Red Dots, Telrad and other 1x finders

The Baader Planetarium Sky Surfer Red Dot Finder. Credit: Baader Planetarium

Why sometimes, the best magnification, is no magnification at all.

Here’s a true story. The very first telescope I had as a kid – a slim, 40mm aperture, department store Newtonian reflector – had the most primitive finder imaginable: a simple plastic tube with open pinholes on either end. Nothing to adjust, nothing to focus. And yet, it worked, at least in terms of getting my seven-year old eyes to aim it at bright targets such as the Moon and planets.


The World of 1x Finders

In the decades since, I’ve moved on to bigger telescopes and fainter targets and yet, I find myself attaching a Telrad mounting bracket to every new telescope I own. When I operated the observatory telescope at the Flandrau Science Center and Planetarium at the University of Arizona in Tucson, we used two similar finders on the main 16-inch telescope, one mounted on either side of the telescope tube.

Telrad finder on a Celestron Telescope – Credit: David Dickinson

Welcome to the world of 1x (zero magnification) finder scopes. These are great to use when star-hopping to a target, as they give you an unmagnified, ‘true view’ of the sky, as opposed to the often-inverted view at a telescope’s main eyepiece.

Most 1x finders are red-light illuminated with a dimmable center ‘red- ’ finder or – as is the case with the Telrad – a triple circle reticle marking off one, two and five degrees of apparent diameter. These are also adjustable to bore-sight to the telescope in the daytime prior to using.

The Telrad has illuminated circles to help zero in on your target. Credit: Guermo Peron

Introduced in the 1970s, the Telrad operates off two AA batteries, and is popular enough that the same reticle marker can now be found on the pages and maps of several modern star atlases. As a USAF veteran, I always thought the Telrad setup resembles the illuminated, heads-up gunsight display on an F-15C Eagle jet fighter.

There are several 1x finders on the market today, including:

Using a 1x finder in the field is as simple as turning it on and peering through the glass at the sky. Many have a flip mirror, allowing the user to look down at the sight from a 90-degree angle. That’s handy when the tube is pointed near the zenith.

Like the telescope’s main objective, the glass on a 1x finder can quickly become coated with dew on cool, damp nights. Telrad sells a dew shield for its finder, or you can make a simple cardboard mask to accomplish the same thing.

We’ve also used a green laser pointer for a mounted telescope using nothing more than mounting screws and binder clips. A creative setup with a red LED light and bracket-mounted glass can also serve as a ‘do-it-yourself’ 1x finder scope.

Be sure to check out a 1x finder as an intuitive means to find your way around the night sky.


About David Dickinson

David is a freelance science writer, frequent contributor to Sky & Telescope and Universe Today, author of several astronomy books and long-time amateur astronomer. He lives with his wife Myscha in Norfolk, Virginia.

Related posts