Re: ATM Precision of focuser attachement

[Brian Nestel <blast@aloha.net>]

Jan Saver wrote:
> I would like to hear from you guys how you manage to attach the focuser
> precisely 90° on the optical axis.

If your tube is round most focusers will mount at 90deg. You can check
the
squareness of the focuser mount by making a mark on the other side of
the
tube exactly 180deg from where you mount the focuser, then after you
mount
the focuser take a laser pointer mounted in the 1 1/2 plug mount it in
the
focuser and see where the dot appears, then rotate the pointer and see
if 
dot stays true, even if the dot is offset when you first check if it
describes a true circle around the mark its true 90deg, you can do the
same with a straight metal rod inserted in a 1 1/2" or 2" plug. If its 
off you can shim the focuser to make sure its true.

> Also, some people have said they own a Lumicon (non-rotating or other)
> helical focuser : is this a sturdy design ; I mean, does it block out all
> lateral movement and tilting ?  And when Lumicon says 1 1/2 " high : is
> this from the base plate to the 2" eyepiece adapter ?  And just how high is
> the profile of the non-rotating one ?
The Lumicon non-rotating focuser is 1 1/2" high from the outside of the
OTA
with the draw tube fully in. I have no play to speak of on the focuser
with the draw tube in with it all the way out there is a small amount of
play which can be eliminated totally by tightening the nylon screw that
keeps the focuser from rotating

-- 
Aloha   159 36 W, 21 58 45 N
Brian   Middle of the Pacific,
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