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New planetary ep essay and Edmund RKEs

Started by darkhop, 08/26/2002 12:16PM
Posted 08/26/2002 12:16PM Opening Post

Very interesting in general, but one of the author's high recommendations was for Edmund RKEs. I haven't seen these mentioned much, nor seen any for sale unless I blinked at the wrong time. Is this some kind of open secret or am I looking in the wrong places? TIA.

/John H.
Posted 08/26/2002 03:43PM #1
I am missing in this review the NIKON, Zeiss West, Olympus eyepieces

best wishes


clear skies

Markus Ludes
Posted 08/27/2002 03:13PM #2
Hey the RKE's are not a bad ep but to compare them to a good fully multi coated plossl is a little long in the tooth and the UO ortho's I am afraid its too hard to take. The RKE's or UO Kellners are very good ep's on a budget both well made and back in the 60ies these were top rated. But todays UO ortho's, Koning's, Vixen SW,TV Radian's, Meade and TV plossl's, Ultima's, Tak LE's, Pentax widefield's all have there place. We all have personal likes and dislikes and some ep's just match up with some scopes with better results but the RKE's are not close at all to the obove ep's. Maybe if you are using a lower end scope this might be so but it didn't look like that from what they stated were the observing tools.
Posted 08/27/2002 07:35PM #3
No correction. I never said RKEs were 4-element eyepieces. RKEs are 3-element eyepieces (field doublet with eye singlet) with 4 air-to-glass surfaces. Obviously, the number of air-to-glass surfaces must always be an even number. What many people do not realize is that cemented interfaces are very efficient compared to air-to-glass surfaces, so the fact that, say, Plossls and Abbes have one additional element and one additional cemented interface doesn't handicap them much. Glass transparency is an issue that really should be modeled in, but it's not easy to do a good job of it without specific, technical data. I guess the best possible implementation of a Kellner or RKE should be able to edge out the best possible implementation of a Plossl or Abbe in transmission, but we're not usually comparing apples to apples like that, and different coatings, glasses, and surface smoothness and accuracy can make the difference.