Morgantown
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Morgantown clear sky chart from 2005-11-06 to 2024-12-24.

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% 9% 3 7% 4 4 4 4 6% 7% 38%	101444
	Night	14% 10% 3 7% 4 4 4 3 5% 6% 38%	98677
Transparency	Day	43% 6% 12% 23% 15% 2	105099
	Night	44% 6% 11% 22% 16% 2	103162
Seeing	Day	17% 13% 27% 23% 14% 5%	15689
	Night	18% 11% 29% 27% 14% 2	25544

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	14% 18% 6% 9% 4 4 4 4 5% 6% 27%	2527
	11th to 20th	Day	16% 12% 4 14% 7% 5% 4 4 5% 4 25%	2530
	21st to end	Day	24% 19% 7% 9% 4 3 3 2 4 4 21%	2956
February	1st to 10th	Day	17% 14% 5% 8% 5% 4 4 3 4 6% 30%	1900
	11th to 20th	Day	15% 10% 4 9% 5% 5% 4 3 5% 7% 32%	1848
	21st to end	Day	17% 15% 4 10% 3 3 2 3 4 6% 32%	1570
March	1st to 10th	Day	23% 16% 3 7% 4 3 3 2 3 4 32%	3120
	11th to 20th	Day	13% 8% 3 6% 4 4 3 4 5% 6% 44%	3352
	21st to end	Day	14% 11% 3 9% 5% 5% 5% 4 5% 7% 32%	3995
April	1st to 10th	Day	14% 11% 3 7% 4 5% 4 4 5% 7% 36%	2280
	11th to 20th	Day	15% 11% 2 7% 4 3 5% 3 5% 6% 39%	2254
	21st to end	Day	19% 8% 3 7% 5% 4 4 3 4 7% 35%	2427
May	1st to 10th	Day	18% 9% 3 8% 5% 5% 5% 4 6% 8% 29%	4082
	11th to 20th	Day	21% 7% 3 6% 4 3 4 4 5% 6% 38%	4081
	21st to end	Day	9% 7% 3 7% 6% 5% 5% 5% 8% 9% 37%	4536
June	1st to 10th	Day	11% 6% 3 6% 4 5% 4 5% 6% 8% 41%	2660
	11th to 20th	Day	9% 6% 2 5% 5% 5% 5% 4 5% 9% 45%	2660
	21st to end	Day	9% 6% 2 6% 5% 5% 5% 5% 7% 9% 41%	2660
July	1st to 10th	Day	13% 7% 2 7% 4 4 4 4 7% 11% 37%	4440
	11th to 20th	Day	6% 4 2 5% 4 5% 5% 5% 7% 10% 47%	4440
	21st to end	Day	10% 7% 3 7% 5% 6% 6% 6% 8% 10% 32%	4641
August	1st to 10th	Day	8% 4 2 5% 4 4 5% 4 7% 10% 47%	4104
	11th to 20th	Day	9% 5% 2 6% 4 5% 6% 5% 8% 12% 39%	3827
	21st to end	Day	5% 4 2 5% 4 4 4 4 6% 9% 54%	4180
September	1st to 10th	Day	12% 6% 2 6% 4 4 4 4 6% 7% 44%	2252
	11th to 20th	Day	10% 6% 2 5% 3 3 5% 4 6% 8% 47%	2090
	21st to end	Day	13% 5% 2 5% 3 4 3 3 5% 7% 49%	2090
October	1st to 10th	Day	10% 5% 2 6% 4 4 4 3 5% 7% 50%	2090
	11th to 20th	Day	13% 7% 2 6% 3 4 4 4 5% 6% 45%	1954
	21st to end	Day	17% 10% 3 7% 4 3 4 3 5% 6% 37%	1881
November	1st to 10th	Day	8% 6% 2 5% 4 4 4 3 4 6% 53%	1762
	11th to 20th	Day	16% 10% 4 7% 3 3 4 3 6% 6% 38%	1800
	21st to end	Day	18% 12% 4 8% 4 4 2 3 4 6% 37%	1800
December	1st to 10th	Day	17% 15% 4 9% 5% 3 3 3 4 5% 33%	1800
	11th to 20th	Day	15% 15% 6% 10% 3 4 5% 3 4 6% 30%	2048
	21st to end	Day	20% 21% 7% 8% 5% 4 4 3 5% 5% 20%	2807
January	1st to 10th	Night	17% 16% 6% 11% 5% 4 4 3 5% 5% 25%	4428
	11th to 20th	Night	13% 18% 6% 15% 6% 5% 4 3 4 4 21%	4440
	21st to end	Night	24% 18% 7% 8% 4 3 2 2 3 4 24%	4689
February	1st to 10th	Night	20% 12% 5% 10% 5% 4 4 3 5% 5% 28%	2280
	11th to 20th	Night	14% 12% 5% 9% 5% 4 4 3 6% 6% 32%	2218
	21st to end	Night	19% 14% 5% 9% 4 4 4 3 4 5% 30%	1884
