South Nation Space Station
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the South Nation Space Station clear sky chart from 2005-11-06 to 2026-02-01.

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% 3 8% 5% 5% 5% 4 5% 7% 32%	127811
	Night	17% 12% 4 9% 5% 4 4 3 5% 6% 30%	124210
Transparency	Day	51% 6% 12% 20% 10% 1	131263
	Night	53% 6% 11% 19% 10% 1	128845
Seeing	Day	22% 13% 28% 22% 11% 3	15948
	Night	23% 9% 28% 29% 11% 1	25113

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% 19% 7% 16% 6% 5% 4 3 4 4 19%	3677
	11th to 20th	Day	13% 15% 6% 14% 6% 5% 4 4 5% 4 22%	3650
	21st to end	Day	11% 18% 7% 11% 6% 6% 5% 4 5% 5% 21%	4119
February	1st to 10th	Day	13% 16% 5% 12% 7% 4 4 4 4 6% 26%	1800
	11th to 20th	Day	14% 16% 4 12% 6% 5% 4 4 4 5% 26%	1788
	21st to end	Day	20% 13% 4 10% 6% 4 5% 4 5% 5% 25%	1650
March	1st to 10th	Day	19% 13% 4 11% 6% 5% 4 3 5% 5% 25%	4476
	11th to 20th	Day	13% 12% 4 10% 6% 5% 4 4 6% 7% 30%	4882
	21st to end	Day	19% 11% 3 8% 5% 4 4 3 4 4 36%	5832
April	1st to 10th	Day	21% 12% 3 7% 4 4 4 3 4 5% 33%	2400
	11th to 20th	Day	21% 10% 3 6% 5% 3 4 3 5% 6% 35%	2374
	21st to end	Day	22% 10% 4 8% 6% 4 4 4 4 5% 31%	2543
May	1st to 10th	Day	23% 10% 3 9% 5% 5% 5% 4 6% 6% 24%	6346
	11th to 20th	Day	19% 9% 3 9% 5% 5% 5% 4 5% 7% 31%	6318
	21st to end	Day	22% 8% 3 7% 4 4 4 4 5% 7% 32%	6949
June	1st to 10th	Day	21% 8% 3 7% 5% 4 5% 4 6% 7% 30%	2800
	11th to 20th	Day	13% 7% 2 6% 5% 5% 5% 5% 7% 8% 38%	2800
	21st to end	Day	19% 7% 2 7% 5% 5% 5% 5% 7% 8% 31%	2800
July	1st to 10th	Day	14% 6% 3 7% 6% 5% 5% 5% 7% 9% 34%	6360
	11th to 20th	Day	12% 6% 2 6% 5% 5% 5% 4 6% 8% 41%	6360
	21st to end	Day	9% 5% 2 5% 4 4 4 4 6% 10% 47%	6926
August	1st to 10th	Day	13% 6% 2 8% 5% 5% 6% 5% 6% 8% 36%	4563
	11th to 20th	Day	15% 6% 3 6% 4 4 4 4 6% 9% 39%	4090
	21st to end	Day	15% 5% 2 6% 5% 4 5% 4 7% 8% 39%	4312
September	1st to 10th	Day	14% 5% 2 6% 4 5% 5% 4 6% 8% 43%	2400
	11th to 20th	Day	13% 4 2 5% 3 4 4 4 5% 7% 50%	2371
	21st to end	Day	18% 6% 2 5% 3 4 4 4 5% 7% 41%	2178
October	1st to 10th	Day	20% 8% 3 5% 4 4 4 3 5% 7% 37%	2000
	11th to 20th	Day	21% 10% 3 8% 4 5% 4 4 5% 5% 30%	2000
	21st to end	Day	24% 9% 4 9% 5% 4 4 3 5% 5% 28%	2000
November	1st to 10th	Day	17% 10% 3 6% 6% 4 5% 4 5% 6% 34%	1851
	11th to 20th	Day	18% 13% 4 9% 5% 5% 5% 3 4 6% 28%	1722
	21st to end	Day	23% 14% 5% 9% 5% 4 5% 3 4 6% 21%	1680
December	1st to 10th	Day	21% 20% 5% 10% 5% 4 4 4 5% 5% 16%	2680
	11th to 20th	Day	18% 17% 5% 10% 5% 5% 4 3 4 4 26%	3066
	21st to end	Day	23% 17% 4 9% 5% 4 4 3 4 4 22%	4048
January	1st to 10th	Night	15% 20% 8% 15% 5% 4 4 2 4 4 20%	6489
