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 2024-01-13.

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	4 7% 3 5% 5% 3 5% 5% 5% 7% 51%	74653
	Night	4 7% 3 5% 4 3 4 4 5% 7% 55%	75099
Transparency	Day	32% 5% 10% 21% 22% 10%	74377
	Night	28% 5% 11% 22% 24% 10%	74897
Seeing	Day	10% 18% 30% 26% 12% 3	14089
	Night	8% 10% 25% 34% 20% 4	24375

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	4 11% 4 6% 4 3 4 4 5% 7% 47%	1708
	11th to 20th	Day	2 11% 3 6% 5% 3 3 4 5% 6% 50%	1638
	21st to end	Day	4 11% 4 8% 4 3 4 3 5% 6% 48%	1782
February	1st to 10th	Day	3 13% 4 8% 6% 3 4 4 4 5% 47%	1620
	11th to 20th	Day	3 11% 5% 9% 5% 4 4 5% 5% 7% 43%	1586
	21st to end	Day	2 14% 6% 9% 6% 3 4 4 3 6% 44%	1511
March	1st to 10th	Day	6% 10% 5% 7% 6% 3 4 4 5% 6% 44%	1980
	11th to 20th	Day	3 8% 4 6% 6% 3 4 5% 5% 7% 48%	1980
	21st to end	Day	3 13% 4 7% 5% 3 5% 5% 5% 7% 43%	2178
April	1st to 10th	Day	4 9% 3 6% 5% 3 5% 5% 5% 6% 50%	2142
	11th to 20th	Day	3 9% 4 7% 7% 3 5% 5% 5% 6% 45%	2131
	21st to end	Day	4 8% 3 5% 4 3 5% 5% 5% 8% 48%	2160
May	1st to 10th	Day	6% 7% 3 6% 6% 3 5% 5% 6% 6% 46%	2326
	11th to 20th	Day	4 6% 2 5% 5% 4 5% 7% 6% 7% 47%	2301
	21st to end	Day	4 4 2 5% 4 2 5% 5% 6% 7% 55%	2694
June	1st to 10th	Day	3 2 1 3 4 3 5% 4 6% 8% 61%	2520
	11th to 20th	Day	3 3 1 3 3 2 4 3 4 7% 68%	2520
	21st to end	Day	2 2 1 3 4 4 5% 5% 5% 8% 62%	2520
July	1st to 10th	Day	4 4 2 5% 6% 4 7% 6% 6% 8% 49%	2445
	11th to 20th	Day	4 3 2 5% 7% 5% 8% 8% 8% 9% 43%	2340
	21st to end	Day	7% 5% 3 6% 9% 5% 8% 8% 7% 10% 32%	2545
August	1st to 10th	Day	6% 5% 3 7% 7% 4 6% 6% 8% 8% 40%	2328
	11th to 20th	Day	3 4 2 6% 7% 4 6% 5% 7% 8% 46%	2258
	21st to end	Day	5% 4 2 6% 7% 4 6% 6% 7% 7% 45%	2376
September	1st to 10th	Day	6% 4 2 5% 5% 4 5% 5% 5% 8% 51%	2160
	11th to 20th	Day	5% 4 2 4 5% 4 4 5% 5% 6% 56%	2110
	21st to end	Day	4 4 2 4 4 2 3 3 3 7% 64%	1922
October	1st to 10th	Day	8% 5% 2 4 3 2 4 4 5% 6% 56%	1800
	11th to 20th	Day	4 3 1 3 3 2 3 3 3 6% 69%	1800
	21st to end	Day	4 6% 3 3 4 2 3 3 4 5% 63%	1980
November	1st to 10th	Day	2 3 2 3 3 2 4 4 4 6% 66%	1859
	11th to 20th	Day	4 6% 2 4 4 3 3 3 4 6% 62%	1673
	21st to end	Day	4 9% 4 7% 3 2 3 2 3 6% 57%	1520
December	1st to 10th	Day	5% 10% 4 6% 4 2 3 3 4 7% 51%	1520
	11th to 20th	Day	5% 10% 4 7% 6% 3 5% 4 5% 7% 43%	1926
	21st to end	Day	3 9% 5% 8% 6% 2 3 3 4 6% 50%	2794
January	1st to 10th	Night	3 10% 4 5% 5% 2 4 3 5% 7% 53%	2472
	11th to 20th	Night	3 10% 4 5% 4 2 3 3 3 6% 56%	2378
	21st to end	Night	4 10% 4 6% 4 3 4 3 5% 6% 52%	2574
February	1st to 10th	Night	3 10% 3 7% 5% 2 4 3 4 7% 52%	2340
	11th to 20th	Night	4 9% 3 7% 5% 3 4 4 5% 5% 50%	2259
	21st to end	Night	3 12% 4 7% 4 2 4 4 5% 6% 47%	1742
March	1st to 10th	Night	3 9% 4 5% 5% 3 4 5% 5% 6% 52%	1980
	11th to 20th	Night	3 8% 3 4 4 3 4 5% 4 7% 55%	1980
