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Meade Instruments Corporation - How Telescopes Work (1750 words) |
 | Altazimuth Mountings: The simplest type of telescope mount allows the telescope to be moved up-and-down (in vertical, or altitude) and left-to-right (in horizontal, or azimuth). |
| The altazimuth mount, owing to its simplicity and relatively lower cost, is widely used with telescopes in both land-viewing and astronomical applications. |
| Equatorial Mountings: Although celestial objects are essentially fixed in their positions in the sky (on the celestial sphere, the imaginary spherical surface on which all astronomical objects are located), they appear to move in an arc across the sky, as the earth rotates underneath the sky once every 24 hours. |
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altazimuth mounting (0 words) |
| A telescope mounting, also known as an alt-azimuth mount, that allows up and down pivoting (changes in altitude, or elevation, from 0° to 90°) together with horizontal rotation (changes in azimuth by ± 180°). |
| Drawbacks, in addition to dual-axis tracking, are that the tracking rate varies with position in the sky and that the field of view rotates, which, though not a problem for point sources such as stars, must be addressed for any extended source by either rotating the instrument or by de-rotating the image. |
| A popular version of the alt-azimuth mount used widely by amateur astronomers is the Dobsonian. |
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