Clarion University of Pennsylvania
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Clarion University of Pennsylvania clear sky chart from 2005-11-06 to 2024-11-08.

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% 11% 4 8% 5% 5% 4 4 5% 7% 30%	101280
	Night	18% 12% 4 9% 5% 4 4 3 5% 6% 30%	97760
Transparency	Day	54% 3 11% 21% 10% 1	104922
	Night	55% 3 10% 20% 11% 1	102258
Seeing	Day	25% 14% 28% 20% 10% 3	14680
	Night	24% 12% 27% 26% 11% 1	24227

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	18% 24% 11% 13% 4 4 3 2 2 4 16%	2654
	11th to 20th	Day	12% 21% 10% 18% 8% 5% 3 2 2 3 16%	2840
	21st to end	Day	26% 18% 9% 16% 7% 4 3 2 3 3 9%	3124
February	1st to 10th	Day	18% 20% 5% 12% 8% 5% 4 2 4 4 18%	1710
	11th to 20th	Day	16% 14% 7% 14% 8% 5% 5% 3 5% 5% 19%	1663
	21st to end	Day	21% 16% 3 11% 5% 5% 5% 3 4 5% 23%	1542
March	1st to 10th	Day	21% 10% 4 9% 5% 4 4 4 5% 7% 28%	3435
	11th to 20th	Day	13% 15% 6% 10% 5% 5% 5% 3 4 5% 29%	3480
	21st to end	Day	18% 12% 3 8% 5% 5% 5% 4 5% 7% 30%	3815
April	1st to 10th	Day	17% 15% 3 7% 5% 4 4 3 5% 7% 29%	2228
	11th to 20th	Day	18% 13% 3 7% 5% 4 4 4 5% 5% 32%	2258
	21st to end	Day	23% 10% 3 6% 4 4 4 3 4 6% 32%	2470
May	1st to 10th	Day	24% 10% 3 7% 5% 4 4 4 6% 6% 28%	4082
	11th to 20th	Day	21% 9% 3 8% 5% 5% 5% 4 6% 8% 27%	4171
	21st to end	Day	13% 6% 2 7% 5% 4 5% 4 6% 8% 39%	4823
June	1st to 10th	Day	16% 8% 3 6% 5% 5% 5% 4 7% 8% 33%	2660
	11th to 20th	Day	15% 7% 3 7% 5% 6% 5% 4 6% 9% 34%	2660
	21st to end	Day	16% 6% 2 6% 4 5% 5% 4 8% 9% 35%	2660
July	1st to 10th	Day	10% 7% 3 7% 5% 5% 5% 5% 7% 9% 38%	4440
	11th to 20th	Day	11% 6% 2 6% 5% 6% 5% 4 7% 9% 38%	4199
	21st to end	Day	10% 7% 3 7% 5% 5% 6% 5% 7% 8% 37%	4466
August	1st to 10th	Day	17% 9% 4 9% 5% 5% 6% 4 6% 8% 28%	4104
	11th to 20th	Day	13% 8% 3 7% 5% 5% 6% 5% 7% 9% 33%	4044
	21st to end	Day	11% 6% 2 6% 5% 5% 6% 5% 7% 10% 37%	4281
September	1st to 10th	Day	18% 7% 3 6% 4 4 3 3 4 6% 43%	2280
	11th to 20th	Day	12% 8% 3 6% 4 4 4 5% 6% 7% 40%	2155
	21st to end	Day	21% 8% 4 7% 5% 4 4 3 5% 7% 33%	2056
October	1st to 10th	Day	18% 9% 2 6% 4 4 4 4 6% 7% 36%	1900
	11th to 20th	Day	22% 9% 2 6% 5% 4 5% 3 5% 6% 32%	1900
	21st to end	Day	24% 12% 3 7% 4 4 4 4 5% 6% 28%	2090
November	1st to 10th	Day	12% 9% 3 7% 5% 4 5% 4 5% 7% 39%	1848
	11th to 20th	Day	19% 14% 4 8% 5% 4 5% 3 5% 5% 29%	1520
	21st to end	Day	20% 19% 5% 7% 5% 4 5% 3 5% 6% 22%	1520
December	1st to 10th	Day	20% 24% 7% 12% 6% 4 4 3 3 4 15%	1520
	11th to 20th	Day	19% 19% 9% 11% 4 4 4 3 4 5% 18%	1910
	21st to end	Day	27% 24% 7% 10% 5% 3 3 2 3 3 12%	2772
January	1st to 10th	Night	17% 22% 10% 15% 5% 4 3 2 3 4 15%	4287
	11th to 20th	Night	16% 19% 9% 17% 6% 6% 5% 3 4 4 13%	4120
	21st to end	Night	27% 17% 9% 13% 5% 3 3 2 3 3 14%	4532
February	1st to 10th	Night	19% 15% 5% 11% 7% 5% 4 3 3 4 22%	2470
