Using plate solve for next target position

There seems to be a curious ‘gotcha’ trap that I keep falling into. My misunderstanding I suppose.

I use Carte du Ciel at the start of a session and then take a sample image to check the general levels - eg background sky level near the end of twilight. Using plate solve produces the current position - but it includes an option to ‘use this position for the next target’ (or some similar wording). My assumption was that it meant ‘tick this box if you want the schedule to know where the scope is for moving to the actual target’, and so I would usually tick it. The scope does drive a bit and so I believed that it was starting the schedule OK. However, that is not what happens. What seems to happen is that the solved coords are transferred, not to the ‘go to the first target from here’, but in fact becomes the actual ‘target’ position. So a night or two back I was on Betelegeuse for first check, then ticked the box, then left the scope to supposedly drive to the first target on the schedule. However the scope then set about taking 17 images of Betelgeuse. It had driven away and then back. I realised things were not right when the first image came in - not NGCxxx.

I am therefore wondering about the labeling of this option. How do I misinterpret it every time? All runs well as long as I don’t tick that box!

Lawrence Harris

The language seems pretty clear to me. It says “Use these results as the reference image for target xxx”. Plate solving will give you coordinates for wherever your scope is pointed in the sky. If you want those plate solve coordinates to be the coordinates of an existing target, enable the checkbox and choose the target. If you don’t want those coordinates as the target coordinates, then leave that checkbox unchecked.

You’ve already figured this out. Just don’t check the checkbox.

I don’t believe I have ever checked the box because my targets already have coordinate data from the Framing and Mosaic Wizard, or from another source.

Yes, but I admitted that I had misunderstood the message. I believed that it was telling me something different. My targets also always have the correct target data.