Liverpool
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Liverpool clear sky chart from 2005-11-06 to 2025-01-22.

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% 10% 4 9% 5% 5% 5% 4 5% 7% 30%	105282
	Night	19% 13% 4 10% 5% 4 4 3 5% 6% 27%	104085
Transparency	Day	52% 7% 13% 19% 9% 1	108817
	Night	57% 6% 11% 17% 8% 1	108639
Seeing	Day	24% 17% 29% 19% 8% 3	14815
	Night	25% 16% 26% 24% 8% 1	24143

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	14% 21% 7% 15% 5% 5% 5% 3 4 4 16%	2597
	11th to 20th	Day	14% 22% 8% 16% 8% 6% 4 3 4 3 12%	2600
	21st to end	Day	20% 19% 6% 14% 6% 6% 5% 3 5% 4 11%	3080
February	1st to 10th	Day	17% 16% 6% 14% 11% 6% 5% 3 4 4 14%	1710
	11th to 20th	Day	16% 16% 5% 17% 9% 6% 5% 4 4 4 15%	1688
	21st to end	Day	20% 17% 4 13% 8% 4 4 3 4 5% 18%	1570
March	1st to 10th	Day	24% 13% 5% 9% 6% 4 4 3 3 4 26%	3194
	11th to 20th	Day	12% 21% 4 9% 6% 5% 4 3 4 5% 27%	3480
	21st to end	Day	18% 12% 3 10% 4 4 3 3 4 6% 34%	3992
April	1st to 10th	Day	20% 13% 3 7% 5% 4 4 4 4 5% 30%	2280
	11th to 20th	Day	19% 10% 2 6% 4 3 4 4 5% 6% 36%	2254
	21st to end	Day	22% 10% 3 6% 4 4 3 3 5% 5% 33%	2313
May	1st to 10th	Day	24% 9% 2 7% 5% 4 4 3 4 5% 33%	4379
	11th to 20th	Day	17% 8% 3 8% 6% 5% 5% 4 5% 8% 32%	4398
	21st to end	Day	13% 5% 2 5% 4 4 4 5% 6% 9% 41%	4837
June	1st to 10th	Day	19% 6% 2 7% 6% 4 5% 4 6% 7% 34%	2660
	11th to 20th	Day	16% 5% 2 6% 4 5% 5% 4 7% 9% 37%	2660
	21st to end	Day	15% 6% 3 7% 6% 5% 5% 4 6% 9% 35%	2660
July	1st to 10th	Day	11% 5% 2 6% 4 5% 5% 5% 7% 11% 38%	4440
	11th to 20th	Day	9% 5% 2 7% 5% 5% 5% 5% 8% 11% 37%	4440
	21st to end	Day	10% 5% 2 7% 5% 5% 6% 5% 7% 9% 38%	4814
August	1st to 10th	Day	18% 5% 2 6% 5% 5% 5% 4 6% 8% 36%	4144
	11th to 20th	Day	17% 7% 3 7% 4 5% 5% 4 6% 8% 34%	3948
	21st to end	Day	17% 6% 2 7% 4 4 4 3 5% 7% 41%	4180
September	1st to 10th	Day	15% 6% 2 5% 4 4 4 5% 5% 8% 42%	2280
	11th to 20th	Day	15% 6% 2 6% 4 4 4 4 5% 7% 43%	2280
	21st to end	Day	17% 7% 3 7% 5% 4 5% 4 5% 6% 36%	2022
October	1st to 10th	Day	19% 7% 3 8% 5% 5% 4 3 5% 7% 34%	1900
	11th to 20th	Day	22% 8% 2 8% 4 4 4 4 5% 7% 32%	1900
	21st to end	Day	24% 12% 3 9% 5% 5% 4 4 5% 7% 23%	2005
November	1st to 10th	Day	14% 12% 4 9% 6% 5% 5% 4 4 7% 30%	1761
	11th to 20th	Day	17% 14% 4 9% 5% 6% 5% 4 5% 7% 25%	1670
	21st to end	Day	22% 16% 5% 10% 7% 4 4 4 4 6% 19%	1600
December	1st to 10th	Day	20% 20% 8% 16% 7% 5% 5% 3 4 4 9%	2600
	11th to 20th	Day	19% 16% 7% 12% 6% 5% 5% 3 4 5% 18%	2986
	21st to end	Day	22% 16% 6% 12% 6% 4 4 4 4 5% 16%	3960
January	1st to 10th	Night	18% 20% 8% 17% 6% 5% 4 3 4 4 11%	4569
	11th to 20th	Night	14% 19% 8% 16% 8% 6% 4 3 3 4 16%	4580
	21st to end	Night	23% 19% 7% 15% 8% 5% 4 2 3 3 12%	4597
February	1st to 10th	Night	16% 17% 6% 14% 7% 5% 5% 3 4 5% 18%	2470
	11th to 20th	Night	15% 15% 6% 16% 8% 6% 5% 4 3 5% 17%	2376
