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 2024-11-03.

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	5% 6% 2 5% 4 4 4 3 5% 7% 56%	101213
	Night	7% 7% 2 6% 4 4 4 3 5% 7% 51%	97930
Transparency	Day	27% 5% 11% 20% 20% 16%	100957
	Night	32% 6% 12% 20% 17% 13%	97776
Seeing	Day	8% 9% 24% 29% 22% 8%	14504
	Night	10% 6% 22% 39% 21% 2	23867

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% 14% 4 9% 5% 5% 6% 6% 6% 7% 31%	2539
	11th to 20th	Day	10% 16% 4 11% 7% 6% 6% 4 5% 7% 25%	2540
	21st to end	Day	11% 12% 3 10% 6% 6% 5% 5% 5% 8% 29%	2794
February	1st to 10th	Day	9% 9% 3 8% 5% 4 4 4 7% 7% 39%	1729
	11th to 20th	Day	8% 10% 3 7% 5% 5% 4 4 5% 7% 41%	1850
	21st to end	Day	5% 11% 4 7% 5% 5% 5% 4 6% 9% 39%	1570
March	1st to 10th	Day	6% 11% 4 10% 6% 7% 6% 5% 6% 8% 32%	3138
	11th to 20th	Day	4 5% 2 5% 3 3 4 4 5% 6% 59%	3393
	21st to end	Day	6% 8% 3 9% 6% 6% 6% 5% 8% 9% 34%	3938
April	1st to 10th	Day	8% 7% 3 6% 5% 4 5% 4 6% 9% 43%	2280
	11th to 20th	Day	4 7% 2 6% 5% 3 4 4 7% 7% 51%	2304
	21st to end	Day	6% 5% 2 4 4 4 4 4 6% 8% 52%	2470
May	1st to 10th	Day	6% 8% 2 6% 4 5% 4 3 5% 6% 50%	4110
	11th to 20th	Day	3 3 1 3 2 3 3 3 4 6% 69%	4071
	21st to end	Day	5% 3 1 4 4 4 5% 4 6% 8% 57%	4813
June	1st to 10th	Day	5% 5% 2 5% 4 4 4 4 6% 8% 51%	2660
	11th to 20th	Day	4 4 1 3 3 3 4 3 5% 6% 64%	2660
	21st to end	Day	2 2 1 3 2 2 2 2 5% 6% 73%	2660
July	1st to 10th	Day	1 1 2 2 2 2 2 3 4 82%	4420
	11th to 20th	Day	2 1 1 2 2 2 3 3 3 5% 76%	4420
	21st to end	Day	2 2 1 3 2 3 3 2 4 5% 73%	4790
August	1st to 10th	Day	3 3 1 4 3 3 3 4 5% 7% 65%	4128
	11th to 20th	Day	1 1 1 2 2 2 2 2 4 4 79%	4028
	21st to end	Day	2 2 1 3 2 2 2 2 3 4 77%	4221
September	1st to 10th	Day	2 2 1 1 2 2 2 3 3 5% 77%	2268
	11th to 20th	Day	4 3 1 4 3 3 3 3 4 5% 68%	2090
	21st to end	Day	5% 3 1 3 2 2 2 3 3 5% 70%	2090
October	1st to 10th	Day	6% 4 1 5% 3 3 3 3 4 6% 62%	2090
	11th to 20th	Day	4 3 2 4 3 3 4 3 4 8% 62%	1866
	21st to end	Day	5% 4 2 4 3 3 4 4 7% 8% 56%	1881
November	1st to 10th	Day	9% 7% 2 7% 5% 4 4 4 5% 8% 45%	1692
	11th to 20th	Day	10% 5% 2 6% 4 5% 5% 4 7% 9% 44%	1710
	21st to end	Day	9% 9% 2 7% 4 4 4 4 6% 8% 41%	1710
December	1st to 10th	Day	12% 8% 3 8% 4 3 4 4 5% 7% 42%	1568
	11th to 20th	Day	11% 10% 4 11% 6% 5% 6% 3 7% 8% 30%	1928
	21st to end	Day	9% 9% 4 10% 6% 5% 5% 4 7% 7% 35%	2794
January	1st to 10th	Night	10% 13% 4 10% 6% 5% 6% 4 6% 7% 30%	4406
	11th to 20th	Night	13% 17% 5% 12% 7% 5% 4 3 4 5% 23%	4420
	21st to end	Night	12% 11% 4 11% 5% 5% 5% 3 5% 7% 31%	4862
February	1st to 10th	Night	12% 10% 3 7% 5% 5% 4 5% 6% 7% 37%	2444
	11th to 20th	Night	9% 8% 3 7% 4 4 4 4 6% 7% 46%	2218
	21st to end	Night	7% 11% 2 5% 5% 5% 5% 4 7% 8% 41%	1884
March	1st to 10th	Night	7% 9% 3 9% 5% 4 5% 4 6% 8% 38%	3736
	11th to 20th	Night	6% 6% 2 5% 4 3 4 3 4 5% 57%	3586
	21st to end	Night	8% 8% 3 8% 6% 5% 5% 4 6% 9% 39%	3710
April	1st to 10th	Night	9% 7% 2 6% 5% 5% 5% 4 6% 6% 46%	1900
	11th to 20th	Night	7% 8% 2 5% 5% 4 4 4 6% 7% 49%	1824
	21st to end	Night	5% 5% 2 6% 4 4 4 3 7% 9% 52%	1710
