# Pickering scale

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**The Pickering scale** is a [scale](/source/Scale_(ratio)) of rating [astronomical seeing](/source/Astronomical_seeing), the blurring of images caused by [atmospheric turbulence](/source/Atmospheric_turbulence).[1][2] The scale was developed by [William H. Pickering](/source/William_Henry_Pickering) (1858–1938) of [Harvard College Observatory](/source/Harvard_College_Observatory), using a 5" (13 cm) [refractor](/source/Refractor).[3][4] Seeing of 1 to 3 is considered very poor, 4 to 5 is poor, 6 to 7 is good, and 8 to 10 is excellent.[5][6]

## References

1. ["A Scale of Seeing"](https://skyandtelescope.org/astronomy-resources/a-scale-of-seeing/). *Sky & Telescope*. 2006-07-17. Retrieved 2022-07-07.

1. Canada, Environment (2013-04-16). ["Astronomy Sky Condition - Environment Canada"](https://weather.gc.ca/astro/seeing_e.html). *weather.gc.ca*. Retrieved 2022-07-07.

1. ["astronomical seeing, part 2: seeing measurement methods"](https://www.handprint.com/ASTRO/seeing2.html). *www.handprint.com*. Retrieved 2022-07-07.

1. ["Courses in Astrophotography"](https://www.damianpeach.com/pickering.htm). *www.damianpeach.com*. Retrieved 2022-07-07.

1. Wlasuk, Peter (2000). [*Observing the Moon*](https://books.google.com/books?id=TWtLIOlPwS4C&dq=Pickering+scale&pg=PA123). Springer Science & Business Media. ISBN 978-1-85233-193-1.

1. ["RASC Calgary Centre - Atmospheric Seeing"](https://calgary.rasc.ca/seeing.htm). *calgary.rasc.ca*. Retrieved 2022-07-07.

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Adapted from the Wikipedia article [Pickering scale](https://en.wikipedia.org/wiki/Pickering_scale) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Pickering_scale?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.