A couple of quick, easy and basically free methods of gaining finer control of your focuser along with how I made my DIY Dual Speed Focuser (3.75 to 1 ratio).

The 60/20 pulley wheels & belt cost less than £8 (3:1 ratio).
A pack of 5 x 16 teeth pulley wheels were about the same.
Bracketry, nuts & bolts I consider free as I hoard these things.

Chapters :
00:00 Intro
00:35 Dual Speed Focusers
01:09 The Larger Wheel Method & Alternative
02:04 DIY Dual Speed System

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