Williamsport
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Williamsport clear sky chart from 2005-11-06 to 2024-10-24.

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 8% 5% 5% 5% 4 6% 7% 34%	101304
	Night	17% 8% 3 7% 5% 4 4 4 5% 7% 35%	97448
Transparency	Day	47% 8% 13% 21% 11% 1	101067
	Night	46% 8% 13% 20% 11% 1	97304
Seeing	Day	22% 16% 26% 21% 11% 4	14734
	Night	21% 12% 26% 29% 11% 1	24061

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	14% 12% 4 9% 6% 6% 4 4 5% 5% 31%	2517
	11th to 20th	Day	13% 14% 7% 15% 7% 7% 5% 3 4 5% 20%	2689
	21st to end	Day	20% 15% 6% 11% 7% 5% 4 3 4 4 21%	3124
February	1st to 10th	Day	16% 14% 4 9% 7% 5% 5% 5% 5% 5% 26%	1710
	11th to 20th	Day	13% 11% 3 10% 7% 5% 5% 5% 6% 6% 30%	1682
	21st to end	Day	19% 10% 4 9% 7% 5% 4 3 3 6% 30%	1570
March	1st to 10th	Day	24% 9% 3 7% 5% 4 4 3 5% 5% 31%	3303
	11th to 20th	Day	11% 9% 3 8% 6% 5% 5% 4 5% 6% 38%	3480
	21st to end	Day	17% 10% 3 7% 4 5% 4 3 5% 6% 37%	3910
April	1st to 10th	Day	17% 10% 3 8% 6% 5% 5% 3 4 7% 33%	2280
	11th to 20th	Day	17% 9% 3 6% 5% 4 4 5% 5% 6% 36%	2254
	21st to end	Day	18% 6% 3 7% 5% 6% 4 4 5% 6% 36%	2304
May	1st to 10th	Day	27% 7% 2 6% 4 4 4 3 5% 6% 31%	4190
	11th to 20th	Day	21% 10% 4 9% 5% 5% 5% 3 5% 6% 27%	4398
	21st to end	Day	14% 5% 2 5% 4 5% 5% 4 7% 9% 41%	4837
June	1st to 10th	Day	14% 6% 2 7% 6% 5% 6% 4 6% 8% 35%	2660
	11th to 20th	Day	14% 6% 2 7% 6% 5% 4 4 7% 9% 36%	2660
	21st to end	Day	12% 5% 2 6% 5% 5% 5% 5% 7% 10% 38%	2660
July	1st to 10th	Day	7% 6% 2 7% 6% 6% 6% 5% 7% 10% 37%	4440
	11th to 20th	Day	7% 5% 2 7% 5% 5% 6% 5% 8% 11% 37%	4440
	21st to end	Day	10% 7% 3 8% 7% 6% 6% 5% 8% 7% 34%	4597
August	1st to 10th	Day	19% 7% 2 8% 5% 4 5% 4 6% 8% 31%	4104
	11th to 20th	Day	15% 6% 2 6% 5% 5% 6% 5% 7% 9% 33%	3933
	21st to end	Day	15% 6% 2 5% 3 4 5% 5% 6% 9% 41%	4180
September	1st to 10th	Day	17% 5% 2 5% 4 4 4 4 5% 8% 42%	2280
	11th to 20th	Day	13% 6% 2 5% 4 3 4 4 5% 6% 48%	2280
	21st to end	Day	22% 6% 3 7% 3 4 4 3 5% 6% 37%	2003
October	1st to 10th	Day	18% 7% 2 6% 4 4 4 3 5% 7% 40%	1900
	11th to 20th	Day	18% 6% 2 7% 4 5% 5% 4 6% 7% 35%	1900
	21st to end	Day	20% 7% 2 8% 5% 5% 4 4 6% 6% 33%	2010
November	1st to 10th	Day	13% 7% 2 7% 5% 4 5% 2 6% 6% 43%	1680
	11th to 20th	Day	17% 8% 2 7% 6% 4 4 4 6% 7% 35%	1611
	21st to end	Day	17% 8% 2 7% 6% 5% 4 4 6% 6% 34%	1520
December	1st to 10th	Day	20% 12% 5% 10% 7% 5% 5% 3 5% 5% 24%	1520
	11th to 20th	Day	21% 11% 3 8% 4 5% 4 4 5% 6% 29%	1906
	21st to end	Day	23% 13% 4 12% 6% 5% 5% 4 4 5% 20%	2772
January	1st to 10th	Night	17% 10% 3 9% 6% 5% 5% 3 5% 6% 30%	4429
	11th to 20th	Night	16% 9% 6% 12% 6% 5% 5% 3 6% 6% 25%	4266
	21st to end	Night	24% 12% 4 11% 5% 4 5% 3 5% 4 23%	4532
February	1st to 10th	Night	16% 12% 3 7% 5% 4 5% 4 6% 6% 31%	2470
	11th to 20th	Night	15% 10% 3 8% 5% 5% 5% 4 5% 7% 31%	2382
