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 2025-02-06.

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% 12% 4 9% 5% 4 4 4 5% 7% 30%	108873
	Night	16% 13% 5% 10% 5% 4 4 3 5% 6% 30%	109340
Transparency	Day	53% 4 11% 20% 11% 1	112549
	Night	55% 4 10% 19% 11% 1	113804
Seeing	Day	22% 12% 28% 22% 12% 4	15194
	Night	22% 11% 26% 27% 12% 1	24862

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	15% 22% 8% 24% 5% 3 3 2 3 3 12%	4056
	11th to 20th	Day	14% 23% 8% 16% 8% 5% 6% 2 3 4 12%	4060
	21st to end	Day	22% 20% 10% 13% 7% 5% 3 2 3 3 12%	4466
February	1st to 10th	Day	17% 20% 5% 11% 6% 4 4 3 4 4 21%	1755
	11th to 20th	Day	14% 15% 7% 16% 8% 5% 4 4 4 5% 20%	1739
	21st to end	Day	18% 14% 4 13% 6% 4 4 4 5% 6% 22%	1570
March	1st to 10th	Day	22% 15% 6% 8% 4 4 3 3 4 7% 25%	3330
	11th to 20th	Day	13% 15% 5% 11% 5% 4 4 2 4 5% 33%	3480
	21st to end	Day	21% 13% 6% 9% 4 3 3 3 4 6% 29%	3815
April	1st to 10th	Day	15% 14% 4 7% 5% 4 4 4 5% 6% 31%	2109
	11th to 20th	Day	18% 12% 3 6% 4 5% 5% 3 5% 6% 33%	2442
	21st to end	Day	21% 11% 3 7% 3 4 4 3 5% 6% 33%	2470
May	1st to 10th	Day	19% 9% 3 8% 5% 4 5% 4 6% 6% 31%	4082
	11th to 20th	Day	18% 9% 3 6% 4 4 4 4 6% 7% 35%	4081
	21st to end	Day	10% 7% 3 7% 5% 5% 5% 5% 7% 9% 39%	4476
June	1st to 10th	Day	14% 7% 2 6% 5% 5% 5% 4 7% 9% 37%	2631
	11th to 20th	Day	12% 6% 3 7% 5% 5% 5% 4 6% 8% 39%	2696
	21st to end	Day	11% 6% 1 5% 5% 4 5% 5% 8% 9% 40%	2774
July	1st to 10th	Day	10% 6% 3 8% 5% 4 5% 4 7% 10% 39%	4326
	11th to 20th	Day	9% 5% 2 6% 4 4 5% 4 7% 10% 44%	4120
	21st to end	Day	10% 6% 3 7% 5% 5% 5% 4 7% 8% 40%	4466
August	1st to 10th	Day	12% 7% 3 6% 5% 5% 5% 4 6% 9% 38%	4104
	11th to 20th	Day	12% 7% 2 6% 4 5% 5% 5% 7% 10% 37%	4044
	21st to end	Day	10% 5% 2 6% 5% 5% 5% 4 7% 10% 40%	4483
September	1st to 10th	Day	13% 6% 2 4 5% 5% 5% 4 5% 8% 41%	2149
	11th to 20th	Day	11% 6% 3 7% 5% 4 4 4 5% 8% 44%	2090
	21st to end	Day	19% 9% 3 7% 4 3 3 3 5% 7% 37%	2090
October	1st to 10th	Day	14% 6% 3 7% 5% 3 5% 4 6% 9% 38%	1981
	11th to 20th	Day	19% 10% 3 7% 4 4 4 4 5% 5% 36%	1900
	21st to end	Day	22% 12% 3 8% 5% 4 5% 3 5% 6% 28%	2057
November	1st to 10th	Day	14% 12% 4 7% 5% 4 4 3 5% 6% 36%	1762
	11th to 20th	Day	18% 18% 4 8% 4 3 5% 3 4 6% 28%	1800
	21st to end	Day	18% 20% 6% 10% 6% 5% 4 3 4 6% 18%	1615
December	1st to 10th	Day	17% 17% 7% 15% 7% 4 4 3 4 5% 18%	2600
	11th to 20th	Day	21% 20% 7% 12% 5% 4 3 2 4 5% 17%	2990
	21st to end	Day	25% 22% 6% 13% 6% 5% 4 3 4 3 10%	4264
January	1st to 10th	Night	15% 20% 10% 23% 5% 3 3 2 3 3 13%	5889
	11th to 20th	Night	12% 22% 11% 18% 9% 5% 6% 4 3 3 9%	5900
	21st to end	Night	22% 19% 7% 14% 5% 3 4 2 3 4 18%	6490
February	1st to 10th	Night	21% 15% 5% 13% 6% 4 3 3 4 5% 20%	2536
	11th to 20th	Night	17% 16% 6% 11% 6% 5% 5% 4 4 5% 22%	2323
	21st to end	Night	19% 14% 6% 12% 6% 5% 4 2 4 4 23%	1884
