Description
Figure 1. is a 3-D representation of the instrument's light path and principal components.
The optical interface, outlined in green in Figure 1., bolts to the telescope and supports the camera's other components. A dichroic beamsplitter reflects the infrared part of the telescope beam to the dewar, where it is filtered and reimaged on the array by the dewar's internal optics. The visual part of the beam is transmitted by the beamsplitter and reflected by two plane mirrors to the boresite camera for acquisition and guiding.
The TUB diagonal and TUB camera are permanently mounted on the telescope above LIRC-II's optical interface and below the primary mirror. While not parts of the instrument itself, the TUB components may be used with LIRC-II for acquisition and guiding.
Figure 2. above illustrates the dewar's internal optics. The telescope
focal plane lies approximately 70-mm in front of the dewar window.
Just behind the window, a three-element lens assembly collimates the beam.
This is followed by independentally positioned "front" and "back"
filter wheels with four and twelve positions respectively.
Table 1. below lists their contents.
Filter transmission curves can be found elsewhere in thei manual.
Figure 3. below shows the globular cluster M97 as it appears on the
array at the 3-meter telescope, with each field of view. Field size and
plate scale are given for each of the three lenses at each telescope.
North is at bottom, East at left, on the data-taking system displays at both
telescopes.
The observer opeartes the instrument from the telescope control room via
the data-taking, motor control, and "lirctop" programs, all of which run in
X-windows on the user's terminal. Figure 4. shows how the various parts
of LIRC-II and its associated systems fit together.
The data-taking program permits the user to
input observing parameters, control the array, provide information for the
FITS header, and control data recording.
The motor-control program
operates the lens and
filter wheels and the moveable dichroic beamsplitter.
Lirctop is a collection of Vista routines
which automate various
observing procedures such as dithering, mosaicing, and calibrating.
The links in this paragraph lead to detailed guides for these programs.
The bore-site and TUB guide cameras share the same standard Lick TV
camera controller. Either can be used for acquisition and to provide
the signal for the Lick autoguider, however, the two cameras differ in
some important respects. Choosing the best TV camera is discussed in
the section on Acquisition/Guide Cameras.
Output devices for LIRC-II data include an X-Window terminal, high-capacity
disk drive, 8-mm Exabyte tape drive, and a laser printer.
Filter Bandpass or
Central Wavelength
at 77 ° KK 1.98 to 2.39 J 1.10 to 1.44 Open - OII 1.237 (within 1%) FeII 1.644 (within 1%) H2 S(I) 1-0 2.122 (within 1%) Brackett Gamma 2.166 (within 1%) H2 S(I) 2-1 2.248 (within 15) CO 2.295 (within 3%) K-prime 1.95 to 2.35 H 1.50 to 1.82 Dark between filters
Filter Bandpass or
Central Wavelength
at 77 ° KOpen - ND2 2% transmission Open - Open - Dark between filters