9
ASTRONOMICAL OBSERVATION TIPS
SEEING AND TRANSPARENCY
Atmospheric conditions are of the utmost importance when
considering viewing conditions for your astronomical binoculars.
These conditions are commonly referred to as “seeing.” When seeing
is good, star twinkling is minimal and objects appear steady in your
lenses. Seeing is best overhead, worst at the horizon, and generally
better after midnight. You can’t see the stars without looking through
the atmosphere, so the clearer the air and the higher your altitude, the
better seeing conditions you will encounter.
A reliably quick way to judge seeing conditions is to look at bright stars
about 40° above the horizon. If the stars appear to twinkle, there is
significant atmospheric distortion and viewing at high magnification will
not be ideal. If these stars are steadily bright, chances of successful
viewing at high magnification are much better.
Judging the transparency of the air is also important in determining
viewing conditions. The best air is free of moisture, dust, and smoke,
which tend to scatter light, reducing a viewed object’s brightness.
How many stars can you see with your naked eye? If you are unable
to see stars of magnitude 3.5 or dimmer, transparency in your area is
poor. A good indicator star for this test is Megrez (mag. 3.4) - the star
in the Big Dipper connecting the handle to the dipper. If Megrez is not
visible, elements in the air will negatively affect your view.
