Wild Duck Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wild Duck Observatory clear sky chart from 2005-11-06 to 2024-11-08.

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	14% 8% 3 7% 4 4 4 4 6% 7% 39%	101260
	Night	14% 9% 3 7% 4 4 4 3 5% 7% 40%	97810
Transparency	Day	42% 6% 11% 23% 15% 2	104956
	Night	42% 6% 11% 22% 17% 3	102253
Seeing	Day	17% 9% 23% 25% 18% 8%	15304
	Night	18% 7% 25% 31% 17% 2	25002

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	14% 13% 7% 9% 5% 5% 4 3 4 7% 28%	2527
	11th to 20th	Day	17% 11% 5% 14% 5% 6% 5% 3 4 4 26%	2711
	21st to end	Day	28% 13% 8% 7% 4 3 3 2 4 5% 23%	3124
February	1st to 10th	Day	18% 12% 5% 8% 5% 3 3 3 4 6% 32%	1896
	11th to 20th	Day	17% 11% 4 8% 4 4 5% 3 4 6% 35%	1848
	21st to end	Day	19% 13% 4 7% 4 4 5% 3 5% 6% 30%	1570
March	1st to 10th	Day	25% 13% 4 7% 3 3 3 3 3 5% 32%	3120
	11th to 20th	Day	13% 7% 2 6% 4 4 4 3 5% 7% 44%	3442
	21st to end	Day	14% 8% 3 8% 5% 4 4 3 6% 9% 37%	3844
April	1st to 10th	Day	15% 8% 3 6% 4 4 4 4 5% 7% 39%	2280
	11th to 20th	Day	17% 8% 2 6% 5% 5% 4 3 4 6% 40%	2254
	21st to end	Day	17% 7% 2 6% 4 5% 4 4 5% 6% 38%	2458
May	1st to 10th	Day	20% 9% 3 6% 5% 4 6% 4 6% 8% 30%	4082
	11th to 20th	Day	19% 8% 3 6% 4 4 4 3 5% 6% 39%	4081
	21st to end	Day	11% 7% 2 7% 5% 5% 6% 5% 7% 9% 37%	4476
June	1st to 10th	Day	11% 4 2 7% 5% 5% 5% 4 6% 8% 43%	2479
	11th to 20th	Day	8% 5% 2 5% 5% 5% 6% 5% 8% 9% 44%	2660
	21st to end	Day	8% 5% 2 5% 5% 6% 5% 5% 7% 10% 42%	2660
July	1st to 10th	Day	13% 7% 2 6% 4 4 6% 4 7% 10% 37%	4440
	11th to 20th	Day	6% 5% 2 6% 4 4 5% 5% 8% 10% 46%	4317
	21st to end	Day	11% 10% 4 10% 7% 6% 6% 5% 7% 8% 26%	4466
August	1st to 10th	Day	7% 5% 2 5% 4 4 5% 5% 7% 10% 47%	4104
	11th to 20th	Day	8% 5% 2 6% 5% 5% 5% 5% 8% 10% 40%	3894
	21st to end	Day	5% 4 2 5% 4 4 4 4 6% 8% 55%	4180
September	1st to 10th	Day	13% 6% 2 5% 5% 4 5% 4 4 7% 45%	2195
	11th to 20th	Day	11% 4 2 5% 4 4 4 4 6% 8% 48%	2090
	21st to end	Day	15% 5% 2 5% 4 4 4 3 5% 6% 47%	2090
October	1st to 10th	Day	10% 4 1 6% 4 4 4 3 5% 6% 54%	2090
	11th to 20th	Day	12% 5% 2 6% 5% 3 4 3 5% 7% 48%	1986
	21st to end	Day	18% 7% 3 6% 3 4 3 3 5% 5% 43%	1910
November	1st to 10th	Day	13% 5% 2 5% 3 3 3 3 4 6% 54%	1735
	11th to 20th	Day	15% 10% 3 6% 4 3 3 3 5% 5% 43%	1710
	21st to end	Day	18% 9% 3 6% 4 3 4 3 4 6% 40%	1710
December	1st to 10th	Day	22% 13% 3 7% 4 4 4 3 4 5% 31%	1710
	11th to 20th	Day	14% 13% 4 10% 5% 5% 4 4 4 5% 32%	2153
	21st to end	Day	19% 17% 5% 9% 4 4 5% 4 5% 5% 23%	2968
January	1st to 10th	Night	16% 15% 5% 10% 5% 4 4 3 5% 6% 27%	4428
	11th to 20th	Night	16% 15% 5% 13% 6% 4 3 3 3 4 27%	4246
	21st to end	Night	24% 14% 5% 7% 4 3 3 3 4 5% 27%	4532
February	1st to 10th	Night	20% 12% 4 7% 5% 5% 4 4 4 6% 29%	2280
	11th to 20th	Night	18% 10% 3 8% 5% 4 4 3 4 6% 35%	2218
	21st to end	Night	21% 12% 4 8% 5% 3 4 3 4 5% 30%	1884
March	1st to 10th	Night	23% 12% 3 7% 4 4 3 3 4 5% 33%	3733
	11th to 20th	Night	14% 7% 2 6% 4 3 4 3 5% 6% 47%	3517
	21st to end	Night	15% 8% 3 7% 5% 4 4 3 5% 6% 40%	3803
April	1st to 10th	Night	14% 6% 3 6% 5% 4 5% 4 5% 7% 41%	1900
	11th to 20th	Night	16% 8% 2 6% 4 4 4 3 4 6% 42%	1875
	21st to end	Night	17% 7% 2 7% 5% 5% 4 3 6% 6% 39%	1720
May	1st to 10th	Night	19% 10% 3 8% 6% 5% 4 4 5% 7% 27%	2813
	11th to 20th	Night	18% 5% 1 5% 5% 4 4 4 6% 7% 41%	2812
	21st to end	Night	8% 5% 2 7% 5% 4 5% 5% 7% 10% 42%	3079
June	1st to 10th	Night	9% 4 2 5% 4 4 5% 3 7% 9% 48%	1694
	11th to 20th	Night	6% 4 2 6% 4 3 5% 5% 7% 9% 50%	1520
	21st to end	Night	5% 4 1 5% 5% 5% 4 5% 8% 11% 47%	1520
July	1st to 10th	Night	8% 5% 2 7% 5% 5% 4 3 6% 9% 47%	2530
	11th to 20th	Night	6% 4 2 5% 3 4 5% 4 6% 10% 52%	2644
	21st to end	Night	10% 9% 3 10% 6% 6% 5% 4 7% 9% 31%	3087
August	1st to 10th	Night	6% 4 2 5% 3 3 4 3 7% 10% 52%	2825
	11th to 20th	Night	5% 6% 2 7% 5% 5% 5% 4 6% 10% 44%	2931
	21st to end	Night	3 3 1 4 2 3 3 3 6% 10% 61%	3476
September	1st to 10th	Night	10% 6% 2 4 3 4 4 3 6% 8% 50%	1966
	11th to 20th	Night	9% 5% 2 5% 3 3 3 4 6% 6% 53%	2090
	21st to end	Night	12% 6% 2 5% 3 3 4 3 4 6% 51%	2090
October	1st to 10th	Night	8% 5% 2 5% 3 3 3 2 4 6% 58%	2090
	11th to 20th	Night	13% 5% 2 6% 3 5% 4 3 4 7% 48%	2193
	21st to end	Night	17% 7% 2 5% 4 4 3 3 4 6% 45%	2686
November	1st to 10th	Night	13% 6% 2 5% 4 4 3 3 5% 6% 50%	2504
	11th to 20th	Night	14% 8% 3 6% 5% 3 4 3 4 7% 44%	2470
	21st to end	Night	17% 10% 3 6% 4 4 3 3 4 7% 39%	2470
December	1st to 10th	Night	21% 10% 4 7% 4 4 4 4 5% 5% 33%	2470
	11th to 20th	Night	19% 11% 4 8% 5% 4 3 3 4 5% 34%	3042
	21st to end	Night	19% 16% 4 10% 6% 6% 6% 3 5% 5% 20%	4672

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	56% 5% 11% 17% 10% 1	2528
	11th to 20th	Day	61% 5% 8% 18% 7% 1	2711
	21st to end	Day	64% 4 7% 19% 4 1	3124
February	1st to 10th	Day	53% 5% 8% 22% 10% 2	1896
	11th to 20th	Day	51% 6% 8% 21% 12% 2	1858
	21st to end	Day	54% 5% 9% 20% 10% 3	1570
March	1st to 10th	Day	56% 4 7% 18% 10% 4	3120
	11th to 20th	Day	39% 6% 11% 25% 17% 2	3442
	21st to end	Day	44% 7% 13% 23% 12% 1	3844
April	1st to 10th	Day	42% 7% 12% 23% 14% 2	2280
	11th to 20th	Day	45% 5% 9% 22% 16% 3	2254
	21st to end	Day	45% 6% 10% 25% 11% 3	2458
May	1st to 10th	Day	50% 9% 13% 19% 9%	4120
	11th to 20th	Day	46% 7% 11% 23% 13% 1	4085
	21st to end	Day	40% 8% 14% 18% 19% 2	4489
June	1st to 10th	Day	37% 8% 11% 25% 17% 3	2479
	11th to 20th	Day	33% 9% 13% 24% 18% 2	2660
	21st to end	Day	34% 9% 14% 20% 18% 4	2660
July	1st to 10th	Day	40% 8% 12% 21% 17% 2	4371
	11th to 20th	Day	30% 9% 12% 33% 15% 2	4242
	21st to end	Day	53% 9% 12% 15% 10% 1	4324
August	1st to 10th	Day	28% 9% 15% 34% 13% 1	4091
	11th to 20th	Day	34% 8% 13% 28% 16% 2	3933
	21st to end	Day	25% 7% 13% 34% 17% 4	4179
September	1st to 10th	Day	38% 5% 11% 21% 19% 6%	2195
	11th to 20th	Day	33% 6% 12% 23% 22% 4	2090
	21st to end	Day	37% 5% 8% 23% 23% 3	2090
October	1st to 10th	Day	20% 4 5% 28% 39% 4	3480
	11th to 20th	Day	25% 4 10% 27% 31% 2	3278
	21st to end	Day	31% 4 8% 29% 21% 7%	3122
November	1st to 10th	Day	33% 4 9% 28% 22% 4	1735
	11th to 20th	Day	43% 4 8% 23% 18% 5%	1710
	21st to end	Day	45% 5% 8% 23% 17% 1	1710
December	1st to 10th	Day	55% 4 10% 20% 9% 1	1710
	11th to 20th	Day	54% 6% 8% 19% 13% 1	2150
	21st to end	Day	61% 6% 10% 15% 7% 1	2968
January	1st to 10th	Night	56% 6% 10% 16% 10% 1	4428
	11th to 20th	Night	61% 5% 8% 17% 8% 1	4246
	21st to end	Night	59% 4 9% 17% 9% 1	4532
February	1st to 10th	Night	56% 5% 10% 19% 8% 1	2280
	11th to 20th	Night	51% 4 8% 22% 13% 1	2219
	21st to end	Night	57% 5% 10% 14% 11% 3	1884
March	1st to 10th	Night	54% 5% 7% 21% 12% 1	3733
	11th to 20th	Night	37% 5% 12% 26% 17% 3	3517
	21st to end	Night	43% 7% 10% 25% 14% 1	3803
April	1st to 10th	Night	40% 6% 11% 23% 16% 3	1900
	11th to 20th	Night	43% 4 9% 18% 20% 6%	1875
	21st to end	Night	45% 6% 11% 22% 13% 3	1720
May	1st to 10th	Night	53% 10% 10% 18% 7% 2	2840
	11th to 20th	Night	40% 8% 15% 26% 10% 1	2813
	21st to end	Night	32% 10% 15% 23% 16% 3	3087
June	1st to 10th	Night	31% 6% 12% 28% 19% 4	1694
	11th to 20th	Night	28% 8% 15% 23% 21% 5%	1520
	21st to end	Night	28% 9% 18% 22% 18% 7%	1520
July	1st to 10th	Night	35% 7% 12% 24% 19% 3	2490
	11th to 20th	Night	26% 7% 13% 35% 17% 2	2596
	21st to end	Night	47% 9% 13% 19% 11% 1	2988
August	1st to 10th	Night	25% 8% 15% 36% 14% 2	2814
	11th to 20th	Night	32% 9% 13% 28% 17% 1	2958
	21st to end	Night	18% 6% 16% 34% 22% 5%	3476
September	1st to 10th	Night	32% 7% 12% 23% 21% 6%	1966
	11th to 20th	Night	31% 6% 10% 26% 23% 5%	2090
	21st to end	Night	34% 5% 9% 23% 24% 5%	2090
October	1st to 10th	Night	20% 4 7% 19% 47% 3	3480
	11th to 20th	Night	25% 3 7% 25% 34% 5%	3640
	21st to end	Night	31% 3 8% 21% 29% 7%	4424
November	1st to 10th	Night	36% 4 9% 23% 23% 4	2504
	11th to 20th	Night	41% 4 8% 20% 22% 5%	2470
	21st to end	Night	47% 4 9% 23% 16% 1	2470
December	1st to 10th	Night	53% 5% 11% 19% 12% 1	2470
	11th to 20th	Night	52% 4 9% 21% 12% 2	3044
	21st to end	Night	64% 6% 10% 13% 7% 1	4672

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% 17% 34% 18% 9% 1	270
	11th to 20th	Day	27% 19% 35% 13% 6%	270
	21st to end	Day	26% 18% 36% 17% 2	297
February	1st to 10th	Day	22% 19% 39% 16% 4	270
	11th to 20th	Day	25% 23% 38% 10% 4	270
	21st to end	Day	31% 17% 33% 14% 5%	225
March	1st to 10th	Day	23% 18% 37% 18% 4	270
	11th to 20th	Day	22% 15% 35% 19% 7% 1	435
	21st to end	Day	25% 15% 32% 21% 6%	506
April	1st to 10th	Day	20% 15% 28% 22% 13% 1	460
	11th to 20th	Day	23% 13% 26% 21% 12% 5%	452
	21st to end	Day	19% 12% 32% 25% 8% 3	460
May	1st to 10th	Day	19% 12% 28% 24% 13% 5%	463
	11th to 20th	Day	20% 6% 23% 26% 17% 8%	487
	21st to end	Day	14% 6% 19% 26% 22% 13%	529
June	1st to 10th	Day	12% 5% 18% 25% 26% 14%	499
	11th to 20th	Day	8% 4 16% 35% 25% 11%	680
	21st to end	Day	10% 4 22% 28% 24% 12%	680
July	1st to 10th	Day	16% 2 14% 23% 24% 21%	671
	11th to 20th	Day	9% 3 16% 27% 31% 14%	597
	21st to end	Day	12% 3 14% 27% 27% 17%	532
August	1st to 10th	Day	10% 2 13% 28% 29% 19%	486
	11th to 20th	Day	12% 4 14% 30% 28% 12%	479
	21st to end	Day	9% 2 8% 29% 31% 21%	539
September	1st to 10th	Day	16% 1 13% 27% 30% 13%	490
	11th to 20th	Day	10% 3 10% 27% 35% 15%	490
	21st to end	Day	18% 5% 17% 24% 26% 11%	490
October	1st to 10th	Day	10% 4 16% 35% 26% 9%	490
	11th to 20th	Day	12% 10% 31% 27% 14% 6%	490
	21st to end	Day	19% 12% 35% 21% 13% 1	359
November	1st to 10th	Day	16% 9% 28% 30% 12% 4	291
	11th to 20th	Day	19% 17% 29% 25% 9% 2	270
	21st to end	Day	23% 8% 32% 29% 8%	270
December	1st to 10th	Day	21% 21% 28% 21% 8% 1	270
	11th to 20th	Day	23% 10% 39% 18% 10%	270
	21st to end	Day	29% 18% 30% 19% 4	297
January	1st to 10th	Night	23% 15% 31% 26% 5%	950
	11th to 20th	Night	28% 14% 34% 21% 3	834
	21st to end	Night	25% 12% 37% 24% 2	836
February	1st to 10th	Night	26% 11% 33% 27% 3	760
	11th to 20th	Night	25% 12% 38% 23% 2	743
	21st to end	Night	28% 12% 39% 20% 1	628
March	1st to 10th	Night	23% 13% 32% 26% 6%	760
	11th to 20th	Night	23% 11% 35% 24% 7% 1	760
	21st to end	Night	22% 10% 31% 30% 7%	834
April	1st to 10th	Night	15% 11% 33% 32% 8%	570
	11th to 20th	Night	18% 10% 27% 32% 11% 2	563
	21st to end	Night	19% 6% 32% 32% 9% 1	570
May	1st to 10th	Night	19% 7% 29% 29% 15% 1	570
	11th to 20th	Night	16% 6% 16% 39% 21% 3	561
	21st to end	Night	9% 3 18% 36% 28% 5%	617
June	1st to 10th	Night	11% 2 16% 41% 26% 4	570
	11th to 20th	Night	7% 4 12% 44% 31% 4	570
	21st to end	Night	7% 1 16% 42% 30% 4	570
July	1st to 10th	Night	12% 2 8% 30% 38% 9%	555
	11th to 20th	Night	9% 2 9% 36% 41% 5%	552
	21st to end	Night	12% 2 9% 37% 33% 7%	624
August	1st to 10th	Night	9% 2 7% 33% 45% 5%	567
	11th to 20th	Night	7% 1 9% 41% 35% 7%	564
	21st to end	Night	7% 7% 35% 44% 7%	627
September	1st to 10th	Night	12% 1 9% 36% 36% 5%	636
	11th to 20th	Night	12% 3 11% 30% 39% 5%	760
	21st to end	Night	14% 4 17% 33% 29% 3	760
October	1st to 10th	Night	10% 4 17% 37% 27% 5%	760
	11th to 20th	Night	15% 7% 26% 34% 17% 1	760
	21st to end	Night	20% 7% 29% 31% 13%	836
November	1st to 10th	Night	15% 7% 28% 32% 16% 2	771
	11th to 20th	Night	17% 10% 33% 29% 11%	760
	21st to end	Night	22% 10% 27% 30% 11% 1	760
December	1st to 10th	Night	26% 10% 30% 28% 6%	760
	11th to 20th	Night	26% 9% 34% 24% 7% 1	760
	21st to end	Night	29% 12% 31% 24% 4	924

Page generated at 2024-11-05 08:15:49. Version ac07

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