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Asteroid Hunter: The Hunt

by Perry Pezzolanella

In the previous article, the Asteroid Hunter explained what asteroids are and how important it is for scientists and amateurs to study them. In order to hunt for anything, it is important to be familiar with the territory where the game resides. To begin hunting for asteroids, the hunter must be familiar with the night sky, namely the constellations.

It is important to be familiar with the stars and constellations that will be visible on the night of the year that the hunt will occur. Asteroids are usually found along the ecliptic, therefore they can be seen in all of the familiar constellations of the zodiac such as Taurus and Scorpius. Several others, including Pallas, can often be found well away from the ecliptic and in dim, obscure constellations such as Microscopium. It is important to also have clear, calm weather and most important, no Moon. A trip away from light pollution is also best, however a handful of asteroids are brighter than magnitude +10, which makes it possible to see them from less than ideal locations. The Asteroid Hunter found scores of asteroids in his early hunting days under city skyglow.

There is one thing that will hamper the hunt, but nothing can be done about the Milky Way. An asteroid passing in front of the glow of the Milky Way will surely be lost among its millions of stars. The Milky Way is only a brief nuisance in June but if an asteroid is at opposition in Scorpius or Sagittarius, it is almost not worth hunting. An asteroid is easiest to see when it is near opposition. At that time it is closest to Earth, at its brightest, visible all night, and moves the most from night to night among the stars. It is also best to pick a night when the Moon does not rise until after midnight, or set before midnight for those who like to hunt during the wee hours. Now all that is needed is a clear sky with very little wind as it is important to be as comfortable as possible. Temperature is not too much of an issue unless it is close to 0ºF, then it is best to stay inside and read about asteroids. All hunters know how to dress, so always bundle warmly in layers as it is easier to take off clothing if it becomes too toasty.

Here in Upstate New York the Asteroid Hunter can usually be heard saying that the asteroid hunting season runs from “April Fool’s Day until Halloween”, although March and November are occasionally acceptable, but very rarely December, January, or February. Those three winter months are almost always hampered by snow, ice, biting cold, and endless nights of lake-effect clouds even when clear weather is forecasted. Even the summer can be challenging with haze, humidity, sudden pop-up thunderstorms, and mosquitoes, but nothing stops the Asteroid Hunter except lightning. Careful planning and common sense are all that is needed.

The Asteroid Hunter has offered advice for when and how to approach the game, but what weapons should be used? The basic weaponry are: sketch pad, pencil with eraser, watch, red flashlight, star atlas, asteroid software, binoculars, and a telescope. No go-to is required, but if it is used, it will take the fun out of the hunt. Star hopping to find an asteroid is like a hunter walking through the fields and woods, identifying all the objects around him along the way to make the trail familiar, and finally finding game. It is a fine art to learn and those who star hop become very familiar with the night sky. It is also interesting to note that star hopping can lead the asteroid hunter to vaguely known galaxies, clusters, and double stars for an added reward, much like a real hunter stumbling across a $20 bill lying on the ground.

A star atlas is very important and the Wil Tirion Sky Atlas 2000 is a good investment as it covers the entire sky with easy to read star charts. It is strongly suggested that software be purchased that can actually plot the position of an asteroid among the stars for the given night of the hunt. The Minor Planet Observer software is available from the Palmer Divide Observatory ( for a very reasonable price. It has a directory for thousands of asteroids during the year complete with opposition dates. Simply pick an asteroid and plug it in the section that generates the maps, set the parameters such as the dates the hunt will occur. A star chart can then be printed showing the position and path of the asteroid perfect for use in the field. TheSky 6 and TheSkyX are also excellent software. It is best to protect the charts from dew by using plastic sheet inserts. This printout should be matched with a star chart indoors first in order to become familiar with the location of the asteroid within the constellation before going outside. Hopefully the asteroid will be near a bright star or little asterism to make star hopping easier.

Any pair of binoculars will do as long as they are capable of focusing stars at night. These are needed to find the area of the sky where the asteroid is located. The most important weapon, save for the eyes, is a telescope. Since asteroids are never more than stars in any telescope, it does not matter what type of telescope is used. Size matters: the larger the telescope, the more asteroids that can be seen. A simple 3” refractor can easily reveal 100 asteroids and any telescope 4” or more will bring the count to at least 1000. The number visible is endless with the MVAS Apollo Observatory’s 16” Meade Schmidt Cassegrain telescope. Armed with all of this, the asteroid hunter is now ready for the hunt.

The Asteroid Hunter heads for his club’s observatory site beneath dark country skies armed with his faithful 115 mm Stellarvue refractor. He sets up quickly and begins the hunt with the asteroid chart in hand. Guided by the star atlas, he points his binoculars towards the sky and scans the constellation where the asteroid resides. He identifies the stars he needs to begin the hunt. The Asteroid Hunter points his telescope at the star where he will begin his star hop. The hunt is on as he works his way among several stars and identifies many little patterns in case he has to retrace his path. He carefully plots all of the stars in the field of view once he finds the pattern of stars where the asteroid is suspected, noting the date and time. If there are other asteroids he wishes to pursue, he resumes his hunt in different territory.

The Asteroid Hunter needs another clear night to confirm his catch, for if a star on his carefully plotted sketch moved, it is confirmation that he has caught another asteroid. A night or two later, he points his trusty telescope again toward the now-familiar star field and quickly star hops back to where the asteroid resides. He checks his sketch against what he sees through the eyepiece. Sure enough, one of the stars has moved exactly as plotted by the software. The Asteroid Hunter has caught another asteroid! So now what?