Starfield Bahtinov Focus Mask (180mm)

This Bahtinov Focus Mask from Starfield provides an easy way to focus on the deep sky. Simply place it over the aperture of your telescope and focus on a bright star in the dark sky. When the image your camera captures shows even diffraction spikes with a neatly bisected X, the deep-sky objects in your view are in perfect focus. This mask fits tubes or dew shields with an outside diameter of 185-210mm.