Modest Pinon Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Modest Pinon Observatory clear sky chart from 2005-11-06 to 2024-03-08.

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	3 3 1 3 4 3 4 5% 6% 8% 60%	78767
	Night	3 3 2 4 4 3 4 5% 6% 8% 60%	80853
Transparency	Day	21% 4 8% 22% 29% 17%	78492
	Night	21% 3 9% 22% 29% 17%	80649
Seeing	Day	7% 14% 25% 28% 20% 6%	14073
	Night	5% 9% 26% 38% 20% 2	24380

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 3 2 4 4 3 4 5% 6% 8% 59%	2858
	11th to 20th	Day	1 2 1 3 3 2 3 3 5% 6% 70%	2860
	21st to end	Day	3 5% 2 4 5% 3 5% 6% 6% 8% 54%	3146
February	1st to 10th	Day	2 4 2 5% 3 3 4 4 5% 7% 61%	1733
	11th to 20th	Day	2 4 2 4 4 2 4 4 5% 8% 61%	1849
	21st to end	Day	1 3 1 4 4 3 5% 3 4 7% 65%	1570
March	1st to 10th	Day	2 3 1 4 3 3 4 6% 6% 8% 59%	1981
	11th to 20th	Day	2 5% 2 4 4 2 4 4 5% 7% 61%	1980
	21st to end	Day	2 3 2 3 3 2 4 5% 7% 9% 60%	2240
April	1st to 10th	Day	2 2 1 2 2 2 3 4 6% 8% 68%	2160
	11th to 20th	Day	3 3 2 4 4 2 3 4 5% 6% 64%	2131
	21st to end	Day	2 3 1 3 3 2 4 3 5% 7% 67%	2160
May	1st to 10th	Day	2 2 1 2 3 2 4 4 6% 9% 66%	2160
	11th to 20th	Day	4 3 2 4 5% 3 5% 5% 5% 7% 57%	2177
	21st to end	Day	2 2 2 3 3 2 4 5% 5% 7% 66%	2714
June	1st to 10th	Day	1 2 1 3 3 2 4 5% 7% 9% 62%	2520
	11th to 20th	Day	2 2 1 2 3 2 4 4 5% 6% 70%	2520
	21st to end	Day	4 3 1 4 4 3 4 6% 6% 8% 57%	2520
July	1st to 10th	Day	4 3 2 5% 6% 4 6% 8% 7% 10% 45%	2438
	11th to 20th	Day	3 3 1 3 5% 4 7% 6% 9% 11% 47%	2340
	21st to end	Day	5% 3 3 5% 7% 5% 7% 9% 8% 10% 38%	2545
August	1st to 10th	Day	3 2 2 4 6% 5% 6% 8% 9% 10% 44%	2267
	11th to 20th	Day	4 3 2 5% 6% 4 7% 7% 8% 10% 45%	2123
	21st to end	Day	3 3 1 5% 5% 3 5% 6% 8% 10% 49%	2376
September	1st to 10th	Day	5% 4 2 4 5% 3 5% 5% 7% 9% 50%	2160
	11th to 20th	Day	5% 3 1 4 4 3 4 5% 6% 7% 58%	2160
	21st to end	Day	4 2 1 3 3 1 3 3 5% 6% 69%	1954
October	1st to 10th	Day	7% 2 1 4 5% 3 4 4 4 6% 61%	1800
	11th to 20th	Day	3 3 1 2 2 2 2 2 2 5% 76%	1800
	21st to end	Day	3 2 1 3 2 2 2 3 3 5% 73%	1980
November	1st to 10th	Day	2 1 2 2 2 3 3 5% 7% 73%	1833
	11th to 20th	Day	1 2 1 2 2 2 3 4 4 6% 72%	1710
	21st to end	Day	3 4 1 3 3 2 3 3 5% 7% 66%	1710
December	1st to 10th	Day	2 3 1 3 4 2 3 4 4 7% 67%	1568
	11th to 20th	Day	2 3 2 4 4 3 5% 5% 6% 8% 57%	1926
	21st to end	Day	2 3 2 3 3 2 3 3 4 7% 67%	2798
January	1st to 10th	Night	1 3 3 4 5% 4 4 5% 6% 8% 59%	4120
	11th to 20th	Night	2 2 1 2 2 2 4 5% 5% 7% 69%	4110
	21st to end	Night	2 4 2 5% 5% 3 5% 5% 6% 9% 55%	4521
February	1st to 10th	Night	1 4 2 3 3 2 3 4 5% 7% 66%	2444
	11th to 20th	Night	2 5% 1 3 4 3 3 4 5% 8% 61%	2218
	21st to end	Night	1 3 2 4 3 2 4 4 5% 6% 65%	1884
March	1st to 10th	Night	2 3 2 3 4 3 3 4 6% 8% 62%	2136
	11th to 20th	Night	4 4 1 4 3 3 4 4 4 7% 61%	1980
