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Just for general FYI, RCOS OTA's have terrible secondary mirror-based focusers that are notorious for going berserk and slamming into one extreme of the focus range and then jamming. Best fix is adding a Moonlight Crayford and stop using the secondary-based focus mechanism.
I hope the "RC" is one of the great ones; ie. An RCOS which were/are incredibly stable.
RCOS' motto was "Focus and forget it", as well a no optical flexure issues.
If a Chinese RC, you probably won't experience this.
From: Steven Panish <scpanish1@...
Sent: Thu, May 19, 2022 1:06 pm
Subject: Re: [ap-gto] AP1100 autoguiding
Chris's points are good. I'm hoping the RC arriving shortly will be stable.
Dovetail bars and radius blocks or rings are just about always quite a ways farther apart than the ends of dovetail brackets and hence a better place to attempt fine adjustments of cone error. Further, the actual error is almost always in the OTA and its support structure, not the mount and dovetail bracket. Routinely swapping OTA's on the same mount (as I often do) would be a real problem.
And make sure that OTA is precisely collimated before attempting any cone error adjustments.
And a compound OTA with a floating primary might have a lot of variability in its cone error as it points around the sky and shifts the primary mirror's orientation to gravity.
On Sun, May 15, 2022 at 02:40 PM, Steven Panish wrote:
Unfortunately it is rare to find cone adjustment screws actually on plates or rings.
@steven Panish. You make a good point. I wish the saddle plates came with adjustment screws to be able to correct for cone error. It would be so easy to adjust if there where screws that would allow you to adjsut the angle of the dovetail plate in the saddle. Shims are OK, but it woudl be much easier if this was built into the saddle plate. Just my 2 cents....
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