	11th to 20th	Night	12% 16% 7% 15% 8% 6% 5% 3 4 4 20%	6455
	21st to end	Night	13% 18% 6% 12% 6% 6% 5% 3 5% 5% 22%	7078
February	1st to 10th	Night	14% 14% 6% 12% 6% 5% 6% 4 5% 6% 25%	2601
	11th to 20th	Night	13% 13% 4 12% 6% 5% 4 4 4 4 28%	2496
	21st to end	Night	15% 14% 4 10% 5% 5% 4 3 5% 6% 28%	1980
March	1st to 10th	Night	22% 14% 4 8% 5% 4 3 3 4 4 28%	5364
	11th to 20th	Night	13% 13% 4 8% 5% 5% 5% 4 6% 8% 31%	5076
	21st to end	Night	18% 11% 3 9% 5% 4 4 3 4 5% 33%	5100
April	1st to 10th	Night	21% 11% 3 8% 5% 4 4 3 4 6% 32%	2000
	11th to 20th	Night	19% 9% 3 7% 5% 4 4 3 4 6% 35%	1975
	21st to end	Night	21% 9% 3 7% 4 3 4 3 5% 5% 35%	1875
May	1st to 10th	Night	22% 9% 4 9% 5% 5% 5% 4 6% 7% 25%	3594
	11th to 20th	Night	18% 8% 3 7% 5% 4 5% 4 6% 6% 35%	3575
	21st to end	Night	18% 10% 3 8% 6% 4 5% 3 5% 6% 30%	3926
June	1st to 10th	Night	16% 7% 2 7% 5% 5% 5% 4 7% 10% 32%	1600
	11th to 20th	Night	14% 7% 3 7% 4 4 4 5% 5% 7% 41%	1600
	21st to end	Night	18% 8% 2 7% 4 4 5% 4 6% 7% 35%	1600
July	1st to 10th	Night	15% 7% 2 7% 5% 5% 6% 5% 7% 8% 32%	3600
	11th to 20th	Night	13% 6% 3 7% 4 4 4 3 6% 8% 43%	3600
	21st to end	Night	10% 5% 2 6% 4 4 5% 4 6% 7% 47%	3926
August	1st to 10th	Night	13% 7% 3 8% 4 5% 5% 5% 6% 8% 38%	2586
	11th to 20th	Night	15% 7% 2 5% 4 4 4 4 5% 6% 43%	2921
	21st to end	Night	14% 6% 2 7% 4 5% 4 4 6% 7% 41%	3586
September	1st to 10th	Night	11% 6% 2 5% 5% 5% 4 4 5% 7% 46%	2000
	11th to 20th	Night	14% 5% 2 5% 3 3 4 4 5% 6% 50%	2028
	21st to end	Night	17% 6% 2 5% 4 5% 3 3 5% 7% 44%	2219
October	1st to 10th	Night	18% 7% 3 7% 4 4 4 3 5% 6% 40%	2400
	11th to 20th	Night	19% 9% 3 7% 6% 5% 4 4 5% 5% 34%	2400
	21st to end	Night	22% 9% 3 8% 5% 5% 4 3 4 6% 30%	2840
November	1st to 10th	Night	20% 10% 3 7% 5% 4 4 4 6% 6% 32%	2667
	11th to 20th	Night	18% 11% 4 8% 5% 5% 5% 3 4 5% 30%	2895
	21st to end	Night	20% 14% 4 9% 5% 5% 4 3 5% 6% 23%	2940
December	1st to 10th	Night	19% 17% 6% 11% 6% 5% 5% 4 5% 5% 18%	4720
	11th to 20th	Night	24% 14% 5% 9% 5% 4 3 2 4 4 26%	5348
	21st to end	Night	27% 18% 3 9% 4 4 3 3 4 5% 21%	7150

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	70% 6% 6% 14% 4 1	3678
	11th to 20th	Day	63% 5% 10% 13% 8% 1	3680
	21st to end	Day	63% 6% 10% 11% 9% 1	4119
February	1st to 10th	Day	61% 5% 9% 17% 7% 2	1800
	11th to 20th	Day	60% 5% 10% 15% 9% 1	1797
	21st to end	Day	61% 5% 9% 13% 11% 1	1650
March	1st to 10th	Day	62% 4 8% 12% 11% 3	4479
	11th to 20th	Day	52% 6% 17% 14% 10% 1	4882
	21st to end	Day	52% 4 7% 17% 18% 2	5832
April	1st to 10th	Day	55% 4 8% 18% 13% 3	2400
	11th to 20th	Day	51% 4 7% 20% 15% 2	2374
	21st to end	Day	55% 6% 8% 15% 13% 4	2543
