This code is inspired on Zackay & Ofek 2017 papers How to coadd images?

• It can perform a PSF estimation using Karhunen-Löeve expansion, which is based on Lauer 2002 work.

• It can perform the statistical proper coadd of several images.

• It can also perform a proper-subtraction of images.

• Images need to be aligned and registered, or at least github.com/toros-astro/astroalign must be installed.

• Contains a nice plot module for PSF visualization (needs matplotlib)

Documentation at https://properimage.readthedocs.io .

Zackay, B., & Ofek, E. O. (2017). How to COAAD Images. I. Optimal Source Detection and Photometry of Point Sources Using Ensembles of Images. The Astrophysical Journal, 836(2), 187. http://arxiv.org/abs/1512.06872

Zackay, B., & Ofek, E. O. (2017). How to COAAD Images. II. A Coaddition Image that is Optimal for Any Purpose in the Background-dominated Noise Limit. The Astrophysical Journal, 836(2), 188. http://arxiv.org/abs/1512.06879

Zackay, B., Ofek, E. O., & Gal-Yam, A. (2016). PROPER IMAGE SUBTRACTION—OPTIMAL TRANSIENT DETECTION, PHOTOMETRY, AND HYPOTHESIS TESTING. The Astrophysical Journal, 830(1), 27.

Lauer, T. (2002, December). Deconvolution with a spatially-variant PSF. In Astronomical Data Analysis II (Vol. 4847, pp. 167-174). International Society for Optics and Photonics.