	21st to end	Night	18% 10% 3 8% 6% 4 4 4 5% 6% 31%	1884
March	1st to 10th	Night	23% 11% 3 8% 5% 4 4 3 4 5% 30%	3533
	11th to 20th	Night	12% 11% 4 7% 4 5% 5% 4 5% 7% 35%	3479
	21st to end	Night	16% 9% 3 6% 4 4 4 3 4 5% 42%	3722
April	1st to 10th	Night	19% 10% 3 8% 5% 5% 4 4 5% 6% 31%	1900
	11th to 20th	Night	18% 7% 3 6% 4 4 4 5% 5% 8% 37%	1875
	21st to end	Night	19% 6% 2 6% 5% 3 4 3 4 7% 41%	1891
May	1st to 10th	Night	30% 8% 3 6% 4 4 3 4 4 5% 30%	2750
	11th to 20th	Night	24% 8% 3 8% 5% 5% 4 4 5% 6% 29%	2495
	21st to end	Night	13% 6% 2 6% 5% 4 5% 5% 6% 9% 40%	2738
June	1st to 10th	Night	14% 6% 2 7% 4 4 3 4 6% 8% 42%	1520
	11th to 20th	Night	12% 6% 2 5% 5% 5% 4 4 7% 10% 40%	1520
	21st to end	Night	11% 5% 2 7% 4 4 5% 4 7% 10% 40%	1520
July	1st to 10th	Night	9% 6% 3 8% 4 5% 5% 4 6% 8% 41%	2520
	11th to 20th	Night	7% 5% 2 7% 5% 5% 5% 4 8% 11% 41%	2520
	21st to end	Night	13% 6% 3 6% 6% 4 5% 4 5% 6% 41%	2952
August	1st to 10th	Night	19% 6% 2 7% 5% 5% 4 4 6% 8% 34%	2825
	11th to 20th	Night	17% 8% 2 6% 4 4 3 3 5% 7% 41%	2849
	21st to end	Night	15% 5% 2 5% 5% 4 5% 4 6% 8% 42%	3476
September	1st to 10th	Night	16% 5% 3 5% 4 4 4 3 5% 6% 45%	1900
	11th to 20th	Night	12% 5% 2 5% 4 4 4 3 5% 7% 51%	1900
	21st to end	Night	20% 6% 3 5% 3 4 4 3 6% 7% 40%	2173
October	1st to 10th	Night	20% 7% 2 5% 4 4 3 3 5% 6% 42%	2280
	11th to 20th	Night	17% 6% 2 6% 4 4 4 3 5% 6% 42%	2280
	21st to end	Night	22% 8% 2 6% 4 3 4 3 5% 6% 37%	2413
November	1st to 10th	Night	12% 7% 3 6% 4 3 3 3 5% 7% 47%	2397
	11th to 20th	Night	20% 8% 3 5% 5% 4 4 4 6% 7% 35%	2565
	21st to end	Night	15% 9% 3 8% 5% 4 4 4 6% 7% 34%	2660
December	1st to 10th	Night	20% 11% 4 8% 5% 5% 5% 4 5% 6% 27%	2660
	11th to 20th	Night	19% 9% 3 8% 6% 5% 4 4 5% 6% 29%	3288
	21st to end	Night	23% 11% 4 8% 5% 5% 5% 4 5% 7% 22%	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	51% 8% 14% 18% 6% 2	2518
	11th to 20th	Day	63% 8% 9% 13% 6% 1	2689
	21st to end	Day	63% 7% 10% 14% 4 1	3124
February	1st to 10th	Day	58% 7% 12% 15% 8%	1710
	11th to 20th	Day	51% 8% 10% 22% 8% 1	1691
	21st to end	Day	56% 5% 10% 20% 8% 2	1570
March	1st to 10th	Day	52% 7% 11% 22% 6% 1	3306
	11th to 20th	Day	41% 10% 16% 20% 10% 3	3480
	21st to end	Day	46% 6% 10% 21% 15% 2	3910
April	1st to 10th	Day	50% 6% 10% 19% 11% 3	2280
	11th to 20th	Day	46% 8% 11% 18% 14% 2	2254
	21st to end	Day	46% 7% 10% 20% 14% 3	2304
May	1st to 10th	Day	52% 7% 10% 20% 10% 1	4202
	11th to 20th	Day	54% 10% 12% 16% 7% 1	4402
	21st to end	Day	35% 10% 15% 24% 15% 2	4837
June	1st to 10th	Day	43% 9% 13% 20% 13% 2	2660
	11th to 20th	Day	43% 9% 13% 21% 13% 2	2660
	21st to end	Day	37% 10% 15% 26% 12%	2660
July	1st to 10th	Day	39% 9% 15% 24% 11% 1	4370
	11th to 20th	Day	36% 8% 18% 23% 13% 1	4365
	21st to end	Day	44% 8% 13% 19% 14% 1	4450
August	1st to 10th	Day	49% 8% 14% 18% 10%	4091