	11th to 20th	Night	18% 15% 5% 13% 5% 5% 5% 3 4 5% 22%	2403
	21st to end	Night	21% 13% 4 11% 5% 6% 4 4 3 4 24%	1908
March	1st to 10th	Night	21% 14% 3 7% 5% 4 3 3 4 6% 30%	3418
	11th to 20th	Night	17% 15% 7% 8% 4 3 3 3 4 6% 30%	3480
	21st to end	Night	17% 10% 3 7% 5% 4 3 3 4 6% 37%	3817
April	1st to 10th	Night	18% 13% 4 7% 5% 4 4 3 5% 6% 31%	1952
	11th to 20th	Night	18% 10% 3 5% 4 4 4 4 6% 7% 36%	1875
	21st to end	Night	15% 10% 3 8% 5% 4 4 3 5% 8% 35%	1723
May	1st to 10th	Night	28% 8% 3 6% 4 4 4 4 4 5% 30%	2813
	11th to 20th	Night	19% 11% 3 6% 4 4 4 4 6% 6% 33%	2720
	21st to end	Night	12% 7% 2 5% 4 4 4 4 6% 10% 41%	2732
June	1st to 10th	Night	10% 6% 2 7% 5% 4 4 4 6% 9% 42%	1520
	11th to 20th	Night	12% 6% 2 7% 5% 5% 5% 5% 6% 9% 40%	1520
	21st to end	Night	13% 7% 3 6% 5% 3 5% 4 6% 9% 41%	1520
July	1st to 10th	Night	12% 8% 3 8% 5% 5% 5% 3 6% 8% 39%	2520
	11th to 20th	Night	11% 6% 2 6% 5% 4 4 4 7% 9% 43%	2743
	21st to end	Night	11% 7% 3 6% 5% 5% 5% 4 6% 7% 42%	3087
August	1st to 10th	Night	14% 9% 4 9% 4 4 4 4 5% 7% 35%	2825
	11th to 20th	Night	15% 7% 3 7% 5% 4 4 4 6% 7% 39%	2785
	21st to end	Night	9% 5% 2 5% 4 4 6% 4 6% 9% 45%	3343
September	1st to 10th	Night	15% 5% 2 5% 3 4 4 4 4 6% 48%	1900
	11th to 20th	Night	11% 5% 2 5% 3 4 4 3 5% 8% 51%	2023
	21st to end	Night	20% 8% 3 6% 5% 4 4 3 5% 6% 37%	2123
October	1st to 10th	Night	16% 7% 2 7% 4 3 3 3 5% 8% 42%	2280
	11th to 20th	Night	19% 8% 3 7% 4 4 4 3 5% 7% 37%	2280
	21st to end	Night	22% 11% 2 7% 4 4 4 4 4 6% 32%	2508
November	1st to 10th	Night	14% 9% 3 6% 4 3 4 3 5% 6% 42%	2384
	11th to 20th	Night	19% 15% 3 7% 5% 5% 4 3 5% 6% 27%	2660
	21st to end	Night	20% 16% 5% 8% 5% 4 4 3 5% 6% 25%	2660
December	1st to 10th	Night	22% 18% 6% 12% 5% 5% 4 3 5% 4 15%	2660
	11th to 20th	Night	19% 18% 7% 12% 6% 4 3 3 3 4 21%	3285
	21st to end	Night	25% 20% 7% 11% 6% 4 5% 3 4 4 11%	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	77% 1 6% 11% 4	2655
	11th to 20th	Day	77% 1 8% 10% 3	2840
	21st to end	Day	83% 1 6% 6% 2 1	3124
February	1st to 10th	Day	72% 1 8% 12% 6%	1710
	11th to 20th	Day	68% 3 8% 15% 6%	1672
	21st to end	Day	65% 2 9% 16% 6% 1	1542
March	1st to 10th	Day	58% 2 9% 25% 6%	3435
	11th to 20th	Day	58% 2 15% 18% 5% 1	3480
	21st to end	Day	56% 2 9% 21% 12% 1	3815
April	1st to 10th	Day	56% 3 10% 17% 12% 1	2228
	11th to 20th	Day	54% 3 10% 18% 13% 2	2258
	21st to end	Day	54% 3 9% 21% 12% 2	2470
May	1st to 10th	Day	57% 2 8% 24% 7% 1	4120
	11th to 20th	Day	57% 3 9% 21% 8% 1	4175
	21st to end	Day	43% 4 13% 25% 14% 2	4837
June	1st to 10th	Day	48% 4 11% 24% 12% 1	2660
	11th to 20th	Day	47% 4 14% 21% 13% 1	2660
	21st to end	Day	44% 5% 12% 27% 12% 1	2660
July	1st to 10th	Day	42% 6% 11% 25% 15% 2	4370
	11th to 20th	Day	41% 4 11% 28% 15%	4127
	21st to end	Day	43% 5% 12% 22% 17% 1	4324
August	1st to 10th	Day	53% 5% 11% 22% 7%	4091
