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Hi All,
I was going to add to this but much of it is good advice and I'd only add what I normally preach about -- Exit pupil.
Think about the exit pupil of the 'scope eyepiece combination. Small LSB (small galaxies and PNe) think about an exit pupil around or just under the 2mm mark, for large LSB a bit more, say around the 4mm exit pupil mark.
One real challenge to test all this advice coming up in a few months time is the galaxy NGC 45 in Cetus (not too far from NGC 247 & 253). It is one of the lowest surface brightness galaxies around and a serious challenge in 12" 'scopes under a very dark sky even though it has an integrated magnitude of 10.5v the SB mag is in the low 14s because it is 8 arc-mins across. It has almost no core and the disc is thin and wispy enough to see background galaxies through (in the DSS).
This is how I saw it a couple of years ago in the 18" under a superb rural sky at Mudgee:
x139 35' TF NGC 45 Galaxy
*RA: 00h 14m 04.1s Dec: -23° 10' 54"
Mag: 11.3 (B) S.B.: 14.6 B-V: +0.71Size: 8.5'x5.8'
Class: SA(s)dm P.A.: 142
Inclination: --- R.V.: +468
This is a very, very LSB eg found to the ENE of a mag 6* which is not far outside the halo on the SW flank. There is also in the outer halo of the eg a much fainter mag 10 * almost directly south of centre. Fairly large, probably 4' - 5' diameter, appearing round with a very LSB halo rising weakly, if at all to the centre without any sign of structure or nucleus. Would be very easily passed over in sweeping.
Many experienced observers feel 12" is probably the minimum aperture, but who knows? For those in the 10-12" range it is a really testing LSB challenge to try-out the above advice. Good luck with it!
Best,
Les D
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