Robofocus on Meade Microfocuser
The standard Meade #1209 Microfocuser has a simple DC motor. This motor works well to position the focuser manually. For imaging applications, more precise and repeatable focus is required. One option is to install a position sensor - either a dial gauge, or an optical encoder on the focuser drive shaft in order to measure focus position. A more common method is to use a step-motor to drive the focuser. This is the method used by Robofocus.
The first steps involve disassembly of the Meade focuser to remove the DC motor. Take all the little Allen screws out, and we can see inside.
Technical Innovations supplied a coupler to connect the step-motor to the drive shaft. The coupler did not quite fit according to the assembly instructions, so I replaced it with a spare coupler from the ’warehouse’.
With the motor attached to the coupler, work can begin on the mounting bracket.The next image shows the required position of the focuser. An ST-7 with CFW-8 is being used with this telesocpe. The motor which drives the filter wheel sticks out in front of the filter wheel assembly - towards the telescope, so it interferes with the focuser housing. The filter wheel motor is at the same end of the camera as the communication cables. These cables will interfere with the telescope mount if they are below the focuser.
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The following pictures show the motor-focuser assembly mounted on the telescope.