Brooke Stream Manor Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Brooke Stream Manor Observatory clear sky chart from 2005-11-06 to 2024-01-14.

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% 5% 2 5% 5% 3 5% 5% 6% 8% 42%	74668
	Night	15% 6% 2 5% 5% 3 4 5% 5% 7% 43%	75085
Transparency	Day	40% 4 12% 25% 17% 3	74380
	Night	40% 3 11% 25% 18% 3	74892
Seeing	Day	20% 13% 26% 23% 13% 5%	13808
	Night	18% 12% 27% 29% 12% 1	23474

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	15% 6% 2 5% 5% 3 5% 5% 5% 6% 43%	1594
	11th to 20th	Day	15% 8% 3 5% 5% 2 4 6% 6% 6% 40%	1647
	21st to end	Day	15% 8% 3 5% 6% 3 4 5% 4 6% 41%	1782
February	1st to 10th	Day	13% 9% 3 6% 6% 3 5% 6% 5% 7% 37%	1620
	11th to 20th	Day	17% 7% 3 5% 5% 3 4 4 5% 7% 39%	1592
	21st to end	Day	18% 7% 4 5% 5% 2 5% 4 4 6% 40%	1480
March	1st to 10th	Day	13% 5% 2 4 5% 3 4 3 5% 7% 48%	1975
	11th to 20th	Day	17% 6% 2 4 5% 4 5% 5% 5% 6% 41%	1980
	21st to end	Day	18% 6% 3 7% 6% 3 4 4 5% 7% 38%	2188
April	1st to 10th	Day	11% 6% 3 6% 5% 3 5% 5% 6% 8% 41%	2160
	11th to 20th	Day	14% 4 3 5% 5% 2 4 4 6% 6% 46%	2134
	21st to end	Day	18% 5% 3 5% 6% 2 5% 4 5% 6% 41%	2160
May	1st to 10th	Day	16% 7% 2 5% 5% 3 6% 5% 6% 9% 37%	2340
	11th to 20th	Day	19% 6% 3 5% 5% 3 4 4 6% 8% 37%	2375
	21st to end	Day	15% 5% 2 5% 5% 3 4 5% 7% 7% 41%	2725
June	1st to 10th	Day	11% 4 2 4 5% 3 4 5% 7% 9% 43%	2520
	11th to 20th	Day	11% 5% 3 5% 5% 4 6% 7% 7% 8% 40%	2520
	21st to end	Day	10% 3 2 4 5% 4 5% 6% 7% 11% 44%	2520
July	1st to 10th	Day	9% 4 3 5% 6% 4 6% 6% 7% 9% 42%	2520
	11th to 20th	Day	6% 4 2 5% 5% 4 6% 7% 8% 10% 44%	2405
	21st to end	Day	10% 5% 3 5% 6% 4 7% 6% 7% 10% 37%	2547
August	1st to 10th	Day	8% 6% 2 6% 7% 4 6% 6% 7% 10% 37%	2327
	11th to 20th	Day	12% 4 2 6% 6% 3 5% 6% 6% 8% 40%	2240
	21st to end	Day	11% 5% 2 5% 5% 3 6% 6% 7% 9% 42%	2376
September	1st to 10th	Day	16% 5% 2 5% 5% 3 4 5% 5% 7% 44%	2160
	11th to 20th	Day	13% 5% 2 5% 4 4 3 4 5% 8% 48%	2156
	21st to end	Day	19% 6% 2 6% 5% 2 4 4 5% 7% 40%	1880
October	1st to 10th	Day	16% 5% 2 5% 4 2 4 3 5% 8% 46%	1800
	11th to 20th	Day	17% 4 2 4 5% 2 4 4 4 5% 48%	1800
	21st to end	Day	15% 5% 2 4 4 2 4 4 5% 6% 50%	1980
November	1st to 10th	Day	12% 6% 2 4 3 3 4 4 5% 7% 51%	1793
	11th to 20th	Day	15% 4 3 4 3 3 3 4 5% 6% 50%	1650
	21st to end	Day	15% 4 3 4 4 2 5% 5% 4 7% 46%	1520
December	1st to 10th	Day	16% 8% 2 5% 5% 3 6% 5% 6% 7% 39%	1520
	11th to 20th	Day	16% 5% 2 4 5% 3 4 5% 5% 8% 44%	1910
	21st to end	Day	18% 6% 2 5% 5% 3 5% 5% 6% 8% 35%	2772
January	1st to 10th	Night	14% 7% 3 5% 4 3 4 4 5% 7% 44%	2569
	11th to 20th	Night	18% 6% 3 5% 5% 3 4 4 5% 7% 39%	2386
	21st to end	Night	15% 7% 2 6% 4 2 4 5% 5% 6% 44%	2574
February	1st to 10th	Night	14% 8% 3 5% 5% 3 5% 5% 5% 7% 40%	2340
	11th to 20th	Night	17% 7% 2 6% 4 2 4 5% 5% 6% 41%	2252
	21st to end	Night	18% 7% 3 5% 5% 2 4 4 5% 6% 40%	1776
