Generally, the ultimate PypeIt spectrum output is a single spectrum per source, fully calibrated and (as desired) with a Telluric correction performed.

The standard way to generate this file is with the pypeit_coadd_1dspec script script.

The naming of this file is user-generated, i.e. it can be anything you wish.

The header of the primary extension includes the core_meta of PypeIt, e.g. RA, DEC, MJD, and configuration parameters of the instrument.

In addition, for echelle spectrograph reductions, the PypeIt output will include the coadded orders for each echelle setup used per spectrum per source, fully calibrated but not yet telluric corrected. See OrderStack for more details.


You view the spectrum using the lt_xspec script (pypeit_show_1dspec will not work), which loads the data and launches a GUI from the linetools package. e.g.:

lt_xspec J1217p3905_coadd.fits

Current Data Model

Internally, the spectrum for a single object is held by the OneSpec class.

Here is its datamodel, which is written as an in the first HDU of the file.

Version 1.0.2

HDU Name

HDU Type

Data Type



Empty data HDU. Contains basic header information.


Single spectrum data; see OneSpec.

All wavelengths are in vacuum and flux units depend on whether Fluxing was performed.