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Equipment Discussions >> Eyepieces

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planet earth
Pooh-Bah
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Reged: 09/07/10

Loc: Ontario Canada
Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: ibase]
      #5155990 - 04/04/12 10:59 AM Attachment (26 downloads)

I've got the 28mm RKE from 1981 and like it a lot. It came with a Edmund 8 f5 #4001 ota.
I usually use the eyecup.
Some 1980's Edmunds ads reads 60* but 45 degree is more like it unless some where 60*
Another RKE I've seen but never owned is the 8mm Wide angle.
Anyone have info of these and where there others.
Any ways, good purchase.
Clear Skies
Sam


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BillP
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Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: planet earth]
      #5156031 - 04/04/12 11:28 AM

Quote:

Another RKE I've seen but never owned is the 8mm Wide angle.




Edmunds sells these with their Plossls. It however is not a Plossl but a positive-negative design (i.e., it has a Smyth group in the barrel). Stats on it are (my measures):

Eye Relief = 8.5mm (from housing), 9.5mm (from lens surface)
AFOV = 59.7 deg
Eye Lens Diameter = 13.6mm

Here's my first light report with the Plossl line - Thread.


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planet earth
Pooh-Bah
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Reged: 09/07/10

Loc: Ontario Canada
Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: BillP]
      #5156080 - 04/04/12 12:13 PM

Thanks Bill
Clear Skies
Sam


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Andy Taylor
Twisted, but in a Good Way
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Reged: 09/24/08

Loc: Epsom - UK
Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: planet earth]
      #5156197 - 04/04/12 01:54 PM

>I have read on you blog - nice blog by the way - it exhibited >field curvature on your f5.9 scope. Do you have a higher >focal ratio scope to try it on?

Yup - on my rich field there is noticeable softness towards the edge but on my 100mm F13 Carton...

Sublime just about describes it.


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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: Andy Taylor]
      #5156228 - 04/04/12 02:19 PM

Are edmund plossl, asymmetrical design?

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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: Simoes Pedro]
      #5156641 - 04/04/12 07:33 PM

Thanks Simoes Pedro! And thanks too for all the info on the RKE's!

Yes, this RKE28 on hand is the "Edmund Scientific" version, which Vondragonnoggin (who owned both) had mentioned was optically same as the "Edmund Optics" version.

Will be trying out the RKE28 in my other scopes - F/12.9 Nexstar 4SE Mak, 4" refrac F/7 William Optics Megrez 102ED, F/10 SCT C8, 5" refractor F/7.5 Antares 1529 and an F/5 Orion ST80.

Looking forward to seeing the pic, and any machining developments.

Quote:

Hi Hernando,

I can guarantee yours is not in the most recent housing. Yours reads Edmund Scientific. That brand ceased to exist in the 70's.

I have purchased a set of RKE's from Edmund optics. They came in three different barrel types. I have only kept the 28mm, which was the only one in a modern barrel. By the way, the 8mm arrived chipped.

15, 12 and 8mm models have too tight eye relief to have any use.

28.7mm model(28mm) feels special, due to the famous "eyepiece vanish effect".

I have read on you blog - nice blog by the way - it exhibited field curvature on your f5.9 scope. Do you have a higher focal ratio scope to try it on?

I have a f8 scope and the field curvature problem is not that prominent.

I will post pictures of mine as soon as I can.

I am tempted to machine to field stop to meet the barrel inner diameter. this will yield about 60º of AFOV.

ATTENTION: Do not unscrew the barrel with the field lens facing down. The optics will fall on the floor.

Congratulations on your purchase. It will be a future classic




Best,


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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: BillB9430]
      #5156669 - 04/04/12 07:52 PM

Quote:

I bought an Edmund 1 1/8" "Kellner" new nearly 50 years ago (still have and use it) and now just received a new 28 mm RKE. Both are nice eyepieces, but I do like the defined field stop in the RKE instead than the rather reflective inner barrel visible in the old "Kellner". I will use the RKE without the rubber eye guard that was sent in the package, but offer this caution for those who try that guard. In applying the rubber eye guard to the eyepiece, I carelessly allowed the forward edge to brush the field lens. Big mistake! Apparently there is some material on the rubber that transfers to the glass, making a mark. It was NOT removable with my standard lens cleaner! Fortunately, a little acetone on a Q-tip removed the mark completely. If you don't have acetone handy, be very careful. -Bill




Thanks Bill, yes putting the rubber boot on can be quite tricky the first time around, struggled with it too when I tried it out initially.

Best,


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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: Vondragonnoggin]
      #5156689 - 04/04/12 08:03 PM

Quote:

Hernando, keep using the RKE. It will grow on you the more you use it. The eye placement issue becomes a non-issue very fast. I thought it was a cool eyepiece when I first used mine, but after some time using it, I moved it to the "must keep" category and it has become one of my most used eyepieces. Sometimes I just go out and view with a 2x barlow, a 5x Powermate, and the 28mm RKE. Three magnifications all with that floaty effect and barlowing it gets rid of any edge artifacts.

