Why track past the meridian?
I have two mounts, a CGEM on a permanent pier that can view a lot of the sky, but due to my neighbor’s trees, can’t see towards the southern horizon. Thus, much of the southern part of the ecliptic and the Scorpius-Sagittarius region is blocked.
My second mount is a old CG5GT, which I recently mounted on a pier in a different area on my property that has an excellent view toward the southern horizon, but very limited views toward the east and west, also because of neighbors’ trees.
Annoyingly, the CG5 has a built-in stop that prevents it from tracking past the meridian. (The CGEM will track 20 degrees past the meridian.)
I quickly got tired of starting an observing session with the CG5 and almost immediately having to do a meridian flip. Then I noticed that only 2 M6 bolts hold the Dec section to the RA section. And I realized that if I could rotate the Dec section by 30 degrees from its ’normal’ position, I could track an object from 1 hour before the meridian to 2 hours past the meridian. I’d just have to adjust the time input when I started the mount.
So I made an adapter that fit between the RA and Dec sections that holds the Dec section at a 30 degree angle.
I bought a 3.5 inch diameter disk from McMaster-Carr and drilled 2 countersink holes to hold the disk to the RA section. (Shown as the B-B holes.) And I drilled and tapped two holes to hold the Dec section to the adapter at 30 degrees from its’normal’ position. (Shown as the A-A holes.)
When I start the mount, the counterweight rod is now angled 30 degrees from plumb. Facing South looking at the mount, the scope is rotated 30 degrees clockwise from its ’normal’ home position. To compensate, I have to subtract 2 hours from the actual time when I start the mount. Ie., if it’s 9:05 PM I input 7:05 PM.
So happily, I can now begin following an obect like Saturn one hour before it transits to 2 hours after it transits without being interrupted by the need to meridian flip.
(There’s a second set of countersink holes C-C that would let me mount the Dec section at 30 degrees counterclockwise, if I ever need to.)
The second photo shows the adapter disk mounted between the Dec and RA sections.
As far as the CG5 knows, it starts at the normal Home position. It is of course unaware that the Dec section has been rotated.
By the way, in case anyone is wondering: Before I added the adapter, I had tried just starting the CG5 with The Dec section pre-rotated by 30 degrees. But that didn’t work. When the mount reached the Meridian it stopped.
Thus the need for the adapter.
Edit: The photo of mount got turned 90 degrees here. Don’t be confused by its odd orientation; that’s not part of the modification.
Also, notice the 1/2 inch center hole. That allows the polar scope to see Polaris and the surrounding part of the sky.
Edited by KLWalsh, 24 September 2023 - 09:14 PM.