1. DES Kentools
  2. DES Kentools

DES Kentools

What is it?

The "kentools" package is an updated version of a portion of the SDSS software framework. It is installed on the SISPI machine observer2.

The original kentools has been augmented with code to aid in quick viewing and simple analyses of DECam data. The functions provided include the ability to list an inventory of all exposures from a given night, load the image of one CCD frame from a DECam exposure, measure the seeing from the image of an isolated star, analyze a focus sequence, and compute the true location on the sky of an exposure and determine offsets from where the telescope thinks it is pointed. The goal is simplicity - for example, an exposure can be identified by just the last few digits of the exposure number, without having to specify the subdirectory or the full file name.

Startup

One logs into observer2 using the DECamObserver account. Type:

observer

 

The environment is setup and the kentools program is launched. The working directory is set to the top of the
DECam data tree. Files are stored under here organized by program ID.

Commands
 

Core Commands

The following commands are useful for everyone.

data Change directory to the top of the data tree.
  This is normally /home3/data_local/images/fits
   
inventory [n] List frames from n days ago (default 0). n can also be a date (e.g., 20140821)
   
inv [n] (abbreviation for above)
   
invPrint [n] Print the inventory listing to a file in home area.
   
load [expnum] [ccd-id] Launch a ds9 window and display one CCD from an exposure. expnum,
  if specified is the exposure number. It is not necessary to give
  all 6 digits; the last 3 or 4 should suffice. If expnum is not
  specified, the most recent exposure will be used. If ccd-id is
  specified, it determines which CCD will be displayed. The default
  is S4. Alternatively, one can specify the HDU number, but one
  needs to know the mapping between ccd-id and HDU number for this to
  be useful. (Note that this is NOT the same as CCDNUM).
   
bigload [expnum] Display a complete mosaic of an exposure. expnum, if specified
  is the exposure number. It is not necessary to give all 6 digits;
  the last 3 or 4 should suffice. If expnum is not specified, the
  most recent exposure will be used. The image is compressed by
  a factor 8 and bias subtracted, so it looks nicer. A crude WCS
  is supplied.
   
center [expnum] [maxoff] Compute RA, DEC and offsets of an image center relative to the
  desired target position. The offsets are given as corrections that can
  be fed into SISPI in order to center-up an object. expnum, if specified
  is the exposure number. It is not necessary to give all 6 digits; the
  last 3 or 4 should suffice. If expnum is not specified or entered as
  a null, the most recent exposure will be used. if maxoff is specified,
  it is the maximum size for the search window to find a match between the
  star field and the Nomad catalog. The default is 1024 pixels
  (about 269 arcsec). Occassionally the telescope pointing is bad enough
  that a bigger window is needed (but the run time is increased.)
   
seeingall [expnum] Measure the PSF size for stars in a selection of CCDs. Stars are found
  automatically. If expnum is specified, it is the exposure number.
  It is not necessary to give all 6 digits; the last 3 or 4 should suffice. If
  expnum is not specified, the most recent exposure is used.
   
pdu [expnum] List the content of a FITS file primary header. expnum, if specified is
  the exposure number. It is not necessary to give all 6 digits; the last 3 or 4
  should suffice. If expnum is not specified, the most recent exposure will be
  used. (to exit this command, type q.)
   
seeing Measure the PSF size of a single star. It is first necessary to display the image
  using the load command. The cursor is positioned on a single, isolated,
  bright but not saturated star image and left-clicked.
   
nick [expnum] Calculate the approximate limiting magnitude of an exposure based on image FWHM
  and sky background. The limiting magnitude refers to a point source and computed
  by a calculation that uses parameters taken from the image header plus a nominal
  value for telescope throughput. The calculation is only valid for data taken in
  clear conditions. If expnum is not specified, the most recent exposure
  will be used.
   
psc [expnum] This command combined several others in one. It computes PSF size, ellipicity
  pointing error, sky brightness (relative to dark sky), a measure of
  cloudiness (which, in this context is also referred to as extinction),
  and an overall "teff" effective exposure time, normalized to 1 for
  good seeing on a dark night pointing at the zenith. Cloudiness is a rough
  estimate and derived by comparing stars against either the APASS or NOMAD
  star catalogs. Six CCDs are searched for this comparison. A cloudiness of
  < 0.2 mag is not significant. If expnum is not specified, the most
  recent exposure will be used. More details on teff can be found here