I am waiting for Explore Scientiics barlows to come out. I think they are reintroducing the Meade 5000 series teleXtenders in 1.25". I have a 2", 2x TeleXtender, but really want the 1.25" 2x, and 3x teleXtender telecentrics. With a 2x, 3x, and 5x Telecentric design, I'll get the 28mm RKE in 4 magnifications and no added eye relief. Hmmmm, maybe a 2.5 Powermate is in order to make the 28 RKE an eyepiece case application.



I also saw you noticed the 45 degree AFOV appears wider in use. I think it does too.

Now that I'm thinking about this, all those telecentrics plus my 28 RKE and 35mm Parks Gold would be just about everything I'd need to be happy with my views and make the rest of my eyepieces collect dust.

I think I just created my list for purchases....




Thanks Eric, yes the possibility of the RKE28 growing on me is positive, and am sure it will be a better match, edge-wise, on one of my slower scopes. Will try it with my Powermate 2.5x barlow too, it's just that I'm no great fan of using barlows (also have the TV 2x, 3x, and 2" ones like the Antares 1.6x and GSO ED 2x), and find them a bit unwieldy to use, except the compact 2.25x; but will try these out with the RKE28 when the opportunity arises. And yes, the views looked wider than 45° to me too, which is a pleasant finding. That's a fine prospect using only 2 EP's w/barlows, very minimalist - if it works out well for you, great! Thanks again.

Best,


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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]
      #5156698 - 04/04/12 08:09 PM

Quote:

Quote:

I bought an Edmund 1 1/8" "Kellner" new nearly 50 years ago (still have and use it) and now just received a new 28 mm RKE.




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.




Thanks for chiming in Bill. Been curious for sometime already about the Clave plossl, hmmm..

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: planet earth]
      #5156707 - 04/04/12 08:15 PM

Quote:

I've got the 28mm RKE from 1981 and like it a lot. It came with a Edmund 8 f5 #4001 ota.
I usually use the eyecup.
Some 1980's Edmunds ads reads 60* but 45 degree is more like it unless some where 60*
Another RKE I've seen but never owned is the 8mm Wide angle.
Anyone have info of these and where there others.
Any ways, good purchase.
Clear Skies
Sam





Thanks Sam, glad you like much the RKE28 and nice pic too, thanks for posting. Doesn't the rubber eyecup cancel the "floating" effect on you? That's good if it doesn't, as it does for me. The bigger than 45° view was my impression, will have to look more into that, thanks.

Best,


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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: Andy Taylor]
      #5156765 - 04/04/12 09:18 PM

Quote:

>I have read on you blog - nice blog by the way - it exhibited >field curvature on your f5.9 scope. Do you have a higher >focal ratio scope to try it on?

Yup - on my rich field there is noticeable softness towards the edge but on my 100mm F13 Carton...
Sublime just about describes it.




Thanks Andy; I'll try the RKE28 with my F/12.9 4" Nexstar mak and see how it fares on the slower scope - I like the word you chose to describe it, "sublime."

Best,


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Simoes Pedro
sage
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Reged: 02/03/09

Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: ibase]
      #5157317 - 04/05/12 09:50 AM Attachment (28 downloads)

Here goes a picture of mine

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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: Simoes Pedro]
      #5157465 - 04/05/12 11:17 AM

Thanks, nice pics! They look like the one I have, except for the "Optics" part - so you mean this "Edmund Scientific" version of mine goes all the way back to before the 70's? (p.s. glad you like the blog, thanks)

Best,


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Simoes Pedro
sage
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Reged: 02/03/09

Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: ibase]
      #5157478 - 04/05/12 11:28 AM

I believe so. This is what I could find in wikipedia.

http://en.wikipedia.org/wiki/Edmund_Scientific_Corporation

The 70's information could be wrong.

When the company was split in the 1970's, edmund optics kept producing the eyepieces (as they still do to this day). It is fair to assume they were relabeled at that time.

Edmund Scientific was split into Edmund Optics and Edmund Scientifics (note the "s"). Scientifics also sell an eyepiece line, which are labeled "edmund scientific" (no "s")

http://www.scientificsonline.com/edmund-scientific-plossl-eyepieces-10012.html


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ibase
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Loc: Manila, Philippines 121*E 14*N
Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: Simoes Pedro]
      #5157565 - 04/05/12 12:33 PM

Thanks for the links! Considering that this "Scientific" RKE28 could date back to the 70's, I think if given the choice, I'd prefer it to the current version, all things considered equal optically, there's something about old vintage optics that make 'em more appealing to some. Wish EP's were like wine - the better they become as they age.

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: BillP]
      #5167205 - 04/11/12 04:41 PM

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: Jaimo!]
      #5167877 - 04/12/12 01:28 AM

Very nice dis-assembly photo Jaimo!, thanks for posting!

Best,


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Warren914
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Reged: 03/21/12

Loc: Nova Scotia, Canada
Re: RKE 28mm on the way! What to expect vs. 27-36mm's? new [Re: ibase]
      #5167947 - 04/12/12 05:45 AM Attachment (20 downloads)

My 1-1/4" Edmund Scientific RKE28 looks different inside.

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ibase
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Re: RKE 28mm on the way! What to expect vs. 27-36mm's? [Re: Warren914]
      #5168134 - 04/12/12 09:20 AM

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,


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BillP
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Re: RKE 28mm on the way! What to expect vs. 27-36mm's? [Re: ibase]
      #5168181 - 04/12/12 09:57 AM

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.


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