March	1st to 10th	Night	21% 16% 3 7% 4 3 3 3 4 5% 33%	3733
	11th to 20th	Night	12% 8% 3 6% 4 3 3 3 4 7% 47%	3608
	21st to end	Night	15% 9% 3 8% 5% 4 4 3 4 6% 39%	3666
April	1st to 10th	Night	13% 10% 3 7% 5% 3 4 3 5% 7% 39%	1900
	11th to 20th	Night	16% 9% 3 7% 4 4 3 3 5% 6% 41%	1875
	21st to end	Night	16% 7% 3 7% 4 5% 5% 4 7% 6% 37%	1753
May	1st to 10th	Night	18% 12% 3 8% 5% 4 5% 4 6% 7% 28%	2813
	11th to 20th	Night	19% 6% 3 5% 4 3 4 3 5% 8% 41%	2812
	21st to end	Night	10% 5% 2 6% 5% 5% 5% 4 7% 9% 43%	3004
June	1st to 10th	Night	8% 6% 3 6% 5% 3 4 4 5% 10% 47%	1520
	11th to 20th	Night	8% 5% 2 7% 4 4 4 4 7% 8% 49%	1520
	21st to end	Night	5% 5% 2 4 5% 4 5% 4 7% 11% 48%	1520
July	1st to 10th	Night	9% 6% 2 6% 4 4 3 3 6% 8% 48%	2530
	11th to 20th	Night	5% 4 2 4 4 3 4 4 7% 9% 54%	2530
	21st to end	Night	10% 6% 2 7% 4 5% 5% 5% 7% 10% 38%	2903
August	1st to 10th	Night	9% 6% 2 6% 3 4 4 3 5% 8% 50%	2825
	11th to 20th	Night	8% 5% 2 6% 5% 4 5% 4 6% 8% 48%	2999
	21st to end	Night	4 3 2 5% 4 4 5% 3 6% 8% 58%	3476
September	1st to 10th	Night	11% 5% 2 6% 4 4 4 3 5% 7% 50%	1909
	11th to 20th	Night	7% 5% 2 5% 3 3 4 4 5% 9% 54%	2090
	21st to end	Night	13% 5% 2 6% 4 4 3 3 4 6% 49%	2090
October	1st to 10th	Night	8% 4 2 5% 4 3 3 3 5% 7% 56%	2090
	11th to 20th	Night	16% 7% 2 5% 3 4 3 3 4 6% 48%	2222
	21st to end	Night	17% 8% 3 6% 4 4 4 3 4 7% 40%	2717
November	1st to 10th	Night	12% 7% 2 5% 4 4 3 3 5% 6% 48%	2536
	11th to 20th	Night	14% 9% 3 7% 4 3 3 4 4 7% 40%	2600
	21st to end	Night	18% 13% 4 8% 5% 4 3 2 4 5% 33%	2600
December	1st to 10th	Night	18% 13% 4 9% 6% 3 3 3 5% 6% 31%	2600
	11th to 20th	Night	17% 14% 5% 10% 4 3 3 3 4 6% 31%	3364
	21st to end	Night	21% 20% 7% 9% 5% 5% 4 3 4 4 18%	4933

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	57% 5% 9% 21% 8% 1	2528
	11th to 20th	Day	60% 4 13% 17% 6%	2530
	21st to end	Day	67% 4 9% 15% 3 1	2956
February	1st to 10th	Day	56% 4 11% 17% 10% 1	1900
	11th to 20th	Day	52% 5% 9% 22% 10% 1	1858
	21st to end	Day	54% 5% 9% 20% 9% 3	1570
March	1st to 10th	Day	57% 4 6% 18% 11% 3	3120
	11th to 20th	Day	39% 6% 11% 28% 14% 1	3352
	21st to end	Day	49% 8% 13% 21% 8% 1	3995
April	1st to 10th	Day	45% 7% 12% 20% 14% 1	2280
	11th to 20th	Day	45% 6% 10% 23% 13% 3	2254
	21st to end	Day	49% 6% 10% 21% 12% 3	2427
May	1st to 10th	Day	49% 9% 14% 20% 7%	4120
	11th to 20th	Day	45% 9% 10% 25% 11%	4085
	21st to end	Day	37% 11% 13% 18% 18% 2	4549
June	1st to 10th	Day	38% 7% 12% 24% 16% 3	2660
	11th to 20th	Day	35% 8% 13% 22% 20% 2	2660
	21st to end	Day	36% 9% 16% 19% 16% 4	2660
July	1st to 10th	Day	40% 6% 12% 23% 16% 2	4371
	11th to 20th	Day	30% 6% 15% 30% 18% 1	4365
	21st to end	Day	44% 7% 16% 17% 14% 2	4494
August	1st to 10th	Day	31% 7% 16% 31% 14% 1	4091
	11th to 20th	Day	35% 7% 12% 31% 14% 1	3866
	21st to end	Day	27% 6% 15% 31% 18% 4	4179
