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Re: Gemini 2 response to pulses that are smaller than minimum

 

Ed,

Two things I suggest you evaluate:

You have the option of using ASCOM pulse guiding (sending commands to the Gemini to move) or using the ST4 port (the autoguide camera sends electrical signals to the Gemini).

I've always read they work identically, but I think it's worth it for you to do a comparison.? I tried both mothods and found good results from either way.? But since you are experiencing some problems perhaps one method is superior and minimizes your issue.

The other factor you might try is this: eliminate the SLW movement if your DEC uses this spring system.? You only need to adjust the worm for smooth jam-free rotation into the ring gear, then tighten down the bottom two worm block mounting bolts so the DEC assembly cannot shift in the pivot hole (left block) and cannot shift in or outward (right block).? This will cut the hysteresis time needed for those motions. Compare your autoguide results.? Use the best method for real practice and don't be concerned about theory.? (Again, friction matters here and for lowest friction of the worm to ring gear I suggest CRC Brake and Caliper Grease ...that has the best technical ratings and I feel the smoothest worm behavior (no chatter) on my G11T RA worm.)

All the best,
Michael


On Sat, May 22, 2021, 12:23 PM Edward Beshore via <ebeshore=[email protected]> wrote:
Hi Brian,

I was mostly concerned about the Dec axis with my GM811.

The default minmov for PhD2 in Dec is 0.2 pix. I am using my 480mm Pronto (206.265/480 = 0.43"/¦Ì?plate scale) and a Lodestar 2 (8.6?¦Ì?pixels) for my guidescope setup which yields 8.6 ¦Ì * 0.43"/¦Ì?= 3.7"/pix. With a 0.2 pix min move that is 0.2 * 3.7" = 0.74" in Dec. Seems like I should be setting my Dec min move to ~1.15 " / 3.7 "/pix = ?0.32 pix?

Given Paul's response, it sounds like the Dec move commands would be getting ignored until the error gets past the minimum step. In the final analysis, that may be fine, since the error will eventually move past that and a correction will make it through but seems a bit pointless to set a minmov to a value that the mount can't accommodate.

What do you think?

Cheers, Ed

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