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 2024-11-04.

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% 6% 2 6% 4 4 4 4 6% 8% 43%	101068
	Night	15% 6% 2 6% 4 4 4 3 5% 7% 43%	97887
Transparency	Day	20% 48% 8% 13% 9% 2	104702
	Night	21% 48% 6% 13% 10% 2	102393
Seeing	Day	16% 10% 29% 27% 14% 4	15193
	Night	17% 10% 28% 29% 13% 2	24716

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 3 3 3 4 5% 52%	2617
	11th to 20th	Day	12% 8% 3 7% 4 4 3 3 5% 6% 46%	2840
	21st to end	Day	15% 10% 3 7% 4 4 3 3 5% 6% 41%	3124
February	1st to 10th	Day	12% 9% 2 6% 4 5% 5% 4 6% 7% 40%	1710
	11th to 20th	Day	19% 6% 2 4 3 3 3 3 4 6% 46%	1792
	21st to end	Day	15% 9% 3 5% 5% 6% 4 5% 5% 5% 37%	1570
March	1st to 10th	Day	21% 8% 3 7% 4 4 3 3 5% 6% 37%	3308
	11th to 20th	Day	10% 4 2 4 3 3 4 3 5% 7% 56%	3480
	21st to end	Day	19% 8% 2 4 4 3 4 4 5% 6% 41%	3932
April	1st to 10th	Day	12% 5% 2 5% 4 4 3 4 5% 7% 49%	2280
	11th to 20th	Day	10% 6% 2 5% 4 5% 4 4 4 7% 50%	2254
	21st to end	Day	14% 6% 1 5% 4 4 4 4 5% 7% 45%	2280
May	1st to 10th	Day	19% 6% 3 7% 4 5% 4 4 6% 9% 32%	3811
	11th to 20th	Day	21% 6% 2 7% 5% 4 4 4 5% 7% 34%	4284
	21st to end	Day	10% 4 2 5% 4 4 4 4 7% 9% 48%	4823
June	1st to 10th	Day	11% 4 1 4 5% 4 5% 5% 8% 10% 43%	2660
	11th to 20th	Day	10% 4 2 5% 4 4 5% 5% 8% 11% 43%	2660
	21st to end	Day	7% 4 2 6% 5% 5% 5% 5% 7% 10% 44%	2660
July	1st to 10th	Day	6% 4 2 6% 5% 5% 5% 5% 8% 12% 42%	4440
	11th to 20th	Day	12% 6% 2 6% 5% 5% 6% 5% 7% 10% 36%	4264
	21st to end	Day	9% 5% 2 8% 6% 6% 6% 6% 8% 11% 34%	4466
August	1st to 10th	Day	14% 8% 3 7% 5% 5% 5% 5% 8% 10% 30%	4104
	11th to 20th	Day	10% 5% 3 7% 6% 6% 6% 5% 7% 9% 37%	3735
	21st to end	Day	9% 4 1 4 3 3 4 4 7% 11% 48%	4180
September	1st to 10th	Day	14% 5% 2 6% 4 4 4 4 6% 7% 45%	2280
	11th to 20th	Day	14% 6% 3 6% 4 4 4 3 6% 7% 43%	2280
	21st to end	Day	21% 8% 2 5% 4 3 4 3 5% 6% 38%	2031
October	1st to 10th	Day	16% 5% 2 6% 4 4 3 3 4 7% 45%	1900
	11th to 20th	Day	16% 5% 2 4 2 3 3 3 4 5% 52%	1900
	21st to end	Day	13% 5% 2 4 4 3 4 4 5% 6% 51%	2090
November	1st to 10th	Day	15% 5% 2 5% 2 2 3 3 4 6% 52%	1781
	11th to 20th	Day	14% 6% 2 5% 3 4 4 3 4 6% 50%	1710
	21st to end	Day	16% 4 2 4 3 4 3 3 5% 5% 51%	1620
December	1st to 10th	Day	16% 7% 2 5% 3 3 3 3 6% 6% 43%	1520
	11th to 20th	Day	16% 5% 2 6% 3 3 3 2 3 5% 51%	1910
	21st to end	Day	16% 7% 2 6% 4 3 3 3 5% 6% 44%	2772
January	1st to 10th	Night	14% 6% 2 5% 4 4 4 3 5% 6% 45%	4324
	11th to 20th	Night	16% 7% 2 6% 4 4 3 2 4 5% 45%	4120
