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Introduction to fpostgres (via the godb command)

What is it?

fpostgres is a software package that provides a command line interface to access the SISPI database.
The main use at present is to print out quality control information computed for each science
exposure. This information is now generated automatically by SISPI for each science exposure by calling
the "psc" command from the kentools package and written to the database. A simple
interface is provided to read the database and print out this information to a terminal screen.

Startup

One logs into observer2.ctio.noao.edu using the DECamObserver account. Type:

godb

The environment is setup and the fpostgres program is launched. The program connects to the SISPI
database (read-only mode).

Commands

The following commands are useful for everyone.

inv [n] List frames from n days ago (default 0). n can also b a date (e.g., 20140821).
invPrint [n] Print the inventory listing to a file in the home area.
qcInv [n] List quality control information for frames from n days ago (default 0). n can also be a date.
qcInvPrint [n] Print the QC listing to a file in the home area.
expInfo <expnum> Lists much information for the specified exposure number.
alarm Prints out all alarms (chicken squawks, etc.) since 0H UT

The interesting columns are psf, sky, cloud, and teff. These are described in the psc command
of kentools, but are repeated here for convenience. psf gives the FWHM in arcsec. sky gives the
sky background expressed in magnitudes relative to a dark sky at zenith for the particular filter.
cloud gives a measure of cloudiness (in magnitudes) relative to clear sky at zenith. This value should
be used with care. It is computed by comparing stars in an exposure to either the NOMAD or APASS catalogs.
These catalogs have not been validated over the entire sky and are known to have issues, sometimes at the
level of several tenths of a magnitude. teff is the effective exposure time one would need to use when
pointed at zenith with a dark sky and median site seeing in order to have the same limiting magnitude for point
sources as the actual exposure. It is normalized to the actual exposure time. Be aware that sky and cloud
have not been calibrated for the u band yet.

The following command is useful for DES observers.

snstatus [n] List supernova exposures from n days ago (default 0). n can also b a date (e.g., 20140821). A summary by field is printed at the end.
default = no assesment applied. good/bad = assessments applied. Note that if one exposure is declared bad, the entire sequence is bad, regardless of other exposures.