Cosmic Orchard Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cosmic Orchard Observatory clear sky chart from 2005-11-06 to 2024-01-27.

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	16% 11% 4 7% 6% 3 5% 5% 5% 7% 31%	75043
	Night	16% 11% 5% 7% 6% 3 4 4 5% 6% 31%	74968
Transparency	Day	52% 4 11% 20% 11% 1	74763
	Night	54% 4 11% 19% 11% 2	74768
Seeing	Day	22% 12% 28% 22% 12% 5%	13842
	Night	23% 10% 26% 27% 12% 1	23528

By Month

Percentage Cloud Cover SE (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	18% 18% 8% 11% 9% 4 4 4 4 4 17%	1706
	11th to 20th	Day	20% 19% 9% 12% 8% 4 5% 4 4 4 12%	1710
	21st to end	Day	19% 19% 9% 14% 8% 4 4 4 4 4 12%	1836
February	1st to 10th	Day	18% 19% 6% 10% 8% 4 4 4 4 4 20%	1620
	11th to 20th	Day	15% 13% 8% 15% 9% 4 4 5% 4 5% 18%	1645
	21st to end	Day	18% 13% 4 12% 7% 4 4 5% 4 6% 22%	1480
March	1st to 10th	Day	19% 14% 6% 7% 5% 3 4 3 4 7% 26%	1912
	11th to 20th	Day	17% 14% 5% 9% 5% 3 4 3 4 5% 30%	1980
	21st to end	Day	22% 12% 4 8% 6% 3 4 4 4 6% 26%	2178
April	1st to 10th	Day	15% 13% 5% 7% 5% 3 4 5% 5% 6% 32%	1998
	11th to 20th	Day	18% 11% 3 5% 5% 4 5% 4 5% 6% 33%	2312
	21st to end	Day	22% 10% 3 7% 4 3 4 3 5% 6% 33%	2340
May	1st to 10th	Day	18% 8% 4 7% 6% 4 6% 5% 6% 7% 31%	2340
	11th to 20th	Day	18% 9% 3 6% 5% 4 4 5% 7% 7% 34%	2301
	21st to end	Day	9% 6% 3 6% 6% 4 5% 6% 7% 10% 38%	2531
June	1st to 10th	Day	14% 6% 3 5% 6% 3 5% 5% 6% 9% 37%	2492
	11th to 20th	Day	12% 6% 3 6% 7% 3 5% 6% 6% 7% 39%	2554
	21st to end	Day	11% 5% 2 5% 5% 4 5% 6% 7% 10% 40%	2629
July	1st to 10th	Day	10% 5% 3 6% 5% 3 4 5% 6% 9% 43%	2462
	11th to 20th	Day	10% 6% 3 6% 5% 3 5% 5% 7% 11% 41%	2340
	21st to end	Day	10% 6% 3 5% 5% 3 6% 6% 8% 10% 40%	2547
August	1st to 10th	Day	8% 6% 2 5% 6% 4 6% 6% 7% 9% 41%	2327
	11th to 20th	Day	11% 7% 2 6% 6% 3 5% 6% 7% 10% 37%	2303
	21st to end	Day	11% 5% 2 6% 5% 4 6% 5% 7% 10% 39%	2553
September	1st to 10th	Day	14% 6% 3 4 5% 4 5% 6% 6% 8% 39%	2036
	11th to 20th	Day	12% 6% 3 6% 6% 3 4 5% 5% 8% 42%	1980
	21st to end	Day	17% 8% 3 6% 5% 2 4 4 6% 8% 39%	1980
October	1st to 10th	Day	15% 6% 3 7% 6% 3 4 5% 5% 9% 37%	1877
	11th to 20th	Day	19% 9% 3 6% 5% 3 4 5% 5% 6% 35%	1800
	21st to end	Day	23% 12% 4 7% 6% 3 4 5% 5% 5% 27%	1949
November	1st to 10th	Day	14% 11% 5% 6% 5% 3 4 3 4 7% 37%	1672
	11th to 20th	Day	18% 16% 5% 7% 5% 2 4 4 4 6% 28%	1710
	21st to end	Day	18% 17% 7% 9% 6% 3 4 4 4 7% 19%	1535
December	1st to 10th	Day	17% 21% 8% 11% 7% 3 4 3 3 5% 17%	1520
	11th to 20th	Day	18% 18% 8% 14% 6% 3 4 4 5% 5% 16%	1910
	21st to end	Day	25% 23% 8% 9% 7% 3 3 4 4 4 10%	2978
January	1st to 10th	Night	19% 17% 8% 12% 7% 3 4 4 3 4 20%	2459
	11th to 20th	Night	20% 19% 7% 12% 9% 3 4 3 3 4 15%	2470
	21st to end	Night	19% 18% 7% 12% 8% 3 4 3 3 5% 18%	2664
February	1st to 10th	Night	22% 14% 6% 12% 7% 3 4 4 4 5% 20%	2340
