SharpCap Forums

I have been using Plate Solving with Sharpcap and I amazed how well it works but I am trying to figure our how it knows to go to the object and I looking for and centers it perfectly on my screen?

So I use the Polar Alignment feature within Sharpcap Pro to Polar Align my equatorial mount. I use Stellarium and Stellarium scope to tell my mount to go an object like M31 (Andromeda Galaxy). I don’t expect the M31 is going to be on my screen since I have not done any kind of 2 or 3 star alignment. I then hit the circle on the slew controls and Sharpcap does his magic and the mount moves slightly and before you know it, M31 is smack dab in the center of my screeen and I am ready to image.

How does Sharpcap know that I wanted to go to M31? It must do some kind of communication between Sharpcap and Stellarium because I told Stellarium to go to M31?

It’s works very well but I just want to understand the process better.

Hi,

there isn't any direct communication between SharpCap and Stellarium, but SharpCap is talking to your Ascom mount. Stellarium tells the mount to go to the coordinates of M31, but you most likely end up pointing slightly off centre. This is what happens when you press the plate solve button:

1. SharpCap asks your mount where it thinks it is pointing – this gets back the coordinates that you chose in Stellarium
2. SharpCap captures a frame and send it to the plate solving engine - this gets SharpCap the coordinates that you are actually pointing at.
3. If you have the default option setup then SharpCap will now send a synchronisation command to your mount – it's coordinates will now update to the coordinates that it is really pointing at.
4. SharpCap now sends a go to command the mount to go to the coordinates it recovered in step one (the coordinates you want to be pointing at). This go to will now be very accurate because the synchronisation in step three has basically corrected for all the mounts error in this area of the sky.

Hope that makes sense, Robin

Hello,

Here is the option to change (or confirm) ...

Jean-Francois

Here is my settings:

[attachment=0]SS.PNG[/attachment]

Hello,

I have the version Pro 3.2.6421, 64 bit.
You have the Pro 3.2.6248, 32 bit ... install the last version and you will have maybe more option.

Jean-Francois

Hi Robin

I have a follow-up question to this : If I repeat the plate-solve and resync command in using SC Sequencer over a period of 20 minutes (without touching the planetarium app, in my case the Synscan App), each time for step 1, does SC receive the original coordinates of the target (from time zero), or does it receive updated target coordinates (at say Tim +5 mins, +10 mins etc), OR do the coordinates obtained from the planetarium app contain a time indicator (JNOW format ?))

In other words, if there is a large time gap between pressing the GOTO command in the planetarium app and pressing the plate-solve and resent button, will SC plate-solve send the scope to the wrong target. How does SC/platesolving adjust for this?

Best

Mike

Hi Mike,

it depends on the options that you have set up in the plate solving part of the SharpCap settings.

If you have set 'Sync mount and recenter target' (the default) then repeated plate solving should do exactly what you want, since after each attempt the mount co-ordinates will match the target co-ordinates before the solve.

If you have set 'Offset the mount position to recenter' then the repeats will not do what you want - after each plate solve, the target will be in the center of the frame, but the co-ordinates will not match the original target ones, so the next plate solve will work from the new co-ordinates, not the original ones. This mode is typically used by those whose mounts have a complex pointing model enabled, which stops the simple 'sync and recenter' option from working.

In either case, guiding/dithering adjustments may change the co-ordinates slightly between two plate solves, which will not be corrected as each solve is a separate action that looks at the current mount co-ordinates, does the solve/sync etc and recenters those co-ordinates that it stored just before the action started.

If you *really* want to go back to the exact same spot repeatedly, set up your sequence to re-run the GOTO of the target co-ordinates just before each plate solve and resync.

cheers,

Robin

Hi Robin

Ok, so I think your answer means Im doing it correctly. I set plate solve to 'plate-solve and resync (not the offset option). What I want is that the scope continues to recenter on the original targeted DSO as it moves through the sky (or as the earth rotates to be more precise). I dont want it to recenter on the exact same spot in the sky, It seems to work, most times, Im trying to figure out why it doesn't always work, thats all.

Best

Mike

Hi Mike,

have a dig through the main SharpCap log if you see a problem - there is a lot of information stored about the plate solve/resync process including the results of the plate solve, the mount position before and after the sync/regoto, etc. That should reveal what is going on.

cheers,

Robin