Picture Canyon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Picture Canyon clear sky chart from 2005-11-06 to 2024-11-08.

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% 4 1 4 3 3 3 3 5% 7% 61%	105015
	Night	5% 4 2 4 3 3 4 3 5% 7% 58%	102784
Transparency	Day	22% 5% 10% 22% 27% 14%	104761
	Night	24% 5% 10% 22% 25% 13%	102628
Seeing	Day	7% 7% 27% 32% 20% 6%	15444
	Night	7% 7% 34% 39% 12% 1	25399

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 7% 2 7% 3 3 3 2 4 6% 59%	2538
	11th to 20th	Day	3 3 2 5% 4 4 4 4 5% 6% 60%	2543
	21st to end	Day	5% 5% 1 4 3 3 4 4 5% 6% 59%	3266
February	1st to 10th	Day	4 7% 2 6% 4 3 3 3 4 6% 58%	1900
	11th to 20th	Day	3 5% 3 5% 4 4 3 3 4 7% 58%	1849
	21st to end	Day	3 5% 2 4 2 3 3 3 5% 5% 65%	1570
March	1st to 10th	Day	3 5% 2 4 2 2 2 2 4 6% 67%	3130
	11th to 20th	Day	8% 5% 2 4 3 3 3 3 4 6% 59%	3250
	21st to end	Day	4 6% 2 4 3 4 3 3 6% 7% 56%	4152
April	1st to 10th	Day	4 4 1 4 3 2 3 3 5% 6% 65%	2280
	11th to 20th	Day	7% 5% 1 4 3 3 4 3 5% 6% 58%	2251
	21st to end	Day	7% 5% 2 4 3 3 4 3 5% 8% 57%	2280
May	1st to 10th	Day	8% 5% 1 4 3 4 4 3 5% 6% 58%	4117
	11th to 20th	Day	7% 4 2 5% 4 4 4 4 4 7% 56%	4082
	21st to end	Day	4 3 1 3 2 3 4 3 5% 8% 63%	4534
June	1st to 10th	Day	4 3 1 4 3 3 3 5% 7% 10% 56%	2660
	11th to 20th	Day	4 3 1 3 2 3 3 3 6% 8% 63%	2660
	21st to end	Day	4 4 2 5% 3 4 4 4 7% 9% 55%	2660
July	1st to 10th	Day	5% 3 1 4 4 4 5% 5% 7% 9% 54%	4430
	11th to 20th	Day	2 2 1 3 3 3 4 4 6% 10% 62%	4430
	21st to end	Day	4 3 1 5% 3 4 4 4 7% 9% 56%	4655
August	1st to 10th	Day	6% 4 1 5% 4 4 5% 5% 7% 10% 50%	3819
	11th to 20th	Day	4 3 1 3 3 3 3 4 6% 9% 60%	3726
	21st to end	Day	3 3 1 4 3 4 5% 5% 7% 10% 55%	4180
September	1st to 10th	Day	7% 4 1 3 3 3 4 4 5% 7% 60%	2280
	11th to 20th	Day	7% 4 1 4 2 3 3 2 5% 6% 63%	2137
	21st to end	Day	5% 3 1 3 2 3 3 2 4 5% 68%	2090
October	1st to 10th	Day	5% 2 1 2 2 2 2 2 4 5% 73%	3480
	11th to 20th	Day	7% 4 1 3 2 2 3 2 3 5% 66%	3222
	21st to end	Day	4 3 1 2 1 1 2 2 3 4 78%	3186
November	1st to 10th	Day	3 4 1 3 2 1 2 2 4 4 73%	1736
	11th to 20th	Day	3 3 1 4 2 2 2 2 4 6% 71%	1710
	21st to end	Day	5% 6% 2 4 2 2 2 2 4 5% 65%	1710
December	1st to 10th	Day	2 6% 2 5% 2 3 4 3 5% 6% 63%	1710
	11th to 20th	Day	5% 5% 2 3 2 2 3 3 5% 7% 64%	1998
	21st to end	Day	3 5% 2 5% 3 3 3 3 6% 7% 60%	2794
January	1st to 10th	Night	3 5% 2 6% 4 5% 4 3 5% 6% 56%	4417
	11th to 20th	Night	3 5% 2 4 3 3 4 4 5% 7% 61%	4430
	21st to end	Night	4 6% 2 5% 2 3 3 3 5% 7% 60%	4425
February	1st to 10th	Night	4 6% 3 5% 3 3 3 3 4 5% 60%	2280
	11th to 20th	Night	4 5% 3 5% 4 4 4 4 6% 7% 52%	2218
	21st to end	Night	5% 4 2 3 2 2 3 2 5% 6% 66%	1884
March	1st to 10th	Night	4 4 1 4 2 2 2 2 4 5% 70%	3734
	11th to 20th	Night	7% 6% 2 5% 4 4 4 4 5% 7% 53%	3715
