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Question on Radians

Started by Larry Seguin, 04/10/2004 02:00PM
Posted 04/10/2004 02:00PM Opening Post
I've been reading the posts comparing Pentax XL's to Radian's, and want to ask the question in a slightly different way. When I was using Radian's I came to feel that the contrast was not what it should be--rather as though the lens was always just a little grimy or fogged. When I compared them to Pentax XL's I thought that the XL's were noticeably "clearer", with better contrast. Yes, the Radian's really were clean, and no, I don't think I had a bad sample because I was using 6, 8, and 10mm Radians, and they couldn't all be bad samples, could they? Has anyone else felt that the Radians lacked something in contrast, or weren't as clear as they should be, or am I the only one? Maybe it's time for a visit to the optometrist!
Larry Seguin
Posted 04/10/2004 07:16PM #1
Hey Larry,

One night I tested an 8mm radian (mine), a 7mm Pentax XL, and a 7mmNT6 (in a 10" f4.5 newtonian). I looked at deep sky (galaxies, clusters) and Jupiter.

Quite frankly I couldn't seem much difference. Seeing wasn't good enough to push the eyepieces on Jupiter. I did pay attention to eye reflections (a problem I had with a 6mm Radian), contrast, and sharpness. No real standouts, although I was impressed by how far Al had come with the coatings on the Naglers.

Eye relief was a bit tight on the Nagler, but usable. The Radian and Pentax were both very comfortable to use.

I also noticed a weird optical illusion caused by the fields of view. For example, an open cluster appeared bigger in the Pentax because the field was smaller than in the Nagler.

Bottom line, I think differences in design (eye relief, field of view) will be a much bigger factor to the user than performance differences.

I have actually been contemplating the purchase of a 5mm Pentax XW for high power deep sky work (to replace my 5mm Tak LE).

But on planets I generally use U.O orthos.

Take care,
john

Posted 04/11/2004 04:43PM #2
Thanks for some great thoughts on this topic, guys. I really appreciate all your input. I had never heard before the remarks by Roland Christensen about optics not being assembled in clean enough environments )so just how DO they assemble them, hmmm?), and the idea that Radians may not perform that well under less than dark skies is intriguing--makes me want to get another one just to try that out!Concerning eyepiece satisfaction, I'm beginning to suspect that there must be some equation involving your particular eyes/scope/skies that, when combined with your particular preferences in viewing criteria, results in all the differing preferences in eyepieces. So--back to the drawing board, the search for the perfect eyepiece goes on!
Larry