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 2024-11-02.

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 5% 4 4 5% 4 6% 9% 43%	100904
	Night	13% 6% 2 5% 4 4 4 4 6% 8% 46%	98149
Transparency	Day	20% 50% 10% 12% 6% 2	100717
	Night	20% 50% 9% 12% 7% 3	98006
Seeing	Day	11% 4 15% 29% 31% 10%	14581
	Night	14% 5% 16% 32% 28% 5%	24488

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	19% 8% 2 6% 3 4 4 4 5% 7% 38%	2847
	11th to 20th	Day	16% 7% 2 4 3 3 4 4 5% 7% 46%	2850
	21st to end	Day	23% 7% 2 5% 4 3 5% 4 6% 6% 35%	3309
February	1st to 10th	Day	21% 9% 3 5% 3 3 3 3 4 6% 41%	1900
	11th to 20th	Day	19% 9% 3 5% 3 3 4 3 5% 6% 42%	1849
	21st to end	Day	18% 8% 2 5% 4 3 3 3 5% 5% 43%	1653
March	1st to 10th	Day	21% 9% 3 7% 5% 4 5% 3 5% 7% 31%	3436
	11th to 20th	Day	23% 10% 4 9% 5% 5% 4 3 5% 6% 27%	3480
	21st to end	Day	13% 4 2 5% 4 4 4 3 5% 7% 48%	3814
April	1st to 10th	Day	15% 7% 2 5% 3 3 4 4 6% 8% 41%	2090
	11th to 20th	Day	16% 8% 3 6% 4 4 4 3 5% 7% 39%	2066
	21st to end	Day	12% 7% 3 5% 5% 4 4 3 6% 8% 44%	2280
May	1st to 10th	Day	18% 8% 3 7% 5% 4 5% 4 6% 8% 31%	4019
	11th to 20th	Day	12% 6% 2 6% 5% 4 6% 4 7% 9% 39%	4082
	21st to end	Day	7% 5% 2 5% 4 5% 6% 6% 9% 11% 40%	4477
June	1st to 10th	Day	3 4 1 5% 3 3 5% 4 9% 12% 51%	2470
	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% 8% 46%	1868
	11th to 20th	Day	15% 6% 2 5% 4 4 3 3 5% 6% 47%	1900
	21st to end	Day	18% 5% 2 6% 4 5% 5% 3 5% 6% 41%	1782
December	1st to 10th	Day	19% 8% 2 5% 4 3 4 3 5% 7% 39%	1710
	11th to 20th	Day	15% 9% 3 8% 4 4 4 3 4 6% 40%	2161
	21st to end	Day	17% 7% 2 6% 4 3 4 2 5% 7% 43%	3135
January	1st to 10th	Night	22% 7% 2 6% 4 4 4 3 5% 6% 39%	4108
	11th to 20th	Night	14% 7% 2 5% 3 3 2 3 5% 7% 50%	4120
	21st to end	Night	23% 7% 3 7% 4 3 4 3 6% 7% 34%	4372
February	1st to 10th	Night	20% 9% 2 6% 3 4 3 3 4 6% 40%	2280
	11th to 20th	Night	18% 7% 3 4 3 3 4 3 4 7% 44%	2218
	21st to end	Night	19% 9% 2 5% 4 4 4 3 4 6% 41%	1799
March	1st to 10th	Night	22% 10% 2 6% 3 3 4 4 6% 8% 33%	3419
	11th to 20th	Night	22% 9% 3 8% 6% 5% 5% 4 4 6% 28%	3480
	21st to end	Night	14% 6% 2 4 2 3 3 3 4 5% 54%	3817
April	1st to 10th	Night	14% 10% 2 6% 5% 4 4 4 6% 8% 38%	2090
	11th to 20th	Night	19% 7% 2 6% 3 3 3 3 4 8% 42%	2060
	21st to end	Night	15% 7% 2 6% 5% 4 4 3 6% 8% 40%	1900
May	1st to 10th	Night	23% 7% 2 5% 4 4 3 3 6% 8% 36%	2868
	11th to 20th	Night	14% 7% 2 6% 4 4 5% 3 6% 8% 41%	2823
	21st to end	Night	10% 6% 2 6% 4 4 5% 4 7% 10% 41%	3090
June	1st to 10th	Night	5% 3 1 4 3 4 5% 4 8% 10% 54%	1710
	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% 2 4 4 4 3 4 5% 7% 53%	2244
	11th to 20th	Night	16% 6% 2 5% 4 3 3 2 5% 6% 49%	2280
	21st to end	Night	16% 7% 2 6% 4 4 4 3 5% 6% 43%	2394
December	1st to 10th	Night	18% 7% 3 5% 3 3 3 3 4 7% 44%	2470
	11th to 20th	Night	17% 9% 3 5% 3 4 4 4 6% 8% 37%	3036
	21st to end	Night	15% 7% 3 6% 4 4 4 4 5% 6% 42%	4532

