North Falmouth
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the North Falmouth 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	18% 8% 3 6% 4 4 4 3 5% 7% 39%	101109
	Night	19% 9% 3 6% 4 4 4 3 5% 6% 37%	97851
Transparency	Day	45% 5% 13% 22% 13% 2	100870
	Night	48% 5% 11% 21% 13% 2	97710
Seeing	Day	20% 10% 29% 26% 12% 3	15200
	Night	21% 11% 29% 27% 10% 1	24049

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	16% 9% 2 5% 3 3 4 3 4 6% 44%	2517
	11th to 20th	Day	21% 9% 3 5% 4 3 3 3 5% 5% 40%	2520
	21st to end	Day	21% 12% 4 8% 4 4 3 3 3 4 34%	2814
February	1st to 10th	Day	20% 10% 3 7% 4 3 4 4 5% 6% 35%	1808
	11th to 20th	Day	15% 8% 2 6% 4 4 4 4 4 7% 43%	1848
	21st to end	Day	19% 10% 3 5% 4 3 4 3 5% 6% 37%	1570
March	1st to 10th	Day	26% 16% 3 7% 3 2 3 3 3 4 31%	3116
	11th to 20th	Day	12% 7% 3 6% 4 4 4 3 6% 7% 46%	3399
	21st to end	Day	24% 11% 3 7% 3 4 3 2 4 4 35%	3937
April	1st to 10th	Day	21% 9% 2 5% 3 3 3 4 4 6% 39%	2280
	11th to 20th	Day	18% 8% 3 6% 4 3 4 4 5% 6% 40%	2287
	21st to end	Day	20% 8% 2 5% 4 4 3 4 5% 7% 37%	2470
May	1st to 10th	Day	27% 11% 4 7% 4 3 3 3 5% 6% 27%	4106
	11th to 20th	Day	23% 13% 3 6% 3 3 3 3 5% 7% 31%	4081
	21st to end	Day	16% 7% 2 6% 4 3 4 3 5% 8% 42%	4736
June	1st to 10th	Day	20% 7% 2 6% 4 3 4 4 6% 9% 35%	2660
	11th to 20th	Day	17% 7% 2 5% 5% 4 4 4 6% 8% 39%	2660
	21st to end	Day	15% 8% 3 5% 3 4 4 3 7% 9% 40%	2660
July	1st to 10th	Day	16% 9% 3 7% 4 4 4 4 5% 7% 36%	4440
	11th to 20th	Day	14% 7% 3 6% 4 4 5% 4 7% 9% 37%	4440
	21st to end	Day	18% 7% 3 7% 4 4 4 4 6% 8% 34%	4726
August	1st to 10th	Day	18% 8% 3 8% 5% 4 4 3 5% 8% 34%	4105
	11th to 20th	Day	12% 7% 3 6% 4 5% 5% 4 7% 8% 40%	4045
	21st to end	Day	8% 4 1 5% 4 3 4 4 7% 9% 52%	4180
September	1st to 10th	Day	14% 6% 2 6% 4 4 4 4 5% 6% 47%	2238
	11th to 20th	Day	14% 6% 2 5% 3 3 4 3 5% 7% 49%	2090
	21st to end	Day	20% 7% 2 6% 4 4 3 4 4 6% 41%	2090
October	1st to 10th	Day	21% 6% 2 5% 3 3 4 3 4 6% 42%	2090
	11th to 20th	Day	15% 6% 2 4 4 3 3 3 4 7% 48%	1893
	21st to end	Day	19% 6% 2 6% 3 3 3 3 5% 7% 44%	1881
November	1st to 10th	Day	18% 9% 2 6% 3 4 4 2 4 5% 44%	1671
	11th to 20th	Day	17% 7% 2 4 4 3 4 4 5% 6% 43%	1710
	21st to end	Day	17% 7% 2 6% 4 3 4 3 5% 6% 43%	1710
December	1st to 10th	Day	21% 8% 3 5% 4 3 4 3 4 6% 38%	1653
	11th to 20th	Day	21% 8% 3 6% 4 3 3 2 4 6% 40%	1906
	21st to end	Day	21% 12% 3 6% 4 4 4 3 5% 5% 33%	2772
January	1st to 10th	Night	18% 7% 2 4 3 3 3 3 4 5% 48%	4429
	11th to 20th	Night	17% 12% 3 7% 3 3 3 2 4 4 41%	4440
	21st to end	Night	22% 13% 4 9% 5% 4 3 3 4 4 29%	4839
February	1st to 10th	Night	17% 9% 3 8% 4 4 4 3 4 7% 37%	2371
	11th to 20th	Night	19% 9% 3 6% 4 4 3 3 4 6% 39%	2218
	21st to end	Night	17% 10% 3 6% 4 3 3 3 4 5% 42%	1884
March	1st to 10th	Night	30% 13% 2 4 2 3 2 3 3 5% 32%	3724
