Pinon Wood Ranch Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pinon Wood Ranch Observatory clear sky chart from 2005-11-06 to 2025-11-18.

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 6% 2 6% 4 4 5% 4 6% 7% 53%	135452
	Night	3 7% 3 5% 4 3 4 3 5% 7% 56%	132387
Transparency	Day	31% 4 9% 20% 25% 12%	130341
	Night	28% 4 9% 22% 26% 11%	128514
Seeing	Day	10% 18% 30% 27% 12% 3	16628
	Night	8% 10% 27% 34% 18% 3	26788

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 10% 4 11% 5% 4 5% 3 5% 6% 45%	4098
	11th to 20th	Day	2 10% 3 9% 6% 5% 4 4 5% 6% 46%	4100
	21st to end	Day	2 10% 4 7% 4 4 4 3 4 5% 52%	4510
February	1st to 10th	Day	3 14% 4 9% 5% 4 4 3 4 5% 46%	1800
	11th to 20th	Day	3 13% 4 10% 4 5% 3 4 5% 6% 43%	1767
	21st to end	Day	2 14% 5% 9% 5% 4 4 3 4 5% 46%	1685
March	1st to 10th	Day	2 9% 4 8% 5% 4 5% 3 6% 6% 48%	4954
	11th to 20th	Day	3 14% 4 9% 5% 5% 6% 5% 6% 7% 36%	5000
	21st to end	Day	2 12% 4 7% 5% 5% 5% 4 6% 8% 42%	5486
April	1st to 10th	Day	4 9% 3 6% 5% 5% 4 4 5% 6% 50%	2380
	11th to 20th	Day	3 10% 3 8% 5% 4 5% 4 5% 6% 46%	2371
	21st to end	Day	4 9% 2 6% 4 5% 5% 4 6% 7% 48%	2400
May	1st to 10th	Day	4 7% 3 7% 6% 5% 6% 5% 7% 7% 43%	5866
	11th to 20th	Day	2 4 2 6% 5% 5% 5% 5% 7% 7% 52%	5841
	21st to end	Day	2 3 1 4 3 3 4 4 6% 7% 63%	6853
June	1st to 10th	Day	3 2 1 4 4 4 4 4 6% 8% 60%	2800
	11th to 20th	Day	3 3 1 3 3 3 3 2 4 7% 69%	2800
	21st to end	Day	2 2 1 4 4 5% 4 4 5% 8% 62%	2800
July	1st to 10th	Day	2 2 1 3 4 3 4 3 4 4 68%	6138
	11th to 20th	Day	2 2 1 4 4 5% 6% 6% 10% 12% 48%	5880
	21st to end	Day	3 3 1 5% 5% 5% 6% 5% 6% 8% 53%	6401
August	1st to 10th	Day	3 3 2 5% 5% 5% 7% 5% 9% 11% 46%	5779
	11th to 20th	Day	2 3 1 5% 5% 5% 5% 4 7% 8% 54%	5679
	21st to end	Day	3 4 1 6% 5% 6% 6% 6% 9% 10% 44%	5984
September	1st to 10th	Day	6% 4 2 5% 4 5% 4 4 5% 8% 53%	2400
	11th to 20th	Day	5% 4 2 5% 4 4 4 4 6% 6% 56%	2344
	21st to end	Day	4 4 2 4 3 3 3 3 3 7% 63%	2134
October	1st to 10th	Day	4 3 1 3 2 2 2 2 3 5% 73%	3270
	11th to 20th	Day	4 4 2 6% 5% 5% 5% 4 5% 7% 53%	3250
	21st to end	Day	3 5% 3 3 3 3 3 2 4 6% 65%	3548
November	1st to 10th	Day	2 4 2 4 3 3 3 3 5% 7% 64%	2059
	11th to 20th	Day	4 6% 2 4 4 3 3 2 4 6% 62%	1825
	21st to end	Day	3 10% 4 6% 2 3 3 2 4 5% 58%	1600
December	1st to 10th	Day	3 8% 3 4 3 2 2 2 4 8% 62%	2620
	11th to 20th	Day	3 8% 3 6% 3 3 4 3 6% 9% 52%	3026
	21st to end	Day	2 10% 4 8% 5% 3 4 3 5% 6% 51%	4004
January	1st to 10th	Night	1 9% 7% 12% 5% 4 4 3 5% 6% 44%	5895
	11th to 20th	Night	2 13% 5% 6% 5% 4 3 3 4 5% 50%	5880
	21st to end	Night	2 11% 4 7% 3 3 3 3 4 5% 53%	6468
February	1st to 10th	Night	3 11% 4 8% 4 3 4 2 4 7% 51%	2600
	11th to 20th	Night	3 10% 3 8% 4 3 3 3 5% 5% 50%	2518
	21st to end	Night	3 13% 4 8% 4 3 4 3 5% 6% 47%	1942
March	1st to 10th	Night	1 12% 4 7% 4 3 4 4 5% 5% 51%	4940
