Sheldon Lake State Park & Environmental Learning Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sheldon Lake State Park & Environmental Learning Center clear sky chart from 2005-11-06 to 2024-11-11.

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% 6% 2 7% 5% 5% 5% 4 6% 8% 39%	101078
	Night	14% 6% 2 5% 4 4 4 3 5% 7% 45%	98170
Transparency	Day	41% 5% 12% 20% 16% 7%	104766
	Night	37% 4 13% 21% 17% 8%	102609
Seeing	Day	14% 4 17% 27% 25% 13%	14858
	Night	16% 3 18% 34% 25% 3	24693

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	20% 10% 2 5% 3 3 3 3 4 5% 41%	2847
	11th to 20th	Day	16% 7% 2 4 3 2 3 2 3 6% 53%	2850
	21st to end	Day	23% 8% 3 7% 4 3 3 3 5% 7% 34%	3135
February	1st to 10th	Day	23% 10% 3 7% 4 4 3 3 5% 6% 34%	1780
	11th to 20th	Day	21% 10% 3 6% 4 3 4 2 4 6% 37%	1887
	21st to end	Day	20% 9% 2 6% 4 3 4 3 5% 5% 39%	1727
March	1st to 10th	Day	19% 9% 3 9% 6% 4 5% 4 6% 7% 29%	3436
	11th to 20th	Day	20% 8% 3 7% 6% 6% 6% 4 6% 6% 28%	3480
	21st to end	Day	18% 6% 2 6% 4 4 4 3 5% 6% 41%	3814
April	1st to 10th	Day	16% 8% 3 9% 5% 5% 5% 4 5% 5% 37%	2090
	11th to 20th	Day	18% 7% 3 7% 5% 4 4 3 5% 6% 38%	2226
	21st to end	Day	10% 7% 3 7% 5% 4 5% 4 5% 7% 42%	2280
May	1st to 10th	Day	18% 9% 3 8% 6% 6% 5% 4 6% 6% 30%	3789
	11th to 20th	Day	14% 6% 2 8% 4 5% 4 4 5% 7% 42%	4082
	21st to end	Day	9% 7% 2 7% 5% 6% 6% 5% 7% 11% 35%	4477
June	1st to 10th	Day	6% 5% 2 6% 6% 6% 6% 6% 8% 9% 40%	2470
	11th to 20th	Day	5% 4 1 6% 6% 7% 7% 7% 8% 10% 38%	2470
	21st to end	Day	7% 7% 2 8% 7% 8% 7% 7% 9% 9% 29%	2470
July	1st to 10th	Day	8% 5% 2 8% 6% 7% 7% 6% 9% 11% 30%	4120
	11th to 20th	Day	7% 8% 3 10% 7% 7% 9% 6% 8% 10% 25%	4120
	21st to end	Day	14% 8% 3 8% 7% 6% 6% 5% 7% 10% 26%	4465
August	1st to 10th	Day	2 2 1 3 4 4 5% 4 7% 10% 57%	4104
	11th to 20th	Day	2 3 1 4 4 5% 6% 7% 8% 13% 46%	3850
	21st to end	Day	9% 5% 2 7% 6% 7% 7% 6% 8% 9% 35%	4157
September	1st to 10th	Day	7% 5% 3 8% 6% 7% 7% 5% 7% 9% 36%	2090
	11th to 20th	Day	14% 6% 2 8% 5% 6% 7% 4 6% 6% 36%	2090
	21st to end	Day	8% 6% 2 6% 4 5% 4 4 6% 7% 48%	2090
October	1st to 10th	Day	7% 4 1 4 4 4 4 3 5% 7% 56%	1960
	11th to 20th	Day	10% 5% 2 6% 4 3 4 4 5% 7% 50%	1900
	21st to end	Day	13% 6% 2 4 3 2 3 3 4 5% 54%	2090
November	1st to 10th	Day	11% 6% 2 6% 4 4 6% 4 5% 6% 46%	1958
	11th to 20th	Day	11% 7% 2 6% 4 4 4 4 5% 6% 46%	1900
	21st to end	Day	17% 7% 2 8% 5% 3 4 3 4 7% 40%	1868
December	1st to 10th	Day	16% 9% 4 6% 5% 4 4 3 5% 7% 39%	1710
	11th to 20th	Day	15% 7% 2 6% 4 4 5% 4 5% 6% 41%	2161
	21st to end	Day	17% 7% 2 5% 4 4 4 3 4 6% 44%	3135
January	1st to 10th	Night	19% 8% 2 6% 3 4 3 3 5% 6% 42%	4108
	11th to 20th	Night	18% 7% 2 5% 3 2 3 2 3 5% 50%	4120
	21st to end	Night	24% 9% 3 5% 3 3 3 3 5% 7% 35%	4532
February	1st to 10th	Night	20% 9% 2 7% 4 3 3 3 5% 6% 38%	2415
	11th to 20th	Night	21% 8% 2 6% 4 3 3 2 3 5% 43%	2178
