Broemmelsiek Park Astronomy Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Broemmelsiek Park Astronomy Area clear sky chart from 2005-11-06 to 2024-02-25.

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	13% 7% 3 6% 5% 3 4 5% 5% 7% 42%	78495
	Night	13% 8% 3 6% 5% 3 4 4 5% 6% 43%	80853
Transparency	Day	41% 6% 11% 24% 16% 2	78206
	Night	43% 5% 10% 23% 16% 3	80664
Seeing	Day	16% 12% 27% 26% 15% 4	14599
	Night	17% 11% 30% 28% 12% 1	24622

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	9% 13% 6% 9% 6% 4 5% 5% 6% 7% 31%	2527
	11th to 20th	Day	12% 9% 4 8% 7% 5% 4 5% 4 7% 36%	2766
	21st to end	Day	21% 15% 6% 6% 5% 3 3 3 4 4 30%	3135
February	1st to 10th	Day	14% 11% 4 8% 5% 4 4 5% 4 6% 35%	1710
	11th to 20th	Day	14% 8% 4 5% 6% 3 5% 5% 5% 6% 39%	1802
	21st to end	Day	15% 11% 4 7% 4 3 4 4 5% 6% 38%	1520
March	1st to 10th	Day	14% 8% 4 6% 5% 3 5% 4 4 5% 42%	1849
	11th to 20th	Day	19% 9% 4 7% 5% 3 4 4 5% 5% 35%	1980
	21st to end	Day	21% 10% 5% 7% 7% 3 3 4 5% 5% 30%	2274
April	1st to 10th	Day	10% 6% 3 6% 6% 4 5% 4 6% 7% 43%	2160
	11th to 20th	Day	17% 7% 3 6% 4 3 4 4 4 6% 41%	2134
	21st to end	Day	18% 6% 3 6% 6% 3 4 5% 6% 6% 37%	2160
May	1st to 10th	Day	17% 7% 3 6% 5% 3 5% 5% 6% 8% 36%	2190
	11th to 20th	Day	17% 6% 2 5% 5% 3 4 4 5% 8% 41%	2479
	21st to end	Day	11% 5% 3 5% 6% 4 6% 6% 6% 9% 38%	2725
June	1st to 10th	Day	8% 4 3 4 5% 4 5% 4 6% 9% 48%	2520
	11th to 20th	Day	8% 4 2 4 5% 2 5% 5% 6% 10% 49%	2520
	21st to end	Day	4 3 2 4 5% 3 5% 6% 8% 12% 46%	2520
July	1st to 10th	Day	9% 4 2 4 5% 4 5% 6% 7% 11% 44%	2520
	11th to 20th	Day	5% 3 1 4 5% 4 5% 6% 7% 9% 53%	2520
	21st to end	Day	9% 4 2 5% 5% 3 5% 5% 6% 9% 47%	2581
August	1st to 10th	Day	8% 4 2 6% 6% 3 5% 6% 7% 10% 42%	2328
	11th to 20th	Day	9% 5% 3 5% 6% 4 6% 6% 6% 11% 41%	2142
	21st to end	Day	8% 5% 2 4 4 3 4 5% 6% 8% 51%	2376
September	1st to 10th	Day	13% 4 2 4 5% 3 3 5% 5% 8% 49%	2160
	11th to 20th	Day	10% 5% 2 4 4 3 3 4 5% 9% 51%	2154
	21st to end	Day	8% 4 2 5% 3 3 4 5% 5% 7% 55%	1945
October	1st to 10th	Day	10% 5% 2 4 5% 2 4 4 3 7% 54%	1800
	11th to 20th	Day	15% 6% 3 4 4 2 2 3 4 6% 52%	1800
	21st to end	Day	18% 8% 2 5% 3 2 3 4 4 4 47%	1980
November	1st to 10th	Day	11% 6% 2 3 4 2 4 3 4 6% 55%	1676
	11th to 20th	Day	13% 7% 2 5% 5% 3 4 3 5% 6% 48%	1710
	21st to end	Day	15% 9% 4 6% 5% 3 4 3 4 5% 43%	1611
December	1st to 10th	Day	13% 12% 3 6% 4 3 4 4 4 7% 40%	1520
	11th to 20th	Day	13% 10% 3 7% 5% 3 4 4 4 6% 41%	1918
	21st to end	Day	19% 11% 5% 8% 7% 4 5% 4 5% 5% 26%	2783
January	1st to 10th	Night	14% 10% 7% 8% 6% 3 4 4 4 5% 36%	4428
	11th to 20th	Night	13% 11% 4 9% 7% 5% 7% 5% 4 4 31%	4202
	21st to end	Night	23% 15% 5% 7% 5% 2 3 3 4 5% 28%	4532
February	1st to 10th	Night	15% 12% 5% 7% 5% 3 4 5% 4 6% 34%	2470
	11th to 20th	Night	15% 7% 4 7% 5% 3 4 3 5% 6% 41%	2261
