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Re: Is this typical guiding performance for an older g8? RMS around.25 px , 1.0 to 1.6 arc seconds

 

Hi Robert,

My GM8 had a loose DEC saddle dovetail.? I discovered the 2 top mounting bolts were slightly too long...the dovetail was slightly loose.??

My solution was to file off the 1/4-20 bolt ends so the plate was finally snug.??

Please check your dovetail plate for any wiggle.

After that, mount your scope.? Grab the front and back of the scope and try to wiggle it in DEC.? It should ideally not wiggle at all. If it dies wiggle, figure out where:. Is the worm shifting left to right?? Is the worm lightly snug into the ring gear?

All the best,
Michael

On Thu, Mar 4, 2021, 2:55 AM McFarlane, Gilbert via <gilboastro=[email protected]> wrote:
Stuck at home, I decided to learn more about phd2, and try to tweak my mount.? ?All my efforts did not seem to have much of an effect.? ?I generally achieve RMS of about? .25px ,? and about 1.0" to 1.6 ".? ?This doesn't sound great to me, I was hoping for about half of that - but my images seem to be ok.? ?(Guide camera is QHY 5L-II with 3.75 um, with 130mm QHY mini guide scope.? ?Camera for imaging is a K5 Pentax dslr.? Imaging scope is an 80mm f6 APO with a Televue 0.8x flattener.)? ?

The most irritating part has been trying to reduce the Dec backlash measured by PHd2 - which has stayed at 6 - 9 seconds despite numerous lubes, adjustments, and even Belleview washers.? ? Motor is attached very tight.? I have tried changing the balance, tight axis, loose axis.? Everything I know to try other than replacing the motors or the little plastic motor connectors - but they seem tight.? ?I tried switching the motors, but no change in Dec backlash.? ?Any thoughts?

The mount has the separate worm blocks and brass worms.? ?Using the 492 controller and the ST4 camera controlled interface and USB 3.0.

Thanks, Gil
Ventura, CA

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