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 2026-06-01.

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	15% 11% 4 9% 5% 4 4 3 5% 7% 30%	132291
	Night	16% 13% 5% 10% 5% 4 4 3 5% 6% 30%	130824
Transparency	Day	53% 4 11% 20% 11% 1	135923
	Night	55% 4 10% 19% 11% 1	135263
Seeing	Day	22% 13% 28% 21% 11% 4	16947
	Night	22% 11% 27% 27% 12% 1	26564

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	16% 21% 7% 23% 6% 4 3 2 4 4 12%	5258
	11th to 20th	Day	13% 21% 9% 17% 9% 5% 5% 2 3 4 13%	5280
	21st to end	Day	19% 18% 8% 14% 8% 7% 4 3 3 4 12%	5780
February	1st to 10th	Day	16% 20% 5% 11% 6% 5% 4 3 4 4 22%	1890
	11th to 20th	Day	14% 15% 7% 16% 8% 5% 4 3 4 5% 19%	1927
	21st to end	Day	17% 14% 4 13% 5% 4 4 4 5% 6% 22%	1730
March	1st to 10th	Day	17% 14% 6% 12% 4 4 3 3 4 6% 27%	4880
	11th to 20th	Day	12% 13% 4 11% 4 4 4 3 4 5% 36%	5090
	21st to end	Day	20% 14% 5% 9% 4 4 4 3 4 6% 27%	5586
April	1st to 10th	Day	16% 14% 4 8% 5% 4 4 4 5% 6% 30%	2331
	11th to 20th	Day	17% 12% 3 7% 5% 4 5% 3 5% 6% 33%	2702
	21st to end	Day	20% 11% 2 7% 4 4 4 3 5% 6% 33%	2730
May	1st to 10th	Day	21% 10% 3 8% 5% 4 4 4 5% 6% 30%	5992
	11th to 20th	Day	17% 8% 3 8% 4 4 5% 4 6% 7% 33%	5991
	21st to end	Day	17% 8% 3 6% 5% 4 5% 4 6% 8% 35%	6576
June	1st to 10th	Day	14% 7% 2 6% 5% 4 5% 4 6% 8% 37%	2770
	11th to 20th	Day	12% 6% 3 7% 5% 5% 5% 4 6% 7% 38%	2838
	21st to end	Day	11% 6% 1 5% 5% 4 5% 5% 8% 9% 40%	2920
July	1st to 10th	Day	9% 6% 3 7% 4 4 5% 4 6% 10% 43%	6204
	11th to 20th	Day	10% 6% 2 7% 5% 4 6% 4 7% 10% 39%	5900
	21st to end	Day	12% 6% 3 6% 5% 4 5% 4 6% 8% 41%	6424
August	1st to 10th	Day	12% 7% 3 6% 5% 5% 5% 4 6% 9% 39%	4234
	11th to 20th	Day	12% 7% 2 6% 4 5% 5% 5% 7% 10% 38%	4174
	21st to end	Day	10% 5% 2 6% 5% 5% 5% 4 7% 10% 41%	4625
September	1st to 10th	Day	13% 6% 2 4 5% 5% 5% 4 5% 8% 43%	2262
	11th to 20th	Day	11% 6% 3 6% 5% 4 4 4 5% 8% 45%	2200
	21st to end	Day	18% 8% 3 7% 4 3 4 3 6% 7% 37%	2200
October	1st to 10th	Day	14% 6% 3 7% 5% 3 5% 4 6% 8% 40%	2085
	11th to 20th	Day	18% 9% 3 7% 4 4 4 4 5% 6% 37%	2000
	21st to end	Day	22% 12% 3 8% 5% 3 4 3 5% 5% 29%	2165
November	1st to 10th	Day	14% 11% 5% 7% 5% 4 4 3 5% 6% 36%	1852
	11th to 20th	Day	18% 17% 4 7% 4 4 5% 3 4 6% 28%	1890
	21st to end	Day	18% 20% 6% 9% 6% 5% 4 3 4 6% 18%	1696
December	1st to 10th	Day	17% 17% 8% 15% 7% 4 4 3 4 5% 17%	2680
	11th to 20th	Day	21% 20% 7% 12% 5% 4 3 3 4 5% 17%	3070
	21st to end	Day	25% 22% 6% 13% 6% 5% 4 3 4 3 10%	4359
January	1st to 10th	Night	16% 21% 9% 23% 6% 4 3 2 3 3 12%	7635
	11th to 20th	Night	11% 20% 10% 18% 8% 5% 6% 4 3 3 12%	7680
	21st to end	Night	18% 18% 6% 13% 6% 5% 4 3 4 5% 19%	8401
February	1st to 10th	Night	19% 15% 5% 13% 6% 4 3 3 4 5% 21%	2730
	11th to 20th	Night	17% 16% 6% 12% 6% 5% 5% 4 5% 5% 21%	2574
	21st to end	Night	19% 15% 6% 12% 6% 5% 4 2 4 4 23%	2076
