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 2026-08-30.

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% 7% 3 7% 4 4 4 4 6% 8% 42%	144018
	Night	13% 8% 3 7% 4 4 4 3 5% 7% 43%	138507
Transparency	Day	40% 5% 11% 25% 17% 2	147612
	Night	41% 4 11% 24% 18% 3	142994
Seeing	Day	16% 12% 28% 25% 14% 4	18159
	Night	17% 12% 30% 28% 12% 1	27880

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	10% 12% 6% 13% 5% 4 4 3 5% 6% 33%	4691
	11th to 20th	Day	7% 8% 3 9% 5% 5% 4 4 4 7% 43%	5170
	21st to end	Day	16% 13% 5% 8% 4 3 3 2 4 4 37%	5812
February	1st to 10th	Day	14% 11% 4 9% 4 4 4 4 4 5% 36%	1890
	11th to 20th	Day	14% 10% 4 7% 5% 4 4 4 4 6% 38%	1998
	21st to end	Day	14% 10% 3 8% 4 4 4 3 5% 6% 40%	1730
March	1st to 10th	Day	16% 10% 2 5% 3 3 3 2 3 4 49%	4716
	11th to 20th	Day	9% 6% 2 5% 3 3 4 3 6% 6% 52%	5090
	21st to end	Day	12% 7% 3 7% 6% 5% 5% 4 6% 7% 36%	5851
April	1st to 10th	Day	12% 7% 3 7% 5% 5% 4 4 6% 7% 41%	2520
	11th to 20th	Day	16% 8% 3 7% 4 4 4 3 4 5% 42%	2494
	21st to end	Day	16% 7% 3 8% 5% 4 4 4 6% 7% 37%	2520
May	1st to 10th	Day	15% 8% 3 8% 5% 5% 5% 4 7% 9% 33%	7134
	11th to 20th	Day	14% 8% 3 7% 4 4 4 3 6% 7% 40%	8222
	21st to end	Day	14% 8% 3 8% 6% 5% 5% 4 5% 7% 34%	9047
June	1st to 10th	Day	8% 5% 2 5% 4 4 4 4 6% 9% 47%	2940
	11th to 20th	Day	7% 4 2 4 5% 4 4 4 7% 10% 49%	2940
	21st to end	Day	4 4 2 5% 5% 4 5% 5% 8% 11% 46%	2940
July	1st to 10th	Day	8% 5% 2 6% 4 4 5% 4 7% 10% 45%	8280
	11th to 20th	Day	5% 5% 2 6% 5% 5% 5% 5% 7% 10% 44%	8280
	21st to end	Day	8% 5% 2 6% 4 5% 5% 5% 7% 11% 42%	8455
August	1st to 10th	Day	5% 4 2 5% 4 4 5% 5% 7% 10% 50%	4364
	11th to 20th	Day	13% 5% 2 5% 4 5% 5% 4 7% 10% 42%	3988
	21st to end	Day	6% 4 2 5% 4 4 4 4 6% 9% 52%	4420
September	1st to 10th	Day	12% 4 2 5% 4 3 4 3 5% 8% 50%	2400
	11th to 20th	Day	10% 5% 2 5% 3 3 4 4 5% 9% 51%	2392
	21st to end	Day	9% 5% 2 6% 3 4 4 4 4 7% 53%	2161
October	1st to 10th	Day	9% 5% 2 5% 4 3 3 3 3 7% 56%	2000
	11th to 20th	Day	14% 5% 2 5% 3 3 3 2 4 6% 54%	2000
	21st to end	Day	18% 8% 2 5% 3 3 3 3 4 4 47%	2200
November	1st to 10th	Day	11% 6% 1 4 3 4 3 3 4 6% 54%	1856
	11th to 20th	Day	13% 7% 2 6% 4 4 3 3 5% 6% 48%	1890
	21st to end	Day	15% 10% 4 7% 4 3 4 2 4 5% 41%	1779
December	1st to 10th	Day	8% 11% 3 7% 4 4 3 2 4 6% 50%	2690
	11th to 20th	Day	12% 9% 4 9% 5% 4 4 3 4 6% 40%	3088
	21st to end	Day	22% 15% 5% 10% 5% 4 4 3 4 4 23%	4070
January	1st to 10th	Night	13% 11% 6% 11% 5% 4 4 3 4 4 37%	8232
	11th to 20th	Night	9% 9% 4 10% 5% 6% 5% 3 4 5% 40%	7818
	21st to end	Night	16% 13% 4 8% 5% 4 4 3 4 5% 35%	8402
February	1st to 10th	Night	15% 12% 4 8% 4 4 4 4 5% 6% 35%	2730
	11th to 20th	Night	16% 8% 3 8% 4 3 4 2 5% 7% 40%	2505
	21st to end	Night	15% 8% 3 9% 4 4 3 2 5% 5% 43%	2076
March	1st to 10th	Night	19% 11% 3 5% 3 3 3 3 3 4 43%	5399