	11th to 20th	Night	11% 10% 4 6% 5% 4 4 4 5% 5% 39%	3559
	21st to end	Night	25% 9% 3 7% 5% 4 5% 3 4 4 32%	3692
April	1st to 10th	Night	19% 9% 3 7% 5% 4 4 3 4 5% 37%	1900
	11th to 20th	Night	20% 9% 3 6% 4 4 3 3 6% 6% 37%	1840
	21st to end	Night	20% 8% 3 7% 4 5% 4 3 5% 5% 37%	1710
May	1st to 10th	Night	25% 12% 5% 8% 5% 3 3 3 5% 5% 24%	2834
	11th to 20th	Night	25% 12% 3 7% 5% 4 4 3 6% 6% 25%	2813
	21st to end	Night	16% 9% 4 7% 5% 4 5% 4 6% 7% 32%	2866
June	1st to 10th	Night	18% 10% 4 6% 4 4 5% 4 6% 8% 33%	1520
	11th to 20th	Night	19% 7% 2 7% 3 3 5% 3 5% 7% 39%	1520
	21st to end	Night	20% 9% 3 6% 4 3 4 2 7% 10% 33%	1520
July	1st to 10th	Night	21% 14% 3 6% 4 3 4 3 5% 7% 30%	2520
	11th to 20th	Night	17% 9% 3 7% 4 4 5% 4 6% 9% 33%	2520
	21st to end	Night	18% 10% 3 8% 5% 5% 4 4 6% 6% 30%	2793
August	1st to 10th	Night	22% 9% 3 7% 4 4 5% 4 6% 7% 28%	2825
	11th to 20th	Night	10% 8% 2 8% 6% 4 6% 4 7% 7% 37%	2782
	21st to end	Night	9% 5% 2 5% 4 3 4 4 6% 8% 52%	3472
September	1st to 10th	Night	14% 6% 2 6% 4 4 4 3 5% 6% 45%	1941
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 5% 6% 50%	2090
	21st to end	Night	20% 7% 2 6% 4 4 4 3 5% 4 40%	2090
October	1st to 10th	Night	20% 8% 3 7% 4 4 4 3 4 5% 38%	2090
	11th to 20th	Night	16% 5% 2 5% 4 3 3 3 5% 7% 47%	2284
	21st to end	Night	19% 9% 3 6% 4 4 4 3 4 6% 39%	2717
November	1st to 10th	Night	17% 6% 2 6% 4 4 4 4 4 5% 44%	2414
	11th to 20th	Night	16% 9% 2 6% 4 4 4 3 4 6% 43%	2470
	21st to end	Night	15% 6% 2 6% 3 3 3 3 5% 7% 45%	2470
December	1st to 10th	Night	22% 7% 2 7% 5% 4 3 3 5% 5% 38%	2522
	11th to 20th	Night	19% 9% 3 5% 4 3 3 3 5% 6% 40%	3288
	21st to end	Night	19% 12% 4 7% 4 4 4 2 4 5% 35%	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	42% 4 9% 29% 15% 2	2518
	11th to 20th	Day	46% 5% 11% 25% 10% 3	2520
	21st to end	Day	56% 3 9% 22% 9% 1	2814
February	1st to 10th	Day	50% 4 12% 19% 12% 2	1808
	11th to 20th	Day	43% 5% 12% 25% 15% 2	1857
	21st to end	Day	48% 3 12% 20% 14% 3	1570
March	1st to 10th	Day	58% 3 12% 15% 10% 2	3119
	11th to 20th	Day	35% 4 16% 29% 13% 2	3399
	21st to end	Day	54% 3 6% 16% 15% 6%	3937
April	1st to 10th	Day	45% 5% 9% 21% 17% 3	2280
	11th to 20th	Day	44% 5% 9% 24% 16% 2	2287
	21st to end	Day	46% 5% 9% 21% 15% 4	2470
May	1st to 10th	Day	60% 5% 12% 14% 8% 1	4120
	11th to 20th	Day	54% 5% 14% 16% 10% 1	4085
	21st to end	Day	42% 5% 12% 22% 18% 1	4736
June	1st to 10th	Day	46% 6% 13% 23% 11%	2660
	11th to 20th	Day	42% 6% 15% 23% 13% 1	2660
	21st to end	Day	41% 6% 17% 24% 12% 1	2660
July	1st to 10th	Day	47% 7% 12% 20% 13% 1	4370
	11th to 20th	Day	41% 6% 17% 23% 12% 1	4365
	21st to end	Day	47% 6% 13% 20% 12% 1	4575
August	1st to 10th	Day	49% 5% 17% 21% 7%	4092
	11th to 20th	Day	41% 6% 16% 29% 8% 1	4084
	21st to end	Day	28% 6% 16% 30% 19% 1	4180
