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 2024-02-05.

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	18% 12% 4 7% 6% 3 4 4 5% 6% 30%	78079
	Night	17% 13% 5% 8% 6% 3 4 4 4 6% 29%	80769
Transparency	Day	55% 6% 10% 19% 10% 1	77780
	Night	57% 6% 10% 17% 9% 1	80603
Seeing	Day	25% 13% 31% 21% 8% 2	13970
	Night	25% 11% 28% 26% 9% 1	23207

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% 13% 12% 5% 2 3 2 3 4 17%	2208
	11th to 20th	Day	11% 17% 7% 14% 11% 5% 6% 5% 4 4 15%	2481
	21st to end	Day	18% 24% 9% 10% 6% 3 3 4 3 4 16%	3124
February	1st to 10th	Day	14% 18% 7% 13% 9% 4 5% 3 4 4 20%	1656
	11th to 20th	Day	13% 19% 6% 10% 7% 4 3 4 3 5% 25%	1573
	21st to end	Day	16% 19% 6% 11% 9% 3 4 4 3 5% 21%	1358
March	1st to 10th	Day	14% 14% 5% 8% 7% 4 4 5% 4 6% 27%	1958
	11th to 20th	Day	13% 14% 5% 10% 6% 4 4 4 5% 5% 30%	1980
	21st to end	Day	18% 10% 5% 7% 5% 3 4 4 4 5% 35%	2178
April	1st to 10th	Day	21% 14% 5% 7% 5% 3 3 5% 5% 6% 27%	2124
	11th to 20th	Day	21% 11% 3 4 4 3 4 3 3 6% 36%	2263
	21st to end	Day	22% 12% 3 7% 4 3 4 4 4 4 34%	2340
May	1st to 10th	Day	20% 8% 3 6% 6% 3 4 4 5% 7% 34%	2376
	11th to 20th	Day	18% 9% 3 5% 4 2 5% 5% 5% 7% 36%	2478
	21st to end	Day	15% 6% 2 4 5% 3 5% 5% 5% 8% 41%	2725
June	1st to 10th	Day	19% 7% 3 6% 5% 2 5% 4 5% 7% 36%	2614
	11th to 20th	Day	15% 6% 3 6% 5% 4 6% 5% 5% 8% 39%	2700
	21st to end	Day	18% 7% 3 7% 6% 3 5% 5% 5% 7% 33%	2700
July	1st to 10th	Day	13% 4 3 4 5% 3 5% 5% 5% 8% 44%	2700
	11th to 20th	Day	13% 6% 2 5% 6% 4 5% 5% 6% 9% 39%	2654
	21st to end	Day	13% 6% 3 5% 6% 3 5% 5% 6% 9% 39%	2647
August	1st to 10th	Day	14% 6% 3 6% 5% 4 4 6% 6% 9% 38%	2327
	11th to 20th	Day	15% 5% 3 6% 6% 3 5% 5% 6% 8% 38%	2303
	21st to end	Day	16% 6% 3 6% 6% 4 5% 5% 6% 8% 36%	2520
September	1st to 10th	Day	15% 7% 3 6% 5% 3 4 5% 5% 7% 39%	2160
	11th to 20th	Day	16% 7% 2 5% 5% 3 4 5% 5% 7% 41%	2044
	21st to end	Day	23% 8% 3 6% 5% 4 4 4 4 6% 34%	1953
October	1st to 10th	Day	20% 10% 3 6% 5% 4 3 5% 4 6% 33%	1800
	11th to 20th	Day	28% 11% 4 7% 6% 4 4 4 5% 5% 23%	1800
	21st to end	Day	31% 14% 4 8% 5% 3 3 3 4 5% 21%	1954
November	1st to 10th	Day	19% 15% 4 7% 5% 3 4 5% 6% 7% 25%	1524
	11th to 20th	Day	21% 15% 7% 6% 7% 3 5% 5% 4 5% 23%	1520
	21st to end	Day	23% 21% 6% 9% 6% 3 4 4 3 5% 17%	1520
December	1st to 10th	Day	18% 24% 7% 9% 6% 3 4 4 5% 4 16%	1520
	11th to 20th	Day	21% 20% 6% 10% 6% 3 4 3 3 5% 20%	1866
	21st to end	Day	24% 22% 7% 13% 6% 3 2 3 3 3 13%	2431
January	1st to 10th	Night	16% 21% 12% 11% 7% 3 4 3 4 4 14%	4748
	11th to 20th	Night	13% 16% 6% 14% 10% 4 6% 4 5% 5% 16%	4462
	21st to end	Night	15% 22% 11% 11% 6% 4 4 3 3 4 18%	4532
February	1st to 10th	Night	13% 18% 6% 11% 9% 4 5% 5% 5% 5% 20%	2399
	11th to 20th	Night	12% 15% 7% 12% 8% 3 4 4 4 5% 26%	2273
	21st to end	Night	15% 15% 7% 11% 7% 4 5% 4 4 6% 21%	1894
March	1st to 10th	Night	13% 13% 5% 9% 6% 3 4 3 4 7% 33%	1988
	11th to 20th	Night	14% 13% 4 9% 5% 3 4 4 4 6% 33%	1979
	21st to end	Night	15% 11% 4 7% 5% 3 4 4 4 6% 38%	2178
April	1st to 10th	Night	21% 14% 5% 5% 5% 3 4 3 5% 6% 29%	1836
