13
adjust to more than a 40° temperature change, allow at least
one hour.
Let Your Eyes Dark-Adapt
Don’t expect to go from a lighted house into the darkness of
the outdoors at night and immediately see faint nebulas, galax-
ies, and star clusters—or even very many stars, for that matter.
Your eyes take about 30 minutes to reach perhaps 80% of their
full dark-adapted sensitivity. As your eyes become dark-adapt-
ed, more stars will glimmer into view and you’ll be able to see
fainter details in objects you view in your telescope.
To see what you’re doing in the darkness, use a red-filtered
flashlight rather than a white light. Red light does not spoil
your eyes’ dark adaptation like white light does. A flashlight
with a red LED light is ideal, or you can cover the front of a
regular incandescent flashlight with red cellophane or paper.
Beware, too, that nearby porch and streetlights and car head-
lights will ruin your night vision.
Aiming the Telescope
To view an object in the main telescope, first loosen both the
R.A. and Dec. lock levers. Aim the telescope at the object you
wish to observe by “eyeballing” along the length of the tele-
scope tube (or use the setting circles to “dial in” the object’s
coordinates). Then look through the (aligned) finder scope and
move the telescope tube until the object is in the finder’s field
of view. Retighten the R.A. and Dec. lock levers. Then center
the object on the finder’s crosshairs using the R.A. and Dec.
slow-motion controls. The object should now be visible in the
main telescope with a low-power (long focal length) eyepiece.
Calculating the Magnification
It is desirable to have a range of eyepieces of different focal
lengths, to allow viewing over a range of magnifications. To
calculate the magnification, or power, of a telescope, simply
divide the focal length of the telescope by the focal length of
the eyepiece:
For example, the SkyView Deluxe 6", which has a focal length
of 750mm, used in combination with a 25mm eyepiece, yields
a power of
Every telescope has a useful limit of power of about 45x–60x
per inch of aperture. 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 funda-
mental law of optics). The steadiness of the air (the “seeing”)
will also limit how much magnification an image can tolerate.
Always start viewing with your lowest-power (longest-focal-
length) eyepiece in the telescope. After you have located and
looked at the object with it, you can try switching to a higher-
power eyepiece to ferret out more detail, if atmospheric
conditions permit. If the image you see is not crisp and
steady, reduce the magnification by switching to a longer-
focal-length eyepiece. As a general rule, a small but
well-resolved image will show more detail and provide a more
enjoyable view than a dim and fuzzy, over-magnified image.
Eyepiece Selection
By using eyepieces of varying focal lengths, it is possible to
attain a great many magnifications with the SkyView Deluxe
6". The telescopes come with two high-quality Plössl eye-
pieces: a 25mm, which gives a magnification of 30x, and a
9mm, which gives a magnification of 83x. Other eyepieces
can be used to achieve higher or lower powers. It is quite
common for an observer to own five or more eyepieces to
access a wide range of magnifications. This allows the
observer to choose the best eyepiece to use depending on
the object being viewed. At least to begin with, the two sup-
plied eyepieces will suffice nicely.
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 galax-
ies 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.
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-chang-
ing phases, you’ll get a new view of the Moon every night. The
best time to observe our one and only natural satellite is dur-
ing 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
Telescope focal length
Eyepiece focal length
= Magnification
750mm
25mm
= 30x
