Randolph State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Randolph 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	10% 6% 3 6% 4 4 4 3 5% 7% 48%	101131
	Night	10% 6% 2 6% 3 3 4 3 5% 7% 51%	98121
Transparency	Day	35% 5% 12% 26% 19% 3	104834
	Night	32% 4 12% 27% 21% 4	102545
Seeing	Day	13% 10% 31% 29% 14% 3	15708
	Night	12% 9% 34% 34% 10% 1	25567

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	10% 11% 4 12% 5% 5% 5% 4 6% 7% 32%	2847
	11th to 20th	Day	8% 12% 4 9% 5% 5% 5% 3 4 7% 38%	2850
	21st to end	Day	9% 13% 6% 11% 4 4 4 3 4 6% 37%	3135
February	1st to 10th	Day	10% 11% 3 8% 5% 4 4 4 5% 6% 40%	1710
	11th to 20th	Day	8% 8% 2 6% 4 4 4 4 6% 8% 44%	1770
	21st to end	Day	7% 7% 3 7% 5% 3 5% 3 5% 6% 48%	1570
March	1st to 10th	Day	11% 7% 2 5% 4 3 3 2 4 6% 52%	3373
	11th to 20th	Day	10% 7% 2 5% 3 3 3 3 4 5% 55%	3480
	21st to end	Day	13% 9% 4 7% 4 4 4 4 5% 6% 40%	3814
April	1st to 10th	Day	13% 6% 2 7% 5% 3 3 3 5% 7% 48%	2099
	11th to 20th	Day	11% 8% 3 6% 5% 5% 5% 4 5% 5% 44%	2366
	21st to end	Day	18% 6% 2 6% 4 4 4 3 5% 7% 40%	2470
May	1st to 10th	Day	15% 9% 3 6% 4 4 4 4 5% 6% 42%	4082
	11th to 20th	Day	14% 7% 3 6% 4 4 3 3 5% 7% 44%	4082
	21st to end	Day	13% 6% 2 5% 4 5% 5% 4 6% 7% 43%	4477
June	1st to 10th	Day	7% 3 2 5% 3 4 4 4 5% 9% 55%	2470
	11th to 20th	Day	7% 4 2 5% 4 4 5% 5% 6% 8% 51%	2470
	21st to end	Day	6% 3 2 4 4 4 5% 4 7% 8% 54%	2470
July	1st to 10th	Day	10% 6% 2 6% 5% 4 4 4 6% 8% 44%	4120
	11th to 20th	Day	6% 3 2 5% 4 5% 5% 4 7% 9% 51%	4120
	21st to end	Day	5% 4 2 4 4 4 5% 5% 7% 10% 52%	4465
August	1st to 10th	Day	7% 4 2 5% 4 4 4 3 5% 8% 53%	4104
	11th to 20th	Day	12% 5% 2 6% 5% 4 3 3 5% 6% 49%	4041
	21st to end	Day	5% 4 1 4 4 4 4 3 6% 9% 58%	4450
September	1st to 10th	Day	10% 4 2 4 3 2 3 3 5% 8% 56%	2133
	11th to 20th	Day	10% 4 2 5% 4 4 3 3 5% 7% 53%	2090
	21st to end	Day	10% 4 2 5% 3 3 4 4 4 5% 57%	2090
October	1st to 10th	Day	13% 4 2 5% 3 3 2 3 4 5% 55%	1981
	11th to 20th	Day	11% 4 2 4 2 3 3 2 4 5% 61%	1900
	21st to end	Day	12% 6% 2 5% 4 4 3 2 4 5% 53%	2090
November	1st to 10th	Day	8% 4 1 5% 3 4 3 4 5% 6% 56%	1801
	11th to 20th	Day	9% 7% 2 5% 3 3 3 3 4 5% 56%	1710
	21st to end	Day	13% 7% 3 4 3 3 4 3 5% 6% 52%	1710
December	1st to 10th	Day	8% 6% 3 6% 5% 4 5% 4 5% 7% 47%	1538
	11th to 20th	Day	9% 9% 3 8% 6% 4 3 3 5% 6% 45%	2118
	21st to end	Day	14% 12% 4 16% 4 4 4 4 5% 6% 27%	3135
January	1st to 10th	Night	8% 10% 4 14% 5% 5% 4 3 4 5% 38%	4108
	11th to 20th	Night	7% 9% 3 7% 4 5% 6% 4 4 6% 45%	4120
	21st to end	Night	13% 12% 5% 7% 3 3 4 2 4 5% 42%	4532
February	1st to 10th	Night	10% 10% 3 7% 5% 4 4 4 5% 6% 42%	2470
	11th to 20th	Night	9% 8% 3 6% 4 4 5% 3 5% 7% 46%	2315
	21st to end	Night	8% 6% 2 7% 4 4 4 3 4 5% 52%	1884
March	1st to 10th	Night	10% 6% 2 5% 3 3 3 3 4 6% 56%	3482
