Re: ATM Re: ATM Cassegrainian coudé: weird image at focal plane

[Bernard Maugoust <maugoust@free.fr>]

In message <200305232250.PAA06493@clulw009.amd.com>, 
 "Dwight K. Elvey" <dwightk.elvey@amd.com> wrote:
 
> Hi Bernard
>  One thing you can try, take one of those mini-maglight type
> flashlights. Remove the reflector so it is just the bulb.
> Put this light where you think the focal point should be.
> Work in a darkened room so you can see the beam on a wall,
> about 10 or so feet away. You should see two spots on the
> wall, one is from the light that passes by your secondary
> because you don't have the baffle on it yet. The other would
> be the beam from the primary. You should be able to move
> the flashlight bulb so that the diameter of the beam from the
> primary matches the diameter of the primary. This will be
> the correct focal point for your system.
>  Looking at it this way, you can also determine the effects
> of the placement of your tertiary mirror, secondary baffling
> and such.

Thanks for this Dwight, your suggestion is worth a try too. The telescope is
currently being re-assembled. I'll let you know how I get on, but don't hold
your breath, I'm rather slow ;-)

Bernard

-- 
Bernard Maugoust 3°59'E 44°28'N