Aliquippa
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Aliquippa 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	15% 10% 4 9% 5% 5% 5% 4 5% 7% 31%	125439
	Night	16% 11% 4 9% 5% 4 4 3 5% 6% 31%	122614
Transparency	Day	52% 4 10% 22% 11% 1	129044
	Night	53% 4 10% 21% 11% 2	127078
Seeing	Day	23% 13% 28% 21% 11% 4	15630
	Night	22% 10% 25% 28% 13% 1	25330

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% 19% 8% 22% 4 3 3 2 3 4 15%	4056
	11th to 20th	Day	13% 23% 9% 16% 8% 6% 3 2 3 3 15%	4060
	21st to end	Day	21% 19% 6% 12% 8% 5% 3 3 4 4 14%	4466
February	1st to 10th	Day	20% 17% 6% 12% 7% 5% 4 2 3 5% 22%	1800
	11th to 20th	Day	16% 15% 6% 13% 6% 5% 4 4 4 5% 22%	1753
	21st to end	Day	20% 14% 5% 10% 5% 4 3 4 4 5% 25%	1654
March	1st to 10th	Day	17% 12% 5% 10% 5% 5% 3 3 4 6% 29%	4935
	11th to 20th	Day	12% 9% 4 9% 6% 5% 5% 3 5% 6% 37%	4980
	21st to end	Day	18% 11% 4 9% 5% 4 4 4 6% 6% 30%	5465
April	1st to 10th	Day	15% 14% 4 8% 5% 5% 4 4 5% 7% 29%	2297
	11th to 20th	Day	17% 9% 4 8% 5% 5% 4 3 6% 5% 33%	2425
	21st to end	Day	21% 9% 3 7% 4 4 5% 3 4 7% 33%	2600
May	1st to 10th	Day	21% 9% 3 9% 5% 4 5% 4 6% 6% 27%	5862
	11th to 20th	Day	17% 9% 3 8% 5% 5% 5% 4 6% 8% 30%	5861
	21st to end	Day	18% 7% 3 7% 4 4 5% 5% 7% 8% 32%	6770
June	1st to 10th	Day	14% 7% 3 6% 5% 5% 6% 5% 7% 9% 34%	2800
	11th to 20th	Day	15% 7% 3 7% 4 5% 5% 5% 6% 9% 35%	2800
	21st to end	Day	13% 6% 2 7% 5% 4 5% 4 7% 9% 38%	2800
July	1st to 10th	Day	8% 6% 3 7% 5% 5% 5% 4 6% 9% 41%	6133
	11th to 20th	Day	10% 7% 3 7% 5% 6% 6% 5% 7% 10% 33%	5900
	21st to end	Day	11% 6% 3 7% 5% 6% 5% 4 7% 8% 39%	6424
August	1st to 10th	Day	13% 7% 4 8% 6% 6% 6% 5% 6% 9% 31%	4156
	11th to 20th	Day	11% 7% 3 7% 6% 5% 6% 5% 7% 9% 35%	4044
	21st to end	Day	8% 5% 2 7% 5% 6% 5% 5% 7% 9% 40%	4340
September	1st to 10th	Day	15% 7% 2 5% 3 3 5% 3 5% 7% 44%	2271
	11th to 20th	Day	11% 6% 3 5% 4 4 5% 4 6% 9% 43%	2090
	21st to end	Day	19% 8% 4 7% 4 4 4 3 5% 6% 36%	2090
October	1st to 10th	Day	15% 6% 3 6% 4 4 5% 4 7% 8% 39%	1907
	11th to 20th	Day	19% 8% 2 8% 5% 5% 5% 3 5% 5% 35%	1900
	21st to end	Day	22% 11% 2 7% 4 4 4 3 4 7% 32%	2090
November	1st to 10th	Day	12% 8% 2 7% 5% 5% 5% 4 4 5% 42%	1859
	11th to 20th	Day	16% 14% 3 9% 5% 4 4 4 5% 6% 31%	1680
	21st to end	Day	17% 15% 5% 11% 5% 4 4 3 5% 6% 24%	1600
December	1st to 10th	Day	19% 14% 7% 16% 6% 4 3 3 4 5% 20%	2600
	11th to 20th	Day	24% 17% 7% 10% 4 3 3 2 4 5% 21%	2990
	21st to end	Day	23% 21% 6% 12% 5% 4 4 3 4 5% 13%	3981
January	1st to 10th	Night	14% 17% 8% 22% 7% 5% 3 3 3 3 15%	5889
	11th to 20th	Night	15% 17% 8% 16% 9% 6% 4 3 3 4 15%	5900
	21st to end	Night	23% 16% 6% 13% 6% 4 4 2 3 3 19%	6490
February	1st to 10th	Night	21% 14% 5% 11% 6% 4 4 3 4 5% 23%	2600
	11th to 20th	Night	19% 13% 4 12% 6% 5% 4 3 4 5% 24%	2533
