Gothenburg
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gothenburg clear sky chart from 2005-11-06 to 2025-04-11.

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	8% 6% 2 5% 4 3 4 3 5% 7% 54%	117222
	Night	7% 6% 2 5% 4 4 4 3 5% 7% 53%	119836
Transparency	Day	30% 5% 13% 27% 20% 5%	116972
	Night	31% 5% 13% 26% 20% 5%	119676
Seeing	Day	11% 8% 31% 32% 15% 2	16245
	Night	10% 8% 35% 37% 9%	26349

By Month

Percentage Cloud Cover SW (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	9% 12% 3 6% 4 3 4 2 4 5% 46%	3638
	11th to 20th	Day	5% 8% 3 8% 4 4 5% 4 6% 6% 48%	3640
	21st to end	Day	3 5% 3 7% 5% 5% 4 3 5% 7% 54%	4250
February	1st to 10th	Day	7% 9% 3 9% 7% 4 5% 3 6% 6% 41%	1900
	11th to 20th	Day	5% 7% 3 8% 4 3 5% 3 6% 7% 47%	1949
	21st to end	Day	6% 7% 3 6% 3 3 3 2 5% 6% 57%	1650
March	1st to 10th	Day	11% 7% 2 4 2 2 3 3 4 5% 56%	4500
	11th to 20th	Day	8% 6% 2 4 3 3 3 3 4 6% 58%	4926
	21st to end	Day	9% 8% 2 7% 4 3 4 4 6% 7% 46%	5504
April	1st to 10th	Day	10% 6% 2 4 3 3 3 4 5% 7% 52%	2400
	11th to 20th	Day	13% 7% 2 5% 5% 4 4 3 5% 7% 44%	2298
	21st to end	Day	15% 6% 2 4 4 3 3 3 5% 7% 48%	2470
May	1st to 10th	Day	10% 5% 2 5% 5% 4 4 3 6% 7% 48%	4120
	11th to 20th	Day	13% 4 2 5% 3 3 3 3 5% 8% 50%	4082
	21st to end	Day	13% 6% 2 5% 4 4 4 3 5% 7% 47%	4564
June	1st to 10th	Day	6% 3 1 3 3 3 3 4 7% 9% 57%	2660
	11th to 20th	Day	7% 4 1 4 4 4 4 4 6% 8% 53%	2660
	21st to end	Day	4 3 1 4 3 4 4 4 7% 9% 57%	2660
July	1st to 10th	Day	7% 4 2 5% 3 4 4 4 6% 8% 55%	4430
	11th to 20th	Day	4 3 2 4 3 4 4 4 7% 10% 55%	4430
	21st to end	Day	4 3 1 4 3 3 4 4 6% 10% 58%	4627
August	1st to 10th	Day	10% 5% 2 5% 4 4 5% 4 6% 9% 47%	4103
	11th to 20th	Day	10% 6% 2 6% 4 4 5% 4 5% 8% 46%	4041
	21st to end	Day	5% 4 2 4 3 3 3 2 5% 7% 63%	4192
September	1st to 10th	Day	9% 4 2 4 3 3 3 3 4 6% 58%	2230
	11th to 20th	Day	7% 4 1 5% 3 3 4 3 5% 7% 58%	2090
	21st to end	Day	10% 4 2 3 1 2 3 2 4 5% 64%	2090
October	1st to 10th	Day	7% 3 1 2 1 1 2 2 2 4 74%	3480
	11th to 20th	Day	5% 4 1 4 3 2 3 3 4 6% 65%	3165
	21st to end	Day	9% 5% 2 4 3 3 3 3 4 7% 58%	3091
November	1st to 10th	Day	7% 6% 2 4 4 4 4 3 5% 6% 56%	1763
	11th to 20th	Day	5% 7% 1 4 3 3 3 3 4 6% 62%	1800
