William Optics 172-235mm Bahtinov Focus Mask

William Optics 172-235mm Bahtinov Focus Mask: Focus Without Guessing

The William Optics Bahtinov mask makes focusing on a star measurable. You place the mask in front of your telescope's aperture and point it at a bright star: the pattern will draw three spikes of light in your image. If the middle spike is exactly between the other two, the focus is perfect. No more guesswork, even with a camera.

This mask is cut from optical acrylic glass with 92% light transmission, and its design provides approximately three times as much curvature as traditional metal masks: the spikes are brighter and can therefore be used even on fainter stars. This size fits 6- to 8-inch Newtons and Schmidt-Cassegrains.

Features

• Fits pipe diameters of 172-235 mm thanks to adjustable mounting pins
• Optical acrylic glass with 92% light transmission
• About three times brighter diffraction pattern than metal masks
• Indispensable for sharp astrophotos, also visually useful

Compatibility

Measure the outer diameter of your tube or dew shield: it must be between 172-235 mm. Other versions in the series are available for different sizes.

Specifications

You can find more accessories for this merk at the William Optics merk Page.