Manchester
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Manchester clear sky chart from 2005-11-06 to 2024-02-20.

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% 6% 3 5% 5% 3 5% 5% 5% 7% 39%	78238
	Night	17% 7% 3 5% 5% 3 4 4 5% 6% 40%	80940
Transparency	Day	44% 6% 11% 22% 15% 2	77943
	Night	44% 5% 12% 22% 14% 2	80769
Seeing	Day	24% 17% 31% 19% 8% 2	13955
	Night	22% 15% 32% 24% 7% 1	23017

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	15% 7% 3 5% 5% 3 4 5% 5% 6% 43%	2517
	11th to 20th	Day	17% 6% 3 7% 6% 3 5% 5% 5% 5% 39%	2520
	21st to end	Day	19% 11% 3 6% 6% 4 4 4 5% 5% 34%	2772
February	1st to 10th	Day	18% 7% 3 5% 5% 4 6% 6% 5% 6% 36%	1729
	11th to 20th	Day	13% 8% 3 5% 6% 3 5% 5% 5% 8% 39%	1838
	21st to end	Day	17% 9% 4 7% 6% 3 4 3 5% 6% 35%	1480
March	1st to 10th	Day	15% 8% 4 6% 6% 3 4 5% 5% 7% 37%	1797
	11th to 20th	Day	16% 7% 4 7% 5% 2 4 5% 5% 7% 38%	1890
	21st to end	Day	18% 8% 3 6% 6% 3 4 3 4 6% 40%	2305
April	1st to 10th	Day	19% 8% 3 5% 5% 3 4 4 4 7% 38%	2160
	11th to 20th	Day	17% 6% 2 5% 6% 3 5% 5% 5% 8% 38%	2152
	21st to end	Day	22% 6% 3 7% 6% 3 4 4 5% 6% 34%	2340
May	1st to 10th	Day	23% 9% 2 6% 5% 3 4 5% 4 6% 33%	2340
	11th to 20th	Day	18% 6% 3 5% 6% 3 4 5% 4 6% 40%	2375
	21st to end	Day	15% 5% 2 5% 6% 3 6% 5% 5% 7% 42%	2725
June	1st to 10th	Day	20% 5% 3 6% 7% 3 6% 5% 6% 9% 31%	2520
	11th to 20th	Day	17% 5% 3 6% 5% 4 5% 5% 6% 8% 37%	2520
	21st to end	Day	18% 6% 3 6% 6% 4 5% 5% 6% 7% 34%	2520
July	1st to 10th	Day	15% 5% 3 5% 5% 3 5% 5% 7% 8% 40%	2520
	11th to 20th	Day	12% 6% 3 5% 6% 3 5% 6% 6% 10% 37%	2520
	21st to end	Day	13% 5% 3 6% 6% 3 6% 7% 6% 8% 38%	2744
August	1st to 10th	Day	12% 5% 2 6% 6% 5% 5% 7% 7% 9% 37%	2386
	11th to 20th	Day	13% 6% 2 5% 6% 3 6% 6% 7% 8% 38%	2286
	21st to end	Day	12% 4 2 4 5% 3 5% 6% 6% 8% 44%	2376
September	1st to 10th	Day	14% 5% 2 5% 4 3 4 5% 6% 7% 45%	2160
	11th to 20th	Day	15% 5% 3 4 4 2 3 3 4 5% 52%	1985
	21st to end	Day	16% 5% 2 5% 5% 3 4 3 4 7% 46%	1980
October	1st to 10th	Day	24% 6% 2 5% 4 3 4 3 4 5% 39%	1980
	11th to 20th	Day	15% 5% 2 5% 5% 3 4 5% 5% 7% 44%	1739
	21st to end	Day	24% 7% 2 5% 5% 3 4 4 3 5% 38%	1782
November	1st to 10th	Day	15% 6% 3 5% 5% 2 3 3 4 5% 49%	1671
	11th to 20th	Day	20% 5% 2 4 4 3 3 4 4 6% 46%	1710
	21st to end	Day	20% 6% 3 4 4 3 5% 4 4 6% 42%	1701
December	1st to 10th	Day	20% 6% 3 6% 4 4 5% 4 5% 6% 36%	1520
	11th to 20th	Day	22% 6% 2 4 4 3 4 4 4 5% 42%	1906
	21st to end	Day	23% 11% 3 5% 5% 3 4 5% 5% 5% 31%	2772
January	1st to 10th	Night	18% 7% 2 4 4 3 4 4 5% 6% 45%	4429
	11th to 20th	Night	14% 8% 3 7% 6% 4 4 5% 5% 7% 37%	4440
	21st to end	Night	21% 13% 4 6% 5% 3 4 4 4 5% 31%	4884
February	1st to 10th	Night	16% 9% 3 6% 5% 3 4 5% 5% 7% 38%	2444
	11th to 20th	Night	13% 8% 3 6% 5% 3 5% 5% 5% 7% 40%	2213
	21st to end	Night	17% 8% 2 4 5% 3 4 4 5% 7% 40%	1776