	11th to 20th	Night	2 12% 4 7% 4 4 4 4 5% 8% 46%	5000
	21st to end	Night	3 13% 4 7% 4 4 4 4 6% 7% 43%	5489
April	1st to 10th	Night	4 11% 3 6% 4 4 4 4 5% 7% 48%	2020
	11th to 20th	Night	4 9% 3 7% 5% 4 5% 4 5% 6% 48%	1977
	21st to end	Night	5% 7% 2 5% 4 3 4 3 7% 7% 52%	2000
May	1st to 10th	Night	4 7% 2 5% 4 4 5% 4 7% 8% 49%	4110
	11th to 20th	Night	4 4 2 4 4 4 4 4 6% 8% 57%	4074
	21st to end	Night	3 3 1 3 2 2 3 2 4 6% 69%	4027
June	1st to 10th	Night	2 3 1 3 3 3 4 3 6% 8% 65%	1600
	11th to 20th	Night	3 3 1 3 3 3 3 3 5% 7% 68%	1600
	21st to end	Night	2 2 1 3 3 3 4 3 7% 7% 66%	1600
July	1st to 10th	Night	2 2 1 3 3 3 5% 3 5% 5% 68%	3822
	11th to 20th	Night	1 1 1 4 3 4 5% 5% 9% 13% 53%	4100
	21st to end	Night	2 2 1 4 4 4 5% 4 7% 11% 55%	4472
August	1st to 10th	Night	2 2 1 4 4 5% 6% 5% 8% 12% 51%	4033
	11th to 20th	Night	2 2 1 3 3 4 5% 4 7% 10% 59%	4156
	21st to end	Night	3 3 2 6% 5% 5% 6% 6% 8% 10% 46%	4993
September	1st to 10th	Night	3 3 2 5% 3 3 4 5% 7% 9% 57%	2000
	11th to 20th	Night	3 2 1 4 3 4 5% 3 5% 8% 62%	2051
	21st to end	Night	4 2 1 3 3 3 3 3 4 5% 70%	2265
October	1st to 10th	Night	4 2 1 2 2 2 2 2 3 5% 75%	3920
	11th to 20th	Night	3 4 1 3 3 4 4 4 6% 8% 60%	3898
	21st to end	Night	4 6% 1 4 2 2 2 3 3 5% 67%	4252
November	1st to 10th	Night	3 4 1 3 3 2 3 3 4 6% 66%	2460
	11th to 20th	Night	4 6% 1 3 3 2 3 2 4 5% 66%	2700
	21st to end	Night	3 9% 3 5% 4 2 2 3 4 6% 58%	2800
December	1st to 10th	Night	2 6% 2 4 2 2 2 2 4 5% 68%	4570
	11th to 20th	Night	2 8% 2 6% 4 3 4 3 6% 7% 55%	5181
	21st to end	Night	3 11% 4 8% 4 4 4 4 4 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	39% 4 13% 24% 17% 2	4099
	11th to 20th	Day	39% 3 13% 16% 20% 9%	4100
	21st to end	Day	34% 4 8% 23% 23% 8%	4510
February	1st to 10th	Day	41% 4 15% 18% 17% 6%	1800
	11th to 20th	Day	42% 4 8% 22% 19% 5%	1776
	21st to end	Day	42% 4 6% 19% 25% 6%	1685
March	1st to 10th	Day	35% 4 5% 22% 27% 6%	4954
	11th to 20th	Day	46% 4 8% 23% 16% 2	5000
	21st to end	Day	39% 4 12% 27% 16% 1	5486
April	1st to 10th	Day	35% 4 7% 23% 22% 8%	2380
	11th to 20th	Day	38% 4 8% 22% 22% 6%	2374
	21st to end	Day	33% 5% 10% 24% 24% 4	2400
May	1st to 10th	Day	35% 5% 9% 22% 22% 7%	5866
	11th to 20th	Day	28% 5% 8% 20% 30% 9%	5844
	21st to end	Day	20% 3 5% 19% 41% 13%	6854
June	1st to 10th	Day	22% 4 8% 21% 29% 16%	2800
	11th to 20th	Day	18% 3 5% 14% 30% 31%	2800
	21st to end	Day	21% 3 6% 15% 27% 29%	2800
July	1st to 10th	Day	20% 3 5% 7% 16% 48%	6074
	11th to 20th	Day	27% 4 10% 24% 23% 12%	5811
	21st to end	Day	29% 4 12% 17% 21% 17%	6217
August	1st to 10th	Day	39% 5% 19% 16% 10% 10%	4208
	11th to 20th	Day	33% 5% 13% 14% 23% 13%	4114
	21st to end	Day	32% 5% 12% 18% 23% 11%	4311
September	1st to 10th	Day	30% 5% 8% 15% 25% 17%	2400
	11th to 20th	Day	27% 6% 8% 16% 26% 17%	2344
