An OTA mounted control module that allows you to remotely manage your astro rig

Let's begin with some common problems: cable management is one of the problems that started me down this path, but the main problem is the weight and inconvenience that comes along with the duplication of power cables (most running 12 vdc 1 - 2.5 amps), and communications (USB) cables that need to plug into the main CCD, guide CCD, focuser, filter wheel, and mount--five USB cables running from my control box, up the mount, and then to each of the devices. I don't have anything unusual in my setup, and my expectation is that these five devices are the most common in any astro imaging rig. My hope is that anything I'm building and testing here will be useful to many.

Here are some shots of my gear, with a dozen power and comms cables running from the "control box" to all the devices. I have built in a lot of slack so that cables don't pull from sockets when the scope heads toward the zenith or the opposite horizon. And I have spent considerable time learning, through trial-and-error, where to tie-down and loop the cable bundle so that its weight doesn't affect tracking or guiding.

The Goal
I want to have fewer cables running to the mount. Ideally I will end up with just a single power cord--12 vdc--running to an OTA-mounted control box. That's where all the communications (via USB) will begin--and end, with each of the devices all within inches of the USB hub. The following plan shows what I'm building, sketched out over lunch. The idea is to make a control box that's mounted with, to, or under the OTA, possibly inline between the saddle and scope. My prototype is mounted on top, bolted to a dovetail I have running along the GT-81's "handle" for the guide scope.

Another goal is to enclose or fix the electronics components (Astro controller, power converters, USB hub, focuser module, dew controller) to 1/4" (6.35 mm) aluminum, or something equally as rigid, drillable/tappable that can be mounted with the OTA and not shake or move about during gotos or tracking. I'm thinking of this as a DIY, inexpensive version of the "EAGLE - Control unit for telescopes and astrophotography" by Primaluce Lab ( The main difference--as far as functionality--is the Eagle runs Windows, along with the availability of ASCOM, EQMOD, SGP, MaximDL, etc., while I'm running linux on a Raspberry Pi with Indi, KStars, and Ekos. But you can replace the "astro controller" and any of the software in this scheme with an equally small Windows machine and your favorite astro software. From a hardware standpoint the goal is the same: an OTA mounted control module that allows you to remotely manage your astro rig.

The Prototype
Going by the pic below of my prototype OTA-mounted astro controller it may look as if my cabling problems have increased--okay, yeah, I admit looks a bit sloppy right now. The important thing to notice is that I have a single 12 vdc wire running the whole thing. That's it. No more "cable harness" with five USB cables and five power cables bundled up and running to various points on the mount, scope, guider, filter, ccd, and dew controller.

Power and Comms for Components:
  • 1. Atik 414ex Main CCD (USB, 12vdc)
  • 2. Atik EFW2 Filter Wheel (USB, 12vdc)
  • 3. Raspberry Pi3/Ubuntu Mate Astro Controller (5vdc)
  • 4. ZWO ASI 120MM-S Guide Camera (USB 3)
  • 5. Focus Module - FCUSB (USB)
  • 6. Orion Atlas EQ-G or iOptron CEM25P (USB to Serial, 12vdc)
  • 7. Dew Control for William Optics GT-81, WO 5mm guide scope

Here's a newer pic of my GT-81 setup, with everything mounted on a smaller aluminum plate, and the system has a dedicated wifi router that I use to control everything remotely.


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Saltwater Witch copyright © 2017 Chris Howard