Re: Meridian Flip - Flop & Flexure compensation factor

Richard Moore

Hi Joe,

When I first got my scope brand new from RCOS, I was surprised that my target was at the edge of the FOV
after a meridian flip. After ruling out mirror movement, I determined the amount of pixels that the target moved.
From knowing the amount of arc seconds per pixel of the camera, I calculated the total amount of arc seconds
that the target moved. Then it just took simple trigonometry to figure out the thickness of a shim to place between
one of the scope rings and the male dovetail plate that came with the scope.

If the target moves outside of the FOV, just start with the target off centered before the meridian flip. Just figure
out how many pixels the target moves using the meridian delay feature. In that way you do not have to wait for
the meridian crossing and trying to find a suitable star.

I too am portable a lot of the time to avoid the light pollution of San Jose, CA, and this solution works well for me.

----- Original Message -----
From: Joseph Zeglinski
Sent: 9/3/2013 12:04:32
Subject: Re: [ap-gto] Meridian Flip - Flop & Flexure compensation factor

Thanks Ray,

That is interesting indeed. Based on your observations, have you seen as
many cases of Truss tube flexure compared to flexure in "solid" carbon tube
OTA's? Maybe I should have chosen a different OTA construction.

I had thought that the truss members were solidly fixed/epoxied in their
truss joints. However, I do notice that each end of the carbon member is
pinned with a tiny (maybe 2-56 thread) grub screw through its truss joints.
Perhaps it isn't (also) glued in place, and thus the truss can stretch
unequally, back & forth on that tiny pin/screw, inside those supposedly
joints. I guess a truss OTA isn't as well fixed in place as a "riveted truss
plate & beam" on a bridge construction. Scary !

I'm confident your APCC will easily solve the problem.


-----Original Message-----
From: Ray Gralak
Sent: Tuesday, September 03, 2013 2:39 PM
Subject: RE: [ap-gto] Meridian Flip - Flop & Flexure compensation factor



well as the solidly built RCOS truss.
That doesn't mean it doesn't flex. It does. I have seen several instances
where flexure in a RCOS truss tube has turned
out to be one of major contributors to pointing errors.

-Ray Gralak
Author of Astro-Physics Command Center (APCC)
Author of PEMPro:
Author of Astro-Physics V2 ASCOM Driver:
Author of PulseGuide:
Author of Sigma:

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