March	1st to 10th	Night	16% 8% 3 5% 5% 3 4 4 5% 6% 41%	2150
	11th to 20th	Night	17% 7% 3 5% 5% 3 5% 5% 5% 7% 37%	2069
	21st to end	Night	17% 9% 2 5% 5% 2 4 4 4 5% 43%	2048
April	1st to 10th	Night	18% 9% 3 5% 5% 3 5% 4 4 7% 37%	1800
	11th to 20th	Night	20% 7% 3 4 4 2 4 4 5% 5% 41%	1757
	21st to end	Night	21% 6% 3 5% 6% 3 4 4 5% 6% 37%	1620
May	1st to 10th	Night	21% 8% 3 6% 5% 3 5% 4 5% 7% 32%	1620
	11th to 20th	Night	19% 6% 2 6% 5% 4 5% 5% 4 6% 37%	1534
	21st to end	Night	17% 6% 2 5% 6% 3 4 5% 5% 8% 39%	1550
June	1st to 10th	Night	18% 8% 3 6% 5% 3 4 4 5% 7% 37%	1440
	11th to 20th	Night	20% 6% 2 5% 4 3 4 6% 4 8% 38%	1440
	21st to end	Night	18% 6% 2 5% 5% 3 5% 4 5% 10% 38%	1440
July	1st to 10th	Night	15% 5% 2 5% 6% 4 5% 4 6% 7% 41%	1440
	11th to 20th	Night	13% 5% 3 5% 5% 3 5% 5% 7% 10% 39%	1440
	21st to end	Night	13% 4 2 4 4 2 5% 5% 7% 9% 45%	1574
August	1st to 10th	Night	10% 5% 2 4 5% 3 6% 6% 5% 8% 46%	1535
	11th to 20th	Night	13% 6% 3 6% 6% 4 6% 5% 6% 8% 37%	1611
	21st to end	Night	15% 4 2 4 4 3 4 4 5% 8% 48%	1980
September	1st to 10th	Night	13% 5% 2 4 5% 3 3 3 6% 6% 49%	1800
	11th to 20th	Night	15% 5% 2 4 3 2 3 3 4 6% 52%	1975
	21st to end	Night	16% 4 3 4 3 2 4 3 5% 7% 49%	1980
October	1st to 10th	Night	22% 6% 2 5% 5% 3 4 3 4 5% 41%	1980
	11th to 20th	Night	16% 5% 2 4 5% 3 5% 5% 6% 7% 43%	2214
	21st to end	Night	23% 6% 3 5% 5% 2 3 4 4 6% 37%	2574
November	1st to 10th	Night	16% 6% 2 4 5% 2 4 5% 4 5% 46%	2407
	11th to 20th	Night	17% 7% 2 5% 4 3 3 3 4 5% 46%	2470
	21st to end	Night	16% 7% 3 4 5% 2 4 5% 5% 6% 43%	2474
December	1st to 10th	Night	20% 8% 4 5% 5% 3 4 4 5% 6% 37%	2660
	11th to 20th	Night	19% 7% 2 5% 4 3 4 4 5% 6% 40%	3288
	21st to end	Night	21% 10% 3 6% 6% 3 4 3 4 6% 34%	4884

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	41% 5% 11% 31% 11% 1	2518
	11th to 20th	Day	46% 6% 11% 25% 11% 2	2520
	21st to end	Day	52% 6% 9% 23% 9% 2	2772
February	1st to 10th	Day	48% 6% 12% 22% 10% 2	1729
	11th to 20th	Day	43% 7% 11% 20% 15% 3	1847
	21st to end	Day	51% 4 9% 19% 15% 3	1480
March	1st to 10th	Day	47% 4 13% 20% 12% 4	1800
	11th to 20th	Day	45% 5% 10% 20% 16% 5%	1890
	21st to end	Day	47% 4 7% 19% 17% 6%	2305
April	1st to 10th	Day	47% 5% 9% 18% 17% 4	2160
	11th to 20th	Day	44% 5% 11% 20% 17% 3	2152
	21st to end	Day	52% 5% 7% 16% 16% 4	2340
May	1st to 10th	Day	52% 5% 8% 20% 13% 2	2340
	11th to 20th	Day	44% 6% 9% 20% 18% 3	2379
	21st to end	Day	41% 7% 14% 22% 13% 3	2725
June	1st to 10th	Day	49% 7% 13% 20% 11% 1	2520
	11th to 20th	Day	44% 7% 11% 19% 16% 3	2520
	21st to end	Day	48% 6% 13% 21% 12% 1	2520
July	1st to 10th	Day	41% 7% 11% 22% 17% 2	2450
	11th to 20th	Day	41% 8% 13% 25% 13% 1	2445
	21st to end	Day	39% 8% 14% 24% 13% 3	2591
August	1st to 10th	Day	41% 8% 15% 23% 13% 1	2372
	11th to 20th	Day	41% 8% 14% 23% 12% 2	2286
