Albion
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Albion clear sky chart from 2005-11-06 to 2024-12-24.

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	12% 7% 3 7% 5% 4 4 4 5% 8% 41%	101509
	Night	14% 8% 3 6% 4 4 4 3 5% 6% 42%	98657
Transparency	Day	22% 47% 6% 14% 10% 1	105153
	Night	22% 46% 6% 14% 11% 1	103154
Seeing	Day	15% 8% 24% 25% 19% 8%	15692
	Night	17% 7% 26% 32% 16% 2	25548

By Month

Percentage Cloud Cover SE (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% 11% 6% 10% 5% 5% 4 4 4 5% 34%	2527
	11th to 20th	Day	16% 9% 3 10% 7% 5% 5% 4 5% 6% 30%	2530
	21st to end	Day	26% 17% 4 8% 4 3 3 3 3 5% 25%	3075
February	1st to 10th	Day	16% 11% 4 8% 4 4 4 3 4 6% 35%	1876
	11th to 20th	Day	16% 10% 3 9% 5% 3 4 4 5% 6% 35%	1848
	21st to end	Day	15% 10% 4 8% 5% 4 4 4 5% 7% 35%	1570
March	1st to 10th	Day	22% 13% 4 6% 4 3 3 2 3 4 36%	3120
	11th to 20th	Day	13% 6% 3 6% 3 3 3 3 5% 6% 47%	3272
	21st to end	Day	14% 8% 3 7% 5% 5% 5% 4 6% 7% 35%	4165
April	1st to 10th	Day	12% 8% 2 6% 4 4 4 4 4 9% 42%	2280
	11th to 20th	Day	14% 8% 3 7% 5% 4 4 3 5% 6% 41%	2254
	21st to end	Day	17% 7% 2 6% 4 5% 4 3 6% 7% 39%	2295
May	1st to 10th	Day	15% 7% 3 7% 6% 4 5% 5% 7% 9% 31%	4082
	11th to 20th	Day	17% 7% 3 7% 4 3 4 4 6% 7% 38%	4081
	21st to end	Day	9% 6% 3 6% 5% 5% 5% 5% 6% 9% 41%	4721
June	1st to 10th	Day	9% 6% 3 5% 4 4 5% 4 6% 8% 46%	2660
	11th to 20th	Day	6% 5% 2 5% 5% 5% 6% 4 6% 9% 48%	2660
	21st to end	Day	7% 5% 2 6% 5% 4 5% 4 8% 9% 45%	2660
July	1st to 10th	Day	12% 4 2 6% 5% 5% 5% 5% 7% 10% 41%	4440
	11th to 20th	Day	5% 5% 2 5% 4 5% 5% 4 6% 11% 47%	4440
	21st to end	Day	8% 6% 3 8% 7% 6% 7% 6% 8% 9% 32%	4813
August	1st to 10th	Day	6% 4 1 4 4 4 4 3 6% 11% 52%	3889
	11th to 20th	Day	8% 5% 3 6% 5% 4 5% 5% 7% 9% 43%	3729
	21st to end	Day	4 4 2 5% 4 4 4 4 6% 9% 54%	4180
September	1st to 10th	Day	11% 5% 2 6% 4 4 4 3 6% 8% 47%	2280
	11th to 20th	Day	7% 5% 1 7% 4 4 4 3 6% 8% 50%	2140
	21st to end	Day	11% 5% 2 4 4 3 4 3 4 7% 52%	2090
October	1st to 10th	Day	11% 4 2 5% 4 3 3 3 4 6% 58%	2090
	11th to 20th	Day	12% 7% 2 6% 4 3 3 3 4 7% 50%	1901
	21st to end	Day	18% 7% 2 6% 3 4 3 3 4 5% 45%	1929
November	1st to 10th	Day	9% 5% 2 6% 4 5% 4 2 4 6% 54%	1762
	11th to 20th	Day	15% 7% 3 7% 4 3 3 2 5% 7% 45%	1800
