Valutare il seeing (con la Pickering scale)
Una simulazione di stella ed anelli di diffrazione ottenuti da Damian Peach (www.damianpeach.com) con il softwere Aberrator V2. I commenti sono della scala di Pickering (1858-1938) sulla valutazione del disco di Airy
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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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