Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Edmund RKE, Pre RKE myth, more RKE

  • Please log in to reply
61 replies to this topic

#51 Mitrovarr

Mitrovarr

    Skylab

  • *****
  • Posts: 4,123
  • Joined: 12 Sep 2004
  • Loc: Boise, Idaho

Posted 19 October 2021 - 11:06 PM

Does anyone know a way to give it a 2" barrel diameter? That 1.25" one cuts the field down a great deal.



#52 apfever

apfever

    Fly Me to the Moon

  • *****
  • topic starter
  • Posts: 6,471
  • Joined: 13 May 2008
  • Loc: Colorado

Posted 19 October 2021 - 11:38 PM

Which size?  An RKE right?  Doesn't need a 2" barrel.



#53 John Rogers

John Rogers

    Viking 1

  • *****
  • Posts: 885
  • Joined: 08 Feb 2008

Posted Yesterday, 08:34 AM

Does anyone know a way to give it a 2" barrel diameter? That 1.25" one cuts the field down a great deal.

I designed and 3D printed my adapter:

 

Edmund_5160_1.jpg Edmund_5160_2.jpg Edmund_5160_2-inch_Adapter.jpg

 

I forgot to mention that this eyepiece is essentially identical to the Edmund 32mm RKE eyepiece.


  • clamchip, PawPaw and Bomber Bob like this

#54 Mitrovarr

Mitrovarr

    Skylab

  • *****
  • Posts: 4,123
  • Joined: 12 Sep 2004
  • Loc: Boise, Idaho

Posted Yesterday, 09:36 AM

Wouldn't that mean the 32mm RKE isn't an RKE? The ad claims this has three achromats, so clearly it wouldn't be an RKE design.



#55 apfever

apfever

    Fly Me to the Moon

  • *****
  • topic starter
  • Posts: 6,471
  • Joined: 13 May 2008
  • Loc: Colorado

Posted Yesterday, 09:40 AM

I designed and 3D printed my adapter:

 

I forgot to mention that this eyepiece is essentially identical to the Edmund 32mm RKE eyepiece.

Is this the same optical design, at least to the naked eye, as the RKE just bigger?  There is no 32mm RKE I know of. I have a smaller brass military that came with my baseball size radioactive one. I'll have to see if it is the same. I have no idea where that box of that type stuff is.

Is t



#56 John Rogers

John Rogers

    Viking 1

  • *****
  • Posts: 885
  • Joined: 08 Feb 2008

Posted Yesterday, 09:50 AM

Is this the same optical design, at least to the naked eye, as the RKE just bigger?  There is no 32mm RKE I know of. I have a smaller brass military that came with my baseball size radioactive one. I'll have to see if it is the same. I have no idea where that box of that type stuff is.

Is t

Ah, but there is!

 

1989_Catalog_32mm_RKE.jpg


  • Bomber Bob likes this

#57 John Rogers

John Rogers

    Viking 1

  • *****
  • Posts: 885
  • Joined: 08 Feb 2008

Posted Yesterday, 10:02 AM

Wouldn't that mean the 32mm RKE isn't an RKE? The ad claims this has three achromats, so clearly it wouldn't be an RKE design.

Exactly.  It is a Kaspereit design, even though they called it an Erfle.  It is my opinion that this eyepiece was created and promoted to ride the RKE popularity wave.  It only appeared in their catalog for a few years.

 

I have had both the 5160 and 32mm RKE eyepieces, exploded side-by-side and they appear identical, down to the diameters, thicknesses and diopter measurements of the surfaces.  There might have been changes to the glass composition, but I have no way of measuring the refractive indices.



#58 apfever

apfever

    Fly Me to the Moon

  • *****
  • topic starter
  • Posts: 6,471
  • Joined: 13 May 2008
  • Loc: Colorado

Posted Yesterday, 10:31 AM

GO here about 2/3 down. The Erfle and Kaspereit are right next to each other and the RKE just a few down. 

 

description link

 

I'm curious if "RKE" is imprinted on the 32mm eyepiece.  Edmund makes it official by way of an ad but still curious if it's on the ep. Chores to do but I'll crack open a 15mm RKE to see if it is the same as the 21.5 and 28.  I'll go with John's comment on "...created..to ride the RKE popularity..."   I think I have a 32mm Erfle 2",  should check that too.

 

My Anares 2" 32mm Erfle is a Kaspereit.It seems to be the 'Erfle' of choice. At any rate not the 5 focal set of RKE red band (or black body 28mm).  The Kaspereit is getting way off line by way of having twice the glass, three more elements. 


Edited by apfever, Yesterday, 11:03 AM.


#59 John Rogers

John Rogers

    Viking 1

  • *****
  • Posts: 885
  • Joined: 08 Feb 2008

Posted Yesterday, 11:22 AM

RKE does not appear anywhere on the eyepiece.  Dr. Rank passed away in 1981, a few short years after the RKEs were developed.  The 32mm did not appear in the Edmund catalog until 1988 and disappeared after 1989, leading me to suspect that it was completely a marketing ploy.  If it had been "Computer designed" by Dr. Rank, then he had to have done it at the same time he was designing the original RKE, so why was it not introduced at that time?



#60 Terra Nova

Terra Nova

    ISS

  • *****
  • Posts: 25,583
  • Joined: 29 May 2012
  • Loc: 39.07°N, 229m AMSL, USA

Posted Yesterday, 03:13 PM

Does anyone know a way to give it a 2" barrel diameter? That 1.25" one cuts the field down a great deal.

I don’t know about that particular eyepiece but some with huge glass really need the 1.25 reducer as a field stop. You might get boatloads of edge distortion without it.


  • rcwolpert and Bomber Bob like this

#61 Bomber Bob

Bomber Bob

    ISS

  • *****
  • Posts: 20,242
  • Joined: 09 Jul 2013
  • Loc: The Swamp, LA (Lower Alabama)

Posted Yesterday, 05:28 PM

Ah, but there is!

 

attachicon.gif1989_Catalog_32mm_RKE.jpg

I have the 2" Edmund ER 32mm & the UO 2" ER 32mm.  They look similar, but the Edmund has a flatter field than the UO. If I get a chance this weekend, I'll take them apart, and post some pix...

 

If I think about it, the Edmund does very well with the Triple Nickle 5" F5 Frac, and the UO does well with Stubby 6" F4 Newt (with the Paracor).  In fact, I keep the UO on the AR-1 accessory tray when Stubby is on that mount.


Edited by Bomber Bob, Yesterday, 05:31 PM.

  • Terra Nova likes this

#62 Mitrovarr

Mitrovarr

    Skylab

  • *****
  • Posts: 4,123
  • Joined: 12 Sep 2004
  • Loc: Boise, Idaho

Posted Yesterday, 06:46 PM

I don’t know about that particular eyepiece but some with huge glass really need the 1.25 reducer as a field stop. You might get boatloads of edge distortion without it.

That's entirely possible, but it would be fun to try. Apparently this eyepiece has 6 elements in 3 pairs so it's possible the correction might actually be pretty decent.




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics