Observe the Stars at Minus 84 Degrees – Telescope Motors

Concordia Station in Antarctica houses a remarkable telescope mount that has been in operation for several years. In 2010, the temperature at this station reached a record low of -84.6 °C. Few devices can withstand such extreme conditions, but the telescope mount used by the Laboratoire Universitaire d’Astrophysique de Nice (LUAN) for scientific studies has proven to be one of the exceptions.

Astro-Physics, a company specializing in telescope mounts, has successfully demonstrated the effectiveness of their 900GTO and 1200GTO mounts in Antarctica. These mounts have been continuously operating at Dome C since the early 2000s. This is particularly significant because maintenance work is extremely challenging in this harsh environment. The frigid temperatures and perilous wind conditions make it nearly impossible for technicians to work outdoors. Therefore, the telescope mount must be reliable 24 hours a day throughout the six-month-long polar night. The most recent addition to the site is the 3600GTO mount, the largest one ever used at Dome C.

How does it work?

The gear reduction system employed in the mounting apparatus is crucial for the functionality of telescopes worldwide. In order to track a specific star or celestial object consistently, a telescope must move continuously. Without a driven mechanism, the image of a star would quickly move out of view. Higher magnifications cause targets to appear to move even faster.

To keep a target fixed within the telescope’s field of view, the mount must have continuous movement. Astro-Physics designs precision mounting systems that cater to telescopes ranging from 50 pounds to heavy instruments like the one used in Antarctica, weighing a quarter ton. Wally Piorkowski, Head of Mount Production/Scientist for Astro-Physics, explains that every system they build incorporates maxon motors. These motors utilise grease in their bearings that is ideal for extreme temperatures, such as the severe conditions experienced at Dome C. Once in place, the maxon motors do not require additional greasing, which would be impractical given the harsh climate at Dome C. maxon motors also feature an ironless core with neodymium magnets, providing a high power-to-volume ratio. The motors are equipped with either graphite or precious metal brushes for mechanical commutation. Their linear characteristics make them easy to implement in mount applications. Reliability is a crucial characteristic that makes maxon motors particularly well-suited for this purpose.

Each mount consists of two axes. The right ascension axis is parallel to the Earth’s axis and tracks the Earth’s movement. Interestingly, the motor moves in the opposite direction of the Earth’s rotation, creating the illusion that the target object remains fixed in the sky. Astro-Physics designs the reduction drive, employing maxon’s motors and encoders.

The declination axis is positioned at a right angle to the ascension axis, enabling operators to aim the telescope in any desired direction. The encoder ensures that the motor can periodically adjust and correct its position.

“For our smaller mounts, we use A-max motors, and for mounts like the one at Dome C, we use RE25 motors,” says Wally. The RE25 motor offers the highest torque per unit size in its class. “One significant advantage of maxon motors is their absence of cogging,” he explains. Cogging refers to the jerky motion typically exhibited by iron core motors when operating at slow speeds. maxon motors, with their ironless core design, eliminate cogging, even during the slow movements required for telescope mounting systems.

Wally notes that their mounts are often purchased separately from the telescopes themselves. Astronomy clubs, schools, associations, and other organizations acquire telescopic equipment and mounting systems independently and assemble them. In addition to their use in Antarctica, Astro-Physics’ 3600GTO and 3600.

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