Okie-Tex Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Okie-Tex Star Party clear sky chart from 2005-11-05 to 2008-12-24.

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% 5% 8% 57%	12516
	Night	5% 5% 7% 58%	12521
Cloud Cover	Day	6% 5% 7% 58%	12509
	Night	5% 5% 7% 58%	12529
Transparency	Day	14% 28% 27% 13%	10261
	Night	14% 27% 28% 13%	10447
Seeing	Day	11% 29% 36% 16%	731
	Night	8% 34% 39% 12%	4023

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% 5% 65%	787
	Night	5% 63%	1254
February	Day	5% 8% 59%	809
	Night	5% 8% 59%	970
March	Day	6% 5% 8% 55%	999
	Night	7% 6% 54%	1041
April	Day	9% 7% 59%	1077
	Night	7% 6% 62%	899
May	Day	6% 5% 5% 9% 58%	1211
	Night	8% 6% 5% 5% 8% 51%	834
June	Day	6% 5% 8% 10% 56%	1260
	Night	6% 5% 8% 10% 50%	720
July	Day	6% 6% 6% 7% 10% 50%	1289
	Night	7% 10% 12% 48%	752
August	Day	12% 5% 5% 5% 11% 40%	1108
	Night	11% 5% 5% 6% 13% 41%	929
September	Day	9% 7% 56%	1024
	Night	6% 6% 8% 59%	951
October	Day	7% 5% 65%	933
	Night	7% 66%	1096
November	Day	7% 71%	1039
	Night	5% 7% 69%	1495
December	Day	6% 7% 6% 59%	980
	Night	7% 5% 6% 59%	1580

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	65%	786
	Night	5% 63%	1257
February	Day	5% 7% 60%	809
	Night	5% 5% 7% 60%	970
March	Day	6% 5% 5% 5% 9% 55%	1000
	Night	6% 5% 6% 55%	1043
April	Day	8% 7% 60%	1077
	Night	7% 6% 62%	899
May	Day	6% 5% 8% 59%	1210
	Night	8% 6% 5% 7% 52%	834
June	Day	5% 5% 7% 10% 57%	1260
	Night	7% 8% 10% 50%	720
July	Day	6% 5% 6% 6% 10% 50%	1289
	Night	7% 5% 9% 11% 49%	753
August	Day	12% 5% 5% 6% 10% 42%	1102
	Night	12% 5% 5% 7% 13% 40%	930
September	Day	9% 5% 57%	1026
	Night	7% 6% 7% 59%	951
October	Day	7% 5% 5% 65%	934
	Night	7% 66%	1096
November	Day	6% 71%	1036
	Night	5% 7% 69%	1495
December	Day	7% 7% 6% 59%	980
	Night	6% 5% 6% 59%	1581

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	9% 33% 36% 12%	637
	Night	8% 29% 37% 12%	1055
February	Day	13% 35% 29% 9%	694
	Night	9% 34% 37% 6%	817
March	Day	17% 28% 31% 7%	818
	Night	17% 24% 30% 12%	821
April	Day	9% 28% 26% 24%	862
	Night	15% 25% 25% 22%	744
May	Day	6% 18% 21% 31% 13%	986
	Night	6% 20% 19% 25% 16%	640
June	Day	5% 15% 28% 27% 14%	1056
	Night	7% 24% 25% 20% 12%	560
July	Day	8% 15% 29% 18% 12%	773
	Night	26% 26% 18% 8%	472
August	Day	8% 19% 24% 16% 6%	914
	Night	9% 21% 24% 16% 6%	772
September	Day	11% 29% 22% 13%	897
	Night	6% 16% 26% 24% 10%	866
October	Day	8% 19% 33% 22%	842
	Night	5% 18% 35% 23%	995
November	Day	10% 30% 33% 17%	949
	Night	10% 29% 33% 17%	1355
December	Day	17% 35% 22% 8%	833
	Night	13% 35% 26% 7%	1350

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	10% 42% 35% 9%	417
February	Night	7% 46% 33% 8%	312
March	Day	40% 46% 13%	30
	Night	16% 43% 29% 6%	322
April	Day	28% 43% 19%	82
	Night	16% 47% 29%	253
May	Day	15% 33% 32% 13%	171
	Night	8% 46% 30% 11%	262
June	Day	9% 31% 40% 16%	169
	Night	5% 35% 43% 12%	251
July	Day	14% 44% 33%	156
	Night	16% 51% 26%	241
August	Day	9% 18% 50% 17%	87
	Night	10% 47% 26%	257
September	Day	36% 36% 8%	36
	Night	29% 45% 14%	253
October	Night	6% 30% 39% 14%	339
November	Night	30% 45% 15%	559
December	Night	12% 33% 40% 8%	557

Page generated at 2008-12-24 21:45:11. Version ab11