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Autofocus motors, DC Servo or stepper


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Hi,

I'm still deliberating about the Pegasus autofocus system but can't quite understand why there are 2 types of motor, the DC servo and the unipolar stepper. Which would be the best for imaging with a Newtonian Skywatcher 200p.

Any help is gratefully received,

Regards,

P.

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Stepper motors give an absolute position, dc motors like the SW autofocus kit only work to a speed and time input.  Programmes like APT make a 'guess' on position based on these inputs, but to goto a repeatable position you need a stepper motor with a non-slip connection to the focus knob.

That's as i understand it..

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As above. I swapped out my JMI DC Motor driven focuser on my C11 for a Pegasus Focuscube. It's so much easier to return to focussing positions for the various combinations of kit that I have - just type in the step number and press go. with the JMI - it became a matter of counting the seconds between focus points while pressing the correct forward or reverse button - and that also meant remembering where I had left it on the previous session - or not as was the usual outcome. I've also got on one my Apo. And I must say both the pre-sale and post-sale support from the guys at Pegasus has been exemplary

Neil

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