September	1st to 10th	Day	37% 7% 11% 24% 17% 4	2252
	11th to 20th	Day	34% 6% 11% 26% 21% 3	2090
	21st to end	Day	35% 5% 11% 24% 24% 2	2090
October	1st to 10th	Day	23% 4 7% 31% 34% 2	3480
	11th to 20th	Day	33% 4 8% 26% 27% 2	3222
	21st to end	Day	39% 3 9% 23% 24% 2	3081
November	1st to 10th	Day	33% 4 11% 29% 18% 4	1762
	11th to 20th	Day	46% 4 10% 20% 15% 4	1800
	21st to end	Day	51% 4 9% 22% 14% 1	1800
December	1st to 10th	Day	55% 4 12% 19% 10%	1800
	11th to 20th	Day	56% 5% 8% 21% 9% 1	2045
	21st to end	Day	66% 6% 10% 12% 6%	2807
January	1st to 10th	Night	59% 7% 11% 15% 7%	4428
	11th to 20th	Night	66% 5% 10% 13% 7%	4440
	21st to end	Night	65% 4 8% 15% 8% 1	4689
February	1st to 10th	Night	59% 5% 11% 17% 7% 1	2280
	11th to 20th	Night	51% 6% 11% 19% 12% 1	2219
	21st to end	Night	56% 4 10% 17% 10% 2	1884
March	1st to 10th	Night	55% 5% 7% 22% 10% 1	3733
	11th to 20th	Night	36% 7% 12% 23% 20% 1	3608
	21st to end	Night	45% 6% 10% 28% 9% 1	3666
April	1st to 10th	Night	44% 6% 11% 24% 13% 2	1900
	11th to 20th	Night	44% 5% 10% 19% 17% 5%	1875
	21st to end	Night	44% 7% 10% 22% 14% 3	1753
May	1st to 10th	Night	52% 10% 11% 18% 7% 2	2840
	11th to 20th	Night	42% 7% 14% 26% 11% 1	2813
	21st to end	Night	33% 10% 16% 22% 15% 4	3012
June	1st to 10th	Night	33% 8% 11% 24% 22% 3	1520
	11th to 20th	Night	31% 8% 11% 24% 21% 5%	1520
	21st to end	Night	27% 10% 16% 23% 19% 5%	1520
July	1st to 10th	Night	34% 8% 9% 26% 19% 4	2490
	11th to 20th	Night	26% 5% 14% 32% 21% 2	2482
	21st to end	Night	40% 5% 16% 23% 13% 4	2810
August	1st to 10th	Night	33% 6% 14% 34% 12% 1	2814
	11th to 20th	Night	34% 5% 13% 29% 18% 1	3026
	21st to end	Night	25% 5% 14% 30% 22% 4	3476
September	1st to 10th	Night	33% 6% 11% 22% 20% 7%	1909
	11th to 20th	Night	26% 6% 12% 26% 26% 4	2090
	21st to end	Night	36% 5% 10% 22% 23% 4	2090
October	1st to 10th	Night	19% 4 7% 23% 45% 3	3480
	11th to 20th	Night	27% 3 8% 24% 36% 2	3693
	21st to end	Night	35% 3 9% 23% 25% 5%	4467
November	1st to 10th	Night	37% 5% 10% 24% 21% 4	2536
	11th to 20th	Night	43% 5% 10% 21% 17% 4	2600
	21st to end	Night	53% 4 10% 21% 12% 1	2600
December	1st to 10th	Night	55% 5% 11% 19% 11% 1	2600
	11th to 20th	Night	53% 6% 10% 18% 13% 1	3366
	21st to end	Night	68% 6% 8% 11% 6% 1	4933

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% 21% 32% 18% 3 1	270
	11th to 20th	Day	30% 22% 32% 14% 2	270
	21st to end	Day	28% 23% 31% 16% 2	297
February	1st to 10th	Day	27% 25% 32% 13% 3	270
	11th to 20th	Day	24% 29% 29% 16% 2	270
	21st to end	Day	30% 21% 41% 7%	225
March	1st to 10th	Day	26% 29% 31% 13% 2	270
	11th to 20th	Day	27% 21% 34% 12% 5% 1	384
	21st to end	Day	31% 19% 30% 14% 4 1	506
April	1st to 10th	Day	22% 20% 30% 22% 6% 1	460
	11th to 20th	Day	22% 21% 26% 21% 9% 2	452
	21st to end	Day	22% 21% 35% 14% 7% 2	460
