View Full Version here: : I tried a couple of better eyepieces

30-04-2007, 11:04 PM
Many thanks to Steve (Janoskiss) who very kindly lent me two eyepieces for my recent week away, after I had posted seeking comments on a better 9mm eyepiece. I had figured that a shorter focal length eyepiece should be my first eyepiece upgrade (when I could afford it).

Steve lent me an 8.5mm Pentax XF and a 13mm Orion Stratus.

I read what all you experts say and am embarrassed to try and say anything from my position of very little knowledge and experience, but I can only tell you what I can.

All I have to compare with are the Bintel 9mm and 15mm Plossls ($39 retail each) that come "packaged" with the telescope (8" 1200mm focal length reflector). (see attached photos - excuse the rubber o-ring plus "yellow tac" on the 9mm - that gets it close to parfocal with the 15mm :P)

Not surprisingly, I much preferred using the Pentax and the Orion to these Plossls. It was a delightful surprise the first time I looked into a wide field of view, compared to that of the Plossls. I felt so much less constrained and could easily find the right place for my eye in both eyepieces to enjoy a clean and bright view of the whole field. Given they retail for at least 5 times as much, I would have been disappointed if I hadn't said "Wow!", which I did!

There were a few times the seeing was good enough that I was able to get to a 2x Barlowed (using Bintel's 2" ED Barlow) 8.5mm lens which had the magnification up over 280x. At that point, my inexperienced eye/brain was working hard to pull enough photons out of the eyepiece, but I know I did spend a while studying and enjoying the images I was seeing - I didn't give up early - so I must have found it satisfactory. I didn't get onto the planets (or I think seeing was very poor when I tried Saturn) but I recall looking deeply into 47Tuc and enjoying the detail.

I did notice, however, that I only used the Orion on one night. The second night I took it out, it sat mostly unused and the last night it didn't even come out. It was the bulk and weight of the eyepiece, not the quality of view or eye relief. Though I wasn't comparing the same focal lengths, I could not see why I would select the bulk and weight of the Orion over the slender elegance of the Pentax. Yes, I know it is a good bit bigger and heavier than the Plossls, but it never really felt that way as I handled the eyepieces in the dark - nothing like the Orion.

I suspect I'll be in the market for one of these 8.5mm Pentax XFs when I have the funds available.

I warned you - I didn't know much! But there it is. :)

30-04-2007, 11:43 PM
The Pentax XF is also available in 12mm focal length and is also small and lightweight. Both XFs are $215 from Frontier Optics.

Haven't used them myself, but the 12mm is on my 'possible' list.


01-05-2007, 02:44 PM
the 12mm XF is on my long-term shopping list also... Unfortunately not all the Pentax EPs are so lightweight. The XWs are more like the Stratus as far as size and weight. I think it's the combination of a well corrected 65+ degree FOV and 20mm eye relief that demands large lenses and a lot of glass. The XF with 60 deg FOV and 18mm ER is a great package - it is amazing how small and light they are esp when compared with Radians which have similar specs.

Eric, you would probably like the Burgess planetaries also if you don't wear glasses to observe - good EPs but not quite up to spec, esp in ER - not enough for eyeglasses. 3 for 2 deal from Frontier Optics is great value.

02-05-2007, 03:12 AM
Got a 8.5mm XF but don't have the time to compare it with my 9mm ortho and 8mm Hyperion (though I already have it for 4 months). I'll post a comparison as soon as I get my scope out (last time was 6 months ago).

06-05-2007, 09:48 PM
OK, had the scope out last night and compared the XF 8.5 with the 9mm Genuine ortho.

The ortho gave me a me “brighter" image of Polaris (and companion), Venus and M94 most of the time. I guess the smaller FOV is the number one reason for the difference in image brightness between the XF8.5 and 9mm ortho. The smaller FOV lets the object (and its details) really pop out. Sharpness was almost identical to me.

Though the ortho gave me a brighter image I kept using the XF for the rest of the night. The larger ER and bigger FOV makes it a nice EP for DSO-hunting with hand guided telescopes. I bagged 2 galaxies of magnitude 12.6 last night without difficulties (NELM here is 4.8 so 12.6 is really faint for me :) ).