	11th to 20th	Day	45% 5% 13% 28% 9% 1	4083
	21st to end	Day	41% 6% 12% 28% 12% 1	4281
September	1st to 10th	Day	44% 4 9% 23% 17% 2	2280
	11th to 20th	Day	42% 5% 11% 26% 16% 1	2155
	21st to end	Day	52% 3 10% 22% 13%	2056
October	1st to 10th	Day	40% 4 10% 28% 18% 1	3160
	11th to 20th	Day	47% 3 12% 21% 14% 4	3140
	21st to end	Day	44% 3 13% 28% 13%	3428
November	1st to 10th	Day	46% 3 12% 21% 15% 2	1848
	11th to 20th	Day	58% 3 10% 19% 8% 2	1520
	21st to end	Day	64% 3 11% 15% 5% 1	1520
December	1st to 10th	Day	75% 3 10% 9% 3	1520
	11th to 20th	Day	71% 2 11% 13% 3	1906
	21st to end	Day	80% 2 8% 9% 1	2772
January	1st to 10th	Night	76% 1 7% 13% 3	4287
	11th to 20th	Night	78% 2 8% 10% 2	4120
	21st to end	Night	78% 1 7% 11% 3	4532
February	1st to 10th	Night	68% 2 9% 15% 6%	2470
	11th to 20th	Night	67% 3 8% 16% 6%	2405
	21st to end	Night	65% 2 8% 15% 8% 1	1908
March	1st to 10th	Night	58% 2 8% 26% 6%	3418
	11th to 20th	Night	58% 2 12% 20% 6% 1	3480
	21st to end	Night	50% 2 6% 24% 16% 2	3817
April	1st to 10th	Night	56% 3 9% 19% 13% 1	1952
	11th to 20th	Night	48% 4 10% 21% 14% 2	1875
	21st to end	Night	49% 3 9% 25% 12% 3	1723
May	1st to 10th	Night	58% 3 8% 18% 11% 2	2840
	11th to 20th	Night	52% 4 10% 24% 9% 1	2721
	21st to end	Night	39% 4 13% 25% 15% 4	2739
June	1st to 10th	Night	39% 4 14% 26% 15% 1	1520
	11th to 20th	Night	40% 6% 14% 25% 14% 2	1520
	21st to end	Night	41% 5% 13% 24% 16% 1	1520
July	1st to 10th	Night	45% 5% 9% 22% 18% 2	2480
	11th to 20th	Night	37% 4 15% 27% 16% 1	2693
	21st to end	Night	42% 5% 10% 20% 22% 2	2988
August	1st to 10th	Night	48% 5% 13% 23% 11% 1	2814
	11th to 20th	Night	43% 4 12% 30% 10% 1	2812
	21st to end	Night	34% 6% 13% 32% 13% 2	3343
September	1st to 10th	Night	39% 4 10% 25% 18% 4	1900
	11th to 20th	Night	33% 4 11% 28% 22% 1	2023
	21st to end	Night	49% 3 11% 20% 15% 1	2123
October	1st to 10th	Night	40% 3 9% 25% 22% 1	3800
	11th to 20th	Night	42% 4 12% 21% 16% 6%	3779
	21st to end	Night	40% 3 13% 24% 19% 1	4120
November	1st to 10th	Night	44% 3 12% 24% 14% 3	2384
	11th to 20th	Night	59% 2 9% 18% 9% 3	2660
	21st to end	Night	62% 3 10% 20% 5% 1	2660
December	1st to 10th	Night	73% 3 9% 10% 4	2660
	11th to 20th	Night	70% 2 10% 14% 4	3288
	21st to end	Night	78% 2 9% 10% 1	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% 30% 25% 9% 3	220
	11th to 20th	Day	35% 28% 28% 6% 1 2	270
	21st to end	Day	33% 23% 34% 8% 2	297
February	1st to 10th	Day	32% 26% 33% 9% 1	270
	11th to 20th	Day	39% 24% 30% 7% 1	270
	21st to end	Day	40% 23% 29% 8% 1	279
March	1st to 10th	Day	30% 21% 32% 15% 2	460
	11th to 20th	Day	34% 17% 33% 11% 3 1	460
	21st to end	Day	33% 21% 27% 14% 4 1	506
April	1st to 10th	Day	31% 21% 25% 16% 5% 1	460
	11th to 20th	Day	28% 19% 27% 15% 8% 2	452
	21st to end	Day	29% 18% 31% 16% 6% 1	460
