Passing pointing information to PhD2

[avitam]

Hello All,

I am new to this forum and relatively new to all things AP, including Sharpcap.

I have an old non-goto Losmandy GM8 (with the 492 controller) that I have been quite happy with. I am perfectly happy using Sharpcap's excellent plate solving feature to manually push to my targets, so I don't particularly miss goto.

What I would absolutely love to do, if possible, is to avoid doing a guide calibration each time I switch location or targets. Re-doing guide calibration is really not that big a deal, but if there is a elegant solution here, I would like to make use of it. Onto my specific question:

I do my PA using Sharpcap Pro. Then switch over to PhD2 to start the guide calibration process. I set the mount to either ST4 on camera or GPUSB and set the Aux mount to "Ask for coordinates". I get the pointing coordinates by doing a plate solve in PhD2 and manually set things like "side of pier" etc. After calibration, I start guiding. What I am told is with non-ASCOM mounts or ST4 based guiding, I need to repeat the calibration process each time I switch targets because the mount has no way off passing on the pointing info to PhD2....something I am not very clear about.

I know Sharpcap and PhD can be setup establish a one way communication channel (Sharpcap to PhD2). My question is can Sharpcap pass on pointing and side of pier info to PhD2 so I can get ASCOM like benefits of not having to redo guide calibration every single time? What I am not following is what is the fundamental issue with ST4 based guiding where the calibration has to be redone each time for a new target? If the only miss piece of info is pointing information, then maybe that is a solvable problem?

Does the above question even make sense?

Appreciate the help!

Thanks.

Avi

[admin]

Hi Avi,

I see what you are asking, but as far as I can tell there isn't a direct way for an application like SharpCap to tell PHD2 the current celestial co-ordinates (the communcations available to SharpCap are documented here : https://github.com/OpenPHDGuiding/phd2/ ... Monitoring - no mention of co-ordinates apart from the 'lock' co-ordinates for the selected guide star).

However, there may be a way to do this anyway (perhaps) - try something like the following...

* Set up PHD2 to talk to the ASCOM simulator mount (Telescope Simulator .NET) as the 'Aux Mount'
* Set up SharpCap to also talk to the Telescope Simulator .NET mount
* Set up a small sequence in the SharpCap sequencer - just the step 'Plate solve a single frame and sync the mount only'
* Set a large radius for plate solve and sync search radius (90 + degrees) in the SharpCap plate solving settings

Now, when you run the sequence in SharpCap, it should plate solve and then set the mount position to the solve results position. Because PHD2 is also monitoring that ASCOM mount, it will pick up the new position and should adapt the guiding calculations accordingly.

Hope this helps,

Robin

[avitam]

Hi Robin,

This is awesome advice.

I will try it the next time and see what I get.

Thanks!

Avi

[avitam]

Hi Robin

Just wanted to report back and mention that it works! It took some tinkering to nail it down but eventually got it to work.

Ran a few tests at different locations and the PhD2 calibration assistant nicely picks up the location each time. There is a slightly offset between sharpcap and Phd2 recorded Dec locations (less than a degree) but maybe that is a rounding error ?

Thanks again..this is brilliant!

[admin]

Hi Avi,

good to hear that it worked

I suspect that the dec offset might be down to the difference between J2000 and JNOW co-ordinates - that would turn out the be a few minutes of arc difference, mostly in declination. For this use case, it won't be important.

cheers,

Robin