William Optics Bahtinov Focusing Mask 243–308 mm

William Optics Bahtinov Focusing Mask 243–308 mm

A diffraction-spike Bahtinov mask in the manufacturer's 243–308 mm fitting-diameter option.

Choosing the size

Match the mask to the outside diameter at its mounting position. The fitting range is not the telescope's optical aperture.

William Optics manufacturer specifications

Adjustment and use

The manufacturer variant image shows three mounting pins in radial slots. Set the pins to fit the front of the telescope within the stated diameter range. The diffraction pattern helps identify focus on a star: adjust the focuser until the central spike is centred between the crossing spikes, then remove the mask before recording the final images.

Compatibility notes

Fit by telescope/dew-shield outside diameter, not optical aperture. Remove before imaging.

Additional specifications