Equipment

Telescopes, binoculars, and accessories for amateur astronomy.

An Ode to Small Telescopes

April 2, 2023 by Joe Bergeron Filed Under: Astronomy Equipment

A small telescope faces the Milky Way. Image credit: Brian Ventrudo.

Sometime in 1955, Mr. David Coffeen of New Orleans, Louisiana came up with $75. In today’s currency, that’s about $700, a respectable sum. And what did Mr. Coffeen do with his hard-earned savings?

He purchased a telescope.

Which telescope? A Unitron altazimuth refractor with an aperture of just 40mm, less than that of most finder scopes today. It came with three eyepieces, a star diagonal, and a wooden storage case, because it was an honest astronomical instrument.

Mr. Coffeen used his telescope from atop his modest trailer home. There was a lot to see with that 40mm scope: loads of lunar detail, the rings of Saturn, the Galilean moons of Jupiter and a couple of belts, hundreds of double stars, many of the Messier objects, and a lot more [Read more…] about An Ode to Small Telescopes

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Maksutov-Cassegrain Telescopes

June 17, 2020 by Brian Ventrudo Filed Under: Astronomy Equipment

A Questar 3.5" Maksutov-Cassegrain telescope. — A Questar 3.5″ Maksutov-Cassegrain telescope.

Small Maksutov-Cassegrain telescopes are a godsend for urban observers who need a compact scope with good optics. And “Maks” are back in style, so there’s a good selection on the market. But Maks aren’t for everyone. Here’s how to tell if a Mak is right for you [Read more…] about Maksutov-Cassegrain Telescopes

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Refracting Telescopes for Astronomy

June 15, 2020 by Brian Ventrudo Filed Under: Astronomy Equipment

A top-quality refractor telescope (credit: Televue)

When the members of the great unwashed masses think of an astronomical telescope, they usually think of a refractor. With a large glass objective lens at the top of the tube and an eyepiece down at the bottom, refractors are the most robust and conceptually simplest type of telescope. They offer amazingly crisp views of the Moon and planets and double stars. But they are not for everyone. This short article goes through the pros and cons of refractors for astronomy and helps you decide if such a telescope is right for you [Read more…] about Refracting Telescopes for Astronomy

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Newtonian Reflectors and Dobsonian Telescopes

May 26, 2020 by Brian Ventrudo Filed Under: Astronomy Equipment

A Newtonian reflector telescope on an equatorial mount (credit: Skywatcher).

Reflecting telescopes (or reflectors) collect light using a curved mirror at the rear of the main tube rather than a lens at the front end. Isaac Newton gets credit for inventing the first reflecting telescope in the late 17^th century. He used a second small diagonal mirror to direct light out the side of the telescope to an eyepiece. His immensely practical design, now called the Newtonian reflector, is the main type of purely reflecting telescope in use today by amateur astronomers [Read more…] about Newtonian Reflectors and Dobsonian Telescopes

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Schmidt-Cassegrain Telescopes

May 14, 2020 by Brian Ventrudo Filed Under: Astronomy Equipment

A Schmidt-Cassegrain telescope (credit: Celestron)

In the most recent article on telescopes, you had a look at Newtonian reflectors, the oldest type of mirror-based telescope for astronomy. Newtonians, as you learned, have one big drawback: they are big. Because they use a single primary mirror to direct light back to a flat secondary mirror, which in turn reflects light to the eyepiece at the side of the tube, the physical length of a Newtonian is roughly equal to its focal length. So a 12″ aperture f/6 Newtonian, for example, is at least six feet long and more than a foot wide. But in 1672, shortly after Issac Newton developed his famous design, an obscure French Catholic priest named Laurent Cassegrain invented a reflector that used two mirrors to fold a long optical path into a much shorter tube. Now many reflectors, and nearly all professional astronomy telescopes, use some variation of the Cassegrain design [Read more…] about Schmidt-Cassegrain Telescopes

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