Keck HIRES

Overview

This file summarizes several instrument specific settings that are related to the Keck/HIRES spectrograph. Currently, PypeIt only supports the reduction of the post detector upgrade HIRES data (around August 2004). Information on the frame typing and instrument configuration can be found in ref:hiresframes and Automated sorting of HIRES frames by instrument configuration.

Default Settings

See KECK HIRES (keck_hires) for a list of modifications to the default settings. You do not have to add these changes to your PypeIt reduction file! This is just a list of how the parameters used for HIRES differ from the defaults listed in the preceding tables on that page. Moreover, additional modifications may have been made for specific setups, e.g, for different binning, etc. You can see a list of all the used parameters in the keck_hires_XXX.par file generated by PypeIt at the beginning of the reduction.

MOSAIC

PypeIt, by default, uses a mosaic approach for the reduction. It basically constructs a mosaic of the blue, green, and red detector data and reduces it, instead of processing the detector data individually. The mosaic reduction is switched on by setting the parameter detnum in ReduxPar Keywords to be a tuple of the detector indices that are mosaiced together. For HIRES, it looks like:

[rdx]
    spectrograph = keck_hires
    detnum = (1,2,3)

This is already the default for HIRES, but the user can modify it in the PypeIt Reduction File to turn off the mosaic reduction.

Calibrations

Flat Fielding

Special type of “slitless” flat images are sometime used for correcting pixel-to-pixel variations in the HIRES data. These flats images are taken with the cross disperser cover on, so that the light is somewhat diffused and the orders are not visible. If this type of frames are present in the PypeIt Reduction File, during the main reduction PypeIt will be able to identify them, assign the correct frame type (slitless_pixflat), and use them for creating a “slitless” pixel flat. Since, these frames are taken with different exposure time and cross-disperser angle for each detector, PypeIt is able to select the correct observations for each detector. The pixelflat is generated by first scaling each flat frame to have the same mean counts, then median combining them. A pixelflat file will be generated and stored in the reduction folder. In addition, the constructed pixelflat is saved to the PypeIt cache (see ref:data_installation). This allows you to use the file for both current and future reductions. To use this file in future reductions, the user can add the slitless pixelflat file name to the PypeIt Reduction File as shown below:

[calibrations]
   [[flatfield]]
      pixelflat_file = pixelflat_keck_hires_RED_1x2_20160330.fits.gz

See more in Generate a Slitless PixelFlat.

Wavelengths

See Echelle Spectrographs for details on the wavelength calibration.

Additional Reading

Here are additional docs related to Keck/HIRES. Note all of them are related to the development of PypeIt for use with HIRES data:

• Automated typing of HIRES frames
• Automated sorting of HIRES frames by instrument configuration