.title
Faint Object Camera
.synonym
spectrographic

.description
An extremely sensitive camera capable of pinpointing and electronically
intensifying dim objects.
.contents

.para
     This instrument, being built by the .~ European Space Agency~, uses
the spatial resolution of the .~ telescope~ to capture images of very
faint objects in the universe .~ (fig. 1)~.


.para
     It is expected to be able to detect stars as faint as the 28th
magnitude and will easily pick out stars of magnitude 24, which is about
the best a large ground observatory can now do. Magnitude is a
designation of brightness - the lower the number, the brighter the
object.  The dimmest star the average person can see with the naked eye
are magnitude 6. The planet Venus is magnitude -4.


.para
     The Faint Object Camera has a basic focal ratio of f/96 and is
capable of observing faint objects or extended structures near bright
sources.  This device will have four .~ filter wheels~, each containing a
variety of filters in 12 positions, which can be inserted in the optical
path.


.para
     The system works by gathering and focusing incoming feeble
starlight on an electronic image intensifier.  The intensifier's output
is scanned by a vidicon camera tube and an image consisting of 250,000 
picture elements is obtained.  Exposure times for very faint objects
could run as long as ten hours.


.para
     An f/48 focal ratio camera system will permit the camera to operate
in a .~ spectrographic~ mode which is ideal for studying the structure and
dynamics of the center regions of galaxies, the area where black holes
are thought to occur. Thus the Faint Object Camera serves as a third,
general-purpose spectrograph.  This mode of operation will employ
fourteen insertable filters.