Hi - I'm back here again - this time with some information to share and with more questions! I picked up a Pan 35, Pan 27, TV Big Barlow, and the Interface Lens to work with my C-14. (Thank the stars for AstroMart!) I also have a 30mm 1rpd, Meade 40mm SWA, GSO 42mm, and a couple of older Meade Research Grade Erfles that I thought I'd compare against each other. I have a Lumicon Giant EZ Guider with the focal reducer lens that takes the scope down to about f/5.5. So, I tried the EPs out on the C-14 last night, straight through at f/11, then using the FR, and finally with the TV Barlow. To keep information overload under control, I concentrated on looking at faint extensions in M42, the star cluster M46 and its associated planetary nebula, NGC2438. Here's what I found:
1. Using the Pans, star images were pinpoints across the entire field at f/22 and f/11. The images were a bit soft near the edge of the field at f/5.5. Contrast was excellent - best of all the EPs I used. There was a pronounced "3-D effect" of the nebula standing out in relief against the sky using the Pans. This effect was not as dramatic with any of the other EPs. The 65-degree AFOV was pleasing and I could see almost all of it with my glasses on. On the downside - found myself having to hold extremely still to avoid "blackouts." This was particularly bothersome on the 35mm, less so with the 27mm. Field distortion was quite pronounced as well - enough to bother me. I could see fainter stars with the 30mm 1rpd. I tried this several times to be sure.
2. The 30mm 1rpd with its 80-degree AFOV has almost exactly the same TFOV as the GSO 42mm! Plus, it's sharper and contrastier. Which leads to the obvious question.
The 30mm 1rpd was excellent at f/22. The Pan had sharper stars to the very edge of the field, but the 1rpd was close. The wider AFOV, coupled with the much more forgiving "head positioning," made the 1rpd very pleasant to use. The 1rpd was very good at f/11, although the gap in edge performance between the Pans and the 1rpd widened in favor of the Pans. At f/5.5, the 1rpd fell apart with soft star images becoming bothersome less than halfway across the FOV. The 1rpd outperformed the Meade 40mm SWA at f/5.5, however.
3. The Meade RG Erfles - that I've owned since the 80's, both showed a lot of distortion and some field curvature at f/11 - something I never noticed when using them in my old 16" Newt. Perhaps that's an artifact of the SCT optical design. As a result, I did not test them at f/5.5 or f/22.
Result: The 30mm 1rpd is a "keeper." So is the 27mm Pan. The 40mm Meade and the 42mm GSO will get traded off. The jury's still out on the 35mm Pan. I can use it, and it performs well, but I do a lot of public programs and I think the "astronomically-uninitiated" would have a hard time looking through it.
This is all subjective, of course. Your mileage may vary. The cool thing is, I was able to use a single scope, in mutiple configurations, to at least maintain some consistency as I tested these EPs at various f/ ratios. I also like the concept of having a total arsenal of 3 EPs that all work well with a Barlow and a Focal Reducer. That way, it's like having NINE EPs!
Can anyone here steer me toward a 35mm + eyepiece that has a wide, flat field, good eye relief etc.? Thanks! - Chuck
The GSO performed fairly well at f/22 and f/11, but
1. Eye relief on the Pans was good, but IContrast was excellentthe Pan 35