	11th to 20th	Night	18% 16% 6% 10% 7% 4 5% 5% 4 5% 21%	2197
	21st to end	Night	20% 13% 6% 10% 7% 4 4 3 4 5% 24%	1776
March	1st to 10th	Night	18% 11% 6% 8% 6% 3 4 4 4 5% 31%	2048
	11th to 20th	Night	17% 11% 4 6% 5% 3 4 6% 6% 6% 34%	1980
	21st to end	Night	20% 12% 5% 7% 5% 3 4 4 4 5% 32%	2178
April	1st to 10th	Night	15% 11% 5% 7% 6% 2 5% 4 5% 6% 32%	1962
	11th to 20th	Night	16% 9% 4 6% 5% 3 5% 5% 5% 7% 33%	1612
	21st to end	Night	16% 8% 3 7% 5% 3 5% 4 6% 6% 37%	1620
May	1st to 10th	Night	18% 10% 4 7% 6% 3 4 5% 6% 7% 29%	1620
	11th to 20th	Night	16% 9% 3 5% 5% 3 4 5% 6% 7% 36%	1592
	21st to end	Night	9% 5% 3 4 5% 4 5% 6% 7% 10% 42%	1744
June	1st to 10th	Night	10% 5% 3 6% 5% 4 5% 5% 6% 6% 44%	1463
	11th to 20th	Night	9% 5% 3 6% 6% 4 5% 5% 7% 10% 40%	1397
	21st to end	Night	10% 5% 2 4 5% 3 6% 4 6% 11% 44%	1323
July	1st to 10th	Night	9% 5% 2 5% 5% 4 4 5% 5% 8% 48%	1494
	11th to 20th	Night	7% 5% 2 5% 5% 4 5% 5% 6% 10% 46%	1620
	21st to end	Night	8% 6% 2 5% 5% 4 5% 6% 6% 9% 44%	1771
August	1st to 10th	Night	7% 5% 3 5% 5% 3 4 6% 6% 9% 48%	1611
	11th to 20th	Night	9% 5% 3 6% 6% 3 4 5% 7% 9% 44%	1598
	21st to end	Night	8% 5% 3 6% 5% 4 5% 5% 6% 8% 44%	1783
September	1st to 10th	Night	11% 6% 2 5% 5% 3 5% 5% 5% 7% 44%	1920
	11th to 20th	Night	11% 4 2 4 5% 3 4 4 6% 8% 50%	1980
	21st to end	Night	15% 7% 2 6% 5% 4 5% 4 5% 7% 41%	1980
October	1st to 10th	Night	14% 6% 2 5% 5% 3 4 4 6% 7% 43%	2082
	11th to 20th	Night	20% 8% 3 6% 6% 3 3 5% 5% 6% 34%	2160
	21st to end	Night	27% 9% 3 6% 5% 3 4 4 5% 5% 28%	2402
November	1st to 10th	Night	16% 10% 4 5% 5% 4 4 4 5% 7% 36%	2406
	11th to 20th	Night	17% 16% 5% 7% 6% 3 4 4 5% 5% 28%	2470
	21st to end	Night	22% 16% 5% 8% 6% 3 5% 4 4 6% 23%	2641
December	1st to 10th	Night	20% 19% 8% 9% 5% 3 4 3 4 6% 19%	2660
	11th to 20th	Night	18% 19% 6% 10% 6% 3 4 4 5% 5% 22%	3285
	21st to end	Night	25% 21% 7% 9% 7% 3 4 4 4 5% 12%	4660

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	72% 4 9% 11% 4	1707
	11th to 20th	Day	77% 3 10% 8% 2	1710
	21st to end	Day	77% 3 7% 8% 5%	1836
February	1st to 10th	Day	69% 3 10% 12% 5%	1620
	11th to 20th	Day	68% 5% 7% 14% 5% 1	1654
	21st to end	Day	63% 4 11% 13% 7% 1	1480
March	1st to 10th	Day	59% 3 11% 20% 6%	1912
	11th to 20th	Day	58% 3 9% 18% 10% 1	1980
	21st to end	Day	60% 3 8% 19% 8% 1	2178
April	1st to 10th	Day	53% 4 10% 19% 13% 1	1998
	11th to 20th	Day	52% 4 10% 18% 14% 2	2312
	21st to end	Day	53% 3 10% 22% 10% 2	2340
May	1st to 10th	Day	52% 5% 10% 21% 10% 2	2340
	11th to 20th	Day	49% 5% 10% 18% 15% 3	2305
	21st to end	Day	40% 6% 14% 25% 14% 2	2531
June	1st to 10th	Day	44% 4 11% 26% 14% 1	2492
	11th to 20th	Day	42% 6% 14% 23% 14% 2	2554
	21st to end	Day	37% 7% 13% 24% 17% 3	2629
July	1st to 10th	Day	38% 5% 10% 25% 18% 3	2396
	11th to 20th	Day	36% 6% 13% 27% 16% 2	2271
	21st to end	Day	37% 6% 13% 26% 16% 3	2405
