Falling Water Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Falling Water Observatory clear sky chart from 2005-11-06 to 2025-02-06.

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	12% 6% 2 5% 4 4 4 3 5% 7% 48%	109052
	Night	14% 6% 2 4 3 3 3 3 4 6% 52%	109441
Transparency	Day	34% 6% 10% 20% 19% 10%	112909
	Night	32% 5% 10% 20% 20% 13%	113711
Seeing	Day	14% 8% 22% 29% 21% 6%	15092
	Night	15% 7% 25% 36% 16% 1	25165

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	13% 8% 3 5% 3 2 3 2 3 4 52%	4077
	11th to 20th	Day	14% 7% 2 4 2 2 3 3 4 5% 55%	4080
	21st to end	Day	23% 7% 2 5% 2 2 2 2 3 6% 46%	4976
February	1st to 10th	Day	15% 8% 2 6% 3 3 3 2 4 5% 49%	1950
	11th to 20th	Day	17% 7% 2 5% 3 2 3 3 5% 5% 47%	1849
	21st to end	Day	14% 7% 2 4 2 3 3 3 4 5% 52%	1570
March	1st to 10th	Day	16% 8% 2 6% 3 4 4 3 4 5% 45%	3311
	11th to 20th	Day	21% 10% 3 8% 4 4 4 3 4 4 35%	3480
	21st to end	Day	14% 6% 2 5% 4 3 4 3 6% 6% 46%	3814
April	1st to 10th	Day	14% 8% 3 5% 4 4 4 3 4 6% 46%	2090
	11th to 20th	Day	19% 6% 2 5% 4 3 3 3 5% 5% 44%	2155
	21st to end	Day	14% 7% 2 6% 5% 3 3 3 4 6% 46%	2363
May	1st to 10th	Day	21% 9% 2 6% 4 3 4 4 5% 7% 34%	4082
	11th to 20th	Day	15% 7% 2 6% 4 4 4 3 5% 7% 44%	4082
	21st to end	Day	12% 6% 2 6% 5% 5% 5% 4 7% 8% 39%	4477
June	1st to 10th	Day	6% 6% 2 5% 4 5% 5% 5% 6% 8% 48%	2470
	11th to 20th	Day	7% 6% 1 6% 4 4 5% 4 7% 9% 46%	2470
	21st to end	Day	7% 6% 2 5% 7% 6% 6% 4 7% 9% 41%	2470
July	1st to 10th	Day	7% 5% 2 6% 5% 5% 5% 4 6% 9% 47%	4120
	11th to 20th	Day	5% 4 1 4 4 5% 4 4 7% 9% 53%	4120
	21st to end	Day	8% 6% 2 6% 5% 5% 6% 5% 8% 10% 40%	4465
August	1st to 10th	Day	1 2 1 3 3 3 3 3 6% 10% 66%	3922
	11th to 20th	Day	4 3 1 4 3 3 4 3 6% 10% 60%	3726
	21st to end	Day	4 3 2 6% 5% 6% 6% 5% 7% 11% 46%	4092
September	1st to 10th	Day	11% 6% 2 7% 5% 6% 5% 4 5% 6% 42%	2090
	11th to 20th	Day	11% 6% 3 6% 6% 5% 5% 4 6% 7% 42%	2090
	21st to end	Day	9% 4 2 6% 6% 4 5% 3 6% 7% 49%	2090
October	1st to 10th	Day	6% 5% 2 5% 5% 4 4 3 5% 7% 54%	2090
	11th to 20th	Day	14% 5% 2 4 3 3 3 3 4 6% 52%	2019
	21st to end	Day	12% 4 2 5% 3 3 2 2 4 5% 57%	2090
November	1st to 10th	Day	15% 8% 2 5% 4 4 3 3 4 7% 45%	1953
	11th to 20th	Day	11% 7% 2 5% 3 3 4 4 5% 6% 52%	1800
	21st to end	Day	16% 7% 2 5% 4 3 3 2 4 6% 48%	1800
December	1st to 10th	Day	24% 9% 3 6% 3 2 2 2 4 4 41%	2940
	11th to 20th	Day	16% 7% 2 6% 4 4 3 3 5% 5% 45%	3391
	21st to end	Day	13% 6% 2 3 3 2 2 2 3 4 60%	4488
January	1st to 10th	Night	17% 5% 2 5% 2 3 3 2 4 5% 53%	5888
	11th to 20th	Night	11% 4 1 2 2 2 2 2 4 5% 65%	5900
	21st to end	Night	28% 5% 2 5% 3 3 2 2 4 5% 42%	6030
February	1st to 10th	Night	15% 8% 2 5% 3 2 3 2 4 4 52%	2340
	11th to 20th	Night	17% 6% 2 4 3 2 2 2 4 5% 51%	2218
	21st to end	Night	16% 7% 2 5% 4 3 4 3 4 5% 48%	1884
