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 2026-09-29.

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	13% 7% 3 8% 5% 4 4 3 5% 6% 42%	158682
	Night	15% 8% 3 8% 5% 4 4 3 5% 6% 39%	150125
Transparency	Day	43% 6% 12% 21% 14% 4	153466
	Night	46% 6% 12% 19% 12% 4	146341
Seeing	Day	19% 10% 22% 27% 18% 5%	17095
	Night	21% 7% 19% 32% 18% 2	25972

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	29% 16% 6% 14% 7% 6% 5% 3 3 4 7%	4722
	11th to 20th	Day	21% 7% 2 10% 7% 5% 4 3 5% 6% 30%	4740
	21st to end	Day	18% 9% 4 11% 7% 5% 5% 4 5% 5% 26%	5816
February	1st to 10th	Day	25% 11% 4 11% 7% 6% 5% 4 5% 6% 14%	1890
	11th to 20th	Day	25% 14% 4 11% 7% 5% 4 3 4 5% 16%	1845
	21st to end	Day	26% 13% 4 11% 6% 5% 4 4 4 5% 17%	1632
March	1st to 10th	Day	16% 12% 4 11% 8% 7% 6% 5% 7% 6% 18%	4888
	11th to 20th	Day	21% 13% 4 9% 6% 5% 4 4 5% 5% 24%	5110
	21st to end	Day	19% 12% 5% 12% 7% 7% 7% 5% 7% 6% 14%	5690
April	1st to 10th	Day	23% 11% 4 10% 7% 6% 5% 3 6% 6% 18%	2520
	11th to 20th	Day	19% 11% 3 9% 5% 5% 5% 4 5% 6% 27%	2489
	21st to end	Day	18% 9% 3 8% 6% 5% 5% 4 5% 8% 28%	2730
May	1st to 10th	Day	11% 5% 2 6% 4 5% 4 4 6% 7% 46%	7967
	11th to 20th	Day	9% 6% 2 8% 5% 5% 5% 4 6% 8% 41%	8160
	21st to end	Day	11% 6% 3 7% 5% 5% 5% 5% 6% 8% 40%	8992
June	1st to 10th	Day	17% 9% 3 7% 5% 4 4 4 5% 7% 36%	2940
	11th to 20th	Day	14% 7% 2 7% 6% 5% 5% 5% 6% 8% 34%	2940
	21st to end	Day	8% 5% 2 5% 4 4 4 4 5% 7% 53%	2940
July	1st to 10th	Day	2 2 1 2 2 2 3 2 3 5% 75%	8219
	11th to 20th	Day	3 2 1 2 2 2 2 2 3 4 78%	8220
	21st to end	Day	3 2 1 2 1 2 2 2 3 4 77%	8853
August	1st to 10th	Day	2 2 1 3 2 3 3 3 3 6% 72%	7547
	11th to 20th	Day	4 3 2 5% 3 3 4 3 6% 8% 60%	7563
	21st to end	Day	5% 5% 2 4 3 3 4 3 6% 8% 57%	7979
September	1st to 10th	Day	6% 3 1 4 3 3 3 3 5% 7% 61%	2520
	11th to 20th	Day	8% 7% 3 8% 4 4 5% 3 6% 6% 45%	2501
	21st to end	Day	14% 5% 3 7% 4 3 5% 3 4 6% 46%	2200
October	1st to 10th	Day	12% 6% 2 7% 5% 4 4 4 5% 5% 46%	3280
	11th to 20th	Day	14% 8% 3 9% 6% 6% 6% 5% 7% 8% 29%	3261
	21st to end	Day	18% 11% 4 11% 7% 6% 4 3 6% 8% 21%	3530
November	1st to 10th	Day	25% 14% 6% 12% 7% 5% 5% 4 5% 5% 14%	1738
	11th to 20th	Day	26% 13% 5% 12% 8% 5% 5% 3 4 5% 16%	1680
	21st to end	Day	23% 11% 4 14% 6% 4 5% 4 5% 6% 19%	1680
December	1st to 10th	Day	20% 8% 5% 12% 7% 5% 4 3 4 6% 26%	2700
	11th to 20th	Day	24% 13% 5% 16% 8% 6% 6% 4 5% 4 7%	3108
	21st to end	Day	30% 16% 6% 17% 7% 5% 5% 3 3 3 6%	4092
January	1st to 10th	Night	27% 16% 6% 13% 7% 5% 5% 3 4 4 11%	8172
	11th to 20th	Night	20% 9% 3 9% 7% 5% 4 3 4 5% 32%	8220
	21st to end	Night	20% 10% 4 11% 5% 4 4 3 4 5% 30%	8393
February	1st to 10th	Night	22% 13% 5% 11% 7% 6% 5% 3 5% 6% 17%	2730
	11th to 20th	Night	24% 12% 4 9% 6% 5% 4 3 5% 5% 24%	2662
	21st to end	Night	24% 13% 3 9% 6% 5% 5% 4 5% 6% 21%	2173
