Union Grove State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Union Grove 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% 7% 3 7% 4 4 4 3 5% 7% 43%	101481
	Night	10% 7% 3 7% 4 4 4 3 5% 7% 45%	97541
Transparency	Day	40% 7% 14% 25% 13% 2	101280
	Night	37% 7% 14% 25% 15% 2	97413
Seeing	Day	15% 10% 31% 29% 13% 3	15901
	Night	13% 9% 34% 34% 10% 1	25752

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	8% 13% 4 14% 8% 8% 6% 4 5% 5% 24%	2506
	11th to 20th	Day	6% 14% 5% 10% 6% 6% 8% 3 6% 8% 27%	2770
	21st to end	Day	6% 12% 6% 16% 8% 7% 6% 4 5% 6% 24%	3135
February	1st to 10th	Day	10% 11% 4 10% 7% 8% 6% 4 4 6% 30%	1710
	11th to 20th	Day	10% 11% 4 7% 6% 5% 4 3 5% 7% 38%	1696
	21st to end	Day	12% 11% 3 9% 6% 5% 5% 3 6% 6% 35%	1570
March	1st to 10th	Day	11% 10% 4 8% 3 3 4 3 4 7% 44%	3315
	11th to 20th	Day	9% 9% 3 6% 5% 4 4 3 5% 6% 46%	3480
	21st to end	Day	25% 11% 4 11% 5% 4 4 3 4 6% 24%	3814
April	1st to 10th	Day	15% 9% 3 7% 4 4 4 4 5% 6% 39%	2136
	11th to 20th	Day	18% 10% 2 5% 4 4 4 3 5% 6% 39%	2442
	21st to end	Day	22% 7% 3 6% 3 4 4 3 4 6% 38%	2470
May	1st to 10th	Day	16% 7% 2 6% 5% 5% 5% 4 6% 8% 35%	4082
	11th to 20th	Day	11% 6% 2 6% 4 4 3 3 4 6% 50%	4082
	21st to end	Day	16% 6% 2 6% 4 4 4 3 5% 7% 41%	4730
June	1st to 10th	Day	11% 5% 2 5% 4 3 4 4 6% 8% 49%	2700
	11th to 20th	Day	13% 5% 2 5% 5% 4 4 4 6% 7% 45%	2850
	21st to end	Day	9% 4 2 5% 4 4 4 4 7% 8% 49%	2850
July	1st to 10th	Day	11% 5% 2 6% 4 4 4 4 7% 10% 44%	4656
	11th to 20th	Day	7% 3 2 4 4 3 3 3 5% 7% 58%	4285
	21st to end	Day	4 3 1 5% 3 4 4 4 7% 10% 55%	4465
August	1st to 10th	Day	8% 6% 2 5% 4 4 5% 4 6% 8% 48%	4104
	11th to 20th	Day	17% 7% 3 6% 4 4 4 4 5% 7% 39%	4041
	21st to end	Day	9% 5% 1 5% 4 3 4 3 5% 7% 54%	4532
September	1st to 10th	Day	14% 5% 2 5% 3 4 3 3 4 5% 52%	2197
	11th to 20th	Day	9% 5% 2 5% 3 3 3 3 5% 6% 55%	2090
	21st to end	Day	11% 4 2 5% 3 3 3 4 5% 6% 56%	2090
October	1st to 10th	Day	15% 5% 2 5% 3 4 3 2 4 6% 51%	1962
	11th to 20th	Day	13% 6% 1 4 3 3 3 2 5% 6% 53%	1900
	21st to end	Day	15% 7% 2 6% 3 3 3 3 4 5% 47%	2024
November	1st to 10th	Day	9% 7% 3 4 3 4 4 4 5% 7% 49%	1682
	11th to 20th	Day	9% 8% 3 9% 5% 5% 4 3 5% 6% 43%	1605
	21st to end	Day	12% 8% 2 8% 4 4 4 3 6% 7% 42%	1520
December	1st to 10th	Day	8% 9% 3 10% 5% 5% 4 3 6% 8% 39%	1520
	11th to 20th	Day	8% 11% 4 10% 6% 6% 5% 4 5% 6% 34%	1918
	21st to end	Day	16% 10% 4 14% 6% 5% 5% 3 5% 7% 26%	2552
January	1st to 10th	Night	9% 12% 3 13% 10% 6% 6% 4 5% 6% 26%	4446
	11th to 20th	Night	5% 11% 4 9% 7% 5% 8% 5% 10% 6% 30%	4182
	21st to end	Night	6% 12% 7% 13% 5% 5% 5% 4 6% 7% 30%	4532
February	1st to 10th	Night	10% 11% 3 8% 6% 5% 4 3 5% 6% 39%	2470
	11th to 20th	Night	9% 11% 3 8% 5% 4 4 3 5% 7% 42%	2388
	21st to end	Night	9% 9% 3 7% 4 4 5% 4 6% 5% 44%	1884
