Wilder Skies Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wilder Skies Observatory clear sky chart from 2005-11-06 to 2024-04-25.

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% 7% 3 5% 5% 3 5% 5% 5% 7% 40%	83135
	Night	18% 7% 3 5% 5% 3 4 4 5% 6% 40%	85971
Transparency	Day	44% 6% 11% 22% 15% 3	82840
	Night	44% 6% 12% 22% 15% 2	85800
Seeing	Day	23% 16% 32% 20% 8% 2	14266
	Night	22% 15% 33% 23% 6% 1	23342

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	14% 7% 3 6% 5% 3 5% 4 4 5% 45%	2517
	11th to 20th	Day	16% 7% 3 6% 6% 3 5% 4 4 5% 40%	2520
	21st to end	Day	21% 10% 3 6% 6% 2 4 4 4 5% 35%	2772
February	1st to 10th	Day	18% 7% 3 6% 5% 3 5% 5% 6% 6% 36%	1767
	11th to 20th	Day	13% 7% 3 6% 5% 3 6% 6% 4 7% 40%	1848
	21st to end	Day	19% 9% 3 6% 6% 3 4 4 3 6% 37%	1570
March	1st to 10th	Day	23% 13% 3 6% 5% 3 3 4 4 5% 31%	3116
	11th to 20th	Day	13% 6% 2 5% 5% 3 5% 6% 6% 8% 42%	3311
	21st to end	Day	21% 10% 2 5% 4 3 4 4 5% 7% 34%	4061
April	1st to 10th	Day	18% 9% 3 6% 6% 3 4 4 4 6% 38%	2280
	11th to 20th	Day	18% 5% 3 5% 5% 3 5% 5% 5% 8% 39%	2254
	21st to end	Day	20% 7% 3 5% 5% 4 5% 5% 4 6% 36%	2395
May	1st to 10th	Day	24% 8% 3 5% 4 3 5% 4 5% 7% 32%	2340
	11th to 20th	Day	18% 7% 3 5% 5% 3 5% 3 5% 7% 40%	2360
	21st to end	Day	14% 5% 3 5% 5% 3 5% 4 6% 7% 44%	2725
June	1st to 10th	Day	18% 6% 3 4 6% 4 5% 5% 7% 8% 35%	2520
	11th to 20th	Day	17% 5% 3 4 5% 4 5% 7% 6% 8% 37%	2520
	21st to end	Day	17% 6% 3 5% 6% 4 5% 6% 6% 9% 34%	2520
July	1st to 10th	Day	13% 5% 3 6% 5% 4 5% 5% 5% 8% 41%	2520
	11th to 20th	Day	11% 5% 2 5% 6% 3 6% 6% 6% 9% 40%	2520
	21st to end	Day	11% 5% 2 5% 5% 4 5% 6% 7% 9% 40%	2744
August	1st to 10th	Day	9% 6% 2 7% 6% 4 6% 5% 7% 9% 39%	2377
	11th to 20th	Day	13% 6% 2 5% 5% 4 6% 5% 6% 7% 40%	2258
	21st to end	Day	12% 4 2 5% 5% 3 4 6% 6% 8% 45%	2376
September	1st to 10th	Day	14% 6% 2 4 4 3 4 6% 5% 7% 45%	2160
	11th to 20th	Day	15% 6% 2 4 3 2 4 4 4 6% 50%	1990
	21st to end	Day	15% 6% 2 6% 4 3 4 3 4 6% 46%	1980
October	1st to 10th	Day	23% 6% 2 4 4 2 4 5% 4 5% 40%	1980
	11th to 20th	Day	13% 6% 3 4 4 3 4 4 6% 7% 46%	1753
	21st to end	Day	21% 7% 2 5% 5% 3 3 4 4 5% 40%	1782
November	1st to 10th	Day	15% 6% 3 5% 5% 3 4 3 4 4 49%	1671
	11th to 20th	Day	19% 6% 2 4 3 2 4 4 4 5% 47%	1710
	21st to end	Day	18% 6% 3 5% 5% 3 4 4 6% 5% 43%	1710
December	1st to 10th	Day	17% 8% 3 6% 5% 3 4 5% 5% 6% 38%	1530
	11th to 20th	Day	22% 7% 2 4 4 2 3 3 5% 5% 45%	1906
	21st to end	Day	21% 10% 3 6% 4 3 3 4 5% 6% 34%	2772
January	1st to 10th	Night	18% 7% 2 4 3 2 4 3 3 6% 47%	4429
	11th to 20th	Night	14% 8% 3 8% 6% 3 4 4 4 6% 39%	4440
	21st to end	Night	22% 12% 4 6% 6% 3 4 4 4 5% 31%	4884
February	1st to 10th	Night	17% 8% 3 5% 5% 3 4 4 6% 6% 39%	2410
	11th to 20th	Night	14% 8% 3 6% 5% 3 5% 4 6% 7% 40%	2218
	21st to end	Night	17% 9% 2 6% 5% 3 4 4 4 7% 40%	1884
