Palomar / LFC

   As a graduate student at Caltech, I participated in construction of the LFC, or Large Format Camera.  The LFC is a mosaic of six 2048 / 4096 pixel CCDs operating at UV/Optical wavelengths, commissioned in 1999.  It resides at the prime focus of the historic Palomar 200 inch Hale telescope.  You can see LFC installed in the prime focus cage below; the blue vessel at the photo center is the CCD dewar, being refilled with liquid nitrogen.

The 200″ is often called the Big Eye, and reigned as the largest telescope on the planet for 45 years even thoguh it has now been surpassed.  An excellent history of this observatory may be found in the book The Perfect Machine.

Before the days of digital imagers, astronomers would spend the night riding inside the telescope when observing at prime focus, as shown in the photo below.  I was probably one of the last to ride in the PF cage as the telescope was operating during an LFC commissioning run.  To balance the telescope, they needed to calculate how much torque someone with my weight would exert on the telescope at a 15 meter lever arm, a somewhat humbling number.

The images below illustrate an astronomer situated in the cage, and the size of the telescope for scale.

At prime focus, the LFC can image an area over 20 arcminutes in diameter on the sky, an area somewhat similar to the size of the full moon.  With the light collecting area of the 200″ (5080mm) diameter primary at F/3.5 (for prime focus), it enables fast imaging of faint targets.  My involvement with LFC ended in 2001 but as of 2012 it still sees fairly regular use at Palomar.  The image below is of a distant galaxy cluster, taken with LFC.  This image has a negative color stretch, so that the sky appears white and galaxy images appear as black.  The black squares mark locations of masked regions that are bright/saturated.