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 2024-04-03.

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	17% 10% 4 7% 6% 3 5% 5% 5% 7% 30%	78897
	Night	17% 10% 4 7% 6% 3 5% 4 5% 6% 32%	81233
Transparency	Day	54% 4 11% 20% 10% 1	78617
	Night	54% 3 10% 20% 11% 2	81032
Seeing	Day	23% 12% 28% 21% 12% 4	13834
	Night	22% 10% 26% 28% 13% 2	23699

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	20% 19% 9% 10% 6% 3 4 3 4 5% 18%	2836
	11th to 20th	Day	14% 22% 9% 12% 8% 4 3 3 3 4 18%	2840
	21st to end	Day	26% 18% 9% 11% 8% 3 3 3 3 4 11%	3124
February	1st to 10th	Day	20% 15% 6% 10% 8% 4 4 3 3 5% 22%	1710
	11th to 20th	Day	16% 14% 6% 12% 7% 4 4 5% 4 6% 22%	1663
	21st to end	Day	20% 13% 5% 9% 6% 3 4 4 4 5% 25%	1573
March	1st to 10th	Day	18% 10% 5% 7% 6% 4 4 4 5% 7% 30%	2090
	11th to 20th	Day	17% 11% 4 8% 7% 4 5% 4 4 6% 30%	2090
	21st to end	Day	21% 10% 4 7% 6% 2 4 5% 6% 7% 27%	2299
April	1st to 10th	Day	15% 11% 5% 7% 6% 4 4 5% 5% 7% 31%	2089
	11th to 20th	Day	18% 9% 4 7% 5% 4 5% 4 6% 6% 33%	2179
	21st to end	Day	22% 8% 3 7% 5% 3 4 5% 5% 6% 32%	2340
May	1st to 10th	Day	19% 9% 3 7% 6% 4 5% 5% 6% 8% 29%	2340
	11th to 20th	Day	20% 8% 4 6% 7% 4 6% 5% 6% 7% 30%	2301
	21st to end	Day	11% 5% 2 5% 5% 4 6% 6% 8% 10% 38%	2659
June	1st to 10th	Day	14% 7% 4 5% 6% 4 6% 6% 6% 9% 34%	2520
	11th to 20th	Day	15% 7% 2 6% 6% 3 6% 5% 6% 9% 35%	2520
	21st to end	Day	14% 5% 3 6% 6% 3 5% 5% 6% 9% 38%	2520
July	1st to 10th	Day	10% 7% 3 6% 6% 4 5% 5% 6% 8% 40%	2433
	11th to 20th	Day	11% 6% 3 6% 6% 4 5% 5% 7% 10% 36%	2340
	21st to end	Day	12% 5% 3 6% 7% 4 6% 6% 7% 9% 35%	2547
August	1st to 10th	Day	9% 6% 3 6% 7% 5% 6% 7% 7% 11% 35%	2327
	11th to 20th	Day	13% 6% 3 6% 7% 4 5% 6% 7% 9% 34%	2303
	21st to end	Day	11% 5% 2 6% 6% 4 5% 6% 7% 9% 37%	2466
September	1st to 10th	Day	15% 7% 3 4 4 3 5% 4 5% 7% 43%	2152
	11th to 20th	Day	11% 5% 2 5% 4 3 5% 5% 6% 10% 42%	1980
	21st to end	Day	17% 7% 4 6% 5% 4 4 4 5% 6% 38%	1980
October	1st to 10th	Day	15% 6% 3 5% 5% 3 5% 5% 7% 9% 38%	1807
	11th to 20th	Day	20% 8% 3 6% 6% 3 5% 5% 5% 5% 34%	1800
	21st to end	Day	23% 11% 3 6% 5% 3 4 4 4 7% 30%	1980
November	1st to 10th	Day	12% 8% 3 7% 6% 3 5% 5% 4 6% 42%	1764
	11th to 20th	Day	17% 12% 5% 7% 5% 3 4 4 5% 6% 32%	1596
	21st to end	Day	17% 14% 5% 10% 6% 3 4 4 5% 7% 26%	1520
December	1st to 10th	Day	21% 16% 8% 11% 7% 3 3 4 3 6% 18%	1520
	11th to 20th	Day	20% 16% 8% 11% 5% 3 4 3 4 6% 20%	1910
	21st to end	Day	25% 21% 7% 10% 6% 3 4 4 3 5% 13%	2779
January	1st to 10th	Night	16% 19% 9% 11% 6% 4 4 4 4 4 18%	4109
	11th to 20th	Night	18% 16% 8% 13% 8% 4 5% 4 4 4 16%	4120
	21st to end	Night	29% 15% 8% 9% 9% 3 3 3 3 3 16%	4532
February	1st to 10th	Night	21% 13% 5% 9% 6% 3 4 4 4 6% 24%	2470
	11th to 20th	Night	19% 12% 5% 10% 7% 3 5% 4 4 5% 25%	2403
	21st to end	Night	21% 12% 5% 9% 7% 3 5% 5% 4 5% 24%	1880
