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Next you can enter your Magellan-formatted observing catalog into the second box. This is used by the software to match exposures of the same object when organizing for the reduction process. It is more efficient than using header information since it groups objects by where the telescope was pointing and matching that to your object list, thereby avoiding operator errors at the telescope. It also checks against the FIRE list of known telluric standards to determine which exposures are science targets versus calibrators. If you choose not to enter the catalog, firehose will attempt to organize based on header information. All settings can be over-ridden manually later in the process.
Locating the Order Boundaries
The first reduction step consists of indexing the echelle order boundaries. This is done using a flat field exposure. Using the browser, select a single internal quartz lamp spectrum from your run and then click "Trace Orders." The software will run for 15-20 seconds and then present an atv window showing the flat field image with order boundaries marked in either black or another color, depending on your display settings.
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You will know that the software worked correctly if: the slit boundaries are located correctly on the image, and a file is produced in the subdirectory redux/Flat with the name "Orders_0123.fits" where 0123 is the frame number of whatever file you used to trace the slits.
Generating Flat Fields
The next step is to generate the pixel flat field and slit illumination images. The pixel flat corrects gain variations on the detector, and the illumination function corrects for the fact that the internal quartz lamp has a slight gradient in intensity across the slit (~5%).
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You will know that the software worked correctly if: The pixel flat looks like a flat image centered around 1.00 with fairly little structure, and the illumination image shows a smooth gradient with amplitude of 1.0 +/- ~0.05. Also, two files should be created in the redux/Flat directory. One named Pixflat_0123to0223.fits where the numbers again represent the range of files used. And another named Illumflat_0.60_0122.fits where the 0.60 represents the slit used, and the 0122 is the frame number of the sky flat.
Generating the FIRE Structure
Firehose stores all information about which flat, arc, and telluric files are paired with which science frames in an IDL structure for portability. The next step of the reduction process is to generate this structure, and then edit it to ensure it reflects the pairings you want (e.g. eliminating saturated tellurics, etc.). This procedure is done by a largely automated, and fairly complicated procedure. It performs the following procedures without user intervention:
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Once you have created the structure, it is advisable to inspect and (if appropriate) edit it by hand to ensure there are no errors. To do this, click "Edit Structure." You will be presented with a window that looks like the following:
The first column is an index number in the FIRE structure, used for bookkeeping. The second and third columns show the fits file and object name as determined by matching with teh catalog, or, failing a match, form the OBJECT field in the header. The third column shows how firehose has classified the frame. All files classified as SCIENCE frames are tagged with an object ID, and grouped with telluric and arc calibrators, shown in the rightmost fields. Actual telluric frames are paired with an arc image.
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We are working on a utility to dump the contents of the structure to a text file that may be edited and read back in as a scriptable version of the pipeline; this feature will be available soon.
Object Extraction
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Telluric Correction / Flux Calibration
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Combining Orders and Exposures to 1D
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