electric focuser for c14

[icytailmark]

i am looking at buying a electric focuser for my c14. I have been trying to image mars but everytime i turn my focus knob i lose mars off the center of my camera.

http://www.myastroshop.com.au/products/details.asp?id=MAS-051C

Would this be a good focuser?

[pmrid]

The JMI line of electric focusers is good. I have 2 of them and can report that they work well and are easily controlled from the PC.
The thing about these focusers is that you don't need a great deal of travel in the drawtube since the coarse focus is done with the standard SCT focuser. Set the drawtube to a mid-point and get your rough focus set for there, then don't touch it again.
The problems can occur where you use a reducer - the standard Celestron .63 reducer is designd to screw onto the rear cell of the scope. That means you can't put a focuser like this onto the scope.
What you need is a focuser that can accept a reducer in the end of the drawtube so it moves with the drawtube - i.e. you maintain a precise and constant back-focus and stilla are able to screw the body of the focuser onto the rear cell. Moonlite make a line of focuser with the ability to accept a reducer like that.
Peter

[icytailmark]

peter can you take the reducer out when you wanna image planets?

[Poita]

I use one of these, and have been very happy with it.
http://www.optecinc.com/astronomy/catalog/tcf/tcf-s.htm

[pmrid]

Yes. It does mean taking the whole focuser assembly off and unscrewing the reducer. In reality it is only a 2 minute job, but just a pita.

Peter

[asimov]

I've been using the EV-3c for 4 years now & love it. It's that good that I took the motor off it though & use it manually.

[Merlin66]

Mark,
On my C11, I use a SW focus motor, belt drive to the existing knob.
This allows me to accurately focus the target star onto a 20 micron spectroscope slit.
Cheap and works well. Using the Shoestring FCusb connection I can control the focus from the PC.
( I left the Vegemite manual fine focus knob in place...)