	21st to end	Night	6% 5% 2 4 3 3 4 3 5% 5% 60%	3487
April	1st to 10th	Night	5% 4 1 3 3 4 3 3 4 8% 62%	1900
	11th to 20th	Night	8% 4 1 4 3 4 5% 3 5% 8% 55%	1877
	21st to end	Night	11% 4 1 3 3 2 3 4 5% 6% 55%	1900
May	1st to 10th	Night	8% 5% 2 4 3 3 4 3 4 7% 57%	2850
	11th to 20th	Night	11% 4 1 5% 3 4 4 4 5% 7% 51%	2823
	21st to end	Night	6% 4 2 5% 3 3 4 4 5% 7% 57%	3049
June	1st to 10th	Night	4 4 1 4 3 4 4 4 7% 11% 53%	1520
	11th to 20th	Night	2 3 1 3 3 3 3 4 6% 11% 61%	1520
	21st to end	Night	5% 3 1 5% 4 4 5% 6% 7% 10% 49%	1520
July	1st to 10th	Night	5% 3 1 4 3 4 5% 5% 8% 10% 52%	2540
	11th to 20th	Night	4 3 1 6% 4 4 5% 4 9% 12% 48%	2540
	21st to end	Night	5% 4 2 6% 5% 5% 6% 5% 7% 9% 45%	2906
August	1st to 10th	Night	11% 4 2 5% 4 4 5% 4 7% 11% 42%	3115
	11th to 20th	Night	5% 3 1 3 3 5% 6% 6% 9% 13% 45%	3113
	21st to end	Night	3 4 2 6% 5% 6% 6% 5% 8% 11% 44%	3487
September	1st to 10th	Night	6% 3 1 3 2 4 3 3 5% 7% 61%	1900
	11th to 20th	Night	7% 4 1 3 3 3 3 3 5% 6% 61%	2042
	21st to end	Night	5% 3 1 4 2 3 3 2 4 6% 66%	2090
October	1st to 10th	Night	6% 2 1 3 2 2 3 3 5% 5% 69%	3480
	11th to 20th	Night	10% 3 1 3 3 2 3 3 4 7% 62%	3700
	21st to end	Night	6% 3 1 2 1 2 2 2 4 5% 72%	4341
November	1st to 10th	Night	4 3 1 3 2 2 2 3 4 5% 70%	2503
	11th to 20th	Night	2 3 1 3 2 2 3 3 4 4 74%	2470
	21st to end	Night	4 6% 1 4 3 3 3 3 5% 5% 64%	2470
December	1st to 10th	Night	3 5% 2 5% 3 2 4 2 4 7% 63%	2470
	11th to 20th	Night	4 4 1 4 3 3 3 2 4 7% 63%	3195
	21st to end	Night	4 4 2 5% 4 4 4 4 5% 5% 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	27% 4 7% 26% 30% 6%	2539
	11th to 20th	Day	23% 4 14% 21% 26% 11%	2543
	21st to end	Day	24% 5% 9% 27% 29% 6%	3266
February	1st to 10th	Day	28% 3 11% 22% 23% 14%	1900
	11th to 20th	Day	28% 3 7% 23% 25% 13%	1859
	21st to end	Day	21% 3 6% 20% 29% 21%	1570
March	1st to 10th	Day	18% 4 7% 17% 29% 25%	3130
	11th to 20th	Day	25% 5% 9% 22% 31% 8%	3250
	21st to end	Day	25% 4 11% 23% 28% 8%	4152
April	1st to 10th	Day	20% 4 8% 22% 27% 19%	2280
	11th to 20th	Day	26% 5% 9% 22% 22% 16%	2254
	21st to end	Day	26% 4 12% 24% 26% 9%	2280
May	1st to 10th	Day	26% 7% 10% 19% 20% 18%	4117
	11th to 20th	Day	27% 7% 11% 22% 23% 10%	4086
	21st to end	Day	19% 7% 12% 20% 23% 19%	4534
June	1st to 10th	Day	20% 8% 16% 26% 19% 10%	2660
	11th to 20th	Day	17% 6% 10% 21% 24% 22%	2660
	21st to end	Day	24% 6% 11% 23% 21% 15%	2660
July	1st to 10th	Day	24% 8% 11% 21% 27% 9%	4361
	11th to 20th	Day	16% 6% 15% 23% 30% 10%	4355
	21st to end	Day	23% 7% 13% 23% 25% 9%	4507
August	1st to 10th	Day	27% 9% 17% 26% 17% 5%	3806
	11th to 20th	Day	19% 6% 14% 22% 28% 11%	3762
	21st to end	Day	21% 7% 14% 27% 24% 8%	4179
September	1st to 10th	Day	23% 6% 10% 21% 23% 17%	2280
	11th to 20th	Day	22% 5% 7% 20% 27% 19%	2137
