Wind River Special Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wind River Special Observatory clear sky chart from 2005-11-06 to 2024-02-25.

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	3 4 2 4 4 3 4 5% 6% 9% 57%	78481
	Night	3 4 2 4 4 2 4 4 6% 9% 59%	80872
Transparency	Day	23% 8% 16% 27% 20% 7%	78194
	Night	20% 8% 17% 29% 20% 6%	80681
Seeing	Day	8% 13% 30% 31% 14% 3	14682
	Night	5% 11% 37% 33% 12% 1	24968

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	2 2 5% 4 2 4 4 6% 13% 56%	2538
	11th to 20th	Day	2 1 5% 6% 4 4 5% 7% 11% 55%	2778
	21st to end	Day	2 1 3 3 3 3 3 5% 9% 66%	3146
February	1st to 10th	Day	1 3 2 6% 5% 3 4 4 5% 10% 57%	1710
	11th to 20th	Day	4 2 6% 5% 2 5% 5% 6% 8% 57%	1665
	21st to end	Day	3 3 6% 3 3 4 5% 7% 9% 58%	1412
March	1st to 10th	Day	1 4 2 3 4 2 3 5% 7% 11% 58%	1980
	11th to 20th	Day	2 5% 3 3 4 2 3 4 6% 11% 57%	1980
	21st to end	Day	4 6% 3 5% 5% 3 5% 6% 6% 9% 48%	2178
April	1st to 10th	Day	3 7% 2 5% 4 2 5% 5% 7% 11% 50%	2134
	11th to 20th	Day	3 6% 3 6% 5% 3 5% 5% 6% 11% 46%	2156
	21st to end	Day	7% 9% 4 5% 6% 3 6% 5% 7% 8% 40%	2340
May	1st to 10th	Day	8% 8% 3 6% 5% 3 5% 5% 6% 9% 42%	2340
	11th to 20th	Day	10% 7% 3 5% 4 3 5% 6% 7% 10% 42%	2464
	21st to end	Day	10% 7% 2 4 5% 4 6% 6% 8% 11% 37%	2724
June	1st to 10th	Day	5% 3 1 3 4 3 5% 7% 7% 12% 49%	2520
	11th to 20th	Day	5% 2 1 3 4 3 4 5% 6% 9% 57%	2520
	21st to end	Day	2 2 1 2 4 3 3 5% 6% 7% 65%	2520
July	1st to 10th	Day	3 2 1 3 3 3 5% 6% 8% 8% 58%	2520
	11th to 20th	Day	1 1 1 3 3 3 5% 6% 6% 8% 64%	2520
	21st to end	Day	4 3 1 3 4 3 6% 5% 7% 7% 57%	2566
August	1st to 10th	Day	4 2 1 3 4 3 5% 6% 6% 9% 55%	2328
	11th to 20th	Day	3 3 1 4 4 3 4 5% 6% 7% 61%	2299
	21st to end	Day	2 3 1 3 3 3 4 4 5% 8% 64%	2477
September	1st to 10th	Day	4 3 2 3 4 3 4 5% 5% 7% 63%	2160
	11th to 20th	Day	6% 3 1 2 3 2 3 3 5% 6% 67%	2067
	21st to end	Day	5% 3 1 3 3 2 3 4 3 6% 64%	1950
October	1st to 10th	Day	8% 8% 2 4 4 2 4 3 4 6% 54%	1800
	11th to 20th	Day	5% 3 1 3 2 1 3 4 4 8% 66%	1800
	21st to end	Day	2 5% 2 4 3 3 3 4 5% 8% 62%	1980
November	1st to 10th	Day	1 3 2 3 3 2 3 4 5% 9% 63%	1629
	11th to 20th	Day	2 1 3 2 2 4 4 5% 11% 65%	1520
	21st to end	Day	1 6% 2 5% 4 2 3 4 5% 8% 61%	1520
December	1st to 10th	Day	3 2 4 3 2 2 3 6% 10% 64%	1520
	11th to 20th	Day	1 3 2 2 3 3 4 5% 5% 11% 60%	1926
	21st to end	Day	1 5% 3 5% 4 3 3 4 5% 7% 60%	2794
January	1st to 10th	Night	2 2 6% 6% 3 5% 5% 6% 11% 54%	4417
	11th to 20th	Night	2 2 4 6% 3 5% 4 8% 13% 53%	4208
	21st to end	Night	1 4 2 4 3 3 4 4 6% 9% 60%	4521
February	1st to 10th	Night	1 4 3 6% 5% 3 4 5% 6% 9% 56%	2470
	11th to 20th	Night	1 3 3 5% 4 2 4 5% 5% 8% 58%	2402
	21st to end	Night	4 2 6% 4 3 4 4 5% 9% 59%	1934
March	1st to 10th	Night	1 4 2 5% 3 2 4 5% 5% 10% 59%	1980
