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 2026-07-01.

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	16% 12% 4 9% 5% 4 4 3 5% 6% 32%	138176
	Night	15% 14% 5% 10% 5% 4 4 3 5% 6% 29%	134228
Transparency	Day	53% 5% 10% 21% 10% 1	141729
	Night	55% 5% 10% 19% 10% 1	138765
Seeing	Day	25% 13% 32% 20% 8% 2	17167
	Night	24% 11% 29% 26% 9% 1	26202

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	13% 18% 9% 11% 5% 5% 4 3 5% 6% 21%	4094
	11th to 20th	Day	10% 21% 9% 17% 8% 6% 6% 3 4 3 12%	4618
	21st to end	Day	11% 17% 7% 18% 7% 5% 5% 4 3 4 18%	5780
February	1st to 10th	Day	13% 20% 6% 14% 8% 5% 4 2 4 4 21%	1890
	11th to 20th	Day	12% 20% 6% 13% 6% 5% 3 3 4 4 24%	1843
	21st to end	Day	15% 20% 6% 12% 7% 5% 4 3 3 5% 20%	1588
March	1st to 10th	Day	18% 17% 5% 10% 5% 4 4 2 4 5% 27%	4996
	11th to 20th	Day	14% 14% 6% 11% 5% 5% 4 3 6% 7% 26%	5090
	21st to end	Day	17% 17% 5% 8% 5% 4 3 3 4 5% 29%	5586
April	1st to 10th	Day	20% 15% 4 7% 4 4 4 4 5% 6% 27%	2478
	11th to 20th	Day	23% 13% 3 5% 4 4 3 3 4 5% 35%	2646
	21st to end	Day	22% 12% 3 8% 4 4 4 3 4 5% 33%	2730
May	1st to 10th	Day	16% 9% 3 8% 6% 5% 5% 4 6% 7% 32%	7760
	11th to 20th	Day	17% 10% 3 7% 4 4 4 4 5% 6% 36%	8221
	21st to end	Day	20% 8% 2 5% 4 4 4 3 4 6% 39%	9060
June	1st to 10th	Day	19% 9% 3 6% 5% 4 4 4 5% 7% 36%	3050
	11th to 20th	Day	15% 7% 3 6% 5% 5% 5% 4 5% 7% 38%	3150
	21st to end	Day	19% 8% 3 7% 5% 4 5% 4 6% 7% 32%	3150
July	1st to 10th	Day	16% 6% 2 7% 5% 5% 5% 4 6% 8% 36%	6820
	11th to 20th	Day	14% 5% 2 5% 4 4 4 3 5% 7% 45%	6690
	21st to end	Day	10% 5% 2 5% 4 4 4 3 6% 8% 50%	6664
August	1st to 10th	Day	12% 6% 3 7% 5% 5% 6% 5% 7% 8% 36%	4234
	11th to 20th	Day	18% 6% 3 6% 4 4 5% 4 6% 8% 36%	4174
	21st to end	Day	10% 5% 2 6% 5% 5% 4 5% 6% 9% 44%	4576
September	1st to 10th	Day	15% 7% 3 7% 4 4 4 4 6% 7% 39%	2400
	11th to 20th	Day	15% 7% 2 5% 4 4 4 3 5% 7% 44%	2270
	21st to end	Day	22% 8% 3 6% 4 5% 3 3 4 6% 35%	2169
October	1st to 10th	Day	19% 9% 3 7% 4 5% 3 4 4 6% 35%	2000
	11th to 20th	Day	25% 12% 3 8% 5% 4 4 3 5% 5% 25%	2000
	21st to end	Day	29% 15% 4 9% 4 4 3 2 4 4 22%	2170
November	1st to 10th	Day	20% 16% 4 7% 5% 3 4 3 6% 6% 25%	1688
	11th to 20th	Day	20% 16% 6% 8% 6% 4 4 3 5% 5% 23%	1680
	21st to end	Day	21% 23% 7% 10% 5% 4 4 2 4 4 16%	1680
December	1st to 10th	Day	15% 24% 8% 13% 5% 5% 5% 3 4 4 13%	2680
	11th to 20th	Day	20% 20% 5% 13% 5% 3 3 2 3 4 21%	2998
	21st to end	Day	23% 22% 7% 14% 5% 3 2 3 3 4 15%	3553
January	1st to 10th	Night	12% 18% 10% 13% 7% 5% 4 3 4 5% 18%	8831
	11th to 20th	Night	10% 22% 8% 18% 7% 5% 4 3 4 4 15%	8258
	21st to end	Night	9% 17% 9% 17% 7% 6% 5% 3 4 5% 19%	8401
February	1st to 10th	Night	12% 18% 5% 12% 8% 5% 5% 4 5% 4 22%	2730
	11th to 20th	Night	12% 16% 7% 13% 7% 5% 4 3 5% 5% 24%	2663
	21st to end	Night	14% 17% 7% 12% 6% 6% 5% 3 4 6% 20%	2213
