I think the other axis for equatorial is the altitude. A star is known from its hour angle (round the equator from the first point of Aries) and altitude (above the equator) Azimuthal is degrees down from the zenith (overhead) and the angle in degrees round from north on the horizon. (no good if you are at the pole). Its all spherical triangles. You can convert from azimuthal to equatorial using a spherical triangle computation (quite complicated but which I did know once but have forgotten) or with an analogue computer consisting of potentiometers mounted on gimbals in a complicated sort of way. They went out when digital computers came in. The conversion depends on where the telescope is on the earths surface and assumes that the earth is spherical. I really like spherical triangles like every navigator should. All forgotten now. Not that I ever did navigation for real, I've only held a sextant a couple of times. Chris. http://www.chrisspages.co.uk -----Original Message----- From: owner-photoforum@listserver.isc.rit.edu [mailto:owner-photoforum@listserver.isc.rit.edu]On Behalf Of ADavidhazy Sent: 19 November 2003 18:45 To: List for Photo/Imaging Educators - Professionals - Students Cc: andpph@vmsmail.rit.edu Subject: Altazimuth telescope mounts correction Altitude and azimuth - thus they actually have two axes of rotation. OK - sue me!! But then equatorial still stands methinks! :) andy
