The Mechanical Unit
Shutters are developped in various sizes, for single CCD cameras as well as for the largest mosaic cameras.
Left: A 60mm square aperture shutter complete with control electronics and power supply.
Right: The 600mm cicular aperture shutter for Decam.
Despite the huge range of aperture sizes the mechanics is basically the same for all types. Everything is mounted on a single aluminum base plate with the aperture in the center. The shutter blades are usually made from carbon fiber material. For the large PS1 shutter (e.g. Pan-STARRS, 480mm square aperture) a sandwich structure was used to reduce weight. Both blades move on linear ball bearings. The movement is monitored by encoders and absolute position reference is provided.
To prove the reliability of the moving parts a complete drive
section of a 200mm aperture) was copied and
an endurance test was performed.
Horizontal as well as vertical operation was possible. Most of the time the set up was in the vertical position (up-down movement) with maximum load for motor and toothed belt. Temperatures were: room, dome (6C), fridge (-20C). An operation (amplitude 220mm) was initiated every second.
After 10 Million cycles without failure (about 4 months of continuous operation) the experiment was switched off. No indications of critical abrasion could be found. (After several years this endurance teststand is still in use for motor tests.)
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