Orion SKYQUEST XT6 - Manual (Page 15)

E. Deep-Sky Objects
Under dark skies, you can observe a wealth of fascinating
deep-sky objects; that is, objects that reside outside of our
solar system. These include gaseous nebulas, open and glob-
ular star clusters, and a variety of different types of galaxies.
The large apertures of SkyQuest XT Dobsonians are particu-
larly well suited to gathering light, which is critical for
observing these usually faint celestial entities. For deep-sky
observing 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. As you become more experienced and
your observing skills get sharper, you will be able to ferret out
more and more subtle details and structure from these fasci-
nating objects. Do not expect to see color in deep-sky objects,
however, as human eyes are not sensitive to color from faint
light.
How to Find Deep-sky Objects: Starhopping
Starhopping, as it is called by astronomers, is perhaps the
simplest way to hunt down objects to view in the night sky. It
entails first pointing the telescope at a star close to the object
you wish to observe, and then progressing to other stars clos-
er and closer to the object until it is in the field of view of the
eyepiece. It is a very intuitive technique that has been
employed for hundreds of years by professional and amateur
astronomers alike. Keep in mind, as with any new task, that
starhopping may seem challenging at first, but will become
easier over time and with practice.
To starhop, only a minimal amount of additional equipment is
necessary. A star chart or atlas that shows stars to at least
magnitude 5 is required. Select one that shows the positions
of many deep-sky objects, so you will have a lot of options to
choose from. If you do not know the positions of the constella-
tions in the night sky, you will need to get a planisphere to
identify them.
Start by choosing bright objects to view. The brightness of an
object is measured by its visual magnitude; the brighter an
object, the lower its magnitude. Choose an object with a visu-
al magnitude of 9 or lower. Many beginners start with the
Messier objects, which represent some of the best and bright-
est deep-sky objects, first catalogued about 200 years ago by
the French astronomer Charles Messier.
Determine in which constellation the object lies. Now, find the
constellation in the sky. If you do not recognize the constella-
tion on sight, consult a planisphere. The planisphere gives an
all-sky view and shows which constellations are visible on a
given night at a given time.
Now look at your star chart and find the brightest star in the
constellation that is near the object that you are trying to find.
Using the finder scope, point the telescope at this star and
center it on the crosshairs Next, look again at the star chart
and find another suitably bright star near the bright star cur-
rently centered in the finder. Keep in mind that the field of view
of the finder scope is 7°, so you should choose a star that is
no more than 7° from the first star, if possible. Move the tele-
scope slightly, until the telescope is centered on the new star.
Continue using stars as guideposts in this way until you are
the approximate position of the object you are trying to find
15
(Figure 19). Look in the telescope’s eyepiece, and the object
should be somewhere within the field of view. If it’s not, sweep
the telescope carefully around the immediate vicinity until the
object is found.
If you have trouble finding the object, start the starhop again
from the brightest star near the object you wish to view. This
time, be sure the stars indicated on the star chart are in fact
the stars you are centering in the finder scope and telescope
eyepiece. Remember the telescope and the finder scope will
give you inverted images, keep this in mind when you are
starhopping from star to star.
Note About Astrophotography
SkyQuest Dobsonians are designed for visual, not photo-
graphic use. The Dobsonian mount is not an equatorial-type
mount, so it cannot be motor driven for long exposure
astrophotography. SkyQuests have also been optically opti-
mized for visual use, since photographic optimization
degrades visual performance.
With that in mind, however, it is possible to do some simple
astrophotography with a SkyQuest. With the use of afocal
photography techniques (where the camera is simply placed
to the eyepiece to take a picture) and digital cameras, it is
possible to take pictures of bright objects. Certain photograph-
ic aids, such as the Orion SteadyPix, can help in taking
photos by the afocal method.
Figure 19. Starhopping is a good way to locate hard-to-find
objects. Refer to a star chart to map a route to the object that uses
bright stars as guideposts. Center the first star you’ve chosen in the
finder scope and telescope eyepiece
(1) . Now move the scope
carefully in the direction of the next bright star (2) , until it is
centered. Repeat (3&4) . The last hop (5) should place the desired
object in the eyepiece.