	11th to 20th	Day	43% 8% 16% 25% 8%	3972
	21st to end	Day	37% 7% 14% 30% 10% 1	4180
September	1st to 10th	Day	41% 7% 12% 24% 15% 2	2280
	11th to 20th	Day	35% 6% 12% 24% 20% 2	2280
	21st to end	Day	47% 5% 13% 17% 16% 1	2003
October	1st to 10th	Day	44% 7% 12% 22% 14% 1	1900
	11th to 20th	Day	44% 7% 14% 23% 11%	1900
	21st to end	Day	50% 7% 14% 19% 10% 1	2010
November	1st to 10th	Day	41% 6% 13% 22% 15% 3	1680
	11th to 20th	Day	46% 7% 13% 21% 11% 2	1611
	21st to end	Day	47% 8% 14% 23% 7% 1	1520
December	1st to 10th	Day	60% 6% 13% 14% 6% 1	1520
	11th to 20th	Day	53% 8% 16% 18% 5%	1906
	21st to end	Day	63% 10% 11% 12% 4	2772
January	1st to 10th	Night	48% 10% 14% 20% 6% 1	4429
	11th to 20th	Night	55% 10% 13% 14% 7% 1	4266
	21st to end	Night	60% 9% 10% 15% 6% 1	4532
February	1st to 10th	Night	50% 8% 13% 20% 8% 1	2470
	11th to 20th	Night	50% 8% 11% 19% 10% 1	2384
	21st to end	Night	51% 7% 11% 18% 11% 2	1884
March	1st to 10th	Night	54% 7% 10% 19% 8% 1	3543
	11th to 20th	Night	43% 9% 16% 22% 9% 1	3480
	21st to end	Night	44% 5% 9% 20% 17% 4	3722
April	1st to 10th	Night	51% 7% 9% 18% 13% 2	1900
	11th to 20th	Night	43% 8% 11% 20% 16% 3	1875
	21st to end	Night	42% 7% 12% 21% 16% 3	1891
May	1st to 10th	Night	55% 6% 9% 21% 7% 2	2757
	11th to 20th	Night	52% 10% 13% 14% 9% 1	2496
	21st to end	Night	37% 11% 17% 18% 13% 4	2739
June	1st to 10th	Night	41% 7% 11% 25% 15% 1	1520
	11th to 20th	Night	37% 9% 15% 23% 13% 2	1520
	21st to end	Night	35% 11% 13% 26% 14% 1	1520
July	1st to 10th	Night	39% 7% 14% 21% 17% 2	2480
	11th to 20th	Night	34% 9% 17% 24% 15% 1	2472
	21st to end	Night	41% 8% 13% 17% 20% 2	2858
August	1st to 10th	Night	46% 9% 15% 21% 9%	2814
	11th to 20th	Night	42% 6% 13% 26% 13%	2876
	21st to end	Night	37% 7% 13% 30% 12% 1	3476
September	1st to 10th	Night	39% 6% 12% 25% 16% 3	1900
	11th to 20th	Night	32% 6% 12% 26% 21% 2	1900
	21st to end	Night	42% 7% 11% 21% 18% 1	2173
October	1st to 10th	Night	43% 6% 14% 21% 15% 1	2280
	11th to 20th	Night	40% 7% 14% 24% 13% 2	2280
	21st to end	Night	46% 6% 13% 21% 12% 1	2413
November	1st to 10th	Night	38% 6% 14% 23% 17% 2	2397
	11th to 20th	Night	46% 7% 13% 21% 11% 3	2565
	21st to end	Night	47% 9% 14% 22% 8% 1	2660
December	1st to 10th	Night	54% 9% 14% 17% 7%	2660
	11th to 20th	Night	53% 9% 12% 18% 8%	3288
	21st to end	Night	56% 11% 14% 15% 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	27% 24% 31% 14% 3 1	180
	11th to 20th	Day	32% 24% 31% 12% 1	229
	21st to end	Day	27% 25% 33% 12% 2 1	297
February	1st to 10th	Day	28% 27% 30% 12% 2	270
	11th to 20th	Day	30% 26% 36% 8% 1	289
	21st to end	Day	33% 20% 29% 16% 2	382
March	1st to 10th	Day	30% 21% 28% 17% 4	460
	11th to 20th	Day	27% 24% 28% 17% 3 1	460
	21st to end	Day	29% 24% 26% 15% 4 2	506
April	1st to 10th	Day	26% 26% 25% 15% 6% 1	460
	11th to 20th	Day	23% 27% 22% 16% 8% 4	452
