Walcott Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Walcott Site clear sky chart from 2005-11-06 to 2024-03-08.

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	5% 4 2 3 3 2 4 4 5% 7% 62%	79010
	Night	4 4 2 3 3 2 4 4 5% 7% 61%	80600
Transparency	Day	23% 4 8% 22% 28% 15%	78732
	Night	22% 4 9% 21% 27% 16%	80401
Seeing	Day	6% 7% 27% 33% 22% 6%	14264
	Night	6% 7% 38% 37% 12% 1	24441

By Month

Percentage Cloud Cover SW (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	5% 9% 4 5% 4 2 3 3 3 6% 56%	2538
	11th to 20th	Day	3 2 1 1 2 1 2 3 4 6% 74%	2700
	21st to end	Day	7% 5% 2 4 5% 3 4 4 6% 7% 53%	3487
February	1st to 10th	Day	3 6% 2 4 3 2 3 4 4 6% 63%	1900
	11th to 20th	Day	5% 6% 2 5% 4 1 3 3 3 6% 62%	1849
	21st to end	Day	4 3 2 4 3 3 4 4 4 5% 65%	1570
March	1st to 10th	Day	4 5% 2 4 3 3 3 4 4 7% 60%	1870
	11th to 20th	Day	7% 5% 2 3 4 2 3 3 5% 7% 59%	1840
	21st to end	Day	4 4 2 4 4 2 3 3 4 7% 62%	2368
April	1st to 10th	Day	3 2 1 3 3 2 4 3 5% 7% 68%	2160
	11th to 20th	Day	6% 4 2 3 4 2 3 3 4 6% 62%	2131
	21st to end	Day	4 3 1 3 3 1 4 3 4 7% 67%	2160
May	1st to 10th	Day	6% 3 2 3 3 2 4 3 5% 6% 63%	2272
	11th to 20th	Day	8% 4 2 3 3 2 4 4 5% 6% 59%	2302
	21st to end	Day	5% 2 1 3 3 2 4 5% 5% 7% 63%	2531
June	1st to 10th	Day	4 3 2 4 3 2 4 6% 6% 9% 57%	2385
	11th to 20th	Day	3 2 1 2 3 2 4 5% 5% 7% 67%	2520
	21st to end	Day	3 3 1 3 4 2 3 4 6% 8% 63%	2520
July	1st to 10th	Day	6% 3 1 4 5% 4 5% 6% 6% 9% 52%	2520
	11th to 20th	Day	3 3 1 3 3 3 5% 5% 6% 8% 60%	2516
	21st to end	Day	3 2 2 3 4 3 6% 6% 8% 10% 53%	2460
August	1st to 10th	Day	3 2 1 4 5% 3 5% 6% 7% 11% 54%	2149
	11th to 20th	Day	5% 4 1 4 4 2 5% 6% 7% 10% 53%	2123
	21st to end	Day	6% 3 2 4 4 3 5% 4 7% 10% 53%	2376
September	1st to 10th	Day	7% 3 2 3 4 2 4 5% 6% 7% 57%	2160
	11th to 20th	Day	7% 4 2 3 3 2 4 4 5% 6% 58%	2016
	21st to end	Day	6% 3 1 2 3 1 3 3 3 6% 69%	1980
October	1st to 10th	Day	8% 3 2 3 3 2 4 4 4 6% 61%	1980
	11th to 20th	Day	6% 4 1 2 2 1 2 2 4 4 71%	1877
	21st to end	Day	6% 4 2 3 2 1 2 2 4 5% 71%	1882
November	1st to 10th	Day	3 2 1 3 2 2 3 3 4 6% 71%	1673
	11th to 20th	Day	2 3 1 3 3 2 4 4 4 6% 69%	1710
