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 2005-11-06 to 2024-03-18.

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	6% 6% 2 5% 5% 3 4 4 5% 7% 53%	78624
	Night	8% 7% 3 6% 5% 3 4 5% 5% 7% 48%	81171
Transparency	Day	30% 6% 13% 21% 19% 12%	78328
	Night	35% 6% 13% 21% 16% 9%	80989
Seeing	Day	8% 9% 24% 29% 22% 8%	13605
	Night	10% 6% 22% 39% 21% 2	23151

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	8% 13% 4 7% 6% 3 5% 7% 6% 7% 31%	2539
	11th to 20th	Day	11% 16% 4 9% 8% 4 6% 5% 5% 7% 25%	2540
	21st to end	Day	11% 11% 3 9% 7% 5% 5% 6% 5% 8% 30%	2794
February	1st to 10th	Day	9% 9% 3 7% 6% 3 4 5% 7% 7% 40%	1729
	11th to 20th	Day	8% 10% 3 6% 6% 3 5% 5% 5% 8% 41%	1850
	21st to end	Day	5% 10% 4 7% 5% 3 5% 5% 6% 9% 39%	1570
March	1st to 10th	Day	7% 8% 5% 7% 7% 4 6% 6% 7% 7% 36%	1900
	11th to 20th	Day	7% 7% 3 6% 5% 3 5% 6% 6% 8% 44%	1997
	21st to end	Day	8% 8% 3 7% 6% 4 5% 5% 7% 8% 38%	2240
April	1st to 10th	Day	8% 6% 3 5% 5% 3 6% 6% 6% 9% 43%	2160
	11th to 20th	Day	5% 6% 3 5% 5% 3 4 4 7% 7% 50%	2181
	21st to end	Day	6% 5% 2 3 4 3 4 5% 6% 8% 53%	2340
May	1st to 10th	Day	4 5% 1 4 5% 3 4 4 6% 8% 56%	2340
	11th to 20th	Day	5% 4 2 5% 4 3 5% 5% 6% 8% 51%	2301
	21st to end	Day	7% 5% 2 4 5% 3 6% 5% 7% 10% 46%	2723
June	1st to 10th	Day	6% 4 2 5% 4 3 4 5% 6% 8% 52%	2520
	11th to 20th	Day	4 4 1 3 3 2 4 4 5% 6% 64%	2520
	21st to end	Day	2 2 1 3 2 1 3 3 4 6% 73%	2520
July	1st to 10th	Day	2 2 1 2 3 2 2 3 5% 6% 72%	2520
	11th to 20th	Day	2 1 1 2 2 1 2 2 2 5% 79%	2520
	21st to end	Day	3 2 1 3 3 2 3 3 4 5% 72%	2741
August	1st to 10th	Day	4 3 1 3 3 2 3 4 4 6% 65%	2352
	11th to 20th	Day	1 2 1 1 2 2 3 3 5% 6% 75%	2299
	21st to end	Day	2 1 1 2 3 2 2 3 3 5% 76%	2404
September	1st to 10th	Day	2 2 1 1 2 2 2 3 3 5% 77%	2149
	11th to 20th	Day	4 3 1 3 3 2 3 3 4 5% 69%	1980
	21st to end	Day	5% 3 1 3 3 2 3 4 3 6% 68%	1980
October	1st to 10th	Day	6% 4 1 4 4 2 3 4 4 6% 61%	1980
	11th to 20th	Day	5% 3 2 4 3 3 4 3 4 8% 62%	1769
	21st to end	Day	5% 4 2 3 3 2 4 5% 6% 8% 56%	1782
November	1st to 10th	Day	9% 7% 3 6% 5% 3 4 5% 5% 8% 45%	1674
	11th to 20th	Day	10% 5% 2 5% 5% 3 5% 5% 7% 9% 44%	1710
	21st to end	Day	10% 8% 3 6% 5% 3 5% 5% 5% 9% 41%	1710
December	1st to 10th	Day	12% 7% 3 7% 5% 3 4 5% 5% 7% 42%	1568
	11th to 20th	Day	11% 9% 4 9% 7% 3 6% 5% 7% 8% 31%	1928
	21st to end	Day	9% 9% 5% 8% 7% 4 5% 5% 6% 7% 35%	2794
January	1st to 10th	Night	11% 12% 4 8% 7% 3 6% 5% 6% 7% 30%	4406
	11th to 20th	Night	14% 16% 5% 11% 9% 4 5% 4 4 5% 23%	4420
	21st to end	Night	12% 11% 5% 10% 6% 4 5% 4 5% 7% 32%	4862
February	1st to 10th	Night	12% 9% 3 5% 6% 3 4 6% 6% 7% 37%	2444
	11th to 20th	Night	9% 8% 3 6% 4 3 4 5% 5% 7% 46%	2218
	21st to end	Night	8% 10% 3 4 5% 3 5% 6% 7% 8% 41%	1884
March	1st to 10th	Night	8% 8% 3 7% 7% 4 6% 5% 6% 8% 39%	2280
