Determination of Instrumental Response

The instrumental response of our equipment can be found by dividing the wavelength calibrated spectral profile that has been corrected for atmospheric effects by the published reference profile, the profile that would be observed with a perfect telescope, spectrograph and camera outside the atmosphere.

Instrumental Response = (Corrected observed profile) / (Reference profile)

We follow section 11. Preparing Data for the Evaluation of the Spectral Response on p12 of Toolbox2. Again, we use the star 10 Lacertae, for which a reference profile is available.

The reference profile below has been normalized using the configuration file CONF_MAKE_NORM on p22 of the Toolbox2. It has also been cropped to the range of wavelengths we are interested in (3800-7400 A) using vSpec Edit | Crop.

Our own spectral profile for 10 Lacertae, with Planck and atmospheric corrections is shown below:

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To find our instrumental response, we use the configuration file CONF_MAKE_RESPONSE on p28 of Toolbox2. There are three steps:

Remove O2 absorption bands between 6850 and 6990 Angstroms from our observation profile.
Divide corrected observation profile by reference profile
Smooth the result to eliminate absorption lines

Here are the key relevant steps in the configuration file:

# Remove telluric lines, divide by reference, smooth #
_pro_clean: [_10lac_20231221_059, 6850, 6990, 10-Lac-without-O2] # Remove O2 absorption bands
_pro_div: [10-Lac-without-O2, 10-Lac_ref_3800-7400, IR-rough] # Divide our observation with atmospheric corrections profile
_pro_blur2: [IR-rough, 1000, InstResp] # Smooth result for InstResp

The resulting instrumental response function, InstResp.fits is shown below:

Because this function describes the net effect of equipment only (telescope, spectrograph, camera), it can be used in all subsequent observations, as long as nothing changes in the setup.

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