FLUOROSTAR 91 F/5.9 APO TRIPLET

The new William Optics Fluorostar FLT 91 is a three element air-spaced apochromatic refractor with a focal ratio of f/5.9 and a focal length of 540mm. Utilizing FPL-53 synthetic fluorite glass with STM coatings, this telescope provides excellent aberration correction and amazing optical performance.

The 3.3" dual speed rack & pinion focuser is smooth, stable and reliable, providing no slippage over long imaging sessions. The super smooth field rotator includes markings for every degree, and a solid thumbscrew position lock.

The CNC-machined and anodized handle bar with finder-style saddle is perfect for attaching a guide scope or other accessories. The FLT 91 also includes William Optics' innovative clear Bahtinov mask integrated into the lens cap. The Rotolock 2 inch adapter provides for a solid and efficient connection for a William Optics 2 inch diagonal, and other accessories.

William Optics uses high quality steel lens cells for their Gran Turismo and FLT triplet refractors. This is perfect for temperature compensation and will prevent pinched optics in cold weather conditions.

For best imaging results, it is recommended to pair the FLT 91 with its matching Flat6AIII 0.8x field flattener/reducer (with M92 adapter ring) or Flat68AIII 1.0x flattener.

Note: As the Flat6AIII / Flat68AIII an adjustable flattener, you must adjust the distance for your specific telescope. See the Instructions tab above.

Specifications

Included items

• Fluorostar 91
• Lens cap with Bahtinov mask
• Finder saddle handle bar
• 290 mm Vixen-style dovetail bar
• Visual extension tube
• Soft carry case

Instructions

Note: Once you have unscrewed the rear adapter to the appropriate value in the table below, the remaining backfocus distance to make up will be 55mm from the rear M48 thread.  

Distance adjustment needed for correct backfocus with Flat6AIII 0.8x reducer