	11th to 20th	Night	8% 6% 3 6% 5% 3 5% 6% 6% 7% 46%	2128
	21st to end	Night	10% 8% 4 6% 6% 3 5% 5% 5% 8% 41%	2111
April	1st to 10th	Night	9% 6% 3 6% 6% 4 5% 5% 6% 6% 45%	1800
	11th to 20th	Night	8% 7% 3 5% 5% 3 5% 4 6% 7% 48%	1727
	21st to end	Night	6% 4 2 4 5% 3 4 4 6% 8% 53%	1620
May	1st to 10th	Night	6% 5% 2 4 4 3 3 4 4 7% 58%	1620
	11th to 20th	Night	6% 4 2 4 4 3 4 6% 7% 10% 50%	1590
	21st to end	Night	7% 6% 2 4 5% 4 4 6% 8% 8% 46%	1552
June	1st to 10th	Night	5% 5% 2 6% 6% 4 6% 5% 6% 8% 49%	1440
	11th to 20th	Night	5% 3 1 3 3 2 4 3 5% 8% 63%	1440
	21st to end	Night	1 1 2 3 2 3 4 4 6% 72%	1440
July	1st to 10th	Night	1 1 1 1 3 2 4 4 5% 7% 71%	1440
	11th to 20th	Night	1 1 1 2 2 1 3 3 3 4 79%	1440
	21st to end	Night	2 2 1 2 2 2 3 4 4 6% 71%	1576
August	1st to 10th	Night	4 3 1 4 3 2 3 3 5% 7% 66%	1584
	11th to 20th	Night	1 1 2 1 2 3 4 4 6% 75%	1602
	21st to end	Night	2 2 1 2 2 2 3 3 3 6% 74%	1948
September	1st to 10th	Night	2 2 1 2 3 1 2 3 4 4 76%	1809
	11th to 20th	Night	4 3 1 3 3 2 4 4 4 6% 67%	1980
	21st to end	Night	6% 2 1 2 3 2 3 3 4 5% 69%	1980
October	1st to 10th	Night	7% 4 1 4 3 2 4 4 4 6% 62%	1980
	11th to 20th	Night	7% 3 2 3 4 3 3 4 5% 6% 61%	2186
	21st to end	Night	5% 4 2 5% 5% 2 4 5% 6% 8% 55%	2574
November	1st to 10th	Night	10% 6% 2 6% 5% 3 5% 4 5% 6% 47%	2405
	11th to 20th	Night	12% 6% 3 5% 5% 3 4 4 5% 8% 44%	2470
	21st to end	Night	9% 6% 3 5% 6% 3 5% 6% 5% 7% 46%	2470
December	1st to 10th	Night	11% 10% 3 6% 5% 3 4 5% 6% 7% 39%	2607
	11th to 20th	Night	13% 10% 4 9% 7% 3 5% 6% 6% 8% 30%	3276
	21st to end	Night	11% 9% 3 7% 6% 4 6% 5% 5% 8% 37%	4862

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	48% 11% 24% 15% 3	2539
	11th to 20th	Day	56% 12% 18% 13% 2	2540
	21st to end	Day	52% 11% 22% 13% 2	2794
February	1st to 10th	Day	42% 7% 21% 23% 6% 1	1729
	11th to 20th	Day	41% 8% 18% 24% 9%	1860
	21st to end	Day	42% 6% 18% 23% 11% 1	1570
March	1st to 10th	Day	44% 8% 14% 23% 8% 2	1900
	11th to 20th	Day	36% 7% 17% 27% 12% 2	1997
	21st to end	Day	43% 7% 17% 22% 10% 2	2240
April	1st to 10th	Day	36% 6% 16% 23% 16% 4	2160
	11th to 20th	Day	32% 6% 13% 25% 19% 5%	2184
	21st to end	Day	29% 5% 12% 27% 23% 4	2340
May	1st to 10th	Day	25% 5% 11% 26% 26% 7%	2340
	11th to 20th	Day	28% 7% 11% 27% 21% 5%	2304
	21st to end	Day	31% 7% 16% 24% 17% 5%	2724
June	1st to 10th	Day	29% 6% 11% 26% 24% 4	2520
	11th to 20th	Day	21% 5% 8% 21% 33% 12%	2520
	21st to end	Day	13% 3 6% 17% 35% 26%	2520
July	1st to 10th	Day	13% 3 5% 15% 31% 33%	2451
	11th to 20th	Day	10% 1 3 10% 26% 49%	2445
	21st to end	Day	15% 2 5% 8% 26% 44%	2589
August	1st to 10th	Day	20% 3 6% 14% 26% 30%	2335
	11th to 20th	Day	11% 2 6% 16% 33% 32%	2299
	21st to end	Day	12% 2 4 14% 37% 29%	2404
September	1st to 10th	Day	12% 3 5% 14% 32% 35%	2149
	11th to 20th	Day	18% 4 7% 24% 27% 21%	1980
