Celestron 70 manual Using the Setting Circles

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The two stars in the front of the bowl of the Big Dipper point to Polaris which is less than one degree from the true (north) celestial pole. Cassiopeia, the “W” shaped constellation, is on the opposite side of the pole from the Big Dipper. The North Celestial Pole (N.C.P.) is marked by the “+” sign.

Using the Setting Circles

Setting Circles are dials (or gauges) for right ascension and declination that allow you to locate celestial objects easily from their coordinates as listed in a star chart or atlas.

1.The declination setting circle (#16) is scaled in degrees and the right ascension setting circle is incremented in minutes. The circles will get you close to your target but not directly on it. Also, the accuracy of your polar alignment will affect how accurate your setting circles read.

2.The declination setting circle is factory set and should not need any adjustment if it reads accurately.

3.The right ascension setting circle (#14) must be aligned. Choose a bright and easy to find star in a star chart and note the coordinates (right ascension and declination). Find the star in the Star Pointer and then in the telescope. Now, rotate the right ascension circle to match the coordinates of the star with the indicator mark. If you polar aligned the telescope accurately, the declination circle should be correctly set to the proper coordinates.

You may notice that there are two sets of numbers on the right ascension dial, one for the northern hemisphere

Note and one for the southern. Observers in the northern hemisphere should use the upper set of numbers while southern observers should use the lower set of numbers. Remember in the northern hemisphere, the right ascension should decrease as the telescope is moved towards the west.

4.The right ascension setting circle does not move as the telescope moves in right ascension and thus it must by aligned each time you want to use it to find a new object. However, you do not need to use a bright star each time but you can use the object you are currently observing.

5.Now, using a star chart or atlas you can find numerous objects. First move the telescope in declination to the correct declination coordinate. Then move the telescope in right ascension until the indicator points to the correct coordinate.

6.After moving the telescope to the correct celestial coordinates, look through the lower power eyepiece to see if you have located the object you wish to view. Center the object in eyepiece. If the object is not visible in the eyepiece, gradually pan the telescope, using the right ascension and declination cables, until the object is visible. Always start by using your lowest power eyepiece (20mm) then switching to higher power once you have found the desired object.

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