Making a MyFocuserPro2 electronic focuser
An Open Hardware project
I’ve ordered a side-by-side dovetail and saddle so my Celestron C8 and Skywatcher Evolux 62ED can ride on my Skywatcher NEQ6 mount in my observatory. The C8 uses a JMI Motofocus driven by a Shoestring Astronomy FCUSB focus motor controller. Still, I wanted to create something that was out there using Open Hardware (e.g. Arduino) as a sample project for my upcoming book, Open Astronomy. So, I looked around and found MyFocuserPro, a project by British amateur astronomy Robert Brown. Actually, it’s a few projects!
MyFocuserPro was originally a project to create an Arduino-based electronic focuser that was Moonlite compatible and widely supported by drivers, including ASCOM/Alpaca (Windows) and INDI (Linux/Mac). This first version project is still around, but Robert has also posted MyFocuserPro2, an enhanced version of the project. Initially, I decided to go ahead with a MyFocuserPro (v1) project so I could use the Moonlite driver in INDI since I run Linux for all my astronomy equipment. I quickly realized that a dedicated MyFocuserPro2 driver existed for INDI, so I promptly changed plans since MyFocuserPro2 has many more options and can support more configurations than the original version.
Everyone has experienced picking up a restaurant menu and discovering a bewildering variety of options, and that’s what my initial MyFocuserPro2 experience looked like - there are a lot of different choices to be made. A lot of these decisions must be made upfront to have a successful project. However, I knew in general what my setup needed to look like since I knew what I had in my parts drawer!!
These components included an Arduino Nano (which was nice anyway since it keeps things small versus a large format Arduino) using a DRV8825 motor driver to translate pulses on the pins of the Arduino to movement from the motor. The motor I had on hand was also a perfect fit for an electronic focuser because I’d bought it for an earlier abortive project. The motor was a 12v 1.68A NEMA17 .9deg per step motor with a 27:1 planetary gearbox attached. This motor would provide very fine motion and a lot of torque to move the focuser on the telescope.
For the a la carte portion of the menu, I decided to add a rotary encoder so I could “manually” focus at the telescope by moving the knob of the encoder, which the driver would translate into in/out motion of the focuser, and also a temperature probe to change focus based on temperature changes at the telescope. So, I ordered a KY-040 Rotary Encoder Module and a DS18B20 temperature module, both from Amazon so the parts arrived in a few days. I also ordered some screw terminal boards for the Nano and the DRV8825 so I could just assemble the components without having to solder.
Next, I needed to mount the whole thing on the telescope, so I designed a mounting on Fusion 360, to be 3D printed on my Ender Pro 3 3D Printer. After 11 hours of printing, I had all the pieces I needed to assemble my focuser. Next time, some details on how everything went together, how the software works, and how the focuser performs in testing. See you next time!
