Tessaro Granite 125 ED refractor, tube only

Specifications

Description

The Granite 125 ED is a doublet refractor with one extra-low-dispersion element in its objective. With 125 mm of aperture and 900 mm of focal length, it works at f/7.2. At low power the field is moderately wide, and at high power the instrument reaches detail on the Moon and planets with less color fringing on bright limbs than an achromatic doublet of the same size and ratio would show.

The objective is fully multi-coated. The tube has several internal baffles, and the retractable dew shield limits stray light from nearby streetlights and windows. When you observe Saturn, the rings and the division between them are visible at moderate magnification, and on the Moon the terminator stays well defined at high power.

The 2.5 in dual-speed rack-and-pinion focuser holds a star diagonal and a heavy eyepiece without slipping. The fine-focus knob gives a 10:1 reduction for planetary detail. The tube weighs 6.8 kg, so you will need a medium equatorial mount or a sturdy alt-az mount rated for the tube plus accessories. Allow the tube to reach outdoor temperature before you attempt high-power planetary work, since a larger refractor takes longer to settle than a small one.

Typical targets include double stars such as Albireo and Epsilon Lyrae, and bright open clusters such as the Pleiades, which fill a 2 in wide-field eyepiece at low power. Under dark skies, brighter planetary nebulae show clear shapes, while galaxies such as M81 and M82 appear as faint elongated patches that benefit from a dark site and a low-power eyepiece.

About this configuration

The Tessaro Granite 125 ED refractor is offered in several configurations, and the notes below describe what this particular combination adds or changes. Buying the tube alone makes sense if you already own a suitable mount or plan to choose one separately. Without a mount in the package, check the tube weight against the payload rating of your mount, with some margin to spare. Carbon fiber saves some weight compared with a metal tube, which eases the load on the mount and on your arms.

The planetary kit adds a short focal length eyepiece and a set of color filters for the Moon and the bright planets. This is the 2023 edition of the Granite line, the earliest version that is still listed in the catalog. Check the specifications table for the optical figures, since they stay the same across every configuration of the Granite line.

What's in the box

• Optical tube with retractable dew shield
• Tube rings with Vixen-style dovetail bar
• 2.5 in star diagonal
• 8x50 right-angle finder
• Front and rear dust caps
• 6 mm planetary eyepiece (1.25 in)
• Four color filters (1.25 in)

Compatibility notes

• Accepts 2.5 in eyepieces directly and 2 in or 1.25 in eyepieces through the supplied adapters.
• The Vixen-style dovetail bar fits medium equatorial and alt-az mounts rated for at least 7 kg.
• The focuser has a T2 thread for camera adapters once the 2.5 in nosepiece is removed.