|Interaction with the camera is managed through the Camera Control Window. The window consists of a Header, Top Level, 2nd Level, and an engineering level. The header is always visible at the top of the window; the levels are selected by tabs along its lefthand edge. Items on the engineering level should not be changed by users, and are not covered in this manual.|
|The header portion, illustrated above, displays the exposure time elapsed and remaining. (Note that the counter is only useful for exposures greater than about 0.5 seconds.) The box in the upper righthand corner displays warnings. The camera's detector is also identified here as a Lawrence Berkeley National Laboratory 690 by 400 pixel CCD (other guiders may use different detectors).|
|Set Camera:||This button must be clicked in order to effect changes you have made to most
camera control parameters. The button turns yellow after you have changed a parameter,
to remind you that you must click it in order to make your changes take effect.
If this button is still
yellow, one or more of your
camera parameter settings will not be reflected in the camera's behavior!
(Exceptions are the Exposure and Gain parameters which take effect without pushing
the Set Camera button.)
Note that if the cursor is on the "Set Camera" button, it goes green regardless of the state of the camera settings.
|Stop and read out:||Not applicable to autoguiding. Used only if the camera is in a data-recording mode.|
|Abort and throw away:||Not applicable to autoguiding. Used only if the camera is in a data-recording mode or when troublshooting problems.|
Allows up to ten camera setups to be saved. The
selection bar produces a pulldown menu from which a saved setup can
be selected. Selecting a new setup will cause the new setup's parameters
to appear in both levels of the camera control window, but the change
will not take affect until the Set Camera button
Once a setup is selected and invoked, it can be edited by simply changing the value of any parameter. The new value is automatically saved as part of the current setup. Setups can be named from the 2nd Level.
|The exposure slider can be set to any value from zero to
n seconds (n can be changed from the
2nd Level). New exposure times take effect
automatically when slider is moved.
Because this is a shutterless system, actual exposure time is the number of seconds selected on the slider plus the CCD readout time. Thus, "zero" exposure is actually a minimum integration equal to the CCD read time (about 2 seconds for an unbinned exposure of the whole chip at slow readout, less than 1 second for fast readout). This is generally short enough for all but the brightest stars, or for occasions when an especially high frame rate is desirable.
There are, however, several ways to decrease the readout time and therefore the "minimum" integration. Binning or increasing readout speed (both are options in this window) decrease readout time, but while these approaches can be useful for acquisition, they should not be used for guiding as they decrease resolution, change plate scale, or cause aberrations.
The correct method for decreasing exposure time (and increasing frame rate) is to window the CCD. See the next paragraphs.
|These three options control the CCD windowing (i.e., the portion of the chip actually read out). Note that when changing window size or restoring to full readout, one or two garbage frames will be read out before the new window takes effect.|
|From Display||Tells the camera to read out only that portion of the chip that has been graphically defined in the Image Display Window using the "box" function.|
|Whole CCD||Restores the windowed CCD to the full image pixel readout.|
|nr nc sr sc||
Numerically defines the portion of the chip to be read out.
The variables nr, nc, sr, and sc stand for "number of rows, "number of columns," "starting row," and "starting column" respectively. Values of nr, nc, sr, and sc for the current readout window are displayed below each variable. New values are typed into the box below, entered with a carriage return, and initiated by pushing the Set Camera button.
Note that though the CCD is 690 x 400 pixels, the largest possible window is 345 x 400 because it is a frame transfer system and the other half of the detector is devoted to reading out the image. Also note that on the guider display, the origin (0,0) is at the upper left corner of the image.
|BINNING, GAIN, & READOUT SPEED|
Sets onboard binning.
Binning 1 = no binning and is used for all guiding, though there may be instances when it is convenient to increase binning for acquisition. Guiding will not work with binning > 1. Binning may not be available on all guiders.
|Gain:||Gain is generally left at 0. Gain greater than 0 may not be available for all guiders.|
|Read Speed:||Read speed should be left at "slow" for guiding. For acquisition or when high frame rates are needed, increasing read speed may be useful.|
|Images may be saved as FITS files.|
Observation number is the number that will be given to the next recorded
exposure. The file holding that exposure will be given a name of the form
[root name] + observation number + [.extension]
and written to the designated directory. The root name, extension, and directory may be set in the 2nd Level. Default directory and name are /data/g[#].fits
The observation number will increment with each recorded image. The number may set by the user, but remember that if you set the number back, files with the same name will be overwritten without warning.
Selecting "Record" writes the next n images to disk;
n may be set on the 2nd Level
(Setting n to -1 will record all images until recording is turned off.)
The Set Camera button must be pushed to initiate recording.
Recorded images will be named and saved according to the rule described in "Observation Number," above.
|Object:||The string entered in the "Object" box will be recorded as the value of the OBJECT keyword in the FITS header of the images.|
|NAMING SAVED SETUPS|
|The saved setup bar here is the same one that appears on the Top Level. Just below it is a space in which to record a name for the currently selected setup. These names will appear in the saved setup pulldown menu, and remain associated with a given setup number until the name is changed.|
|NAMING RECORDED IMAGES|
|This widget allows parameters to be set for recorded images. The number
of consecutive images to be recorded is set in "Record count." If record count is
set to -1, all images will be recorded as long as record
is selected in the top level.
Directory, Root, and Suffix allow a directory to be specified where recorded images will be stored, and a naming scheme to be chosen. The values shown here (the default values) would save files to the /data directory in the form g[#].fits.
Recorded images are in FITS format.
|AMP & MPP|
|These parameters should not be changed by the user|
|SETTING EXPOSURE RANGE|
|You may set the maximum exposure time, thereby setting the range of the exposure slider in the top level. 30-60 seconds is a practical maximum for most guiding operations.|
|SETTING & MONITORING CCD TEMPERATURE|
|Monitor temperature should generally set to "no" unless you are actively monitoring
the CCD temperature. Selecting "yes" will display the current temperature but may also cause some
noise in the guider image. Thus, it's fine to check the temperature, but best to turn off
monitoring the rest of the time.
Our thermoelectrically cooled cameras have been holding the CCD at about -40 to -50 degrees in cool weather. CCD temperatures will be somewhat higher in summertime.
Desired CCD temperature is set well below the attainable temperature (e.g., -100.0) to maintain the lowest possible temperature.