Varrow Cinder 90 refractor, tube only

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. This is the optical tube on its own, so you need to supply a mount that can carry its weight steadily. Buying the tube alone makes sense if you already own a suitable mount or plan to choose one separately. Matte black paint gives the telescope a low-key look, although a dark tube is harder to find on a moonless night.

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 Cinder line, the earliest version that is still listed in the catalog. 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
• 6 mm planetary eyepiece (1.25 in)
• Four color filters (1.25 in)

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.