Schumann Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Schumann Observatory clear sky chart from 2005-11-06 to 2024-04-10.

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	14% 5% 2 5% 5% 3 4 5% 6% 8% 44%	83243
	Night	15% 6% 2 5% 5% 3 4 4 5% 7% 44%	85532
Transparency	Day	37% 8% 13% 23% 16% 3	82954
	Night	39% 7% 11% 23% 17% 3	85341
Seeing	Day	17% 10% 29% 26% 14% 4	14362
	Night	17% 11% 28% 29% 13% 2	24042

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% 4 2 4 3 2 3 4 4 5% 52%	2617
	11th to 20th	Day	13% 7% 3 5% 5% 3 4 4 5% 6% 46%	2840
	21st to end	Day	15% 9% 3 7% 5% 3 3 3 4 6% 41%	3124
February	1st to 10th	Day	12% 9% 2 5% 5% 4 5% 5% 5% 7% 41%	1710
	11th to 20th	Day	20% 6% 2 3 3 2 4 4 4 6% 46%	1792
	21st to end	Day	15% 9% 3 4 6% 4 5% 5% 5% 5% 37%	1570
March	1st to 10th	Day	21% 8% 3 6% 5% 3 3 4 5% 6% 37%	3308
	11th to 20th	Day	10% 4 2 3 3 2 4 4 5% 7% 56%	3480
	21st to end	Day	19% 8% 2 4 4 2 4 5% 5% 6% 42%	3932
April	1st to 10th	Day	12% 5% 2 4 4 3 3 4 5% 7% 50%	2270
	11th to 20th	Day	10% 5% 2 4 5% 4 5% 4 4 7% 50%	2134
	21st to end	Day	15% 6% 2 4 5% 3 4 5% 5% 8% 44%	2160
May	1st to 10th	Day	15% 5% 2 5% 5% 3 4 5% 5% 9% 42%	2178
	11th to 20th	Day	17% 4 3 5% 6% 3 5% 5% 5% 8% 40%	2406
	21st to end	Day	14% 5% 2 4 4 2 4 5% 6% 8% 45%	2725
June	1st to 10th	Day	12% 4 1 4 5% 3 5% 6% 8% 10% 43%	2520
	11th to 20th	Day	11% 4 2 4 5% 3 5% 6% 8% 10% 42%	2520
	21st to end	Day	8% 3 2 5% 5% 3 6% 6% 7% 11% 44%	2520
July	1st to 10th	Day	9% 4 3 5% 6% 4 5% 6% 7% 10% 42%	2520
	11th to 20th	Day	6% 4 2 5% 6% 4 6% 7% 8% 11% 41%	2428
	21st to end	Day	7% 3 2 5% 7% 4 6% 7% 8% 12% 38%	2547
August	1st to 10th	Day	10% 6% 2 5% 6% 4 5% 7% 8% 10% 37%	2327
	11th to 20th	Day	13% 4 2 6% 6% 4 6% 6% 7% 10% 37%	2131
	21st to end	Day	12% 5% 2 5% 5% 3 5% 6% 7% 11% 40%	2376
September	1st to 10th	Day	14% 5% 2 5% 4 3 4 5% 5% 8% 44%	2160
	11th to 20th	Day	14% 6% 3 5% 4 3 4 4 6% 7% 44%	2160
	21st to end	Day	20% 7% 2 4 5% 3 4 4 5% 7% 39%	1925
October	1st to 10th	Day	16% 5% 2 5% 5% 3 3 3 5% 7% 45%	1800
	11th to 20th	Day	17% 5% 2 4 3 2 3 4 4 5% 51%	1800
	21st to end	Day	13% 5% 2 4 4 3 3 5% 5% 6% 49%	1980
November	1st to 10th	Day	15% 5% 2 4 3 2 3 3 4 6% 52%	1751
	11th to 20th	Day	14% 6% 2 5% 3 2 5% 3 3 6% 51%	1710
	21st to end	Day	16% 4 2 3 4 3 3 4 5% 6% 51%	1620
December	1st to 10th	Day	16% 7% 3 4 4 2 4 4 6% 7% 44%	1520
	11th to 20th	Day	17% 5% 2 5% 3 2 3 3 3 5% 52%	1910
	21st to end	Day	17% 6% 3 5% 5% 2 3 4 5% 6% 45%	2772
January	1st to 10th	Night	14% 6% 2 5% 5% 3 4 4 5% 6% 45%	4324
	11th to 20th	Night	16% 7% 3 6% 4 3 4 3 4 6% 45%	4120
	21st to end	Night	18% 8% 3 5% 5% 2 3 3 4 5% 43%	4532
February	1st to 10th	Night	16% 8% 3 5% 4 2 4 4 5% 7% 42%	2470
	11th to 20th	Night	20% 6% 3 5% 4 2 4 4 5% 5% 43%	2271
	21st to end	Night	18% 7% 3 4 3 2 3 3 5% 5% 46%	1884
March	1st to 10th	Night	24% 7% 3 5% 4 2 4 3 4 6% 36%	3542
