Bruneau Dunes Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bruneau Dunes 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	9% 5% 5% 7% 52%	8723
	Night	11% 6% 5% 7% 47%	8443
Cloud Cover	Day	9% 5% 5% 7% 52%	8716
	Night	11% 6% 5% 7% 47%	8453
Transparency	Day	14% 13% 29% 26% 15%	6092
	Night	17% 18% 29% 21% 12%	5517
Seeing	Day	9% 30% 32% 22%	533
	Night	7% 18% 38% 31%	2668

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% 7% 8% 5% 5% 6% 6% 6% 8% 27%	488
	Night	17% 6% 6% 5% 5% 8% 5% 5% 9% 26%	866
February	Day	17% 7% 43%	552
	Night	13% 6% 5% 6% 8% 41%	702
March	Day	11% 6% 5% 6% 46%	664
	Night	10% 6% 5% 7% 53%	700
April	Day	9% 5% 6% 5% 5% 7% 45%	745
	Night	9% 5% 7% 6% 6% 8% 42%	574
May	Day	13% 7% 5% 6% 8% 39%	826
	Night	13% 7% 7% 7% 44%	526
June	Day	7% 6% 6% 9% 56%	840
	Night	8% 6% 6% 12% 52%	478
July	Day	71%	865
	Night	5% 7% 66%	496
August	Day	5% 7% 67%	1180
	Night	6% 67%	861
September	Day	5% 5% 69%	988
	Night	7% 6% 5% 64%	947
October	Day	8% 7% 8% 5% 9% 44%	613
	Night	11% 5% 6% 6% 50%	750
November	Day	19% 5% 6% 7% 40%	469
	Night	16% 7% 6% 6% 5% 5% 7% 5% 33%	698
December	Day	19% 6% 5% 6% 6% 5% 7% 7% 28%	493
	Night	25% 5% 6% 6% 5% 5% 7% 29%	845

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	14% 6% 8% 6% 5% 8% 5% 9% 27%	488
	Night	16% 6% 6% 6% 5% 9% 10% 27%	866
February	Day	16% 7% 43%	543
	Night	13% 5% 5% 6% 9% 41%	702
March	Day	12% 5% 6% 5% 47%	663
	Night	10% 5% 5% 5% 5% 53%	699
April	Day	10% 5% 6% 5% 6% 6% 46%	746
	Night	10% 6% 5% 6% 8% 43%	574
May	Day	13% 5% 7% 5% 7% 7% 39%	828
	Night	12% 7% 6% 5% 6% 43%	535
June	Day	6% 6% 5% 10% 54%	840
	Night	8% 7% 6% 10% 53%	478
July	Day	5% 71%	856
	Night	6% 8% 66%	496
August	Day	7% 68%	1181
	Night	5% 6% 67%	861
September	Day	5% 69%	997
	Night	7% 6% 5% 64%	949
October	Day	7% 7% 7% 6% 8% 45%	613
	Night	12% 6% 5% 5% 8% 49%	750
November	Day	20% 5% 7% 40%	468
	Night	16% 6% 6% 7% 6% 5% 6% 32%	698
December	Day	19% 5% 6% 5% 6% 7% 7% 28%	493
	Night	24% 5% 5% 5% 6% 5% 7% 6% 29%	845

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	61% 23% 15%	196
	Night	40% 39% 19%	319
February	Day	33% 23% 33% 9%	286
	Night	35% 19% 34% 10%	367
March	Day	19% 15% 41% 23%	406
	Night	21% 15% 38% 21%	448
April	Day	15% 22% 36% 21%	461
	Night	15% 27% 34% 18%	347
May	Day	16% 12% 40% 22% 7%	455
	Night	18% 17% 40% 21%	319
June	Day	9% 10% 39% 33% 6%	649
	Night	14% 12% 42% 22% 7%	343
July	Day	5% 15% 39% 39%	718
	Night	5% 5% 17% 37% 34%	391
August	Day	6% 18% 35% 36%	954
	Night	8% 16% 33% 37%	698
September	Day	10% 24% 37% 22%	820
	Night	5% 9% 23% 35% 25%	736
October	Day	13% 21% 38% 20% 6%	644
	Night	11% 15% 39% 26% 6%	768
November	Day	37% 29% 27% 5%	289
	Night	27% 31% 35% 5%	393
December	Day	42% 31% 23%	214
	Night	34% 41% 24%	388

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	9% 23% 32% 30%	222
February	Day	8% 25% 41% 16% 8%	36
	Night	8% 23% 43% 20%	204
March	Day	16% 35% 28% 17%	56
	Night	7% 19% 44% 26%	230
April	Day	7% 44% 23% 17% 7%	52
	Night	12% 25% 36% 22%	199
May	Day	12% 38% 35% 12%	57
	Night	8% 16% 44% 30%	150
June	Day	13% 41% 28% 13%	60
	Night	5% 25% 42% 25%	116
July	Day	6% 32% 32% 22%	61
	Night	14% 39% 39%	123
August	Day	11% 44% 36%	85
	Night	10% 35% 46% 5%	296
September	Day	11% 25% 24% 33% 5%	87
	Night	13% 31% 42% 7%	343
October	Day	12% 23% 38% 20% 5%	39
	Night	6% 12% 40% 33% 6%	351
November	Night	8% 21% 42% 24%	226
December	Night	14% 22% 41% 19%	208

Page generated at 2008-05-11 02:45:53. Version ab11