	21st to end	Day	19% 3 8% 18% 32% 19%	2090
October	1st to 10th	Day	15% 3 6% 16% 37% 23%	3480
	11th to 20th	Day	21% 3 7% 22% 32% 15%	3222
	21st to end	Day	14% 2 4 16% 41% 23%	3186
November	1st to 10th	Day	16% 2 7% 22% 31% 22%	1736
	11th to 20th	Day	16% 2 7% 25% 34% 16%	1710
	21st to end	Day	23% 2 7% 15% 29% 23%	1710
December	1st to 10th	Day	22% 4 11% 27% 25% 12%	1710
	11th to 20th	Day	20% 3 9% 21% 35% 13%	1996
	21st to end	Day	22% 5% 10% 22% 24% 16%	2794
January	1st to 10th	Night	28% 4 7% 29% 25% 7%	4417
	11th to 20th	Night	22% 4 12% 24% 26% 11%	4430
	21st to end	Night	24% 4 12% 24% 30% 6%	4425
February	1st to 10th	Night	27% 4 9% 21% 29% 11%	2280
	11th to 20th	Night	30% 5% 9% 22% 24% 11%	2218
	21st to end	Night	20% 3 4 21% 33% 18%	1884
March	1st to 10th	Night	18% 3 5% 17% 26% 30%	3734
	11th to 20th	Night	28% 6% 11% 21% 22% 12%	3715
	21st to end	Night	24% 6% 8% 27% 25% 11%	3487
April	1st to 10th	Night	22% 5% 9% 21% 25% 18%	1900
	11th to 20th	Night	27% 5% 12% 21% 21% 14%	1877
	21st to end	Night	28% 6% 14% 24% 20% 10%	1900
May	1st to 10th	Night	26% 7% 14% 17% 15% 21%	2850
	11th to 20th	Night	30% 8% 14% 21% 17% 10%	2824
	21st to end	Night	25% 8% 13% 16% 18% 20%	3050
June	1st to 10th	Night	23% 9% 20% 24% 14% 10%	1520
	11th to 20th	Night	18% 7% 14% 22% 21% 18%	1520
	21st to end	Night	27% 7% 13% 24% 18% 11%	1520
July	1st to 10th	Night	26% 9% 13% 27% 19% 6%	2500
	11th to 20th	Night	26% 7% 16% 22% 24% 5%	2492
	21st to end	Night	32% 8% 13% 22% 19% 8%	2815
August	1st to 10th	Night	34% 8% 17% 22% 16% 4	3105
	11th to 20th	Night	25% 9% 17% 26% 20% 4	3143
	21st to end	Night	31% 8% 13% 25% 19% 4	3487
September	1st to 10th	Night	23% 6% 12% 25% 21% 13%	1900
	11th to 20th	Night	23% 5% 12% 18% 24% 18%	2042
	21st to end	Night	20% 4 7% 21% 32% 16%	2090
October	1st to 10th	Night	17% 4 7% 17% 35% 19%	3480
	11th to 20th	Night	23% 4 8% 22% 28% 16%	3700
	21st to end	Night	16% 3 5% 19% 41% 17%	4341
November	1st to 10th	Night	17% 3 8% 20% 29% 23%	2503
	11th to 20th	Night	15% 3 5% 24% 36% 17%	2470
	21st to end	Night	22% 4 7% 17% 28% 22%	2470
December	1st to 10th	Night	22% 4 10% 27% 27% 11%	2470
	11th to 20th	Night	22% 3 8% 19% 36% 12%	3196
	21st to end	Night	24% 5% 10% 22% 28% 11%	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% 5% 34% 37% 14% 3	270
	11th to 20th	Day	9% 10% 30% 34% 13% 4	270
	21st to end	Day	4 7% 34% 30% 22% 3	297
February	1st to 10th	Day	6% 10% 48% 24% 10% 1	270
	11th to 20th	Day	5% 8% 46% 28% 10% 3	270
	21st to end	Day	5% 15% 42% 31% 6% 1	225
March	1st to 10th	Day	3 11% 37% 33% 13% 2	270
	11th to 20th	Day	11% 12% 30% 29% 16% 3	270
	21st to end	Day	13% 17% 38% 22% 9% 1	493
April	1st to 10th	Day	7% 14% 41% 25% 10% 3	460
	11th to 20th	Day	11% 19% 36% 24% 8% 2	452
	21st to end	Day	14% 15% 35% 26% 8% 2	460
