Using SharpCap and plate solve with ServoCAT driven (ASCOM) scope

[ngc2359]

Hello, I have the ASCOM driver installed (and of course ASCOM itself) and can use it with Stellarium to control the telescope through the ServoCAT/AN system. The tracking is currently being done using the Argo Navis to drive the ServoCAT. I'm very pleased with the imaging results getting round stars for 10 - 15 sec exposures (although I like to do DSLI and run 2 - 3 sec exposures w/ FWHM filtering for smallest stars). I have used SharpCaps' "Push-To assistant" and it works well using a virtual ServoCAT hand controller to move the scope. But I believe, since ASCOM is installed, that I can have SharpCap move the scope automatically after a plate solve. Note ASCOM is not, for this attempt, connected to Stellarium or anything else. I can go to the HARDWARE tab and see that ServoCAT is listed under the mount. But when I select it it says that it has displayed a panel to set the settings for the ServoCAT - - when in reality no other panel is displayed other than this one - what am I missing?

Gary Myers
designer of ServoCAT
StellarCAT

[admin]

Hi Gary,

I'm guessing that the message from SharpCap that you are seeing is one like this...

Screenshot 2024-10-19 134244.png (20.94 KiB) Viewed 292 times

You will see that if you hit the 'Properties' button against the mount in the SharpCap hardware settings or the 'Setup' button in the mount area on the right (not sure why I ended up with different words on those two, but never mind).

That message shows when SharpCap has asked the ASCOM driver to display its configuration window. Unfortunately ASCOM doesn't have a mechanism to ensure that the configuration window appears 'on top' of all the other stuff on screen, so it's quite possible that a window to configure the ServoCAT ASCOM driver has appeared somewhere, but it behind other applications (including SharpCap). You might spot a new icon appear in the taskbar when you do this, which will be the setup window you are looking for, or alternatively you might find it by pressing ALT-Tab to switch between applications and see what other windows are available. If you try this out with only SharpCap running, it makes it harder for the other window to hide!

Typically, the setup window you are looking for will allow you to do things like configure the COM port that the ASCOM driver uses to talk to the hardware, and so on.

Hope this helps,

Robin

[ngc2359]

Robin, Thanks for the reply. So first yes, that is what I am seeing, and second there is no other panel. I've looked - there's nothing else. Nothing on the taskbar to suggest there is something else.

The ASCOM driver for the ServoCAT is installed. The ServoCAT is connected to an Argo Navis and once aligned this system allows for control of the position of the ServoCAT, even GOTO's from a planetarium program. That all works great and has been in place for a very long time.

Since I don't know a lot about ASCOM, one thing being if more than one device can be using the driver, for this test nothing had been connected to the ServoCAT using the ASCOM driver. Yet - as mentioned - no panel appears. Note additionally the ASCOM driver has already been 'programmed' with the correct com port. I can see that if I pull up the ASCOM DIAGNOSTICS tool (I think that is the one). It shows the driver - the com port and its capabilities.

So ... I'd like to use this for plate solve and correct/move and I believe all the things are there to make this happen. Additionally I'd like to continue to use the connection capability to use the "Feature Tracking" that SharpCap offers. NOTE: my goal isn't to correct like a standard guider to < 1 arcsec total RMS... rather it is just to limit the excursions to say < 10 pixels or some such. This will provide a larger image window over time with its limitations only being field rotation. Since SharpCap has a FILTER by FWHM capability either it would toss that image that might have happened when it was commanding a move to readjust OR it would know not to image when commanding that adjustment move.

[the 'drift' of course isn't due to the ServoCAT's inability to track with the Argo Navis... given a perfect mount and perfect alignment it would track perfectly... but these are not perfect mounts and therefore the alignment isn't perfect. The ServoCAT system, when used with the Argo Navis DSC, has built in closed loop tracking so it will resolve any errors and track with zero accumulated error all-night-long. However because the alignment is not perfect due to user error and/or more than likely the mount itself, typically a wooden dob, has orthogonality errors, that point that is being tracked ISN'T constant.]

So ... please... hopefully we can make this work!

Gary Myers
StellarCAT

[admin]

Hi Gary,

OK, so let's try to track down exactly what sequence of steps is causing you to get into this 'stuck' situation with no window. My expectaction of how you would walk through connecting SharpCap to your ASCOM driver for the ServoCat is...

1) Before opening camera - goto SharpCap settings
2) In hardware settings, choose the appropriate ASCOM driver entry for the ServoCat from the dropdown in the mount hardware list
3) Press OK to save the settings - no need to press the 'Properties' button at this stage as you have already setup the ASCOM settings for the mount

[1 to 3 above only need to be done once]

4) Open camera
5) In the control stack on the right, scroll down 'Scope Controls' which should contain a mount control box labelled for the ServoCat ascom driver
6) Tick the 'connected' checkbox to connect to the hardware if not already connected.
7) Drive mount as required from within SharpCap.

