Tonopah
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tonopah clear sky chart from 2005-11-06 to 2024-03-28.

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	2 3 2 3 3 2 3 4 5% 7% 66%	78881
	Night	3 4 2 4 4 2 3 4 5% 7% 64%	81139
Transparency	Day	18% 4 9% 19% 26% 25%	78590
	Night	20% 5% 10% 22% 25% 19%	80952
Seeing	Day	5% 9% 21% 27% 24% 14%	14176
	Night	4 6% 20% 39% 27% 4	23892

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	3 5% 3 4 3 2 4 5% 6% 8% 59%	2539
	11th to 20th	Day	2 5% 2 5% 4 3 5% 5% 7% 8% 53%	2540
	21st to end	Day	5% 6% 2 5% 4 3 4 5% 7% 12% 48%	3093
February	1st to 10th	Day	3 4 2 4 4 2 3 3 4 7% 62%	1900
	11th to 20th	Day	4 4 2 4 3 3 5% 4 6% 8% 59%	1850
	21st to end	Day	2 5% 1 4 3 2 4 4 6% 8% 61%	1570
March	1st to 10th	Day	2 5% 2 5% 5% 3 4 4 5% 7% 57%	1900
	11th to 20th	Day	2 5% 2 4 3 2 4 5% 5% 9% 58%	1970
	21st to end	Day	2 4 2 4 4 2 4 4 5% 9% 57%	2409
April	1st to 10th	Day	3 5% 2 4 4 2 4 4 5% 7% 60%	2160
	11th to 20th	Day	3 3 2 3 3 2 3 4 5% 6% 66%	2129
	21st to end	Day	2 3 1 3 3 2 3 3 5% 8% 67%	2218
May	1st to 10th	Day	3 3 2 4 4 2 3 4 5% 7% 64%	2340
	11th to 20th	Day	3 3 2 3 4 2 3 4 4 7% 65%	2301
	21st to end	Day	2 4 2 4 4 3 4 4 5% 8% 59%	2570
June	1st to 10th	Day	2 3 1 3 3 2 3 4 5% 7% 66%	2520
	11th to 20th	Day	2 1 1 3 3 2 3 4 4 5% 74%	2520
	21st to end	Day	1 2 1 2 2 2 2 3 3 4 78%	2520
July	1st to 10th	Day	2 2 1 3 3 1 3 4 4 6% 73%	2520
	11th to 20th	Day	2 2 1 2 3 3 3 4 4 6% 70%	2520
	21st to end	Day	3 2 2 3 4 2 4 4 4 8% 64%	2665
August	1st to 10th	Day	2 2 1 2 2 2 2 2 3 3 77%	2260
	11th to 20th	Day	2 1 1 2 2 1 2 2 4 6% 78%	2122
	21st to end	Day	1 2 1 2 2 1 2 2 3 4 80%	2376
September	1st to 10th	Day	1 2 1 2 2 1 3 3 3 5% 77%	2160
	11th to 20th	Day	2 2 1 2 2 1 2 2 3 4 81%	2006
	21st to end	Day	2 1 1 2 2 1 1 2 3 5% 81%	1980
October	1st to 10th	Day	1 3 1 3 2 2 2 3 3 6% 74%	1980
	11th to 20th	Day	2 1 1 2 2 1 2 2 3 4 78%	1868
	21st to end	Day	2 2 1 1 2 1 2 3 3 6% 77%	1805
November	1st to 10th	Day	2 2 1 4 4 2 2 4 5% 8% 67%	1674
	11th to 20th	Day	1 3 1 2 1 2 3 3 4 7% 73%	1710
	21st to end	Day	2 4 2 3 3 2 3 4 5% 7% 66%	1710
December	1st to 10th	Day	3 5% 1 3 3 1 3 5% 5% 7% 64%	1710
	11th to 20th	Day	5% 9% 3 6% 4 2 4 5% 6% 10% 45%	1972
	21st to end	Day	2 5% 2 5% 4 3 5% 7% 8% 9% 51%	2794
January	1st to 10th	Night	2 5% 2 5% 5% 2 2 3 5% 8% 59%	4406
	11th to 20th	Night	1 5% 2 5% 5% 3 4 4 5% 8% 55%	4420
	21st to end	Night	6% 9% 2 3 3 2 4 4 6% 9% 51%	4566
February	1st to 10th	Night	3 5% 2 5% 4 2 3 3 4 7% 63%	2280
	11th to 20th	Night	3 4 1 3 4 2 3 4 5% 8% 63%	2218
	21st to end	Night	3 5% 2 5% 3 2 4 4 5% 7% 60%	1884
March	1st to 10th	Night	2 4 1 6% 5% 3 4 5% 6% 9% 56%	2280
	11th to 20th	Night	3 5% 2 5% 4 2 4 5% 5% 8% 56%	2209
