Millersburg
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Millersburg clear sky chart from 2005-11-06 to 2025-08-05.

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	14% 8% 3 7% 5% 5% 5% 4 6% 7% 36%	125839
	Night	14% 9% 3 7% 5% 4 4 4 5% 7% 38%	122187
Transparency	Day	44% 7% 11% 22% 14% 2	129513
	Night	44% 6% 11% 21% 16% 2	126569
Seeing	Day	18% 13% 25% 22% 15% 7%	15965
	Night	18% 10% 26% 28% 16% 2	25754

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% 16% 7% 10% 5% 4 4 3 5% 6% 26%	4056
	11th to 20th	Day	14% 13% 5% 15% 5% 5% 3 2 3 4 31%	4060
	21st to end	Day	21% 11% 6% 7% 5% 5% 4 3 4 5% 28%	4466
February	1st to 10th	Day	19% 12% 4 9% 6% 4 4 3 4 6% 30%	1915
	11th to 20th	Day	19% 11% 4 8% 5% 5% 3 3 5% 4 31%	1948
	21st to end	Day	19% 11% 3 8% 5% 4 4 4 6% 6% 32%	1650
March	1st to 10th	Day	18% 13% 3 7% 5% 4 4 3 4 5% 35%	4567
	11th to 20th	Day	13% 7% 2 6% 4 4 4 4 6% 8% 42%	4980
	21st to end	Day	16% 8% 3 7% 5% 5% 4 4 5% 7% 36%	5465
April	1st to 10th	Day	15% 9% 3 7% 4 4 4 4 6% 6% 37%	2320
	11th to 20th	Day	16% 8% 3 6% 4 4 4 4 5% 7% 39%	2427
	21st to end	Day	17% 7% 3 7% 5% 5% 5% 3 5% 8% 36%	2600
May	1st to 10th	Day	18% 9% 3 8% 5% 6% 6% 5% 7% 8% 26%	5862
	11th to 20th	Day	18% 9% 3 8% 4 4 5% 4 6% 7% 32%	5861
	21st to end	Day	14% 6% 2 7% 5% 5% 5% 5% 8% 10% 32%	6433
June	1st to 10th	Day	11% 5% 2 6% 5% 5% 4 5% 7% 8% 42%	2600
	11th to 20th	Day	8% 6% 2 7% 5% 5% 6% 4 7% 9% 41%	2600
	21st to end	Day	9% 6% 2 7% 5% 5% 5% 4 6% 10% 41%	2762
July	1st to 10th	Day	11% 6% 2 6% 5% 5% 5% 4 7% 9% 41%	6094
	11th to 20th	Day	9% 6% 3 7% 6% 7% 7% 5% 8% 10% 33%	5900
	21st to end	Day	12% 8% 3 9% 6% 7% 6% 5% 6% 8% 29%	6424
August	1st to 10th	Day	8% 5% 2 7% 4 5% 5% 5% 7% 11% 43%	4156
	11th to 20th	Day	9% 6% 2 7% 5% 5% 5% 4 8% 11% 38%	4044
	21st to end	Day	6% 4 1 5% 4 4 5% 3 6% 9% 54%	4196
September	1st to 10th	Day	15% 5% 2 5% 4 4 5% 4 6% 7% 44%	2138
	11th to 20th	Day	11% 5% 2 5% 4 4 4 4 5% 8% 48%	2090
	21st to end	Day	15% 7% 2 6% 3 3 4 2 4 7% 46%	2090
October	1st to 10th	Day	11% 5% 2 4 3 3 4 3 5% 7% 53%	2090
	11th to 20th	Day	14% 5% 2 5% 4 4 3 3 5% 6% 50%	1924
	21st to end	Day	18% 8% 3 5% 4 3 3 2 6% 6% 43%	1990
November	1st to 10th	Day	13% 5% 2 5% 4 4 3 3 4 5% 54%	1762
	11th to 20th	Day	15% 10% 3 6% 5% 3 4 3 5% 6% 41%	1800
	21st to end	Day	18% 10% 3 6% 4 3 3 3 5% 6% 38%	1800
December	1st to 10th	Day	19% 11% 3 7% 4 3 3 3 4 4 39%	2930
	11th to 20th	Day	20% 12% 4 8% 5% 6% 5% 3 4 4 28%	3373
	21st to end	Day	20% 16% 5% 10% 5% 5% 4 3 5% 5% 21%	4466
January	1st to 10th	Night	15% 14% 5% 15% 6% 5% 4 4 5% 6% 22%	5889
	11th to 20th	Night	16% 13% 6% 12% 5% 4 4 3 4 4 28%	5900
	21st to end	Night	20% 10% 4 8% 4 4 4 3 4 5% 35%	6490
February	1st to 10th	Night	22% 11% 5% 8% 4 4 4 3 5% 5% 29%	2481
	11th to 20th	Night	20% 12% 4 8% 5% 5% 3 3 4 5% 31%	2338
	21st to end	Night	21% 13% 4 7% 4 3 4 3 5% 4 31%	1980
