APPENDIX B: Terrestrial Viewing, Celestial Movement, and Polar Alignment
Terrestrial Viewing
The 4504 is an excellent,
Astronomical Observing
Used as an astronomical instrument, your telescope has many optical and electro- mechanical capabilities. It is in astronomical applications where the high level of opti- cal performance is readily visible. The range of observable astronomical objects is, with minor qualification, limited only by the observer’s motivation.
Polar Alignment
Lunar or planetary photography requires that the telescope be Polar aligned. In Polar Alignment, the telescope is oriented so that the horizontal and vertical axes of the tele- scope are lined up with the celestial coordinate system.
In order to understand Polar Alignment, it is essential to have an understanding of how and where to locate celestial objects as they move across the sky. This section pro- vides a basic introduction to the terminology of
Understanding Celestial Movements and Coordinates
Understanding where to locate celestial objects and how those objects move across the sky is fundamental to enjoying the hobby of astronomy. Most amateur astronomers adopt the simple practice of
Understanding How Astronomical Objects Move
Due to the Earth’s rotation, celestial bodies appear to move from East to West in a curved path through the sky. The path they follow is known as their line of Right Ascension (R.A.). The angle of the path that they follow is known as their line of Declination (Dec). The system of R.A. and Dec is analogous to the
Understanding Celestial Coordinates
Celestial objects are mapped according to the R.A. and Dec coordinate system on the “celestial sphere” (Fig. 31), the imaginary sphere on which all stars appear to be placed. The Poles of the celestial coordinate system are defined as those two points where the Earth's rotational axis, if extended to infinity, North and South, intersect the celestial sphere. Thus, the North Celestial Pole is that point in the sky where an exten- sion of the Earth's axis through the North Pole intersects the celestial sphere. In fact, this point in the sky is located near the North Star, or Polaris.
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