	21st to end	Day	7% 7% 2 4 3 3 3 3 5% 7% 56%	1800
December	1st to 10th	Day	4 4 2 5% 4 3 3 3 4 6% 62%	2940
	11th to 20th	Day	4 6% 2 6% 4 3 3 3 4 6% 58%	3075
	21st to end	Day	9% 12% 3 9% 5% 4 3 3 4 6% 41%	4004
January	1st to 10th	Night	7% 11% 4 11% 6% 5% 4 3 5% 6% 39%	6327
	11th to 20th	Night	3 7% 3 8% 4 4 4 4 5% 7% 53%	6340
	21st to end	Night	3 7% 3 8% 4 5% 4 3 5% 6% 51%	6713
February	1st to 10th	Night	8% 9% 4 7% 4 4 4 4 5% 7% 44%	2518
	11th to 20th	Night	4 9% 3 7% 5% 5% 4 4 5% 8% 46%	2338
	21st to end	Night	4 7% 2 6% 4 3 4 4 5% 5% 56%	1980
March	1st to 10th	Night	9% 7% 2 5% 3 3 3 3 4 5% 57%	5374
	11th to 20th	Night	9% 5% 2 4 3 3 3 3 4 7% 58%	5036
	21st to end	Night	10% 8% 3 7% 5% 5% 5% 5% 6% 8% 39%	5424
April	1st to 10th	Night	11% 7% 2 5% 4 3 4 3 6% 7% 48%	2000
	11th to 20th	Night	12% 5% 2 4 3 4 5% 4 6% 6% 48%	1836
	21st to end	Night	12% 7% 2 4 4 4 4 4 6% 8% 47%	1710
May	1st to 10th	Night	18% 5% 2 5% 3 4 4 4 6% 7% 41%	2850
	11th to 20th	Night	10% 5% 2 7% 4 4 4 3 6% 7% 48%	2823
	21st to end	Night	14% 5% 2 5% 4 4 4 4 6% 9% 45%	3019
June	1st to 10th	Night	6% 3 2 5% 5% 4 5% 4 6% 8% 54%	1520
	11th to 20th	Night	10% 4 1 4 4 3 4 3 6% 9% 51%	1520
	21st to end	Night	5% 3 1 5% 4 4 5% 5% 6% 9% 53%	1520
July	1st to 10th	Night	9% 4 2 4 4 4 4 4 6% 8% 51%	2540
	11th to 20th	Night	4 3 2 6% 5% 5% 5% 5% 7% 10% 48%	2540
	21st to end	Night	3 3 1 4 3 3 3 4 6% 10% 61%	2934
August	1st to 10th	Night	6% 4 2 6% 5% 4 5% 4 8% 11% 46%	2836
	11th to 20th	Night	11% 6% 2 6% 5% 4 3 4 6% 7% 46%	2798
	21st to end	Night	5% 4 1 4 3 3 5% 4 7% 9% 55%	3472
September	1st to 10th	Night	7% 4 1 3 2 3 3 3 5% 6% 61%	1948
	11th to 20th	Night	6% 3 1 4 3 3 4 3 5% 6% 61%	2090
	21st to end	Night	8% 3 1 4 3 3 3 2 4 6% 63%	2090
October	1st to 10th	Night	8% 2 1 2 2 2 2 1 3 3 73%	3480
	11th to 20th	Night	7% 4 1 3 2 2 2 2 3 6% 67%	3719
	21st to end	Night	8% 4 2 5% 3 3 3 3 4 6% 59%	4467
November	1st to 10th	Night	5% 4 2 4 3 3 3 3 5% 7% 61%	2535
	11th to 20th	Night	6% 6% 2 5% 3 3 3 4 4 7% 58%	2600
	21st to end	Night	6% 6% 2 4 3 3 3 3 5% 7% 56%	2600
December	1st to 10th	Night	3 4 2 3 3 2 3 3 5% 6% 65%	4250
	11th to 20th	Night	4 5% 2 5% 4 3 4 3 6% 8% 57%	5115
	21st to end	Night	10% 13% 3 6% 4 4 4 3 4 6% 43%	6974

