From: "Tim" <tjp314@pacbell.net>

Date: November 14, 2005 2:34:30 PM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: Unibrain adaptor

Jim and Milton:

--- In Astro_IIDC@yahoogroups.com, Milton Aupperle <milton@o...> wrote:

Hi Jim;

On 14-Nov-05, at 7:04 AM, jimchung2338 wrote:

Thanks to everyone for their insightful advice concerning my Mars

imaging.  I'll try again with attention to red gain and see if more

details arise, should be getting my JMI Motofocuser soon which will

greatly aid in focusing - now I understand what the fuss is about with

Feathertouch focusers and the like!

Yep. Focussing is all sorts of Fun. With my Orion MAK scope I get  

mirror shift as I focus and when I double size the image for  

focussing it shifts nearly out of the field of view. I'll buy another  

focuser for it someday.

I researched this subject for quite a while before I made my decision to buy a Robofocus 

motor and kit for mounting on my 9.25".  What I needed was something that would give 

me the ability to focus without being within 10 feet of the telescope (since it's mounted in 

my roof).  Most of the electric focusers have cables to the controller that are too short.  

The Robofocus isn't cheap, but it can be moved among scopes (by buying a second motor, 

for example).  It's also supposed to be only PC compatible, but I noticed that EquinoX lists 

Robofocus control on their website.  

Another neat thing about it is that it always ends focusing from the same direction, so if 

you have mirror shift, the subject will come back to center if it's deflected off during the 

focus change.  With my C-9.25", I find the mirror shift to be on the order of 40-50 arc 

seconds, whereas the Meade 16" up at Mt Wilson (which replaced a Brashear 6" refractor! - 

which ought to be a felony...  ...but I digress) had at least several minutes of arc of mirror 

movement when focusing when I looked through it several years ago.

My only complaint about the Robofocus is that it's mounted to the backplate of the C-9.25 

with double-stick tape.  And during the daytime it gets warm enough up in my roof that 

the tape lets go.  I've routed the ribbon cable through the handle on the back of the 9.25 

so it doesn't fall to the floor if it comes all the way loose.  Someone recommended that I 

clean the components with alcohol before taping the motor on, but I haven't done that yet 

(which shows you just how "inconvenient" it really isn't!:o) ).

-Tim.