platesolve and resync failing to solve

[nigeld]

Hi

I was running some tests on my mount hardware last night and needed to power everything off while pointing at a particular point (in this case Deneb). When I powered things back on I wanted to carry on taking images, however when I did a platesolve and resync the platesolve failed. Doing a platesolve on its own did a full scan in a few seconds and found a solution. Tried both a couple of times with different exposure durations with the same result.

Windows 11
Sharpcap 4.1.11294

log to follow

[nigeld]

Logfile

[admin]

Hi Nigel,

the 'plate solve and resync' tool only searches within a limited distance of the current mount position (default distance is 15 degrees, although this can be tweaked in the settings in the most recent versions of SharpCap).

Looking through your log, I can see that the ASCOM mount driver was reporting the telescope pointing as follows before the plate solve and resync

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Info   	19:46:12.351763	#1 	Before plate solving mount points to RA=05:54:18,Dec=+90:00:00

That's essentially the North Celestial Pole, so the plate solve and resync will search within 15 degrees of the NCP.

On the other hand, when you tried the blind plate solve, the results that come out are

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Info   	19:47:34.487055	#28	Plate solving result found : Center at RA=20:50:13,Dec=+45:17:40

So, you were actually pointing at Dec=+45, RA=~21h - a long way away from the position reported by the mount - which stopped the plate solve and resync from working.

Essentially, you need to make sure that the mount is at least roughly aligned for the plate solve and resync to work.

cheers,

Robin

[nigeld]

ok perhaps I’m trying to do something that’s not possible in sharpcap (currently… )

What i had done is setup, polar align and then used goto catalog target to point my scope at Deneb. I then took a set of images and videos. Then I powered down everything and changed a jumper on the mounts circuit board.

After that I powered everything up - mount, pc and software.

The mount would still have been physically pointing at Deneb, but at power up it expects to be pointing at the pole. I was hoping that platesolve and resync would re-align the mount and softwares idea of where it was pointing with where it was actually pointing. I’m sure I did something similar when using ekos, it’s a bit like refining the pointing at a target but the other way round.

Reading the manual I see that isn’t what this is intended for and that it’s just to realign with a target. However what would the target be at this point after a restart? Will it have recorded that I was previously targeting Deneb? If it did and a blind platesolve (especially with the new solver being so quick) said it was near Deneb wouldn’t a slew to Deneb along with syncing the mount to the actual coords be an option? If it didn’t know the target shouldn’t the option be greyed out because I did wonder about that at the time? Or is it “dangerous” to ignore where the mount thinks it’s pointing to if it’s a long way out, which I can understand it wouldn’t be under normal usage?

Alternatively would it be possible to have an option to blind platesolve and sync things to the calculated coords?

[admin]

Hi,

you can try increasing the 'Search radius for plate solve and resync' in the Plate Solving settings in the latest versions of SharpCap. By turning that up to 180 you are allowing the plate solve and resync to search the whole sky, which means that it should send the sync command to your mount with the right co-ordinates in the scenario that you describe.

There's still no guarantee that it will do what you want though... Some mount ASCOM drivers will reject the sync command if the position is too far from the currently recorded position (the EQMOD driver that I use does this), so even if SharpCap sends the right command, there is no guarantee that it will work as you intend.

cheers,

Robin