March	1st to 10th	Night	14% 9% 3 6% 4 4 3 3 4 6% 44%	3546
	11th to 20th	Night	21% 10% 2 6% 4 4 4 3 4 5% 36%	3480
	21st to end	Night	15% 8% 2 5% 3 3 4 3 4 6% 47%	3817
April	1st to 10th	Night	12% 7% 2 5% 4 2 3 3 5% 6% 50%	2090
	11th to 20th	Night	17% 6% 2 5% 3 4 2 3 4 6% 47%	1969
	21st to end	Night	17% 7% 2 5% 4 3 2 2 4 5% 49%	1815
May	1st to 10th	Night	24% 10% 2 4 3 2 3 3 4 6% 40%	2823
	11th to 20th	Night	11% 6% 2 5% 4 3 4 3 5% 6% 50%	2823
	21st to end	Night	15% 6% 1 5% 3 3 4 3 6% 9% 46%	3090
June	1st to 10th	Night	5% 3 1 2 2 3 3 4 7% 8% 61%	1710
	11th to 20th	Night	5% 3 2 4 3 4 3 2 5% 8% 61%	1710
	21st to end	Night	7% 5% 1 4 3 3 4 4 6% 8% 54%	1710
July	1st to 10th	Night	6% 4 1 4 3 4 4 4 6% 11% 54%	2850
	11th to 20th	Night	3 3 2 4 3 4 4 3 7% 9% 58%	2850
	21st to end	Night	9% 7% 3 5% 4 4 4 3 6% 10% 45%	3098
August	1st to 10th	Night	1 1 3 2 2 3 2 4 8% 74%	3013
	11th to 20th	Night	3 2 1 3 3 3 3 4 6% 12% 61%	3113
	21st to end	Night	4 5% 2 5% 3 4 5% 4 6% 10% 54%	3570
September	1st to 10th	Night	8% 5% 2 6% 5% 4 4 4 5% 7% 50%	2090
	11th to 20th	Night	10% 7% 2 6% 4 4 4 3 6% 8% 47%	2090
	21st to end	Night	7% 6% 2 5% 4 5% 5% 3 6% 7% 52%	2090
October	1st to 10th	Night	6% 4 2 4 3 3 3 3 4 6% 63%	2090
	11th to 20th	Night	13% 4 1 4 3 3 3 3 5% 5% 56%	2140
	21st to end	Night	14% 4 2 4 2 2 1 2 3 4 62%	2508
November	1st to 10th	Night	13% 6% 2 5% 3 3 3 2 3 6% 54%	2340
	11th to 20th	Night	10% 6% 2 4 2 2 3 2 5% 7% 57%	2600
	21st to end	Night	17% 7% 1 4 3 3 3 3 4 7% 49%	2600
December	1st to 10th	Night	22% 8% 2 6% 3 3 3 3 4 5% 40%	4250
	11th to 20th	Night	19% 9% 2 5% 3 3 2 2 3 5% 48%	4816
	21st to end	Night	16% 6% 2 3 2 2 2 2 3 4 58%	6490

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	36% 3 4 19% 23% 14%	4078
	11th to 20th	Day	33% 2 4 16% 25% 20%	4080
	21st to end	Day	42% 3 5% 11% 25% 14%	4976
February	1st to 10th	Day	38% 4 6% 12% 22% 18%	1950
	11th to 20th	Day	39% 4 7% 17% 18% 15%	1859
	21st to end	Day	35% 4 6% 17% 21% 17%	1570
March	1st to 10th	Day	41% 5% 7% 13% 22% 13%	3311
	11th to 20th	Day	52% 7% 6% 10% 16% 10%	3480
	21st to end	Day	36% 6% 10% 16% 18% 14%	3814
April	1st to 10th	Day	40% 4 8% 17% 18% 13%	2090
	11th to 20th	Day	42% 5% 6% 17% 18% 12%	2155
	21st to end	Day	40% 5% 8% 18% 19% 11%	2363
May	1st to 10th	Day	48% 8% 9% 14% 15% 6%	4120
	11th to 20th	Day	39% 6% 9% 18% 20% 8%	4086
	21st to end	Day	38% 10% 12% 27% 11% 2	4489
June	1st to 10th	Day	29% 8% 13% 26% 19% 3	2470
	11th to 20th	Day	32% 6% 13% 25% 18% 5%	2470
	21st to end	Day	38% 9% 11% 23% 15% 4	2470
July	1st to 10th	Day	31% 8% 16% 37% 7% 1	4056
	11th to 20th	Day	24% 8% 16% 32% 16% 2	4051
	21st to end	Day	32% 10% 17% 29% 11% 1	4325
August	1st to 10th	Day	14% 6% 12% 39% 28% 1	3908
	11th to 20th	Day	20% 6% 22% 37% 12% 2	3762
	21st to end	Day	28% 11% 18% 23% 18% 2	4091
