Altoona
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Altoona 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	14% 9% 4 7% 7% 4 5% 5% 6% 7% 31%	78860
	Night	14% 8% 4 7% 6% 3 5% 5% 5% 7% 34%	81254
Transparency	Day	50% 7% 13% 18% 10% 1	78570
	Night	48% 7% 14% 20% 11% 1	81063
Seeing	Day	23% 17% 27% 19% 10% 3	13915
	Night	20% 15% 27% 27% 10% 1	23595

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% 11% 7% 10% 8% 4 5% 4 5% 5% 26%	2595
	11th to 20th	Day	10% 16% 7% 14% 11% 4 6% 4 4 5% 19%	2840
	21st to end	Day	18% 15% 10% 12% 10% 4 5% 4 3 4 16%	3124
February	1st to 10th	Day	14% 14% 5% 9% 8% 4 6% 4 5% 6% 25%	1710
	11th to 20th	Day	13% 9% 5% 11% 9% 4 5% 6% 6% 7% 25%	1663
	21st to end	Day	16% 11% 5% 10% 7% 4 4 5% 4 6% 28%	1551
March	1st to 10th	Day	13% 8% 3 8% 6% 4 6% 6% 5% 6% 34%	2090
	11th to 20th	Day	16% 9% 3 9% 7% 4 5% 5% 5% 7% 30%	2090
	21st to end	Day	17% 10% 4 7% 6% 4 4 4 5% 8% 32%	2299
April	1st to 10th	Day	13% 10% 5% 8% 6% 4 5% 4 6% 7% 31%	2171
	11th to 20th	Day	14% 10% 3 7% 7% 3 5% 5% 5% 6% 34%	2134
	21st to end	Day	20% 9% 3 7% 5% 3 4 5% 5% 6% 33%	2255
May	1st to 10th	Day	17% 9% 3 6% 6% 4 6% 6% 6% 7% 29%	2340
	11th to 20th	Day	20% 7% 4 6% 5% 5% 5% 5% 6% 7% 32%	2388
	21st to end	Day	13% 6% 3 6% 5% 3 6% 5% 6% 9% 37%	2725
June	1st to 10th	Day	14% 6% 3 6% 6% 4 6% 6% 7% 8% 35%	2520
	11th to 20th	Day	12% 7% 3 6% 7% 4 7% 6% 7% 9% 33%	2520
	21st to end	Day	12% 5% 2 6% 7% 4 5% 5% 6% 10% 38%	2520
July	1st to 10th	Day	9% 6% 3 6% 7% 4 7% 6% 7% 8% 37%	2520
	11th to 20th	Day	8% 6% 3 5% 6% 4 6% 7% 8% 8% 39%	2434
	21st to end	Day	10% 7% 3 7% 8% 5% 6% 6% 7% 9% 34%	2547
August	1st to 10th	Day	9% 6% 2 6% 6% 5% 8% 8% 7% 10% 31%	2327
	11th to 20th	Day	13% 6% 2 7% 6% 4 6% 7% 7% 8% 34%	2303
	21st to end	Day	12% 7% 2 6% 6% 3 6% 5% 8% 9% 35%	2376
September	1st to 10th	Day	17% 6% 2 4 5% 4 5% 4 4 7% 41%	2160
	11th to 20th	Day	14% 5% 2 4 4 3 5% 4 7% 7% 44%	2108
	21st to end	Day	18% 8% 2 5% 5% 3 5% 5% 6% 7% 35%	1908
October	1st to 10th	Day	15% 8% 2 7% 7% 4 4 5% 6% 6% 36%	1800
	11th to 20th	Day	17% 8% 3 6% 5% 3 5% 5% 5% 7% 35%	1800
	21st to end	Day	17% 9% 4 6% 5% 3 4 5% 5% 7% 34%	1980
November	1st to 10th	Day	11% 6% 4 6% 5% 3 4 5% 6% 7% 42%	1791
	11th to 20th	Day	15% 7% 4 7% 7% 4 5% 6% 5% 8% 32%	1549
	21st to end	Day	14% 10% 5% 7% 7% 4 7% 6% 5% 6% 29%	1520
December	1st to 10th	Day	16% 12% 6% 9% 8% 4 6% 6% 5% 7% 21%	1520
	11th to 20th	Day	15% 13% 5% 8% 7% 3 5% 4 6% 7% 26%	1910
	21st to end	Day	20% 16% 7% 10% 8% 4 5% 4 5% 5% 16%	2772
January	1st to 10th	Night	12% 10% 6% 11% 8% 5% 6% 6% 5% 7% 23%	4333
	11th to 20th	Night	13% 13% 8% 12% 10% 4 5% 4 5% 5% 21%	4120
	21st to end	Night	21% 13% 7% 10% 10% 3 4 4 5% 4 20%	4532
February	1st to 10th	Night	14% 9% 5% 9% 6% 4 6% 5% 6% 8% 30%	2470
	11th to 20th	Night	13% 10% 3 8% 8% 4 6% 6% 7% 8% 28%	2403
	21st to end	Night	15% 11% 4 8% 7% 4 5% 6% 5% 6% 29%	1900
