I'm taking a break from a night of okay seeing. I've been out with my 10" Teleport and testing my new 21.5mm, 15mm and 12mm Edmund RKEs, mostly in the 5x Powermate. I purchased these RKEs new from Edmund, and the first thing that I noticed was that this 15mm has the same "ragged" field stop that the one I owned years ago had. It's partly because it is sharp as a knife (cut my finger on it, actually).
One thing about these RKEs that I hadn't remembered is how generous the eye relief is for a scaled design. The 12mm is okay still--no chance of getting eyelashes on the eye lens. Coatings look great--just like single-layer MgF2 coatings are supposed to look. This is the way the cheap Chinese eyepieces ought to look. When you attach an eyepiece to a powerful Barlow or Powermate and point it at a light, you can see the sillouettes and diffraction effects of imperfections in the optical path, usually dust. The RKEs arrived in their yellow boxes, but inside they were just wrapped in paper (no caps), so there were paper particles that needed to be removed. There are little indications here and there that they could be cleaner inside, but the problem is small enough that it cannot be detected without a Barlow's assistance.
I'm fairly pleased with them at f/25 in the 10" Teleport w/the 5x Powermate. I thought the 21.5mm would be interesting to compare to the 20mm Tele Vue Plossl, but I'm afraid I can't choose between them very easily. Sometimes it seems like the Tele Vue is better, but other times they seem the same.
It turned out that the night was a pretty good one for viewing the Alpine rille, which I could see most of in the higher magnifications. If there's anything lacking in quality and performance of the modern RKEs versus those manufactured long ago, I didn't see any evidence of it. Didn't see any internal reflections, either.
I tried them without the Powermate in the Teleport and viewed M42 and Saturn. Loss of sharpness near the edge of field was only slightly worse than in the 20mm Tele Vue Plossl (slightly wider field there, though), and the image in the center of the field was fine. E.g. The E and F stars in the trapezium were bright and clear with direct vision, especially in the 15mm and 12mm.
I like the RKEs, but on the other hand, I don't think there is anything unique about them as compared to UO orthos, Ultrascopics, and other quality 1.25" eyepieces.
--
Mike
One thing about these RKEs that I hadn't remembered is how generous the eye relief is for a scaled design. The 12mm is okay still--no chance of getting eyelashes on the eye lens. Coatings look great--just like single-layer MgF2 coatings are supposed to look. This is the way the cheap Chinese eyepieces ought to look. When you attach an eyepiece to a powerful Barlow or Powermate and point it at a light, you can see the sillouettes and diffraction effects of imperfections in the optical path, usually dust. The RKEs arrived in their yellow boxes, but inside they were just wrapped in paper (no caps), so there were paper particles that needed to be removed. There are little indications here and there that they could be cleaner inside, but the problem is small enough that it cannot be detected without a Barlow's assistance.
I'm fairly pleased with them at f/25 in the 10" Teleport w/the 5x Powermate. I thought the 21.5mm would be interesting to compare to the 20mm Tele Vue Plossl, but I'm afraid I can't choose between them very easily. Sometimes it seems like the Tele Vue is better, but other times they seem the same.
It turned out that the night was a pretty good one for viewing the Alpine rille, which I could see most of in the higher magnifications. If there's anything lacking in quality and performance of the modern RKEs versus those manufactured long ago, I didn't see any evidence of it. Didn't see any internal reflections, either.
I tried them without the Powermate in the Teleport and viewed M42 and Saturn. Loss of sharpness near the edge of field was only slightly worse than in the 20mm Tele Vue Plossl (slightly wider field there, though), and the image in the center of the field was fine. E.g. The E and F stars in the trapezium were bright and clear with direct vision, especially in the 15mm and 12mm.
I like the RKEs, but on the other hand, I don't think there is anything unique about them as compared to UO orthos, Ultrascopics, and other quality 1.25" eyepieces.
--
Mike
