Canonsburg
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Canonsburg clear sky chart from 2005-11-06 to 2024-10-25.

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	15% 10% 4 8% 5% 5% 5% 4 6% 7% 32%	100953
	Night	16% 11% 4 8% 5% 4 4 3 5% 6% 33%	97787
Transparency	Day	52% 3 10% 22% 11% 1	100765
	Night	52% 3 10% 22% 11% 2	97645
Seeing	Day	22% 14% 27% 21% 11% 4	14698
	Night	22% 11% 27% 27% 12% 1	24426

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	19% 18% 8% 12% 5% 3 4 3 4 5% 20%	2836
	11th to 20th	Day	14% 21% 8% 17% 7% 4 3 3 3 4 18%	2840
	21st to end	Day	23% 21% 7% 13% 6% 4 3 2 3 4 14%	3124
February	1st to 10th	Day	20% 17% 4 10% 6% 4 4 3 4 5% 23%	1710
	11th to 20th	Day	16% 15% 7% 11% 5% 4 4 3 6% 6% 22%	1663
	21st to end	Day	21% 14% 4 10% 6% 3 3 3 5% 4 27%	1583
March	1st to 10th	Day	21% 14% 4 8% 5% 4 4 3 4 6% 28%	3435
	11th to 20th	Day	13% 10% 4 9% 6% 5% 5% 3 5% 5% 34%	3480
	21st to end	Day	18% 10% 3 8% 5% 4 4 4 5% 6% 32%	3815
April	1st to 10th	Day	15% 13% 3 8% 5% 4 5% 3 6% 7% 29%	2180
	11th to 20th	Day	15% 10% 3 9% 5% 4 4 4 4 6% 35%	2290
	21st to end	Day	20% 9% 3 7% 4 4 4 4 6% 6% 33%	2470
May	1st to 10th	Day	22% 10% 3 7% 5% 5% 5% 4 5% 6% 28%	4082
	11th to 20th	Day	19% 9% 3 8% 5% 4 5% 4 6% 7% 31%	4081
	21st to end	Day	11% 6% 3 7% 5% 6% 5% 5% 7% 10% 36%	4666
June	1st to 10th	Day	12% 8% 3 6% 5% 6% 5% 5% 7% 9% 35%	2660
	11th to 20th	Day	11% 7% 3 7% 5% 5% 5% 6% 6% 8% 36%	2660
	21st to end	Day	12% 7% 2 6% 5% 5% 6% 5% 6% 10% 36%	2660
July	1st to 10th	Day	9% 6% 3 7% 5% 6% 6% 4 7% 8% 40%	4226
	11th to 20th	Day	9% 6% 2 6% 5% 5% 5% 5% 7% 11% 39%	4120
	21st to end	Day	12% 7% 3 8% 6% 5% 6% 5% 6% 8% 34%	4466
August	1st to 10th	Day	13% 7% 3 9% 6% 6% 6% 5% 7% 9% 30%	4104
	11th to 20th	Day	10% 7% 2 7% 5% 5% 6% 5% 8% 9% 36%	4044
	21st to end	Day	7% 4 2 6% 5% 6% 7% 6% 8% 9% 39%	4318
September	1st to 10th	Day	14% 6% 3 5% 4 4 4 4 6% 7% 44%	2271
	11th to 20th	Day	11% 6% 2 6% 4 4 3 4 5% 8% 46%	2090
	21st to end	Day	19% 9% 4 7% 5% 3 4 3 5% 5% 36%	2090
October	1st to 10th	Day	15% 7% 2 7% 5% 4 4 3 6% 6% 41%	1906
	11th to 20th	Day	18% 8% 2 7% 4 5% 4 4 5% 6% 36%	1900
	21st to end	Day	21% 11% 3 7% 4 4 3 3 4 5% 35%	2027
November	1st to 10th	Day	11% 10% 2 7% 4 4 4 4 5% 7% 42%	1781
	11th to 20th	Day	16% 14% 4 6% 6% 4 5% 3 5% 6% 31%	1611
	21st to end	Day	16% 14% 6% 8% 6% 4 4 3 6% 6% 28%	1520
December	1st to 10th	Day	21% 16% 7% 10% 5% 5% 4 4 4 4 19%	1520
	11th to 20th	Day	19% 17% 7% 11% 4 4 3 3 5% 6% 22%	1910
	21st to end	Day	22% 21% 7% 12% 5% 4 3 3 4 5% 15%	2814
January	1st to 10th	Night	15% 18% 7% 13% 6% 5% 5% 3 5% 5% 20%	4109
	11th to 20th	Night	17% 17% 7% 16% 6% 5% 5% 3 4 4 17%	4120
	21st to end	Night	27% 16% 7% 12% 6% 3 3 2 3 3 18%	4532
February	1st to 10th	Night	19% 13% 4 11% 6% 5% 4 4 4 5% 26%	2470
	11th to 20th	Night	19% 13% 4 11% 6% 4 4 5% 4 5% 25%	2403
