Goose Island State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Goose Island State Park clear sky chart from 2005-11-06 to 2025-06-10.

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	12% 6% 2 6% 4 4 5% 4 6% 8% 42%	119777
	Night	14% 6% 2 5% 4 4 4 3 5% 8% 45%	118670
Transparency	Day	24% 42% 9% 13% 8% 4	123561
	Night	24% 40% 8% 13% 9% 5%	123015
Seeing	Day	12% 4 16% 29% 31% 9%	15330
	Night	14% 5% 16% 32% 28% 5%	25323

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	24% 9% 3 6% 3 3 4 3 4 6% 34%	4077
	11th to 20th	Day	18% 8% 2 5% 3 3 4 4 5% 6% 42%	4080
	21st to end	Day	26% 9% 3 6% 4 3 4 4 5% 5% 32%	4746
February	1st to 10th	Day	21% 9% 3 5% 3 3 3 3 4 6% 40%	2000
	11th to 20th	Day	19% 9% 3 5% 3 3 3 3 5% 6% 40%	1949
	21st to end	Day	18% 8% 2 6% 5% 4 3 3 5% 5% 43%	1738
March	1st to 10th	Day	16% 8% 3 6% 4 3 4 3 5% 7% 41%	4936
	11th to 20th	Day	17% 7% 3 6% 4 4 3 2 4 6% 45%	4980
	21st to end	Day	18% 7% 2 5% 3 4 4 3 5% 6% 42%	5462
April	1st to 10th	Day	15% 7% 2 5% 3 3 4 4 6% 8% 43%	2200
	11th to 20th	Day	16% 7% 3 6% 4 4 4 3 5% 7% 40%	2176
	21st to end	Day	12% 7% 3 6% 5% 4 4 4 6% 8% 42%	2400
May	1st to 10th	Day	17% 8% 3 8% 6% 6% 6% 4 6% 8% 27%	5771
	11th to 20th	Day	9% 5% 2 5% 4 4 5% 4 7% 10% 46%	5862
	21st to end	Day	7% 5% 2 6% 5% 6% 7% 6% 9% 12% 34%	6434
June	1st to 10th	Day	3 3 1 5% 3 3 5% 4 9% 12% 51%	2588
	11th to 20th	Day	4 4 2 5% 4 5% 5% 5% 8% 14% 46%	2470
	21st to end	Day	7% 5% 1 4 4 5% 6% 6% 10% 13% 38%	2470
July	1st to 10th	Day	7% 5% 2 6% 5% 5% 5% 5% 6% 9% 46%	4120
	11th to 20th	Day	5% 7% 3 8% 6% 6% 7% 6% 8% 12% 32%	4120
	21st to end	Day	8% 6% 2 6% 5% 4 5% 5% 8% 12% 38%	4465
August	1st to 10th	Day	1 1 1 2 2 2 3 3 5% 9% 72%	4104
	11th to 20th	Day	2 2 1 2 3 4 5% 5% 9% 13% 52%	3792
	21st to end	Day	4 3 1 6% 5% 6% 6% 6% 9% 13% 41%	3828
September	1st to 10th	Day	9% 5% 2 8% 6% 6% 7% 7% 7% 10% 34%	2090
	11th to 20th	Day	10% 6% 3 6% 5% 5% 5% 5% 6% 9% 40%	2090
	21st to end	Day	9% 4 2 5% 4 3 4 4 7% 9% 48%	2090
October	1st to 10th	Day	5% 3 2 5% 4 4 4 4 5% 8% 55%	2090
	11th to 20th	Day	11% 5% 2 4 4 3 4 3 5% 7% 53%	1907
	21st to end	Day	9% 5% 2 4 4 4 3 3 4 6% 57%	2090
November	1st to 10th	Day	10% 5% 2 5% 4 4 5% 4 6% 9% 46%	1958
	11th to 20th	Day	15% 6% 2 5% 4 4 3 3 4 6% 48%	2000
	21st to end	Day	17% 5% 2 6% 4 5% 5% 3 5% 6% 41%	1875
December	1st to 10th	Day	26% 12% 3 7% 4 4 4 3 4 5% 28%	2940
	11th to 20th	Day	11% 8% 3 9% 4 4 5% 3 6% 7% 40%	3391
	21st to end	Day	13% 6% 2 6% 4 3 4 2 5% 6% 49%	4488
January	1st to 10th	Night	24% 8% 2 6% 4 4 3 2 4 5% 38%	5888
	11th to 20th	Night	15% 7% 2 6% 3 3 3 3 5% 7% 46%	5900
	21st to end	Night	28% 8% 3 7% 4 3 4 3 5% 6% 30%	6260
February	1st to 10th	Night	20% 9% 2 6% 3 3 3 3 4 6% 40%	2400
	11th to 20th	Night	19% 7% 3 4 3 3 4 3 4 7% 43%	2338
