Posts Made By: Tom Allyn

Since either of these can be used as a beam splitter, why do some manufacturers use prisms while others use mirrors? Are there any advantages or disadvantages to either method? Which are more expensive to produce? Are both systems equally robust? Do they have similar transmission specs?

I just had this same dilemna, plugging a hole between my 14mm UWA and 30mm Superview for a 8" F/6 dob. One of my first thoughts was the 19 Pan, but it has almost the same TFOV as my 14mm UWA. This is the trap of wide field EP's. Once you have one you just can't go back. So I narrowed my choices to the 24 Pan, 22 T4 and 20 T5. Talking with friends convinced me to go with the 20 T5. The 20 T5 and 24 Pan have almost the same TFOV, likewise with the 22 T4 and the 27 Pan. You get higher mags with the Nags, but you pay for it.

An unbranded prototype of that 35mm was sold on ebay a few weeks ago. The buyer sent it to me to review along with several other eyepieces of similar focal length and FOV. Preliminary results in my f/6 dob are very good. I want to look at it in my friends' f/5 and f/7 scopes before making any final judgements.

Here's a pic of it standing next to my 35 Pan for comparison.

I guess it depends on what scopes you're using them in. With a newt, I'd sell the Pentax first because its' positive field curvature will be compounded by the positive field curvature of the newt. In a flat field refractor the Pentax would be OK.

Then I'd think about AFOV. Some people say they really can't see or use all of an 82* AFOV, if you're one of those then, that's a mark for the 24 Pan or the 20 XW. Between the 20 T2 and the 22 T4 the biggest difference is probably the weight, 24 oz. for the T4 vs 40 oz. for the T2.

About a year ago I was looking at all of these and I ended up with a 20mm T5. For my little 8" dob it seemed the best fit. Plus if I eventually upgrade to a larger faster dob it will still be a great eyepiece.

Finally, if you plan to use it in daytime, I'd steer toward the Pentax for its' lack of rectilinear distortion.

Depending on your finances I'd recommend the following. First the wide angle finder eyepiece.

If you can afford it get the 35mm Stratus. It's 90% of a Pan at half the cost. Nothing will touch it for $200. A 35 Pan is still obviously better, but at a cost. Below the Stratus I'd look at the TV 32 plossl, the 30mm Celestron Ultima or Orion Ultrascopic. If those are still too expensive then try a 32mm GSO plossl. It's a heckuva bargain at Agena Astro.

For planetary use look at the B/TMB planetaries. Especially the 'garage sale' 6mm if you can find one. It's the best $50 eyepiece that ever sold. It gets tons of use in my 8" dob and in my refractors. I have the 'full-price' 4mm, 5mm, 7mm & 9mm B/TMBs but I still use the 6mm more than any of them. It's just the right focal length.

We saw them up at Table Mtn. Star Party one night. Very impressive.

They need to find a way to shield that.