March	1st to 10th	Night	14% 12% 5% 11% 7% 8% 7% 5% 7% 6% 20%	5211
	11th to 20th	Night	18% 11% 4 10% 6% 5% 5% 3 5% 5% 28%	5110
	21st to end	Night	18% 12% 5% 12% 8% 7% 5% 4 6% 6% 17%	5526
April	1st to 10th	Night	23% 10% 3 9% 6% 5% 4 4 5% 6% 25%	2100
	11th to 20th	Night	17% 11% 3 8% 4 5% 4 3 6% 7% 34%	2076
	21st to end	Night	17% 9% 2 8% 5% 4 5% 4 6% 6% 34%	1890
May	1st to 10th	Night	12% 5% 2 5% 4 3 4 3 4 8% 50%	4963
	11th to 20th	Night	10% 7% 3 7% 4 4 4 3 5% 6% 46%	4700
	21st to end	Night	9% 6% 2 6% 4 4 5% 4 7% 8% 44%	5181
June	1st to 10th	Night	15% 6% 4 6% 5% 4 5% 3 4 7% 41%	1680
	11th to 20th	Night	11% 7% 2 6% 4 4 4 3 5% 7% 46%	1680
	21st to end	Night	6% 5% 2 4 4 3 3 3 4 6% 60%	1680
July	1st to 10th	Night	2 2 2 2 1 2 2 3 6% 78%	4740
	11th to 20th	Night	2 2 1 2 2 2 2 2 2 3 81%	4740
	21st to end	Night	2 2 1 2 2 2 2 2 3 4 78%	5210
August	1st to 10th	Night	2 3 1 3 2 2 3 2 4 5% 74%	5275
	11th to 20th	Night	7% 4 1 4 3 4 3 3 4 6% 62%	5292
	21st to end	Night	6% 3 1 4 2 3 3 3 4 6% 65%	6256
September	1st to 10th	Night	5% 4 1 3 2 3 3 3 5% 5% 66%	2100
	11th to 20th	Night	8% 4 3 6% 4 5% 5% 3 4 6% 53%	2116
	21st to end	Night	9% 5% 2 6% 4 3 4 2 5% 7% 54%	2375
October	1st to 10th	Night	10% 5% 2 6% 4 4 4 4 5% 7% 49%	3920
	11th to 20th	Night	14% 6% 2 6% 5% 5% 5% 4 7% 8% 38%	3897
	21st to end	Night	18% 9% 3 10% 6% 5% 5% 4 5% 6% 28%	4279
November	1st to 10th	Night	25% 9% 3 9% 5% 5% 5% 4 6% 7% 22%	2776
	11th to 20th	Night	28% 13% 4 9% 5% 4 4 3 4 5% 20%	2940
	21st to end	Night	21% 11% 3 11% 6% 5% 5% 3 5% 5% 25%	2940
December	1st to 10th	Night	18% 8% 3 8% 7% 6% 5% 4 6% 6% 31%	4700
	11th to 20th	Night	29% 14% 6% 13% 7% 5% 4 3 4 4 10%	5316
	21st to end	Night	26% 13% 6% 13% 7% 7% 5% 4 5% 4 11%	7106

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	82% 6% 4 5% 2	4723
	11th to 20th	Day	54% 4 8% 13% 14% 7%	4740
	21st to end	Day	59% 6% 6% 12% 15% 3	5816
February	1st to 10th	Day	69% 7% 9% 10% 4	1890
	11th to 20th	Day	69% 8% 8% 9% 5% 2	1854
	21st to end	Day	70% 6% 8% 8% 6% 2	1632
March	1st to 10th	Day	61% 8% 13% 15% 4	4888
	11th to 20th	Day	60% 7% 8% 17% 7% 1	5110
	21st to end	Day	67% 10% 12% 8% 3	5690
April	1st to 10th	Day	65% 8% 11% 13% 3	2520
	11th to 20th	Day	57% 8% 11% 14% 8% 2	2492
	21st to end	Day	54% 9% 13% 14% 8% 1	2730
May	1st to 10th	Day	36% 6% 13% 30% 15%	7967
	11th to 20th	Day	39% 6% 20% 26% 8% 1	8163
	21st to end	Day	37% 10% 24% 23% 6%	8994
June	1st to 10th	Day	48% 7% 16% 21% 7% 1	2940
	11th to 20th	Day	45% 9% 18% 19% 8% 1	2940
	21st to end	Day	31% 6% 17% 30% 13% 3	2940
July	1st to 10th	Day	12% 3 13% 35% 19% 18%	8151
	11th to 20th	Day	13% 2 6% 18% 41% 20%	8145
	21st to end	Day	13% 2 14% 38% 28% 4	8655
August	1st to 10th	Day	13% 3 7% 27% 32% 18%	5976
	11th to 20th	Day	22% 4 19% 37% 15% 3	5962
	21st to end	Day	24% 4 15% 33% 19% 5%	6258
