The mirror was a front-surface aluminised mirror taken from a broken SLR camera. I used it successfully for a while until it was replaced with the multi-purpose unit described later. This accessory was made to hold filters for visual use. The filters are well protected inside the slide box from finger marks, scratches, dewing etc. Faint planetary nebulae are now a cinch to spot in a complex star background.
Filters can be 'stacked' - a combination of filters can be used together.
This prototype proved the value of the idea, and again, it's functionality was incorporated into the combined unit described later on. Combined sliding filter carrier and slide prism. This device combines the functionality of both prototypes described above. The rods on the prototype would tend to move of their own volition when the telescope was pointed at certain angles. A prism was used instead of the front-surface mirror.