Skywatcher Coma Corrector for fast Newtonian Telescopes - 2" Connection

Skywatcher Coma Corrector for fast f/4 Newtonian Telescopes

The Skywatcher telescope coma corrector, optimized for astrophotography with the fast f/4 Quattro photo Newtonians, delivers an impressive image. You can expect pinpoint stars to the edge of the flat visual field. The magnification remains the same.

The system consists of 4 lenses with one element made of FPL51 ED glass. The back focus (working distance) is 55 mm, the image circle diameter 28 mm for APS-C format. The coma corrector has a 2" barrel. To mount your camera you need an adapter from M48x0.75 to your camera mount.

♦ Coma corrector
♦ Dust caps

Question:
How do you have to measure the working distance

Answer from Teleskop-Service:
The working distance is measured from the beginning of the connection thread on the housing of the corrector (see example picture):