	21st to end	Day	26% 19% 30% 14% 8% 2	460
May	1st to 10th	Day	30% 17% 27% 14% 9% 3	463
	11th to 20th	Day	21% 18% 27% 20% 9% 4	487
	21st to end	Day	19% 11% 26% 23% 16% 6%	529
June	1st to 10th	Day	18% 14% 26% 26% 13% 3	490
	11th to 20th	Day	16% 15% 25% 27% 14% 2	490
	21st to end	Day	15% 12% 29% 27% 12% 4	490
July	1st to 10th	Day	12% 7% 25% 31% 19% 5%	485
	11th to 20th	Day	8% 8% 25% 32% 21% 5%	484
	21st to end	Day	14% 8% 27% 30% 17% 4	532
August	1st to 10th	Day	14% 7% 26% 26% 20% 8%	486
	11th to 20th	Day	16% 6% 23% 27% 18% 9%	479
	21st to end	Day	15% 7% 23% 27% 16% 12%	539
September	1st to 10th	Day	19% 10% 21% 23% 18% 9%	490
	11th to 20th	Day	14% 7% 22% 24% 23% 10%	490
	21st to end	Day	27% 11% 21% 22% 15% 4	490
October	1st to 10th	Day	23% 12% 23% 21% 15% 6%	490
	11th to 20th	Day	22% 14% 27% 24% 10% 2	490
	21st to end	Day	25% 15% 29% 21% 10% 1	507
November	1st to 10th	Day	22% 14% 24% 24% 15% 1	369
	11th to 20th	Day	25% 20% 28% 18% 7% 1	271
	21st to end	Day	23% 23% 36% 16% 3 1	180
December	1st to 10th	Day	27% 27% 29% 12% 5% 1	180
	11th to 20th	Day	33% 21% 29% 13% 3 1	180
	21st to end	Day	32% 21% 31% 14% 3	198
January	1st to 10th	Night	20% 18% 38% 20% 3	760
	11th to 20th	Night	24% 15% 32% 25% 4	760
	21st to end	Night	20% 19% 34% 24% 2	836
February	1st to 10th	Night	21% 19% 32% 26% 1	760
	11th to 20th	Night	23% 21% 36% 17% 1	743
	21st to end	Night	27% 18% 34% 19% 3	628
March	1st to 10th	Night	25% 19% 30% 23% 3	760
	11th to 20th	Night	25% 18% 30% 22% 5%	760
	21st to end	Night	23% 18% 34% 19% 6% 1	836
April	1st to 10th	Night	22% 22% 29% 22% 5%	760
	11th to 20th	Night	21% 15% 32% 24% 7% 1	751
	21st to end	Night	22% 13% 29% 30% 7%	751
May	1st to 10th	Night	25% 11% 22% 29% 12%	526
	11th to 20th	Night	18% 9% 31% 33% 9%	374
	21st to end	Night	18% 5% 21% 35% 20% 1	411
June	1st to 10th	Night	14% 6% 23% 40% 16% 1	380
	11th to 20th	Night	16% 4 21% 43% 16% 1	380
	21st to end	Night	12% 4 24% 45% 15%	380
July	1st to 10th	Night	12% 4 20% 40% 23% 2	370
	11th to 20th	Night	10% 2 15% 44% 26% 2	368
	21st to end	Night	14% 3 16% 41% 25% 1	541
August	1st to 10th	Night	14% 2 13% 43% 26% 2	567
	11th to 20th	Night	16% 2 14% 36% 29% 3	602
	21st to end	Night	15% 4 16% 31% 31% 2	836
September	1st to 10th	Night	18% 5% 19% 33% 24% 1	760
	11th to 20th	Night	14% 5% 17% 31% 28% 5%	760
	21st to end	Night	22% 7% 18% 32% 19% 2	760
October	1st to 10th	Night	23% 8% 21% 27% 19% 2	760
	11th to 20th	Night	20% 11% 24% 33% 12%	760
	21st to end	Night	27% 11% 26% 28% 7%	805
November	1st to 10th	Night	16% 11% 30% 32% 11%	740
	11th to 20th	Night	23% 16% 26% 26% 8% 1	760
	21st to end	Night	21% 16% 28% 31% 5% 1	760
December	1st to 10th	Night	27% 17% 30% 22% 4	760
	11th to 20th	Night	23% 15% 30% 26% 5%	760
	21st to end	Night	27% 13% 31% 26% 3	836

Page generated at 2024-10-21 02:20:04. Version ac07

Copyright © 2024 Attilla Danko.