March	1st to 10th	Night	12% 8% 2 5% 6% 4 5% 6% 7% 8% 38%	2090
	11th to 20th	Night	15% 7% 4 6% 6% 3 4 5% 4 7% 38%	2090
	21st to end	Night	15% 9% 4 6% 5% 3 4 4 4 7% 38%	2299
April	1st to 10th	Night	15% 10% 3 7% 7% 3 5% 4 6% 7% 33%	1832
	11th to 20th	Night	13% 7% 3 5% 5% 4 6% 5% 6% 8% 39%	1775
	21st to end	Night	18% 6% 2 6% 5% 3 4 4 5% 8% 38%	1720
May	1st to 10th	Night	16% 8% 3 6% 6% 3 6% 5% 5% 8% 34%	1620
	11th to 20th	Night	19% 6% 3 5% 5% 3 5% 4 6% 7% 38%	1501
	21st to end	Night	11% 6% 3 5% 5% 2 5% 5% 6% 10% 42%	1550
June	1st to 10th	Night	11% 5% 3 5% 6% 3 5% 4 6% 9% 44%	1440
	11th to 20th	Night	10% 5% 2 6% 5% 3 5% 7% 6% 9% 40%	1440
	21st to end	Night	9% 4 2 5% 4 3 6% 6% 6% 10% 46%	1440
July	1st to 10th	Night	9% 5% 3 5% 5% 3 6% 6% 6% 9% 45%	1440
	11th to 20th	Night	6% 3 2 4 4 3 4 5% 6% 9% 52%	1521
	21st to end	Night	7% 5% 2 6% 5% 4 6% 6% 8% 10% 40%	1771
August	1st to 10th	Night	6% 5% 2 5% 5% 3 5% 5% 7% 11% 45%	1611
	11th to 20th	Night	9% 6% 2 5% 5% 2 4 6% 6% 8% 46%	1598
	21st to end	Night	12% 5% 3 4 5% 3 4 5% 7% 8% 45%	1962
September	1st to 10th	Night	15% 6% 2 4 5% 3 4 5% 5% 5% 45%	1800
	11th to 20th	Night	11% 5% 2 3 3 3 3 5% 5% 9% 51%	1848
	21st to end	Night	16% 6% 2 5% 4 3 4 5% 5% 7% 43%	2052
October	1st to 10th	Night	15% 7% 3 5% 5% 3 4 5% 4 8% 43%	2160
	11th to 20th	Night	17% 6% 2 5% 5% 3 4 5% 5% 7% 41%	2160
	21st to end	Night	19% 9% 2 5% 4 3 5% 4 5% 7% 37%	2376
November	1st to 10th	Night	9% 6% 3 6% 6% 3 4 4 5% 7% 47%	2285
	11th to 20th	Night	14% 7% 4 6% 6% 3 6% 5% 6% 7% 35%	2626
	21st to end	Night	14% 8% 4 6% 7% 3 6% 5% 6% 8% 33%	2660
December	1st to 10th	Night	16% 9% 5% 8% 8% 4 7% 5% 7% 7% 23%	2660
	11th to 20th	Night	15% 8% 4 9% 7% 5% 6% 6% 6% 7% 28%	3285
	21st to end	Night	18% 12% 6% 9% 9% 4 6% 5% 5% 7% 19%	4884

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	60% 7% 12% 16% 4 1	2596
	11th to 20th	Day	68% 5% 9% 10% 7% 1	2840
	21st to end	Day	71% 5% 9% 10% 3 1	3124
February	1st to 10th	Day	60% 5% 14% 14% 7% 1	1710
	11th to 20th	Day	56% 7% 13% 17% 7%	1672
	21st to end	Day	57% 5% 13% 15% 7% 3	1551
March	1st to 10th	Day	50% 6% 14% 21% 8% 1	2090
	11th to 20th	Day	53% 6% 12% 18% 8% 2	2090
	21st to end	Day	52% 5% 11% 19% 11% 2	2299
April	1st to 10th	Day	51% 7% 11% 17% 12% 2	2171
	11th to 20th	Day	49% 6% 10% 16% 15% 3	2134
	21st to end	Day	51% 6% 10% 20% 11% 2	2255
May	1st to 10th	Day	52% 8% 10% 18% 11% 1	2340
	11th to 20th	Day	51% 7% 12% 15% 13% 2	2392
	21st to end	Day	43% 9% 17% 20% 10% 2	2725
June	1st to 10th	Day	45% 8% 12% 21% 13% 1	2520
	11th to 20th	Day	45% 9% 14% 18% 12% 1	2520
	21st to end	Day	40% 9% 14% 25% 12%	2520
July	1st to 10th	Day	43% 10% 12% 19% 12% 3	2450
	11th to 20th	Day	37% 10% 15% 22% 15% 1	2359
	21st to end	Day	44% 8% 12% 20% 14% 2	2405
August	1st to 10th	Day	42% 11% 17% 20% 9%	2314
	11th to 20th	Day	44% 10% 12% 22% 11% 1	2303