September	1st to 10th	Day	23% 4 14% 28% 20% 11%	2520
	11th to 20th	Day	37% 7% 13% 22% 15% 6%	2501
	21st to end	Day	38% 6% 13% 22% 16% 5%	2200
October	1st to 10th	Day	38% 5% 9% 22% 23% 3	3280
	11th to 20th	Day	52% 6% 15% 15% 12% 1	3261
	21st to end	Day	60% 6% 7% 16% 10% 1	3530
November	1st to 10th	Day	70% 7% 9% 10% 4	1738
	11th to 20th	Day	71% 6% 9% 8% 5% 2	1680
	21st to end	Day	67% 7% 8% 8% 10% 1	1680
December	1st to 10th	Day	59% 4 10% 14% 13% 1	2700
	11th to 20th	Day	76% 9% 7% 7% 1	3108
	21st to end	Day	82% 7% 6% 4 2	4092
January	1st to 10th	Night	77% 6% 7% 6% 3 1	8172
	11th to 20th	Night	54% 5% 7% 14% 14% 6%	8220
	21st to end	Night	57% 4 6% 12% 17% 4	8393
February	1st to 10th	Night	66% 8% 9% 11% 5% 1	2730
	11th to 20th	Night	62% 7% 11% 11% 6% 2	2664
	21st to end	Night	63% 7% 11% 11% 6% 2	2173
March	1st to 10th	Night	59% 8% 13% 14% 5%	5211
	11th to 20th	Night	56% 8% 10% 16% 8% 1	5110
	21st to end	Night	65% 11% 14% 9% 1	5526
April	1st to 10th	Night	59% 8% 15% 13% 5%	2100
	11th to 20th	Night	50% 9% 15% 16% 7% 3	2076
	21st to end	Night	49% 8% 14% 19% 8% 2	1890
May	1st to 10th	Night	32% 7% 11% 36% 12% 1	4961
	11th to 20th	Night	37% 6% 19% 29% 7% 1	4700
	21st to end	Night	33% 11% 28% 24% 4	5182
June	1st to 10th	Night	42% 8% 16% 27% 6% 1	1680
	11th to 20th	Night	36% 10% 17% 27% 9% 1	1680
	21st to end	Night	26% 6% 18% 34% 14% 4	1680
July	1st to 10th	Night	10% 3 13% 35% 22% 17%	4700
	11th to 20th	Night	12% 2 9% 18% 41% 20%	4692
	21st to end	Night	12% 2 18% 37% 26% 4	5097
August	1st to 10th	Night	9% 2 7% 31% 36% 15%	4169
	11th to 20th	Night	21% 3 20% 40% 12% 3	4169
	21st to end	Night	19% 4 16% 38% 18% 5%	4901
September	1st to 10th	Night	21% 5% 14% 29% 21% 10%	2100
	11th to 20th	Night	31% 7% 15% 24% 16% 8%	2116
	21st to end	Night	30% 6% 16% 24% 17% 7%	2375
October	1st to 10th	Night	34% 5% 9% 28% 22% 2	3920
	11th to 20th	Night	43% 6% 21% 18% 11% 2	3897
	21st to end	Night	55% 7% 11% 16% 10% 1	4279
November	1st to 10th	Night	60% 9% 10% 14% 6%	2776
	11th to 20th	Night	67% 7% 9% 9% 7% 2	2940
	21st to end	Night	60% 8% 8% 10% 11% 2	2940
December	1st to 10th	Night	52% 6% 9% 19% 14% 1	4700
	11th to 20th	Night	77% 8% 6% 7% 2	5316
	21st to end	Night	73% 11% 8% 6% 2	7106

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	40% 16% 18% 16% 7% 2	220
	11th to 20th	Day	29% 9% 22% 25% 11% 5%	220
	21st to end	Day	26% 12% 22% 21% 14% 4	459
February	1st to 10th	Day	32% 11% 21% 19% 13% 3	430
	11th to 20th	Day	33% 12% 27% 16% 9% 2	425
	21st to end	Day	32% 15% 21% 20% 10% 2	396
March	1st to 10th	Day	29% 14% 26% 20% 9% 1	540
	11th to 20th	Day	29% 14% 22% 20% 12% 2	540
	21st to end	Day	27% 17% 25% 21% 9% 1	594
April	1st to 10th	Day	29% 13% 21% 19% 12% 4	540
	11th to 20th	Day	23% 15% 26% 20% 10% 4	532
	21st to end	Day	21% 14% 24% 22% 16% 3	540
May	1st to 10th	Day	16% 13% 23% 28% 15% 5%	543
