ZENITHSTAR 81 WIFD F/6.9 APO DOUBLET

The William Optics Zenithstar 81 WIFD is a game-changing new two element apochromatic refractor featuring a patented internal focus design. The WIFD series has been designed from the ground up to support the latest large and heavy high-resolution cooled cameras and accessories.

The focuser movement is integrated inside the main OTA, so no external focuser drawtube is needed. This will reduce tilt caused by focuser sag and mechanical flex and lessen vignetting.

The focuser utilizes a zero image shift rack & pinion mechanism for precise adjustability of critical focus, with an external graduated display showing focus position. The lens cell is protected from the elements and is designed to not come out of alignment. The focuser is fully compatible with the ZWO EAF without the need for optional accessories.

Like the Zenithstar 81, the WIFD has a focal ratio of f/6.9 and a focal length of 559mm. Utilizing FPL-53 synthetic fluorite glass, this telescope provides excellent aberration correction. As the imaging train is connected to the rear of the solid tube, no flex will be introduced when heavy accessories are connected.

The CNC-machined and anodized handle bar with finder-style saddle is perfect for attaching a guide scope or other accessories. The Zenithstar 81 WIFD also includes William Optics' innovative clear Bahtinov mask integrated into the lens cap. The included field rotator features exceptionally smooth operation with degree markings and a locking thumbscrew to prevent accidental movement.

Available in Red or Gold.

For best imaging results, it is recommended to pair the Zenithstar 81 WIFD with its matching Flat6AIII 0.8x field flattener.

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

Specifications

Included items

• Zenithstar 81 WIFD
• Lens cap with Bahtinov mask
• Finder saddle handle bar
• Vixen-style dovetail bar
• M92 to M63 adapter
• Allen key set
• 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