Astronomical Telescope Bahtinov Focusing Mask High Quality Aluminium

Field of View : Monocular Telescope Eyepiece diameter : Monocular Telescope Prism Description : BAK4 Water Resistance Level : IPX5 Objective Lens Diameter : Monocular Telescope Lens Coating Description : FMC Magnification : Monocular Telescope Focus Type : CENTRAL Material : Plastic Model Number : Telescope Type : Monocular Origin : Mainland China Telescope : Vision Night starscope : Monocular Telescope Binoculars : Powerful Monocular Hunting : Binoculars Telescope Camping : Camping Binoculars Monocular Telescope : Binoculars Powerful Monocular : Telescope Binoculars Telescope : Powerful Monocular Camping Telescope : Night vision Binoculars Hunting Telescope : Telescope Hunting Astronomical Telescope Bahtinov Focusing Mask High Quality Aluminium Alloy Focusing-mask with Fixed Diameter 60-80mm/80-120mm Product Parameters: Item: Telescope Bahtinov Focusing Mask Material: Aluminium Alloy CNC made Size: 60mm/80mm 60mm: Suitable caliber: 60~80 caliber telescope (fixed outer diameter 63~85mm; fixed inner diameter 77~99mm) 80mm: Suitable caliber: 85-100 caliber telescope (fixed outer diameter 83-115mm; fixed inner diameter 97-129mm) Weight: 70g Color: Black Function: D eep space photography focus Attention: There is 1-3mm error because of manual measurement. Place the Bahtinov Focus-Mask over the end of your telescope, then locate a bright star near your target, take a 3-5 second picture and view the diffraction spikes. Change your focus, take another picture and again, view your diffraction spikes. Is the center spike moving further from center? Then change the direction your focusing and try another picture. Watch the direction the