Pinon Ridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pinon Ridge Observatory clear sky chart from 2005-11-06 to 2026-07-16.

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 4 2 5% 4 4 5% 4 6% 8% 57%	146838
	Night	2 5% 2 5% 3 3 4 4 6% 7% 58%	143414
Transparency	Day	24% 5% 11% 23% 25% 11%	141726
	Night	23% 5% 12% 25% 25% 10%	139535
Seeing	Day	6% 12% 26% 30% 19% 6%	17603
	Night	5% 7% 25% 39% 21% 3	27733

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	1 6% 3 10% 5% 4 4 4 8% 8% 47%	5181
	11th to 20th	Day	1 4 2 7% 4 3 3 3 5% 7% 61%	5340
	21st to end	Day	1 7% 3 7% 4 3 4 3 5% 6% 58%	5844
February	1st to 10th	Day	2 8% 2 7% 6% 5% 5% 4 7% 6% 48%	1890
	11th to 20th	Day	2 8% 4 7% 4 5% 5% 5% 8% 7% 46%	1871
	21st to end	Day	1 7% 4 8% 5% 5% 4 4 5% 6% 49%	1738
March	1st to 10th	Day	1 6% 2 5% 3 4 4 4 7% 8% 55%	5064
	11th to 20th	Day	1 10% 3 7% 6% 5% 5% 4 6% 8% 44%	5110
	21st to end	Day	1 5% 2 6% 4 5% 6% 5% 8% 10% 47%	5607
April	1st to 10th	Day	3 6% 2 5% 3 4 4 4 6% 7% 55%	2516
	11th to 20th	Day	2 7% 2 7% 5% 4 5% 4 7% 8% 49%	2491
	21st to end	Day	3 6% 2 5% 5% 4 4 5% 6% 9% 52%	2520
May	1st to 10th	Day	3 4 2 5% 4 4 5% 4 6% 8% 56%	7560
	11th to 20th	Day	1 3 1 4 4 4 5% 4 7% 9% 58%	7651
	21st to end	Day	1 2 1 3 3 4 5% 4 7% 9% 61%	9026
June	1st to 10th	Day	2 3 1 3 3 4 4 3 6% 9% 62%	2940
	11th to 20th	Day	2 2 1 3 3 3 3 3 5% 6% 69%	2940
	21st to end	Day	1 2 1 3 3 3 4 4 6% 7% 65%	2940
July	1st to 10th	Day	2 2 1 3 3 4 4 4 5% 5% 69%	6418
	11th to 20th	Day	1 1 1 3 3 5% 7% 7% 11% 12% 49%	5946
	21st to end	Day	2 3 1 4 4 5% 6% 6% 7% 9% 53%	6401
August	1st to 10th	Day	2 2 1 4 4 5% 6% 6% 9% 11% 49%	5779
	11th to 20th	Day	2 2 1 4 4 4 5% 5% 7% 9% 57%	5668
	21st to end	Day	3 3 1 5% 4 5% 7% 6% 9% 11% 46%	5984
September	1st to 10th	Day	5% 3 1 4 4 4 5% 4 6% 6% 56%	2400
	11th to 20th	Day	3 3 1 4 4 4 5% 4 6% 7% 61%	2370
	21st to end	Day	4 3 1 4 3 3 4 3 4 6% 66%	2119
October	1st to 10th	Day	3 2 1 2 2 2 2 2 3 6% 74%	3270
	11th to 20th	Day	3 3 2 5% 4 4 5% 5% 7% 8% 55%	3250
	21st to end	Day	3 4 1 4 2 2 2 2 3 6% 70%	3548
November	1st to 10th	Day	1 3 1 3 2 3 4 3 5% 7% 68%	2041
	11th to 20th	Day	1 4 2 5% 3 3 4 4 4 6% 65%	1837
	21st to end	Day	2 6% 3 5% 3 3 3 3 5% 4 62%	1680
December	1st to 10th	Day	1 6% 2 5% 3 2 3 2 4 5% 66%	2700
	11th to 20th	Day	1 4 3 5% 4 3 3 3 5% 8% 61%	3106
	21st to end	Day	1 8% 3 8% 4 4 4 4 6% 7% 51%	4092
January	1st to 10th	Night	1 9% 5% 9% 5% 5% 5% 4 7% 7% 43%	7783
	11th to 20th	Night	1 4 2 6% 4 3 3 3 5% 5% 64%	7650
	21st to end	Night	1 8% 3 6% 3 3 4 3 5% 6% 57%	8370
February	1st to 10th	Night	2 9% 3 7% 5% 4 4 3 4 6% 54%	2730
	11th to 20th	Night	3 8% 2 7% 4 5% 4 4 6% 7% 51%	2635
	21st to end	Night	2 8% 3 6% 3 4 5% 4 6% 6% 53%	2065
March	1st to 10th	Night	1 6% 2 6% 4 4 5% 5% 6% 7% 52%	5050