March	1st to 10th	Night	21% 14% 4 9% 4 3 3 2 4 5% 31%	5193
	11th to 20th	Night	13% 10% 3 7% 4 4 4 4 6% 7% 39%	5090
	21st to end	Night	17% 12% 4 9% 4 4 4 3 4 5% 32%	5588
April	1st to 10th	Night	17% 14% 3 8% 5% 4 4 3 5% 6% 30%	2289
	11th to 20th	Night	16% 10% 4 7% 5% 5% 5% 4 5% 7% 32%	1884
	21st to end	Night	16% 9% 2 8% 4 3 4 4 6% 6% 37%	1890
May	1st to 10th	Night	22% 12% 3 8% 5% 4 5% 4 5% 6% 27%	4123
	11th to 20th	Night	14% 8% 3 7% 5% 4 4 4 6% 7% 37%	4122
	21st to end	Night	17% 7% 2 5% 4 4 5% 4 6% 8% 38%	4520
June	1st to 10th	Night	10% 6% 2 7% 5% 6% 5% 3 6% 6% 44%	1625
	11th to 20th	Night	9% 5% 3 8% 5% 5% 6% 4 8% 9% 39%	1551
	21st to end	Night	10% 6% 2 5% 5% 5% 5% 3 7% 10% 43%	1471
July	1st to 10th	Night	9% 5% 2 6% 4 4 4 4 6% 9% 45%	3750
	11th to 20th	Night	10% 5% 2 6% 4 5% 5% 5% 6% 9% 43%	4057
	21st to end	Night	8% 6% 2 6% 4 4 4 4 6% 9% 47%	4427
August	1st to 10th	Night	10% 6% 3 7% 4 4 5% 4 6% 9% 42%	2915
	11th to 20th	Night	12% 8% 3 7% 4 3 3 2 5% 7% 44%	2875
	21st to end	Night	7% 5% 3 7% 5% 5% 6% 4 6% 8% 43%	3238
September	1st to 10th	Night	11% 6% 2 5% 4 5% 5% 4 5% 7% 46%	2134
	11th to 20th	Night	10% 4 2 5% 4 4 4 3 6% 8% 52%	2200
	21st to end	Night	16% 8% 2 7% 4 5% 4 4 5% 6% 39%	2200
October	1st to 10th	Night	13% 6% 2 6% 4 4 4 4 5% 7% 45%	2314
	11th to 20th	Night	20% 8% 3 7% 5% 4 4 3 5% 6% 36%	2400
	21st to end	Night	25% 10% 3 7% 4 4 4 3 5% 5% 30%	2670
November	1st to 10th	Night	14% 11% 3 6% 4 4 4 4 6% 6% 37%	2666
	11th to 20th	Night	17% 18% 4 7% 6% 4 4 3 5% 5% 28%	2730
	21st to end	Night	22% 17% 4 8% 5% 4 4 3 4 6% 22%	2920
December	1st to 10th	Night	16% 17% 7% 12% 6% 5% 4 3 5% 6% 19%	4720
	11th to 20th	Night	19% 22% 7% 11% 5% 4 4 3 4 4 19%	5345
	21st to end	Night	22% 21% 6% 12% 5% 4 4 3 4 5% 13%	6821

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	79% 2 9% 8% 2	5259
	11th to 20th	Day	78% 2 7% 8% 5%	5280
	21st to end	Day	79% 2 6% 10% 3	5780
February	1st to 10th	Day	66% 3 10% 14% 7%	1890
	11th to 20th	Day	68% 5% 7% 15% 5% 1	1936
	21st to end	Day	62% 4 12% 14% 7% 1	1730
March	1st to 10th	Day	60% 3 9% 22% 6%	4880
	11th to 20th	Day	51% 3 13% 24% 7% 1	5090
	21st to end	Day	60% 3 9% 17% 11% 1	5586
April	1st to 10th	Day	54% 5% 10% 19% 12% 1	2331
	11th to 20th	Day	51% 4 10% 18% 13% 2	2702
	21st to end	Day	51% 4 11% 22% 11% 2	2730
May	1st to 10th	Day	55% 4 8% 19% 11% 2	6027
	11th to 20th	Day	49% 5% 12% 21% 12% 1	5995
	21st to end	Day	46% 5% 11% 21% 13% 4	6590
June	1st to 10th	Day	43% 4 10% 26% 14% 1	2770
	11th to 20th	Day	43% 6% 14% 22% 14% 2	2838
	21st to end	Day	37% 6% 14% 24% 17% 2	2920
July	1st to 10th	Day	36% 5% 11% 29% 17% 2	6138
	11th to 20th	Day	38% 7% 13% 25% 16% 1	5831
	21st to end	Day	39% 6% 12% 22% 20% 1	6240
August	1st to 10th	Day	41% 6% 14% 26% 13% 1	4221
	11th to 20th	Day	39% 6% 11% 31% 10% 1	4213