March	1st to 10th	Night	21% 15% 4 7% 4 3 3 3 4 5% 33%	3523
	11th to 20th	Night	15% 11% 3 7% 4 5% 4 4 5% 6% 35%	3480
	21st to end	Night	18% 12% 5% 8% 4 4 4 3 5% 5% 33%	3817
April	1st to 10th	Night	16% 14% 3 8% 5% 4 4 4 5% 6% 31%	2071
	11th to 20th	Night	16% 10% 3 7% 5% 5% 5% 4 5% 7% 33%	1702
	21st to end	Night	16% 9% 3 8% 4 4 4 4 6% 5% 37%	1710
May	1st to 10th	Night	21% 10% 4 8% 5% 4 5% 3 5% 7% 28%	2813
	11th to 20th	Night	16% 9% 3 6% 4 4 4 4 6% 7% 37%	2812
	21st to end	Night	10% 5% 2 4 4 4 5% 4 6% 9% 46%	3079
June	1st to 10th	Night	10% 6% 2 6% 5% 5% 5% 4 6% 6% 44%	1544
	11th to 20th	Night	9% 5% 3 8% 4 5% 6% 4 8% 9% 40%	1474
	21st to end	Night	10% 6% 2 5% 5% 5% 5% 3 6% 10% 43%	1397
July	1st to 10th	Night	10% 6% 2 6% 3 4 4 4 6% 9% 47%	2623
	11th to 20th	Night	9% 4 2 5% 4 4 5% 5% 6% 9% 48%	2840
	21st to end	Night	7% 6% 2 6% 5% 5% 5% 4 7% 9% 44%	3087
August	1st to 10th	Night	11% 6% 3 7% 4 4 5% 4 6% 9% 41%	2825
	11th to 20th	Night	13% 8% 3 7% 4 4 4 2 5% 7% 43%	2785
	21st to end	Night	7% 5% 3 7% 5% 5% 6% 4 6% 8% 44%	3139
September	1st to 10th	Night	11% 6% 2 5% 4 5% 5% 4 5% 7% 45%	2027
	11th to 20th	Night	10% 4 2 5% 4 4 4 3 6% 8% 51%	2090
	21st to end	Night	16% 7% 2 7% 4 5% 4 3 5% 7% 39%	2090
October	1st to 10th	Night	13% 6% 2 6% 4 4 4 4 6% 7% 44%	2198
	11th to 20th	Night	20% 8% 3 7% 5% 4 4 3 5% 6% 35%	2280
	21st to end	Night	25% 10% 3 7% 4 4 4 3 6% 5% 29%	2536
November	1st to 10th	Night	15% 11% 4 6% 4 4 4 3 6% 6% 37%	2536
	11th to 20th	Night	17% 18% 4 7% 6% 4 3 3 5% 5% 28%	2600
	21st to end	Night	22% 17% 4 8% 5% 4 4 3 5% 6% 22%	2781
December	1st to 10th	Night	17% 17% 7% 12% 6% 5% 4 3 5% 6% 19%	4580
	11th to 20th	Night	19% 22% 7% 11% 5% 4 4 3 4 4 18%	5205
	21st to end	Night	22% 21% 6% 12% 6% 4 4 3 4 5% 12%	6674

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 7% 8% 3	4057
	11th to 20th	Day	79% 2 8% 7% 4	4060
	21st to end	Day	80% 2 5% 9% 3	4466
February	1st to 10th	Day	67% 4 10% 13% 6%	1755
	11th to 20th	Day	67% 5% 6% 15% 6% 1	1748
	21st to end	Day	62% 4 11% 14% 7% 1	1570
March	1st to 10th	Day	62% 2 9% 23% 5%	3330
	11th to 20th	Day	55% 3 12% 22% 7% 1	3480
	21st to end	Day	59% 3 11% 17% 10% 1	3815
April	1st to 10th	Day	53% 4 10% 19% 13% 1	2109
	11th to 20th	Day	51% 4 10% 18% 14% 2	2442
	21st to end	Day	52% 3 11% 22% 11% 2	2470
May	1st to 10th	Day	53% 4 9% 23% 10% 1	4120
	11th to 20th	Day	48% 4 12% 24% 10% 1	4085
	21st to end	Day	40% 5% 13% 21% 16% 5%	4489
June	1st to 10th	Day	44% 4 10% 26% 14% 1	2631
	11th to 20th	Day	41% 5% 14% 23% 15% 2	2696
	21st to end	Day	37% 7% 13% 24% 16% 2	2774
July	1st to 10th	Day	40% 5% 11% 24% 18% 2	4260
	11th to 20th	Day	33% 6% 12% 29% 19% 2	4051
	21st to end	Day	40% 6% 14% 19% 20% 2	4324
August	1st to 10th	Day	41% 6% 13% 26% 13%	4091
	11th to 20th	Day	40% 6% 11% 31% 10% 1	4083
