Thursday, January 07, 2021

drove Super Polaris with Stellarium

Wow. It worked. The following documents how to drive a GoToStar motor drive system with Stellarium 0.20.4 via ASCOM.

I was not hopeful at the early stages...

With the intermediate level 2 Stellarium training course for RASC members coming up soon, I wanted to make sure I had a working solution for showing the Stellarium software actually slewing a telescope mount in real time. 

mount setup

With no estate items around or mounts in the repair workshop, the only immediate option was to drive my old mount. In theory, this is possible: it works fine with SkyTools (via ASCOM, using a Vixen driver). But I hadn't done it with Stellarium, ever, I think...

I vaguely recalled getting Stellarium to drive Phil's Losmandy mount, after building a custom cable.

I considered making a simple platform for supporting the Vixen Super Polaris mount. For quick tests in the past, I just held the mount to make sure it didn't tip over. For the course, I'd want to operate it, mostly hands free, and put a camera on it, to show it moving and working. Perhaps a large piece of wood, a square or rectangle, could work, with a hole in the centre, and a bolt into the mount. I've lots of plywood lying around...

But I'd have to counter-sink it... Or layer two sheets...

Couldn't find a large bolt compatible with the SP mount. Metric?

Briefly ruminated on attaching it to the Motomaster work table, like what I did for Wayne's Sky-Watcher equatorial mount, as I reviewed the EQMOD software. Stared at the knob used to hold the Vixen mount to the tripod. Was this long enough to go through the table top? I decide this option was too bulky. And too far from my desk. I needed something in arm's reach, particularly if a slew went bad...

When it slowly dawned on me... Just use the tripod! 

Huh. Set the tripod up by the desk without opening it fully. This would work. Attached the mount. Hey, look at this! It was in the field of view of the TANDBERG camera. Serendipitously, I realised I just solved the problem of "filming" or showing the (portable) mount in action while operating the software. A few checkboxes ticked for the future course prep.

Attached all the GoToStar bits including the amazing hand controller and the AC power.

Stellarium plug-in

Fired up John Gomez, the Windows 10 laptop with the 64-bit version of the OS installed.

Jumped into Stellarium 0.20.4 (64-bit), last used for the introductory training on 28 Dec. Activated the Telescope Control [SIC] plug-in.

Saw there is built-in "direct" driver support for Celestron NexStar telescope mounts, the Losmandy G-11, a few Meade products, a couple of Sky-Watcher mounts, and Wildcard Innovations Argo Navis. Neat. Noted other connection options. I've no idea what RTS2 telescope is. INDI/INDIGO is for the Linux platform, I believe. And by using the "nothing" option, one can employ the simulator mode.

No ASCOM. Hmm. I wondered why...


I connected the GoToStar "data" cable to the hand controller. This is the computer-control cable terminated in a serial DB9 connector and 4-conducter registered jack.

Moving on, getting more of the puzzle pieces, I grabbed my USB-serial adapter. And I recalled this might not work, the adapter being too old to work with Windows 10. I surfed the internets to see if there was a new driver for the Prolific chipset. And confirmed my adapter, with the HXA circuitry, was too long in the tooth. Physical parts too old so no software workaround. A dead end. Hmm. 

Hold on a sec'. I checked a bin in the workshop and saw a loaner USB-serial dongle. w00t! I recalled using this one during the EQMOD testing, in fact. So, known-good adapter. I connected it to the Dell laptop. Boop-beep. Looked up the assigned port number. OK. Next?

ASCOM software

Checked if I had ASCOM installed on the Win10 machine. Couldn't tell. But I'd need the mount driver anyway.

Downloaded and installed ASCOM Platform 6. It checked out OK.

Downloaded and installed the Vixen SkySensor 2000 PC driver. This is a known-good driver for my hacked IDEA GoToStar motor mount kit.

mount profile (part 1)

Back in Stellarium, in the telescope-mount plug-in, I spotted a new item: ASCOM. Yes! Stellarium had automatically detected the presence of the previously-installed platform. That was easy. 

Still, to be nit-picky: it's too bad an ASCOM entry does not show in Stellarium but perhaps dimmed and with a pop-up note. That would show it's possible but you have do something first...

I attempted to build a profile to the Vixen/GoToStar mount.

And hit a wall...

In the ASCOM "telescope" section, on choosing the Vixen SS2K driver, I received an error message. I interpreted the message to mean that the SS2K driver was not compatible with the 64-bit environment. 

Kicked off some research for find a solution and starting going down a gloomy rabbit hole. Various posts in forums were discouraging. I quickly read the notes on the ASCOM website and found them disheartening.

The SS2K driver 32-bit. Would a solution require the developer of the SS2K driver to make a new version, compiled for 64-bit? I didn't think it likely that could happen.

Windows was 64-bit. There was no way in the-heart-of-a-star I was going to roll that back.

The ASCOM platform was 64-bit, I assumed. I started to pursue a path of trying to get the ASCOM platform to work in a particular way. I could just download the 32-bit version of that. But after a lot of searching I couldn't find anything. Where was the 32-bit version?

Was this a dead end? 

It sure felt like it.

a rethink

So, I actually stopped progress along this path. While not ideal, I wondered I could use the old ASUS netbook. Old version of Windows, 32-bit—so be it. It had ASCOM. And the SS2K driver. Already working fine. A known-good USB-serial adapter too. John Repeat Dance had Stellarium loaded, although I knew it was old. I could update it and then it should work, right?

