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 2024-10-25.

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	12% 7% 3 6% 4 4 4 4 6% 8% 43%	101136
	Night	13% 8% 3 6% 4 4 4 3 5% 7% 44%	97741
Transparency	Day	39% 6% 12% 25% 16% 2	100931
	Night	41% 5% 11% 24% 16% 3	97619
Seeing	Day	16% 12% 28% 26% 15% 4	15610
	Night	17% 11% 30% 28% 12% 1	25399

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% 10% 6% 5% 4 3 6% 7% 31%	2527
	11th to 20th	Day	12% 10% 4 9% 5% 6% 4 4 4 6% 36%	2766
	21st to end	Day	20% 16% 6% 7% 5% 3 3 3 4 4 29%	3135
February	1st to 10th	Day	14% 11% 4 9% 5% 4 4 4 4 5% 35%	1710
	11th to 20th	Day	14% 10% 4 6% 5% 4 4 4 4 6% 39%	1802
	21st to end	Day	15% 11% 3 8% 4 3 4 3 5% 6% 39%	1570
March	1st to 10th	Day	18% 11% 3 6% 3 3 3 3 4 4 42%	3211
	11th to 20th	Day	12% 7% 2 5% 3 3 4 3 5% 6% 49%	3480
	21st to end	Day	16% 8% 3 7% 6% 5% 4 4 6% 7% 35%	3993
April	1st to 10th	Day	11% 7% 3 7% 5% 5% 4 4 6% 7% 42%	2280
	11th to 20th	Day	16% 8% 3 7% 4 4 4 3 4 6% 42%	2254
	21st to end	Day	18% 6% 3 8% 5% 4 4 4 6% 6% 36%	2280
May	1st to 10th	Day	14% 8% 3 8% 5% 4 5% 5% 7% 10% 32%	3837
	11th to 20th	Day	17% 8% 2 6% 4 4 4 3 5% 8% 38%	4399
	21st to end	Day	9% 6% 2 6% 5% 4 5% 4 5% 8% 45%	4824
June	1st to 10th	Day	8% 5% 2 5% 5% 4 4 3 6% 9% 48%	2660
	11th to 20th	Day	7% 4 2 4 4 4 4 4 7% 9% 50%	2660
	21st to end	Day	4 4 2 5% 5% 4 6% 5% 8% 11% 46%	2660
July	1st to 10th	Day	13% 6% 2 6% 4 4 5% 4 7% 9% 40%	4440
	11th to 20th	Day	4 4 1 5% 4 5% 5% 5% 7% 10% 50%	4440
	21st to end	Day	7% 5% 2 6% 5% 5% 5% 5% 8% 11% 41%	4528
August	1st to 10th	Day	5% 4 2 5% 4 4 5% 5% 7% 10% 50%	4104
	11th to 20th	Day	13% 5% 2 5% 4 5% 5% 4 6% 9% 42%	3746
	21st to end	Day	6% 4 2 5% 4 4 4 4 6% 9% 52%	4180
September	1st to 10th	Day	12% 4 2 5% 4 3 3 3 5% 8% 50%	2280
	11th to 20th	Day	10% 5% 2 5% 3 3 4 4 5% 9% 50%	2273
	21st to end	Day	9% 5% 2 6% 3 4 4 4 5% 7% 53%	2053
October	1st to 10th	Day	10% 5% 2 5% 3 3 3 3 3 7% 56%	1900
	11th to 20th	Day	14% 6% 3 5% 3 3 3 2 4 6% 53%	1900
	21st to end	Day	18% 8% 2 5% 3 3 3 3 4 4 48%	2026
November	1st to 10th	Day	11% 6% 1 4 3 4 3 3 4 6% 55%	1676
	11th to 20th	Day	13% 7% 2 6% 4 4 3 3 5% 6% 48%	1710
	21st to end	Day	15% 10% 3 7% 4 4 4 2 4 5% 42%	1611
December	1st to 10th	Day	12% 12% 3 6% 4 4 4 3 4 7% 40%	1520
	11th to 20th	Day	13% 11% 3 7% 4 4 4 3 4 6% 41%	1918
	21st to end	Day	19% 11% 5% 9% 6% 5% 5% 4 5% 5% 26%	2783
January	1st to 10th	Night	14% 11% 6% 10% 5% 3 4 4 4 4 36%	4428
	11th to 20th	Night	13% 11% 4 10% 6% 7% 6% 4 3 4 31%	4202
	21st to end	Night	23% 16% 5% 8% 4 3 3 3 4 5% 28%	4532
February	1st to 10th	Night	15% 13% 4 8% 5% 4 4 4 5% 5% 34%	2470
	11th to 20th	Night	15% 8% 4 8% 4 3 4 3 5% 6% 41%	2261
	21st to end	Night	16% 9% 3 9% 4 3 3 2 5% 5% 40%	1884
March	1st to 10th	Night	22% 11% 2 4 3 3 2 2 3 4 43%	3669
	11th to 20th	Night	14% 5% 2 5% 3 3 3 3 4 6% 51%	3480
	21st to end	Night	17% 11% 4 8% 5% 4 5% 3 5% 5% 33%	3636
April	1st to 10th	Night	11% 7% 2 7% 4 3 4 3 4 7% 47%	1900
	11th to 20th	Night	13% 6% 2 6% 4 4 4 4 6% 6% 45%	1875
	21st to end	Night	18% 7% 2 6% 4 3 3 3 5% 6% 41%	1900