	21st to end	Night	3 3 1 3 3 2 4 5% 5% 8% 63%	2116
April	1st to 10th	Night	3 2 2 3 3 2 3 4 5% 8% 66%	1800
	11th to 20th	Night	3 3 2 4 3 2 3 4 5% 8% 63%	1777
	21st to end	Night	3 2 1 4 4 2 3 4 5% 6% 66%	1800
May	1st to 10th	Night	2 3 1 3 3 2 3 4 5% 7% 65%	1800
	11th to 20th	Night	5% 4 3 4 4 3 4 5% 5% 8% 54%	1714
	21st to end	Night	3 3 1 3 4 2 3 5% 4 6% 67%	1561
June	1st to 10th	Night	2 3 2 5% 4 3 5% 5% 6% 11% 55%	1440
	11th to 20th	Night	3 2 1 3 3 2 3 4 5% 7% 67%	1440
	21st to end	Night	5% 3 2 4 4 3 6% 6% 7% 8% 52%	1440
July	1st to 10th	Night	4 4 3 4 7% 5% 7% 7% 7% 10% 41%	1516
	11th to 20th	Night	3 3 2 6% 6% 4 7% 7% 9% 13% 40%	1620
	21st to end	Night	5% 4 3 7% 7% 5% 7% 7% 10% 14% 32%	1773
August	1st to 10th	Night	3 4 2 5% 6% 4 7% 9% 9% 11% 40%	1672
	11th to 20th	Night	5% 5% 2 5% 6% 4 7% 7% 9% 10% 39%	1778
	21st to end	Night	3 2 1 4 6% 4 6% 6% 8% 12% 47%	1980
September	1st to 10th	Night	6% 3 2 4 5% 4 5% 6% 8% 9% 46%	1800
	11th to 20th	Night	5% 5% 2 4 4 3 4 5% 5% 8% 56%	1800
	21st to end	Night	4 2 2 3 3 3 3 3 4 6% 67%	2001
October	1st to 10th	Night	6% 3 2 4 4 2 3 4 5% 6% 62%	2160
	11th to 20th	Night	3 3 1 1 2 2 3 3 4 4 76%	2160
	21st to end	Night	4 2 1 3 3 1 3 3 4 5% 73%	2376
November	1st to 10th	Night	2 2 1 2 2 2 2 2 4 5% 76%	2224
	11th to 20th	Night	1 1 2 2 2 3 4 4 6% 74%	2470
	21st to end	Night	3 3 2 3 4 3 3 4 4 6% 64%	2470
December	1st to 10th	Night	2 3 1 3 3 2 3 4 6% 7% 67%	2608
	11th to 20th	Night	2 3 1 3 4 2 5% 5% 6% 9% 60%	3271
	21st to end	Night	2 4 2 3 4 3 4 4 5% 6% 64%	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	20% 2 6% 29% 36% 7%	2859
	11th to 20th	Day	16% 1 8% 37% 32% 5%	2860
	21st to end	Day	26% 2 9% 23% 32% 8%	3146
February	1st to 10th	Day	20% 3 7% 26% 29% 15%	1733
	11th to 20th	Day	21% 2 5% 25% 31% 15%	1859
	21st to end	Day	18% 1 4 20% 33% 23%	1570
March	1st to 10th	Day	20% 3 5% 20% 32% 20%	1981
	11th to 20th	Day	22% 1 7% 18% 35% 16%	1980
	21st to end	Day	19% 3 7% 20% 35% 16%	2240
April	1st to 10th	Day	14% 3 6% 18% 37% 22%	2160
	11th to 20th	Day	20% 3 3 18% 33% 23%	2134
	21st to end	Day	17% 2 5% 21% 38% 18%	2160
May	1st to 10th	Day	15% 3 6% 18% 34% 24%	2160
	11th to 20th	Day	25% 5% 8% 18% 26% 18%	2180
	21st to end	Day	17% 3 7% 17% 26% 29%	2714
June	1st to 10th	Day	16% 5% 9% 20% 27% 23%	2520
	11th to 20th	Day	14% 3 4 13% 24% 42%	2520
	21st to end	Day	24% 4 7% 19% 22% 24%	2520
July	1st to 10th	Day	29% 7% 13% 17% 17% 16%	2373
	11th to 20th	Day	27% 6% 16% 25% 17% 10%	2271
	21st to end	Day	35% 9% 19% 26% 9% 2	2404
August	1st to 10th	Day	28% 10% 16% 22% 15% 8%	2252
	11th to 20th	Day	31% 7% 14% 22% 19% 7%	2123
	21st to end	Day	27% 7% 13% 25% 23% 5%	2376
September	1st to 10th	Day	29% 6% 10% 20% 23% 11%	2160
	11th to 20th	Day	24% 4 9% 18% 27% 18%	2160