March	1st to 10th	Night	20% 10% 4 6% 5% 3 4 4 5% 6% 33%	2090
	11th to 20th	Night	19% 10% 4 6% 5% 3 4 4 4 6% 35%	2090
	21st to end	Night	18% 11% 4 7% 6% 4 3 4 4 6% 34%	2299
April	1st to 10th	Night	18% 10% 4 6% 6% 3 4 4 4 6% 35%	1915
	11th to 20th	Night	16% 8% 3 6% 6% 3 5% 4 5% 8% 36%	1745
	21st to end	Night	16% 9% 3 6% 5% 3 4 5% 6% 8% 36%	1620
May	1st to 10th	Night	17% 9% 3 7% 5% 3 6% 5% 5% 9% 32%	1620
	11th to 20th	Night	16% 8% 3 6% 5% 3 5% 5% 5% 8% 36%	1592
	21st to end	Night	10% 5% 2 4 4 3 5% 6% 6% 10% 44%	1612
June	1st to 10th	Night	10% 5% 3 6% 4 4 4 5% 7% 8% 44%	1440
	11th to 20th	Night	12% 6% 3 5% 5% 3 5% 5% 6% 8% 42%	1440
	21st to end	Night	10% 3 3 5% 5% 4 5% 6% 6% 8% 45%	1440
July	1st to 10th	Night	7% 5% 2 6% 6% 3 5% 6% 7% 8% 45%	1521
	11th to 20th	Night	8% 4 3 5% 4 4 4 6% 6% 9% 46%	1620
	21st to end	Night	9% 7% 3 6% 6% 3 6% 6% 7% 9% 40%	1771
August	1st to 10th	Night	6% 5% 3 5% 5% 3 6% 5% 8% 9% 44%	1611
	11th to 20th	Night	9% 7% 2 5% 5% 4 5% 5% 5% 8% 45%	1598
	21st to end	Night	11% 6% 1 5% 5% 3 4 6% 6% 9% 45%	1872
September	1st to 10th	Night	13% 5% 1 4 4 2 5% 5% 5% 7% 48%	1804
	11th to 20th	Night	11% 3 2 3 4 2 5% 5% 5% 9% 51%	1980
	21st to end	Night	15% 7% 3 5% 4 3 5% 4 5% 7% 42%	1980
October	1st to 10th	Night	14% 6% 2 5% 5% 2 5% 4 4 7% 45%	2152
	11th to 20th	Night	19% 7% 3 5% 5% 4 4 4 5% 6% 38%	2160
	21st to end	Night	24% 8% 2 5% 4 3 5% 4 4 6% 35%	2376
November	1st to 10th	Night	14% 8% 3 5% 5% 2 5% 4 5% 7% 43%	2311
	11th to 20th	Night	19% 10% 4 6% 5% 3 5% 4 5% 6% 33%	2582
	21st to end	Night	20% 11% 5% 7% 6% 3 4 4 5% 5% 30%	2660
December	1st to 10th	Night	24% 15% 7% 9% 5% 3 4 4 4 6% 20%	2660
	11th to 20th	Night	19% 17% 6% 10% 6% 3 4 4 4 5% 23%	3285
	21st to end	Night	26% 18% 6% 9% 7% 3 4 4 4 5% 14%	4873

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	71% 2 9% 13% 5%	2837
	11th to 20th	Day	73% 1 7% 13% 4 1	2840
	21st to end	Day	78% 2 8% 9% 2	3124
February	1st to 10th	Day	67% 2 9% 14% 7% 1	1710
	11th to 20th	Day	64% 4 8% 16% 8%	1672
	21st to end	Day	61% 3 10% 16% 8% 1	1573
March	1st to 10th	Day	55% 2 12% 23% 8%	2090
	11th to 20th	Day	56% 3 10% 20% 9% 1	2090
	21st to end	Day	57% 3 9% 18% 11% 2	2299
April	1st to 10th	Day	53% 3 11% 20% 12% 2	2089
	11th to 20th	Day	52% 4 10% 17% 15% 2	2179
	21st to end	Day	53% 4 9% 22% 11% 2	2340
May	1st to 10th	Day	54% 4 12% 20% 9% 2	2340
	11th to 20th	Day	54% 4 11% 17% 11% 2	2305
	21st to end	Day	39% 6% 17% 25% 10% 2	2659
June	1st to 10th	Day	46% 5% 14% 23% 11% 1	2520
	11th to 20th	Day	45% 5% 13% 24% 12% 1	2520
	21st to end	Day	42% 5% 13% 26% 13% 1	2520
July	1st to 10th	Day	43% 5% 12% 23% 15% 3	2367
	11th to 20th	Day	42% 4 12% 26% 15% 1	2271
	21st to end	Day	43% 6% 12% 24% 14% 1	2405
August	1st to 10th	Day	42% 5% 14% 29% 10%	2314
	11th to 20th	Day	44% 5% 13% 27% 10% 1	2303