March	1st to 10th	Night	15% 15% 5% 10% 4 4 4 3 5% 6% 30%	5063
	11th to 20th	Night	11% 14% 6% 10% 5% 5% 5% 4 5% 7% 28%	5089
	21st to end	Night	20% 13% 4 8% 5% 4 4 3 4 4 31%	5588
April	1st to 10th	Night	21% 15% 3 7% 4 4 4 3 5% 6% 29%	2141
	11th to 20th	Night	19% 10% 3 7% 4 4 4 4 5% 6% 35%	1941
	21st to end	Night	20% 10% 3 8% 5% 5% 3 4 4 6% 31%	1890
May	1st to 10th	Night	16% 8% 3 6% 4 4 4 4 6% 8% 36%	5139
	11th to 20th	Night	15% 8% 2 6% 4 3 4 3 5% 8% 42%	4639
	21st to end	Night	16% 8% 2 6% 4 4 3 3 5% 7% 42%	5114
June	1st to 10th	Night	14% 9% 2 6% 4 5% 5% 4 6% 8% 38%	1565
	11th to 20th	Night	14% 5% 2 5% 4 4 4 4 6% 9% 42%	1470
	21st to end	Night	14% 7% 2 6% 5% 4 5% 4 7% 7% 39%	1470
July	1st to 10th	Night	15% 6% 3 6% 4 3 4 4 5% 7% 42%	3160
	11th to 20th	Night	15% 5% 2 5% 3 3 4 3 4 6% 48%	3282
	21st to end	Night	11% 6% 2 5% 3 3 3 3 5% 8% 50%	4171
August	1st to 10th	Night	12% 6% 2 5% 4 4 4 4 5% 8% 46%	2915
	11th to 20th	Night	15% 7% 2 5% 4 3 4 3 6% 8% 43%	2875
	21st to end	Night	15% 5% 1 5% 3 3 3 3 5% 6% 50%	3288
September	1st to 10th	Night	13% 6% 2 5% 4 4 4 3 5% 7% 48%	2000
	11th to 20th	Night	12% 5% 2 5% 3 3 4 4 4 7% 50%	2126
	21st to end	Night	18% 7% 3 6% 4 4 4 2 5% 6% 42%	2230
October	1st to 10th	Night	19% 8% 3 6% 4 4 4 3 5% 6% 38%	2400
	11th to 20th	Night	25% 11% 3 7% 5% 5% 5% 3 5% 6% 26%	2400
	21st to end	Night	26% 13% 4 8% 5% 3 4 3 4 5% 26%	2669
November	1st to 10th	Night	21% 14% 4 7% 5% 4 4 3 4 6% 29%	2827
	11th to 20th	Night	18% 15% 5% 9% 6% 5% 5% 3 4 6% 25%	2940
	21st to end	Night	23% 20% 5% 9% 6% 4 3 3 4 5% 16%	2940
December	1st to 10th	Night	16% 24% 7% 12% 6% 4 4 4 5% 4 13%	4720
	11th to 20th	Night	17% 22% 6% 13% 6% 4 4 3 4 4 17%	5413
	21st to end	Night	21% 21% 6% 15% 4 4 4 2 3 3 15%	7667

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	63% 5% 7% 18% 6% 1	4095
	11th to 20th	Day	78% 3 6% 7% 6% 1	4649
	21st to end	Day	71% 4 5% 10% 9% 1	5780
February	1st to 10th	Day	69% 3 7% 14% 6% 1	1890
	11th to 20th	Day	64% 5% 9% 12% 9% 1	1852
	21st to end	Day	68% 4 6% 16% 6%	1588
March	1st to 10th	Day	62% 4 10% 8% 14% 2	4999
	11th to 20th	Day	57% 5% 12% 15% 8% 2	5090
	21st to end	Day	58% 3 9% 17% 10% 2	5586
April	1st to 10th	Day	58% 5% 10% 16% 10% 1	2478
	11th to 20th	Day	53% 4 7% 21% 14% 1	2646
	21st to end	Day	54% 4 8% 18% 13% 2	2730
May	1st to 10th	Day	49% 5% 9% 22% 10% 5%	7769
	11th to 20th	Day	47% 6% 9% 24% 13% 1	8225
	21st to end	Day	47% 4 10% 22% 15% 2	9061
June	1st to 10th	Day	48% 7% 7% 23% 15%	3050
	11th to 20th	Day	45% 6% 9% 25% 15% 1	3150
	21st to end	Day	49% 7% 11% 21% 10% 1	3150
July	1st to 10th	Day	44% 7% 15% 25% 9% 1	6747
	11th to 20th	Day	37% 5% 12% 35% 10%	6609
	21st to end	Day	32% 6% 13% 33% 15%	6473
August	1st to 10th	Day	42% 8% 13% 27% 10% 1	4221
	11th to 20th	Day	45% 7% 13% 26% 9%	4213
