A few people asked me to show I motorized my manual SkyTee2 alt/az mount to full GoTo with OnStep. The SkyTee2 mount is sold under different brands but the mount is always the same. Mine is called Omegon TwinMaster AZ.
The cost for the full setup is about 350 EUR for the mount, 150 EUR for the tripod and 100 EUR for the electronics. The beauty of this modification is that it does not require a 3D printer or fancy custom parts. For about 600 EUR you can get a mount that handles a C8 effortlessly. With upgraded clamps and properly balanced I woud put a C9.25 on it without hesitation.
Visual it is a joy with negligible focus wobble even at 500x. Photographically it does 10s unguided at 1300mm and with guiding I do 90s exposures at that focal length with 95% keep-rate (field-rotation is the bigger issue). I show some examples here: https://www.cloudyni...mages-included/
- 2x M4x14 screws (and better 2x M4x16 as backup)
- 2x NEMA17 mounting brackets (image with measurements in the gallery)
- 2x NEMA17 motors (200 steps per rotation, 1.5A)
- 2x 16T 6mm GT2 pulleys
- 2x 48T 6mm GT2 pulleys
- 1x 166T 6mm GT2 belt for ALT axis
- 1x 164T 6mm GT2 belt for AZ axis
- 1x OnStep controller (MKS Gen L 2.0 with TMC5160 drivers)
The AZ bracket can be easily installed. It directly fits. Note that I only use one screw to attach it. I was skeptical at first, but 18 months of usage showed that it's solid enough. There's only little torque applied during operation.
I used a MKS Gen L 2.0 3D printer board and added TMC5160 drivers. The drivers are on the expensive side (10 EUR per piece on AliExpress), but they're quiet and cool. I bought 1.5A motors which I couldn't drive with the TMC2130s that are usually recommended. Most people on OnStep recommend 400 step 0.9A motors - those will work fine with TMC2130s.
In the OnStep config, I use 32 microsteps for tracking. This gives 7680 steps per degree. I set the motor current via SPI to 1200mA for tracking and 1400mA for GoTo. For good GoTo speed (since the MKS Gen L is a slow board) I use 8 microsteps during slews. This is a nice feature of the TMC5160/2130 drivers. My base slew-rate is 2 degrees/second.
The controller needs 12V. I control it with SkySafari and the inbuilt web-interface from OnStep. If you don't use the MKS Gen L but build your own board you can add a ST4 port which can be used for a handcontroller. I demo'ed a wireless handcontroller which was now added to the standard repository which means you can use a handcontroller even on builds such as this.
Below is my final build stage, with the controller nicely attached to the legs of the mount:
Edited by jesco_t, 04 April 2022 - 09:08 AM.