	11th to 20th	Night	2 9% 5% 6% 3 3 4 4 6% 7% 51%	5110
	21st to end	Night	1 8% 3 7% 4 4 5% 4 7% 8% 49%	5610
April	1st to 10th	Night	3 6% 2 6% 4 4 4 4 7% 7% 52%	2102
	11th to 20th	Night	4 7% 2 5% 4 3 5% 4 7% 8% 51%	2077
	21st to end	Night	5% 6% 3 4 3 3 4 3 5% 8% 55%	2100
May	1st to 10th	Night	3 6% 2 5% 3 4 4 4 7% 9% 53%	5383
	11th to 20th	Night	3 4 1 4 3 3 5% 4 6% 7% 59%	5237
	21st to end	Night	2 2 1 3 2 2 3 3 5% 6% 70%	5181
June	1st to 10th	Night	2 2 1 2 3 2 3 4 5% 9% 67%	1680
	11th to 20th	Night	2 2 1 3 2 3 3 3 4 6% 72%	1680
	21st to end	Night	1 1 1 3 2 3 4 4 5% 8% 68%	1680
July	1st to 10th	Night	1 1 4 3 3 4 4 7% 6% 68%	3763
	11th to 20th	Night	1 1 1 3 3 3 4 4 9% 14% 56%	4145
	21st to end	Night	1 2 1 4 4 4 4 4 7% 10% 58%	4472
August	1st to 10th	Night	2 2 1 3 3 4 5% 5% 9% 11% 55%	4033
	11th to 20th	Night	2 2 1 3 2 4 5% 4 7% 10% 62%	4179
	21st to end	Night	2 3 2 6% 5% 5% 6% 5% 8% 10% 48%	4993
September	1st to 10th	Night	3 2 1 4 3 3 4 4 6% 9% 61%	2000
	11th to 20th	Night	2 2 1 3 3 3 4 3 6% 7% 65%	2025
	21st to end	Night	4 3 1 3 2 2 2 2 4 6% 71%	2280
October	1st to 10th	Night	3 2 1 2 2 2 2 1 3 5% 79%	3920
	11th to 20th	Night	3 3 1 4 3 3 4 4 6% 7% 62%	3898
	21st to end	Night	4 5% 1 4 2 2 3 2 3 4 69%	4252
November	1st to 10th	Night	2 4 1 3 3 3 3 3 5% 6% 68%	2460
	11th to 20th	Night	3 5% 2 3 3 3 2 3 4 5% 67%	2772
	21st to end	Night	3 6% 3 5% 3 3 3 3 5% 6% 60%	2940
December	1st to 10th	Night	1 5% 2 4 2 2 2 3 4 6% 68%	4710
	11th to 20th	Night	1 5% 2 4 3 3 4 4 6% 8% 60%	5321
	21st to end	Night	2 8% 3 8% 4 4 4 4 5% 6% 50%	7128

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	32% 4 19% 30% 13% 1	5184
	11th to 20th	Day	23% 4 18% 25% 23% 6%	5340
	21st to end	Day	26% 4 10% 28% 25% 5%	5844
February	1st to 10th	Day	35% 5% 16% 22% 17% 6%	1890
	11th to 20th	Day	33% 5% 12% 24% 20% 5%	1880
	21st to end	Day	36% 4 7% 24% 24% 6%	1738
March	1st to 10th	Day	24% 4 12% 24% 28% 8%	5064
	11th to 20th	Day	32% 6% 17% 25% 16% 3	5110
	21st to end	Day	27% 8% 18% 30% 15% 2	5607
April	1st to 10th	Day	27% 5% 11% 27% 21% 9%	2516
	11th to 20th	Day	32% 4 10% 23% 24% 7%	2494
	21st to end	Day	29% 4 11% 26% 25% 4	2520
May	1st to 10th	Day	24% 7% 11% 29% 24% 6%	7560
	11th to 20th	Day	20% 6% 10% 23% 33% 9%	7654
	21st to end	Day	17% 6% 8% 23% 36% 10%	9027
June	1st to 10th	Day	20% 4 7% 21% 30% 17%	2940
	11th to 20th	Day	17% 3 6% 14% 29% 32%	2940
	21st to end	Day	18% 4 7% 15% 26% 30%	2940
July	1st to 10th	Day	17% 4 5% 9% 15% 49%	6351
	11th to 20th	Day	20% 9% 13% 23% 21% 14%	5877
	21st to end	Day	24% 8% 14% 15% 19% 21%	6217
August	1st to 10th	Day	31% 11% 17% 18% 13% 10%	4208
	11th to 20th	Day	27% 8% 13% 15% 22% 15%	4103
	21st to end	Day	25% 8% 13% 19% 23% 12%	4311
September	1st to 10th	Day	29% 4 8% 14% 26% 18%	2400
	11th to 20th	Day	23% 5% 10% 17% 30% 16%	2370
