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 2024-10-24.

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% 7% 2 6% 4 4 5% 4 5% 7% 37%	101174
	Night	18% 8% 2 6% 4 4 4 3 5% 6% 39%	97593
Transparency	Day	45% 6% 12% 22% 14% 2	100932
	Night	45% 5% 12% 22% 14% 2	97455
Seeing	Day	24% 16% 31% 19% 8% 2	14934
	Night	22% 15% 31% 24% 7% 1	23801

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% 4 4 3 5% 6% 43%	2517
	11th to 20th	Day	17% 7% 3 8% 5% 4 5% 4 5% 5% 39%	2520
	21st to end	Day	19% 11% 2 6% 5% 5% 4 3 5% 5% 34%	2772
February	1st to 10th	Day	18% 8% 3 5% 5% 5% 6% 5% 5% 6% 35%	1729
	11th to 20th	Day	13% 8% 3 6% 5% 4 4 4 5% 8% 39%	1848
	21st to end	Day	17% 10% 3 8% 5% 4 4 3 6% 6% 36%	1570
March	1st to 10th	Day	23% 13% 3 7% 5% 4 4 3 3 5% 29%	3116
	11th to 20th	Day	14% 7% 2 7% 4 5% 5% 5% 6% 7% 38%	3320
	21st to end	Day	21% 9% 2 7% 4 4 4 3 5% 7% 33%	4053
April	1st to 10th	Day	19% 8% 3 6% 5% 4 4 3 4 7% 37%	2280
	11th to 20th	Day	17% 7% 2 6% 5% 4 5% 4 5% 8% 38%	2273
	21st to end	Day	21% 7% 3 8% 5% 4 4 3 5% 5% 35%	2470
May	1st to 10th	Day	22% 12% 3 8% 5% 5% 4 4 5% 6% 27%	4106
	11th to 20th	Day	21% 7% 3 8% 5% 4 4 4 5% 6% 32%	4225
	21st to end	Day	15% 4 2 5% 4 4 5% 4 6% 8% 43%	4837
June	1st to 10th	Day	19% 6% 3 7% 5% 5% 5% 4 6% 9% 32%	2660
	11th to 20th	Day	16% 5% 3 7% 4 5% 5% 4 7% 8% 37%	2660
	21st to end	Day	18% 6% 3 7% 6% 5% 4 4 6% 7% 34%	2660
July	1st to 10th	Day	13% 6% 2 7% 5% 5% 6% 4 7% 9% 36%	4440
	11th to 20th	Day	11% 6% 2 6% 5% 5% 5% 5% 7% 11% 38%	4440
	21st to end	Day	16% 8% 3 7% 4 4 5% 4 6% 7% 35%	4814
August	1st to 10th	Day	15% 6% 2 7% 5% 6% 5% 5% 6% 8% 34%	4206
	11th to 20th	Day	15% 7% 3 7% 5% 5% 5% 4 6% 7% 36%	3999
	21st to end	Day	8% 5% 2 6% 4 5% 6% 4 7% 10% 43%	4180
September	1st to 10th	Day	13% 5% 1 5% 3 4 4 3 6% 7% 47%	2280
	11th to 20th	Day	14% 6% 2 4 3 3 3 3 4 5% 52%	2095
	21st to end	Day	16% 5% 2 6% 4 4 4 3 4 6% 44%	2090
October	1st to 10th	Day	23% 6% 2 6% 3 4 4 3 4 5% 39%	2090
	11th to 20th	Day	15% 5% 2 5% 4 3 4 3 5% 7% 45%	1835
	21st to end	Day	23% 7% 2 6% 4 3 4 3 3 5% 39%	1809
November	1st to 10th	Day	15% 6% 2 6% 4 3 3 3 4 5% 49%	1671
	11th to 20th	Day	20% 5% 2 5% 3 3 3 4 4 5% 46%	1710
	21st to end	Day	20% 7% 2 5% 3 3 4 3 4 6% 42%	1701
December	1st to 10th	Day	19% 7% 3 7% 4 5% 4 3 5% 6% 36%	1520
	11th to 20th	Day	22% 6% 2 5% 3 4 3 3 4 5% 42%	1906
