Re: [APML] OT: KEF Update Questions

[steve banbury <banburys@sonic.net>]

Hi Steve--faint stars didn't work well for me either. When using my C11 I try to
use a 'reasonably' bright star pretty close to the portion of the sky I plan on
shooting. I always worry the focus may shift if I focus a long way away from
where I'm going to be imaging. This hasn't been an issue on my refractor.

Chuck Vaughn has a nice article on using a KEF at:
http://www.aa6g.org/Astronomy/articles.html

The only thing I would add is that as you get close to focus, you may want to
slew the scope slightly to carefully watch that slightly curved line straighten
out perfectly just before the point of "extinction" at focus.

Happy focussing--now I know who made it rain here in California!

Steve



Steve Lindsey wrote:

> I tried out the new Mitsuboshi focuser with my SCT and after a bit of trial
> and error I think I got the idea.  Here's a couple of things I noted with
> some questions:
>
> 1. What I see is actually a donut shaped image with the enlarged star image
> on the donut and the center blackened out.  I didn't expect the star image
> to look so large but I guess it makes sense since my eye is not at the focal
> plane.  Is the donut a function of my SCT or the circular KEF construction?
>
> 2. For dim stars the image was next to non existent for seeing the KE
> pattern.  I'm assuming this was worse with my long focal length scope.  I
> ended up sticking with medium to bright stars to practice on and found that
> the image blinking out was most distinct on medium brightness stars.  Does
> this make sense?
>
> 3. And a related question...  I had some trouble centering a star so that I
> could get it in the KEF field of view to even check focus (potentially a
> slight downside of the relatively small circular FOV with this version KEF
> used with a long focal length SCT).  This proved much easier with very
> bright stars, not too hard with moderately bright stars, and impossible for
> the reason in #2 on dim stars.  I assume it's ok to just slew off the object
> to a brighter star for focusing.  Sound ok?
>
> Otherwise I think this should work out fine and the device seems very well
> built.  The optional adapter to use with a diagonal turned out to be a must
> on an SCT.  I'd have been at the chiropractor for sure today with out it!!
>
> Steve
>
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