Integrating Video Camera operating guidelines

Report
By Tony George for 2013 IOTA Conference
INTEGRATING VIDEO CAMERA
OPERATING GUIDELINES
Issues:
 Many IOTA members are purchasing
integrating CCD video cameras to expand the
range of occultations they can observe
 CCD video cameras have a variety of
‘settings’, not all of which are appropriate for
getting good video data
 Establishing a set of ‘guidelines’ will help
IOTA members get the best possible results
from their integrating CCD video camera
observations
Cameras most commonly used:
 WAT 120N+
 PC165DNR
 Mintron
 Mallincam
Note: It is the observers responsibility to understand the operating
characteristics and controls of their camera. Too many times we receive
videos with compromised data due to incorrect settings or operation. If in
doubt, ask for advice from experienced observers prior to your observation.
Important settings:
 Shutter – fast and/or slow
 Gain – manual and/or automatic
 Gamma – off/LO/HI (if applicable)
 Color mode (if applicable) – B/W or color
WAT 120N+ Control Box
PC165DNR Control Menu
Shutter (integration)
guidelines:
 Operate the shutter at the fastest possible speed
setting necessary to get a ‘stable’ target star
image. The target star doesn’t have to be
constantly visible if there is atmospheric
instability, but it should only blink out
occasionally. Operating at the fastest possible
shutter speed gives the best time resolution for
disappearance and reappearance timing, as well
as for capturing other photometric phenomena
such as double star step events
Shutter (integration)
guidelines (cont.):
 Avoid sub-frame shutter speeds. Some
cameras allow a setting that will give
exposures at less than 1/60th second.
Observers have used short-speed settings to
reduce star brightness. However shorter
exposures give no information during the
field when the shutter is closed and valuable
timing information can be lost. The fastest
setting that should be used is 1/6oth setting
(field level timing).
Shutter (integration)
guidelines (cont.):
 Operate the shutter in ‘manual’ mode. Some
cameras (Mallincam) adjust the shutter speed
(integration rate) automatically if not set
manually. This is very problematic for the
proper analysis of the light curve.
Gamma guidelines:
 Gamma is the relative brightness of faint objects compared to bright
objects. No gamma means that the relative brightness is ‘linear’,
which is preferred for observations where relative magnitude
photometry is an important objective – such as NEO photometry
 Cameras with manual gamma settings should be set to gamma off
(1.0 gamma) as a first choice. This gives the best photometry for
analysis of the light curve.
 WAT 120N+ can also be set to gamma LO (0.45) or gamma HI (0.35),
if needed to enhance the visibility of the target star for a given
shutter setting.
 Use the combination of gamma and shutter speed that gives a
stable target star image (if possible) at the fastest possible shutter
speed.
 Don’t set gamma off if it means you have to integrate at ¼ second, if
instead you can set gamma HI and integrate at 1/30th second.
Gain guidelines:
 Cameras with manual gain control should be
operated in manual mode.
 Set gain to MAX to allow using the shortest
possible shutter (integration) speed
 Use gain control (adjust downward) to reduce
target star brightness to avoid image saturation
if the shutter is already set as fast as possible
(1/30th second)
 Mallincam AGC should always be OFF. This
camera allows for variable shutter settings under
AGC and therefore proper event timing cannot
be assured when analyzing the light curve.
Color mode guidelines:
 B/W cameras are preferred over color
cameras. On-chip resolution is better.
Photometry is better. If color information is
desired, filters should be used.
 Color cameras, if possible, should be set to
B/W mode.
 Recording in color can result in odd results
when the data is captured to a PC, as some
capture programs only capture one of the
three color channels
Observation object
guidelines:
 Asteroids: events are typically short – maximum
time resolution is preferred – use lowest possible
shutter speed consistent with getting a stable
combined asteroid+target star image – asteroid
does not need to be visible.
 Lunar double star: step events are expected –
maximum time resolution is preferred – use lowest
possible shutter speed.
 TNO’s: events are typically longer duration – target
stars are typically faint with the TNO even fainter –
use integration as needed to get stable combined
TNO+target star image – TNO does not need to be
visible.
Conclusions:
 Integrating CCD video cameras allow IOTA
observers to attempt a broader range of
event magnitudes
 Proper camera settings are important to
getting good light curves
 Use of these integrating camera guidelines
will help to get the best possible light curve
 If in doubt, ask an experience observer for
advice before investing time and energy into
your observation

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