March	1st to 10th	Night	10% 6% 2 6% 4 4 3 2 4 6% 52%	3542
	11th to 20th	Night	10% 7% 3 5% 3 3 3 3 5% 8% 50%	3480
	21st to end	Night	21% 11% 3 9% 5% 5% 5% 4 5% 6% 28%	3817
April	1st to 10th	Night	14% 8% 2 7% 4 4 4 3 6% 6% 41%	2040
	11th to 20th	Night	15% 9% 2 6% 4 3 3 3 6% 6% 43%	1689
	21st to end	Night	19% 7% 2 5% 4 3 4 3 5% 6% 41%	1710
May	1st to 10th	Night	17% 6% 2 4 4 3 4 3 5% 7% 45%	2823
	11th to 20th	Night	9% 4 2 6% 4 4 4 3 5% 7% 51%	2823
	21st to end	Night	14% 6% 2 6% 4 3 4 4 5% 7% 44%	2819
June	1st to 10th	Night	7% 4 2 3 3 3 5% 3 6% 9% 54%	1475
	11th to 20th	Night	8% 4 1 4 3 2 4 4 8% 9% 52%	1330
	21st to end	Night	7% 3 1 4 4 4 4 4 5% 10% 56%	1330
July	1st to 10th	Night	7% 5% 2 6% 4 4 4 3 6% 8% 53%	2309
	11th to 20th	Night	6% 2 1 3 2 3 3 3 6% 7% 65%	2681
	21st to end	Night	2 3 1 4 3 3 3 3 7% 10% 61%	3098
August	1st to 10th	Night	6% 6% 2 5% 4 3 5% 4 6% 9% 50%	2836
	11th to 20th	Night	10% 5% 2 5% 3 3 3 4 6% 8% 50%	2798
	21st to end	Night	7% 4 2 4 4 3 4 3 6% 9% 54%	3135
September	1st to 10th	Night	9% 4 2 4 3 4 3 3 4 6% 59%	1980
	11th to 20th	Night	9% 4 1 4 3 3 4 3 5% 7% 58%	2090
	21st to end	Night	8% 5% 1 3 3 2 3 2 5% 6% 61%	2090
October	1st to 10th	Night	16% 5% 1 4 2 3 4 3 4 5% 54%	2198
	11th to 20th	Night	12% 5% 2 5% 4 3 3 2 4 6% 54%	2280
	21st to end	Night	14% 7% 2 5% 3 3 3 3 5% 5% 51%	2570
November	1st to 10th	Night	8% 5% 1 5% 4 3 3 3 6% 6% 55%	2419
	11th to 20th	Night	9% 6% 2 7% 4 4 4 3 5% 7% 48%	2573
	21st to end	Night	9% 8% 2 5% 4 3 3 3 6% 7% 49%	2660
December	1st to 10th	Night	8% 9% 4 9% 5% 4 4 4 5% 7% 42%	2660
	11th to 20th	Night	9% 9% 3 8% 5% 4 4 3 6% 8% 41%	3279
	21st to end	Night	16% 11% 4 14% 5% 4 4 4 4 6% 28%	5105

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	59% 7% 14% 15% 5%	2507
	11th to 20th	Day	54% 5% 11% 23% 6%	2770
	21st to end	Day	57% 9% 15% 13% 6%	3135
February	1st to 10th	Day	55% 6% 15% 15% 8% 1	1710
	11th to 20th	Day	46% 6% 14% 21% 11% 1	1705
	21st to end	Day	50% 6% 12% 21% 10% 2	1570
March	1st to 10th	Day	40% 7% 11% 30% 11% 1	3315
	11th to 20th	Day	38% 7% 10% 30% 12% 3	3480
	21st to end	Day	61% 8% 13% 14% 3 1	3814
April	1st to 10th	Day	45% 6% 13% 24% 11% 1	2136
	11th to 20th	Day	45% 6% 12% 20% 14% 2	2442
	21st to end	Day	47% 6% 11% 23% 12% 1	2470
May	1st to 10th	Day	42% 10% 13% 22% 13%	4120
	11th to 20th	Day	33% 7% 13% 27% 17% 3	4086
	21st to end	Day	41% 9% 12% 24% 14% 1	4743
June	1st to 10th	Day	31% 8% 16% 29% 13% 2	2700
	11th to 20th	Day	37% 7% 14% 24% 15% 3	2850
	21st to end	Day	30% 7% 17% 30% 13% 3	2850
July	1st to 10th	Day	35% 7% 19% 24% 13% 1	4584
	11th to 20th	Day	26% 6% 13% 33% 18% 4	4210
	21st to end	Day	23% 8% 18% 29% 21% 3	4325
August	1st to 10th	Day	33% 7% 15% 30% 14% 2	4090
	11th to 20th	Day	44% 7% 13% 27% 9%	4080
	21st to end	Day	30% 7% 15% 27% 17% 3	4531
September	1st to 10th	Day	34% 6% 11% 29% 19% 2	2197
