Tessaro Granite 125 ED refractor, tube with GoTo mount

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

Every configuration of the Tessaro Granite 125 ED refractor shares the same optics; the choices below change how the telescope is mounted, finished, and equipped. The GoTo mount finds objects from its database after a short alignment on two or three bright stars. Motorized tracking on the GoTo mount keeps objects in view, which helps when several people take turns at the eyepiece. The carbon fiber tube expands less as the temperature drops, so the focus point drifts less as the night cools.

The starter kit adds two eyepieces and a Barlow lens, which gives you four magnifications from three pieces. The 2023 edition uses the same optical design as later years, with small differences in fittings and labels. The optical figures in the specifications table apply to this configuration and to every other version of the Tessaro Granite 125 ED refractor.

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
• GoTo mount with steel tripod
• Hand controller and 12 V power cable
• 25 mm and 10 mm eyepieces (1.25 in)
• 2x Barlow lens (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.