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 2025-03-12.

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 5% 2 5% 4 4 5% 4 6% 8% 55%	112898
	Night	2 5% 2 5% 3 4 4 4 6% 7% 58%	114970
Transparency	Day	26% 5% 12% 22% 24% 11%	112659
	Night	24% 5% 12% 24% 25% 10%	114799
Seeing	Day	6% 12% 26% 30% 19% 6%	15692
	Night	5% 7% 24% 39% 22% 4	25995

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 11% 6% 4 4 4 8% 7% 46%	3987
	11th to 20th	Day	1 5% 2 10% 5% 4 4 4 6% 8% 51%	4100
	21st to end	Day	1 7% 3 6% 4 3 4 3 6% 7% 57%	4510
February	1st to 10th	Day	2 9% 2 7% 6% 5% 5% 4 7% 6% 47%	1800
	11th to 20th	Day	2 8% 4 6% 4 5% 5% 4 7% 7% 47%	1780
	21st to end	Day	1 8% 4 9% 6% 5% 5% 4 5% 6% 48%	1658
March	1st to 10th	Day	2 7% 3 5% 3 4 4 4 7% 8% 52%	3554
	11th to 20th	Day	2 10% 3 7% 5% 5% 4 4 7% 8% 46%	3502
	21st to end	Day	1 7% 3 7% 5% 6% 6% 6% 8% 10% 41%	3825
April	1st to 10th	Day	4 6% 2 6% 4 4 4 4 6% 7% 54%	2276
	11th to 20th	Day	2 7% 2 7% 5% 4 5% 4 7% 8% 48%	2251
	21st to end	Day	3 7% 2 5% 5% 4 4 4 6% 8% 52%	2280
May	1st to 10th	Day	3 5% 2 6% 5% 4 5% 4 6% 8% 53%	4070
	11th to 20th	Day	2 4 1 4 4 5% 6% 5% 7% 9% 53%	4098
	21st to end	Day	2 3 1 4 3 4 5% 4 7% 8% 57%	4825
June	1st to 10th	Day	2 3 1 3 3 4 4 3 6% 8% 63%	2660
	11th to 20th	Day	2 2 2 3 3 3 4 3 5% 6% 67%	2660
	21st to end	Day	2 2 1 3 4 3 4 4 6% 8% 64%	2660
July	1st to 10th	Day	2 2 1 3 3 3 4 4 5% 5% 69%	4384
	11th to 20th	Day	1 2 1 3 4 5% 7% 7% 11% 12% 47%	4110
	21st to end	Day	2 3 1 4 4 4 5% 5% 7% 8% 56%	4454
August	1st to 10th	Day	3 3 1 5% 5% 6% 8% 8% 10% 13% 38%	4092
	11th to 20th	Day	3 3 1 4 4 5% 6% 5% 8% 10% 51%	3937
	21st to end	Day	2 2 1 4 4 4 6% 6% 9% 11% 50%	4180
September	1st to 10th	Day	5% 3 1 4 4 4 5% 4 6% 6% 56%	2280
	11th to 20th	Day	3 3 1 4 4 3 5% 3 6% 6% 61%	2252
	21st to end	Day	4 3 1 4 3 3 4 2 4 6% 67%	2013
October	1st to 10th	Day	3 2 1 2 2 2 2 2 3 6% 75%	3170
	11th to 20th	Day	3 3 1 5% 4 4 5% 5% 7% 8% 55%	3150
	21st to end	Day	3 4 1 4 2 2 2 2 3 6% 70%	3438
November	1st to 10th	Day	1 3 1 3 2 3 4 3 5% 7% 68%	1942
	11th to 20th	Day	1 4 2 5% 2 3 4 4 4 5% 65%	1750
	21st to end	Day	2 6% 3 5% 3 3 3 3 5% 4 62%	1600
December	1st to 10th	Day	1 6% 2 5% 3 2 3 3 4 5% 66%	2620
	11th to 20th	Day	1 5% 3 5% 4 3 3 3 5% 8% 61%	3026
	21st to end	Day	1 8% 3 8% 4 4 4 4 5% 7% 51%	4004
January	1st to 10th	Night	1 9% 5% 10% 5% 5% 5% 4 7% 6% 45%	6007
	11th to 20th	Night	1 6% 3 8% 5% 4 4 3 6% 6% 54%	5880
	21st to end	Night	1 8% 3 7% 4 4 4 3 6% 6% 53%	6468
February	1st to 10th	Night	2 9% 3 7% 5% 4 4 3 4 6% 52%	2600
	11th to 20th	Night	3 7% 2 7% 3 5% 4 4 5% 7% 52%	2507
	21st to end	Night	2 9% 3 6% 3 4 5% 4 6% 6% 52%	1970
March	1st to 10th	Night	1 6% 2 6% 4 4 5% 5% 7% 8% 52%	3540
	11th to 20th	Night	3 9% 3 6% 4 4 4 4 6% 8% 48%	3506
	21st to end	Night	2 9% 3 7% 5% 5% 6% 4 8% 9% 42%	3828
April	1st to 10th	Night	3 6% 2 6% 4 4 4 5% 7% 7% 51%	1902
	11th to 20th	Night	4 8% 2 5% 4 3 5% 4 7% 7% 51%	1877
	21st to end	Night	6% 6% 3 4 3 3 4 3 5% 8% 54%	1900
May	1st to 10th	Night	3 7% 2 4 3 4 4 4 6% 9% 54%	2896
	11th to 20th	Night	4 3 1 4 3 3 4 4 6% 8% 58%	2803
	21st to end	Night	3 3 2 4 2 2 4 3 4 5% 67%	2762
June	1st to 10th	Night	2 2 1 2 3 3 3 4 6% 8% 67%	1520
	11th to 20th	Night	2 2 1 3 2 3 3 3 4 6% 71%	1520
	21st to end	Night	1 2 1 3 2 3 4 4 5% 8% 67%	1520
July	1st to 10th	Night	2 1 3 2 3 3 3 6% 5% 71%	2568
	11th to 20th	Night	1 1 1 3 3 3 4 4 9% 13% 58%	2860
	21st to end	Night	2 2 1 4 4 4 4 5% 7% 9% 58%	3109
August	1st to 10th	Night	2 2 1 4 4 6% 7% 7% 11% 13% 43%	2847
	11th to 20th	Night	2 2 1 3 3 4 6% 5% 7% 9% 56%	2900
	21st to end	Night	2 3 1 6% 4 4 5% 5% 7% 9% 55%	3487
September	1st to 10th	Night	3 2 1 4 3 3 4 4 6% 9% 60%	1900
	11th to 20th	Night	2 2 1 3 3 3 4 3 6% 7% 65%	1924
	21st to end	Night	4 3 1 3 2 2 2 2 4 5% 72%	2166
October	1st to 10th	Night	3 2 1 2 2 2 2 1 3 5% 79%	3800
	11th to 20th	Night	2 3 1 4 3 3 4 4 6% 7% 62%	3778
	21st to end	Night	3 5% 1 4 2 2 3 2 3 4 69%	4120
November	1st to 10th	Night	2 5% 1 3 3 3 3 3 5% 6% 67%	2340
	11th to 20th	Night	3 5% 2 4 3 3 2 3 4 5% 68%	2640
	21st to end	Night	3 6% 3 5% 3 3 3 3 5% 6% 60%	2800
December	1st to 10th	Night	1 4 2 4 2 2 2 3 4 6% 69%	4570
	11th to 20th	Night	1 5% 2 4 3 3 4 4 6% 8% 59%	5181
	21st to end	Night	2 8% 3 8% 4 4 4 4 5% 6% 50%	6974

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	34% 4 18% 26% 16% 1	3988
	11th to 20th	Day	30% 5% 20% 19% 22% 5%	4100
	21st to end	Day	27% 4 11% 28% 24% 5%	4510
February	1st to 10th	Day	36% 5% 17% 21% 16% 6%	1800
	11th to 20th	Day	34% 4 12% 25% 20% 5%	1789
	21st to end	Day	37% 4 7% 22% 24% 6%	1658
March	1st to 10th	Day	27% 4 14% 27% 24% 4	3554
	11th to 20th	Day	35% 4 20% 26% 12% 2	3502
	21st to end	Day	34% 8% 17% 22% 16% 2	3825
April	1st to 10th	Day	29% 4 12% 26% 21% 9%	2276
	11th to 20th	Day	34% 4 11% 22% 22% 7%	2254
	21st to end	Day	31% 3 12% 27% 24% 4	2280
May	1st to 10th	Day	28% 5% 10% 22% 25% 9%	4070
	11th to 20th	Day	25% 6% 11% 27% 23% 9%	4101
	21st to end	Day	21% 5% 10% 19% 36% 9%	4825
June	1st to 10th	Day	20% 4 7% 21% 30% 18%	2660
	11th to 20th	Day	18% 3 6% 14% 28% 31%	2660
	21st to end	Day	19% 4 7% 17% 27% 27%	2660
July	1st to 10th	Day	18% 4 6% 10% 16% 46%	4316
	11th to 20th	Day	22% 9% 12% 23% 20% 14%	4041
	21st to end	Day	24% 7% 12% 16% 15% 26%	4314
August	1st to 10th	Day	31% 11% 18% 18% 12% 10%	4078
	11th to 20th	Day	27% 9% 13% 15% 22% 14%	3976
	21st to end	Day	25% 8% 12% 19% 23% 12%	4179
September	1st to 10th	Day	29% 4 8% 14% 26% 19%	2280
	11th to 20th	Day	23% 5% 10% 16% 29% 17%	2252
	21st to end	Day	21% 3 6% 19% 36% 14%	2013
