Featuring 80 mm of travel, this focuser is an ultra-precise dual speed unit that is threaded for our field flatteners that have the -25 designation (SFF7-25, SFFR80-25, etc). For visual use, our precision compression ring 2” and 1.25” adapters are included. This model comes with an adapter that replaces the old rack and pinion focuser and some Crayford focusers on earlier Stellarvue's. It is designed for the telescopes that used a 90 mm OD tube (like our original Nighthawk and the 80/9D) when the focuser was attached to the tube using three side screws. Below is a picture with two of the three screws indicated by red arrows:
If your older Stellarvue has this type of attachment, this adapter will work in most cases. It may be necessary to use a small round file to get all of the holes in the tube lined up with the focuser adapter but it can be made to work. Contact us at firstname.lastname@example.org if you have any questions.