Celestron G-9.25 - Observing Deep-Sky Objects; Using the Setting Circles

36 • Celestial Observing
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. The Celestron Sky Maps
(#93722) can help you locate the brightest deep-sky objects.
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 color
seen in long exposure photographs. Instead, they have a black and white appear-
ance. 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.
Using the Setting CirclesUsing the Setting Circles
Using the Setting CirclesUsing the Setting Circles
Using the Setting Circles
Once the setting circles are aligned you can use them to find any object with known
coordinates.
1. Select an object to observe. Use a seasonal star chart or planisphere to make
sure the object you chose is above the horizon. As you become more familiar
with the night sky, this will no longer be necessary.
2. Look up the coordinates in an atlas or reference book.
3. Move the telescope in declination until the indicator is pointing at the correct
declination coordinate.
4. Move the telescope in R.A. until the indicator points to the correct coordinate
(do NOT move the R.A. circle). The telescope will track in R.A. as long as a
motor drive is operating and the R.A. clamp is in the locked position.
5. Look through the finder to see if you have located the object.
6. Center the object in the finder.
7. Look in the main optics using a low power eyepiece; the object should be
there. The telescope will track in R.A. as long as the motor drive is operating.
8. Repeat the process for each object observed throughout the observing session.
You may not be able to see fainter objects in the finder. When this happens,
gradually sweep the telescope around until the object is visible.
The declination setting circle is scaled in degrees while the R.A. setting circle is
incremented in minutes with a marker every fifth minute. As a result, the setting
circles will get you close to your target, but not directly on it. Also, the accuracy of
your polar alignment will also affect how accurately your setting circles read.
At the end of this manual there is a list of deep-sky objects well within reach of
your Celestron telescope.
Observing Deep-SkyObserving Deep-Sky
Observing Deep-SkyObserving Deep-Sky
Observing Deep-Sky
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