Brunswick
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Brunswick clear sky chart from 2005-11-06 to 2024-04-25.

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	11% 5% 2 5% 5% 4 5% 5% 6% 9% 42%	83741
	Night	11% 6% 3 5% 5% 3 5% 5% 6% 8% 42%	85372
Transparency	Day	27% 34% 10% 13% 11% 4	83464
	Night	28% 34% 9% 13% 12% 5%	85168
Seeing	Day	10% 7% 20% 30% 24% 10%	14658
	Night	12% 6% 20% 32% 26% 5%	24826

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	11% 7% 2 5% 5% 3 5% 4 5% 7% 46%	2836
	11th to 20th	Day	12% 6% 3 6% 5% 3 5% 4 5% 7% 44%	2840
	21st to end	Day	12% 7% 3 6% 5% 3 4 4 5% 7% 44%	3124
February	1st to 10th	Day	16% 8% 2 5% 4 3 5% 5% 5% 6% 42%	1852
	11th to 20th	Day	13% 5% 2 5% 4 3 3 5% 4 6% 48%	1848
	21st to end	Day	13% 5% 3 5% 4 3 3 4 4 8% 48%	1641
March	1st to 10th	Day	15% 9% 3 6% 5% 3 5% 4 5% 7% 37%	3435
	11th to 20th	Day	7% 3 2 4 4 3 4 5% 6% 8% 54%	3480
	21st to end	Day	16% 7% 2 5% 4 2 4 4 5% 7% 44%	3815
April	1st to 10th	Day	8% 5% 2 5% 4 3 4 4 6% 8% 51%	2090
	11th to 20th	Day	10% 5% 3 5% 5% 3 4 4 5% 8% 48%	2157
	21st to end	Day	6% 3 1 3 4 3 4 4 5% 8% 58%	2259
May	1st to 10th	Day	6% 3 1 3 4 3 4 5% 6% 10% 56%	2340
	11th to 20th	Day	8% 5% 2 5% 5% 3 5% 5% 7% 10% 45%	2301
	21st to end	Day	9% 4 2 5% 6% 4 6% 7% 7% 10% 40%	2531
June	1st to 10th	Day	10% 6% 2 5% 5% 4 6% 7% 10% 12% 33%	2340
	11th to 20th	Day	5% 4 2 5% 7% 5% 6% 7% 9% 12% 37%	2340
	21st to end	Day	8% 5% 2 7% 7% 5% 8% 10% 8% 12% 29%	2340
July	1st to 10th	Day	7% 5% 2 6% 6% 5% 7% 9% 8% 12% 32%	2340
	11th to 20th	Day	7% 5% 3 5% 7% 5% 7% 8% 10% 12% 31%	2340
	21st to end	Day	6% 3 3 6% 7% 5% 7% 9% 8% 11% 35%	2547
August	1st to 10th	Day	7% 4 3 7% 7% 5% 8% 8% 9% 13% 29%	2327
	11th to 20th	Day	7% 5% 3 6% 8% 5% 7% 7% 9% 13% 29%	2299
	21st to end	Day	14% 6% 3 7% 7% 4 7% 7% 8% 10% 27%	2238
September	1st to 10th	Day	11% 6% 3 7% 7% 5% 8% 7% 7% 9% 31%	1980
	11th to 20th	Day	14% 7% 3 7% 7% 5% 7% 7% 6% 8% 30%	1980
	21st to end	Day	13% 7% 3 6% 6% 4 5% 6% 6% 9% 37%	1980
October	1st to 10th	Day	11% 7% 2 6% 6% 3 6% 5% 5% 8% 42%	1926
	11th to 20th	Day	8% 5% 2 3 4 3 4 4 6% 8% 53%	1800
	21st to end	Day	10% 5% 2 4 4 2 3 4 5% 8% 51%	1980
November	1st to 10th	Day	11% 5% 2 5% 4 4 4 4 5% 7% 50%	1857
	11th to 20th	Day	11% 7% 2 4 5% 3 4 3 4 6% 50%	1881
	21st to end	Day	12% 6% 3 5% 4 2 4 4 6% 8% 45%	1710
December	1st to 10th	Day	11% 6% 2 6% 6% 3 4 4 5% 8% 46%	1710
	11th to 20th	Day	16% 5% 2 5% 4 2 4 4 5% 7% 45%	2153
	21st to end	Day	15% 8% 3 6% 5% 3 4 4 4 5% 43%	3124
January	1st to 10th	Night	14% 6% 3 6% 5% 2 3 4 6% 8% 42%	4109
	11th to 20th	Night	9% 7% 4 6% 5% 3 4 6% 6% 8% 42%	4120
	21st to end	Night	12% 8% 4 7% 6% 3 4 4 5% 7% 41%	4532
February	1st to 10th	Night	16% 6% 3 6% 4 3 4 4 5% 6% 42%	2323
	11th to 20th	Night	14% 8% 3 6% 5% 3 4 3 4 6% 46%	2218
	21st to end	Night	13% 6% 2 4 5% 3 5% 5% 5% 6% 45%	1810
