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 2024-11-25.

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	14% 6% 2 6% 4 4 4 4 6% 8% 41%	101395
	Night	15% 6% 2 6% 4 4 4 4 6% 7% 43%	98022
Transparency	Day	40% 3 11% 25% 17% 3	105036
	Night	40% 3 11% 25% 17% 3	102520
Seeing	Day	20% 13% 26% 23% 13% 5%	15009
	Night	18% 12% 27% 29% 12% 1	24570

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	17% 5% 2 5% 4 4 4 4 5% 6% 45%	2646
	11th to 20th	Day	14% 11% 3 7% 5% 4 4 3 6% 5% 39%	2840
	21st to end	Day	17% 10% 3 7% 5% 4 4 4 5% 6% 36%	3124
February	1st to 10th	Day	13% 9% 2 6% 5% 5% 5% 5% 5% 7% 38%	1710
	11th to 20th	Day	17% 8% 3 5% 5% 4 3 3 5% 7% 39%	1683
	21st to end	Day	17% 8% 3 6% 5% 3 5% 3 4 6% 39%	1570
March	1st to 10th	Day	22% 8% 2 6% 4 4 5% 3 5% 6% 35%	3430
	11th to 20th	Day	10% 5% 1 5% 4 5% 5% 4 6% 7% 48%	3480
	21st to end	Day	20% 6% 2 6% 4 3 4 3 5% 6% 40%	3838
April	1st to 10th	Day	12% 7% 2 7% 5% 4 5% 4 6% 8% 40%	2280
	11th to 20th	Day	13% 5% 3 6% 4 3 4 3 6% 6% 46%	2254
	21st to end	Day	18% 6% 2 6% 5% 4 4 4 6% 5% 41%	2280
May	1st to 10th	Day	22% 7% 2 7% 4 4 5% 4 6% 8% 30%	4082
	11th to 20th	Day	24% 7% 2 5% 4 3 4 3 6% 8% 32%	4225
	21st to end	Day	11% 4 2 6% 4 4 5% 4 7% 9% 44%	4823
June	1st to 10th	Day	11% 4 2 5% 5% 4 4 5% 7% 9% 43%	2660
	11th to 20th	Day	11% 5% 2 6% 4 5% 6% 5% 7% 8% 42%	2660
	21st to end	Day	10% 3 2 5% 5% 5% 5% 5% 7% 11% 44%	2660
July	1st to 10th	Day	6% 4 2 6% 5% 5% 6% 5% 8% 10% 43%	4440
	11th to 20th	Day	8% 5% 2 6% 5% 5% 5% 5% 7% 11% 40%	4227
	21st to end	Day	11% 6% 3 7% 6% 6% 5% 4 7% 8% 38%	4466
August	1st to 10th	Day	15% 6% 2 7% 5% 5% 5% 5% 7% 9% 34%	4104
	11th to 20th	Day	9% 4 2 6% 5% 5% 5% 6% 7% 9% 42%	3925
	21st to end	Day	11% 4 2 5% 4 4 5% 4 6% 8% 48%	4180
September	1st to 10th	Day	15% 6% 2 5% 4 4 4 4 4 7% 45%	2280
	11th to 20th	Day	13% 5% 2 6% 3 4 3 4 5% 8% 47%	2275
	21st to end	Day	21% 6% 2 6% 4 3 4 3 5% 7% 38%	1984
October	1st to 10th	Day	16% 6% 2 6% 3 4 3 2 5% 7% 46%	1900
	11th to 20th	Day	16% 4 2 4 4 3 4 3 4 5% 49%	1900
	21st to end	Day	14% 5% 2 5% 3 3 3 3 5% 6% 51%	2090
November	1st to 10th	Day	11% 6% 2 4 3 3 3 3 5% 7% 51%	1889
	11th to 20th	Day	14% 5% 2 5% 3 4 3 4 5% 6% 49%	1736
	21st to end	Day	15% 5% 2 5% 4 4 5% 3 4 7% 45%	1552
December	1st to 10th	Day	16% 8% 2 6% 4 5% 5% 4 6% 6% 38%	1520
	11th to 20th	Day	16% 5% 2 4 5% 4 4 4 6% 7% 43%	1910
	21st to end	Day	18% 6% 2 6% 5% 4 5% 4 6% 8% 35%	2772
January	1st to 10th	Night	13% 8% 2 5% 4 4 4 3 5% 7% 45%	4297
	11th to 20th	Night	19% 7% 2 5% 3 3 3 2 4 6% 45%	4120
	21st to end	Night	18% 9% 3 6% 3 2 4 3 5% 6% 40%	4532
February	1st to 10th	Night	14% 8% 3 6% 5% 4 4 4 5% 6% 41%	2470
	11th to 20th	Night	18% 8% 2 6% 4 4 4 4 5% 5% 41%	2381
	21st to end	Night	17% 8% 3 6% 4 3 4 3 5% 6% 40%	1884
March	1st to 10th	Night	20% 7% 3 6% 4 4 3 3 5% 6% 38%	3418
	11th to 20th	Night	11% 5% 1 5% 3 4 5% 4 5% 7% 50%	3480
	21st to end	Night	14% 9% 2 5% 3 3 3 3 4 5% 47%	3793
April	1st to 10th	Night	14% 8% 2 6% 4 4 4 4 6% 6% 39%	1900
	11th to 20th	Night	13% 5% 2 7% 4 4 4 4 6% 7% 45%	1875
	21st to end	Night	16% 6% 2 4 4 4 4 4 6% 6% 44%	1900
May	1st to 10th	Night	23% 8% 3 7% 4 4 4 3 5% 8% 31%	2827
	11th to 20th	Night	24% 8% 3 7% 4 3 3 3 5% 6% 32%	2664
	21st to end	Night	11% 4 2 6% 3 4 5% 5% 8% 9% 42%	2732
June	1st to 10th	Night	11% 5% 2 4 4 5% 5% 5% 6% 8% 45%	1520
	11th to 20th	Night	11% 6% 2 5% 4 4 5% 5% 7% 8% 43%	1520
	21st to end	Night	8% 5% 2 6% 4 4 4 4 8% 11% 44%	1520
July	1st to 10th	Night	6% 5% 2 7% 5% 5% 7% 5% 8% 10% 40%	2520
	11th to 20th	Night	6% 5% 3 7% 6% 5% 5% 7% 7% 10% 39%	2729
	21st to end	Night	10% 6% 2 7% 4 6% 6% 5% 7% 9% 38%	3087
August	1st to 10th	Night	15% 6% 2 7% 4 6% 6% 5% 7% 9% 33%	2825
	11th to 20th	Night	9% 6% 2 7% 6% 5% 6% 4 7% 8% 40%	2871
	21st to end	Night	13% 4 2 4 4 4 5% 3 5% 8% 48%	3476
September	1st to 10th	Night	15% 4 2 6% 4 4 3 4 7% 6% 45%	1900
	11th to 20th	Night	11% 6% 3 5% 4 3 4 2 4 6% 52%	1900
	21st to end	Night	21% 6% 3 6% 4 3 4 3 4 5% 41%	2195
October	1st to 10th	Night	20% 5% 2 4 3 3 4 2 4 6% 46%	2280
	11th to 20th	Night	14% 4 2 5% 3 3 3 2 4 7% 53%	2280
	21st to end	Night	15% 5% 2 4 3 3 3 3 4 6% 52%	2508
November	1st to 10th	Night	12% 5% 2 5% 3 2 3 3 5% 6% 54%	2406
	11th to 20th	Night	14% 7% 2 4 3 3 3 4 5% 6% 49%	2660
	21st to end	Night	14% 4 2 6% 4 3 4 4 5% 8% 47%	2723
December	1st to 10th	Night	17% 7% 3 6% 4 4 4 3 6% 6% 41%	2660
	11th to 20th	Night	17% 6% 2 6% 4 4 3 3 6% 7% 42%	3285
	21st to end	Night	17% 6% 2 6% 5% 4 6% 4 7% 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	41% 2 6% 31% 15% 4	2647
	11th to 20th	Day	48% 2 8% 20% 17% 5%	2840
	21st to end	Day	49% 2 9% 24% 12% 2	3124
February	1st to 10th	Day	45% 4 12% 24% 13% 3	1710
	11th to 20th	Day	45% 4 7% 24% 17% 3	1692
	21st to end	Day	47% 3 10% 21% 16% 4	1570
March	1st to 10th	Day	51% 2 8% 22% 13% 4	3430
	11th to 20th	Day	36% 2 6% 29% 23% 4	3480
	21st to end	Day	46% 2 11% 21% 16% 3	3838
April	1st to 10th	Day	42% 3 11% 20% 19% 5%	2280
	11th to 20th	Day	38% 3 10% 23% 20% 6%	2254
	21st to end	Day	45% 3 9% 23% 17% 4	2280
May	1st to 10th	Day	52% 4 11% 22% 10% 1	4120
	11th to 20th	Day	52% 3 11% 24% 9% 1	4229
	21st to end	Day	36% 3 14% 26% 18% 2	4837
June	1st to 10th	Day	36% 5% 14% 27% 17% 1	2660
	11th to 20th	Day	37% 7% 14% 26% 15% 2	2660
	21st to end	Day	32% 5% 16% 28% 17% 2	2660
July	1st to 10th	Day	35% 6% 18% 25% 12% 5%	4370
	11th to 20th	Day	37% 5% 15% 30% 12% 1	4154
	21st to end	Day	43% 5% 10% 23% 18% 1	4324
August	1st to 10th	Day	45% 5% 15% 26% 9% 1	4091
	11th to 20th	Day	36% 6% 13% 28% 16% 1	3964
	21st to end	Day	34% 4 13% 29% 18% 2	4180
September	1st to 10th	Day	39% 4 11% 20% 22% 5%	2280
	11th to 20th	Day	36% 3 7% 28% 22% 3	2275
	21st to end	Day	47% 4 8% 20% 19% 2	1984
October	1st to 10th	Day	37% 2 8% 20% 28% 5%	3160
	11th to 20th	Day	26% 2 8% 29% 25% 10%	3140
	21st to end	Day	23% 2 9% 31% 29% 6%	3428
November	1st to 10th	Day	33% 2 11% 27% 22% 5%	1889
	11th to 20th	Day	36% 2 11% 24% 22% 5%	1736
	21st to end	Day	38% 4 11% 29% 16% 2	1552
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% 2 7% 29% 19% 3	4297
	11th to 20th	Night	42% 2 10% 25% 19% 3	4120
	21st to end	Night	47% 2 8% 28% 14% 1	4532
February	1st to 10th	Night	43% 3 11% 27% 14% 2	2470
	11th to 20th	Night	44% 3 8% 24% 16% 5%	2383
	21st to end	Night	45% 2 10% 23% 15% 5%	1884
March	1st to 10th	Night	49% 2 7% 28% 12% 2	3418
	11th to 20th	Night	35% 2 8% 29% 22% 4	3480
	21st to end	Night	41% 2 8% 24% 20% 5%	3793
April	1st to 10th	Night	43% 4 9% 21% 20% 4	1900
	11th to 20th	Night	39% 3 12% 21% 20% 6%	1875
	21st to end	Night	39% 4 10% 28% 14% 4	1900
May	1st to 10th	Night	54% 3 10% 20% 10% 3	2854
	11th to 20th	Night	54% 3 10% 22% 9% 1	2665
	21st to end	Night	37% 4 17% 27% 12% 4	2739
June	1st to 10th	Night	36% 5% 12% 27% 18% 2	1520
	11th to 20th	Night	37% 5% 15% 27% 14% 2	1520
	21st to end	Night	32% 5% 15% 26% 18% 3	1520
July	1st to 10th	Night	38% 6% 20% 20% 12% 5%	2480
	11th to 20th	Night	38% 7% 18% 22% 13% 1	2679
	21st to end	Night	41% 6% 15% 20% 17% 1	2988
August	1st to 10th	Night	46% 5% 15% 24% 8% 1	2814
	11th to 20th	Night	40% 5% 11% 27% 15% 1	2898
	21st to end	Night	34% 4 13% 31% 16% 2	3476
September	1st to 10th	Night	39% 4 11% 22% 19% 5%	1900
	11th to 20th	Night	35% 3 7% 29% 23% 3	1900
	21st to end	Night	46% 3 8% 22% 18% 3	2195
October	1st to 10th	Night	41% 3 9% 22% 21% 4	3800
	11th to 20th	Night	25% 2 10% 23% 32% 7%	3779
	21st to end	Night	24% 2 9% 33% 27% 6%	4120
November	1st to 10th	Night	33% 3 9% 26% 23% 5%	2406
	11th to 20th	Night	36% 3 7% 26% 23% 6%	2660
	21st to end	Night	36% 3 12% 26% 20% 4	2723
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	36% 21% 28% 13% 1	270
	21st to end	Day	28% 31% 27% 10% 2 1	297
February	1st to 10th	Day	22% 29% 34% 11% 4	270
	11th to 20th	Day	37% 27% 30% 4 2	290
	21st to end	Day	31% 20% 31% 15% 2	382
March	1st to 10th	Day	26% 21% 30% 19% 3	460
	11th to 20th	Day	26% 24% 28% 15% 5% 2	460
	21st to end	Day	24% 20% 33% 17% 5% 1	506
April	1st to 10th	Day	23% 23% 30% 16% 8% 1	460
