Astromania Bahtinov Mask Focusing Mask for Telescopes - FM80mm for a Tube Outer Diameter (OD) from 85mm-120mm - can be Mounted with The Brass Screws Inside or Outside The drawtube

Features

• Bahtinov masks take the guesswork out of focusing and even get over the seeing conditions as it is a mathematical type approach to the task; the best focus for your telescope quickly and easily
• Suitable for use on all types of telescope; they are made from precision laser cut enforced plexiglass that is stiff and long lasting; they will never be brittle in the cold; unlike some other masks which are made from normal plastics
• The masks grip the telescope tube gently but firmly with three metal posts which have non-scratching silicon sleeves to protect valued telescope surface; mask remains centered since 3-post mounting; while fitting a wider range of telescopes
• Made from 2mm thick laser cut plexiglass and securing screws are capped with soft plastic so that do not damage telescope; They have adjustment latitude of about 85-120mm that adjustable to fit optical tubes unlike masks which only fit one telescope
• Please be assured these focusing masks will work excellently for both reflectors and refractors with whatever focal length; all you need to do is to measure telescope tube size and choose right size of mask contact us if not sure where to measure