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Hello,
Very interresting subject ! I'm also currently looking for a zoom eyepiece. I would like to have the best possible optical quality and the less "tunnel effect" as possible in wide FOV.
There are quite a lot of 8-24mm zooms (TV, Vixen, Meade...) but those are almost all the same and they are not satisfying. I Tried the TV 8-24 on my tak FS60 and I found that the image sharpness was not very good, and that there was a yellow color in the image.
During my searches on the net, I found that the best zoom eyepiece were not the astronomical ones, but the eyepieces for quality spotting-scopes. People who tried them for astronomy all agree that they are far better than the astronomical classical 8-24mm.
Here you can find :
- the NIKON 7-21mm "SpottingScope" zoom eyepiece (not the "FieldScope" one). FoV is 38-60°. You will need to find a 1.25" adaptator to use it. It is described to be the sharpest, and to have the better light transmission abd therefore the best contrast. No image distortion. Tunnel effect exists, but less than in the classical 8-24mm. This one is quite cheap : around $300.
- the LEICA 7.3-22mm zoom. FoV is 38-68°. A 1.25" adaptor is available. Sharpness is just a little bit lower than the Nikon. Curiously, it is described as having no noticable "tunnel effect" at 22mm. Around $750.
- the ZEISS 8.4-21.5mm zoom. FoV is the best of all : 49-68°, "No tunnel effect" ! It is as sharp as the Nikon but has a small amount of image distortion at 21.5mm. It can be purchased with a Zeiss 1.25" barrel. Around $600.
- There is also a SWAROVSKI zoom eyepiece which should also be a good one, but I found nobody who tried it for astronomy. Around $650.
I will probably purchase the NIKON one as it is excellent optically and quite cheap. My second choice would be the Zeiss because of it's amazing 49-68° FoV.
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