	21st to end	Day	38% 6% 13% 29% 12% 2	4483
September	1st to 10th	Day	39% 6% 14% 22% 16% 3	2149
	11th to 20th	Day	39% 4 13% 26% 16% 2	2090
	21st to end	Day	46% 4 9% 23% 17% 1	2090
October	1st to 10th	Day	33% 5% 13% 29% 19% 1	3293
	11th to 20th	Day	47% 4 9% 20% 18% 1	3140
	21st to end	Day	44% 4 12% 23% 17% 1	3371
November	1st to 10th	Day	48% 4 10% 23% 14% 1	1762
	11th to 20th	Day	59% 3 9% 18% 10% 2	1800
	21st to end	Day	68% 4 9% 13% 6%	1615
December	1st to 10th	Day	70% 4 12% 11% 2	2600
	11th to 20th	Day	73% 2 8% 13% 3	2986
	21st to end	Day	80% 3 7% 8% 2	4264
January	1st to 10th	Night	78% 2 5% 11% 3	5889
	11th to 20th	Night	83% 3 6% 7% 2	5900
	21st to end	Night	73% 2 9% 10% 5%	6490
February	1st to 10th	Night	68% 3 9% 14% 5% 1	2536
	11th to 20th	Night	65% 4 7% 17% 7%	2325
	21st to end	Night	65% 3 9% 14% 7% 2	1884
March	1st to 10th	Night	56% 2 10% 23% 8%	3523
	11th to 20th	Night	49% 5% 14% 20% 11% 1	3480
	21st to end	Night	53% 3 7% 25% 10% 1	3817
April	1st to 10th	Night	53% 4 11% 17% 13% 2	2071
	11th to 20th	Night	50% 4 11% 17% 15% 3	1702
	21st to end	Night	47% 4 11% 21% 14% 3	1710
May	1st to 10th	Night	55% 4 9% 20% 10% 2	2840
	11th to 20th	Night	47% 3 11% 24% 13% 2	2813
	21st to end	Night	33% 4 14% 27% 18% 4	3087
June	1st to 10th	Night	41% 5% 10% 26% 15% 3	1544
	11th to 20th	Night	38% 5% 15% 20% 18% 3	1474
	21st to end	Night	36% 5% 13% 26% 17% 2	1397
July	1st to 10th	Night	34% 5% 12% 24% 18% 6%	2580
	11th to 20th	Night	32% 5% 13% 28% 18% 3	2786
	21st to end	Night	34% 7% 13% 20% 23% 2	2988
August	1st to 10th	Night	39% 6% 12% 26% 15% 1	2814
	11th to 20th	Night	40% 5% 12% 29% 13% 1	2812
	21st to end	Night	37% 5% 12% 28% 14% 2	3139
September	1st to 10th	Night	37% 4 12% 26% 16% 4	2027
	11th to 20th	Night	32% 4 11% 28% 22% 2	2090
	21st to end	Night	46% 3 11% 21% 18% 1	2090
October	1st to 10th	Night	31% 3 9% 31% 24% 1	3666
	11th to 20th	Night	47% 4 8% 20% 19% 1	3779
	21st to end	Night	43% 3 9% 26% 17% 2	4172
November	1st to 10th	Night	48% 3 11% 23% 13% 2	2536
	11th to 20th	Night	60% 2 8% 19% 9% 2	2600
	21st to end	Night	65% 3 11% 16% 5%	2781
December	1st to 10th	Night	66% 5% 12% 14% 4	4580
	11th to 20th	Night	70% 3 9% 15% 2	5208
	21st to end	Night	75% 3 11% 10% 1	6674

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% 19% 33% 12% 5% 1	300
	11th to 20th	Day	31% 27% 31% 8% 3 1	300
	21st to end	Day	31% 24% 31% 12% 2 1	330
February	1st to 10th	Day	33% 20% 35% 10% 2	285
	11th to 20th	Day	29% 26% 33% 10% 2	270
	21st to end	Day	32% 29% 32% 7%	225
March	1st to 10th	Day	28% 20% 30% 16% 5%	389
	11th to 20th	Day	27% 13% 37% 17% 5% 1	460
	21st to end	Day	33% 16% 28% 18% 6%	506
April	1st to 10th	Day	26% 14% 34% 18% 7% 1	460
	11th to 20th	Day	28% 16% 27% 18% 8% 4	452
	21st to end	Day	30% 13% 33% 15% 7% 2	460
May	1st to 10th	Day	25% 13% 29% 22% 8% 3	463