March	1st to 10th	Night	18% 13% 2 7% 4 3 3 4 4 5% 36%	5286
	11th to 20th	Night	13% 7% 2 5% 4 3 4 3 5% 7% 47%	4980
	21st to end	Night	15% 9% 3 9% 5% 5% 5% 4 6% 7% 33%	5467
April	1st to 10th	Night	14% 6% 2 7% 6% 5% 4 5% 6% 6% 39%	2095
	11th to 20th	Night	14% 7% 3 6% 4 4 5% 3 5% 6% 44%	1920
	21st to end	Night	15% 8% 3 6% 4 4 5% 4 6% 7% 39%	1800
May	1st to 10th	Night	17% 10% 3 9% 5% 5% 5% 4 6% 8% 28%	4033
	11th to 20th	Night	16% 8% 3 8% 5% 5% 6% 5% 7% 8% 31%	4032
	21st to end	Night	11% 6% 3 7% 5% 5% 5% 4 7% 9% 38%	4421
June	1st to 10th	Night	8% 5% 1 5% 5% 4 4 5% 6% 10% 47%	1800
	11th to 20th	Night	6% 4 3 4 5% 4 5% 5% 8% 10% 46%	1800
	21st to end	Night	7% 4 2 5% 4 5% 6% 4 8% 10% 46%	1623
July	1st to 10th	Night	7% 6% 2 7% 5% 5% 5% 4 6% 9% 45%	3833
	11th to 20th	Night	8% 6% 2 7% 5% 4 6% 4 7% 9% 41%	4057
	21st to end	Night	11% 7% 3 8% 5% 5% 5% 4 6% 9% 36%	4427
August	1st to 10th	Night	8% 5% 2 6% 5% 4 4 5% 7% 10% 46%	2861
	11th to 20th	Night	7% 6% 3 6% 5% 5% 5% 5% 7% 9% 44%	2785
	21st to end	Night	4 3 1 4 3 3 4 3 5% 9% 60%	3442
September	1st to 10th	Night	12% 5% 2 4 3 4 4 3 5% 9% 49%	2022
	11th to 20th	Night	10% 5% 2 5% 3 4 3 3 4 7% 53%	2090
	21st to end	Night	13% 6% 3 6% 4 4 3 3 5% 6% 48%	2090
October	1st to 10th	Night	10% 4 1 5% 2 3 4 3 5% 8% 56%	2090
	11th to 20th	Night	13% 6% 2 5% 4 3 4 3 5% 7% 48%	2254
	21st to end	Night	16% 8% 2 6% 4 4 3 3 4 6% 44%	2603
November	1st to 10th	Night	12% 6% 2 6% 4 4 4 3 4 5% 50%	2536
	11th to 20th	Night	15% 8% 3 6% 4 3 4 3 4 7% 42%	2600
	21st to end	Night	17% 12% 3 6% 4 3 3 3 5% 5% 38%	2600
December	1st to 10th	Night	19% 12% 4 7% 4 3 3 3 4 4 38%	4250
	11th to 20th	Night	20% 10% 5% 8% 4 4 3 3 4 6% 33%	4822
	21st to end	Night	19% 15% 5% 11% 6% 5% 5% 4 4 6% 20%	6490

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	58% 6% 9% 18% 8%	4057
	11th to 20th	Day	58% 4 7% 17% 12% 2	4060
	21st to end	Day	58% 4 8% 21% 6% 3	4466
February	1st to 10th	Day	56% 5% 9% 18% 10% 2	1915
	11th to 20th	Day	55% 5% 9% 18% 10% 2	1958
	21st to end	Day	52% 5% 9% 20% 11% 2	1650
March	1st to 10th	Day	51% 5% 7% 17% 15% 6%	4567
	11th to 20th	Day	38% 6% 10% 26% 17% 2	4980
	21st to end	Day	45% 7% 12% 23% 12% 1	5465
April	1st to 10th	Day	45% 6% 11% 23% 12% 3	2320
	11th to 20th	Day	44% 6% 9% 22% 15% 4	2427
	21st to end	Day	46% 7% 12% 22% 11% 2	2600
May	1st to 10th	Day	51% 8% 13% 17% 9% 1	5897
	11th to 20th	Day	50% 7% 11% 21% 10%	5865
	21st to end	Day	41% 9% 17% 19% 12% 1	6447
June	1st to 10th	Day	38% 10% 11% 23% 18% 1	2600
	11th to 20th	Day	37% 10% 14% 22% 16% 2	2600
	21st to end	Day	36% 9% 14% 21% 16% 3	2762
July	1st to 10th	Day	37% 7% 12% 23% 19% 1	6029
	11th to 20th	Day	41% 10% 14% 24% 10% 1	5831
	21st to end	Day	50% 8% 12% 17% 11% 1	6240
August	1st to 10th	Day	33% 8% 14% 34% 11% 1	4143
	11th to 20th	Day	36% 8% 12% 30% 14% 1	4083
