Shingletown
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Shingletown 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	11% 5% 61%	8713
	Night	16% 5% 54%	8454
Cloud Cover	Day	12% 5% 61%	8708
	Night	17% 5% 54%	8462
Transparency	Day	11% 9% 26% 29% 23%	6599
	Night	13% 10% 24% 29% 21%	5840
Seeing	Day	15% 30% 41% 12%	632
	Night	8% 18% 34% 34%	2575

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	22% 5% 5% 7% 5% 6% 5% 31%	522
	Night	28% 5% 5% 6% 6% 6% 30%	831
February	Day	29% 6% 5% 6% 31%	535
	Night	30% 5% 5% 6% 5% 6% 29%	719
March	Day	17% 5% 5% 51%	678
	Night	18% 6% 55%	685
April	Day	13% 6% 7% 48%	719
	Night	13% 5% 5% 6% 5% 45%	600
May	Day	12% 5% 5% 7% 48%	847
	Night	13% 5% 7% 52%	507
June	Day	5% 6% 70%	840
	Night	5% 5% 8% 61%	478
July	Day	89%	847
	Night	84%	514
August	Day	83%	1161
	Night	5% 79%	880
September	Day	82%	1010
	Night	80%	925
October	Day	9% 8% 65%	620
	Night	13% 5% 6% 62%	744
November	Day	26% 6% 43%	446
	Night	26% 5% 45%	721
December	Day	34% 31%	488
	Night	37% 33%	850

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	24% 7% 6% 5% 31%	522
	Night	30% 5% 6% 5% 5% 31%	831
February	Day	31% 5% 6% 31%	526
	Night	31% 5% 5% 6% 29%	719
March	Day	19% 5% 6% 50%	677
	Night	19% 6% 55%	684
April	Day	17% 6% 48%	720
	Night	16% 5% 5% 5% 46%	600
May	Day	14% 5% 5% 7% 47%	849
	Night	14% 6% 6% 51%	515
June	Day	6% 7% 69%	840
	Night	5% 8% 62%	478
July	Day	89%	838
	Night	85%	514
August	Day	83%	1162
	Night	79%	880
September	Day	81%	1020
	Night	80%	926
October	Day	9% 8% 63%	620
	Night	13% 5% 6% 62%	744
November	Day	26% 6% 44%	446
	Night	26% 5% 45%	721
December	Day	35% 31%	488
	Night	38% 33%	850

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	32% 20% 33% 13%	227
	Night	30% 18% 31% 15%	332
February	Day	31% 14% 25% 16% 11%	204
	Night	27% 21% 9% 27% 13%	273
March	Day	15% 6% 37% 31% 9%	425
	Night	17% 7% 31% 35% 7%	434
April	Day	18% 20% 20% 24% 15%	468
	Night	16% 18% 18% 29% 16%	336
May	Day	24% 9% 26% 31% 7%	526
	Night	21% 14% 29% 28% 6%	324
June	Day	10% 8% 41% 34%	699
	Night	15% 6% 44% 29%	362
July	Day	15% 24% 53%	802
	Night	5% 14% 27% 51%	474
August	Day	16% 36% 40%	1068
	Night	5% 5% 16% 37% 34%	785
September	Day	7% 21% 31% 34%	958
	Night	5% 6% 18% 31% 38%	844
October	Day	9% 17% 29% 25% 17%	746
	Night	13% 13% 27% 26% 19%	874
November	Day	14% 17% 34% 21% 10%	273
	Night	17% 13% 36% 25% 7%	455
December	Day	25% 36% 29%	203
	Night	22% 10% 30% 34%	347

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	Day	35% 29% 32%	31
	Night	10% 25% 37% 25%	192
February	Day	26% 39% 23% 10%	46
	Night	11% 27% 40% 18%	172
March	Day	24% 37% 24% 14%	54
	Night	10% 24% 35% 27%	214
April	Day	25% 37% 29% 7%	51
	Night	16% 29% 34% 16%	218
May	Day	21% 36% 32% 7%	55
	Night	8% 16% 37% 34%	127
June	Day	14% 30% 46% 8%	56
	Night	5% 11% 35% 47%	117
July	Day	29% 53% 14%	62
	Night	26% 69%	142
August	Day	6% 21% 64% 7%	92
	Night	6% 25% 57% 7%	318
September	Day	17% 25% 39% 16%	89
	Night	15% 29% 42% 9%	356
October	Day	14% 29% 45% 10%	91
	Night	10% 12% 36% 33% 7%	352
November	Day	20% 20% 40% 20%	5
	Night	8% 30% 41% 18%	196
December	Night	11% 28% 39% 21%	171

Page generated at 2008-05-14 10:55:42. Version ab11