	21st to end	Night	19% 9% 2 5% 4 4 4 3 4 6% 41%	1890
March	1st to 10th	Night	19% 8% 2 6% 3 3 3 3 5% 7% 40%	4919
	11th to 20th	Night	16% 7% 2 6% 4 4 3 3 3 5% 46%	4980
	21st to end	Night	18% 6% 2 4 2 3 3 3 4 5% 50%	5467
April	1st to 10th	Night	14% 10% 3 6% 5% 4 4 4 5% 8% 40%	2200
	11th to 20th	Night	18% 7% 2 6% 3 3 2 3 4 8% 43%	2170
	21st to end	Night	14% 7% 2 6% 5% 4 4 3 6% 8% 39%	2000
May	1st to 10th	Night	22% 9% 3 7% 5% 5% 4 3 5% 7% 29%	4111
	11th to 20th	Night	12% 5% 2 5% 3 3 4 3 6% 9% 47%	4053
	21st to end	Night	10% 7% 3 8% 6% 5% 5% 4 7% 11% 33%	4443
June	1st to 10th	Night	5% 3 1 4 3 4 5% 4 8% 11% 54%	1796
	11th to 20th	Night	5% 4 1 5% 5% 5% 5% 5% 6% 12% 47%	1710
	21st to end	Night	6% 5% 1 4 4 4 6% 7% 9% 13% 42%	1710
July	1st to 10th	Night	5% 4 1 5% 4 3 5% 4 7% 10% 52%	2850
	11th to 20th	Night	3 5% 2 6% 6% 6% 6% 6% 9% 13% 39%	2850
	21st to end	Night	7% 5% 2 6% 4 5% 5% 4 8% 13% 41%	3098
August	1st to 10th	Night	1 1 2 2 2 2 4 9% 77%	2836
	11th to 20th	Night	2 2 1 3 3 3 3 3 7% 15% 58%	3038
	21st to end	Night	3 2 1 3 3 4 4 4 7% 14% 56%	3828
September	1st to 10th	Night	7% 6% 2 7% 5% 5% 7% 5% 7% 9% 42%	2090
	11th to 20th	Night	8% 6% 2 7% 5% 4 4 4 5% 9% 46%	2090
	21st to end	Night	7% 3 1 5% 4 4 4 4 7% 8% 52%	2090
October	1st to 10th	Night	5% 3 1 4 4 4 5% 4 5% 8% 58%	2090
	11th to 20th	Night	10% 5% 1 3 2 2 3 3 5% 7% 59%	2251
	21st to end	Night	9% 4 2 4 3 3 3 3 4 6% 62%	2508
November	1st to 10th	Night	9% 5% 1 5% 4 4 3 4 5% 7% 53%	2340
	11th to 20th	Night	15% 6% 2 5% 4 3 3 2 5% 6% 50%	2400
	21st to end	Night	15% 7% 3 6% 4 4 4 3 5% 6% 44%	2520
December	1st to 10th	Night	30% 12% 4 7% 4 3 3 2 3 4 29%	4250
	11th to 20th	Night	14% 8% 3 6% 4 4 4 4 5% 7% 43%	4816
	21st to end	Night	11% 6% 2 5% 4 4 3 3 5% 6% 50%	6490

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% 29% 5% 14% 6% 4	4078
	11th to 20th	Day	29% 31% 8% 13% 13% 5%	4080
	21st to end	Day	42% 29% 4 8% 10% 7%	4746
February	1st to 10th	Day	22% 63% 2 4 5% 5%	2000
	11th to 20th	Day	18% 61% 4 9% 6% 2	1959
	21st to end	Day	19% 63% 3 6% 4 4	1738
March	1st to 10th	Day	33% 33% 6% 13% 3 11%	4936
	11th to 20th	Day	30% 31% 4 9% 13% 14%	4980
	21st to end	Day	31% 31% 6% 16% 12% 4	5464
April	1st to 10th	Day	15% 62% 4 6% 7% 6%	2200
	11th to 20th	Day	16% 64% 6% 6% 5% 3	2176
	21st to end	Day	15% 63% 5% 10% 5% 2	2400
May	1st to 10th	Day	39% 33% 11% 9% 6% 2	5808
	11th to 20th	Day	22% 31% 14% 17% 12% 5%	5866
	21st to end	Day	27% 35% 14% 22% 2	6447
June	1st to 10th	Day	7% 65% 9% 15% 4	2588
	11th to 20th	Day	12% 67% 6% 10% 5%	2470
	21st to end	Day	11% 67% 10% 11% 2	2470
July	1st to 10th	Day	16% 39% 25% 19% 2	4056
	11th to 20th	Day	32% 40% 17% 8% 3	4051
	21st to end	Day	28% 38% 18% 15% 1	4325
August	1st to 10th	Day	4 38% 12% 37% 8%	4090
	11th to 20th	Day	10% 40% 28% 21% 1	3831
