Amateur Astronomer’s Guide on How to Use a Telescope
At some point we look up at the sky at night and wonder a bit. What is all of this stuff and why is it there? For some of us, we find ourselves with our first telescope. It’s typically a simple combination of a refractor telescope on a wooden tripod.
As we discover more we learn what a refractor is and how a wooden tripod that gave us such wonderful views of the Moon betrayed us when we wanted to see further. It’s then that we begin to invest and develop our equipment for the simple reason, “we are hooked.” Hooked on the ability to see the planets, objects and distant galaxies in what we perceive as real-time.
And then we learn that there is no real-time because most of what we are observing is an event that happened minutes, hours, years, and millions of years ago. It’s at that point that our observations become a bit deeper on an intellectual level, and for some of us – an emotional level.
What should I know about the equipment?
If you’ve made the decision to watch the night-sky for whatever reason, you have some options to consider from an equipment standpoint. Before we get into some of the basics of how to use a telescope, it’s good to understand some equipment fundamentals that will affect your viewing. To put it simply there are 4 kinds of telescopes you can buy. One is a refractor, two is a reflector or “Newtonian“, three is a “Dobsonian” and the fourth is a Schmitt-Cassegrain.
If all of that sounds confusing, rest assured it is and it will not get simpler. But you can make some simple decisions as you develop your strategy for night-sky viewing and the tactics you choose to use.
How does the type of telescope affect my viewing?
A refractor is a concept that goes back as far as Copernicus and Galileo. It’s a tube with lenses that magnify an object. It’s the simplest scope to use and typically costs more than a reflector telescope.
A reflector telescope uses a concave mirror to reflect light to a prism that directs it to an eyepiece. Basic scopes are inexpensive and easy to use. However, you may have to collimate the scope from time to time. This involves aligning the mirror with the prism and the eyepiece and is fairly easy to use once you understand the concept.
A Dobsonian telescope is essentially a very large tube that functions like a reflector but provides a very wide field of view. As a result, the mounts for Dobsonian scopes are somewhat simple. There are a range of sizes and prices. The downside to a Dobsonian scope is that they are large and somewhat cumbersome. This makes it difficult to transport beyond your backyard.
The Cassegrain telescope (also knows as a catadioptric) is essentially a hybrid of a reflector and refractor. They tend to be very compact, are easily portable and also the most expensive scope across their range. While all scopes can be used for astrophotography, many people prefer a Cassegrain style scope for photography due to its compact size.
Why do people say the tripod and mount are so important?
Many amateur astronomers wish they had made a significant investment in their first tripod and mount. The tendency is to focus on the telescope and accept whatever tripod or mount accompanies it. A good tripod and mount allows you to accurately track celestial objects as they move across the sky.
There are two fundamental types of mounts. The alt-azimuth mount and the equatorial mount. The alt-azimuth is the most basic mount and will do just fine for most amateur astronomers. The Equatorial mount is designed to work with motor-drives and computerized drives and are both complex and more expensive.
One thing to keep in mind is the total weight. If you regularly travel to remote locations you may struggle a bit with a very heavy tripod and mount. If you’re just starting out an alt-azimuth mount should work just fine although it does not work as well as an equatorial mount when it comes to astrophotography.
Do I need a motor drive or computer capability?
You can purchase a scope with a motor-drive or computer capability or add them at a later date. If you are considering deep space observations and especially astrophotography, a motor drive is somewhat of a necessity for any object at significant distance. The computer option will actually direct your scope to the object in the sky once you have calibrated it to your exact latitude and longitude.
How can I learn to use my telescope when it’s the dark?
One of the hardest lessons that many of us learn occurs the first time we take our scope out into the darkness of night. Suddenly, all of the fundamental things we need to do to adjust the tripod and mount; get pointed in the right direction; locate our first object and then learn how to track it – it can be overwhelming. Especially when it’s cold and dark. There is a simple solution.
It’s the daylight-Moon. Many times when we look up at the sky during the day we’ll see the Moon high in the sky. That’s the perfect time to get your scope out and learn the fundamentals. It’s easier to practice when you can see.
What should I practice?
Study all of the adjustments that both your scope and your mount are capable of doing. Teach yourself to remember exactly what each adjustment does so you can make these adjustments automatically in the dark. This includes focusing, tracking azimuth and altitude, and the location and effect of various eyepieces, filters and lenses.
Some scopes have two focusing knobs. One for a rough focus on an object and a second for final focus. Practice with these and remember which is which.
This is the horizontal adjustment you need to make as celestial objects move across the sky due to the rotation of the Earth. Figure out where the adjustment know is on your scope and learn to track horizontal motion.
This is the second type of adjustment and it’s a vertical adjustment that allows you to track objects moving up or down through your field of view. In actual fact you’ll probably need to adjust both altitude and azimuth simultaneously so practice that with your daylight moon observation.
- Eyepieces and accessories
Most have a tray for eyepieces and accessories on the tripod. Develop a system so you always know where each eyepiece is located, remember its power or magnification, and consistently return them to the same spot in the tray.
How do I use a star chart?
A star chart is fundamentally based on constellations. You should learn the basic constellations so you can recognize them in the night-sky. Charts also vary by season. What we see in the summer is different than the night-sky in winter to some degree.
A new development is the growing number of apps that can be downloaded to wireless mobile devices and computers. This gives you significant flexibility and many of the wireless mobile apps are keyed to the GPS system in your device. As a result you can hold your device up to the sky and the app will track across the sky and identify objects, planets and constellations.
There are so many accessories. Which ones do I need?
There are numerous accessories you can buy for your telescope, but remember that you’ll have to carry it all with you if you’re going far afield to watch the sky. Here are some of the most popular that you might want to consider.
- A red LED flashlight or a flashlight with a red lens. This is what every astronomer uses to make adjustments, change lenses, or consult star charts. The red light does not affect our eyes light white light allowing our retina’s to remain wide open to the night sky.
- A Barlow lens. A Barlow lens doubles the magnification of your scope.
- Hunter gloves. These are gloves that have cuts in the material at the fingertips. They’re designed to allow a hunter to feel the trigger, but can help a great deal on a cold, winter night when you are trying to do precise focus or adjustments on your scope.
- A Diary. This allows you to keep a record of your viewing so you can find an object easier the next time, or want to remember the settings or adjustments for viewing a particular object or photograph.
Ultimately, the best way to learn how to use your telescope is to simply use it on a regular basis. Over time you will master the mechanics of the scope and will discover more and more objects and events that the night sky never fails to deliver.