	21st to end	Night	23% 8% 2 6% 4 3 3 3 4 5% 39%	1727
March	1st to 10th	Night	26% 12% 3 6% 3 3 3 3 5% 6% 29%	3419
	11th to 20th	Night	25% 9% 3 8% 5% 4 4 3 5% 6% 30%	3480
	21st to end	Night	15% 7% 2 6% 4 4 4 3 4 5% 45%	3817
April	1st to 10th	Night	15% 7% 2 7% 5% 4 4 4 6% 6% 39%	2090
	11th to 20th	Night	20% 7% 2 5% 4 3 3 3 5% 7% 43%	1900
	21st to end	Night	16% 5% 2 6% 4 4 5% 3 4 7% 45%	1900
May	1st to 10th	Night	28% 9% 2 6% 4 4 3 3 5% 7% 29%	3101
	11th to 20th	Night	14% 7% 3 6% 5% 5% 4 4 6% 6% 42%	2823
	21st to end	Night	15% 6% 3 6% 4 5% 5% 5% 8% 10% 34%	3090
June	1st to 10th	Night	5% 4 2 3 3 3 4 3 6% 11% 58%	1710
	11th to 20th	Night	5% 3 2 3 3 4 4 3 7% 12% 56%	1710
	21st to end	Night	6% 4 2 6% 4 5% 5% 5% 9% 11% 44%	1710
July	1st to 10th	Night	5% 5% 2 5% 4 5% 5% 4 7% 11% 47%	2850
	11th to 20th	Night	3 5% 2 6% 5% 6% 5% 4 7% 12% 45%	2850
	21st to end	Night	10% 7% 2 8% 5% 4 4 5% 7% 9% 39%	3098
August	1st to 10th	Night	1 1 1 2 2 3 3 2 5% 10% 69%	2836
	11th to 20th	Night	2 2 1 2 3 2 4 3 7% 13% 61%	2982
	21st to end	Night	5% 4 1 5% 3 5% 5% 5% 8% 12% 47%	3494
September	1st to 10th	Night	6% 5% 3 6% 4 4 5% 4 7% 11% 46%	2090
	11th to 20th	Night	11% 7% 2 5% 3 5% 4 3 5% 8% 46%	2090
	21st to end	Night	9% 4 2 5% 3 3 3 4 5% 7% 54%	2090
October	1st to 10th	Night	5% 3 1 4 4 3 4 3 5% 7% 60%	2199
	11th to 20th	Night	10% 3 1 4 3 3 3 3 5% 6% 60%	2280
	21st to end	Night	11% 5% 2 5% 3 2 3 3 3 4 60%	2508
November	1st to 10th	Night	11% 6% 2 5% 4 3 3 4 4 6% 53%	2340
	11th to 20th	Night	12% 6% 2 4 4 3 4 3 5% 6% 50%	2287
	21st to end	Night	16% 6% 2 6% 3 4 4 3 4 6% 45%	2308
December	1st to 10th	Night	18% 8% 2 5% 4 4 4 2 5% 6% 42%	2470
	11th to 20th	Night	17% 8% 2 7% 4 3 4 3 4 5% 43%	3036
	21st to end	Night	16% 7% 3 6% 4 3 4 3 5% 6% 45%	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	47% 2 4 17% 20% 10%	2848
	11th to 20th	Day	35% 3 5% 24% 24% 10%	2850
	21st to end	Day	50% 2 4 16% 17% 10%	3135
February	1st to 10th	Day	53% 2 5% 14% 15% 11%	1780
	11th to 20th	Day	51% 2 6% 14% 17% 9%	1897
	21st to end	Day	49% 3 8% 16% 14% 10%	1727
March	1st to 10th	Day	54% 3 13% 13% 13% 4	3436
	11th to 20th	Day	54% 4 10% 13% 14% 6%	3480
	21st to end	Day	44% 3 9% 18% 22% 4	3814
April	1st to 10th	Day	47% 4 8% 17% 15% 9%	2090
	11th to 20th	Day	47% 3 9% 17% 16% 9%	2226
	21st to end	Day	39% 3 11% 20% 21% 6%	2280
May	1st to 10th	Day	52% 5% 11% 17% 11% 4	3824
	11th to 20th	Day	42% 3 9% 20% 22% 4	4086
	21st to end	Day	39% 6% 14% 31% 10% 1	4489
June	1st to 10th	Day	35% 6% 16% 26% 16% 1	2470
	11th to 20th	Day	35% 6% 16% 27% 14% 2	2470
	21st to end	Day	45% 7% 18% 22% 8% 1	2470
July	1st to 10th	Day	41% 8% 28% 20% 3	4056
	11th to 20th	Day	49% 9% 19% 17% 6%	4051
	21st to end	Day	50% 8% 19% 20% 2 1	4325
August	1st to 10th	Day	19% 5% 17% 40% 17%	4090
	11th to 20th	Day	25% 9% 32% 30% 5% 1	3889
