Question Motorized Polar Alignment Azimuth Motor Stalls

Hi,
During polar alignment of my M-Zero mount, my azimuth motor stalls. It made a few turns in both directions before stalling so I know it is working correctly, except for the stalling. The tangent arm is close to the middle of the thread and has not reached the end of its travel. The mount has not been used for several months. I assume that there is some binding in the components and I decided to loosen the 3 bolts on the slotted holes that secure the mount to the base plate. This did not solve the problem so the binding must be elsewhere in the components. I am going to take a closer look at the assembly during daylight tomorrow. Do you have any instructions for setting up and adjusting this assembly? Do you recommend placing oil on the tangent arm thread?

Thanks, Richard

The motors for the Motorized Polar Alignment have dual shafts, one that drives the gears and one that drives the motor, before reduction gears. Maybe you can turn the motor end of the shaft, without applying power to the motors, and see if the azimuth axis turns either ways without resistance. It may take long before you get to see some movement because of the reduction gears but you should see that the azimuth as changed after some time. Access to the motor shafts are from the south end of the mount.

One thing I noticed with mine is that there is backlash when you change azimuth direction and it takes some time before the azimuth axis show any position change. That may be what you are experiencing. It is a bit frustrating as, if you overshoot the polar alignment azimuth adjustment, the backlash will hit you again when you change azimuth direction.

Hope this helps.

BTW, I love the M-Zero OBS mount. It's very compact and much appropriate for small automated observatories.

As I run it under the KStars/Ekos/Indi suite, there is no support for the motorized polar alignment feature, so I built a control box from a spare Teensy 4.0 and TMC2209 drivers I had, with an UP-DOWN-EAST-WEST keypad to control the ALT-AZ motors. I have yet to write some (python) code so I can feed it the Altitude and Azimuth corrections for proper polar alignment.

G_Gagnon,

Thanks for your reply to my question. I tried turning the azimuth polar alignment motor knob by hand and it reached a point when it would no longer turn in either direction. I then removed the black cover over the crown gears in the base of the mount to investigate further. I found that the red aluminum mounting block that holds the motor to the mount fork arms was twisted with respect to the base plate (twisted in vertical plane) and this was causing the gears to become misaligned and bind. It also caused the bubble level to be out of level. I adjusted the block, put some light oil on the tangent thread and was then able to run the azimuth polar alignment assembly through its full range of motion.

So problem solved. I imagine that the screws holding the red aluminum block might have come loose over time, due to temperature change and traveling with the mount, although it has seen little use from new. To avoid this happening again, my suggestion to the manufacturer would be to add 2 screws going up through the base plate into the red aluminum block so that it could not twist and cause this problem again. This would also ensure that the bubble level always reads correctly.

- Richard

Thanks for your reply Richard,

It makes me realize that I should check the azimuth control of my mount, once in a while, to make sure everything is OK. It's a place we do not tend to check, as it is hidden by the azimuth adjustment cover.

Gilles