Re: Meridian Flip - Flop & Flexure compensation factor

Richard Moore

Hi Joe,

If you decide to use a shim to solve your non-orthogonality, here is the trigonometric formula for the thickness of the shim:

(thickness of the shim) equals (distance between fore and aft connection to the male D plate) times
( cosine( arc seconds that the target moves after the meridian flip ))

The scientific calculator on my computer required me to convert the arc seconds to arc degrees by dividing by 3600.

I then went to the hardware store with my micrometer and measured their brass sheet stock until I found the right combination.

Sketch the geometry of the scope and camera on both sides of the meridian to find whether to shim fore or aft, (or just trial and error),

Good Luck


----- Original Message -----
From: Joseph Zeglinski
Sent: 9/4/2013 18:03:29
Subject: Re: [ap-gto] Meridian Flip - Flop & Flexure compensation factor

Thanks for the confirmation, Rolando.

Spent all last night using Pempro-2 to adjust the alignment, but as it turned out - much to my regret - there wasn’t much to tweak to what I had done initially with my original manual drift alignment. The alignment seemed to be pretty decent already. Sky testing clouded out tonight, to see if it made any difference, or if the target comes closer to FOV on both sides of the pier.

As for shimming, I am a little dubious about trying to slip a thin piece of copper under that hefty 75 lb scope. Not much room under the D-plate, or even knowing which end – fore or aft. Are there procedures to determine which way the OTA is tilted in its saddle, and roughly how thick a shim might be needed, and where to place the brass shim? Sure would be a neat feature to add to Pempro, or any other alignment software

The software modeling approach might be the easiest.


Sent: Wednesday, September 04, 2013 3:36 PM
Subject: Re: [ap-gto] Meridian Flip - Flop & Flexure compensation factor

What you have is classic non-orthogonality. The scope optics point slightly different direction from the scope mechanical axis. Although it always looks like a mount problem, it is really simply an inherent offset in the scope itself. You can try shimming the mounting plate, or you can use one of the software programs to compensate for this offset.


[Non-text portions of this message have been removed]

Join to automatically receive all group messages.