Telescope Hints and Conditions
1. Your telescope is a very sensitive instrument. For best
results and fewer vibrations set your telescope up on a
level location on the ground rather than your concrete
driveway or your wooden deck. This will provide a more
stable foundation for viewing, especially if you’ve drawn
a crowd with your new telescope.
2. If possible view from a location that has relatively few
lights. This will allow you to see much fainter objects.
You’d be surprised how much more you’ll see from your
local lake or park when compared to a backyard in the
city.
3. Using your telescope out a window is NEVER
recommended.
4. View objects that are high in the sky if possible. Waiting
until the object rises well above the horizon will provide
a brighter and crisper image. Objects on the horizon are
viewed through several layers of Earth’s atmosphere.
Have you ever wondered why the moon appears orange
as it sets on the horizon? It’s because you are looking
through a considerable more amount of atmosphere than
you would directly overhead. (Note: If objects high in
the sky are distorted or wavy, you are probably viewing
on a very humid night.) During nights of unstable
atmosphere, viewing through a telescope can be
frustrating if not impossible. Astronomers refer to crisp,
clear nights as nights of "good seeing."
5. Check your local educational institutions and public
library to locate an astronomy club in your area. Being
around other people who enjoy viewing the night sky is
an excellent way to become more proficient at using
your telescope.
THE BEGINNER should put in an hour or so of practice on
land objects. Even though the image is upside down, you
will gain valuable experience in setting up the telescope,
focusing the eyepiece and other basic operations, all of
which must be learned by actual practice. Then, in the
night sky, the best starting sky is at dusk. This also of
course is the only time you can see Mercury or Venus as
evening stars.
WEATHER: If the weather is cold set up your telescope a
few minutes before you plan to use it so the telescope can
adapt to the cold air.
EYES MUST BE DARK-ADAPTED. It takes at least ten
minutes to dark-adapt your eyes and night vision continues
to improve for up to thirty minutes. If the weather outdoors
is a bit chilly, you can get your night eyes more
comfortably by staying indoors with your eyes closed or in
a dark room. Meanwhile, you have already setup the
telescope and it too is undergoing a slight change in
adapting to the weather. If you want to look at maps or
notes outdoors, use a lamp or flashlight covered with red or
brown paper or a red filter.
EYE POSITION: Your eye must not touch the eyepiece
but at the same time it must be centered on the emergent
light beam. This is impossible to do when your eyes are
not dark-adapted. After you get your night eyes, you will
note that the sky as seen in the telescope is not really black
but a rather bright, luminous gray. Given this target, your
eye will automatically center on the eyepiece. Obviously, a
low-power eyepiece is easier to use because it has a bigger
exit pupil. If desired, you can cup your hand around the
eyepiece to serve as a guide until you get your eye centered
on the light beam.
A second feature of proper eye position is that your eye
must be at or near the exit pupil point. If you are too close,
you will get a hit-and-miss shadow effect; if too far, you
will lose valuable area in the field-of-view. High-power
eyepieces always require a closer eye position than low
power.
If possible, try to master the trick of keeping both eyes
open since this is much less tiring than the usual one-eye
squint. Two-eye viewing is easy on daytime objects or any
bright night object, such as the moon. For other night
targets where the emergent beam is of low luminosity, your
only chance of staying “on target” is the one-eye squint.
However, practice with two eyes open whenever you can.
IF YOU WEAR GLASSES: Take them off if you are far
sighted. Your unaided eyes will then see distant objects
clearly, while the removal of the glasses will let you crowd
the eyepiece when necessary. Those with myopia have a
different problem: if you remove your glasses you lose
your eyes for distant objects. The best practical solution
here is to keep your glasses on and use only eyepieces with
long eye relief of _ inch or more. Note, however, that even
with eyepieces having short eye relief, a long eye position
means only that you lose field.
FOCUSING: There is no such thing as exact focusing of a
telescope. What happens is that the image forms at a very
precise and exact image plane, but you can see the image at
various settings of the eyepiece because the eye can adjust
for either long or short focus. The best general practice is
to focus “long”. This is done by extending the eyepiece a
little more than necessary and then focusing in just enough
to get a sharp image. The “long” focus causes your eye to
focus as for a distant object—the most comfortable
position. If you focus to the maximum “in” position, which
yet retains a sharp image, the eye accommodates as for a
close object. This position gives slightly greater
magnification but is somewhat more tiring. In actual
practice, you will use both the long and short focus since
frequent changes will allow you to see more clearly without
eye fatigue. Also, as a matter of fact, objects low in the sky
require a slightly different focus than objects at the zenith;
a bright object like the moon may require different focusing
than a dim nebula. Exact focus on star objects is simply a
matter of obtaining the smallest possible star image.
Out-of-focus focusing is sometimes useful. For example, if
the finderscope is set slightly outside focus, the star images
will be big and easily seen; you can even make fine
crosshairs visible in this manner. Colored doubles are
sometimes seen better slightly outside focus although too
much of this tends to dilute the colors rather than improve
them. When you use a series from low to high-power for
finding and observing, it is sometimes practical to focus
only the high-power eyepieces. The others, if not too much
out-of-focus, will show large star images which serve quite
well for finding and tracking. If you want to see something
spectacular, off-focus on a bright star near the horizon and
then tap the eyepiece tube slightly with your finger—you
will see a flaming pinwheel shooting off red and green
sparks!
Loading...