March	1st to 10th	Night	19% 12% 4 6% 4 2 4 4 4 5% 37%	3418
	11th to 20th	Night	8% 5% 2 3 4 3 4 4 6% 10% 52%	3480
	21st to end	Night	13% 6% 3 5% 5% 3 4 4 5% 7% 47%	3817
April	1st to 10th	Night	9% 5% 2 4 4 3 4 5% 6% 9% 49%	2090
	11th to 20th	Night	9% 5% 2 5% 5% 3 4 4 5% 7% 51%	1970
	21st to end	Night	6% 3 1 4 4 3 5% 3 7% 9% 56%	1814
May	1st to 10th	Night	6% 4 2 4 4 2 4 4 5% 7% 58%	1620
	11th to 20th	Night	7% 3 3 5% 5% 3 5% 5% 7% 10% 49%	1592
	21st to end	Night	9% 5% 2 4 6% 3 5% 6% 7% 10% 43%	1744
June	1st to 10th	Night	10% 5% 2 6% 5% 5% 7% 6% 8% 13% 34%	1620
	11th to 20th	Night	6% 4 2 6% 6% 3 7% 6% 10% 12% 38%	1620
	21st to end	Night	8% 3 3 5% 6% 4 7% 7% 9% 15% 33%	1620
July	1st to 10th	Night	8% 4 2 6% 6% 4 8% 7% 8% 12% 34%	1620
	11th to 20th	Night	6% 5% 3 6% 6% 4 7% 8% 10% 12% 33%	1620
	21st to end	Night	5% 4 3 5% 5% 4 6% 7% 9% 15% 37%	1771
August	1st to 10th	Night	7% 5% 3 7% 6% 4 7% 7% 9% 13% 33%	1611
	11th to 20th	Night	6% 6% 3 5% 8% 5% 6% 7% 9% 13% 33%	1598
	21st to end	Night	13% 6% 2 5% 7% 5% 7% 7% 8% 10% 28%	2097
September	1st to 10th	Night	11% 6% 3 8% 7% 4 6% 7% 9% 10% 30%	1980
	11th to 20th	Night	15% 6% 3 7% 7% 4 6% 6% 7% 10% 29%	1980
	21st to end	Night	12% 6% 4 7% 7% 3 5% 5% 8% 8% 36%	1980
October	1st to 10th	Night	12% 6% 2 6% 5% 3 4 5% 6% 9% 43%	2031
	11th to 20th	Night	8% 3 1 4 4 3 4 5% 5% 7% 55%	2160
	21st to end	Night	9% 4 2 5% 4 3 5% 4 5% 7% 52%	2376
November	1st to 10th	Night	10% 5% 2 5% 5% 3 4 5% 5% 7% 50%	2221
	11th to 20th	Night	11% 6% 2 5% 5% 3 5% 5% 4 6% 47%	2296
	21st to end	Night	13% 6% 2 4 5% 3 5% 4 6% 8% 44%	2470
December	1st to 10th	Night	12% 5% 3 5% 5% 3 5% 4 5% 10% 44%	2470
	11th to 20th	Night	14% 5% 3 5% 6% 2 4 4 4 5% 47%	3042
	21st to end	Night	15% 8% 3 7% 6% 4 5% 4 5% 6% 38%	4532

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	28% 25% 5% 13% 21% 9%	2837
	11th to 20th	Day	32% 25% 5% 12% 17% 9%	2840
	21st to end	Day	32% 24% 9% 13% 12% 10%	3124
February	1st to 10th	Day	29% 34% 6% 11% 13% 7%	1852
	11th to 20th	Day	27% 35% 5% 9% 14% 9%	1858
	21st to end	Day	24% 34% 6% 16% 14% 7%	1641
March	1st to 10th	Day	41% 23% 7% 15% 11% 4	3435
	11th to 20th	Day	20% 24% 15% 14% 13% 13%	3480
	21st to end	Day	34% 23% 8% 16% 14% 6%	3815
April	1st to 10th	Day	21% 35% 8% 15% 14% 7%	2090
	11th to 20th	Day	21% 34% 9% 15% 14% 7%	2157
	21st to end	Day	17% 35% 10% 17% 17% 4	2259
May	1st to 10th	Day	17% 37% 9% 22% 12% 3	2340
	11th to 20th	Day	21% 38% 15% 16% 9% 1	2305
	21st to end	Day	24% 39% 11% 14% 10% 1	2531
June	1st to 10th	Day	25% 40% 13% 16% 6%	2340
	11th to 20th	Day	24% 39% 14% 18% 5%	2340
	21st to end	Day	29% 42% 14% 11% 5%	2340
July	1st to 10th	Day	30% 41% 16% 11% 2 1	2275
	11th to 20th	Day	27% 42% 18% 10% 4	2271
	21st to end	Day	25% 42% 17% 14% 2	2405
August	1st to 10th	Day	26% 41% 18% 14% 1	2314
	11th to 20th	Day	30% 40% 18% 10% 2	2299
	21st to end	Day	36% 41% 13% 8% 2	2238