	21st to end	Day	41% 10% 16% 19% 13% 1	4156
September	1st to 10th	Day	41% 9% 15% 17% 14% 4	2090
	11th to 20th	Day	46% 6% 11% 17% 16% 4	2090
	21st to end	Day	34% 3 13% 21% 17% 11%	2090
October	1st to 10th	Day	21% 3 6% 16% 15% 40%	3259
	11th to 20th	Day	22% 4 5% 17% 36% 15%	3140
	21st to end	Day	28% 2 5% 17% 36% 12%	3428
November	1st to 10th	Day	38% 4 9% 20% 21% 9%	1958
	11th to 20th	Day	38% 3 10% 15% 22% 12%	1900
	21st to end	Day	45% 3 6% 17% 18% 11%	1868
December	1st to 10th	Day	46% 2 9% 19% 17% 7%	1710
	11th to 20th	Day	44% 3 8% 14% 21% 9%	2159
	21st to end	Day	42% 2 7% 16% 21% 11%	3135
January	1st to 10th	Night	45% 3 7% 17% 17% 12%	4108
	11th to 20th	Night	39% 3 5% 17% 27% 10%	4120
	21st to end	Night	50% 2 4 17% 18% 9%	4532
February	1st to 10th	Night	48% 2 7% 13% 16% 13%	2415
	11th to 20th	Night	46% 2 7% 14% 19% 12%	2178
	21st to end	Night	48% 3 6% 14% 16% 12%	1727
March	1st to 10th	Night	56% 3 9% 15% 12% 5%	3419
	11th to 20th	Night	56% 3 10% 13% 13% 5%	3480
	21st to end	Night	42% 3 10% 15% 23% 7%	3817
April	1st to 10th	Night	44% 4 9% 18% 15% 9%	2090
	11th to 20th	Night	42% 3 10% 17% 16% 13%	1900
	21st to end	Night	41% 4 9% 22% 18% 7%	1900
May	1st to 10th	Night	55% 5% 10% 16% 9% 5%	3131
	11th to 20th	Night	43% 4 10% 19% 20% 5%	2824
	21st to end	Night	43% 5% 20% 24% 7% 1	3099
June	1st to 10th	Night	22% 4 22% 33% 18%	1710
	11th to 20th	Night	24% 4 19% 32% 19% 3	1710
	21st to end	Night	31% 6% 23% 29% 10% 1	1710
July	1st to 10th	Night	30% 7% 35% 26% 3	2805
	11th to 20th	Night	31% 10% 28% 26% 6%	2796
	21st to end	Night	40% 10% 24% 22% 3	2999
August	1st to 10th	Night	12% 4 20% 48% 16%	2826
	11th to 20th	Night	15% 6% 38% 36% 5% 1	3009
	21st to end	Night	28% 12% 22% 27% 9% 1	3494
September	1st to 10th	Night	32% 8% 23% 21% 14% 3	2090
	11th to 20th	Night	37% 6% 15% 22% 17% 4	2090
	21st to end	Night	30% 4 14% 23% 19% 11%	2090
October	1st to 10th	Night	18% 3 7% 18% 16% 37%	3667
	11th to 20th	Night	16% 3 5% 23% 33% 19%	3779
	21st to end	Night	22% 2 5% 16% 38% 16%	4120
November	1st to 10th	Night	33% 3 11% 22% 20% 10%	2340
	11th to 20th	Night	34% 3 9% 21% 21% 12%	2287
	21st to end	Night	41% 2 8% 20% 18% 9%	2308
December	1st to 10th	Night	44% 2 9% 21% 15% 10%	2470
	11th to 20th	Night	44% 3 8% 12% 19% 14%	3037
	21st to end	Night	43% 3 7% 14% 26% 8%	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	27% 6% 34% 23% 9% 1	270
	11th to 20th	Day	23% 9% 29% 30% 7% 2	270
	21st to end	Day	22% 10% 31% 27% 9%	297
February	1st to 10th	Day	26% 9% 33% 24% 8%	270
	11th to 20th	Day	27% 14% 30% 20% 8% 1	270
	21st to end	Day	24% 10% 45% 18% 2	225
March	1st to 10th	Day	30% 10% 32% 20% 8%	270
	11th to 20th	Day	20% 11% 43% 18% 7% 1	270
	21st to end	Day	21% 12% 34% 23% 9% 1	297
April	1st to 10th	Day	19% 13% 36% 23% 9%	270
	11th to 20th	Day	25% 9% 28% 21% 15% 1	424
