Eldorado Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Eldorado 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	15% 6% 5% 7% 41%	8664
	Night	12% 5% 5% 8% 46%	8505
Cloud Cover	Day	15% 6% 7% 42%	8677
	Night	12% 5% 5% 8% 46%	8498
Transparency	Day	14% 11% 30% 30% 12%	5226
	Night	15% 14% 26% 27% 16%	5526
Seeing	Day	6% 25% 41% 23%	469
	Night	7% 26% 42% 22%	2637

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	17% 5% 5% 5% 6% 6% 7% 35%	585
	Night	20% 7% 6% 5% 37%	769
February	Day	27% 5% 6% 38%	561
	Night	26% 5% 5% 6% 33%	684
March	Day	18% 52%	660
	Night	15% 6% 54%	702
April	Day	18% 5% 5% 50%	716
	Night	12% 6% 49%	604
May	Day	15% 9% 11% 38%	800
	Night	6% 7% 5% 11% 48%	563
June	Day	8% 6% 5% 5% 10% 44%	780
	Night	5% 5% 10% 14% 47%	537
July	Day	11% 5% 5% 5% 7% 5% 6% 9% 39%	784
	Night	8% 6% 9% 13% 39%	569
August	Day	12% 5% 8% 6% 7% 10% 31%	1115
	Night	6% 5% 6% 5% 7% 12% 40%	928
September	Day	17% 5% 5% 5% 6% 7% 36%	981
	Night	10% 5% 6% 7% 5% 6% 7% 40%	964
October	Day	17% 5% 5% 5% 5% 6% 8% 34%	664
	Night	13% 5% 9% 44%	698
November	Day	19% 52%	470
	Night	19% 50%	696
December	Day	65%	548
	Night	5% 76%	791

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	17% 5% 5% 5% 6% 6% 6% 35%	585
	Night	20% 7% 6% 5% 37%	769
February	Day	26% 5% 7% 39%	570
	Night	26% 5% 6% 33%	684
March	Day	18% 5% 52%	660
	Night	16% 6% 54%	704
April	Day	18% 5% 50%	716
	Night	13% 5% 5% 51%	604
May	Day	15% 9% 10% 38%	797
	Night	6% 8% 6% 11% 47%	555
June	Day	8% 6% 5% 6% 10% 44%	780
	Night	5% 5% 10% 14% 47%	537
July	Day	11% 5% 5% 7% 5% 6% 10% 39%	789
	Night	8% 6% 9% 13% 39%	570
August	Day	12% 5% 8% 6% 7% 10% 31%	1115
	Night	6% 5% 6% 5% 8% 12% 40%	928
September	Day	17% 5% 5% 5% 6% 7% 36%	983
	Night	10% 5% 5% 7% 5% 6% 7% 40%	962
October	Day	17% 5% 5% 5% 5% 6% 5% 8% 34%	662
	Night	13% 6% 9% 44%	698
November	Day	19% 52%	472
	Night	19% 50%	696
December	Day	5% 65%	548
	Night	5% 76%	791

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	17% 11% 45% 22%	280
	Night	17% 10% 33% 27% 11%	407
February	Day	10% 9% 31% 43%	283
	Night	19% 9% 24% 37% 9%	310
March	Day	9% 8% 26% 35% 19%	429
	Night	9% 9% 24% 33% 23%	447
April	Day	8% 5% 28% 32% 25%	433
	Night	14% 6% 25% 33% 20%	376
May	Day	17% 14% 34% 24% 9%	454
	Night	28% 19% 25% 22% 5%	372
June	Day	11% 9% 43% 29% 5%	488
	Night	27% 12% 29% 23% 7%	369
July	Day	23% 8% 32% 30%	425
	Night	20% 23% 33% 18%	344
August	Day	30% 26% 29% 9%	572
	Night	24% 31% 29% 10%	591
September	Day	17% 13% 29% 24% 15%	526
	Night	17% 15% 28% 21% 16%	563
October	Day	11% 15% 27% 36% 8%	588
	Night	9% 19% 23% 33% 13%	655
November	Day	8% 6% 15% 37% 32%	324
	Night	7% 8% 17% 26% 40%	432
December	Day	6% 22% 43% 24%	424
	Night	25% 36% 32%	660

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	9% 38% 42% 8%	226
February	Night	14% 44% 33% 7%	183
March	Night	7% 40% 44% 7%	183
April	Day	16% 56% 27%	48
	Night	13% 46% 36%	165
May	Day	8% 25% 43% 20%	104
	Night	6% 31% 47% 14%	182
June	Day	28% 45% 23%	113
	Night	5% 29% 47% 16%	176
July	Day	5% 19% 43% 28%	106
	Night	14% 51% 32%	183
August	Day	15% 43% 31%	85
	Night	5% 34% 51%	270
September	Day	15% 7% 30% 30% 15%	13
	Night	9% 43% 40%	255
October	Night	6% 19% 42% 29%	268
November	Night	13% 27% 43% 14%	249
December	Night	6% 31% 39% 20%	297

Page generated at 2008-09-30 04:41:05. Version ab11