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% 3 10% 30% 14% 1	3639
	11th to 20th	Day	36% 7% 9% 25% 21% 3	3640
	21st to end	Day	31% 5% 14% 26% 21% 4	4250
February	1st to 10th	Day	42% 7% 15% 20% 12% 4	1900
	11th to 20th	Day	35% 5% 15% 25% 16% 4	1959
	21st to end	Day	29% 4 13% 28% 20% 6%	1650
March	1st to 10th	Day	31% 4 8% 22% 29% 6%	4500
	11th to 20th	Day	28% 3 9% 24% 29% 6%	4926
	21st to end	Day	35% 8% 19% 27% 11% 1	5504
April	1st to 10th	Day	31% 5% 16% 27% 18% 3	2400
	11th to 20th	Day	39% 6% 14% 22% 15% 4	2301
	21st to end	Day	36% 6% 12% 28% 17% 1	2470
May	1st to 10th	Day	31% 8% 17% 21% 16% 8%	4120
	11th to 20th	Day	31% 9% 15% 29% 15% 2	4086
	21st to end	Day	33% 8% 16% 28% 12% 2	4564
June	1st to 10th	Day	21% 8% 21% 34% 14% 2	2660
	11th to 20th	Day	28% 7% 14% 27% 18% 7%	2660
	21st to end	Day	21% 8% 14% 31% 22% 5%	2660
July	1st to 10th	Day	28% 5% 12% 26% 26% 3	4361
	11th to 20th	Day	24% 5% 16% 32% 20% 3	4355
	21st to end	Day	21% 6% 15% 29% 23% 7%	4480
August	1st to 10th	Day	34% 6% 15% 24% 19% 2	4090
	11th to 20th	Day	36% 6% 15% 24% 18% 1	4080
	21st to end	Day	22% 4 16% 27% 19% 12%	4191
September	1st to 10th	Day	27% 4 10% 25% 24% 9%	2230
	11th to 20th	Day	24% 7% 12% 28% 25% 5%	2090
	21st to end	Day	24% 4 9% 30% 27% 6%	2090
October	1st to 10th	Day	17% 3 5% 23% 37% 16%	3480
	11th to 20th	Day	21% 3 12% 37% 21% 6%	3165
	21st to end	Day	28% 3 7% 34% 23% 6%	3091
November	1st to 10th	Day	28% 5% 12% 29% 22% 4	1763
	11th to 20th	Day	25% 3 11% 30% 25% 6%	1800
	21st to end	Day	29% 3 14% 27% 23% 4	1800
December	1st to 10th	Day	25% 3 11% 34% 24% 4	2940
	11th to 20th	Day	28% 3 18% 32% 17% 2	3073
	21st to end	Day	46% 3 8% 28% 14% 1	4004
January	1st to 10th	Night	45% 5% 11% 22% 15% 2	6327
	11th to 20th	Night	30% 4 15% 24% 24% 2	6340
	21st to end	Night	34% 6% 10% 25% 21% 5%	6713
February	1st to 10th	Night	39% 6% 13% 23% 15% 4	2518
	11th to 20th	Night	36% 6% 13% 27% 15% 3	2338
	21st to end	Night	30% 4 12% 25% 22% 7%	1980
March	1st to 10th	Night	30% 4 7% 24% 28% 7%	5374
	11th to 20th	Night	27% 4 8% 23% 27% 12%	5036
	21st to end	Night	41% 8% 18% 22% 11% 1	5424
April	1st to 10th	Night	34% 6% 14% 24% 18% 4	2000
	11th to 20th	Night	33% 8% 14% 25% 17% 3	1836
	21st to end	Night	33% 8% 15% 27% 15% 2	1710
May	1st to 10th	Night	38% 8% 14% 22% 14% 3	2850
	11th to 20th	Night	32% 10% 17% 28% 12% 1	2824
	21st to end	Night	34% 11% 18% 25% 10% 2	3020
June	1st to 10th	Night	26% 9% 22% 28% 13% 2	1520
	11th to 20th	Night	30% 6% 16% 27% 16% 6%	1520
	21st to end	Night	25% 8% 17% 27% 20% 3	1520
July	1st to 10th	Night	31% 6% 13% 31% 17% 2	2500
	11th to 20th	Night	31% 5% 18% 25% 18% 4	2492
	21st to end	Night	18% 6% 17% 25% 24% 11%	2842
August	1st to 10th	Night	32% 6% 16% 27% 17% 2	2826
	11th to 20th	Night	36% 6% 16% 26% 15% 2	2825
	21st to end	Night	26% 4 14% 28% 19% 8%	3472
September	1st to 10th	Night	23% 5% 10% 25% 27% 10%	1948
	11th to 20th	Night	23% 6% 12% 27% 25% 7%	2090
	21st to end	Night	24% 5% 9% 27% 29% 7%	2090
October	1st to 10th	Night	18% 3 5% 18% 46% 10%	3480
	11th to 20th	Night	21% 3 11% 30% 25% 10%	3719
	21st to end	Night	28% 3 10% 27% 27% 6%	4467
November	1st to 10th	Night	23% 5% 12% 29% 24% 8%	2535
	11th to 20th	Night	26% 5% 10% 27% 25% 7%	2600
	21st to end	Night	27% 4 11% 29% 24% 5%	2600
December	1st to 10th	Night	21% 3 15% 37% 21% 4	4250
	11th to 20th	Night	25% 3 14% 38% 17% 2	5116
	21st to end	Night	42% 4 11% 29% 13% 1	6974

