Hutville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hutville 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	23% 6% 5% 5% 6% 7% 27%	8736
	Night	23% 6% 5% 5% 6% 31%	8433
Transparency	Day	21% 17% 41% 17%	3820
	Night	18% 16% 39% 23%	4044
Seeing	Day	9% 15% 27% 29% 17%	494
	Night	11% 27% 34% 24%	2388

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	32% 11% 9% 7% 6% 5% 11%	551
	Night	39% 6% 7% 5% 5% 7% 14%	802
February	Day	30% 8% 6% 5% 5% 6% 23%	545
	Night	26% 9% 6% 5% 5% 27%	709
March	Day	32% 9% 7% 6% 5% 5% 6% 19%	672
	Night	29% 9% 8% 5% 6% 6% 23%	692
April	Day	31% 6% 5% 5% 30%	741
	Night	28% 5% 5% 34%	580
May	Day	16% 5% 6% 6% 6% 7% 7% 31%	802
	Night	14% 5% 8% 5% 6% 5% 7% 37%	551
June	Day	13% 6% 5% 5% 6% 8% 5% 5% 7% 31%	795
	Night	11% 5% 6% 5% 7% 6% 7% 6% 36%	519
July	Day	17% 5% 5% 5% 5% 11% 6% 8% 23%	809
	Night	10% 5% 5% 9% 6% 7% 9% 33%	552
August	Day	16% 5% 6% 5% 5% 9% 5% 5% 8% 29%	1205
	Night	12% 5% 5% 7% 6% 9% 37%	835
September	Day	17% 5% 7% 42%	971
	Night	16% 5% 8% 47%	972
October	Day	25% 6% 9% 32%	625
	Night	25% 5% 7% 36%	736
November	Day	35% 7% 5% 5% 5% 20%	473
	Night	32% 8% 6% 5% 26%	694
December	Day	34% 11% 5% 5% 6% 20%	547
	Night	34% 11% 6% 5% 20%	791

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	46% 25% 21% 6%	115
	Night	38% 19% 28% 13%	214
February	Day	28% 20% 30% 18%	195
	Night	25% 8% 43% 18%	271
March	Day	27% 27% 41%	207
	Night	22% 21% 42% 12%	237
April	Day	21% 10% 45% 21%	314
	Night	11% 9% 43% 29% 6%	277
May	Day	24% 20% 43% 11%	374
	Night	18% 22% 41% 17%	279
June	Day	23% 10% 36% 26%	364
	Night	18% 17% 33% 30%	269
July	Day	22% 12% 43% 15% 6%	326
	Night	20% 13% 38% 24%	281
August	Day	20% 20% 44% 13%	537
	Night	23% 17% 38% 19%	477
September	Day	11% 12% 40% 32%	561
	Night	7% 11% 35% 41%	614
October	Day	15% 23% 44% 15%	451
	Night	15% 17% 37% 25%	564
November	Day	12% 27% 42% 15%	193
	Night	14% 23% 47% 11%	317
December	Day	27% 14% 43% 14%	183
	Night	19% 15% 50% 15%	244

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	20% 53% 20%	154
February	Night	12% 37% 42% 7%	166
March	Day	19% 31% 46%	41
	Night	16% 40% 36% 5%	186
April	Day	19% 27% 29% 21%	47
	Night	17% 35% 31% 13%	161
May	Day	11% 16% 37% 25% 9%	54
	Night	8% 29% 44% 16%	168
June	Day	7% 17% 31% 23% 19%	67
	Night	6% 20% 42% 28%	164
July	Day	11% 12% 22% 35% 17%	62
	Night	13% 47% 31%	173
August	Day	6% 17% 40% 34%	82
	Night	5% 11% 30% 43% 7%	257
September	Day	8% 24% 36% 28%	75
	Night	13% 27% 45% 8%	314
October	Day	9% 22% 22% 34% 10%	66
	Night	10% 20% 30% 34%	297
November	Night	11% 38% 36% 13%	184
December	Night	23% 36% 30% 7%	164

Page generated at 2008-05-14 13:55:36. Version ab11