Astrophotography - Orion SKYWATCHER 9024 Instruction Manual

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 visi-
ble 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 differ-
ent colors of the stars and locate many pretty double and
multiple stars. The famous "Double-Double" in the constella-
tion Lyra and the gorgeous 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 globu-
lar star clusters, and different types of galaxies. Most deep-sky
objects are very faint, so it is important that you find an observ-
ing 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 maga-
zines; 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 observing skills get
sharper, you will be able to discern more subtle details.
Remember that the higher the magnification you use, the dim-
mer the image will appear. So stick with low power when
observing deep-sky objects, because they're already very faint.
Consult a star atlas or observing guide for information on find-
ing and identifying deep-sky objects. A good source to start
with is the Orion DeepMap 600 (part #4150).

7. Astrophotography

There are several different types of astrophotography that can
be successfully attempted with the Skywatcher 90:
Moon Photography
This is perhaps the simplest form of astrophotography, as no
motor drive is required. All that is needed is a Universal 1.25"
Camera Adapter (part #5264) and a t-ring for your specific
camera. Connect the t-ring to your camera body, and then
connect the nosepiece of the camera adapter to the t-ring (the
body of the camera adapter is not needed). Insert the camera,
with the camera adapter attached, directly into the telescope's
focuser drawtube (remove the star diagonal), and secure firm-
ly with the setscrew on the drawtube. Make sure the setscrew
is tight, or your camera may fall to the ground!
Now you're ready to shoot. Point the telescope toward the
Moon, and center it within the camera's viewfinder. Focus the
image with the telescope's focuser. Try several exposure
times, all less than 1 second, depending on the phase of the
Moon and the ISO (film speed) of the film being used. A
remote shutter release is recommended (part #5232), since
touching the camera's shutter release can vibrate the camera
enough to ruin the exposure.
This method of taking pictures is the same method with which
a daytime, terrestrial photograph could be taken through the
Skywatcher 90.
Planetary Photography
Once you've mastered basic Moon photography, you're ready
to get images of the planets. This type of astrophotography
also may be used to capture highly magnified shots of the
Moon. In addition to the adapters already mentioned, the sin-
gle-axis motor drive is also required. This is because a longer
exposure is necessary, which would cause the image to blur
if no motor drive were used for tracking. The equatorial mount
must be precisely polar aligned, too.
As before, connect the t-ring to your camera. Before connecting
the camera adapter to the t-ring, an eyepiece must now be
inserted and locked into the body of the camera adapter. Start
by using a medium-low power eyepiece (about 25mm); you can
increase the magnification later by using a higher-power eye-
piece. Then connect the entire camera adapter, with eyepiece
inside, to the t-ring. Insert the whole system into the telescope's
focuser drawtube and secure firmly with the setscrew.
Aim the telescope at the planet (or Moon) you wish to shoot.
The image will be highly magnified, so you may need to use
the finder scope to center it within the camera's viewfinder.
Turn the motor drive on. Adjust the telescope's focuser so that
the image appears sharp. The camera's shutter is now ready
to be opened. A remote shutter release must be used or the
image will be blurred beyond recognition! Try exposure times
between 1 and 10 seconds, depending on the brightness of
9