CGEM RA Axis Backlash
Posted 12 November 2012 - 04:40 PM
While I am waiting for an answer from Ed Thomas, I thought this forum's brain trust could also help. I recently finished a hypertune of my CGEM (which went reasonably well and taught me a lot about the mount) and believe I have increased the backlash! The RA axis wiggles (whether fully loaded or not) about 3/32". When slewing under power the motors sound fine and are responsive. Since I did the hypertune to improve the mount's imaging capabilities, I welcome all suggestions that would reduce this slop. I would love to avoid having to disassemble the mount again. Thanks in advance for the help.
Posted 12 November 2012 - 05:24 PM
Posted 13 November 2012 - 07:11 AM
i notice that the closer the worm is set to the ring gear, the noisier the RA motor will be.
you cannot eliminate all the backlash so don't even try; backlash in RA is not a big deal, just make sure to be slightly east heavy.
Posted 13 November 2012 - 09:31 AM
Posted 13 November 2012 - 09:40 AM
notice the RMS error for the RA which is 0.18 - with my finder-guider and Meade DSI, that's about 1.4" to 1.8" - not fantastic, but that's what you get for the money.
Another of Ed's words of wisdom - don't kill yourself trying for perfection, you won't get it. Not with the CGEM anyway. Personally getting 2" accurate guiding is a bit annoying but it is what it is.
It all depends on the magnitude of your CGEM's 8/3 (the famous 2.6667X harmonic). If it's large - like mine - then guiding is always a challenge. If it's small, then lucky you. My CGEM has an Aeroquest worm, but since the 8/3 is so large (larger than the fundamental) it still screws things up.