	11th to 20th	Night	16% 5% 2 4 4 2 4 4 4 5% 50%	3480
	21st to end	Night	17% 8% 3 5% 4 2 4 3 3 4 47%	3699
April	1st to 10th	Night	15% 7% 3 5% 5% 3 4 5% 5% 7% 42%	1900
	11th to 20th	Night	12% 5% 2 5% 4 2 4 4 5% 8% 50%	1775
	21st to end	Night	17% 5% 2 4 4 3 4 4 5% 7% 45%	1800
May	1st to 10th	Night	15% 6% 3 5% 6% 3 5% 5% 6% 8% 39%	1796
	11th to 20th	Night	15% 7% 3 6% 5% 3 5% 4 5% 8% 39%	1483
	21st to end	Night	15% 4 1 5% 5% 3 5% 5% 5% 8% 43%	1550
June	1st to 10th	Night	12% 4 2 5% 5% 3 7% 5% 7% 8% 41%	1440
	11th to 20th	Night	11% 4 2 4 5% 4 6% 5% 8% 10% 41%	1440
	21st to end	Night	9% 4 2 5% 7% 4 5% 6% 8% 10% 41%	1440
July	1st to 10th	Night	9% 4 3 6% 6% 5% 5% 5% 7% 10% 41%	1440
	11th to 20th	Night	5% 4 2 5% 5% 4 5% 7% 7% 12% 45%	1527
	21st to end	Night	8% 4 2 5% 6% 4 6% 7% 7% 11% 40%	1771
August	1st to 10th	Night	8% 4 3 7% 8% 5% 5% 8% 8% 10% 36%	1611
	11th to 20th	Night	9% 7% 3 7% 6% 3 4 5% 7% 10% 38%	1752
	21st to end	Night	10% 6% 2 6% 6% 3 5% 6% 7% 9% 40%	1980
September	1st to 10th	Night	14% 5% 2 4 4 2 4 5% 6% 8% 46%	1800
	11th to 20th	Night	12% 5% 3 5% 5% 3 4 5% 5% 7% 47%	1800
	21st to end	Night	22% 7% 3 5% 4 2 5% 4 5% 7% 37%	2030
October	1st to 10th	Night	16% 5% 2 5% 5% 3 4 4 5% 8% 44%	2160
	11th to 20th	Night	17% 5% 2 4 4 3 4 3 4 6% 49%	2160
	21st to end	Night	16% 5% 2 4 4 2 3 4 4 7% 49%	2376
November	1st to 10th	Night	15% 6% 2 4 5% 2 4 3 4 6% 49%	2325
	11th to 20th	Night	16% 6% 2 4 5% 2 4 4 4 6% 49%	2470
	21st to end	Night	12% 5% 2 4 4 3 4 4 5% 7% 51%	2555
December	1st to 10th	Night	17% 7% 3 6% 4 3 5% 4 5% 5% 41%	2660
	11th to 20th	Night	17% 6% 2 4 4 2 4 4 4 6% 45%	3285
	21st to end	Night	14% 7% 3 5% 4 3 4 4 5% 8% 43%	4884

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	33% 5% 10% 31% 18% 3	2618
	11th to 20th	Day	39% 5% 9% 21% 21% 5%	2840
	21st to end	Day	45% 6% 10% 22% 15% 2	3124
February	1st to 10th	Day	41% 6% 12% 26% 13% 3	1710
	11th to 20th	Day	39% 5% 10% 22% 19% 5%	1801
	21st to end	Day	45% 7% 12% 16% 16% 4	1570
March	1st to 10th	Day	46% 8% 11% 17% 15% 4	3308
	11th to 20th	Day	25% 7% 11% 26% 24% 7%	3480
	21st to end	Day	42% 8% 11% 18% 18% 3	3932
April	1st to 10th	Day	33% 6% 13% 23% 20% 6%	2270
	11th to 20th	Day	33% 7% 12% 23% 20% 6%	2134
	21st to end	Day	37% 8% 11% 23% 16% 5%	2160
May	1st to 10th	Day	37% 9% 15% 22% 15% 3	2178
	11th to 20th	Day	40% 10% 13% 24% 11% 2	2410
	21st to end	Day	34% 10% 15% 27% 13% 1	2725
June	1st to 10th	Day	32% 10% 17% 27% 12% 1	2520
	11th to 20th	Day	32% 11% 18% 23% 14% 2	2520
	21st to end	Day	32% 11% 17% 23% 16% 1	2520
July	1st to 10th	Day	32% 13% 16% 21% 15% 2	2450
	11th to 20th	Day	29% 13% 20% 27% 9% 1	2354
	21st to end	Day	33% 12% 19% 20% 14% 1	2405
August	1st to 10th	Day	35% 12% 18% 25% 9% 1	2314
	11th to 20th	Day	40% 10% 15% 23% 12% 1	2131
	21st to end	Day	34% 10% 15% 24% 13% 3	2376
