Getting your bearings

Most celestial objects of interest are not visible without instruments such as telescopes or binoculars. Yet from their nature telescopes and binoculars have a much smaller field of view than the unaided eye, and directing these instruments to exactly where intended may present difficulties. Here are some hints on how to find your way around the night sky.
Equatorial Coordinates
Finding Polaris

Equatorial Mounts

An equatorial mount is a mount used for moving a telescope or camera along two perpendicular axes of motion known as right ascension and declination. The telescope mount's axis of right ascension should be pointed directly towards whichever celestial pole is above the horizon to work correctly. Setting the axis of the mount to the polar axis completes alignment. This polar alignment is dependent on the location of the observer and corresponds with the latitude of the observer's location. Equatorial mounts are often equipped with a motor drive for automatic tracking of objects across the night sky. They may also be equipped with setting circles to allow for the location of objects by their celestial coordinates.

Alt-azimuth Mounts

An Altazimuth or alt-azimuth mount is a simple mount used for moving a telescope along two perpendicular axes of motion. The vertical movement is known as the altitude, while the horizontal motion is called the azimuth. The biggest advantage of alt-azimuth mounts is their simplicity in both manufacture and use. They are often used for beginner telescopes, or for spotting scopes, but are still widely in use for more advanced telescopes. In the latter case, advanced electronics and motors are sometimes attached to compensate for the restrictions of the mount's simplicity. In astronomy, alt-azimuth mounts were, for a time, surpassed in popularity by the more complex equatorial mount. The latter is more naturally suited for tracking astronomical objects in the night sky as the Earth spins on its axis, since its polar alignment means that only one axis need be adjusted rather than the two of an alt-azimuth mount. Being able to track such objects reliably is particularly important for astrophotography, as well as more advanced amateur astronomy, both of which became more accessible when equatorial mounts became affordable.

Astrophotography

Astrophotography is used to reveal objects that are too faint to observe with the naked eye, as both film and digital cameras can accumulate and sum photons over long periods of time. Astrophotography poses challenges that are distinct from normal photography, because most subjects are usually quite faint, and are often small in angular size.
Focusing using a Hartmann Mask