May	1st to 10th	Day	59% 5% 8% 18% 8% 2	6357
	11th to 20th	Day	51% 8% 13% 17% 10% 1	6322
	21st to end	Day	51% 6% 11% 19% 12% 1	6949
June	1st to 10th	Day	52% 7% 11% 18% 12% 1	2800
	11th to 20th	Day	42% 7% 12% 23% 13% 2	2800
	21st to end	Day	49% 9% 12% 19% 10% 1	2800
July	1st to 10th	Day	46% 6% 14% 26% 9%	6290
	11th to 20th	Day	39% 6% 14% 30% 11%	6285
	21st to end	Day	32% 6% 15% 35% 10%	6728
August	1st to 10th	Day	45% 7% 16% 23% 9%	4549
	11th to 20th	Day	40% 7% 16% 28% 7% 1	4129
	21st to end	Day	41% 7% 17% 23% 12% 1	4312
September	1st to 10th	Day	39% 7% 14% 28% 13%	2400
	11th to 20th	Day	34% 7% 14% 32% 13% 1	2371
	21st to end	Day	42% 7% 14% 26% 11%	2178
October	1st to 10th	Day	48% 5% 10% 28% 8%	3260
	11th to 20th	Day	48% 7% 14% 24% 7% 1	3240
	21st to end	Day	49% 5% 19% 21% 6%	3212
November	1st to 10th	Day	51% 6% 13% 22% 7% 1	1851
	11th to 20th	Day	59% 4 12% 15% 10% 1	1722
	21st to end	Day	65% 6% 11% 12% 6% 1	1680
December	1st to 10th	Day	69% 6% 12% 12% 2	2680
	11th to 20th	Day	64% 4 10% 15% 7%	3066
	21st to end	Day	65% 4 8% 17% 6%	4048
January	1st to 10th	Night	68% 5% 12% 11% 4	6489
	11th to 20th	Night	66% 6% 10% 12% 5%	6500
	21st to end	Night	65% 4 9% 9% 12% 1	7078
February	1st to 10th	Night	59% 5% 11% 16% 8% 1	2601
	11th to 20th	Night	58% 5% 10% 19% 8% 1	2498
	21st to end	Night	56% 5% 9% 18% 11% 1	1980
March	1st to 10th	Night	60% 4 7% 13% 12% 4	5374
	11th to 20th	Night	51% 6% 15% 16% 9% 3	5077
	21st to end	Night	53% 3 8% 21% 12% 2	5100
April	1st to 10th	Night	54% 5% 10% 16% 14% 2	2000
	11th to 20th	Night	50% 5% 8% 20% 16% 1	1975
	21st to end	Night	50% 4 9% 18% 15% 3	1875
May	1st to 10th	Night	57% 7% 8% 18% 8% 2	3600
	11th to 20th	Night	47% 8% 12% 18% 13% 2	3576
	21st to end	Night	53% 7% 9% 17% 13% 1	3927
June	1st to 10th	Night	46% 8% 12% 22% 12% 1	1600
	11th to 20th	Night	42% 8% 10% 22% 16% 2	1600
	21st to end	Night	46% 9% 11% 19% 14% 1	1600
July	1st to 10th	Night	46% 7% 17% 20% 10% 1	3560
	11th to 20th	Night	39% 6% 14% 31% 10%	3552
	21st to end	Night	35% 6% 13% 31% 15%	3809
August	1st to 10th	Night	43% 7% 15% 27% 8%	2576
	11th to 20th	Night	40% 6% 16% 30% 8%	2948
	21st to end	Night	40% 7% 16% 23% 12% 2	3586
September	1st to 10th	Night	37% 7% 12% 27% 15% 1	2000
	11th to 20th	Night	34% 7% 12% 35% 11% 1	2028
	21st to end	Night	41% 6% 12% 29% 13%	2219
October	1st to 10th	Night	42% 6% 15% 25% 12% 1	3920
	11th to 20th	Night	45% 6% 14% 25% 10%	3899
	21st to end	Night	48% 5% 17% 19% 10%	4578
November	1st to 10th	Night	53% 5% 13% 20% 8%	2667
	11th to 20th	Night	56% 5% 11% 17% 9% 1	2895
	21st to end	Night	62% 6% 12% 14% 5%	2940
