Celestron PowerSeeker 70AZ Telescope PowerSeeker 40AZ Manual (English, French, - Page 17

Observing Deep-Sky Objects

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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. Most deep-sky objects have a large angular size. Therefore, low-to-moderate power 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. And, 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. Light Pollution Reduction filters help reduce the background sky brightness, thus increasing contrast. Star Hopping One convenient way to find deep-sky objects is by star hopping. 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 20 mm eyepiece with the PowerSeeker telescope, your field of view is approximately 1.4º or so. If you know an object is 3º away from your present location, then you just need to move about two 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 (Figure 5-1), 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 (D) Andromedae. 3. Move northeast approximately 7°. There you will find two stars of equal brightness-Delta (G) and Pi (S) Andromeda-about 3° apart. 4. Continue in the same direction another 8°. There you will find two stars-Beta (E) and Mu (P) Andromedae-also about 3° apart. 5. Move 3° northwest-the same distance between the two stars-to the Andromeda galaxy. Figure 5-1 17

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17
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.
Most deep-sky objects have a large
angular size.
Therefore, low-to-moderate power 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.
And, 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.
Light Pollution Reduction filters help reduce the background
sky brightness, thus increasing contrast.
Star Hopping
One convenient way to find deep-sky objects is by star hopping.
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 20 mm eyepiece with the PowerSeeker telescope, your field of view is approximately 1.4º or so.
If you know an
object is 3º away from your present location, then you just need to move about two 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 (Figure 5-1), 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 (
) Andromedae.
3.
Move northeast approximately 7°.
There you will find two stars of equal brightness—Delta ( ) and Pi ( )
Andromeda—about 3° apart.
4.
Continue in the same direction another 8°.
There you will find two stars—Beta (
) and Mu (
) Andromedae—also
about 3° apart.
5.
Move 3° northwest—the same distance between the two stars—to the Andromeda galaxy.
Figure 5-1