sensasi: Re: [sct-user] Re: RoboFocus settings

Jumat, 08 Februari 2008

Re: [sct-user] Re: RoboFocus settings

> I have an older classic with metal gears, so I hope not to have as
> much backlash as people with newer classics.

Not sure what gears you're talking about here... there aren't any in the
focusing mechanism. AFAIK, classics have always used a plastic thrust
bearing (basically, just a washer) between the focus knob and scope
back, and this is a major source of backlash. You can considerably
improve the focuser by replacing this washer with a roller thrust
bearing. There's an expensive kit you can buy, or you can do it with
hardware store parts for a couple of dollars.

I use FocusMax (which I'd recommend you switch to), so I can't comment
on @Focus settings. But for my RoboFocus settings themselves, on a 12"
classic LX200 with the focuser mod mentioned above, I use a step size of
4, 250 steps of backlash compensation, and I finish in the "out"
direction (mirror pulled back). For smaller LX200s you need to finish in
the "in" direction (mirror pushed forward). The direction you finish is
very important.

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

----- Original Message -----
From: "carter646831" <carter646831@bellsouth.net>
To: <sct-user@yahoogroups.com>
Sent: Friday, February 08, 2008 7:55 AM
Subject: RE: [sct-user] Re: RoboFocus settings

> Hi Leo,
>
> Thanks for the response, and information. I always like people's
> answers. ;{) I have an older classic with metal gears, so I hope not
> to have as
> much backlash as people with newer classics. The numbers you're
> reporting are
> very close to what I use. I use a total travel of 65326 and backlash
> of 50. I
> have my @Focus set for a small step of 1 and large step of 10 and no
> backlash I
> use 50 iterations and averaging of 3. The seeing in Northern Florida
> is very
> soft also. I think what I'm looking for is the step size in the
> RoboFocus to get
> the recommended 1/2 CFZ.
>
> The algorithm you use is very close to the algorithm the RoboFocus
> manual says to use. I like your idea of starting from set points in
> RoboFocus.
> Once I get good starting points, I'll go that route. I may use a
> combination of
> both methods. Start with the focus point in RoboFocus and then use
> either @Focus
> or FocusMax to get the fine focus.
>
> Tandy W. Carter Jr.