	21st to end	Day	41% 8% 14% 21% 12% 3	2376
September	1st to 10th	Day	43% 8% 11% 20% 15% 4	2160
	11th to 20th	Day	37% 5% 12% 27% 17% 2	2108
	21st to end	Day	46% 7% 13% 18% 15% 1	1908
October	1st to 10th	Day	46% 7% 12% 20% 13% 2	1800
	11th to 20th	Day	47% 7% 12% 24% 10%	1800
	21st to end	Day	48% 7% 14% 19% 11% 1	1980
November	1st to 10th	Day	39% 6% 16% 19% 15% 4	1791
	11th to 20th	Day	50% 5% 14% 18% 10% 2	1549
	21st to end	Day	54% 6% 13% 20% 7%	1520
December	1st to 10th	Day	62% 8% 15% 12% 4	1520
	11th to 20th	Day	57% 5% 13% 21% 4	1906
	21st to end	Day	68% 6% 11% 11% 3	2772
January	1st to 10th	Night	59% 5% 14% 15% 6%	4333
	11th to 20th	Night	62% 6% 14% 13% 4	4120
	21st to end	Night	67% 5% 9% 14% 4 1	4532
February	1st to 10th	Night	53% 7% 14% 19% 7%	2470
	11th to 20th	Night	53% 7% 13% 18% 9%	2405
	21st to end	Night	54% 7% 11% 16% 9% 2	1900
March	1st to 10th	Night	42% 7% 15% 23% 12% 1	2090
	11th to 20th	Night	47% 6% 13% 21% 11% 2	2090
	21st to end	Night	47% 5% 13% 18% 15% 3	2299
April	1st to 10th	Night	51% 7% 11% 17% 13% 1	1832
	11th to 20th	Night	42% 6% 13% 21% 15% 2	1775
	21st to end	Night	45% 6% 11% 23% 12% 3	1720
May	1st to 10th	Night	47% 8% 10% 20% 11% 4	1620
	11th to 20th	Night	46% 8% 13% 17% 14% 2	1502
	21st to end	Night	36% 10% 16% 24% 12% 2	1551
June	1st to 10th	Night	37% 8% 13% 27% 14% 2	1440
	11th to 20th	Night	38% 10% 15% 22% 13% 2	1440
	21st to end	Night	32% 10% 17% 26% 14% 1	1440
July	1st to 10th	Night	36% 11% 14% 22% 15% 3	1400
	11th to 20th	Night	29% 8% 17% 25% 19% 2	1473
	21st to end	Night	34% 12% 17% 20% 15% 2	1672
August	1st to 10th	Night	31% 11% 19% 25% 13% 1	1600
	11th to 20th	Night	34% 9% 17% 24% 15% 1	1598
	21st to end	Night	36% 8% 14% 25% 14% 3	1962
September	1st to 10th	Night	41% 6% 11% 22% 17% 3	1800
	11th to 20th	Night	31% 6% 14% 28% 19% 2	1848
	21st to end	Night	41% 6% 12% 23% 17% 1	2052
October	1st to 10th	Night	40% 8% 14% 23% 14% 1	2160
	11th to 20th	Night	41% 6% 13% 25% 13% 1	2160
	21st to end	Night	46% 6% 12% 22% 13% 1	2376
November	1st to 10th	Night	38% 6% 14% 21% 17% 3	2285
	11th to 20th	Night	46% 7% 13% 21% 11% 3	2626
	21st to end	Night	49% 6% 15% 20% 8% 1	2660
December	1st to 10th	Night	57% 8% 17% 13% 4	2660
	11th to 20th	Night	54% 7% 13% 20% 5%	3288
	21st to end	Night	64% 7% 15% 12% 3	4884

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	33% 28% 25% 10% 2	204
	11th to 20th	Day	38% 25% 29% 7% 1	270
	21st to end	Day	28% 29% 33% 8% 2	297
February	1st to 10th	Day	32% 29% 27% 10% 1	270
	11th to 20th	Day	41% 26% 29% 4	270
	21st to end	Day	37% 25% 26% 11% 1	340
March	1st to 10th	Day	32% 21% 27% 17% 3	460
	11th to 20th	Day	32% 23% 27% 13% 4 1	460
	21st to end	Day	29% 25% 27% 14% 4 1	506
April	1st to 10th	Day	30% 24% 25% 15% 5% 1	428
	11th to 20th	Day	26% 17% 26% 18% 9% 3	412
	21st to end	Day	32% 21% 26% 14% 6% 1	420
