'Move Here..." command

With the installation of a new mount in my observatory, I need to do a new TPoint mapping run with TheSky6. In the past this was done using a cross hair eyepiece to center the target stars selected for the mapping run using the keypad on the handbox. I am interested in using SGP and camera to perform the mapping run and thought the “Center Here” command would make that easy. However, the documentation indicates that “Center Here” sync’s the scope and then slews to the “click point.” Unfortunately, the sync will mess up the TPoint model.

It occurred to me that it might be possible to add a “Move Here” command that would not use a sync but rather just “move” the mount the required number of arcseconds in both DEC and RA to bring the click point to the center of the frame. Since SGP knows the plate scale of the camera, it could calculate the distance in both RA and DEC between the click point and the center of the frame and simply move the scope that amount – just like pushing the buttons on the hand box. I believe the current rotational position of the camera would need to be known accurately for this to work but that is a reasonable requirement.

I realize that plate solving and slewing can largely remove the need for a TPoint model but with PinPoint’s need for a fairly accurate “hint”, having the initial slew be TPoint assisted would greatly improve the reliability of plate solving with PinPoint.

I don’t consider this a “must have” feature but I think it would be a useful feature to see in a future release.

A small modification to this:

This is fairly identical to the request I recently made to use “nudges” to center the image rather than a solve/slew. By “nudge” I meant direct motion in RA/Dec rather than a slew. It should be faster and would converge - unlike repeated solve/sync/slews.


We likely won’t be implementing this with move features… Just slew without plate solve. Precise nudge is difficult to do and not too many mounts even support it.

One way to do a precise nudge would be to use guide commands through the ASCOM PulseGuide commands. This would give fine control over short distances but need calibrating.

Another way is to read the Ra/Dec position from the mount and the plate solver, calculate the offset between them, and apply this to subsequent slews and positions. I do this for sync in the Celestron driver for mounts that don’t support the HC sync command.