Tessaro Lumen 203 Schmidt-Cassegrain, tube with equatorial mount

Specifications

Description

The Lumen 203 is an 8-inch Schmidt-Cassegrain telescope with a 203 mm aperture and a 2,032 mm focal length, at f/10. The folded light path puts that long focal length into a tube about 43 cm long, so you get the aperture of an 8-inch reflector in a package that fits on a medium mount.

A thin Schmidt corrector plate at the front seals the tube and holds the secondary mirror. Because the tube is closed, dust and air currents stay out, and the optics stay clean for years. Collimation is done with three screws on the secondary mirror holder and rarely needs adjustment after transport.

The long focal length suits the planets, the Moon, and small deep-sky objects. With a 10 mm eyepiece the Lumen 203 reaches 203x, enough to show the polar caps of Mars near opposition and the Great Red Spot on Jupiter. Planetary nebulae such as the Ring and the Cat's Eye show color and shape, and globular clusters resolve well.

Focusing moves the primary mirror, which allows a wide range of accessories behind the telescope. A mirror lock holds the primary in place once you reach focus, which reduces image shift when you image with a camera. A focal reducer to around f/6.3 widens the field and shortens exposure times.

The tube weighs 5.7 kg, so it needs a mount rated for at least 8 kg with accessories. Allow 30 to 45 minutes of cooling on cold nights; a dew shield over the corrector plate is useful on humid evenings. The rear cell accepts both visual and imaging accessories.

About this configuration

The Tessaro Lumen 203 Schmidt-Cassegrain is offered in several configurations, and the notes below describe what this particular combination adds or changes. With the equatorial mount, slow-motion controls let you keep a planet centered at high magnification with one hand. Balancing the tube and the counterweight before each session helps the equatorial mount move smoothly in both axes. 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 Lumen 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 Lumen line.

What's in the box

• Optical tube with corrector dust cover
• Vixen-style dovetail bar
• 90-degree star diagonal (1.25 in)
• 6x30 optical finder with bracket
• Equatorial mount with steel tripod
• Counterweight and counterweight shaft
• 6 mm planetary eyepiece (1.25 in)
• Four color filters (1.25 in)

Compatibility notes

• The rear cell has a standard SCT thread for diagonals, reducers, and camera adapters.
• The Vixen-style dovetail bar fits mounts rated for at least 8 kg.
• f/6.3 reducer-correctors made for 8-inch SCTs thread onto the rear cell.