	21st to end	Day	20% 2 6% 21% 36% 14%	1980
October	1st to 10th	Day	25% 5% 10% 27% 25% 8%	1980
	11th to 20th	Day	23% 5% 8% 36% 24% 5%	1769
	21st to end	Day	25% 6% 17% 32% 18% 3	1782
November	1st to 10th	Day	36% 7% 14% 26% 14% 2	1674
	11th to 20th	Day	36% 8% 20% 28% 7% 1	1710
	21st to end	Day	40% 7% 20% 27% 6%	1710
December	1st to 10th	Day	42% 8% 23% 20% 7% 1	1568
	11th to 20th	Day	49% 11% 23% 16% 2	1928
	21st to end	Day	46% 7% 18% 24% 4	2794
January	1st to 10th	Night	51% 9% 21% 15% 3	4406
	11th to 20th	Night	61% 8% 16% 13% 2	4420
	21st to end	Night	51% 11% 19% 16% 3	4862
February	1st to 10th	Night	45% 8% 20% 22% 4 1	2444
	11th to 20th	Night	37% 7% 19% 26% 11% 1	2219
	21st to end	Night	39% 7% 18% 25% 11% 1	1884
March	1st to 10th	Night	41% 9% 15% 24% 10% 2	2280
	11th to 20th	Night	36% 5% 13% 30% 15% 2	2128
	21st to end	Night	42% 6% 17% 24% 10% 1	2111
April	1st to 10th	Night	38% 4 13% 24% 17% 4	1800
	11th to 20th	Night	34% 6% 11% 25% 20% 4	1727
	21st to end	Night	29% 5% 11% 29% 22% 4	1620
May	1st to 10th	Night	26% 5% 8% 22% 32% 7%	1620
	11th to 20th	Night	28% 5% 11% 24% 26% 5%	1591
	21st to end	Night	33% 8% 12% 24% 18% 5%	1552
June	1st to 10th	Night	33% 6% 10% 23% 23% 4	1440
	11th to 20th	Night	21% 4 9% 20% 34% 12%	1440
	21st to end	Night	13% 4 6% 17% 30% 30%	1440
July	1st to 10th	Night	13% 3 6% 12% 30% 38%	1400
	11th to 20th	Night	10% 2 3 10% 22% 53%	1392
	21st to end	Night	15% 2 3 8% 23% 48%	1488
August	1st to 10th	Night	20% 3 5% 13% 23% 36%	1576
	11th to 20th	Night	11% 2 5% 11% 30% 40%	1602
	21st to end	Night	13% 2 5% 13% 31% 36%	1948
September	1st to 10th	Night	13% 3 4 11% 31% 39%	1809
	11th to 20th	Night	19% 3 6% 18% 27% 27%	1980
	21st to end	Night	19% 2 5% 20% 33% 21%	1980
October	1st to 10th	Night	24% 4 8% 23% 29% 12%	1980
	11th to 20th	Night	24% 4 8% 30% 30% 5%	2186
	21st to end	Night	27% 5% 13% 29% 22% 3	2574
November	1st to 10th	Night	36% 6% 11% 26% 18% 2	2405
	11th to 20th	Night	38% 6% 13% 30% 12% 1	2470
	21st to end	Night	37% 6% 16% 32% 8%	2470
December	1st to 10th	Night	44% 9% 21% 18% 7% 1	2607
	11th to 20th	Night	50% 10% 19% 19% 2	3276
	21st to end	Night	44% 10% 20% 20% 5%	4862

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	14% 16% 24% 31% 13% 2	180
	11th to 20th	Day	13% 9% 29% 28% 17% 3	180
	21st to end	Day	14% 8% 24% 33% 19% 3	198
February	1st to 10th	Day	14% 14% 32% 24% 14% 2	304
	11th to 20th	Day	13% 13% 33% 24% 16% 3	455
	21st to end	Day	13% 16% 30% 30% 10% 2	382
March	1st to 10th	Day	11% 15% 34% 28% 10% 1	460
	11th to 20th	Day	10% 12% 30% 32% 14% 2	449
	21st to end	Day	13% 15% 32% 26% 13% 2	462
April	1st to 10th	Day	14% 17% 22% 25% 16% 5%	420
	11th to 20th	Day	10% 15% 33% 27% 10% 5%	412
	21st to end	Day	9% 15% 33% 24% 16% 3	420
May	1st to 10th	Day	6% 13% 29% 29% 16% 7%	423
