Dunchurch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dunchurch clear sky chart from 2005-11-06 to 2025-02-25.

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% 12% 4 8% 5% 4 4 3 5% 6% 31%	108668
	Night	16% 14% 5% 10% 5% 4 4 3 5% 6% 29%	110039
Transparency	Day	53% 6% 10% 20% 10% 1	112265
	Night	56% 5% 10% 18% 9% 1	114606
Seeing	Day	25% 13% 31% 20% 8% 2	15338
	Night	24% 11% 29% 26% 9% 1	24562

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	12% 19% 10% 12% 4 5% 4 3 5% 6% 21%	3158
	11th to 20th	Day	10% 20% 7% 16% 7% 7% 6% 3 5% 4 14%	3534
	21st to end	Day	14% 21% 8% 15% 6% 4 4 3 3 4 17%	4466
February	1st to 10th	Day	14% 20% 6% 14% 8% 5% 4 2 4 4 20%	1800
	11th to 20th	Day	12% 20% 7% 12% 6% 5% 3 3 4 4 25%	1753
	21st to end	Day	15% 20% 6% 12% 7% 5% 4 3 3 4 21%	1477
March	1st to 10th	Day	18% 17% 5% 8% 5% 4 4 3 4 6% 26%	3401
	11th to 20th	Day	11% 17% 7% 12% 5% 5% 4 3 5% 5% 27%	3480
	21st to end	Day	14% 14% 5% 8% 5% 5% 4 3 4 5% 33%	3815
April	1st to 10th	Day	20% 15% 4 7% 4 4 3 4 5% 6% 27%	2242
	11th to 20th	Day	22% 12% 3 5% 4 4 3 3 4 5% 35%	2391
	21st to end	Day	22% 12% 3 8% 4 4 4 2 4 5% 34%	2470
May	1st to 10th	Day	20% 8% 3 7% 5% 5% 5% 3 5% 6% 32%	4172
	11th to 20th	Day	14% 8% 3 7% 4 4 4 4 6% 8% 38%	4398
	21st to end	Day	19% 6% 2 5% 4 4 4 3 5% 7% 41%	4837
June	1st to 10th	Day	19% 9% 3 6% 5% 4 4 4 5% 7% 35%	2760
	11th to 20th	Day	14% 6% 2 7% 5% 5% 5% 4 5% 7% 39%	2850
	21st to end	Day	19% 8% 3 7% 5% 4 5% 4 6% 7% 32%	2850
July	1st to 10th	Day	17% 6% 3 7% 5% 4 5% 4 5% 7% 35%	4760
	11th to 20th	Day	14% 6% 2 6% 4 4 5% 4 6% 8% 41%	4672
	21st to end	Day	12% 5% 2 5% 4 4 4 3 6% 7% 48%	4636
August	1st to 10th	Day	12% 6% 3 7% 5% 5% 6% 5% 7% 8% 36%	4104
	11th to 20th	Day	18% 6% 3 6% 4 4 5% 4 6% 8% 35%	4044
	21st to end	Day	10% 5% 2 6% 5% 5% 4 5% 6% 8% 44%	4436
September	1st to 10th	Day	15% 7% 3 7% 4 4 4 4 5% 7% 40%	2280
	11th to 20th	Day	15% 7% 2 5% 4 4 4 3 5% 7% 43%	2157
	21st to end	Day	22% 8% 3 6% 4 5% 3 3 4 6% 35%	2061
October	1st to 10th	Day	20% 9% 4 7% 4 5% 3 4 4 6% 34%	1900
	11th to 20th	Day	26% 12% 3 8% 5% 4 4 3 5% 5% 24%	1900
	21st to end	Day	30% 14% 4 9% 4 4 3 2 4 5% 21%	2062
November	1st to 10th	Day	20% 16% 4 7% 5% 4 5% 4 6% 7% 25%	1606
	11th to 20th	Day	20% 16% 6% 8% 6% 4 5% 3 5% 5% 23%	1600
	21st to end	Day	22% 23% 6% 10% 5% 4 4 2 4 4 16%	1600
December	1st to 10th	Day	16% 24% 8% 13% 5% 6% 5% 3 4 4 13%	2600
	11th to 20th	Day	20% 20% 5% 13% 5% 3 3 2 3 4 21%	2920
	21st to end	Day	23% 22% 7% 14% 5% 3 2 3 3 4 14%	3476
January	1st to 10th	Night	13% 18% 9% 12% 7% 5% 4 3 4 5% 19%	6808
	11th to 20th	Night	11% 19% 7% 18% 7% 6% 5% 3 5% 4 15%	6338
	21st to end	Night	11% 21% 10% 16% 6% 5% 4 3 4 4 17%	6490
February	1st to 10th	Night	13% 18% 5% 12% 8% 5% 5% 4 5% 4 21%	2600
	11th to 20th	Night	12% 16% 7% 13% 7% 5% 4 3 5% 5% 24%	2533
