Qualifies for Free Ground Economy Shipping (CONUS Only)
The 30th Anniversary Difference
The first 30 units feature exclusive commemorative details:
-
Individual Numbering: Each unit is serialized (1–30).
-
Founder’s Signature: Personally hand-signed by William Yang on the lens cover.
-
Limited Engraving: A unique laser-engraved emblem of a cat embracing the number “30.”
-
Anniversary Certificate: Included with every limited edition set.
Technical Highlights
The Ultra-Cat 131 is William Optics most advanced astrograph to date, featuring a massive 60mm image circle to support medium-format and full-frame sensors:
-
Optics: 5-Element Advanced Petzval (Super ED & Lanthanum glass).
-
Aperture: 131mm | Focal Ratio: $f/4.9 | Focal Length: 648mm.
-
Focuser: Patented WIFD (Internal Focuser) to eliminate vignetting and tilt.
-
Included: Sensor Tilt Xterminator, Rotator, and built-in Bahtinov Mask.
Spot Diagram
Longitudinal Aberration
Specifications
|
Lens Type
|
5 Elements Advanced Petzval Design |
|
Focal Length
|
648 mm |
|
Diameter
|
131 mm |
|
Focal Ratio
|
f/4.9 |
|
Image Circle
|
60 mm |
|
Focuser
|
WIFD R&P Focuser
|
|
Focuser Travel Length
|
0-20 mm |
|
Adapter Included
|
Sensor Tilt Xterminator
Rotator
M79 → M68 Adapter
M79 → M54 Adapter
M79 → M48 Adapter
|
|
Optional Flattener
|
No Flattener Required
|
|
Camera Format
|
Medium Format
Full Frame
APS-C
M4/3
|
|
OTA Weight
|
9.95 kg / 21.94 lbs |
|
Tube Length
|
650 mm - 785.5 mm |
Back Spacing Range on Petzval Systems
Size Diagram
Parts
