Sesquicentennial State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sesquicentennial State Park 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 6% 4 4 5% 4 6% 8% 42%	101233
	Night	13% 6% 2 6% 4 4 4 4 6% 7% 43%	97886
Transparency	Day	38% 6% 12% 20% 18% 6%	104936
	Night	38% 6% 11% 19% 19% 7%	102322
Seeing	Day	14% 8% 22% 24% 21% 10%	15376
	Night	15% 7% 22% 33% 21% 3	25443

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	16% 5% 1 5% 3 3 3 3 5% 8% 47%	2836
	11th to 20th	Day	12% 6% 2 4 3 4 3 3 4 6% 53%	2840
	21st to end	Day	18% 9% 3 7% 4 3 3 3 3 4 44%	3124
February	1st to 10th	Day	15% 7% 2 7% 4 3 4 4 5% 7% 41%	1710
	11th to 20th	Day	20% 6% 2 6% 4 3 3 3 4 5% 45%	1848
	21st to end	Day	19% 6% 2 6% 3 5% 3 2 4 6% 42%	1636
March	1st to 10th	Day	22% 10% 3 7% 4 3 3 3 4 5% 37%	3435
	11th to 20th	Day	9% 5% 2 5% 4 4 4 3 5% 6% 53%	3480
	21st to end	Day	18% 7% 3 6% 4 4 3 3 5% 6% 42%	3815
April	1st to 10th	Day	10% 4 2 5% 4 4 4 4 6% 7% 51%	2090
	11th to 20th	Day	10% 5% 2 5% 4 3 4 5% 6% 8% 48%	2237
	21st to end	Day	8% 5% 2 4 4 3 4 4 6% 8% 51%	2380
May	1st to 10th	Day	9% 6% 3 7% 5% 5% 5% 3 7% 10% 41%	4082
	11th to 20th	Day	16% 8% 3 6% 4 4 4 4 5% 7% 39%	4081
	21st to end	Day	6% 4 2 5% 4 5% 5% 4 7% 9% 48%	4476
June	1st to 10th	Day	9% 6% 2 7% 5% 5% 5% 5% 9% 10% 37%	2470
	11th to 20th	Day	7% 5% 1 5% 5% 5% 6% 5% 8% 11% 42%	2470
	21st to end	Day	6% 5% 2 6% 6% 6% 7% 6% 9% 11% 38%	2470
July	1st to 10th	Day	12% 7% 2 8% 6% 5% 7% 6% 9% 10% 28%	4120
	11th to 20th	Day	6% 5% 2 7% 6% 6% 7% 6% 10% 13% 31%	4120
	21st to end	Day	9% 7% 3 8% 7% 6% 7% 6% 10% 13% 24%	4466
August	1st to 10th	Day	22% 6% 2 7% 5% 6% 6% 5% 7% 10% 23%	4104
	11th to 20th	Day	11% 6% 3 7% 5% 6% 5% 5% 8% 11% 35%	4044
	21st to end	Day	7% 4 1 5% 4 4 5% 5% 8% 11% 46%	4195
September	1st to 10th	Day	8% 5% 2 6% 6% 4 6% 4 7% 9% 42%	2099
	11th to 20th	Day	13% 6% 3 7% 5% 5% 5% 4 6% 8% 40%	2090
	21st to end	Day	17% 6% 2 5% 4 4 5% 4 6% 6% 42%	2090
October	1st to 10th	Day	13% 7% 2 5% 4 3 3 3 5% 6% 50%	1976
	11th to 20th	Day	10% 4 2 5% 3 3 3 3 3 7% 58%	1900
	21st to end	Day	11% 5% 2 4 3 3 4 3 3 4 58%	2090
November	1st to 10th	Day	12% 6% 1 4 4 5% 3 2 4 5% 53%	1957
	11th to 20th	Day	14% 6% 2 4 3 2 3 3 4 5% 53%	1805
	21st to end	Day	14% 6% 2 5% 5% 4 3 3 3 5% 50%	1710
December	1st to 10th	Day	18% 8% 2 6% 4 4 4 3 5% 7% 39%	1710
	11th to 20th	Day	16% 4 1 5% 3 3 3 3 4 6% 51%	2153
	21st to end	Day	20% 7% 2 5% 3 3 3 3 4 6% 44%	3124
January	1st to 10th	Night	17% 6% 2 5% 3 3 4 3 4 6% 47%	4109
	11th to 20th	Night	10% 7% 2 6% 5% 4 5% 4 6% 7% 44%	4120
	21st to end	Night	17% 8% 3 6% 4 3 3 3 4 4 45%	4532
February	1st to 10th	Night	16% 6% 2 5% 4 4 4 3 5% 6% 44%	2466
	11th to 20th	Night	18% 6% 3 6% 4 4 3 3 4 4 45%	2218
	21st to end	Night	15% 6% 3 7% 4 4 3 4 5% 6% 44%	1816
March	1st to 10th	Night	23% 10% 3 6% 4 3 3 3 4 6% 35%	3418
