Kevin Gurney

Just watched Andrew’s video (joint BAA/AAVSO)… Incredible rig, and I think I can see the differences with mine..

(i) Use of on axis guiding (ONAG) to help locate star

(ii) accurate pointing model

(iii) A guiding algorithm that ‘pulls in’ the star onto a *hole* – not a slit

I don’t bother with a pointing model – I sync to one star and then ‘star-hop’ using a guidescope with ZWO camera. I take my scope down periodically (if we are going to be away for more than a few days), so I figured getting a good pointing model would be a waste of time…

I dont have ONAG.

I use slit guiding with the target star (23mu or 34mu slit). I haven’t tested this to the limit to see how good it is as ‘pulling’ something in that isnt actually on the slit, but it does lose DEC sometimes and can oscillate in RA if not parameterised well, so I am not confident it would do this.

On the other hand I have written a script for attempting to position the star, once its in the guide cam image. It gets pretty close, but relies on human interaction to position cross hairs on the star in the first place.  I am happy with remote control just now without the full robotic thing but –  one day, one day 🙂