	21st to end	Night	20% 15% 4 11% 5% 4 4 3 4 4 25%	1867
March	1st to 10th	Night	23% 10% 3 8% 4 4 3 3 4 5% 33%	3418
	11th to 20th	Night	14% 10% 5% 9% 5% 4 4 3 4 6% 36%	3480
	21st to end	Night	17% 9% 3 7% 4 4 4 3 4 6% 39%	3817
April	1st to 10th	Night	17% 11% 3 8% 5% 4 4 3 5% 7% 34%	1999
	11th to 20th	Night	15% 10% 3 6% 4 4 5% 4 5% 7% 38%	1855
	21st to end	Night	15% 9% 3 6% 4 4 4 4 4 7% 38%	1710
May	1st to 10th	Night	23% 11% 4 8% 5% 5% 4 3 5% 6% 26%	2813
	11th to 20th	Night	16% 10% 3 7% 5% 4 4 3 5% 6% 37%	2812
	21st to end	Night	10% 7% 3 7% 4 5% 5% 4 7% 11% 38%	2874
June	1st to 10th	Night	9% 6% 2 7% 6% 4 4 3 7% 7% 45%	1520
	11th to 20th	Night	10% 6% 2 6% 5% 5% 6% 5% 6% 11% 39%	1520
	21st to end	Night	9% 5% 2 6% 5% 4 5% 4 6% 10% 43%	1520
July	1st to 10th	Night	9% 8% 3 7% 5% 4 4 4 5% 8% 42%	2729
	11th to 20th	Night	9% 6% 2 7% 4 4 5% 4 7% 9% 43%	2840
	21st to end	Night	7% 8% 3 8% 5% 6% 5% 4 6% 7% 40%	3087
August	1st to 10th	Night	11% 9% 3 8% 5% 5% 5% 5% 7% 10% 33%	2825
	11th to 20th	Night	9% 8% 3 7% 5% 5% 5% 4 5% 8% 41%	2785
	21st to end	Night	7% 5% 2 6% 4 5% 6% 5% 7% 9% 44%	3306
September	1st to 10th	Night	11% 5% 2 6% 4 4 4 3 5% 7% 50%	1905
	11th to 20th	Night	10% 4 2 4 4 3 4 4 5% 8% 52%	2090
	21st to end	Night	15% 7% 3 7% 4 4 4 2 5% 7% 42%	2090
October	1st to 10th	Night	13% 6% 3 6% 4 4 4 3 5% 6% 46%	2273
	11th to 20th	Night	16% 7% 2 7% 4 4 4 4 6% 6% 39%	2280
	21st to end	Night	21% 9% 3 6% 4 3 4 3 5% 5% 37%	2435
November	1st to 10th	Night	12% 8% 3 7% 4 4 4 3 4 7% 46%	2295
	11th to 20th	Night	17% 11% 3 7% 5% 5% 5% 4 5% 6% 33%	2565
	21st to end	Night	18% 12% 3 8% 5% 5% 4 4 4 6% 30%	2660
December	1st to 10th	Night	22% 15% 6% 9% 5% 3 4 3 5% 5% 22%	2660
	11th to 20th	Night	17% 17% 6% 11% 6% 4 3 3 4 6% 24%	3285
	21st to end	Night	22% 18% 6% 11% 6% 5% 4 3 4 5% 15%	4838

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	69% 2 10% 14% 5%	2837
	11th to 20th	Day	74% 1 6% 13% 5% 1	2840
	21st to end	Day	77% 1 6% 12% 3	3124
February	1st to 10th	Day	65% 2 9% 14% 8% 1	1710
	11th to 20th	Day	63% 2 8% 18% 8%	1672
	21st to end	Day	62% 2 9% 17% 8% 2	1583
March	1st to 10th	Day	60% 2 8% 24% 6%	3435
	11th to 20th	Day	53% 2 9% 26% 9% 1	3480
	21st to end	Day	54% 1 8% 23% 12% 1	3815
April	1st to 10th	Day	54% 3 9% 20% 11% 2	2180
	11th to 20th	Day	51% 3 10% 17% 16% 2	2290
	21st to end	Day	51% 4 9% 23% 12% 2	2470
May	1st to 10th	Day	58% 2 9% 22% 9% 1	4120
	11th to 20th	Day	53% 3 9% 25% 9% 1	4085
	21st to end	Day	43% 4 13% 25% 13% 3	4680
June	1st to 10th	Day	45% 4 14% 24% 12% 1	2660
	11th to 20th	Day	44% 5% 13% 24% 13% 1	2660
	21st to end	Day	42% 5% 13% 25% 14% 1	2660
July	1st to 10th	Day	41% 5% 12% 25% 15% 3	4161
	11th to 20th	Day	38% 5% 11% 29% 16% 1	4051
	21st to end	Day	46% 5% 10% 21% 16% 2	4324
August	1st to 10th	Day	49% 6% 12% 23% 9%	4091
