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Total Lunar Eclipse. March 2007 Simon Dawes CMHAS. Site. Sex. Hya. P1 20:18:11 UT U1 21:30:22 UT. 19:48 – 22:35. Thought you would get away without some maths…. Why are the Images so poor?. Dawes Limit of Camera Lens = 2.4” Moon angular size ~ 1800” Therefore 1800/2.4 = 750 - PowerPoint PPT Presentation
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Total Lunar EclipseTotal Lunar Eclipse
March 2007March 2007Simon Dawes CMHASSimon Dawes CMHAS
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SiteSiteSex
Hya
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P1 20:18:11 UTP1 20:18:11 UTU1 21:30:22 UTU1 21:30:22 UT
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19:48 – 22:3519:48 – 22:35
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Thought you would get away Thought you would get away without some maths…without some maths…
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Why are the Images so poor?Why are the Images so poor?
Dawes Limit of Camera Lens = 2.4” Dawes Limit of Camera Lens = 2.4” Moon angular size ~ 1800”Moon angular size ~ 1800”
Therefore 1800/2.4 = 750 Therefore 1800/2.4 = 750 Double sampling = 1500 pixelsDouble sampling = 1500 pixels
So I should be able to support a Lunar So I should be able to support a Lunar image of 1500x1500 pixels…image of 1500x1500 pixels…
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However…However…
23 Pixels
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Therefore…Therefore…
The image is smeared out by the lack of The image is smeared out by the lack of tracking and seeing conditionstracking and seeing conditions(px res = 2”, 2s exp = 30arc” = 15 px)(px res = 2”, 2s exp = 30arc” = 15 px)
1500/15 = 100 Pixels1500/15 = 100 Pixels
So an Image 100x100 pixels should be So an Image 100x100 pixels should be enough to capture all the information…enough to capture all the information…
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800 pixels
100 pixels
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Original 800x800Original 800x800
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800x800 recovered from 100x100800x800 recovered from 100x100
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ConclusionsConclusions
The maths does describe the optical The maths does describe the optical performance quite well.performance quite well.To take decent images of the moon at the To take decent images of the moon at the maximum resolution you do need to track the maximum resolution you do need to track the sky.sky.I need a dew heater!I need a dew heater!To create high quality time lapse video you need To create high quality time lapse video you need to take images more regularly than every ten to take images more regularly than every ten minutes for a lunar Eclipse (estimate every minutes for a lunar Eclipse (estimate every minute) minute)
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Thank YouThank You
