Waterville Public Libarary
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Waterville Public Libarary clear sky chart from 2005-11-06 to 2024-11-01.

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% 12% 4 9% 5% 4 4 4 5% 7% 28%	101492
	Night	18% 13% 5% 10% 5% 4 4 3 4 5% 27%	97476
Transparency	Day	54% 7% 11% 18% 9% 1	101250
	Night	57% 7% 11% 17% 8% 1	97338
Seeing	Day	27% 18% 28% 17% 8% 2	14703
	Night	26% 18% 27% 21% 7% 1	23831

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	12% 23% 9% 14% 6% 4 4 3 3 4 17%	2517
	11th to 20th	Day	14% 19% 10% 20% 8% 4 3 2 3 4 13%	2520
	21st to end	Day	18% 22% 8% 12% 10% 6% 4 3 3 4 11%	3004
February	1st to 10th	Day	16% 20% 5% 16% 7% 5% 5% 3 5% 3 14%	1710
	11th to 20th	Day	12% 17% 8% 17% 8% 5% 4 4 4 4 18%	1736
	21st to end	Day	19% 18% 5% 15% 8% 4 4 3 3 3 19%	1570
March	1st to 10th	Day	25% 15% 5% 11% 4 3 3 3 4 4 23%	3116
	11th to 20th	Day	10% 23% 7% 10% 5% 4 3 2 4 5% 26%	3468
	21st to end	Day	19% 12% 6% 11% 4 3 3 3 3 5% 31%	4052
April	1st to 10th	Day	19% 17% 4 8% 4 4 4 2 4 5% 29%	2280
	11th to 20th	Day	19% 14% 3 7% 4 3 4 4 5% 5% 32%	2254
	21st to end	Day	22% 14% 3 6% 4 3 3 2 5% 6% 31%	2286
May	1st to 10th	Day	24% 10% 3 6% 4 4 4 3 5% 6% 30%	4384
	11th to 20th	Day	18% 9% 3 8% 5% 5% 5% 4 6% 8% 29%	4398
	21st to end	Day	13% 7% 2 6% 4 4 5% 5% 6% 9% 37%	4837
June	1st to 10th	Day	19% 8% 3 7% 6% 5% 5% 5% 5% 8% 30%	2660
	11th to 20th	Day	20% 6% 2 7% 5% 4 5% 4 7% 9% 32%	2660
	21st to end	Day	19% 7% 3 7% 5% 4 5% 4 7% 9% 30%	2660
July	1st to 10th	Day	13% 6% 3 6% 5% 5% 6% 5% 7% 11% 33%	4440
	11th to 20th	Day	11% 6% 3 7% 6% 6% 6% 5% 9% 10% 32%	4440
	21st to end	Day	13% 6% 3 8% 5% 5% 5% 5% 7% 7% 35%	4814
August	1st to 10th	Day	19% 6% 3 7% 5% 5% 5% 5% 7% 7% 31%	4236
	11th to 20th	Day	16% 8% 3 8% 5% 5% 6% 5% 7% 8% 29%	3863
	21st to end	Day	16% 7% 3 7% 4 4 4 4 6% 8% 37%	4180
September	1st to 10th	Day	16% 6% 2 6% 4 4 6% 4 6% 7% 38%	2280
	11th to 20th	Day	17% 7% 3 6% 4 4 3 3 5% 6% 43%	2261
	21st to end	Day	17% 8% 2 7% 5% 5% 5% 5% 6% 6% 34%	2066
October	1st to 10th	Day	21% 10% 3 7% 4 4 5% 3 5% 6% 31%	1900
	11th to 20th	Day	20% 10% 3 7% 4 4 4 3 5% 7% 32%	1900
	21st to end	Day	26% 14% 3 7% 5% 5% 3 3 6% 5% 23%	1967
November	1st to 10th	Day	16% 14% 3 8% 4 5% 4 4 5% 6% 32%	1671
	11th to 20th	Day	16% 20% 4 9% 5% 4 3 3 4 5% 27%	1644
	21st to end	Day	18% 18% 5% 11% 5% 4 4 4 5% 4 21%	1520
December	1st to 10th	Day	19% 23% 7% 13% 5% 4 4 3 4 5% 14%	1520
	11th to 20th	Day	21% 19% 9% 11% 5% 4 2 3 4 5% 17%	1906
	21st to end	Day	24% 22% 9% 10% 5% 3 4 3 3 5% 13%	2772
January	1st to 10th	Night	15% 20% 9% 19% 5% 4 4 3 3 4 13%	4429
	11th to 20th	Night	12% 20% 8% 17% 9% 6% 4 3 3 4 15%	4440
	21st to end	Night	19% 19% 7% 17% 9% 6% 3 2 3 3 11%	4651
February	1st to 10th	Night	15% 18% 5% 16% 9% 4 4 3 3 4 18%	2470