	11th to 20th	Night	12% 4 2 4 4 4 4 4 6% 7% 51%	3480
	21st to end	Night	18% 5% 2 5% 5% 3 4 3 5% 7% 43%	3817
April	1st to 10th	Night	10% 5% 2 5% 4 4 3 5% 5% 7% 50%	2090
	11th to 20th	Night	11% 4 2 5% 4 3 4 3 4 6% 53%	1889
	21st to end	Night	10% 4 1 5% 3 4 3 3 5% 8% 53%	1815
May	1st to 10th	Night	10% 6% 2 6% 4 4 5% 4 7% 10% 42%	2813
	11th to 20th	Night	14% 7% 2 7% 4 5% 4 4 5% 9% 40%	2812
	21st to end	Night	6% 4 2 6% 4 5% 5% 4 7% 9% 47%	3079
June	1st to 10th	Night	12% 6% 2 6% 6% 5% 5% 5% 9% 10% 34%	1710
	11th to 20th	Night	8% 5% 2 6% 5% 6% 5% 5% 8% 10% 39%	1710
	21st to end	Night	6% 6% 2 6% 5% 6% 7% 6% 10% 14% 32%	1710
July	1st to 10th	Night	12% 9% 3 8% 5% 5% 5% 5% 8% 9% 30%	2840
	11th to 20th	Night	9% 6% 2 7% 6% 7% 6% 6% 10% 12% 29%	2840
	21st to end	Night	13% 8% 3 10% 6% 6% 7% 6% 8% 9% 22%	3087
August	1st to 10th	Night	22% 6% 3 8% 5% 5% 7% 5% 7% 9% 22%	2825
	11th to 20th	Night	10% 6% 3 7% 5% 5% 7% 5% 7% 9% 35%	2785
	21st to end	Night	6% 4 1 5% 4 4 4 4 7% 12% 50%	3426
September	1st to 10th	Night	8% 5% 3 7% 6% 5% 5% 5% 8% 10% 39%	2077
	11th to 20th	Night	13% 6% 3 8% 5% 6% 4 4 5% 7% 39%	2090
	21st to end	Night	16% 6% 3 6% 4 4 4 4 5% 6% 42%	2090
October	1st to 10th	Night	14% 6% 2 5% 3 3 4 3 4 6% 53%	2202
	11th to 20th	Night	13% 4 2 4 3 2 3 2 4 6% 55%	2280
	21st to end	Night	10% 5% 1 5% 2 3 3 4 5% 5% 56%	2508
November	1st to 10th	Night	13% 6% 2 4 3 3 4 3 4 6% 53%	2341
	11th to 20th	Night	14% 6% 2 4 3 3 3 3 4 5% 53%	2377
	21st to end	Night	13% 6% 2 5% 3 3 4 3 6% 7% 47%	2470
December	1st to 10th	Night	17% 7% 2 5% 4 4 4 3 5% 6% 42%	2470
	11th to 20th	Night	17% 5% 2 5% 3 2 3 3 4 5% 52%	3042
	21st to end	Night	19% 7% 2 6% 4 4 4 3 5% 6% 40%	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	35% 4 6% 25% 23% 7%	2837
	11th to 20th	Day	34% 3 6% 17% 30% 10%	2840
	21st to end	Day	45% 4 3 16% 24% 9%	3124
February	1st to 10th	Day	42% 4 10% 19% 20% 6%	1710
	11th to 20th	Day	42% 4 5% 19% 25% 6%	1858
	21st to end	Day	44% 3 8% 15% 20% 9%	1636
March	1st to 10th	Day	50% 4 7% 16% 14% 10%	3435
	11th to 20th	Day	31% 5% 9% 16% 28% 11%	3480
	21st to end	Day	44% 4 7% 19% 22% 5%	3815
April	1st to 10th	Day	31% 5% 11% 20% 26% 7%	2090
	11th to 20th	Day	34% 5% 11% 19% 21% 11%	2237
	21st to end	Day	30% 6% 11% 26% 23% 4	2380
May	1st to 10th	Day	38% 6% 17% 24% 13% 2	4120
	11th to 20th	Day	44% 6% 11% 21% 16% 1	4085
	21st to end	Day	29% 6% 18% 21% 23% 3	4489
June	1st to 10th	Day	39% 8% 17% 23% 11% 2	2470
	11th to 20th	Day	33% 8% 18% 27% 13% 1	2470
	21st to end	Day	36% 10% 17% 22% 13% 2	2470
July	1st to 10th	Day	45% 10% 19% 17% 7% 2	4055
	11th to 20th	Day	38% 15% 27% 16% 4 1	4051
	21st to end	Day	46% 14% 18% 17% 5% 1	4324
August	1st to 10th	Day	54% 9% 18% 14% 4 1	4091
	11th to 20th	Day	40% 10% 17% 20% 13%	4083
	21st to end	Day	30% 7% 15% 32% 14% 2	4195
