Re: [APML] Precise alignment of a 500 mm lens and a guidescope

[Emmanuele Sordini <vega@bloomingstars.com>]

>At 15.22 03/02/2003 -0500, you wrote:
>Emmanuele,
>
>You'll want to be able to adjust the aim of the guide scope by at least a
>degree away from the center of the camera's FOV.  This will enable you to
>both compose your picture and choose a good guide star.  If desired, you
>can easily align the two instruments in the field by centering the lens on
>a bright star, then adjusting the guide scope to be centered on the same
>star.

Yes, but that should be done at every outing, shouldn't it? What a bore! :-((
At first I wanted to get an adapter to attach an eyepiece to the lens, then 
I realized that lack of back focus is too much of an issue; anyway, I think 
that a Nikon F3+Nikon F3 should make do, shouldn't they?


>I prefer the over/under configuration for guiding.  Although it may also
>provide less opportunity for flexure, the main benefit (over side by side)
>is that it is much easier to balance in DEC.  See photo here:
>http://starmatt.com/gallery/equipment/130.html

Yes, but that way the platform was perhaps a little too complicate to 
build. The concept is very primitive: just bolt the 500mm lens in place, 
and adjust the guiding "scope" by fiddling with its 3/8" screw. Think it's 
too inaccurate?


>Does the guide scope have a movable primary (for focus)?  Do you have a
>reliable mirror lockdown?  If not, it may not be a good choice for a guide
>scope.

No, it's a mirror Mak-Cass lens used as a scope: so, you focus it by simply 
turning the front part of the lens. Luckily, it provides enough back-focus 
for a diagonal+eyepiece to be added.

Emmanuele

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