	11th to 20th	Day	41% 5% 11% 30% 13%	4083
	21st to end	Day	37% 7% 12% 28% 14% 2	4318
September	1st to 10th	Day	39% 4 10% 22% 21% 4	2271
	11th to 20th	Day	37% 3 12% 30% 16% 2	2090
	21st to end	Day	50% 3 9% 23% 15% 1	2090
October	1st to 10th	Day	43% 4 11% 24% 17% 1	1906
	11th to 20th	Day	49% 3 10% 25% 12% 1	1900
	21st to end	Day	52% 2 10% 21% 14% 1	2027
November	1st to 10th	Day	42% 3 10% 25% 16% 3	1781
	11th to 20th	Day	54% 4 8% 20% 12% 2	1611
	21st to end	Day	57% 3 12% 20% 8% 1	1520
December	1st to 10th	Day	69% 3 9% 14% 4	1520
	11th to 20th	Day	65% 1 10% 18% 5%	1906
	21st to end	Day	74% 1 10% 11% 3	2814
January	1st to 10th	Night	68% 2 9% 16% 5%	4109
	11th to 20th	Night	73% 2 9% 12% 4	4120
	21st to end	Night	74% 1 6% 15% 3 1	4532
February	1st to 10th	Night	62% 2 9% 19% 8%	2470
	11th to 20th	Night	61% 3 8% 19% 9%	2405
	21st to end	Night	63% 2 8% 16% 10% 1	1867
March	1st to 10th	Night	55% 2 8% 26% 9%	3418
	11th to 20th	Night	51% 1 10% 29% 8% 1	3480
	21st to end	Night	49% 1 7% 27% 14% 2	3817
April	1st to 10th	Night	52% 3 9% 21% 14% 3	1999
	11th to 20th	Night	46% 3 11% 20% 16% 4	1855
	21st to end	Night	47% 3 9% 25% 13% 3	1710
May	1st to 10th	Night	60% 3 7% 18% 10% 2	2840
	11th to 20th	Night	48% 3 10% 27% 10% 2	2813
	21st to end	Night	41% 4 14% 26% 12% 4	2881
June	1st to 10th	Night	38% 5% 13% 25% 17% 2	1520
	11th to 20th	Night	39% 5% 15% 26% 14% 2	1520
	21st to end	Night	36% 6% 15% 25% 17% 2	1520
July	1st to 10th	Night	41% 5% 10% 24% 17% 4	2684
	11th to 20th	Night	36% 6% 13% 28% 16% 1	2786
	21st to end	Night	42% 5% 11% 19% 19% 4	2988
August	1st to 10th	Night	46% 6% 13% 24% 11%	2814
	11th to 20th	Night	41% 5% 10% 26% 18% 1	2812
	21st to end	Night	35% 5% 12% 32% 13% 2	3306
September	1st to 10th	Night	35% 4 9% 25% 21% 6%	1905
	11th to 20th	Night	32% 3 12% 29% 24% 1	2090
	21st to end	Night	44% 3 10% 23% 19% 1	2090
October	1st to 10th	Night	40% 4 10% 28% 15% 3	2273
	11th to 20th	Night	45% 3 9% 25% 15% 2	2280
	21st to end	Night	50% 2 9% 22% 15% 2	2435
November	1st to 10th	Night	40% 3 10% 25% 18% 4	2295
	11th to 20th	Night	52% 3 8% 22% 13% 2	2565
	21st to end	Night	56% 2 10% 23% 8% 1	2660
December	1st to 10th	Night	65% 3 10% 17% 5% 1	2660
	11th to 20th	Night	64% 2 10% 19% 5%	3288
	21st to end	Night	73% 2 9% 13% 3	4838

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	31% 27% 26% 10% 4 1	270
	11th to 20th	Day	34% 27% 30% 6% 2	270
	21st to end	Day	28% 35% 26% 7% 3	297
February	1st to 10th	Day	34% 21% 35% 10% 1	270
	11th to 20th	Day	37% 31% 26% 5% 1	270
	21st to end	Day	38% 24% 32% 5% 1	251
March	1st to 10th	Day	30% 22% 28% 17% 3	460
	11th to 20th	Day	32% 18% 33% 12% 4 1	460
	21st to end	Day	32% 19% 30% 14% 4 1	506
April	1st to 10th	Day	29% 17% 30% 16% 7% 1	460
	11th to 20th	Day	24% 22% 28% 14% 9% 3	452
	21st to end	Day	27% 17% 32% 15% 7% 2	460