	21st to end	Night	3 5% 2 3 3 2 4 3 4 7% 63%	2098
April	1st to 10th	Night	4 3 2 3 4 2 4 4 4 6% 64%	1800
	11th to 20th	Night	3 3 1 3 4 2 3 3 4 5% 69%	1779
	21st to end	Night	4 4 2 3 4 2 3 3 5% 6% 65%	1742
May	1st to 10th	Night	3 3 1 3 4 3 5% 4 5% 8% 61%	1620
	11th to 20th	Night	4 4 1 3 3 2 4 3 5% 7% 65%	1594
	21st to end	Night	4 4 2 4 5% 3 4 4 5% 7% 58%	1702
June	1st to 10th	Night	1 2 1 3 3 2 4 4 6% 7% 67%	1440
	11th to 20th	Night	3 2 1 3 3 2 3 3 3 6% 71%	1440
	21st to end	Night	2 2 1 2 2 2 2 3 4 5% 77%	1440
July	1st to 10th	Night	2 3 1 4 3 3 3 3 3 5% 69%	1440
	11th to 20th	Night	3 3 2 4 4 3 4 5% 6% 6% 61%	1440
	21st to end	Night	4 3 2 4 5% 4 5% 5% 5% 7% 55%	1651
August	1st to 10th	Night	3 3 1 3 3 3 3 4 4 5% 68%	1675
	11th to 20th	Night	1 1 1 1 2 2 3 4 4 7% 73%	1780
	21st to end	Night	2 2 1 2 3 2 2 3 4 5% 76%	1980
September	1st to 10th	Night	2 1 2 2 2 3 2 4 5% 77%	1800
	11th to 20th	Night	2 2 1 1 2 1 3 3 3 4 79%	1953
	21st to end	Night	2 2 1 2 1 2 2 3 4 80%	1980
October	1st to 10th	Night	3 2 1 2 2 2 3 3 3 5% 74%	1980
	11th to 20th	Night	1 2 1 2 2 2 2 3 3 5% 76%	2089
	21st to end	Night	1 1 1 2 2 2 3 2 3 5% 79%	2549
November	1st to 10th	Night	2 3 1 2 3 2 2 3 3 7% 73%	2405
	11th to 20th	Night	2 3 1 3 2 2 3 3 4 7% 72%	2470
	21st to end	Night	2 4 2 4 3 2 3 3 4 6% 66%	2470
December	1st to 10th	Night	2 5% 2 4 3 2 5% 4 6% 7% 60%	2470
	11th to 20th	Night	5% 9% 2 4 4 3 4 4 6% 10% 48%	3227
	21st to end	Night	3 5% 3 6% 6% 4 6% 7% 7% 9% 46%	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	22% 6% 21% 31% 20% 1	2539
	11th to 20th	Day	25% 7% 18% 29% 15% 5%	2540
	21st to end	Day	28% 6% 18% 26% 18% 3	3093
February	1st to 10th	Day	22% 4 12% 29% 25% 9%	1900
	11th to 20th	Day	22% 4 10% 27% 30% 7%	1860
	21st to end	Day	21% 5% 12% 29% 26% 7%	1570
March	1st to 10th	Day	23% 5% 10% 27% 27% 7%	1900
	11th to 20th	Day	22% 4 10% 27% 26% 11%	1970
	21st to end	Day	22% 5% 14% 28% 24% 7%	2409
April	1st to 10th	Day	22% 4 9% 25% 23% 16%	2160
	11th to 20th	Day	19% 4 8% 20% 31% 18%	2132
	21st to end	Day	17% 3 8% 25% 34% 13%	2218
May	1st to 10th	Day	18% 4 7% 17% 37% 17%	2340
	11th to 20th	Day	18% 3 7% 19% 36% 17%	2304
	21st to end	Day	21% 4 9% 21% 30% 15%	2570
June	1st to 10th	Day	17% 4 8% 14% 27% 30%	2520
	11th to 20th	Day	12% 3 5% 10% 27% 44%	2520
	21st to end	Day	10% 2 3 6% 21% 58%	2520
July	1st to 10th	Day	13% 3 3 8% 14% 60%	2451
	11th to 20th	Day	15% 3 4 9% 18% 51%	2445
	21st to end	Day	18% 4 7% 14% 20% 38%	2517
August	1st to 10th	Day	13% 2 4 7% 18% 57%	2245
	11th to 20th	Day	8% 2 4 8% 21% 56%	2122
	21st to end	Day	10% 1 3 7% 24% 55%	2376
September	1st to 10th	Day	10% 3 4 7% 21% 55%	2160
	11th to 20th	Day	9% 1 4 11% 29% 45%	2006
	21st to end	Day	9% 1 3 11% 34% 41%	1980