	21st to end	Night	16% 9% 3 8% 5% 3 3 3 4 5% 40%	1831
March	1st to 10th	Night	17% 9% 3 5% 5% 2 4 4 3 5% 43%	2124
	11th to 20th	Night	20% 7% 4 7% 5% 3 4 4 5% 6% 37%	1980
	21st to end	Night	20% 11% 4 5% 5% 3 5% 5% 5% 6% 30%	2080
April	1st to 10th	Night	11% 6% 3 6% 5% 2 4 4 4 7% 48%	1800
	11th to 20th	Night	13% 6% 2 5% 5% 3 4 4 6% 7% 43%	1775
	21st to end	Night	19% 7% 2 6% 5% 2 4 3 5% 6% 41%	1800
May	1st to 10th	Night	15% 7% 3 4 4 2 3 4 6% 8% 44%	1766
	11th to 20th	Night	15% 6% 3 6% 4 3 3 4 5% 7% 44%	1416
	21st to end	Night	9% 5% 3 5% 6% 4 4 6% 7% 9% 43%	1551
June	1st to 10th	Night	7% 4 2 4 5% 4 4 5% 6% 9% 50%	1440
	11th to 20th	Night	6% 3 2 3 4 3 4 4 5% 10% 54%	1440
	21st to end	Night	4 2 2 4 5% 3 4 5% 6% 10% 55%	1440
July	1st to 10th	Night	9% 4 2 4 5% 3 5% 5% 5% 10% 49%	1440
	11th to 20th	Night	5% 4 2 3 5% 3 4 3 6% 10% 56%	1440
	21st to end	Night	6% 4 2 5% 4 3 5% 5% 5% 9% 51%	1732
August	1st to 10th	Night	7% 3 2 4 4 3 5% 5% 6% 8% 52%	1611
	11th to 20th	Night	7% 4 2 5% 4 3 4 5% 5% 9% 51%	1759
	21st to end	Night	5% 3 1 4 5% 3 4 4 5% 9% 57%	1980
September	1st to 10th	Night	13% 4 2 5% 3 3 3 4 5% 6% 52%	1800
	11th to 20th	Night	7% 5% 2 5% 5% 3 5% 4 5% 7% 52%	1800
	21st to end	Night	9% 3 2 3 4 2 4 5% 5% 7% 56%	1997
October	1st to 10th	Night	9% 4 2 3 4 3 4 3 4 6% 58%	2160
	11th to 20th	Night	13% 6% 2 3 4 2 3 4 4 7% 52%	2160
	21st to end	Night	17% 8% 2 4 3 2 3 3 4 6% 47%	2376
November	1st to 10th	Night	10% 5% 2 4 4 2 3 3 4 6% 56%	2401
	11th to 20th	Night	13% 6% 3 4 4 2 4 4 4 7% 49%	2470
	21st to end	Night	18% 7% 3 5% 4 2 3 3 4 5% 45%	2568
December	1st to 10th	Night	14% 10% 4 7% 6% 4 4 4 5% 7% 36%	2660
	11th to 20th	Night	16% 8% 3 6% 6% 3 4 4 4 5% 41%	3279
	21st to end	Night	18% 18% 5% 8% 7% 3 5% 4 4 5% 23%	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	52% 5% 10% 23% 9% 1	2528
	11th to 20th	Day	49% 4 13% 20% 13%	2766
	21st to end	Day	58% 4 9% 15% 12% 1	3135
February	1st to 10th	Day	51% 5% 11% 21% 11% 1	1710
	11th to 20th	Day	47% 6% 9% 20% 15% 4	1812
	21st to end	Day	48% 4 9% 23% 13% 4	1520
March	1st to 10th	Day	45% 4 9% 23% 15% 2	1849
	11th to 20th	Day	52% 5% 10% 17% 14% 2	1980
	21st to end	Day	57% 6% 10% 17% 9% 1	2274
April	1st to 10th	Day	40% 5% 11% 26% 17% 1	2160
	11th to 20th	Day	46% 5% 10% 22% 14% 3	2134
	21st to end	Day	47% 6% 11% 22% 13% 1	2160
May	1st to 10th	Day	46% 8% 13% 22% 10% 1	2190
	11th to 20th	Day	41% 8% 12% 23% 15% 1	2483
	21st to end	Day	40% 10% 13% 22% 13% 2	2725
June	1st to 10th	Day	33% 8% 13% 27% 17% 2	2520
	11th to 20th	Day	29% 7% 13% 25% 23% 3	2520
	21st to end	Day	28% 10% 17% 25% 15% 5%	2520
July	1st to 10th	Day	33% 8% 16% 27% 12% 4	2451
	11th to 20th	Day	26% 8% 15% 27% 20% 3	2445
	21st to end	Day	33% 7% 13% 30% 15% 2	2438
August	1st to 10th	Day	34% 9% 14% 27% 16% 1	2314
	11th to 20th	Day	36% 9% 13% 28% 14% 1	2142