	21st to end	Day	19% 41% 16% 19% 5% 1	3827
September	1st to 10th	Day	14% 64% 7% 8% 6% 1	2090
	11th to 20th	Day	13% 62% 8% 11% 6% 1	2090
	21st to end	Day	14% 63% 8% 10% 3 2	2090
October	1st to 10th	Day	12% 37% 5% 7% 17% 22%	3480
	11th to 20th	Day	14% 38% 8% 11% 21% 7%	3147
	21st to end	Day	18% 39% 4 16% 20% 4	3428
November	1st to 10th	Day	20% 58% 8% 7% 4 2	1958
	11th to 20th	Day	22% 58% 4 7% 4 6%	2000
	21st to end	Day	20% 58% 5% 7% 8% 2	1875
December	1st to 10th	Day	45% 36% 3 5% 9% 1	2940
	11th to 20th	Day	25% 35% 6% 15% 11% 9%	3389
	21st to end	Day	27% 28% 5% 17% 13% 10%	4488
January	1st to 10th	Night	39% 29% 5% 10% 9% 8%	5888
	11th to 20th	Night	28% 28% 5% 15% 17% 6%	5900
	21st to end	Night	42% 29% 4 8% 11% 6%	6260
February	1st to 10th	Night	21% 62% 3 3 5% 6%	2400
	11th to 20th	Night	16% 61% 5% 8% 6% 4	2338
	21st to end	Night	19% 62% 3 6% 5% 4	1890
March	1st to 10th	Night	35% 31% 7% 12% 7% 8%	4919
	11th to 20th	Night	31% 30% 4 7% 12% 15%	4980
	21st to end	Night	26% 30% 7% 16% 16% 4	5467
April	1st to 10th	Night	16% 62% 5% 6% 6% 5%	2200
	11th to 20th	Night	15% 63% 5% 6% 5% 5%	2170
	21st to end	Night	16% 63% 5% 9% 5% 2	2000
May	1st to 10th	Night	42% 31% 9% 10% 5% 2	4138
	11th to 20th	Night	23% 31% 10% 20% 11% 5%	4054
	21st to end	Night	33% 32% 15% 18% 2	4452
June	1st to 10th	Night	7% 63% 8% 16% 6%	1796
	11th to 20th	Night	14% 67% 3 11% 6%	1710
	21st to end	Night	13% 66% 6% 13% 2	1710
July	1st to 10th	Night	12% 37% 24% 24% 2	2805
	11th to 20th	Night	26% 40% 18% 13% 2	2796
	21st to end	Night	26% 38% 19% 15% 2	2999
August	1st to 10th	Night	4 37% 9% 41% 10%	2826
	11th to 20th	Night	9% 39% 28% 23% 1	3065
	21st to end	Night	9% 41% 21% 23% 6%	3828
September	1st to 10th	Night	11% 63% 10% 8% 6% 1	2090
	11th to 20th	Night	12% 62% 7% 12% 6% 1	2090
	21st to end	Night	13% 63% 8% 11% 4 2	2090
October	1st to 10th	Night	11% 38% 5% 9% 13% 25%	3480
	11th to 20th	Night	9% 37% 8% 13% 23% 10%	3737
	21st to end	Night	13% 38% 4 16% 24% 5%	4120
November	1st to 10th	Night	19% 58% 6% 8% 5% 3	2340
	11th to 20th	Night	21% 57% 5% 6% 6% 4	2400
	21st to end	Night	22% 57% 4 7% 7% 3	2520
December	1st to 10th	Night	47% 35% 3 5% 7% 2	4250
	11th to 20th	Night	25% 34% 7% 13% 11% 11%	4817
	21st to end	Night	26% 29% 5% 15% 15% 11%	6490

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	20% 9% 28% 30% 11% 2	300
	11th to 20th	Day	23% 11% 22% 35% 8% 1	300
	21st to end	Day	21% 7% 33% 26% 11% 1	330
February	1st to 10th	Day	25% 8% 25% 26% 14% 2	300
	11th to 20th	Day	27% 8% 25% 31% 9%	300
	21st to end	Day	20% 4 40% 28% 8%	249
March	1st to 10th	Day	17% 6% 33% 34% 9% 1	300
	11th to 20th	Day	18% 10% 33% 31% 7% 1	300
	21st to end	Day	15% 7% 36% 35% 6% 1	330
April	1st to 10th	Day	17% 6% 38% 27% 11% 1	300
	11th to 20th	Day	17% 10% 29% 30% 13% 1	294
	21st to end	Day	14% 7% 30% 37% 11% 1	500
