 LE which is more a typical level of RD.  Given how large the AFOV is of the XWs, they have only a very small amount in the furthest off-axis.  So LEs and XWs are very well controlled as far as RD is concerned.

Interesting.

 

From my own observations, I'm not surprised by your impressions regarding the relative level of rectilinear distortion present in the RKE's. Being a 3-element eyepiece, invariably there will be evident design trade-offs such as that which you note.

 

No worries, If I want to enjoy a very geometrically corrected FOV, I can just grab my KK Abbe orthos. "Different horses for different courses" wink.gif

 

On the Tak LE series: I've not yet had the opportunity to try an LE, but from the reports I've read I've gleaned that they are a very well-engineered and balanced design. I wonder how the  LE's  would compare to my trusty old 5-element Meade 4000 series 'Super Plossl's' ?  I have to imagine if the two series may well share quite similar virtues.

 

Also: your initial faint star observations with the new RKE's sound promising.  I'm enjoying your ongoing RKE reportage. waytogo.gif


Edited by Thomas_M44, 06 November 2020 - 01:24 AM.


#15 izar187

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Posted 06 November 2020 - 01:59 AM

BillP Quote: "Btw, the AFOV on the RKEs, even though the data table says is 45 degrees, is really 51 degrees, so not so constraining of a view. "

 

You know, I wonder if Edmund very conservatively claimed a 45-degrees AFOV for the RKE  *perhaps* because the orthoscopic FOV may actually about 45-degrees when the eyepieces are used with an f/4.5 telescope.

 

I believe it was CN member Lyler who stated he was informed by Edmund that f/4.5 was the f-ratio the RKE series was originally designed to accommodate.

 

The above I present only as a conjecture. This would be interesting however, to investigate further.

RKE's have a better corrected field than kellners in f/4.5 newts.

Japan VT ortho's are significantly better than both in f/4.5 newts.

Plossls have the larger field than all three, in f/4.5 newts.

Plossls (GSO and Carton) and RKE's are about as soft near the edge in f/4.5 newts, but that soft is farther out in the plossl, so the plossl has a larger well corrected field, that is more helpful when chasing DSO's hand tracking.

Traditional VT type orthos have the best corrected edge to edge field in f/4.5 newts, of all 4 of the afore mentioned type ep's.

 

FWIW, a set of a few long focal length plossls combined with a few short focal length ortho's is a workable set for f/4.5 newt.

But pretty much an anachronistic collection by today's standards, with all the other great yet still affordable options now.

 

The preceding is IMHO+E only.


Edited by izar187, 06 November 2020 - 02:00 AM.

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#16 BillP

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Posted 06 November 2020 - 10:03 AM

RKE's have a better corrected field than kellners in f/4.5 newts.

Japan VT ortho's are significantly better than both in f/4.5 newts.

Plossls have the larger field than all three, in f/4.5 newts.

Plossls (GSO and Carton) and RKE's are about as soft near the edge in f/4.5 newts, but that soft is farther out in the plossl, so the plossl has a larger well corrected field, that is more helpful when chasing DSO's hand tracking.

Traditional VT type orthos have the best corrected edge to edge field in f/4.5 newts, of all 4 of the afore mentioned type ep's.

All I can say is three things...

 

1. Thanks for the observations!

2. Glad I don't need eyepiece designs that work well in fast Newts!!

3. Very glad eyepiece producers realize that many do not care or need or want eyepiece designs that work well in fast Newts!!!

 

Telescope.gifhamsterdance.gif"A perfect eyepiece works well at f/7"


Edited by BillP, 06 November 2020 - 10:06 AM.

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#17 Thomas_M44

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Posted 06 November 2020 - 04:48 PM

I find life is just plain easier above f/6

 

Having said that, I do understand why so many larger aperture telescopes and also imaging telescopes are faster --often of sheer physical necessity.

 

Thank goodness TeleVue has the f/4ish visual people well covered!  ; )

 

The first serious telescope I had access too as a teenager was my stepfather's ancient f/9 or f/10 6-inch Newt. The FOV was just so sweet and clean, and the depth of focus so Cadillac smooth.

 

My last telescope was an f/7 8-inch Newt, and for my sort of visual viewing preferences it was near ideal.

 

I presently own a TV85 which is also f/7.  Now that I have the wide-field and high-portability boxes checked with the TV85, I'm considering having an 180mm f/8 mirror ground and gathering additional pieces to construct another visual-optimized Newtonian. I'd gladly trade a bit of aperture for to go from f/7 to f/8 in a similar length/size telescope.

 

I'm pretty spoiled by having a relatively gentle light cone of f/7 and above to work with.  I like the crisp, well-corrected fields, comfortable depth of focus, and the benefit of having a scope which works well with classic minimal-glass eyepieces.

 

There is no right or wrong here, only relative virtues and preferences.

 

If I had a 14" f/4.5 Dob or similar, I'd surely be using a Paracorr and  Powermates most of the time to get the views I like.


Edited by Thomas_M44, 06 November 2020 - 04:52 PM.