	11th to 20th	Night	13% 15% 7% 16% 10% 5% 5% 3 5% 5% 16%	2329
	21st to end	Night	16% 16% 6% 17% 8% 5% 4 3 4 5% 18%	1884
March	1st to 10th	Night	21% 12% 5% 12% 6% 5% 4 3 4 5% 23%	3724
	11th to 20th	Night	14% 23% 7% 10% 5% 3 3 3 4 4 24%	3489
	21st to end	Night	19% 15% 4 11% 5% 4 3 3 3 4 29%	3579
April	1st to 10th	Night	19% 16% 4 7% 5% 4 4 4 4 6% 28%	1900
	11th to 20th	Night	20% 12% 3 7% 5% 5% 4 3 4 5% 33%	1875
	21st to end	Night	21% 11% 4 6% 4 3 3 3 5% 5% 34%	1892
May	1st to 10th	Night	26% 10% 3 7% 4 4 3 3 4 6% 29%	2585
	11th to 20th	Night	15% 10% 3 9% 6% 5% 4 4 5% 6% 33%	2495
	21st to end	Night	13% 8% 3 7% 4 4 5% 5% 6% 7% 38%	2738
June	1st to 10th	Night	18% 7% 3 7% 6% 4 4 4 6% 7% 35%	1520
	11th to 20th	Night	19% 7% 1 5% 4 3 4 4 7% 8% 38%	1520
	21st to end	Night	15% 5% 2 6% 4 5% 3 4 6% 8% 39%	1520
July	1st to 10th	Night	11% 6% 2 8% 6% 6% 5% 4 6% 7% 38%	2520
	11th to 20th	Night	13% 7% 2 6% 4 5% 4 4 5% 7% 42%	2520
	21st to end	Night	14% 7% 3 7% 4 4 3 3 6% 7% 42%	2739
August	1st to 10th	Night	23% 7% 2 6% 4 3 4 3 5% 7% 37%	2689
	11th to 20th	Night	15% 8% 3 8% 5% 4 4 3 5% 6% 38%	2933
	21st to end	Night	14% 7% 2 7% 4 4 4 3 6% 7% 42%	3476
September	1st to 10th	Night	14% 7% 2 6% 4 4 5% 4 4 7% 43%	1900
	11th to 20th	Night	17% 7% 2 4 3 3 3 2 4 6% 48%	1919
	21st to end	Night	18% 7% 3 6% 4 4 4 4 6% 7% 38%	2112
October	1st to 10th	Night	22% 9% 2 8% 4 4 4 4 5% 6% 33%	2280
	11th to 20th	Night	22% 10% 3 7% 4 4 4 3 5% 6% 32%	2280
	21st to end	Night	27% 15% 3 6% 4 4 4 3 4 5% 24%	2631
November	1st to 10th	Night	15% 16% 4 8% 5% 4 4 3 5% 5% 32%	2414
	11th to 20th	Night	19% 15% 4 8% 5% 5% 4 3 4 6% 26%	2531
	21st to end	Night	16% 18% 6% 9% 6% 5% 4 3 5% 6% 22%	2660
December	1st to 10th	Night	19% 22% 7% 13% 5% 5% 3 3 5% 4 15%	2660
	11th to 20th	Night	21% 16% 7% 14% 6% 4 4 3 4 4 17%	3288
	21st to end	Night	25% 18% 10% 10% 5% 4 4 3 4 5% 14%	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	69% 6% 10% 11% 4	2518
	11th to 20th	Day	75% 5% 8% 8% 3 1	2520
	21st to end	Day	77% 5% 8% 6% 3 1	3004
February	1st to 10th	Day	73% 5% 7% 11% 3	1710
	11th to 20th	Day	71% 5% 7% 13% 4	1745
	21st to end	Day	70% 4 9% 11% 6%	1570
March	1st to 10th	Day	64% 5% 10% 13% 7% 1	3119
	11th to 20th	Day	60% 6% 14% 11% 9% 1	3468
	21st to end	Day	56% 5% 8% 16% 14% 1	4052
April	1st to 10th	Day	58% 4 7% 19% 9% 2	2280
	11th to 20th	Day	53% 6% 11% 19% 11% 1	2254
	21st to end	Day	55% 5% 9% 18% 12% 2	2286
May	1st to 10th	Day	53% 6% 11% 18% 11% 1	4398
	11th to 20th	Day	50% 9% 12% 21% 7% 1	4402
	21st to end	Day	40% 9% 13% 25% 12% 1	4837
June	1st to 10th	Day	51% 8% 11% 18% 11% 1	2660
	11th to 20th	Day	47% 8% 13% 22% 9% 1	2660
	21st to end	Day	49% 8% 14% 19% 9%	2660
July	1st to 10th	Day	42% 9% 14% 24% 11%	4370
	11th to 20th	Day	41% 10% 14% 27% 8%	4365
	21st to end	Day	45% 8% 14% 23% 10%	4661
August	1st to 10th	Day	49% 9% 12% 19% 10% 1	4222
