Dodgeville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dodgeville 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	17% 6% 6% 5% 6% 5% 7% 32%	8739
	Night	19% 6% 6% 5% 5% 6% 35%	8435
Transparency	Day	18% 19% 42% 17%	4360
	Night	16% 20% 41% 20%	4478
Seeing	Day	9% 28% 30% 24% 7%	588
	Night	10% 33% 36% 17%	2458

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	33% 8% 9% 6% 6% 16%	502
	Night	28% 8% 9% 5% 5% 5% 25%	851
February	Day	24% 7% 10% 7% 6% 7% 19%	539
	Night	26% 10% 10% 5% 5% 5% 25%	715
March	Day	27% 11% 5% 6% 5% 5% 26%	676
	Night	29% 7% 7% 6% 29%	690
April	Day	13% 6% 6% 9% 6% 5% 7% 34%	722
	Night	17% 6% 6% 6% 44%	597
May	Day	20% 7% 8% 7% 5% 8% 5% 7% 22%	858
	Night	20% 5% 5% 5% 7% 7% 7% 33%	495
June	Day	12% 8% 6% 9% 37%	840
	Night	11% 5% 5% 7% 7% 10% 40%	476
July	Day	10% 9% 6% 7% 9% 34%	866
	Night	7% 6% 6% 9% 46%	496
August	Day	12% 5% 5% 7% 5% 7% 7% 35%	1175
	Night	9% 8% 5% 6% 7% 41%	867
September	Day	9% 5% 7% 55%	1023
	Night	8% 5% 9% 56%	918
October	Day	17% 11% 7% 5% 5% 7% 34%	603
	Night	18% 8% 6% 5% 5% 7% 36%	759
November	Day	25% 9% 6% 5% 7% 25%	448
	Night	29% 7% 5% 5% 5% 5% 27%	719
December	Day	23% 10% 6% 5% 5% 5% 6% 26%	487
	Night	22% 8% 8% 5% 5% 6% 6% 23%	852

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	35% 20% 32% 12%	125
	Night	27% 17% 49% 6%	281
February	Day	32% 16% 42% 8%	159
	Night	23% 26% 34% 15%	253
March	Day	21% 24% 41% 11%	236
	Night	12% 26% 48% 13%	283
April	Day	24% 14% 42% 14%	361
	Night	14% 8% 46% 26%	361
May	Day	29% 20% 43% 6%	330
	Night	16% 33% 40% 9%	255
June	Day	17% 16% 47% 18%	445
	Night	24% 13% 49% 11%	281
July	Day	12% 18% 48% 16%	456
	Night	18% 11% 45% 18% 5%	317
August	Day	16% 17% 41% 22%	614
	Night	16% 17% 41% 22%	512
September	Day	8% 18% 40% 28%	725
	Night	7% 22% 35% 31%	685
October	Day	22% 27% 33% 16%	489
	Night	13% 17% 41% 26%	590
November	Day	14% 20% 49% 14%	224
	Night	12% 23% 43% 19%	344
December	Day	27% 20% 44% 8%	196
	Night	22% 28% 30% 18%	316

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% 49% 27% 6%	219
February	Night	8% 50% 23% 14%	181
March	Day	25% 25% 37% 12%	8
	Night	14% 37% 37% 10%	145
April	Day	41% 32% 18%	53
	Night	5% 41% 35% 17%	150
May	Day	16% 46% 27% 7%	102
	Night	5% 41% 44% 7%	156
June	Day	6% 35% 31% 22%	109
	Night	31% 46% 17%	164
July	Day	8% 16% 31% 30% 11%	113
	Night	6% 18% 40% 32%	176
August	Day	9% 17% 29% 29% 13%	123
	Night	6% 15% 42% 30% 5%	262
September	Day	7% 20% 30% 35% 7%	80
	Night	6% 22% 40% 27%	281
October	Night	12% 25% 38% 22%	304
November	Night	18% 46% 28% 5%	194
December	Night	19% 38% 30% 10%	226

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