May	1st to 10th	Night	16% 8% 2 6% 3 3 3 4 6% 8% 40%	3055
	11th to 20th	Night	15% 6% 2 6% 4 4 4 3 5% 7% 43%	2506
	21st to end	Night	9% 5% 2 6% 5% 5% 5% 4 6% 9% 44%	2743
June	1st to 10th	Night	8% 4 2 5% 4 5% 4 4 6% 9% 49%	1520
	11th to 20th	Night	6% 4 2 4 3 4 4 4 5% 11% 54%	1520
	21st to end	Night	4 3 1 5% 3 4 4 4 7% 9% 55%	1520
July	1st to 10th	Night	12% 6% 2 5% 4 4 4 4 5% 9% 44%	2530
	11th to 20th	Night	5% 4 1 4 4 3 3 3 6% 9% 57%	2530
	21st to end	Night	7% 5% 3 7% 5% 6% 5% 4 6% 11% 42%	3030
August	1st to 10th	Night	5% 3 1 4 3 4 4 4 6% 8% 58%	2836
	11th to 20th	Night	11% 6% 2 5% 4 4 4 3 5% 8% 48%	3071
	21st to end	Night	5% 3 1 4 3 4 4 3 5% 10% 58%	3476
September	1st to 10th	Night	12% 4 2 5% 3 4 3 3 5% 6% 53%	1900
	11th to 20th	Night	7% 6% 2 6% 4 4 4 4 5% 6% 52%	1900
	21st to end	Night	9% 4 2 4 4 3 4 4 5% 7% 53%	2109
October	1st to 10th	Night	8% 4 2 4 3 4 3 2 4 5% 60%	2280
	11th to 20th	Night	13% 6% 2 4 3 2 3 3 4 7% 53%	2280
	21st to end	Night	17% 8% 2 5% 3 3 3 2 4 6% 48%	2436
November	1st to 10th	Night	10% 5% 2 5% 3 3 3 3 4 6% 56%	2401
	11th to 20th	Night	13% 7% 2 5% 3 3 3 3 4 7% 49%	2470
	21st to end	Night	18% 8% 3 5% 4 2 4 3 5% 5% 44%	2568
December	1st to 10th	Night	14% 11% 4 7% 5% 4 4 3 5% 6% 36%	2660
	11th to 20th	Night	16% 9% 3 7% 5% 4 4 3 5% 5% 41%	3279
	21st to end	Night	18% 19% 5% 9% 6% 4 5% 3 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	47% 4 8% 22% 14% 4	1570
March	1st to 10th	Day	47% 4 7% 20% 17% 5%	3211
	11th to 20th	Day	36% 5% 10% 26% 17% 5%	3480
	21st to end	Day	47% 7% 15% 22% 9% 1	3993
April	1st to 10th	Day	41% 5% 11% 26% 17% 1	2280
	11th to 20th	Day	44% 5% 9% 23% 15% 4	2254
	21st to end	Day	46% 6% 11% 22% 14% 1	2280
May	1st to 10th	Day	45% 9% 13% 22% 10% 1	3872
	11th to 20th	Day	44% 7% 10% 25% 13% 1	4403
	21st to end	Day	36% 8% 10% 23% 22% 1	4837
June	1st to 10th	Day	32% 9% 12% 27% 17% 2	2660
	11th to 20th	Day	28% 7% 13% 26% 23% 3	2660
	21st to end	Day	28% 9% 17% 26% 15% 5%	2660
July	1st to 10th	Day	39% 6% 11% 29% 12% 2	4371
	11th to 20th	Day	28% 6% 14% 32% 18% 2	4365
	21st to end	Day	35% 7% 18% 27% 11% 1	4386
August	1st to 10th	Day	27% 7% 15% 36% 15%	4090
	11th to 20th	Day	38% 7% 12% 26% 16% 1	3782
	21st to end	Day	28% 6% 15% 33% 15% 3	4179
September	1st to 10th	Day	33% 5% 10% 26% 21% 5%	2280
	11th to 20th	Day	32% 5% 9% 26% 25% 3	2273
	21st to end	Day	31% 5% 9% 28% 24% 3	2053
October	1st to 10th	Day	30% 5% 8% 24% 28% 4	1900
	11th to 20th	Day	35% 3 9% 24% 24% 5%	1900
	21st to end	Day	41% 4 9% 26% 17% 3	2026
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% 14% 4	1884
March	1st to 10th	Night	47% 4 7% 24% 16% 2	3669
	11th to 20th	Night	36% 4 11% 24% 21% 4	3480
	21st to end	Night	53% 6% 10% 25% 7%	3636
April	1st to 10th	Night	39% 4 10% 25% 18% 4	1900
	11th to 20th	Night	38% 5% 10% 23% 19% 5%	1875
	21st to end	Night	44% 4 8% 25% 17% 1	1900
May	1st to 10th	Night	41% 8% 15% 20% 14% 1	3085
	11th to 20th	Night	41% 7% 12% 27% 12% 1	2507
	21st to end	Night	35% 9% 13% 24% 18% 2	2751
June	1st to 10th	Night	29% 9% 14% 26% 18% 4	1520
	11th to 20th	Night	26% 6% 11% 27% 26% 4	1520
