20mm f.l. diverging lens for Bath Interferometer (mounted)

Description

Focal length 20mm. Good for testing telescope mirrors down to F/8 (using cheaper laser with 1.7mm beam I sell) or down to F/5.4 (using glass laser with 2.6mm diameter beam that I sell)

Each lens is cleaned and tested to be sure it is defect free.

Mount for lens is included. Lens will arrive mounted similar to photo (the 20mm lens is actually twice the diameter as the one in the picture).