Woody Schlom <woody@...>
I suspect the reason your rig is “top-heavy” is because of the piggy-backed 71mm being mounted on top of the main scope. The piggy-backed scope moves your balance axis further away from the mount’s balance axis. The result is that you can get the setup balanced for one point only. Tip too far either direction and the mount is off-balance.
I call this situation “off-axis balance.” Because of the piggy-backed scope, your balance axis has moved away from the main balance plane axis. To correct this, you need to add a second set of counter-weights opposite the piggy-backed scope. And this is where ADM’s and Losmandy’s off-axis counter-weight systems come into play. These systems are primarily designed to use dovetail rails to position new smaller CW’s to your piggy-backed scope.
Both ADM’s and Losmandy’s off-axis CW systems use ½” SS threaded rods to position the additional CW’s at the correct distance for correct balance. You slide the CW on its dovetail rail fore and aft for on-axis balance, and then screw the new CW out away from the scopes to compensate for the off-axis imbalance.
In addition to the new CW’s being threaded so you can move them in and out to balance, you can buy longer threaded rods (ADM’s come in 3” and 6” lengths I believe, and Losmandy’s come in 2” – and a couple of longer lengths. And both companies make their CW’s in a couple of sizes – again to compensate for more or less off-axis imbalance.
So far I haven’t needed one of these off-axis CW systems with my Mach-1 imaging configurations. But I need one for every one of my various Alt/Az mounts – both visual (to compensate for big heavy 2” diagonals and heavy eyepieces and finder-scopes), as well as imaging configurations to compensate for piggy-backed scopes and off-axis guide cameras and systems.
For most of my off-axis solutions, I mount a Vixen dovetail on top of my SCT or RC scope, and a “D” dovetail under. To compensate for a piggy-backed scope configuration, the off-axis CW system goes on the bottom rail – pointing away (180°) from the piggy-backed scope/s.
But again, so far, I’ve not run into this off-axis problem with my Mach-1 (or any GEM), just Alt/Az mounts. And I assume you’d have similar problems with a fork-mount on a wedge.
If you don’t have a clue what I’m talking about, visit ADM’s or Losmandy’s websites and look at their off-axis CW systems, or I can post a couple of photos here. But my photos will only show my scopes mounted on Alt/Az mounts with these CW systems – not my Mach1.
From: firstname.lastname@example.org <email@example.com>
Sent: Sunday, March 18, 2018 8:13 AM
Subject: [ap-gto] Weights Configuration
I have four 9lb weights on my Mach One. I have a small refractor and an even smaller (71mm) refractor mounted on top of the larger OTA.
I can not configure the weight distribution following the instructions on the AP site. The only way I have found to bring this set up to balance, is mounting two weights at the top of the weight bar and two very near the bottom. About a five inch gap between the two groups of weights.
Do I need more weights or is having the smaller refractor on top of the bigger scope causing problems? The setup does seem to be top heavy. But the setup is under 40lbs.
I thought of re-mounting the 71mm in a side x side config. I would then hopefully have my weights in a more appropriate configuration based on the instructions at AP.
Thanks for your help as always.
Gregory Gig Harbor, WA.
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