	21st to end	Day	7% 5% 2 3 3 2 2 2 4 6% 64%	1710
December	1st to 10th	Day	4 5% 2 3 4 1 3 4 4 6% 64%	1710
	11th to 20th	Day	4 4 2 4 4 3 4 4 5% 7% 59%	2161
	21st to end	Day	4 5% 2 3 4 2 3 3 4 5% 65%	2904
January	1st to 10th	Night	3 5% 3 5% 4 2 3 4 5% 6% 60%	4417
	11th to 20th	Night	3 2 1 3 4 2 4 4 5% 7% 65%	4294
	21st to end	Night	4 5% 2 4 4 2 4 4 5% 7% 58%	4180
February	1st to 10th	Night	4 4 2 5% 3 2 3 3 4 6% 63%	2280
	11th to 20th	Night	5% 5% 2 4 2 2 4 4 4 7% 60%	2218
	21st to end	Night	5% 3 1 3 3 2 3 3 5% 8% 63%	1884
March	1st to 10th	Night	5% 5% 2 3 3 2 4 4 5% 6% 61%	2250
	11th to 20th	Night	8% 5% 2 4 3 2 4 3 4 7% 61%	2120
	21st to end	Night	5% 4 3 3 3 2 3 4 5% 6% 62%	1984
April	1st to 10th	Night	4 3 1 2 3 2 3 4 5% 6% 67%	1800
	11th to 20th	Night	6% 3 2 3 3 2 4 4 5% 6% 61%	1777
	21st to end	Night	5% 3 1 3 3 2 4 4 5% 7% 65%	1800
May	1st to 10th	Night	5% 4 1 2 4 2 4 4 5% 7% 63%	1688
	11th to 20th	Night	6% 4 2 3 4 2 4 4 6% 7% 58%	1593
	21st to end	Night	6% 3 1 4 4 2 4 5% 5% 8% 59%	1745
June	1st to 10th	Night	5% 2 2 3 3 3 5% 5% 8% 12% 52%	1569
	11th to 20th	Night	2 2 1 3 3 2 3 4 6% 9% 65%	1440
	21st to end	Night	3 4 1 4 3 3 4 5% 6% 10% 57%	1440
July	1st to 10th	Night	3 4 2 5% 5% 3 5% 5% 7% 9% 53%	1440
	11th to 20th	Night	2 3 1 4 4 3 5% 4 6% 11% 56%	1440
	21st to end	Night	3 3 1 4 5% 4 5% 6% 7% 12% 51%	1853
August	1st to 10th	Night	2 2 2 4 5% 4 5% 7% 10% 13% 47%	1790
	11th to 20th	Night	5% 3 2 4 4 4 5% 6% 8% 11% 46%	1778
	21st to end	Night	5% 3 2 4 5% 2 3 6% 8% 11% 51%	1980
September	1st to 10th	Night	5% 3 2 3 4 3 4 4 5% 9% 59%	1800
	11th to 20th	Night	7% 5% 2 4 4 2 3 5% 5% 7% 56%	1944
	21st to end	Night	6% 3 1 2 2 2 2 3 4 6% 69%	1980
October	1st to 10th	Night	7% 4 2 4 2 2 2 4 5% 6% 62%	1980
	11th to 20th	Night	5% 2 1 2 2 2 2 3 3 4 74%	2078
	21st to end	Night	5% 3 1 3 3 1 3 3 3 5% 69%	2454
November	1st to 10th	Night	4 2 1 1 2 2 3 3 4 6% 73%	2405
	11th to 20th	Night	2 3 1 2 3 1 2 3 3 6% 73%	2470
	21st to end	Night	6% 3 1 3 3 2 3 3 4 6% 65%	2470
December	1st to 10th	Night	4 4 1 4 4 2 4 4 4 6% 63%	2470
	11th to 20th	Night	4 3 2 4 4 3 3 4 5% 8% 62%	3036
	21st to end	Night	3 4 2 4 4 2 4 4 4 6% 62%	4753

