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Sedona
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sedona clear sky chart from 2003-08-01 to 2005-11-07.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	10% 6% 56%	8685
	Night	10% 5% 57%	8484
Transparency	Day	7% 7% 21% 35% 27%	6391
	Night	7% 8% 20% 33% 29%	6268
Seeing	Day	16% 36% 37% 9%	512
	Night	7% 19% 33% 35%	2821

By Month

Percentage Cloud Cover
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month		Occurrence of each Forecast	Data Points
January	Day	25% 7% 6% 36%	549
	Night	23% 5% 6% 6% 37%	804
February	Day	28% 5% 5% 6% 33%	545
	Night	25% 6% 6% 37%	700
March	Day	11% 5% 55%	681
	Night	12% 55%	681
April	Day	7% 5% 64%	714
	Night	9% 5% 64%	604
May	Day	5% 11% 70%	806
	Night	5% 5% 6% 72%	558
June	Day	5% 80%	780
	Night	86%	537
July	Day	7% 6% 5% 9% 55%	795
	Night	7% 6% 5% 5% 62%	558
August	Day	12% 5% 5% 5% 6% 7% 6% 7% 34%	1179
	Night	6% 6% 5% 5% 9% 50%	863
September	Day	6% 6% 66%	969
	Night	5% 5% 66%	977
October	Day	10% 62%	634
	Night	10% 6% 63%	730
November	Day	12% 5% 6% 55%	484
	Night	11% 5% 7% 54%	682
December	Day	11% 5% 62%	549
	Night	11% 5% 5% 5% 54%	790

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	15% 9% 45% 22% 6%	263
	Night	12% 10% 35% 29% 11%	401
February	Day	13% 13% 36% 29% 7%	257
	Night	10% 15% 28% 35% 11%	327
March	Day	7% 13% 27% 32% 19%	440
	Night	7% 14% 22% 31% 24%	439
April	Day	7% 5% 20% 46% 19%	550
	Night	8% 7% 14% 44% 25%	453
May	Day	9% 23% 34% 29%	713
	Night	7% 8% 15% 36% 31%	475
June	Day	11% 34% 47%	719
	Night	12% 36% 45%	495
July	Day	12% 12% 25% 45%	571
	Night	8% 7% 13% 21% 49%	410
August	Day	17% 10% 24% 28% 19%	593
	Night	14% 13% 22% 26% 23%	568
September	Day	16% 39% 35%	792
	Night	5% 5% 14% 32% 41%	790
October	Day	5% 8% 22% 42% 21%	719
	Night	6% 23% 37% 28%	824
November	Day	14% 24% 41% 15%	378
	Night	11% 12% 24% 28% 22%	550
December	Day	9% 18% 44% 25%	396
	Night	6% 19% 43% 27%	536

Seeing (when cloud cover <= 80%)
Color Meanings: Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month		Occurrence of each Forecast	Data Points
January	Night	14% 23% 33% 27%	213
February	Day	35% 32% 32%	28
	Night	17% 33% 30% 16%	185
March	Day	20% 31% 35% 12%	54
	Night	9% 27% 34% 25%	237
April	Day	32% 39% 19% 8%	56
	Night	7% 30% 36% 24%	194
May	Day	25% 36% 32% 5%	58
	Night	24% 34% 34%	186
June	Day	10% 57% 31%	57
	Night	16% 42% 39%	180
July	Day	6% 40% 43% 9%	62
	Night	5% 25% 59% 7%	185
August	Day	9% 26% 48% 14%	88
	Night	6% 17% 63% 11%	283
September	Day	11% 37% 40% 10%	87
	Night	11% 34% 45% 6%	346
October	Day	13% 13% 54% 18%	22
	Night	6% 19% 35% 34%	355
November	Night	14% 17% 37% 27%	230
December	Night	12% 26% 41% 18%	227

Page generated at 2008-09-30 02:41:07. Version ab11