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Equipment Discussions >> Eyepieces

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ibase
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Reged: 03/20/08

Loc: Manila, Philippines 121*E 14*N
Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: BillP]
      #5168535 - 04/12/12 01:18 PM

Quote:

Quote:

Thanks for posting your exploded view! Yes, very obvious difference is that the lens edges are not blackened in your RKE28mm version. Not sure if the optical performance is identical.

Best,




The RKE is a 3 element 2 group eyepiece. It also has a field stop in the barrel.

The 1-1/8" is a 4 element 2 group eyepiece. It has no field stop and uses the barrel as the field stop whcich gives it about 10 degrees more AFOV than the RKE.

Performance-wise both give the "floating" effect they are famous for. I do notice a subtly better performance on-axis for planetary with the 1-1/8" over the RKE, giving a little more clarity and apparent contrast, which is why I prefer those over the RKE for bino with a 3.5x for planetary. It is subtle, but there to my eye.




Thanks much for explaining the differences and for sharing your experience with the vintage and more recent RKE28's. Will be looking out for the 1-1/8" version to add to the stable, but doubt if there are owners willing to part with them at this time.

Best,


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BillB9430
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Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: Bob Clift]
      #5173450 - 04/15/12 10:33 AM

For the handful of people on CN who do not have an Edmund 28mm RKE yet, Surplus Shed has them (unused) in their "New This Week" category now (April 15) for $35! If you put "Please apply my discount" in the Comments box, you'll get 15% off THAT for just $29.75! If you are a VIP member of Surplus Shed, there's another 10% off and free shipping, too (otherwise shipping is $5). Seems like a no-brainer if you don't have one of these eyepieces yet.

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rdandrea
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Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: BillB9430]
      #5173871 - 04/15/12 02:56 PM

Quote:

For the handful of people on CN who do not have an Edmund 28mm RKE yet, Surplus Shed has them (unused) in their "New This Week" category now (April 15) for $35! If you put "Please apply my discount" in the Comments box, you'll get 15% off THAT for just $29.75!




Good tip, thanks. I have had a 15mm RKE for 30+ years and have always loved it. However, no soap on the "Please apply my discount" unless they are going to apply it manually later. Looks like they charged me $35 plus shipping.

Still, even at $35 it's a no-brainer. That's just a little over half price.


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BillB9430
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Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: rdandrea]
      #5173973 - 04/15/12 04:11 PM

rdandrea, Surplus Shed usually applies the discount when they charge your card just before shipping, so you may get that discount after all. The extra discount deal is good for orders through tomorrow only, however.

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rdandrea
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Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: BillB9430]
      #5174000 - 04/15/12 04:32 PM

Quote:

rdandrea, Surplus Shed usually applies the discount when they charge your card just before shipping, so you may get that discount after all. The extra discount deal is good for orders through tomorrow only, however.




Thanks. Good deal. I ordered today. Hard not to at that price.


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Blake Andrews
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Reged: 07/31/08

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Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: BillB9430]
      #5174137 - 04/15/12 06:16 PM

Quote:

For the handful of people on CN who do not have an Edmund 28mm RKE yet, Surplus Shed has them (unused) in their "New This Week" category now (April 15) for $35! If you put "Please apply my discount" in the Comments box, you'll get 15% off THAT for just $29.75! If you are a VIP member of Surplus Shed, there's another 10% off and free shipping, too (otherwise shipping is $5). Seems like a no-brainer if you don't have one of these eyepieces yet.




Thanks for the "heads up"!


I've had a single Edmund 28mm RKE for years. It's always been in my eyepiece case and is one of my favorite galaxy-hopping EPs.

Just bought another pair of these for future bino-viewing. I'll keep my fingers crossed that they are a matched set.


Cheers!
Blake


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Paraclete
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Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: Blake Andrews]
      #5174190 - 04/15/12 06:44 PM

What a fantastic deal!

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ibase
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Reged: 03/20/08

Loc: Manila, Philippines 121*E 14*N
Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: Paraclete]
      #5174358 - 04/15/12 08:41 PM

Yeah, great deal, thanks for the heads-up too BillB! I paid $42 for mine "used" (plus shipping) so yes, this tip sure is a fantastic deal! Come on people, join the RKE28 club now! (It's one of the hottest franchises there is in the forum just like the Pentaxes, Brandons, TVs or ahem.. Baader Hyp Zoom)

Best,


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Jaimo!
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Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: ibase]
      #5176214 - 04/16/12 11:21 PM

I bought 2...

Jaimo!


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ibase
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Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: Blake Andrews]
      #5176530 - 04/17/12 08:22 AM

Quote:


Just bought another pair of these for future bino-viewing. I'll keep my fingers crossed that they are a matched set.





Congrats on the in-coming RKE 28mm pair for the bino-v. In all likelihood they'd probably be a matched set, coming as they are from maybe the same batch. At one time I even took a leap of faith and blindly bought another UO 12.5mm hoping that it would work on my binoviewer together with the one I already had:



The two VT's shown above were obviously from different batches/versions (the one on the left has the infamous undercut) and yet they worked wonderfully when used as a pair!

