William Optics ZenithStar 110 Triplet (TMB)

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William Optics ZenithStar 110 TMB Review: Premium APO Performance

After countless nights under the stars testing various instruments, the William Optics ZenithStar 110 (ZS 110) TMB stands out as an exceptional achievement in optical engineering. This review reflects my extensive experience using this premium apochromatic refractor for both imaging and visual astronomy.

Optical System: Engineering Excellence

At the heart of the ZS 110 lies its Thomas M. Back (TMB) designed 110mm triplet lens system. The optical train features advanced STM (Super Transmission Multicoating) coatings on all surfaces, maximizing light transmission while minimizing internal reflections. These coatings, combined with the precision-engineered triplet design, deliver remarkable performance:

  • Virtually zero chromatic aberration, even on challenging targets like Vega

  • Exceptional contrast when imaging deep-sky objects

  • Crystal-clear planetary detail

  • Superior performance at high magnifications, particularly along the lunar terminator

The 770mm focal length (f/7) proves to be incredibly versatile. For astrophotography, I pair it with the William Optics AFR IV 0.8 reducer/flattener, which also features STM coatings. This combination delivers: - A perfectly flat 50mm image circle, ideal for full-frame sensors - Enhanced light transmission across the visual spectrum - Minimal vignetting - Sharp corner-to-corner performance

Build Quality: Professional-Grade Engineering

The scope's anodized aluminum construction exemplifies practical durability. Key features include: - Robust retractable dew shield with effective light-blocking properties - Precision-machined components that maintain alignment in varying conditions - Thoughtful balance points for easy mounting - Weather-resistant construction that has proven reliable in humid conditions

Crawford Focuser: Precision Control

The 2.5" dual-speed Crawford focuser deserves special attention. Its performance remains consistently excellent across various equipment loads: - Zero focus shift with imaging trains up to 4kg - Smooth, precise dual-speed control - Built-in rotator for exact framing of complex targets - Rock-solid stability during long exposure sequences

Imaging Performance

The ZS 110 truly excels in astrophotography applications. The combination of premium optics and STM coatings delivers: - Exceptional star color fidelity - High contrast in narrowband imaging, particularly in hydrogen-alpha - Clean separation of faint nebulosity - Outstanding performance on both broadband and narrowband targets

The f/7 focal ratio strikes an ideal balance for deep-sky work – fast enough for capturing faint details without requiring excessive exposure times, while maintaining optimal sampling with modern astro-cameras.

Modifications and Accessories

The telescope ships with carefully selected accessories: - High-quality 2" diagonal for visual use - V-style dovetail plate - Robust aluminum carrying case

My optimizations include: -

  • Upgrading to a Losmandy dovetail for enhanced stability -

  • Adding an Electronic Auto Focuser (EAF) with ZWO hand controller -

  • Installing a 2" spacer for optimal visual focus

Note: While the EAF addition means the scope no longer fits its original case, the precision focusing capabilities more than justify this compromise.

Value Proposition

While the ZS 110's new price positions it in the premium segment, the used market offers an attractive entry point to this level of optical excellence. The build quality, premium coatings, and included accessories justify the investment for serious observers seeking a versatile, high-performance instrument.

Considerations

Two factors to consider:

  1. The premium price point, though competitive within its class

  2. The f/7 focal ratio, while versatile, may not suit those primarily seeking ultra-wide field views of large nebulae.

Final Assessment

The William Optics ZenithStar 110 TMB represents the pinnacle of modern apochromatic refractor design. Its combination of premium STM coatings, exceptional build quality, and versatile focal ratio creates an instrument capable of delivering professional-grade results for both visual and photographic applications. Whether purchased new or pre-owned, it's an investment that continues to impress with each use, proving itself as a primary instrument worthy of years of serious astronomical pursuit.