March	1st to 10th	Night	13% 4 3 4 5% 3 4 5% 6% 6% 49%	1980
	11th to 20th	Night	18% 6% 2 4 4 3 4 4 4 6% 45%	1980
	21st to end	Night	16% 7% 3 6% 5% 3 4 4 6% 6% 41%	2167
April	1st to 10th	Night	14% 7% 3 6% 4 3 4 5% 6% 7% 40%	1800
	11th to 20th	Night	13% 5% 2 6% 4 3 4 5% 6% 7% 45%	1775
	21st to end	Night	17% 6% 2 4 4 3 5% 4 6% 7% 44%	1800
May	1st to 10th	Night	17% 6% 2 5% 5% 4 4 5% 6% 8% 39%	1634
	11th to 20th	Night	18% 7% 2 6% 4 3 4 4 6% 9% 37%	1514
	21st to end	Night	13% 5% 3 6% 4 3 5% 5% 6% 10% 41%	1550
June	1st to 10th	Night	12% 4 2 4 4 3 5% 6% 7% 8% 45%	1440
	11th to 20th	Night	12% 5% 2 5% 4 3 5% 6% 7% 8% 43%	1440
	21st to end	Night	8% 4 2 5% 5% 3 5% 5% 8% 11% 44%	1440
July	1st to 10th	Night	9% 5% 3 5% 6% 3 6% 6% 7% 10% 39%	1440
	11th to 20th	Night	6% 3 3 4 6% 3 5% 8% 6% 10% 46%	1551
	21st to end	Night	8% 4 3 4 4 3 7% 6% 8% 12% 41%	1771
August	1st to 10th	Night	8% 5% 2 6% 6% 5% 6% 7% 7% 9% 40%	1611
	11th to 20th	Night	10% 6% 2 7% 6% 4 5% 5% 6% 8% 41%	1642
	21st to end	Night	12% 4 3 4 5% 4 6% 5% 7% 9% 42%	1980
September	1st to 10th	Night	16% 4 2 5% 5% 3 3 5% 6% 7% 44%	1800
	11th to 20th	Night	11% 5% 3 5% 4 3 4 3 4 6% 53%	1800
	21st to end	Night	19% 6% 3 5% 5% 3 4 4 5% 6% 43%	2079
October	1st to 10th	Night	20% 5% 2 3 4 2 4 3 4 6% 46%	2160
	11th to 20th	Night	15% 4 2 4 4 2 4 3 3 6% 52%	2160
	21st to end	Night	16% 5% 2 4 4 3 3 4 4 6% 50%	2376
November	1st to 10th	Night	13% 5% 2 5% 4 2 3 3 5% 6% 54%	2282
	11th to 20th	Night	14% 6% 2 4 3 1 4 4 5% 6% 50%	2527
	21st to end	Night	14% 4 2 5% 5% 2 4 5% 5% 8% 47%	2660
December	1st to 10th	Night	17% 7% 3 5% 5% 3 5% 4 6% 6% 41%	2660
	11th to 20th	Night	17% 5% 2 5% 5% 3 4 4 6% 7% 42%	3285
	21st to end	Night	17% 6% 2 5% 5% 3 6% 6% 6% 8% 36%	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	42% 4 9% 25% 16% 4	1595
	11th to 20th	Day	44% 3 11% 25% 15% 2	1647
	21st to end	Day	45% 3 8% 25% 15% 4	1782
February	1st to 10th	Day	46% 4 12% 23% 12% 3	1620
	11th to 20th	Day	45% 4 7% 25% 16% 3	1601
	21st to end	Day	47% 3 10% 21% 16% 4	1480
March	1st to 10th	Day	37% 3 11% 26% 20% 3	1975
	11th to 20th	Day	44% 3 10% 19% 19% 6%	1980
	21st to end	Day	46% 3 10% 20% 17% 4	2188
April	1st to 10th	Day	41% 4 11% 20% 20% 5%	2160
	11th to 20th	Day	38% 3 10% 23% 20% 6%	2134
	21st to end	Day	45% 3 9% 23% 17% 4	2160
May	1st to 10th	Day	44% 4 12% 21% 16% 2	2340
	11th to 20th	Day	47% 4 13% 20% 14% 2	2379
	21st to end	Day	41% 5% 14% 27% 12% 1	2725
June	1st to 10th	Day	36% 5% 15% 27% 17% 1	2520
	11th to 20th	Day	38% 7% 15% 24% 14% 2	2520
	21st to end	Day	33% 5% 16% 28% 16% 1	2520
July	1st to 10th	Day	38% 5% 13% 24% 17% 2	2450
	11th to 20th	Day	33% 6% 14% 29% 16% 2	2332
	21st to end	Day	39% 6% 13% 23% 18% 2	2405
August	1st to 10th	Day	40% 5% 14% 27% 12% 1	2314
	11th to 20th	Day	40% 6% 14% 23% 16% 2	2240