	21st to end	Night	14% 17% 6% 12% 6% 6% 5% 3 4 6% 20%	2068
March	1st to 10th	Night	14% 14% 5% 9% 5% 4 4 3 5% 7% 30%	3438
	11th to 20th	Night	12% 16% 7% 9% 5% 4 4 3 4 5% 30%	3479
	21st to end	Night	14% 11% 4 8% 6% 5% 5% 3 5% 5% 34%	3817
April	1st to 10th	Night	21% 16% 3 6% 4 4 3 3 5% 6% 29%	1937
	11th to 20th	Night	19% 10% 3 6% 4 4 4 3 4 6% 36%	1754
	21st to end	Night	21% 10% 3 8% 5% 5% 3 4 4 6% 31%	1710
May	1st to 10th	Night	17% 7% 2 5% 4 4 5% 4 6% 7% 38%	2769
	11th to 20th	Night	11% 8% 3 7% 5% 4 4 4 7% 9% 40%	2495
	21st to end	Night	12% 8% 2 6% 4 4 4 4 6% 8% 42%	2738
June	1st to 10th	Night	15% 9% 2 7% 4 5% 5% 4 6% 8% 36%	1416
	11th to 20th	Night	14% 5% 2 5% 4 4 4 4 6% 8% 43%	1330
	21st to end	Night	15% 7% 2 6% 5% 4 5% 4 6% 7% 40%	1330
July	1st to 10th	Night	13% 6% 3 6% 4 3 4 3 5% 7% 46%	2210
	11th to 20th	Night	16% 5% 2 6% 3 3 4 3 5% 7% 46%	2293
	21st to end	Night	10% 6% 2 5% 3 3 4 4 6% 8% 49%	2914
August	1st to 10th	Night	12% 6% 2 5% 4 4 4 4 5% 8% 46%	2825
	11th to 20th	Night	15% 7% 2 6% 4 3 4 3 6% 8% 43%	2785
	21st to end	Night	15% 5% 1 4 3 3 4 3 5% 6% 50%	3187
September	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 5% 7% 48%	1900
	11th to 20th	Night	13% 6% 2 5% 3 3 4 4 4 7% 50%	2019
	21st to end	Night	18% 7% 3 6% 4 4 4 3 5% 6% 41%	2118
October	1st to 10th	Night	20% 9% 3 7% 4 4 4 3 5% 6% 37%	2280
	11th to 20th	Night	25% 11% 3 7% 5% 5% 5% 3 5% 6% 26%	2280
	21st to end	Night	27% 14% 5% 8% 5% 3 4 3 4 5% 24%	2535
November	1st to 10th	Night	22% 13% 3 7% 5% 4 3 3 4 6% 30%	2689
	11th to 20th	Night	18% 14% 5% 8% 6% 5% 5% 3 4 6% 25%	2800
	21st to end	Night	24% 19% 5% 9% 6% 4 3 3 4 5% 17%	2800
December	1st to 10th	Night	17% 24% 7% 12% 6% 4 4 4 5% 5% 13%	4580
	11th to 20th	Night	17% 23% 6% 13% 6% 4 4 3 4 4 17%	5272
	21st to end	Night	21% 21% 6% 15% 4 4 4 2 3 3 15%	7502

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	64% 6% 7% 17% 6%	3159
	11th to 20th	Day	74% 3 7% 9% 6% 1	3565
	21st to end	Day	72% 4 5% 10% 7% 1	4466
February	1st to 10th	Day	69% 3 7% 14% 6% 1	1800
	11th to 20th	Day	63% 5% 9% 12% 9% 1	1762
	21st to end	Day	68% 4 6% 15% 7%	1477
March	1st to 10th	Day	60% 5% 12% 11% 11% 1	3404
	11th to 20th	Day	59% 6% 10% 16% 8% 1	3480
	21st to end	Day	51% 4 11% 19% 12% 2	3815
April	1st to 10th	Day	57% 5% 11% 15% 10% 1	2242
	11th to 20th	Day	53% 4 7% 22% 14% 1	2391
	21st to end	Day	54% 5% 8% 17% 14% 3	2470
May	1st to 10th	Day	50% 6% 9% 22% 11% 2	4184
	11th to 20th	Day	41% 7% 11% 30% 9% 1	4402
	21st to end	Day	42% 6% 13% 18% 18% 3	4837
June	1st to 10th	Day	48% 8% 8% 23% 13% 1	2760
	11th to 20th	Day	44% 6% 9% 25% 16% 1	2850
	21st to end	Day	50% 7% 11% 20% 11% 1	2850
July	1st to 10th	Day	45% 7% 15% 23% 10% 1	4686
	11th to 20th	Day	39% 6% 15% 30% 10%	4591
	21st to end	Day	35% 6% 11% 29% 18%	4488
August	1st to 10th	Day	43% 8% 12% 27% 10% 1	4091