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% 40% 4 10% 8% 6%	2848
	11th to 20th	Day	19% 44% 9% 12% 10% 7%	2850
	21st to end	Day	30% 41% 4 10% 12% 4	3309
February	1st to 10th	Day	19% 66% 2 4 4 5%	1900
	11th to 20th	Day	15% 64% 4 9% 6% 2	1859
	21st to end	Day	18% 66% 4 5% 4 3	1653
March	1st to 10th	Day	37% 45% 5% 9% 3	3436
	11th to 20th	Day	40% 44% 5% 6% 4 1	3480
	21st to end	Day	18% 43% 7% 14% 11% 6%	3814
April	1st to 10th	Day	15% 65% 4 5% 7% 5%	2090
	11th to 20th	Day	16% 67% 5% 5% 4 3	2066
	21st to end	Day	13% 66% 4 10% 5% 2	2280
May	1st to 10th	Day	31% 45% 11% 6% 4 2	4056
	11th to 20th	Day	24% 44% 8% 11% 9% 4	4086
	21st to end	Day	17% 47% 12% 22% 2	4489
June	1st to 10th	Day	7% 67% 8% 14% 4	2470
	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	11% 61% 7% 10% 8% 3	2090
	11th to 20th	Day	11% 61% 6% 8% 9% 5%	1907
	21st to end	Day	16% 60% 3 8% 9% 4	2090
November	1st to 10th	Day	19% 61% 9% 6% 3 2	1868
	11th to 20th	Day	22% 60% 4 6% 3 4	1900
	21st to end	Day	20% 60% 4 7% 7% 1	1782
December	1st to 10th	Day	20% 60% 4 7% 8% 2	1710
	11th to 20th	Day	20% 50% 4 6% 12% 8%	2159
	21st to end	Day	29% 38% 4 12% 9% 7%	3135
January	1st to 10th	Night	32% 40% 5% 6% 6% 11%	4108
	11th to 20th	Night	20% 40% 5% 14% 15% 8%	4120
	21st to end	Night	31% 40% 3 8% 12% 5%	4372
February	1st to 10th	Night	19% 65% 3 3 5% 5%	2280
	11th to 20th	Night	13% 64% 4 8% 6% 4	2218
	21st to end	Night	17% 65% 3 6% 5% 4	1799
March	1st to 10th	Night	36% 43% 8% 8% 4	3419
	11th to 20th	Night	41% 43% 6% 5% 3 2	3480
	21st to end	Night	16% 42% 8% 12% 17% 5%	3817
April	1st to 10th	Night	15% 65% 4 5% 6% 4	2090
	11th to 20th	Night	16% 66% 5% 5% 4 4	2060
	21st to end	Night	14% 66% 5% 9% 5% 2	1900
May	1st to 10th	Night	31% 42% 9% 10% 4 3	2895
	11th to 20th	Night	25% 44% 8% 13% 7% 3	2824
	21st to end	Night	22% 44% 11% 21% 3	3099
June	1st to 10th	Night	7% 66% 7% 14% 6%	1710
	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	10% 62% 7% 12% 5% 4	2090
	11th to 20th	Night	8% 60% 4 11% 11% 5%	2251
	21st to end	Night	13% 60% 4 7% 10% 6%	2508
November	1st to 10th	Night	18% 60% 7% 7% 5% 3	2244
	11th to 20th	Night	22% 60% 5% 6% 4 3	2280
	21st to end	Night	21% 60% 3 7% 6% 2	2394
December	1st to 10th	Night	17% 60% 4 7% 8% 3	2470
	11th to 20th	Night	20% 51% 5% 6% 8% 10%	3037
	21st to end	Night	30% 40% 5% 8% 11% 6%	4532