	21st to end	Day	16% 6% 30% 31% 17% 2	460
May	1st to 10th	Day	17% 6% 29% 30% 17% 1	474
	11th to 20th	Day	14% 3 25% 34% 20% 4	675
	21st to end	Day	12% 2 23% 37% 21% 5%	734
June	1st to 10th	Day	9% 1 10% 35% 31% 15%	680
	11th to 20th	Day	7% 2 9% 36% 31% 15%	680
	21st to end	Day	9% 8% 29% 33% 21%	680
July	1st to 10th	Day	10% 1 3 24% 37% 25%	671
	11th to 20th	Day	6% 1 3 20% 40% 30%	668
	21st to end	Day	6% 1 3 23% 39% 28%	739
August	1st to 10th	Day	2 1 2 22% 42% 32%	676
	11th to 20th	Day	6% 1 13% 41% 39%	552
	21st to end	Day	10% 1 4 16% 34% 34%	529
September	1st to 10th	Day	10% 2 4 21% 32% 30%	300
	11th to 20th	Day	13% 2 4 25% 35% 22%	300
	21st to end	Day	12% 3 28% 36% 21%	300
October	1st to 10th	Day	7% 10% 38% 34% 12%	300
	11th to 20th	Day	8% 3 13% 41% 23% 12%	300
	21st to end	Day	18% 6% 22% 29% 18% 7%	330
November	1st to 10th	Day	17% 4 20% 31% 23% 6%	300
	11th to 20th	Day	17% 3 20% 39% 17% 4	270
	21st to end	Day	20% 11% 30% 20% 17% 2	270
December	1st to 10th	Day	19% 3 30% 27% 15% 6%	270
	11th to 20th	Day	18% 9% 31% 30% 10% 1	270
	21st to end	Day	20% 6% 35% 27% 9% 2	297
January	1st to 10th	Night	23% 5% 30% 31% 10%	950
	11th to 20th	Night	24% 6% 25% 36% 8% 1	950
	21st to end	Night	23% 6% 27% 37% 7%	1045
February	1st to 10th	Night	26% 7% 27% 34% 6%	895
	11th to 20th	Night	27% 6% 28% 31% 8%	704
	21st to end	Night	26% 8% 35% 26% 6%	471
March	1st to 10th	Night	24% 5% 29% 34% 7%	570
	11th to 20th	Night	21% 7% 27% 36% 9%	570
	21st to end	Night	18% 5% 31% 35% 10% 1	627
April	1st to 10th	Night	19% 5% 32% 35% 9%	570
	11th to 20th	Night	25% 5% 25% 36% 9% 1	563
	21st to end	Night	19% 5% 26% 37% 13% 1	570
May	1st to 10th	Night	19% 4 25% 41% 10%	570
	11th to 20th	Night	12% 2 21% 44% 19% 2	561
	21st to end	Night	9% 2 18% 41% 27% 2	617
June	1st to 10th	Night	6% 1 6% 45% 38% 4	570
	11th to 20th	Night	6% 1 8% 41% 41% 3	570
	21st to end	Night	7% 1 7% 29% 49% 8%	570
July	1st to 10th	Night	6% 1 1 26% 53% 12%	555
	11th to 20th	Night	5% 1 23% 59% 12%	552
	21st to end	Night	4 1 2 25% 59% 10%	624
August	1st to 10th	Night	2 2 20% 65% 10%	567
	11th to 20th	Night	6% 1 19% 62% 12%	564
	21st to end	Night	7% 1 1 21% 55% 14%	627
September	1st to 10th	Night	8% 1 4 21% 53% 12%	570
	11th to 20th	Night	14% 2 25% 49% 9%	570
	21st to end	Night	10% 1 5% 27% 50% 7%	570
October	1st to 10th	Night	6% 1 9% 36% 42% 6%	679
	11th to 20th	Night	10% 1 15% 42% 29% 3	760
	21st to end	Night	13% 4 19% 37% 25% 3	836
November	1st to 10th	Night	13% 3 16% 40% 26% 2	780
	11th to 20th	Night	14% 4 22% 40% 19%	763
	21st to end	Night	19% 5% 25% 36% 14% 1	788
December	1st to 10th	Night	22% 4 23% 33% 17% 1	950
	11th to 20th	Night	24% 4 24% 37% 10% 1	950
	21st to end	Night	22% 5% 27% 36% 9%	1045

Page generated at 2024-11-08 05:44:50. Version ac07

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