When I first took delivery of the Mary Rose in March 2007, it had a Moonlite filter slide. I have found this device to be immensely useful (the alternative of changing filters manually on individual eyepieces through the evening can be a real chore). The slide has space for three 2 inch filters to be fitted at once, as well as having an open position (filterless).
The only problem I have encountered with the filter slide in the past is the tendency for it to dew up on particularly wet nights. Placed near the top of the secondary cage, the filters are unfortunately rather more exposed to the elements.
The filter slide now has heating for those wet nights. No more dewy filters. Ah, that is better!
