Tierra del Sol
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tierra del Sol clear sky chart from 2005-11-05 to 2008-11-10.

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	6% 67%	12099
	Night	6% 66%	11977
Transparency	Day	15% 32% 38%	10240
	Night	14% 31% 39%	10112
Seeing	Day	19% 35% 36% 6%	784
	Night	10% 18% 31% 29% 9%	3966

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	5% 6% 57%	878
	Night	5% 5% 6% 58%	1159
February	Day	5% 5% 5% 6% 5% 9% 47%	809
	Night	5% 5% 6% 6% 5% 9% 47%	970
March	Day	6% 7% 52%	988
	Night	5% 8% 5% 6% 52%	1052
April	Day	5% 6% 64%	1077
	Night	5% 6% 64%	899
May	Day	5% 77%	1204
	Night	6% 75%	842
June	Day	83%	1170
	Night	5% 83%	810
July	Day	6% 5% 5% 8% 61%	1198
	Night	6% 5% 6% 62%	842
August	Day	71%	1108
	Night	6% 73%	929
September	Day	80%	1005
	Night	86%	970
October	Day	77%	971
	Night	75%	1062
November	Day	5% 7% 62%	854
	Night	7% 61%	1235
December	Day	7% 61%	837
	Night	7% 64%	1207

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	8% 17% 34% 23%	734
	Night	9% 15% 25% 33%	983
February	Day	7% 19% 34% 25%	602
	Night	18% 28% 32%	729
March	Day	7% 15% 43% 25%	718
	Night	6% 12% 34% 35%	764
April	Day	21% 38% 32%	851
	Night	7% 12% 40% 36%	699
May	Day	16% 37% 38%	1100
	Night	14% 37% 40%	764
June	Day	9% 21% 66%	1056
	Night	7% 23% 67%	742
July	Day	10% 16% 21% 40%	772
	Night	6% 19% 25% 41%	535
August	Day	17% 32% 31%	1060
	Night	21% 31% 33%	887
September	Day	6% 32% 49%	989
	Night	7% 28% 56%	945
October	Day	12% 22% 54%	901
	Night	10% 22% 56%	960
November	Day	5% 16% 33% 31%	753
	Night	5% 13% 38% 28%	1083
December	Day	5% 23% 36% 23%	704
	Night	6% 24% 36% 23%	1021

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	Day	23% 60% 16%	43
	Night	20% 25% 32% 17%	364
February	Day	31% 31% 27% 6%	74
	Night	19% 20% 30% 22% 5%	313
March	Day	34% 36% 19% 7%	82
	Night	15% 26% 32% 18% 6%	344
April	Day	31% 41% 21%	79
	Night	18% 32% 27% 15% 5%	349
May	Day	23% 41% 26% 5%	91
	Night	8% 21% 31% 28% 9%	283
June	Day	11% 44% 38%	90
	Night	14% 33% 36% 12%	254
July	Day	5% 24% 57% 12%	78
	Night	31% 50% 13%	250
August	Day	21% 62% 6%	89
	Night	21% 56% 17%	356
September	Day	11% 28% 47% 11%	88
	Night	8% 28% 44% 13%	350
October	Day	27% 41% 30%	70
	Night	9% 21% 32% 24% 10%	365
November	Night	7% 17% 38% 27% 7%	379
December	Night	11% 21% 35% 24% 6%	359

Page generated at 2008-11-11 04:54:41. Version ab11