ghost2ms: Convert Gemini/DRAGONS GHOST format to IRAF multispec format

Package: proto

Name ghost2ms -- convert gemini/dragons ghost format to iraf multispec format

Usage ghost2ms input output

Parameters

input: Input GHOST file from DRAGONS.

output = "": Output base name.

order1 = 1: Starting order to extract.

order2 = 33: Ending order to extract.

version = 1: Version to extract.

clobber = no: Clobber existing output?

verbose = yes: Verbose output?

Description the ghost2ms task converts the dragons-calibrated output for the

red and blue arms on the GHOST instrument to a standard IRAF multispec format to permit further analysis and visualization using standard ONEDSPEC tasks. It makes use of a task from the artdata package to set up the echelle structure and then the linear spectrum WCS and the flux values are added. The default is to extract all the orders from extension version 1.

For context: this data format is specific to the GHOST instrument. When reduced using DRAGONS, two different outputs are produced (for each "blue" and "red" arms of the spectrograph):

*_calibrated.fits: Reduced spectra before stitching the orders. The flux pixels are in a 3D array with the first axis of size 2, one for the target, one for the sky, then a second axis for the wavelength direction, and finally a third axis with several orders. The WAVL extension contains the wavelength at each pixel in the wavelength-order array.

*_dragons.fits: 1D extracted spectrum. Orders have been stitched together. The algorithm resamples the order wavelengths to a common log-spaced scale, interpolates the orders to that new wavelength scale, and then averages the fluxes from each order with an inverse variance weighting.

There are two issues here: the "*dragons.fits" file opens on "splot" but the wavelength solution is wrong. The DRAGONS team provided a recipe to fix that, so we have a file called "_dragons_irafCompatible.fits". However, many of our users want to normalize the spectra order-by-order, so none of those are good options.

This task is a script and so users may copy it and modify it as desired.

Examples

1. Compute the ring averages with labels and output to the terminal.

# Convert the red arm calibrated frame.
onedspec> ghost2ms S20230416S0079_red001_calibrated.fits
S20230416S0079_red_calib[SCI,1][*,1:33] -> S20230416S0079_red_calib_iraf

# Convert the blue arm calibrated frame.
onedspec> ghost2ms S20240322S0068_blue001_calibrated.fits
S20240322S0068_blue_calib[SCI,1][*,1:33] -> S20240322S0068_blue_calib_iraf

# Use SPLOT to view the result.
onedspec> splot S20230416S0079_red_calib_iraf 1 unit=nm
onedspec> splot S20240322S0068_blue_calib_iraf 1 unit=nm