H-BETA IMAGER BRIEF DESCRIPTION

Our  current  generation  of  H-Beta  imagers  employ   fast
fish-eye  lenses  and  intensified  scientific-grade CCDs to
image   weak   auroral   emissions    simultaneously    from
horizon-to-horizon.   High optical throughput is achieved by
using fast lenses throughout  the  optical  chain.   Further
contributing   to   enhanced   imaging  performance  is  the
large-diameter   optics   with    its    3-inch    diameter,
high-transmittance   interference   filters.   Five-position
filter-wheels accommodate filters with passbands centered on
(currently)  427.8 nm, 486.1 nm, 557.7 nm, 630.0, as well as
a  background  filter  (480.6  nm).   High  sensitivity  and
corresponding  high  low-light-level  spatial resolution are
further  ensured  by  adopting  a  special  cooled,  thinned
``blue-enhanced''  intensifier  photocathode  material and a
customized fast phosphor at the image  intensifier's  anode.
The      image-intensifiers      utilize     high-efficiency
microchannel-plates.  The resulting image  is  digitized  at
16-bits-per-pixel,   ensuring   a   large   dynamic   range,
permitting the detection of both faint H-Beta emissions,  as
well  as  the more intense green/red-line features.  Shutter
operation,  filter-wheel  position/temperature,  intensifier
power  and  gain, image integration and acquisition, as well
as other auxiliary data (such as  GPS/UPS  parameters),  are
controlled  and  monitored  digitally  by  a dedicated Linux
workstation.  Images, along with headers containing GPS time
stamps,  are  losslessly  compressed  and  saved  onto  4-mm
digital tape (DAT), with a transition  to  the  DVD  storage
medium anticipated within a few years.