October	1st to 10th	Day	12% 2 6% 14% 34% 30%	1980
	11th to 20th	Day	11% 2 3 17% 36% 31%	1868
	21st to end	Day	11% 3 4 21% 40% 20%	1805
November	1st to 10th	Day	15% 4 9% 25% 32% 15%	1674
	11th to 20th	Day	12% 3 9% 29% 36% 10%	1710
	21st to end	Day	17% 4 10% 27% 29% 13%	1710
December	1st to 10th	Day	19% 6% 12% 29% 25% 9%	1710
	11th to 20th	Day	32% 7% 11% 26% 19% 5%	1972
	21st to end	Day	25% 9% 22% 23% 19% 3	2794
January	1st to 10th	Night	24% 5% 19% 32% 19% 2	4406
	11th to 20th	Night	27% 6% 16% 29% 17% 6%	4420
	21st to end	Night	29% 7% 16% 28% 16% 3	4566
February	1st to 10th	Night	23% 3 12% 28% 25% 9%	2280
	11th to 20th	Night	19% 5% 10% 26% 33% 9%	2219
	21st to end	Night	22% 5% 12% 29% 25% 7%	1884
March	1st to 10th	Night	22% 5% 13% 27% 24% 9%	2280
	11th to 20th	Night	23% 5% 11% 26% 25% 10%	2209
	21st to end	Night	20% 4 13% 33% 23% 6%	2098
April	1st to 10th	Night	20% 5% 10% 28% 25% 12%	1800
	11th to 20th	Night	17% 6% 7% 24% 30% 16%	1779
	21st to end	Night	20% 3 8% 26% 32% 11%	1742
May	1st to 10th	Night	19% 5% 7% 20% 33% 15%	1620
	11th to 20th	Night	19% 4 7% 16% 35% 18%	1595
	21st to end	Night	25% 5% 11% 18% 28% 13%	1702
June	1st to 10th	Night	15% 5% 8% 14% 32% 26%	1440
	11th to 20th	Night	15% 4 3 11% 26% 40%	1440
	21st to end	Night	11% 3 3 7% 23% 53%	1440
July	1st to 10th	Night	18% 3 4 10% 11% 54%	1400
	11th to 20th	Night	19% 6% 7% 9% 15% 44%	1392
	21st to end	Night	25% 6% 10% 12% 15% 33%	1559
August	1st to 10th	Night	17% 3 4 9% 17% 50%	1666
	11th to 20th	Night	10% 4 7% 10% 19% 50%	1780
	21st to end	Night	11% 2 4 10% 20% 53%	1980
September	1st to 10th	Night	10% 2 4 10% 20% 53%	1800
	11th to 20th	Night	10% 3 5% 12% 26% 45%	1953
	21st to end	Night	10% 2 4 11% 31% 42%	1980
October	1st to 10th	Night	14% 2 6% 16% 31% 31%	1980
	11th to 20th	Night	12% 3 5% 17% 32% 32%	2089
	21st to end	Night	10% 3 4 20% 40% 23%	2549
November	1st to 10th	Night	13% 2 9% 26% 34% 17%	2405
	11th to 20th	Night	13% 4 8% 27% 35% 13%	2470
	21st to end	Night	19% 3 8% 23% 35% 12%	2470
December	1st to 10th	Night	22% 6% 12% 25% 26% 9%	2470
	11th to 20th	Night	30% 6% 14% 25% 20% 4	3227
	21st to end	Night	31% 8% 15% 23% 19% 4	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	11% 7% 27% 33% 14% 7%	180
	11th to 20th	Day	6% 9% 24% 28% 21% 12%	180
	21st to end	Day	6% 8% 20% 28% 23% 14%	345
February	1st to 10th	Day	5% 14% 29% 27% 15% 10%	460
	11th to 20th	Day	9% 11% 29% 26% 18% 7%	455
	21st to end	Day	6% 16% 29% 30% 15% 4	382
March	1st to 10th	Day	5% 17% 30% 27% 16% 5%	460
	11th to 20th	Day	7% 16% 28% 24% 19% 6%	460
	21st to end	Day	8% 19% 30% 25% 14% 4	491
April	1st to 10th	Day	10% 15% 24% 23% 18% 9%	420
	11th to 20th	Day	7% 20% 29% 27% 14% 4	412
	21st to end	Day	5% 18% 27% 27% 10% 12%	420
May	1st to 10th	Day	7% 13% 31% 25% 16% 8%	423
