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 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% 5% 5% 7% 51%	8699
	Night	10% 6% 5% 7% 49%	8466
Transparency	Day	10% 14% 32% 27% 15%	6184
	Night	11% 15% 29% 27% 16%	5842
Seeing	Day	11% 31% 40% 16%	537
	Night	7% 33% 43% 14%	2752

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	10% 5% 5% 7% 48%	518
	Night	11% 5% 5% 7% 48%	836
February	Day	14% 5% 6% 7% 45%	561
	Night	13% 6% 5% 7% 5% 5% 39%	684
March	Day	12% 6% 54%	669
	Night	10% 5% 5% 55%	692
April	Day	17% 5% 5% 6% 49%	720
	Night	14% 5% 52%	600
May	Day	7% 6% 5% 9% 53%	808
	Night	10% 6% 5% 8% 48%	556
June	Day	7% 5% 6% 7% 8% 55%	840
	Night	7% 5% 7% 7% 7% 49%	477
July	Day	8% 7% 5% 6% 10% 47%	849
	Night	12% 8% 6% 7% 9% 42%	504
August	Day	13% 5% 6% 8% 8% 39%	1115
	Night	10% 8% 6% 7% 8% 38%	927
September	Day	5% 5% 6% 61%	1007
	Night	8% 5% 6% 56%	938
October	Day	9% 5% 7% 56%	628
	Night	7% 8% 57%	732
November	Day	16% 6% 6% 46%	470
	Night	14% 6% 5% 44%	696
December	Day	8% 5% 5% 7% 59%	514
	Night	5% 7% 60%	824

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	16% 16% 33% 26% 6%	320
	Night	11% 17% 36% 24% 9%	535
February	Day	10% 16% 50% 14% 7%	353
	Night	18% 12% 37% 23% 7%	364
March	Day	7% 15% 40% 25% 11%	427
	Night	5% 21% 38% 27% 7%	457
April	Day	9% 11% 23% 31% 22%	454
	Night	11% 11% 17% 28% 31%	369
May	Day	10% 17% 22% 27% 22%	582
	Night	13% 20% 24% 15% 25%	352
June	Day	13% 9% 30% 26% 21%	622
	Night	13% 15% 27% 25% 17%	305
July	Day	14% 10% 27% 28% 19%	589
	Night	15% 15% 22% 30% 16%	295
August	Day	17% 19% 35% 22% 5%	673
	Night	16% 22% 33% 20% 7%	531
September	Day	7% 13% 29% 30% 18%	764
	Night	7% 14% 26% 33% 18%	672
October	Day	17% 31% 28% 18%	664
	Night	10% 15% 23% 29% 20%	817
November	Day	15% 11% 30% 23% 19%	355
	Night	13% 10% 21% 30% 23%	497
December	Day	9% 42% 35% 9%	381
	Night	6% 36% 35% 15%	648

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	37% 40% 16%	254
February	Night	8% 40% 40% 9%	202
March	Day	19% 52% 19% 9%	21
	Night	6% 39% 43% 10%	199
April	Day	27% 47% 20%	48
	Night	11% 43% 37% 6%	158
May	Day	18% 35% 28% 17%	114
	Night	11% 43% 35% 9%	172
June	Day	9% 29% 44% 15%	117
	Night	5% 43% 37% 13%	169
July	Day	18% 50% 26%	116
	Night	6% 24% 52% 16%	174
August	Day	6% 25% 52% 12%	86
	Night	6% 14% 49% 27%	262
September	Day	5% 42% 45% 5%	35
	Night	5% 35% 43% 15%	253
October	Night	6% 31% 38% 21%	339
November	Night	8% 34% 46% 10%	278
December	Night	7% 29% 49% 13%	292

Page generated at 2008-05-11 03:45:58. Version ab11