Editing Telescope mount (section)

== Altazimuth mounts ==
{{Main|Altazimuth mount}}
[[Image:Herschel 40 foot.jpg|thumb|right|[[William Herschel]]'s {{convert|49|in|mm|adj=on}} [[40-foot telescope]] on an altazimuth mount.]]
Altazimuth, altitude-azimuth,  or ''alt-az mounts'' allow telescopes to be moved in altitude (up and down), or azimuth (side to side), as separate motions. This mechanically simple mount was used in early telescope designs and until the second half of the 20th century was used as a "less sophisticated" alternative to equatorial mounts since it did not allow tracking of the night sky. This meant until recently it was normally used with inexpensive commercial and hobby constructions. Since the invention of digital tracking systems, altazimuth mounts have come to be used in practically all modern large research telescopes. Digital tracking has also made it a popular telescope mount used in [[amateur astronomy]].<ref>[http://planetfacts.org/altazimuth-mount/ Altazimuth Telescope Mount]. Planetfacts.org. Accessed April 13, 2012.</ref>

Besides the mechanical inability to easily follow celestial motion the altazimuth mount does have other limitations. The telescope's field-of-view rotates at varying speed as the telescope tracks, whilst the telescope body does not, requiring a system to counter-rotate the field of view when used for [[astrophotography]] or other types of astronomical imaging.<ref>[http://www.astronomics.com/main/altazimuth_mounts.asp/catalog_name/astronomics/category_name/455bs0f9rd968kref4bq6fgr63/page/1 Altazimuth Mounts]. Astronomics.com. Accessed April 13, 2012.</ref> The mount also has blind spot or "zenith hole", a spot near the zenith where the tracking rate in the azimuth coordinate becomes too high to accurately follow equatorial motion (if the elevation is limited to +90 degrees).<ref name="astr.ua.edu">[http://www.astr.ua.edu/keel/techniques/mountings.html Bill Keel's Lecture Notes - Astronomical Techniques - Telescope Mountings]</ref>