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 2024-02-25.

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	16% 10% 4 7% 6% 3 5% 5% 5% 7% 31%	78487
	Night	16% 10% 4 7% 6% 3 4 4 5% 6% 33%	80814
Transparency	Day	53% 3 11% 21% 11% 1	78208
	Night	53% 3 10% 21% 11% 2	80612
Seeing	Day	23% 14% 27% 21% 11% 4	13726
	Night	22% 11% 27% 27% 12% 1	23622

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% 10% 6% 3 4 3 4 5% 20%	2836
	11th to 20th	Day	14% 20% 8% 15% 9% 3 3 3 3 4 18%	2840
	21st to end	Day	23% 20% 8% 11% 8% 3 3 3 3 4 14%	3124
February	1st to 10th	Day	20% 15% 5% 9% 7% 3 5% 4 4 5% 23%	1710
	11th to 20th	Day	16% 14% 8% 10% 7% 3 4 4 6% 6% 23%	1663
	21st to end	Day	21% 13% 5% 9% 6% 3 4 3 5% 4 27%	1531
March	1st to 10th	Day	17% 11% 5% 7% 5% 3 5% 4 5% 6% 32%	1980
	11th to 20th	Day	18% 12% 4 7% 6% 4 4 4 5% 6% 29%	1980
	21st to end	Day	19% 11% 4 7% 7% 3 5% 4 5% 7% 27%	2178
April	1st to 10th	Day	15% 11% 5% 7% 6% 3 5% 4 6% 7% 31%	2065
	11th to 20th	Day	15% 10% 4 8% 6% 4 4 5% 4 6% 35%	2168
	21st to end	Day	21% 9% 3 6% 5% 4 4 5% 5% 7% 32%	2340
May	1st to 10th	Day	18% 9% 3 6% 7% 4 6% 6% 5% 7% 29%	2340
	11th to 20th	Day	20% 8% 3 7% 6% 3 6% 6% 6% 7% 29%	2301
	21st to end	Day	11% 5% 3 6% 6% 4 6% 6% 7% 10% 35%	2638
June	1st to 10th	Day	13% 7% 3 5% 6% 4 6% 5% 7% 9% 35%	2520
	11th to 20th	Day	12% 8% 3 6% 6% 4 5% 7% 6% 8% 35%	2520
	21st to end	Day	12% 6% 2 5% 6% 4 6% 6% 6% 10% 36%	2520
July	1st to 10th	Day	11% 6% 3 6% 6% 4 7% 6% 7% 8% 37%	2404
	11th to 20th	Day	11% 6% 3 6% 6% 4 6% 6% 7% 10% 35%	2340
	21st to end	Day	12% 6% 3 6% 6% 4 7% 7% 7% 8% 33%	2547
August	1st to 10th	Day	10% 6% 3 6% 6% 5% 7% 7% 8% 10% 31%	2327
	11th to 20th	Day	11% 8% 2 5% 6% 4 6% 7% 7% 9% 35%	2303
	21st to end	Day	11% 6% 2 5% 6% 4 5% 7% 7% 8% 37%	2458
September	1st to 10th	Day	14% 6% 3 5% 5% 3 4 5% 6% 7% 42%	2152
	11th to 20th	Day	12% 6% 2 5% 5% 3 3 5% 6% 8% 45%	1980
	21st to end	Day	18% 8% 4 6% 5% 3 4 4 5% 5% 38%	1980
October	1st to 10th	Day	15% 7% 2 6% 5% 2 4 4 6% 7% 40%	1806
	11th to 20th	Day	18% 8% 2 6% 6% 4 5% 4 5% 6% 35%	1800
	21st to end	Day	22% 10% 3 6% 4 3 3 4 4 5% 34%	1980
November	1st to 10th	Day	11% 9% 2 6% 5% 3 4 5% 5% 7% 43%	1781
	11th to 20th	Day	16% 12% 5% 5% 6% 3 5% 5% 5% 6% 32%	1611
	21st to end	Day	17% 13% 6% 7% 6% 3 4 4 5% 7% 28%	1520
December	1st to 10th	Day	21% 15% 8% 9% 6% 3 5% 5% 4 4 19%	1520
