Best eyepieces for 8" SCT.

[tico]

Hello,

 I have a new SCT 8", which is the best eyepieces for this telescopes, in 1.25" or 2"  size ?

Thanks.

Tico

[michael.h.f.wilkinson]

Eyepiece quality has little to do with size: my 1.25" fit Pentax XW 10mm is every bit as good as the 2" Nagler 31mm. What differs is the maximum field of view they can provide. If your SCT has a 1.25" visual back, and a 1.25" star diagonal, you are limited to 1.25" EPs, and the only way to escape the limited FOV  (roughly 0.76 degree) that provides is to use a focal reducer. I used to do that and it works fine, but it is a bit of a faff installing it and removing it as needed by the object you want to observe. Some years back, I installed a 2" visual back (not expensive) and a 2" star diagonal (a bit more expensive) and started using 2" EPs which give me up to 1.33 deg FOV. Otherwise, at F/10 an SCT is not very picky in terms of EP quality, although better EPs do give better results. Having said that, I enjoyed using decent quality Plossl EPs for years before switching towards more up-market kit like TeleVue and Pentax EPs.

[tico]

Is it really worth using a 2 "diagonal star with 2" eyepieces for an 8 "SC, or would this add more weight?
Do you really get more visual field than with 1 1/4 size eyepieces?
Could you recommend some ep. of 2 "and of 1.1 / 4" for small-medium magnification?

Thanks.

Paul

[michael.h.f.wilkinson]

47 minutes ago, tico said:

Is it really worth using a 2 "diagonal star with 2" eyepieces for an 8 "SC, or would this add more weight?
Do you really get more visual field than with 1 1/4 size eyepieces?
Could you recommend some ep. of 2 "and of 1.1 / 4" for small-medium magnification?

Thanks.

Paul

As I said above, without the focal reducer, the maximum view with a 1.25" EP is just 0.76 deg. Enough to fit the entire moon in the FOV, but not a huge deal more. With a 2" visual back, you get 1.33 deg, or 75 % more  linearly, and more than 3x the area of sky. That is significant in my book. You can achieve roughly the same with a focal reducer, but it is not as comfortable. Regarding EPs, much depends on budget. The Moonfish 30 mm 80 deg EP apparently works nicely at F/10 in the C8 (I haven't ever tried it), but the Nagler 31 T5 does an outstanding job, for a lot more money. The Skywatcher Aero 40mm is worth considering. It is a clone of the TMB Paragon I used to have, which was excellent, and not too heavy. Weight is rarely a big issue with the C8, I find, as it is a compact and light OTA that is easily balanced. A 24mm 68 deg EP would be great if you want to stick to 1.25" format. The MaxVision is very good, but hard to get except second hand, Panoptics are great, but much more expensive. Plossls work very nicely, but then I would opt for a 32mm to et the maximum FOV at 1.25" barrel diameter

[RT65CB-SWL]

If you go down the 2" eyepiece route, I recommend that you get an star diagonal for an SCT, not a 2" pushfit. It will, (or should), include a 1.25" reducer as well.

The photo above of my Altair Astro 2" SCT star diagonal attached to my 're modded' Meade ETX105. The white cap, (just visible), is the 1.25" reducer.