Old Tunnel State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Old Tunnel State Park clear sky chart from 2005-11-06 to 2024-11-05.

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	11% 6% 2 5% 4 4 4 3 5% 7% 48%	101010
	Night	12% 6% 2 5% 3 3 3 3 5% 7% 52%	98152
Transparency	Day	34% 6% 10% 21% 20% 10%	104854
	Night	32% 5% 11% 20% 20% 12%	102435
Seeing	Day	13% 7% 22% 30% 22% 6%	14822
	Night	15% 7% 25% 36% 16% 1	24732

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	12% 9% 2 4 3 2 3 2 4 5% 54%	2847
	11th to 20th	Day	14% 6% 2 4 2 2 2 3 4 5% 57%	2850
	21st to end	Day	15% 7% 2 5% 3 3 3 2 4 7% 48%	3456
February	1st to 10th	Day	16% 8% 2 6% 4 3 3 3 5% 5% 48%	1900
	11th to 20th	Day	17% 7% 2 5% 3 3 4 3 5% 6% 47%	1849
	21st to end	Day	17% 6% 2 4 2 2 2 3 4 5% 52%	1570
March	1st to 10th	Day	15% 9% 3 6% 4 3 3 3 4 6% 44%	3330
	11th to 20th	Day	19% 11% 3 9% 4 3 4 4 4 4 35%	3480
	21st to end	Day	13% 7% 2 5% 3 4 4 4 5% 7% 47%	3814
April	1st to 10th	Day	12% 8% 3 5% 4 3 3 3 4 7% 46%	2090
	11th to 20th	Day	17% 8% 2 5% 3 4 3 3 5% 5% 44%	2145
	21st to end	Day	14% 7% 2 6% 4 4 4 3 4 6% 46%	2374
May	1st to 10th	Day	19% 10% 3 7% 4 4 4 4 5% 6% 34%	4082
	11th to 20th	Day	14% 7% 3 6% 4 4 4 3 5% 7% 44%	4082
	21st to end	Day	11% 6% 2 6% 5% 5% 5% 5% 7% 9% 38%	4477
June	1st to 10th	Day	6% 5% 2 4 4 4 5% 4 7% 9% 48%	2470
	11th to 20th	Day	6% 5% 2 5% 5% 4 5% 3 7% 11% 47%	2470
	21st to end	Day	6% 5% 2 7% 5% 5% 7% 5% 7% 9% 41%	2470
July	1st to 10th	Day	7% 4 2 6% 5% 5% 5% 4 7% 9% 47%	4120
	11th to 20th	Day	5% 3 1 4 4 4 5% 4 6% 11% 53%	4120
	21st to end	Day	9% 5% 2 6% 6% 5% 6% 4 7% 9% 41%	4465
August	1st to 10th	Day	1 2 1 2 3 3 4 3 6% 9% 66%	3951
	11th to 20th	Day	4 3 1 4 3 3 3 3 6% 10% 60%	3726
	21st to end	Day	4 3 2 5% 5% 6% 6% 5% 7% 11% 47%	4084
September	1st to 10th	Day	11% 6% 3 7% 5% 4 5% 4 5% 7% 44%	2090
	11th to 20th	Day	11% 5% 3 7% 4 6% 5% 4 6% 9% 41%	2090
	21st to end	Day	8% 5% 1 6% 4 5% 5% 4 6% 7% 49%	2090
October	1st to 10th	Day	6% 5% 2 5% 4 5% 4 3 5% 6% 56%	2090
	11th to 20th	Day	14% 5% 1 4 4 3 3 3 5% 7% 52%	2009
	21st to end	Day	11% 5% 2 5% 3 3 2 2 4 4 59%	2090
November	1st to 10th	Day	14% 8% 2 6% 4 3 4 3 5% 6% 45%	1898
	11th to 20th	Day	11% 7% 2 6% 3 4 3 3 5% 7% 50%	1715
	21st to end	Day	16% 7% 3 6% 3 3 3 3 4 5% 48%	1710
December	1st to 10th	Day	14% 8% 2 5% 3 3 3 3 4 6% 49%	1710
	11th to 20th	Day	15% 7% 3 6% 4 3 4 3 5% 5% 46%	2161
	21st to end	Day	14% 7% 2 4 3 2 2 2 3 5% 57%	3135
January	1st to 10th	Night	17% 5% 2 5% 2 2 2 2 4 5% 54%	4108
	11th to 20th	Night	12% 4 2 3 2 2 2 1 2 4 66%	4120
	21st to end	Night	18% 7% 3 6% 3 3 2 2 4 6% 45%	4240
February	1st to 10th	Night	15% 8% 3 5% 3 3 2 3 4 5% 50%	2280
	11th to 20th	Night	16% 7% 2 4 3 2 2 2 5% 5% 51%	2218
	21st to end	Night	16% 7% 2 5% 3 3 3 3 5% 5% 48%	1884
