Specifications

94 AUTOSTAR CCD PHOTOMETRY
Light Sources – Small incandescent battery–operated lamps or
LEDs are typically preferred, although some heavy–duty designs
for larger telescopes in observatories have employed AC lamps
and/or fluorescent tubes.
Wiring and Electrical Supply – Batteries or low–voltage AC
transformer adapters may be used, with the lamps or LEDs wired
either in series or parallel. Some designs feature adjustable voltage
to control the illumination. Some designs have experimented with
both incandescent lamps and LEDs, selectable with switches.
Flashlight bulbs do not seem to be very useful, as the molded bulbs
project disturbing dark and light patterns. LEDs present several
concerns: they may only be adjusted through a short range with a
conventional potentiometer (voltage adjustment) circuit; a series
resistor must be employed, to limit the current; and the proper
polarity of the DC voltage must be observed.
The color temperature of the lamps or LEDs (typically the bright
white type) has been discussed in detail by some workers, but this
is less of a factor in photometry, as the exposure is adjusted
separately for each filter. A simple battery box with an On–Off
switch can be constructed, and attached to the outside of the box
with hook–and–loop fasteners. The switch may even be dispensed
with, and the battery or power supply simply disconnected when
not in use.
Light Arrangement – The lights are carefully arranged to shine
upward against the inside of the top of the box, so that the light is
evenly diffused. It is important that the lights not be permitted to
shine directly into the diffuser panel(s). Some constructions use
small baffles, made of the same foamcore material as the box and
light mountings, typically placed in the corners of the box. A small
piece of translucent frosted material, perhaps mylar tape, placed
over the individual bulbs or LEDs may help to soften and diffuse
the light pattern.