Barlow lens

And the Alpy 600 becomes compatible with your Digital Camera (DSLR)!

The mechanical backfocus of the Alpy 600 (distance between the Alpy 600 and your camera’s sensor) should be between 10 and 20mm. If you have a large backfocus camera (as is the case for cameras with a filter wheel), or wish to use a digital camera (DSLR), this barlow increases the backfocus distance from 44.7 to 55.2mm.

The Barlow is screwed to the rear of the ALPY 600.