Texas Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Texas 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	8% 6% 5% 5% 7% 48%	8654
	Night	8% 5% 5% 6% 7% 49%	8515
Transparency	Day	9% 10% 28% 30% 21%	6089
	Night	10% 11% 25% 29% 22%	6094
Seeing	Day	10% 16% 38% 30%	471
	Night	10% 18% 40% 29%	2727

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	9% 6% 6% 6% 10% 44%	611
	Night	9% 5% 5% 5% 6% 7% 46%	742
February	Day	15% 10% 7% 5% 6% 6% 37%	561
	Night	20% 6% 5% 41%	684
March	Day	11% 7% 63%	676
	Night	8% 5% 6% 60%	686
April	Day	10% 5% 6% 59%	720
	Night	7% 5% 5% 6% 53%	600
May	Day	5% 6% 5% 6% 8% 52%	762
	Night	6% 5% 6% 5% 9% 53%	601
June	Day	7% 6% 7% 9% 51%	780
	Night	6% 6% 6% 9% 52%	537
July	Day	13% 6% 8% 8% 6% 8% 35%	735
	Night	8% 10% 7% 8% 10% 39%	617
August	Day	8% 6% 6% 9% 9% 7% 8% 33%	1115
	Night	8% 8% 13% 12% 38%	928
September	Day	11% 6% 5% 6% 8% 41%	1011
	Night	12% 5% 5% 5% 8% 44%	934
October	Day	7% 5% 6% 6% 7% 48%	646
	Night	8% 5% 6% 5% 6% 7% 46%	718
November	Day	9% 5% 59%	482
	Night	11% 6% 57%	682
December	Day	7% 70%	555
	Night	5% 69%	786

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	13% 10% 38% 30% 6%	394
	Night	10% 13% 35% 31% 8%	480
February	Day	7% 13% 24% 40% 14%	285
	Night	7% 11% 25% 37% 18%	348
March	Day	7% 5% 30% 36% 19%	538
	Night	5% 27% 42% 21%	499
April	Day	6% 5% 23% 26% 37%	532
	Night	8% 18% 32% 35%	405
May	Day	7% 10% 22% 27% 31%	559
	Night	12% 14% 24% 20% 27%	429
June	Day	11% 20% 26% 37%	551
	Night	16% 5% 25% 25% 27%	380
July	Day	13% 17% 24% 29% 15%	413
	Night	17% 17% 26% 28% 11%	389
August	Day	17% 23% 36% 16% 5%	631
	Night	22% 27% 33% 13%	636
September	Day	8% 8% 37% 30% 13%	634
	Night	9% 16% 26% 30% 17%	597
October	Day	15% 31% 38% 9%	673
	Night	5% 15% 22% 34% 21%	737
November	Day	5% 7% 14% 34% 37%	401
	Night	6% 7% 23% 31% 31%	557
December	Day	5% 22% 35% 31%	478
	Night	15% 31% 48%	637

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	11% 24% 50% 13%	228
February	Night	16% 33% 43% 6%	187
March	Day	22% 29% 41% 6%	31
	Night	17% 25% 44% 12%	214
April	Day	29% 50% 16%	55
	Night	11% 42% 41%	170
May	Day	11% 25% 43% 19%	78
	Night	6% 12% 60% 19%	181
June	Day	9% 38% 42% 5%	119
	Night	6% 45% 42%	180
July	Day	9% 8% 39% 40%	61
	Night	5% 40% 50%	174
August	Day	5% 45% 38% 6%	88
	Night	27% 60% 6%	273
September	Day	7% 7% 43% 38%	39
	Night	11% 5% 30% 48% 5%	253
October	Night	8% 14% 40% 35%	310
November	Night	15% 26% 31% 26%	269
December	Night	13% 23% 37% 22%	288

Page generated at 2008-09-30 04:41:06. Version ab11