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	13% 6% 35% 33% 11% 2	300
	11th to 20th	Day	11% 13% 35% 34% 6% 1	300
	21st to end	Day	10% 7% 48% 21% 11% 3	330
February	1st to 10th	Day	10% 16% 43% 26% 5%	300
	11th to 20th	Day	10% 8% 44% 27% 8% 2	300
	21st to end	Day	12% 14% 42% 28% 4	249
March	1st to 10th	Day	12% 9% 41% 27% 10% 1	300
	11th to 20th	Day	14% 9% 36% 31% 9% 1	300
	21st to end	Day	20% 13% 39% 18% 9% 1	345
April	1st to 10th	Day	15% 21% 37% 21% 6%	500
	11th to 20th	Day	18% 18% 33% 25% 5%	499
	21st to end	Day	19% 14% 31% 25% 9% 1	650
May	1st to 10th	Day	13% 12% 35% 29% 10% 1	653
	11th to 20th	Day	20% 8% 28% 27% 15% 1	675
	21st to end	Day	15% 9% 33% 29% 12% 1	734
June	1st to 10th	Day	5% 6% 28% 32% 21% 8%	680
	11th to 20th	Day	8% 8% 35% 35% 13% 1	680
	21st to end	Day	6% 6% 29% 41% 17% 2	680
July	1st to 10th	Day	8% 4 23% 36% 25% 4	671
	11th to 20th	Day	6% 2 21% 41% 27% 3	668
	21st to end	Day	5% 1 18% 44% 26% 6%	739
August	1st to 10th	Day	8% 4 17% 42% 25% 4	676
	11th to 20th	Day	9% 2 22% 43% 22% 2	665
	21st to end	Day	6% 3 23% 42% 22% 4	551
September	1st to 10th	Day	9% 3 24% 44% 16% 4	440
	11th to 20th	Day	4 6% 25% 38% 22% 5%	300
	21st to end	Day	12% 10% 25% 30% 18% 4	300
October	1st to 10th	Day	18% 5% 23% 30% 19% 5%	300
	11th to 20th	Day	8% 10% 39% 31% 10% 2	300
	21st to end	Day	20% 12% 27% 28% 12% 1	330
November	1st to 10th	Day	14% 9% 39% 24% 13% 1	300
	11th to 20th	Day	13% 12% 35% 29% 11% 1	300
	21st to end	Day	15% 9% 38% 25% 11% 2	300
December	1st to 10th	Day	7% 10% 40% 32% 10% 1	300
	11th to 20th	Day	13% 9% 38% 30% 9% 1	300
	21st to end	Day	15% 12% 37% 28% 7% 1	330
January	1st to 10th	Night	10% 10% 36% 35% 9% 1	1000
	11th to 20th	Night	8% 13% 38% 34% 7% 1	1000
	21st to end	Night	8% 8% 45% 32% 7%	1100
February	1st to 10th	Night	12% 9% 42% 30% 6%	918
	11th to 20th	Night	9% 10% 42% 35% 5%	784
	21st to end	Night	8% 12% 41% 34% 5%	660
March	1st to 10th	Night	11% 10% 42% 33% 5%	800
	11th to 20th	Night	13% 9% 41% 32% 5%	630
	21st to end	Night	15% 12% 40% 28% 5%	660
April	1st to 10th	Night	14% 14% 42% 28% 2	600
	11th to 20th	Night	15% 15% 42% 27% 2	565
	21st to end	Night	16% 11% 35% 30% 8%	570
May	1st to 10th	Night	16% 8% 39% 31% 6%	570
	11th to 20th	Night	16% 9% 35% 32% 8%	561
	21st to end	Night	18% 6% 36% 30% 9% 1	617
June	1st to 10th	Night	7% 7% 30% 43% 13% 1	570
	11th to 20th	Night	11% 6% 36% 37% 10%	570
	21st to end	Night	6% 4 32% 49% 10%	570
July	1st to 10th	Night	7% 3 26% 44% 19%	555
	11th to 20th	Night	3 1 25% 55% 14% 1	552
	21st to end	Night	5% 2 21% 51% 20% 1	624
August	1st to 10th	Night	5% 2 19% 54% 19%	567
	11th to 20th	Night	8% 3 22% 50% 16%	564
	21st to end	Night	6% 2 23% 49% 18% 1	627
September	1st to 10th	Night	8% 3 28% 49% 12% 1	570
	11th to 20th	Night	7% 4 31% 43% 14% 1	570
	21st to end	Night	9% 6% 33% 36% 15% 1	570
October	1st to 10th	Night	16% 6% 31% 34% 12% 1	570
	11th to 20th	Night	11% 11% 32% 34% 11%	715
	21st to end	Night	14% 10% 33% 34% 9%	1045
November	1st to 10th	Night	8% 7% 36% 40% 8% 1	975
	11th to 20th	Night	10% 9% 38% 35% 8%	1000
	21st to end	Night	9% 8% 33% 37% 12% 1	1000
December	1st to 10th	Night	8% 10% 40% 37% 5%	1000
	11th to 20th	Night	11% 9% 40% 32% 8% 1	1000
	21st to end	Night	15% 10% 35% 34% 6%	1100

Page generated at 2025-04-08 08:17:30. Version ac07

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