Eyepieces for f5.

[cotterless45]

I keep a hardback A4 book and write down any useful info . Flicking back I found a note that the minimum ep for f5 is 8mm. This seems to make sense.

I was at a recent beginners night. Some one turned up with a new 150 f5, fitted a 4mm UWA Meade (cur"ching) and a x2 Barlow and complained that Jupiter was "fuzzy".So that's x375 , I'll stick to my 8mm.

[en51nm]

My 200P f5 came with a 2mm EP - I've never used it, x2 Barlow and a 10mm is already quite fuzzy.

[Capricorn]

A 2mm equivilent is a bit daft, wouldn't suggest a 4mm in normal use, as I have one and it's use is very limited to put it mildly.

I can only suppose they knew little about scopes and using one.

A 6mm on an f/5 should be usable, just which 6mm is the question. Not sure how well something like a BST 5mm would work, although sure I have read that they are good.

[Peter Drew]

Depends on F5 what, 8mm is not near the limit for a good 6" but might be pushing it a bit for a 20".

[Double Kick Drum]

A 5mm Celestron X-Cel LX on my F5 is just about at my scope's limit. Anything smaller would be virtually unusable - barlowed 4mm - uuurgh!

The 8mm X-Cel ED produces quite sharp images.

[Moonshane]

I work on 1.5x the aperture in mm as a general rule for absolute max. so 150x1.5=225 = 3.5mm max. but seeing would generally restrict this of course to maybe 150x-200x.

it really depends on the optical quality and in my experience the focal ratio. I can often get much higher magnification from my 6"f11 than my 6"f6 of inferior optical quality. for things like the moon and double stars I regularly use 300-400x magnifications with my 6" f11 which would equate to a 2.5mm or a 1.9mm eyepiece in a 6" f5.