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Some of my favorite memories are of dark, crisp nights with the stars shining steadily against the blackness, so close I can almost touch them. Coyotes howl in the distance, tiny creatures are rustling in the bushes nearby, when suddenly out of the celestial darkness the corner of my eye catches a little spark. In an instant a “shooting star” makes a quick streak spanning ten or twenty degrees, flashes, and disappears. A particularly bright meteor might leave a thinly glowing trail, faintly visible after the meteor itself is gone. A real fireball might take a few seconds to streak from one horizon to the other, dropping occasional sparks or splitting into two or more pieces before its terminal flash. During the Leonid meteor shower of 2003, with the constellation Leo near the zenith, I watched a nearly head-on meteor flash and explode. It left a ghostly glowing smoke-ring that remained clearly visible for 5 minutes, as it slowly expanded and dissipated.

Astronomers attempt to make precise measurements of the size and shape of astronomical objects for a variety of reasons. Let’s suppose that we want to know the size and shape of a particular object. One way would be to try to carefully photograph the target at high magnification. We’d quickly discover that this technique doesn’t work for many types of objects. In a well-done astronomical image, all of the stars will have blur circles that are essentially the same size. This size is set by optical diffraction or (more commonly) atmospheric “seeing”. Typically, “seeing” restricts you to no better than 1–2 arc-sec resolution. The image of a star does not tell us anything about the star’s actual size.

The 19th century astronomers who laid many of the foundations of our modern understanding of the heavens did so by actually through their telescopes. No electronic sensors and computer-controlled data gathering for them! It turns out that there are still important measurements that can be made in the same way—eyeballs to eyepiece—and that amateur astronomers can contribute to science using the equipment that you probably use for every stargazing session.

CCD imagers have revolutionized amateur astrophotography. They have also given amateur astronomers the ability to conduct a variety of projects that entail the accurate measurement of the brightness of celestial objects. That is the essence of the science of photometry: accurate characterization of the quantity of light that is coming from an object. In this introductory section, I’ll cover the barest summary of what you’ll want to know about light, the atmosphere, and the CCD. Photometry is a broad subject, and one where amateur astronomers are actively collaborating with professionals on a wide variety of projects. It is also one of those subjects where “the more you know, the more you realize you need to learn.” The references at the end of this chapter are well worth reading (and owning for reference) as your knowledge and skill increases and you discover yet more things that you don’t know.

When the Lord placed the stars in the sky, he did not glue them to their places. Pretty much everything in the universe is in motion, including the Earth from which we observe the heavens. Astrometry is the science of measuring the positions and motions of celestial objects. Astrometry has a long and wonderful history. In diverse times and places, it has provided the evidence that drove mankind’s ever more sophisticated understanding of the universe, and our place in it.

There are many interesting things in the universe that haven’t been discovered yet, or which are so poorly known that each new observation offers the chance to discover more about them. Some of these discovery opportunities are well within the range of amateur equipment and amateur efforts to bring them to light. For some types of discoveries, amateur astronomers can effectively compete with the professionals because we have a lot more freedom to use our telescope time on projects that entail a lot of “just looking around7#x201D;. Imagine trying to present that idea to the scheduling committee of a major observatory—“I’m not sure if I’ll find anything, but I’d like to schedule a month of nights to just look around in the sky ...”—not likely!

In the previous chapters I described observational research projects that can be done using equipment that is commonly available in the amateur astronomer’s toolkit, or which can be added at modest expense. I avoided projects that require the use of math beyond standard high-school algebra. There are, of course, valuable projects that go outside these arbitrary boundaries. The purpose of this chapter is to identify additional projects that may be of interest to the amateur researcher. If you are willing to invest in some specialized equipment, or do some more complex math, then these projects can be brought within the boundaries of your universe. The equipment needed for some of them is likely to cost you a couple of thousand dollars, and may also require that you do some custom design, construction, and de-bugging. Depending on your budget and your enthusiasm for a particular area of research, these can be extremely rewarding investments in your hobby.