March	1st to 10th	Night	13% 9% 3 7% 4 3 4 3 5% 6% 44%	3525
	11th to 20th	Night	19% 11% 3 7% 4 4 4 3 4 5% 36%	3480
	21st to end	Night	14% 8% 2 5% 3 3 4 3 5% 6% 46%	3817
April	1st to 10th	Night	10% 8% 2 6% 3 3 3 3 5% 7% 49%	2090
	11th to 20th	Night	16% 7% 3 6% 3 3 3 3 4 6% 47%	1981
	21st to end	Night	17% 7% 2 5% 4 3 3 2 3 4 49%	1805
May	1st to 10th	Night	24% 10% 2 4 3 3 3 2 4 6% 39%	2823
	11th to 20th	Night	9% 7% 2 5% 4 4 4 3 5% 6% 50%	2823
	21st to end	Night	13% 6% 2 5% 4 3 4 3 6% 9% 46%	3090
June	1st to 10th	Night	5% 3 1 4 2 3 3 3 7% 9% 60%	1710
	11th to 20th	Night	5% 4 2 4 4 3 3 3 4 9% 61%	1710
	21st to end	Night	7% 5% 2 4 3 3 4 4 6% 10% 54%	1710
July	1st to 10th	Night	6% 4 1 4 3 3 5% 4 6% 10% 54%	2850
	11th to 20th	Night	4 3 1 4 3 4 3 4 6% 9% 59%	2850
	21st to end	Night	10% 8% 2 5% 3 4 4 3 6% 9% 44%	3098
August	1st to 10th	Night	1 2 2 2 2 3 3 4 6% 75%	2984
	11th to 20th	Night	3 2 1 3 3 3 3 3 6% 12% 61%	3113
	21st to end	Night	4 5% 2 4 4 3 4 4 6% 9% 54%	3577
September	1st to 10th	Night	8% 5% 2 5% 5% 4 4 3 5% 7% 51%	2090
	11th to 20th	Night	8% 8% 2 6% 4 4 4 4 6% 8% 46%	2090
	21st to end	Night	7% 6% 2 4 5% 4 4 4 6% 6% 52%	2090
October	1st to 10th	Night	6% 4 1 4 3 3 3 3 4 7% 63%	2090
	11th to 20th	Night	13% 4 1 4 3 3 3 3 5% 5% 55%	2149
	21st to end	Night	14% 5% 2 4 2 2 2 1 3 5% 61%	2508
November	1st to 10th	Night	13% 7% 2 5% 3 3 3 2 4 6% 53%	2280
	11th to 20th	Night	10% 7% 2 4 3 3 3 2 5% 7% 56%	2461
	21st to end	Night	17% 7% 2 4 3 3 3 3 4 6% 48%	2470
December	1st to 10th	Night	14% 7% 1 3 3 3 3 3 5% 6% 53%	2470
	11th to 20th	Night	14% 9% 2 7% 3 3 3 3 4 4 48%	3036
	21st to end	Night	16% 7% 2 3 2 2 2 2 3 4 56%	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	33% 3 4 16% 25% 18%	2848
	11th to 20th	Day	32% 3 5% 13% 31% 16%	2850
	21st to end	Day	37% 4 6% 12% 29% 12%	3456
February	1st to 10th	Day	40% 4 6% 12% 22% 17%	1900
	11th to 20th	Day	39% 4 6% 17% 19% 15%	1859
	21st to end	Day	35% 4 5% 17% 21% 17%	1570
March	1st to 10th	Day	41% 5% 6% 13% 21% 14%	3330
	11th to 20th	Day	52% 7% 6% 10% 16% 10%	3480
	21st to end	Day	36% 6% 10% 15% 19% 14%	3814
April	1st to 10th	Day	40% 4 8% 17% 18% 13%	2090
	11th to 20th	Day	42% 5% 7% 16% 19% 12%	2145
	21st to end	Day	39% 6% 7% 19% 19% 10%	2374
May	1st to 10th	Day	49% 7% 9% 14% 15% 6%	4120
	11th to 20th	Day	40% 6% 8% 17% 21% 8%	4086
	21st to end	Day	37% 11% 12% 27% 11% 2	4489
June	1st to 10th	Day	29% 8% 13% 26% 20% 3	2470
	11th to 20th	Day	31% 7% 12% 26% 19% 5%	2470
	21st to end	Day	37% 8% 12% 22% 16% 4	2470
July	1st to 10th	Day	31% 8% 17% 37% 7% 1	4056
	11th to 20th	Day	25% 8% 16% 33% 16% 3	4051
	21st to end	Day	34% 8% 17% 29% 11% 1	4325
August	1st to 10th	Day	15% 5% 12% 40% 27% 1	3937
	11th to 20th	Day	20% 5% 23% 38% 12% 2	3762
	21st to end	Day	29% 11% 17% 24% 17% 2	4083
September	1st to 10th	Day	40% 6% 10% 18% 18% 8%	2090
