Corvane Talus 70 refractor, tube with alt-az mount

Specifications

Description

The Talus 70 is a small achromatic refractor intended as a first telescope. Its 70 mm objective has a focal length of 700 mm, which gives a focal ratio of f/10. That slow ratio keeps the color fringe of a simple doublet low, so the Moon and bright planets look clean at the magnifications this aperture supports.

A refractor needs no collimation, so the Talus 70 is ready to use as soon as you take it outside. The sealed tube keeps dust off the optics, and the lens cools to the outdoor temperature within a few minutes. The 1.25 in rack-and-pinion focuser is simple and smooth enough for the 25 mm and 10 mm eyepieces that most beginners start with.

Through a 70 mm telescope you can see the craters and mountain ranges of the Moon, the phases of Venus, the four bright moons of Jupiter and its two main cloud belts, and the rings of Saturn. Bright star clusters such as the Pleiades and the Beehive look good at low power, and the Orion Nebula shows its brighter core on winter evenings.

The tube weighs 1.9 kg, so a light photo tripod with a sturdy head can carry it for low-power views, while the alt-az bundle gives smoother motion at higher magnification. The focal length also makes the Talus 70 useful during the day for distant landscapes when you add a correct-image diagonal.

The useful magnification limit for 70 mm of aperture is around 140x on a steady night. In practice, most views look best between 30x and 100x. A Barlow lens doubles the magnification of each eyepiece and gives you more steps in that range without extra eyepieces.

About this configuration

The Corvane Talus 70 refractor is offered in several configurations, and the notes below describe what this particular combination adds or changes. 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. This is the 2023 edition of the Talus 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 Talus line.

What's in the box

• Optical tube with dew shield
• Mounting bracket with 1/4-20 thread and Vixen-style foot
• 90-degree star diagonal (1.25 in)
• Red-dot finder
• Dust caps
• Alt-az mount with aluminum tripod
• T-ring and T-adapter
• Bahtinov focusing mask

Compatibility notes

• Accepts standard 1.25 in eyepieces and filters.
• The mounting foot fits photo tripods with a 1/4-20 thread and Vixen-style saddles.
• Prime-focus imaging needs a 1.25 in T-adapter and a T-ring for your camera.