Best,


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Scanning4Comets
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Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: ibase]
      #5176546 - 04/17/12 08:33 AM

Nice Hernando!

Cheers,


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ibase
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Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: Scanning4Comets]
      #5176732 - 04/17/12 10:52 AM

Thanks Mark!

Best,


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ibase
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Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: Jaimo!]
      #5176743 - 04/17/12 10:59 AM

Quote:

I bought 2...




That's great Jaimo! If ever you have the time to compare your 1 1/8" Edmunds "Pre-RKE" (in the pic you posted earlier in the thread) and the new one's you just bought, I'd (maybe others too) be very interested to know your impressions on how they stack up against each other, thanks!

Best,


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Vondragonnoggin
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Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: ibase]
      #5176796 - 04/17/12 11:33 AM

Haha, very nice hint about surplus shed. I just ordered another pair. I'll pick the best two matches out of 4 and sell off the other two later, or loan em out. That was the same price I paid for one plus shipping at Edmunds.

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Vondragonnoggin
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Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: Vondragonnoggin]
      #5176818 - 04/17/12 11:44 AM

Hmmm, think I have different plan. My eyepiece tray holds three ep's. I have a 5x Powermate, and 2x Parks Gold Barlow. I need to buy a 3x Barlow, then keep the Barlow/28RKE combos in the tray and swap out with the single I keep in the diagonal. All 28RKE sessions at 4 different powers.

Love this eyepiece.

Think I'll get a 2x Powermate 1.25" to keep eye relief the same and try to get the 1.25" 3x TeleXtender from Meade.

I'm RKE crazy.



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ibase
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Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: Vondragonnoggin]
      #5176845 - 04/17/12 11:59 AM

Quote:


I'm RKE crazy.






Hahaha LOL
One can never have too many RKE28's!

Best,


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Simoes Pedro
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Reged: 02/03/09

Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: Jaimo!]
      #5177132 - 04/17/12 02:50 PM Attachment (8 downloads)

Quote:

Quote:

If you take the 1-1/8" apart, you will find it is not a Kellner but an asymetrical Plossl design, perhaps a Clave-style Plossl. So it is 4 elements in 2 groups.




Sorry, for the late response... I've been away.

1 1/8" Edmunds "Pre-RKE":


Jaimo!




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ibase
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Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: Simoes Pedro]
      #5177582 - 04/17/12 08:08 PM

Why, are you trying to buy Jaimo's 1 1/8" Edmunds "Pre-RKE?" Hey, I was first in line!

Best,


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Jaimo!
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Re: RKE 28mm on the way! What to expect vs. 27-36mm's? [Re: ibase]
      #5177755 - 04/17/12 10:48 PM

I have to hold on to it for a while... I need to compare it to my new RKE when it arrives.

Jaimo!


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iluxo
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Reged: 09/23/08

Re: RKE eyepieces - used them for years [Re: Jaimo!]
      #5178031 - 04/18/12 07:10 AM

Hmph... Sorry I've been away from CN a while...

I had an original set of RKE's - full set - 8, 12, 15, 21 and 28mm when they first were made in the early 1980's and used them with a variety of scopes:

- 4" f/10 Meade SCT,
- 8" Celestron 8,
- 6" f/5 Newtonian,
- 12" f/3.7 Newtonian.

Originally Edmund designed and sold the RKE's for the little Astroscan telescope, a 4.25" f/4.2 Newtonian on a ball mount. There appeared to have been some attempt to optimise the RKE design to match the optical characteristics of this scope and it is quite noticeable that they perform very well for such a simple eyepiece when used in a Newtonian around f/4 to f/5.

Other budget eyepieces of that era were primarily orthos, Kellners, Erfles or Konigs and the RKE stood out against that crop for being admirably sharp in a Newtonian, with the apparent field of view being fairly typical for that era (we can leave Naglers out of this as they cost 10X as much at that time).

Characteristics:

The good:

- Excellent transparency and little colour thanks to the relatively short glass path and low number of glass-air surfaces compared to modern ultra wide designs, and they're coated.

The 28mm and 21mm had nice eye relief and fine for modest wide field views. The 15mm was ok but I didn't have much use for it. While the 8 and 12mm were OK for planetary, they were painful to use (impossibly short eye relief) and had a LOT of pincushion distortion.

The bad:

- Pincushion distortion - lots of it, and bad enough to distort jupiter or saturn quite badly when off-axis in the 8mm.

- Very limited field of view by modern standards.

- You must take care not to scratch the eye lens of the 28mm, it is convex and protrudes beyond the barrel - it is a shame Edmund didn't extend the barrel a few mm to protect it.

A few years ago I donated the RKE set to a worthy cause, and replaced it with a set Vixen LV's which are a whole lot better thanks to the consistent eye relief and better glass, with no regrets.

Edited by iluxo (04/18/12 07:12 AM)


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