September	1st to 10th	Day	36% 9% 14% 17% 19% 5%	2099
	11th to 20th	Day	42% 8% 11% 16% 21% 3	2090
	21st to end	Day	42% 5% 9% 21% 17% 6%	2090
October	1st to 10th	Day	34% 3 8% 18% 27% 9%	3288
	11th to 20th	Day	18% 2 5% 18% 28% 29%	3140
	21st to end	Day	25% 3 5% 22% 30% 15%	3428
November	1st to 10th	Day	34% 3 7% 18% 27% 12%	1957
	11th to 20th	Day	34% 3 7% 20% 25% 11%	1805
	21st to end	Day	37% 3 9% 19% 22% 10%	1710
December	1st to 10th	Day	45% 5% 8% 20% 16% 6%	1710
	11th to 20th	Day	36% 2 6% 22% 24% 9%	2150
	21st to end	Day	42% 4 6% 21% 23% 3	3124
January	1st to 10th	Night	38% 4 6% 20% 24% 8%	4109
	11th to 20th	Night	38% 5% 8% 19% 23% 7%	4120
	21st to end	Night	43% 4 5% 14% 26% 8%	4532
February	1st to 10th	Night	41% 4 7% 19% 20% 9%	2466
	11th to 20th	Night	43% 3 6% 18% 21% 8%	2219
	21st to end	Night	40% 4 8% 18% 19% 11%	1816
March	1st to 10th	Night	51% 5% 9% 14% 15% 7%	3418
	11th to 20th	Night	32% 5% 8% 14% 25% 16%	3480
	21st to end	Night	41% 4 8% 21% 18% 8%	3817
April	1st to 10th	Night	33% 5% 12% 19% 23% 10%	2090
	11th to 20th	Night	32% 4 9% 21% 22% 11%	1889
	21st to end	Night	29% 5% 12% 25% 24% 5%	1815
May	1st to 10th	Night	36% 9% 14% 25% 13% 3	2840
	11th to 20th	Night	41% 7% 14% 20% 17%	2813
	21st to end	Night	30% 9% 12% 27% 20% 3	3087
June	1st to 10th	Night	40% 10% 18% 20% 11% 1	1710
	11th to 20th	Night	37% 8% 19% 23% 10% 2	1710
	21st to end	Night	37% 14% 19% 19% 10% 2	1710
July	1st to 10th	Night	47% 10% 20% 15% 7% 2	2795
	11th to 20th	Night	42% 14% 25% 14% 4 1	2786
	21st to end	Night	53% 13% 16% 13% 5%	2988
August	1st to 10th	Night	55% 9% 18% 14% 3 1	2814
	11th to 20th	Night	42% 10% 22% 19% 7%	2812
	21st to end	Night	26% 7% 16% 32% 17% 2	3426
September	1st to 10th	Night	38% 9% 16% 19% 13% 6%	2077
	11th to 20th	Night	44% 7% 11% 16% 18% 4	2090
	21st to end	Night	43% 6% 12% 18% 16% 5%	2090
October	1st to 10th	Night	34% 4 9% 18% 28% 7%	3670
	11th to 20th	Night	21% 2 5% 16% 26% 31%	3779
	21st to end	Night	25% 4 6% 19% 28% 19%	4120
November	1st to 10th	Night	34% 4 8% 15% 26% 14%	2341
	11th to 20th	Night	35% 4 6% 17% 24% 13%	2377
	21st to end	Night	36% 4 8% 19% 24% 10%	2470
December	1st to 10th	Night	43% 5% 8% 18% 19% 6%	2470
	11th to 20th	Night	36% 4 6% 19% 25% 10%	3044
	21st to end	Night	45% 3 7% 20% 21% 4	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% 17% 43% 17% 4	270
	11th to 20th	Day	19% 18% 36% 21% 6% 1	270
	21st to end	Day	21% 21% 39% 15% 4	297
February	1st to 10th	Day	20% 17% 38% 19% 6%	270
	11th to 20th	Day	31% 14% 37% 15% 3	270
	21st to end	Day	22% 17% 37% 19% 4	291
March	1st to 10th	Day	18% 15% 30% 27% 10%	460
	11th to 20th	Day	16% 16% 38% 22% 7% 1	460
	21st to end	Day	18% 13% 36% 22% 10% 1	506
April	1st to 10th	Day	15% 15% 32% 25% 12% 1	460
	11th to 20th	Day	12% 13% 29% 23% 18% 5%	452
	21st to end	Day	12% 10% 25% 28% 18% 8%	460
