Astromart and TV Radians..(?)

This is a legit question and NOT any attempt at a TeleVue slam!

I tried (tested?) numerous eyepieces and instantly returned the only Radian I ever bought. Many strange colors dancing around inside, and lots of "ghosts". (12mm Radian)

Has anyone else noticed how many Radians have been for sale on Astromart in the last two-three months..? I am just wondering why the owners are selling. Is it that they don't like their Radians, or are they (you folks who know) changing to something they like better? I ask because there have been some good deals on Radians, but maybe I should steer away.(?)

Steve Sherrod

Steve, I tried a few Radians and never saw these colors and ghosts, however I have heard many say they are there. It might be that I did not look at the right objects?
I only own Naglers in the TV line, I might accept a Panoptic or two though. ;^)
You might like the Pentax's better, the XL line is a bit like the Radian in FOV and eyerelief.

Floyd

I don't know what was going on with your 12mm Radian. Despite Tele Vue's 100% QC practice, defects do slip through. The 7mm Nagler Type 6 that I have had a warranty repair (came with a scratch at the edge of one of the internal lenses), and the 5mm Nagler Type 6 was a replacement of the one I bought new because the latter had serious optical problems.

Another possibility (besides a defect) is that you were moving your eye around in the exit pupil too much. This will cause slight color fringing around objects anywhere in the view, not just lateral color at the edge (in fact the technique of eye placement in the exit pupil can be used to partially null out lateral color at a given point in the view). You might need to use the pupil guide for awhile to train your eye for the eyepiece if that is the problem.

Anyway, I've owned all of them except for the 6mm. I've only used the 6mm briefly but saw nothing unexpected, and I've used the others fairly extensively. I have NEVER seen an internal reflection in a Radian, only external reflections off the eyeball, to the eye lens, and back to the eye. Unfortunately, I get that with all wide-angle long-eye relief eyepieces, ALL of them, and I noticed that effect first with a Plossl in a Barlow (looking at Jupiter, naturally).

Radians do have some LATERAL color, but so do all other super wide angle eyepieces I've seen, although some have more than others. Performance of the Radians is more or less uniformly on a par with a high quality Plossl in a good Barlow, with an extra 10 degrees of field, of course. In my old MK-66 Deluxe, I got better planetary performance out of an 8mm Radian than anything else I tried in that scope.

Radians are sold on Astromart at a steady pace and have been for years now. If anything, I see fewer of them for sale lately.

I own no Radians now, however. I prefer the Type 6 Naglers.
--
Mike

Stephen, I'm one of the folks buying up the Radians on AM. Over the past few months I've picked up a 4mm, 5mm, and 14mm. I love them all.

I compared the 4mm with my 4.8mm Nagler in my 8-inch f/8 during the Mars opposition and found:
- The Radian was slightly sharper, right out to the edge
- The Radian had less distortion. Mars had a distinctly out-of-round appearance near the edge in the Nagler, but was perfectly round in the Radian.
- No ghosting in either.
- Some false color in the Radian when my eye was not centered in the exit pupil correctly. Not possible in the Nagler because of the short eye relief, but with the Radian the eye lens is large even in short FLs, so it's harder to keep your eye centered. Setting the sliding sleeve helps.

Ditto the 5mm.

I also compared the 14mm with a 13mm Nagler (type 1) with in my 13" f/4.5. Again, the Radian was sharper.

Perhaps the new Naglers (Type 5, Type 6, etc.) are better, but eye relief is still a problem for me in the short FLs. So I've since sold both Naglers and kept the Radians. Right now I'm saving my pennies for a 6mm and maybe a 10.

Best regards,
Doug Scobel