Susquehanna University
Clear Sky Chart
History

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

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	16% 8% 3 7% 5% 5% 5% 4 6% 7% 36%	101430
	Night	16% 9% 3 7% 5% 4 4 3 5% 7% 37%	97635
Transparency	Day	45% 7% 13% 22% 12% 2	105032
	Night	44% 7% 12% 22% 13% 2	102121
Seeing	Day	21% 16% 27% 20% 11% 3	14835
	Night	19% 13% 29% 27% 10% 1	24181

By Month

Percentage Cloud Cover NE (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	15% 12% 3 7% 5% 4 5% 3 4 4 37%	2517
	11th to 20th	Day	13% 14% 6% 15% 6% 6% 5% 3 4 6% 22%	2716
	21st to end	Day	20% 14% 5% 11% 5% 4 4 4 4 6% 24%	3124
February	1st to 10th	Day	17% 11% 3 8% 6% 5% 5% 4 5% 6% 28%	1710
	11th to 20th	Day	14% 11% 3 10% 5% 6% 4 4 5% 7% 32%	1699
	21st to end	Day	18% 11% 3 9% 6% 4 4 4 4 4 32%	1570
March	1st to 10th	Day	25% 8% 3 7% 5% 4 4 3 4 5% 33%	3298
	11th to 20th	Day	11% 9% 3 8% 5% 4 5% 3 5% 7% 39%	3480
	21st to end	Day	18% 10% 3 7% 3 3 3 2 4 5% 41%	3927
April	1st to 10th	Day	16% 10% 3 8% 5% 5% 4 4 6% 6% 34%	2280
	11th to 20th	Day	16% 8% 3 6% 5% 4 4 4 5% 5% 39%	2254
	21st to end	Day	18% 7% 2 6% 5% 5% 4 4 6% 6% 37%	2280
May	1st to 10th	Day	27% 6% 3 7% 4 4 5% 3 4 6% 31%	4166
	11th to 20th	Day	23% 8% 4 8% 5% 5% 5% 4 5% 6% 27%	4398
	21st to end	Day	12% 5% 2 5% 4 5% 5% 4 6% 9% 42%	4837
June	1st to 10th	Day	13% 6% 2 7% 6% 5% 5% 5% 6% 8% 38%	2660
	11th to 20th	Day	13% 6% 2 7% 5% 5% 5% 4 6% 9% 38%	2660
	21st to end	Day	11% 5% 2 6% 4 5% 5% 4 7% 10% 41%	2660
July	1st to 10th	Day	6% 5% 2 7% 6% 6% 6% 6% 8% 10% 38%	4440
	11th to 20th	Day	6% 6% 2 7% 5% 5% 6% 5% 8% 11% 38%	4440
	21st to end	Day	10% 8% 3 8% 6% 5% 6% 5% 6% 8% 34%	4570
August	1st to 10th	Day	19% 7% 3 7% 5% 5% 5% 5% 6% 8% 31%	4104
	11th to 20th	Day	14% 6% 3 6% 4 6% 6% 5% 7% 9% 36%	3916
	21st to end	Day	13% 6% 2 5% 4 4 5% 3 6% 10% 43%	4180
September	1st to 10th	Day	16% 6% 2 5% 4 3 4 4 5% 6% 45%	2280
	11th to 20th	Day	14% 5% 2 4 4 4 4 3 5% 7% 50%	2280
	21st to end	Day	21% 8% 2 6% 3 4 3 3 4 7% 38%	2008
October	1st to 10th	Day	18% 7% 2 6% 4 4 4 3 5% 6% 40%	1900
	11th to 20th	Day	17% 7% 2 6% 4 4 5% 4 5% 7% 39%	1900
	21st to end	Day	18% 7% 2 6% 5% 5% 4 4 5% 6% 37%	2090
November	1st to 10th	Day	13% 7% 2 5% 4 4 4 3 5% 6% 46%	1730
	11th to 20th	Day	19% 7% 2 6% 4 6% 4 4 6% 5% 38%	1638
	21st to end	Day	17% 7% 2 7% 5% 5% 4 5% 6% 6% 36%	1520
December	1st to 10th	Day	18% 11% 5% 9% 6% 4 5% 4 5% 6% 28%	1520
	11th to 20th	Day	21% 10% 2 7% 5% 3 3 3 6% 7% 33%	1906
	21st to end	Day	21% 12% 4 9% 6% 5% 5% 4 5% 4 23%	2772
January	1st to 10th	Night	15% 13% 4 8% 6% 4 4 3 4 6% 33%	4429
	11th to 20th	Night	16% 10% 5% 11% 5% 5% 4 3 5% 5% 30%	4242
	21st to end	Night	23% 11% 3 10% 5% 4 4 3 5% 5% 27%	4532
February	1st to 10th	Night	17% 11% 3 7% 6% 4 4 4 6% 5% 34%	2470
	11th to 20th	Night	16% 9% 3 8% 6% 5% 4 4 5% 7% 33%	2366