	21st to end	Day	30% 8% 13% 24% 20% 6%	2376
September	1st to 10th	Day	33% 6% 11% 27% 18% 5%	2160
	11th to 20th	Day	31% 6% 9% 26% 26% 3	2154
	21st to end	Day	29% 5% 9% 29% 25% 3	1945
October	1st to 10th	Day	32% 5% 9% 25% 25% 4	1800
	11th to 20th	Day	36% 3 9% 24% 22% 5%	1800
	21st to end	Day	42% 4 9% 26% 17% 4	1980
November	1st to 10th	Day	32% 4 12% 26% 21% 5%	1676
	11th to 20th	Day	38% 4 9% 24% 20% 5%	1710
	21st to end	Day	46% 4 8% 27% 15%	1611
December	1st to 10th	Day	46% 4 11% 26% 12% 1	1520
	11th to 20th	Day	46% 4 11% 24% 13% 2	1915
	21st to end	Day	59% 5% 11% 15% 9% 1	2783
January	1st to 10th	Night	52% 4 10% 24% 10% 1	4428
	11th to 20th	Night	58% 3 8% 21% 9% 1	4202
	21st to end	Night	61% 4 8% 20% 7% 1	4532
February	1st to 10th	Night	51% 5% 10% 20% 13% 1	2470
	11th to 20th	Night	45% 4 9% 22% 18% 3	2262
	21st to end	Night	48% 4 10% 21% 13% 3	1831
March	1st to 10th	Night	46% 4 8% 23% 16% 3	2124
	11th to 20th	Night	50% 4 9% 22% 12% 3	1980
	21st to end	Night	55% 6% 11% 19% 9% 1	2080
April	1st to 10th	Night	38% 4 10% 25% 19% 4	1800
	11th to 20th	Night	39% 6% 10% 23% 17% 5%	1775
	21st to end	Night	45% 4 8% 25% 17% 2	1800
May	1st to 10th	Night	39% 7% 13% 23% 16% 1	1766
	11th to 20th	Night	41% 6% 12% 25% 15% 2	1417
	21st to end	Night	37% 9% 15% 20% 16% 3	1552
June	1st to 10th	Night	29% 8% 15% 27% 18% 3	1440
	11th to 20th	Night	26% 6% 11% 27% 25% 4	1440
	21st to end	Night	24% 6% 16% 27% 20% 6%	1440
July	1st to 10th	Night	31% 8% 13% 30% 13% 5%	1400
	11th to 20th	Night	25% 5% 15% 30% 22% 4	1392
	21st to end	Night	29% 7% 12% 32% 19% 2	1636
August	1st to 10th	Night	28% 8% 13% 33% 16% 2	1601
	11th to 20th	Night	29% 7% 13% 28% 21% 2	1759
	21st to end	Night	25% 7% 15% 25% 23% 5%	1980
September	1st to 10th	Night	33% 5% 10% 24% 22% 6%	1800
	11th to 20th	Night	31% 5% 8% 26% 26% 5%	1800
	21st to end	Night	28% 6% 10% 24% 28% 4	1997
October	1st to 10th	Night	28% 4 11% 25% 27% 5%	2160
	11th to 20th	Night	33% 5% 7% 28% 21% 7%	2160
	21st to end	Night	41% 3 9% 21% 22% 4	2376
November	1st to 10th	Night	31% 4 12% 25% 22% 6%	2401
	11th to 20th	Night	37% 4 8% 26% 22% 4	2470
	21st to end	Night	42% 4 11% 24% 17% 2	2568
December	1st to 10th	Night	49% 5% 9% 24% 12% 1	2660
	11th to 20th	Night	46% 4 10% 24% 16% 1	3281
	21st to end	Night	65% 5% 9% 14% 7% 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	20% 25% 35% 15% 4	270
	11th to 20th	Day	29% 24% 33% 15%	270
	21st to end	Day	19% 25% 39% 16% 2	297
February	1st to 10th	Day	23% 25% 37% 13% 2	270
	11th to 20th	Day	25% 27% 30% 14% 4	270
	21st to end	Day	31% 22% 35% 10% 2	210
March	1st to 10th	Day	18% 26% 44% 10% 2	240
	11th to 20th	Day	32% 20% 31% 13% 3 1	240
	21st to end	Day	34% 19% 31% 13% 3	360
April	1st to 10th	Day	18% 17% 40% 17% 8% 1	420
	11th to 20th	Day	22% 19% 32% 18% 8%	412
	21st to end	Day	24% 15% 36% 19% 5%	420