Launched the planetarium app. Ha! Version 0.12.4. Really old. Had a look around before removing it. A lot has changed. I was confident I wouldn't lose anything critical. I had all the custom landscapes (DDO in the winter, CAO with Dietmar's high-quality images, etc.) archived. Potentially I'd lose some solar system stuff but then... I couldn't think of any specific thing that was relevant.

Downloaded 0.20.4 in 32-bit and started the installer. Boom. It wouldn't run. Oh oh. New Stellarium no longer works on Windows XP (I know, I know). New roadblock.

How far back would I have to go? Searched the Stellarium archives and found that I only had to go to 0.19.0 for XP support. All right, that version should be fairly similar to the 0.20.x. The installation went OK. But on launching the app, I received a strange error message in reference to the dynamic link library msvcrt.dll. Another roadblock, this time, something to do with the .NET framework, it seemed. Ugh. I did not want to have to sort that.

Rebooted. Tried again. Dead end. 

And I had broken Stellarium on the netbook in the process. Crikey!


Slept on it but was feeling downtrodden about the whole thing. And getting nervous for my course prep.

Dove back into the ASCOM website and re-read the note in the FAQ. The question below was my issue:

The ASCOM Diagnostics program gives me the error "Incompatible Driver xxxxx.  This 32 bit only driver won't work in a 64 bit application even though it is correctly registered as a 32bit COM driver.  Please contact the driver author and request an updated driver.

I read the remarks and somehow something clicked. A light-bulb moment. I think I had not fully understood this particular statement.

If you see the same error when you try to choose the driver in the Application then this is a problem because the application is running as 64 bits and a 32 bit application will not work.

They were talking about planetarium application. Stellarium, not the ASCOM platform. Oh! So if I have the 32-bit Stellarium, it will talk to the 32-bit mount driver... Bingo. There it was. There was the answer.

the app

Hopeful, I uninstalled Stellarium from John Gomez. I had no attachment to the current setup, so nothing stopped me. No significant investment in terms of settings, configuration, customisations. 

Downloaded and installed Stellarium 0.20.4 compiled for 32-bit (x86 for those in the know). Of course, that went swimmingly.

mount profile (redux)

Launched the fresh app and activated the telescope-mount plug-in. Shutdown.

Launched Stellarium again and accessed the telescope-mount plug-in. 

ASCOM entry present, no surprise. Told Stellarium I wanted to use the ASCOM method.

At the ASCOM platform stage, held my breath and selected the Vixen SS2K mount driver. It worked! No error. Just a warning... Don't forget to set the port. Right!

Hit the Properties button. Ah. Familiar Vixen SkySensor 2000 dialogue box. Configured the communications COM port to match the Win 10 assignment. Done! A big milestone.

This signified that 32-bit mount drive was happy receiving commands from a 32-bit planetarium app.

Finished the Stellarium mount profile.

mount config

Now, I needed to configure the Vixen/GoToStar mount hardware, to get it in normal operating mode.

Did the usual stuff: powered up, verified the location, set the date, time, time zone, did a quick (fake) one-star alignment (it suggested Albireo), and I ensured the mount was tracking in sidereal mode.


I was ready to test intercommunications. Ready to connect the Stellarium software app to the Vixen/GoToStar mount equipment.

Zoomed out in Stellarium to see the whole sky.

Accessed the telescope-mount plug-in. 

Hit the Connect button. Of course, the Status column shows a positive indicator but that may not mean anything. It's a milestone but may be misleading... the incorrect mount driver may not send proper commands for slewing. The connection indication does not verify a full working system.

I was thrilled though to see the reticule (labelled with the mount profile name) suddenly appear in the Stellarium sky display and then move. Woo hoo! This was a major milestone. And then, and then, the reticule settled on beta Cygni! That was huge. The significance of this milestone was that it showed two-way communication. The mount was telling Stellarium where it was! 

I was so happy.


Immediately I wanted to conduct the next test, the most important one. I tried the slewing keyboard shortcut. Clicked a nearby star in the Stellarium display then pressed the Ctrl key with the appropriate telescope-mount profile number. 

It worked! 

Holy Universe! 

The Vixen Super Polaris mount hacked with the GoToStar motor drive system slewed to the target. Of course the reticule mimicked the movement through the sky.


Tried the slew-to-the-centre-of-the-screen trick with Alt and the profile number. Never used that before. It worked just fine. Neat.

And had a good look at the Move telescope window in Stellarium, also new to me.

finish line

Wow. Relief, joy, satisfaction, elation, pride, calmness... 

I had surmounted this little mountain. Lots of moving parts in this scenario. But I had a solution too. Happy that I would have the ability to show a full run of driving a mount with Stellarium. The key takeaway was that I needed a 32-bit version of Stellarium to properly talk to the 32-bit mount driver. 

screen snap from test video, Stellarium commanding Vixen mount

And along the way, found a way to capture it. In fact, I immediately recorded session in Zoom to see it all work, shared screen from John Gomez with Stellarium, with a head shot including the mount and hand controller working by manual and software control.


Wrote up notes in a slide deck... A bit more course prep.

Obviously, this is only one solution. But some of the broad strokes will be the same for all. Hopefully this might help others too, in some of the technical issues that may arise.

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