	11th to 20th	Day	19% 17% 8% 10% 5% 3 3 3 4 7% 22%	1910
	21st to end	Day	23% 20% 8% 11% 6% 3 3 4 4 5% 15%	2814
January	1st to 10th	Night	15% 17% 8% 12% 7% 3 5% 4 4 5% 20%	4109
	11th to 20th	Night	17% 17% 7% 14% 8% 4 6% 4 4 4 17%	4120
	21st to end	Night	27% 15% 7% 9% 10% 2 3 2 3 3 19%	4532
February	1st to 10th	Night	20% 12% 5% 10% 6% 4 4 4 4 5% 26%	2470
	11th to 20th	Night	20% 11% 5% 9% 7% 3 4 5% 4 6% 26%	2403
	21st to end	Night	20% 14% 5% 9% 6% 3 4 4 4 5% 26%	1816
March	1st to 10th	Night	17% 10% 4 7% 7% 3 4 5% 4 5% 35%	1980
	11th to 20th	Night	18% 9% 4 6% 4 3 4 4 5% 7% 35%	1980
	21st to end	Night	19% 10% 4 7% 5% 3 4 4 4 6% 34%	2178
April	1st to 10th	Night	17% 10% 4 7% 5% 3 4 3 5% 7% 35%	1894
	11th to 20th	Night	15% 9% 3 5% 5% 3 5% 5% 4 7% 38%	1757
	21st to end	Night	16% 9% 4 6% 5% 3 4 5% 4 7% 38%	1620
May	1st to 10th	Night	15% 9% 4 7% 6% 4 6% 6% 6% 6% 32%	1620
	11th to 20th	Night	17% 9% 3 6% 6% 2 4 4 5% 7% 37%	1592
	21st to end	Night	8% 6% 2 5% 4 3 5% 6% 7% 11% 43%	1636
June	1st to 10th	Night	10% 5% 2 5% 7% 3 5% 4 7% 8% 45%	1440
	11th to 20th	Night	11% 6% 2 5% 5% 4 6% 6% 6% 12% 39%	1440
	21st to end	Night	9% 4 2 5% 6% 3 5% 5% 6% 10% 45%	1440
July	1st to 10th	Night	9% 6% 3 5% 5% 3 5% 5% 5% 9% 45%	1551
	11th to 20th	Night	9% 4 3 5% 4 3 5% 5% 6% 10% 48%	1620
	21st to end	Night	8% 6% 3 5% 5% 4 6% 7% 8% 9% 40%	1771
August	1st to 10th	Night	7% 4 3 6% 6% 4 5% 5% 8% 11% 41%	1611
	11th to 20th	Night	7% 7% 3 6% 5% 4 5% 6% 6% 9% 43%	1598
	21st to end	Night	11% 6% 2 4 3 3 5% 6% 6% 8% 46%	1880
September	1st to 10th	Night	11% 5% 2 5% 5% 3 4 4 5% 7% 49%	1804
	11th to 20th	Night	10% 4 2 4 4 3 4 4 5% 8% 52%	1980
	21st to end	Night	14% 7% 3 6% 5% 3 4 3 5% 7% 44%	1980
October	1st to 10th	Night	13% 6% 3 4 5% 3 4 4 5% 7% 45%	2153
	11th to 20th	Night	17% 7% 3 6% 6% 3 4 5% 6% 6% 37%	2160
	21st to end	Night	22% 8% 3 6% 5% 2 4 4 4 5% 36%	2376
November	1st to 10th	Night	12% 7% 3 6% 4 3 4 4 4 6% 47%	2295
	11th to 20th	Night	17% 10% 4 6% 5% 3 5% 5% 4 6% 33%	2565
	21st to end	Night	19% 11% 4 7% 5% 4 4 5% 4 6% 31%	2660
December	1st to 10th	Night	22% 14% 7% 8% 6% 2 4 4 4 5% 22%	2660
	11th to 20th	Night	18% 16% 6% 9% 7% 3 4 3 4 6% 24%	3285
	21st to end	Night	22% 17% 7% 9% 8% 4 4 4 4 5% 16%	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% 16% 8% 3	1531
March	1st to 10th	Day	53% 3 11% 24% 8% 1	1980