March	1st to 10th	Night	27% 11% 3 5% 3 2 4 4 4 5% 33%	3724
	11th to 20th	Night	11% 9% 4 6% 5% 4 5% 4 5% 6% 41%	3646
	21st to end	Night	23% 8% 3 5% 5% 2 4 5% 6% 6% 35%	3567
April	1st to 10th	Night	18% 7% 3 6% 6% 3 4 4 6% 7% 37%	1900
	11th to 20th	Night	18% 6% 2 5% 5% 3 4 4 5% 6% 39%	1875
	21st to end	Night	21% 7% 3 5% 4 3 3 3 5% 6% 40%	1665
May	1st to 10th	Night	24% 8% 3 6% 5% 3 4 5% 5% 5% 32%	1620
	11th to 20th	Night	17% 7% 2 5% 5% 3 4 5% 6% 7% 38%	1548
	21st to end	Night	15% 7% 2 6% 5% 3 5% 3 5% 7% 39%	1550
June	1st to 10th	Night	18% 8% 3 5% 5% 3 4 3 6% 7% 38%	1440
	11th to 20th	Night	20% 6% 3 5% 5% 3 5% 5% 4 7% 38%	1440
	21st to end	Night	14% 5% 3 5% 5% 3 5% 5% 7% 8% 41%	1440
July	1st to 10th	Night	14% 5% 1 4 6% 3 5% 6% 5% 8% 42%	1440
	11th to 20th	Night	12% 6% 3 5% 6% 3 5% 6% 6% 9% 39%	1440
	21st to end	Night	12% 5% 2 4 5% 3 5% 4 6% 9% 45%	1574
August	1st to 10th	Night	9% 5% 2 4 6% 3 5% 6% 6% 8% 45%	1544
	11th to 20th	Night	12% 4 2 5% 6% 4 6% 7% 7% 10% 37%	1639
	21st to end	Night	15% 4 2 4 4 2 4 3 5% 8% 48%	1980
September	1st to 10th	Night	13% 5% 2 4 6% 2 3 4 5% 7% 48%	1800
	11th to 20th	Night	14% 5% 2 4 3 2 3 4 4 6% 53%	1970
	21st to end	Night	16% 6% 2 5% 4 2 4 4 5% 6% 46%	1980
October	1st to 10th	Night	21% 6% 3 5% 4 2 3 3 5% 5% 43%	1980
	11th to 20th	Night	16% 5% 2 4 4 3 4 4 6% 7% 46%	2204
	21st to end	Night	23% 8% 2 5% 4 3 4 3 4 6% 37%	2574
November	1st to 10th	Night	15% 5% 2 4 5% 3 4 4 4 5% 49%	2407
	11th to 20th	Night	18% 7% 2 4 3 2 4 4 4 5% 46%	2470
	21st to end	Night	16% 7% 2 4 4 3 4 4 5% 7% 45%	2470
December	1st to 10th	Night	18% 8% 3 5% 5% 3 4 4 4 6% 39%	2647
	11th to 20th	Night	19% 6% 2 5% 4 2 4 4 5% 6% 42%	3288
	21st to end	Night	20% 9% 4 6% 5% 3 4 4 5% 6% 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	41% 4 9% 33% 11% 2	2518
	11th to 20th	Day	47% 5% 9% 24% 13% 2	2520
	21st to end	Day	51% 6% 10% 21% 10% 2	2772
February	1st to 10th	Day	47% 6% 13% 20% 13% 2	1767
	11th to 20th	Day	44% 6% 11% 21% 15% 3	1857
	21st to end	Day	49% 5% 9% 20% 14% 3	1570
March	1st to 10th	Day	56% 5% 11% 14% 11% 3	3119
	11th to 20th	Day	36% 7% 16% 24% 14% 3	3311
	21st to end	Day	49% 3 6% 17% 17% 6%	4061
April	1st to 10th	Day	48% 5% 10% 19% 16% 3	2280
	11th to 20th	Day	42% 6% 11% 20% 18% 3	2254
	21st to end	Day	49% 5% 9% 17% 17% 4	2395
May	1st to 10th	Day	52% 6% 8% 19% 12% 2	2340
	11th to 20th	Day	44% 6% 10% 19% 18% 3	2364
	21st to end	Day	40% 7% 13% 24% 13% 2	2725
June	1st to 10th	Day	46% 8% 13% 22% 10% 1	2520
	11th to 20th	Day	43% 9% 12% 19% 15% 2	2520
	21st to end	Day	46% 8% 11% 22% 12% 1	2520
July	1st to 10th	Day	41% 7% 11% 23% 16% 2	2450
	11th to 20th	Day	39% 8% 14% 25% 12% 1	2445
	21st to end	Day	38% 8% 14% 23% 14% 3	2591
August	1st to 10th	Day	40% 9% 14% 23% 13% 1	2363
	11th to 20th	Day	41% 7% 14% 24% 12% 1	2258
	21st to end	Day	36% 8% 11% 25% 18% 3	2376
September	1st to 10th	Day	38% 7% 11% 24% 19% 2	2160
	11th to 20th	Day	35% 5% 9% 25% 23% 3	1990
	21st to end	Day	40% 4 9% 22% 22% 2	1980
October	1st to 10th	Day	46% 6% 8% 22% 14% 4	1980
	11th to 20th	Day	37% 5% 12% 29% 15% 2	1753
	21st to end	Day	46% 6% 12% 19% 14% 3	1782
November	1st to 10th	Day	39% 4 12% 25% 17% 2	1671
	11th to 20th	Day	39% 4 10% 23% 21% 2	1710
	21st to end	Day	43% 5% 15% 24% 12% 2	1710
December	1st to 10th	Day	46% 6% 14% 16% 17% 1	1530
	11th to 20th	Day	43% 4 14% 18% 18% 4	1906
	21st to end	Day	51% 6% 11% 20% 11% 1	2772
January	1st to 10th	Night	39% 4 12% 29% 12% 3	4429
	11th to 20th	Night	46% 5% 13% 22% 12% 3	4440
	21st to end	Night	57% 4 9% 17% 11% 2	4884
February	1st to 10th	Night	45% 5% 14% 20% 13% 2	2410
	11th to 20th	Night	44% 5% 11% 20% 17% 4	2220
	21st to end	Night	45% 5% 7% 24% 15% 4	1884
March	1st to 10th	Night	54% 4 9% 20% 10% 2	3734
	11th to 20th	Night	43% 6% 15% 19% 15% 3	3647
	21st to end	Night	50% 3 7% 13% 19% 7%	3567
April	1st to 10th	Night	47% 5% 10% 19% 16% 3	1900
	11th to 20th	Night	44% 6% 9% 20% 19% 2	1875
	21st to end	Night	46% 5% 10% 19% 15% 5%	1665
May	1st to 10th	Night	52% 6% 9% 18% 12% 3	1620
	11th to 20th	Night	44% 8% 13% 17% 16% 3	1549
	21st to end	Night	45% 8% 13% 20% 13% 1	1551
June	1st to 10th	Night	46% 8% 11% 23% 12% 1	1440
	11th to 20th	Night	47% 7% 12% 20% 13% 1	1440
	21st to end	Night	36% 10% 15% 23% 15% 1	1440
July	1st to 10th	Night	40% 8% 13% 22% 16% 1	1400
	11th to 20th	Night	40% 10% 15% 25% 10% 1	1392
	21st to end	Night	35% 8% 15% 27% 12% 2	1486
August	1st to 10th	Night	35% 10% 14% 25% 15% 1	1534
	11th to 20th	Night	39% 10% 16% 22% 12%	1639
	21st to end	Night	34% 6% 12% 27% 20% 1	1980
September	1st to 10th	Night	37% 6% 12% 25% 18% 1	1800
	11th to 20th	Night	34% 5% 10% 23% 26% 2	1970
	21st to end	Night	39% 5% 8% 26% 20% 3	1980
October	1st to 10th	Night	43% 5% 13% 22% 13% 4	1980
	11th to 20th	Night	37% 6% 13% 27% 15% 1	2204
	21st to end	Night	49% 4 12% 20% 14% 1	2574
November	1st to 10th	Night	38% 5% 11% 22% 20% 4	2407
	11th to 20th	Night	41% 4 11% 21% 19% 3	2470
	21st to end	Night	39% 5% 14% 26% 14% 2	2470
December	1st to 10th	Night	47% 4 13% 22% 13% 1	2647
	11th to 20th	Night	42% 6% 15% 18% 18% 2	3288
	21st to end	Night	49% 6% 10% 24% 11% 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	27% 25% 28% 15% 5%	180
	11th to 20th	Day	33% 23% 31% 8% 4	180
	21st to end	Day	25% 24% 35% 12% 4	198
February	1st to 10th	Day	31% 22% 31% 14% 2	357
	11th to 20th	Day	27% 29% 31% 11% 2	456
	21st to end	Day	31% 20% 32% 12% 4 1	382
March	1st to 10th	Day	30% 21% 33% 13% 3	460
	11th to 20th	Day	28% 25% 30% 14% 3 1	460
	21st to end	Day	32% 19% 32% 12% 5% 2	506
April	1st to 10th	Day	32% 21% 29% 12% 6% 1	460
	11th to 20th	Day	30% 21% 31% 11% 6%	452
	21st to end	Day	29% 19% 33% 14% 3 2	437
May	1st to 10th	Day	32% 20% 29% 13% 4 1	423
	11th to 20th	Day	23% 14% 41% 16% 4 1	447
	21st to end	Day	19% 14% 34% 23% 9% 2	485
June	1st to 10th	Day	17% 13% 38% 20% 10% 2	450
	11th to 20th	Day	19% 12% 39% 22% 6% 2	450
	21st to end	Day	19% 11% 36% 22% 9% 3	450
July	1st to 10th	Day	17% 10% 29% 27% 15% 2	445
	11th to 20th	Day	14% 7% 31% 32% 13% 3	444
	21st to end	Day	13% 8% 35% 33% 10% 2	488
August	1st to 10th	Day	9% 10% 31% 33% 14% 2	446
	11th to 20th	Day	17% 7% 30% 30% 13% 3	439
	21st to end	Day	13% 9% 32% 28% 14% 5%	495
September	1st to 10th	Day	19% 9% 28% 24% 15% 6%	450
	11th to 20th	Day	21% 8% 30% 22% 11% 8%	450
	21st to end	Day	19% 12% 30% 25% 9% 5%	450
October	1st to 10th	Day	28% 12% 25% 21% 10% 4	450
	11th to 20th	Day	17% 17% 30% 23% 10% 2	407
	21st to end	Day	30% 12% 30% 20% 7% 1	396
November	1st to 10th	Day	21% 16% 32% 20% 9% 2	365
	11th to 20th	Day	30% 21% 25% 19% 4 1	370
	21st to end	Day	28% 19% 31% 17% 6%	370
December	1st to 10th	Day	19% 30% 29% 17% 4	190
	11th to 20th	Day	31% 27% 32% 7% 3	180
	21st to end	Day	27% 22% 32% 14% 4 1	198
January	1st to 10th	Night	22% 19% 40% 17% 2	760
	11th to 20th	Night	27% 19% 36% 16% 2	760
	21st to end	Night	21% 20% 37% 19% 3	836
February	1st to 10th	Night	24% 18% 40% 18% 2	760
	11th to 20th	Night	22% 22% 40% 15% 1	743
	21st to end	Night	26% 20% 34% 17% 2	628
March	1st to 10th	Night	25% 18% 36% 17% 3	760
	11th to 20th	Night	21% 22% 38% 16% 3	760
	21st to end	Night	25% 20% 33% 18% 4	836
April	1st to 10th	Night	24% 21% 31% 20% 3	760
	11th to 20th	Night	23% 20% 33% 19% 6%	751
	21st to end	Night	23% 21% 34% 19% 3	555
May	1st to 10th	Night	30% 15% 30% 21% 3	540
	11th to 20th	Night	21% 18% 37% 20% 5%	487
	21st to end	Night	19% 9% 36% 30% 6%	389
June	1st to 10th	Night	21% 5% 37% 29% 8%	360
	11th to 20th	Night	22% 8% 34% 31% 5% 1	360
	21st to end	Night	15% 4 38% 36% 7%	360
July	1st to 10th	Night	15% 5% 29% 39% 11% 1	350
	11th to 20th	Night	14% 4 28% 42% 12%	348
	21st to end	Night	13% 4 30% 43% 9%	394
August	1st to 10th	Night	11% 4 31% 41% 12% 1	470
	11th to 20th	Night	13% 5% 29% 38% 14% 1	575
	21st to end	Night	15% 5% 25% 39% 15% 2	792
September	1st to 10th	Night	16% 6% 31% 33% 13% 1	720
	11th to 20th	Night	17% 8% 26% 29% 18% 2	720
	21st to end	Night	20% 8% 29% 28% 13% 2	720
October	1st to 10th	Night	26% 10% 28% 24% 10% 2	720
	11th to 20th	Night	20% 12% 32% 24% 11% 1	720
	21st to end	Night	28% 14% 32% 19% 6%	792
November	1st to 10th	Night	20% 13% 32% 26% 8% 1	740
	11th to 20th	Night	24% 18% 33% 18% 7% 1	760
	21st to end	Night	23% 19% 33% 19% 5% 1	760
December	1st to 10th	Night	26% 19% 34% 17% 4	760
	11th to 20th	Night	25% 18% 34% 21% 3	760
	21st to end	Night	27% 17% 37% 17% 3	836

Page generated at 2024-04-22 09:25:47. Version ac07

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