More information at this Telescan tribute site.
1979: Mark 1 - 1200W HMI source, two colour wheels each containing 2 colours plus open white, iris, manual zoom & focus, mirror with 90 degrees of pan and 70 degrees of tilt. External ballast for lamp.
1986: Mark 2 - 3 colour mixing, frost filter, six position gobo wheel
1989: Added 180 degrees of pan and 90 degrees of tilt and rotating gobos.
1990: Mark 3 - Smaller unit, dichroic colour, motorised focus, 260 degrees pan, optional 'le voyage dans l'image' - glass images across the beam
1994: Mark 4 - 2500W HMI lamp. Replaced gobos with film scroller, adding moving effects. Prism effect to rotate images. 36 of these used on the 1994 Pink Floyd Division Bell tour (along with 300 Vari*Lites).
?: Mark 5 - added a second scrolling image film and wide angle lens option.
Exhibits in the Backstage Heritage Collection
Catalogue & Journal Entries for Telescan in the Backstage Heritage Collection