	11th to 20th	Night	2 4 3 5% 4 2 3 4 5% 10% 59%	1980
	21st to end	Night	4 5% 3 5% 5% 2 5% 5% 5% 9% 51%	2178
April	1st to 10th	Night	3 7% 3 4 3 2 3 5% 5% 9% 56%	1824
	11th to 20th	Night	5% 7% 3 5% 4 2 5% 4 6% 9% 49%	1749
	21st to end	Night	7% 8% 2 6% 5% 3 4 5% 6% 8% 45%	1620
May	1st to 10th	Night	11% 7% 2 4 4 2 4 3 5% 8% 51%	1620
	11th to 20th	Night	11% 7% 2 5% 5% 3 4 4 7% 8% 45%	1431
	21st to end	Night	12% 5% 2 4 4 3 3 5% 6% 11% 44%	1552
June	1st to 10th	Night	4 3 2 3 3 2 4 4 7% 10% 58%	1440
	11th to 20th	Night	6% 4 1 2 3 2 5% 4 5% 8% 60%	1440
	21st to end	Night	3 2 1 2 3 2 3 3 4 8% 69%	1440
July	1st to 10th	Night	2 1 1 2 3 1 3 4 7% 9% 66%	1440
	11th to 20th	Night	1 1 2 2 1 2 3 5% 10% 73%	1440
	21st to end	Night	3 1 1 2 2 1 3 3 5% 8% 71%	1748
August	1st to 10th	Night	3 3 1 3 3 2 3 5% 6% 8% 64%	1611
	11th to 20th	Night	3 1 2 2 2 3 4 5% 9% 70%	1602
	21st to end	Night	2 2 1 3 2 2 3 4 5% 9% 66%	1878
September	1st to 10th	Night	4 2 1 2 2 2 2 3 5% 6% 71%	1800
	11th to 20th	Night	4 2 2 3 3 2 3 3 5% 7% 64%	1890
	21st to end	Night	6% 3 2 2 3 2 3 3 4 6% 68%	2009
October	1st to 10th	Night	8% 7% 2 5% 5% 2 3 4 4 6% 54%	2160
	11th to 20th	Night	4 4 1 4 3 2 3 3 4 6% 66%	2160
	21st to end	Night	2 4 2 5% 4 2 4 4 5% 9% 59%	2376
November	1st to 10th	Night	2 3 1 3 3 2 4 4 6% 9% 64%	2428
	11th to 20th	Night	1 3 1 3 3 2 3 4 6% 10% 64%	2660
	21st to end	Night	1 4 2 4 4 3 4 4 5% 9% 59%	2660
December	1st to 10th	Night	3 2 4 4 2 4 4 6% 10% 62%	2660
	11th to 20th	Night	1 2 1 3 3 2 3 5% 7% 11% 61%	3271
	21st to end	Night	1 4 3 4 4 2 3 4 5% 10% 59%	4873

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	19% 8% 19% 31% 22% 2	2539
	11th to 20th	Day	18% 13% 22% 28% 18% 2	2778
	21st to end	Day	14% 8% 26% 33% 15% 5%	3146
February	1st to 10th	Day	23% 7% 23% 30% 15% 2	1710
	11th to 20th	Day	23% 8% 20% 31% 14% 4	1674
	21st to end	Day	21% 10% 18% 30% 18% 3	1412
March	1st to 10th	Day	18% 7% 21% 36% 15% 2	1980
	11th to 20th	Day	21% 7% 21% 33% 15% 1	1980
	21st to end	Day	32% 8% 21% 30% 8% 1	2178
April	1st to 10th	Day	27% 9% 21% 28% 12% 3	2134
	11th to 20th	Day	31% 8% 19% 29% 11% 1	2159
	21st to end	Day	40% 9% 14% 29% 9%	2340
May	1st to 10th	Day	35% 10% 16% 26% 12% 1	2340
	11th to 20th	Day	35% 9% 17% 27% 10% 1	2468
	21st to end	Day	36% 10% 19% 25% 9%	2724
June	1st to 10th	Day	24% 12% 21% 24% 15% 4	2520
	11th to 20th	Day	21% 8% 16% 21% 24% 11%	2520
	21st to end	Day	14% 8% 9% 27% 28% 13%	2520
July	1st to 10th	Day	19% 8% 10% 26% 24% 13%	2451
	11th to 20th	Day	16% 6% 8% 18% 29% 24%	2445
	21st to end	Day	21% 8% 8% 19% 25% 20%	2423
August	1st to 10th	Day	23% 7% 11% 20% 25% 14%	2313
	11th to 20th	Day	21% 6% 9% 22% 27% 15%	2299
	21st to end	Day	18% 5% 8% 20% 33% 15%	2477
September	1st to 10th	Day	20% 6% 9% 16% 31% 17%	2160
	11th to 20th	Day	20% 4 9% 26% 29% 12%	2067