May	1st to 10th	Day	21% 17% 32% 19% 9% 3	463
	11th to 20th	Day	24% 11% 26% 24% 10% 5%	487
	21st to end	Day	12% 8% 28% 24% 19% 7%	563
June	1st to 10th	Day	12% 9% 28% 29% 18% 5%	680
	11th to 20th	Day	12% 6% 26% 32% 17% 6%	680
	21st to end	Day	12% 6% 31% 25% 20% 5%	680
July	1st to 10th	Day	12% 5% 19% 24% 23% 16%	671
	11th to 20th	Day	7% 4 23% 34% 23% 9%	668
	21st to end	Day	11% 2 21% 32% 25% 8%	642
August	1st to 10th	Day	9% 4 16% 32% 27% 13%	486
	11th to 20th	Day	14% 5% 20% 28% 25% 9%	479
	21st to end	Day	7% 3 17% 28% 33% 12%	539
September	1st to 10th	Day	10% 6% 17% 31% 27% 9%	490
	11th to 20th	Day	11% 2 17% 28% 29% 13%	490
	21st to end	Day	16% 10% 21% 25% 21% 7%	490
October	1st to 10th	Day	12% 7% 27% 32% 19% 4	490
	11th to 20th	Day	16% 15% 33% 22% 12% 1	421
	21st to end	Day	30% 13% 38% 18% 2	330
November	1st to 10th	Day	12% 22% 32% 24% 8% 2	300
	11th to 20th	Day	22% 24% 30% 17% 7% 1	300
	21st to end	Day	27% 16% 35% 18% 4	300
December	1st to 10th	Day	20% 26% 35% 14% 3 1	300
	11th to 20th	Day	23% 19% 39% 14% 3 1	300
	21st to end	Day	24% 27% 35% 10% 4	306
January	1st to 10th	Night	21% 20% 34% 22% 4	950
	11th to 20th	Night	26% 17% 38% 16% 3	950
	21st to end	Night	23% 17% 35% 22% 3	951
February	1st to 10th	Night	26% 16% 36% 20% 3	760
	11th to 20th	Night	22% 21% 36% 20% 2	743
	21st to end	Night	28% 15% 36% 19% 1	628
March	1st to 10th	Night	23% 18% 33% 24% 2	760
	11th to 20th	Night	22% 15% 37% 21% 5%	760
	21st to end	Night	24% 12% 34% 24% 5% 1	749
April	1st to 10th	Night	16% 14% 39% 23% 8%	570
	11th to 20th	Night	19% 13% 32% 25% 9% 1	563
	21st to end	Night	19% 11% 39% 22% 7% 1	570
May	1st to 10th	Night	18% 9% 36% 27% 9% 1	570
	11th to 20th	Night	17% 7% 26% 30% 17% 3	561
	21st to end	Night	9% 5% 25% 36% 23% 2	617
June	1st to 10th	Night	11% 4 23% 41% 21% 1	570
	11th to 20th	Night	10% 3 22% 44% 20% 1	570
	21st to end	Night	7% 4 23% 37% 26% 2	570
July	1st to 10th	Night	10% 2 14% 36% 31% 8%	555
	11th to 20th	Night	6% 5% 16% 36% 33% 5%	552
	21st to end	Night	9% 3 13% 42% 30% 3	624
August	1st to 10th	Night	8% 2 14% 38% 34% 4	567
	11th to 20th	Night	6% 3 15% 39% 33% 5%	564
	21st to end	Night	6% 2 16% 33% 37% 6%	627
September	1st to 10th	Night	12% 4 12% 38% 30% 4	579
	11th to 20th	Night	8% 3 14% 34% 37% 4	760
	21st to end	Night	16% 6% 21% 32% 24% 3	760
October	1st to 10th	Night	10% 6% 25% 33% 23% 4	760
	11th to 20th	Night	19% 11% 28% 27% 15% 2	760
	21st to end	Night	21% 11% 36% 24% 7% 1	836
November	1st to 10th	Night	16% 10% 33% 28% 12% 1	780
	11th to 20th	Night	20% 16% 32% 25% 8% 1	800
	21st to end	Night	27% 14% 27% 27% 6%	800
December	1st to 10th	Night	25% 14% 36% 20% 5%	800
	11th to 20th	Night	26% 13% 33% 21% 6% 1	945
	21st to end	Night	29% 16% 34% 18% 4	1063

Page generated at 2024-12-21 04:13:49. Version ac07

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