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kp84

Kitt Peak 84 inch scripts
The Kitt Peak Electron Multiplying CCD (EMCCD) demonstrator is a new instrument that has been developed for use at the Kitt Peak National Observatory's 84-inch telescope. The immediate goal is to search for rotation period of merged white dwarfs, timing follow-up of short period binaries, as well as short duration transient and periodic sources identified by large field-of-view all-sky surveys such as the Zwicky Transient Facility. For more details please see the instrument paper: Coughlin et al. 2019.

If you want to submit an observation

Email mcoughlin your object in the following comma separated format:
llaria_object,1,WDJ0123-5678,hh:mm:ss.s,dd:mm:ss.s,2000,0.00,0.00,20.0,3600,FILTER_SLOAN_G,9,Coughlin,5.0_0.06528,0

  1. The request ID for this entry, this is an alphanumeric identifier for the observation
  2. The program ID for the science program being executed
  3. The object ID for the target coordinates; this must be a single word, no spaces, /, _, or : characters
  4. The right ascension, in sexagesimal format (12:34:56.789)
  5. The declination, in sexagesimal format
  6. The epoch for the coordinates
  7. The RA rate (in arcsec per hour) for the object
  8. The Dec rate (in arcsec per hour) for the object
  9. The object magnitude
  10. The exposure time, in seconds, for the observation
  11. The filter (using the filter codes, FILTER_SLOAN_R, etc) for the observation
  12. The mode for the camera for this observation (integer, 1,2,…, do not use 0!)
  13. The science program PI
  14. A comment about the observation
  15. A flag (redo observation or not)

Data Reduction

The following list steps to reduce photometric data.

(i) kp84_setup_reduction.py

python kp84_setup_reduction.py --day 20191117

  1. Basic calibration steps: create master bias, dark, and flat frames.
    For calibration files done in mode 0, they need to be downsampled by 2x2.
    Master bias file is not used, as it is essentially the same as the master dark in mode 0.
    Typically, flats are taken with filter sloan gr (or very seldom Johnson (U)BVRI).
  2. Processing science frames (subtract dark, divide flat).
  3. Make register folder; Solve astrometry and save the wcs, using astrometry.net.
    The wcs in the original fits header is (in good case) off by 1--2 arcmin, and in bad case off by a hemisphere... Is this fixed?!
  • Default upload image is the best frame in each cube (the one with most point sources identified).
  • If astrometry failed after trying 3 minutes, then stack all images, using the first extension as referencce.
    I took the median of un-shifted region, try 5 minutes this time. Shifts between each frames in the multi-extension cubes are also calculated in this step and saved to the registration folder.
  • If astrometry still fails using the stacked image, then the object's position (x, y) must be given to the following script, see below.

Note

a. There are two ways to call astrometry.net:

  • DEFAULT OPTION: Run solve-field locally by downloading this software: see the instruction here.
  • PREVIOUS VERSION: Query API: Call kp84_get_wcs.py.

b. To eliminate the time spent on this step, we should guess the ra and dec on thee center of the image, and provide the uncertainty of the guess (radius). There are two ways to do this:

  • DEFAULT --wcsmode 1: for each objecct, search for the objName in the input/observed.dat file and use the ra and dec there. radius=0.5 deg, so please be sure to add this info!
  • --wcsmode 0: Do not specify the rough coordinate
  • --wcsmode 2: Trust the wcs in the raw fits file header, radius=0.5 deg.

(ii) kp84_sextraction.py

python kp84_sextraction.py --day 20200105 --objName ZTFJ0538+1953 This runs Source Extractor to identify point sources.
python kp84_sextraction.py --day 20200105 --objName ZTFJ0538+1953 --doOnlyPrintPars This will print the mags and fwhms of all objects found by SExtractor
sex science.fits -c default.sex -PARAMETERS_NAME daofind.param -FILTER_NAME default.conv -CHECKIMAGE_TYPE BACKGROUND -CHECKIMAGE_NAME science.background.fits -CATALOG_NAME science.cat -MAG_ZEROPOINT 0.0
See this page for columns in the .cat file.
All default files are in the /defualt directory.