	21st to end	Day	21% 5% 10% 27% 31% 5%	1950
October	1st to 10th	Day	31% 6% 11% 26% 20% 6%	1800
	11th to 20th	Day	17% 7% 15% 34% 21% 6%	1800
	21st to end	Day	21% 6% 17% 30% 23% 3	1980
November	1st to 10th	Day	17% 10% 17% 27% 23% 6%	1629
	11th to 20th	Day	14% 7% 22% 30% 22% 5%	1520
	21st to end	Day	22% 7% 17% 28% 21% 5%	1520
December	1st to 10th	Day	16% 8% 23% 30% 17% 7%	1520
	11th to 20th	Day	16% 10% 27% 30% 15% 1	1924
	21st to end	Day	23% 8% 11% 30% 21% 7%	2794
January	1st to 10th	Night	20% 11% 18% 29% 21% 1	4417
	11th to 20th	Night	18% 10% 27% 23% 18% 4	4208
	21st to end	Night	19% 7% 22% 36% 13% 2	4521
February	1st to 10th	Night	23% 8% 19% 34% 14% 2	2470
	11th to 20th	Night	21% 9% 18% 30% 18% 3	2403
	21st to end	Night	22% 8% 17% 30% 20% 4	1934
March	1st to 10th	Night	21% 7% 19% 36% 17% 1	1980
	11th to 20th	Night	20% 8% 20% 32% 18% 1	1980
	21st to end	Night	28% 9% 18% 33% 10% 2	2178
April	1st to 10th	Night	23% 10% 21% 26% 15% 4	1824
	11th to 20th	Night	29% 9% 19% 27% 14% 2	1749
	21st to end	Night	33% 9% 15% 30% 12%	1620
May	1st to 10th	Night	31% 8% 15% 30% 14% 2	1620
	11th to 20th	Night	35% 8% 16% 29% 10% 2	1432
	21st to end	Night	33% 9% 21% 26% 11% 1	1552
June	1st to 10th	Night	22% 9% 23% 25% 18% 3	1440
	11th to 20th	Night	21% 8% 13% 20% 24% 14%	1440
	21st to end	Night	14% 6% 9% 23% 31% 18%	1440
July	1st to 10th	Night	14% 6% 12% 28% 26% 14%	1400
	11th to 20th	Night	9% 4 8% 22% 30% 27%	1392
	21st to end	Night	11% 5% 9% 24% 27% 25%	1651
August	1st to 10th	Night	16% 6% 10% 25% 28% 15%	1602
	11th to 20th	Night	12% 5% 9% 28% 31% 14%	1602
	21st to end	Night	14% 7% 9% 22% 29% 19%	1878
September	1st to 10th	Night	14% 6% 8% 18% 36% 18%	1800
	11th to 20th	Night	19% 6% 8% 26% 29% 12%	1890
	21st to end	Night	20% 5% 9% 30% 32% 5%	2009
October	1st to 10th	Night	31% 6% 10% 28% 18% 5%	2160
	11th to 20th	Night	20% 6% 13% 35% 21% 5%	2160
	21st to end	Night	20% 8% 17% 32% 19% 4	2376
November	1st to 10th	Night	15% 11% 18% 29% 23% 5%	2428
	11th to 20th	Night	15% 7% 20% 34% 19% 3	2660
	21st to end	Night	19% 9% 16% 30% 20% 5%	2660
December	1st to 10th	Night	17% 8% 22% 31% 17% 5%	2660
	11th to 20th	Night	15% 9% 25% 34% 16% 1	3272
	21st to end	Night	20% 8% 13% 31% 19% 9%	4873

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	6% 18% 28% 31% 14% 3	270
	11th to 20th	Day	7% 17% 35% 24% 14% 3	270
	21st to end	Day	6% 15% 41% 23% 11% 3	297
February	1st to 10th	Day	10% 27% 41% 16% 5% 1	270
	11th to 20th	Day	7% 20% 42% 22% 7% 1	270
	21st to end	Day	6% 17% 39% 27% 10%	218
March	1st to 10th	Day	6% 23% 39% 28% 5% 1	420
	11th to 20th	Day	7% 21% 36% 26% 9% 1	420
	21st to end	Day	11% 21% 32% 28% 9% 1	462
April	1st to 10th	Day	10% 24% 32% 26% 8%	420
	11th to 20th	Day	12% 22% 33% 25% 7%	412
	21st to end	Day	15% 18% 27% 25% 13% 2	420