May	1st to 10th	Day	30% 13% 29% 18% 8% 2	463
	11th to 20th	Day	27% 11% 28% 21% 9% 4	487
	21st to end	Day	17% 10% 26% 25% 16% 5%	529
June	1st to 10th	Day	20% 13% 28% 24% 13% 2	490
	11th to 20th	Day	20% 12% 25% 27% 13% 3	490
	21st to end	Day	19% 12% 30% 25% 12% 2	490
July	1st to 10th	Day	15% 6% 23% 27% 21% 8%	485
	11th to 20th	Day	13% 5% 29% 27% 19% 6%	484
	21st to end	Day	14% 5% 30% 27% 17% 7%	532
August	1st to 10th	Day	16% 7% 23% 27% 21% 7%	486
	11th to 20th	Day	18% 5% 24% 28% 14% 10%	479
	21st to end	Day	15% 6% 24% 29% 18% 8%	539
September	1st to 10th	Day	21% 7% 20% 26% 20% 7%	490
	11th to 20th	Day	14% 4 21% 31% 21% 9%	490
	21st to end	Day	28% 10% 24% 22% 12% 3	490
October	1st to 10th	Day	20% 10% 27% 22% 16% 5%	490
	11th to 20th	Day	25% 16% 31% 19% 7% 2	490
	21st to end	Day	34% 13% 29% 19% 6%	539
November	1st to 10th	Day	21% 17% 31% 19% 9% 2	415
	11th to 20th	Day	34% 20% 27% 13% 4 1	180
	21st to end	Day	27% 26% 34% 11% 1	180
December	1st to 10th	Day	39% 21% 28% 8% 2 2	180
	11th to 20th	Day	37% 17% 36% 7% 3 1	180
	21st to end	Day	35% 21% 30% 11% 3	198
January	1st to 10th	Night	29% 21% 33% 13% 4	760
	11th to 20th	Night	33% 20% 29% 15% 2	760
	21st to end	Night	27% 20% 32% 18% 2	836
February	1st to 10th	Night	31% 17% 29% 21% 1	760
	11th to 20th	Night	30% 20% 35% 14% 1	743
	21st to end	Night	30% 21% 30% 17% 2	628
March	1st to 10th	Night	25% 18% 34% 20% 3	760
	11th to 20th	Night	29% 18% 28% 19% 6%	760
	21st to end	Night	26% 15% 35% 19% 5%	836
April	1st to 10th	Night	27% 14% 33% 20% 6%	760
	11th to 20th	Night	24% 15% 30% 22% 7% 1	751
	21st to end	Night	20% 9% 36% 28% 6% 1	583
May	1st to 10th	Night	24% 10% 24% 33% 9% 1	570
	11th to 20th	Night	22% 9% 28% 31% 9%	508
	21st to end	Night	12% 5% 26% 36% 18% 2	411
June	1st to 10th	Night	11% 5% 29% 38% 16% 1	380
	11th to 20th	Night	13% 6% 22% 43% 16%	380
	21st to end	Night	15% 4 28% 38% 14% 1	380
July	1st to 10th	Night	12% 2 19% 42% 21% 3	370
	11th to 20th	Night	12% 2 17% 40% 26% 3	498
	21st to end	Night	13% 4 13% 42% 27% 1	624
August	1st to 10th	Night	13% 2 14% 42% 27% 2	567
	11th to 20th	Night	14% 4 11% 39% 28% 4	564
	21st to end	Night	13% 4 18% 34% 27% 4	755
September	1st to 10th	Night	18% 5% 20% 31% 23% 3	760
	11th to 20th	Night	14% 4 17% 34% 27% 4	760
	21st to end	Night	23% 9% 21% 28% 16% 4	760
October	1st to 10th	Night	20% 6% 24% 28% 19% 3	760
	11th to 20th	Night	25% 10% 28% 26% 10% 1	760
	21st to end	Night	29% 12% 28% 25% 6%	836
November	1st to 10th	Night	22% 10% 30% 28% 9%	771
	11th to 20th	Night	28% 17% 28% 20% 6% 1	760
	21st to end	Night	31% 15% 29% 20% 5%	760
December	1st to 10th	Night	33% 20% 28% 15% 4	760
	11th to 20th	Night	30% 21% 28% 16% 4	760
	21st to end	Night	31% 19% 30% 19% 2	836

Page generated at 2024-11-05 08:15:52. Version ac07

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