May	1st to 10th	Night	9% 6% 2 6% 3 3 3 3 5% 7% 50%	2860
	11th to 20th	Night	4 3 1 3 2 3 3 3 5% 7% 66%	2816
	21st to end	Night	5% 5% 2 4 4 4 4 4 6% 6% 58%	2762
June	1st to 10th	Night	5% 5% 2 7% 5% 6% 5% 4 6% 7% 49%	1520
	11th to 20th	Night	5% 3 1 4 3 3 3 3 5% 7% 64%	1520
	21st to end	Night	1 2 2 2 3 3 3 4 6% 73%	1520
July	1st to 10th	Night	1 1 2 2 3 2 3 4 82%	2540
	11th to 20th	Night	1 1 2 2 2 3 3 4 4 77%	2540
	21st to end	Night	2 2 1 3 3 3 3 3 5% 7% 68%	2761
August	1st to 10th	Night	4 3 1 4 2 3 4 3 6% 7% 63%	2807
	11th to 20th	Night	1 1 1 1 2 3 3 3 5% 78%	2811
	21st to end	Night	2 3 1 3 2 2 2 2 3 4 77%	3452
September	1st to 10th	Night	2 2 1 2 2 2 2 2 4 4 75%	1910
	11th to 20th	Night	4 3 1 3 3 3 4 3 4 6% 66%	2090
	21st to end	Night	6% 2 1 3 2 3 2 2 4 5% 71%	2090
October	1st to 10th	Night	6% 4 1 4 2 3 3 3 4 6% 63%	2090
	11th to 20th	Night	7% 3 2 3 3 3 3 3 5% 6% 61%	2308
	21st to end	Night	6% 4 2 5% 4 3 5% 3 6% 8% 55%	2717
November	1st to 10th	Night	10% 7% 2 7% 5% 4 4 4 6% 6% 47%	2431
	11th to 20th	Night	11% 7% 3 7% 4 4 4 3 5% 8% 43%	2470
	21st to end	Night	8% 7% 2 6% 5% 5% 5% 5% 5% 7% 45%	2470
December	1st to 10th	Night	10% 10% 4 7% 4 4 4 4 7% 7% 38%	2607
	11th to 20th	Night	13% 11% 3 11% 5% 4 5% 4 6% 7% 30%	3276
	21st to end	Night	11% 9% 3 8% 5% 5% 5% 4 6% 8% 36%	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% 9% 14% 24% 8% 1	3138
	11th to 20th	Day	24% 6% 14% 38% 17% 1	3393
	21st to end	Day	40% 9% 19% 23% 8% 1	3938
April	1st to 10th	Day	36% 6% 16% 24% 15% 4	2280
	11th to 20th	Day	31% 6% 13% 25% 19% 5%	2307
	21st to end	Day	29% 5% 12% 28% 22% 4	2470
May	1st to 10th	Day	31% 4 13% 22% 24% 7%	4110
	11th to 20th	Day	16% 4 7% 24% 34% 14%	4074
	21st to end	Day	23% 5% 14% 26% 26% 6%	4814
June	1st to 10th	Day	29% 6% 11% 26% 25% 3	2660
	11th to 20th	Day	20% 5% 8% 21% 33% 13%	2660
	21st to end	Day	13% 3 6% 17% 35% 27%	2660
July	1st to 10th	Day	8% 2 3 9% 18% 61%	4351
	11th to 20th	Day	11% 2 3 8% 19% 58%	4345
	21st to end	Day	13% 2 4 8% 28% 45%	4639
August	1st to 10th	Day	19% 3 4 12% 24% 38%	4112
	11th to 20th	Day	10% 2 4 12% 35% 38%	4067
	21st to end	Day	13% 2 3 12% 37% 34%	4220
September	1st to 10th	Day	12% 3 5% 13% 33% 34%	2268
	11th to 20th	Day	19% 4 7% 24% 26% 20%	2090
	21st to end	Day	19% 2 6% 21% 37% 15%	2090
October	1st to 10th	Day	24% 5% 9% 26% 27% 9%	2090
	11th to 20th	Day	23% 5% 8% 35% 24% 5%	1866
	21st to end	Day	25% 6% 16% 32% 18% 3	1881
November	1st to 10th	Day	36% 7% 14% 26% 14% 2	1692
	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	40% 8% 16% 26% 9% 1	3736
	11th to 20th	Night	29% 4 12% 34% 18% 3	3586
	21st to end	Night	39% 8% 17% 27% 8% 1	3710
April	1st to 10th	Night	38% 5% 13% 24% 16% 4	1900
	11th to 20th	Night	33% 5% 11% 26% 21% 4	1824
	21st to end	Night	29% 5% 11% 29% 23% 4	1710
May	1st to 10th	Night	30% 5% 11% 23% 24% 8%	2860
	11th to 20th	Night	17% 3 9% 18% 40% 13%	2817
	21st to end	Night	26% 5% 11% 22% 31% 6%	2762
June	1st to 10th	Night	33% 6% 10% 24% 23% 4	1520
	11th to 20th	Night	20% 4 9% 19% 35% 13%	1520
