Brooklyn Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Brooklyn Lake clear sky chart from 2005-11-06 to 2024-11-04.

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	3 6% 3 7% 5% 5% 5% 5% 7% 8% 47%	105315
	Night	2 4 2 5% 4 4 5% 5% 7% 10% 53%	102414
Transparency	Day	33% 5% 11% 25% 19% 7%	105062
	Night	26% 4 15% 29% 20% 6%	102257
Seeing	Day	16% 28% 30% 16% 8% 1	15680
	Night	12% 32% 25% 20% 10% 1	25699

By Month

Percentage Cloud Cover SW (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	3 2 8% 5% 6% 6% 5% 9% 11% 45%	2538
	11th to 20th	Day	3 1 6% 8% 8% 7% 6% 8% 11% 42%	2618
	21st to end	Day	3 3 8% 6% 4 5% 4 7% 10% 50%	3146
February	1st to 10th	Day	3 3 9% 8% 8% 5% 6% 9% 9% 38%	1710
	11th to 20th	Day	4 3 8% 7% 6% 7% 5% 9% 9% 42%	1725
	21st to end	Day	5% 3 10% 8% 7% 7% 4 9% 9% 38%	1570
March	1st to 10th	Day	5% 4 12% 6% 5% 5% 4 7% 9% 42%	3210
	11th to 20th	Day	1 6% 4 8% 5% 4 4 3 6% 9% 49%	3490
	21st to end	Day	1 8% 3 11% 7% 6% 6% 5% 6% 9% 38%	3976
April	1st to 10th	Day	2 8% 4 9% 7% 5% 5% 5% 7% 9% 39%	2280
	11th to 20th	Day	3 13% 4 8% 6% 6% 6% 4 6% 9% 35%	2251
	21st to end	Day	5% 12% 4 8% 6% 5% 5% 5% 7% 7% 36%	2280
May	1st to 10th	Day	4 16% 6% 11% 7% 7% 5% 4 6% 7% 27%	4220
	11th to 20th	Day	6% 9% 2 6% 4 5% 4 5% 7% 9% 43%	4388
	21st to end	Day	4 6% 2 6% 5% 5% 6% 5% 8% 10% 43%	4825
June	1st to 10th	Day	5% 5% 2 6% 5% 4 5% 5% 8% 10% 45%	2660
	11th to 20th	Day	5% 5% 2 4 4 4 5% 4 6% 8% 52%	2660
	21st to end	Day	2 3 1 5% 4 5% 5% 5% 7% 9% 53%	2660
July	1st to 10th	Day	4 4 1 5% 4 4 5% 5% 7% 8% 54%	4430
	11th to 20th	Day	3 3 2 5% 5% 5% 6% 6% 8% 9% 48%	4430
	21st to end	Day	5% 5% 2 6% 4 5% 6% 5% 8% 8% 47%	4691
August	1st to 10th	Day	3 5% 3 7% 5% 6% 6% 6% 9% 10% 40%	4092
	11th to 20th	Day	4 5% 2 6% 5% 6% 6% 4 7% 7% 50%	3891
	21st to end	Day	5% 4 2 5% 4 4 4 4 6% 7% 56%	4180
September	1st to 10th	Day	5% 6% 2 5% 4 4 4 3 5% 7% 55%	2280
	11th to 20th	Day	5% 5% 2 4 4 4 4 3 5% 6% 58%	2280
	21st to end	Day	5% 6% 2 5% 3 3 3 2 4 5% 61%	2042
October	1st to 10th	Day	3 3 1 4 3 2 3 2 4 4 70%	3170
	11th to 20th	Day	2 6% 2 5% 4 4 4 5% 7% 7% 54%	3150
	21st to end	Day	2 7% 3 5% 3 3 4 3 6% 7% 57%	3359
November	1st to 10th	Day	1 3 1 4 3 5% 5% 4 7% 9% 57%	1700
	11th to 20th	Day	1 6% 2 6% 5% 4 5% 5% 8% 10% 49%	1653
	21st to end	Day	2 2 9% 7% 4 6% 3 8% 9% 50%	1520
December	1st to 10th	Day	4 2 6% 7% 6% 6% 5% 8% 11% 45%	1520
	11th to 20th	Day	1 4 2 6% 6% 6% 4 6% 8% 13% 46%	1926
	21st to end	Day	5% 2 8% 7% 6% 6% 6% 7% 10% 43%	2794
January	1st to 10th	Night	2 1 6% 7% 6% 7% 7% 9% 10% 43%	4417
	11th to 20th	Night	1 1 2 4 6% 7% 7% 11% 12% 47%	4367
	21st to end	Night	3 2 6% 4 4 5% 5% 7% 10% 54%	4521
February	1st to 10th	Night	3 2 5% 5% 6% 6% 6% 11% 14% 41%	2470
	11th to 20th	Night	4 2 5% 4 4 6% 5% 13% 10% 48%	2341
	21st to end	Night	3 3 8% 5% 5% 5% 7% 9% 10% 44%	1884
March	1st to 10th	Night	3 2 6% 4 4 6% 6% 8% 9% 52%	3655
	11th to 20th	Night	1 7% 4 8% 3 3 3 2 5% 9% 55%	3490
	21st to end	Night	1 7% 2 6% 5% 4 6% 5% 8% 10% 47%	3671
April	1st to 10th	Night	6% 2 6% 5% 4 6% 5% 7% 9% 49%	1900
	11th to 20th	Night	3 8% 3 8% 4 5% 6% 5% 6% 9% 44%	1877
	21st to end	Night	5% 10% 2 7% 3 4 4 3 7% 8% 48%	1900
May	1st to 10th	Night	4 9% 3 8% 5% 4 4 4 6% 8% 43%	2745
	11th to 20th	Night	4 9% 2 5% 3 4 4 4 7% 10% 48%	2517
	21st to end	Night	3 4 1 4 3 5% 5% 4 7% 8% 54%	2762
June	1st to 10th	Night	3 3 1 3 3 4 4 6% 8% 9% 58%	1520
	11th to 20th	Night	4 3 1 4 3 3 4 4 6% 8% 60%	1520
	21st to end	Night	2 4 1 4 2 3 4 4 5% 6% 64%	1520
July	1st to 10th	Night	2 2 1 3 4 4 4 4 6% 9% 60%	2540
	11th to 20th	Night	1 2 1 3 3 3 5% 5% 8% 11% 58%	2540
	21st to end	Night	1 2 1 3 3 4 6% 5% 7% 9% 59%	2869
August	1st to 10th	Night	1 3 1 5% 4 5% 5% 5% 9% 10% 52%	2847
	11th to 20th	Night	2 3 1 4 4 5% 6% 5% 9% 11% 51%	2934
	21st to end	Night	2 4 2 5% 4 4 4 4 6% 7% 58%	3487
September	1st to 10th	Night	5% 4 1 3 2 3 3 3 4 8% 63%	1900
	11th to 20th	Night	3 3 1 4 3 3 3 3 6% 8% 62%	1900
	21st to end	Night	4 4 1 3 2 3 4 3 5% 7% 65%	2136
October	1st to 10th	Night	3 3 1 2 2 2 2 2 4 5% 75%	3800
	11th to 20th	Night	2 4 2 4 4 4 4 4 6% 9% 56%	3778
	21st to end	Night	2 5% 2 4 3 3 3 3 6% 10% 59%	4166
November	1st to 10th	Night	1 3 2 2 3 3 4 4 7% 10% 61%	2451
	11th to 20th	Night	3 1 4 4 4 5% 6% 8% 11% 53%	2525
	21st to end	Night	1 4 2 6% 5% 4 5% 4 8% 9% 52%	2660
December	1st to 10th	Night	3 2 5% 4 4 5% 5% 9% 13% 50%	2660
	11th to 20th	Night	1 4 1 4 4 5% 5% 6% 10% 15% 45%	3271
	21st to end	Night	4 2 7% 4 5% 6% 7% 10% 12% 43%	4873

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	31% 9% 14% 23% 20% 3	2539
	11th to 20th	Day	38% 6% 21% 20% 12% 3	2618
	21st to end	Day	33% 3 17% 28% 16% 3	3146
February	1st to 10th	Day	37% 8% 19% 19% 14% 2	1710
	11th to 20th	Day	38% 5% 16% 24% 13% 4	1734
	21st to end	Day	42% 5% 14% 20% 15% 3	1570
March	1st to 10th	Day	43% 2 9% 29% 14% 3	3210
	11th to 20th	Day	34% 2 17% 37% 8% 2	3490
	21st to end	Day	47% 2 11% 33% 6% 1	3976
April	1st to 10th	Day	42% 4 14% 21% 15% 4	2280
	11th to 20th	Day	47% 3 12% 23% 13% 2	2254
	21st to end	Day	44% 3 11% 31% 11% 1	2280
May	1st to 10th	Day	57% 2 6% 16% 15% 3	4220
	11th to 20th	Day	37% 2 10% 35% 15% 1	4392
	21st to end	Day	37% 2 7% 30% 20% 3	4825
June	1st to 10th	Day	33% 5% 14% 25% 18% 6%	2660
	11th to 20th	Day	29% 4 9% 20% 26% 13%	2660
	21st to end	Day	25% 5% 6% 23% 28% 13%	2660
July	1st to 10th	Day	23% 6% 8% 17% 26% 20%	4361
	11th to 20th	Day	24% 8% 10% 19% 21% 17%	4355
	21st to end	Day	28% 8% 9% 17% 22% 16%	4543
August	1st to 10th	Day	29% 9% 13% 23% 17% 9%	4078
	11th to 20th	Day	31% 6% 9% 17% 28% 9%	3930
	21st to end	Day	26% 6% 8% 19% 27% 15%	4179
September	1st to 10th	Day	28% 4 6% 19% 30% 13%	2280
	11th to 20th	Day	26% 4 9% 24% 25% 11%	2280
	21st to end	Day	26% 2 7% 31% 29% 4	2042
October	1st to 10th	Day	20% 2 6% 23% 40% 11%	3170
	11th to 20th	Day	25% 7% 11% 35% 19% 3	3150
	21st to end	Day	26% 5% 12% 37% 17% 2	3359
November	1st to 10th	Day	24% 5% 17% 30% 23% 2	1700
	11th to 20th	Day	28% 4 20% 26% 19% 3	1653
	21st to end	Day	29% 4 16% 30% 16% 4	1520
December	1st to 10th	Day	30% 6% 26% 22% 14% 3	1520
	11th to 20th	Day	30% 5% 17% 35% 13% 1	1924
	21st to end	Day	37% 5% 11% 23% 15% 9%	2794
January	1st to 10th	Night	35% 4 15% 30% 13% 3	4417
	11th to 20th	Night	29% 5% 25% 23% 12% 6%	4367
	21st to end	Night	29% 2 20% 28% 17% 5%	4521
February	1st to 10th	Night	29% 7% 22% 26% 14% 2	2470
	11th to 20th	Night	28% 5% 18% 30% 15% 4	2342
	21st to end	Night	35% 2 17% 24% 17% 5%	1884
March	1st to 10th	Night	31% 3 11% 36% 13% 6%	3655
	11th to 20th	Night	30% 2 15% 34% 17% 3	3490
	21st to end	Night	33% 2 17% 39% 8% 1	3671
April	1st to 10th	Night	31% 4 18% 24% 18% 5%	1900
	11th to 20th	Night	37% 4 15% 29% 14% 2	1877
	21st to end	Night	35% 2 12% 33% 17% 1	1900
May	1st to 10th	Night	42% 3 7% 26% 17% 4	2745
	11th to 20th	Night	31% 2 13% 40% 10% 4	2518
	21st to end	Night	27% 2 10% 40% 19% 1	2762
June	1st to 10th	Night	21% 3 22% 29% 20% 5%	1520
	11th to 20th	Night	22% 3 12% 23% 28% 12%	1520
	21st to end	Night	20% 3 7% 26% 30% 15%	1520
July	1st to 10th	Night	19% 4 9% 19% 28% 19%	2500
	11th to 20th	Night	16% 6% 11% 28% 25% 15%	2492
	21st to end	Night	19% 5% 12% 24% 23% 16%	2779
August	1st to 10th	Night	19% 9% 19% 25% 21% 7%	2838
	11th to 20th	Night	23% 11% 14% 21% 20% 12%	2961
	21st to end	Night	24% 5% 9% 19% 29% 14%	3487
September	1st to 10th	Night	21% 3 9% 20% 32% 15%	1900
	11th to 20th	Night	20% 3 11% 29% 26% 12%	1900
	21st to end	Night	20% 3 8% 28% 34% 6%	2136
October	1st to 10th	Night	15% 2 5% 24% 43% 11%	3800
	11th to 20th	Night	21% 7% 12% 33% 23% 4	3778
	21st to end	Night	20% 4 17% 35% 21% 3	4166
November	1st to 10th	Night	18% 5% 19% 31% 23% 4	2451
	11th to 20th	Night	24% 4 20% 31% 16% 5%	2525
	21st to end	Night	27% 5% 15% 33% 16% 4	2660
December	1st to 10th	Night	25% 7% 22% 27% 15% 4	2660
	11th to 20th	Night	27% 5% 18% 35% 15% 1	3272
	21st to end	Night	33% 4 13% 25% 15% 10%	4873

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	23% 41% 17% 14% 4 1	270
	11th to 20th	Day	23% 50% 15% 7% 4	270
	21st to end	Day	15% 53% 22% 7% 3	297
February	1st to 10th	Day	29% 53% 14% 4	270
	11th to 20th	Day	31% 44% 17% 8%	270
	21st to end	Day	32% 44% 19% 5%	225
March	1st to 10th	Day	25% 42% 23% 7% 2	311
	11th to 20th	Day	18% 34% 37% 8% 2	460
	21st to end	Day	19% 44% 27% 9% 2	506
April	1st to 10th	Day	23% 41% 28% 7% 1	460
	11th to 20th	Day	24% 38% 29% 7% 2	452
	21st to end	Day	23% 29% 33% 12% 3	460
May	1st to 10th	Day	24% 26% 31% 13% 6% 1	562
	11th to 20th	Day	18% 18% 35% 18% 10% 2	675
	21st to end	Day	15% 21% 32% 20% 11% 2	734
June	1st to 10th	Day	9% 20% 27% 26% 16% 2	680
	11th to 20th	Day	11% 27% 33% 19% 10% 1	680
	21st to end	Day	7% 19% 35% 23% 13% 2	680
July	1st to 10th	Day	9% 10% 30% 29% 20% 3	671
	11th to 20th	Day	6% 9% 42% 25% 15% 3	668
	21st to end	Day	10% 10% 27% 34% 17% 3	677
August	1st to 10th	Day	8% 15% 41% 28% 8% 1	487
	11th to 20th	Day	8% 16% 37% 26% 10% 3	477
	21st to end	Day	9% 17% 31% 31% 10% 2	539
September	1st to 10th	Day	10% 19% 35% 21% 13% 2	490
	11th to 20th	Day	13% 22% 38% 17% 8% 2	490
	21st to end	Day	14% 24% 32% 17% 9% 5%	333
October	1st to 10th	Day	12% 25% 38% 13% 8% 4	300
	11th to 20th	Day	19% 37% 28% 9% 6% 1	300
	21st to end	Day	24% 38% 28% 7% 2	330
November	1st to 10th	Day	21% 46% 22% 6% 5%	279
	11th to 20th	Day	24% 42% 27% 6% 2	270
	21st to end	Day	15% 48% 27% 7% 2	270
December	1st to 10th	Day	30% 41% 21% 6% 1 1	270
	11th to 20th	Day	23% 49% 22% 6%	270
	21st to end	Day	26% 44% 22% 5% 3	297
January	1st to 10th	Night	16% 45% 22% 10% 6% 1	950
	11th to 20th	Night	19% 48% 19% 10% 4 1	913
	21st to end	Night	10% 53% 24% 9% 4	836
February	1st to 10th	Night	17% 51% 21% 7% 4 1	760
	11th to 20th	Night	14% 47% 22% 13% 4	744
	21st to end	Night	20% 45% 24% 8% 2	628
March	1st to 10th	Night	14% 43% 25% 12% 4 1	760
	11th to 20th	Night	9% 37% 29% 20% 5% 1	760
	21st to end	Night	11% 39% 31% 13% 5% 1	743
April	1st to 10th	Night	11% 37% 36% 14% 2	570
	11th to 20th	Night	16% 31% 31% 16% 5%	563
	21st to end	Night	15% 26% 29% 21% 8% 1	570
May	1st to 10th	Night	14% 23% 30% 22% 11% 1	570
	11th to 20th	Night	14% 11% 29% 29% 15% 1	561
	21st to end	Night	10% 16% 26% 31% 16% 1	617
June	1st to 10th	Night	6% 13% 29% 31% 20% 1	570
	11th to 20th	Night	9% 18% 32% 31% 10% 1	570
	21st to end	Night	5% 10% 26% 40% 18% 1	570
July	1st to 10th	Night	5% 5% 18% 41% 30% 1	555
	11th to 20th	Night	3 5% 25% 39% 26% 2	552
	21st to end	Night	2 3 17% 44% 30% 4	624
August	1st to 10th	Night	4 5% 25% 43% 22% 1	567
	11th to 20th	Night	5% 5% 23% 43% 22% 2	564
	21st to end	Night	4 9% 18% 38% 28% 3	627
September	1st to 10th	Night	8% 7% 28% 33% 21% 4	570
	11th to 20th	Night	9% 9% 32% 32% 15% 3	570
	21st to end	Night	7% 19% 28% 28% 15% 4	649
October	1st to 10th	Night	10% 26% 28% 24% 12% 1	760
	11th to 20th	Night	12% 33% 28% 19% 8% 1	760
	21st to end	Night	15% 37% 31% 11% 5% 2	858
November	1st to 10th	Night	13% 48% 25% 9% 5% 1	943
	11th to 20th	Night	17% 49% 24% 8% 2	950
	21st to end	Night	11% 46% 30% 9% 3	950
December	1st to 10th	Night	19% 49% 21% 8% 2	950
	11th to 20th	Night	14% 53% 22% 9% 2	950
	21st to end	Night	21% 46% 19% 10% 3 1	1045

Page generated at 2024-11-01 20:47:40. Version ac07

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