Assessments - 5, GPA: 3.2 ( )

Fabricante : Celestron Arquivo Tamanho: 1.02 mb Arquivo Nome : Língua de Ensino:

Manually move the telescope tube past the object you want to view, then use the slow motion control, in the opposite direction, to go back to the object. Tighten the knob and reverse the direction of the declination cable. Do not try to force movement when the declination cable has reached the end of its range. There are the same two options for moving the telescope in right ascension (east/west). For large and quick movements, release the right ascension knob (24), move the telescope toward the object you want to view, then tighten the knob when you’re near the object. For very small movements and fine adjustments, use the right ascension cable (31). For quick horizontal movement, loosen the horizontal adjustment knob. In order for the telescope to move smoothly on both axes it must be properly balanced. To balance the right ascension axis, move the counterweight shaft so it is parallel with the ground. Slowly release the right ascension knob (24) and check to see if the optical tube moves. If the optical tube does move, then slide the counterweight up or down the counterweight shaft until the optical tube remains stationary in a position parallel to the ground. When you have achieved balance, tighten the counterweight lock nut. To balance the declination axis, follow the same procedure, using the declination knob (22) and the tube mounting knob (28). Focusing the Telescope and Aligning the Finderscope This procedure will be easiest to do during daylight hours. Remove the front lens cover. Put a low power eyepiece in the diagonal and position the telescope tube to look at an object about one mile away that’s easy to focus on, such as a stop sign. You may need to use the declination and/or right ascension slow motion cables to get the object in the center of your field of view. Use the focus knob to get the object in sharp focus. Remove the lens covers from the finderscope and look through it. If the object you’re observing either isn’t visible in the finderscope or isn’t centered in its cross hairs, then you need to align the finderscope. Use the finderscope adjustment screws to align the finderscope with the main telescope by tightening and loosening these screws until the object is centered in the cross hairs. Once the finderscope is aligned with the main telescope, it becomes a great tool for finding celestial objects because it has a wide field of view. First, find the object you wish to view in the finderscope, then look at the narrower, but much more powerful field of view in the main telescope for detailed views. If the image in the finderscope isn’t sharply focused, turn the finderscope eyepiece (6) to get a focused image. Don’t be alarmed when you look through the finderscope and telescope, and the object is upside down and reversed left to right. This is normal with an astronomical telescope. Preparation for Astronomical Observing 1. Orient the telescope so that the right ascension (polar) axis is pointing as close to true north as possible. You can use a magnetic compass to determine which direction is north. 2. Adjust the mount so that it’s level. You may find using a carpenter’s level helpful. 3. Recheck all hardware and knobs to make sure they’re tight. UNDERSTANDING THE SKY The Celestial-Coordinate System The celestial-coordinate system is an imaginary projection of the earth's geographical coordinate system onto the celestial sphere, which gives the appearance of rotating overhead at night. This celestial grid is complete with equator, latitudes, longitudes and poles. The celestial equator is a full 360° circle dividing the celestial sphere into the northern celestial hemisphere and the southern celestial hemisphere. Like the earth's equator, it is the prime parallel of latitude and is designated 0°. The celestial parallels of latitude are called “coordinates of declination (DEC).” As with the earth's latitudes, they’re named for their angular distances from the equator. These distances are measured in degrees, minutes and seconds of arc. There are 60 minutes of arc in each degree, and 60 seconds of arc in each arc minute. Declinations north of the celestial equator are "+" and declinations south are The north pole is +90 and the south pole is -90 . Figure 2 The celestial meridians of longitude are called “coordinates of right ascension” (RA). Like the Earth's longitude meridians, they extend from pole to pole. There are 24 major RA coordinates, evenly spaced around the 360° equator, one every 15°. Like the earth's longitudes, RA coordinates are a measure of time, as well as angular distance. We speak of each of the earth's major longitude meridians as being separated by one hour of time because the earth rotates once every 24 hours (one hour = 15°). The same principle applies to celestial longitudes since the celestial sphere appears to rotate once every 24 hours. Right ascension hours are also divided into minutes of arc and seconds of arc, with each hour having 60 minutes o...

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