MKS Gen L build

Rick Foust

I haven't seen any pics of MKS Gen L builds, so I thought I would share mine. 

In my opinion, the MKS Gen L provides the path of least resistance if you want to build an OnStep controller.  The Gen L is an all-in-one 3D printer controller that includes all the hardware that you need except an optional wireless access point, which can be easily added.  It uses the Ramps 1.4 config file in the OnStep firmware.  I found no bugs in the firmware.  Kudos to Howard and everyone else involved in the development.

I built mine into an old police scanner chassis.  As a bonus, the scanner had LEDs on the front panel to show which frequency channel the scanner was monitoring.  I retained the LEDs and connected them, via resistors, to provide status on power and stepper activity.  They aren't necessary, but they are handy for troubleshooting.

I labeled my pic of the completed controller to show where the connections are made.  This will will be helpful, but it won't be enough information to build one.  You will still need to carefully read and understand the available OnStep documentation.  All of the information that you need is provided, but you will have to do some detective work because it is in various locations and is mixed in with info on other controllers that OnStep also supports. 

I am using it to control a large 1960s GEM carrying a 16in Skywatcher Newt.  The mount came complete with it's original 7watt synchronous drive motors, but no controller.  After disassembling everything and cleaning out the dried grease I cobbled together an ST4 controller using relays and vintage drive correctors.  This worked OK, but when I heard of the OnStep Project I knew this was the way to go.

Please don't laugh too hard at the 4 wheel cart and the scope cradle.  They were built out of scrap that I had laying around (2x10s, old farm equipment, etc).  The whole monstrosity weighs 1200lbs.  I roll it in and out of my hangar.  This is intended to let me assess the capabilities of this mount/telescope so that I can decide how much I want to invest in a more permanent solution (observatory).

Rick Foust

Here are some pics of the focusers.  They use NEMA 17 steppers, home made pulleys and vacuum sweeper belts.  I was concerned that the motors might not have enough torque, but they work well.

Khalid Baheyeldin


This is one heck of a setup! Pretty impressive. The images from 16 inch should be fantastic.
Good to see the S109s work well.

I added a link to this thread on the show case page.

Rick Foust

Thank you for the compliments Khalid.  And thank you for pointing out that the S109s are available.  They were just what I needed for this build.  After I have had a little more time with them I will provide an update in one of the other threads.  Meanwhile, we are having an unusually wet fall/winter.

If anyone is curious about what kind of images can be taken with a 16in Newt, I have posted occasionally over on the Cloudy nights EAA forum. 

I can't thank you guys enough for developing OnStep.  It has brought new life to a retired mount that was probably cutting edge in its day, but until OnStep, was like bass fishing from a tug boat.  I paid a ridiculously low price for it because it has a home made look to it.  No-one, myself included, expected it to be much more than a boat anchor.  Once I had a chance to take it apart, I discovered what a gem it is.  It is well designed and precisely fabricated.  It just needed a new up to date controller.

Now that I can control it remotely, I went ahead and built a warm room in the hangar.  I am really looking forward to putting it to use if the weather will ever clear up!!!

Howard Dutton

I love setups like this and I'm glad to help with the software side of things!

The MKS Gen-L really avoids a ton of hassle and definitely gets the job done.  You could even argue that it's the best OnStep controller there is regardless of price.  Lots of I/O, 5 axes supported, on-board MOSFET dew heater control.

I have a pair of S109's on order and will test here too.

Khalid Baheyeldin

On Fri, Dec 28, 2018 at 07:24 AM, Howard Dutton wrote:
I love setups like this

Is this the biggest aperture on OnStep (16 inch Newtonian)?

I know that there is some observatory somewhere using OnStep, but no idea how big the scope on it is ...

Howard Dutton

AFAIK the largest aperture "biggest" OnStep controlled 'scope is a 0.8M RC in Italy (fork mount.) 

There's at least one Dobsonian out there that's a 20" I believe ....


He was the fellow that nudged me to add de-rotator support for Alt/Az mounts to OnStep (for his planetary imaging.)