The acquisition TV [B] is a very sensitive instrument which will be destroyed by excessive light levels. DO NOT allow any extraneous light to fall anywhere around the TV while the high voltage is up, and remember to bring it down before any lamp exposures are taken.
The TV has both zoom and focus adjustments. The zoom may be set by turning on the TV (with the operator's help) and turning the plastic gear on top of the TV periscope [J] until the picture fills the screen as desired. To focus the TV, make sure the mirror covers are closed and dome lights are off. Then put in the 2.5 arcsec slit (see Chapter 3) and turn the high voltage all the way up. Have someone watch the monitor while another person turns the knurled ring that encircles the TV periscope until the slit is focused on the monitor. Make sure to turn the high voltage back down again! Note that if the zoom is changed during observation, the TV must be refocused.
Since the acquisition TV is more sensitive to red wavelengths, there is a blue filter available for viewing the TV field at shorter wavelengths. This is put in place with a switch [K] at the top of the TV tube. Please leave the switch in the default out position at the end of your run.