	11th to 20th	Day	29% 6% 14% 32% 17% 1	2090
	21st to end	Day	28% 7% 12% 29% 22% 2	2090
October	1st to 10th	Day	36% 5% 10% 28% 19% 2	1962
	11th to 20th	Day	31% 5% 12% 30% 17% 4	1900
	21st to end	Day	40% 4 12% 24% 17% 3	2024
November	1st to 10th	Day	33% 6% 18% 26% 16% 2	1682
	11th to 20th	Day	39% 7% 15% 24% 14% 1	1605
	21st to end	Day	41% 5% 16% 23% 14% 1	1520
December	1st to 10th	Day	43% 5% 18% 22% 10% 2	1520
	11th to 20th	Day	49% 7% 18% 22% 5%	1915
	21st to end	Day	56% 8% 12% 18% 5% 1	2552
January	1st to 10th	Night	57% 7% 11% 17% 7%	4446
	11th to 20th	Night	48% 7% 15% 21% 7% 2	4182
	21st to end	Night	51% 9% 15% 17% 8% 1	4532
February	1st to 10th	Night	46% 6% 13% 23% 11% 1	2470
	11th to 20th	Night	42% 5% 13% 24% 12% 3	2389
	21st to end	Night	40% 6% 13% 24% 13% 3	1884
March	1st to 10th	Night	33% 6% 12% 27% 21% 2	3542
	11th to 20th	Night	32% 7% 11% 28% 19% 4	3480
	21st to end	Night	54% 11% 15% 15% 5% 1	3817
April	1st to 10th	Night	42% 7% 13% 23% 15% 1	2040
	11th to 20th	Night	40% 6% 11% 24% 17% 2	1689
	21st to end	Night	43% 5% 13% 23% 14% 2	1710
May	1st to 10th	Night	37% 7% 14% 21% 20% 1	2850
	11th to 20th	Night	29% 8% 13% 25% 21% 4	2824
	21st to end	Night	36% 8% 12% 26% 15% 2	2827
June	1st to 10th	Night	24% 9% 16% 28% 18% 4	1475
	11th to 20th	Night	26% 6% 17% 26% 20% 5%	1330
	21st to end	Night	24% 7% 16% 30% 21% 2	1330
July	1st to 10th	Night	30% 6% 21% 28% 12% 3	2272
	11th to 20th	Night	19% 5% 14% 38% 20% 4	2633
	21st to end	Night	18% 7% 19% 30% 22% 4	2999
August	1st to 10th	Night	29% 8% 14% 31% 16% 3	2826
	11th to 20th	Night	31% 8% 17% 29% 14% 2	2825
	21st to end	Night	27% 7% 18% 23% 22% 4	3135
September	1st to 10th	Night	26% 6% 11% 29% 23% 5%	1980
	11th to 20th	Night	25% 6% 14% 32% 20% 3	2090
	21st to end	Night	24% 6% 10% 33% 24% 3	2090
October	1st to 10th	Night	33% 5% 11% 26% 24% 2	2198
	11th to 20th	Night	32% 5% 9% 29% 22% 4	2280
	21st to end	Night	36% 4 14% 25% 20% 1	2570
November	1st to 10th	Night	28% 5% 16% 24% 22% 4	2419
	11th to 20th	Night	35% 6% 15% 24% 17% 2	2573
	21st to end	Night	34% 6% 15% 28% 17% 1	2660
December	1st to 10th	Night	42% 6% 16% 27% 10%	2660
	11th to 20th	Night	40% 6% 21% 26% 7%	3281
	21st to end	Night	57% 6% 11% 19% 6%	5105

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	16% 13% 32% 25% 12% 2	270
	11th to 20th	Day	19% 12% 32% 29% 8% 1	270
	21st to end	Day	16% 9% 36% 28% 11% 1	297
February	1st to 10th	Day	13% 19% 37% 29% 3	270
	11th to 20th	Day	15% 14% 40% 25% 5% 1	270
	21st to end	Day	20% 12% 40% 23% 5%	225
March	1st to 10th	Day	14% 17% 38% 26% 3 1	270
	11th to 20th	Day	21% 11% 37% 22% 7% 1	270
	21st to end	Day	29% 13% 37% 16% 4 1	297
April	1st to 10th	Day	22% 17% 37% 19% 4	316
	11th to 20th	Day	24% 16% 32% 22% 6%	640
	21st to end	Day	25% 13% 31% 20% 9% 2	650