May	1st to 10th	Day	9% 11% 29% 25% 19% 6%	463
	11th to 20th	Day	16% 6% 17% 26% 23% 12%	487
	21st to end	Day	13% 5% 13% 26% 26% 18%	529
June	1st to 10th	Day	9% 3 13% 31% 31% 12%	490
	11th to 20th	Day	9% 3 14% 24% 30% 20%	490
	21st to end	Day	7% 2 13% 30% 30% 18%	490
July	1st to 10th	Day	9% 1 7% 22% 32% 29%	485
	11th to 20th	Day	10% 4 6% 22% 34% 26%	484
	21st to end	Day	5% 3 9% 28% 34% 22%	532
August	1st to 10th	Day	15% 3 10% 23% 29% 21%	486
	11th to 20th	Day	16% 3 8% 22% 29% 23%	479
	21st to end	Day	12% 2 9% 21% 32% 23%	539
September	1st to 10th	Day	11% 3 9% 27% 32% 19%	490
	11th to 20th	Day	16% 4 13% 21% 33% 13%	490
	21st to end	Day	18% 3 14% 25% 30% 11%	490
October	1st to 10th	Day	14% 4 20% 29% 23% 10%	490
	11th to 20th	Day	9% 5% 22% 33% 22% 10%	490
	21st to end	Day	12% 5% 24% 29% 23% 7%	539
November	1st to 10th	Day	15% 6% 25% 31% 19% 5%	495
	11th to 20th	Day	19% 10% 30% 28% 11% 2	365
	21st to end	Day	12% 12% 31% 27% 15% 2	270
December	1st to 10th	Day	24% 14% 36% 18% 7% 1	270
	11th to 20th	Day	21% 11% 36% 21% 11% 1	270
	21st to end	Day	25% 13% 32% 18% 9% 2	297
January	1st to 10th	Night	21% 11% 32% 29% 7%	760
	11th to 20th	Night	18% 10% 33% 32% 7%	760
	21st to end	Night	19% 9% 36% 33% 3	836
February	1st to 10th	Night	21% 11% 28% 35% 5%	760
	11th to 20th	Night	22% 12% 31% 32% 3	743
	21st to end	Night	18% 12% 36% 29% 5%	628
March	1st to 10th	Night	17% 11% 31% 36% 6%	760
	11th to 20th	Night	16% 9% 36% 31% 8%	760
	21st to end	Night	17% 10% 34% 30% 9%	836
April	1st to 10th	Night	13% 13% 32% 32% 10%	760
	11th to 20th	Night	13% 11% 26% 35% 15%	751
	21st to end	Night	12% 6% 28% 39% 15%	675
May	1st to 10th	Night	10% 6% 27% 39% 17%	570
	11th to 20th	Night	12% 4 23% 38% 21% 2	561
	21st to end	Night	9% 1 13% 39% 33% 4	617
June	1st to 10th	Night	13% 3 11% 39% 30% 5%	570
	11th to 20th	Night	9% 3 11% 32% 35% 10%	570
	21st to end	Night	8% 2 10% 39% 34% 7%	570
July	1st to 10th	Night	10% 2 7% 30% 42% 8%	555
	11th to 20th	Night	9% 1 5% 30% 48% 8%	552
	21st to end	Night	8% 2 7% 33% 45% 6%	624
August	1st to 10th	Night	13% 2 6% 27% 44% 9%	567
	11th to 20th	Night	12% 2 6% 30% 41% 8%	564
	21st to end	Night	12% 2 9% 28% 41% 8%	799
September	1st to 10th	Night	10% 3 8% 30% 43% 6%	760
	11th to 20th	Night	15% 4 10% 30% 36% 5%	760
	21st to end	Night	20% 3 11% 32% 31% 3	760
October	1st to 10th	Night	14% 4 17% 32% 28% 5%	760
	11th to 20th	Night	15% 5% 20% 35% 23% 3	760
	21st to end	Night	12% 6% 23% 32% 25% 3	836
November	1st to 10th	Night	16% 5% 22% 35% 18% 3	780
	11th to 20th	Night	16% 9% 27% 34% 13% 1	763
	21st to end	Night	15% 8% 23% 36% 17% 1	760
December	1st to 10th	Night	19% 8% 27% 36% 10% 1	760
	11th to 20th	Night	19% 7% 25% 37% 11% 1	760
	21st to end	Night	22% 10% 25% 33% 10%	836

Page generated at 2024-11-08 06:44:46. Version ac07

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