	21st to end	Day	17% 10% 3 8% 4 4 3 3 4 4 40%	1800
December	1st to 10th	Day	16% 12% 3 6% 5% 4 3 3 4 5% 38%	1745
	11th to 20th	Day	15% 11% 5% 11% 4 4 4 3 5% 6% 32%	1998
	21st to end	Day	23% 14% 6% 9% 5% 4 3 3 4 5% 24%	2807
January	1st to 10th	Night	17% 11% 4 9% 5% 4 4 4 5% 6% 32%	4428
	11th to 20th	Night	14% 12% 5% 10% 5% 6% 6% 3 4 4 30%	4440
	21st to end	Night	25% 14% 6% 7% 4 3 3 3 4 6% 27%	4587
February	1st to 10th	Night	19% 11% 4 7% 5% 4 4 3 5% 5% 32%	2301
	11th to 20th	Night	15% 9% 3 8% 5% 3 4 3 4 6% 39%	2218
	21st to end	Night	20% 10% 3 8% 4 3 4 2 5% 4 37%	1884
March	1st to 10th	Night	22% 11% 3 7% 4 4 3 3 4 5% 33%	3733
	11th to 20th	Night	12% 7% 2 6% 4 3 3 3 4 6% 50%	3717
	21st to end	Night	16% 8% 3 7% 5% 4 4 4 6% 6% 38%	3466
April	1st to 10th	Night	11% 7% 2 6% 4 4 4 4 4 7% 46%	1900
	11th to 20th	Night	16% 8% 2 4 3 4 4 4 5% 7% 44%	1875
	21st to end	Night	18% 7% 3 7% 5% 4 3 3 6% 6% 38%	1882
May	1st to 10th	Night	16% 9% 2 7% 5% 5% 5% 3 7% 7% 36%	2813
	11th to 20th	Night	15% 7% 2 6% 4 4 4 3 5% 6% 44%	2812
	21st to end	Night	8% 5% 3 8% 5% 5% 6% 4 7% 9% 40%	2838
June	1st to 10th	Night	9% 6% 2 5% 4 4 4 4 7% 8% 48%	1520
	11th to 20th	Night	6% 4 2 5% 4 4 4 4 5% 9% 53%	1520
	21st to end	Night	5% 3 2 4 4 4 5% 4 8% 9% 52%	1520
July	1st to 10th	Night	10% 5% 2 5% 3 3 4 4 6% 8% 49%	2530
	11th to 20th	Night	4 3 1 4 3 3 5% 4 6% 8% 58%	2530
	21st to end	Night	9% 7% 3 9% 5% 5% 5% 5% 7% 9% 35%	2750
August	1st to 10th	Night	5% 3 1 4 3 3 3 4 6% 9% 57%	3036
	11th to 20th	Night	6% 4 2 5% 4 4 4 5% 6% 8% 52%	3100
	21st to end	Night	4 3 1 4 3 4 5% 4 6% 9% 58%	3476
September	1st to 10th	Night	9% 5% 3 6% 3 3 3 3 5% 6% 55%	1900
	11th to 20th	Night	8% 4 2 5% 4 4 4 4 5% 7% 53%	2019
	21st to end	Night	11% 5% 1 5% 3 3 4 4 6% 7% 50%	2090
October	1st to 10th	Night	8% 4 2 4 3 4 3 3 5% 5% 60%	2090
	11th to 20th	Night	14% 5% 2 5% 3 3 3 2 4 6% 53%	2275
	21st to end	Night	18% 8% 2 5% 4 3 3 2 4 5% 46%	2667
November	1st to 10th	Night	11% 6% 2 5% 3 3 3 4 4 5% 53%	2536
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 5% 6% 49%	2600
	21st to end	Night	19% 7% 3 6% 4 3 3 2 4 6% 44%	2600
December	1st to 10th	Night	18% 10% 3 6% 4 4 4 4 5% 7% 36%	2652
	11th to 20th	Night	18% 9% 3 7% 4 4 4 3 4 6% 39%	3419
	21st to end	Night	23% 15% 4 8% 5% 5% 4 4 4 4 24%	4933

