There are, I suppose, many reasons to hunt and measure asteroids, all of which can bring great personal satisfaction. For me, 'saving' asteroids from becoming 'lost' is very enjoyable. Asteroids are tracked by the Minor Planet Center of the International Astronomical Union at Harvard. There are two broad classes: those with permanent numbers assigned and those with only provisional designations. Numbered asteroids are also eligible to be named by their discoverers. Numbered asteroids have been measured to such a precision that one can predict their position to a high accuracy for years ahead (just how closely they can be predicted, I've never learned). Newly discovered asteroids are assigned provisional designations, usually the year of discovery follwed by some letters and numbers which is coded to indicate the date of discovery as in 1998 DU7. Asteroids with provisional designations cannot be predicted as well as numbered asteroids (otherwise they would receive a permanent number).
Being able to predict where an asteroid will be at any given time implies knowledge of its orbit about the Sun which can be expressed mathematically and involves several parameters known as orbital elements. These orbital elements can never be known with absolute precision, but can be estimated to finer and finer precision with more and more positional measurements. Calculating orbital elements from positional measurements is far too esoteric for me, but the MPC handles that task for us measurers. We can also use Find_Orb from Bill Gray to come up with our own orbital elements should the need arise, which it does when we find a new discovery. The orbital elements of asteroids with provisional designations are in constant need of refining by new measurements. But, small uncertainties in the orbital elements of even the numbered asteroids can build up over time, especially as their orbits are perturbed by the major planets in the solar system such that there is a need to measure the numbered asteroids at least once in a while. The MPC keeps track of inadequately observed numbered asteroids and issues a Critical Minor Planet List monthly. There is great value in tracking these asteroids, and I try to do a few every month. It is in, however, the measurements on non-numbered asteroids that I find the greatest pleasure. I especially like to find large errors in the actual versus predicted positions because I feel that correcting these errors does the most to prevent the asteroid from becoming 'lost.' My personal record to date (April 1998) when looking for a specific asteroid is some 1300 arcsecs of error. I have found many in the 600 arcsec range. As of December 1997, the MPC has started issuing daily orbit updates by email which are computed automatically from the measurement data they receive. I find it a really positive feedback to see the orbit of one of my targets updated after I have submitted a data set on it. It is also quite gratifying to find a previously unknown asteroid which is given a new provisional designation. Of course, sometimes these 'previously unknown' asteroids HAD been observed before, but had become 'lost' because the ability to predict where it should be was too poor to do so. Nevertheless, if the 'new' discovery can be followed long enough to establish a reasonable orbit, the orbit mavens can often trace the newly-computed orbit back in time to find linkages with past 'discoveries.' In such cases, the knowledge of that particular orbit is refined greatly because measurements over large arcs of the orbit contribute the most to the precision of the orbital elements. Getting credit for a 'new discovery' is enjoyable and the possibility of doing so with any two images aligned and blinked adds excitement to every night. But, the only strategy I can suggest for finding new asteroids is to follow a regular program of measuring known asteroids. You are able to contribute even when you 'strike out' on new discoveries. So, how do I select my targets. I use Guide6 from Project Pluto. I suppose there are other computerized catalogs available, but I have always been satisfied with the Guide series. It is up-to-date as to its publication date, and the author Bill Gray is constantly improving it and is very good to work with by email when problems arise. Guide6 can be set to show asteroids at any field scale and adjustable as to brightness. Tables of visible asteroids can be listed (printed, saved to file) from which targets can be selected. Detailed information on each asteroid is a mouse click away. Vital information such as the asteroid's brightness (with the 8 inch SCT I limit myself to 17th mag and brighter), its motion (speed and direction) and the probable error in the prediction are also available. I usually try to select asteroids within two hours of transiting the meridian at the time I want to observe. I try to avoid moon light so up to first quarter I wait for the moon to go down. After first quarter, I try to get up early in the morning after the moon has set. Guide6 gives good current information on moonrise, moonset and twilight times as well.