How to turn a crawford electric

[blinky]

I recieved my dual speed antares crawford this week. Got it all fitted up but I really wanted to retain the electric focus, especially for Saturn at high magnification and I also feel it was quite good for focusing the DSLR.

Anyway I had the skywatcher electric focuser, after 10 mins of staring at the scope and then the motor I figured it out!

Mount the motor slightly below the fine focus knob of the crawford and connect it up with a thick rubber band (It actually looks like a pulley but I dont know where it came from). I can now have very very fine control via the electric focuser or by detatching the band I get normal dual speed crawford focusing!

Next step is to convert the electric focus handset to 12volts to speed up the motor a bit as it's a bit too fine at the moment, but otherwise a very well spend morning!

I will post an image when I get a minute, maybe this afternoon but rain is forecast!

[blinky]

Here are some images

(click to enlarge)

[blinky]

(click to enlarge)

[barkis]

How is the motor attached to the OTA Craig? I imagine it is Velcro for the controller.

Ron.

[blinky]

a couple of screws I was gonna glue it on but then thought better of it

[Vega]

No more Nails ?

[blinky]

My RDF is actually glued on but with epoxy resin, works great

The only problem I have with the electric focuser is it's too slow (I can only get it to turn the 10X reduction knob) so I have to remove the pulley to get rough focus then use the eceltric focuser for fine focus. I also modded the control box to accept 12V rather than the 9v it took before. I think I might try and swap the motor for a faster one but will see how it goes.

[radioactive]

Yeh that's why they use stepper motors on these things for a speed control.

You will soon crack mate well done upto press :hello1:

[blinky]

I know a stepper motor is next on my list. They look a little complex though!

[barkis]

Well you would get a 12volt one with enough torque to turn the focuser OK, but you will need to make a control board for speed and reversing. Maybe Maplin do a kit for stepper control cheap.

[blinky]

I have seen a couple of USB control boards for stepper motors. It will have to wait a couple of months till I come back from Holiday. The accountant has warned me, no more spending till we come back!

[blinky]

One thing I need to ask though. The screws that I screwed it in with protrude into the tube my maybe 1/4 of an inch. I plan on painting them black but will this cause any problems, by the length of the screws in the tube?

[gary1968]

Craig, I figure that if the screws dont protrude into the diameter of the main mirror you will be fine, if so just take em out and cut them.........

Nice work BTW, and that focuser looks the biz.

Gary