Re: ATM Secondary Mirrors

[Dave McCarter <McCarterD@claven.fanshawec.on.ca>]

Fred Maxwell wrote:
>Well, I for one, feel that it's about time we start demanding that
>telescope manufactuers produce egg-shaped diagonals.

Fred, I can go you one better! I wish manufacturers would put the proper
secondary mirror in the scope to begin with!

The other day I was out observing, and noticed while some one else was
looking at the moon through my scope that a ring of light was passing
around the diagonal mirror! This is a MEADE STARFINDER 10", and in the
catalog the secondary is listed as 2.60 inches. I measured it when I got
home, and found it was 2.25 inches. Mel, run that through your vignette
program! Man am I steamed!

Playing around with NEWT20 I find the mirror limits the effective aperture
to 8.9 inches. I suppose that's to limit the effect of turned edge.

I have written Meade a nice letter about it, and will let you know how it
goes.

I would really appreciate it if any other owners of the ten inch Meade
would check their secondary minor axis size and let me know what they find,
preferably by private email so as to not clog up the list.

By the way, eight inch f6 scopes which use the 1.52 inch are also
undersized, and would benifit from a lower profile focuser, but is there
enough room in the tube to move the mirror back? I know there is not in the
10 inch. :-(


David McCarter   McCarterD@claven.fanshawec.on.ca
R.A.S.C. London Centre VP & Observers Chair
ATM: Mirrors, Electronics, Heaters, etc.
Amateur Radio VE3GSO