William Optics Fluorostar 156

A 156mm f/7.8 Triplet with FPL-53 and Lanthanum

The Fluorostar 156 delivers crisp, color-corrected visuals thanks to its triplet lens system incorporating FPL-53 glass and a lanthanum element.

• 156mm aperture: a Dawes limit of about 0.74 arcseconds, and about 1.4 times the light of a 132mm objective.
• 1217mm focal length: full frame covers about 1.7 x 1.1 degrees, and APS-C (about 23.5 x 15.6mm) about 1.1 x 0.7 degrees, a scale for galaxies, globular clusters and planetary nebulae.

Steel Objective Cell

The sturdy steel objective cell mitigates thermal expansion and maintains alignment under varying temperatures.

3.7-inch Rack-and-Pinion Focuser

William Optics fits a 3.7-inch rack-and-pinion focuser for seamless, precise focusing adjustments. It does not publish payload or travel figures, so we do not.

Image Circle and Flatteners

Our specification gives an image circle greater than 44mm, which would cover a full-frame sensor (43.3mm diagonal). That figure and the flatteners in our table come from dealer listings rather than William Optics' own page, so ask us to confirm the flattener and back focus for your camera before ordering.

Bahtinov Mask, Three Tube Rings and Losmandy Bar

The Fluorostar 156 comes standard with a Bahtinov mask integrated into the dust cover, three anodized CNC-made tube rings and a Losmandy-type dovetail bar. The white tube carries red, gold or space grey accents.

To focus with the mask, fit the dust cover, aim at a bright star and adjust focus until the central spike is centred between the other two.

Visual Use and Solar Safety

Avid stargazers are among its intended users. At 1217mm, a 25mm eyepiece gives about 49x and a 7mm about 174x; how much detail you see on planets depends on the seeing.

Never aim the telescope or finder at the Sun without proper solar filters installed on the front of the telescope; doing so for even a moment may permanently damage your vision. Solar eyepiece filters are not considered safe.