	11th to 20th	Day	45% 7% 13% 26% 9%	4083
	21st to end	Day	36% 6% 11% 35% 11% 1	4436
September	1st to 10th	Day	43% 7% 11% 26% 12% 1	2280
	11th to 20th	Day	40% 7% 12% 29% 12%	2157
	21st to end	Day	51% 7% 10% 24% 9%	2061
October	1st to 10th	Day	48% 5% 12% 24% 10% 1	3160
	11th to 20th	Day	52% 7% 12% 23% 6%	3140
	21st to end	Day	62% 5% 12% 15% 5%	3376
November	1st to 10th	Day	58% 8% 12% 17% 5%	1606
	11th to 20th	Day	63% 6% 11% 13% 6% 1	1600
	21st to end	Day	72% 7% 9% 9% 3 1	1600
December	1st to 10th	Day	73% 6% 11% 7% 2	2600
	11th to 20th	Day	70% 3 6% 13% 8%	2920
	21st to end	Day	75% 3 5% 11% 5%	3476
January	1st to 10th	Night	68% 5% 7% 14% 6%	6808
	11th to 20th	Night	72% 5% 9% 7% 7%	6382
	21st to end	Night	72% 4 6% 9% 8% 1	6490
February	1st to 10th	Night	64% 7% 9% 13% 6% 1	2600
	11th to 20th	Night	63% 4 9% 16% 8% 1	2535
	21st to end	Night	65% 6% 9% 14% 7% 1	2068
March	1st to 10th	Night	53% 5% 13% 16% 12% 1	3448
	11th to 20th	Night	55% 6% 12% 16% 8% 2	3480
	21st to end	Night	49% 5% 10% 21% 12% 2	3817
April	1st to 10th	Night	56% 5% 8% 18% 11% 2	1937
	11th to 20th	Night	50% 4 8% 21% 16% 1	1754
	21st to end	Night	55% 5% 9% 14% 15% 2	1710
May	1st to 10th	Night	43% 7% 12% 25% 11% 2	2776
	11th to 20th	Night	39% 8% 11% 26% 15% 2	2496
	21st to end	Night	39% 6% 12% 24% 17% 2	2739
June	1st to 10th	Night	45% 7% 11% 22% 13% 3	1416
	11th to 20th	Night	38% 4 12% 26% 19%	1330
	21st to end	Night	42% 6% 14% 25% 12% 1	1330
July	1st to 10th	Night	38% 5% 14% 26% 15% 2	2175
	11th to 20th	Night	37% 7% 12% 34% 9% 1	2251
	21st to end	Night	33% 7% 10% 29% 20%	2821
August	1st to 10th	Night	36% 6% 16% 25% 15% 2	2814
	11th to 20th	Night	38% 7% 18% 26% 10% 1	2812
	21st to end	Night	35% 4 12% 35% 13% 1	3187
September	1st to 10th	Night	36% 6% 16% 27% 13% 1	1900
	11th to 20th	Night	34% 7% 14% 31% 13%	2019
	21st to end	Night	44% 5% 13% 27% 11%	2118
October	1st to 10th	Night	39% 5% 10% 30% 16%	3800
	11th to 20th	Night	51% 6% 14% 22% 7%	3779
	21st to end	Night	57% 5% 16% 15% 6%	4171
November	1st to 10th	Night	56% 6% 12% 21% 6%	2689
	11th to 20th	Night	59% 7% 12% 14% 7% 1	2800
	21st to end	Night	70% 6% 10% 10% 4	2800
December	1st to 10th	Night	73% 6% 11% 8% 2	4580
	11th to 20th	Night	73% 4 6% 10% 7%	5272
	21st to end	Night	75% 4 6% 11% 5%	7502

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	23% 24% 31% 17% 6% 2	200
	11th to 20th	Day	25% 16% 35% 18% 5% 1	237
	21st to end	Day	30% 14% 34% 18% 5%	330
February	1st to 10th	Day	32% 23% 34% 9% 1 1	300
	11th to 20th	Day	26% 24% 38% 11% 1	300
	21st to end	Day	39% 22% 32% 7%	237
March	1st to 10th	Day	25% 20% 36% 15% 3	440
	11th to 20th	Day	23% 19% 37% 15% 4	460
	21st to end	Day	30% 18% 30% 16% 5% 1	506
April	1st to 10th	Day	28% 17% 32% 16% 5% 1	460
	11th to 20th	Day	38% 14% 23% 15% 8% 2	452
	21st to end	Day	30% 16% 33% 12% 8% 1	460