September	1st to 10th	Day	36% 9% 17% 18% 16% 4	2160
	11th to 20th	Day	37% 6% 12% 23% 19% 2	2160
	21st to end	Day	44% 7% 9% 23% 15% 3	1925
October	1st to 10th	Day	38% 7% 10% 24% 18% 3	1800
	11th to 20th	Day	35% 6% 10% 24% 21% 4	1800
	21st to end	Day	35% 6% 8% 24% 22% 6%	1980
November	1st to 10th	Day	34% 5% 10% 28% 20% 4	1751
	11th to 20th	Day	36% 5% 12% 19% 22% 6%	1710
	21st to end	Day	35% 4 11% 26% 20% 4	1620
December	1st to 10th	Day	41% 5% 13% 24% 14% 3	1520
	11th to 20th	Day	38% 5% 8% 27% 16% 6%	1906
	21st to end	Day	40% 6% 11% 27% 14% 1	2772
January	1st to 10th	Night	38% 5% 10% 25% 18% 4	4324
	11th to 20th	Night	42% 5% 8% 22% 20% 3	4120
	21st to end	Night	45% 5% 8% 22% 16% 3	4532
February	1st to 10th	Night	41% 4 12% 24% 15% 3	2470
	11th to 20th	Night	43% 4 8% 21% 18% 6%	2273
	21st to end	Night	40% 5% 10% 22% 18% 5%	1884
March	1st to 10th	Night	49% 5% 9% 20% 15% 2	3542
	11th to 20th	Night	35% 6% 8% 22% 23% 6%	3480
	21st to end	Night	41% 4 8% 23% 18% 5%	3699
April	1st to 10th	Night	40% 6% 10% 17% 21% 4	1900
	11th to 20th	Night	33% 6% 11% 23% 22% 5%	1775
	21st to end	Night	38% 7% 13% 22% 16% 4	1800
May	1st to 10th	Night	40% 9% 13% 21% 14% 3	1796
	11th to 20th	Night	42% 8% 14% 21% 14% 1	1484
	21st to end	Night	38% 10% 15% 24% 12% 1	1551
June	1st to 10th	Night	37% 10% 15% 22% 15% 1	1440
	11th to 20th	Night	36% 12% 16% 21% 14% 2	1440
	21st to end	Night	37% 9% 14% 23% 14% 3	1440
July	1st to 10th	Night	38% 10% 16% 22% 13% 3	1400
	11th to 20th	Night	28% 12% 21% 29% 9% 1	1479
	21st to end	Night	34% 12% 17% 24% 12%	1672
August	1st to 10th	Night	39% 13% 19% 21% 9%	1600
	11th to 20th	Night	39% 11% 17% 19% 13% 1	1752
	21st to end	Night	38% 11% 15% 22% 13% 2	1980
September	1st to 10th	Night	35% 10% 16% 20% 16% 4	1800
	11th to 20th	Night	36% 7% 9% 26% 20% 2	1800
	21st to end	Night	46% 8% 10% 16% 17% 2	2030
October	1st to 10th	Night	39% 7% 10% 23% 18% 3	2160
	11th to 20th	Night	37% 5% 9% 23% 22% 4	2160
	21st to end	Night	35% 5% 9% 25% 21% 4	2376
November	1st to 10th	Night	38% 4 11% 24% 18% 4	2325
	11th to 20th	Night	38% 5% 10% 21% 19% 8%	2470
	21st to end	Night	34% 5% 9% 26% 21% 4	2555
December	1st to 10th	Night	45% 5% 10% 22% 15% 3	2660
	11th to 20th	Night	40% 6% 10% 22% 19% 4	3288
	21st to end	Night	38% 7% 14% 26% 14% 2	4884

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	22% 18% 39% 16% 4	209
	11th to 20th	Day	21% 26% 38% 11% 3	270
	21st to end	Day	18% 19% 41% 21% 2	297
February	1st to 10th	Day	17% 20% 44% 15% 4	270
	11th to 20th	Day	27% 20% 38% 14% 2	400
	21st to end	Day	24% 18% 39% 15% 5%	382
March	1st to 10th	Day	18% 20% 41% 16% 5%	460
	11th to 20th	Day	20% 20% 37% 16% 5% 1	460
	21st to end	Day	19% 16% 44% 16% 4 1	506
April	1st to 10th	Day	16% 21% 39% 18% 5% 1	457
	11th to 20th	Day	11% 15% 40% 24% 7% 3	412
	21st to end	Day	18% 14% 38% 24% 5% 1	420
