Equatorial platform
Encyclopedia
Astronomical object
Astronomical objects or celestial objects are naturally occurring physical entities, associations or structures that current science has demonstrated to exist in the observable universe. The term astronomical object is sometimes used interchangeably with astronomical body...
s in the sky on an equatorial axis. They are used to give equatorial tracking to any device sitting on them, from small camera's up to entire observatory buildings. They are often used with altazimuth mount
Altazimuth mount
An altazimuth or alt-azimuth mount is a simple two-axis mount for supporting and rotating an instrument about two mutually perpendicular axes; one vertical and the other horizontal. Rotation about the vertical axis varies the azimuth of the pointing direction of the instrument...
ed telescopes, such as the common Dobsonian telescope
Dobsonian telescope
A Dobsonian telescope is an alt-azimuth mounted newtonian telescope design popularized by the amateur astronomer John Dobson starting in the 1960s. Dobson's telescopes featured a simplified mechanical design that was easy to manufacture from readily available components to create a large, portable,...
type, to over come that type of mounts inability to track the night sky.
Types
There are many types of equatorial platforms that have been used over the years. The mid-1960s saw the introduction of the RussiaRussia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
n AFU-75 satellite-tracking camera which consisted of an 3 axis altitude-altitude-azimuth mount mounted on a three point equatorial platform. Two of the points were aligned on a polar axis the third was a jack screw actuator
Actuator
An actuator is a type of motor for moving or controlling a mechanism or system. It is operated by a source of energy, usually in the form of an electric current, hydraulic fluid pressure or pneumatic pressure, and converts that energy into some kind of motion. An actuator is the mechanism by which...
to drive the platform. This gave the mount a few minutes of equatorial tracking to allow stars in the field of view to be imaged as points for accurate measurement.
The late 1970s saw the publication of Adrien Poncet's "Poncet Platform
Poncet Platform
A Poncet Platform or Poncet mount is a type of equatorial platform that uses a simple polar pivot and an inclined plane. The motion of the mount allows any device sitting on that platform to track the apparent motion of the stars in the night sky...
", a very simple design for amateur telescope makers
Amateur telescope making
Amateur telescope making is the activity of building telescopes as a hobby, as opposed to being a paid professional. Amateur telescope makers build their instruments for personal enjoyment of a technical challenge, as a way to obtain an inexpensive or personally customized telescope, or as a...
that used a pivot point and an incline plane that made a very low profile "table". This type of mount has been a popular retrofit
Retrofit
Retrofitting refers to the addition of new technology or features to older systems.* power plant retrofit, improving power plant efficiency / increasing output / reducing emissions...
for altazimuth mount
Altazimuth mount
An altazimuth or alt-azimuth mount is a simple two-axis mount for supporting and rotating an instrument about two mutually perpendicular axes; one vertical and the other horizontal. Rotation about the vertical axis varies the azimuth of the pointing direction of the instrument...
ed telescopes, such as the common Dobsonian telescope
Dobsonian telescope
A Dobsonian telescope is an alt-azimuth mounted newtonian telescope design popularized by the amateur astronomer John Dobson starting in the 1960s. Dobson's telescopes featured a simplified mechanical design that was easy to manufacture from readily available components to create a large, portable,...
type, adding equatorial tracing for high magnification work and astrophotography
Astrophotography
Astrophotography is a specialized type of photography that entails recording images of astronomical objects and large areas of the night sky. The first photographs of an astronomical object were taken in the 1840s, but it was not until the late 19th century that advances in technology allowed for...
.
Since the Poncet Platform's simple bearing surfaces suffers from high mechanical loadings when used with heavy telescopes or at at low geographic latitudes more sophisticated equatorial platform designs were invented in the 1980s. One was Alan Gee's design that uses a cylindrical bearing surface and a pivot making a mount similar in structure to a horseshoe mount that has been "cut flat". In 1988 Georges D'Autume's proposed a more sophisticated design which used conical bearings surfaces all around to raise the height of the "virtual polar axis" to make it the mount better balanced for heavier loads.
Poncet based platforms are usually designed to track for 1 hour (15° of tilt) since longer tracking exceeds their range of motion and could cause the instrument on top of it to topple off. At the end of their drive limit the mount has to be pivoted back to the east to reset the clock drive
Clock drive
In astronomy a Clock drive is a regulatory mechanism used to move an equatorial mounted telescope along one axis to keep the telescope in exact sync with the apparent motion of the celestial sky...
mechanism.