The SkyWatcher Evoguide 50ED is a compact guide scope that can be attached to the quick release finder scope bracket of the majority of telescopes. The objective lens has a diameter of 50mm, which is all you need for guiding with the majority of astrophotography set-ups.
Unlike all the other guide scopes, the Evoguide 50ED features a doublet with an extra low dispersion lens that provides "tighter" stars for a better guiding. The ED lens reduces the chromatic aberration and therefore the apparent size of the stars.
It is compatible with 31.8mm eyepieces and cameras and the rings allow for a quick alignment to the main telescope.
The helical focuser rotates with the focuser; the focusing procedure with a guiding camera is generally done one time only. Then it can be locked and the focusing distance is maintained for all times.