Wednesday, 9 March 2016

Telescope with Raspberry Pi

Notes and Info on using a Raspberry Pi with my telescope

Not going to say much about my scope other than it is using a Vixen GP mount which had an ra drive fitted when I bought it, and I am fitting a dec motor to it. Both motors are vixen MT1 and I have a hand controller DD-1.

I'm first of all planning to add an ST4 interface to the controller, which looks pretty simple, and then use a PiFace to drive the interface. I'll then use Linguider to give me an autoguide capability. I'll look at adding goto later.

(Well, adding an ST4 interface to the DD1 didn't go too well.... )

I'm using Raspberry Pi, 'cos I have a couple already doing other things and I like them, plus it's nice low power so I can run on batteries, and lots of people are using them as telescope controllers. The GPIO on the pi means I can drive various things direct, rather than through various adapters, although I will use a PiFace to protect the pi and give me a bit more drive (the built in output pins are only 3.3v and very limited current).

I'm using linguider 'cos I've read in many places that it works far better on pi than the other obvious alternative - openphd, plus I relatively easily added support for driving piface outputs to it.

This setup all works, although I need to tweak the settings of lin_guider and / or the scope alignment to get a nice tight tracking. lin_guider reports a swing on tracking of around 6 - 8 arc seconds on 1 axis (the other axis is < 1 arc second). This is a 2 minute exposure with a 560mm lens on a crop frame camera. If you open up this piccy (which is a big crop from the original) you will see all the smaller stars are slight stripes.

This setup looks like it will work well for tracking, but as I can't change the speed of the motors except by moving the switch on the DD-1, goto is not going to be seamless.