SharpStar 150mm f/2.8 HNT Hyperbolic Newtonian Astrograph

150mm f/2.8 Hyperbolic Optics: A 44mm Flat-Field System

The optical core of the 150HNT is its 150mm hyperbolic primary mirror, which achieves a native f/2.8 focal ratio. Unlike a standard parabolic mirror, a hyperbolic figure is designed to work as part of a system with a dedicated corrector, enabling superior off-axis correction across a large 44mm image circle. The primary mirror is made from PZ33, a low-expansion Pyrex-type glass that ensures thermal stability as ambient temperatures change.

Both the primary and 70mm secondary mirrors feature enhanced aluminum coatings, guaranteeing light reflectivity of over 96%. This high throughput, combined with the fast focal ratio, allows you to capture faint details with significantly shorter exposure times, maximizing the data collected during clear nights.

Integrated 3-Element Corrector for a 6° Field of View

To deliver its expansive 6-degree field of view, the 150HNT incorporates a three-element, air-spaced corrector directly into the focuser assembly. This design, which includes one ED (Extra-low Dispersion) glass element, is optimized specifically for the hyperbolic primary, eliminating coma and ensuring pinpoint stars to the edge of a full-frame sensor. By integrating the corrector, the system removes the complexity of matching a third-party coma corrector and guarantees the specified 55mm back-focus distance.

Rigid 2-Speed Focuser for Precise Control

An astrograph's focuser must be rigid enough to carry a modern imaging train without flexure. The 150HNT is equipped with a dual-speed rack-and-pinion focuser capable of supporting a 3kg payload. The focuser includes a built-in camera rotator for effortless framing and is compatible with most electronic auto-focusers.

Mechanical stability is reinforced throughout the optical tube. The CNC-machined secondary mirror support is a single, rigid piece designed to prevent misalignment and produce clean, sharp diffraction spikes. The primary mirror cell features three sets of adjustment screws for precise and stable collimation.

Astrograph-Ready Build: 6 kg Total Weight with Rings & Plate

Designed for portability and rapid deployment, the SharpStar 150HNT has a total weight of just 6kg, including its tube rings and a 200mm Losmandy-style dovetail plate. The compact 443mm tube length makes it easy to balance on a wide range of equatorial mounts. The package also includes a 200mm handle bar that adds rigidity and provides a convenient mounting point for guide scopes or other accessories via its integrated finder base.

SharpStar 15028HNT vs. Standard 6" f/4 Newtonians: Speed and Correction

While a standard 6" f/4 Newtonian is a capable imaging instrument, the SharpStar 150HNT is purpose-built for a higher tier of astrophotography. The primary differences lie in optical speed and field correction.

• Exposure Time: At f/2.8, the 150HNT gathers light approximately twice as fast as an f/4 system. This means a 5-minute exposure on the 150HNT collects the same signal as a 10-minute exposure on an f/4 scope, effectively doubling your imaging efficiency.
• Integrated Correction: The 150HNT's hyperbolic mirror and built-in corrector are designed as a single optical system to produce a flat 44mm field. A standard f/4 Newtonian requires a separate, often generic, coma corrector that may not fully correct the field or illuminate a full-frame sensor without vignetting.
• Optical Design: The hyperbolic design allows for sharper stars at the edge of the field compared to what a standard parabolic mirror and separate corrector can typically achieve, especially on large sensors.