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	19% 9% 28% 32% 11% 1	270
	11th to 20th	Day	22% 11% 21% 36% 9% 1	270
	21st to end	Day	19% 8% 34% 25% 12% 1	297
February	1st to 10th	Day	24% 7% 27% 27% 13% 2	270
	11th to 20th	Day	26% 7% 25% 32% 10%	270
	21st to end	Day	20% 4 43% 26% 7%	225
March	1st to 10th	Day	18% 7% 31% 34% 9% 1	270
	11th to 20th	Day	20% 10% 31% 30% 7% 1	270
	21st to end	Day	13% 8% 37% 35% 5% 1	297
April	1st to 10th	Day	17% 5% 38% 27% 12%	270
	11th to 20th	Day	18% 10% 30% 28% 13% 1	264
	21st to end	Day	13% 7% 29% 38% 12% 1	460
May	1st to 10th	Day	12% 5% 32% 38% 13%	615
	11th to 20th	Day	11% 4 22% 42% 17% 3	675
	21st to end	Day	7% 4 16% 45% 25% 3	734
June	1st to 10th	Day	4 1 7% 37% 41% 9%	680
	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% 17% 30% 28% 6%	330
November	1st to 10th	Day	15% 4 10% 29% 36% 6%	273
	11th to 20th	Day	21% 3 11% 36% 21% 7%	270
	21st to end	Day	23% 8% 25% 27% 13% 4	270
December	1st to 10th	Day	20% 6% 18% 34% 18% 4	270
	11th to 20th	Day	24% 10% 21% 30% 13% 2	270
	21st to end	Day	20% 8% 24% 32% 15% 2	297
January	1st to 10th	Night	22% 8% 24% 32% 14% 1	950
	11th to 20th	Night	20% 8% 22% 37% 12%	950
	21st to end	Night	20% 8% 26% 33% 11%	950
February	1st to 10th	Night	25% 8% 23% 34% 10%	760
	11th to 20th	Night	23% 9% 20% 37% 11%	744
	21st to end	Night	22% 8% 28% 34% 8%	543
March	1st to 10th	Night	21% 6% 23% 37% 13%	570
	11th to 20th	Night	20% 9% 19% 42% 9%	570
	21st to end	Night	16% 6% 27% 39% 11% 1	627
April	1st to 10th	Night	16% 6% 27% 39% 11%	570
	11th to 20th	Night	20% 8% 24% 34% 14%	563
	21st to end	Night	18% 5% 25% 38% 14%	570
May	1st to 10th	Night	15% 5% 25% 43% 12%	570
	11th to 20th	Night	11% 3 19% 48% 18% 1	561
	21st to end	Night	8% 2 14% 44% 30% 2	617
June	1st to 10th	Night	5% 2 4 37% 48% 4	570
	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 10% 34% 37% 5%	748
	11th to 20th	Night	18% 4 16% 33% 27% 3	760
	21st to end	Night	19% 5% 22% 33% 18% 2	874
December	1st to 10th	Night	20% 5% 20% 31% 21% 3	950
	11th to 20th	Night	21% 7% 23% 33% 15% 1	950
	21st to end	Night	21% 7% 23% 34% 14% 1	1045

Page generated at 2024-10-30 12:19:23. Version ac07

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