18
Observing Deep-Sky Objects
Deep-sky objects are simply those objects outside the boundaries of our solar system. They include star
clusters, planetary nebulae, diffuse nebulae, double stars and other galaxies outside our own Milky Way.
Unlike the sun, moon and our five major planets, most deep-sky objects are not visible to the naked eye.
Finding them requires a method called star hopping, described below.
Celestron
Sky Maps (#93722) can
help you locate the brightest deep-sky objects.
Most deep-sky objects have a large angular size. Therefore, a low-to-moderate power eyepiece is all you
need to see them. Visually, they are too faint to reveal any of the color seen in long exposure
photographs. Instead, they appear black and white. Because of their low surface brightness, they should
be observed from a “dark-sky” location. Light pollution around large urban areas washes out most
nebulae making them difficult, if not impossible, to observe.
Star Hopping
One way to find deep-sky objects is by star hopping and a finderscope is very helpful. Star hopping is
done by using bright stars to "guide" you to an object. For successful star hopping, it is helpful to know the
field of view of you telescope. If you’re using the standard
Celestron
25mm eyepiece with the
Star
Hopper
®
8
, your field of view is approximately 1º. If you know an object is 3º away from your present
location, than you just need to move 3 fields of view. If you’re using another eyepiece, then consult the
section on determining field of view. Listed below are directions for locating two popular objects.
The Andromeda Galaxy, also known as M31, is an easy target. To find M31:
1. Locate the constellation of Pegasus, a large square visible in the fall (in the eastern sky, moving
toward the point overhead) and winter months (overhead, moving toward the west).
2. Start at the star in the northeast corner—Alpha (
α
) Andromedae.
3. Move northeast approximately 7°. There you will find two stars of equal brightness—Delta (
δ
) and Pi
(
π
) Andromeda—about 3° apart.
4. Continue in the same direction another 8°. There you will find two stars—Beta (
β
) and Mu (
µ
)
Andromedae—also about 3° apart.
5. Move 3° northwest—the same distance between the two stars—to the Andromeda galaxy.