October	1st to 10th	Day	14% 3 6% 16% 39% 22%	3170
	11th to 20th	Day	23% 5% 8% 28% 29% 7%	3150
	21st to end	Day	16% 3 8% 26% 39% 7%	3438
November	1st to 10th	Day	17% 4 11% 26% 35% 7%	1942
	11th to 20th	Day	21% 4 9% 33% 26% 7%	1750
	21st to end	Day	25% 4 10% 29% 25% 8%	1600
December	1st to 10th	Day	22% 3 10% 39% 24% 3	2620
	11th to 20th	Day	24% 4 14% 29% 29% 2	3024
	21st to end	Day	31% 7% 11% 26% 21% 5%	4004
January	1st to 10th	Night	36% 5% 16% 26% 16% 1	6007
	11th to 20th	Night	27% 6% 19% 21% 21% 7%	5880
	21st to end	Night	28% 5% 12% 25% 25% 4	6468
February	1st to 10th	Night	33% 5% 15% 24% 19% 5%	2600
	11th to 20th	Night	31% 4 14% 26% 20% 5%	2508
	21st to end	Night	31% 4 11% 23% 26% 5%	1970
March	1st to 10th	Night	25% 6% 15% 25% 26% 3	3540
	11th to 20th	Night	31% 8% 15% 30% 15% 2	3506
	21st to end	Night	32% 10% 17% 24% 15% 2	3828
April	1st to 10th	Night	29% 5% 10% 26% 23% 7%	1902
	11th to 20th	Night	31% 4 10% 24% 23% 8%	1877
	21st to end	Night	29% 3 13% 26% 25% 4	1900
May	1st to 10th	Night	25% 5% 10% 21% 34% 5%	2896
	11th to 20th	Night	21% 6% 10% 31% 25% 8%	2804
	21st to end	Night	18% 5% 7% 17% 36% 18%	2762
June	1st to 10th	Night	12% 6% 7% 22% 34% 19%	1520
	11th to 20th	Night	15% 4 5% 16% 24% 36%	1520
	21st to end	Night	15% 4 5% 18% 27% 30%	1520
July	1st to 10th	Night	15% 4 7% 11% 12% 50%	2528
	11th to 20th	Night	15% 5% 12% 33% 17% 19%	2806
	21st to end	Night	20% 8% 14% 18% 18% 22%	3011
August	1st to 10th	Night	25% 12% 22% 16% 14% 12%	2838
	11th to 20th	Night	22% 7% 21% 15% 17% 18%	2927
	21st to end	Night	25% 7% 11% 21% 24% 13%	3487
September	1st to 10th	Night	20% 5% 10% 18% 25% 22%	1900
	11th to 20th	Night	18% 5% 11% 18% 28% 20%	1924
	21st to end	Night	16% 3 5% 19% 41% 16%	2166
October	1st to 10th	Night	12% 2 6% 15% 39% 27%	3800
	11th to 20th	Night	18% 4 9% 27% 33% 8%	3778
	21st to end	Night	19% 3 6% 24% 38% 10%	4120
November	1st to 10th	Night	17% 5% 11% 27% 31% 8%	2340
	11th to 20th	Night	19% 3 10% 30% 31% 6%	2640
	21st to end	Night	26% 3 9% 26% 28% 8%	2800
December	1st to 10th	Night	18% 3 11% 38% 28% 3	4570
	11th to 20th	Night	21% 4 12% 34% 27% 2	5182
	21st to end	Night	33% 6% 12% 22% 24% 2	6974

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	5% 15% 26% 31% 16% 6%	300
	11th to 20th	Day	7% 13% 26% 38% 12% 3	300
	21st to end	Day	3 6% 31% 38% 16% 5%	330
February	1st to 10th	Day	8% 18% 36% 29% 7% 2	300
	11th to 20th	Day	7% 24% 37% 23% 7% 2	300
	21st to end	Day	10% 19% 30% 30% 9% 2	257
March	1st to 10th	Day	12% 21% 32% 24% 9% 2	500
	11th to 20th	Day	7% 20% 32% 27% 12% 2	465
	21st to end	Day	14% 25% 33% 21% 7% 1	506
April	1st to 10th	Day	11% 18% 36% 23% 8% 3	460
	11th to 20th	Day	13% 26% 32% 18% 9% 2	452
	21st to end	Day	9% 23% 35% 21% 11% 2	460
May	1st to 10th	Day	10% 21% 36% 22% 8% 2	463