	21st to end	Night	25% 6% 16% 27% 20% 6%	1520
July	1st to 10th	Night	37% 6% 11% 30% 14% 3	2490
	11th to 20th	Night	24% 4 11% 37% 21% 3	2482
	21st to end	Night	35% 6% 19% 25% 13% 1	2934
August	1st to 10th	Night	23% 7% 15% 34% 19% 1	2826
	11th to 20th	Night	35% 5% 12% 26% 19% 2	3101
	21st to end	Night	24% 5% 16% 34% 18% 3	3476
September	1st to 10th	Night	32% 5% 9% 23% 24% 6%	1900
	11th to 20th	Night	32% 5% 8% 25% 26% 5%	1900
	21st to end	Night	30% 6% 9% 24% 27% 4	2109
October	1st to 10th	Night	27% 4 10% 24% 29% 5%	2280
	11th to 20th	Night	31% 5% 7% 27% 23% 7%	2280
	21st to end	Night	40% 3 8% 21% 22% 4	2436
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% 36% 10% 2	225
March	1st to 10th	Day	19% 24% 46% 10% 1	270
	11th to 20th	Day	30% 21% 31% 13% 3 1	270
	21st to end	Day	32% 19% 32% 13% 4	399
April	1st to 10th	Day	20% 18% 38% 16% 7% 1	460
	11th to 20th	Day	22% 21% 32% 18% 7%	452
	21st to end	Day	24% 16% 36% 18% 6%	460
May	1st to 10th	Day	18% 18% 34% 23% 6% 2	468
	11th to 20th	Day	19% 13% 30% 23% 13% 2	675
	21st to end	Day	13% 9% 31% 28% 13% 6%	734
June	1st to 10th	Day	9% 6% 25% 33% 22% 6%	680
	11th to 20th	Day	8% 5% 23% 40% 21% 4	680
	21st to end	Day	5% 7% 33% 34% 17% 4	680
July	1st to 10th	Day	11% 4 16% 29% 28% 12%	671
	11th to 20th	Day	6% 3 24% 37% 25% 4	668
	21st to end	Day	10% 4 20% 33% 29% 5%	739
August	1st to 10th	Day	8% 3 17% 39% 25% 7%	676
	11th to 20th	Day	13% 4 18% 31% 26% 7%	496
	21st to end	Day	9% 2 17% 32% 31% 10%	539
September	1st to 10th	Day	11% 5% 17% 35% 25% 8%	490
	11th to 20th	Day	11% 2 17% 30% 30% 11%	490
	21st to end	Day	12% 9% 21% 30% 21% 7%	453
October	1st to 10th	Day	10% 13% 27% 33% 14% 4	300
	11th to 20th	Day	19% 17% 32% 24% 7%	300
	21st to end	Day	29% 20% 30% 17% 4	311
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	24% 18% 40% 17% 2	628
March	1st to 10th	Night	23% 16% 39% 19% 3	722
	11th to 20th	Night	25% 12% 35% 23% 5%	570
	21st to end	Night	26% 15% 35% 19% 5%	627
April	1st to 10th	Night	16% 18% 38% 23% 6%	570
	11th to 20th	Night	18% 14% 35% 25% 7%	563
	21st to end	Night	20% 13% 38% 24% 5%	570
May	1st to 10th	Night	17% 10% 33% 31% 8% 1	570
	11th to 20th	Night	17% 8% 29% 30% 14% 1	561
	21st to end	Night	11% 6% 26% 37% 19% 2	617
June	1st to 10th	Night	9% 3 22% 39% 26% 1	570
	11th to 20th	Night	8% 2 25% 45% 19% 1	570
	21st to end	Night	4 2 27% 45% 20% 1	570
July	1st to 10th	Night	12% 2 13% 38% 30% 6%	555
	11th to 20th	Night	5% 1 19% 42% 31% 2	552
	21st to end	Night	7% 1 18% 40% 32% 2	624
August	1st to 10th	Night	8% 2 13% 41% 34% 2	567
	11th to 20th	Night	7% 2 16% 40% 30% 5%	564
	21st to end	Night	6% 1 13% 42% 35% 3	627
September	1st to 10th	Night	14% 3 15% 36% 28% 5%	570
	11th to 20th	Night	9% 4 16% 34% 32% 5%	570
	21st to end	Night	11% 7% 23% 32% 23% 4	746
October	1st to 10th	Night	9% 6% 28% 31% 22% 4	760
	11th to 20th	Night	16% 12% 32% 29% 11%	760
	21st to end	Night	23% 13% 36% 24% 5%	812
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 2024-10-22 19:21:02. Version ac07

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