	21st to end	Night	20% 13% 5% 11% 6% 4 5% 3 5% 5% 24%	1975
March	1st to 10th	Night	22% 12% 4 8% 5% 3 3 2 4 5% 32%	4918
	11th to 20th	Night	13% 10% 4 7% 4 4 3 3 5% 7% 40%	4980
	21st to end	Night	17% 10% 4 9% 5% 4 4 3 4 5% 34%	5467
April	1st to 10th	Night	18% 12% 3 7% 6% 4 4 3 4 6% 33%	2102
	11th to 20th	Night	16% 9% 3 7% 5% 5% 4 4 5% 7% 35%	1941
	21st to end	Night	15% 9% 3 7% 4 4 4 4 6% 8% 37%	1800
May	1st to 10th	Night	24% 12% 4 8% 4 4 4 3 4 7% 25%	4033
	11th to 20th	Night	16% 10% 3 7% 5% 4 4 3 5% 8% 36%	4032
	21st to end	Night	18% 8% 2 6% 4 4 4 4 6% 9% 35%	4066
June	1st to 10th	Night	10% 6% 3 7% 4 5% 4 4 7% 8% 44%	1600
	11th to 20th	Night	12% 6% 3 6% 4 5% 5% 4 6% 8% 41%	1600
	21st to end	Night	9% 5% 2 6% 4 6% 5% 4 6% 8% 44%	1600
July	1st to 10th	Night	10% 8% 3 7% 5% 4 4 4 6% 8% 42%	3819
	11th to 20th	Night	10% 7% 3 7% 5% 5% 5% 5% 7% 9% 37%	4057
	21st to end	Night	8% 7% 3 7% 5% 5% 5% 4 6% 8% 43%	4427
August	1st to 10th	Night	11% 9% 4 8% 5% 5% 6% 4 7% 7% 35%	2861
	11th to 20th	Night	11% 9% 3 7% 4 4 5% 3 5% 7% 42%	2785
	21st to end	Night	8% 5% 2 6% 5% 5% 5% 5% 6% 9% 44%	3284
September	1st to 10th	Night	13% 5% 2 4 3 3 5% 4 5% 7% 49%	1905
	11th to 20th	Night	10% 4 2 4 3 3 5% 4 6% 8% 52%	2090
	21st to end	Night	16% 8% 3 6% 4 4 4 3 5% 7% 40%	2090
October	1st to 10th	Night	14% 6% 2 6% 4 3 5% 3 4 7% 45%	2272
	11th to 20th	Night	18% 7% 3 6% 4 5% 4 3 5% 5% 40%	2280
	21st to end	Night	23% 9% 2 6% 4 4 4 3 4 6% 36%	2508
November	1st to 10th	Night	13% 8% 2 6% 4 4 4 3 5% 7% 44%	2436
	11th to 20th	Night	19% 11% 3 8% 4 4 4 3 5% 6% 32%	2718
	21st to end	Night	20% 13% 5% 8% 5% 4 3 4 5% 5% 29%	2800
December	1st to 10th	Night	18% 16% 9% 14% 5% 4 3 3 4 5% 18%	4580
	11th to 20th	Night	22% 17% 6% 11% 5% 4 3 3 3 5% 22%	5205
	21st to end	Night	23% 18% 5% 11% 6% 5% 4 3 4 5% 16%	6971

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	74% 2 8% 10% 5%	4057
	11th to 20th	Day	76% 2 6% 10% 4 2	4060
	21st to end	Day	74% 2 7% 11% 5%	4466
February	1st to 10th	Day	67% 2 9% 15% 7% 1	1800
	11th to 20th	Day	65% 4 7% 16% 7%	1762
	21st to end	Day	61% 3 11% 16% 8% 1	1654
March	1st to 10th	Day	57% 2 9% 24% 8% 1	4935
	11th to 20th	Day	49% 3 11% 26% 10% 2	4980
	21st to end	Day	54% 3 8% 21% 13% 1	5465
April	1st to 10th	Day	54% 3 11% 19% 11% 2	2297
	11th to 20th	Day	51% 4 10% 19% 14% 2	2425
	21st to end	Day	52% 4 8% 24% 11% 2	2600
May	1st to 10th	Day	55% 4 10% 18% 9% 3	5897
	11th to 20th	Day	51% 4 10% 23% 10% 1	5865
	21st to end	Day	47% 5% 13% 23% 10% 3	6785
June	1st to 10th	Day	46% 5% 13% 23% 12% 1	2800
	11th to 20th	Day	45% 5% 13% 24% 12% 1	2800
	21st to end	Day	41% 5% 13% 26% 14% 1	2800
July	1st to 10th	Day	39% 5% 11% 27% 16% 2	6067
	11th to 20th	Day	43% 6% 13% 26% 12%	5831
	21st to end	Day	41% 6% 10% 24% 19% 1	6240
August	1st to 10th	Day	48% 6% 12% 24% 10%	4143
	11th to 20th	Day	42% 5% 11% 31% 10% 1	4083