	21st to end	Day	16% 2 6% 23% 34% 19%	1954
October	1st to 10th	Day	24% 4 7% 20% 26% 20%	1800
	11th to 20th	Day	14% 2 3 13% 33% 34%	1800
	21st to end	Day	15% 1 6% 21% 38% 19%	1980
November	1st to 10th	Day	11% 3 4 22% 41% 20%	1833
	11th to 20th	Day	13% 2 6% 23% 40% 14%	1710
	21st to end	Day	18% 2 5% 21% 36% 18%	1710
December	1st to 10th	Day	17% 2 8% 34% 25% 13%	1568
	11th to 20th	Day	22% 2 11% 24% 28% 12%	1924
	21st to end	Day	18% 2 8% 21% 32% 20%	2798
January	1st to 10th	Night	23% 2 7% 25% 33% 10%	4120
	11th to 20th	Night	13% 2 9% 34% 32% 9%	4110
	21st to end	Night	25% 2 9% 25% 31% 8%	4521
February	1st to 10th	Night	17% 3 8% 25% 30% 17%	2444
	11th to 20th	Night	21% 3 7% 22% 30% 17%	2218
	21st to end	Night	18% 2 5% 19% 33% 24%	1884
March	1st to 10th	Night	19% 2 5% 23% 32% 19%	2136
	11th to 20th	Night	22% 2 6% 20% 34% 16%	1980
	21st to end	Night	18% 3 8% 20% 35% 16%	2116
April	1st to 10th	Night	15% 3 5% 21% 33% 23%	1800
	11th to 20th	Night	19% 3 4 19% 30% 25%	1777
	21st to end	Night	18% 2 6% 19% 37% 18%	1800
May	1st to 10th	Night	18% 3 7% 14% 33% 24%	1800
	11th to 20th	Night	26% 4 9% 19% 23% 19%	1715
	21st to end	Night	17% 4 8% 16% 26% 29%	1561
June	1st to 10th	Night	23% 4 12% 17% 20% 23%	1440
	11th to 20th	Night	16% 3 4 14% 21% 41%	1440
	21st to end	Night	28% 5% 11% 15% 17% 24%	1440
July	1st to 10th	Night	33% 7% 14% 17% 13% 15%	1472
	11th to 20th	Night	29% 9% 19% 22% 13% 8%	1566
	21st to end	Night	36% 9% 23% 22% 8% 1	1674
August	1st to 10th	Night	31% 9% 21% 21% 10% 9%	1663
	11th to 20th	Night	35% 7% 16% 21% 13% 7%	1778
	21st to end	Night	26% 7% 17% 27% 15% 7%	1980
September	1st to 10th	Night	29% 7% 14% 20% 20% 10%	1800
	11th to 20th	Night	25% 5% 10% 18% 21% 21%	1800
	21st to end	Night	20% 3 7% 18% 30% 22%	2001
October	1st to 10th	Night	23% 3 8% 19% 22% 24%	2160
	11th to 20th	Night	14% 2 3 14% 33% 33%	2160
	21st to end	Night	16% 2 5% 18% 39% 21%	2376
November	1st to 10th	Night	11% 2 3 22% 41% 20%	2224
	11th to 20th	Night	11% 3 6% 22% 41% 18%	2470
	21st to end	Night	21% 3 5% 19% 32% 20%	2470
December	1st to 10th	Night	17% 3 8% 29% 30% 12%	2608
	11th to 20th	Night	20% 3 9% 25% 32% 12%	3272
	21st to end	Night	19% 1 8% 23% 33% 17%	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% 20% 32% 29% 12%	270
	11th to 20th	Day	12% 21% 30% 26% 11%	270
	21st to end	Day	2 16% 34% 31% 14% 2	297
February	1st to 10th	Day	8% 25% 31% 25% 10% 1	270
	11th to 20th	Day	9% 23% 43% 20% 5%	270
	21st to end	Day	16% 30% 30% 19% 5%	225
March	1st to 10th	Day	9% 29% 31% 20% 10% 1	372
	11th to 20th	Day	11% 27% 29% 22% 10% 1	420
	21st to end	Day	11% 34% 32% 16% 7% 1	462
April	1st to 10th	Day	10% 25% 35% 20% 7% 3	420
	11th to 20th	Day	13% 29% 34% 14% 9% 1	412
	21st to end	Day	11% 25% 37% 20% 6% 1	420
