Okay, problem identified. When Celestron GPS starts up with my Evolution mount, it says "WARNING: Mount firmware does not support getting pier side". However, the Celestron GPS driver exits ReadScopeStatus when it doesn't have a pier side (line 781) - and that's happening before requesting the focuser position.

I'll set up a PR for a fix.

I need the full log, not a fragment lasting a couple of seconds.

The Celestron focuser needs to be calibrated, this can be done using the standalone INDI focuser driver.

Read your second message, see what you mean. Are you going to fix it?

Already done. I've added you to the PR.

For what it's worth, I can use my Celestron focus motor (a original #94155, not the redesigned #94155-A) on my Nexstar 8 SE, using both the direct USB connection driver (celestron_sct_focus), and through the hand controller driver (celestron_gps).

I use a Lenovo laptop with Gentoo. The two interfaces (HC and direct USB to focuser) both emulate different USB serial adapters (my HC has the newer-style mini-USB port on the bottom), and so need separate drivers in the kernel. The HC needs the "USB Prolific 2303 Single Port Serial Driver" (CONFIG_USB_SERIAL_PL2303), and the focus motor direct-USB port needs the "USB Modem (CDC ACM) support" (CONFIG_USB_ACM). Kernel is 5.3.11. I used the newest INDIlib 1.8.2 release, which is available in the Gentoo tree. After choosing the correct driver, and port (/dev/ttyUSBx for HC, /dev/ttyACMx for direct USB), I can control the motor in both KStars device manager and Ekos.

One odd thing: I had been using the focus motor through the hand controlle's buttons until yesterday. It was calibrated. However, when establishing an INDI connection for the first time, it said the min and max limits were both 0. I performed a calibration through the celestron_sct_focus driver in kstars, and after that, I got sensible limits, and could move the focuser at will using either the USB connection, or the connection through the HC. And I can also still move the focuser using the HC's pushbuttons.

For good measure, I also tried all the above again through my RPI3 with astroberry. Both connecton modes also work through the 2 indi drivers in astroberry, and the limits were set correctly (no need to calibrate again). Only issue is, the power from the USB port alone on RPI3 seemed not quite enough, as the focus motor was struggling a bit. But it still got to the desired focus position in the end

So all in all, both drivers are working well for me!

Hi James,

How did you get the calibration going through Ekos. If I get all equipment connected then the sct focuser gives min max values of 0 and the calibration does not work.

Cheers Mark

Mark,

in the past, calibration was only available via the Celestron SCT driver. As I don't use a Celestron mount anymore, I can't say whether that's still the case.
Can you connect the focuser directly (via USB) to your computer and try that?

Cheers
Boris

It should not matter what is used to run the focuser calibration because the calibration data is stored in the focuser BUT it must be run AND it must be allowed to run to completion, Motor stopped after the return to the original position and all the focus calibration steps completed.

If you finish the focus run early, even after it has run to both stops, then the calibration data is not saved and you get the situation you are in with the limits both reading zero.

I don't allow the focuser to run without a good calibration on the advice of Celestron because if the focuser is driven into a hard stop at full power it can jam and may cause damage.

Chris,

quick question: are there any instructions on how to correctly configure backlash?

Quick reply; No.

Slightly longer, set a number try it. See what happens. Think about how you compensate for backlash when moving the focus knob by hand. SCTs tend to need a lot of correction, 500 is half a turn.

Thanks, Chris. Is 500 just an arbitrary number? Or in the ballpark of what you've been seeing? Just don't want to start my experiment in a completely wrong direction..

Actually, I think that was a stupid question. Half a turn sounds pretty huge.

Hi Boris,

I can get the calibration done by connecting the focuser direct to the laptop via usb and the celestron software. I was wondering if I could get the calibration done by Ekos.

Mark