	11th to 20th	Day	39% 9% 11% 18% 18% 6%	2090
	21st to end	Day	33% 7% 8% 20% 18% 13%	2090
October	1st to 10th	Day	18% 4 6% 11% 26% 36%	3480
	11th to 20th	Day	25% 4 7% 19% 24% 21%	3314
	21st to end	Day	28% 3 5% 16% 35% 13%	3428
November	1st to 10th	Day	39% 5% 9% 19% 18% 10%	1898
	11th to 20th	Day	35% 5% 7% 16% 21% 16%	1715
	21st to end	Day	40% 4 5% 15% 21% 14%	1710
December	1st to 10th	Day	37% 4 7% 18% 23% 10%	1710
	11th to 20th	Day	39% 5% 8% 9% 21% 17%	2159
	21st to end	Day	32% 3 5% 14% 29% 17%	3135
January	1st to 10th	Night	34% 3 4 14% 25% 20%	4108
	11th to 20th	Night	26% 2 4 17% 27% 24%	4120
	21st to end	Night	42% 4 4 11% 26% 13%	4240
February	1st to 10th	Night	39% 4 6% 11% 22% 19%	2280
	11th to 20th	Night	37% 4 6% 16% 20% 17%	2218
	21st to end	Night	38% 5% 6% 13% 20% 18%	1884
March	1st to 10th	Night	41% 6% 7% 15% 21% 11%	3525
	11th to 20th	Night	49% 7% 8% 11% 14% 11%	3480
	21st to end	Night	37% 7% 10% 16% 18% 12%	3817
April	1st to 10th	Night	35% 6% 9% 18% 16% 16%	2090
	11th to 20th	Night	40% 5% 8% 15% 17% 16%	1981
	21st to end	Night	40% 5% 8% 19% 19% 10%	1805
May	1st to 10th	Night	47% 6% 8% 18% 12% 9%	2850
	11th to 20th	Night	33% 7% 11% 22% 17% 9%	2824
	21st to end	Night	35% 8% 14% 28% 11% 4	3099
June	1st to 10th	Night	20% 8% 16% 32% 20% 3	1710
	11th to 20th	Night	22% 6% 15% 29% 21% 6%	1710
	21st to end	Night	27% 8% 16% 28% 17% 4	1710
July	1st to 10th	Night	23% 9% 25% 36% 6% 1	2805
	11th to 20th	Night	22% 8% 20% 34% 16% 1	2796
	21st to end	Night	35% 7% 22% 27% 8%	2999
August	1st to 10th	Night	12% 4 14% 45% 24% 1	2974
	11th to 20th	Night	18% 6% 29% 35% 10% 2	3143
	21st to end	Night	25% 11% 20% 25% 18% 2	3577
September	1st to 10th	Night	33% 6% 14% 20% 18% 8%	2090
	11th to 20th	Night	34% 8% 15% 22% 15% 6%	2090
	21st to end	Night	31% 6% 12% 20% 18% 13%	2090
October	1st to 10th	Night	14% 4 8% 15% 22% 37%	3480
	11th to 20th	Night	22% 4 9% 16% 30% 19%	3570
	21st to end	Night	27% 2 5% 18% 33% 15%	4120
November	1st to 10th	Night	34% 5% 7% 19% 22% 13%	2280
	11th to 20th	Night	30% 5% 8% 21% 20% 17%	2461
	21st to end	Night	38% 4 8% 15% 20% 15%	2470
December	1st to 10th	Night	32% 4 9% 19% 22% 13%	2470
	11th to 20th	Night	40% 3 5% 12% 19% 20%	3037
	21st to end	Night	35% 3 4 14% 29% 16%	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	22% 12% 36% 23% 6% 1	270
	11th to 20th	Day	21% 14% 31% 24% 8% 1	270
	21st to end	Day	18% 14% 36% 23% 8%	297
February	1st to 10th	Day	26% 16% 28% 24% 6%	270
	11th to 20th	Day	26% 17% 34% 19% 3 1	270
	21st to end	Day	27% 16% 40% 16% 1	225
March	1st to 10th	Day	22% 14% 39% 21% 3	270
	11th to 20th	Day	19% 19% 34% 20% 7%	270
	21st to end	Day	17% 19% 41% 18% 5% 1	297
April	1st to 10th	Day	20% 15% 41% 19% 4	270
	11th to 20th	Day	20% 15% 38% 21% 6%	343
	21st to end	Day	17% 16% 38% 23% 6%	554