	11th to 20th	Day	13% 9% 20% 29% 23% 7%	448
	21st to end	Day	9% 7% 17% 29% 23% 15%	485
June	1st to 10th	Day	6% 6% 26% 27% 23% 13%	450
	11th to 20th	Day	6% 10% 29% 30% 18% 7%	450
	21st to end	Day	3 6% 23% 34% 23% 11%	450
July	1st to 10th	Day	2 2 22% 35% 29% 11%	446
	11th to 20th	Day	1 3 23% 36% 27% 10%	444
	21st to end	Day	3 2 14% 34% 38% 10%	487
August	1st to 10th	Day	5% 3 17% 33% 31% 12%	447
	11th to 20th	Day	2 4 14% 29% 31% 20%	437
	21st to end	Day	2 4 17% 29% 31% 16%	495
September	1st to 10th	Day	4 3 17% 22% 37% 16%	450
	11th to 20th	Day	8% 4 16% 28% 31% 13%	450
	21st to end	Day	6% 7% 20% 30% 27% 10%	450
October	1st to 10th	Day	6% 8% 17% 29% 27% 13%	450
	11th to 20th	Day	8% 8% 24% 25% 25% 11%	333
	21st to end	Day	10% 6% 22% 37% 19% 6%	297
November	1st to 10th	Day	15% 9% 24% 29% 21% 2	270
	11th to 20th	Day	10% 6% 30% 31% 18% 4	270
	21st to end	Day	14% 9% 21% 36% 17% 4	270
December	1st to 10th	Day	18% 8% 19% 33% 15% 7%	203
	11th to 20th	Day	15% 13% 31% 27% 9% 5%	180
	21st to end	Day	15% 8% 27% 31% 14% 6%	198
January	1st to 10th	Night	15% 7% 24% 35% 17% 2	760
	11th to 20th	Night	15% 5% 26% 36% 17% 2	760
	21st to end	Night	14% 6% 21% 36% 20% 3	836
February	1st to 10th	Night	17% 6% 28% 36% 13%	760
	11th to 20th	Night	11% 6% 27% 39% 15% 1	744
	21st to end	Night	12% 5% 33% 36% 13%	628
March	1st to 10th	Night	10% 8% 34% 36% 11% 1	760
	11th to 20th	Night	10% 7% 24% 40% 16% 2	752
	21st to end	Night	14% 10% 25% 37% 13% 1	792
April	1st to 10th	Night	12% 7% 25% 38% 15% 2	720
	11th to 20th	Night	10% 9% 28% 36% 15% 2	659
	21st to end	Night	7% 6% 30% 39% 16% 2	540
May	1st to 10th	Night	8% 8% 28% 36% 17% 2	540
	11th to 20th	Night	8% 7% 20% 38% 24% 3	527
	21st to end	Night	9% 6% 20% 33% 29% 4	389
June	1st to 10th	Night	7% 6% 17% 40% 27% 3	360
	11th to 20th	Night	7% 7% 24% 37% 23% 2	360
	21st to end	Night	1 3 24% 44% 28% 1	360
July	1st to 10th	Night	1 1 15% 54% 27% 1	350
	11th to 20th	Night	2 2 18% 53% 24%	348
	21st to end	Night	3 1 9% 54% 31% 2	394
August	1st to 10th	Night	5% 3 14% 49% 28% 1	510
	11th to 20th	Night	1 1 12% 50% 34% 1	534
	21st to end	Night	2 3 14% 43% 34% 4	760
September	1st to 10th	Night	3 2 12% 45% 32% 5%	720
	11th to 20th	Night	5% 3 12% 39% 36% 6%	720
	21st to end	Night	8% 4 16% 36% 29% 8%	720
October	1st to 10th	Night	8% 5% 17% 41% 26% 3	720
	11th to 20th	Night	8% 5% 19% 38% 25% 5%	720
	21st to end	Night	7% 5% 23% 38% 22% 5%	792
November	1st to 10th	Night	12% 6% 19% 39% 21% 2	740
	11th to 20th	Night	15% 7% 22% 38% 16% 1	760
	21st to end	Night	11% 4 23% 39% 19% 3	760
December	1st to 10th	Night	14% 6% 23% 38% 17% 1	760
	11th to 20th	Night	19% 7% 22% 36% 15% 2	760
	21st to end	Night	21% 9% 26% 33% 10% 1	836

Page generated at 2024-03-15 12:01:43. Version ac07

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