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To calculate the magnification of a telescope-eyepiece com-
bination, simply divide the focal length of the telescope by
the focal length of the eyepiece.
Telescope Focal Length (mm)
= Magnification
Eyepiece Focal Length (mm)
For example, the StarBlast 6, which has a focal length of
750mm, used in combination with the 25mm eyepiece,
yields a magnification of
750mm = 30x
25mm
Whatever you choose to view, always start by inserting your
lowest-power (longest focal length) eyepiece to locate and
center the object. Low magnification yields a wide field of
view, which shows a larger area of sky in the eyepiece. This
makes finding and centering an object much easier. Trying
to find and center objects with a high-power (narrow field of
view) eyepiece is like trying to find a needle in a haystack!
Once you’ve centered the object in the eyepiece, you can
switch to a higher magnification (shorter focal length) eye-
piece, if you wish. This is recommended for small and bright
objects, like planets and double stars. The Moon also takes
higher magnifications well.
The best rule of thumb with eyepiece selection is to start
with a low-power, wide-field eyepiece, and then work your
way up in magnification. If the object looks better, try an
even higher magnification eyepiece. If the object looks
worse, then back off the magnification a little by using a
lower-power eyepiece.
What to Expect
So what will you see with your telescope? You should be
able to see bands on Jupiter, the rings of Saturn, craters on
the Moon, the waxing and waning of Venus, and many bright
deep-sky objects. Do not expect to see color as you do in
NASA photos, since those are taken with long-exposure
cameras and have “false color” added. Our eyes are not
sensitive enough to see color in deep-sky objects except in
a few of the brightest ones.
Remember that you are seeing these objects using your
own telescope with your own eyes! The object you see in
your eyepiece is in real-time, and not some conveniently
provided image from an expensive space probe. Each ses-
sion with your telescope will be a learning experience. Each
time you work with your telescope it will get easier to use,
and stellar objects will become easier to find. There is big
difference between looking at a well-made full-color NASA
image of a deep-sky object in a lit room during the daytime,
and seeing that same object in your telescope at night. One
can merely be a pretty image someone gave to you. The
other is an experience you will never forget!
objects to observe
Now that you are all set up and ready to go, one critical
decision must be made: what to look at?
A. The Moon
With its rocky surface, the Moon is one of the easiest and
most interesting targets to view with your telescope. Lunar
craters, marias, and even mountain ranges can all be
clearly seen from a distance of 238,000 miles away! With
its ever-changing phases, you’ll get a new view of the Moon
every night. The best time to observe our one and only natu-
ral satellite is during a partial phase, that is, when the Moon
is NOT full. During partial phases, shadows are cast on the
surface, which reveal more detail, especially right along
the border between the dark and light portions of the disk
(called the “terminator”). A full Moon is too bright and devoid
of surface shadows to yield a pleasing view. Make sure to
observe the Moon when it is well above the horizon to get
the sharpest images.
Use an optional Moon filter to dim the Moon when it is very
bright. It simply threads onto the bottom of the eyepieces
(you must first remove the eyepiece from the focuser to
attach a filter). You’ll find that the Moon filter improves view-
ing comfort, and also helps to bring out subtle features on
the lunar surface.
B. The Sun
You can change your nighttime telescope into a daytime Sun
viewer by installing an optional full-aperture solar filter over
the front opening of the StarBlast 6. The primary attraction
is sunspots, which change shape, appearance, and location
daily. Sunspots are directly related to magnetic activity in
the Sun. Many observers like to make drawings of sunspots
to monitor how the Sun is changing from day to day.
Important Note: Do not look at the Sun with any optical
instrument without a professionally made solar filter, or per-
manent eye damage could result.
Magnification limits
Every telescope has a useful magnification limit of about
2X per millimeter of aperture. This comes to 300X for
the StarBlast 6. Some telescope manufacturers will use
misleading claims of excess magnification, such as “See
distant galaxies at 640X!”. While such magnifications are
technically possible, the actual image at that magnifica-
tion would be an indistinct blur.
Moderate magnifications are what give the best views.
It is better to view a small, but bright and detailed image
than a dim, unclear, oversized image.
