YAFD (Yet another focuser drive)

[Merlin66]

I mentioned on another thread about mounting a Skywatcher Accufocus motor onto my C11 to assist in getting better control of the focusing routine.

The initial "cheap and nasty" approach worked for one night!

Trying to use the knurled adaptor (used to connect the ED80 focuser shaft) doesn't work! It's only located by an O ring (tight!), and this flops around.

The answer, as others have found, is to use a small toothed pulley and belt.

I bought a 30 tooth MXL pulley (PL030AL) and a matching 8" belt (BMXL 100) from MotionCo - excellent service with delivery the day after!

I'm using the rubber covered Celestron knob as the second "pulley", this is about 1.25" diameter, and for the purposes of working out belt sizes and centre distance is equivalent to a 48 tooth pulley.

The chosen belt size gives a centre distance of 61mm which seems a good solution.

The SW motor is mounted on a length of bent 20 x 3 flat aluminium which is mounted to the OTA using the "spare" M4 finder screws.

The final assembly works very well and gives a smooth precise control of focusing.

( I've recently bought a Pololu Maestro servo controller ( see other thread) which I'm convinced would allow the SW motor to be controlled via the PC and a would make thing even easier)

I'll post some images of the set-up later.

A very simple, straight forward job with excellent results.

[Merlin66]

Well,

put it through it's paces tonight...works 100%

I'm impressed!!

[Ericgraham]

How do you control it? A box with buttons? Pictures please!

[Merlin66]

I can use the original SW hand controller, or alternatively through the PC via the ShoeString adaptor.

[oldturk]

looking forward to the pics as this is a very attractive option.

[Merlin66]

OK,

The attached images show the SW Accufocuser motor fitted with the pulley and the belt just wrapped around the Celestron rubber knob.

The motor support bracket is fitted to the OTA using the "spare" M4 screws in the rear cell.

I have made up a 5 mtr RJ11 cable to a 2.5mm stereo plug; this fits either the JMI handcontroller or to the Shoestring FCusb adaptor which then allows control via the PC...

(You could just use a 4 wire RJ11 extension and the original SW handcontroller - I had the JMI from a previous "project")

HTH

[oldturk]

Thanks Merlin.