Bahtinov masks and focusing aids from Starfield and William Optics, sized from 80mm to 308mm. A focus mask turns a bright star into a diffraction pattern so you can nail critical focus by eye, then comes straight back off before you start imaging.
Goods ship factory-sealed. Sizes go by the outside diameter of your tube or dew shield — measure it, or tell us your telescope and we'll confirm the fit before you order.