	21st to end	Night	12% 3 6% 17% 30% 31%	1520
July	1st to 10th	Night	8% 2 3 7% 19% 62%	2500
	11th to 20th	Night	11% 2 2 7% 16% 62%	2492
	21st to end	Night	15% 3 3 8% 28% 43%	2674
August	1st to 10th	Night	20% 3 4 10% 21% 42%	2799
	11th to 20th	Night	9% 2 4 11% 29% 45%	2838
	21st to end	Night	14% 1 3 11% 32% 38%	3452
September	1st to 10th	Night	13% 3 4 11% 31% 39%	1910
	11th to 20th	Night	20% 4 6% 19% 26% 26%	2090
	21st to end	Night	18% 2 5% 21% 33% 21%	2090
October	1st to 10th	Night	24% 4 8% 21% 30% 14%	2090
	11th to 20th	Night	23% 4 8% 29% 30% 5%	2308
	21st to end	Night	27% 5% 13% 29% 22% 3	2717
November	1st to 10th	Night	37% 6% 11% 26% 18% 2	2431
	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% 31% 14% 3	460
	21st to end	Day	12% 14% 33% 27% 12% 2	506
April	1st to 10th	Day	13% 18% 23% 25% 15% 6%	460
	11th to 20th	Day	10% 15% 33% 26% 11% 4	452
	21st to end	Day	8% 16% 32% 25% 16% 3	460
May	1st to 10th	Day	6% 14% 30% 27% 16% 7%	463
	11th to 20th	Day	12% 10% 19% 30% 22% 7%	488
	21st to end	Day	9% 8% 16% 30% 23% 14%	529
June	1st to 10th	Day	6% 6% 24% 28% 23% 12%	490
	11th to 20th	Day	6% 10% 28% 31% 18% 7%	490
	21st to end	Day	3 6% 24% 34% 23% 10%	490
July	1st to 10th	Day	1 3 23% 34% 29% 10%	486
	11th to 20th	Day	1 3 22% 34% 28% 12%	484
	21st to end	Day	2 2 13% 34% 37% 11%	531
August	1st to 10th	Day	5% 3 17% 33% 31% 11%	487
	11th to 20th	Day	2 4 15% 31% 31% 18%	477
	21st to end	Day	2 5% 18% 28% 30% 17%	539
September	1st to 10th	Day	3 3 17% 22% 38% 17%	490
	11th to 20th	Day	8% 5% 16% 29% 31% 12%	490
	21st to end	Day	6% 7% 20% 29% 28% 10%	490
October	1st to 10th	Day	6% 8% 17% 29% 28% 14%	490
	11th to 20th	Day	8% 8% 22% 25% 25% 11%	366
	21st to end	Day	10% 5% 23% 37% 18% 5%	330
November	1st to 10th	Day	15% 9% 25% 28% 21% 2	276
	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% 39% 17% 2	760
	21st to end	Night	13% 10% 25% 38% 14% 1	836
April	1st to 10th	Night	12% 8% 25% 39% 15% 2	760
	11th to 20th	Night	9% 9% 28% 36% 15% 2	696
	21st to end	Night	7% 6% 29% 39% 16% 2	570
May	1st to 10th	Night	9% 8% 29% 36% 16% 2	570
	11th to 20th	Night	8% 7% 20% 39% 24% 3	556
	21st to end	Night	9% 6% 20% 33% 28% 3	411
June	1st to 10th	Night	7% 6% 18% 40% 27% 3	380
	11th to 20th	Night	6% 7% 24% 38% 22% 2	380
	21st to end	Night	1 3 24% 45% 26% 1	380
July	1st to 10th	Night	1 1 16% 54% 26% 1	370
	11th to 20th	Night	2 2 17% 53% 26%	368
	21st to end	Night	2 1 9% 53% 32% 2	416
August	1st to 10th	Night	5% 3 14% 49% 28% 1	539
	11th to 20th	Night	1 2 14% 50% 32% 1	564
	21st to end	Night	2 3 15% 42% 33% 4	803
September	1st to 10th	Night	3 2 12% 45% 33% 5%	760
	11th to 20th	Night	6% 3 11% 39% 35% 6%	760
	21st to end	Night	7% 4 15% 36% 29% 8%	760
October	1st to 10th	Night	8% 5% 16% 41% 26% 3	760
	11th to 20th	Night	8% 5% 18% 38% 26% 5%	760
	21st to end	Night	7% 6% 23% 39% 21% 5%	836
November	1st to 10th	Night	12% 7% 20% 39% 21% 2	748
	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 2024-10-31 01:39:25. Version ac07

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