	21st to end	Day	23% 11% 3 6% 4 4 4 4 5% 5% 31%	2772
January	1st to 10th	Night	17% 8% 2 4 3 4 3 3 5% 6% 45%	4429
	11th to 20th	Night	14% 8% 3 8% 5% 5% 4 4 6% 6% 37%	4440
	21st to end	Night	21% 14% 4 8% 4 4 4 3 4 4 31%	4884
February	1st to 10th	Night	15% 9% 3 6% 5% 4 4 4 6% 7% 37%	2444
	11th to 20th	Night	13% 9% 2 7% 4 4 5% 4 6% 6% 39%	2218
	21st to end	Night	17% 9% 2 5% 5% 4 4 3 5% 6% 40%	1884
March	1st to 10th	Night	27% 10% 2 5% 3 4 4 3 4 5% 33%	3724
	11th to 20th	Night	12% 9% 3 7% 6% 5% 5% 4 5% 7% 36%	3639
	21st to end	Night	23% 9% 2 5% 3 3 4 3 6% 6% 34%	3576
April	1st to 10th	Night	19% 9% 2 6% 5% 4 5% 3 4 7% 36%	1900
	11th to 20th	Night	20% 8% 2 5% 4 3 4 3 5% 5% 40%	1856
	21st to end	Night	20% 6% 3 6% 4 4 4 4 4 6% 38%	1710
May	1st to 10th	Night	24% 12% 3 8% 4 4 4 3 5% 7% 26%	2834
	11th to 20th	Night	18% 8% 3 9% 5% 6% 6% 4 6% 6% 27%	2698
	21st to end	Night	16% 6% 2 6% 4 4 4 4 6% 8% 41%	2738
June	1st to 10th	Night	17% 9% 3 7% 5% 4 4 3 5% 7% 37%	1520
	11th to 20th	Night	19% 6% 2 5% 4 4 5% 5% 5% 8% 38%	1520
	21st to end	Night	18% 6% 2 6% 4 4 4 4 5% 10% 37%	1520
July	1st to 10th	Night	11% 5% 2 7% 6% 6% 6% 4 7% 9% 37%	2520
	11th to 20th	Night	13% 6% 3 7% 4 4 5% 4 6% 9% 41%	2520
	21st to end	Night	16% 6% 3 7% 4 4 5% 3 6% 7% 40%	2739
August	1st to 10th	Night	21% 6% 2 7% 5% 4 5% 4 4 6% 34%	2693
	11th to 20th	Night	12% 8% 3 7% 5% 5% 6% 4 6% 8% 37%	2811
	21st to end	Night	9% 4 1 5% 3 3 4 3 6% 8% 54%	3476
September	1st to 10th	Night	13% 6% 1 5% 4 4 2 3 6% 6% 50%	1900
	11th to 20th	Night	14% 6% 2 5% 3 2 3 3 5% 6% 52%	2085
	21st to end	Night	16% 5% 3 5% 3 3 3 3 5% 7% 47%	2090
October	1st to 10th	Night	21% 6% 2 6% 4 4 4 2 4 6% 40%	2090
	11th to 20th	Night	15% 5% 2 5% 4 4 4 4 6% 7% 44%	2338
	21st to end	Night	23% 7% 3 6% 4 3 3 3 4 6% 38%	2614
November	1st to 10th	Night	16% 6% 2 5% 4 3 4 4 4 5% 46%	2407
	11th to 20th	Night	17% 7% 2 5% 4 4 3 3 4 5% 46%	2470
	21st to end	Night	16% 8% 2 5% 5% 4 4 4 5% 6% 43%	2474
December	1st to 10th	Night	20% 9% 3 6% 4 4 4 3 5% 5% 37%	2660
	11th to 20th	Night	19% 7% 2 5% 3 4 4 4 5% 6% 40%	3288
	21st to end	Night	21% 10% 3 7% 5% 4 4 3 4 5% 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% 21% 15% 3	1857
	21st to end	Day	50% 4 10% 20% 14% 3	1570
March	1st to 10th	Day	59% 3 10% 14% 11% 3	3119
	11th to 20th	Day	40% 7% 14% 22% 14% 3	3320
	21st to end	Day	49% 4 6% 17% 18% 6%	4053
