Sky Subtraction Tool

The Sky Subtraction Tool allows to subtract two observations from each other. This is of particular use when the data concern solar system objects, in which the same spot of the sky is observed with and without the object.

If calibration is applied to the data, then the same calibration table is used to simultaneously calibrate the sky data. Note that the calibration factors can differ between the object and sky observations, as both observations could have been made during different epochs.

The process of subtraction takes places AFTER the individual offset corrections to both the object and the sky observations.

important

If you want to save the results of the subtraction to a .res file using the ‘save’ button in the main widget (see save results), then the Sky Subtraction Tool must be open!

Text windows and buttons

Load Sky Data File

sky_load_obs.pro

Load a file that contains the sky observation. The format of the file and the loading process are entirly similar to the Load Data File in the main widget. This includes the averaging. The result is shown in a plot with the same structure as the Results plot.

Observation information window

Shows information (name, time, etc.) of the current observation loaded into NCDRT.

Process information window

Shows information (warnings etc.) of the current process.

Main Slider Tracking Switch

sky_subtract_event.pro switch main_slider_track

By default, the offset cutting sliders of the sky observation are set to the same values as the object observation. If the main sliders are changed, the sky sliders will also change. Pressing this button will give independent control of the sky sliders. Pressing it again will undo this control and set the sliders back to the main slider values.

Sky Offset Low

sky_subtract_event.pro

The cutting value for the low offset. The value is shown in the top left frame of the plot (with a dotted line). The default value is the offset value from the main widget.

Sky Offset High

sky_subtract_event.pro

The cutting value for the high offset. The value is shown in the top left frame of the plot (with a dotted line). The default value is the offset value from the main widget.

Sky Shift

sky_apply_lin_cut.pro

The time shift in the sky observation before subtracting from the object. The extremes are set to -25 and +25, and can of course be changed (in sky_subtract_display.pro). The shifting takes places after the offset correction has been performed. The time points left blank are set to zero.

Do Sky Subtraction

sky_subtract_event.pro switch sky_subtract_apply

Apply the sky subtraction to the data.

Undo Sky Subtraction

sky_subtract_event.pro switch sky_subtract_apply

Undo the sky subtraction.

Dismiss

Dismiss the Sky Subtraction Tool.