August	1st to 10th	Day	38% 6% 12% 29% 14% 1	2314
	11th to 20th	Day	41% 6% 13% 26% 12% 2	2303
	21st to end	Day	39% 7% 12% 24% 16% 3	2553
September	1st to 10th	Day	40% 6% 14% 21% 16% 3	2036
	11th to 20th	Day	40% 4 13% 26% 15% 2	1980
	21st to end	Day	44% 4 10% 24% 18% 1	1980
October	1st to 10th	Day	44% 6% 10% 24% 15% 1	1877
	11th to 20th	Day	50% 4 11% 22% 12% 2	1800
	21st to end	Day	59% 4 12% 15% 9% 1	1949
November	1st to 10th	Day	49% 4 10% 22% 14% 1	1672
	11th to 20th	Day	58% 3 9% 18% 9% 2	1710
	21st to end	Day	67% 4 9% 14% 6%	1535
December	1st to 10th	Day	72% 3 10% 12% 3	1520
	11th to 20th	Day	72% 2 8% 14% 3	1906
	21st to end	Day	80% 3 9% 7% 2	2978
January	1st to 10th	Night	70% 3 7% 14% 6%	2459
	11th to 20th	Night	74% 3 9% 11% 2	2470
	21st to end	Night	71% 3 9% 13% 4 1	2664
February	1st to 10th	Night	68% 3 10% 14% 4 1	2340
	11th to 20th	Night	65% 4 8% 16% 7%	2199
	21st to end	Night	65% 3 9% 14% 7% 2	1776
March	1st to 10th	Night	56% 3 9% 22% 9% 1	2048
	11th to 20th	Night	50% 5% 10% 20% 12% 2	1980
	21st to end	Night	56% 4 7% 21% 10% 2	2178
April	1st to 10th	Night	53% 4 11% 18% 13% 2	1962
	11th to 20th	Night	50% 4 11% 17% 15% 3	1612
	21st to end	Night	47% 4 11% 21% 14% 3	1620
May	1st to 10th	Night	53% 5% 11% 17% 11% 3	1620
	11th to 20th	Night	47% 4 11% 18% 17% 3	1593
	21st to end	Night	35% 6% 16% 26% 14% 2	1745
June	1st to 10th	Night	40% 5% 10% 27% 14% 3	1463
	11th to 20th	Night	39% 6% 15% 20% 18% 2	1397
	21st to end	Night	36% 6% 13% 27% 17% 2	1323
July	1st to 10th	Night	34% 5% 12% 25% 20% 5%	1451
	11th to 20th	Night	33% 5% 14% 26% 19% 3	1566
	21st to end	Night	36% 7% 12% 23% 18% 4	1672
August	1st to 10th	Night	31% 6% 14% 29% 19% 1	1600
	11th to 20th	Night	36% 5% 16% 27% 13% 2	1598
	21st to end	Night	37% 4 12% 25% 18% 3	1783
September	1st to 10th	Night	39% 4 13% 25% 15% 4	1920
	11th to 20th	Night	33% 4 11% 28% 22% 2	1980
	21st to end	Night	44% 3 11% 22% 19% 1	1980
October	1st to 10th	Night	40% 4 12% 24% 19% 1	2082
	11th to 20th	Night	51% 4 10% 21% 13% 1	2160
	21st to end	Night	58% 3 9% 18% 9% 1	2402
November	1st to 10th	Night	48% 3 11% 22% 13% 2	2406
	11th to 20th	Night	59% 2 8% 19% 9% 2	2470
	21st to end	Night	64% 3 11% 16% 5%	2641
December	1st to 10th	Night	69% 3 10% 12% 5%	2660
	11th to 20th	Night	66% 3 12% 16% 3	3288
	21st to end	Night	77% 2 11% 8% 2	4660

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	30% 20% 31% 13% 6% 1	270
	11th to 20th	Day	31% 24% 32% 9% 3 1	270
	21st to end	Day	32% 23% 31% 12% 2 1	282
February	1st to 10th	Day	34% 20% 36% 10% 1	240
	11th to 20th	Day	30% 26% 33% 10% 1	240
	21st to end	Day	31% 30% 31% 7% 1	198
March	1st to 10th	Day	28% 20% 31% 16% 5%	352
	11th to 20th	Day	26% 12% 37% 18% 5% 1	420
	21st to end	Day	34% 15% 27% 18% 6%	462
April	1st to 10th	Day	25% 14% 33% 20% 7% 1	420
	11th to 20th	Day	27% 15% 26% 19% 8% 4	412