	11th to 20th	Day	24% 11% 19% 25% 16% 5%	568
	21st to end	Day	14% 9% 22% 29% 20% 6%	617
June	1st to 10th	Day	17% 12% 22% 27% 19% 3	570
	11th to 20th	Day	14% 8% 27% 34% 14% 2	570
	21st to end	Day	7% 7% 20% 38% 24% 5%	570
July	1st to 10th	Day	4 4 19% 41% 24% 8%	566
	11th to 20th	Day	4 3 25% 37% 24% 6%	564
	21st to end	Day	3 2 18% 37% 33% 7%	619
August	1st to 10th	Day	4 3 16% 38% 29% 10%	567
	11th to 20th	Day	3 3 12% 40% 30% 11%	557
	21st to end	Day	5% 5% 21% 36% 27% 7%	627
September	1st to 10th	Day	8% 4 23% 32% 26% 7%	570
	11th to 20th	Day	12% 7% 19% 30% 25% 7%	570
	21st to end	Day	15% 9% 22% 30% 19% 5%	563
October	1st to 10th	Day	17% 9% 22% 25% 19% 7%	530
	11th to 20th	Day	19% 9% 18% 26% 22% 6%	530
	21st to end	Day	25% 13% 25% 20% 11% 5%	567
November	1st to 10th	Day	31% 14% 24% 17% 11% 3	269
	11th to 20th	Day	27% 13% 24% 17% 15% 5%	220
	21st to end	Day	29% 13% 18% 21% 15% 4	220
December	1st to 10th	Day	35% 10% 17% 20% 14% 5%	220
	11th to 20th	Day	40% 13% 22% 16% 8% 2	220
	21st to end	Day	38% 12% 19% 19% 11% 2	242
January	1st to 10th	Night	35% 12% 19% 21% 11% 2	840
	11th to 20th	Night	32% 8% 18% 22% 18% 3	840
	21st to end	Night	27% 8% 16% 29% 17% 3	924
February	1st to 10th	Night	26% 10% 20% 26% 16% 2	840
	11th to 20th	Night	30% 10% 21% 25% 14%	824
	21st to end	Night	30% 12% 19% 27% 12%	692
March	1st to 10th	Night	25% 10% 22% 30% 12% 1	840
	11th to 20th	Night	25% 11% 20% 28% 15% 1	840
	21st to end	Night	26% 11% 24% 26% 13% 1	924
April	1st to 10th	Night	27% 9% 18% 28% 18% 1	840
	11th to 20th	Night	20% 11% 24% 30% 15% 1	828
	21st to end	Night	19% 8% 22% 33% 17% 1	630
May	1st to 10th	Night	13% 5% 26% 36% 18% 1	504
	11th to 20th	Night	16% 6% 22% 35% 20% 1	414
	21st to end	Night	16% 5% 20% 37% 20% 1	455
June	1st to 10th	Night	17% 5% 19% 41% 17%	420
	11th to 20th	Night	11% 6% 27% 44% 11% 1	420
	21st to end	Night	9% 1 26% 48% 16%	420
July	1st to 10th	Night	4 2 15% 56% 23%	410
	11th to 20th	Night	4 3 25% 50% 17% 1	408
	21st to end	Night	2 2 16% 55% 24% 1	479
August	1st to 10th	Night	4 1 13% 45% 33% 4	627
	11th to 20th	Night	6% 1 8% 47% 36% 2	624
	21st to end	Night	6% 2 19% 44% 26% 2	833
September	1st to 10th	Night	8% 2 19% 45% 25% 1	840
	11th to 20th	Night	9% 4 15% 37% 30% 5%	840
	21st to end	Night	10% 5% 18% 39% 25% 4	832
October	1st to 10th	Night	15% 4 21% 34% 24% 3	800
	11th to 20th	Night	18% 6% 16% 33% 23% 4	800
	21st to end	Night	24% 9% 21% 27% 16% 3	880
November	1st to 10th	Night	28% 9% 17% 30% 15% 1	820
	11th to 20th	Night	34% 9% 19% 24% 13% 1	840
	21st to end	Night	25% 8% 18% 29% 18% 2	840
December	1st to 10th	Night	29% 7% 15% 28% 17% 3	840
	11th to 20th	Night	35% 10% 18% 21% 15% 1	840
	21st to end	Night	35% 13% 19% 22% 10% 1	924

Page generated at 2026-09-26 01:18:39. Version ac07

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