	11th to 20th	Day	22% 10% 29% 23% 11% 4	487
	21st to end	Day	15% 8% 26% 29% 16% 6%	529
June	1st to 10th	Day	16% 7% 31% 30% 13% 3	490
	11th to 20th	Day	15% 8% 23% 34% 16% 4	526
	21st to end	Day	15% 8% 32% 28% 14% 4	680
July	1st to 10th	Day	12% 5% 23% 30% 19% 11%	612
	11th to 20th	Day	15% 5% 22% 30% 20% 8%	484
	21st to end	Day	12% 5% 24% 30% 22% 7%	532
August	1st to 10th	Day	14% 5% 20% 28% 23% 10%	486
	11th to 20th	Day	15% 4 23% 27% 20% 10%	479
	21st to end	Day	13% 5% 21% 27% 24% 10%	539
September	1st to 10th	Day	16% 6% 22% 25% 20% 11%	490
	11th to 20th	Day	12% 4 16% 29% 26% 12%	490
	21st to end	Day	23% 12% 24% 20% 12% 9%	490
October	1st to 10th	Day	14% 9% 28% 24% 18% 7%	490
	11th to 20th	Day	23% 15% 31% 20% 9% 2	490
	21st to end	Day	30% 16% 31% 18% 5%	506
November	1st to 10th	Day	21% 21% 33% 16% 9% 1	300
	11th to 20th	Day	31% 22% 28% 14% 5% 1	300
	21st to end	Day	32% 19% 34% 14% 1	207
December	1st to 10th	Day	26% 22% 36% 12% 4 2	200
	11th to 20th	Day	27% 25% 34% 11% 4	200
	21st to end	Day	29% 22% 33% 14% 1	287
January	1st to 10th	Night	29% 19% 32% 16% 4	800
	11th to 20th	Night	32% 18% 30% 15% 4 1	800
	21st to end	Night	30% 18% 30% 19% 3	880
February	1st to 10th	Night	30% 17% 30% 21% 3	781
	11th to 20th	Night	26% 17% 34% 20% 3	743
	21st to end	Night	28% 17% 34% 19% 2	628
March	1st to 10th	Night	24% 15% 32% 24% 5%	760
	11th to 20th	Night	23% 15% 32% 23% 6% 1	760
	21st to end	Night	26% 11% 28% 25% 9%	836
April	1st to 10th	Night	22% 14% 30% 27% 6%	760
	11th to 20th	Night	23% 10% 32% 24% 10% 1	578
	21st to end	Night	20% 9% 33% 29% 8% 1	570
May	1st to 10th	Night	23% 6% 27% 34% 9% 1	570
	11th to 20th	Night	21% 5% 24% 35% 13% 2	561
	21st to end	Night	11% 4 23% 38% 21% 2	617
June	1st to 10th	Night	11% 4 26% 42% 16% 1	404
	11th to 20th	Night	12% 5% 23% 43% 17% 1	380
	21st to end	Night	12% 4 23% 41% 19%	447
July	1st to 10th	Night	11% 2 15% 40% 29% 3	555
	11th to 20th	Night	11% 2 20% 38% 27% 3	552
	21st to end	Night	11% 2 15% 42% 28% 2	624
August	1st to 10th	Night	10% 2 14% 44% 26% 4	567
	11th to 20th	Night	13% 4 13% 38% 28% 4	564
	21st to end	Night	10% 3 15% 37% 30% 4	629
September	1st to 10th	Night	15% 6% 15% 35% 25% 5%	760
	11th to 20th	Night	13% 3 16% 34% 29% 5%	760
	21st to end	Night	19% 6% 23% 29% 18% 4	760
October	1st to 10th	Night	18% 7% 22% 32% 19% 2	760
	11th to 20th	Night	25% 12% 27% 25% 9% 1	760
	21st to end	Night	30% 12% 27% 25% 6%	836
November	1st to 10th	Night	23% 12% 29% 25% 9% 1	780
	11th to 20th	Night	30% 14% 31% 17% 7% 1	800
	21st to end	Night	33% 14% 30% 17% 6%	800
December	1st to 10th	Night	33% 14% 31% 17% 5%	800
	11th to 20th	Night	30% 18% 31% 19% 3	800
	21st to end	Night	32% 14% 33% 20% 2	880

Page generated at 2025-02-03 03:05:49. Version ac07

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