	21st to end	Night	19% 13% 6% 15% 8% 5% 4 4 3 5% 19%	1884
March	1st to 10th	Night	21% 12% 4 10% 6% 4 3 3 5% 6% 26%	3642
	11th to 20th	Night	17% 21% 5% 9% 5% 4 4 3 4 5% 23%	3479
	21st to end	Night	20% 12% 4 10% 4 4 3 3 4 4 32%	3640
April	1st to 10th	Night	21% 12% 3 8% 6% 4 4 4 5% 6% 27%	1900
	11th to 20th	Night	20% 10% 3 8% 5% 4 5% 3 4 6% 33%	1875
	21st to end	Night	21% 10% 3 7% 3 4 5% 4 5% 5% 35%	1881
May	1st to 10th	Night	25% 9% 3 8% 5% 4 4 3 5% 5% 29%	2560
	11th to 20th	Night	18% 8% 3 7% 5% 4 5% 4 6% 7% 35%	2495
	21st to end	Night	13% 6% 3 6% 4 4 4 4 6% 9% 40%	2738
June	1st to 10th	Night	16% 7% 3 7% 4 4 5% 3 6% 7% 37%	1520
	11th to 20th	Night	14% 7% 2 6% 4 4 4 4 6% 8% 39%	1520
	21st to end	Night	14% 6% 2 7% 4 5% 4 4 6% 8% 39%	1520
July	1st to 10th	Night	11% 5% 3 8% 6% 5% 5% 4 7% 8% 38%	2520
	11th to 20th	Night	11% 5% 2 7% 4 4 5% 4 6% 8% 43%	2520
	21st to end	Night	13% 6% 2 6% 5% 4 5% 4 6% 7% 43%	2739
August	1st to 10th	Night	15% 7% 3 6% 4 4 4 4 6% 8% 39%	2782
	11th to 20th	Night	14% 7% 3 7% 5% 4 4 4 6% 7% 40%	2849
	21st to end	Night	12% 6% 3 6% 4 4 5% 4 6% 8% 44%	3476
September	1st to 10th	Night	15% 7% 2 6% 4 3 4 3 5% 7% 44%	1900
	11th to 20th	Night	16% 6% 2 5% 4 3 4 3 4 6% 48%	1900
	21st to end	Night	18% 7% 2 5% 4 5% 5% 4 5% 7% 37%	2155
October	1st to 10th	Night	23% 7% 2 8% 4 5% 5% 3 5% 5% 32%	2280
	11th to 20th	Night	24% 8% 2 7% 4 4 5% 3 5% 7% 31%	2280
	21st to end	Night	28% 12% 3 8% 5% 4 4 3 4 6% 24%	2592
November	1st to 10th	Night	18% 13% 3 8% 5% 4 4 3 5% 5% 32%	2537
	11th to 20th	Night	18% 15% 4 8% 5% 4 4 4 5% 6% 28%	2725
	21st to end	Night	19% 18% 5% 9% 5% 5% 4 4 5% 7% 21%	2800
December	1st to 10th	Night	21% 21% 7% 12% 7% 6% 6% 3 4 4 10%	4580
	11th to 20th	Night	23% 16% 7% 10% 5% 4 4 4 4 4 19%	5208
	21st to end	Night	26% 18% 5% 11% 6% 4 3 2 4 5% 16%	6996

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	71% 7% 12% 9% 2	2598
	11th to 20th	Day	75% 8% 8% 6% 2	2600
	21st to end	Day	75% 7% 10% 5% 2	3080
February	1st to 10th	Day	73% 6% 9% 10% 2	1710
	11th to 20th	Day	72% 7% 7% 11% 3	1697
	21st to end	Day	69% 5% 11% 11% 4	1570
March	1st to 10th	Day	62% 6% 10% 16% 5%	3197
	11th to 20th	Day	57% 8% 16% 10% 8% 1	3480
	21st to end	Day	52% 6% 10% 21% 10% 1	3992
April	1st to 10th	Day	56% 6% 8% 18% 10% 2	2280
	11th to 20th	Day	48% 6% 12% 21% 12% 1	2254
	21st to end	Day	52% 7% 9% 18% 12% 2	2313
May	1st to 10th	Day	52% 6% 11% 18% 12% 1	4393
	11th to 20th	Day	48% 9% 13% 21% 8% 1	4402
	21st to end	Day	38% 9% 14% 24% 14% 1	4837
June	1st to 10th	Day	48% 8% 12% 19% 13% 1	2660
	11th to 20th	Day	43% 8% 14% 22% 12% 1	2660
	21st to end	Day	44% 9% 15% 20% 11% 1	2660
July	1st to 10th	Day	39% 6% 15% 27% 13% 1	4370
	11th to 20th	Day	38% 8% 16% 27% 11%	4365
	21st to end	Day	40% 8% 16% 25% 11%	4661
August	1st to 10th	Day	45% 7% 15% 19% 13% 1	4130