September	1st to 10th	Day	28% 41% 14% 13% 4	1980
	11th to 20th	Day	35% 39% 10% 10% 4 1	1980
	21st to end	Day	31% 37% 9% 10% 11% 2	1980
October	1st to 10th	Day	24% 38% 6% 13% 11% 7%	1926
	11th to 20th	Day	22% 36% 6% 13% 19% 5%	1800
	21st to end	Day	22% 38% 5% 15% 13% 8%	1980
November	1st to 10th	Day	20% 41% 4 12% 14% 9%	1857
	11th to 20th	Day	23% 39% 5% 12% 15% 5%	1881
	21st to end	Day	25% 40% 5% 13% 12% 5%	1710
December	1st to 10th	Day	24% 40% 6% 15% 11% 4	1710
	11th to 20th	Day	29% 32% 8% 12% 17% 2	2150
	21st to end	Day	34% 25% 5% 14% 17% 6%	3124
January	1st to 10th	Night	30% 25% 5% 10% 19% 10%	4109
	11th to 20th	Night	33% 26% 5% 11% 19% 7%	4120
	21st to end	Night	35% 24% 7% 12% 12% 9%	4532
February	1st to 10th	Night	31% 34% 4 10% 12% 8%	2323
	11th to 20th	Night	30% 35% 4 9% 12% 10%	2219
	21st to end	Night	25% 34% 6% 17% 11% 8%	1810
March	1st to 10th	Night	44% 23% 10% 9% 9% 5%	3418
	11th to 20th	Night	21% 23% 12% 21% 14% 10%	3480
	21st to end	Night	31% 22% 9% 14% 16% 8%	3817
April	1st to 10th	Night	21% 36% 10% 13% 14% 7%	2090
	11th to 20th	Night	21% 34% 6% 17% 16% 7%	1970
	21st to end	Night	15% 36% 10% 19% 16% 5%	1814
May	1st to 10th	Night	17% 37% 9% 21% 13% 3	1620
	11th to 20th	Night	20% 40% 16% 13% 9% 2	1593
	21st to end	Night	23% 39% 11% 16% 10% 1	1745
June	1st to 10th	Night	26% 39% 13% 15% 7%	1620
	11th to 20th	Night	24% 39% 15% 16% 5%	1620
	21st to end	Night	25% 41% 17% 12% 4 1	1620
July	1st to 10th	Night	31% 42% 12% 11% 2 1	1575
	11th to 20th	Night	29% 41% 18% 9% 4	1566
	21st to end	Night	22% 43% 17% 16% 2	1672
August	1st to 10th	Night	22% 44% 19% 13% 3	1600
	11th to 20th	Night	26% 41% 19% 12% 2	1598
	21st to end	Night	35% 41% 11% 9% 2 1	2097
September	1st to 10th	Night	30% 41% 11% 13% 4 1	1980
	11th to 20th	Night	34% 40% 11% 10% 5%	1980
	21st to end	Night	31% 38% 8% 9% 11% 3	1980
October	1st to 10th	Night	24% 38% 8% 12% 9% 8%	2031
	11th to 20th	Night	20% 37% 6% 13% 19% 5%	2160
	21st to end	Night	22% 39% 6% 11% 16% 7%	2376
November	1st to 10th	Night	19% 40% 4 11% 16% 10%	2221
	11th to 20th	Night	24% 40% 4 12% 14% 6%	2296
	21st to end	Night	26% 39% 6% 13% 11% 5%	2470
December	1st to 10th	Night	23% 39% 10% 13% 11% 4	2470
	11th to 20th	Night	30% 33% 5% 13% 16% 4	3044
	21st to end	Night	36% 25% 7% 12% 16% 3	4532

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	11% 16% 41% 25% 7%	270
	11th to 20th	Day	4 14% 33% 34% 12% 2	270
	21st to end	Day	16% 17% 41% 23% 3	297
February	1st to 10th	Day	18% 13% 30% 31% 8%	270
	11th to 20th	Day	19% 10% 40% 26% 6%	270
	21st to end	Day	11% 13% 34% 36% 5%	296
March	1st to 10th	Day	11% 13% 33% 31% 12%	460
	11th to 20th	Day	12% 12% 32% 31% 10% 3	460
	21st to end	Day	12% 11% 35% 30% 10% 2	506
April	1st to 10th	Day	10% 14% 32% 29% 14% 2	460
	11th to 20th	Day	11% 10% 28% 31% 16% 4	452
	21st to end	Day	5% 6% 29% 35% 19% 6%	437