	11th to 20th	Day	57% 3 9% 19% 10% 2	1980
	21st to end	Day	58% 2 8% 18% 12% 2	2178
April	1st to 10th	Day	53% 3 10% 21% 11% 2	2065
	11th to 20th	Day	52% 3 10% 16% 16% 3	2168
	21st to end	Day	52% 4 9% 22% 11% 2	2340
May	1st to 10th	Day	54% 4 10% 21% 9% 2	2340
	11th to 20th	Day	54% 5% 11% 17% 12% 2	2305
	21st to end	Day	42% 6% 16% 24% 10% 2	2638
June	1st to 10th	Day	45% 4 14% 24% 11% 1	2520
	11th to 20th	Day	45% 5% 13% 24% 12% 1	2520
	21st to end	Day	43% 5% 13% 25% 13% 1	2520
July	1st to 10th	Day	44% 5% 12% 22% 14% 3	2339
	11th to 20th	Day	43% 4 12% 24% 15% 1	2271
	21st to end	Day	46% 5% 11% 24% 13% 2	2405
August	1st to 10th	Day	46% 5% 13% 26% 10%	2314
	11th to 20th	Day	42% 6% 12% 28% 11% 1	2303
	21st to end	Day	41% 6% 12% 25% 13% 3	2458
September	1st to 10th	Day	41% 4 10% 22% 19% 4	2152
	11th to 20th	Day	38% 3 12% 30% 15% 2	1980
	21st to end	Day	49% 2 9% 24% 16% 1	1980
October	1st to 10th	Day	44% 4 11% 23% 17% 1	1806
	11th to 20th	Day	50% 3 10% 26% 12%	1800
	21st to end	Day	53% 2 10% 21% 13% 1	1980
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 7% 17% 10% 1	1816
March	1st to 10th	Night	53% 3 9% 23% 13% 1	1980
	11th to 20th	Night	51% 2 11% 23% 11% 2	1980
	21st to end	Night	52% 2 7% 21% 14% 3	2178
April	1st to 10th	Night	51% 3 9% 21% 14% 3	1894
	11th to 20th	Night	46% 3 10% 20% 17% 4	1757
	21st to end	Night	47% 3 8% 25% 13% 3	1620
May	1st to 10th	Night	51% 4 9% 20% 13% 3	1620
	11th to 20th	Night	47% 4 12% 19% 15% 3	1593
	21st to end	Night	34% 6% 19% 26% 14% 1	1637
June	1st to 10th	Night	37% 5% 13% 26% 16% 2	1440
	11th to 20th	Night	40% 5% 14% 26% 14% 2	1440
	21st to end	Night	35% 6% 15% 26% 17% 2	1440
July	1st to 10th	Night	37% 6% 12% 24% 17% 4	1506
	11th to 20th	Night	32% 4 15% 27% 19% 2	1566
	21st to end	Night	38% 6% 15% 24% 13% 3	1672
August	1st to 10th	Night	35% 5% 14% 29% 16%	1600
	11th to 20th	Night	38% 5% 14% 26% 16% 2	1598
	21st to end	Night	35% 5% 12% 28% 15% 4	1880
September	1st to 10th	Night	36% 4 10% 25% 20% 6%	1804
	11th to 20th	Night	32% 3 12% 29% 23% 1	1980
	21st to end	Night	42% 3 10% 24% 20% 1	1980
October	1st to 10th	Night	40% 4 11% 28% 14% 3	2153
	11th to 20th	Night	46% 3 9% 25% 15% 1	2160
	21st to end	Night	51% 2 9% 22% 13% 2	2376
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	37% 23% 33% 6% 1	234
March	1st to 10th	Day	28% 24% 29% 16% 3	420