Given that workflow, I wouldn't expect SharpCap to be requesting the ASCOM mount setup to show, so I wouldn't expect the message that I included in my screenshot in the previous post to appear.

It would be good to know at what stage you are seeing the message (or how your workflow differs from the one above). A screenshot of what you see and also a SharpCap log captured after you get stuck would also help me understand.

thanks,

Robin

[ngc2359]

Robin, Thanks - I'll get to this. Sorry for the late reply - but out of town.

Gary

[ngc2359]

Although - that stated - I've been thinking through this. I don't think, at least as is, this will indeed work even if SharpCap is communicating via the ASCOM driver. Here's why.

The ServoCAT PC Port, I added this in like 2004, was a means to allow a planetarium program to move the scope and then 'see/show' where it is. The first effort was done with Emil of Megastar fame (super program - great guy). We worked on implementing this and in the end it was a fantastic system for using a planetarium in real time. To work it can query where the scope is - the reply is in RA/DEC. Or it can ask for the scope to move to a particular RA/DEC. That was all that was needed.

Jump forward. If the DSC is aligned BUT due to mount errors and/or user alignment errors the alignment is not perfect (of course it won't be - just how bad it is is the issue) then drift will happen and the system has no idea of knowing it is drifting. With closed loop tracking, added with AutoLOCK (specific to the Argo Navis as the DSC) in 2014, the USER becomes part of the loop. The user centers the object - this info then becomes the determinor of where "center" is. And it locks on that point. This works perfectly even allowing tracking satellites with a dob.

But here's the rub. Since the alignment is not right ultimately drift will be inevitable. This drift isn't of that point as defined - but rather the point relative to the actual sky. So the sky will move in the background - and the scope will lock on a point as defined in the DSC as an RA/DEC point BUT that RA/DEC related to the actual RA/DEC is changing. Thus the system (DSC/CAT) thinks it is at a particular RA/DEC, say for an object - in reality it is not at that RA/DEC. Actual values: lets say Altair. Altair is at RA 19° 52' and DEC 8° 56'. The DSC/CAT THINK they are on that point - but due to errors in the mount etc they're not (over time).

So using SharpCap to center an object. You do a plate solve - SharpCap knows where it is based on this result. There's an offset from there to where Altair actually is - you know what that is in AZ/ALT offset ... but this won't work because the driver only uses RA/DEC. The system, DSC/CAT, already thinks it is at RA 19° 52' and DEC 8° 56'. So if SharpCap sends that value there's no movement! The only way to move the scope using the existing driver would be to calculate the offset as a difference in RA/DEC - add/subtract that and command THAT point to be the center. That would then accurately move the mount. But that I'm sure is far too centric to one mount and over the top for SharpCap to do.

We'd need to add an offset command to the ASCOM driver. Ideally, an ALT/AZ offset since indeed it is driven in ALT/AZ. If the driver/CAT firmware were changed to support this would SharpCap then be able to move it using an ALT/AZ offset sent through the driver? (does ASCOM even support ALT/AZ offset commands?!). I know that "Push To Assistant" already calculates the needed offset in ALT/AZ.

Gary

[ngc2359]

Ok so I did what you had asked. First note that an effort to get the ServoCAT ASCOM driver acknowledged by SharpCap is still productive assuming you could do a plate solve and then do a GOTO to a particular RA/DEC value. That exists and has worked for a long time.

I got these errors. First, when I opened the camera it put up a message that said. Then I x'ed out of that and scrolled down. Indeed I could see the mount controls for the ServoCAT. I clicked the "Connected" button and got a similar warning.

I ran the ASCOM ... not the troubleshooter but a different program. It listed all the ASCOM items. Under Telescope Driver it had ServoCAT listed, it had the com port, RA/DEC, aperture size and a few other parameters.

g.

[admin]

Hi,

OK, that's helpful...

There are two possible causes for that error really:

1) The ASCOM driver is not properly installed and needs a reinstall - unlikely in this case since it is working in other applications, which counts against this possibility.

2) The ASCOM driver only supports 32-bit applications, but you are using the default 64-bit version of SharpCap.

If it's the second problem (as I strongly suspect) then you have two options - one is just to use the 32 bit version of SharpCap and the other is to run the ASCOM driver via the ASCOM Device Hub (Device Hub is a 32-bit application that hosts the driver, SharpCap then talks to the device hub application).

If you want to try the latter, set the selected mount in SharpCap to 'Device Hub Telescope', then press the properties button and find the 'Device Hub Telescope Setup' window that may either pop up or appear in the task bar. In that window, use the 'Choose' button to select the Servocat ASCOM driver, then press OK a few times - that should get SharpCap talking to the Servocat via the device hub, which should bypass the error shown above.

cheers,

Robin

[ngc2359]

Robin,

You hit it on the head - it is a 32 bit application. I think I am running it through the hub as I believe Stellarium wouldn't work for the same reason. I'll give this a try. Thanks.

Gary