ERICKSON: Talking telescopes | Community Alert

A good telescope needs a good mount. Question is, what’s a good mount? Let’s explore that piece of equipment underpinning the thing you look into that’s pointed at some object far away.

For a good dance band, it’s all about the bass. The bass provides a groove that holds the music together and the dancers on the dance floor.

The same goes for your telescope. The mount is supposed to hold it all together, so your observing time isn’t wasted trying to steady the view.

A good mount must be stable! Its action needs to be smooth and precise.

Any mount, however, is dependent on its foundation.

Like a dance band, the bass provides a groove, but percussion provides the beat, the foundation.

For a mount, the foundation comes in a few forms: A pier, a tripod, or is integrated with what’s called a rocker box.

So, when talking about mounts, the foundation must be addressed, because it needs to be stable, too. But first I’ll discuss mounts.

There are two basic types of telescope mount: Altitude-Azimuth (A-Z), and Equatorial.

A-Z mounts are simple — altitude is up and down; azimuth is left and right. A-Z mounts are easiest to work with, especially for beginners, and veterans who use what’s called “star hopping” to find objects. A-Z mount motions are linear, so it’s easy to move from one object to another.

Examples of A-Z mounts are Fork Mounts, Dobsonian Mounts and Tabletop Mounts. Because A-Z mounts are simpler, they tend to be less costly than Equatorial Mounts.

Fork Mounts have a U-shape, with the telescope tube held between the vertical posts.

The bottom of the U is made so it can spin left and right while the telescope tube can rotate up and down.

The Dobsonian Mount (invented by John Dobson) starts with what’s called a rocker box.

The box base is made of two round, flat disks of plywood or other material, large enough to support the telescope. One of the disks is the bottom and has three stubby legs. The other disk is above and rides on a bearing between them so it can spin.

Two side panels and a short, stabilizing front panel are attached to the top circle. A round groove cut into the top of each side panel accepts round disks attached to the telescope tube so the tube can be rotated up and down. The mount can spin left and right while the telescope tube can rotate up and down.

Tabletop mounts are a variation of the Dobsonian mount. The weak link for tabletop mounts is the table. It needs to be stable and reasonably level.

There are other iterations of the A-Z mount, and they all follow the same up-down, left-right principle.

For illustrations of A-Z mounts see: telescope.com or agenaastro.com

A stable A-Z mount will have little to no wiggle, also called slop.

Next time, equatorial mounts and foundations.

What’s in the Sky?

December 1 after 9 p.m., west-southwest: A waxing gibbous Moon is just east of bright Jupiter