# What causes difraction patterns in difference images?

**URL:** <https://www.rubin.community/t/what-causes-difraction-patterns-in-difference-images/6829>\
**Category:** Support\
**Tags:** imagedifference, difference-imaging\
**Created:** [July 1, 2022, 6:38am UTC](https://www.rubin.community/t/what-causes-difraction-patterns-in-difference-images/6829 "2022-07-01T06:38:23Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![stevenstetzler](https://sea2.discourse-cdn.com/flex002/user_avatar/www.rubin.community/stevenstetzler/32/1457_2.png) [@stevenstetzler](https://www.rubin.community/u/stevenstetzler)\
**Post date:** [July 1, 2022, 6:38am UTC](https://www.rubin.community/t/what-causes-difraction-patterns-in-difference-images/6829/1 "2022-07-01T06:38:23Z")

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Hi, I am just wondering what causes patterns like this in a difference image:

 ![976786_62](https://us1.discourse-cdn.com/flex002/uploads/rubin/original/2X/4/43451cbfd33535de441a94bc0796553d04bf6056.png)

Does it have to do with a mismatch between the template and calexp PSF during PSF matching? Was either the template or calexp PSF model miscalculated?

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**Author:** ![ebellm](https://sea2.discourse-cdn.com/flex002/user_avatar/www.rubin.community/ebellm/32/771_2.png) [@ebellm](https://www.rubin.community/u/ebellm)\
**Post date:** [July 1, 2022, 3:23pm UTC](https://www.rubin.community/t/what-causes-difraction-patterns-in-difference-images/6829/2 "2022-07-01T15:23:53Z")

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These “ringing” artifacts are typically the result of effective deconvolution, typically when the science image has better seeing than the template in standard Alard & Lupton image differencing.