Meade 5000 Series Super wide angle, why mostly 2" eyepi

Jeff,

Thanks for that, I think I will go for a lie down now
There are so many ingenious designs eyepiece optics around and more appearing every day it is hard to keep up.
I have noticed that pincushion defect is present in a lot of cheap binocular eyepieces and is noticeable as a concave distortion of straight lines near the edges of the FOV.

Michael --

Yeah, pincushion can be pretty objectionable in binoculars, with wonky telephone poles and the like. For the night sky, though, I'd much rather have pincushion than field curvature (the outside of the field having a slightly different focal position than the center), which is normally the trade-off for reducing pincushion.

Indeed TeleVue makes this trade-off, with many of their wider designs exhibiting quite a bit of pincushion. One popular alternative is Pentax, but then you have to deal with considerably more field curvature. Me? I'd much rather have the whole field in focus than worry about whether or not a few stars are a bit out of position (after all, there aren't that many straight lines out there ).

Cheers,
-- Jeff.

Interesting points there lads,
I find that field curvature is very obvious (and objectionable), especially if you panning the scope along the sky, I have never really noticed pincushion in a star field, I suppose it might be noticeable when looking at the moon?

Dave --

The worst thing about field curvature (for me) is panning around looking for a small Planetary Nebula, or a small stellar-cored galaxy. Every star in the outer portion of the field looks like one (a bit fuzzy) until it gets to the center of the field, when you realize it's not. :evil:

But I've heard some swear by Pentax's because the pincushion in Panoptics makes them seasick when panning. (The Naglers also have pincushion, but IIRC, a bit less than the Pans.)

Now I'm probably the only guy on the planet that can get motion sick in a rocking chair, but that appears to be a separate circuit in the brain -- the fact that stars in the outer portion of the field move in a non-linear fashion strikes me as a bit odd, but it doesn't make me feel ill. And, I'm a GoTo guy anyway, so it's not like I'm doing a lot of star-hopping.

Cheers,
-- Jeff.

Hi Jeff,
I have a few naglers and haven't found the pincushion effect annoying or even noticable on the shorter focal length naglers, I guess I've a stronger stomach for it. :lol: