Minto-Brown Island Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Minto-Brown Island Park clear sky chart from 2005-11-06 to 2025-05-26.

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	16% 8% 3 8% 5% 5% 4 3 5% 6% 36%	118238
	Night	17% 9% 3 8% 5% 5% 4 3 5% 5% 35%	119843
Transparency	Day	48% 7% 11% 17% 13% 4	117983
	Night	50% 7% 11% 17% 11% 3	119688
Seeing	Day	19% 10% 21% 27% 18% 5%	15325
	Night	21% 7% 19% 32% 19% 2	24379

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	32% 16% 6% 14% 6% 5% 4 2 3 4 8%	3639
	11th to 20th	Day	27% 10% 3 10% 8% 5% 5% 3 5% 6% 19%	3640
	21st to end	Day	20% 10% 4 10% 6% 5% 5% 3 4 5% 27%	4483
February	1st to 10th	Day	26% 12% 4 12% 7% 6% 5% 4 5% 6% 14%	1800
	11th to 20th	Day	26% 14% 4 11% 6% 5% 4 3 4 5% 16%	1755
	21st to end	Day	26% 13% 4 11% 6% 5% 4 4 4 5% 17%	1556
March	1st to 10th	Day	16% 11% 4 11% 8% 7% 7% 5% 7% 6% 18%	4782
	11th to 20th	Day	21% 13% 4 9% 6% 5% 4 4 5% 4 24%	5000
	21st to end	Day	19% 12% 5% 12% 7% 7% 7% 5% 7% 6% 14%	5567
April	1st to 10th	Day	24% 12% 4 10% 7% 6% 5% 3 6% 6% 18%	2400
	11th to 20th	Day	19% 11% 4 9% 5% 5% 4 4 5% 6% 28%	2369
	21st to end	Day	18% 10% 3 8% 6% 5% 5% 4 6% 8% 28%	2600
May	1st to 10th	Day	19% 8% 3 7% 5% 5% 4 3 6% 5% 35%	4432
	11th to 20th	Day	10% 5% 2 5% 4 4 4 3 5% 6% 52%	4517
	21st to end	Day	15% 7% 3 8% 7% 6% 6% 5% 7% 7% 29%	4886
June	1st to 10th	Day	18% 10% 3 7% 5% 4 4 4 5% 6% 34%	2660
	11th to 20th	Day	15% 8% 3 8% 6% 5% 5% 5% 6% 8% 32%	2660
	21st to end	Day	8% 5% 2 5% 4 4 4 4 4 6% 55%	2660
July	1st to 10th	Day	3 2 1 3 2 2 3 2 3 5% 74%	4420
	11th to 20th	Day	4 2 1 2 2 2 2 2 3 4 76%	4420
	21st to end	Day	4 2 1 2 1 2 2 2 3 4 77%	4747
August	1st to 10th	Day	2 2 1 3 3 3 3 3 4 6% 70%	4091
	11th to 20th	Day	4 4 2 5% 4 3 4 4 6% 8% 57%	4026
	21st to end	Day	6% 6% 1 5% 3 4 4 3 5% 7% 56%	4309
September	1st to 10th	Day	6% 3 1 4 3 3 3 2 5% 7% 64%	2280
	11th to 20th	Day	9% 7% 3 8% 4 4 5% 3 6% 6% 44%	2263
	21st to end	Day	14% 5% 2 7% 4 3 5% 3 4 6% 46%	2008
October	1st to 10th	Day	12% 6% 2 6% 5% 4 4 4 5% 5% 46%	3180
	11th to 20th	Day	14% 8% 3 9% 6% 6% 6% 5% 7% 8% 29%	3161
	21st to end	Day	19% 11% 4 11% 7% 6% 4 3 6% 8% 21%	3421
November	1st to 10th	Day	25% 14% 6% 11% 6% 5% 5% 4 4 5% 15%	1654
	11th to 20th	Day	26% 13% 4 12% 8% 5% 5% 3 4 5% 16%	1600
	21st to end	Day	23% 12% 4 14% 6% 4 4 3 5% 5% 19%	1600
December	1st to 10th	Day	20% 8% 5% 12% 7% 5% 4 3 4 6% 27%	2620
	11th to 20th	Day	24% 13% 5% 16% 8% 6% 6% 4 5% 4 7%	3028
	21st to end	Day	30% 16% 6% 17% 7% 5% 5% 3 3 3 5%	4004
January	1st to 10th	Night	29% 16% 6% 11% 6% 4 4 3 4 4 12%	6306
	11th to 20th	Night	26% 12% 3 8% 7% 5% 4 3 4 4 23%	6320
	21st to end	Night	24% 10% 4 9% 5% 4 4 3 4 4 31%	6490
February	1st to 10th	Night	22% 14% 5% 11% 7% 6% 5% 3 5% 6% 17%	2600
	11th to 20th	Night	25% 12% 4 9% 6% 5% 4 3 5% 4 24%	2532
	21st to end	Night	24% 13% 3 9% 6% 5% 5% 4 4 6% 21%	2073
March	1st to 10th	Night	14% 12% 5% 11% 7% 8% 7% 5% 7% 6% 20%	5097
	11th to 20th	Night	17% 11% 4 10% 6% 5% 5% 3 5% 5% 28%	5000
	21st to end	Night	18% 13% 5% 12% 8% 7% 5% 4 6% 6% 16%	5407
April	1st to 10th	Night	23% 10% 3 9% 6% 5% 4 4 5% 6% 24%	2000
	11th to 20th	Night	17% 10% 2 7% 4 5% 4 3 6% 7% 35%	1976
	21st to end	Night	18% 9% 3 8% 5% 4 5% 4 6% 6% 33%	1800
May	1st to 10th	Night	18% 7% 3 7% 5% 4 4 3 4 5% 40%	2752
	11th to 20th	Night	8% 6% 2 5% 4 3 3 3 4 6% 57%	2596
	21st to end	Night	12% 7% 3 6% 4 4 5% 4 8% 8% 39%	2805
June	1st to 10th	Night	16% 6% 4 7% 5% 4 5% 3 4 7% 39%	1520
	11th to 20th	Night	12% 7% 3 6% 4 4 4 3 5% 7% 44%	1520
	21st to end	Night	6% 5% 2 4 4 3 3 3 4 6% 61%	1520
July	1st to 10th	Night	2 2 1 2 2 1 1 2 2 4 82%	2540
	11th to 20th	Night	3 3 1 2 1 1 2 2 2 4 79%	2540
	21st to end	Night	2 2 1 2 1 1 2 1 3 4 82%	2790
August	1st to 10th	Night	1 2 1 2 2 1 2 2 4 5% 77%	2848
	11th to 20th	Night	5% 4 1 4 3 4 4 3 5% 6% 62%	2812
	21st to end	Night	8% 4 2 4 2 2 2 2 3 5% 65%	3363
September	1st to 10th	Night	5% 3 1 3 2 2 2 2 5% 5% 69%	1900
	11th to 20th	Night	8% 5% 3 6% 4 5% 5% 3 4 6% 52%	1914
	21st to end	Night	9% 5% 2 6% 4 3 4 2 5% 8% 53%	2171
October	1st to 10th	Night	10% 5% 2 6% 4 4 4 3 5% 7% 50%	3800
	11th to 20th	Night	14% 6% 2 6% 5% 5% 5% 4 7% 8% 38%	3777
	21st to end	Night	19% 9% 3 10% 6% 5% 5% 4 5% 6% 28%	4146
November	1st to 10th	Night	25% 9% 3 8% 5% 5% 5% 4 6% 7% 23%	2640
	11th to 20th	Night	28% 13% 3 9% 5% 4 4 3 4 5% 21%	2800
	21st to end	Night	21% 11% 3 11% 6% 5% 5% 3 5% 5% 25%	2800
December	1st to 10th	Night	17% 8% 3 8% 7% 6% 5% 4 6% 6% 31%	4560
	11th to 20th	Night	29% 14% 6% 13% 7% 5% 4 3 4 4 10%	5176
	21st to end	Night	26% 13% 6% 13% 7% 7% 5% 4 5% 4 11%	6952

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	81% 6% 4 6% 3	3639
	11th to 20th	Day	64% 5% 7% 15% 8% 1	3640
	21st to end	Day	58% 7% 6% 11% 15% 3	4483
February	1st to 10th	Day	70% 7% 9% 10% 4	1800
	11th to 20th	Day	69% 8% 8% 8% 5% 2	1764
	21st to end	Day	69% 6% 9% 8% 5% 2	1556
March	1st to 10th	Day	61% 8% 13% 15% 4	4782
	11th to 20th	Day	60% 7% 8% 17% 7% 1	5000
	21st to end	Day	67% 10% 13% 8% 3	5567
April	1st to 10th	Day	66% 8% 11% 12% 3	2400
	11th to 20th	Day	57% 8% 11% 14% 8% 2	2372
	21st to end	Day	55% 9% 14% 14% 7% 1	2600
May	1st to 10th	Day	47% 9% 12% 19% 12%	4432
	11th to 20th	Day	32% 6% 17% 31% 13% 1	4520
	21st to end	Day	46% 16% 21% 15% 2	4887
June	1st to 10th	Day	51% 7% 16% 20% 6% 1	2660
	11th to 20th	Day	48% 10% 19% 17% 6%	2660
	21st to end	Day	30% 7% 18% 30% 13% 4	2660
July	1st to 10th	Day	14% 3 9% 19% 23% 32%	4351
	11th to 20th	Day	14% 3 6% 18% 37% 21%	4345
	21st to end	Day	13% 3 11% 28% 39% 7%	4597
August	1st to 10th	Day	16% 4 9% 30% 28% 12%	4076
	11th to 20th	Day	25% 5% 18% 32% 16% 4	4065
	21st to end	Day	27% 5% 13% 25% 24% 6%	4308
September	1st to 10th	Day	20% 4 13% 30% 21% 12%	2280
	11th to 20th	Day	38% 7% 13% 20% 15% 6%	2263
	21st to end	Day	38% 7% 13% 21% 15% 5%	2008
October	1st to 10th	Day	38% 5% 9% 22% 23% 3	3180
	11th to 20th	Day	52% 6% 15% 14% 11% 1	3161
	21st to end	Day	60% 7% 7% 16% 10% 1	3421
November	1st to 10th	Day	70% 7% 9% 10% 4	1654
	11th to 20th	Day	71% 6% 9% 8% 5% 2	1600
	21st to end	Day	66% 7% 8% 8% 11% 1	1600
December	1st to 10th	Day	58% 4 10% 14% 13% 1	2620
	11th to 20th	Day	76% 9% 7% 7% 1	3028
	21st to end	Day	83% 7% 5% 4 2	4004
January	1st to 10th	Night	76% 7% 7% 6% 4 1	6306
	11th to 20th	Night	62% 6% 8% 15% 8% 1	6320
	21st to end	Night	57% 5% 6% 12% 15% 4	6490
February	1st to 10th	Night	67% 8% 9% 11% 5% 1	2600
	11th to 20th	Night	62% 7% 12% 11% 7% 2	2534
	21st to end	Night	63% 7% 12% 11% 6% 2	2073
March	1st to 10th	Night	59% 9% 13% 14% 5%	5097
	11th to 20th	Night	56% 9% 11% 16% 8% 1	5000
	21st to end	Night	65% 11% 14% 9% 1	5407
April	1st to 10th	Night	60% 9% 14% 13% 5%	2000
	11th to 20th	Night	49% 9% 16% 17% 7% 3	1976
	21st to end	Night	50% 9% 14% 17% 7% 2	1800
May	1st to 10th	Night	43% 12% 11% 22% 10% 1	2752
	11th to 20th	Night	28% 6% 16% 36% 12% 2	2596
	21st to end	Night	36% 17% 29% 15% 3	2805
June	1st to 10th	Night	44% 8% 16% 26% 5% 1	1520
	11th to 20th	Night	38% 11% 18% 25% 8%	1520
	21st to end	Night	25% 7% 18% 34% 13% 4	1520
July	1st to 10th	Night	11% 3 8% 20% 27% 31%	2500
	11th to 20th	Night	13% 3 7% 19% 32% 27%	2492
	21st to end	Night	9% 2 12% 31% 39% 8%	2703
August	1st to 10th	Night	11% 3 9% 37% 31% 9%	2839
	11th to 20th	Night	23% 4 22% 34% 12% 4	2839
	21st to end	Night	23% 4 14% 30% 22% 7%	3363
September	1st to 10th	Night	17% 5% 13% 31% 22% 11%	1900
	11th to 20th	Night	32% 7% 15% 24% 14% 9%	1914
	21st to end	Night	30% 6% 16% 23% 17% 8%	2171
October	1st to 10th	Night	33% 6% 8% 28% 22% 2	3800
	11th to 20th	Night	43% 6% 21% 18% 10% 2	3777
	21st to end	Night	55% 7% 11% 16% 10% 1	4146
November	1st to 10th	Night	59% 9% 11% 14% 7%	2640
	11th to 20th	Night	66% 7% 9% 9% 7% 2	2800
	21st to end	Night	59% 8% 8% 10% 12% 3	2800
December	1st to 10th	Night	51% 6% 9% 19% 14% 1	4560
	11th to 20th	Night	77% 8% 6% 7% 3	5176
	21st to end	Night	73% 11% 8% 6% 2	6952

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	41% 16% 18% 17% 7% 2	200
	11th to 20th	Day	32% 10% 22% 21% 12% 4	200
	21st to end	Day	27% 12% 21% 21% 14% 5%	426
February	1st to 10th	Day	33% 12% 21% 19% 12% 4	400
	11th to 20th	Day	33% 13% 26% 16% 9% 3	395
	21st to end	Day	32% 16% 20% 20% 11% 2	368
March	1st to 10th	Day	29% 13% 27% 20% 10% 1	500
	11th to 20th	Day	28% 14% 21% 21% 13% 3	500
	21st to end	Day	27% 16% 25% 21% 9% 1	550
April	1st to 10th	Day	31% 14% 22% 19% 11% 4	500
	11th to 20th	Day	23% 15% 26% 21% 10% 4	492
	21st to end	Day	22% 15% 24% 21% 16% 3	500
May	1st to 10th	Day	17% 13% 23% 27% 15% 5%	503
	11th to 20th	Day	25% 10% 18% 25% 17% 5%	528
	21st to end	Day	15% 9% 21% 28% 20% 7%	550
June	1st to 10th	Day	18% 10% 21% 27% 21% 3	490
	11th to 20th	Day	16% 9% 25% 33% 14% 2	490
	21st to end	Day	6% 7% 20% 37% 26% 5%	490
July	1st to 10th	Day	5% 5% 19% 39% 24% 8%	486
	11th to 20th	Day	4 3 22% 38% 25% 7%	484
	21st to end	Day	3 2 17% 38% 34% 6%	531
August	1st to 10th	Day	3 2 15% 38% 31% 10%	487
	11th to 20th	Day	3 4 11% 40% 31% 11%	477
	21st to end	Day	4 5% 22% 35% 27% 7%	539
September	1st to 10th	Day	7% 4 23% 32% 27% 7%	490
	11th to 20th	Day	12% 7% 19% 30% 25% 7%	490
	21st to end	Day	14% 9% 22% 30% 19% 5%	490
October	1st to 10th	Day	17% 9% 22% 26% 20% 7%	490
	11th to 20th	Day	20% 8% 17% 27% 21% 6%	490
	21st to end	Day	25% 13% 25% 20% 12% 5%	524
November	1st to 10th	Day	30% 15% 24% 17% 11% 3	245
	11th to 20th	Day	28% 14% 22% 17% 16% 5%	200
	21st to end	Day	28% 14% 17% 22% 16% 4	200
December	1st to 10th	Day	31% 10% 18% 21% 16% 6%	200
	11th to 20th	Day	40% 12% 24% 17% 7% 2	200
	21st to end	Day	38% 13% 19% 18% 11% 2	220
January	1st to 10th	Night	35% 12% 18% 21% 12% 2	800
	11th to 20th	Night	33% 9% 17% 21% 18% 2	800
	21st to end	Night	27% 8% 16% 29% 18% 3	880
February	1st to 10th	Night	27% 11% 20% 25% 16% 2	800
	11th to 20th	Night	30% 9% 21% 25% 15%	784
	21st to end	Night	30% 12% 19% 27% 12%	660
March	1st to 10th	Night	25% 11% 22% 30% 12% 1	800
	11th to 20th	Night	25% 10% 20% 29% 15% 1	800
	21st to end	Night	26% 11% 23% 26% 13% 1	880
April	1st to 10th	Night	28% 9% 18% 27% 18% 1	800
	11th to 20th	Night	19% 11% 24% 30% 15% 1	788
	21st to end	Night	19% 9% 21% 33% 18% 1	600
May	1st to 10th	Night	14% 6% 26% 36% 17% 1	480
	11th to 20th	Night	16% 6% 20% 35% 21% 2	394
	21st to end	Night	17% 6% 19% 36% 20% 1	422
June	1st to 10th	Night	18% 5% 18% 41% 18%	380
	11th to 20th	Night	12% 7% 26% 44% 11% 1	380
	21st to end	Night	8% 2 26% 48% 16%	380
July	1st to 10th	Night	4 3 14% 55% 24%	370
	11th to 20th	Night	4 3 23% 51% 18% 1	368
	21st to end	Night	3 2 16% 55% 23% 1	433
August	1st to 10th	Night	3 1 11% 46% 34% 4	567
	11th to 20th	Night	6% 1 8% 46% 37% 2	564
	21st to end	Night	6% 3 19% 44% 27% 2	753
September	1st to 10th	Night	7% 2 18% 45% 26% 1	760
	11th to 20th	Night	9% 3 14% 37% 31% 6%	760
	21st to end	Night	10% 5% 18% 38% 26% 4	760
October	1st to 10th	Night	15% 4 21% 34% 24% 3	760
	11th to 20th	Night	18% 5% 16% 33% 24% 4	760
	21st to end	Night	25% 8% 20% 27% 17% 3	836
November	1st to 10th	Night	28% 9% 17% 30% 16% 1	780
	11th to 20th	Night	33% 9% 18% 24% 14% 1	800
	21st to end	Night	25% 7% 18% 29% 18% 2	800
December	1st to 10th	Night	28% 8% 15% 29% 18% 3	800
	11th to 20th	Night	34% 10% 18% 22% 15% 1	800
	21st to end	Night	36% 13% 18% 22% 10% 1	880

Page generated at 2025-05-23 06:20:59. Version ac07

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