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the best eyepiece to use depending on the object being
viewed.
To calculate the magnification, or power, of a telescope and
eyepiece combination, simply divide the focal length of the
telescope by the focal length of the eyepiece:
focal length of telescope
Magnification =
focal length of eyepiece
For example, the StarMax 127mm EQ, which has a focal
length of 1540mm, used in combination with the 25mm eye-
piece, yields a power of
1540mm ÷ 25mm = 62x
Every telescope has a useful limit of power of about 2x per
mm of aperture (about 254x for the StarMax 127mm EQ).
Claims of higher power by some telescope manufacturers are
a misleading advertising gimmick and should be dismissed.
Keep in mind that at higher powers, an image will always be
dimmer and less sharp (this is a fundamental law of optics).
The steadiness of the air (the “seeing”) will also limit how
much magnification an image can tolerate.
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 acquiring and centering an object much easier. If you
try to find and center objects with high power (narrow field of
view), it’s like trying to find a needle in a haystack!
Once you’ve centered the object in the eyepiece, you can
switch to higher magnification (shorter focal length eyepiece),
if you wish. This is especially recommended for small and
bright objects, like planets and double stars. The Moon also
takes higher magnifications well.
Deep-sky objects, however, typically look better at medium or
low magnifications. This is because many of them are quite
faint, yet have some extent (apparent width). Deep-sky
objects will often disappear at higher magnifications, since
greater magnification inherently yields dimmer images. This is
not the case for all deep-sky objects, however. Many galaxies
are quite small, yet are somewhat bright, so higher power
may show more detail.
The best rule of thumb with eyepiece selection is to start with
a low power, wide field, and then work your way up in magni-
fication. If the object looks better, try an even higher
magnification. If the object looks worse, then back off the
magnification a little by using a lower-power eyepiece.
Rotating the Diagonal
When looking at objects in different areas of the night sky, the
eyepiece may become positioned so that is uncomfortable or
impossible to look through. If the eyepiece is in an undesirable
position, the diagonal can be rotated in order to provide a
more comfortable viewing angle. First, loosen the thumb-
screws on the eyepiece adapter, but make sure to hold the
diagonal in place so that it won’t fall to the ground. Also,
secure the eyepiece in the diagonal so that it won’t fall out
when rotating the diagonal. Retighten the thumbscrews on
the eyepiece adapter once the diagonal has been rotated to
an appropriate position.
Objects to Observe
Now that you are all set up and ready to go, one critical deci-
sion 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 natural satel-
lite 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 “ter-
minator”). 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 fil-
ter). You’ll find that the Moon filter improves viewing comfort,
and also helps to bring out subtle features on the lunar sur-
face.
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 StarMax 127mm EQ. Leave the cover
caps on the finder scope or, better yet, completely remove the
finder scope when solar viewing. 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
permanent eye damage could result.
C. The Planets
The planets don’t stay put like the stars, so to find them you
should refer to Sky Calendar at our website (telescope.com),
or to charts published monthly in Astronomy, Sky &
Telescope, or other astronomy magazines. Venus, Mars,
Jupiter, and Saturn are the brightest objects in the sky after
the Sun and the Moon. Your StarMax 127mm EQ is capable
of showing you these planets in some detail. Other planets
may be visible but will likely appear star-like. Because planets
are quite small in apparent size, optional higher-power eye-
pieces are recommended and often needed for detailed
observations. Not all the planets are generally visible at any
one time.
JUPITER The largest planet, Jupiter, is a great subject for
observation. You can see the disk of the giant planet and
