The most obvious use of the Locator is to simply set the inner rotating star chart’s outer circumference with months and dates on it to the desired date and opposite the time of night shown on the fixed inner circle. It then shows the sky as it appears overhead. A related use is to determine the rising or setting time of any object shown on the star chart. For example, the star Sirius—brightest of the entire heavenly host—rises at 9 p.m. local time on December 1st.
Note that you can also find the rising and setting time of the five naked-eye planets. They are not actually show anywhere on the star chart itself since their positions are constantly changing (the name “planets” means “wanderers”). The reverse side of the Locator lists when they will be visible throughout the year—either in the evening or morning sky. If you see a bright object that’s not on the star chart at the time, it’s that planet (sometimes more than one, as indicated on the table).
Another wonderful use of the Locator is its use in identifying the brighter stars and their host constellations. There are 25 First-Magnitude stars, 16 of which are visible from mid-northern latitudes. They are shown and named on the star chart itself—and are also listed on the back of the Locator along with their constellations. (Also given there are their perceived colors and distance in lightyears.) These stars are bright enough to easily spot at first glance. But so are their host constellations which are labeled along with the stars themselves, making it a snap to identify them. Using the star Sirius again as an example, it’s positioned in Canis Major, the Big Dog of the sky. Find the star and you have also found a constellation!
So not only is the Star and Planet Locator a truly amazing and useful little device, but it is the most affordable of all the aides available to those who love the night sky.
— James Mullaney
Former assistant editor at Sky & Telescope magazine & author of 10 books on stargazing. His latest, Celebrating the Universe!, is available from HayHouse.com.