April	1st to 10th	Day	49% 5% 8% 18% 17% 4	2280
	11th to 20th	Day	45% 5% 11% 20% 17% 3	2273
	21st to end	Day	51% 5% 7% 17% 17% 3	2470
May	1st to 10th	Day	57% 6% 10% 15% 10% 1	4120
	11th to 20th	Day	50% 7% 15% 16% 10% 2	4229
	21st to end	Day	36% 7% 13% 24% 18% 2	4837
June	1st to 10th	Day	48% 7% 12% 21% 11% 1	2660
	11th to 20th	Day	43% 7% 12% 19% 15% 3	2660
	21st to end	Day	48% 6% 13% 21% 12% 1	2660
July	1st to 10th	Day	43% 6% 12% 21% 17% 1	4370
	11th to 20th	Day	39% 6% 16% 25% 13% 1	4365
	21st to end	Day	46% 5% 12% 21% 14% 2	4661
August	1st to 10th	Day	46% 7% 15% 22% 10%	4192
	11th to 20th	Day	45% 5% 14% 25% 9% 1	4038
	21st to end	Day	34% 6% 12% 29% 17% 2	4180
September	1st to 10th	Day	36% 6% 12% 25% 20% 2	2280
	11th to 20th	Day	35% 5% 8% 27% 23% 2	2095
	21st to end	Day	41% 5% 8% 23% 21% 2	2090
October	1st to 10th	Day	47% 5% 8% 21% 15% 3	2090
	11th to 20th	Day	38% 6% 11% 29% 14% 3	1835
	21st to end	Day	48% 5% 9% 22% 13% 3	1809
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% 21% 16% 3	2220
	21st to end	Night	43% 6% 10% 24% 14% 4	1884
March	1st to 10th	Night	54% 4 10% 19% 11% 3	3734
	11th to 20th	Night	45% 6% 13% 19% 15% 2	3640
	21st to end	Night	49% 4 7% 14% 20% 6%	3576
April	1st to 10th	Night	48% 4 11% 18% 16% 3	1900
	11th to 20th	Night	45% 4 9% 21% 18% 2	1856
	21st to end	Night	46% 5% 11% 19% 16% 4	1710
May	1st to 10th	Night	57% 5% 12% 16% 8% 2	2840
	11th to 20th	Night	54% 8% 14% 15% 8% 2	2699
	21st to end	Night	40% 7% 17% 21% 13% 2	2739
June	1st to 10th	Night	48% 5% 12% 22% 12% 1	1520
	11th to 20th	Night	44% 8% 12% 21% 13% 3	1520
	21st to end	Night	43% 8% 14% 21% 13% 1	1520
July	1st to 10th	Night	42% 7% 14% 23% 14% 1	2480
	11th to 20th	Night	41% 7% 14% 23% 15%	2472
	21st to end	Night	43% 5% 11% 24% 15% 1	2651
August	1st to 10th	Night	50% 6% 13% 20% 11% 1	2683
	11th to 20th	Night	45% 7% 15% 23% 11% 1	2838
	21st to end	Night	28% 5% 16% 30% 21% 1	3476
September	1st to 10th	Night	35% 5% 13% 27% 20% 1	1900
	11th to 20th	Night	34% 4 11% 26% 24% 2	2085
	21st to end	Night	38% 4 10% 28% 18% 2	2090
October	1st to 10th	Night	46% 4 12% 22% 13% 3	2090
	11th to 20th	Night	37% 7% 13% 28% 15% 1	2338
	21st to end	Night	48% 5% 12% 21% 12% 1	2614
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	456
	21st to end	Day	30% 23% 31% 13% 3	382
March	1st to 10th	Day	31% 18% 34% 14% 3	460
