I don't have an 8" SCT but...
Linton & Mark already gave the "by the book" answer, ~20mm that would give you 2mm exit pupil and 100X, pretty much the ideal all-around magnification for diverse DSO.
Personally however, it would be the spectacular 12mm Brandon, which is very inexpensive when you can find a pre-owned one (a couple times a year). This magnification (167X) is ideal for planets, planetary nebulae, and globular clusters -- after all the SCT's forte! -- so it would become the VIEWING eyepiece (as opposed to finding or scanning). You wouldn't like the Brandon's FOV, but after one look you also wouldn't care
I would not recommend a zoom because their widest AFOV typically occurs at the high-power end. So the great 8-24 Pentax XL at 8mm gives 250X (60* AFOV); at 12mm its AFOV is still quite respectable, but at 20mm it's down to about 40*.
-- William Chang (Saratoga, CA)
Linton & Mark already gave the "by the book" answer, ~20mm that would give you 2mm exit pupil and 100X, pretty much the ideal all-around magnification for diverse DSO.
Personally however, it would be the spectacular 12mm Brandon, which is very inexpensive when you can find a pre-owned one (a couple times a year). This magnification (167X) is ideal for planets, planetary nebulae, and globular clusters -- after all the SCT's forte! -- so it would become the VIEWING eyepiece (as opposed to finding or scanning). You wouldn't like the Brandon's FOV, but after one look you also wouldn't care
I would not recommend a zoom because their widest AFOV typically occurs at the high-power end. So the great 8-24 Pentax XL at 8mm gives 250X (60* AFOV); at 12mm its AFOV is still quite respectable, but at 20mm it's down to about 40*.
-- William Chang (Saratoga, CA)