	11th to 20th	Night	12% 7% 2 5% 3 3 3 3 4 7% 49%	5090
	21st to end	Night	15% 10% 3 8% 5% 4 5% 4 5% 6% 35%	5318
April	1st to 10th	Night	11% 7% 2 7% 5% 4 4 3 5% 7% 45%	2100
	11th to 20th	Night	13% 6% 2 6% 4 4 4 4 6% 7% 44%	2075
	21st to end	Night	17% 7% 2 6% 4 3 3 3 5% 6% 41%	2100
May	1st to 10th	Night	16% 8% 3 7% 4 4 4 4 6% 8% 36%	5690
	11th to 20th	Night	13% 6% 2 5% 4 4 4 4 6% 8% 44%	4670
	21st to end	Night	15% 7% 4 8% 6% 5% 5% 4 6% 8% 33%	5139
June	1st to 10th	Night	8% 5% 2 5% 4 5% 4 4 6% 9% 48%	1680
	11th to 20th	Night	7% 4 2 4 3 4 4 4 6% 11% 51%	1680
	21st to end	Night	4 3 1 5% 3 4 4 4 7% 10% 54%	1680
July	1st to 10th	Night	8% 5% 2 6% 4 4 4 4 5% 9% 47%	4708
	11th to 20th	Night	5% 4 2 6% 5% 5% 5% 4 7% 10% 48%	4707
	21st to end	Night	6% 4 2 6% 4 5% 6% 4 7% 11% 45%	5647
August	1st to 10th	Night	5% 3 1 4 3 4 4 4 6% 8% 58%	3016
	11th to 20th	Night	11% 6% 2 5% 4 4 4 3 6% 8% 47%	3269
	21st to end	Night	5% 3 1 4 3 4 4 3 5% 10% 58%	3676
September	1st to 10th	Night	12% 4 2 5% 3 4 4 3 5% 6% 52%	2000
	11th to 20th	Night	7% 6% 2 6% 4 4 4 4 5% 7% 52%	2000
	21st to end	Night	10% 4 2 4 4 3 4 4 5% 7% 54%	2221
October	1st to 10th	Night	8% 4 2 4 3 4 3 2 4 5% 60%	2400
	11th to 20th	Night	13% 6% 2 4 3 2 3 3 4 7% 53%	2400
	21st to end	Night	17% 8% 2 5% 3 3 3 2 4 6% 47%	2640
November	1st to 10th	Night	10% 6% 2 5% 3 3 4 3 4 6% 55%	2661
	11th to 20th	Night	12% 7% 2 5% 4 3 4 3 4 7% 49%	2730
	21st to end	Night	18% 8% 3 6% 4 2 4 3 5% 5% 43%	2839
December	1st to 10th	Night	11% 9% 3 7% 5% 4 4 2 4 5% 46%	4720
	11th to 20th	Night	14% 8% 3 7% 5% 4 4 4 5% 6% 41%	5339
	21st to end	Night	23% 17% 4 9% 5% 4 4 3 4 4 22%	7150

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	53% 4 10% 22% 9% 2	4692
	11th to 20th	Day	42% 3 10% 23% 17% 4	5170
	21st to end	Day	52% 3 9% 17% 15% 4	5812
February	1st to 10th	Day	50% 4 12% 22% 10% 1	1890
	11th to 20th	Day	48% 5% 9% 20% 15% 4	2008
	21st to end	Day	46% 4 8% 23% 15% 4	1730
March	1st to 10th	Day	41% 3 5% 22% 24% 4	4716
	11th to 20th	Day	32% 4 8% 25% 25% 6%	5090
	21st to end	Day	45% 6% 13% 27% 9% 1	5853
April	1st to 10th	Day	42% 5% 11% 25% 17% 1	2520
	11th to 20th	Day	44% 5% 10% 22% 15% 4	2494
	21st to end	Day	46% 6% 11% 24% 13% 1	2520
May	1st to 10th	Day	47% 6% 11% 23% 12%	7169
	11th to 20th	Day	43% 6% 10% 23% 17% 1	8226
	21st to end	Day	49% 6% 9% 19% 16% 1	9061
June	1st to 10th	Day	33% 8% 13% 27% 17% 2	2940
	11th to 20th	Day	30% 7% 12% 26% 22% 3	2940
	21st to end	Day	29% 9% 17% 25% 15% 5%	2940
July	1st to 10th	Day	34% 5% 14% 28% 17% 1	8211
	11th to 20th	Day	34% 7% 16% 24% 18% 1	8205
	21st to end	Day	35% 5% 19% 32% 8% 1	8271
August	1st to 10th	Day	27% 7% 15% 36% 15%	4350
	11th to 20th	Day	37% 7% 13% 26% 15% 1	4024
	21st to end	Day	28% 6% 15% 33% 16% 3	4419
