Connecting WWT to telescopes: the importance of an ASCOM hub (a GitHub recap)

Here at Harvard we had a high school student, Aidan Cook, work on a summer project to set up a basic telescope to be driven by WWT. It was a great success! Along the way, a couple of issues arose that required a bit of insight to understand how to set things up. I initially directed that conversation onto GitHub (issues wwt-windows-client#141 and wwt-windows-client#143) but I belatedly realized that this forum would have been the better place to discuss them. So, here’s a recap!

The first issue was in debugging ASCOM errors. Paraphrasing Aidan,

ASCOM apparently has a relatively strong and specific error reporting system and does a good job of determining the problem with badly connected telescopes. There is no error log in WWT which makes it hard for people to connect their telescopes. I believe that other applications (such as Cartes du Ciel) use an error log directly from ASCOM. This would require investigating the ASCOM error log and implementing it into WWT.

Here’s a paraphrase of @astrojonathan’s reply:

The best practice for WWT is:

  1. Start an ASCOM hub. Setup, connect and debug your telescope and dome connection using the hub.

  2. When your ASCOM connections are stable, connect to the hub from WWT.

This probably should be documented as the ONLY supported way to do it.

ASCOM drivers are so varied in behavior that we can’t test them all with WWT and while most other astronomy software is not as interactive like WWT is, generally almost no ASCOM users use a bare telescope from any ASCOM software because of this.

Relatedly, Aidan also asked:

When a telescope is connected to the application through a miniUSB port, the performance of WWT (frame rate, etc.) decreases remarkably. This makes the viewing experience less pleasant and the tools harder to use. I believe that this is an issue in the rate of tracking through ASCOM. The application and telescope are constantly in communication and making tiny adjustments even though the telescope is supposed to be tracking (following the same point in the sky).

And once again @astrojonathan brought the wisdom:

Some drivers are synchronous and wait while you poll them. You absolutely need to use a Telescope Hub. Connect WWT to an ASCOM hub, then connect the telescope to the hub. The hub will poll the telescope in the background and return data to WWT instantly when called and won’t impact the performance.