	21st to end	Day	38% 6% 11% 29% 14% 2	4340
September	1st to 10th	Day	39% 4 10% 24% 20% 4	2271
	11th to 20th	Day	37% 3 13% 29% 16% 2	2090
	21st to end	Day	50% 3 9% 24% 14%	2090
October	1st to 10th	Day	32% 3 10% 33% 20% 1	3167
	11th to 20th	Day	46% 5% 9% 23% 14% 4	3140
	21st to end	Day	39% 3 12% 28% 18%	3428
November	1st to 10th	Day	43% 4 10% 23% 17% 2	1859
	11th to 20th	Day	55% 2 9% 20% 11% 2	1680
	21st to end	Day	60% 3 11% 17% 7% 1	1600
December	1st to 10th	Day	67% 3 12% 13% 4	2600
	11th to 20th	Day	68% 3 11% 14% 5%	2986
	21st to end	Day	75% 3 8% 11% 3	3981
January	1st to 10th	Night	75% 3 6% 12% 4	5889
	11th to 20th	Night	75% 3 8% 10% 4 1	5900
	21st to end	Night	71% 2 8% 12% 5% 1	6490
February	1st to 10th	Night	64% 3 8% 18% 7%	2600
	11th to 20th	Night	63% 3 9% 18% 7%	2535
	21st to end	Night	63% 3 8% 16% 10% 1	1975
March	1st to 10th	Night	57% 2 9% 22% 9% 1	4918
	11th to 20th	Night	45% 3 12% 28% 9% 3	4980
	21st to end	Night	53% 3 8% 20% 15% 1	5467
April	1st to 10th	Night	53% 3 9% 20% 13% 2	2102
	11th to 20th	Night	48% 3 11% 19% 15% 3	1941
	21st to end	Night	45% 3 10% 25% 14% 3	1800
May	1st to 10th	Night	59% 4 8% 16% 9% 3	4060
	11th to 20th	Night	48% 4 9% 25% 12% 1	4033
	21st to end	Night	46% 4 12% 24% 11% 3	4073
June	1st to 10th	Night	38% 4 14% 24% 18% 2	1600
	11th to 20th	Night	40% 5% 14% 25% 15% 2	1600
	21st to end	Night	37% 6% 13% 24% 18% 2	1600
July	1st to 10th	Night	40% 5% 9% 24% 19% 2	3777
	11th to 20th	Night	40% 7% 16% 24% 12% 1	4006
	21st to end	Night	38% 5% 10% 21% 24% 2	4297
August	1st to 10th	Night	45% 7% 12% 24% 12% 1	2850
	11th to 20th	Night	41% 4 10% 29% 15% 1	2812
	21st to end	Night	35% 6% 13% 31% 13% 2	3284
September	1st to 10th	Night	34% 5% 10% 25% 21% 5%	1905
	11th to 20th	Night	30% 4 13% 28% 23% 1	2090
	21st to end	Night	44% 3 11% 23% 18% 1	2090
October	1st to 10th	Night	36% 3 8% 27% 24% 2	3792
	11th to 20th	Night	39% 4 10% 24% 15% 7%	3779
	21st to end	Night	36% 2 8% 31% 21% 2	4120
November	1st to 10th	Night	41% 2 11% 25% 18% 3	2436
	11th to 20th	Night	53% 3 8% 22% 11% 3	2718
	21st to end	Night	58% 2 10% 22% 6% 1	2800
December	1st to 10th	Night	69% 3 9% 15% 3	4580
	11th to 20th	Night	67% 2 12% 15% 3	5208
	21st to end	Night	71% 3 9% 14% 3	6971

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% 26% 28% 10% 3 2	300
	11th to 20th	Day	30% 28% 31% 8% 2 1	300
	21st to end	Day	29% 27% 33% 7% 3 1	330
February	1st to 10th	Day	35% 18% 36% 9% 1	300
	11th to 20th	Day	36% 26% 29% 8%	300
	21st to end	Day	37% 22% 30% 10%	269
March	1st to 10th	Day	28% 20% 30% 18% 4	500
	11th to 20th	Day	30% 19% 31% 13% 5% 1	500
	21st to end	Day	32% 18% 30% 15% 5% 1	550
April	1st to 10th	Day	31% 18% 26% 17% 7% 1	500
	11th to 20th	Day	24% 20% 28% 17% 7% 3	492
	21st to end	Day	29% 14% 32% 18% 6% 1	500