	21st to end	Day	24% 2 6% 20% 34% 14%	2134
October	1st to 10th	Day	17% 2 5% 14% 37% 25%	3270
	11th to 20th	Day	32% 2 3 27% 28% 8%	3250
	21st to end	Day	23% 2 5% 24% 40% 6%	3548
November	1st to 10th	Day	21% 3 10% 26% 34% 7%	2059
	11th to 20th	Day	24% 3 8% 32% 27% 7%	1825
	21st to end	Day	30% 3 8% 27% 23% 10%	1600
December	1st to 10th	Day	25% 2 9% 34% 25% 5%	2620
	11th to 20th	Day	30% 3 10% 27% 29% 1	3024
	21st to end	Day	34% 4 9% 25% 21% 7%	4004
January	1st to 10th	Night	42% 2 11% 21% 21% 2	5895
	11th to 20th	Night	37% 3 11% 18% 23% 9%	5880
	21st to end	Night	34% 2 8% 25% 23% 9%	6468
February	1st to 10th	Night	36% 3 14% 21% 20% 6%	2600
	11th to 20th	Night	37% 4 9% 24% 21% 5%	2519
	21st to end	Night	37% 4 7% 21% 25% 5%	1942
March	1st to 10th	Night	33% 4 6% 18% 30% 8%	4940
	11th to 20th	Night	36% 5% 9% 24% 23% 4	5000
	21st to end	Night	38% 5% 10% 31% 15% 1	5489
April	1st to 10th	Night	35% 4 9% 22% 23% 7%	2020
	11th to 20th	Night	35% 5% 8% 20% 23% 8%	1977
	21st to end	Night	29% 5% 9% 26% 27% 4	2000
May	1st to 10th	Night	28% 5% 12% 27% 25% 4	4107
	11th to 20th	Night	23% 5% 7% 25% 33% 6%	4075
	21st to end	Night	16% 4 5% 18% 39% 18%	4027
June	1st to 10th	Night	16% 5% 7% 21% 34% 17%	1600
	11th to 20th	Night	16% 5% 5% 13% 24% 36%	1600
	21st to end	Night	15% 5% 5% 16% 26% 33%	1600
July	1st to 10th	Night	19% 3 7% 10% 11% 50%	3779
	11th to 20th	Night	20% 4 10% 29% 21% 16%	4046
	21st to end	Night	23% 4 13% 21% 20% 19%	4344
August	1st to 10th	Night	32% 5% 23% 15% 13% 13%	2928
	11th to 20th	Night	25% 4 21% 13% 19% 17%	3009
	21st to end	Night	27% 4 12% 19% 25% 12%	3597
September	1st to 10th	Night	23% 6% 11% 16% 25% 20%	2000
	11th to 20th	Night	19% 6% 10% 18% 28% 18%	2051
	21st to end	Night	18% 3 5% 20% 38% 16%	2265
October	1st to 10th	Night	13% 3 5% 13% 38% 27%	3920
	11th to 20th	Night	23% 2 7% 28% 33% 8%	3898
	21st to end	Night	22% 2 5% 23% 40% 9%	4252
November	1st to 10th	Night	20% 3 10% 26% 33% 8%	2460
	11th to 20th	Night	21% 3 8% 29% 33% 7%	2700
	21st to end	Night	28% 3 7% 23% 26% 11%	2800
December	1st to 10th	Night	20% 2 7% 35% 30% 4	4570
	11th to 20th	Night	28% 3 7% 32% 26% 4	5182
	21st to end	Night	37% 3 9% 23% 23% 6%	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	14% 17% 34% 20% 12% 2	300
	11th to 20th	Day	14% 18% 32% 24% 10% 1	300
	21st to end	Day	7% 16% 40% 27% 8% 2	330
February	1st to 10th	Day	17% 26% 32% 19% 4 1	300
	11th to 20th	Day	16% 31% 34% 14% 5%	300
	21st to end	Day	15% 30% 33% 19% 3	284
March	1st to 10th	Day	20% 29% 26% 21% 4	500
	11th to 20th	Day	14% 26% 33% 19% 6% 1	500
	21st to end	Day	18% 35% 28% 15% 3 1	550
April	1st to 10th	Day	13% 26% 35% 19% 6% 1	500
	11th to 20th	Day	20% 33% 30% 13% 4 1	492
	21st to end	Day	15% 28% 32% 18% 6%	500
May	1st to 10th	Day	17% 26% 33% 18% 6% 1	503
	11th to 20th	Day	12% 22% 33% 22% 10% 1	528