	21st to end	Day	37% 6% 13% 30% 12% 2	4625
September	1st to 10th	Day	38% 6% 14% 23% 16% 3	2262
	11th to 20th	Day	37% 4 13% 28% 16% 2	2200
	21st to end	Day	46% 4 9% 22% 18% 1	2200
October	1st to 10th	Day	33% 5% 13% 29% 20% 1	3397
	11th to 20th	Day	46% 4 10% 20% 19% 1	3240
	21st to end	Day	44% 4 12% 23% 17% 1	3479
November	1st to 10th	Day	49% 5% 9% 23% 13% 1	1852
	11th to 20th	Day	59% 4 9% 18% 9% 2	1890
	21st to end	Day	68% 4 9% 14% 6%	1696
December	1st to 10th	Day	70% 4 12% 11% 2	2680
	11th to 20th	Day	73% 2 8% 13% 3	3066
	21st to end	Day	80% 3 7% 8% 2	4359
January	1st to 10th	Night	80% 3 5% 10% 3	7636
	11th to 20th	Night	78% 3 7% 8% 3	7680
	21st to end	Night	69% 3 9% 14% 5%	8401
February	1st to 10th	Night	67% 3 9% 15% 5% 1	2730
	11th to 20th	Night	65% 4 8% 16% 6%	2576
	21st to end	Night	65% 3 9% 14% 7% 1	2076
March	1st to 10th	Night	57% 2 12% 20% 8%	5193
	11th to 20th	Night	45% 4 13% 26% 11% 1	5090
	21st to end	Night	54% 4 7% 21% 13% 1	5588
April	1st to 10th	Night	55% 3 10% 17% 13% 2	2289
	11th to 20th	Night	51% 4 11% 18% 14% 3	1884
	21st to end	Night	47% 4 10% 22% 15% 3	1890
May	1st to 10th	Night	57% 4 9% 15% 10% 4	4150
	11th to 20th	Night	46% 4 11% 24% 14% 1	4123
	21st to end	Night	43% 5% 13% 23% 14% 3	4528
June	1st to 10th	Night	41% 5% 10% 26% 16% 3	1625
	11th to 20th	Night	39% 6% 15% 21% 18% 2	1551
	21st to end	Night	36% 6% 13% 26% 17% 2	1471
July	1st to 10th	Night	34% 6% 14% 24% 17% 4	3709
	11th to 20th	Night	36% 6% 13% 27% 15% 3	4006
	21st to end	Night	33% 6% 11% 21% 26% 2	4297
August	1st to 10th	Night	38% 6% 13% 26% 15% 1	2904
	11th to 20th	Night	40% 5% 12% 30% 13% 1	2902
	21st to end	Night	37% 5% 12% 29% 14% 2	3238
September	1st to 10th	Night	36% 4 12% 28% 16% 4	2134
	11th to 20th	Night	31% 4 11% 29% 22% 2	2200
	21st to end	Night	46% 3 10% 20% 19% 2	2200
October	1st to 10th	Night	31% 3 9% 31% 25% 1	3782
	11th to 20th	Night	47% 4 8% 20% 20% 1	3899
	21st to end	Night	43% 3 9% 26% 17% 2	4306
November	1st to 10th	Night	47% 3 11% 24% 13% 2	2666
	11th to 20th	Night	59% 2 9% 19% 9% 2	2730
	21st to end	Night	65% 3 11% 16% 5%	2920
December	1st to 10th	Night	66% 4 11% 14% 4	4720
	11th to 20th	Night	70% 3 9% 15% 2	5348
	21st to end	Night	75% 3 10% 10% 1	6821

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% 21% 33% 11% 5% 1	330
	11th to 20th	Day	34% 27% 29% 7% 2 1	330
	21st to end	Day	32% 24% 30% 11% 1 1	363
February	1st to 10th	Day	31% 23% 33% 10% 2	330
	11th to 20th	Day	30% 26% 32% 10% 2	330
	21st to end	Day	30% 30% 33% 6%	273
March	1st to 10th	Day	28% 20% 31% 16% 4	461
	11th to 20th	Day	29% 14% 36% 15% 5% 1	540
	21st to end	Day	32% 19% 27% 16% 5%	594
April	1st to 10th	Day	28% 16% 31% 17% 6% 1	540
	11th to 20th	Day	28% 18% 26% 18% 7% 3	532
	21st to end	Day	29% 13% 33% 16% 7% 2	540
May	1st to 10th	Day	26% 15% 29% 20% 7% 3	543
