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 2024-09-29.

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	17% 12% 4 8% 5% 4 4 3 5% 6% 32%	101359
	Night	16% 13% 5% 9% 5% 4 4 3 5% 6% 30%	96887
Transparency	Day	52% 6% 10% 20% 10% 1	101111
	Night	55% 6% 11% 18% 9% 1	96755
Seeing	Day	25% 13% 31% 20% 8% 2	14936
	Night	24% 11% 28% 26% 9% 1	23940

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	16% 24% 12% 13% 4 3 3 2 3 4 16%	2208
	11th to 20th	Day	11% 17% 7% 17% 8% 7% 6% 4 4 4 15%	2481
	21st to end	Day	17% 25% 8% 11% 5% 4 4 3 3 4 16%	3124
February	1st to 10th	Day	13% 20% 6% 14% 8% 5% 4 2 4 4 20%	1710
	11th to 20th	Day	12% 19% 7% 11% 6% 5% 3 3 4 4 25%	1663
	21st to end	Day	15% 19% 6% 12% 7% 5% 4 3 3 5% 21%	1441
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	23% 8% 3 6% 4 5% 3 3 4 6% 34%	2042
October	1st to 10th	Day	20% 10% 4 7% 4 5% 3 4 4 6% 33%	1800
	11th to 20th	Day	27% 12% 3 8% 5% 4 4 3 5% 5% 23%	1800
	21st to end	Day	30% 14% 4 9% 4 4 3 2 4 5% 21%	1954
November	1st to 10th	Day	19% 16% 4 7% 5% 4 5% 4 6% 7% 24%	1524
	11th to 20th	Day	20% 16% 6% 8% 6% 4 5% 3 5% 5% 22%	1520
	21st to end	Day	22% 22% 6% 10% 5% 4 4 2 4 4 16%	1520
December	1st to 10th	Day	17% 26% 5% 11% 5% 4 4 3 5% 5% 16%	1520
	11th to 20th	Day	21% 21% 5% 11% 5% 3 4 3 3 5% 20%	1866
	21st to end	Day	24% 23% 7% 15% 5% 3 2 3 3 3 13%	2431
January	1st to 10th	Night	16% 22% 12% 13% 6% 4 4 2 3 4 14%	4748
	11th to 20th	Night	13% 17% 6% 17% 7% 6% 6% 3 5% 5% 16%	4462
	21st to end	Night	15% 23% 10% 12% 5% 4 3 3 3 4 17%	4532
February	1st to 10th	Night	13% 19% 5% 12% 8% 5% 5% 4 6% 4 20%	2470
	11th to 20th	Night	12% 16% 7% 13% 7% 5% 4 3 4 5% 25%	2403
	21st to end	Night	15% 17% 6% 12% 6% 6% 5% 3 4 6% 21%	2009
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 7% 4 4 4 3 5% 7% 40%	2105
October	1st to 10th	Night	21% 9% 3 7% 4 4 4 3 5% 5% 36%	2160
	11th to 20th	Night	26% 11% 3 7% 5% 5% 5% 3 5% 6% 25%	2160
	21st to end	Night	27% 14% 5% 8% 5% 3 4 3 4 5% 24%	2401
November	1st to 10th	Night	21% 13% 3 7% 5% 5% 3 3 4 6% 30%	2551
	11th to 20th	Night	18% 15% 5% 8% 6% 5% 5% 3 4 6% 25%	2660
	21st to end	Night	24% 19% 5% 9% 6% 4 3 3 5% 5% 17%	2660
December	1st to 10th	Night	18% 24% 7% 11% 6% 4 4 3 4 3 15%	2660
	11th to 20th	Night	19% 24% 6% 10% 5% 3 4 3 4 4 18%	3324
	21st to end	Night	22% 23% 7% 15% 5% 4 3 2 3 3 13%	5236