	21st to end	Night	4 13% 3 4 5% 3 4 5% 6% 8% 45%	2178
April	1st to 10th	Night	4 10% 4 6% 4 3 4 5% 6% 7% 47%	1818
	11th to 20th	Night	5% 8% 3 6% 5% 3 5% 5% 5% 7% 49%	1777
	21st to end	Night	6% 6% 3 4 4 2 5% 4 6% 7% 51%	1800
May	1st to 10th	Night	5% 6% 3 4 5% 3 4 5% 6% 7% 53%	1630
	11th to 20th	Night	5% 4 2 4 5% 2 4 5% 5% 6% 57%	1594
	21st to end	Night	4 5% 2 4 4 3 5% 4 5% 7% 57%	1579
June	1st to 10th	Night	2 3 1 2 3 2 3 4 7% 7% 66%	1440
	11th to 20th	Night	3 3 1 3 3 2 3 3 4 7% 68%	1440
	21st to end	Night	2 1 1 3 3 2 4 4 6% 8% 66%	1440
July	1st to 10th	Night	3 3 1 3 5% 3 5% 6% 6% 8% 57%	1510
	11th to 20th	Night	2 1 2 5% 5% 4 7% 8% 8% 10% 49%	1620
	21st to end	Night	5% 3 2 5% 6% 4 7% 7% 9% 13% 38%	1773
August	1st to 10th	Night	3 2 1 3 6% 3 5% 6% 7% 11% 52%	1611
	11th to 20th	Night	4 4 2 4 4 3 5% 4 7% 9% 54%	1642
	21st to end	Night	3 4 2 4 4 3 5% 5% 5% 9% 56%	1980
September	1st to 10th	Night	4 3 2 5% 4 3 4 6% 7% 9% 55%	1800
	11th to 20th	Night	3 2 1 3 4 3 5% 5% 5% 8% 62%	1845
	21st to end	Night	5% 2 1 2 3 2 3 4 4 5% 70%	2038
October	1st to 10th	Night	6% 3 1 3 4 3 4 4 5% 7% 60%	2160
	11th to 20th	Night	2 4 1 2 2 2 2 3 4 6% 73%	2160
	21st to end	Night	5% 6% 2 3 3 2 2 3 3 6% 65%	2376
November	1st to 10th	Night	4 4 2 3 3 1 3 4 4 7% 66%	2220
	11th to 20th	Night	4 6% 2 2 3 2 3 3 3 5% 66%	2479
	21st to end	Night	3 8% 5% 5% 4 2 3 3 5% 6% 58%	2660
December	1st to 10th	Night	4 10% 3 6% 4 2 4 4 4 4 55%	2660
	11th to 20th	Night	4 10% 3 7% 5% 3 4 5% 7% 8% 44%	3271
	21st to end	Night	4 11% 4 7% 5% 3 3 4 4 6% 49%	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	37% 4 15% 25% 16% 2	1709
	11th to 20th	Day	35% 4 14% 26% 18% 3	1638
	21st to end	Day	37% 4 12% 29% 12% 5%	1782
February	1st to 10th	Day	41% 3 16% 19% 17% 4	1620
	11th to 20th	Day	42% 4 9% 22% 19% 5%	1595
	21st to end	Day	44% 4 6% 19% 23% 4	1511
March	1st to 10th	Day	41% 4 9% 21% 22% 3	1980
	11th to 20th	Day	33% 4 12% 30% 17% 4	1980
	21st to end	Day	40% 6% 11% 23% 17% 3	2178
April	1st to 10th	Day	35% 5% 8% 23% 21% 9%	2142
	11th to 20th	Day	39% 4 9% 22% 20% 6%	2134
	21st to end	Day	33% 5% 11% 26% 22% 4	2160
May	1st to 10th	Day	36% 5% 9% 21% 24% 5%	2326
	11th to 20th	Day	33% 6% 11% 24% 21% 6%	2304
	21st to end	Day	27% 4 8% 21% 28% 11%	2694
June	1st to 10th	Day	21% 4 8% 21% 29% 17%	2520
	11th to 20th	Day	19% 3 5% 14% 30% 29%	2520
	21st to end	Day	21% 4 6% 16% 27% 28%	2520
July	1st to 10th	Day	30% 7% 9% 12% 19% 21%	2380
	11th to 20th	Day	33% 9% 15% 17% 14% 12%	2271
	21st to end	Day	44% 10% 18% 13% 11% 5%	2404
August	1st to 10th	Day	39% 9% 13% 13% 13% 13%	2313
	11th to 20th	Day	34% 7% 11% 15% 20% 13%	2258
	21st to end	Day	36% 7% 10% 18% 19% 10%	2376
September	1st to 10th	Day	32% 6% 9% 13% 24% 18%	2160
	11th to 20th	Day	28% 6% 9% 16% 25% 16%	2110