May	1st to 10th	Day	29% 14% 29% 18% 8% 3	503
	11th to 20th	Day	22% 13% 31% 21% 9% 4	527
	21st to end	Day	17% 7% 27% 24% 19% 5%	573
June	1st to 10th	Day	15% 12% 28% 27% 14% 5%	530
	11th to 20th	Day	19% 9% 24% 28% 15% 5%	530
	21st to end	Day	15% 8% 31% 28% 14% 5%	530
July	1st to 10th	Day	14% 4 19% 31% 22% 10%	525
	11th to 20th	Day	13% 4 26% 30% 19% 8%	524
	21st to end	Day	14% 4 22% 32% 18% 10%	576
August	1st to 10th	Day	12% 5% 22% 30% 21% 10%	502
	11th to 20th	Day	16% 4 22% 30% 18% 10%	479
	21st to end	Day	12% 3 24% 27% 22% 12%	539
September	1st to 10th	Day	19% 5% 21% 27% 20% 8%	490
	11th to 20th	Day	12% 4 17% 31% 23% 12%	490
	21st to end	Day	24% 10% 23% 23% 14% 5%	490
October	1st to 10th	Day	16% 7% 28% 25% 19% 5%	490
	11th to 20th	Day	23% 14% 28% 25% 9% 2	490
	21st to end	Day	29% 13% 32% 19% 7%	539
November	1st to 10th	Day	19% 15% 36% 16% 11% 3	397
	11th to 20th	Day	29% 18% 32% 13% 8%	240
	21st to end	Day	27% 21% 40% 12% 1	200
December	1st to 10th	Day	30% 25% 31% 11% 3 2	200
	11th to 20th	Day	33% 21% 31% 13% 2	200
	21st to end	Day	36% 21% 28% 13% 2	225
January	1st to 10th	Night	29% 19% 32% 16% 3	800
	11th to 20th	Night	30% 16% 31% 20% 4	800
	21st to end	Night	27% 17% 31% 22% 3	880
February	1st to 10th	Night	29% 17% 28% 24% 3	800
	11th to 20th	Night	30% 19% 33% 17% 1	783
	21st to end	Night	28% 16% 32% 21% 3	660
March	1st to 10th	Night	27% 16% 30% 24% 4	800
	11th to 20th	Night	26% 17% 27% 24% 6% 1	800
	21st to end	Night	25% 14% 31% 23% 6% 1	880
April	1st to 10th	Night	27% 14% 29% 25% 6%	800
	11th to 20th	Night	22% 12% 31% 24% 9% 1	757
	21st to end	Night	21% 8% 34% 31% 7%	600
May	1st to 10th	Night	22% 9% 23% 36% 9% 2	600
	11th to 20th	Night	21% 6% 26% 33% 14% 1	591
	21st to end	Night	13% 3 23% 36% 23% 3	502
June	1st to 10th	Night	12% 4 24% 40% 19% 1	400
	11th to 20th	Night	15% 3 22% 39% 21% 1	400
	21st to end	Night	10% 2 27% 35% 25% 2	400
July	1st to 10th	Night	9% 1 16% 43% 24% 7%	477
	11th to 20th	Night	9% 2 18% 36% 31% 5%	582
	21st to end	Night	11% 2 13% 43% 28% 3	657
August	1st to 10th	Night	9% 1 15% 43% 28% 3	579
	11th to 20th	Night	11% 2 11% 40% 30% 5%	564
	21st to end	Night	14% 2 17% 34% 28% 6%	722
September	1st to 10th	Night	17% 2 16% 35% 26% 4	760
	11th to 20th	Night	11% 3 14% 35% 33% 4	760
	21st to end	Night	19% 6% 23% 27% 21% 4	760
October	1st to 10th	Night	17% 6% 22% 31% 23% 2	760
	11th to 20th	Night	23% 10% 28% 25% 12% 2	760
	21st to end	Night	28% 10% 26% 28% 8%	836
November	1st to 10th	Night	18% 11% 27% 30% 14%	780
	11th to 20th	Night	29% 12% 27% 24% 7% 2	800
	21st to end	Night	29% 13% 28% 23% 7%	800
December	1st to 10th	Night	33% 14% 27% 20% 5%	800
	11th to 20th	Night	28% 17% 30% 22% 4	800
	21st to end	Night	29% 14% 30% 25% 2	880

Page generated at 2025-08-02 01:32:28. Version ac07

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