Edson
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Edson clear sky chart from 2005-11-06 to 2024-02-10.

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	11% 10% 4 8% 7% 4 6% 6% 6% 8% 31%	77540
	Night	9% 11% 5% 9% 7% 4 6% 5% 6% 7% 30%	81360
Transparency	Day	50% 7% 16% 19% 8% 1	77234
	Night	51% 7% 14% 19% 8% 1	81246
Seeing	Day	16% 12% 29% 26% 13% 3	15010
	Night	15% 10% 29% 31% 13% 2	23630

By Month

Percentage Cloud Cover NW (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% 16% 5% 10% 9% 4 6% 7% 6% 8% 24%	1899
	11th to 20th	Day	6% 9% 6% 10% 7% 4 7% 6% 9% 8% 29%	2096
	21st to end	Day	7% 11% 5% 8% 6% 3 5% 5% 7% 8% 34%	2794
February	1st to 10th	Day	8% 13% 5% 10% 9% 5% 7% 5% 8% 8% 23%	1512
	11th to 20th	Day	6% 11% 8% 10% 8% 4 6% 6% 7% 7% 27%	1431
	21st to end	Day	4 12% 5% 12% 10% 4 6% 6% 7% 7% 27%	1480
March	1st to 10th	Day	5% 13% 6% 11% 8% 5% 6% 5% 5% 8% 28%	1800
	11th to 20th	Day	7% 11% 4 9% 7% 4 6% 5% 7% 8% 32%	1871
	21st to end	Day	9% 14% 6% 10% 7% 4 6% 6% 6% 8% 23%	2322
April	1st to 10th	Day	7% 12% 6% 10% 9% 4 7% 7% 6% 9% 23%	2162
	11th to 20th	Day	12% 15% 5% 8% 7% 4 5% 5% 6% 6% 27%	2310
	21st to end	Day	11% 13% 4 9% 7% 4 6% 6% 6% 7% 29%	2430
May	1st to 10th	Day	14% 11% 5% 9% 8% 5% 6% 5% 6% 6% 25%	2553
	11th to 20th	Day	12% 7% 4 7% 6% 4 6% 6% 5% 7% 36%	2654
	21st to end	Day	21% 7% 3 6% 8% 3 5% 5% 5% 7% 30%	2917
June	1st to 10th	Day	20% 7% 3 8% 6% 3 6% 6% 7% 8% 28%	2849
	11th to 20th	Day	21% 8% 5% 8% 8% 4 6% 6% 6% 7% 21%	2880
	21st to end	Day	13% 7% 3 7% 7% 5% 6% 6% 8% 9% 30%	2880
July	1st to 10th	Day	15% 7% 4 6% 6% 4 6% 5% 6% 9% 31%	2880
	11th to 20th	Day	13% 5% 3 7% 7% 5% 7% 7% 7% 9% 30%	2828
	21st to end	Day	12% 5% 2 5% 6% 4 6% 7% 7% 8% 38%	2881
August	1st to 10th	Day	14% 6% 3 6% 6% 3 6% 7% 7% 8% 34%	2507
	11th to 20th	Day	10% 6% 2 7% 5% 4 5% 7% 6% 9% 38%	2471
	21st to end	Day	14% 7% 2 6% 6% 5% 6% 6% 7% 7% 35%	2574
September	1st to 10th	Day	14% 7% 3 7% 5% 3 5% 5% 6% 7% 38%	2178
	11th to 20th	Day	15% 7% 3 4 5% 2 4 5% 5% 8% 41%	2057
	21st to end	Day	11% 9% 3 7% 6% 3 4 5% 5% 8% 38%	1980
October	1st to 10th	Day	12% 11% 4 8% 6% 3 4 5% 6% 7% 36%	1872
	11th to 20th	Day	10% 11% 4 7% 6% 3 5% 4 7% 7% 35%	1620
	21st to end	Day	12% 12% 5% 8% 6% 4 5% 4 5% 6% 31%	1782
November	1st to 10th	Day	10% 15% 6% 9% 7% 4 5% 6% 7% 7% 24%	1491
