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Stability Of E/Mount

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Posted by anthony/">anthony on April 28, 1998 14:45:39 UTC

Are there any ATM's out there that can help me with a small problem I have been having with my 12.5" Newt. on a equatorial mount. I built the mounting years ago when I was in the process of building a 8" Newtonian. A terrible tragedy occured when the table I was using was knocked over by our hound and cracked the unfinished 8" mirror. After that episode I rebuilt a massive grinding table and then proceeded with a 12.5" blank I had, building the scope and other mechanics around the mounting. My first problem is, the shafts and head are built to support a 10-15lb tube assembly. The 12.5" scope is considerably heavier, around 30lb. or so. My counterweight total about 37lb. You can see I've got about 65lb sitting on my fabricated aluminum tripod. A lot of weight. The guts of the mount include 1" diameter shafts on the R.A. and Dec. axis. It is built from machined steel pipe and plate. The bearings are sealed roller bearings. The scope tends to resonate when it's balanced, vibrating with any movement east, or west. Around the Dec. axis the vibration is not noticable. The second problem is, with all this weight I am getting quite a bit of backlash in my fabricated R.A. Drive motor and gearbox. I have tried to compensate for the backlash by un-balancing the scope, but to no avail. The gearing is made of all spurs, no worms in this set. I know there are ways to solve the backlash problem, but what about the annoying resonances in the tripod and equatorial mount. Has anyone else had a similar problem, or offer any suggestions. Thanks Anthony

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