HAMO Bahtinov Focusing Mask for Telescopes Dew Shield Diameter From 95mm -140mm (3.74inch - 5.50inch) - For 100mm,120mm Skywatcher Refractors, Celestron 4 SE Etc

Description

Colour Name:100mm About Bahtinov mask The Bahtinov mask is a device used to focus small astronomical telescopes accurately. It was invented by Russian amateur astrophotographer Pavel Bahtinov in 2008. Accurate focusing of telescopes and astrographs is particularly of concern to those involved in astrophotography. The telescope is pointed at a bright star, and a mask is placed in front of the telescope's objective (e.g. primary mirror). How does it work? Set up your telescope and imaging equipment as normal. Then simply locate a bright star (maybe Spica?) with your telescope, attach the Bahtinov mask to your telescope and watch the diffraction spike pattern around the star as you adjust the focus. When the middle diffraction spike is centered in the outer spikes, you're in focus. Very little focusing travel is required to move the inner diffraction spike, which means the focus is extremely accurate. Program type Suitable for telescopes Dew Shield or Front Outer Diameter From 95mm -140mm (3.74inch - 5.50inch) - For 100mm,120mm Skywatcher Refractors, Celestron 4 SE Etc. Package Include: Bahtinov Mask 3 X Brass bolt