[ATM] source for mirrors/focusers/spiders

[DU <desiredusername@gmail.com>]

I did a little research before I started building a 6" f/8 dob and it looked
like I could save a significant amount of money by making my own.  Now I'm
trying to actually purchase the optical parts and while I still think I can
come in under budget I think I must be missing something because it seems
like this should be a little simpler.

1) Why are there no comprehensive sources?  Some sites have
primaries/secondaries but no focusers.  Some sites have focusers but no
spiders.  Other sites have everything except mirrors.  Only Meridian
Telescopes seems to have all 4 of these vital pieces that I've found.

2) Why do mirror prices vary so wildly?  E-Scopes sells a 6" f/8 for $150
and Scopetronix sells the same thing for $100.  (Anacortes sells it for
$190, but I assume that must be because they don't really want to sell parts
and are trying to discourage people.)  Is the difference between 1/8 wave
and 1/4 wave really that much?  Other parts seems to vary just as much if
not more.  For instance, a 4 vane spider at Meridian is $40 while they are
only $30 at E-Scopes (the latter are definitely adjustable, I'm not sure
about the former--if they aren't, it's even more inexplicable).
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