Allows you to quickly attach your SLR camera to any telescope with a 2" focuser
T-2 external thread on the accessory side; safety groove to stop lens falling out
Black anodized to minimise reflections; filter thread for 2" filters
It helps you to adjust the brightness effectively; The variable polarizing filter allows for selective adjustment of brightness; which is useful for terrestrial observation and objects of the Solar System
These filters have a very large range of effectiveness; Light transmission of polarizing filters is between 1% and 40%; Such adjustable control is highly desirable for lunar observing as the Moon's brightness varies with its phase and also with the aperture and magnification of the telescope you are using; It is also a must for viewing the Moon in daylight hours