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 2024-11-04.

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% 3 8% 6% 5% 5% 4 6% 7% 33%	101270
	Night	14% 8% 3 8% 5% 5% 5% 4 6% 7% 35%	97676
Transparency	Day	48% 7% 12% 20% 11% 1	104909
	Night	46% 7% 13% 21% 11% 1	102176
Seeing	Day	23% 17% 27% 20% 10% 3	14775
	Night	20% 14% 26% 27% 11% 1	24277

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% 12% 7% 12% 7% 6% 4 4 5% 5% 26%	2595
	11th to 20th	Day	10% 17% 7% 17% 8% 4 5% 3 4 5% 18%	2840
	21st to end	Day	18% 16% 9% 14% 8% 5% 4 3 4 4 16%	3124
February	1st to 10th	Day	14% 15% 4 11% 7% 5% 5% 3 5% 6% 24%	1710
	11th to 20th	Day	13% 10% 4 13% 7% 5% 6% 5% 7% 7% 25%	1663
	21st to end	Day	15% 12% 5% 11% 6% 5% 4 4 5% 5% 28%	1551
March	1st to 10th	Day	19% 10% 4 8% 6% 5% 5% 4 6% 7% 27%	3435
	11th to 20th	Day	10% 8% 4 11% 6% 5% 5% 4 6% 7% 33%	3480
	21st to end	Day	14% 9% 3 8% 5% 5% 5% 4 5% 6% 37%	3815
April	1st to 10th	Day	13% 12% 4 9% 5% 5% 5% 3 6% 7% 30%	2267
	11th to 20th	Day	14% 10% 3 8% 6% 4 5% 3 5% 6% 35%	2254
	21st to end	Day	19% 9% 3 8% 5% 4 4 4 5% 6% 33%	2381
May	1st to 10th	Day	26% 8% 2 7% 5% 5% 5% 4 5% 6% 28%	4082
	11th to 20th	Day	22% 9% 3 8% 5% 5% 4 4 5% 7% 28%	4252
	21st to end	Day	11% 6% 3 6% 5% 5% 5% 4 7% 10% 38%	4823
June	1st to 10th	Day	13% 7% 2 6% 5% 5% 6% 5% 7% 8% 35%	2660
	11th to 20th	Day	11% 7% 3 7% 6% 5% 6% 5% 8% 9% 34%	2660
	21st to end	Day	11% 5% 2 7% 6% 6% 4 5% 6% 10% 38%	2660
July	1st to 10th	Day	7% 5% 2 7% 6% 6% 7% 5% 7% 9% 39%	4440
	11th to 20th	Day	6% 6% 2 6% 5% 6% 7% 5% 8% 9% 40%	4284
	21st to end	Day	9% 7% 3 8% 6% 5% 6% 5% 6% 7% 37%	4466
August	1st to 10th	Day	18% 6% 2 6% 5% 6% 6% 5% 7% 9% 30%	4104
	11th to 20th	Day	10% 6% 2 8% 5% 7% 7% 6% 7% 8% 35%	4044
	21st to end	Day	12% 6% 2 6% 4 5% 5% 4 7% 9% 41%	4180
September	1st to 10th	Day	16% 6% 2 5% 4 5% 5% 3 4 6% 43%	2280
	11th to 20th	Day	14% 6% 2 5% 3 4 4 3 6% 7% 45%	2225
	21st to end	Day	20% 8% 2 6% 4 4 5% 5% 6% 7% 33%	2013
October	1st to 10th	Day	15% 8% 2 7% 5% 5% 4 4 6% 6% 37%	1900
	11th to 20th	Day	16% 8% 3 7% 4 4 5% 4 6% 7% 36%	1900
	21st to end	Day	16% 9% 3 7% 4 4 4 4 5% 7% 36%	2090
November	1st to 10th	Day	10% 6% 3 7% 4 5% 4 4 6% 6% 43%	1821
	11th to 20th	Day	14% 8% 4 8% 7% 5% 5% 4 5% 8% 32%	1549
	21st to end	Day	14% 11% 5% 8% 6% 6% 6% 4 5% 6% 29%	1520
December	1st to 10th	Day	16% 13% 6% 10% 7% 6% 5% 5% 5% 7% 21%	1520
	11th to 20th	Day	15% 13% 5% 10% 6% 4 4 3 6% 7% 26%	1910
	21st to end	Day	20% 17% 6% 11% 7% 5% 5% 3 5% 5% 16%	2772
January	1st to 10th	Night	12% 11% 5% 12% 7% 6% 6% 4 6% 7% 23%	4333
	11th to 20th	Night	13% 14% 7% 14% 8% 5% 5% 3 5% 5% 21%	4120
	21st to end	Night	20% 13% 7% 11% 8% 4 4 3 5% 4 20%	4532
February	1st to 10th	Night	14% 10% 4 9% 6% 5% 5% 4 6% 8% 30%	2470
	11th to 20th	Night	13% 11% 2 9% 7% 6% 6% 5% 7% 7% 28%	2403
	21st to end	Night	14% 12% 3 10% 6% 5% 5% 5% 5% 5% 29%	1900
March	1st to 10th	Night	21% 12% 3 7% 5% 4 4 4 6% 6% 31%	3418
	11th to 20th	Night	10% 6% 6% 8% 5% 5% 4 5% 5% 7% 38%	3480
	21st to end	Night	12% 9% 3 7% 5% 4 4 3 4 7% 42%	3817
April	1st to 10th	Night	14% 11% 3 9% 6% 5% 4 4 6% 6% 32%	1911
