An observer at AAT's prime focus
AAO image reference AAT 4b.     « Previous || Next »

An observer (David Malin) in the prime focus cage of the Anglo-Australian Telescope
Image and text © 1991 Australian Astronomical Observatory, photograph by David Malin.

When the telescope is used to take photographs it acts as huge camera. The camera 'lens' is the AAT's 4m primary mirror which operates at f/3.3. It has a focal length of 12.7m and a field of view 1 degree square. In this configuration the observer rides in the prime focus 'cage' at the top end of the telescope where light from the primary mirror is brought to a focus. With his back to the sky, he can spend many hours taking photographs on specially sensitised glass plates each of which is 10 inches square and which may require exposure times of 60-90 minutes to reveal the faintest objects. As the telescope moves across the sky the small seat can be rotated around the plate holder to provide the observer with some degree of comfort. The prime focus cage is currently being modified for remote observing using electronic detectors (CCDs). Click here for bigger image.

The plates taken with this camera were mostly intended for scientific purposes, but many of them have been used to make the 3-colour images seen elsewhere on these pages. Some care has been taken to ensure that the colour in the images derived from these plates is realistic. This picture was made in 1991.

Related Images
AAT 4a.  A younger observer at AAT prime focus
AAT 4c.  An observer displaced from the AAT prime focus

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