William Optics Super ZenithStar 73 AP 73/430 Red OTA

Description

Eliminating chromatic optical aberration while maintaining a lightweight field setup, the William Optics Super ZenithStar 73 AP 73/430 Red OTA is an extra-low dispersion doublet refractor optical tube assembly built for mobile astrophotography. Operating at an f/5.9 optical speed with a 430mm focal length, this 73mm (2.87 in) clear aperture instrument delivers a 1.59 arcseconds theoretical resolving power and reaches magnitude 12.0, gathering light for high-contrast lunar observing, wide-field deep-sky scanning, and daylight spotting.

The optical system features an air-spaced extra-low dispersion doublet objective combining Ohara FPL-53 Super ED glass with a matched lanthanum element, treated with fully multi-coated STM broad-band anti-reflection coatings with an unobstructed 0% central profile. Built inside an aluminum chassis measuring 315mm retracted and 375mm extended with a 92mm outer dew shield diameter, the tube assembly supplies 140mm of back focus from the rear visual back (55mm standard from M48 threads on optional Flat73A or Flat73R correctors). Supported by a 2.5-inch dual-speed rack-and-pinion focuser with a 1:10 reduction drive, an integrated 360-degree field rotator, and red anodized accents, this 2.50 kg (5.51 lbs) refractor illuminates a 44mm full-frame image circle when paired with dedicated correctors.

Key Features of William Optics Super ZenithStar 73 AP 73/430 Red OTA

Designed for traveling imagers seeking high color correction on portable tracking mounts, this 73mm doublet couples Ohara FPL-53 optics with a 2.5-inch rack-and-pinion focuser. CNC-machined split tube rings, a reversible Vixen and Arca-Swiss dovetail bar, a red top saddle handle with an integrated guiding slot, and an integrated Bahtinov mask cap deliver dependable field performance.

• 73mm (2.87 in) clear aperture with 430mm focal length and fast f/5.9 optical speed
• Air-spaced ED doublet objective featuring Ohara FPL-53 and lanthanum glass elements
• Fully multi-coated STM broadband anti-reflection coatings with 0% central obstruction
• 2.5-inch dual-speed rack-and-pinion focuser 1:10 with red accents and 360-degree field rotator
• Generous 140mm back focus distance from visual back (55mm from M48 thread on Flat73A/R)
• Corrected 44mm full-frame image circle when paired with dedicated Flat73A or Flat73R optics
• Reversible Vixen/Arca-Swiss dovetail bar with CNC tube rings and red top saddle handle
• Patented clear Bahtinov focus mask cap and top saddle handle with guiding slot included

STM Broadband Optical Coatings & Wavefront Transmission

The combination of Ohara FPL-53 glass and high-index lanthanum elements suppresses secondary spectrum chromatic aberration across visible wavelengths. The STM broadband multi-coatings maximize light transmission across an unobstructed 73mm clear aperture, supporting practical visual magnifications from 10.4x up to 146x.

Integrated 360-Degree Camera Framing & Saddle Handle

Focusing precision is delivered through a 2.5-inch rack-and-pinion focuser featuring a 1:10 micro-reduction gear, an integrated 360-degree camera field rotator, and an engraved millimeter focus scale. The red CNC saddle handle accommodates guide scopes and accessories, while the reversible dovetail bar secures the 2.50 kg assembly onto tracker saddles.

• 2.5-inch dual-speed rack-and-pinion focuser with 1:10 micro-reduction to eliminate drawtube flexure
• Built-in 360-degree camera field rotator for rapid target orientation without losing focus
• Patented clear Bahtinov focus mask integrated into the metal lens cap for precise focus acquisition

ZenithStar 73 Red Edition Warranty Coverage

The William Optics Super ZenithStar 73 AP 73/430 Red OTA is backed by a 2-year limited warranty against material and manufacturing defects. The complete factory package contains the ZenithStar 73 Red OTA, integrated patented Bahtinov focus mask cap, CNC tube rings, dual-sided dovetail bar, and a top saddle handle with guiding slot.