September	1st to 10th	Day	38% 5% 10% 25% 19% 1	2238
	11th to 20th	Day	35% 4 11% 27% 20% 3	2090
	21st to end	Day	44% 5% 8% 23% 18% 2	2090
October	1st to 10th	Day	44% 4 11% 24% 14% 3	2090
	11th to 20th	Day	37% 4 11% 30% 16% 1	1893
	21st to end	Day	41% 4 15% 22% 14% 3	1881
November	1st to 10th	Day	44% 5% 13% 21% 15% 2	1671
	11th to 20th	Day	41% 5% 12% 23% 17% 2	1710
	21st to end	Day	42% 5% 13% 27% 11% 2	1710
December	1st to 10th	Day	48% 4 14% 17% 15% 2	1653
	11th to 20th	Day	48% 3 15% 18% 13% 3	1906
	21st to end	Day	52% 5% 13% 22% 7% 1	2772
January	1st to 10th	Night	40% 3 11% 32% 11% 3	4429
	11th to 20th	Night	49% 4 11% 23% 11% 2	4440
	21st to end	Night	60% 3 8% 18% 10% 1	4839
February	1st to 10th	Night	49% 4 13% 22% 11% 1	2371
	11th to 20th	Night	48% 4 9% 23% 14% 3	2220
	21st to end	Night	45% 3 10% 25% 14% 3	1884
March	1st to 10th	Night	56% 3 10% 18% 11% 2	3734
	11th to 20th	Night	44% 5% 13% 20% 15% 2	3560
	21st to end	Night	58% 3 6% 12% 16% 5%	3692
April	1st to 10th	Night	50% 5% 8% 18% 16% 3	1900
	11th to 20th	Night	48% 4 9% 20% 17% 3	1840
	21st to end	Night	48% 4 9% 20% 15% 3	1710
May	1st to 10th	Night	62% 4 12% 14% 7% 1	2840
	11th to 20th	Night	60% 4 13% 14% 7% 2	2814
	21st to end	Night	52% 6% 11% 19% 12% 1	2867
June	1st to 10th	Night	49% 6% 12% 21% 12% 1	1520
	11th to 20th	Night	44% 5% 11% 25% 14% 1	1520
	21st to end	Night	47% 5% 14% 22% 11% 1	1520
July	1st to 10th	Night	54% 5% 9% 18% 14%	2480
	11th to 20th	Night	47% 7% 16% 21% 10% 1	2472
	21st to end	Night	52% 6% 13% 17% 10% 1	2704
August	1st to 10th	Night	53% 8% 13% 18% 9% 1	2813
	11th to 20th	Night	42% 7% 16% 27% 8%	2809
	21st to end	Night	29% 5% 16% 28% 21% 1	3472
September	1st to 10th	Night	38% 6% 11% 25% 19% 1	1941
	11th to 20th	Night	35% 4 11% 25% 22% 2	2090
	21st to end	Night	46% 6% 6% 21% 18% 3	2090
October	1st to 10th	Night	49% 4 8% 23% 13% 3	2090
	11th to 20th	Night	37% 4 13% 28% 16% 1	2284
	21st to end	Night	47% 5% 12% 20% 14% 2	2717
November	1st to 10th	Night	43% 5% 11% 22% 15% 3	2414
	11th to 20th	Night	43% 4 11% 22% 16% 3	2470
	21st to end	Night	39% 5% 15% 28% 12% 2	2470
December	1st to 10th	Night	49% 4 14% 20% 12% 1	2522
	11th to 20th	Night	45% 5% 15% 18% 15% 2	3288
	21st to end	Night	51% 6% 12% 22% 9% 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	24% 17% 34% 19% 6%	180
	11th to 20th	Day	23% 19% 34% 17% 6%	180
	21st to end	Day	18% 14% 43% 18% 5% 2	227
February	1st to 10th	Day	26% 16% 35% 20% 3	417
	11th to 20th	Day	23% 19% 38% 17% 2	456
	21st to end	Day	22% 20% 35% 18% 4 1	382
March	1st to 10th	Day	25% 13% 37% 20% 5%	460
	11th to 20th	Day	18% 18% 38% 22% 3	460
	21st to end	Day	23% 16% 34% 17% 8% 2	506
April	1st to 10th	Day	26% 12% 34% 20% 7% 1	460
	11th to 20th	Day	22% 14% 35% 24% 5% 1	452
	21st to end	Day	23% 11% 32% 23% 8% 2	460