May	1st to 10th	Day	19% 18% 33% 22% 6% 2	427
	11th to 20th	Day	20% 13% 30% 23% 12% 2	625
	21st to end	Day	14% 8% 30% 28% 14% 6%	679
June	1st to 10th	Day	9% 5% 23% 34% 23% 6%	630
	11th to 20th	Day	8% 5% 23% 38% 21% 4	630
	21st to end	Day	5% 7% 31% 35% 18% 4	630
July	1st to 10th	Day	10% 3 14% 29% 30% 13%	621
	11th to 20th	Day	6% 2 24% 37% 27% 4	618
	21st to end	Day	10% 4 20% 32% 29% 5%	684
August	1st to 10th	Day	8% 3 15% 40% 26% 8%	626
	11th to 20th	Day	12% 4 16% 32% 29% 8%	456
	21st to end	Day	9% 2 17% 30% 31% 10%	495
September	1st to 10th	Day	12% 5% 17% 34% 24% 8%	450
	11th to 20th	Day	9% 3 17% 30% 30% 11%	450
	21st to end	Day	9% 9% 20% 32% 22% 7%	415
October	1st to 10th	Day	11% 14% 27% 34% 11% 3	270
	11th to 20th	Day	20% 19% 33% 21% 6%	270
	21st to end	Day	30% 20% 30% 17% 4	297
November	1st to 10th	Day	14% 12% 38% 23% 10% 4	270
	11th to 20th	Day	19% 20% 31% 21% 7% 2	270
	21st to end	Day	25% 16% 32% 23% 4 1	270
December	1st to 10th	Day	17% 23% 35% 16% 6% 3	270
	11th to 20th	Day	21% 19% 35% 21% 5%	270
	21st to end	Day	23% 27% 37% 11% 3	297
January	1st to 10th	Night	19% 19% 37% 21% 4	950
	11th to 20th	Night	23% 20% 34% 19% 3	950
	21st to end	Night	20% 20% 38% 21% 2	1045
February	1st to 10th	Night	22% 17% 38% 21% 2	950
	11th to 20th	Night	21% 20% 38% 19% 2	786
	21st to end	Night	23% 18% 41% 17% 2	611
March	1st to 10th	Night	23% 16% 39% 19% 4	684
	11th to 20th	Night	25% 11% 36% 23% 5%	540
	21st to end	Night	26% 14% 35% 20% 5%	594
April	1st to 10th	Night	16% 17% 38% 24% 6%	540
	11th to 20th	Night	18% 14% 35% 26% 8%	533
	21st to end	Night	21% 12% 38% 24% 5%	540
May	1st to 10th	Night	17% 10% 32% 32% 8% 1	540
	11th to 20th	Night	18% 8% 29% 30% 14% 1	531
	21st to end	Night	11% 6% 26% 36% 19% 2	584
June	1st to 10th	Night	9% 3 21% 40% 27% 1	540
	11th to 20th	Night	9% 2 24% 44% 19% 1	540
	21st to end	Night	4 2 26% 45% 20% 1	540
July	1st to 10th	Night	11% 2 12% 38% 31% 6%	525
	11th to 20th	Night	5% 2 19% 42% 31% 2	522
	21st to end	Night	7% 1 18% 40% 32% 2	591
August	1st to 10th	Night	8% 2 12% 42% 34% 2	537
	11th to 20th	Night	7% 2 15% 40% 31% 5%	534
	21st to end	Night	6% 2 13% 42% 35% 3	594
September	1st to 10th	Night	14% 3 14% 37% 27% 5%	540
	11th to 20th	Night	9% 4 16% 35% 31% 6%	540
	21st to end	Night	10% 6% 24% 33% 24% 4	706
October	1st to 10th	Night	10% 6% 28% 30% 21% 4	720
	11th to 20th	Night	17% 12% 32% 29% 10%	720
	21st to end	Night	23% 13% 35% 24% 5%	792
November	1st to 10th	Night	14% 10% 38% 27% 11% 1	740
	11th to 20th	Night	17% 17% 34% 26% 6%	760
	21st to end	Night	23% 15% 33% 23% 6%	858
December	1st to 10th	Night	22% 16% 34% 23% 5% 1	950
	11th to 20th	Night	23% 13% 32% 27% 4	950
	21st to end	Night	27% 18% 33% 20% 2	1045

Page generated at 2024-02-22 05:05:47. Version ac07

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