	21st to end	Day	37% 5% 14% 27% 13% 3	2376
September	1st to 10th	Day	40% 4 12% 21% 20% 4	2160
	11th to 20th	Day	36% 3 7% 28% 22% 3	2156
	21st to end	Day	45% 4 8% 21% 20% 2	1880
October	1st to 10th	Day	39% 3 11% 27% 17% 3	1800
	11th to 20th	Day	39% 2 9% 26% 21% 3	1800
	21st to end	Day	37% 3 7% 28% 23% 3	1980
November	1st to 10th	Day	34% 2 11% 27% 21% 5%	1793
	11th to 20th	Day	36% 2 10% 25% 22% 5%	1650
	21st to end	Day	38% 3 10% 29% 17% 2	1520
December	1st to 10th	Day	44% 4 12% 26% 12% 2	1520
	11th to 20th	Day	41% 2 10% 32% 12% 4	1906
	21st to end	Day	47% 2 13% 25% 12% 1	2772
January	1st to 10th	Night	40% 3 9% 25% 18% 5%	2569
	11th to 20th	Night	45% 3 13% 23% 15% 2	2386
	21st to end	Night	41% 3 8% 28% 18% 2	2574
February	1st to 10th	Night	44% 4 11% 25% 14% 2	2340
	11th to 20th	Night	44% 3 8% 23% 16% 5%	2254
	21st to end	Night	45% 2 9% 23% 15% 5%	1776
March	1st to 10th	Night	37% 3 10% 29% 19% 3	1980
	11th to 20th	Night	41% 4 10% 22% 20% 4	1980
	21st to end	Night	44% 3 10% 22% 16% 5%	2167
April	1st to 10th	Night	42% 4 9% 21% 20% 4	1800
	11th to 20th	Night	38% 3 11% 21% 20% 6%	1775
	21st to end	Night	40% 4 11% 28% 14% 5%	1800
May	1st to 10th	Night	43% 4 11% 23% 14% 5%	1634
	11th to 20th	Night	45% 5% 13% 19% 16% 2	1515
	21st to end	Night	38% 5% 18% 25% 12% 1	1551
June	1st to 10th	Night	36% 5% 12% 26% 18% 2	1440
	11th to 20th	Night	38% 5% 15% 25% 14% 2	1440
	21st to end	Night	32% 5% 15% 26% 18% 3	1440
July	1st to 10th	Night	39% 5% 16% 22% 13% 4	1400
	11th to 20th	Night	33% 7% 16% 23% 19% 2	1501
	21st to end	Night	32% 6% 19% 25% 17% 1	1672
August	1st to 10th	Night	40% 6% 14% 24% 14% 1	1600
	11th to 20th	Night	40% 6% 13% 24% 15% 2	1642
	21st to end	Night	38% 4 14% 25% 16% 3	1980
September	1st to 10th	Night	39% 4 11% 22% 18% 5%	1800
	11th to 20th	Night	35% 3 8% 29% 23% 3	1800
	21st to end	Night	44% 3 9% 23% 19% 3	2079
October	1st to 10th	Night	40% 3 10% 26% 18% 3	2160
	11th to 20th	Night	36% 2 8% 28% 23% 2	2160
	21st to end	Night	36% 2 8% 27% 23% 3	2376
November	1st to 10th	Night	33% 3 9% 27% 22% 5%	2282
	11th to 20th	Night	36% 3 7% 26% 23% 6%	2527
	21st to end	Night	36% 3 11% 27% 20% 4	2660
December	1st to 10th	Night	45% 3 11% 26% 14% 2	2660
	11th to 20th	Night	42% 2 10% 25% 18% 4	3288
	21st to end	Night	46% 3 15% 21% 14% 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	31% 24% 28% 14% 2	217
	11th to 20th	Day	33% 21% 30% 14% 1	249
	21st to end	Day	29% 33% 25% 9% 2 1	264
February	1st to 10th	Day	24% 30% 34% 8% 4	240
	11th to 20th	Day	37% 27% 31% 4 1	259
	21st to end	Day	31% 21% 32% 16% 1	346
March	1st to 10th	Day	25% 23% 30% 20% 2	420
	11th to 20th	Day	26% 24% 28% 15% 5% 2	420
	21st to end	Day	23% 21% 32% 17% 6% 1	462
April	1st to 10th	Day	22% 23% 30% 17% 8% 1	420
	11th to 20th	Day	18% 16% 29% 19% 13% 4	412
	21st to end	Day	26% 16% 30% 18% 9% 2	420