May	1st to 10th	Day	9% 10% 36% 29% 14% 2	650
	11th to 20th	Day	11% 7% 29% 32% 17% 5%	675
	21st to end	Day	8% 9% 35% 34% 11% 3	734
June	1st to 10th	Day	5% 4 25% 34% 23% 9%	680
	11th to 20th	Day	6% 4 28% 38% 19% 5%	680
	21st to end	Day	6% 3 25% 37% 23% 6%	680
July	1st to 10th	Day	4 2 18% 37% 28% 10%	671
	11th to 20th	Day	4 1 10% 38% 35% 12%	668
	21st to end	Day	5% 1 10% 32% 40% 12%	739
August	1st to 10th	Day	4 1 15% 32% 36% 12%	509
	11th to 20th	Day	4 1 19% 38% 28% 9%	477
	21st to end	Day	4 1 14% 43% 26% 13%	539
September	1st to 10th	Day	6% 1 17% 38% 30% 8%	490
	11th to 20th	Day	5% 2 18% 42% 21% 12%	347
	21st to end	Day	7% 5% 20% 26% 29% 13%	300
October	1st to 10th	Day	12% 6% 20% 28% 24% 10%	300
	11th to 20th	Day	4 6% 30% 31% 19% 10%	300
	21st to end	Day	13% 6% 29% 25% 21% 7%	330
November	1st to 10th	Day	9% 8% 30% 29% 20% 5%	291
	11th to 20th	Day	6% 9% 24% 36% 20% 5%	270
	21st to end	Day	11% 14% 27% 26% 15% 7%	270
December	1st to 10th	Day	3 7% 34% 36% 16% 4	270
	11th to 20th	Day	10% 6% 36% 31% 15% 2	270
	21st to end	Day	8% 13% 38% 32% 9%	297
January	1st to 10th	Night	4 7% 36% 41% 11% 1	950
	11th to 20th	Night	7% 7% 34% 38% 11% 2	950
	21st to end	Night	6% 5% 37% 39% 12% 1	851
February	1st to 10th	Night	7% 7% 40% 36% 9%	760
	11th to 20th	Night	6% 9% 49% 28% 7%	744
	21st to end	Night	9% 9% 49% 29% 5%	628
March	1st to 10th	Night	6% 11% 43% 34% 6%	760
	11th to 20th	Night	10% 10% 37% 36% 7% 1	714
	21st to end	Night	7% 13% 50% 24% 5%	627
April	1st to 10th	Night	7% 11% 48% 30% 4	570
	11th to 20th	Night	11% 11% 48% 26% 3	563
	21st to end	Night	13% 10% 41% 29% 6% 1	570
May	1st to 10th	Night	8% 12% 37% 35% 7%	570
	11th to 20th	Night	10% 5% 37% 36% 12% 1	561
	21st to end	Night	9% 8% 45% 30% 7%	617
June	1st to 10th	Night	5% 5% 37% 41% 12% 1	570
	11th to 20th	Night	3 5% 47% 37% 8%	570
	21st to end	Night	5% 3 32% 45% 14%	570
July	1st to 10th	Night	5% 1 22% 50% 21% 1	555
	11th to 20th	Night	4 1 16% 54% 23% 1	552
	21st to end	Night	8% 1 16% 45% 28% 2	624
August	1st to 10th	Night	8% 1 14% 46% 30% 2	567
	11th to 20th	Night	9% 1 15% 52% 22% 1	564
	21st to end	Night	4 1 19% 48% 25% 2	627
September	1st to 10th	Night	7% 1 21% 52% 18% 1	570
	11th to 20th	Night	8% 1 33% 41% 16% 1	570
	21st to end	Night	6% 5% 29% 44% 15% 2	570
October	1st to 10th	Night	11% 4 31% 41% 12% 1	570
	11th to 20th	Night	6% 5% 33% 40% 14% 3	708
	21st to end	Night	8% 7% 29% 36% 17% 2	969
November	1st to 10th	Night	6% 5% 28% 46% 13% 2	963
	11th to 20th	Night	4 7% 35% 39% 13% 2	950
	21st to end	Night	7% 8% 31% 38% 13% 3	950
December	1st to 10th	Night	5% 7% 36% 41% 11% 1	950
	11th to 20th	Night	7% 7% 37% 38% 10% 1	950
	21st to end	Night	8% 10% 38% 34% 9%	1045

Page generated at 2024-11-05 06:15:47. Version ac07

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