May	1st to 10th	Day	5% 7% 24% 38% 21% 5%	423
	11th to 20th	Day	7% 1 19% 36% 29% 8%	447
	21st to end	Day	9% 3 11% 30% 33% 15%	485
June	1st to 10th	Day	14% 2 10% 30% 32% 13%	450
	11th to 20th	Day	8% 2 12% 27% 31% 20%	450
	21st to end	Day	7% 2 8% 28% 36% 20%	450
July	1st to 10th	Day	5% 2 5% 21% 43% 25%	445
	11th to 20th	Day	6% 1 2 19% 46% 27%	444
	21st to end	Day	6% 1 6% 22% 46% 18%	488
August	1st to 10th	Day	6% 2 6% 23% 42% 22%	446
	11th to 20th	Day	5% 1 3 19% 42% 29%	439
	21st to end	Day	10% 3 8% 21% 37% 21%	495
September	1st to 10th	Day	10% 3 7% 26% 36% 19%	450
	11th to 20th	Day	12% 5% 10% 32% 31% 10%	450
	21st to end	Day	13% 2 11% 26% 35% 13%	450
October	1st to 10th	Day	12% 5% 20% 35% 21% 7%	450
	11th to 20th	Day	8% 5% 22% 35% 24% 6%	450
	21st to end	Day	12% 5% 17% 39% 22% 4	495
November	1st to 10th	Day	15% 6% 23% 33% 18% 4	455
	11th to 20th	Day	16% 9% 29% 34% 11% 2	441
	21st to end	Day	14% 11% 27% 36% 11%	270
December	1st to 10th	Day	11% 9% 33% 34% 10% 3	270
	11th to 20th	Day	20% 10% 29% 32% 9%	270
	21st to end	Day	13% 11% 29% 34% 11% 1	297
January	1st to 10th	Night	14% 11% 36% 30% 8% 1	760
	11th to 20th	Night	11% 10% 30% 36% 13% 1	760
	21st to end	Night	16% 11% 37% 31% 5%	836
February	1st to 10th	Night	18% 9% 31% 33% 10% 1	760
	11th to 20th	Night	18% 11% 30% 33% 8%	743
	21st to end	Night	15% 8% 31% 39% 6%	628
March	1st to 10th	Night	10% 9% 31% 38% 12%	760
	11th to 20th	Night	13% 8% 28% 37% 13% 1	760
	21st to end	Night	11% 8% 28% 38% 14% 1	836
April	1st to 10th	Night	10% 8% 32% 36% 13% 1	760
	11th to 20th	Night	10% 8% 28% 33% 19% 2	751
	21st to end	Night	6% 5% 21% 46% 20% 1	704
May	1st to 10th	Night	7% 4 20% 42% 25% 3	540
	11th to 20th	Night	6% 1 18% 34% 33% 8%	531
	21st to end	Night	10% 3 7% 32% 42% 6%	584
June	1st to 10th	Night	10% 2 8% 37% 36% 7%	540
	11th to 20th	Night	7% 1 7% 31% 40% 14%	540
	21st to end	Night	8% 1 6% 28% 45% 13%	540
July	1st to 10th	Night	8% 1 6% 24% 47% 14%	525
	11th to 20th	Night	5% 1 3 21% 49% 20%	522
	21st to end	Night	5% 1 5% 23% 55% 11%	591
August	1st to 10th	Night	7% 1 6% 21% 51% 14%	537
	11th to 20th	Night	8% 1 3 17% 52% 19%	534
	21st to end	Night	14% 2 6% 22% 41% 16%	776
September	1st to 10th	Night	11% 2 7% 25% 45% 10%	720
	11th to 20th	Night	14% 3 9% 25% 42% 8%	720
	21st to end	Night	14% 3 9% 26% 40% 8%	720
October	1st to 10th	Night	16% 3 17% 29% 29% 6%	720
	11th to 20th	Night	8% 5% 16% 36% 30% 4	720
	21st to end	Night	11% 5% 20% 31% 31% 3	792
November	1st to 10th	Night	13% 5% 23% 37% 21% 2	740
	11th to 20th	Night	14% 8% 27% 31% 18% 2	760
	21st to end	Night	15% 8% 26% 33% 16% 2	760
December	1st to 10th	Night	13% 10% 24% 33% 19% 1	760
	11th to 20th	Night	14% 10% 26% 31% 16% 3	760
	21st to end	Night	17% 10% 25% 33% 15%	836

Page generated at 2024-04-22 09:25:40. Version ac07

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