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	73% 5% 8% 9% 4	2209
	11th to 20th	Day	74% 4 8% 8% 5% 1	2481
	21st to end	Day	74% 5% 6% 9% 6% 1	3124
February	1st to 10th	Day	69% 4 7% 14% 5% 1	1710
	11th to 20th	Day	62% 5% 9% 13% 10% 1	1672
	21st to end	Day	67% 4 7% 15% 7%	1441
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	52% 7% 10% 24% 7%	2042
October	1st to 10th	Day	52% 6% 11% 19% 11% 1	1800
	11th to 20th	Day	63% 7% 11% 13% 6% 1	1800
	21st to end	Day	68% 6% 9% 11% 6%	1954
November	1st to 10th	Day	58% 8% 12% 17% 5%	1524
	11th to 20th	Day	63% 6% 12% 12% 6% 1	1520
	21st to end	Day	72% 7% 9% 9% 3 1	1520
December	1st to 10th	Day	70% 7% 10% 9% 4 1	1520
	11th to 20th	Day	70% 5% 6% 12% 7%	1866
	21st to end	Day	78% 4 6% 10% 3	2431
January	1st to 10th	Night	74% 6% 7% 9% 4	4748
	11th to 20th	Night	69% 7% 11% 8% 4 1	4462
	21st to end	Night	72% 5% 6% 10% 6% 1	4532
February	1st to 10th	Night	65% 7% 9% 13% 5% 1	2470
	11th to 20th	Night	62% 4 9% 16% 8% 1	2405
	21st to end	Night	64% 6% 9% 14% 7% 1	2009
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% 10%	2105
October	1st to 10th	Night	49% 6% 12% 21% 12%	2160
	11th to 20th	Night	62% 7% 10% 17% 5%	2160
	21st to end	Night	65% 5% 9% 13% 7% 1	2401
November	1st to 10th	Night	55% 6% 12% 21% 6%	2551
	11th to 20th	Night	59% 7% 12% 14% 7% 1	2660
	21st to end	Night	70% 6% 10% 10% 4	2660
December	1st to 10th	Night	75% 6% 6% 10% 4	2660
	11th to 20th	Night	71% 5% 7% 11% 5%	3324
	21st to end	Night	77% 4 6% 9% 3	5236

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	24% 25% 27% 17% 6% 2	180
	11th to 20th	Day	26% 16% 34% 18% 5% 1	213
	21st to end	Day	31% 12% 33% 18% 5%	297
February	1st to 10th	Day	31% 22% 35% 9% 1 1	270
	11th to 20th	Day	26% 21% 41% 11% 1	270
	21st to end	Day	40% 22% 32% 7%	225
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% 24% 14% 2	483
October	1st to 10th	Day	27% 10% 24% 25% 11% 3	450
	11th to 20th	Day	30% 12% 36% 15% 5% 2	450
	21st to end	Day	37% 13% 32% 16% 2	469
November	1st to 10th	Day	29% 18% 36% 13% 5%	198
	11th to 20th	Day	33% 16% 36% 12% 3 1	180
	21st to end	Day	37% 13% 36% 10% 3 1	180
December	1st to 10th	Day	32% 16% 33% 16% 3 1	180
	11th to 20th	Day	37% 14% 36% 10% 2 1	180
	21st to end	Day	34% 18% 29% 14% 4 1	198
January	1st to 10th	Night	30% 13% 31% 20% 5% 1	950
	11th to 20th	Night	31% 14% 28% 21% 5% 1	845
	21st to end	Night	22% 9% 35% 25% 8% 1	836
February	1st to 10th	Night	24% 18% 32% 22% 4	760
	11th to 20th	Night	21% 17% 34% 22% 6%	743
	21st to end	Night	25% 17% 30% 25% 3 1	628
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% 17% 3	756
October	1st to 10th	Night	23% 8% 27% 26% 14% 1	720
	11th to 20th	Night	33% 8% 28% 22% 8% 1	720
	21st to end	Night	34% 12% 28% 20% 5%	792
November	1st to 10th	Night	31% 10% 27% 23% 8% 1	740
	11th to 20th	Night	26% 17% 29% 21% 6%	760
	21st to end	Night	37% 12% 27% 20% 4 1	760
December	1st to 10th	Night	34% 14% 29% 18% 4 1	760
	11th to 20th	Night	30% 14% 34% 17% 4 1	783
	21st to end	Night	34% 14% 30% 18% 4	1045

Page generated at 2024-09-26 09:52:24. Version ac07

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