	21st to end	Day	42% 5% 12% 24% 14% 4	2466
September	1st to 10th	Day	41% 4 11% 23% 18% 4	2152
	11th to 20th	Day	37% 3 14% 29% 15% 2	1980
	21st to end	Day	48% 3 9% 25% 15%	1980
October	1st to 10th	Day	42% 4 12% 24% 17% 1	1807
	11th to 20th	Day	53% 4 9% 24% 11%	1800
	21st to end	Day	55% 3 11% 19% 11% 1	1980
November	1st to 10th	Day	44% 4 10% 23% 17% 2	1764
	11th to 20th	Day	55% 2 9% 21% 11% 2	1596
	21st to end	Day	59% 3 11% 18% 7% 1	1520
December	1st to 10th	Day	71% 3 9% 13% 4	1520
	11th to 20th	Day	67% 3 9% 17% 3	1906
	21st to end	Day	77% 2 9% 9% 3	2779
January	1st to 10th	Night	71% 3 8% 15% 4	4109
	11th to 20th	Night	73% 2 9% 12% 3	4120
	21st to end	Night	76% 1 6% 13% 3	4532
February	1st to 10th	Night	63% 3 9% 19% 7%	2470
	11th to 20th	Night	62% 3 9% 18% 8%	2405
	21st to end	Night	63% 3 8% 15% 10% 1	1880
March	1st to 10th	Night	53% 3 10% 22% 12% 1	2090
	11th to 20th	Night	51% 3 10% 24% 10% 2	2090
	21st to end	Night	53% 2 7% 21% 14% 3	2299
April	1st to 10th	Night	52% 3 9% 20% 14% 2	1915
	11th to 20th	Night	48% 3 11% 19% 16% 4	1745
	21st to end	Night	46% 4 10% 24% 13% 3	1620
May	1st to 10th	Night	50% 5% 9% 21% 12% 3	1620
	11th to 20th	Night	47% 5% 12% 18% 15% 3	1593
	21st to end	Night	35% 6% 16% 28% 14% 2	1613
June	1st to 10th	Night	37% 4 15% 25% 17% 2	1440
	11th to 20th	Night	40% 4 14% 25% 15% 2	1440
	21st to end	Night	36% 6% 13% 25% 17% 2	1440
July	1st to 10th	Night	37% 6% 12% 23% 18% 4	1477
	11th to 20th	Night	32% 6% 15% 27% 19% 2	1566
	21st to end	Night	40% 5% 15% 24% 13% 3	1672
August	1st to 10th	Night	34% 5% 15% 29% 16% 1	1600
	11th to 20th	Night	37% 4 15% 27% 15% 2	1598
	21st to end	Night	35% 5% 13% 27% 16% 4	1872
September	1st to 10th	Night	35% 5% 10% 25% 20% 5%	1804
	11th to 20th	Night	30% 4 14% 28% 22% 1	1980
	21st to end	Night	42% 3 11% 23% 19% 1	1980
October	1st to 10th	Night	40% 4 12% 25% 16% 3	2152
	11th to 20th	Night	48% 3 10% 24% 14% 1	2160
	21st to end	Night	52% 3 9% 22% 12% 2	2376
November	1st to 10th	Night	42% 2 11% 24% 17% 4	2311
	11th to 20th	Night	52% 3 9% 22% 11% 2	2582
	21st to end	Night	57% 2 10% 23% 7% 1	2660
December	1st to 10th	Night	67% 3 10% 15% 5%	2660
	11th to 20th	Night	65% 2 10% 18% 4	3288
	21st to end	Night	74% 3 9% 11% 2	4873

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% 25% 29% 10% 3 2	270
	11th to 20th	Day	31% 25% 32% 9% 2 1	270
	21st to end	Day	30% 25% 34% 7% 3 1	297
February	1st to 10th	Day	35% 16% 37% 10% 1	270
	11th to 20th	Day	34% 27% 30% 8%	270
	21st to end	Day	39% 22% 28% 10%	244
March	1st to 10th	Day	29% 19% 29% 18% 4	460
	11th to 20th	Day	30% 18% 32% 13% 5% 1	460
	21st to end	Day	33% 17% 29% 15% 5% 1	506
April	1st to 10th	Day	29% 18% 27% 17% 8% 1	428
	11th to 20th	Day	22% 19% 28% 18% 8% 4	412
	21st to end	Day	30% 14% 31% 17% 7% 2	420