	11th to 20th	Day	49% 9% 17% 20% 6%	3902
	21st to end	Day	44% 7% 12% 30% 7% 1	4180
September	1st to 10th	Day	43% 7% 12% 26% 11% 1	2280
	11th to 20th	Day	41% 5% 12% 24% 17% 1	2261
	21st to end	Day	48% 8% 10% 22% 11% 1	2066
October	1st to 10th	Day	52% 7% 10% 19% 11% 1	1900
	11th to 20th	Day	50% 8% 13% 21% 8% 1	1900
	21st to end	Day	61% 7% 11% 12% 8% 1	1967
November	1st to 10th	Day	51% 7% 11% 19% 11% 1	1671
	11th to 20th	Day	60% 5% 11% 15% 7% 2	1644
	21st to end	Day	63% 8% 14% 11% 4	1520
December	1st to 10th	Day	73% 6% 8% 9% 3	1520
	11th to 20th	Day	70% 6% 12% 8% 3	1906
	21st to end	Day	75% 5% 7% 9% 4	2772
January	1st to 10th	Night	75% 6% 9% 6% 3	4429
	11th to 20th	Night	71% 7% 6% 10% 5%	4440
	21st to end	Night	79% 4 7% 6% 3 1	4651
February	1st to 10th	Night	70% 5% 8% 11% 5%	2470
	11th to 20th	Night	70% 5% 8% 11% 5%	2331
	21st to end	Night	68% 6% 9% 10% 6% 1	1884
March	1st to 10th	Night	61% 7% 10% 14% 8%	3734
	11th to 20th	Night	62% 5% 11% 16% 5%	3490
	21st to end	Night	58% 5% 6% 18% 11% 2	3579
April	1st to 10th	Night	58% 5% 10% 17% 8% 2	1900
	11th to 20th	Night	53% 6% 10% 18% 13% 1	1875
	21st to end	Night	51% 6% 10% 18% 13% 3	1892
May	1st to 10th	Night	55% 7% 10% 15% 10% 2	2591
	11th to 20th	Night	49% 10% 13% 19% 8% 1	2496
	21st to end	Night	42% 9% 12% 20% 16% 1	2739
June	1st to 10th	Night	46% 6% 12% 22% 13% 1	1520
	11th to 20th	Night	41% 9% 15% 23% 11% 1	1520
	21st to end	Night	40% 10% 12% 26% 11% 1	1520
July	1st to 10th	Night	43% 8% 13% 21% 14% 1	2480
	11th to 20th	Night	40% 8% 14% 25% 12% 1	2472
	21st to end	Night	41% 6% 11% 26% 15% 1	2651
August	1st to 10th	Night	47% 7% 13% 25% 8%	2679
	11th to 20th	Night	45% 7% 14% 26% 8%	2960
	21st to end	Night	40% 7% 12% 32% 9%	3476
September	1st to 10th	Night	41% 6% 14% 26% 12% 1	1900
	11th to 20th	Night	37% 5% 12% 27% 17% 1	1919
	21st to end	Night	45% 7% 11% 24% 11% 1	2112
October	1st to 10th	Night	51% 7% 12% 19% 10% 1	2280
	11th to 20th	Night	51% 7% 14% 17% 10% 1	2280
	21st to end	Night	62% 6% 10% 14% 8% 1	2631
November	1st to 10th	Night	53% 8% 10% 16% 12% 2	2414
	11th to 20th	Night	59% 6% 10% 16% 7% 2	2531
	21st to end	Night	62% 8% 12% 14% 4	2660
December	1st to 10th	Night	72% 6% 11% 9% 2	2660
	11th to 20th	Night	69% 7% 9% 10% 5%	3288
	21st to end	Night	73% 6% 9% 9% 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	31% 27% 27% 10% 5%	180
	11th to 20th	Day	41% 25% 26% 7% 1 1	180
	21st to end	Day	29% 29% 32% 9% 1	265
February	1st to 10th	Day	43% 29% 22% 6%	270
	11th to 20th	Day	38% 31% 26% 5%	343
	21st to end	Day	41% 23% 27% 8% 1	382
March	1st to 10th	Day	33% 25% 28% 12% 2	460
	11th to 20th	Day	36% 23% 27% 12% 2	460
	21st to end	Day	38% 23% 23% 12% 4 1	506
April	1st to 10th	Day	37% 23% 25% 10% 5%	460
	11th to 20th	Day	35% 23% 21% 12% 6% 2	452
	21st to end	Day	37% 18% 27% 12% 5% 2	460
