Flux Calibration

The Flux Calibration window contains the options required for the atmospheric extinction and flux calibration. Click the button in the Main window to pop up the Flux Calibration window.

The button corrects the spectra for extinction and requires that the field Extinction table: contains a valid extinction table name. After clicking a selection list for .bdf files pops up. Click the file you want to correct. A small prompt window asks for the airmass. If the airmass appears in the file header, that value is used as default. The output is stored by default in a file with the original name plus the suffix _ext. Airmass and output file name can be modified before clicking on which activates the command EXTINCTION/LONG.

The button allows the response table to be generated. The field Flux table: must be updated with the name of the standard star flux table. This table can be plotted by clicking on the button . After clicking a file selection window appears requesting the name of the standard star image, which must be a one dimensional reduced, extinction corrected spectrum. Click the name. The name of the resulting intermediate response table is stored in the MIDAS keyword RESPTAB and by default set to resp.tbl. Values of this table can be interactively edited by clicking on .

  

Figure G.8: Flux Calibration window

The response table must be interpolated to generate the final response curve, which name is provided in the field Response curve:. The Section FITTING PARAMETERS allows the different values and options to be selected (See Section G.3.8 and Chapter 6 Vol. B). The button radio button allows the calibration curves to be plotted in two different ways. The first option is the standard plane used by MIDAS. The second option plots $\Delta m$ versus $\lambda$ and generally has the advantage to require lower order curves to fit the response. The button allows fitting the curves with either polynomials or splines.

Clicking on activates the MIDAS command RESPONSE/LONG. The response curve can also be generated by filtering with the button . The response curve can be plotted by clicking on the button .

Reduced, extinction corrected spectra can be corrected for the instrumental response with the button . Clicking on this button pops up a file selection list. Click the name of the spectrum. A small prompt window appears requesting the name of the output file. The default is the input file name with the suffix _cor. Clicking on sends a command CALIBRATE/FLUX to the MIDAS monitor.