Help needed with focusing

[RobertI]

Hi all,

I am using my C8 to image Jupiter (and hopefully Mars and Saturn later in year) and am getting ok initial results but biggest problem is focusing.

To explain, I am using a Canon 1100D connected to a 10mm baader Hyperion with a 20mm extension tube. I capture using backyard EOS which has a focussing help feature using a FWHM measurement. You zoom in on a star and focus in and out until the FWHM figure is lowest. Trouble is, soon as a touch the focus knob, however gently, the star moves out of the focus area, making it really really hard to focus.

What is the solution? A 10 to one focuser, if so which one? A motorized focuser? Anything else? Don't want to spend a huge amount at this point in time.

Any help really appreciated.

Thanks

Rob

[Steve Ward]

I would recommend fitting a focuser to the back of the C8 , therefore eliminating the need to move the mirror .

My Mak180Pro was transformed this way , the finesse of touch is superb now ( enhanced further by use of a USB controlled motor)

The Revelation SCT focusers are very good value at around £110 , way cheaper than some I could mention.

[RobertI]

Thanks Steve, that's really helpful, the Revelation Astro focuser looks really good value for money and I will definitely look closely at that one.

Which USB controlled motor did you use? I see that skywatcher do a cheaper motorised focuser for £45 (http://www.firstlightoptics.com/astronomy-cables-leads-accessories/skywatcher-auto-focuser.html) . Although not USB controlled do you think I could get this to fit and would it be useful?