May	1st to 10th	Day	19% 13% 30% 28% 8% 2	653
	11th to 20th	Day	18% 12% 29% 26% 13% 3	675
	21st to end	Day	20% 8% 31% 27% 11% 2	734
June	1st to 10th	Day	8% 7% 23% 36% 21% 4	680
	11th to 20th	Day	13% 6% 34% 30% 14% 3	680
	21st to end	Day	9% 8% 31% 31% 18% 2	680
July	1st to 10th	Day	8% 3 18% 39% 25% 7%	671
	11th to 20th	Day	8% 4 28% 35% 21% 4	668
	21st to end	Day	5% 3 25% 41% 22% 4	739
August	1st to 10th	Day	10% 4 22% 39% 22% 4	676
	11th to 20th	Day	13% 3 24% 34% 21% 5%	665
	21st to end	Day	8% 4 27% 35% 22% 4	748
September	1st to 10th	Day	16% 5% 27% 32% 16% 4	407
	11th to 20th	Day	7% 5% 37% 31% 16% 4	300
	21st to end	Day	14% 11% 34% 25% 12% 4	300
October	1st to 10th	Day	16% 9% 27% 30% 13% 4	300
	11th to 20th	Day	15% 17% 34% 23% 9% 1	300
	21st to end	Day	21% 14% 36% 22% 6%	330
November	1st to 10th	Day	18% 14% 31% 25% 9% 3	273
	11th to 20th	Day	12% 18% 40% 22% 7%	270
	21st to end	Day	20% 15% 29% 26% 8% 1	270
December	1st to 10th	Day	12% 10% 40% 25% 11% 1	270
	11th to 20th	Day	14% 14% 42% 21% 7%	270
	21st to end	Day	24% 12% 37% 24% 3	297
January	1st to 10th	Night	12% 10% 39% 31% 8% 1	950
	11th to 20th	Night	13% 13% 34% 33% 7% 1	950
	21st to end	Night	15% 10% 39% 29% 7%	1045
February	1st to 10th	Night	15% 10% 40% 30% 5%	950
	11th to 20th	Night	14% 12% 39% 29% 6%	914
	21st to end	Night	14% 10% 37% 30% 8%	628
March	1st to 10th	Night	13% 11% 39% 31% 7%	646
	11th to 20th	Night	17% 11% 37% 31% 5%	570
	21st to end	Night	21% 12% 36% 23% 7%	627
April	1st to 10th	Night	19% 13% 40% 26% 3	570
	11th to 20th	Night	19% 14% 36% 25% 5% 1	563
	21st to end	Night	22% 9% 33% 26% 8% 1	570
May	1st to 10th	Night	17% 9% 34% 31% 8%	570
	11th to 20th	Night	16% 8% 31% 33% 12%	561
	21st to end	Night	17% 6% 31% 36% 9%	617
June	1st to 10th	Night	8% 6% 26% 45% 15% 1	570
	11th to 20th	Night	10% 3 36% 38% 12%	570
	21st to end	Night	7% 5% 26% 45% 16%	570
July	1st to 10th	Night	6% 2 21% 45% 27%	555
	11th to 20th	Night	4 1 23% 53% 18% 1	552
	21st to end	Night	3 2 22% 55% 18%	624
August	1st to 10th	Night	8% 3 22% 45% 21% 1	567
	11th to 20th	Night	7% 3 25% 42% 22% 1	564
	21st to end	Night	6% 3 27% 44% 18% 2	627
September	1st to 10th	Night	9% 5% 25% 43% 16% 1	570
	11th to 20th	Night	9% 5% 32% 39% 13% 2	570
	21st to end	Night	10% 5% 37% 34% 13% 1	570
October	1st to 10th	Night	18% 7% 33% 31% 10% 1	678
	11th to 20th	Night	15% 12% 35% 31% 7% 1	760
	21st to end	Night	17% 13% 31% 30% 9%	898
November	1st to 10th	Night	11% 10% 37% 31% 9% 1	931
	11th to 20th	Night	13% 11% 40% 29% 7%	950
	21st to end	Night	13% 10% 37% 32% 8%	950
December	1st to 10th	Night	13% 11% 38% 32% 6%	950
	11th to 20th	Night	17% 7% 34% 33% 8% 1	950
	21st to end	Night	21% 11% 35% 27% 6%	1045

Page generated at 2024-10-30 00:22:57. Version ac07

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