	11th to 20th	Night	9% 5% 2 5% 3 3 3 3 5% 8% 55%	3480
	21st to end	Night	16% 9% 3 6% 3 3 3 3 4 6% 44%	3817
April	1st to 10th	Night	10% 5% 2 5% 4 3 4 3 6% 6% 53%	2081
	11th to 20th	Night	12% 7% 3 5% 4 4 4 3 5% 6% 47%	1759
	21st to end	Night	14% 7% 1 4 4 4 4 3 6% 7% 45%	1710
May	1st to 10th	Night	16% 7% 2 7% 3 3 4 3 4 6% 46%	2823
	11th to 20th	Night	15% 5% 2 5% 3 3 3 3 5% 9% 47%	2823
	21st to end	Night	12% 5% 2 4 4 3 4 3 6% 8% 49%	3090
June	1st to 10th	Night	5% 4 1 3 3 4 3 4 6% 10% 56%	1710
	11th to 20th	Night	6% 3 1 4 3 3 4 4 6% 10% 53%	1710
	21st to end	Night	5% 2 1 4 3 3 3 4 7% 10% 58%	1710
July	1st to 10th	Night	9% 5% 2 5% 4 4 4 4 5% 8% 50%	2850
	11th to 20th	Night	3 2 1 4 3 3 4 4 6% 9% 60%	2850
	21st to end	Night	5% 3 2 4 4 3 4 4 6% 10% 56%	3098
August	1st to 10th	Night	3 3 1 5% 3 3 4 4 6% 12% 56%	2836
	11th to 20th	Night	9% 5% 2 6% 5% 4 4 3 5% 7% 50%	2798
	21st to end	Night	5% 3 1 4 3 3 3 3 5% 8% 62%	3212
September	1st to 10th	Night	8% 3 1 3 2 3 3 3 5% 7% 60%	2042
	11th to 20th	Night	9% 3 2 4 3 3 4 3 5% 6% 58%	2090
	21st to end	Night	8% 3 2 5% 3 3 3 2 4 6% 61%	2090
October	1st to 10th	Night	11% 5% 2 4 3 3 3 3 5% 7% 54%	2178
	11th to 20th	Night	11% 5% 1 4 2 3 3 2 4 5% 60%	2280
	21st to end	Night	11% 6% 2 5% 3 3 3 3 4 6% 56%	2508
November	1st to 10th	Night	8% 5% 1 5% 3 3 3 3 4 7% 59%	2493
	11th to 20th	Night	8% 5% 2 5% 3 2 4 3 5% 6% 58%	2477
	21st to end	Night	11% 7% 2 3 4 3 3 3 4 6% 54%	2470
December	1st to 10th	Night	8% 6% 2 5% 4 4 4 4 5% 6% 52%	2628
	11th to 20th	Night	9% 8% 3 6% 3 3 4 3 5% 6% 50%	3065
	21st to end	Night	16% 13% 5% 10% 4 3 3 2 3 5% 36%	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	49% 7% 13% 21% 9% 1	2848
	11th to 20th	Day	47% 4 16% 20% 12% 1	2850
	21st to end	Day	49% 5% 11% 22% 13% 1	3135
February	1st to 10th	Day	45% 5% 14% 22% 10% 4	1710
	11th to 20th	Day	38% 5% 13% 27% 14% 4	1779
	21st to end	Day	35% 5% 11% 24% 20% 5%	1570
March	1st to 10th	Day	34% 4 9% 23% 27% 4	3373
	11th to 20th	Day	31% 4 10% 29% 24% 2	3480
	21st to end	Day	44% 7% 15% 26% 7% 1	3814
April	1st to 10th	Day	37% 4 13% 24% 19% 3	2099
	11th to 20th	Day	40% 6% 12% 24% 16% 2	2366
	21st to end	Day	44% 5% 10% 26% 14% 1	2470
May	1st to 10th	Day	42% 6% 10% 24% 14% 4	4120
	11th to 20th	Day	41% 5% 11% 25% 18%	4086
	21st to end	Day	38% 6% 13% 27% 14% 2	4489
June	1st to 10th	Day	26% 7% 16% 35% 15% 2	2470
	11th to 20th	Day	29% 6% 14% 28% 20% 2	2470
	21st to end	Day	26% 6% 15% 29% 19% 4	2470
July	1st to 10th	Day	37% 5% 13% 22% 20% 3	4056
	11th to 20th	Day	28% 6% 12% 32% 19% 4	4051
	21st to end	Day	24% 7% 15% 28% 22% 3	4325
August	1st to 10th	Day	30% 5% 14% 26% 21% 4	4090
	11th to 20th	Day	36% 5% 15% 24% 18% 2	4080
	21st to end	Day	24% 5% 15% 30% 18% 8%	4449
September	1st to 10th	Day	27% 5% 12% 27% 22% 7%	2133