	11th to 20th	Day	31% 25% 29% 10% 3 1	460
	21st to end	Day	31% 20% 31% 12% 4 2	506
April	1st to 10th	Day	32% 22% 27% 12% 6% 1	460
	11th to 20th	Day	31% 21% 29% 13% 5% 2	452
	21st to end	Day	28% 20% 31% 14% 6% 2	460
May	1st to 10th	Day	32% 18% 30% 14% 5% 1	463
	11th to 20th	Day	21% 16% 37% 18% 5% 1	487
	21st to end	Day	19% 15% 35% 23% 7% 1	529
June	1st to 10th	Day	18% 16% 38% 16% 10% 1	490
	11th to 20th	Day	17% 15% 37% 20% 9% 2	490
	21st to end	Day	19% 16% 35% 20% 7% 3	490
July	1st to 10th	Day	19% 8% 30% 28% 12% 3	485
	11th to 20th	Day	14% 7% 35% 28% 12% 3	484
	21st to end	Day	15% 8% 35% 29% 11% 2	532
August	1st to 10th	Day	14% 8% 30% 29% 15% 2	486
	11th to 20th	Day	17% 9% 29% 26% 14% 4	479
	21st to end	Day	14% 10% 31% 26% 14% 5%	539
September	1st to 10th	Day	19% 12% 25% 22% 17% 7%	490
	11th to 20th	Day	20% 13% 25% 18% 14% 10%	490
	21st to end	Day	19% 11% 33% 21% 12% 4	490
October	1st to 10th	Day	28% 13% 24% 21% 11% 4	490
	11th to 20th	Day	22% 14% 32% 19% 11% 2	433
	21st to end	Day	30% 14% 27% 22% 7% 1	405
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% 17% 2	743
	21st to end	Night	26% 19% 33% 18% 3	628
March	1st to 10th	Night	26% 20% 35% 18% 2	760
	11th to 20th	Night	23% 21% 32% 19% 4	760
	21st to end	Night	26% 19% 32% 18% 4	836
April	1st to 10th	Night	27% 18% 33% 19% 4	760
	11th to 20th	Night	25% 19% 33% 18% 5%	732
	21st to end	Night	24% 19% 33% 21% 3	570
May	1st to 10th	Night	25% 15% 34% 21% 5%	570
	11th to 20th	Night	22% 14% 34% 25% 5%	499
	21st to end	Night	21% 6% 33% 33% 7%	411
June	1st to 10th	Night	19% 11% 33% 30% 7% 1	380
	11th to 20th	Night	20% 7% 31% 31% 9% 1	380
	21st to end	Night	17% 6% 33% 37% 7%	380
July	1st to 10th	Night	15% 5% 32% 38% 9% 1	370
	11th to 20th	Night	15% 4 24% 42% 15% 1	368
	21st to end	Night	14% 4 29% 42% 11%	416
August	1st to 10th	Night	16% 3 29% 39% 14%	487
	11th to 20th	Night	15% 6% 29% 35% 14% 1	578
	21st to end	Night	14% 6% 24% 37% 18% 2	836
September	1st to 10th	Night	17% 5% 32% 30% 15% 1	760
	11th to 20th	Night	16% 7% 27% 29% 18% 2	760
	21st to end	Night	18% 8% 30% 28% 13% 2	760
October	1st to 10th	Night	25% 10% 25% 27% 12% 1	760
	11th to 20th	Night	18% 12% 32% 26% 11% 1	760
	21st to end	Night	27% 16% 28% 24% 6%	805
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 2024-10-21 02:20:03. Version ac07

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