May	1st to 10th	Day	29% 10% 30% 23% 7% 1	463
	11th to 20th	Day	22% 8% 30% 29% 9% 2	487
	21st to end	Day	21% 5% 25% 28% 17% 3	529
June	1st to 10th	Day	20% 3 27% 32% 16% 2	490
	11th to 20th	Day	15% 7% 30% 33% 13% 3	490
	21st to end	Day	15% 7% 24% 35% 16% 3	490
July	1st to 10th	Day	17% 4 19% 33% 24% 3	485
	11th to 20th	Day	14% 5% 20% 32% 25% 5%	484
	21st to end	Day	13% 5% 25% 36% 18% 3	532
August	1st to 10th	Day	13% 4 24% 38% 19% 3	486
	11th to 20th	Day	15% 6% 17% 37% 20% 6%	479
	21st to end	Day	13% 4 23% 31% 21% 8%	539
September	1st to 10th	Day	16% 6% 23% 28% 19% 8%	490
	11th to 20th	Day	16% 7% 26% 25% 16% 10%	490
	21st to end	Day	23% 8% 28% 24% 13% 4	490
October	1st to 10th	Day	24% 8% 24% 26% 13% 6%	490
	11th to 20th	Day	17% 11% 30% 25% 13% 4	421
	21st to end	Day	22% 11% 34% 20% 10% 3	429
November	1st to 10th	Day	18% 12% 30% 25% 12% 3	365
	11th to 20th	Day	21% 19% 31% 23% 6%	370
	21st to end	Day	19% 19% 30% 20% 9% 2	370
December	1st to 10th	Day	22% 15% 36% 20% 6%	313
	11th to 20th	Day	26% 21% 34% 14% 4	180
	21st to end	Day	23% 18% 35% 16% 6% 2	198
January	1st to 10th	Night	23% 14% 40% 19% 4	760
	11th to 20th	Night	27% 18% 36% 17% 2	760
	21st to end	Night	22% 17% 35% 21% 4 1	836
February	1st to 10th	Night	22% 15% 36% 25% 2	760
	11th to 20th	Night	25% 17% 41% 16% 1	743
	21st to end	Night	22% 17% 36% 20% 4	628
March	1st to 10th	Night	24% 14% 35% 23% 5%	760
	11th to 20th	Night	21% 13% 37% 23% 5%	760
	21st to end	Night	24% 13% 33% 23% 8%	836
April	1st to 10th	Night	24% 11% 33% 29% 4	760
	11th to 20th	Night	23% 10% 32% 29% 5%	716
	21st to end	Night	22% 9% 32% 27% 10% 1	570
May	1st to 10th	Night	27% 9% 27% 27% 9% 1	570
	11th to 20th	Night	25% 8% 32% 29% 6% 1	562
	21st to end	Night	22% 4 20% 40% 13% 1	487
June	1st to 10th	Night	22% 6% 23% 32% 17% 1	380
	11th to 20th	Night	22% 5% 16% 44% 12% 1	380
	21st to end	Night	22% 6% 17% 39% 15%	380
July	1st to 10th	Night	18% 6% 16% 40% 19% 1	370
	11th to 20th	Night	18% 4 16% 37% 23% 2	368
	21st to end	Night	17% 4 16% 42% 19% 1	446
August	1st to 10th	Night	12% 3 22% 42% 20% 1	568
	11th to 20th	Night	15% 3 17% 41% 23% 1	562
	21st to end	Night	15% 4 15% 38% 25% 4	832
September	1st to 10th	Night	17% 3 21% 36% 21% 2	760
	11th to 20th	Night	17% 4 22% 29% 22% 6%	760
	21st to end	Night	22% 6% 22% 30% 17% 3	760
October	1st to 10th	Night	25% 8% 22% 26% 16% 3	760
	11th to 20th	Night	19% 12% 28% 26% 14% 2	760
	21st to end	Night	23% 12% 32% 23% 9% 1	836
November	1st to 10th	Night	20% 10% 29% 27% 13% 1	743
	11th to 20th	Night	20% 18% 31% 22% 8% 1	760
	21st to end	Night	18% 20% 31% 24% 7% 1	760
December	1st to 10th	Night	25% 17% 34% 19% 5% 1	760
	11th to 20th	Night	24% 19% 34% 19% 4	760
	21st to end	Night	21% 18% 37% 21% 3	836

Page generated at 2024-10-29 11:20:47. Version ac07

Copyright © 2024 Attilla Danko.