	21st to end	Night	18% 10% 3 7% 6% 4 5% 3 5% 5% 34%	1884
March	1st to 10th	Night	22% 12% 3 7% 4 3 3 3 4 5% 33%	3537
	11th to 20th	Night	12% 12% 3 7% 5% 4 4 3 5% 5% 41%	3479
	21st to end	Night	16% 9% 3 6% 4 3 4 3 4 5% 43%	3704
April	1st to 10th	Night	17% 11% 3 7% 5% 4 4 4 5% 7% 33%	1900
	11th to 20th	Night	16% 7% 2 8% 5% 4 4 4 5% 8% 39%	1875
	21st to end	Night	18% 6% 2 6% 4 3 4 4 5% 7% 42%	1900
May	1st to 10th	Night	28% 8% 3 6% 4 4 4 3 4 6% 31%	2787
	11th to 20th	Night	22% 9% 3 7% 4 5% 4 4 7% 7% 28%	2495
	21st to end	Night	11% 6% 3 7% 5% 4 5% 4 6% 9% 41%	2738
June	1st to 10th	Night	14% 6% 3 5% 4 4 4 4 6% 8% 43%	1520
	11th to 20th	Night	11% 6% 2 6% 6% 4 4 4 7% 9% 41%	1520
	21st to end	Night	10% 5% 2 5% 4 4 5% 5% 7% 10% 41%	1520
July	1st to 10th	Night	9% 5% 2 7% 5% 5% 6% 4 6% 9% 41%	2520
	11th to 20th	Night	7% 5% 3 7% 5% 6% 6% 5% 7% 11% 38%	2520
	21st to end	Night	13% 7% 3 5% 5% 5% 4 4 6% 8% 41%	2979
August	1st to 10th	Night	19% 7% 2 7% 4 5% 4 4 6% 8% 34%	2825
	11th to 20th	Night	13% 8% 3 7% 4 4 4 3 5% 8% 41%	2880
	21st to end	Night	13% 5% 2 5% 4 3 4 4 7% 9% 44%	3476
September	1st to 10th	Night	14% 5% 2 6% 5% 3 4 3 5% 7% 46%	1900
	11th to 20th	Night	11% 5% 2 5% 3 3 3 3 4 7% 53%	1900
	21st to end	Night	21% 5% 2 6% 2 4 4 3 5% 6% 42%	2168
October	1st to 10th	Night	19% 7% 2 5% 4 4 3 3 5% 7% 41%	2280
	11th to 20th	Night	16% 6% 2 5% 4 3 4 3 4 7% 44%	2280
	21st to end	Night	19% 7% 2 6% 4 4 4 3 5% 7% 40%	2508
November	1st to 10th	Night	11% 8% 2 5% 4 3 4 3 4 6% 50%	2469
	11th to 20th	Night	17% 10% 2 6% 4 3 4 3 5% 6% 40%	2540
	21st to end	Night	16% 9% 3 6% 6% 4 4 3 5% 7% 37%	2660
December	1st to 10th	Night	18% 12% 3 8% 4 4 5% 4 5% 7% 30%	2660
	11th to 20th	Night	19% 11% 3 7% 4 4 4 3 6% 5% 34%	3288
	21st to end	Night	20% 11% 4 9% 5% 5% 5% 4 6% 7% 25%	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	48% 6% 15% 22% 7% 2	2518
	11th to 20th	Day	62% 7% 10% 12% 8% 1	2716
	21st to end	Day	60% 6% 11% 17% 5% 1	3124
February	1st to 10th	Day	54% 6% 12% 18% 9% 1	1710
	11th to 20th	Day	52% 7% 9% 22% 9% 1	1708
	21st to end	Day	54% 5% 11% 19% 9% 2	1570
March	1st to 10th	Day	51% 7% 10% 24% 7% 1	3301
	11th to 20th	Day	40% 7% 16% 23% 11% 3	3480
	21st to end	Day	46% 4 11% 20% 16% 2	3927
April	1st to 10th	Day	48% 7% 11% 18% 12% 4	2280
	11th to 20th	Day	44% 6% 11% 20% 14% 3	2254
	21st to end	Day	44% 7% 10% 21% 14% 4	2280
May	1st to 10th	Day	53% 7% 9% 19% 10% 2	4178
	11th to 20th	Day	54% 9% 13% 15% 8% 1	4402
	21st to end	Day	35% 8% 14% 25% 15% 2	4837
June	1st to 10th	Day	43% 8% 12% 22% 14% 2	2660
	11th to 20th	Day	42% 8% 14% 21% 13% 2	2660
	21st to end	Day	36% 9% 15% 27% 13% 1	2660
July	1st to 10th	Day	40% 9% 14% 25% 11% 1	4370
	11th to 20th	Day	37% 8% 16% 25% 13% 1	4365
	21st to end	Day	44% 8% 12% 18% 16% 1	4424
August	1st to 10th	Day	49% 8% 14% 19% 9%	4091
	11th to 20th	Day	42% 7% 13% 28% 10% 1	3955