	21st to end	Day	9% 22% 29% 26% 10% 4	756
June	1st to 10th	Day	6% 12% 31% 30% 16% 4	730
	11th to 20th	Day	6% 16% 34% 27% 13% 4	730
	21st to end	Day	4 12% 35% 31% 14% 4	730
July	1st to 10th	Day	5% 5% 26% 35% 23% 6%	641
	11th to 20th	Day	4 4 21% 37% 24% 10%	524
	21st to end	Day	8% 5% 20% 35% 24% 7%	575
August	1st to 10th	Day	6% 7% 24% 40% 17% 6%	527
	11th to 20th	Day	5% 4 26% 41% 19% 5%	517
	21st to end	Day	7% 5% 29% 38% 16% 5%	583
September	1st to 10th	Day	7% 7% 29% 35% 19% 3	530
	11th to 20th	Day	6% 18% 35% 28% 11% 3	530
	21st to end	Day	8% 15% 29% 30% 13% 4	464
October	1st to 10th	Day	9% 19% 24% 26% 17% 5%	330
	11th to 20th	Day	10% 22% 27% 26% 14% 2	330
	21st to end	Day	11% 16% 36% 26% 9% 2	363
November	1st to 10th	Day	12% 22% 30% 25% 10% 1	330
	11th to 20th	Day	8% 18% 36% 25% 11% 2	321
	21st to end	Day	12% 20% 33% 23% 10% 2	300
December	1st to 10th	Day	8% 22% 32% 25% 12% 2	300
	11th to 20th	Day	10% 18% 36% 24% 11% 2	300
	21st to end	Day	15% 18% 33% 24% 8% 1	330
January	1st to 10th	Night	9% 9% 29% 33% 16% 4	815
	11th to 20th	Night	10% 9% 29% 34% 16% 3	800
	21st to end	Night	9% 10% 29% 36% 12% 3	880
February	1st to 10th	Night	9% 12% 34% 34% 10% 2	800
	11th to 20th	Night	9% 15% 35% 30% 10% 2	784
	21st to end	Night	13% 11% 35% 33% 7%	660
March	1st to 10th	Night	12% 18% 31% 29% 10% 1	800
	11th to 20th	Night	8% 11% 30% 31% 19% 1	800
	21st to end	Night	12% 15% 32% 30% 10% 2	880
April	1st to 10th	Night	10% 19% 31% 32% 8%	620
	11th to 20th	Night	10% 18% 30% 30% 10% 1	593
	21st to end	Night	11% 15% 31% 27% 15% 2	600
May	1st to 10th	Night	9% 12% 31% 35% 13% 1	600
	11th to 20th	Night	8% 11% 27% 34% 17% 4	591
	21st to end	Night	7% 12% 29% 31% 19% 3	650
June	1st to 10th	Night	3 8% 25% 36% 25% 2	600
	11th to 20th	Night	4 11% 25% 39% 19% 3	600
	21st to end	Night	2 4 25% 37% 28% 4	600
July	1st to 10th	Night	4 2 18% 36% 35% 5%	585
	11th to 20th	Night	2 1 11% 42% 36% 7%	582
	21st to end	Night	6% 2 9% 36% 40% 8%	657
August	1st to 10th	Night	5% 3 11% 36% 39% 7%	597
	11th to 20th	Night	5% 2 14% 38% 36% 6%	594
	21st to end	Night	5% 4 16% 38% 31% 7%	660
September	1st to 10th	Night	5% 3 16% 44% 28% 6%	600
	11th to 20th	Night	3 7% 24% 35% 27% 5%	651
	21st to end	Night	5% 8% 25% 33% 22% 7%	800
October	1st to 10th	Night	8% 11% 24% 38% 17% 3	800
	11th to 20th	Night	6% 10% 29% 33% 19% 4	800
	21st to end	Night	9% 8% 32% 30% 17% 4	880
November	1st to 10th	Night	7% 9% 30% 33% 17% 3	820
	11th to 20th	Night	8% 10% 33% 30% 14% 4	989
	21st to end	Night	10% 14% 28% 30% 16% 3	1000
December	1st to 10th	Night	8% 13% 28% 39% 10% 2	1000
	11th to 20th	Night	11% 14% 31% 27% 15% 2	1000
	21st to end	Night	12% 12% 31% 35% 9% 1	1100

Page generated at 2025-11-14 22:55:56. Version ac07

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