	21st to end	Day	35% 8% 12% 24% 18% 3	2376
September	1st to 10th	Day	37% 7% 13% 24% 19% 2	2160
	11th to 20th	Day	35% 5% 8% 26% 24% 2	1985
	21st to end	Day	39% 5% 9% 24% 21% 3	1980
October	1st to 10th	Day	47% 5% 9% 22% 14% 3	1980
	11th to 20th	Day	38% 6% 12% 30% 12% 2	1739
	21st to end	Day	49% 5% 9% 21% 13% 3	1782
November	1st to 10th	Day	39% 3 12% 26% 17% 2	1671
	11th to 20th	Day	40% 5% 10% 23% 20% 3	1710
	21st to end	Day	43% 5% 16% 21% 13% 2	1701
December	1st to 10th	Day	48% 5% 15% 17% 14% 1	1520
	11th to 20th	Day	45% 5% 11% 18% 17% 3	1906
	21st to end	Day	53% 6% 11% 18% 10% 1	2772
January	1st to 10th	Night	40% 4 15% 28% 10% 3	4429
	11th to 20th	Night	45% 6% 12% 22% 12% 3	4440
	21st to end	Night	57% 5% 10% 17% 10% 2	4884
February	1st to 10th	Night	45% 6% 14% 20% 13% 2	2444
	11th to 20th	Night	43% 5% 12% 20% 17% 3	2215
	21st to end	Night	43% 6% 10% 23% 14% 4	1776
March	1st to 10th	Night	45% 5% 10% 22% 15% 4	2160
	11th to 20th	Night	47% 6% 11% 17% 16% 4	2070
	21st to end	Night	44% 4 9% 18% 20% 5%	2048
April	1st to 10th	Night	47% 4 11% 19% 17% 3	1800
	11th to 20th	Night	45% 4 9% 22% 18% 2	1757
	21st to end	Night	47% 5% 11% 19% 14% 4	1620
May	1st to 10th	Night	52% 4 10% 18% 13% 3	1620
	11th to 20th	Night	46% 7% 11% 19% 15% 3	1535
	21st to end	Night	44% 7% 14% 22% 12% 2	1551
June	1st to 10th	Night	48% 5% 12% 22% 12% 1	1440
	11th to 20th	Night	45% 8% 11% 20% 13% 3	1440
	21st to end	Night	41% 8% 15% 21% 13% 1	1440
July	1st to 10th	Night	41% 7% 14% 23% 14% 1	1400
	11th to 20th	Night	39% 8% 16% 25% 12%	1392
	21st to end	Night	34% 7% 15% 30% 12% 2	1486
August	1st to 10th	Night	35% 8% 15% 25% 16% 1	1525
	11th to 20th	Night	43% 7% 15% 21% 13% 1	1611
	21st to end	Night	34% 6% 12% 26% 20% 1	1980
September	1st to 10th	Night	35% 5% 13% 27% 19% 1	1800
	11th to 20th	Night	34% 4 11% 26% 24% 2	1975
	21st to end	Night	37% 4 10% 28% 19% 2	1980
October	1st to 10th	Night	46% 4 12% 22% 13% 3	1980
	11th to 20th	Night	38% 7% 13% 28% 13% 1	2214
	21st to end	Night	49% 5% 12% 21% 12% 2	2574
November	1st to 10th	Night	40% 5% 10% 24% 19% 3	2407
	11th to 20th	Night	41% 4 10% 23% 19% 3	2470
	21st to end	Night	41% 4 15% 26% 13% 1	2474
December	1st to 10th	Night	48% 5% 13% 21% 12% 1	2660
	11th to 20th	Night	44% 5% 14% 19% 17% 2	3288
	21st to end	Night	51% 6% 9% 23% 10% 1	4884

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	30% 22% 29% 15% 3	180
	11th to 20th	Day	31% 23% 33% 10% 2 1	180
	21st to end	Day	25% 23% 32% 16% 4	198
February	1st to 10th	Day	31% 25% 31% 12% 2	334
	11th to 20th	Day	31% 28% 27% 13% 1	452
	21st to end	Day	30% 23% 32% 12% 3	346
March	1st to 10th	Day	30% 19% 35% 14% 2	420
	11th to 20th	Day	30% 26% 30% 10% 3 1	420
	21st to end	Day	31% 19% 31% 13% 5% 2	462
April	1st to 10th	Day	32% 22% 27% 12% 6% 1	420
	11th to 20th	Day	29% 21% 31% 12% 6% 2	412
	21st to end	Day	30% 19% 30% 14% 5% 2	420
