Books by Philip S. Harrington

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Apparently standing on the northern perimeter of the Milky Way are the twins Gemini. Marked by the bright stars Castor and Pollux, Gemini is one of the best known of the winter constellations. Within its borders for binocular observers are many fine examples of double and variable stars, open clusters and even a planetary nebula.

M35 (NGC 2168) is one of the premier open clusters of the northern winter sky. Located at the foot of the twin Castor, M35 is a marvelous sight in binoculars, and may even be seen with the unaided eye on crystal clear nights. Low power glasses reveal the brightest half dozen or so cluster stars against the strong glow from an additional 200 fainter orbs that constitute this magnificent stellar gathering. These brightest members are brilliant indeed, and average about 400 times the luminosity of our sun. Estimates place M35 at about 2,800 light years away and some 40 light years across.

Just southwest of M35 is the very rich and very distant open cluster NGC 2158. Although it is listed between magnitude 8 and 9 in many observing handbooks (including this one), I have always felt this to be a bit optimistic. Try as I might, I have never been able to see NGC 2158 in 7x50 binoculars, although it should be visible if it is actually that bright. Instead, I find it requires at least 11x80's to be seen, and even then it is seen as a dim glow against a striking star field.  When we look toward NGC 2158, we are seeing an object nearly 16,000 light years away, close to the outer fringes of our galaxy.

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Note: The circle marks a 7-degree field of view, typical for 7x binoculars.

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