May	1st to 10th	Day	17% 13% 39% 22% 8% 1	423
	11th to 20th	Day	21% 8% 32% 27% 10% 2	447
	21st to end	Day	22% 3 25% 27% 18% 4	485
June	1st to 10th	Day	15% 5% 23% 32% 21% 4	450
	11th to 20th	Day	12% 5% 22% 36% 20% 5%	450
	21st to end	Day	10% 4 24% 38% 21% 4	450
July	1st to 10th	Day	10% 3 15% 36% 29% 6%	445
	11th to 20th	Day	6% 1 13% 43% 30% 8%	444
	21st to end	Day	11% 2 19% 37% 24% 7%	488
August	1st to 10th	Day	11% 4 17% 38% 22% 8%	446
	11th to 20th	Day	14% 2 12% 36% 28% 8%	439
	21st to end	Day	11% 3 18% 31% 26% 11%	495
September	1st to 10th	Day	15% 4 19% 31% 20% 11%	450
	11th to 20th	Day	14% 4 20% 35% 20% 7%	450
	21st to end	Day	28% 6% 22% 27% 13% 4	450
October	1st to 10th	Day	21% 4 24% 28% 17% 6%	450
	11th to 20th	Day	17% 10% 28% 28% 15% 3	450
	21st to end	Day	14% 11% 35% 27% 10% 3	495
November	1st to 10th	Day	19% 11% 29% 24% 12% 5%	404
	11th to 20th	Day	16% 17% 33% 24% 9% 1	370
	21st to end	Day	18% 16% 29% 25% 11% 1	280
December	1st to 10th	Day	23% 14% 38% 19% 5% 1	180
	11th to 20th	Day	21% 15% 33% 24% 6%	180
	21st to end	Day	23% 15% 31% 22% 9%	198
January	1st to 10th	Night	18% 19% 35% 23% 4	760
	11th to 20th	Night	20% 17% 34% 23% 6%	760
	21st to end	Night	20% 17% 37% 24% 2	836
February	1st to 10th	Night	19% 13% 41% 24% 3	760
	11th to 20th	Night	23% 22% 36% 16% 2	743
	21st to end	Night	21% 17% 36% 23% 3	628
March	1st to 10th	Night	18% 16% 36% 25% 6%	760
	11th to 20th	Night	22% 15% 33% 23% 6% 1	760
	21st to end	Night	19% 14% 40% 22% 4	836
April	1st to 10th	Night	18% 16% 40% 20% 5%	760
	11th to 20th	Night	14% 12% 38% 26% 9%	711
	21st to end	Night	19% 9% 34% 30% 8% 1	720
May	1st to 10th	Night	18% 10% 34% 30% 7% 1	716
	11th to 20th	Night	17% 7% 28% 35% 12% 1	422
	21st to end	Night	17% 4 16% 37% 24% 2	389
June	1st to 10th	Night	14% 3 19% 43% 20% 2	360
	11th to 20th	Night	11% 4 23% 38% 20% 5%	360
	21st to end	Night	9% 3 21% 43% 21% 3	360
July	1st to 10th	Night	12% 2 13% 44% 26% 3	350
	11th to 20th	Night	5% 1 11% 44% 33% 6%	435
	21st to end	Night	7% 3 14% 44% 27% 4	591
August	1st to 10th	Night	10% 2 13% 43% 27% 5%	537
	11th to 20th	Night	12% 4 13% 37% 31% 3	688
	21st to end	Night	12% 3 15% 33% 30% 7%	792
September	1st to 10th	Night	17% 3 13% 34% 28% 6%	720
	11th to 20th	Night	14% 3 15% 34% 29% 6%	720
	21st to end	Night	23% 6% 21% 29% 19% 3	720
October	1st to 10th	Night	18% 6% 22% 29% 21% 5%	720
	11th to 20th	Night	19% 10% 24% 29% 15% 2	720
	21st to end	Night	19% 12% 27% 27% 14% 2	792
November	1st to 10th	Night	18% 9% 27% 27% 15% 3	740
	11th to 20th	Night	18% 15% 29% 27% 11% 1	760
	21st to end	Night	14% 18% 27% 31% 9% 2	760
December	1st to 10th	Night	20% 14% 33% 21% 10% 2	760
	11th to 20th	Night	19% 12% 38% 25% 6%	760
	21st to end	Night	19% 14% 29% 31% 6%	836

Page generated at 2024-04-07 09:28:11. Version ac07

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