May	1st to 10th	Day	27% 11% 30% 19% 9% 3	463
	11th to 20th	Day	22% 15% 30% 20% 9% 3	487
	21st to end	Day	20% 16% 31% 20% 10% 2	529
June	1st to 10th	Day	22% 13% 32% 25% 7% 1	590
	11th to 20th	Day	18% 12% 35% 23% 10% 1	680
	21st to end	Day	25% 11% 32% 22% 7% 2	680
July	1st to 10th	Day	15% 10% 33% 30% 12% 1	671
	11th to 20th	Day	16% 10% 31% 28% 12% 3	619
	21st to end	Day	14% 6% 33% 30% 12% 4	532
August	1st to 10th	Day	19% 4 28% 31% 12% 6%	486
	11th to 20th	Day	18% 4 27% 27% 16% 10%	479
	21st to end	Day	18% 10% 28% 25% 14% 4	539
September	1st to 10th	Day	20% 10% 31% 23% 10% 6%	490
	11th to 20th	Day	17% 6% 27% 26% 18% 7%	490
	21st to end	Day	27% 8% 24% 23% 15% 3	490
October	1st to 10th	Day	26% 12% 25% 24% 11% 3	490
	11th to 20th	Day	29% 12% 37% 15% 5% 1	490
	21st to end	Day	37% 13% 32% 16% 2	511
November	1st to 10th	Day	31% 17% 35% 13% 4	220
	11th to 20th	Day	33% 16% 37% 12% 3 1	200
	21st to end	Day	36% 14% 35% 11% 4 1	200
December	1st to 10th	Day	33% 15% 33% 16% 4 1	200
	11th to 20th	Day	36% 15% 36% 11% 2 1	200
	21st to end	Day	35% 16% 29% 15% 5% 1	220
January	1st to 10th	Night	29% 13% 32% 20% 5% 1	1000
	11th to 20th	Night	30% 14% 29% 21% 5% 1	889
	21st to end	Night	21% 10% 34% 25% 8% 1	880
February	1st to 10th	Night	23% 19% 33% 22% 4	800
	11th to 20th	Night	21% 17% 34% 22% 6%	783
	21st to end	Night	24% 17% 31% 24% 2 1	647
March	1st to 10th	Night	22% 18% 34% 22% 4	760
	11th to 20th	Night	24% 18% 31% 22% 5% 1	760
	21st to end	Night	21% 13% 32% 26% 8% 1	836
April	1st to 10th	Night	29% 12% 31% 23% 4	760
	11th to 20th	Night	28% 13% 26% 24% 8% 1	630
	21st to end	Night	29% 9% 26% 24% 11%	570
May	1st to 10th	Night	21% 6% 27% 34% 10% 1	532
	11th to 20th	Night	18% 8% 31% 34% 8% 1	374
	21st to end	Night	14% 9% 34% 34% 9%	411
June	1st to 10th	Night	17% 6% 31% 36% 10% 1	380
	11th to 20th	Night	18% 9% 25% 36% 12%	380
	21st to end	Night	20% 7% 25% 33% 14% 1	380
July	1st to 10th	Night	13% 3 25% 41% 17% 1	370
	11th to 20th	Night	13% 4 27% 36% 20% 1	368
	21st to end	Night	14% 4 25% 36% 19% 2	516
August	1st to 10th	Night	18% 2 17% 38% 23% 2	567
	11th to 20th	Night	14% 4 19% 40% 21% 3	564
	21st to end	Night	19% 5% 24% 31% 20% 2	664
September	1st to 10th	Night	16% 6% 26% 32% 18% 2	760
	11th to 20th	Night	17% 4 23% 31% 21% 4	760
	21st to end	Night	21% 8% 23% 30% 16% 3	760
October	1st to 10th	Night	23% 9% 28% 26% 14% 1	760
	11th to 20th	Night	32% 8% 28% 22% 9% 1	760
	21st to end	Night	34% 13% 28% 20% 5%	836
November	1st to 10th	Night	32% 10% 27% 23% 7% 1	780
	11th to 20th	Night	26% 17% 29% 21% 6%	800
	21st to end	Night	36% 13% 27% 20% 4 1	800
December	1st to 10th	Night	34% 14% 29% 18% 5% 1	800
	11th to 20th	Night	29% 14% 34% 18% 4 1	825
	21st to end	Night	34% 14% 30% 18% 4	1100

Page generated at 2025-02-22 06:51:38. Version ac07

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