Quote:
Originally Posted by Steffen
But that's the difference, for mere tracking the scope just needs to be aligned (the tracking computer needs to know which way the mount is oriented), it doesn't need to know where it's pointing right now, like a goto mount does. EDIT Sorry, strike that, I forgot for a moment that Dobs are alt-az… 
I never quite understood why encoders in goto mounts are always put into (or near) the motors?? They should be placed near the pivots, like you'd find with DSCs. That way it wouldn't matter if the tube gets unclutched from the motors, the computer would always know where it's pointing.
To take this slightly off-topic, I found a curious behaviour with my new HEQ5Pro mount. Without proper polar alignment of the mount I can still perform a 3-star align and goto accuracy would be quite good. However, tracking gets worse with sloppier polar alignment. It appears that while the computer takes the actual mount orientation into account for goto it will track by simply turning in RA at the siderial rate. If that's the case it seems like an odd limitation of the software… 
Cheers
Steffen. |
Hi Steffen;
i) Would that suggest that the Goto software doesn't get involved in the tracking (??) but only gets involved in the pointing (??) (Am I reading you right here ?)
ii) I believe, (read somewhere), that on a GEM, non-orthogonality between the Dec and Optical axes is quite common but analysis using three stars only
is not adequate to compensate for RA to Dec non-orthogonality. Some GEM controllers apparently only offer three star alignment to compensate for this error.
Perhaps what you're pointing out maybe answered by (i) or (ii) above.
Not sure, though.
Interesting.
Cheers & Rgds