Note that this step is necessary for the purpose of (1) identify reference star, and (2) enable background subtraction before performing forced photometry. See below.

(iii) kp84_photometric_reduction.py

  • When all wcs are successfully found: python kp84_photometric_reduction.py --day 20191117 --objName ZTFJ01395245
  • When there are files that astrometry fails (or if you don't want to use the wcs solution found by astrometry.net): python kp84_photometric_reduction.py --day 20200105 --objName ZTFJ0538+1953 --xstar 267*256*234*191*134 --ystar 341*341*343*351*353 --xyext 499*86*519*548*84 --xyfile 033949_ZTFJ0538+1953_4_cl_o*033949_ZTFJ0538+1953_4_cl_o_0000*054524_ZTFJ0538+1953_5_cl_o*074541_ZTFJ0538+1953_5_cl_o*084543_ZTFJ0538+1953_5_cl_o_0000 --doOffTune --aper_size 5 --sky_in 10 --sky_out 28 --aper_size_ref 14 --sky_in_ref 15 --sky_out_ref 33 --xoffref 7.23 --yoffref -48 --refmag 14.838 --doSubtractBackground --doSkipRegis --doSkipFindRef --moviemode 10

Steps

  1. Find the coordinate of object (from the file input/observed.dat). So make sure to add this beforehead.
    Then for each file (kped_20191117_hhmmss_ZTFJ01395245_cl_o*) that belong to the object, do the following steps:
  2. Use the wcs, find the (x, y) of science and reference objects in each frame, save to the processing fits file's headers
    Disgard frames where the object shifted outside of the field.
  • If the xstar, ystar, xyext, xyfile parameters are provided, the wcs solution will be disgarded, this is because sometimes the wcs solution can also be a bit off...!
  • If the xoffref, yoffref, and refmag parameters are not provided, the reference star is selected based on proximity, brightness, FWHM, and roundness (given by SExtractor).
  1. Photometry
  • Copy the pre-processed image into output directory, name it as science.fits
  • Run forced photometry on sci and ref objects using PythonPhot. Currently we only support differential photometry.
    The default aperture size is 10 pixels, and the default annulus radius is [30, 50] pixels.
    You may really want to adjust these parameters depending on how crowded the field is. This can be changed by setting the aper_size, sky_inner, and sky_outer parameters (all in the unit of pixels), as well as the aper_size_ref, sky_inner_ref, and sky_outer_ref parameters for the reference star (preferentially a brighter one).
    We allow the aperture size for science and reference objects to vary since their FWHM can be quite different.

moviemode

If turn on moviemode!=0, the script will make a movie of the indivisual frames (arranged by time of observation). This can be very helpful if you'd like to examine if the choice of aperture size is appropriate.

  • moviemode==1: plot all frames
  • moviemode==10: plot one frame every 10 frames

Some notes: This can be hard sometimes due to the limited field of view (4x4 arcmin)

  • If too faint, then turn on --doStack --nimages 5

Post-processing Examination

kp84_download.py

python kp84_download.py --day 20200105 --objName ZTFJ0538+1953
This script download the output product to your local computer

kp84_marshal_photometry.py

python kp84_marshal_photometry.py --day 20191117 --objName ZTFJ0538+1953
This script upload the light ccurve to ZTF Variable Marhsal

  • --program_name hot subdwarf Current programs are:
  1. skipper
  2. Short Periods
  3. Xray Sources
  4. hot subdwarf
  5. Young Stars
  6. AM CVn
  7. RR Lyr
  8. Short Period Followed Up
  9. Cataclysmic Variables
  10. Fermi Gamma Ray Sources
  11. Infrared variables

Data Product

lightcurve.forced movie.mpg mag_forced.pdf coo.reg filter.txt