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	35% 37% 7% 15% 5% 1	2528
	11th to 20th	Day	36% 37% 11% 12% 5%	2530
	21st to end	Day	45% 39% 5% 7% 4	3075
February	1st to 10th	Day	17% 65% 4 8% 5% 1	1876
	11th to 20th	Day	18% 64% 2 9% 6%	1858
	21st to end	Day	17% 65% 3 8% 6% 2	1570
March	1st to 10th	Day	37% 40% 2 9% 7% 4	3120
	11th to 20th	Day	18% 41% 6% 21% 11% 2	3272
	21st to end	Day	23% 43% 10% 16% 8%	4165
April	1st to 10th	Day	18% 65% 5% 7% 4	2280
	11th to 20th	Day	15% 65% 5% 10% 4 1	2254
	21st to end	Day	16% 65% 3 9% 6% 2	2295
May	1st to 10th	Day	27% 43% 10% 15% 4	4120
	11th to 20th	Day	28% 42% 5% 21% 4	4085
	21st to end	Day	23% 41% 7% 12% 17% 1	4734
June	1st to 10th	Day	13% 66% 3 10% 7% 1	2660
	11th to 20th	Day	14% 66% 3 9% 8% 1	2660
	21st to end	Day	13% 65% 7% 10% 4 1	2660
July	1st to 10th	Day	25% 38% 7% 18% 11% 1	4371
	11th to 20th	Day	18% 38% 7% 25% 12% 1	4365
	21st to end	Day	33% 39% 10% 12% 6% 1	4662
August	1st to 10th	Day	16% 38% 10% 26% 10%	3875
	11th to 20th	Day	24% 39% 9% 16% 11%	3765
	21st to end	Day	17% 38% 10% 25% 10% 1	4179
September	1st to 10th	Day	10% 61% 4 14% 8% 3	2280
	11th to 20th	Day	11% 60% 6% 10% 12% 1	2140
	21st to end	Day	15% 60% 4 12% 9%	2090
October	1st to 10th	Day	9% 36% 2 18% 32% 2	3480
	11th to 20th	Day	12% 37% 5% 15% 28% 3	3141
	21st to end	Day	19% 36% 4 15% 24% 3	3154
November	1st to 10th	Day	18% 56% 4 13% 7% 2	1762
	11th to 20th	Day	17% 56% 2 11% 10% 3	1800
	21st to end	Day	23% 57% 3 11% 6% 1	1800
December	1st to 10th	Day	22% 56% 5% 8% 8%	1745
	11th to 20th	Day	29% 46% 5% 15% 5% 1	1995
	21st to end	Day	46% 37% 6% 6% 5%	2807
January	1st to 10th	Night	36% 37% 8% 13% 5% 1	4428
	11th to 20th	Night	39% 37% 4 13% 6% 1	4440
	21st to end	Night	41% 39% 5% 9% 5%	4587
February	1st to 10th	Night	19% 64% 4 8% 5% 1	2301
	11th to 20th	Night	18% 63% 3 8% 7%	2219
	21st to end	Night	18% 65% 2 7% 7% 1	1884
March	1st to 10th	Night	36% 41% 4 10% 7% 1	3733
	11th to 20th	Night	17% 41% 7% 16% 16% 3	3717
	21st to end	Night	25% 42% 7% 20% 6%	3466
April	1st to 10th	Night	16% 65% 4 9% 5% 1	1900
	11th to 20th	Night	16% 65% 4 9% 6% 1	1875
	21st to end	Night	15% 65% 4 8% 6% 2	1882
May	1st to 10th	Night	26% 45% 11% 14% 4	2840
	11th to 20th	Night	24% 41% 8% 20% 6%	2813
	21st to end	Night	23% 43% 8% 13% 12% 1	2846
June	1st to 10th	Night	12% 65% 4 9% 7% 1	1520
	11th to 20th	Night	12% 65% 4 8% 10% 2	1520
	21st to end	Night	10% 66% 6% 11% 7% 1	1520
July	1st to 10th	Night	24% 37% 6% 18% 14% 2	2490
	11th to 20th	Night	14% 37% 7% 26% 16% 1	2482
	21st to end	Night	32% 38% 11% 12% 6% 1	2662
August	1st to 10th	Night	13% 39% 9% 31% 7%	3026
	11th to 20th	Night	19% 39% 8% 20% 13%	3130
	21st to end	Night	13% 38% 10% 24% 13% 1	3476
September	1st to 10th	Night	10% 59% 3 14% 11% 2	1900
	11th to 20th	Night	10% 60% 4 11% 13% 2	2019
	21st to end	Night	14% 60% 4 11% 9% 1	2090
October	1st to 10th	Night	8% 36% 3 11% 38% 5%	3480
	11th to 20th	Night	11% 36% 3 17% 30% 3	3774
	21st to end	Night	17% 37% 5% 16% 20% 5%	4392
November	1st to 10th	Night	19% 56% 4 11% 8% 3	2536
	11th to 20th	Night	16% 56% 3 10% 13% 2	2600
	21st to end	Night	21% 57% 4 12% 6%	2600
December	1st to 10th	Night	22% 57% 6% 8% 7% 1	2652
	11th to 20th	Night	23% 47% 6% 14% 10%	3421
	21st to end	Night	44% 37% 6% 7% 5% 2	4933