May	1st to 10th	Day	28% 18% 25% 18% 9% 3	463
	11th to 20th	Day	21% 13% 32% 18% 11% 4	487
	21st to end	Day	15% 9% 27% 26% 16% 7%	529
June	1st to 10th	Day	15% 8% 31% 29% 13% 4	490
	11th to 20th	Day	16% 11% 25% 26% 18% 4	490
	21st to end	Day	16% 10% 29% 28% 15% 3	490
July	1st to 10th	Day	13% 7% 20% 30% 17% 13%	485
	11th to 20th	Day	12% 6% 24% 31% 18% 8%	484
	21st to end	Day	14% 5% 28% 29% 17% 8%	532
August	1st to 10th	Day	13% 5% 23% 27% 23% 9%	486
	11th to 20th	Day	16% 6% 20% 30% 16% 12%	479
	21st to end	Day	10% 5% 22% 29% 23% 12%	539
September	1st to 10th	Day	15% 8% 23% 26% 21% 7%	490
	11th to 20th	Day	14% 3 17% 33% 22% 11%	490
	21st to end	Day	26% 9% 25% 20% 16% 4	490
October	1st to 10th	Day	18% 8% 28% 24% 17% 4	490
	11th to 20th	Day	23% 14% 30% 23% 8% 3	490
	21st to end	Day	30% 14% 29% 21% 5% 1	514
November	1st to 10th	Day	20% 16% 32% 20% 9% 4	379
	11th to 20th	Day	32% 17% 28% 16% 6% 2	223
	21st to end	Day	26% 18% 45% 9% 2	180
December	1st to 10th	Day	33% 22% 30% 8% 5% 1	180
	11th to 20th	Day	33% 22% 31% 12% 2	180
	21st to end	Day	36% 22% 27% 11% 3	212
January	1st to 10th	Night	30% 19% 33% 15% 3	760
	11th to 20th	Night	35% 14% 31% 17% 3	760
	21st to end	Night	28% 18% 31% 19% 4	836
February	1st to 10th	Night	29% 17% 29% 23% 2	760
	11th to 20th	Night	31% 19% 35% 15% 1	743
	21st to end	Night	30% 17% 32% 18% 3	628
March	1st to 10th	Night	26% 17% 31% 24% 3	760
	11th to 20th	Night	27% 18% 27% 21% 6% 1	760
	21st to end	Night	25% 14% 32% 23% 4 1	836
April	1st to 10th	Night	25% 15% 31% 23% 5%	760
	11th to 20th	Night	21% 14% 32% 22% 10% 1	731
	21st to end	Night	21% 9% 34% 29% 6%	570
May	1st to 10th	Night	22% 9% 25% 30% 13% 1	570
	11th to 20th	Night	20% 9% 27% 31% 13% 1	561
	21st to end	Night	11% 4 23% 36% 23% 3	502
June	1st to 10th	Night	11% 4 25% 39% 20% 1	380
	11th to 20th	Night	12% 6% 23% 39% 18% 1	380
	21st to end	Night	10% 3 28% 36% 22% 1	380
July	1st to 10th	Night	10% 5% 15% 40% 25% 6%	483
	11th to 20th	Night	9% 3 21% 35% 27% 5%	552
	21st to end	Night	11% 3 17% 39% 29% 2	624
August	1st to 10th	Night	10% 1 17% 41% 28% 2	567
	11th to 20th	Night	10% 4 14% 39% 28% 4	564
	21st to end	Night	13% 3 17% 34% 29% 5%	731
September	1st to 10th	Night	14% 3 18% 36% 25% 4	760
	11th to 20th	Night	11% 5% 15% 37% 28% 4	760
	21st to end	Night	19% 8% 24% 27% 20% 3	760
October	1st to 10th	Night	16% 8% 22% 31% 21% 2	760
	11th to 20th	Night	21% 9% 31% 26% 11% 1	760
	21st to end	Night	26% 11% 28% 27% 7% 1	812
November	1st to 10th	Night	17% 11% 30% 27% 14% 1	740
	11th to 20th	Night	26% 14% 28% 24% 7% 1	760
	21st to end	Night	28% 15% 30% 21% 5% 1	760
December	1st to 10th	Night	33% 15% 28% 20% 4	760
	11th to 20th	Night	27% 18% 30% 21% 4	760
	21st to end	Night	29% 14% 33% 22% 2	836

Page generated at 2024-10-22 20:20:59. Version ac07

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