	21st to end	Night	18% 9% 3 6% 4 3 3 2 4 5% 43%	4532
February	1st to 10th	Night	15% 8% 3 5% 4 3 4 3 6% 6% 42%	2470
	11th to 20th	Night	20% 6% 2 5% 4 3 3 3 5% 5% 43%	2271
	21st to end	Night	18% 7% 2 5% 3 3 3 3 5% 5% 46%	1884
March	1st to 10th	Night	24% 8% 3 6% 4 3 4 2 4 6% 36%	3542
	11th to 20th	Night	16% 5% 2 4 3 3 3 3 4 5% 50%	3480
	21st to end	Night	17% 8% 3 5% 3 3 3 2 3 4 47%	3699
April	1st to 10th	Night	14% 7% 3 5% 4 4 3 4 6% 7% 42%	1900
	11th to 20th	Night	12% 5% 2 6% 3 3 4 3 5% 7% 49%	1875
	21st to end	Night	16% 6% 2 4 4 4 3 3 5% 7% 45%	1900
May	1st to 10th	Night	21% 6% 2 7% 4 4 5% 4 6% 7% 33%	3112
	11th to 20th	Night	24% 8% 2 7% 3 4 4 3 5% 7% 33%	2605
	21st to end	Night	12% 4 2 5% 4 4 5% 4 6% 9% 45%	2732
June	1st to 10th	Night	12% 5% 2 6% 4 5% 6% 4 7% 8% 41%	1520
	11th to 20th	Night	11% 5% 1 5% 5% 5% 5% 4 8% 10% 42%	1520
	21st to end	Night	8% 4 2 6% 6% 5% 5% 5% 8% 10% 42%	1520
July	1st to 10th	Night	9% 4 2 7% 6% 6% 5% 4 8% 11% 39%	2520
	11th to 20th	Night	9% 6% 2 6% 5% 5% 6% 5% 8% 12% 37%	2677
	21st to end	Night	12% 8% 3 8% 6% 5% 6% 5% 6% 9% 31%	3087
August	1st to 10th	Night	16% 8% 3 8% 6% 5% 4 5% 7% 9% 30%	2825
	11th to 20th	Night	8% 6% 3 7% 5% 5% 4 5% 7% 10% 40%	3062
	21st to end	Night	10% 4 2 6% 4 3 4 4 6% 8% 50%	3476
September	1st to 10th	Night	13% 5% 2 4 4 3 4 4 6% 8% 47%	1900
	11th to 20th	Night	12% 5% 3 6% 4 4 4 4 5% 7% 45%	1900
	21st to end	Night	22% 7% 3 6% 3 3 5% 3 5% 6% 36%	2144
October	1st to 10th	Night	16% 5% 2 6% 4 4 4 3 5% 7% 44%	2280
	11th to 20th	Night	16% 5% 2 5% 3 4 3 3 4 6% 50%	2280
	21st to end	Night	15% 5% 2 5% 4 2 3 3 4 7% 51%	2508
November	1st to 10th	Night	14% 6% 2 6% 4 3 4 3 4 6% 49%	2368
	11th to 20th	Night	16% 6% 2 4 4 3 4 3 4 5% 48%	2470
	21st to end	Night	12% 5% 2 5% 3 3 4 3 5% 7% 50%	2555
December	1st to 10th	Night	17% 7% 2 6% 4 4 4 4 5% 5% 41%	2660
	11th to 20th	Night	17% 6% 2 5% 3 3 4 3 5% 6% 45%	3285
	21st to end	Night	14% 7% 2 6% 4 3 4 3 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	21% 37% 6% 21% 13% 2	2618
	11th to 20th	Day	24% 38% 5% 13% 16% 4	2840
	21st to end	Day	30% 42% 6% 13% 8% 1	3124
February	1st to 10th	Day	15% 65% 4 10% 4 1	1710
	11th to 20th	Day	16% 65% 4 7% 6% 2	1801
	21st to end	Day	17% 66% 5% 5% 5% 2	1570
March	1st to 10th	Day	34% 44% 7% 6% 7% 2	3308
	11th to 20th	Day	11% 42% 6% 17% 18% 5%	3480
	21st to end	Day	26% 43% 6% 10% 12% 2	3932
April	1st to 10th	Day	14% 66% 4 8% 7% 1	2280
	11th to 20th	Day	12% 66% 5% 9% 6% 1	2254