	21st to end	Day	22% 3 7% 19% 36% 13%	2119
October	1st to 10th	Day	14% 3 6% 16% 39% 22%	3270
	11th to 20th	Day	23% 5% 8% 28% 29% 7%	3250
	21st to end	Day	16% 3 8% 26% 40% 7%	3548
November	1st to 10th	Day	16% 4 11% 27% 34% 7%	2041
	11th to 20th	Day	20% 4 9% 35% 25% 6%	1837
	21st to end	Day	25% 4 11% 30% 23% 7%	1680
December	1st to 10th	Day	22% 3 10% 38% 23% 3	2700
	11th to 20th	Day	23% 4 14% 29% 29% 2	3104
	21st to end	Day	30% 7% 11% 26% 21% 5%	4092
January	1st to 10th	Night	35% 6% 16% 29% 13% 1	7784
	11th to 20th	Night	21% 5% 17% 27% 23% 7%	7650
	21st to end	Night	27% 4 12% 24% 28% 5%	8370
February	1st to 10th	Night	31% 5% 14% 25% 20% 4	2730
	11th to 20th	Night	31% 5% 14% 26% 20% 5%	2636
	21st to end	Night	30% 4 12% 24% 25% 5%	2065
March	1st to 10th	Night	24% 6% 13% 21% 28% 8%	5050
	11th to 20th	Night	29% 6% 12% 26% 22% 5%	5110
	21st to end	Night	28% 9% 15% 32% 14% 2	5610
April	1st to 10th	Night	28% 5% 10% 26% 23% 7%	2102
	11th to 20th	Night	30% 4 9% 24% 24% 9%	2077
	21st to end	Night	27% 3 12% 25% 28% 5%	2100
May	1st to 10th	Night	24% 6% 11% 28% 27% 4	5381
	11th to 20th	Night	20% 5% 9% 25% 33% 9%	5238
	21st to end	Night	14% 5% 7% 22% 38% 15%	5182
June	1st to 10th	Night	12% 6% 8% 22% 33% 19%	1680
	11th to 20th	Night	14% 4 5% 15% 24% 38%	1680
	21st to end	Night	14% 4 5% 17% 26% 34%	1680
July	1st to 10th	Night	16% 4 7% 11% 11% 50%	3723
	11th to 20th	Night	15% 6% 12% 30% 20% 17%	4091
	21st to end	Night	19% 7% 14% 19% 21% 20%	4344
August	1st to 10th	Night	24% 12% 21% 16% 15% 12%	2928
	11th to 20th	Night	21% 7% 20% 15% 18% 19%	3020
	21st to end	Night	25% 7% 12% 20% 23% 13%	3597
September	1st to 10th	Night	20% 5% 10% 19% 25% 22%	2000
	11th to 20th	Night	18% 5% 11% 18% 29% 19%	2025
	21st to end	Night	16% 3 6% 20% 40% 15%	2280
October	1st to 10th	Night	12% 2 5% 15% 39% 27%	3920
	11th to 20th	Night	18% 4 9% 27% 33% 8%	3898
	21st to end	Night	19% 3 6% 24% 38% 10%	4252
November	1st to 10th	Night	17% 4 11% 28% 32% 8%	2460
	11th to 20th	Night	19% 3 10% 31% 31% 6%	2772
	21st to end	Night	25% 4 9% 27% 26% 8%	2940
December	1st to 10th	Night	18% 3 11% 38% 27% 3	4710
	11th to 20th	Night	20% 4 12% 34% 27% 3	5322
	21st to end	Night	32% 6% 13% 22% 25% 2	7128

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% 15% 28% 31% 15% 6%	330
	11th to 20th	Day	6% 12% 26% 41% 12% 3	330
	21st to end	Day	4 6% 31% 39% 14% 4	363
February	1st to 10th	Day	8% 17% 35% 30% 8% 2	330
	11th to 20th	Day	8% 23% 37% 22% 7% 2	330
	21st to end	Day	9% 17% 31% 31% 9% 2	281
March	1st to 10th	Day	12% 21% 32% 25% 9% 2	540
	11th to 20th	Day	7% 21% 33% 26% 12% 2	540
	21st to end	Day	12% 24% 33% 22% 8% 1	594
April	1st to 10th	Day	10% 17% 35% 24% 10% 3	540
	11th to 20th	Day	12% 27% 32% 17% 9% 2	532
	21st to end	Day	9% 24% 34% 20% 11% 2	540
May	1st to 10th	Day	10% 20% 35% 24% 10% 2	543