	11th to 20th	Day	46% 7% 17% 23% 7%	3987
	21st to end	Day	42% 6% 12% 32% 8% 1	4180
September	1st to 10th	Day	40% 7% 13% 28% 11% 1	2280
	11th to 20th	Day	40% 7% 12% 26% 15% 1	2280
	21st to end	Day	47% 8% 11% 24% 10% 1	2022
October	1st to 10th	Day	44% 6% 13% 28% 9%	3160
	11th to 20th	Day	47% 5% 15% 21% 12%	3140
	21st to end	Day	47% 6% 16% 22% 9%	3282
November	1st to 10th	Day	53% 8% 12% 16% 10% 1	1761
	11th to 20th	Day	58% 5% 12% 15% 7% 2	1670
	21st to end	Day	66% 6% 14% 12% 2	1600
December	1st to 10th	Day	79% 6% 9% 6% 1	2600
	11th to 20th	Day	69% 6% 11% 9% 5%	2986
	21st to end	Day	69% 6% 11% 11% 3	3960
January	1st to 10th	Night	77% 7% 9% 5% 1	4569
	11th to 20th	Night	73% 7% 8% 10% 3	4580
	21st to end	Night	79% 4 9% 5% 2	4597
February	1st to 10th	Night	69% 6% 10% 12% 4	2470
	11th to 20th	Night	70% 6% 9% 10% 4	2378
	21st to end	Night	66% 6% 11% 10% 6%	1884
March	1st to 10th	Night	58% 7% 13% 16% 6%	3652
	11th to 20th	Night	63% 6% 12% 14% 5%	3480
	21st to end	Night	55% 6% 8% 21% 9% 1	3640
April	1st to 10th	Night	57% 8% 10% 17% 7% 2	1900
	11th to 20th	Night	52% 7% 9% 17% 14% 1	1875
	21st to end	Night	51% 6% 10% 18% 13% 3	1881
May	1st to 10th	Night	55% 7% 11% 14% 10% 3	2566
	11th to 20th	Night	46% 9% 16% 20% 9% 1	2496
	21st to end	Night	37% 11% 14% 20% 17% 2	2739
June	1st to 10th	Night	45% 8% 13% 21% 13% 1	1520
	11th to 20th	Night	42% 7% 13% 21% 15% 1	1520
	21st to end	Night	42% 8% 11% 25% 14% 1	1520
July	1st to 10th	Night	42% 7% 12% 21% 15% 2	2480
	11th to 20th	Night	38% 6% 16% 27% 13% 1	2472
	21st to end	Night	40% 7% 11% 27% 15% 1	2651
August	1st to 10th	Night	42% 8% 15% 25% 9% 1	2772
	11th to 20th	Night	43% 6% 18% 24% 9%	2876
	21st to end	Night	37% 6% 13% 33% 10% 1	3476
September	1st to 10th	Night	40% 8% 14% 25% 12% 2	1900
	11th to 20th	Night	38% 5% 12% 29% 16% 1	1900
	21st to end	Night	44% 8% 13% 23% 10% 1	2155
October	1st to 10th	Night	53% 5% 9% 23% 10%	3800
	11th to 20th	Night	51% 5% 13% 17% 13% 1	3779
	21st to end	Night	52% 5% 12% 25% 6% 1	4265
November	1st to 10th	Night	54% 7% 11% 18% 9% 2	2537
	11th to 20th	Night	57% 7% 11% 16% 6% 2	2725
	21st to end	Night	63% 7% 13% 13% 4	2800
December	1st to 10th	Night	77% 5% 10% 6% 1	4580
	11th to 20th	Night	68% 6% 8% 10% 8%	5208
	21st to end	Night	71% 6% 7% 11% 4	6996

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	35% 24% 28% 9% 4	200
	11th to 20th	Day	35% 28% 26% 11% 1 1	200
	21st to end	Day	28% 25% 36% 9% 3	287
February	1st to 10th	Day	34% 29% 30% 6%	270
	11th to 20th	Day	34% 30% 30% 6%	295
	21st to end	Day	37% 23% 29% 11% 1	382
March	1st to 10th	Day	32% 21% 30% 14% 3	460
	11th to 20th	Day	33% 21% 31% 12% 3	460
	21st to end	Day	34% 23% 26% 12% 5% 1	506
April	1st to 10th	Day	34% 21% 27% 12% 6%	460
	11th to 20th	Day	31% 25% 23% 11% 7% 3	452
	21st to end	Day	33% 18% 25% 17% 5% 2	460
