Varrow Cinder 90 refractor, tube with alt-az mount

Specifications

Description

The Cinder 90 is an achromatic doublet refractor with 90 mm of clear aperture and 630 mm of focal length, giving a focal ratio of f/7. Its objective uses two elements of crown and flint glass that bring red and blue light to a common focus. Some residual color remains, so bright planets and the Moon can show a faint violet halo along high-contrast edges, a trait typical of achromats at this focal ratio. At f/7 the instrument gives a moderately wide field at low power and still reaches useful magnification on the Moon and the planets.

The lens is multi-coated on all air surfaces and sits in a tube with internal baffles, which keeps stray light down when a bright planet sits near the edge of the field. The 1.25 in rack-and-pinion focuser holds a standard diagonal and eyepiece steadily, and the fine-focus knob makes small adjustments easier to judge when you are looking at planetary detail. A dew shield on the front of the tube helps slow dew on the objective on humid nights.

At 2.4 kg for the tube, the Cinder 90 suits a light alt-az mount or a small equatorial mount and fits in a compact case for transport. A small refractor reaches outdoor temperature faster than a reflector of similar aperture, so you can start observing soon after carrying it outside. Typical targets include double stars such as Albireo and Epsilon Lyrae, the phases of Venus, the brighter lunar craters near the terminator, and open clusters such as the Double Cluster in Perseus, which fits within one field at low power. Under dark skies you can also see the brighter galaxies and globular clusters, though their structure is subtle at this aperture.

About this configuration

This listing covers one specific configuration of the Varrow Cinder 90 refractor, defined by its bundle, finish, accessory kit, and edition year. The included alt-az mount moves up and down and side to side, so you point the telescope by hand without polar alignment. Manual alt-az motion suits visual observing, though you need to nudge the tube now and then to follow objects as the sky turns. The gloss white tube reflects sunlight, which helps it stay closer to air temperature while you set up before dusk.

With the imaging kit, a camera attaches at prime focus, so the telescope works as a long telephoto lens. The 2025 edition keeps the same optical figures as the earlier years of the Cinder line. The optical figures in the specifications table apply to this configuration and to every other version of the Varrow Cinder 90 refractor.

What's in the box

• Optical tube with dew shield
• Tube rings with dovetail bar
• 1.25 in star diagonal
• 6x30 finder scope with bracket
• Front and rear dust caps
• Alt-az mount with aluminum tripod
• T-ring and T-adapter
• Bahtinov focusing mask

Compatibility notes

• Accepts 1.25 in eyepieces and filters directly in the focuser.
• The dovetail bar fits most small and medium alt-az and equatorial mounts.
• A 1.25 in camera adapter can be fitted to the focuser after the diagonal is removed.