September	1st to 10th	Day	41% 6% 10% 18% 17% 8%	2090
	11th to 20th	Day	38% 9% 11% 19% 18% 5%	2090
	21st to end	Day	34% 7% 9% 20% 17% 13%	2090
October	1st to 10th	Day	18% 4 6% 12% 25% 35%	3480
	11th to 20th	Day	25% 4 8% 19% 24% 21%	3337
	21st to end	Day	27% 4 5% 16% 34% 13%	3428
November	1st to 10th	Day	39% 5% 8% 18% 18% 11%	1953
	11th to 20th	Day	34% 4 8% 16% 20% 18%	1800
	21st to end	Day	39% 4 6% 16% 21% 14%	1800
December	1st to 10th	Day	49% 3 5% 17% 16% 10%	2940
	11th to 20th	Day	40% 6% 7% 12% 21% 14%	3389
	21st to end	Day	30% 3 4 15% 28% 19%	4488
January	1st to 10th	Night	35% 3 5% 17% 25% 15%	5888
	11th to 20th	Night	24% 2 4 19% 27% 25%	5900
	21st to end	Night	46% 3 4 10% 21% 16%	6030
February	1st to 10th	Night	37% 4 6% 12% 22% 19%	2340
	11th to 20th	Night	36% 4 6% 17% 20% 17%	2218
	21st to end	Night	38% 4 7% 13% 20% 18%	1884
March	1st to 10th	Night	40% 6% 7% 15% 20% 12%	3546
	11th to 20th	Night	49% 7% 7% 12% 14% 11%	3480
	21st to end	Night	37% 7% 10% 16% 17% 13%	3817
April	1st to 10th	Night	35% 5% 10% 18% 16% 16%	2090
	11th to 20th	Night	40% 5% 9% 14% 16% 17%	1969
	21st to end	Night	39% 5% 8% 19% 18% 10%	1815
May	1st to 10th	Night	46% 6% 9% 18% 12% 10%	2850
	11th to 20th	Night	33% 7% 11% 22% 18% 9%	2824
	21st to end	Night	34% 9% 14% 29% 11% 4	3099
June	1st to 10th	Night	19% 9% 16% 32% 20% 3	1710
	11th to 20th	Night	22% 6% 15% 30% 21% 5%	1710
	21st to end	Night	26% 9% 17% 28% 17% 4	1710
July	1st to 10th	Night	23% 9% 25% 36% 6% 1	2805
	11th to 20th	Night	21% 9% 20% 33% 16% 2	2796
	21st to end	Night	33% 9% 21% 29% 8% 1	2999
August	1st to 10th	Night	11% 5% 16% 45% 23%	3003
	11th to 20th	Night	17% 7% 30% 35% 9% 2	3143
	21st to end	Night	25% 12% 20% 24% 18% 2	3570
September	1st to 10th	Night	33% 7% 14% 20% 18% 8%	2090
	11th to 20th	Night	34% 9% 15% 21% 15% 5%	2090
	21st to end	Night	30% 7% 12% 21% 18% 13%	2090
October	1st to 10th	Night	15% 4 8% 15% 22% 36%	3480
	11th to 20th	Night	22% 4 9% 16% 29% 19%	3548
	21st to end	Night	25% 3 5% 18% 33% 15%	4120
November	1st to 10th	Night	34% 4 8% 19% 21% 14%	2340
	11th to 20th	Night	29% 4 9% 21% 20% 18%	2600
	21st to end	Night	37% 4 9% 16% 20% 15%	2600
December	1st to 10th	Night	46% 4 7% 16% 16% 12%	4250
	11th to 20th	Night	41% 3 5% 11% 20% 19%	4817
	21st to end	Night	32% 3 4 15% 28% 18%	6490

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	20% 15% 37% 23% 6% 1	300
	11th to 20th	Day	23% 14% 31% 23% 7% 1	300
	21st to end	Day	20% 15% 37% 21% 7%	330
February	1st to 10th	Day	24% 14% 31% 23% 8%	285
	11th to 20th	Day	27% 14% 35% 21% 3 1	270
	21st to end	Day	26% 14% 41% 16% 4	225
March	1st to 10th	Day	22% 15% 38% 21% 3	270
	11th to 20th	Day	18% 18% 38% 20% 6%	270
	21st to end	Day	19% 18% 40% 18% 4 1	297
April	1st to 10th	Day	20% 16% 41% 19% 4	270
	11th to 20th	Day	20% 16% 38% 22% 4	353
	21st to end	Day	18% 14% 40% 22% 6%	543
May	1st to 10th	Day	19% 11% 38% 26% 7%	653
	11th to 20th	Day	19% 9% 28% 32% 9% 2	675
	21st to end	Day	17% 8% 29% 30% 14% 1	734
June	1st to 10th	Day	8% 3 17% 43% 25% 4	680
	11th to 20th	Day	10% 2 16% 48% 21% 3	680
	21st to end	Day	8% 2 14% 35% 32% 9%	680
July	1st to 10th	Day	11% 2 10% 34% 32% 11%	671
	11th to 20th	Day	5% 1 4 35% 47% 8%	668
	21st to end	Day	5% 2 5% 33% 43% 12%	739
August	1st to 10th	Day	2 1 3 34% 46% 13%	572
	11th to 20th	Day	8% 1 4 34% 39% 14%	477
	21st to end	Day	5% 1 6% 27% 41% 20%	490
September	1st to 10th	Day	10% 1 7% 27% 34% 21%	300
	11th to 20th	Day	7% 1 3 27% 45% 17%	300
	21st to end	Day	10% 2 6% 29% 40% 13%	300
October	1st to 10th	Day	6% 2 14% 32% 37% 9%	300
	11th to 20th	Day	11% 3 20% 39% 23% 4	300
	21st to end	Day	19% 13% 24% 27% 14% 4	330
November	1st to 10th	Day	17% 8% 28% 33% 9% 4	300
	11th to 20th	Day	22% 10% 26% 26% 12% 5%	300
	21st to end	Day	22% 15% 32% 19% 9% 3	300
December	1st to 10th	Day	19% 9% 30% 28% 11% 2	300
	11th to 20th	Day	17% 17% 33% 23% 9% 1	300
	21st to end	Day	19% 11% 34% 25% 10% 1	330
January	1st to 10th	Night	18% 9% 31% 34% 8%	1000
	11th to 20th	Night	20% 11% 32% 31% 7%	1000
	21st to end	Night	22% 10% 30% 31% 7%	900
February	1st to 10th	Night	22% 12% 31% 28% 7%	780
	11th to 20th	Night	21% 13% 35% 28% 3	744
	21st to end	Night	22% 11% 45% 21% 1	628
March	1st to 10th	Night	21% 11% 35% 30% 3	650
	11th to 20th	Night	21% 9% 35% 30% 5%	570
	21st to end	Night	16% 12% 40% 27% 4	627
April	1st to 10th	Night	14% 10% 45% 28% 3	570
	11th to 20th	Night	19% 12% 42% 25% 2	563
	21st to end	Night	18% 10% 42% 22% 6%	570
May	1st to 10th	Night	18% 8% 41% 29% 4	570
	11th to 20th	Night	14% 6% 34% 38% 7% 1	561
	21st to end	Night	16% 6% 32% 34% 12%	617
June	1st to 10th	Night	5% 2 22% 49% 21% 1	570
	11th to 20th	Night	6% 2 25% 52% 14% 1	570
	21st to end	Night	7% 2 16% 46% 27% 2	570
July	1st to 10th	Night	9% 3 9% 46% 30% 3	555
	11th to 20th	Night	5% 1 7% 50% 34% 3	552
	21st to end	Night	5% 1 8% 49% 34% 3	624
August	1st to 10th	Night	2 1 4 49% 42% 3	567
	11th to 20th	Night	5% 1 5% 48% 38% 3	564
	21st to end	Night	7% 1 6% 39% 41% 6%	627
September	1st to 10th	Night	9% 1 6% 44% 35% 5%	570
	11th to 20th	Night	11% 2 8% 40% 37% 3	570
	21st to end	Night	10% 2 12% 39% 33% 4	570
October	1st to 10th	Night	7% 2 12% 47% 30% 3	570
	11th to 20th	Night	13% 3 21% 42% 19% 2	620
	21st to end	Night	17% 7% 25% 29% 21% 2	836
November	1st to 10th	Night	16% 7% 19% 41% 17% 1	780
	11th to 20th	Night	14% 7% 25% 37% 15% 1	1000
	21st to end	Night	21% 9% 27% 32% 11% 1	1000
December	1st to 10th	Night	19% 7% 27% 37% 9% 1	1000
	11th to 20th	Night	23% 9% 29% 32% 7%	1000
	21st to end	Night	18% 10% 29% 34% 8%	1100

Page generated at 2025-02-03 02:05:49. Version ac07

Copyright © 2025 Attilla Danko.