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6. observing tips & techniques
seeing limitations
Atmospheric conditions vary significantly from night to night. If the stars are
twinkling noticeably, upper atmospheric turbulence may limit viewing to low
powers. Planetary observing may be very limited under these conditions as the
higher magnifications necessary to see detail will only give a blurry image in
the eyepiece.
cooling Your telescope
Allow at least one-half hour for your scope to cool. In very cold climates (below
freezing), it is essential to store the telescope as cold as possible. If the scope has
to adjust to more than a 40° temperature change, allow at least one hour for the
optics to adjust. All optical instruments need time to reach "thermal equili-bri-
um." The bigger the instrument and the larger the temperature change, the more
time is needed.
Atmospheric distortions (dust in the air, air currents, etc.) will show up at higher
magnifications. With an out-of-focus star image, any movement across the
"disc" will be a result of an unstable atmosphere. Make sure you are not looking
over buildings or any other source of heat; that will also cause the image to
become distorted.
If the movement is on one side of the disc, or there is a distinct slow-moving
bump or spike in one section, this is an indication of tube currents. To solve this
problem, let the telescope cool down longer, or store cold (outside garage or stor-
age facility) to minimize the temperature change needed to reach equilibrium.
Do You Wear Eyeglasses?
Keep your glasses on to begin with. Just look though the eyepiece and adjust the
focus knob for the best image. Many people prefer to remove their glasses and
just re-focus the telescope (especially with higher power eyepieces).
Preserve Your night Vision
Don't expect to walk directly from a normally-lit house into a back yard, and
immediately see faint nebulas, galaxies, or star clusters. Your eyes take about 30
minutes to reach perhaps 80% of their full dark-adapted sensitivity. Many observ-
ers notice improvements after several hours of total darkness. Very bright
daylight for extended times can affect your night vision for days. So please,
give yourself at least a little while to get used to the dark. (Nearby porch and
street lights seriously affect night vision, as do automobile headlights. )
Eyepiece selection
Always start up with your lowest-power, widest-field eyepiece. Of the tele-
scope's standard eyepieces, the 25mm Kellner provides 40x magnification, which
is moderately low and provides very bright images of deep space objects; the
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9mm provides 111x. Many other eyepieces are available for more detailed close-
up viewing, and for even lower power, wider field viewing. Most amateur
astronomers will end up with a selection of three to six eyepieces, making it pos-
sible to choose the right magnification, brightness, and contrast for each object
and for different observing conditions.
Switch up to higher magnification eyepieces only after you've located a small
object. Most viewers use the lowest power eyepiece all the time! Keep in mind
that higher powers will always be fainter and less sharp (this is a fundamental
law of optics). Naturally, higher magnifications are desirable for viewing many
celestial objects; we simply want to emphasize to the beginner that the low mag-
nification eyepiece is definitely the one to use when searching for an object and
for a lot of extended viewing.
Exotic, extra-heavy eyepieces may cause enough imbalance on the tube that you
will need to re-balance the telescope.
7. astronomical Viewing
How to Find Interesting celestial objects
You need to use a star chart or atlas to help find objects so you won't be disap-
pointed at what you see. Except for the moon and bright planets, it's pretty
time-consuming to hunt down impressive nebulas and star clusters by trial-and-
error. You should have specific targets in mind before you begin looking through
the eyepiece.
Don't spend a lot of money on a fancy, expensive star atlas until you have seen
all the brightest objects listed in a basic atlas. The Edmund Mag 6 Star Atlas is
highly recommended for all levels. A Planisphere will help you learn the constel-
lations visible at a given time of night and any particular date. Use a
red-light flashlight to preserve your night-adapted vision.
You can locate Saturn, Jupiter, Venus, Mars, and the other planets by referring to
the charts published in Astronomy or Sky & Telescope magazines each month.
These objects are fun to follow across the skies as the months go by.
Unless you know exactly where to look, you'll need a star atlas to locate celestial
objects. Don't expect to find anything interesting without one! The universe is
vast, and it will take a LONG time to find interesting subjects if you just scan
at random!
the Moon
Night viewing of the moon and its surface detail is one of the easiest and most
interesting ways to first use your telescope. The best time to observe is when the
moon is not full, as the shadows on the surface reveal more detail. You may want
to try using more powerful optional eyepieces for observing the details of the
moon's surface.
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