SharpStar 13028HNT-AL 130mm f/2.8 Hyperbolic Newtonian Astrograph

A 130mm f/2.8 Hyperbolic System with 96% Reflectivity

At the core of the 13028HNT-AL is a fast, light-gathering optical system designed for deep-sky imaging. The 130mm hyperbolic primary mirror is made from low-expansion PZ33 glass to maintain focus during temperature shifts. Unlike a standard parabolic Newtonian that requires a separate coma corrector, this design integrates a two-element corrector into the focuser assembly to deliver sharp stars across the entire 44mm image circle.

• Enhanced Coatings: Both the primary and 65mm secondary mirrors feature an enhanced aluminum coating, ensuring reflectivity greater than 96% for brighter images and a better signal-to-noise ratio.
• ED Glass Corrector: The corrector assembly includes one ED (Extra-low Dispersion) glass element to suppress chromatic aberration, ensuring star colors are rendered accurately without distracting halos.
• PZ33 Primary Mirror: The Pyrex-like PZ33 mirror material minimizes thermal expansion and contraction, helping the telescope hold focus as ambient temperatures change during an imaging session.

44mm Corrected Image Circle for 6.9° Full-Frame Views

The SharpStar 13028HNT-AL is engineered to fully illuminate a 44mm image circle, making it an ideal match for full-frame DSLR, mirrorless, and dedicated astronomy cameras. SharpStar sizes the 65mm secondary mirror to give sufficient illumination for full-frame imaging. This expansive 6.9-degree field of view lets you frame enormous targets like the Andromeda Galaxy (M31) or the entire North American Nebula (NGC 7000) in a single shot.

A 4.8kg All-Metal, CNC-Machined Astrograph

An astrograph's mechanical stability is just as critical as its optical design. The 13028HNT-AL is built from all-metal components, featuring a rigid aluminum main tube and CNC-machined parts for the focuser, secondary bracket, and mirror cell. This construction ensures precise, repeatable collimation and minimizes mechanical flexure, even with a heavy imaging payload weighing up to 3kg.

• Stable Secondary Bracket: The integrated, CNC-machined secondary mirror bracket is designed for rigidity, which not only holds collimation but also produces clean, sharp diffraction spikes on bright stars.
• 3-Point Primary Cell: The primary mirror cell features three sets of locking and adjustment screws for precise collimation, ensuring you can align the optical system for peak performance.
• Lightweight Build: The optical tube alone weighs just 3.8kg, and the included hollow-design tube rings help keep the total assembled weight to a portable 4.8kg.

3kg Capacity Focuser with 360° Rotator and 55mm Back Focus

The imaging train is managed by a heavy-duty, dual-speed rack-and-pinion focuser designed to carry a payload of up to 3kg. This robust focuser can easily support a full-frame camera, filter wheel, and off-axis guider without slipping or tilting. An integrated 360° camera rotator allows you to frame your target perfectly without loosening any other components, while the standard 55mm back focus from the M48x0.75 thread simplifies connecting your camera using standard spacers.

Mounting Hardware: 290mm Vixen Plate, Rings, and Handle

The 13028HNT-AL includes a complete set of mounting hardware to get you started right out of the box. The package contains a set of sturdy, hollow-design tube rings, whose enlarged hand screws open and close without tools, and a 290mm Vixen-style dovetail plate for the many equatorial mounts with a Vixen-style saddle. A handle bar is also included, and a finder base on the side of the tube provides additional mounting positions for a finder scope or other astronomical accessories.

Collimation System: A User-Adjustable Design with Included Tools

The astrograph is collimated and fixed at the factory, but transport knocks or cleaning can shift the optical axis, so there is a procedure for users to realign it themselves. The box includes the collimating adapter, collimating eyepiece, 1.25" adapter, locking ring removal tool and T8 Torx wrench; the mirror adjustment and locking screws take 3mm and 4mm Allen wrenches, which are not in the box list. The secondary mirror sits in a rigid, integrated CNC-machined holder whose angle and height are locked before shipping, so only its tilt needs adjusting, while the primary mirror has three sets of adjustment and locking screws. The corrector comes out of the focuser before collimation, and a final star test with the corrector refitted confirms the result, so you can reach the telescope's theoretical 0.89 arc second resolution.

SharpStar 13028HNT-AL vs. 130mm APO Refractors: The f/2.8 Advantage

While a 130mm apochromatic refractor offers a maintenance-free, sealed optical tube, the SharpStar 13028HNT-AL provides a decisive advantage in speed and field of view. A typical 130mm APO has a focal ratio around f/7, whereas the 13028HNT-AL operates at a native f/2.8.

• Exposure Time: The f/2.8 system gathers light over six times faster than an f/7 system. A 1-minute exposure on the 13028HNT-AL collects the same amount of signal as a 6-minute exposure on the refractor, allowing you to complete projects in a fraction of the time.
• Field of View: With its 364mm focal length, the 13028HNT-AL delivers a much wider field of view than a 130mm refractor, which typically has a focal length over 900mm.
• The Trade-off: The Newtonian design requires periodic collimation to maintain peak optical alignment, a step not needed with a refractor. However, for imagers prioritizing speed and field of view, this is a manageable trade-off for the dramatic reduction in exposure time.