	11th to 20th	Day	6% 16% 30% 25% 17% 5%	584
	21st to end	Day	6% 15% 25% 30% 17% 7%	844
June	1st to 10th	Day	4 8% 25% 33% 22% 8%	780
	11th to 20th	Day	4 9% 31% 32% 20% 5%	780
	21st to end	Day	3 8% 27% 33% 23% 6%	780
July	1st to 10th	Day	2 2 16% 38% 33% 9%	750
	11th to 20th	Day	2 3 12% 35% 33% 15%	545
	21st to end	Day	5% 2 14% 31% 35% 13%	575
August	1st to 10th	Day	4 5% 18% 32% 31% 9%	527
	11th to 20th	Day	3 4 16% 35% 30% 11%	517
	21st to end	Day	4 3 14% 41% 28% 10%	583
September	1st to 10th	Day	6% 4 19% 31% 30% 10%	530
	11th to 20th	Day	5% 9% 27% 35% 18% 6%	530
	21st to end	Day	6% 11% 22% 27% 26% 9%	449
October	1st to 10th	Day	8% 13% 19% 25% 21% 14%	330
	11th to 20th	Day	5% 13% 25% 28% 22% 7%	330
	21st to end	Day	7% 9% 27% 30% 21% 6%	363
November	1st to 10th	Day	7% 12% 28% 28% 19% 6%	330
	11th to 20th	Day	4 9% 31% 33% 17% 6%	330
	21st to end	Day	5% 12% 27% 32% 18% 6%	330
December	1st to 10th	Day	7% 8% 34% 29% 17% 5%	330
	11th to 20th	Day	6% 9% 28% 31% 20% 6%	330
	21st to end	Day	10% 15% 31% 29% 11% 4	363
January	1st to 10th	Night	5% 8% 25% 39% 18% 5%	905
	11th to 20th	Night	5% 7% 27% 39% 18% 3	840
	21st to end	Night	5% 7% 28% 42% 15% 3	924
February	1st to 10th	Night	6% 8% 34% 39% 11% 2	840
	11th to 20th	Night	6% 10% 36% 36% 12% 1	824
	21st to end	Night	7% 10% 35% 38% 9% 1	692
March	1st to 10th	Night	5% 13% 33% 37% 11% 2	840
	11th to 20th	Night	5% 8% 29% 38% 19% 1	840
	21st to end	Night	6% 12% 33% 38% 11% 1	924
April	1st to 10th	Night	7% 11% 32% 39% 9% 1	632
	11th to 20th	Night	9% 13% 33% 34% 11% 1	623
	21st to end	Night	8% 8% 32% 35% 15% 2	630
May	1st to 10th	Night	7% 7% 29% 42% 14% 1	630
	11th to 20th	Night	7% 6% 25% 39% 20% 3	621
	21st to end	Night	6% 9% 26% 36% 20% 3	683
June	1st to 10th	Night	4 4 20% 42% 27% 3	630
	11th to 20th	Night	3 4 26% 43% 21% 3	630
	21st to end	Night	2 4 18% 43% 30% 3	630
July	1st to 10th	Night	3 1 9% 41% 42% 4	615
	11th to 20th	Night	2 2 6% 38% 46% 6%	597
	21st to end	Night	4 2 6% 35% 46% 7%	657
August	1st to 10th	Night	3 3 9% 37% 43% 5%	597
	11th to 20th	Night	3 2 7% 41% 41% 6%	594
	21st to end	Night	4 1 9% 42% 37% 7%	660
September	1st to 10th	Night	4 1 11% 45% 35% 4	600
	11th to 20th	Night	3 2 18% 44% 28% 5%	625
	21st to end	Night	4 4 17% 38% 29% 8%	800
October	1st to 10th	Night	5% 6% 22% 42% 23% 3	800
	11th to 20th	Night	3 5% 26% 40% 21% 6%	800
	21st to end	Night	7% 6% 24% 38% 20% 5%	880
November	1st to 10th	Night	3 7% 27% 38% 20% 4	820
	11th to 20th	Night	5% 9% 28% 38% 18% 4	1045
	21st to end	Night	6% 8% 29% 36% 17% 4	1050
December	1st to 10th	Night	6% 8% 27% 42% 15% 2	1050
	11th to 20th	Night	6% 11% 28% 35% 18% 2	1050
	21st to end	Night	8% 10% 31% 39% 10% 2	1155

Page generated at 2026-07-13 01:14:53. Version ac07

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