May	1st to 10th	Day	30% 13% 28% 18% 8% 3	423
	11th to 20th	Day	23% 12% 32% 22% 9% 3	447
	21st to end	Day	16% 6% 28% 24% 21% 6%	485
June	1st to 10th	Day	14% 10% 29% 28% 14% 5%	450
	11th to 20th	Day	20% 8% 24% 27% 16% 5%	450
	21st to end	Day	15% 7% 32% 30% 13% 3	450
July	1st to 10th	Day	14% 2 18% 31% 22% 12%	445
	11th to 20th	Day	14% 3 26% 29% 19% 8%	444
	21st to end	Day	15% 4 24% 30% 18% 10%	488
August	1st to 10th	Day	12% 4 20% 31% 22% 11%	446
	11th to 20th	Day	16% 3 21% 29% 19% 11%	439
	21st to end	Day	13% 2 24% 27% 21% 13%	495
September	1st to 10th	Day	20% 4 20% 27% 20% 8%	450
	11th to 20th	Day	13% 4 17% 31% 23% 12%	450
	21st to end	Day	21% 10% 24% 24% 16% 6%	450
October	1st to 10th	Day	16% 7% 28% 25% 19% 5%	450
	11th to 20th	Day	24% 14% 28% 24% 8% 1	450
	21st to end	Day	31% 13% 32% 18% 6%	495
November	1st to 10th	Day	19% 15% 35% 16% 12% 3	362
	11th to 20th	Day	29% 19% 28% 14% 9%	216
	21st to end	Day	25% 18% 43% 13% 1	180
December	1st to 10th	Day	30% 25% 29% 11% 3 2	180
	11th to 20th	Day	30% 21% 33% 14% 2	180
	21st to end	Day	36% 21% 28% 12% 2	202
January	1st to 10th	Night	29% 18% 33% 17% 3	760
	11th to 20th	Night	31% 15% 30% 20% 4	760
	21st to end	Night	27% 17% 31% 22% 4	836
February	1st to 10th	Night	28% 17% 28% 25% 3	760
	11th to 20th	Night	29% 19% 34% 17% 1	743
	21st to end	Night	29% 16% 31% 21% 3	628
March	1st to 10th	Night	26% 16% 29% 25% 4	760
	11th to 20th	Night	27% 16% 26% 23% 6% 1	760
	21st to end	Night	25% 14% 31% 24% 6% 1	836
April	1st to 10th	Night	25% 14% 29% 25% 7%	729
	11th to 20th	Night	22% 12% 31% 25% 10% 1	681
	21st to end	Night	21% 8% 35% 30% 6%	540
May	1st to 10th	Night	20% 9% 24% 36% 10% 1	540
	11th to 20th	Night	21% 6% 26% 33% 13% 1	531
	21st to end	Night	11% 3 23% 36% 24% 3	452
June	1st to 10th	Night	12% 3 24% 41% 20% 1	360
	11th to 20th	Night	15% 3 22% 38% 21% 1	360
	21st to end	Night	10% 2 26% 37% 24% 1	360
July	1st to 10th	Night	8% 1 16% 42% 25% 8%	427
	11th to 20th	Night	9% 1 18% 37% 30% 5%	522
	21st to end	Night	12% 2 13% 42% 28% 3	591
August	1st to 10th	Night	9% 1 14% 43% 29% 4	537
	11th to 20th	Night	11% 2 10% 40% 32% 5%	534
	21st to end	Night	14% 2 17% 33% 27% 6%	684
September	1st to 10th	Night	17% 2 15% 34% 27% 4	720
	11th to 20th	Night	12% 3 14% 34% 32% 4	720
	21st to end	Night	18% 6% 24% 27% 22% 4	720
October	1st to 10th	Night	17% 7% 22% 30% 22% 2	720
	11th to 20th	Night	24% 10% 28% 26% 11% 1	720
	21st to end	Night	30% 10% 26% 27% 7%	792
November	1st to 10th	Night	18% 10% 27% 30% 14%	740
	11th to 20th	Night	28% 12% 27% 24% 8% 2	760
	21st to end	Night	29% 13% 28% 23% 7%	760
December	1st to 10th	Night	34% 14% 27% 20% 5%	760
	11th to 20th	Night	27% 17% 30% 22% 4	760
	21st to end	Night	29% 14% 30% 24% 2	836

Page generated at 2024-03-31 06:08:53. Version ac07

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