Astronomy: How to record your study of the night sky
Do you have a question about astronomy or the stars?
Baker City: 44 46' 30" N, 117 49' 59"
BY RYC RIENKS
While the night sky can seem overwhelming and impossible to truly know, it is easier to visualize as a collection of smaller, more comprehensible components.
In a new town you would first learn your immediate neighborhood, then routes to your favorites stores, restaurants and the library. Later you would learn more of the city, the surrounding countryside, and on.
In the sky, we also expand our knowledge in similar increments, starting with those elements available to the naked eye.
Humans have the ability to find familiar patterns in random sounds and sights. Earliest man looking at the night skies found suggestions of familiar shapes in the arrangements of various stars. The Big Dipper is one such example of a chance assortment of stars being defined as a familiar object.
Description and drawings of these patterns were made, studied, argued over and passed from one generation to the next, becoming our current star charts. As you begin your study of the sky, make your own notebook of observations. Any notebook will work, though the best would be one with lined pages backed with blank pages, which offers a place to take notes and a place to make drawings. With this you're on your way to creating a record of your observations.
Your drawings can be of groups of stars that you like and might contain bodies such as the Moon, a track from a satellite or meteor, or a possible planet sighting. For your drawings and notes to have meaning to you later (when you go back through, amazed at how your skills have improved) there is some basic data you want to record each observing session. Let's look at these.
Date: A bit confusing at first, the best way to record the date is in Year Month Day format. Like this: 060703. That is 2006, July 3. Perhaps this is logical, perhaps it satisfies the computer sort process. With a little practice I found it easy to work with.
Time: Astronomers record date and time as Universal Time, known to many as Greenwich Mean Time, in a 24-hour format. For your purposes you can write your local date and time noting the time zone and if it is Daylight Savings Time. For Baker I would write a report date thusly: 060703-2130 PDT. 24 hour time is 12 Noon + 9:30 p.m. = 2130 hours.
Location: It is amazing how easy it is to forget to write this down and then later not be certain where you were when. Under this column's heading are the latitude and longitude for Baker City. Later, should you wish more precision in your site location let me know and perhaps I'll drop by with my GPS. Or you can check the USGS maps.
Altitude of observed object: This is actually fairly easy to estimate. Make a fist and extend your arm so your knuckles make a vertical line. The height of your fist is about 10 of arc. If you assume the horizon to be straight out in front of you, you can measure upwards one fist over the other and arrive at a rough figure for the degrees of altitude (Alt). Try walking one fist over the other a few times. Straight overhead, the zenith, should be 90.
Azimuth: This is the direction in degrees as you would read from a compass. Don't worry about tipping your compass up to get a precise reading. Compass's usually don't work well tipped unless they are made for a boat. But looking at The Big Dipper, you might find your compass saying it lies just west of north, say 342. Record this and note the time. The movement our Earth makes the Azimuth/Altitude valid for that specific date and time. It takes about four minutes for an object to move one degree of arc across the sky. A few hours later and you have different numbers. Also be aware that a magnetic bearing (Az) is not the same as a true bearing so the Az should be noted as: "342C (or M)".
If you start this week you will see some interesting changes in the position of the moon relative to the star field. You will also find, as the days turn to weeks, that The Big Dipper is moving, rotating down, toward the northwestern horizon. With just a short observing session each evening at about the same time you will be gathering evidence of the mechanics of the universe. This is how the first astronomers laid the foundations of our science as we know it today.