	21st to end	Day	36% 6% 12% 35% 10% 1	4576
September	1st to 10th	Day	43% 7% 12% 26% 12% 1	2400
	11th to 20th	Day	39% 7% 12% 30% 12%	2270
	21st to end	Day	51% 6% 10% 24% 9%	2169
October	1st to 10th	Day	47% 5% 12% 24% 10% 1	3260
	11th to 20th	Day	52% 7% 12% 23% 6%	3240
	21st to end	Day	62% 5% 12% 15% 6%	3484
November	1st to 10th	Day	59% 8% 11% 17% 5%	1688
	11th to 20th	Day	63% 6% 11% 13% 7% 1	1680
	21st to end	Day	73% 6% 9% 9% 3	1680
December	1st to 10th	Day	73% 6% 11% 7% 2 1	2680
	11th to 20th	Day	70% 3 6% 13% 8%	2998
	21st to end	Day	75% 3 5% 12% 5%	3553
January	1st to 10th	Night	69% 5% 7% 13% 6%	8831
	11th to 20th	Night	74% 4 7% 7% 8%	8302
	21st to end	Night	69% 4 6% 11% 9% 1	8401
February	1st to 10th	Night	64% 6% 9% 14% 6% 1	2730
	11th to 20th	Night	63% 4 9% 16% 7% 1	2665
	21st to end	Night	65% 6% 8% 14% 6% 1	2213
March	1st to 10th	Night	55% 4 11% 14% 13% 4	5073
	11th to 20th	Night	56% 6% 14% 16% 8% 1	5090
	21st to end	Night	56% 4 8% 18% 12% 2	5588
April	1st to 10th	Night	56% 5% 8% 19% 11% 2	2141
	11th to 20th	Night	50% 4 8% 21% 15% 1	1941
	21st to end	Night	54% 5% 8% 16% 14% 2	1890
May	1st to 10th	Night	45% 5% 8% 26% 12% 3	5146
	11th to 20th	Night	40% 7% 10% 24% 18% 2	4640
	21st to end	Night	42% 4 9% 28% 15% 2	5115
June	1st to 10th	Night	44% 6% 10% 21% 15% 3	1565
	11th to 20th	Night	39% 5% 12% 27% 18%	1470
	21st to end	Night	42% 6% 14% 24% 12% 1	1470
July	1st to 10th	Night	40% 5% 13% 28% 11% 2	3125
	11th to 20th	Night	37% 6% 11% 34% 12% 1	3240
	21st to end	Night	32% 6% 9% 36% 16%	4048
August	1st to 10th	Night	36% 6% 16% 25% 15% 2	2904
	11th to 20th	Night	39% 7% 18% 25% 10% 1	2902
	21st to end	Night	35% 4 12% 36% 12% 1	3288
September	1st to 10th	Night	36% 7% 16% 28% 12% 1	2000
	11th to 20th	Night	33% 7% 14% 32% 14%	2126
	21st to end	Night	44% 5% 13% 26% 12%	2230
October	1st to 10th	Night	38% 5% 10% 30% 16%	3920
	11th to 20th	Night	51% 6% 14% 22% 7%	3899
	21st to end	Night	57% 5% 16% 15% 7%	4305
November	1st to 10th	Night	56% 6% 12% 20% 6%	2827
	11th to 20th	Night	59% 7% 12% 14% 7% 1	2940
	21st to end	Night	70% 6% 9% 10% 4	2940
December	1st to 10th	Night	73% 6% 11% 8% 3	4720
	11th to 20th	Night	73% 4 7% 10% 7%	5413
	21st to end	Night	75% 4 6% 11% 5%	7667

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% 16% 5% 1	220
	11th to 20th	Day	27% 16% 35% 16% 4 1	261
	21st to end	Day	29% 14% 34% 19% 4	363
February	1st to 10th	Day	32% 22% 34% 11% 2 1	330
	11th to 20th	Day	26% 24% 38% 11% 1	330
	21st to end	Day	37% 22% 32% 8%	273
March	1st to 10th	Day	27% 20% 36% 14% 3	518
	11th to 20th	Day	27% 19% 36% 14% 4	540
	21st to end	Day	32% 20% 28% 15% 4 1	594
April	1st to 10th	Day	30% 18% 31% 15% 5% 1	540
	11th to 20th	Day	39% 13% 24% 15% 8% 2	532
	21st to end	Day	30% 15% 33% 13% 7% 1	540
May	1st to 10th	Day	27% 14% 31% 18% 8% 2	543