	21st to end	Day	36% 5% 13% 31% 13% 2	4180
September	1st to 10th	Day	40% 7% 11% 22% 18% 3	2280
	11th to 20th	Day	33% 6% 11% 25% 22% 3	2280
	21st to end	Day	47% 6% 10% 18% 17% 2	2008
October	1st to 10th	Day	40% 5% 9% 23% 18% 4	3160
	11th to 20th	Day	35% 6% 10% 27% 20% 2	3140
	21st to end	Day	30% 4 15% 31% 19% 1	3428
November	1st to 10th	Day	38% 5% 14% 24% 16% 3	1730
	11th to 20th	Day	45% 7% 12% 22% 13% 2	1638
	21st to end	Day	47% 6% 13% 26% 8% 1	1520
December	1st to 10th	Day	56% 7% 14% 16% 7% 1	1520
	11th to 20th	Day	50% 6% 17% 21% 5%	1906
	21st to end	Day	60% 7% 15% 13% 5%	2772
January	1st to 10th	Night	50% 7% 13% 21% 7% 2	4429
	11th to 20th	Night	54% 8% 14% 16% 7% 1	4242
	21st to end	Night	58% 6% 11% 17% 7% 1	4532
February	1st to 10th	Night	49% 7% 13% 22% 8% 1	2470
	11th to 20th	Night	50% 6% 12% 20% 11% 1	2368
	21st to end	Night	50% 6% 10% 19% 13% 2	1884
March	1st to 10th	Night	52% 6% 10% 21% 9% 1	3547
	11th to 20th	Night	41% 7% 13% 26% 10% 1	3480
	21st to end	Night	44% 5% 8% 20% 19% 4	3704
April	1st to 10th	Night	50% 6% 10% 18% 13% 2	1900
	11th to 20th	Night	43% 6% 12% 21% 17% 2	1875
	21st to end	Night	41% 7% 12% 22% 15% 3	1900
May	1st to 10th	Night	55% 6% 8% 19% 9% 2	2794
	11th to 20th	Night	52% 11% 14% 12% 10% 1	2496
	21st to end	Night	38% 9% 15% 20% 13% 5%	2739
June	1st to 10th	Night	38% 8% 12% 23% 18% 1	1520
	11th to 20th	Night	37% 9% 15% 22% 15% 2	1520
	21st to end	Night	35% 9% 14% 27% 14% 1	1520
July	1st to 10th	Night	39% 8% 16% 17% 16% 4	2480
	11th to 20th	Night	37% 9% 14% 24% 14% 1	2472
	21st to end	Night	40% 8% 13% 17% 21% 2	2884
August	1st to 10th	Night	46% 8% 15% 21% 9%	2814
	11th to 20th	Night	41% 7% 12% 24% 15%	2907
	21st to end	Night	34% 7% 12% 32% 14% 1	3476
September	1st to 10th	Night	38% 6% 11% 24% 18% 3	1900
	11th to 20th	Night	31% 6% 11% 29% 21% 3	1900
	21st to end	Night	42% 5% 10% 22% 19% 2	2168
October	1st to 10th	Night	42% 5% 12% 20% 20% 1	3800
	11th to 20th	Night	31% 5% 10% 29% 23% 2	3779
	21st to end	Night	31% 5% 14% 28% 20% 2	4120
November	1st to 10th	Night	35% 5% 13% 25% 18% 3	2469
	11th to 20th	Night	44% 5% 11% 23% 14% 3	2540
	21st to end	Night	44% 6% 15% 23% 9% 2	2660
December	1st to 10th	Night	51% 8% 14% 18% 9%	2660
	11th to 20th	Night	51% 6% 13% 19% 10% 1	3288
	21st to end	Night	54% 8% 16% 17% 4	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% 24% 26% 14% 2 1	180
	11th to 20th	Day	32% 25% 31% 11% 1	236
	21st to end	Day	25% 34% 27% 10% 4	297
February	1st to 10th	Day	29% 28% 31% 11% 1	270
	11th to 20th	Day	31% 27% 37% 4 1	306
	21st to end	Day	33% 22% 28% 15% 2	382
March	1st to 10th	Day	31% 21% 28% 16% 3	460
	11th to 20th	Day	28% 26% 28% 14% 3 1	460
	21st to end	Day	28% 25% 26% 15% 4 2	506
April	1st to 10th	Day	24% 26% 29% 15% 5% 1	460
	11th to 20th	Day	23% 28% 23% 15% 7% 4	452
	21st to end	Day	25% 18% 34% 13% 7% 1	460