May	1st to 10th	Day	33% 19% 29% 13% 5% 1	423
	11th to 20th	Day	21% 17% 38% 18% 4 1	447
	21st to end	Day	19% 15% 35% 22% 8% 1	485
June	1st to 10th	Day	19% 16% 38% 16% 10% 1	450
	11th to 20th	Day	18% 16% 38% 18% 8% 2	450
	21st to end	Day	18% 14% 35% 21% 8% 3	450
July	1st to 10th	Day	20% 8% 29% 28% 13% 3	445
	11th to 20th	Day	16% 6% 34% 28% 12% 4	444
	21st to end	Day	13% 8% 35% 30% 11% 2	488
August	1st to 10th	Day	14% 8% 31% 28% 16% 2	446
	11th to 20th	Day	17% 9% 29% 26% 15% 4	439
	21st to end	Day	14% 11% 30% 26% 14% 4	495
September	1st to 10th	Day	19% 11% 24% 22% 17% 6%	450
	11th to 20th	Day	20% 14% 26% 18% 12% 8%	450
	21st to end	Day	18% 12% 33% 20% 12% 4	450
October	1st to 10th	Day	29% 13% 23% 21% 10% 4	450
	11th to 20th	Day	21% 14% 33% 20% 11% 2	399
	21st to end	Day	31% 14% 28% 21% 6% 1	396
November	1st to 10th	Day	20% 19% 27% 22% 10% 2	365
	11th to 20th	Day	33% 17% 25% 19% 5% 1	370
	21st to end	Day	30% 20% 26% 17% 6% 1	361
December	1st to 10th	Day	22% 31% 29% 14% 4	180
	11th to 20th	Day	32% 24% 29% 13% 2	180
	21st to end	Day	31% 23% 27% 16% 3 1	198
January	1st to 10th	Night	22% 21% 35% 19% 3	760
	11th to 20th	Night	28% 21% 30% 19% 2	760
	21st to end	Night	22% 20% 36% 18% 3	836
February	1st to 10th	Night	23% 19% 35% 21% 2	760
	11th to 20th	Night	24% 21% 36% 18% 2	742
	21st to end	Night	27% 20% 33% 17% 3	592
March	1st to 10th	Night	25% 20% 36% 18% 2	720
	11th to 20th	Night	24% 21% 32% 19% 4	720
	21st to end	Night	25% 19% 33% 19% 4	792
April	1st to 10th	Night	27% 18% 33% 18% 5%	720
	11th to 20th	Night	25% 18% 33% 19% 5%	693
	21st to end	Night	25% 19% 34% 20% 3	540
May	1st to 10th	Night	26% 15% 34% 21% 5%	540
	11th to 20th	Night	22% 15% 34% 24% 4	473
	21st to end	Night	21% 6% 33% 33% 7%	389
June	1st to 10th	Night	19% 10% 32% 30% 8% 1	360
	11th to 20th	Night	21% 8% 31% 32% 9% 1	360
	21st to end	Night	17% 6% 33% 38% 7%	360
July	1st to 10th	Night	16% 5% 32% 37% 9% 1	350
	11th to 20th	Night	14% 3 24% 43% 15% 1	348
	21st to end	Night	13% 4 29% 42% 11%	394
August	1st to 10th	Night	14% 3 29% 39% 14%	461
	11th to 20th	Night	15% 6% 28% 35% 14% 1	547
	21st to end	Night	15% 6% 24% 36% 17% 2	792
September	1st to 10th	Night	17% 5% 32% 30% 15% 1	720
	11th to 20th	Night	17% 8% 29% 28% 17% 2	720
	21st to end	Night	18% 8% 30% 28% 14% 2	720
October	1st to 10th	Night	26% 11% 25% 26% 12% 1	720
	11th to 20th	Night	18% 12% 32% 26% 10% 1	720
	21st to end	Night	27% 16% 28% 23% 5% 1	792
November	1st to 10th	Night	20% 13% 31% 27% 7% 1	740
	11th to 20th	Night	24% 16% 31% 20% 8% 1	760
	21st to end	Night	24% 18% 31% 21% 6%	760
December	1st to 10th	Night	25% 18% 36% 17% 3	760
	11th to 20th	Night	26% 21% 30% 20% 3	760
	21st to end	Night	26% 20% 32% 20% 2	836

Page generated at 2024-02-17 06:28:41. Version ac07

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