	11th to 20th	Day	30% 4 10% 27% 25% 3	2090
	21st to end	Day	29% 4 9% 30% 26% 3	2090
October	1st to 10th	Day	22% 2 8% 19% 45% 6%	3293
	11th to 20th	Day	18% 2 8% 30% 32% 9%	3140
	21st to end	Day	29% 3 9% 25% 30% 4	3428
November	1st to 10th	Day	28% 5% 12% 29% 22% 5%	1801
	11th to 20th	Day	31% 3 10% 27% 26% 3	1710
	21st to end	Day	35% 3 11% 28% 21% 2	1710
December	1st to 10th	Day	36% 4 16% 28% 16% 1	1538
	11th to 20th	Day	41% 4 13% 28% 14% 1	2116
	21st to end	Day	58% 5% 9% 19% 8% 1	3135
January	1st to 10th	Night	48% 5% 11% 22% 13% 1	4108
	11th to 20th	Night	40% 5% 14% 23% 17% 1	4120
	21st to end	Night	46% 3 14% 20% 15% 2	4532
February	1st to 10th	Night	43% 5% 12% 21% 16% 4	2470
	11th to 20th	Night	38% 4 12% 28% 15% 3	2316
	21st to end	Night	34% 4 9% 24% 21% 8%	1884
March	1st to 10th	Night	30% 3 9% 28% 25% 5%	3482
	11th to 20th	Night	29% 4 9% 25% 27% 5%	3480
	21st to end	Night	41% 6% 18% 25% 8% 2	3817
April	1st to 10th	Night	31% 4 12% 25% 23% 4	2081
	11th to 20th	Night	38% 5% 9% 26% 19% 3	1759
	21st to end	Night	38% 5% 12% 26% 17% 2	1710
May	1st to 10th	Night	39% 6% 11% 24% 16% 4	2850
	11th to 20th	Night	35% 5% 14% 27% 19% 1	2824
	21st to end	Night	31% 8% 16% 28% 16% 1	3099
June	1st to 10th	Night	23% 6% 17% 33% 18% 3	1710
	11th to 20th	Night	25% 6% 15% 32% 17% 5%	1710
	21st to end	Night	21% 6% 15% 33% 20% 5%	1710
July	1st to 10th	Night	32% 5% 13% 23% 21% 6%	2805
	11th to 20th	Night	19% 5% 14% 29% 29% 3	2796
	21st to end	Night	22% 5% 15% 31% 24% 3	2999
August	1st to 10th	Night	22% 5% 19% 25% 22% 7%	2826
	11th to 20th	Night	34% 5% 14% 25% 19% 2	2825
	21st to end	Night	21% 5% 15% 33% 20% 6%	3212
September	1st to 10th	Night	24% 4 11% 30% 23% 9%	2042
	11th to 20th	Night	27% 4 10% 28% 26% 5%	2090
	21st to end	Night	26% 3 9% 26% 31% 5%	2090
October	1st to 10th	Night	21% 3 7% 18% 45% 7%	3633
	11th to 20th	Night	19% 2 5% 32% 29% 12%	3779
	21st to end	Night	27% 3 8% 29% 30% 4	4120
November	1st to 10th	Night	27% 3 10% 28% 24% 7%	2493
	11th to 20th	Night	27% 4 10% 30% 24% 4	2477
	21st to end	Night	33% 3 10% 28% 22% 4	2470
December	1st to 10th	Night	32% 5% 15% 29% 19% 1	2628
	11th to 20th	Night	34% 4 11% 33% 17% 1	3066
	21st to end	Night	53% 4 9% 23% 10% 2	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	14% 16% 41% 19% 9% 1	270
	11th to 20th	Day	19% 18% 37% 21% 4	270
	21st to end	Day	11% 13% 47% 24% 5%	297
February	1st to 10th	Day	17% 20% 43% 16% 4	270
	11th to 20th	Day	15% 12% 48% 19% 5% 1	270
	21st to end	Day	13% 23% 43% 19% 3	225
March	1st to 10th	Day	16% 16% 45% 19% 4	270
	11th to 20th	Day	25% 14% 37% 17% 6% 1	270
	21st to end	Day	25% 18% 40% 12% 5%	297
April	1st to 10th	Day	21% 18% 38% 20% 3	279
	11th to 20th	Day	18% 18% 36% 23% 6%	564
	21st to end	Day	22% 19% 31% 19% 8% 2	650