	21st to end	Day	24% 2 6% 20% 34% 14%	1922
October	1st to 10th	Day	29% 4 8% 23% 25% 12%	1800
	11th to 20th	Day	19% 3 6% 25% 35% 12%	1800
	21st to end	Day	25% 3 9% 28% 29% 6%	1980
November	1st to 10th	Day	20% 3 10% 25% 34% 7%	1859
	11th to 20th	Day	24% 4 8% 31% 28% 5%	1673
	21st to end	Day	31% 3 8% 27% 21% 10%	1520
December	1st to 10th	Day	35% 3 16% 24% 18% 5%	1520
	11th to 20th	Day	42% 4 10% 18% 24% 2	1924
	21st to end	Day	35% 6% 9% 18% 23% 10%	2794
January	1st to 10th	Night	32% 4 14% 25% 23% 2	2472
	11th to 20th	Night	32% 3 15% 26% 21% 4	2378
	21st to end	Night	34% 3 9% 30% 18% 5%	2574
February	1st to 10th	Night	35% 3 14% 22% 20% 5%	2340
	11th to 20th	Night	37% 4 10% 23% 21% 6%	2260
	21st to end	Night	38% 4 8% 22% 24% 4	1742
March	1st to 10th	Night	33% 4 10% 22% 27% 4	1980
	11th to 20th	Night	29% 5% 10% 31% 21% 4	1980
	21st to end	Night	36% 7% 11% 24% 19% 3	2178
April	1st to 10th	Night	36% 4 10% 21% 22% 7%	1818
	11th to 20th	Night	34% 5% 9% 21% 24% 7%	1777
	21st to end	Night	30% 5% 10% 26% 24% 4	1800
May	1st to 10th	Night	29% 5% 9% 25% 26% 6%	1630
	11th to 20th	Night	26% 6% 12% 27% 24% 6%	1595
	21st to end	Night	25% 6% 9% 20% 27% 12%	1579
June	1st to 10th	Night	15% 6% 6% 22% 34% 18%	1440
	11th to 20th	Night	16% 5% 6% 13% 23% 36%	1440
	21st to end	Night	15% 5% 4 16% 27% 32%	1440
July	1st to 10th	Night	23% 8% 10% 13% 17% 28%	1467
	11th to 20th	Night	25% 10% 16% 18% 16% 15%	1566
	21st to end	Night	33% 10% 22% 19% 9% 7%	1674
August	1st to 10th	Night	24% 9% 17% 18% 17% 15%	1602
	11th to 20th	Night	25% 5% 15% 16% 21% 17%	1642
	21st to end	Night	25% 5% 12% 19% 23% 15%	1980
September	1st to 10th	Night	24% 7% 11% 14% 23% 21%	1800
	11th to 20th	Night	20% 7% 11% 17% 26% 19%	1845
	21st to end	Night	18% 4 5% 20% 38% 16%	2038
October	1st to 10th	Night	23% 6% 10% 22% 25% 14%	2160
	11th to 20th	Night	14% 3 9% 22% 36% 15%	2160
	21st to end	Night	23% 3 8% 30% 28% 9%	2376
November	1st to 10th	Night	20% 4 11% 25% 32% 9%	2220
	11th to 20th	Night	22% 3 9% 29% 32% 6%	2479
	21st to end	Night	28% 4 8% 24% 25% 11%	2660
December	1st to 10th	Night	33% 4 13% 23% 21% 6%	2660
	11th to 20th	Night	36% 5% 10% 22% 23% 3	3272
	21st to end	Night	37% 4 9% 17% 25% 8%	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	15% 17% 32% 20% 13% 3	270
	11th to 20th	Day	13% 18% 33% 24% 11% 1	246
	21st to end	Day	8% 14% 42% 26% 8% 2	264
February	1st to 10th	Day	12% 28% 33% 22% 5% 1	240
	11th to 20th	Day	15% 31% 33% 15% 6%	240
	21st to end	Day	14% 33% 31% 18% 3	229
March	1st to 10th	Day	19% 30% 28% 20% 4	420
	11th to 20th	Day	13% 25% 34% 20% 7% 1	420
	21st to end	Day	18% 37% 29% 14% 2 1	462
April	1st to 10th	Day	14% 28% 35% 17% 5% 1	420
	11th to 20th	Day	19% 35% 29% 12% 4 1	412
	21st to end	Day	16% 30% 31% 17% 6%	420
May	1st to 10th	Day	16% 28% 32% 18% 6%	423
