The Mistral is a 25cm Schmidt-Cassegrain of a very high quality.
The optical design was made by Rik ter Horst of the former Opticon company. Rik already constructed various Schmidt Cassegrains. All of the highest optical quality. Good optical quality can only perform at its best with perfect
mechanical quality. This resulted in the cooperation with ASH.
The optical tube assembly of the Mistral is made from Phenolic resin which is very stiff and light. The focal adjustment of the mirror is done from the side with a very ingenious construction. This adjustment can be done in a very precise way and completely without shifting or tilting the mirror (many commercially available instruments of this type suffer from this).
The built-in fan allows for an internal airflow that exits the telescope from the central baffle. For that time (1992) this construction was very revolutionary.
The dew cap can be retracted for easy transport.
At the end of the telescope various accessories can be connected with a specially developed, parforcal, quick change, ring dovetail system (same as with the 127mm APO). This allows for a very tight, tilt-free connection of accessories. Various accessories for astrophotography were developed for this system.
The telescope has (of course) been fully baffled.
Because Phenolic resin has a relatively high thermal expansion coefficient, three invar rods have been constructed inside the optical tube assembly. These rods keep the optical components in place under every circumstance. This is one of the reasons the Mistral is one of the best Schmidt-Cassegrains ever built.