William Optics Fluorostar 91/540 Refractor APO Space Gray OTA

The compact Fluorostar: triplet quality in travel size

The William Optics Fluorostar 91 Space Gray brings the Fluorostar triplet line to a compact, portable size. The triplet of FPL-53 and lanthanum glass shows stars as true points with pure colors: double stars clearly separated and fine details on Jupiter and Saturn.

Lots of light, large field of view

The 91mm aperture at a 540mm focal length (f/5.9) combines light-gathering power with a generous field of view, suitable for both bright deep-sky images and high-contrast planetary observations. The 1:10 rack-and-pinion focuser achieves micron-level sharpness and can support a full camera rig. The retractable dew shield helps keep the lens clear for longer, and the deluxe carrying case offers protection during transport.

In the box

• Optical tube Fluorostar 91/540 triplet, Space Gray
• Retractable lens hood
• 1:10 rack-and-pinion focuser
• Losmandy dovetail
• Handle
• Bahtinov mask
• Luxury transport bag

Featured accessories

The William Optics FLT91 Flat6A III Special Edition (429 euros) is the exact matching flattener-reducer for this tube; the UniGuide 32 mm guidescope (159 euros) enables guided imaging.

For whom yes, for whom no

For: astrophotographers who want Fluorostar triplet quality in a travel-friendly, light-mount-compatible package. Not for: those seeking maximum aperture for a fixed setup; the Fluorostar 120 or 132 will provide more light and resolution.

Specifications

Unsure about the right tube for your camera and mount? The telescope selection aid helps you choose. Also view all Refracting telescopes and the full range of William Optics.