May	1st to 10th	Day	24% 17% 28% 17% 10% 3	423
	11th to 20th	Day	22% 12% 28% 22% 14% 3	447
	21st to end	Day	20% 7% 21% 24% 21% 6%	485
June	1st to 10th	Day	15% 8% 28% 26% 18% 5%	450
	11th to 20th	Day	16% 8% 26% 28% 16% 6%	450
	21st to end	Day	10% 7% 31% 30% 16% 6%	450
July	1st to 10th	Day	13% 4 16% 29% 27% 11%	445
	11th to 20th	Day	6% 3 21% 31% 31% 9%	444
	21st to end	Day	13% 4 21% 34% 20% 9%	488
August	1st to 10th	Day	12% 5% 20% 27% 21% 14%	446
	11th to 20th	Day	12% 5% 19% 31% 23% 11%	439
	21st to end	Day	10% 3 21% 33% 20% 14%	495
September	1st to 10th	Day	21% 6% 17% 24% 22% 11%	450
	11th to 20th	Day	15% 5% 20% 32% 17% 12%	450
	21st to end	Day	24% 9% 24% 26% 13% 4	450
October	1st to 10th	Day	20% 6% 20% 26% 20% 7%	450
	11th to 20th	Day	18% 14% 25% 28% 13% 2	450
	21st to end	Day	18% 15% 32% 23% 9% 2	495
November	1st to 10th	Day	19% 12% 30% 25% 10% 4	424
	11th to 20th	Day	21% 15% 34% 19% 10% 1	310
	21st to end	Day	21% 21% 33% 17% 6% 1	180
December	1st to 10th	Day	20% 23% 37% 15% 3 1	180
	11th to 20th	Day	22% 28% 26% 20% 4	180
	21st to end	Day	22% 24% 31% 17% 6% 1	198
January	1st to 10th	Night	22% 21% 36% 18% 3	760
	11th to 20th	Night	25% 15% 30% 26% 4	735
	21st to end	Night	20% 20% 37% 21% 2	792
February	1st to 10th	Night	19% 18% 35% 25% 2	720
	11th to 20th	Night	25% 23% 33% 17% 2	703
	21st to end	Night	27% 18% 35% 18% 3	592
March	1st to 10th	Night	21% 20% 36% 21% 3	720
	11th to 20th	Night	25% 20% 30% 20% 5% 1	720
	21st to end	Night	21% 17% 36% 20% 5% 1	792
April	1st to 10th	Night	19% 19% 34% 23% 4	720
	11th to 20th	Night	17% 13% 34% 28% 8%	711
	21st to end	Night	22% 13% 29% 29% 8%	720
May	1st to 10th	Night	20% 8% 27% 32% 13%	554
	11th to 20th	Night	22% 5% 23% 38% 11% 1	453
	21st to end	Night	17% 5% 20% 41% 17% 1	389
June	1st to 10th	Night	12% 4 24% 37% 22% 1	360
	11th to 20th	Night	13% 4 21% 38% 21% 2	360
	21st to end	Night	9% 3 22% 47% 18% 1	360
July	1st to 10th	Night	11% 3 17% 38% 27% 5%	350
	11th to 20th	Night	7% 2 13% 39% 35% 4	457
	21st to end	Night	9% 2 16% 41% 27% 4	591
August	1st to 10th	Night	11% 2 11% 42% 31% 4	537
	11th to 20th	Night	11% 4 11% 40% 31% 3	578
	21st to end	Night	13% 3 15% 38% 27% 4	792
September	1st to 10th	Night	18% 2 17% 32% 26% 4	720
	11th to 20th	Night	12% 5% 19% 33% 28% 4	720
	21st to end	Night	21% 7% 19% 30% 22% 1	720
October	1st to 10th	Night	21% 6% 20% 30% 19% 4	720
	11th to 20th	Night	17% 12% 25% 31% 15% 1	720
	21st to end	Night	19% 13% 29% 27% 11% 1	792
November	1st to 10th	Night	15% 12% 31% 30% 11% 1	740
	11th to 20th	Night	19% 15% 30% 27% 8% 1	760
	21st to end	Night	16% 16% 31% 28% 7% 1	760
December	1st to 10th	Night	23% 17% 33% 21% 7%	760
	11th to 20th	Night	20% 13% 38% 24% 4	760
	21st to end	Night	21% 15% 33% 29% 3	836

Page generated at 2024-01-11 04:22:39. Version ac07

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