	11th to 20th	Day	23% 17% 31% 18% 8% 3	567
	21st to end	Day	22% 17% 31% 19% 9% 2	617
June	1st to 10th	Day	22% 13% 33% 25% 7% 1	680
	11th to 20th	Day	19% 13% 36% 22% 9% 1	780
	21st to end	Day	24% 11% 34% 22% 7% 2	780
July	1st to 10th	Day	14% 11% 33% 29% 12% 1	722
	11th to 20th	Day	16% 10% 31% 28% 11% 3	666
	21st to end	Day	14% 7% 36% 28% 12% 3	576
August	1st to 10th	Day	17% 3 28% 33% 13% 6%	526
	11th to 20th	Day	17% 5% 27% 28% 15% 9%	519
	21st to end	Day	17% 11% 28% 25% 14% 4	583
September	1st to 10th	Day	20% 10% 30% 23% 11% 6%	530
	11th to 20th	Day	16% 6% 26% 27% 17% 8%	530
	21st to end	Day	26% 8% 25% 24% 15% 3	530
October	1st to 10th	Day	24% 12% 25% 26% 11% 2	530
	11th to 20th	Day	29% 12% 37% 15% 5% 1	530
	21st to end	Day	36% 13% 31% 17% 3	553
November	1st to 10th	Day	32% 17% 33% 13% 4	242
	11th to 20th	Day	32% 15% 38% 12% 3	220
	21st to end	Day	36% 15% 34% 11% 3 1	220
December	1st to 10th	Day	33% 16% 31% 16% 4	220
	11th to 20th	Day	36% 15% 35% 10% 2 1	220
	21st to end	Day	36% 17% 29% 14% 4 1	242
January	1st to 10th	Night	28% 13% 33% 20% 5% 1	1050
	11th to 20th	Night	30% 15% 29% 21% 5% 1	933
	21st to end	Night	21% 10% 34% 25% 8% 1	924
February	1st to 10th	Night	23% 19% 32% 22% 4	840
	11th to 20th	Night	21% 17% 33% 22% 7%	823
	21st to end	Night	24% 18% 31% 24% 2 1	692
March	1st to 10th	Night	22% 18% 35% 20% 4	840
	11th to 20th	Night	24% 18% 33% 20% 4 1	840
	21st to end	Night	23% 14% 31% 24% 7% 1	924
April	1st to 10th	Night	29% 14% 31% 22% 4	840
	11th to 20th	Night	27% 14% 26% 23% 8% 1	697
	21st to end	Night	27% 11% 27% 24% 10%	630
May	1st to 10th	Night	21% 7% 27% 34% 10% 1	588
	11th to 20th	Night	19% 8% 32% 33% 8%	414
	21st to end	Night	16% 9% 34% 32% 9%	455
June	1st to 10th	Night	16% 6% 30% 37% 10% 1	420
	11th to 20th	Night	19% 9% 26% 36% 11%	420
	21st to end	Night	19% 7% 26% 34% 14% 1	420
July	1st to 10th	Night	13% 4 25% 41% 17% 1	390
	11th to 20th	Night	12% 4 27% 37% 19% 1	388
	21st to end	Night	14% 4 26% 36% 18% 1	543
August	1st to 10th	Night	17% 2 17% 39% 22% 2	597
	11th to 20th	Night	14% 4 19% 40% 21% 3	594
	21st to end	Night	18% 5% 24% 30% 20% 2	699
September	1st to 10th	Night	16% 6% 26% 32% 18% 2	800
	11th to 20th	Night	17% 4 23% 32% 21% 4	800
	21st to end	Night	21% 8% 23% 30% 17% 2	800
October	1st to 10th	Night	22% 8% 28% 28% 14% 1	800
	11th to 20th	Night	32% 9% 28% 23% 8% 1	800
	21st to end	Night	33% 12% 28% 21% 5%	880
November	1st to 10th	Night	32% 11% 27% 22% 7% 1	820
	11th to 20th	Night	25% 18% 30% 21% 6%	840
	21st to end	Night	36% 13% 27% 19% 4	840
December	1st to 10th	Night	33% 14% 30% 18% 4 1	840
	11th to 20th	Night	28% 14% 35% 18% 4 1	866
	21st to end	Night	34% 14% 30% 18% 4	1155

Page generated at 2026-06-28 02:10:45. Version ac07

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