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	25% 15% 30% 22% 7% 1	270
	11th to 20th	Day	28% 13% 31% 22% 5%	270
	21st to end	Day	24% 16% 36% 18% 7%	297
February	1st to 10th	Day	25% 13% 40% 19% 3	270
	11th to 20th	Day	25% 18% 37% 16% 3 1	270
	21st to end	Day	28% 15% 35% 19% 4	225
March	1st to 10th	Day	21% 16% 36% 21% 5%	270
	11th to 20th	Day	25% 18% 35% 17% 5% 1	298
	21st to end	Day	27% 14% 33% 19% 7%	506
April	1st to 10th	Day	16% 16% 32% 27% 8% 1	460
	11th to 20th	Day	19% 17% 25% 23% 15% 2	452
	21st to end	Day	20% 11% 34% 22% 9% 3	460
May	1st to 10th	Day	16% 13% 29% 29% 10% 3	463
	11th to 20th	Day	20% 7% 22% 28% 14% 9%	487
	21st to end	Day	10% 5% 26% 28% 20% 10%	670
June	1st to 10th	Day	10% 6% 18% 27% 27% 11%	680
	11th to 20th	Day	8% 2 20% 34% 25% 11%	680
	21st to end	Day	8% 4 25% 29% 24% 10%	680
July	1st to 10th	Day	10% 2 15% 24% 26% 23%	671
	11th to 20th	Day	7% 3 13% 30% 30% 16%	668
	21st to end	Day	8% 2 12% 29% 35% 14%	739
August	1st to 10th	Day	9% 3 12% 24% 36% 16%	491
	11th to 20th	Day	12% 1 12% 29% 33% 13%	479
	21st to end	Day	8% 1 10% 23% 37% 20%	539
September	1st to 10th	Day	10% 3 13% 24% 35% 15%	490
	11th to 20th	Day	9% 3 8% 29% 34% 17%	490
	21st to end	Day	15% 3 20% 24% 25% 12%	490
October	1st to 10th	Day	10% 3 19% 36% 23% 8%	490
	11th to 20th	Day	12% 13% 33% 24% 12% 5%	301
	21st to end	Day	24% 11% 31% 26% 8%	330
November	1st to 10th	Day	11% 11% 32% 25% 16% 5%	300
	11th to 20th	Day	13% 21% 30% 23% 10% 3	300
	21st to end	Day	25% 12% 24% 27% 10% 1	300
December	1st to 10th	Day	16% 18% 34% 23% 6% 3	300
	11th to 20th	Day	22% 14% 35% 21% 8%	300
	21st to end	Day	27% 17% 33% 17% 6%	306
January	1st to 10th	Night	21% 13% 34% 28% 4	950
	11th to 20th	Night	24% 14% 36% 22% 4	950
	21st to end	Night	20% 12% 38% 28% 3	1045
February	1st to 10th	Night	26% 11% 35% 26% 2	781
	11th to 20th	Night	21% 15% 36% 27% 2	743
	21st to end	Night	26% 13% 36% 24% 1	628
March	1st to 10th	Night	22% 14% 33% 27% 4	760
	11th to 20th	Night	19% 11% 37% 26% 7%	744
	21st to end	Night	23% 11% 29% 30% 7%	627
April	1st to 10th	Night	14% 11% 34% 35% 7%	570
	11th to 20th	Night	18% 10% 29% 29% 13% 1	563
	21st to end	Night	19% 6% 34% 32% 9% 1	570
May	1st to 10th	Night	17% 6% 28% 37% 10% 1	570
	11th to 20th	Night	14% 4 25% 36% 20% 2	561
	21st to end	Night	8% 2 20% 40% 26% 4	617
June	1st to 10th	Night	11% 3 17% 40% 26% 2	570
	11th to 20th	Night	9% 1 17% 45% 26% 2	570
	21st to end	Night	5% 1 21% 41% 30% 2	570
July	1st to 10th	Night	10% 1 9% 33% 38% 9%	555
	11th to 20th	Night	5% 2 9% 37% 42% 5%	552
	21st to end	Night	9% 3 9% 37% 36% 6%	624
August	1st to 10th	Night	7% 2 7% 40% 38% 7%	567
	11th to 20th	Night	5% 1 10% 40% 40% 4	564
	21st to end	Night	7% 1 7% 36% 43% 7%	627
September	1st to 10th	Night	10% 3 11% 35% 34% 7%	570
	11th to 20th	Night	8% 2 13% 33% 37% 6%	689
	21st to end	Night	13% 3 20% 31% 28% 5%	760
October	1st to 10th	Night	9% 4 21% 36% 26% 4	760
	11th to 20th	Night	17% 6% 30% 29% 16% 2	760
	21st to end	Night	21% 8% 31% 30% 10%	836
November	1st to 10th	Night	14% 6% 31% 36% 13% 1	780
	11th to 20th	Night	15% 10% 33% 31% 10%	800
	21st to end	Night	22% 11% 27% 30% 10%	800
December	1st to 10th	Night	25% 8% 34% 28% 6%	852
	11th to 20th	Night	26% 8% 29% 31% 6% 1	1000
	21st to end	Night	28% 12% 34% 23% 4	1063

Page generated at 2024-12-21 03:13:48. Version ac07

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