Re: A "next mount" question for this group

Kevin Cook

Hi Don - I have spent the past couple evenings since I raised this question reading everything I could find on the harmonic drive mounts.  And I still feel uneasy about them due to the large inherent PE (which can be reduced with the pricey addition of an encoder on RA axis), and the inherent unbalanced nature of the system, which could cause problems depending on the size/weight of your OTA and the mass and footprint of your tripod or pier.  Coupled with the risk of uncontrolled "backdrive" under loss of power situations (some harmonic drives add a brake to prevent this), I just can't get enthused about them as a substitute for my Mach 1 for guided imaging use.

I originally thought maybe a smaller and lighter harmonic mount, such as the AM5 or the NYX-101, might still work for outreach use.  But my practice has been to use live stacking of unguided exposures from 20-90 seconds long, which the Mach 1 easily supports with a decent polar alignment.  Adding a guidescope and camera, and running the guiding calibration routine before any imaging, just adds more time and hassle on the front end setup (when the public is already gathered around at dusk when it is barely dark enough to do polar alignment).  I guess I could use something like an iOptron GEM45 and smaller OTA for outreach.  But getting a smaller mount and smaller scope just for outreach sort of defeats my purpose of downsizing everything I own, including astronomy gear.

So I think I just hold out for my AP110 (another subtle hint) and my Mach Mini.  The cheaper/lighter/smaller alternatives entail too many compromises compared to my current AP gear.  There are smaller and lighter OTA alternatives out there, but I still don't see good alternatives on the mount side.  Life is hard when Roland set the bar so high.  


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