	11th to 20th	Night	19% 9% 4 6% 6% 3 4 3 5% 6% 36%	1661
	21st to end	Night	21% 10% 3 7% 6% 4 4 4 4 6% 31%	1620
May	1st to 10th	Night	18% 8% 2 4 4 3 5% 4 6% 7% 39%	1584
	11th to 20th	Night	14% 6% 3 5% 5% 3 4 5% 7% 9% 40%	1415
	21st to end	Night	11% 5% 3 5% 5% 3 5% 5% 6% 8% 44%	1550
June	1st to 10th	Night	14% 8% 2 6% 5% 4 5% 5% 6% 8% 37%	1342
	11th to 20th	Night	14% 5% 2 5% 4 3 4 5% 6% 8% 44%	1260
	21st to end	Night	14% 6% 3 5% 6% 3 5% 5% 6% 7% 40%	1260
July	1st to 10th	Night	11% 5% 2 4 3 2 4 5% 6% 9% 50%	1260
	11th to 20th	Night	11% 5% 3 6% 4 3 4 6% 6% 8% 45%	1304
	21st to end	Night	11% 6% 2 4 5% 3 4 5% 6% 9% 44%	1668
August	1st to 10th	Night	13% 5% 2 4 4 3 4 5% 5% 8% 46%	1611
	11th to 20th	Night	11% 5% 2 5% 6% 3 5% 4 7% 8% 46%	1598
	21st to end	Night	16% 6% 2 5% 5% 3 4 4 5% 6% 42%	1817
September	1st to 10th	Night	13% 5% 2 5% 4 3 4 3 5% 7% 48%	1800
	11th to 20th	Night	14% 6% 2 5% 4 2 4 5% 4 7% 47%	1912
	21st to end	Night	17% 7% 3 6% 5% 3 4 4 5% 6% 41%	2006
October	1st to 10th	Night	21% 9% 3 6% 5% 2 5% 3 5% 6% 36%	2160
	11th to 20th	Night	26% 11% 3 6% 6% 4 5% 4 5% 6% 25%	2160
	21st to end	Night	27% 13% 5% 7% 6% 2 4 3 4 5% 24%	2401
November	1st to 10th	Night	22% 12% 4 6% 5% 3 4 3 4 6% 30%	2551
	11th to 20th	Night	19% 13% 5% 7% 7% 4 5% 5% 4 6% 25%	2660
	21st to end	Night	24% 18% 6% 8% 7% 3 3 4 4 5% 17%	2660
December	1st to 10th	Night	19% 22% 8% 10% 7% 3 5% 4 4 3 15%	2660
	11th to 20th	Night	20% 22% 7% 9% 6% 2 4 4 4 4 18%	3324
	21st to end	Night	22% 22% 7% 13% 7% 3 3 3 3 4 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	70% 4 6% 14% 6% 1	1656
	11th to 20th	Day	63% 4 9% 13% 10% 1	1582
	21st to end	Day	68% 4 6% 15% 6%	1358
March	1st to 10th	Day	58% 6% 11% 14% 11% 1	1961
	11th to 20th	Day	56% 5% 8% 18% 11% 2	1980
	21st to end	Day	51% 5% 9% 17% 15% 4	2178
April	1st to 10th	Day	57% 5% 11% 15% 10% 2	2124
	11th to 20th	Day	52% 4 7% 22% 14% 1	2263
	21st to end	Day	54% 4 8% 17% 14% 3	2340
May	1st to 10th	Day	49% 5% 9% 20% 14% 3	2376
	11th to 20th	Day	47% 6% 9% 23% 13% 2	2482
	21st to end	Day	41% 7% 13% 22% 14% 3	2725
June	1st to 10th	Day	47% 7% 8% 23% 14% 1	2614
	11th to 20th	Day	44% 6% 9% 24% 16% 1	2700
	21st to end	Day	49% 8% 11% 21% 10% 1	2700
July	1st to 10th	Day	37% 8% 13% 27% 14% 1	2626
	11th to 20th	Day	40% 7% 13% 28% 12% 1	2573
	21st to end	Day	41% 8% 12% 27% 12% 1	2499
August	1st to 10th	Day	41% 10% 12% 25% 11% 1	2314
	11th to 20th	Day	43% 8% 13% 25% 10% 1	2303
	21st to end	Day	45% 7% 13% 23% 11% 1	2520
September	1st to 10th	Day	43% 7% 11% 26% 12% 1	2160
	11th to 20th	Day	41% 7% 12% 29% 10%	2044
	21st to end	Day	52% 7% 10% 25% 7%	1953
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	66% 7% 9% 12% 5% 1	2399
	11th to 20th	Night	62% 4 10% 16% 8% 1	2275
	21st to end	Night	64% 6% 9% 14% 7% 1	1894
March	1st to 10th	Night	52% 4 13% 16% 13% 2	1998
	11th to 20th	Night	53% 6% 10% 18% 12% 2	1980
	21st to end	Night	49% 4 9% 19% 15% 3	2178
April	1st to 10th	Night	56% 5% 7% 18% 11% 2	1836
	11th to 20th	Night	50% 4 8% 21% 16% 2	1661
	21st to end	Night	55% 4 8% 15% 15% 2	1620
