Tripods & Mounts: The support you need…
Nature is Hard to Beat
When you are looking at small items, like point sources of light from stars that are very far away, it requires that you have a very sturdy base upon which to set your astronomical instrument. If you’re using a very high level of magnification, every air current in the atmosphere between you and your target will cause a ripple—and there is absolutely nothing you can do about that—because we live at the bottom of this 300-kilometer deep ocean of air that continually swirls about us…
Control What You Can
What you can control is local phenomena. For example, every step someone takes near your telescope can transfer a vibration that can set your image to quaking for several seconds. If a piece of your clothing touches the scope, it can do the same thing. If a large vehicle drives by, the result will be dramatic shaking, and if the wind is blowing, it can cause all sorts of oscillations.
It’s All About the Base
With thanks to Meghan Trainor for the section heading, flimsy, inexpensive, little tubular tripods, with twist-type friction locks, were never designed to support a telescope of any kind. They are entirely inadequate for anything but an ordinary 35 mm SLR camera, or maybe a smartphone. Do not trust them with anything that is the least bit heavy.
Telescopes are generally not cheap, so why would you depend on such a precarious rig to keep them safe? It is almost sure to fall over, even if you don’t touch it.
Spend A Few Dollars on Quality
The mount shown above lacks a set of braces, or a mid-level tray to hold lenses, adaptors, a star guide, a dim red flashlight, or any of the associated and useful paraphernalia of a dedicated sky-watcher. A proper telescope comes with a tripod that was explicitly designed for it, or at worst, was at least chosen thoughtfully by the telescope’s manufacturer to safeguard all their careful engineering.
More importantly, that tray is a system to assure that the legs won't splay outwards too far, causing them to snap or fold under the weight or strain, dropping your scope on the cold, hard ground.
Square or rounded, extruded aluminum legs with levered friction locks are great. A more traditional style that is sturdy and trustworthy could be constructed from wood, thus being a great addition to a room’s décor, as well as a reliable workhorse. Choose well because it’s all about that base…
There are two fundamental technologies for the mount. The most basic is the altazimuth, which locates something by describing its movement in two perpendicular directions: vertical and horizontal. It is very intuitive to point at the desired object.
The other is an Equatorial Mount, which, although it is more complex, is extremely useful. Instead of being aligned to the horizon, it is attuned to the equatorial plane, and aligned to the rotation axis of the Earth. Let’s look at how each works.
Altazimuth is a portmanteau word combining altitude for how high something is above or below the horizon, and azimuth for the compass direction in 0-359º, where north, east, south, and west are 0º, 90º, 180º, and 270º, respectively.
If you have taken note of the motion of the Sun or Moon across the sky, you may have noticed that when either first rises, it seems to do so mostly vertically (altitude) with just a bit of horizontal movement. By the time it reaches about one-quarter of its trip across the sky, it is moving almost the same amount “up” as it moves “across." When it reaches its maximum height for the day, it is moving almost entirely horizontally.
After the mid-point of its trip, the process reverses with roughly equal "down" and "across" until it reaches the ¾ point from there onwards the "across" decreases and the "down" increases.
Altazimuth is very basic and can help you locate objects relatively easily, but the tracking path of an object is always going to look like a distorted set of stairs. It also means that if you want to automate the tracking on your telescope, you are going to need exact positioning information, and a very sophisticated, computer-driven calculation algorithm to steer the mechanism that moves your telescope. These are somewhat rare, and altazimuth users generally use the manual tracking knobs and contend with the difficulties by continually adjusting.
Low magnification objects spend a lot of time in the view, traveling slowly across the image. High magnification objects can slip out of the view in just a second or two… Altazimuth users generally don’t use high magnification for any length of time.
These mounts really lend themselves to being automated. They make stellar photography a breeze and eliminate conversations like this:
“Quick…look! I found a blue star right next to a red star!”
“Oh, let me see…let me see!” A moment passes. “I don’t see what you’re talking about. There’s nothing like that here…”
“Did you touch it? Did you move anything? Oh, get out of the way and let me look…”
By automating the scope’s movement, whatever you center in the scope stays there, for its complete trip, until it either sets or dawn comes. It is just about the only way to get genuinely profound images of the other planets from Earth. We'll talk about that in a future article on Astrophotography!
How does it work?
First, you must know your latitude. This is relatively easy to acquire by directly consulting the GPS on your smartphone.
Alternatively, you can even ask Amazon’s Alexa by saying “What’s my latitude?” and she’ll reply “The latitude for (your town) is 43 point 2213 degrees north” or whatever it happens to be, and this is more than sufficient for setting your telescope up.
Are you a Google fan? Open Google Maps and touch and hold your location with a fingertip. Your exact GPS numbers will appear in the search box. You only need the first one, on the left, for latitude.
A million easy steps…
- On a traditional equatorial mount, locate the latitude adjustment, which should look like one of these two images. The one on the left is for anywhere in the world. The one on the right is Northern Hemisphere specific.
- Loosen the locking screw and move the mount until it points at your latitude. Lock the mechanism again. You’re done (unless you move to a new location).
- Next, level the tripod. You can permanently attach a round bubble-level to the tool tray for convenience. Alternatively, you can tie a string with a weight to the underside of the tripod mount. Adjust the length of the legs until the tripod is perfectly vertical.
Loosen the tube clamps that hold the main body of your telescope in place. They generally look something like this image. Now slide the tube back and forth until it is balanced. You’ll adjust this many times during a session depending on where your scope is pointing, and which heavy Barlow adaptor, or eyepiece you’re using.
Turn the tube to a reasonably horizontal position. Loosen and then slide the counterweight along the rod, also known as the right ascension axis or RA, until it balances the weight of the scope. Tighten it again.
- Turn the scope to the “starting position," which means with the tube directly over the tripod mount, with the counterweight hanging straight below. The up & down axis is called the declination axis, and it should be aligned with the RA axis.
- If everything is as it should be, there is one leg of your tripod pointing straight backwards. Move the whole tripod until that leg points directly south, and you’re all aligned.
- If it is already dark, look along the top length of the tube and point at Polaris, the North Star. Install a low power eyepiece in the telescope. Adjust the height of the south leg until Polaris is centered in the scope view. If you have Polaris centered, now would be a good time to check that the smaller "finder scope" (attached to the side of the tube) is centered on Polaris. If not, adjust the hand screws until it matches the main scope. You shouldn't have to change that again unless it gets moved.
So, now you know how to choose a tripod and how to set up an equatorial mount. You’re ready to go. Don’t forget to find a local astronomy club to get some practical hands-on advice, and the opportunity to try other people’s equipment so you can decide what suits you and what fits your budget. Clear skies!