	11th to 20th	Day	18% 18% 29% 18% 12% 3	452
	21st to end	Day	25% 16% 30% 18% 9% 2	460
May	1st to 10th	Day	25% 17% 28% 18% 10% 3	463
	11th to 20th	Day	23% 11% 27% 21% 14% 4	487
	21st to end	Day	19% 7% 22% 25% 20% 6%	529
June	1st to 10th	Day	14% 8% 29% 25% 19% 6%	490
	11th to 20th	Day	15% 7% 25% 30% 17% 6%	490
	21st to end	Day	11% 7% 32% 29% 15% 7%	490
July	1st to 10th	Day	12% 4 16% 31% 27% 10%	485
	11th to 20th	Day	7% 3 21% 31% 29% 8%	484
	21st to end	Day	13% 4 21% 35% 19% 9%	532
August	1st to 10th	Day	13% 5% 20% 28% 21% 14%	486
	11th to 20th	Day	11% 4 22% 31% 22% 10%	479
	21st to end	Day	10% 3 21% 33% 20% 13%	539
September	1st to 10th	Day	20% 7% 17% 25% 21% 10%	490
	11th to 20th	Day	15% 5% 20% 32% 17% 12%	490
	21st to end	Day	27% 9% 23% 25% 12% 3	490
October	1st to 10th	Day	20% 8% 21% 25% 19% 7%	490
	11th to 20th	Day	17% 15% 24% 28% 13% 2	490
	21st to end	Day	16% 14% 32% 24% 11% 2	539
November	1st to 10th	Day	18% 12% 31% 25% 10% 4	460
	11th to 20th	Day	20% 15% 36% 19% 9% 1	336
	21st to end	Day	23% 20% 34% 16% 6% 1	188
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	26% 15% 30% 25% 4	760
	21st to end	Night	21% 19% 36% 21% 2	836
February	1st to 10th	Night	19% 18% 35% 27% 2	760
	11th to 20th	Night	25% 23% 33% 16% 2	743
	21st to end	Night	27% 17% 35% 18% 3	628
March	1st to 10th	Night	22% 19% 35% 21% 3	760
	11th to 20th	Night	24% 20% 30% 20% 5% 1	760
	21st to end	Night	21% 18% 36% 20% 5% 1	836
April	1st to 10th	Night	20% 19% 34% 23% 4	760
	11th to 20th	Night	17% 13% 35% 27% 7%	751
	21st to end	Night	20% 13% 29% 29% 8%	760
May	1st to 10th	Night	21% 8% 26% 32% 12%	584
	11th to 20th	Night	22% 5% 23% 38% 11% 1	478
	21st to end	Night	16% 4 21% 40% 18% 1	411
June	1st to 10th	Night	12% 4 24% 38% 21% 1	380
	11th to 20th	Night	13% 4 20% 39% 22% 2	380
	21st to end	Night	9% 3 23% 46% 18% 1	380
July	1st to 10th	Night	11% 3 16% 39% 26% 4	370
	11th to 20th	Night	7% 2 14% 40% 35% 4	484
	21st to end	Night	9% 2 16% 42% 27% 4	624
August	1st to 10th	Night	12% 2 11% 42% 31% 4	567
	11th to 20th	Night	10% 4 12% 41% 30% 3	611
	21st to end	Night	13% 3 15% 39% 26% 4	836
September	1st to 10th	Night	17% 2 18% 33% 26% 4	760
	11th to 20th	Night	12% 5% 18% 34% 28% 4	760
	21st to end	Night	23% 7% 19% 29% 21% 1	760
October	1st to 10th	Night	21% 6% 21% 29% 19% 3	760
	11th to 20th	Night	16% 12% 24% 31% 15% 1	760
	21st to end	Night	18% 12% 29% 28% 12% 1	836
November	1st to 10th	Night	14% 12% 31% 31% 11% 1	780
	11th to 20th	Night	19% 15% 31% 27% 8% 1	800
	21st to end	Night	17% 16% 32% 28% 7% 1	779
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 2024-11-22 08:02:29. Version ac07

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