SUSI2

Fast Photometry

Fast Photometry

It is possible to define sequences of many windowed frames in order to sample the lightcurve of a rapidly varying object.

For example, the window presented above has a size of 100 x 400 pixels. The mean dead time between two images is 13 seconds, with an exposure time of 10 seconds in the 3x3 mode, so a sampling time of 23 seconds. To use this mode, use the following procedure:

acquisition template: SUSI_img_acq_Preset (blind acquisition)
a test exposure with full frame and 1x1 binning, SUSI_img_obs_Jitter, with an offset to move the object of interest out of the gap.
Once this image is displayed, measure the position of the object of interest (x,y in pixels on the RTD), and define the read out window in a SUSI_img_obs_Jitter template: (i.e.)

Number of exposures = 1
CCD Windowing Flag = TRUE
First column of window = 50
First row of window = 50
Number of columns = 400
Number of rows = 100

excute the OB, and check that the object is well centered. Adjust the window parameters as needed and retest.
modify the Number of Exposures to the number required (eg 500), and restart the OB.

Additionally, another template SUSI_img_obs_DoubleW, has been introduced to perform fast photometry of two objects at the same time (e.g. a variable star and a reference star) using two non-overlapping windows. You follow the same procedure outlined above to define the two sub-windows. To decrease the read-out-time between two exposures you can use 2x2 bining or even better 3x3 binning. Usually if you are looking for quick photometric variations, you are not really interested in resolution. More important is to minimize the dead time. The following is an example of a light curve obtained with this method:

Seconds

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Last modified: Wed Nov 5 2003