William Optics Fluorostar 156
- 156mm Aperture Triplet Apochromat
- 1217mm Focal Length (f/7.8)
- FPL-53 & Lanthanum Glass Elements
- 3.7" Rack & Pinion Focuser
- Thermally Stable Steel Objective Cell
- Integrated Bahtinov Mask in Dust Cover
The William Optics Fluorostar 156 combines a large 156mm aperture with a 1217mm (f/7.8) focal length in a precision-engineered, air-spaced triplet optical system. Featuring premium FPL-53 glass and a Lanthanum element, this apochromatic refractor suppresses false color to undetectable levels, supported by a massive 3.7" Rack & Pinion focuser for precise, no-slip focusing with heavy imaging payloads.
At the heart of the Fluorostar 156 lies an air-spaced triplet objective that sets the standard for color correction and contrast. By combining a key element of FPL-53 glass with another of Lanthanum, the optical design brings all wavelengths of visible light to a single, sharp focal point. This eliminates the distracting purple fringing seen on bright stars in lesser instruments, delivering crisp, high-contrast views of planetary details and pinpoint stars across the entire field for astrophotography.
A large 156mm objective lens is susceptible to subtle shifts as ambient temperature drops, which can degrade image sharpness. William Optics addresses this with a robust steel objective cell that mitigates thermal expansion and contraction. This ensures the triplet lens elements remain in perfect alignment throughout a long imaging session, preserving the exquisite optical correction from dusk until dawn.
The Fluorostar 156 is built from the ground up for serious astrophotography. The heavy-duty 3.7" rack and pinion focuser provides a rigid, stable platform for large cameras and filter wheels, eliminating flexure and focus shift. For achieving perfect focus, the lens cap features an integrated Bahtinov mask—a critical tool for hitting sharp focus in seconds. The entire optical tube is secured by three CNC-machined rings and a standard Losmandy-style dovetail plate, creating a solid foundation for any capable equatorial mount.
Due to its aperture and focal length, the Fluorostar 156 is a substantial instrument. A robust equatorial mount with a payload capacity of at least 50-60 lbs (22-27 kg) or more is strongly recommended for stable imaging and visual use. Mounts in the Celestron CGX, Losmandy G11, or Software Bisque Paramount MYT class are appropriate.
This combination of exotic glass types provides exceptional apochromatic performance. For astrophotography, this means:
The Bahtinov mask, integrated directly into the dust cover, is a significant convenience for astrophotographers. It creates a distinctive diffraction pattern around a bright star that instantly shows you when you have achieved perfect focus. This eliminates the guesswork of trying to find the point of sharpest focus by eye, saving valuable imaging time and ensuring your data is critically sharp every time.
Absolutely. While optimized for imaging, the Fluorostar 156 is a superb visual instrument. Its 156mm aperture provides brilliant, high-resolution views of the Moon, planets, and deep-sky objects. The apochromatic optics deliver a pure, high-contrast image that is free of false color, making it ideal for discerning subtle cloud bands on Jupiter or resolving tight double stars.
The Fluorostar 156's combination of 156mm aperture and high-contrast optics makes it an exceptional tool for M42. Visually, you can expect to resolve the E and F stars in the Trapezium cluster under good seeing conditions. For imaging, the 1217mm focal length perfectly frames the nebula's core while the sharp optics will capture the faint, intricate structures of the surrounding nebulosity with stunning clarity.
Yes, the 1217mm focal length is an excellent match for medium-to-small deep-sky objects like M51, the Hercules Cluster (M13), or the Ring Nebula (M57). It provides enough image scale to resolve spiral arms, dust lanes, and individual stars in globular clusters, especially when paired with a modern astronomy camera with small pixels.
| Aperture | 156mm |
| Focal Length | 1217mm |
| Focal Ratio | f/7.8 |
| Optical Design | Air-Spaced Triplet Apochromat |
| Glass Composition | FPL-53 & Lanthanum Elements |
| Focuser | 3.7" Rack & Pinion |
| Objective Cell Construction | Steel |
| Available Accent Colors | Red, Gold, Space Grey |
Fluorostar 156 OTA
× 1
3.7" Rack & Pinion Focuser
× 1
Bahtinov Mask Cover
× 1
CNC Tube Rings
× 3
Losmandy-style Dovetail Plate
× 1
Soft Carry Case
× 1