Re: 16" LX200R on an AP1200

Jeff Young <jey@...>

Joe --

I certainly had too much flexure when I was using a Losmandy dovetail to
mount it. (The biggest problem was differential sag between the front
and rear which caused collimation changes.)

I've since switched to Parallax rings on the 15" ribbed plate -- a
combination which is much more rigid. There is still some flexure left,
but I like that: with a star diagonal rotated to different angles I
never can keep directions straight so I get my bearings by nudging the
OTA and seeing which way the view moves -- and I also sometimes jiggle
the OTA to bring out really low contrast objects or details. But all
the flexure is still in the plate/rings -- I have essentially zero
backlash on both axes and the axes themselves don't exhibit any
measurable flex.

-- Jeff.


From: [] On
Behalf Of Joseph Zeglinski
Sent: Friday, March 30, 2007 10:14 PM
Subject: [ap-gto] Re: 16" LX200R on an AP1200

Glad you are in contact, Jeff.

Just a thought - have you tested shaft and dovetail flexure,
which might
increase if you go to an even larger OTA, even if the cradle
bolts don't shear
off, first?

I wonder if taking a circumpolar exposure, by rotating the mount
might show elliptical paths, if there is any sign of flexure on
the OTA
Perhaps, as a guess, reflecting a laser pointer off the counter
weight shaft,
onto the ceiling or dome, might show the beam angle deflected by
tiny bends of
the shaft.


----- Original Message -----
From: "Jeff Young" < <> >
To: < <> >
Sent: Friday, March 30, 2007 4:48 PM
Subject: RE: [ap-gto] Re: 16" LX200R on an AP1200

> I'm using Parallax rings and the AP 15" ribbed plate, which
likely add
> another 15 lbs. The dovetail, rings and refractor on top are
> good for another 20 lbs. Figure 120 lbs all told. I'm
> enough with those weights on it that I'm considering going to
> considerably heavier OTA....
> -- Jeff.

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