May	1st to 10th	Night	43% 6% 10% 22% 15% 3	1584
	11th to 20th	Night	40% 7% 9% 23% 19% 3	1416
	21st to end	Night	37% 7% 15% 22% 16% 3	1551
June	1st to 10th	Night	45% 7% 11% 22% 13% 3	1342
	11th to 20th	Night	38% 4 12% 26% 19%	1260
	21st to end	Night	42% 6% 14% 25% 12% 1	1260
July	1st to 10th	Night	29% 6% 12% 30% 19% 3	1225
	11th to 20th	Night	35% 9% 13% 28% 13% 2	1262
	21st to end	Night	37% 9% 14% 26% 14% 1	1575
August	1st to 10th	Night	36% 7% 16% 26% 14% 1	1600
	11th to 20th	Night	35% 9% 17% 26% 12% 1	1598
	21st to end	Night	41% 6% 14% 26% 11% 1	1817
September	1st to 10th	Night	36% 7% 16% 27% 13% 2	1800
	11th to 20th	Night	35% 8% 14% 31% 11%	1912
	21st to end	Night	44% 5% 13% 28% 10%	2006
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% 34% 10% 2 2	252
	11th to 20th	Day	28% 21% 40% 10% 1	240
	21st to end	Day	39% 25% 29% 7%	198
March	1st to 10th	Day	25% 20% 36% 14% 4	401
	11th to 20th	Day	24% 19% 36% 15% 5%	420
	21st to end	Day	31% 18% 29% 16% 5% 1	462
April	1st to 10th	Day	27% 18% 31% 17% 5% 1	420
	11th to 20th	Day	35% 15% 23% 16% 8% 3	412
	21st to end	Day	29% 16% 32% 13% 8% 1	420
May	1st to 10th	Day	28% 11% 29% 20% 9% 3	423
	11th to 20th	Day	24% 15% 30% 18% 9% 4	447
	21st to end	Day	19% 17% 30% 21% 11% 3	485
June	1st to 10th	Day	21% 13% 32% 25% 7% 1	544
	11th to 20th	Day	18% 13% 34% 23% 10% 1	630
	21st to end	Day	23% 11% 33% 23% 8% 2	630
July	1st to 10th	Day	14% 10% 32% 31% 12% 1	621
	11th to 20th	Day	17% 9% 30% 28% 13% 4	572
	21st to end	Day	15% 6% 34% 31% 11% 4	488
August	1st to 10th	Day	20% 3 28% 31% 11% 7%	446
	11th to 20th	Day	17% 3 26% 27% 17% 10%	439
	21st to end	Day	19% 10% 28% 24% 14% 5%	495
September	1st to 10th	Day	18% 11% 31% 23% 10% 7%	450
	11th to 20th	Day	18% 7% 29% 26% 16% 5%	450
	21st to end	Day	28% 8% 24% 24% 14% 3	450
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% 21% 4	739
	11th to 20th	Night	20% 17% 33% 23% 7%	703
	21st to end	Night	25% 17% 31% 24% 3 1	592
March	1st to 10th	Night	23% 17% 33% 22% 5%	720
	11th to 20th	Night	24% 18% 30% 21% 5% 1	720
	21st to end	Night	21% 13% 31% 26% 8% 1	792
April	1st to 10th	Night	29% 13% 31% 23% 4	720
	11th to 20th	Night	27% 13% 25% 24% 9% 1	597
	21st to end	Night	28% 10% 26% 25% 11%	540
May	1st to 10th	Night	22% 6% 26% 34% 11% 1	504
	11th to 20th	Night	19% 8% 31% 33% 8% 1	354
	21st to end	Night	14% 8% 35% 33% 10% 1	389
June	1st to 10th	Night	16% 5% 31% 36% 10% 1	360
	11th to 20th	Night	19% 9% 24% 36% 13%	360
	21st to end	Night	19% 6% 24% 34% 15% 1	360
July	1st to 10th	Night	13% 3 24% 41% 18% 1	350
	11th to 20th	Night	13% 4 26% 36% 20% 1	348
	21st to end	Night	14% 5% 26% 36% 17% 2	488
August	1st to 10th	Night	18% 1 18% 38% 23% 2	537
	11th to 20th	Night	13% 3 19% 41% 21% 3	534
	21st to end	Night	19% 5% 24% 30% 20% 2	629
September	1st to 10th	Night	15% 5% 27% 32% 18% 2	720
	11th to 20th	Night	18% 5% 24% 31% 18% 4	720
	21st to end	Night	20% 8% 23% 29% 17% 3	720
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 2024-02-02 05:20:34. Version ac07

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