Re: ATM Aplanetic gregorian speculation

["Jean-Marc.Becker" <Jean-Marc.Becker@wanadoo.fr>]

>
>
> The idea would be to make a Coude-like gregorian,
> but with a centrally pierced diagonal flat placed at
> the focal plane of the primary. The light would go through
> the hole in the diagonal (which size will determine the
> full-illumination FOV), go on the conventional greg.
> secondary, back to the diagonal and out of the OTA.
>
> I made some computations: in order that the
> obstruction caused by the hole to match this
> of the secondary, the constraints are relatively hard
> to satisfy. Typically, the primary and secondary
> must be very fast, for example f/2-f/2.5 for the primary.
> The total system would be fast, f/4->f/6, with an obstruction
> around 20-25%.
>
> An advantage I see regards the baffling: the pierced
> diagonal and the secondary can be enclosed as a whole in a
> tube that has only the diagonal hole and the exit
> as openings.

In french, we say: Pourquoi faire simple quand on peut faire compliqué?

Appromatively translated in:

Why t do simple when one can do complicated...

Friendly

Jean Marc