September	1st to 10th	Day	33% 5% 11% 26% 21% 5%	2400
	11th to 20th	Day	31% 5% 9% 27% 26% 2	2392
	21st to end	Day	31% 5% 8% 27% 25% 3	2161
October	1st to 10th	Day	19% 3 5% 18% 47% 8%	3260
	11th to 20th	Day	24% 2 7% 21% 37% 9%	3240
	21st to end	Day	34% 3 7% 27% 26% 2	3538
November	1st to 10th	Day	33% 4 11% 27% 21% 5%	1856
	11th to 20th	Day	38% 4 9% 25% 20% 5%	1890
	21st to end	Day	47% 3 8% 26% 15%	1779
December	1st to 10th	Day	38% 3 12% 31% 16%	2690
	11th to 20th	Day	48% 3 11% 23% 13% 1	3085
	21st to end	Day	64% 4 12% 12% 7% 1	4070
January	1st to 10th	Night	52% 3 12% 24% 8%	8233
	11th to 20th	Night	48% 3 5% 25% 16% 3	7818
	21st to end	Night	53% 3 10% 19% 14% 1	8402
February	1st to 10th	Night	50% 5% 10% 21% 12% 1	2730
	11th to 20th	Night	46% 4 9% 22% 17% 3	2506
	21st to end	Night	45% 4 9% 24% 15% 3	2076
March	1st to 10th	Night	47% 3 5% 22% 21% 2	5399
	11th to 20th	Night	37% 3 9% 24% 21% 7%	5090
	21st to end	Night	50% 5% 9% 24% 11% 1	5318
April	1st to 10th	Night	40% 4 10% 25% 18% 4	2100
	11th to 20th	Night	38% 5% 11% 23% 18% 4	2075
	21st to end	Night	44% 4 9% 25% 17% 1	2100
May	1st to 10th	Night	46% 6% 13% 22% 11% 1	5720
	11th to 20th	Night	38% 5% 12% 25% 17% 2	4671
	21st to end	Night	48% 6% 11% 19% 14% 1	5149
June	1st to 10th	Night	30% 8% 14% 26% 18% 4	1680
	11th to 20th	Night	27% 6% 11% 27% 25% 4	1680
	21st to end	Night	25% 6% 16% 28% 19% 6%	1680
July	1st to 10th	Night	34% 5% 12% 28% 19% 2	4670
	11th to 20th	Night	31% 6% 15% 28% 18% 2	4662
	21st to end	Night	32% 5% 22% 30% 9% 1	5521
August	1st to 10th	Night	23% 7% 15% 34% 19% 1	3006
	11th to 20th	Night	35% 5% 13% 26% 18% 2	3299
	21st to end	Night	24% 5% 15% 34% 19% 3	3676
September	1st to 10th	Night	33% 5% 9% 23% 24% 6%	2000
	11th to 20th	Night	31% 4 8% 26% 26% 4	2000
	21st to end	Night	30% 6% 9% 23% 27% 5%	2221
October	1st to 10th	Night	16% 3 6% 18% 49% 8%	3920
	11th to 20th	Night	22% 3 6% 23% 35% 10%	3899
	21st to end	Night	32% 3 8% 25% 26% 5%	4252
November	1st to 10th	Night	32% 4 11% 25% 22% 5%	2661
	11th to 20th	Night	36% 3 8% 26% 22% 4	2730
	21st to end	Night	44% 4 11% 24% 16% 2	2839
December	1st to 10th	Night	41% 3 8% 32% 14% 1	4720
	11th to 20th	Night	44% 3 12% 22% 18% 1	5341
	21st to end	Night	66% 4 11% 13% 5% 1	7150

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% 25% 35% 14% 4	330
	11th to 20th	Day	26% 27% 34% 12%	330
	21st to end	Day	18% 26% 40% 14% 1	363
February	1st to 10th	Day	23% 24% 39% 12% 2	330
	11th to 20th	Day	28% 28% 29% 12% 3	330
	21st to end	Day	30% 23% 36% 10% 1	273
March	1st to 10th	Day	22% 21% 44% 11% 2	330
	11th to 20th	Day	31% 21% 33% 12% 3 1	330
	21st to end	Day	31% 20% 34% 12% 3	476
April	1st to 10th	Day	23% 19% 36% 15% 6% 1	540
	11th to 20th	Day	23% 21% 32% 17% 6%	532
	21st to end	Day	23% 15% 37% 18% 6%	540
May	1st to 10th	Day	19% 19% 34% 22% 5% 2	548
