I think I know the problem. Astrometrics implemented the Position=n as an asynchronous operation. I am pretty sure MaxIm expects the wheel to return from the Position=n only when the wheel is finished changing filters, in other words synchronous.

This is a gray area. I just wrote a detailed reply to Dick and Astrometrics in which I explained why it is a gray area. In short, the FilterWheel spec was written for it to be synchronous (change a property value to change the filter). No documented way to see if it completes, it just has to complete. Yeah you can check back to see if the filter is reading the new one. Ugly. With the knowledge that synchronous ops are being phased out (for Alpaca and for them being old fashioned anyway), this is something that should be worked out between Astrometrics and Diffraction.

Iím in a hotel room on holiday, but if you want to chat about this Iíll be back next week,.