May	1st to 10th	Day	12% 5% 33% 38% 12%	663
	11th to 20th	Day	11% 4 24% 41% 17% 3	725
	21st to end	Day	7% 3 16% 46% 25% 3	789
June	1st to 10th	Day	4 1 7% 38% 41% 8%	726
	11th to 20th	Day	7% 1 7% 38% 39% 8%	680
	21st to end	Day	8% 1 7% 28% 45% 12%	680
July	1st to 10th	Day	7% 2 4 22% 48% 17%	671
	11th to 20th	Day	4 1 3 16% 58% 19%	668
	21st to end	Day	6% 1 2 17% 53% 21%	739
August	1st to 10th	Day	1 1 15% 56% 26%	676
	11th to 20th	Day	4 1 13% 57% 25%	520
	21st to end	Day	8% 2 2 11% 43% 34%	330
September	1st to 10th	Day	11% 1 2 18% 46% 21%	300
	11th to 20th	Day	7% 1 3 16% 47% 27%	300
	21st to end	Day	6% 1 7% 18% 47% 20%	300
October	1st to 10th	Day	7% 1 5% 31% 47% 9%	300
	11th to 20th	Day	12% 3 9% 29% 33% 14%	300
	21st to end	Day	13% 5% 16% 30% 28% 6%	330
November	1st to 10th	Day	15% 4 10% 32% 33% 5%	300
	11th to 20th	Day	20% 4 12% 34% 22% 8%	300
	21st to end	Day	22% 8% 24% 27% 14% 5%	300
December	1st to 10th	Day	22% 6% 20% 32% 16% 4	300
	11th to 20th	Day	21% 9% 19% 30% 18% 2	300
	21st to end	Day	18% 8% 24% 31% 17% 2	330
January	1st to 10th	Night	23% 8% 25% 31% 14% 1	1000
	11th to 20th	Night	20% 8% 23% 37% 11%	1000
	21st to end	Night	22% 8% 26% 33% 11%	1000
February	1st to 10th	Night	25% 8% 22% 34% 11%	800
	11th to 20th	Night	23% 10% 20% 36% 10%	784
	21st to end	Night	23% 7% 27% 34% 8%	570
March	1st to 10th	Night	21% 7% 24% 36% 13%	600
	11th to 20th	Night	19% 10% 21% 41% 9%	600
	21st to end	Night	17% 6% 26% 39% 11% 1	660
April	1st to 10th	Night	17% 7% 28% 38% 11%	600
	11th to 20th	Night	19% 8% 24% 35% 14%	593
	21st to end	Night	18% 5% 25% 39% 14%	600
May	1st to 10th	Night	16% 5% 26% 42% 12%	600
	11th to 20th	Night	11% 3 20% 47% 18% 1	591
	21st to end	Night	8% 2 14% 44% 30% 2	650
June	1st to 10th	Night	5% 2 4 38% 48% 4	599
	11th to 20th	Night	6% 6% 43% 42% 3	570
	21st to end	Night	7% 1 7% 29% 45% 11%	570
July	1st to 10th	Night	7% 1 3 26% 48% 16%	555
	11th to 20th	Night	3 1 2 17% 58% 19%	552
	21st to end	Night	4 1 3 19% 60% 14%	624
August	1st to 10th	Night	2 13% 64% 21%	567
	11th to 20th	Night	4 1 1 11% 65% 18%	564
	21st to end	Night	5% 1 15% 54% 25%	627
September	1st to 10th	Night	10% 1 3 18% 52% 17%	570
	11th to 20th	Night	9% 1 4 19% 49% 18%	570
	21st to end	Night	6% 1 5% 22% 53% 12%	570
October	1st to 10th	Night	5% 1 5% 25% 51% 12%	570
	11th to 20th	Night	9% 2 10% 35% 39% 5%	731
	21st to end	Night	10% 5% 13% 36% 31% 4	836
November	1st to 10th	Night	10% 3 11% 35% 36% 5%	780
	11th to 20th	Night	17% 3 16% 33% 27% 3	800
	21st to end	Night	19% 5% 22% 33% 19% 2	920
December	1st to 10th	Night	22% 5% 20% 30% 20% 3	1000
	11th to 20th	Night	20% 7% 23% 32% 16% 1	1000
	21st to end	Night	20% 7% 23% 34% 15% 1	1100

Page generated at 2025-06-07 09:28:16. Version ac07

Copyright © 2025 Attilla Danko.