	21st to end	Day	14% 66% 5% 9% 5% 2	2280
May	1st to 10th	Day	31% 45% 8% 12% 3 1	3846
	11th to 20th	Day	29% 45% 10% 13% 3	4288
	21st to end	Day	14% 45% 11% 15% 12% 2	4837
June	1st to 10th	Day	12% 68% 6% 8% 5% 1	2660
	11th to 20th	Day	10% 67% 7% 10% 7%	2660
	21st to end	Day	10% 66% 7% 10% 7%	2660
July	1st to 10th	Day	19% 43% 19% 11% 6% 2	4370
	11th to 20th	Day	30% 39% 16% 12% 2	4190
	21st to end	Day	28% 40% 10% 11% 10% 1	4324
August	1st to 10th	Day	32% 40% 12% 13% 2	4091
	11th to 20th	Day	23% 42% 8% 18% 8%	3771
	21st to end	Day	14% 39% 11% 22% 14% 1	4180
September	1st to 10th	Day	15% 63% 7% 9% 5% 1	2280
	11th to 20th	Day	16% 61% 7% 8% 6% 2	2280
	21st to end	Day	23% 59% 4 10% 3 1	2031
October	1st to 10th	Day	17% 39% 7% 18% 16% 2	3160
	11th to 20th	Day	12% 37% 3 13% 28% 7%	3140
	21st to end	Day	9% 37% 6% 21% 19% 10%	3428
November	1st to 10th	Day	16% 58% 4 12% 8% 2	1781
	11th to 20th	Day	15% 60% 4 7% 11% 3	1710
	21st to end	Day	15% 59% 3 12% 9% 1	1620
December	1st to 10th	Day	22% 59% 4 8% 4 2	1520
	11th to 20th	Day	18% 48% 3 16% 10% 5%	1906
	21st to end	Day	25% 39% 8% 18% 9%	2772
January	1st to 10th	Night	25% 38% 6% 15% 13% 3	4324
	11th to 20th	Night	26% 37% 4 15% 15% 3	4120
	21st to end	Night	30% 41% 4 13% 9% 2	4532
February	1st to 10th	Night	15% 66% 5% 10% 4 1	2470
	11th to 20th	Night	17% 63% 3 8% 7% 2	2273
	21st to end	Night	14% 65% 4 9% 6% 2	1884
March	1st to 10th	Night	36% 42% 5% 9% 7% 1	3542
	11th to 20th	Night	18% 41% 4 15% 17% 4	3480
	21st to end	Night	25% 41% 4 15% 13% 4	3699
April	1st to 10th	Night	16% 66% 3 6% 8% 1	1900
	11th to 20th	Night	12% 67% 4 9% 7% 1	1875
	21st to end	Night	15% 67% 5% 8% 6% 1	1900
May	1st to 10th	Night	32% 44% 8% 11% 4	3142
	11th to 20th	Night	30% 45% 8% 14% 3	2606
	21st to end	Night	18% 45% 12% 14% 11%	2739
June	1st to 10th	Night	16% 67% 5% 6% 6% 1	1520
	11th to 20th	Night	11% 67% 6% 8% 7% 1	1520
	21st to end	Night	11% 65% 6% 10% 6% 2	1520
July	1st to 10th	Night	25% 44% 11% 12% 6% 1	2480
	11th to 20th	Night	26% 39% 18% 15% 2	2629
	21st to end	Night	35% 40% 7% 10% 8%	2988
August	1st to 10th	Night	35% 40% 10% 12% 2	2814
	11th to 20th	Night	22% 41% 12% 19% 7%	3092
	21st to end	Night	17% 38% 5% 20% 20%	3476
September	1st to 10th	Night	13% 64% 8% 8% 4 2	1900
	11th to 20th	Night	16% 61% 4 9% 8% 2	1900
	21st to end	Night	25% 60% 4 8% 3	2144
October	1st to 10th	Night	23% 39% 8% 13% 15% 2	3800
	11th to 20th	Night	12% 38% 4 15% 23% 8%	3779
	21st to end	Night	8% 36% 4 25% 17% 10%	4120