	11th to 20th	Night	13% 7% 3 6% 5% 5% 5% 4 6% 8% 38%	1875
	21st to end	Night	17% 6% 2 7% 5% 5% 4 3 5% 8% 38%	1815
May	1st to 10th	Night	24% 9% 3 7% 5% 4 5% 4 5% 7% 28%	2813
	11th to 20th	Night	25% 9% 3 6% 4 4 3 3 6% 6% 31%	2637
	21st to end	Night	11% 6% 2 8% 5% 5% 5% 4 7% 10% 37%	2732
June	1st to 10th	Night	11% 6% 2 5% 6% 4 5% 3 6% 9% 43%	1520
	11th to 20th	Night	10% 5% 2 6% 4 5% 5% 5% 6% 9% 41%	1520
	21st to end	Night	9% 5% 1 6% 3 4 6% 4 7% 10% 45%	1520
July	1st to 10th	Night	6% 5% 2 7% 6% 5% 6% 5% 7% 9% 41%	2520
	11th to 20th	Night	5% 3 2 5% 5% 5% 6% 4 7% 10% 46%	2671
	21st to end	Night	9% 7% 2 7% 5% 5% 5% 5% 7% 7% 41%	3087
August	1st to 10th	Night	16% 6% 2 5% 4 4 5% 4 7% 9% 37%	2825
	11th to 20th	Night	11% 6% 2 6% 5% 4 5% 4 7% 8% 43%	2785
	21st to end	Night	14% 4 2 5% 4 3 4 4 6% 7% 48%	3444
September	1st to 10th	Night	15% 6% 2 5% 4 4 5% 4 4 5% 46%	1900
	11th to 20th	Night	11% 5% 1 4 3 3 4 3 5% 9% 51%	1951
	21st to end	Night	20% 6% 2 6% 4 4 4 3 5% 7% 41%	2166
October	1st to 10th	Night	15% 7% 2 6% 4 4 4 4 4 7% 44%	2280
	11th to 20th	Night	16% 6% 2 6% 4 4 5% 3 5% 6% 42%	2280
	21st to end	Night	18% 9% 2 5% 4 4 4 3 5% 7% 39%	2508
November	1st to 10th	Night	9% 7% 3 7% 5% 4 4 3 5% 7% 47%	2328
	11th to 20th	Night	14% 8% 4 7% 5% 5% 6% 4 6% 7% 35%	2626
	21st to end	Night	14% 9% 4 7% 5% 5% 5% 4 6% 8% 33%	2660
December	1st to 10th	Night	16% 9% 5% 10% 6% 6% 6% 4 7% 7% 23%	2660
	11th to 20th	Night	15% 9% 4 10% 6% 6% 6% 5% 6% 7% 28%	3285
	21st to end	Night	18% 13% 6% 11% 7% 6% 5% 4 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	53% 9% 12% 21% 6%	3435
	11th to 20th	Day	48% 6% 16% 21% 8% 1	3480
	21st to end	Day	46% 6% 13% 21% 12% 1	3815
April	1st to 10th	Day	51% 7% 11% 16% 12% 2	2267
	11th to 20th	Day	49% 6% 10% 17% 15% 3	2254
	21st to end	Day	50% 6% 10% 20% 12% 2	2381
May	1st to 10th	Day	56% 7% 8% 19% 10% 1	4120
	11th to 20th	Day	54% 7% 12% 17% 8% 1	4256
	21st to end	Day	38% 9% 15% 22% 14% 2	4837
June	1st to 10th	Day	44% 8% 12% 22% 13% 1	2660
	11th to 20th	Day	43% 9% 15% 19% 13% 1	2660
	21st to end	Day	39% 9% 14% 25% 12% 1	2660
July	1st to 10th	Day	39% 10% 14% 24% 11% 3	4370
	11th to 20th	Day	36% 9% 16% 24% 15%	4209
	21st to end	Day	44% 7% 10% 22% 16% 1	4324
August	1st to 10th	Day	47% 10% 15% 20% 8%	4091
	11th to 20th	Day	43% 9% 11% 26% 10% 1	4083
	21st to end	Day	37% 7% 13% 27% 13% 2	4180
September	1st to 10th	Day	41% 7% 10% 21% 16% 4	2280
	11th to 20th	Day	36% 5% 12% 27% 18% 2	2225
	21st to end	Day	48% 6% 13% 18% 14% 1	2013
October	1st to 10th	Day	38% 6% 9% 26% 18% 3	3160
	11th to 20th	Day	40% 7% 10% 23% 14% 5%	3140
	21st to end	Day	31% 5% 14% 29% 19% 1	3428
November	1st to 10th	Day	39% 6% 16% 20% 15% 4	1821
	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	51% 7% 13% 21% 7% 1	3418
	11th to 20th	Night	43% 6% 16% 26% 8% 1	3480
	21st to end	Night	42% 6% 13% 21% 17% 2	3817
April	1st to 10th	Night	51% 7% 11% 17% 13% 1	1911
	11th to 20th	Night	43% 6% 13% 20% 15% 2	1875
	21st to end	Night	44% 6% 11% 24% 12% 3	1815
May	1st to 10th	Night	56% 6% 8% 17% 10% 2	2840