 

DES Commands

The following commands are specific to DES but may be of more general use as well.

standards [UT] This command only works on observer2. It runs D. Tucker's scripts to
  select a set of 3 standard stars to be observer at time UT. If UT
  is not specified, it is assumed that the standards will be observed immediately.
   
flatCheck [n] Run a quality check on dome flatfields taken n days ago (default 0).
  The mean ADU/sec in each filter are plotted along with some nominal values.
  Small deviations from nominal are to be expected as the LED lamps age.
   
noiseCheck [n] Run a quality check on bias frames taken n days ago (default 0).
  Statistics of the readout noise are checked to look for "spiky" noise that
  has appeared in the past (e.g., once time due to a loose connector). The
  noise is common to all CCDs on a single backplane.
   
ephem [date/mjd] Print out various time-related quantities including sunset, twilight, moon
  rise/set, and sunrise. Both local Chilean time and universal time are listed. The
  date, if specified, can be either the UT MJD at local midnight or a date in the
  form YYYYMMDD of the evening of observation.
   
pointing [n] This command runs A. Drlica-Wagner's script to show position of DECam exposures.
  Use pointing --help to see more options.
  More details on the pointing script can be found in Introduction to pointing

 

Database Commands

The following commands are useful for querying other databases via a call to Firefox.

skyview Display an image from skyview.gsfc.nasa.gov in a web browser that
  matches the field of a DES exposure. It is first necessary to display
  the image using the load command. The cursor is positioned on the location
  of interest and left-clicked. The web browser (firefox) is launched if an
  instance is not already running; else a separate tab is launched.
   
ned Display a list of objects from NED at IPAC in a web browser that matches an object
  in a DES exposure. It is first necessary to display the image using the
  load command. The cursor is positioned on the object of interest and
  left-clicked. The web browser (Firefox) is launched if an instance is not
  already running; else a separate tab is launched.
   
simbad Display a list of objects from the SIMBAD database in a web browser that
  matches an object in a DES exposure. It is first necessary to display the image
  using the load command. The cursor is positioned on the object of interest
  and left-clicked. The web browser (Firefox) is launched if an instance is not
  already running; else a separate tab is launched.

NOTE: If you are running kentools by logging in to observer2 from observer3 and want to use the above commands, you must perform the following:

  • Make sure no firefox is running on observer3
  • ssh -X -Y observer2 (so X windows are displayed via the network on observer3)
  • Type "firefox" - it will run on observer2 but display on observer3
  • Now start kentools.


Engineering Commands

The following commands are mainly used for engineering purposes.

tim [expnum] [maxoff] Compute RA, DEC and offsets of an image center relative to the
  telescope coordinates telra and teldec.This command gives a measure of the
  pointing error of the telescope but is intended for engineering use only.
  (One should use the "center" command for actually centering a field.)
  expnum, if specified is the exposure number. It is not necessary to give
  all 6 digits; the last 3 or 4 should suffice. If expnum is not specified,
  the most recent exposure will be used. The offsets are given in the form of
  corrections (although one probably wants the negative of these - the errors).
   
offset [expnum] This command is used for constructing pointing models. A bright star should
  fall within CCD N4. One clicks on the star, and the offset from a
  fiducial point on the CCD is printed. expnum, if specified is the
  exposure number. It is not necessary to give all 6 digits; the last 3 or 4
  should suffice. If expnum is not specified, the most recent exposure will be
  used.
   
boreset [ccd-id] This command is used for constructing pointing models. A bright star should
  fall within CCD ccd-id. Default is S4. One clicks on the star,
  and the offset from the center of the focal plane is printed. The most recent
  exposure is always displayed. (Use centeroffset expnum ccd-id to specify a
  different exposure, plus ccd-id).
   
focus Measure star PSF sizes in a focus sequence. It is first necessary to display
  the image using the load command. A focus sequence is a series of exposures of
  a field with the CCD clocked by a specified number of rows. The first
  and second exposures are separated by a double-sized space. The cursor is
  positioned on the first star of the sequence and left-clicked. The sequence
  should be relative isolated from other stars.

 

 

Updated on September 12, 2021, 3:05 pm