This file describes the Edges
object.
It contains the core information required to describe the edges
of each slit on a given detector (or orders for echelle).
See below for the Current EdgeTrace Data Model.
This is written to disk as a multi-extension FITS file prefixed by
Edges
in the Calibrations/
folder.
See the :ref:`calib-naming` docs for more.
We also describe how to view the slit edges using pypeit_chk_edges.
The preferred way to view the slit edges identified by PypeIt is with the pypeit_chk_edges script.
The script usage can be displayed by calling the script with the
-h
option:
There are currently 2 options for viewing the slit edges on the image used to construct them. Each uses the pypeit_chk_edges script.
This is the default mode when executing, e.g.:
pypeit_chk_edges Calibrations/Edges_A_1_DET01.fits.gz
Warning
These files can take an annoyingly long time to load because they tend to be large and require decompression.
Two images are shown, the trace image (typically a combination of dome flats) and the Sobel filtered image used to detect the slit edges.
Here is a zoom-in screen shot for the :ref:`keck-lris-red` spectrograph.
A few things to note from this good-performing example:
- The slits run nearly vertically across the image
- The left/right edge of each slit identified is a green/red (purple in more recent versions) line
- There were 13 slits identified (0 indexing)
- The brightest slit is an alignment box and was discarded by the code
To avoid ginga, use the --mpl flag:
pypeit_chk_edges Calibrations/Edges_A_1_DET01.fits.gz --mpl
The color scheme is distinct and the labeling now includes -1 or +1 for left/right edges.
The Edges
file allows one to fully reconstruct its underlying object
(:class:`~pypeit.edgetrace.EdgeTraceSet`) when instantiated from the output
file. Unfortunately, this means the PypeIt object and output file are a bit too
unwieldy to pass through the remainder of the code just to access its primary
product, the slit-edge pixel coordinates. For that reason, we also create a
:ref:`slits` object; follow the link for more description of that object.
See :doc:`slit_tracing` for a discussion of how to customize, debug, and finesse your slit tracing results.
Internally, the processed image is held in :class:`~pypeit.edgetrace.EdgeTraceSet`, which subclasses from :class:`~pypeit.datamodel.DataContainer`.
The datamodel written to disk is: