Duck Creek Conservation Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Duck Creek Conservation Area clear sky chart from 2005-11-06 to 2026-10-29.

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% 6% 2 6% 4 4 4 4 6% 8% 45%	149038
	Night	13% 6% 2 6% 4 4 4 3 5% 7% 47%	143346
Transparency	Day	36% 6% 12% 26% 18% 3	152646
	Night	36% 5% 11% 25% 19% 4	147805
Seeing	Day	14% 8% 23% 27% 20% 8%	18212
	Night	16% 7% 26% 33% 17% 2	27918

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	15% 7% 2 6% 4 4 4 3 5% 6% 43%	4691
	11th to 20th	Day	9% 5% 2 6% 4 4 3 3 5% 6% 53%	5268
	21st to end	Day	18% 7% 2 6% 4 3 3 2 4 5% 45%	5812
February	1st to 10th	Day	17% 9% 3 6% 4 4 3 4 4 6% 40%	1948
	11th to 20th	Day	18% 7% 3 6% 5% 4 3 3 5% 6% 42%	2048
	21st to end	Day	15% 9% 3 7% 4 4 4 4 5% 5% 39%	1730
March	1st to 10th	Day	18% 8% 4 7% 4 4 3 3 4 5% 40%	4622
	11th to 20th	Day	11% 6% 2 4 3 3 3 3 5% 6% 54%	5090
	21st to end	Day	13% 6% 2 6% 5% 5% 4 3 5% 7% 43%	5911
April	1st to 10th	Day	13% 6% 2 5% 4 4 4 3 6% 7% 46%	2520
	11th to 20th	Day	15% 6% 3 6% 5% 4 4 3 5% 6% 42%	2494
	21st to end	Day	16% 7% 3 5% 4 4 4 3 6% 8% 40%	2520
May	1st to 10th	Day	12% 6% 3 7% 6% 6% 6% 5% 7% 9% 33%	7075
	11th to 20th	Day	13% 7% 3 7% 5% 5% 5% 4 6% 7% 37%	7796
	21st to end	Day	18% 9% 3 8% 5% 4 5% 4 6% 7% 32%	9047
June	1st to 10th	Day	8% 5% 2 6% 5% 5% 4 4 6% 9% 45%	2940
	11th to 20th	Day	5% 4 2 5% 4 5% 5% 5% 7% 11% 48%	2940
	21st to end	Day	4 3 2 5% 4 5% 5% 5% 8% 11% 48%	2940
July	1st to 10th	Day	6% 4 2 7% 5% 5% 6% 5% 7% 10% 43%	8280
	11th to 20th	Day	4 3 2 6% 5% 6% 6% 5% 8% 11% 45%	8280
	21st to end	Day	6% 5% 2 6% 4 5% 5% 5% 7% 11% 43%	8341
August	1st to 10th	Day	4 3 2 5% 4 4 5% 4 6% 9% 54%	5803
	11th to 20th	Day	8% 4 1 5% 3 4 4 4 6% 8% 52%	5486
	21st to end	Day	4 4 1 4 3 4 4 3 5% 8% 60%	6080
September	1st to 10th	Day	8% 5% 2 5% 4 4 4 4 6% 8% 51%	2520
	11th to 20th	Day	9% 6% 2 5% 4 4 3 3 6% 7% 50%	2471
	21st to end	Day	10% 5% 2 5% 4 3 4 4 5% 7% 50%	2310
October	1st to 10th	Day	8% 4 1 4 4 3 3 2 5% 6% 59%	2141
	11th to 20th	Day	12% 5% 2 5% 3 3 4 2 4 6% 55%	2100
	21st to end	Day	17% 7% 2 5% 3 3 3 2 5% 6% 48%	2280
November	1st to 10th	Day	11% 5% 2 4 4 3 3 2 5% 6% 54%	1857
	11th to 20th	Day	13% 8% 2 4 4 3 3 3 4 5% 50%	1890
	21st to end	Day	19% 8% 2 5% 4 3 2 3 5% 4 46%	1890
December	1st to 10th	Day	11% 6% 2 6% 4 4 4 3 4 6% 50%	2759
	11th to 20th	Day	16% 6% 2 7% 4 3 4 3 4 5% 45%	3088
	21st to end	Day	24% 12% 4 8% 5% 4 3 3 4 5% 30%	4070
January	1st to 10th	Night	17% 7% 2 7% 4 4 4 3 5% 6% 41%	8232
	11th to 20th	Night	11% 6% 2 6% 4 3 4 3 5% 5% 51%	7703
	21st to end	Night	18% 7% 3 6% 4 4 4 3 4 5% 43%	8402
February	1st to 10th	Night	17% 10% 3 6% 4 3 3 3 4 6% 41%	2669
	11th to 20th	Night	17% 8% 3 6% 3 3 3 3 4 5% 44%	2458
	21st to end	Night	17% 7% 3 5% 4 3 3 3 5% 5% 44%	2076
March	1st to 10th	Night	17% 8% 3 7% 5% 4 4 3 4 4 40%	5493
	11th to 20th	Night	11% 6% 3 7% 4 4 4 3 4 6% 48%	5092
	21st to end	Night	13% 6% 2 6% 5% 5% 4 4 5% 8% 43%	5260
April	1st to 10th	Night	11% 5% 2 5% 3 3 3 3 6% 8% 49%	2100
	11th to 20th	Night	13% 5% 2 6% 4 4 4 4 5% 8% 45%	2075
	21st to end	Night	17% 6% 2 6% 4 4 4 4 5% 7% 40%	2100
May	1st to 10th	Night	15% 7% 3 6% 5% 5% 5% 4 6% 7% 38%	5777
	11th to 20th	Night	13% 7% 3 7% 5% 5% 5% 4 5% 7% 40%	5069
	21st to end	Night	17% 9% 4 8% 5% 5% 5% 4 5% 7% 31%	5139
June	1st to 10th	Night	9% 4 2 6% 5% 4 4 4 7% 9% 46%	1680
	11th to 20th	Night	5% 4 1 4 4 3 4 4 6% 11% 55%	1680
	21st to end	Night	3 3 1 3 4 4 4 4 9% 10% 55%	1680
July	1st to 10th	Night	7% 4 2 6% 5% 4 5% 4 6% 9% 48%	4708
	11th to 20th	Night	3 3 2 6% 5% 6% 6% 5% 8% 10% 45%	4707
	21st to end	Night	6% 5% 2 5% 4 4 4 4 7% 11% 48%	5761
August	1st to 10th	Night	5% 4 1 5% 3 3 4 3 6% 8% 58%	4355
	11th to 20th	Night	5% 3 1 4 4 4 4 3 6% 8% 57%	4560
	21st to end	Night	4 3 1 4 3 3 3 3 6% 10% 60%	5046
September	1st to 10th	Night	10% 5% 2 4 3 3 3 3 5% 7% 57%	2100
	11th to 20th	Night	8% 4 2 5% 4 4 5% 3 5% 7% 52%	2126
	21st to end	Night	9% 5% 2 5% 3 4 3 4 5% 5% 55%	2310
October	1st to 10th	Night	6% 4 1 4 3 3 4 3 4 6% 63%	2475
	11th to 20th	Night	11% 5% 1 4 3 3 3 3 4 5% 58%	2520
	21st to end	Night	18% 5% 2 5% 3 3 3 3 4 4 50%	2737
November	1st to 10th	Night	12% 5% 1 4 3 2 3 2 4 6% 57%	2661
	11th to 20th	Night	14% 5% 2 4 3 3 3 3 4 8% 52%	2730
	21st to end	Night	18% 6% 2 5% 4 3 3 2 4 6% 48%	2730
December	1st to 10th	Night	15% 6% 2 5% 3 4 4 3 5% 5% 48%	4646
	11th to 20th	Night	17% 7% 2 6% 4 4 4 2 4 5% 46%	5339
	21st to end	Night	24% 8% 3 7% 4 4 3 3 4 5% 34%	7150

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	42% 3 13% 29% 12% 2	4692
	11th to 20th	Day	32% 4 6% 31% 21% 5%	5268
	21st to end	Day	42% 4 9% 21% 16% 9%	5812
February	1st to 10th	Day	46% 4 13% 22% 14% 1	1948
	11th to 20th	Day	45% 3 11% 23% 13% 5%	2058
	21st to end	Day	45% 5% 9% 20% 14% 6%	1730
March	1st to 10th	Day	46% 5% 5% 20% 16% 7%	4622
	11th to 20th	Day	31% 4 9% 27% 22% 7%	5090
	21st to end	Day	40% 5% 12% 29% 14% 1	5913
April	1st to 10th	Day	36% 5% 11% 25% 20% 2	2520
	11th to 20th	Day	42% 6% 10% 21% 16% 5%	2494
	21st to end	Day	42% 6% 11% 24% 15% 1	2520
May	1st to 10th	Day	43% 8% 12% 23% 12% 1	7110
	11th to 20th	Day	44% 8% 11% 19% 15% 3	7800
	21st to end	Day	49% 7% 11% 18% 13% 2	9061
June	1st to 10th	Day	34% 8% 14% 25% 19% 1	2940
	11th to 20th	Day	29% 8% 13% 29% 19% 3	2940
	21st to end	Day	27% 8% 17% 26% 17% 5%	2940
July	1st to 10th	Day	33% 8% 14% 26% 17% 2	8211
	11th to 20th	Day	29% 10% 20% 27% 13% 1	8205
	21st to end	Day	33% 8% 20% 32% 8%	8158
August	1st to 10th	Day	25% 7% 14% 30% 23% 1	5789
	11th to 20th	Day	29% 6% 16% 29% 18% 2	5522
	21st to end	Day	22% 5% 12% 38% 19% 3	6079
September	1st to 10th	Day	30% 6% 12% 28% 21% 3	2520
	11th to 20th	Day	33% 6% 9% 25% 25% 2	2471
	21st to end	Day	33% 6% 7% 24% 26% 4	2310
October	1st to 10th	Day	16% 3 5% 19% 42% 15%	3414
	11th to 20th	Day	23% 3 6% 20% 38% 11%	3340
	21st to end	Day	31% 4 5% 28% 27% 5%	3618
November	1st to 10th	Day	32% 5% 10% 26% 21% 7%	1857
	11th to 20th	Day	37% 3 7% 24% 23% 6%	1890
	21st to end	Day	41% 4 8% 25% 20% 2	1890
December	1st to 10th	Day	36% 4 8% 34% 17% 1	2759
	11th to 20th	Day	41% 4 9% 27% 16% 2	3085
	21st to end	Day	57% 5% 11% 16% 9% 2	4070
January	1st to 10th	Night	43% 4 12% 27% 13% 1	8233
	11th to 20th	Night	33% 5% 6% 26% 25% 5%	7703
	21st to end	Night	44% 3 9% 24% 15% 5%	8402
February	1st to 10th	Night	45% 4 10% 23% 16% 2	2669
	11th to 20th	Night	44% 3 11% 22% 18% 4	2459
	21st to end	Night	42% 4 8% 23% 18% 5%	2076
March	1st to 10th	Night	46% 4 6% 18% 17% 8%	5493
	11th to 20th	Night	37% 4 8% 23% 17% 11%	5092
	21st to end	Night	39% 5% 9% 30% 15% 2	5260
April	1st to 10th	Night	33% 5% 12% 26% 20% 4	2100
	11th to 20th	Night	37% 5% 10% 22% 21% 5%	2075
	21st to end	Night	42% 6% 9% 23% 17% 3	2100
May	1st to 10th	Night	43% 7% 15% 25% 9% 1	5807
	11th to 20th	Night	43% 7% 13% 21% 15% 2	5070
	21st to end	Night	50% 8% 10% 17% 11% 3	5149
June	1st to 10th	Night	33% 7% 13% 23% 22% 2	1680
	11th to 20th	Night	23% 7% 12% 29% 22% 7%	1680
	21st to end	Night	21% 8% 16% 29% 18% 8%	1680
July	1st to 10th	Night	31% 8% 13% 25% 20% 3	4670
	11th to 20th	Night	30% 11% 18% 25% 13% 2	4662
	21st to end	Night	29% 7% 22% 30% 12%	5633
August	1st to 10th	Night	24% 6% 15% 32% 23% 1	4345
	11th to 20th	Night	24% 6% 17% 32% 17% 4	4590
	21st to end	Night	20% 5% 12% 37% 24% 3	5046
September	1st to 10th	Night	27% 6% 8% 30% 23% 6%	2100
	11th to 20th	Night	31% 6% 9% 26% 24% 3	2126
	21st to end	Night	29% 7% 9% 21% 29% 6%	2310
October	1st to 10th	Night	15% 2 6% 17% 41% 20%	3969
	11th to 20th	Night	22% 3 5% 18% 40% 13%	4019
	21st to end	Night	29% 3 6% 25% 29% 7%	4349
November	1st to 10th	Night	30% 4 8% 27% 25% 6%	2661
	11th to 20th	Night	32% 3 8% 26% 23% 8%	2730
	21st to end	Night	39% 3 8% 25% 22% 3	2730
December	1st to 10th	Night	37% 4 8% 30% 18% 2	4646
	11th to 20th	Night	41% 3 10% 22% 21% 2	5341
	21st to end	Night	52% 5% 10% 20% 11% 2	7150

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	25% 13% 37% 20% 5%	330
	11th to 20th	Day	23% 16% 45% 14% 2	330
	21st to end	Day	19% 15% 45% 19% 2	363
February	1st to 10th	Day	23% 15% 39% 17% 5%	330
	11th to 20th	Day	28% 19% 35% 16% 2	330
	21st to end	Day	25% 18% 34% 18% 3	273
March	1st to 10th	Day	23% 15% 41% 16% 4 1	330
	11th to 20th	Day	25% 18% 37% 17% 4	330
	21st to end	Day	22% 15% 34% 20% 8%	510
April	1st to 10th	Day	19% 14% 31% 26% 9% 1	540
	11th to 20th	Day	19% 18% 29% 21% 12% 1	532
	21st to end	Day	20% 12% 29% 27% 11% 2	540
May	1st to 10th	Day	16% 14% 29% 30% 10% 2	543
	11th to 20th	Day	17% 8% 25% 26% 17% 7%	620
	21st to end	Day	12% 7% 24% 31% 18% 7%	844
June	1st to 10th	Day	13% 3 18% 28% 26% 12%	780
	11th to 20th	Day	7% 4 14% 40% 26% 10%	780
	21st to end	Day	6% 3 21% 35% 25% 11%	780
July	1st to 10th	Day	8% 2 11% 26% 30% 22%	771
	11th to 20th	Day	6% 2 10% 34% 33% 14%	768
	21st to end	Day	8% 3 10% 29% 35% 15%	849
August	1st to 10th	Day	6% 2 8% 33% 34% 16%	682
	11th to 20th	Day	13% 2 12% 28% 30% 16%	559
	21st to end	Day	8% 2 7% 28% 37% 18%	627
September	1st to 10th	Day	7% 3 9% 29% 35% 16%	570
	11th to 20th	Day	8% 2 10% 26% 34% 20%	570
	21st to end	Day	14% 5% 19% 25% 28% 10%	570
October	1st to 10th	Day	8% 5% 19% 36% 25% 7%	401
	11th to 20th	Day	14% 11% 25% 30% 14% 7%	360
	21st to end	Day	21% 14% 30% 20% 12% 3	387
November	1st to 10th	Day	18% 9% 32% 27% 11% 3	330
	11th to 20th	Day	13% 16% 34% 23% 13% 2	330
	21st to end	Day	22% 13% 33% 22% 9% 1	330
December	1st to 10th	Day	15% 14% 36% 25% 8% 2	330
	11th to 20th	Day	22% 15% 32% 21% 10%	330
	21st to end	Day	24% 19% 35% 18% 4	363
January	1st to 10th	Night	22% 8% 37% 28% 5%	1050
	11th to 20th	Night	21% 12% 41% 23% 4	1050
	21st to end	Night	19% 9% 41% 29% 2	1155
February	1st to 10th	Night	22% 10% 39% 26% 3	989
	11th to 20th	Night	23% 11% 40% 25% 2	823
	21st to end	Night	22% 12% 40% 24% 2	692
March	1st to 10th	Night	21% 11% 37% 28% 3	840
	11th to 20th	Night	20% 11% 34% 29% 6%	632
	21st to end	Night	20% 10% 34% 29% 7%	693
April	1st to 10th	Night	13% 10% 42% 29% 6%	630
	11th to 20th	Night	15% 12% 32% 30% 11% 1	623
	21st to end	Night	18% 6% 34% 31% 10%	630
May	1st to 10th	Night	17% 6% 29% 34% 13% 1	630
	11th to 20th	Night	16% 5% 27% 34% 17% 2	621
	21st to end	Night	12% 4 19% 39% 23% 3	683
June	1st to 10th	Night	10% 3 14% 38% 31% 4	630
	11th to 20th	Night	5% 3 12% 50% 28% 2	630
	21st to end	Night	4 2 14% 46% 31% 4	630
July	1st to 10th	Night	7% 1 7% 33% 43% 8%	615
	11th to 20th	Night	5% 1 6% 41% 38% 9%	612
	21st to end	Night	7% 2 8% 34% 43% 6%	690
August	1st to 10th	Night	6% 1 6% 39% 41% 6%	627
	11th to 20th	Night	8% 2 8% 36% 42% 4	624
	21st to end	Night	5% 2 5% 37% 44% 7%	693
September	1st to 10th	Night	11% 1 7% 33% 40% 6%	630
	11th to 20th	Night	10% 2 9% 34% 38% 8%	656
	21st to end	Night	11% 3 18% 35% 29% 4	840
October	1st to 10th	Night	8% 3 17% 42% 26% 4	840
	11th to 20th	Night	14% 4 29% 33% 18% 1	840
	21st to end	Night	20% 5% 28% 34% 12% 1	913
November	1st to 10th	Night	13% 6% 31% 36% 13% 1	820
	11th to 20th	Night	17% 7% 32% 34% 10% 1	840
	21st to end	Night	21% 8% 29% 32% 9% 1	840
December	1st to 10th	Night	21% 8% 32% 33% 5% 1	1002
	11th to 20th	Night	22% 7% 33% 30% 7%	1050
	21st to end	Night	25% 12% 31% 27% 5%	1155

Page generated at 2026-10-26 03:37:47. Version ac07

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