10
at high powers more severely). Planetary observing may also
be poor.
In conditions of good seeing, star twinkling is minimal and
images appear steady in the eyepiece. Seeing is best over-
head, worst at the horizon. Also, seeing generally gets better
after midnight, when much of the heat absorbed by the Earth
during the day has radiated off into space.
Avoid looking over buildings, pavement, or any other source
of heat, as they will cause “heat wave” disturbances that will
distort the image you see through the telescope.
Especially important for observing faint objects is good “trans-
parency”—air free of moisture, smoke, and dust. All tend to
scatter light, which reduces an object’s brightness. Transparency
is judged by the magnitude of the faintest stars you can see with
the unaided eye (6th magnitude or fainter is desirable).
How to Find interesting celestial objects
To locate celestial objects with your telescope, you first need to
become reasonably familiar with the night sky. Unless you know
how to recognize the constellation Orion, for instance, you won’t
have much luck locating the Orion Nebula, unless, of course,
you look up its celestial coordinates and use the telescope’s set-
ting circles. Even then, it would be good to know in advance
whether that constellation will be above the horizon at the time
you plan to observe. A simple planisphere, or star wheel, can be
a valuable tool both for learning the constellations and for deter-
mining which ones are visible on a given night at a given time.
A good star chart or atlas will come in very handy for helping
find objects among the dizzying multitude of stars overhead.
Except for the Moon and the brighter planets, it’s pretty time-
consuming and frustrating to hunt for objects randomly,
without knowing where to look. You should have specific tar-
gets in mind before you begin observing.
Start with a basic star atlas, one that shows stars no fainter
than 5th or 6th magnitude. In addition to stars, the atlas will
show the positions of a number of interesting deep-sky
objects, with different symbols representing the different
types of objects, such as galaxies, open star clusters, globu-
lar clusters, diffuse nebulas, and planetary nebulas. So, for
example, your atlas might show that there is a globular cluster
sitting just above the lid of the “Teapot” pattern of stars in
Sagittarius. You then know to point your telescope in that
direction to home in on the cluster, which happens to be
6.9-magnitude Messier 28 (M28).
You can see a great number and variety of astronomical
objects with your ShortTube 4.5" EQ, including:
the Moon
With its rocky, cratered surface, the Moon is one of the easi-
est and most interesting targets to view with your telescope.
The best time to observe our one and only natural satellite is
during a partial phase, that is, when the Moon is NOT full.
During partial phases, shadows on the surface 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 pleas-
ing view. Use a Moon Filter (Orion #5662) 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 the Moon filter).
the Planets
The planets don’t stay put like the stars (they don’t have fixed R.A.
and Dec. coordinates), so you’ll have to refer to charts published
monthly in Astronomy, Sky & Telescope, or other astronomy
magazines to locate them. Venus, Mars, Jupiter, and Saturn are
the brightest objects in the sky after the Sun and the Moon. Not
all four of these planets are normally visible at any one time.
JUPITER The largest planet, Jupiter, is a great subject to
observe. You can see the disk of the giant planet and watch the
ever-changing positions of its four largest moons, Io, Callisto,
Europa, and Ganymede. If atmospheric conditions are good,
you may be able to resolve thin cloud bands on the planet’s disk.
SATURN The ringed planet is a breathtaking sight when it is
well positioned. The tilt angle of the rings varies over a period
of many years; sometimes they are seen edge-on, while at
other times they are broadside and look like giant “ears” on
each side of Saturn’s disk. A steady atmosphere (good see-
ing) is necessary for a good view. You may probably see a tiny,
bright “star” close by; that’s Saturn’s brightest moon, Titan.
VENUS At its brightest, Venus is the most luminous object in
the sky, excluding the Sun and the Moon. It is so bright that
sometimes it is visible to the naked eye during full daylight!
Ironically, Venus appears as a thin crescent, not a full disk,
when at its peak brightness. Because it is so close to the Sun,
it never wanders too far from the morning or evening horizon.
No surface markings can be seen on Venus, which is always
shrouded in dense clouds.
MARS If atmospheric conditions are good, you may be able
to see some subtle surface detail on the Red Planet, possibly
even the polar ice cap. Mars makes a close approach to Earth
every two years; during those approaches its disk is larger
and thus more favorable for viewing.
stars
Stars will appear like twinkling points of light in the telescope. Even
powerful telescopes cannot magnify stars to appear as more than
points of light! You can, however, enjoy the different colors of the
stars and locate many pretty double and multiple stars. The
famous “Double-Double” in the constellation Lyra and the gor-
geous two-color double star Albireo in Cygnus are favorites.
Defocusing the image of a star slightly can help bring out its color.
Deep-sky objects
Under dark skies, you can observe a wealth of fascinating
deep-sky objects, including gaseous nebulas, open and
globular star clusters, and different types of galaxies. Most
deep-sky objects are very faint, so it is important that you find
an observing site well away from light pollution. Take plenty of
time to let your eyes adjust to the darkness. Don’t expect
these subjects to appear like the photographs you see in
books and magazines; most will look like dim gray smudges.
(Our eyes are not sensitive enough to see color in such faint
objects.) But as you become more experienced and your observ-