	21st to end	Day	31% 12% 32% 16% 7% 3	420
May	1st to 10th	Day	25% 13% 29% 22% 9% 3	423
	11th to 20th	Day	22% 11% 29% 23% 11% 4	447
	21st to end	Day	15% 7% 26% 28% 17% 7%	485
June	1st to 10th	Day	14% 7% 31% 31% 14% 3	450
	11th to 20th	Day	17% 7% 22% 34% 17% 4	484
	21st to end	Day	14% 8% 31% 29% 14% 4	630
July	1st to 10th	Day	12% 4 22% 30% 20% 12%	566
	11th to 20th	Day	16% 4 20% 30% 20% 9%	444
	21st to end	Day	12% 5% 25% 29% 22% 7%	488
August	1st to 10th	Day	13% 4 18% 29% 25% 11%	446
	11th to 20th	Day	16% 4 20% 28% 21% 10%	439
	21st to end	Day	14% 5% 22% 27% 22% 11%	495
September	1st to 10th	Day	17% 5% 21% 25% 20% 11%	450
	11th to 20th	Day	13% 5% 17% 28% 25% 13%	450
	21st to end	Day	21% 11% 25% 21% 13% 9%	450
October	1st to 10th	Day	15% 8% 27% 24% 19% 7%	450
	11th to 20th	Day	22% 16% 33% 20% 8% 1	450
	21st to end	Day	32% 16% 31% 17% 5%	464
November	1st to 10th	Day	21% 20% 33% 16% 10% 1	270
	11th to 20th	Day	30% 21% 28% 14% 5% 1	270
	21st to end	Day	29% 20% 35% 14% 1	187
December	1st to 10th	Day	26% 21% 36% 12% 4 2	180
	11th to 20th	Day	24% 26% 37% 10% 3	180
	21st to end	Day	29% 21% 34% 14% 2	258
January	1st to 10th	Night	29% 19% 31% 16% 4	760
	11th to 20th	Night	33% 17% 30% 16% 4 1	760
	21st to end	Night	30% 17% 30% 21% 3	820
February	1st to 10th	Night	30% 16% 31% 20% 3	720
	11th to 20th	Night	27% 16% 34% 19% 4	703
	21st to end	Night	29% 17% 34% 19% 2	592
March	1st to 10th	Night	23% 15% 33% 23% 5%	720
	11th to 20th	Night	23% 14% 32% 23% 7% 1	720
	21st to end	Night	26% 11% 27% 26% 9% 1	792
April	1st to 10th	Night	21% 15% 30% 28% 6%	720
	11th to 20th	Night	22% 10% 32% 25% 10% 1	548
	21st to end	Night	20% 9% 33% 29% 8% 1	540
May	1st to 10th	Night	23% 7% 26% 33% 9% 1	540
	11th to 20th	Night	22% 4 24% 36% 13% 2	531
	21st to end	Night	12% 3 23% 38% 22% 3	584
June	1st to 10th	Night	10% 3 27% 43% 16% 1	383
	11th to 20th	Night	12% 5% 22% 43% 18% 1	360
	21st to end	Night	13% 4 23% 41% 19%	423
July	1st to 10th	Night	11% 2 13% 40% 31% 3	525
	11th to 20th	Night	11% 2 19% 38% 27% 3	522
	21st to end	Night	11% 2 16% 41% 28% 2	591
August	1st to 10th	Night	9% 1 14% 44% 27% 4	537
	11th to 20th	Night	13% 4 12% 38% 30% 4	534
	21st to end	Night	11% 3 16% 35% 30% 5%	595
September	1st to 10th	Night	15% 6% 13% 34% 26% 5%	720
	11th to 20th	Night	13% 3 15% 33% 29% 5%	720
	21st to end	Night	17% 6% 23% 30% 19% 4	720
October	1st to 10th	Night	18% 7% 22% 32% 19% 2	720
	11th to 20th	Night	25% 13% 28% 25% 8% 1	720
	21st to end	Night	32% 12% 27% 24% 5%	792
November	1st to 10th	Night	23% 12% 29% 26% 10% 1	740
	11th to 20th	Night	30% 14% 30% 17% 7% 1	760
	21st to end	Night	32% 14% 30% 18% 6%	760
December	1st to 10th	Night	33% 13% 31% 17% 5%	760
	11th to 20th	Night	29% 17% 31% 19% 3	760
	21st to end	Night	32% 14% 33% 19% 2	836

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