	21st to end	Day	26% 7% 15% 30% 19% 3	4195
September	1st to 10th	Day	38% 8% 12% 18% 19% 5%	2138
	11th to 20th	Day	34% 7% 11% 22% 23% 3	2090
	21st to end	Day	38% 5% 9% 24% 20% 3	2090
October	1st to 10th	Day	21% 4 8% 27% 37% 3	3480
	11th to 20th	Day	25% 4 10% 28% 30% 2	3177
	21st to end	Day	31% 4 9% 29% 22% 5%	3253
November	1st to 10th	Day	35% 5% 8% 27% 22% 4	1762
	11th to 20th	Day	44% 4 9% 21% 18% 4	1800
	21st to end	Day	48% 5% 9% 20% 17% 2	1800
December	1st to 10th	Day	50% 5% 7% 22% 16%	2930
	11th to 20th	Day	59% 5% 8% 17% 10% 1	3370
	21st to end	Day	63% 6% 11% 13% 6% 1	4466
January	1st to 10th	Night	62% 7% 8% 14% 9% 1	5889
	11th to 20th	Night	58% 5% 7% 16% 10% 4	5900
	21st to end	Night	52% 4 8% 21% 12% 2	6490
February	1st to 10th	Night	56% 5% 11% 18% 9% 1	2481
	11th to 20th	Night	56% 4 8% 19% 11% 1	2339
	21st to end	Night	56% 4 11% 15% 11% 3	1980
March	1st to 10th	Night	49% 4 7% 23% 13% 3	5286
	11th to 20th	Night	36% 5% 11% 27% 20% 2	4980
	21st to end	Night	48% 7% 9% 21% 13% 1	5467
April	1st to 10th	Night	41% 8% 12% 22% 16% 2	2095
	11th to 20th	Night	40% 6% 10% 20% 19% 6%	1920
	21st to end	Night	42% 7% 13% 22% 13% 2	1800
May	1st to 10th	Night	52% 10% 10% 19% 8% 2	4060
	11th to 20th	Night	48% 9% 13% 21% 9% 1	4033
	21st to end	Night	38% 10% 17% 19% 13% 2	4429
June	1st to 10th	Night	30% 8% 15% 26% 17% 4	1800
	11th to 20th	Night	29% 10% 15% 23% 19% 3	1800
	21st to end	Night	30% 10% 17% 22% 17% 4	1623
July	1st to 10th	Night	35% 9% 11% 22% 21% 2	3791
	11th to 20th	Night	36% 10% 17% 23% 12% 1	4006
	21st to end	Night	44% 8% 13% 21% 14% 1	4297
August	1st to 10th	Night	32% 8% 15% 32% 13% 1	2850
	11th to 20th	Night	34% 9% 12% 27% 17% 1	2812
	21st to end	Night	20% 6% 15% 33% 21% 4	3442
September	1st to 10th	Night	32% 7% 15% 21% 18% 7%	2022
	11th to 20th	Night	31% 6% 11% 24% 24% 4	2090
	21st to end	Night	37% 6% 8% 21% 24% 3	2090
October	1st to 10th	Night	22% 4 8% 23% 40% 3	3480
	11th to 20th	Night	25% 4 8% 26% 34% 4	3740
	21st to end	Night	31% 3 8% 22% 28% 8%	4277
November	1st to 10th	Night	36% 4 10% 23% 23% 4	2536
	11th to 20th	Night	44% 4 9% 19% 20% 5%	2600
	21st to end	Night	47% 5% 10% 23% 14% 2	2600
December	1st to 10th	Night	50% 4 10% 22% 13% 1	4250
	11th to 20th	Night	52% 5% 11% 20% 11% 1	4824
	21st to end	Night	63% 7% 9% 14% 6%	6490

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	25% 24% 33% 13% 5%	300
	11th to 20th	Day	33% 26% 30% 11% 1	300
	21st to end	Day	27% 26% 34% 11% 3	330
February	1st to 10th	Day	29% 21% 35% 14% 2	300
	11th to 20th	Day	33% 28% 28% 9% 2	300
	21st to end	Day	33% 18% 39% 7% 3	249
March	1st to 10th	Day	25% 28% 30% 13% 4	335
	11th to 20th	Day	23% 23% 32% 16% 5%	500
	21st to end	Day	29% 20% 31% 13% 7%	550
April	1st to 10th	Day	22% 20% 28% 19% 9% 1	500
	11th to 20th	Day	20% 22% 29% 18% 8% 4	492
	21st to end	Day	22% 16% 33% 18% 10% 2	500
