Aurel Alder 72 achromatic refractor, tube with GoTo mount

Specifications

Description

The Alder 72 is an achromatic refractor with 72 mm of clear aperture and 504 mm of focal length, which gives a focal ratio of f/7. At that ratio the telescope produces a wide field with low-power eyepieces, and it still offers enough magnification for lunar craters and the disks of Mars and Jupiter. The objective is a two-element cemented achromat that brings red and green light to a shared focus. Bright objects such as Venus and the lunar limb may show a faint violet fringe, a common trait of achromats at this focal ratio. Keeping a bright planet near the center of the field reduces the fringe and sharpens the view.

The optical tube is made of aluminum and has an internal baffle near the objective, along with a retractable dew shield that limits stray light from nearby streetlights. The 1.25 in rack-and-pinion focuser moves smoothly under a light eyepiece and star diagonal, but it has no dual-speed fine adjustment, so planetary focusing depends on careful hand control. A 6x30 finderscope on a bracket lets you locate targets before you move to the main eyepiece. The tube accepts 1.25 in eyepieces directly, and the dew shield slides back for storage.

At 1.4 kg for the tube, the Alder 72 sits well on a small alt-azimuth mount or a lightweight tripod, and it packs into a soft case for transport. Small refractors reach the outdoor temperature quickly, so you can start observing soon after you set up. Typical targets include the Moon, the phases of Venus, the double star Albireo, and the Pleiades, which fill a wide field with a 32 mm eyepiece. Under suburban skies, the telescope also shows the brighter open clusters and larger diffuse nebulae. Faint galaxies and small planetary nebulae need more light than 72 mm collects, so you will see more structure in them through larger apertures.

About this configuration

Every configuration of the Aurel Alder 72 achromatic refractor shares the same optics; the choices below change how the telescope is mounted, finished, and equipped. Motorized tracking on the GoTo mount keeps objects in view, which helps when several people take turns at the eyepiece. The GoTo mount needs a 12 V power source, so plan for a power pack when you observe away from a mains outlet. The matte white coating resists fingerprints and smudges better than a gloss surface does.

No accessory kit is included, which suits observers who already own eyepieces and want to reuse them. This is the 2025 edition, which updated the knobs and clamps so you can operate them with gloves on cold nights. If you plan to add accessories later, compare the compatibility notes with the parts you already own before choosing a configuration.

What's in the box

• Optical tube with retractable dew shield
• Dovetail mounting bar
• 1.25 in star diagonal
• 6x30 finderscope with bracket
• Front and rear dust caps
• GoTo mount with steel tripod
• Hand controller and 12 V power cable

Compatibility notes

• Accepts 1.25 in eyepieces directly through the focuser.
• The dovetail bar fits common Vixen-style mounts.
• The focuser has a T-thread at the drawtube end for camera adapters once the diagonal is removed.