Corydon Ridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Corydon Ridge Observatory 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% 7% 5% 7% 32%	8731
	Night	21% 5% 5% 5% 5% 6% 34%	8440
Cloud Cover	Day	20% 5% 5% 7% 5% 7% 32%	8730
	Night	21% 5% 5% 5% 6% 34%	8442
Transparency	Day	18% 15% 39% 24%	4353
	Night	15% 14% 41% 24%	4487
Seeing	Day	18% 32% 30% 14%	510
	Night	8% 28% 34% 25%	2387

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	31% 10% 7% 5% 24%	514
	Night	32% 6% 6% 6% 24%	838
February	Day	25% 10% 6% 5% 9% 6% 6% 21%	570
	Night	24% 8% 5% 6% 5% 5% 6% 28%	684
March	Day	27% 8% 5% 5% 6% 28%	664
	Night	25% 6% 7% 6% 5% 6% 27%	702
April	Day	24% 5% 5% 5% 37%	735
	Night	21% 6% 5% 5% 42%	584
May	Day	13% 5% 8% 6% 9% 36%	802
	Night	13% 7% 8% 5% 10% 35%	551
June	Day	11% 5% 5% 9% 7% 5% 8% 35%	832
	Night	12% 5% 5% 7% 10% 36%	484
July	Day	16% 5% 5% 6% 8% 5% 7% 8% 27%	845
	Night	11% 5% 5% 5% 10% 5% 6% 9% 34%	516
August	Day	13% 5% 6% 8% 5% 7% 9% 31%	1152
	Night	12% 5% 6% 5% 6% 9% 37%	889
September	Day	14% 6% 5% 5% 6% 42%	993
	Night	14% 5% 6% 50%	949
October	Day	20% 6% 6% 7% 5% 6% 32%	625
	Night	22% 5% 5% 5% 6% 8% 31%	736
November	Day	36% 6% 26%	473
	Night	36% 8% 6% 29%	694
December	Day	30% 6% 7% 6% 5% 5% 27%	526
	Night	25% 5% 7% 5% 32%	813

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	32% 10% 6% 5% 5% 24%	514
	Night	33% 7% 6% 5% 24%	838
February	Day	25% 10% 5% 5% 8% 5% 6% 22%	570
	Night	25% 7% 6% 5% 5% 6% 28%	684
March	Day	28% 5% 7% 6% 28%	664
	Night	26% 5% 8% 5% 6% 6% 27%	702
April	Day	24% 6% 5% 38%	735
	Night	21% 5% 5% 6% 42%	584
May	Day	14% 8% 5% 10% 36%	802
	Night	14% 5% 6% 7% 5% 9% 36%	551
June	Day	11% 5% 5% 9% 7% 5% 8% 34%	832
	Night	12% 5% 5% 8% 10% 37%	485
July	Day	16% 5% 6% 9% 6% 10% 27%	842
	Night	11% 5% 6% 11% 5% 6% 9% 34%	516
August	Day	14% 5% 5% 8% 5% 7% 9% 31%	1153
	Night	13% 6% 5% 6% 9% 37%	889
September	Day	14% 7% 5% 5% 7% 42%	993
	Night	14% 7% 50%	950
October	Day	20% 6% 7% 6% 6% 32%	625
	Night	20% 6% 5% 7% 8% 31%	736
November	Day	37% 6% 5% 26%	474
	Night	38% 9% 29%	694
December	Day	30% 6% 6% 6% 5% 27%	526
	Night	25% 6% 6% 5% 32%	813

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	40% 10% 38% 10%	170
	Night	30% 17% 41% 9%	281
February	Day	33% 13% 36% 15%	211
	Night	13% 13% 50% 20%	297
March	Day	22% 16% 41% 18%	253
	Night	15% 21% 45% 15%	297
April	Day	15% 15% 47% 17%	362
	Night	20% 7% 39% 25% 7%	329
May	Day	20% 19% 35% 24%	430
	Night	13% 18% 50% 16%	291
June	Day	17% 12% 44% 22%	438
	Night	22% 11% 35% 19% 10%	266
July	Day	24% 10% 31% 30%	398
	Night	26% 16% 33% 22%	275
August	Day	17% 21% 43% 18%	571
	Night	18% 21% 38% 21%	496
September	Day	7% 13% 38% 35%	572
	Night	6% 11% 37% 37% 6%	636
October	Day	15% 19% 35% 27%	496
	Night	9% 13% 38% 33% 5%	594
November	Day	16% 14% 39% 25%	233
	Night	12% 10% 49% 27%	353
December	Day	17% 16% 39% 25%	219
	Night	17% 17% 39% 23%	372

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	19% 47% 25% 7%	186
February	Night	13% 54% 27%	174
March	Day	8% 29% 37% 25%	24
	Night	20% 37% 35% 6%	181
April	Day	6% 26% 45% 19%	46
	Night	8% 31% 38% 21%	149
May	Day	7% 20% 35% 28% 7%	53
	Night	23% 44% 27%	164
June	Day	6% 21% 29% 30% 13%	99
	Night	18% 42% 32%	161
July	Day	31% 36% 24% 7%	85
	Night	22% 39% 31%	169
August	Day	8% 20% 31% 36%	82
	Night	10% 31% 45% 8%	247
September	Day	31% 43% 20%	74
	Night	12% 30% 46% 7%	290
October	Day	12% 12% 34% 31% 8%	47
	Night	9% 21% 32% 31%	305
November	Night	9% 38% 35% 16%	165
December	Night	12% 37% 41% 7%	196

Page generated at 2008-08-29 16:03:18. Version ab11