	11th to 20th	Day	6% 15% 30% 25% 19% 5%	502
	21st to end	Day	6% 16% 24% 30% 17% 7%	734
June	1st to 10th	Day	4 8% 25% 33% 22% 9%	680
	11th to 20th	Day	4 9% 31% 31% 20% 5%	680
	21st to end	Day	2 6% 26% 35% 24% 6%	680
July	1st to 10th	Day	2 2 16% 37% 34% 9%	652
	11th to 20th	Day	2 3 12% 35% 32% 15%	484
	21st to end	Day	5% 2 13% 31% 35% 14%	531
August	1st to 10th	Day	4 6% 16% 32% 33% 10%	487
	11th to 20th	Day	4 5% 17% 36% 28% 10%	477
	21st to end	Day	4 3 14% 41% 28% 10%	539
September	1st to 10th	Day	7% 4 20% 30% 30% 10%	490
	11th to 20th	Day	4 9% 27% 34% 19% 6%	490
	21st to end	Day	5% 11% 22% 26% 27% 8%	413
October	1st to 10th	Day	7% 14% 16% 26% 21% 15%	300
	11th to 20th	Day	4 14% 23% 29% 23% 7%	300
	21st to end	Day	8% 8% 28% 30% 21% 5%	330
November	1st to 10th	Day	8% 13% 29% 26% 18% 5%	300
	11th to 20th	Day	4 9% 32% 32% 15% 7%	300
	21st to end	Day	5% 12% 27% 32% 17% 6%	300
December	1st to 10th	Day	6% 9% 34% 29% 17% 5%	300
	11th to 20th	Day	6% 9% 27% 32% 20% 5%	300
	21st to end	Day	10% 15% 29% 30% 11% 4	330
January	1st to 10th	Night	5% 8% 24% 40% 19% 5%	862
	11th to 20th	Night	6% 8% 26% 39% 19% 3	800
	21st to end	Night	6% 7% 27% 42% 15% 3	880
February	1st to 10th	Night	6% 9% 34% 38% 10% 2	800
	11th to 20th	Night	6% 9% 35% 37% 12% 1	784
	21st to end	Night	7% 11% 34% 39% 9% 1	660
March	1st to 10th	Night	5% 13% 32% 37% 11% 2	800
	11th to 20th	Night	5% 7% 26% 40% 20% 1	766
	21st to end	Night	6% 13% 31% 38% 11% 1	836
April	1st to 10th	Night	8% 11% 33% 38% 10% 1	572
	11th to 20th	Night	9% 12% 31% 34% 12% 2	563
	21st to end	Night	9% 9% 29% 35% 16% 2	570
May	1st to 10th	Night	7% 7% 29% 41% 14% 1	570
	11th to 20th	Night	7% 5% 22% 41% 21% 4	561
	21st to end	Night	7% 9% 25% 35% 21% 3	617
June	1st to 10th	Night	4 5% 18% 41% 29% 4	570
	11th to 20th	Night	2 5% 25% 42% 23% 3	570
	21st to end	Night	2 3 15% 45% 33% 4	570
July	1st to 10th	Night	3 1 7% 39% 44% 5%	555
	11th to 20th	Night	2 1 5% 37% 48% 6%	552
	21st to end	Night	4 2 5% 34% 48% 7%	624
August	1st to 10th	Night	3 3 8% 35% 45% 6%	567
	11th to 20th	Night	3 2 7% 41% 41% 6%	564
	21st to end	Night	4 1 9% 42% 36% 7%	627
September	1st to 10th	Night	4 1 11% 44% 36% 4	570
	11th to 20th	Night	3 2 17% 43% 29% 5%	594
	21st to end	Night	4 4 17% 38% 29% 8%	760
October	1st to 10th	Night	5% 6% 21% 41% 24% 3	760
	11th to 20th	Night	3 5% 24% 40% 22% 6%	760
	21st to end	Night	7% 6% 23% 37% 20% 6%	836
November	1st to 10th	Night	4 8% 26% 38% 21% 4	780
	11th to 20th	Night	5% 9% 28% 36% 18% 4	995
	21st to end	Night	6% 9% 29% 34% 18% 4	1000
December	1st to 10th	Night	5% 9% 27% 42% 15% 2	1000
	11th to 20th	Night	7% 11% 28% 35% 18% 2	1000
	21st to end	Night	8% 10% 29% 40% 11% 2	1100

Page generated at 2025-03-09 06:08:44. Version ac07

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