May	1st to 10th	Day	5% 23% 41% 22% 8% 1	423
	11th to 20th	Day	6% 17% 33% 26% 15% 4	448
	21st to end	Day	5% 13% 30% 36% 15% 2	669
June	1st to 10th	Day	2 6% 24% 35% 29% 4	630
	11th to 20th	Day	4 7% 21% 37% 26% 4	630
	21st to end	Day	7% 4 20% 30% 29% 9%	630
July	1st to 10th	Day	5% 2 15% 33% 32% 13%	543
	11th to 20th	Day	5% 1 5% 29% 39% 21%	444
	21st to end	Day	5% 1 6% 24% 37% 27%	487
August	1st to 10th	Day	3 1 11% 28% 38% 18%	447
	11th to 20th	Day	5% 1 16% 35% 28% 14%	437
	21st to end	Day	6% 2 13% 33% 31% 16%	495
September	1st to 10th	Day	5% 4 13% 34% 30% 14%	450
	11th to 20th	Day	3 3 22% 37% 24% 10%	450
	21st to end	Day	6% 7% 25% 30% 22% 10%	298
October	1st to 10th	Day	7% 13% 24% 26% 22% 8%	270
	11th to 20th	Day	10% 8% 27% 26% 22% 6%	270
	21st to end	Day	11% 13% 25% 26% 20% 5%	297
November	1st to 10th	Day	7% 17% 31% 26% 16% 2	270
	11th to 20th	Day	3 12% 31% 32% 19% 3	270
	21st to end	Day	8% 21% 29% 27% 13% 1	270
December	1st to 10th	Day	6% 20% 29% 31% 12% 1	270
	11th to 20th	Day	7% 25% 28% 30% 10% 1	270
	21st to end	Day	12% 25% 28% 29% 6%	297
January	1st to 10th	Night	5% 12% 29% 37% 16% 1	770
	11th to 20th	Night	5% 11% 33% 36% 14% 1	760
	21st to end	Night	5% 11% 31% 36% 16% 1	836
February	1st to 10th	Night	4 15% 32% 38% 9% 1	760
	11th to 20th	Night	6% 13% 40% 33% 7% 1	744
	21st to end	Night	5% 15% 45% 30% 4	628
March	1st to 10th	Night	5% 16% 36% 33% 10% 1	750
	11th to 20th	Night	6% 12% 31% 37% 14%	720
	21st to end	Night	4 15% 36% 36% 9%	730
April	1st to 10th	Night	4 17% 41% 31% 6% 1	540
	11th to 20th	Night	6% 18% 34% 33% 9%	533
	21st to end	Night	4 17% 37% 32% 8% 1	540
May	1st to 10th	Night	4 10% 34% 42% 10%	540
	11th to 20th	Night	7% 7% 27% 41% 16% 2	531
	21st to end	Night	5% 7% 31% 41% 16%	584
June	1st to 10th	Night	3 5% 24% 46% 21% 1	540
	11th to 20th	Night	2 4 27% 46% 20% 1	540
	21st to end	Night	6% 3 16% 44% 29% 2	540
July	1st to 10th	Night	5% 2 10% 40% 39% 4	525
	11th to 20th	Night	4 1 6% 33% 49% 6%	522
	21st to end	Night	6% 2 6% 26% 51% 8%	591
August	1st to 10th	Night	6% 1 5% 28% 48% 11%	537
	11th to 20th	Night	6% 2 8% 38% 41% 5%	534
	21st to end	Night	4 1 8% 35% 46% 6%	594
September	1st to 10th	Night	6% 2 10% 42% 36% 4	540
	11th to 20th	Night	8% 3 12% 40% 34% 4	540
	21st to end	Night	6% 4 18% 41% 29% 2	590
October	1st to 10th	Night	7% 4 20% 43% 22% 3	720
	11th to 20th	Night	5% 7% 22% 44% 21% 2	720
	21st to end	Night	6% 7% 24% 36% 23% 4	792
November	1st to 10th	Night	3 7% 24% 43% 22% 2	744
	11th to 20th	Night	2 9% 28% 41% 19% 2	950
	21st to end	Night	6% 12% 26% 35% 18% 3	950
December	1st to 10th	Night	6% 11% 28% 42% 13% 1	950
	11th to 20th	Night	6% 13% 31% 36% 13%	950
	21st to end	Night	5% 16% 33% 39% 8%	1045

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