	11th to 20th	Day	22% 11% 30% 23% 10% 4	567
	21st to end	Day	18% 9% 27% 27% 14% 5%	617
June	1st to 10th	Day	16% 8% 31% 29% 13% 3	530
	11th to 20th	Day	16% 8% 23% 34% 16% 3	568
	21st to end	Day	15% 8% 31% 29% 14% 4	730
July	1st to 10th	Day	12% 5% 24% 30% 20% 10%	659
	11th to 20th	Day	15% 6% 22% 30% 19% 8%	524
	21st to end	Day	12% 5% 24% 30% 22% 7%	576
August	1st to 10th	Day	13% 4 19% 29% 24% 10%	526
	11th to 20th	Day	15% 4 22% 28% 21% 10%	519
	21st to end	Day	13% 5% 22% 27% 23% 10%	583
September	1st to 10th	Day	16% 7% 22% 24% 21% 12%	530
	11th to 20th	Day	11% 4 16% 29% 26% 14%	530
	21st to end	Day	22% 12% 24% 21% 13% 8%	530
October	1st to 10th	Day	14% 8% 27% 25% 19% 7%	530
	11th to 20th	Day	22% 15% 33% 19% 8% 2	530
	21st to end	Day	30% 16% 32% 18% 5%	548
November	1st to 10th	Day	23% 20% 33% 15% 9% 1	330
	11th to 20th	Day	33% 23% 26% 13% 5% 1	330
	21st to end	Day	33% 19% 34% 13% 1	228
December	1st to 10th	Day	27% 22% 35% 11% 4 1	220
	11th to 20th	Day	29% 25% 32% 10% 4	220
	21st to end	Day	31% 22% 31% 14% 1	316
January	1st to 10th	Night	29% 19% 32% 16% 4	840
	11th to 20th	Night	32% 20% 30% 15% 4	840
	21st to end	Night	30% 18% 30% 19% 3	924
February	1st to 10th	Night	29% 17% 30% 21% 3	840
	11th to 20th	Night	26% 18% 33% 20% 3	823
	21st to end	Night	28% 17% 35% 18% 2	692
March	1st to 10th	Night	25% 15% 33% 22% 5%	840
	11th to 20th	Night	24% 16% 32% 22% 6% 1	840
	21st to end	Night	26% 12% 29% 24% 8%	924
April	1st to 10th	Night	24% 15% 30% 25% 5%	840
	11th to 20th	Night	23% 11% 32% 24% 9% 1	640
	21st to end	Night	20% 10% 33% 30% 7% 1	630
May	1st to 10th	Night	24% 7% 27% 33% 9% 1	630
	11th to 20th	Night	20% 6% 25% 34% 12% 1	621
	21st to end	Night	13% 5% 23% 38% 19% 2	683
June	1st to 10th	Night	11% 4 28% 41% 15% 1	425
	11th to 20th	Night	12% 5% 24% 42% 17% 1	400
	21st to end	Night	12% 4 23% 41% 20%	471
July	1st to 10th	Night	11% 2 15% 41% 29% 3	585
	11th to 20th	Night	10% 2 20% 38% 27% 3	582
	21st to end	Night	11% 2 15% 42% 28% 2	657
August	1st to 10th	Night	10% 2 14% 45% 26% 4	597
	11th to 20th	Night	13% 4 13% 37% 29% 3	594
	21st to end	Night	10% 3 15% 37% 30% 4	662
September	1st to 10th	Night	14% 6% 15% 34% 26% 5%	800
	11th to 20th	Night	12% 3 15% 34% 31% 6%	800
	21st to end	Night	19% 7% 23% 29% 19% 4	800
October	1st to 10th	Night	17% 7% 21% 32% 20% 2	800
	11th to 20th	Night	25% 12% 27% 26% 9% 1	800
	21st to end	Night	30% 12% 28% 25% 6%	880
November	1st to 10th	Night	22% 13% 30% 25% 9% 1	820
	11th to 20th	Night	30% 15% 30% 17% 7% 1	840
	21st to end	Night	34% 14% 30% 17% 5%	840
December	1st to 10th	Night	33% 14% 32% 17% 5%	840
	11th to 20th	Night	29% 18% 31% 18% 3	840
	21st to end	Night	32% 14% 33% 19% 2	924

Page generated at 2026-05-29 01:53:28. Version ac07

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