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Default Data Reduction Steps
The default data reduction steps in 'reduce_red_data.py' and 'reduce_blue_data.py' are outlined below. Most “steps” are numbered by the number of actual operations on data (e.g. step “1” ends when raw data goes through its first processing, and so on). Sub-steps consist of the calibration calculations performed after the conclusion of the previous step, and the final sub-step is always when a new processing of data occurs (e.g., step 3 consists of numerous calibration steps that occur after bias subtraction at the end of step 2, but before creation of multi-extension fits – MEF – files at the end of step 3).
Below is an itemized list of the default data reduction steps, along with the PyWiFeS function that is used to perform the data processing of that step. We also include a brief description of what each step does. For some steps where the PyWiFeS function is similarly named for the red and blue channels e.g. (repair_red_bad_pix and repair_blue_bad_pix), we name the red channel function for simplicity. Steps which do not operate on science data but instead only create or process master calibration files are labeled as CAL.
| Step # | Step Name | Primary PyWiFeS Routine | Description |
|---|---|---|---|
| 00 | 'overscan_sub' | subtract_overscan | Subtracts overscan from raw FITS image. |
| 01 | 'bpm_repair' | repair_red_bad_pix | For the WiFeS 2nd Generation detectors, interpolates over the bad pixels. |
| CAL | 'superbias' | imcombine, generate_wifes_bias_fit | Creates super-bias from bias frame co-add, then fits a smooth model of the bias shape across entire detector. |
| 02 | 'bias_sub' | imarith | Subtracts master bias (or local bias) from science frames. |
| CAL | 'superflat'A | x | x |
| CAL | 'slitlet_profile' | x | x |
| CAL | 'flat_cleanup' | x | x |
| CAL | 'superflat_mef' | x | x |
| 03 | 'slitlet_mef' | x | x |
| CAL | x | x | x |
| 04 | 'cosmic_rays' | x | x |
| 05 | 'sky_sub'B | x | x |
| 06 | 'obs_coadd' | x | x |
| 07 | 'flatfield' | x | x |
| 08 | 'cube_gen' | x | x |
| 09 | 'flux_calib' | x | x |
| 10 | 'telluric_corr' | x | x |
| 11 | 'save_3dcube' | x | x |
A “Superflat” procedures performed for both spectral (quartz lamp) flats and spatial (twilight) flats.
B Currently this step is a strict subtraction of object data and sky data (either “point-and-stare” or “nod-and-shuffle”). This is planned to be moved to after flat-fielding once a sophisticated sky-subtraction model procedure has been devised (part of PyWiFeS “Phase 2”).
