Why to motorize your telescope focuser? A telescope requires adjustment of focus after a temperature drop of a few degrees Celsius only. The temperature influences the APO focus by changing the refractive index of the lenses and less by mechanical contraction of telescope tube. For me too many images did do not have the optimum focus. To cope with this problem I ordered a focuser motor drive with a step motor rather then DC motor and temperature sensor, This will allow direct focus compensation for any temperature change.
To mount the motor and electronic box, I made home made adapter of some 3mm thick aluminum strips. The motor is coupled using a toothed belt. This makes it easier to remove the focuser and allows a very compact design preventing the telescope assembly hitting the pier. It is also easier to remove the focuser for storing the telescope in the storage case.
The motor is coupled with a toothed belt to the fine knob 4 mm shaft. This still allows for me about 40 mm adjustment in 65535 steps (6 mm/10000 steps) and less load on the system. The toothed belt (209520) and toothed pulleys (209514, 209515) where ordered from Conrad. Due to the low load it allows running the focuser on USB 5 volt only without any external supply.
Here some pictures.
USB_focus received:
toothed belt and pulleys:
Adapter home made
Adapter mounted:
Motorised focuser in service:
Last update July 2017