May	1st to 10th	Day	17% 13% 38% 22% 8% 1	653
	11th to 20th	Day	19% 10% 29% 28% 12% 2	675
	21st to end	Day	18% 7% 32% 27% 14% 2	734
June	1st to 10th	Day	5% 5% 24% 37% 24% 6%	680
	11th to 20th	Day	8% 5% 33% 34% 17% 3	680
	21st to end	Day	7% 6% 38% 35% 12% 2	680
July	1st to 10th	Day	10% 3 19% 36% 27% 6%	671
	11th to 20th	Day	5% 3 20% 40% 25% 7%	668
	21st to end	Day	7% 3 17% 39% 28% 5%	739
August	1st to 10th	Day	9% 2 18% 41% 26% 3	676
	11th to 20th	Day	8% 4 19% 44% 21% 4	665
	21st to end	Day	9% 3 20% 34% 28% 6%	705
September	1st to 10th	Day	10% 3 25% 41% 17% 4	343
	11th to 20th	Day	6% 5% 28% 39% 18% 5%	300
	21st to end	Day	14% 5% 32% 31% 14% 3	300
October	1st to 10th	Day	17% 11% 26% 29% 13% 4	300
	11th to 20th	Day	8% 16% 42% 23% 9% 1	300
	21st to end	Day	20% 15% 37% 20% 8% 1	330
November	1st to 10th	Day	16% 15% 39% 23% 6% 1	300
	11th to 20th	Day	17% 16% 37% 24% 5% 1	270
	21st to end	Day	22% 12% 37% 21% 7% 1	270
December	1st to 10th	Day	10% 12% 42% 26% 8% 2	270
	11th to 20th	Day	15% 17% 37% 23% 8%	270
	21st to end	Day	20% 16% 43% 19% 1	297
January	1st to 10th	Night	11% 13% 37% 31% 7%	950
	11th to 20th	Night	13% 12% 38% 29% 7%	950
	21st to end	Night	14% 9% 42% 31% 4	1045
February	1st to 10th	Night	17% 10% 43% 26% 3	950
	11th to 20th	Night	13% 14% 40% 30% 3	841
	21st to end	Night	13% 15% 43% 23% 5%	628
March	1st to 10th	Night	13% 16% 41% 26% 5%	611
	11th to 20th	Night	16% 12% 36% 28% 7%	570
	21st to end	Night	21% 13% 40% 21% 4	627
April	1st to 10th	Night	14% 14% 44% 24% 5%	570
	11th to 20th	Night	18% 14% 38% 26% 3	563
	21st to end	Night	18% 9% 40% 25% 7% 1	570
May	1st to 10th	Night	18% 10% 35% 30% 8% 1	570
	11th to 20th	Night	17% 7% 32% 34% 10% 1	561
	21st to end	Night	14% 7% 30% 35% 13% 1	617
June	1st to 10th	Night	6% 4 27% 41% 21% 1	570
	11th to 20th	Night	6% 4 33% 41% 16% 1	570
	21st to end	Night	6% 3 34% 45% 11% 1	570
July	1st to 10th	Night	7% 2 19% 45% 25% 1	555
	11th to 20th	Night	3 1 21% 49% 24% 1	552
	21st to end	Night	5% 1 16% 49% 25% 2	624
August	1st to 10th	Night	5% 2 20% 47% 25% 1	567
	11th to 20th	Night	6% 3 16% 53% 20% 2	564
	21st to end	Night	7% 3 19% 44% 24% 3	627
September	1st to 10th	Night	9% 4 25% 43% 17% 2	570
	11th to 20th	Night	11% 2 27% 41% 18% 2	570
	21st to end	Night	9% 4 32% 38% 16% 1	570
October	1st to 10th	Night	14% 7% 30% 32% 16% 2	658
	11th to 20th	Night	14% 9% 40% 29% 8%	760
	21st to end	Night	15% 12% 31% 33% 8%	836
November	1st to 10th	Night	11% 10% 33% 36% 9% 1	933
	11th to 20th	Night	11% 12% 41% 30% 6%	953
	21st to end	Night	15% 12% 34% 31% 8%	950
December	1st to 10th	Night	12% 11% 39% 31% 6%	950
	11th to 20th	Night	17% 11% 38% 29% 5%	950
	21st to end	Night	17% 14% 36% 29% 4	1045

Page generated at 2024-11-08 05:44:52. Version ac07

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