# Two-dimensional maps and a python script to correct for position-dependent systematic errors of PS1 photometry.
#
# Author: Xiao, K., a PhD student supervised by Yuan, H.
# Date: 2023-07-05
#
# Refs: [1] Xiao, K. & Yuan, H. 2022, AJ, 163, 185
#       [2] Xiao, K., Yuan, H., Huang, B., et al. 2023, ApJS

- PS1_Correction.fits: Two-dimensional maps mentioned in "Improvement of the Pan-STARRS
                      Photometric Calibration with LAMOST and Gaia" (see [2]).
					
					 * “ra”: right ascension
					 * “dec”: declination
					 * “del_x”: magnitudes offset for the PS1 x band
					 * “num”: standard number in the box
					 * “size”: the box size

- ps1_correction.py: A python script is designed to correct for position-dependent systematic errors
                     of PS1 photometry conveniently.

                     It relies on a 2D correction map (see [2]), utilizing numerical interpolation,
                     to determine the magnitude offset for any given position and PS1 band.

                     By adding the magnitude offset to the original PS1 magnitude,
                     the resulting value represents the corrected PS1 magnitude.

NOTE:
    Prior to using this script or two-dimensional maps to correct the position-dependent systematic errors of PS1,
    it is essential to address the magnitude-dependent systematic errors within PS1.
    However, it should be noted that this particular task is beyond the python script’s capabilities.
    For guidance on addressing magnitude-related systematic errors, please refer to [1] (see Table 3).

Copyright:
   This script is authored and maintained by K. Xiao and H. Yuan.
   If you have already utilized this script, please remember to cite articles [1] and [2] in your work.



When you intend to use the python script, you should read the following information carefully.

0. Setup environment: Python 3.x.
1. Install Dependencies: Make sure to install the required libraries, such as numpy, scipy, astropy, etc.
   (pip/pip3/conda/... install numpy scipy astropy ...)
2. Please make sure to place the "PS1_Correction.fits" file and this script in the same directory.
3. Import Module: Import the provided tool module into your Python script.
4. Perform correction function.

Example Code:

>>> from ps1_correction import correction

>>> band = 'i'
>>> ra, dec = [192.825484], [27.27490232845929]
>>> delmag = correction(ra, dec, band)

>>> print(delmag)

output: 0.00138713