May	1st to 10th	Day	33% 18% 27% 14% 6% 2	463
	11th to 20th	Day	26% 11% 36% 17% 8% 2	487
	21st to end	Day	19% 15% 31% 22% 11% 3	529
June	1st to 10th	Day	25% 14% 29% 23% 8% 1	490
	11th to 20th	Day	19% 14% 32% 22% 11% 1	490
	21st to end	Day	23% 17% 34% 19% 7% 1	490
July	1st to 10th	Day	14% 12% 32% 26% 12% 4	485
	11th to 20th	Day	14% 10% 31% 31% 12% 3	484
	21st to end	Day	16% 9% 38% 25% 11% 2	532
August	1st to 10th	Day	15% 14% 27% 25% 14% 5%	486
	11th to 20th	Day	21% 7% 28% 27% 12% 5%	479
	21st to end	Day	15% 15% 27% 25% 12% 5%	539
September	1st to 10th	Day	17% 13% 28% 21% 15% 5%	490
	11th to 20th	Day	16% 11% 25% 21% 16% 10%	490
	21st to end	Day	20% 17% 28% 20% 12% 4	490
October	1st to 10th	Day	27% 14% 27% 17% 11% 5%	490
	11th to 20th	Day	27% 19% 29% 15% 7% 2	490
	21st to end	Day	37% 20% 24% 15% 4	474
November	1st to 10th	Day	30% 19% 26% 16% 8%	365
	11th to 20th	Day	33% 28% 23% 12% 3	304
	21st to end	Day	37% 24% 33% 6%	180
December	1st to 10th	Day	38% 21% 30% 9% 1 1	180
	11th to 20th	Day	39% 23% 31% 7%	180
	21st to end	Day	37% 29% 29% 5% 1	198
January	1st to 10th	Night	29% 29% 30% 11% 1	760
	11th to 20th	Night	31% 25% 27% 13% 2 1	760
	21st to end	Night	24% 28% 30% 16% 2	836
February	1st to 10th	Night	30% 23% 31% 15% 1	760
	11th to 20th	Night	28% 28% 29% 13% 2	743
	21st to end	Night	32% 25% 27% 14% 1	628
March	1st to 10th	Night	28% 23% 31% 16% 2	760
	11th to 20th	Night	30% 24% 28% 17% 1	760
	21st to end	Night	31% 21% 24% 18% 4	836
April	1st to 10th	Night	27% 21% 32% 18% 3	760
	11th to 20th	Night	29% 20% 28% 16% 7%	751
	21st to end	Night	30% 14% 28% 22% 6%	752
May	1st to 10th	Night	29% 12% 26% 27% 7%	425
	11th to 20th	Night	19% 11% 37% 26% 7% 1	374
	21st to end	Night	16% 8% 35% 32% 9% 1	411
June	1st to 10th	Night	17% 10% 29% 31% 12% 1	380
	11th to 20th	Night	20% 9% 24% 35% 11%	380
	21st to end	Night	17% 8% 28% 38% 9% 1	380
July	1st to 10th	Night	11% 5% 26% 41% 15% 1	370
	11th to 20th	Night	11% 6% 29% 39% 14% 2	368
	21st to end	Night	15% 5% 24% 43% 12% 1	416
August	1st to 10th	Night	15% 5% 27% 35% 18% 1	483
	11th to 20th	Night	15% 5% 22% 33% 21% 3	647
	21st to end	Night	16% 7% 26% 32% 18% 1	836
September	1st to 10th	Night	17% 8% 28% 29% 16% 2	760
	11th to 20th	Night	19% 8% 19% 28% 21% 4	760
	21st to end	Night	21% 12% 24% 27% 15% 1	760
October	1st to 10th	Night	26% 13% 23% 21% 15% 2	760
	11th to 20th	Night	27% 16% 28% 21% 7% 1	760
	21st to end	Night	35% 17% 28% 17% 2	836
November	1st to 10th	Night	26% 20% 30% 18% 6%	743
	11th to 20th	Night	30% 22% 28% 13% 7% 1	760
	21st to end	Night	29% 24% 28% 16% 3	760
December	1st to 10th	Night	36% 24% 26% 11% 2	760
	11th to 20th	Night	32% 26% 27% 12% 3	760
	21st to end	Night	33% 29% 25% 11% 2	836

Page generated at 2024-10-29 11:20:52. Version ac07

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