Thursday, October 4, 2018

It's Red and Round

It's red and round.  And it's Mars inspired.  Sort of.

Another weekend approaching and the weather (again) doesn't look conducive for astronomy.

Rather than pout about it, I'm going to spend some more time tinkering on an astronomy related project.

Red and Round
How is this an astronomy related project?  And what is it?

While sitting outside next to the telescope with the imager attached and capturing video of Mars, sometimes Mars slowly starts to drift out of the field of view.  

Tracking on the telescope is pretty good, but at high magnification and over time, if the telescope's alignment isn't perfect, objects will appear to drift in the field of view.  I usually compensate for the drift by nudging one of the movement buttons on the telescope's hand controller.

The nudging technique works fairly well, but the hand controller needs to be detached from the base of the telescope or pushing the buttons will impart unwanted oscillations on the optical tube assembly.

Usually, I just lay the hand controller on the surface of the table with the laptop.  Unfortunately, the hand controller is tethered to the mount's base with a coiled spring-like cable and the cable has pulled the controller off of the table, launching it onto my concrete driveway. 

When this last happened, while imaging Mars, I decided to do something about it.  I guess that I could have divined a mechanism to keep the controller from being pulled off of the table, but that seemed to be an inelegant solution.

Hence this project.

What is it?  It is a joystick to telescope interface.  Wireless, of course!  And Bluetooth because everything is better with Bluetooth. 

Push left on the stick and the scope moves to the left.  Push right on the stick and the scope moves right. Pull back, up!  Push forward, down!

Slew speed is set via a knob position.

Cool huh?

The Joystick

Here is a photo of the prototype joystick electronics.

Joystick Electronics
Basically, it consists of an Arduino Pro Mini controller, a Bluetooth serial slave device, a 3.3v regulator, some buttons, and some wire.  Oh, and some software.

Barely visible is a 10k linear taper potentiometer that is being used to set the slew speed.

The yellow buttons will be replaced by the actual joystick assembly when I eventually place everything in a box.

The Telescope Interface

The telescope interface is pretty simple too.  Here is a photo of the prototype interface electronics.

Telescope Interface Electronics
The interface to the telescope consists of an Arduino ATMEGA 2560 controller, chosen because it has a bunch of serial interfaces, a Bluetooth serial master device, and two rs232 level converters.  Oh, and some software.

Essentially, the interface receives position and speed information from the joystick electronics via the Bluetooth interface and does a conversion into the necessary telescope control protocol commands.  It does this while interspersing the protocol stream from the Wifi interface connected to the planetarium software. 

I'm thankful that SkyWatcher has released a protocol specification for their telescopes.  Otherwise, I'd still be reverse engineering with my protocol analyzer. 


It's a fun project.  I'm nearly to the stage where I'm going to start packaging it into neat boxes and testing it under the stars.

When its finished, schematics and software will be available upon request.




  1. Skywatcher Galactic Ninja Stick, Bluetooth tracking slayer, Bam!!! Take that you drifting image breaching targets!! BAZZINGA!!

    1. Ahh. Thanks. I almost forgot to include room for the quarter slot and the laser blaster button! 😊

    2. A laser blaster button seems like a must have option, at least to me it does.

    3. I just finished ordering the project boxes (mechanical packaging is hard) and made sure I have room to add extra buttons, blinking lights, and things that go beep or buzz.

  2. "Because everything is better with Bluetooth," that made me smile.:-) I'm looking forward to seeing everything boxed and then your report after its first in-situ use. Thanks for posting!

    1. A telescope controlled via Bluetooth and WiFi! How could that fail to be awesome?!

  3. Hey There. I found your blog using msn. This is a very well written article. I’ll be sure to bookmark it and come back to read more of your useful info. Thanks for the post. I’ll definitely return. why is mars red


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