	11th to 20th	Day	7% 14% 5% 10% 8% 4 6% 5% 5% 6% 32%	1330
	21st to end	Day	7% 14% 7% 11% 7% 4 7% 6% 5% 7% 27%	1330
December	1st to 10th	Day	8% 13% 5% 10% 7% 4 6% 6% 5% 7% 28%	1330
	11th to 20th	Day	11% 12% 4 9% 8% 5% 6% 4 6% 7% 29%	1499
	21st to end	Day	5% 11% 4 8% 7% 4 5% 5% 6% 6% 38%	2090
January	1st to 10th	Night	5% 14% 7% 12% 10% 4 5% 4 5% 7% 27%	5046
	11th to 20th	Night	5% 12% 5% 9% 7% 5% 6% 7% 8% 8% 28%	4813
	21st to end	Night	8% 12% 5% 9% 7% 4 6% 6% 6% 8% 30%	4865
February	1st to 10th	Night	7% 15% 6% 11% 9% 4 6% 5% 7% 7% 24%	2652
	11th to 20th	Night	5% 14% 5% 9% 8% 5% 8% 6% 6% 7% 26%	2412
	21st to end	Night	4 11% 6% 11% 9% 4 6% 5% 6% 6% 30%	1776
March	1st to 10th	Night	6% 13% 6% 9% 9% 5% 6% 6% 5% 6% 28%	2160
	11th to 20th	Night	6% 11% 6% 9% 8% 4 7% 6% 7% 7% 30%	2088
	21st to end	Night	8% 15% 6% 8% 7% 5% 6% 7% 5% 9% 24%	2032
April	1st to 10th	Night	6% 13% 5% 9% 10% 6% 6% 7% 7% 7% 25%	1798
	11th to 20th	Night	11% 13% 5% 9% 7% 3 5% 4 7% 7% 27%	1601
	21st to end	Night	13% 11% 4 8% 6% 3 5% 5% 6% 9% 31%	1526
May	1st to 10th	Night	17% 12% 5% 8% 6% 4 5% 6% 7% 7% 24%	1406
	11th to 20th	Night	12% 9% 3 7% 6% 4 6% 4 6% 7% 35%	1239
	21st to end	Night	21% 7% 3 7% 5% 3 5% 5% 6% 8% 31%	1358
June	1st to 10th	Night	19% 10% 3 8% 6% 2 6% 5% 5% 6% 31%	1108
	11th to 20th	Night	23% 6% 4 7% 8% 5% 6% 5% 7% 8% 22%	1080
	21st to end	Night	14% 7% 4 6% 7% 4 6% 8% 8% 8% 28%	1080
July	1st to 10th	Night	15% 7% 2 6% 5% 3 5% 5% 7% 8% 37%	1080
	11th to 20th	Night	12% 6% 4 7% 8% 5% 7% 7% 7% 8% 29%	1129
	21st to end	Night	12% 5% 3 8% 6% 4 5% 6% 7% 8% 36%	1433
August	1st to 10th	Night	13% 5% 4 6% 6% 3 6% 5% 7% 8% 35%	1432
	11th to 20th	Night	11% 7% 3 5% 6% 3 5% 5% 9% 9% 38%	1428
	21st to end	Night	13% 6% 3 7% 6% 5% 5% 6% 7% 8% 36%	1782
September	1st to 10th	Night	13% 7% 3 5% 5% 4 5% 5% 6% 8% 38%	1779
	11th to 20th	Night	16% 7% 3 6% 5% 3 4 4 5% 7% 41%	1903
	21st to end	Night	12% 7% 3 5% 5% 3 4 6% 6% 8% 39%	1980
October	1st to 10th	Night	13% 10% 3 7% 6% 3 6% 4 6% 7% 35%	2085
	11th to 20th	Night	11% 9% 4 7% 6% 3 5% 5% 6% 7% 35%	2340
	21st to end	Night	9% 13% 5% 9% 7% 4 5% 5% 7% 8% 28%	2574
November	1st to 10th	Night	12% 16% 6% 9% 7% 3 4 5% 5% 6% 27%	2568
	11th to 20th	Night	8% 13% 6% 11% 7% 5% 6% 6% 5% 6% 28%	2850
	21st to end	Night	7% 12% 6% 10% 8% 5% 6% 6% 6% 7% 27%	2850
December	1st to 10th	Night	7% 13% 5% 9% 8% 5% 4 5% 5% 6% 32%	2850
	11th to 20th	Night	9% 13% 5% 10% 7% 5% 7% 6% 6% 7% 25%	3691
	21st to end	Night	4 10% 5% 9% 7% 5% 6% 5% 5% 6% 37%	5566

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	55% 6% 15% 17% 5% 1	1899
	11th to 20th	Day	49% 4 10% 14% 20% 2	2117
	21st to end	Day	46% 7% 21% 19% 7%	2794
February	1st to 10th	Day	57% 6% 13% 13% 10% 1	1512
	11th to 20th	Day	54% 7% 13% 17% 8%	1439
	21st to end	Day	54% 7% 11% 17% 9% 1	1480
March	1st to 10th	Day	54% 6% 14% 17% 8% 1	1800
	11th to 20th	Day	47% 7% 13% 22% 10% 1	1872
	21st to end	Day	59% 6% 16% 14% 5%	2322
April	1st to 10th	Day	55% 8% 14% 16% 6% 1	2162
	11th to 20th	Day	56% 6% 11% 19% 8% 1	2310
	21st to end	Day	52% 7% 13% 20% 7% 1	2430
May	1st to 10th	Day	59% 5% 13% 14% 8% 1	2553
	11th to 20th	Day	46% 6% 13% 23% 11%	2658
	21st to end	Day	53% 6% 14% 17% 9% 1	2918
June	1st to 10th	Day	51% 8% 16% 18% 6%	2849
	11th to 20th	Day	61% 8% 14% 13% 4	2880
	21st to end	Day	48% 8% 18% 19% 7%	2880
July	1st to 10th	Day	47% 7% 19% 20% 6% 1	2801
	11th to 20th	Day	46% 9% 22% 19% 3	2741
	21st to end	Day	38% 10% 25% 22% 4	2721
August	1st to 10th	Day	45% 9% 21% 21% 4	2490
	11th to 20th	Day	40% 7% 24% 22% 6%	2471
	21st to end	Day	44% 8% 21% 20% 6% 1	2574
September	1st to 10th	Day	44% 7% 20% 24% 6% 1	2178
	11th to 20th	Day	40% 6% 19% 27% 8%	2057
	21st to end	Day	44% 6% 15% 21% 12% 2	1980
October	1st to 10th	Day	47% 6% 18% 22% 7%	1872
	11th to 20th	Day	46% 7% 13% 25% 8%	1620
	21st to end	Day	52% 6% 11% 22% 8% 1	1782
November	1st to 10th	Day	57% 6% 14% 17% 6% 1	1491
	11th to 20th	Day	51% 7% 15% 16% 10% 1	1330
	21st to end	Day	55% 7% 16% 13% 7% 2	1330
December	1st to 10th	Day	55% 6% 12% 16% 9% 2	1330
	11th to 20th	Day	53% 6% 17% 16% 7% 1	1501
	21st to end	Day	43% 7% 10% 22% 15% 2	2090
January	1st to 10th	Night	56% 5% 12% 17% 8% 2	5046
	11th to 20th	Night	51% 6% 10% 12% 17% 3	4854
	21st to end	Night	51% 7% 18% 17% 7% 1	4865
February	1st to 10th	Night	58% 5% 11% 15% 9% 2	2652
	11th to 20th	Night	55% 6% 13% 18% 7%	2414
	21st to end	Night	53% 5% 10% 21% 10% 1	1776
March	1st to 10th	Night	53% 7% 13% 19% 7% 1	2160
	11th to 20th	Night	51% 5% 12% 20% 12% 1	2088
	21st to end	Night	55% 7% 13% 17% 7% 1	2032
April	1st to 10th	Night	55% 8% 13% 15% 8% 1	1798
	11th to 20th	Night	54% 7% 11% 19% 8% 2	1601
	21st to end	Night	49% 7% 15% 20% 7% 1	1526
May	1st to 10th	Night	56% 7% 13% 17% 7%	1406
	11th to 20th	Night	46% 7% 13% 22% 12%	1239
	21st to end	Night	50% 6% 15% 20% 9% 1	1358
June	1st to 10th	Night	52% 7% 14% 20% 7%	1108
	11th to 20th	Night	60% 8% 15% 15% 3	1080
	21st to end	Night	49% 10% 17% 18% 5% 1	1080
July	1st to 10th	Night	44% 7% 20% 22% 6% 1	1050
	11th to 20th	Night	52% 10% 18% 14% 5%	1093
	21st to end	Night	41% 10% 25% 21% 3	1353
August	1st to 10th	Night	44% 10% 21% 22% 4	1424
	11th to 20th	Night	39% 9% 22% 23% 7%	1428
	21st to end	Night	43% 9% 20% 22% 7%	1782
September	1st to 10th	Night	42% 7% 19% 23% 7% 2	1779
	11th to 20th	Night	42% 6% 17% 26% 8% 2	1903
	21st to end	Night	40% 7% 16% 25% 11% 1	1980
October	1st to 10th	Night	47% 6% 16% 21% 9% 1	2085
	11th to 20th	Night	47% 6% 16% 23% 8%	2340
	21st to end	Night	53% 7% 13% 19% 7% 1	2574
November	1st to 10th	Night	56% 6% 11% 20% 6%	2568
	11th to 20th	Night	55% 7% 12% 17% 8% 1	2850
	21st to end	Night	55% 6% 14% 16% 7% 2	2850
December	1st to 10th	Night	54% 5% 10% 18% 11% 2	2850
	11th to 20th	Night	57% 6% 15% 16% 6%	3688
	21st to end	Night	46% 6% 13% 23% 11% 2	5566

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	11% 9% 30% 29% 14% 6%	180
	11th to 20th	Day	14% 11% 29% 29% 16% 1	180
	21st to end	Day	13% 16% 31% 28% 9% 4	198
February	1st to 10th	Day	17% 13% 34% 25% 10% 1	178
	11th to 20th	Day	17% 13% 34% 26% 10% 1	176
	21st to end	Day	8% 14% 36% 27% 14% 3	346
March	1st to 10th	Day	13% 17% 30% 28% 10% 2	420
	11th to 20th	Day	13% 16% 34% 22% 12% 4	420
	21st to end	Day	19% 17% 29% 22% 11% 2	462
April	1st to 10th	Day	17% 18% 32% 24% 8% 2	420
	11th to 20th	Day	19% 17% 24% 21% 17% 3	412
	21st to end	Day	18% 16% 33% 22% 9% 2	420
May	1st to 10th	Day	19% 17% 29% 23% 11% 2	456
	11th to 20th	Day	16% 10% 25% 26% 19% 3	625
	21st to end	Day	21% 6% 27% 26% 15% 4	679
June	1st to 10th	Day	18% 15% 31% 25% 10% 2	779
	11th to 20th	Day	24% 10% 26% 26% 12% 3	810
	21st to end	Day	15% 9% 27% 27% 16% 6%	810
July	1st to 10th	Day	16% 7% 28% 30% 16% 4	796
	11th to 20th	Day	14% 9% 28% 30% 16% 3	740
	21st to end	Day	13% 7% 21% 33% 19% 7%	627
August	1st to 10th	Day	15% 7% 27% 27% 18% 6%	447
	11th to 20th	Day	10% 10% 28% 35% 13% 4	437
	21st to end	Day	17% 12% 26% 25% 15% 5%	495
September	1st to 10th	Day	21% 9% 30% 24% 12% 4	450
	11th to 20th	Day	19% 8% 27% 29% 12% 4	450
	21st to end	Day	18% 15% 31% 20% 12% 3	450
October	1st to 10th	Day	18% 13% 25% 23% 16% 5%	430
	11th to 20th	Day	19% 13% 30% 25% 10% 4	270
	21st to end	Day	15% 17% 35% 21% 9% 3	297
November	1st to 10th	Day	20% 10% 25% 33% 9% 3	232
	11th to 20th	Day	13% 14% 41% 26% 6% 1	180
	21st to end	Day	10% 17% 34% 27% 7% 5%	180
December	1st to 10th	Day	14% 8% 31% 33% 11% 3	180
	11th to 20th	Day	13% 16% 34% 24% 12% 1	180
	21st to end	Day	13% 8% 32% 27% 16% 5%	198
January	1st to 10th	Night	13% 12% 33% 31% 10% 2	1040
	11th to 20th	Night	14% 14% 32% 28% 11% 1	980
	21st to end	Night	16% 17% 30% 28% 9%	839
February	1st to 10th	Night	15% 17% 25% 28% 14% 2	758
	11th to 20th	Night	11% 12% 35% 31% 10% 1	704
	21st to end	Night	9% 13% 28% 32% 15% 3	592
March	1st to 10th	Night	12% 10% 33% 29% 13% 2	720
	11th to 20th	Night	9% 10% 34% 32% 12% 2	720
	21st to end	Night	15% 10% 28% 31% 14% 2	792
April	1st to 10th	Night	12% 12% 31% 32% 11% 1	718
	11th to 20th	Night	18% 9% 33% 28% 11% 1	533
	21st to end	Night	18% 11% 30% 30% 11% 1	446
May	1st to 10th	Night	22% 10% 24% 31% 13% 2	360
	11th to 20th	Night	15% 7% 26% 34% 17% 1	354
	21st to end	Night	20% 8% 21% 31% 19% 2	389
June	1st to 10th	Night	24% 8% 25% 26% 16% 1	360
	11th to 20th	Night	23% 4 21% 33% 16% 2	360
	21st to end	Night	18% 6% 23% 33% 18% 3	360
July	1st to 10th	Night	19% 3 16% 41% 19% 1	350
	11th to 20th	Night	14% 5% 25% 33% 22% 1	348
	21st to end	Night	13% 3 20% 36% 24% 3	394
August	1st to 10th	Night	15% 4 18% 27% 32% 4	358
	11th to 20th	Night	11% 5% 18% 39% 25% 2	360
	21st to end	Night	14% 6% 22% 39% 19% 1	594
September	1st to 10th	Night	15% 6% 21% 39% 17% 2	699
	11th to 20th	Night	18% 5% 21% 35% 19% 2	720
	21st to end	Night	14% 8% 29% 32% 15% 2	720
October	1st to 10th	Night	19% 8% 27% 33% 13% 1	720
	11th to 20th	Night	13% 11% 29% 32% 14% 1	720
	21st to end	Night	16% 12% 31% 32% 8% 1	792
November	1st to 10th	Night	21% 10% 27% 30% 11% 1	823
	11th to 20th	Night	14% 14% 37% 26% 7% 1	950
	21st to end	Night	13% 13% 37% 27% 8% 2	950
December	1st to 10th	Night	13% 13% 34% 27% 11% 1	950
	11th to 20th	Night	11% 14% 30% 33% 10% 2	1013
	21st to end	Night	11% 11% 34% 31% 12% 1	1144

Page generated at 2024-02-07 04:11:55. Version ac07

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