	11th to 20th	Day	8% 13% 21% 30% 17% 12%	448
	21st to end	Day	7% 8% 19% 28% 23% 14%	485
June	1st to 10th	Day	3 10% 18% 26% 24% 17%	450
	11th to 20th	Day	4 9% 22% 27% 25% 13%	450
	21st to end	Day	2 6% 16% 28% 30% 18%	450
July	1st to 10th	Day	3 3 14% 30% 33% 17%	446
	11th to 20th	Day	1 3 8% 29% 38% 22%	444
	21st to end	Day	3 2 10% 31% 33% 22%	487
August	1st to 10th	Day	4 3 15% 34% 27% 17%	447
	11th to 20th	Day	3 2 15% 25% 30% 25%	437
	21st to end	Day	3 2 12% 27% 32% 24%	495
September	1st to 10th	Day	2 4 16% 25% 27% 26%	450
	11th to 20th	Day	2 7% 17% 27% 28% 19%	450
	21st to end	Day	3 7% 15% 24% 35% 16%	450
October	1st to 10th	Day	3 12% 20% 21% 25% 19%	450
	11th to 20th	Day	3 9% 18% 27% 28% 15%	450
	21st to end	Day	4 7% 18% 24% 29% 18%	320
November	1st to 10th	Day	2 4 20% 30% 29% 15%	270
	11th to 20th	Day	4 5% 17% 30% 27% 17%	270
	21st to end	Day	4 6% 19% 26% 29% 16%	270
December	1st to 10th	Day	6% 7% 19% 32% 24% 13%	270
	11th to 20th	Day	3 9% 24% 29% 24% 10%	201
	21st to end	Day	6% 12% 27% 28% 21% 7%	198
January	1st to 10th	Night	7% 5% 22% 36% 23% 7%	760
	11th to 20th	Night	3 3 24% 42% 23% 5%	760
	21st to end	Night	8% 4 22% 39% 23% 4	836
February	1st to 10th	Night	5% 6% 26% 36% 24% 3	760
	11th to 20th	Night	5% 7% 23% 40% 22% 3	744
	21st to end	Night	5% 6% 28% 44% 15% 2	628
March	1st to 10th	Night	3 10% 26% 44% 15% 3	760
	11th to 20th	Night	4 8% 24% 38% 23% 3	760
	21st to end	Night	5% 11% 30% 36% 15% 1	820
April	1st to 10th	Night	6% 11% 25% 37% 18% 2	720
	11th to 20th	Night	5% 12% 27% 36% 16% 4	711
	21st to end	Night	6% 11% 24% 36% 18% 4	662
May	1st to 10th	Night	5% 11% 29% 37% 16% 1	540
	11th to 20th	Night	7% 12% 25% 31% 23% 2	531
	21st to end	Night	7% 13% 24% 31% 23% 3	540
June	1st to 10th	Night	2 6% 20% 41% 27% 3	360
	11th to 20th	Night	3 6% 24% 42% 24% 1	360
	21st to end	Night	3 3 17% 48% 29% 1	360
July	1st to 10th	Night	3 2 8% 52% 34% 1	350
	11th to 20th	Night	2 2 10% 45% 38% 3	348
	21st to end	Night	3 3 3 48% 40% 2	469
August	1st to 10th	Night	3 2 14% 46% 32% 2	601
	11th to 20th	Night	1 1 8% 41% 44% 4	712
	21st to end	Night	3 2 8% 41% 43% 3	792
September	1st to 10th	Night	3 3 10% 33% 45% 6%	720
	11th to 20th	Night	3 3 14% 36% 37% 7%	720
	21st to end	Night	2 4 14% 33% 39% 8%	720
October	1st to 10th	Night	3 4 17% 38% 30% 8%	720
	11th to 20th	Night	2 3 16% 38% 33% 7%	720
	21st to end	Night	1 3 20% 35% 31% 10%	792
November	1st to 10th	Night	3 4 18% 35% 32% 8%	740
	11th to 20th	Night	3 3 21% 42% 27% 4	760
	21st to end	Night	4 4 18% 39% 30% 5%	760
December	1st to 10th	Night	5% 4 20% 47% 19% 6%	760
	11th to 20th	Night	9% 3 19% 44% 21% 3	760
	21st to end	Night	6% 5% 28% 41% 19% 2	836

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