	11th to 20th	Day	11% 22% 34% 21% 10% 1	448
	21st to end	Day	9% 23% 29% 25% 10% 4	649
June	1st to 10th	Day	6% 13% 30% 30% 17% 4	630
	11th to 20th	Day	6% 16% 34% 26% 14% 5%	630
	21st to end	Day	3 12% 33% 33% 15% 4	630
July	1st to 10th	Day	5% 5% 24% 35% 25% 6%	550
	11th to 20th	Day	5% 4 20% 37% 25% 9%	444
	21st to end	Day	9% 4 17% 36% 26% 8%	487
August	1st to 10th	Day	6% 6% 23% 42% 17% 6%	447
	11th to 20th	Day	5% 4 25% 41% 18% 6%	437
	21st to end	Day	6% 5% 28% 38% 17% 6%	495
September	1st to 10th	Day	8% 8% 29% 32% 20% 4	450
	11th to 20th	Day	6% 14% 36% 30% 12% 3	450
	21st to end	Day	8% 17% 28% 29% 14% 5%	392
October	1st to 10th	Day	10% 22% 21% 24% 17% 6%	270
	11th to 20th	Day	7% 20% 26% 28% 16% 2	270
	21st to end	Day	9% 19% 34% 26% 10% 2	297
November	1st to 10th	Day	13% 24% 29% 23% 10% 1	270
	11th to 20th	Day	6% 19% 36% 25% 12% 2	270
	21st to end	Day	11% 20% 31% 24% 11% 2	270
December	1st to 10th	Day	9% 23% 32% 24% 11% 1	270
	11th to 20th	Day	10% 19% 35% 22% 12% 2	270
	21st to end	Day	15% 19% 32% 24% 8% 1	297
January	1st to 10th	Night	9% 9% 27% 34% 16% 4	775
	11th to 20th	Night	10% 9% 26% 35% 17% 3	732
	21st to end	Night	10% 9% 27% 38% 13% 4	792
February	1st to 10th	Night	8% 11% 32% 37% 11% 2	720
	11th to 20th	Night	9% 15% 32% 32% 11% 2	704
	21st to end	Night	13% 12% 33% 34% 8%	592
March	1st to 10th	Night	11% 18% 29% 29% 11% 1	720
	11th to 20th	Night	7% 11% 28% 33% 20% 1	720
	21st to end	Night	12% 15% 29% 31% 11% 2	792
April	1st to 10th	Night	10% 20% 29% 32% 9%	558
	11th to 20th	Night	10% 18% 28% 30% 12% 1	533
	21st to end	Night	11% 15% 28% 27% 17% 2	540
May	1st to 10th	Night	9% 11% 29% 35% 14% 1	540
	11th to 20th	Night	8% 10% 25% 34% 19% 5%	531
	21st to end	Night	7% 13% 28% 28% 20% 3	584
June	1st to 10th	Night	3 9% 24% 34% 27% 3	540
	11th to 20th	Night	4 11% 22% 39% 21% 3	540
	21st to end	Night	2 3 23% 37% 31% 4	540
July	1st to 10th	Night	4 2 14% 36% 38% 6%	525
	11th to 20th	Night	2 1 10% 39% 39% 8%	522
	21st to end	Night	6% 2 5% 35% 43% 8%	591
August	1st to 10th	Night	5% 3 9% 33% 43% 7%	537
	11th to 20th	Night	5% 2 13% 34% 39% 6%	534
	21st to end	Night	4 4 15% 36% 33% 8%	594
September	1st to 10th	Night	5% 3 14% 41% 30% 6%	540
	11th to 20th	Night	3 7% 19% 36% 30% 5%	585
	21st to end	Night	5% 8% 21% 33% 24% 8%	720
October	1st to 10th	Night	8% 11% 22% 37% 18% 3	720
	11th to 20th	Night	4 9% 27% 35% 21% 5%	720
	21st to end	Night	9% 8% 27% 32% 19% 5%	792
November	1st to 10th	Night	7% 9% 26% 34% 19% 3	740
	11th to 20th	Night	8% 10% 30% 32% 16% 4	907
	21st to end	Night	9% 14% 26% 31% 17% 3	950
December	1st to 10th	Night	9% 13% 27% 39% 10% 2	950
	11th to 20th	Night	11% 14% 30% 28% 16% 2	950
	21st to end	Night	12% 12% 30% 36% 9% 1	1045

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