	11th to 20th	Day	31% 17% 34% 12% 4 1	420
	21st to end	Day	32% 19% 29% 15% 5% 1	462
April	1st to 10th	Day	28% 16% 30% 16% 7% 1	420
	11th to 20th	Day	23% 21% 28% 15% 9% 3	412
	21st to end	Day	28% 18% 31% 14% 7% 2	420
May	1st to 10th	Day	27% 18% 26% 17% 9% 3	423
	11th to 20th	Day	22% 12% 32% 19% 11% 4	447
	21st to end	Day	15% 8% 26% 26% 17% 7%	485
June	1st to 10th	Day	14% 8% 32% 29% 14% 3	450
	11th to 20th	Day	18% 11% 24% 25% 17% 4	450
	21st to end	Day	15% 8% 30% 28% 16% 3	450
July	1st to 10th	Day	13% 7% 18% 31% 17% 14%	445
	11th to 20th	Day	12% 6% 24% 31% 18% 9%	444
	21st to end	Day	15% 4 27% 28% 17% 8%	488
August	1st to 10th	Day	13% 5% 21% 27% 24% 10%	446
	11th to 20th	Day	17% 5% 19% 30% 17% 13%	439
	21st to end	Day	11% 5% 22% 28% 21% 12%	495
September	1st to 10th	Day	16% 7% 22% 25% 21% 8%	450
	11th to 20th	Day	14% 3 17% 33% 22% 11%	450
	21st to end	Day	23% 8% 26% 21% 17% 5%	450
October	1st to 10th	Day	19% 8% 27% 25% 17% 4	450
	11th to 20th	Day	23% 14% 31% 23% 8% 1	450
	21st to end	Day	31% 14% 29% 21% 4 1	495
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	29% 18% 32% 18% 3	611
March	1st to 10th	Night	25% 18% 31% 24% 3	720
	11th to 20th	Night	26% 17% 28% 21% 7% 1	720
	21st to end	Night	25% 14% 32% 24% 5% 1	792
April	1st to 10th	Night	26% 15% 30% 23% 6%	720
	11th to 20th	Night	21% 13% 32% 22% 10% 1	693
	21st to end	Night	21% 9% 34% 28% 7%	540
May	1st to 10th	Night	22% 9% 26% 31% 13% 1	540
	11th to 20th	Night	20% 8% 27% 31% 12% 1	531
	21st to end	Night	11% 3 24% 36% 24% 3	476
June	1st to 10th	Night	11% 4 24% 41% 19% 1	360
	11th to 20th	Night	13% 6% 24% 39% 18% 1	360
	21st to end	Night	10% 3 28% 37% 22%	360
July	1st to 10th	Night	9% 4 15% 39% 26% 6%	456
	11th to 20th	Night	9% 3 20% 36% 28% 5%	522
	21st to end	Night	11% 3 17% 38% 30% 2	591
August	1st to 10th	Night	9% 1 16% 42% 29% 2	537
	11th to 20th	Night	10% 3 13% 40% 29% 5%	534
	21st to end	Night	14% 3 17% 33% 29% 5%	692
September	1st to 10th	Night	14% 2 17% 36% 26% 5%	720
	11th to 20th	Night	11% 5% 16% 36% 28% 4	720
	21st to end	Night	18% 7% 24% 28% 20% 3	720
October	1st to 10th	Night	17% 8% 21% 31% 21% 2	720
	11th to 20th	Night	22% 10% 31% 26% 10% 1	720
	21st to end	Night	26% 11% 28% 27% 6% 1	792
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 2024-02-22 06:05:48. Version ac07

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