May	1st to 10th	Day	18% 11% 37% 27% 7%	653
	11th to 20th	Day	18% 9% 28% 32% 10% 3	675
	21st to end	Day	18% 7% 27% 30% 16% 2	734
June	1st to 10th	Day	7% 3 16% 41% 28% 4	680
	11th to 20th	Day	8% 2 16% 47% 23% 5%	680
	21st to end	Day	8% 2 14% 35% 33% 9%	680
July	1st to 10th	Day	10% 2 10% 34% 34% 11%	671
	11th to 20th	Day	4 1 5% 32% 48% 9%	668
	21st to end	Day	6% 1 5% 33% 44% 11%	739
August	1st to 10th	Day	2 1 3 33% 46% 15%	588
	11th to 20th	Day	7% 1 6% 33% 39% 15%	477
	21st to end	Day	5% 1 7% 26% 41% 21%	482
September	1st to 10th	Day	10% 2 7% 25% 32% 23%	300
	11th to 20th	Day	6% 5% 28% 42% 19%	300
	21st to end	Day	10% 2 7% 31% 36% 14%	300
October	1st to 10th	Day	6% 1 16% 31% 36% 11%	300
	11th to 20th	Day	11% 3 21% 41% 20% 4	300
	21st to end	Day	19% 11% 25% 27% 14% 3	330
November	1st to 10th	Day	17% 7% 27% 36% 9% 5%	282
	11th to 20th	Day	23% 9% 26% 26% 13% 3	270
	21st to end	Day	23% 16% 30% 20% 8% 3	270
December	1st to 10th	Day	17% 10% 31% 29% 11% 3	270
	11th to 20th	Day	18% 20% 32% 21% 9%	270
	21st to end	Day	18% 11% 35% 26% 8% 1	297
January	1st to 10th	Night	18% 10% 30% 35% 7% 1	950
	11th to 20th	Night	19% 10% 31% 33% 7%	950
	21st to end	Night	20% 11% 29% 32% 8%	870
February	1st to 10th	Night	22% 13% 31% 27% 6%	760
	11th to 20th	Night	22% 13% 33% 29% 3	744
	21st to end	Night	23% 11% 42% 22% 1	628
March	1st to 10th	Night	21% 11% 35% 30% 3	642
	11th to 20th	Night	20% 11% 33% 31% 5%	570
	21st to end	Night	16% 12% 40% 28% 4	627
April	1st to 10th	Night	14% 11% 43% 29% 3	570
	11th to 20th	Night	19% 12% 40% 27% 2	563
	21st to end	Night	19% 10% 39% 25% 6%	570
May	1st to 10th	Night	16% 11% 39% 29% 4	570
	11th to 20th	Night	12% 8% 35% 36% 8% 1	561
	21st to end	Night	15% 7% 30% 36% 12%	617
June	1st to 10th	Night	5% 2 22% 48% 23% 1	570
	11th to 20th	Night	6% 2 25% 51% 15%	570
	21st to end	Night	7% 2 17% 45% 27% 2	570
July	1st to 10th	Night	8% 3 9% 45% 31% 4	555
	11th to 20th	Night	4 9% 48% 37% 2	552
	21st to end	Night	5% 1 7% 48% 36% 3	624
August	1st to 10th	Night	2 1 4 47% 43% 3	567
	11th to 20th	Night	5% 1 6% 46% 38% 4	564
	21st to end	Night	7% 1 6% 38% 41% 6%	627
September	1st to 10th	Night	9% 1 8% 39% 38% 5%	570
	11th to 20th	Night	10% 1 8% 39% 37% 4	570
	21st to end	Night	9% 2 11% 39% 34% 4	570
October	1st to 10th	Night	8% 2 10% 49% 28% 3	570
	11th to 20th	Night	13% 4 19% 42% 20% 2	629
	21st to end	Night	17% 7% 23% 29% 22% 2	836
November	1st to 10th	Night	15% 6% 20% 39% 19% 2	760
	11th to 20th	Night	14% 8% 24% 37% 16% 1	941
	21st to end	Night	21% 8% 27% 32% 10% 1	950
December	1st to 10th	Night	18% 8% 25% 39% 9% 1	950
	11th to 20th	Night	22% 9% 29% 33% 8%	950
	21st to end	Night	19% 9% 30% 34% 8%	1045

Page generated at 2024-11-03 01:11:19. Version ac07

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