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#18 BillP

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Posted 06 November 2020 - 08:09 PM

Excellent post Thomas waytogo.gif



#19 RichA

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Posted 06 November 2020 - 10:56 PM

It has been a long time since I re-assembled an eyepiece line that I used to have.  I usually do not.  But decided that I really want a classic minimum glass design that is also only single coated as these usually excel on planetary and double stars.  Recently tested out an RKE in the planetary role with Mars and it was quite impressive, even next to the likes of my ZAO and XO.  So that sealed it for me.  But there is more too that makes the RKEs a little more special for me.  I grew up in south Jersey and when a young kid would often have my brother drive me to the Edmund Scientific showroom in Barrington, NJ.  That place was an absolute playground of science stuff and they had a huge surplus room filled with old optics and odds and ends.  Could stay there for hours it was so much fun.  Plus I got several of my first telescopes from there as well.  So have a lot of history with that brand.

 

Today just received the last focal length I have been waiting for.  I already had the 28 RKE and I have 2 for binoviewing.  The 15mm I recently got used as this focal length is now discontinued.  The rest I purchased new from Edmund Optical.  These will now become part of my primary observing eyepieces that I keep in my small grab case.  I replaced the anodized aluminum barrels they came with with nice chromed brass ones.  These give the little RKEs a lot nicer heft, plus looks good as well.  The 28 RKE is the only one where the field stop is part of the barrel, so for that one I got a rubber o-ring from Home Depot and cut it to fit and works perfectly as a field stop; the seam is very difficult to notice and you have to search for it.

 

To round out the two ends of the focal length range I placed a Celestron 30mm Pre-Ultima and then a classic single coated Celestron 6mm Ortho that is an amazing performer as well (had to go thru a number of these classic Abbes to find an exceptional one).  Btw, the AFOV on the RKEs, even though the data table says is 45 degrees, is really 51 degrees, so not so constraining of a view smile.gif  They are pictured below on the new 2nd edition of the S&T Jumbo Pocket Atlas that just arrived yesterday!  Can't wait for Orion to make its appearance now laugh.gif

 

attachicon.gifFull Set (web).jpg

 

I've owned a couple sets and just got a 28mm and 8mm by happenstance.  They are impressive, particularly where I used them on fast scopes and the stars at the edge are not as distorted as I've seen in some Plossls or orthos.  I wonder if anyone knows what their (rarer) Plossl set consisted of?



#20 25585

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Posted 07 November 2020 - 05:03 AM

Just need an Astroscan now BillP lol.gif

 

What difference between the 1st & 2nd versions of Sky Atlas? With SA 2000.0, the 2nd edition has Hipparchos data and greater accuracy. Soon be 2050 co-ordinates?



#21 John Rogers

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Posted 07 November 2020 - 09:19 AM

You really need the 32mm RKE to complete the set.

 

1989_Catalog_32mm_RKE.jpg

 


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#22 John Rogers

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Posted 07 November 2020 - 09:38 AM

BillP Quote: "Btw, the AFOV on the RKEs, even though the data table says is 45 degrees, is really 51 degrees, so not so constraining of a view. "

 

You know, I wonder if Edmund very conservatively claimed a 45-degrees AFOV for the RKE  *perhaps* because the orthoscopic FOV may actually about 45-degrees when the eyepieces are used with an f/4.5 telescope.

 

I believe it was CN member Lyler who stated he was informed by Edmund that f/4.5 was the f-ratio the RKE series was originally designed to accommodate.

 

The above I present only as a conjecture. This would be interesting however, to investigate further.

The RKE eyepiece line was developed for the Astroscan telescope.  Here is the announcement from the March 1978 Edmund Astronomy News.  Note that the APOV was specified as 50 degrees.

 

Edmund_RKE_Announcement_March_1978_1.jpg Edmund_RKE_Announcement_March_1978_2.jpg


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#23 BillP

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Posted 07 November 2020 - 10:58 AM

WoW!!  Fantastic sleuth work finding these!!  Nice to see that the meaning of the RKE acronym is consistent with their patent filing.  So nice to see it in their marketing also as a double confirmation and hopefully will put the oddball suggestions for other meanings to rest. waytogo.gif


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#24 25585

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Posted 07 November 2020 - 11:20 AM

From the mists of my memory, I seem to remember Soligor sold a 32mm RKE once.



#25 Thomas_M44

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Posted 07 November 2020 - 12:32 PM

The RKE eyepiece line was developed for the Astroscan telescope.  Here is the announcement from the March 1978 Edmund Astronomy News.  Note that the APOV was specified as 50 degrees.

 

attachicon.gifEdmund_RKE_Announcement_March_1978_1.jpgattachicon.gifEdmund_RKE_Announcement_March_1978_2.jpg

 

Neat find!

 

The fact that the ad claims 50-degree AFOV for the RKE upon release is instructive.

 

My suspicion is that the marketing department may have gently reduced the RKE's claimed AFOV to 45-degrees at some later point, in order to perhaps distinguish their Plossl eyepiece release. Perhaps it was thought to be a product feature clash to have two eyepiece lines claiming 50-degree AFOV.  Wasn't the Edmund Plossl introduced at some years after the RKE? 

 

Also: I'm not reading anything in those ad pages that indicate the RKE eyepieces were designed specifically for the Astroscan telescope.  I have not yet had my coffee today, and so excuse me if I'm simply overlooking it.

 

On the Erfle eyepiece:  it's interesting to note just how many of today's esteemed eyepieces actually are variants and adjustments of the classic Erfle design.

 

Never underestimate the ability of marketing apartments to 'adjust' specifications and facts to suit the exigencies of the moment wink.gif


Edited by Thomas_M44, 07 November 2020 - 12:33 PM.

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