	11th to 20th	Day	19% 14% 31% 22% 12% 1	775
	21st to end	Day	14% 9% 31% 27% 12% 5%	844
June	1st to 10th	Day	11% 6% 26% 32% 20% 5%	780
	11th to 20th	Day	9% 5% 23% 39% 19% 4	780
	21st to end	Day	6% 6% 32% 36% 16% 4	780
July	1st to 10th	Day	10% 4 16% 31% 27% 12%	771
	11th to 20th	Day	7% 3 24% 37% 25% 5%	768
	21st to end	Day	9% 4 20% 34% 28% 5%	849
August	1st to 10th	Day	8% 3 19% 38% 25% 7%	776
	11th to 20th	Day	12% 4 18% 32% 26% 7%	578
	21st to end	Day	8% 3 16% 35% 29% 9%	619
September	1st to 10th	Day	10% 5% 17% 36% 24% 8%	530
	11th to 20th	Day	10% 2 15% 31% 30% 12%	530
	21st to end	Day	12% 9% 20% 30% 21% 8%	491
October	1st to 10th	Day	9% 13% 25% 35% 14% 4	330
	11th to 20th	Day	20% 16% 32% 24% 8%	330
	21st to end	Day	31% 21% 29% 17% 3	363
November	1st to 10th	Day	15% 15% 38% 21% 8% 3	330
	11th to 20th	Day	20% 20% 33% 19% 7% 2	330
	21st to end	Day	29% 15% 30% 21% 4 1	330
December	1st to 10th	Day	19% 22% 37% 15% 5% 3	330
	11th to 20th	Day	22% 20% 35% 19% 4	330
	21st to end	Day	23% 25% 39% 10% 2	363
January	1st to 10th	Night	19% 19% 38% 21% 4	1050
	11th to 20th	Night	23% 22% 34% 18% 3	1050
	21st to end	Night	19% 21% 38% 20% 1	1155
February	1st to 10th	Night	22% 17% 38% 21% 2	1050
	11th to 20th	Night	23% 19% 36% 19% 2	870
	21st to end	Night	23% 18% 41% 17% 2	692
March	1st to 10th	Night	24% 16% 38% 18% 3	798
	11th to 20th	Night	26% 13% 34% 22% 5%	630
	21st to end	Night	25% 16% 35% 19% 4	693
April	1st to 10th	Night	16% 18% 38% 23% 5%	630
	11th to 20th	Night	19% 15% 36% 24% 7%	623
	21st to end	Night	20% 13% 38% 23% 5%	630
May	1st to 10th	Night	17% 10% 33% 31% 8%	630
	11th to 20th	Night	17% 9% 29% 30% 14% 1	621
	21st to end	Night	11% 7% 26% 36% 18% 2	683
June	1st to 10th	Night	10% 4 23% 38% 24% 1	630
	11th to 20th	Night	8% 2 25% 45% 18% 1	630
	21st to end	Night	5% 2 27% 45% 20% 1	630
July	1st to 10th	Night	11% 2 12% 38% 31% 5%	615
	11th to 20th	Night	5% 2 18% 42% 31% 2	612
	21st to end	Night	7% 1 18% 41% 30% 3	690
August	1st to 10th	Night	9% 2 14% 42% 32% 2	627
	11th to 20th	Night	8% 2 15% 41% 30% 4	624
	21st to end	Night	6% 2 12% 43% 35% 3	687
September	1st to 10th	Night	13% 3 15% 36% 28% 5%	600
	11th to 20th	Night	9% 4 16% 34% 33% 5%	600
	21st to end	Night	11% 7% 22% 33% 23% 4	786
October	1st to 10th	Night	9% 6% 28% 32% 22% 4	800
	11th to 20th	Night	16% 12% 31% 29% 12% 1	800
	21st to end	Night	23% 14% 35% 24% 5%	880
November	1st to 10th	Night	14% 10% 38% 27% 10%	820
	11th to 20th	Night	16% 17% 35% 26% 6%	840
	21st to end	Night	25% 15% 32% 22% 6%	949
December	1st to 10th	Night	23% 15% 34% 23% 4 1	1050
	11th to 20th	Night	23% 15% 32% 26% 4	1050
	21st to end	Night	28% 17% 34% 20% 2	1155

Page generated at 2026-08-27 03:07:12. Version ac07

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