On Sat, 11 Dec 2004 06:54:10 +0000, Stephen Tonkin ) said:
in such a way that they maintain collimation to within the tolerances
that are required. (And remember that it is unlikely that they will have
a "base tolerance" of zero error.)

Does this help?

I know you're the expert and I'm not, but I did have a cheap pair of 7-21x
42s that were quite useable for many years for very basic astro purposes.

Easy enough to use the eyepiece diopter correction to correct for any
inherent focus differences between the eyepieces. Eventually fell out of
alignment (fifteen years later) and are now a zoom-lens for my camera.

Personally, I'm missing them now; a pair of rough & ready bins to keep in
the car for when I'd otherwise be without a pair.

Yes, they're not going to be in the same league as proper pair of fixed
10x50s, but I wouldn't be surprised if they'd still make Pleiades look
pretty.

I have to say that, for 15quid, I'd be tempted to get them as a second
'emergency' pair.

--
Julie Brandon http://www.computergeeks.co.uk/
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