May	1st to 10th	Day	29% 21% 27% 14% 8% 2	463
	11th to 20th	Day	22% 19% 28% 20% 9% 2	487
	21st to end	Day	19% 10% 27% 21% 18% 5%	529
June	1st to 10th	Day	17% 13% 29% 25% 12% 3	490
	11th to 20th	Day	15% 14% 28% 25% 15% 3	490
	21st to end	Day	13% 13% 33% 26% 12% 3	490
July	1st to 10th	Day	11% 6% 27% 31% 19% 6%	485
	11th to 20th	Day	5% 7% 28% 33% 22% 5%	484
	21st to end	Day	11% 9% 29% 30% 16% 4	532
August	1st to 10th	Day	15% 8% 22% 28% 21% 7%	486
	11th to 20th	Day	13% 7% 25% 29% 19% 8%	479
	21st to end	Day	13% 8% 23% 30% 15% 11%	539
September	1st to 10th	Day	18% 10% 20% 24% 19% 10%	490
	11th to 20th	Day	15% 6% 23% 25% 22% 9%	490
	21st to end	Day	27% 14% 22% 19% 14% 4	490
October	1st to 10th	Day	23% 10% 24% 22% 16% 5%	490
	11th to 20th	Day	20% 15% 30% 22% 11% 2	490
	21st to end	Day	21% 17% 33% 19% 10% 1	539
November	1st to 10th	Day	20% 16% 28% 22% 11% 2	387
	11th to 20th	Day	27% 19% 28% 17% 9%	298
	21st to end	Day	23% 25% 35% 13% 3 1	180
December	1st to 10th	Day	29% 28% 29% 9% 4 1	180
	11th to 20th	Day	33% 22% 31% 11% 3	180
	21st to end	Day	26% 28% 26% 17% 3	198
January	1st to 10th	Night	20% 21% 40% 17% 3	760
	11th to 20th	Night	24% 19% 33% 21% 3	760
	21st to end	Night	17% 22% 37% 22% 2	836
February	1st to 10th	Night	24% 17% 34% 24% 1	760
	11th to 20th	Night	24% 23% 38% 15% 1	743
	21st to end	Night	26% 20% 34% 17% 2	628
March	1st to 10th	Night	23% 20% 32% 21% 3	760
	11th to 20th	Night	26% 18% 32% 20% 4	760
	21st to end	Night	24% 17% 34% 19% 6%	836
April	1st to 10th	Night	23% 20% 32% 21% 4	760
	11th to 20th	Night	20% 16% 33% 23% 7%	751
	21st to end	Night	20% 16% 31% 27% 6%	760
May	1st to 10th	Night	24% 11% 30% 24% 11%	550
	11th to 20th	Night	18% 8% 34% 32% 9%	374
	21st to end	Night	16% 8% 24% 37% 15%	411
June	1st to 10th	Night	14% 6% 24% 38% 18%	380
	11th to 20th	Night	13% 6% 26% 42% 12%	380
	21st to end	Night	12% 3 26% 46% 13% 1	380
July	1st to 10th	Night	13% 2 24% 38% 20% 2	370
	11th to 20th	Night	9% 3 17% 47% 23% 1	368
	21st to end	Night	11% 4 21% 41% 22% 1	555
August	1st to 10th	Night	13% 2 15% 42% 26% 2	567
	11th to 20th	Night	12% 4 15% 37% 28% 3	620
	21st to end	Night	11% 5% 19% 35% 28% 2	836
September	1st to 10th	Night	15% 4 23% 36% 20% 2	760
	11th to 20th	Night	12% 5% 21% 32% 26% 4	760
	21st to end	Night	21% 7% 22% 31% 17% 2	760
October	1st to 10th	Night	21% 9% 23% 26% 19% 2	760
	11th to 20th	Night	18% 11% 29% 31% 10% 1	760
	21st to end	Night	23% 12% 29% 28% 7%	836
November	1st to 10th	Night	15% 13% 31% 30% 10% 1	764
	11th to 20th	Night	21% 18% 30% 23% 7% 1	760
	21st to end	Night	20% 18% 33% 24% 6%	760
December	1st to 10th	Night	26% 17% 33% 19% 5%	760
	11th to 20th	Night	22% 17% 34% 24% 3	760
	21st to end	Night	23% 17% 34% 24% 2	836

Page generated at 2024-11-03 13:19:00. Version ac07

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