William Optics 105-148mm Bahtinov Focus Mask

William Optics 105-148mm Bahtinov Focusing Mask: Focusing without guesswork

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 spokes are brighter and can therefore be used even for fainter stars. This size fits medium-sized refractors and small Newtonian telescopes.

Features

• Fits pipe diameters of 105-148 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 astrophotography, also visually usable

Compatibility

Measure the outer diameter of your tube or dew shield: it must be between 105-148 mm. For other sizes, there are the other versions in the series.

Specifications

You can find more accessories for this brand at the William Optics brand page.