May	1st to 10th	Day	27% 17% 30% 16% 7% 3	463
	11th to 20th	Day	20% 15% 33% 22% 8% 2	487
	21st to end	Day	19% 13% 29% 24% 12% 3	529
June	1st to 10th	Day	21% 17% 28% 23% 9% 1	490
	11th to 20th	Day	16% 13% 31% 26% 12% 2	490
	21st to end	Day	17% 18% 32% 23% 7% 2	490
July	1st to 10th	Day	12% 9% 32% 28% 15% 4	485
	11th to 20th	Day	12% 8% 30% 32% 16% 3	484
	21st to end	Day	12% 10% 35% 28% 12% 3	532
August	1st to 10th	Day	13% 10% 29% 27% 14% 6%	486
	11th to 20th	Day	15% 11% 28% 26% 14% 6%	479
	21st to end	Day	13% 13% 32% 20% 15% 7%	539
September	1st to 10th	Day	16% 13% 23% 25% 14% 8%	490
	11th to 20th	Day	13% 11% 24% 22% 18% 12%	490
	21st to end	Day	18% 15% 26% 23% 14% 4	490
October	1st to 10th	Day	23% 12% 29% 20% 13% 4	490
	11th to 20th	Day	28% 19% 25% 18% 8% 2	490
	21st to end	Day	35% 16% 28% 17% 4	494
November	1st to 10th	Day	26% 21% 27% 17% 7% 1	395
	11th to 20th	Day	30% 26% 25% 17% 1 1	270
	21st to end	Day	41% 16% 35% 9% 1	200
December	1st to 10th	Day	35% 24% 28% 10% 4	200
	11th to 20th	Day	35% 26% 27% 10% 2	200
	21st to end	Day	32% 25% 26% 14% 2	220
January	1st to 10th	Night	31% 25% 30% 12% 2	800
	11th to 20th	Night	28% 24% 29% 16% 3	800
	21st to end	Night	22% 24% 32% 19% 3	841
February	1st to 10th	Night	30% 21% 31% 17% 1	760
	11th to 20th	Night	26% 26% 32% 14% 2	743
	21st to end	Night	29% 23% 30% 15% 3	628
March	1st to 10th	Night	28% 21% 29% 19% 2	760
	11th to 20th	Night	28% 21% 28% 19% 4	760
	21st to end	Night	28% 19% 27% 20% 6% 1	836
April	1st to 10th	Night	28% 17% 31% 22% 2	760
	11th to 20th	Night	26% 19% 26% 21% 6% 1	751
	21st to end	Night	27% 13% 27% 26% 7%	741
May	1st to 10th	Night	26% 10% 23% 32% 9% 1	413
	11th to 20th	Night	16% 10% 32% 34% 7% 1	374
	21st to end	Night	13% 10% 28% 35% 14%	411
June	1st to 10th	Night	20% 9% 21% 37% 13% 1	380
	11th to 20th	Night	17% 8% 21% 39% 15%	380
	21st to end	Night	14% 6% 29% 43% 8% 1	380
July	1st to 10th	Night	11% 4 21% 44% 19% 2	370
	11th to 20th	Night	12% 4 18% 46% 17% 2	368
	21st to end	Night	15% 5% 22% 43% 14% 1	416
August	1st to 10th	Night	13% 6% 23% 37% 20% 1	537
	11th to 20th	Night	13% 6% 21% 34% 24% 3	602
	21st to end	Night	15% 6% 22% 34% 22% 1	836
September	1st to 10th	Night	18% 6% 23% 31% 19% 2	760
	11th to 20th	Night	17% 8% 19% 30% 23% 4	760
	21st to end	Night	20% 11% 19% 30% 16% 3	760
October	1st to 10th	Night	27% 11% 23% 20% 16% 2	760
	11th to 20th	Night	29% 14% 27% 23% 7% 1	760
	21st to end	Night	36% 15% 26% 20% 3	836
November	1st to 10th	Night	28% 16% 28% 21% 8%	780
	11th to 20th	Night	28% 21% 26% 18% 6% 1	800
	21st to end	Night	30% 23% 28% 15% 4	800
December	1st to 10th	Night	35% 23% 26% 14% 3	800
	11th to 20th	Night	32% 22% 28% 15% 3	800
	21st to end	Night	33% 22% 28% 15% 3	880

Page generated at 2025-01-19 03:06:50. Version ac07

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