November	1st to 10th	Night	19% 58% 4 10% 7% 2	2368
	11th to 20th	Night	15% 60% 3 8% 9% 5%	2470
	21st to end	Night	12% 60% 4 12% 10% 2	2555
December	1st to 10th	Night	23% 60% 4 9% 3 2	2660
	11th to 20th	Night	20% 49% 4 12% 11% 3	3288
	21st to end	Night	24% 40% 10% 17% 8% 1	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% 40% 17% 5% 1	460
	11th to 20th	Day	11% 15% 41% 24% 6% 3	452
	21st to end	Day	18% 14% 38% 23% 6% 1	460
May	1st to 10th	Day	16% 13% 37% 23% 8% 1	463
	11th to 20th	Day	21% 8% 32% 28% 9% 2	487
	21st to end	Day	20% 3 26% 28% 18% 4	529
June	1st to 10th	Day	14% 5% 24% 33% 20% 4	490
	11th to 20th	Day	11% 5% 21% 35% 21% 6%	490
	21st to end	Day	9% 3 23% 39% 22% 4	490
July	1st to 10th	Day	9% 3 15% 35% 32% 6%	485
	11th to 20th	Day	7% 1 12% 42% 30% 8%	484
	21st to end	Day	11% 2 18% 38% 24% 7%	532
August	1st to 10th	Day	13% 3 17% 37% 22% 8%	486
	11th to 20th	Day	14% 2 12% 37% 27% 7%	479
	21st to end	Day	10% 3 17% 31% 28% 11%	539
September	1st to 10th	Day	15% 4 18% 32% 21% 11%	490
	11th to 20th	Day	15% 4 19% 34% 20% 8%	490
	21st to end	Day	29% 6% 22% 28% 12% 3	490
October	1st to 10th	Day	20% 4 23% 28% 18% 7%	490
	11th to 20th	Day	16% 10% 28% 28% 15% 4	490
	21st to end	Day	13% 10% 33% 27% 12% 4	539
November	1st to 10th	Day	18% 11% 29% 24% 13% 5%	416
	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% 41% 19% 5%	760
	11th to 20th	Night	14% 12% 39% 26% 9%	751
	21st to end	Night	18% 9% 35% 30% 7% 1	760
May	1st to 10th	Night	18% 10% 34% 30% 7% 1	755
	11th to 20th	Night	18% 7% 28% 35% 11% 1	445
	21st to end	Night	16% 4 17% 37% 24% 2	411
June	1st to 10th	Night	13% 3 19% 44% 19% 2	380
	11th to 20th	Night	10% 4 22% 39% 21% 4	380
	21st to end	Night	8% 2 21% 43% 22% 3	380
July	1st to 10th	Night	12% 2 13% 43% 27% 3	370
	11th to 20th	Night	6% 1 10% 44% 33% 6%	460
	21st to end	Night	8% 3 14% 44% 27% 3	624
August	1st to 10th	Night	11% 2 13% 43% 27% 5%	567
	11th to 20th	Night	12% 4 13% 38% 31% 3	727
	21st to end	Night	12% 3 14% 34% 31% 7%	836
September	1st to 10th	Night	16% 2 14% 35% 28% 5%	760
	11th to 20th	Night	14% 3 15% 34% 28% 6%	760
	21st to end	Night	24% 5% 20% 29% 19% 3	760
October	1st to 10th	Night	18% 6% 21% 30% 22% 5%	760
	11th to 20th	Night	18% 9% 25% 30% 15% 2	760
	21st to end	Night	18% 11% 26% 28% 15% 3	836
November	1st to 10th	Night	18% 9% 27% 28% 15% 3	755
	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 2024-11-01 22:47:50. Version ac07

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