	11th to 20th	Night	52% 8% 14% 17% 8% 1	2638
	21st to end	Night	38% 10% 17% 21% 11% 4	2739
June	1st to 10th	Night	37% 8% 13% 26% 14% 1	1520
	11th to 20th	Night	36% 10% 15% 24% 13% 2	1520
	21st to end	Night	32% 10% 17% 26% 14% 1	1520
July	1st to 10th	Night	37% 11% 14% 21% 14% 3	2480
	11th to 20th	Night	32% 9% 18% 24% 16% 1	2623
	21st to end	Night	40% 9% 12% 18% 19% 2	2988
August	1st to 10th	Night	42% 10% 17% 22% 9%	2814
	11th to 20th	Night	38% 8% 13% 28% 12% 1	2812
	21st to end	Night	35% 7% 13% 31% 12% 2	3444
September	1st to 10th	Night	39% 6% 10% 22% 18% 3	1900
	11th to 20th	Night	31% 6% 13% 29% 20% 1	1951
	21st to end	Night	43% 6% 12% 22% 16% 1	2166
October	1st to 10th	Night	35% 5% 11% 26% 21% 1	3800
	11th to 20th	Night	32% 7% 11% 25% 19% 6%	3779
	21st to end	Night	31% 5% 13% 27% 21% 2	4120
November	1st to 10th	Night	37% 6% 14% 22% 18% 3	2328
	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% 27% 14% 5% 1	460
	11th to 20th	Day	26% 19% 26% 17% 8% 3	452
	21st to end	Day	31% 20% 28% 14% 6% 1	460
May	1st to 10th	Day	31% 18% 25% 15% 8% 3	463
	11th to 20th	Day	25% 17% 29% 16% 10% 3	487
	21st to end	Day	18% 14% 27% 23% 13% 5%	529
June	1st to 10th	Day	19% 17% 29% 21% 13% 2	490
	11th to 20th	Day	18% 13% 27% 26% 12% 3	490
	21st to end	Day	15% 14% 31% 26% 13% 2	490
July	1st to 10th	Day	10% 8% 31% 27% 17% 8%	485
	11th to 20th	Day	6% 10% 31% 31% 16% 6%	484
	21st to end	Day	11% 10% 30% 28% 16% 5%	532
August	1st to 10th	Day	13% 8% 26% 27% 18% 8%	486
	11th to 20th	Day	14% 8% 26% 25% 18% 9%	479
	21st to end	Day	14% 8% 24% 27% 15% 11%	539
September	1st to 10th	Day	20% 8% 20% 26% 17% 9%	490
	11th to 20th	Day	16% 5% 22% 29% 20% 8%	490
	21st to end	Day	29% 14% 22% 18% 12% 5%	490
October	1st to 10th	Day	21% 13% 21% 25% 16% 4	490
	11th to 20th	Day	25% 18% 26% 22% 9% 2	490
	21st to end	Day	21% 21% 30% 20% 7% 1	539
November	1st to 10th	Day	21% 16% 29% 20% 13% 2	436
	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	25% 23% 30% 19% 4	760
	11th to 20th	Night	21% 17% 27% 28% 7% 1	751
	21st to end	Night	22% 14% 26% 31% 6%	675
May	1st to 10th	Night	23% 12% 24% 31% 10% 1	570
	11th to 20th	Night	20% 9% 26% 35% 10%	464
	21st to end	Night	12% 9% 23% 36% 18% 2	411
June	1st to 10th	Night	11% 7% 26% 39% 16% 1	380
	11th to 20th	Night	12% 7% 25% 39% 17% 1	380
	21st to end	Night	10% 5% 28% 42% 16%	380
July	1st to 10th	Night	10% 4 18% 44% 21% 2	370
	11th to 20th	Night	7% 4 18% 41% 29% 2	454
	21st to end	Night	9% 4 22% 42% 23% 1	624
August	1st to 10th	Night	9% 2 17% 42% 29% 1	567
	11th to 20th	Night	11% 5% 16% 38% 26% 3	564
	21st to end	Night	14% 3 18% 37% 25% 3	817
September	1st to 10th	Night	17% 4 18% 35% 23% 3	760
	11th to 20th	Night	12% 6% 17% 32% 29% 4	760
	21st to end	Night	23% 7% 21% 28% 18% 3	760
October	1st to 10th	Night	18% 9% 23% 30% 18% 2	760
	11th to 20th	Night	20% 13% 29% 27% 10% 1	760
	21st to end	Night	24% 15% 26% 27% 8%	836
November	1st to 10th	Night	14% 13% 31% 31% 10% 1	755
	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 2024-11-01 22:47:53. Version ac07

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