May	1st to 10th	Day	30% 19% 26% 14% 7% 3	423
	11th to 20th	Day	26% 17% 30% 16% 9% 3	447
	21st to end	Day	18% 15% 26% 22% 14% 5%	485
June	1st to 10th	Day	18% 17% 29% 22% 12% 2	450
	11th to 20th	Day	20% 14% 27% 25% 11% 3	450
	21st to end	Day	14% 13% 31% 27% 13% 2	450
July	1st to 10th	Day	11% 8% 29% 27% 18% 9%	445
	11th to 20th	Day	6% 9% 30% 32% 16% 7%	444
	21st to end	Day	12% 10% 29% 28% 16% 5%	488
August	1st to 10th	Day	11% 8% 26% 28% 19% 8%	446
	11th to 20th	Day	14% 7% 26% 25% 18% 10%	439
	21st to end	Day	15% 9% 24% 28% 14% 11%	495
September	1st to 10th	Day	20% 8% 20% 26% 18% 9%	450
	11th to 20th	Day	16% 6% 22% 28% 20% 8%	450
	21st to end	Day	24% 15% 23% 19% 13% 6%	450
October	1st to 10th	Day	21% 13% 20% 25% 17% 4	450
	11th to 20th	Day	26% 17% 26% 22% 8% 1	450
	21st to end	Day	23% 22% 29% 19% 7%	495
November	1st to 10th	Day	21% 15% 29% 20% 13% 2	424
	11th to 20th	Day	29% 23% 29% 15% 4	209
	21st to end	Day	27% 26% 33% 11% 3	180
December	1st to 10th	Day	32% 32% 23% 9% 3 1	180
	11th to 20th	Day	35% 21% 31% 12% 1	180
	21st to end	Day	32% 23% 26% 16% 3	198
January	1st to 10th	Night	24% 23% 35% 15% 2	760
	11th to 20th	Night	29% 19% 32% 18% 3	760
	21st to end	Night	22% 25% 33% 19% 2	836
February	1st to 10th	Night	27% 19% 32% 20% 2	760
	11th to 20th	Night	26% 26% 33% 14% 1	743
	21st to end	Night	27% 20% 32% 19% 2	628
March	1st to 10th	Night	25% 20% 31% 22% 3	760
	11th to 20th	Night	28% 21% 26% 19% 5% 1	760
	21st to end	Night	22% 21% 33% 19% 5%	836
April	1st to 10th	Night	26% 22% 29% 18% 4	729
	11th to 20th	Night	20% 17% 27% 28% 7% 1	711
	21st to end	Night	23% 14% 26% 31% 7%	640
May	1st to 10th	Night	22% 12% 24% 31% 11% 1	540
	11th to 20th	Night	20% 10% 26% 35% 10%	440
	21st to end	Night	12% 9% 22% 37% 18% 2	389
June	1st to 10th	Night	12% 7% 25% 39% 16% 1	360
	11th to 20th	Night	13% 7% 26% 37% 17% 1	360
	21st to end	Night	10% 5% 28% 42% 16%	360
July	1st to 10th	Night	10% 3 18% 43% 22% 3	350
	11th to 20th	Night	7% 3 17% 40% 30% 2	429
	21st to end	Night	9% 4 22% 41% 23% 1	591
August	1st to 10th	Night	8% 2 18% 42% 29% 1	537
	11th to 20th	Night	11% 5% 16% 38% 27% 3	534
	21st to end	Night	14% 3 18% 37% 24% 3	774
September	1st to 10th	Night	18% 4 17% 35% 23% 3	720
	11th to 20th	Night	13% 6% 17% 32% 28% 4	720
	21st to end	Night	20% 7% 22% 29% 19% 4	720
October	1st to 10th	Night	18% 8% 23% 31% 18% 2	720
	11th to 20th	Night	21% 13% 29% 27% 9% 1	720
	21st to end	Night	26% 16% 26% 26% 7% 1	792
November	1st to 10th	Night	15% 13% 31% 31% 10% 1	740
	11th to 20th	Night	24% 19% 26% 24% 6% 1	760
	21st to end	Night	23% 20% 28% 24% 5% 1	760
December	1st to 10th	Night	27% 19% 31% 19% 4	760
	11th to 20th	Night	24% 20% 31% 22% 2	760
	21st to end	Night	23% 22% 29% 25% 1	836

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

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