The Pickering Seeing Scale

The Pickering Seeing Scale.

Below you will find an animated version of the Pickering scale of rating atmospheric turbulence.

This was produced using Abberator V2, and using Pickering's comments on the appearance of the Airy pattern at a giving rating.

The scale was devised by William H. Pickering (1858-1938) using a 5" (13cm) refractor.

Animations produced by Damian Peach.

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Pickering 1 rating - Very Poor.



(1.) Star image 2x the diameter of the 3rd diffraction ring - Star image 13" in diameter.

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Pickering 2 rating - Very Poor.



(2.) Star image occasionally 2x the diameter of the 3rd ring.

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Pickering 3 rating - Poor to Very Poor.



(3.) Star image about the same diameter as the 3rd ring (6.7") and brighter at the centre.

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Pickering 4 rating - Poor.



(4.) Airy disk often visible. Arcs of diffraction rings sometimes seen.

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Pickering 5 rating - Fair.



(5.) Airy disk always visible. Arcs frequently seen.

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Pickering 6 rating - Fair to Good.



(6.) Airy disk always visible. Short arcs constantly seen.

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Pickering 7 rating - Good.



(7.) Disk sometimes sharply defined. Diffraction rings seen as long arcs or complete circles.

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Pickering 8 rating - Good to Excellent.



(8.) Disk always sharply defined. Rings seen as long arcs/complete circles, always in motion.

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Pickering 9 rating - Excellent.



(9.) Inner diffraction ring stationary. Outer rings occasionally stationary.

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Pickering 10 rating - Excellent/Perfect.



(10.) The complete diffraction pattern is stationary.

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