Congaree National Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Congaree National 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	20% 5% 5% 6% 5% 7% 31%	8704
	Night	20% 5% 5% 6% 6% 34%	8467
Transparency	Day	19% 11% 30% 28% 8%	4056
	Night	16% 11% 30% 29% 10%	4218
Seeing	Day	7% 22% 28% 27% 15%	521
	Night	11% 25% 33% 25%	2583

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	16% 5% 5% 5% 5% 41%	551
	Night	17% 7% 6% 41%	802
February	Day	37% 5% 5% 28%	558
	Night	33% 5% 5% 6% 29%	695
March	Day	17% 5% 6% 6% 40%	682
	Night	15% 5% 5% 6% 6% 44%	682
April	Day	14% 5% 5% 6% 47%	708
	Night	14% 5% 6% 5% 49%	613
May	Day	15% 5% 9% 6% 6% 6% 33%	802
	Night	18% 5% 6% 7% 6% 6% 5% 35%	551
June	Day	25% 7% 9% 5% 6% 6% 5% 10% 14%	780
	Night	23% 8% 9% 7% 6% 11% 5% 5% 8% 10%	537
July	Day	18% 8% 5% 5% 9% 6% 7% 13% 17%	801
	Night	14% 6% 9% 5% 8% 5% 9% 5% 6% 10% 18%	558
August	Day	23% 6% 7% 6% 6% 10% 6% 7% 8% 13%	1177
	Night	24% 9% 9% 8% 6% 9% 5% 12%	863
September	Day	21% 5% 5% 5% 5% 7% 35%	972
	Night	26% 5% 6% 5% 9% 29%	972
October	Day	20% 5% 5% 7% 5% 5% 35%	626
	Night	24% 5% 5% 5% 5% 34%	736
November	Day	21% 6% 47%	500
	Night	16% 6% 50%	667
December	Day	13% 54%	547
	Night	13% 56%	791

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	9% 16% 28% 35% 9%	282
	Night	10% 15% 32% 29% 11%	433
February	Day	7% 10% 32% 38% 11%	210
	Night	11% 10% 28% 42% 7%	266
March	Day	22% 7% 31% 32% 5%	367
	Night	15% 7% 34% 34% 8%	400
April	Day	14% 32% 33% 15%	417
	Night	11% 5% 31% 39% 12%	378
May	Day	29% 9% 36% 23%	379
	Night	26% 17% 38% 17%	271
June	Day	42% 17% 26% 11%	202
	Night	51% 20% 24%	127
July	Day	39% 18% 31% 10%	261
	Night	34% 15% 38% 12%	175
August	Day	38% 22% 26% 12%	307
	Night	44% 24% 22% 8%	184
September	Day	15% 13% 35% 25% 10%	493
	Night	16% 17% 30% 26% 9%	474
October	Day	15% 9% 21% 37% 15%	455
	Night	15% 10% 25% 30% 18%	503
November	Day	10% 7% 35% 32% 13%	328
	Night	13% 6% 30% 33% 14%	490
December	Day	11% 28% 39% 16%	355
	Night	5% 7% 29% 39% 17%	517

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	15% 39% 34% 8%	216
February	Day	33% 33% 33%	3
	Night	18% 40% 38%	159
March	Day	12% 33% 38% 14%	54
	Night	17% 42% 31% 8%	216
April	Day	9% 24% 33% 28%	53
	Night	16% 29% 40% 11%	209
May	Day	5% 15% 24% 26% 28%	53
	Night	7% 21% 37% 28%	164
June	Day	10% 17% 27% 31% 12%	47
	Night	10% 16% 38% 34%	150
July	Day	14% 17% 41% 25%	56
	Night	6% 10% 26% 43% 13%	172
August	Day	9% 14% 22% 22% 29%	74
	Night	5% 18% 26% 39% 9%	260
September	Day	21% 27% 32% 13%	73
	Night	7% 18% 31% 40%	294
October	Day	33% 36% 20% 6%	75
	Night	9% 27% 36% 25%	297
November	Day	6% 24% 24% 30% 15%	33
	Night	9% 18% 32% 32% 7%	228
December	Night	11% 27% 36% 23%	218

Page generated at 2008-05-11 04:45:56. Version ab11