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River Valley RV Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the River Valley RV Park 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	19% 6% 6% 5% 6% 5% 6% 8% 28%	8718
	Night	19% 7% 5% 6% 5% 7% 30%	8450
Transparency	Day	21% 22% 40% 14%	3982
	Night	21% 21% 39% 15%	4087
Seeing	Day	11% 27% 30% 21% 9%	576
	Night	15% 34% 31% 16%	2443

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	26% 11% 11% 6% 6% 6% 14%	489
	Night	30% 8% 6% 7% 5% 5% 8% 16%	864
February	Day	26% 13% 7% 7% 5% 9% 5% 14%	546
	Night	24% 11% 7% 6% 6% 23%	706
March	Day	27% 8% 9% 6% 7% 5% 5% 9% 13%	663
	Night	21% 8% 6% 5% 6% 5% 7% 5% 6% 20%	702
April	Day	17% 5% 6% 5% 6% 8% 34%	753
	Night	18% 5% 7% 5% 5% 38%	567
May	Day	25% 6% 6% 5% 7% 5% 5% 8% 21%	822
	Night	16% 7% 5% 6% 6% 10% 29%	531
June	Day	12% 6% 7% 7% 6% 7% 34%	868
	Night	8% 5% 5% 7% 5% 10% 42%	446
July	Day	10% 5% 5% 9% 5% 8% 10% 31%	866
	Night	13% 5% 6% 7% 5% 9% 40%	496
August	Day	12% 5% 7% 5% 5% 6% 5% 5% 9% 34%	1196
	Night	8% 5% 7% 5% 6% 7% 44%	846
September	Day	11% 5% 5% 7% 9% 46%	990
	Night	7% 6% 5% 10% 51%	951
October	Day	22% 7% 6% 5% 5% 6% 6% 28%	608
	Night	19% 9% 6% 5% 5% 7% 32%	754
November	Day	30% 10% 5% 5% 6% 7% 19%	466
	Night	32% 7% 6% 5% 5% 5% 6% 7% 17%	700
December	Day	32% 7% 9% 8% 18%	451
	Night	27% 11% 6% 6% 6% 6% 5% 6% 13%	887

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	39% 19% 35% 5%	112
	Night	37% 21% 34% 7%	229
February	Day	37% 20% 28% 13%	131
	Night	32% 30% 33%	256
March	Day	35% 32% 29%	176
	Night	30% 22% 38% 8%	256
April	Day	21% 15% 40% 19%	376
	Night	13% 7% 43% 32%	294
May	Day	24% 28% 38% 7%	303
	Night	22% 24% 43% 9%	271
June	Day	23% 11% 50% 12%	445
	Night	20% 14% 49% 13%	268
July	Day	19% 17% 41% 17%	467
	Night	17% 16% 43% 19%	284
August	Day	16% 26% 43% 13%	603
	Night	17% 23% 36% 22%	532
September	Day	12% 20% 42% 23%	647
	Night	9% 18% 44% 21% 5%	683
October	Day	16% 27% 38% 15%	401
	Night	22% 33% 31% 12%	503
November	Day	40% 31% 25%	205
	Night	30% 24% 33% 10%	284
December	Day	18% 23% 34% 23%	116
	Night	35% 19% 35% 9%	227

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	30% 39% 23%	217
February	Night	21% 37% 31% 8%	169
March	Day	23% 30% 16% 26%	30
	Night	20% 41% 24% 12%	194
April	Day	11% 37% 29% 15% 5%	51
	Night	14% 47% 29% 9%	150
May	Day	9% 39% 36% 12%	63
	Night	13% 35% 40% 11%	161
June	Day	13% 36% 29% 15%	104
	Night	10% 35% 35% 17%	140
July	Day	12% 23% 38% 14% 10%	116
	Night	10% 23% 36% 26%	169
August	Day	21% 25% 22% 25%	83
	Night	5% 24% 36% 26% 6%	255
September	Day	16% 27% 38% 13%	83
	Night	7% 23% 34% 31%	310
October	Day	19% 15% 30% 32%	46
	Night	15% 33% 28% 20%	307
November	Night	24% 38% 26% 9%	165
December	Night	22% 40% 26% 8%	206

Page generated at 2008-05-11 04:45:48. Version ab11