Quote:
Originally Posted by Moon
I'll use the stock GSO focuser to start with and see how it goes. It should arrive here next week. If you have any suggestions for an upgrade, let me know.
James
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A Newtonian puts greater demands on a focuser than a refractor or Cassegrain because the greatest torque is exerted on the focuser when pointed at the zenith - remember that you have a heavy camera (~4.5 lbs) + Paracorr held near right angles to the tube and several inches out, and that exerts a fair bit of lateral force to be held by bearings that are just one inch apart. I've also found with the STL that this is exacerbated if you have the offset part of the camera positioned above the level of the focuser due to added leverage. You can't rely on the load lift capacity of the focuser to determine the maximum rating for acceptable usage, especially for a Newtonian. The focuser that I have (with stepper motor) is rated at 7lbs lift capacity, yet I have a lot of flex when pointed near the meridian with my STL / Paracorr. I have improved this by tightening the tensioning screws though and I need to test this out a bit more. If I had my time over, I would probably buy an Optec 2" or Moonlite 2.5" focuser for my 200mm - expensive I know, but if I had to nominate one aspect of a Newtonian that can act as its Achilles heel this would be it.