May	1st to 10th	Day	20% 16% 33% 19% 9% 4	503
	11th to 20th	Day	18% 12% 26% 26% 13% 6%	527
	21st to end	Day	15% 10% 24% 23% 19% 9%	573
June	1st to 10th	Day	11% 8% 22% 28% 22% 9%	530
	11th to 20th	Day	10% 7% 21% 29% 24% 8%	530
	21st to end	Day	10% 5% 24% 30% 21% 10%	692
July	1st to 10th	Day	13% 6% 17% 22% 22% 20%	615
	11th to 20th	Day	11% 4 17% 26% 26% 15%	524
	21st to end	Day	12% 3 18% 29% 23% 15%	576
August	1st to 10th	Day	13% 3 18% 25% 25% 16%	502
	11th to 20th	Day	12% 4 19% 31% 22% 12%	479
	21st to end	Day	8% 4 12% 30% 28% 18%	539
September	1st to 10th	Day	14% 4 14% 28% 26% 15%	490
	11th to 20th	Day	12% 3 15% 28% 28% 14%	490
	21st to end	Day	19% 9% 19% 23% 23% 7%	490
October	1st to 10th	Day	12% 5% 23% 31% 22% 8%	490
	11th to 20th	Day	14% 15% 29% 23% 14% 4	490
	21st to end	Day	20% 15% 31% 24% 10% 1	439
November	1st to 10th	Day	18% 14% 33% 23% 9% 3	300
	11th to 20th	Day	25% 19% 28% 20% 7% 1	300
	21st to end	Day	27% 14% 37% 17% 4 1	300
December	1st to 10th	Day	24% 24% 30% 16% 5% 1	300
	11th to 20th	Day	23% 21% 35% 17% 5%	300
	21st to end	Day	29% 20% 36% 13% 2	330
January	1st to 10th	Night	22% 19% 34% 21% 5%	800
	11th to 20th	Night	30% 18% 32% 19% 3	800
	21st to end	Night	23% 15% 36% 24% 2	880
February	1st to 10th	Night	29% 13% 35% 22% 2	800
	11th to 20th	Night	27% 17% 36% 19% 1	783
	21st to end	Night	27% 18% 36% 18% 1	660
March	1st to 10th	Night	23% 16% 32% 23% 6%	800
	11th to 20th	Night	24% 14% 34% 22% 6%	800
	21st to end	Night	21% 13% 33% 26% 7%	880
April	1st to 10th	Night	19% 13% 31% 29% 7%	695
	11th to 20th	Night	16% 13% 30% 27% 12% 1	593
	21st to end	Night	18% 9% 35% 29% 9% 1	600
May	1st to 10th	Night	18% 9% 31% 29% 12% 2	600
	11th to 20th	Night	16% 7% 21% 35% 18% 1	591
	21st to end	Night	10% 5% 20% 34% 27% 4	650
June	1st to 10th	Night	9% 3 19% 41% 25% 3	600
	11th to 20th	Night	9% 2 16% 41% 30% 3	600
	21st to end	Night	7% 3 20% 37% 29% 4	600
July	1st to 10th	Night	10% 2 12% 33% 33% 9%	585
	11th to 20th	Night	6% 3 13% 35% 39% 4	582
	21st to end	Night	11% 2 11% 35% 36% 5%	657
August	1st to 10th	Night	9% 2 10% 34% 39% 5%	579
	11th to 20th	Night	7% 4 11% 38% 34% 6%	564
	21st to end	Night	7% 2 10% 31% 43% 7%	627
September	1st to 10th	Night	13% 2 13% 32% 35% 5%	692
	11th to 20th	Night	12% 3 13% 32% 33% 7%	760
	21st to end	Night	15% 5% 20% 32% 26% 3	760
October	1st to 10th	Night	11% 6% 19% 32% 28% 5%	760
	11th to 20th	Night	16% 7% 26% 33% 17% 2	760
	21st to end	Night	20% 11% 30% 25% 12% 1	836
November	1st to 10th	Night	16% 9% 26% 31% 16% 2	780
	11th to 20th	Night	20% 12% 31% 26% 10% 1	800
	21st to end	Night	24% 12% 26% 28% 9% 1	800
December	1st to 10th	Night	27% 14% 30% 24% 5%	800
	11th to 20th	Night	24% 12% 32% 26% 6% 1	800
	21st to end	Night	27% 16% 31% 23% 4	880

Page generated at 2025-08-02 01:32:24. Version ac07

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