May	1st to 10th	Day	12% 19% 27% 28% 12% 3	423
	11th to 20th	Day	16% 9% 22% 34% 14% 5%	611
	21st to end	Day	15% 9% 21% 31% 19% 5%	679
June	1st to 10th	Day	6% 11% 26% 31% 21% 6%	630
	11th to 20th	Day	8% 13% 33% 31% 13% 2	630
	21st to end	Day	4 8% 29% 35% 19% 4	630
July	1st to 10th	Day	4 5% 21% 39% 24% 7%	621
	11th to 20th	Day	1 7% 27% 41% 21% 3	618
	21st to end	Day	5% 6% 27% 35% 23% 5%	508
August	1st to 10th	Day	6% 3 27% 39% 20% 5%	447
	11th to 20th	Day	4 3 32% 35% 20% 7%	437
	21st to end	Day	3 8% 25% 39% 19% 6%	495
September	1st to 10th	Day	6% 6% 29% 40% 15% 4	450
	11th to 20th	Day	7% 10% 28% 32% 18% 5%	450
	21st to end	Day	8% 11% 26% 34% 17% 4	420
October	1st to 10th	Day	11% 9% 23% 36% 16% 5%	270
	11th to 20th	Day	11% 18% 27% 24% 14% 6%	270
	21st to end	Day	7% 17% 41% 26% 8% 1	297
November	1st to 10th	Day	7% 17% 41% 26% 6% 2	270
	11th to 20th	Day	9% 17% 34% 30% 9% 1	270
	21st to end	Day	6% 22% 34% 25% 11% 2	270
December	1st to 10th	Day	8% 17% 41% 23% 9% 1	270
	11th to 20th	Day	3 24% 41% 21% 10% 1	270
	21st to end	Day	7% 17% 39% 23% 11% 3	297
January	1st to 10th	Night	4 19% 40% 27% 8% 1	950
	11th to 20th	Night	3 20% 48% 17% 10% 2	819
	21st to end	Night	2 17% 47% 25% 7% 2	836
February	1st to 10th	Night	3 22% 44% 22% 8%	760
	11th to 20th	Night	3 17% 47% 23% 8% 2	744
	21st to end	Night	3 15% 53% 21% 8% 1	610
March	1st to 10th	Night	3 13% 46% 30% 7% 1	720
	11th to 20th	Night	3 12% 43% 32% 9% 1	720
	21st to end	Night	6% 10% 42% 34% 7% 1	792
April	1st to 10th	Night	7% 13% 43% 30% 7%	564
	11th to 20th	Night	7% 13% 42% 32% 7%	533
	21st to end	Night	10% 12% 31% 34% 11% 1	540
May	1st to 10th	Night	15% 9% 25% 34% 16% 1	540
	11th to 20th	Night	15% 7% 22% 36% 19% 1	531
	21st to end	Night	15% 6% 23% 35% 20% 1	584
June	1st to 10th	Night	5% 7% 27% 36% 23% 2	540
	11th to 20th	Night	7% 9% 34% 38% 11%	540
	21st to end	Night	3 4 25% 46% 21% 1	540
July	1st to 10th	Night	2 2 17% 47% 30% 2	525
	11th to 20th	Night	1 2 24% 55% 18% 1	522
	21st to end	Night	3 2 17% 53% 24% 2	591
August	1st to 10th	Night	4 1 14% 53% 27% 1	537
	11th to 20th	Night	3 2 16% 52% 26% 1	534
	21st to end	Night	3 2 21% 50% 23% 1	594
September	1st to 10th	Night	4 3 22% 48% 21% 1	540
	11th to 20th	Night	6% 4 25% 44% 17% 4	630
	21st to end	Night	9% 4 29% 36% 18% 4	720
October	1st to 10th	Night	12% 8% 30% 33% 16% 2	720
	11th to 20th	Night	8% 12% 36% 30% 12% 3	720
	21st to end	Night	5% 13% 45% 27% 9% 2	792
November	1st to 10th	Night	3 15% 49% 26% 6% 1	835
	11th to 20th	Night	3 15% 51% 25% 5% 1	950
	21st to end	Night	3 14% 48% 26% 7% 1	950
December	1st to 10th	Night	4 17% 47% 25% 6% 1	950
	11th to 20th	Night	3 16% 49% 24% 7%	950
	21st to end	Night	3 18% 45% 25% 7% 2	1045

Page generated at 2024-02-22 04:05:44. Version ac07

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