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	32% 3 6% 20% 29% 10%	2539
	11th to 20th	Day	13% 2 10% 29% 35% 11%	2700
	21st to end	Day	30% 4 5% 20% 31% 9%	3487
February	1st to 10th	Day	24% 2 8% 21% 29% 15%	1900
	11th to 20th	Day	27% 2 6% 20% 28% 18%	1859
	21st to end	Day	22% 2 3 16% 35% 22%	1570
March	1st to 10th	Day	24% 4 5% 18% 29% 20%	1870
	11th to 20th	Day	26% 4 6% 20% 30% 16%	1840
	21st to end	Day	23% 3 6% 23% 27% 18%	2368
April	1st to 10th	Day	18% 3 7% 18% 30% 25%	2160
	11th to 20th	Day	25% 3 6% 17% 28% 22%	2134
	21st to end	Day	18% 3 9% 23% 30% 16%	2160
May	1st to 10th	Day	22% 4 7% 18% 23% 25%	2272
	11th to 20th	Day	26% 5% 10% 18% 27% 14%	2306
	21st to end	Day	21% 6% 11% 21% 21% 21%	2531
June	1st to 10th	Day	22% 7% 13% 27% 18% 14%	2385
	11th to 20th	Day	16% 5% 8% 19% 24% 28%	2520
	21st to end	Day	20% 5% 11% 24% 25% 15%	2520
July	1st to 10th	Day	27% 8% 13% 21% 21% 10%	2451
	11th to 20th	Day	20% 6% 11% 27% 26% 9%	2441
	21st to end	Day	23% 9% 16% 30% 19% 2	2323
August	1st to 10th	Day	22% 7% 16% 31% 18% 6%	2136
	11th to 20th	Day	25% 8% 14% 26% 20% 7%	2123
	21st to end	Day	26% 7% 12% 24% 22% 8%	2376
September	1st to 10th	Day	25% 6% 11% 20% 23% 13%	2160
	11th to 20th	Day	26% 5% 9% 20% 28% 12%	2016
	21st to end	Day	19% 3 6% 23% 36% 14%	1980
October	1st to 10th	Day	24% 5% 9% 19% 28% 15%	1980
	11th to 20th	Day	19% 3 5% 13% 36% 25%	1877
	21st to end	Day	18% 2 4 21% 36% 19%	1882
November	1st to 10th	Day	16% 3 6% 17% 37% 21%	1673
	11th to 20th	Day	17% 3 5% 23% 33% 18%	1710
	21st to end	Day	24% 3 4 16% 31% 23%	1710
December	1st to 10th	Day	23% 3 9% 24% 30% 11%	1710
	11th to 20th	Day	26% 2 6% 22% 28% 16%	2159
	21st to end	Day	22% 3 6% 22% 31% 16%	2904
January	1st to 10th	Night	25% 3 6% 25% 32% 9%	4417
	11th to 20th	Night	19% 3 11% 23% 33% 11%	4294
	21st to end	Night	25% 4 9% 22% 30% 10%	4180
February	1st to 10th	Night	24% 3 5% 19% 30% 20%	2280
	11th to 20th	Night	25% 4 6% 19% 26% 21%	2218
	21st to end	Night	20% 2 3 18% 32% 25%	1884
March	1st to 10th	Night	25% 3 5% 17% 28% 22%	2250
	11th to 20th	Night	26% 2 5% 21% 27% 19%	2120
	21st to end	Night	23% 4 7% 21% 24% 21%	1984
April	1st to 10th	Night	18% 3 7% 20% 28% 24%	1800
	11th to 20th	Night	24% 4 8% 19% 23% 22%	1777
	21st to end	Night	19% 4 10% 23% 27% 18%	1800
May	1st to 10th	Night	21% 5% 9% 17% 23% 25%	1688
	11th to 20th	Night	25% 7% 11% 19% 22% 16%	1594
	21st to end	Night	24% 7% 12% 17% 16% 24%	1746
June	1st to 10th	Night	22% 9% 15% 22% 18% 13%	1569
	11th to 20th	Night	16% 6% 12% 16% 24% 26%	1440
	21st to end	Night	22% 6% 14% 26% 18% 15%	1440
July	1st to 10th	Night	26% 7% 15% 27% 17% 8%	1400
	11th to 20th	Night	21% 7% 13% 23% 26% 10%	1392
	21st to end	Night	25% 8% 18% 26% 19% 3	1750
August	1st to 10th	Night	24% 9% 16% 28% 16% 7%	1779
	11th to 20th	Night	29% 7% 14% 28% 16% 6%	1778
	21st to end	Night	26% 7% 16% 26% 17% 7%	1980
September	1st to 10th	Night	24% 6% 14% 21% 23% 13%	1800
	11th to 20th	Night	27% 6% 11% 23% 21% 13%	1944
	21st to end	Night	18% 3 8% 22% 34% 16%	1980
October	1st to 10th	Night	23% 6% 9% 17% 28% 17%	1980
	11th to 20th	Night	16% 4 6% 13% 34% 27%	2078
	21st to end	Night	20% 2 5% 19% 33% 21%	2454
November	1st to 10th	Night	15% 3 6% 18% 33% 25%	2405
	11th to 20th	Night	14% 3 3 24% 36% 20%	2470
	21st to end	Night	22% 3 4 17% 32% 22%	2470
December	1st to 10th	Night	24% 4 7% 22% 29% 15%	2470
	11th to 20th	Night	22% 3 5% 18% 35% 16%	3037
	21st to end	Night	23% 3 6% 21% 32% 16%	4753

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	7% 12% 41% 28% 11% 1	270
	11th to 20th	Day	8% 16% 37% 25% 12% 2	270
	21st to end	Day	5% 10% 36% 34% 13% 2	297
February	1st to 10th	Day	5% 14% 40% 29% 10% 1	270
	11th to 20th	Day	12% 11% 41% 25% 10% 1	270
	21st to end	Day	9% 11% 51% 24% 6%	225
March	1st to 10th	Day	5% 11% 44% 30% 9%	261
	11th to 20th	Day	12% 9% 37% 28% 14% 1	240
	21st to end	Day	7% 18% 41% 21% 11% 1	454
April	1st to 10th	Day	4 14% 45% 28% 9% 1	420
	11th to 20th	Day	9% 15% 42% 26% 6% 1	412
	21st to end	Day	6% 15% 40% 26% 10% 1	420
May	1st to 10th	Day	5% 10% 37% 33% 13% 2	535
	11th to 20th	Day	10% 8% 28% 32% 19% 3	625
	21st to end	Day	6% 7% 32% 38% 16% 1	679
June	1st to 10th	Day	5% 4 22% 40% 23% 6%	630
	11th to 20th	Day	3 2 28% 41% 21% 4	630
	21st to end	Day	4 2 19% 43% 27% 4	630
July	1st to 10th	Day	5% 1 8% 35% 36% 14%	621
	11th to 20th	Day	3 1 7% 35% 40% 14%	618
	21st to end	Day	2 1 5% 32% 44% 17%	598
August	1st to 10th	Day	2 1 7% 36% 42% 11%	447
	11th to 20th	Day	4 2 9% 33% 36% 16%	437
	21st to end	Day	6% 1 7% 35% 40% 10%	495
September	1st to 10th	Day	6% 1 11% 39% 34% 11%	450
	11th to 20th	Day	5% 1 10% 38% 36% 10%	306
	21st to end	Day	10% 1 19% 36% 26% 7%	270
October	1st to 10th	Day	11% 6% 27% 30% 21% 5%	270
	11th to 20th	Day	8% 5% 30% 35% 17% 5%	270
	21st to end	Day	11% 7% 29% 27% 21% 5%	297
November	1st to 10th	Day	7% 9% 30% 32% 18% 5%	270
	11th to 20th	Day	4 9% 39% 33% 10% 6%	270
	21st to end	Day	14% 11% 36% 23% 13% 3	270
December	1st to 10th	Day	7% 12% 34% 30% 14% 2	270
	11th to 20th	Day	5% 7% 45% 30% 11% 1	270
	21st to end	Day	10% 12% 44% 23% 10%	297
January	1st to 10th	Night	5% 10% 40% 36% 9%	950
	11th to 20th	Night	6% 9% 41% 34% 9% 1	870
	21st to end	Night	6% 7% 43% 36% 8%	836
February	1st to 10th	Night	7% 9% 48% 30% 6%	760
	11th to 20th	Night	8% 11% 52% 24% 5% 1	744
	21st to end	Night	7% 13% 51% 27% 3	628
March	1st to 10th	Night	7% 12% 48% 29% 4	750
	11th to 20th	Night	10% 13% 39% 31% 6%	680
	21st to end	Night	6% 13% 54% 25% 3	594
April	1st to 10th	Night	5% 11% 54% 28% 2	540
	11th to 20th	Night	7% 11% 56% 23% 3	533
	21st to end	Night	5% 11% 52% 26% 6%	540
May	1st to 10th	Night	6% 9% 49% 31% 5%	540
	11th to 20th	Night	6% 10% 37% 38% 8%	531
	21st to end	Night	7% 6% 46% 35% 7%	584
June	1st to 10th	Night	3 5% 38% 44% 10%	540
	11th to 20th	Night	1 4 47% 40% 7% 1	540
	21st to end	Night	3 3 32% 50% 12%	540
July	1st to 10th	Night	5% 1 15% 53% 25% 1	525
	11th to 20th	Night	3 2 13% 54% 28% 1	522
	21st to end	Night	4 1 9% 56% 29% 1	591
August	1st to 10th	Night	3 12% 51% 32% 3	537
	11th to 20th	Night	4 1 14% 53% 25% 2	534
	21st to end	Night	6% 1 13% 48% 30% 2	594
September	1st to 10th	Night	5% 1 17% 53% 22% 1	540
	11th to 20th	Night	8% 1 29% 46% 16%	540
	21st to end	Night	7% 3 26% 46% 16% 1	540
October	1st to 10th	Night	8% 3 34% 44% 12%	540
	11th to 20th	Night	6% 5% 39% 39% 11% 1	638
	21st to end	Night	7% 7% 33% 35% 17% 1	870
November	1st to 10th	Night	5% 5% 35% 40% 13% 1	925
	11th to 20th	Night	3 7% 39% 37% 13%	950
	21st to end	Night	7% 7% 37% 36% 11% 1	950
December	1st to 10th	Night	7% 9% 39% 36% 9%	950
	11th to 20th	Night	7% 8% 45% 33% 7% 1	950
	21st to end	Night	7% 12% 43% 30% 7%	1045

Page generated at 2024-03-05 06:24:04. Version ac07

Copyright © 2024 Attilla Danko.