So we have learned a few things about observing the night sky: (1) being patient with our eyes to get dark adapted, (2) understanding that observing involves some seeing but observing gets better as you record some of what you see, and (3) discovering there is great value in just using your eyes to observe, even though instruments are fun, too. We also defined a few terms, looked at the night sky a few times, and you have seen some examples of what can be done in terms of an observing record. In the last lesson we introduced the movement of the sky (actually earth’s rotation) and color in the heavens. The last two we want to talk about again because they can be very helpful as well as fun.
There is a little diagram that might be helpful that is shown below. Please take a look at it and feel free to copy it.
Assuming you live north of the equator and you looked north at the night sky during previous lessons, you located the Big Dipper (Ursa Major). During an early spring evening, it looks like the pitcher is being poured out (as if the right side of the paper was at the bottom of your page. If you drew an imaginary line from the last two stars of the dipper, the line will run into Polaris (North Star) that is also the approximate location of the North Celestial Pole. The line from you to the North Star is the axis about which the earth rotates at 15 degree per hour (360 degrees divided by 24 hours). So, stars move 15 degrees westward (counterclockwise if looking at Polaris) every hour. The movement makes a wonderful clock. If you happen to look north around 1 am, what you will see almost looks exactly like what you see in the drawing.
If you watched the moon change positions relative to Mars last week. (Mars, which is a “wandering star,” is bright red-orange and sits high in the southwest in the evening.) Our little exercise was a good example for how it changes position but also an example of color. Now that we are several days after full moon, so the sky is dark again until early morning hours when the moon rises. So, the moon moves differently than planets (wandering stars) and stars. That is another story since the moon makes a phase change during its cycle and moves several degrees to the east each night (if you observe it at the same time). The moon makes a reliable clock as well, which was used for centuries as a calendar as well as a clock. The bottom line: earth rotation makes things appear to move. It gives us a chance to see things, depending on when we look, as well as provide a rough clock.
An annual clock is produced from earth’s motion around the sun. Every month the night sky (that looks away from the sun) will appear to rotate 30 degrees (360 divided by 12).
Rather than try to bend your head (if you are a new observer) around all this, do it the simple way. Buy a little planisphere. We like the Chandler planispheres, which you can buy for less than 20 dollars. Buy the one for the lattitude closest to yours. When you get it, play with it. Change the month and the time that is set and you can see for yourself how the sky moves in an hour or two…or how it moves because the seasons change (dictated by our position around the sun). A planisphere is a valuable tool; we use them all the time for finding constellations and major stars.
Let’s move on to color, which we also introduced in previous lessons. You know that not all star-like objects are white. Once dark adapted, although the eyes are not very good at seeing color at night, but brighter non-white stars become much more apparent. Antares (light red orange) is now rising in the southwest; Mars (a “wandering star” that is orange-red) is pretty high in the South. If you carefully look around, you will find some stars are yellowish, bright white, red-orange, blue-white, etc. Objects (like nebulae and galaxies) are full of color also, but it takes large aperture telescopes or a smaller one with astro-photography or special video cameras to see it. Even the moon has a little color. Earth’s atmosphere adds a little “zing” as it causes stars to flicker and have a little more color when near the horizon. The moon is often golden when on the horizon. While some observers think the atmosphere interferes with good observing. In another sense, however, it adds a beautiful dimension as the stars appear to flicker and dance when they are low in the sky. So try getting out yourself in the next few nights and discover some of what I am explaining.
A Color Example.
A few nights ago I observed M82 again, which is an irregular galaxy to the left of the tip of the dipper in the spring in north lattitudes. I used astro-video equipment on an 8 inch telescope and brought the picture indoors to a monitor, where I frantically painted what I saw (see the picture below). You can see this galaxy and its sister (M81) with a small telescope as faint white objects. M82 will look like a faint white smeared line; M81 is a faint face-on spiral galaxy, but the arms will not be well defined without larger aperture. My video camera, which is sensitive to color, shows dramatic reds/pinks on M82.
During the next lesson we will talk about a couple things to get that help a new observer but also add another observing challenge for the eyes or a binocular. And, remember, God made it all. The gathering of incredible energies into organized objects did not just happen. There is no mechanism self gather energy concentrations like we see. He did it. You can review Genesis 1:14-18, Psalm 19:1-4, and Isaiah 44:24).