December	1st to 10th	Night	67% 5% 13% 12% 3	4720
	11th to 20th	Night	63% 4 7% 15% 11% 1	5348
	21st to end	Night	66% 4 6% 13% 10%	7150

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% 14% 33% 24% 4 1	220
	11th to 20th	Day	30% 14% 36% 15% 5% 1	220
	21st to end	Day	17% 14% 34% 29% 6%	259
February	1st to 10th	Day	29% 24% 33% 12% 3	300
	11th to 20th	Day	26% 23% 36% 14% 1	335
	21st to end	Day	28% 17% 31% 22% 2	414
March	1st to 10th	Day	28% 16% 29% 22% 5%	500
	11th to 20th	Day	23% 19% 33% 20% 5% 1	500
	21st to end	Day	29% 15% 31% 15% 8% 2	550
April	1st to 10th	Day	28% 19% 28% 15% 8% 1	500
	11th to 20th	Day	30% 18% 21% 18% 10% 2	492
	21st to end	Day	29% 16% 31% 16% 7% 1	500
May	1st to 10th	Day	24% 13% 33% 22% 6% 2	503
	11th to 20th	Day	20% 16% 30% 22% 11% 2	527
	21st to end	Day	21% 13% 31% 24% 10% 2	573
June	1st to 10th	Day	25% 11% 28% 24% 11% 2	530
	11th to 20th	Day	15% 13% 30% 26% 14% 3	530
	21st to end	Day	22% 12% 27% 25% 12% 2	530
July	1st to 10th	Day	14% 8% 27% 30% 16% 6%	525
	11th to 20th	Day	13% 7% 31% 28% 17% 4	524
	21st to end	Day	13% 7% 28% 31% 18% 3	576
August	1st to 10th	Day	13% 7% 23% 32% 21% 4	526
	11th to 20th	Day	14% 6% 22% 31% 19% 8%	519
	21st to end	Day	16% 9% 25% 27% 16% 8%	583
September	1st to 10th	Day	18% 8% 26% 22% 18% 8%	530
	11th to 20th	Day	12% 7% 20% 21% 24% 15%	530
	21st to end	Day	20% 11% 27% 20% 15% 7%	530
October	1st to 10th	Day	24% 12% 23% 20% 17% 4	530
	11th to 20th	Day	25% 17% 28% 20% 10% 1	530
	21st to end	Day	31% 11% 29% 22% 7%	473
November	1st to 10th	Day	29% 16% 24% 22% 8% 1	425
	11th to 20th	Day	26% 18% 34% 14% 5% 2	262
	21st to end	Day	32% 20% 25% 18% 5%	220
December	1st to 10th	Day	32% 11% 30% 19% 7%	220
	11th to 20th	Day	26% 17% 40% 14% 3	220
	21st to end	Day	32% 17% 32% 14% 5% 1	242
January	1st to 10th	Night	27% 10% 34% 23% 5%	840
	11th to 20th	Night	29% 11% 29% 24% 6%	840
	21st to end	Night	20% 9% 33% 30% 8% 1	924
February	1st to 10th	Night	20% 11% 37% 27% 5%	801
	11th to 20th	Night	21% 12% 38% 24% 4	783
	21st to end	Night	24% 12% 30% 30% 4	660
March	1st to 10th	Night	24% 12% 31% 27% 5%	800
	11th to 20th	Night	25% 11% 35% 24% 6% 1	800
	21st to end	Night	24% 10% 31% 26% 8%	880
April	1st to 10th	Night	27% 12% 28% 27% 6%	800
	11th to 20th	Night	25% 12% 30% 26% 7% 1	791
	21st to end	Night	26% 9% 30% 27% 7% 1	675
May	1st to 10th	Night	26% 6% 28% 29% 9% 2	400
	11th to 20th	Night	23% 6% 26% 34% 10%	394
	21st to end	Night	18% 6% 33% 30% 13%	433
June	1st to 10th	Night	17% 3 27% 43% 10%	400
	11th to 20th	Night	17% 4 28% 36% 14% 1	400
	21st to end	Night	19% 4 26% 34% 16% 1	400
July	1st to 10th	Night	11% 4 23% 43% 19%	390
	11th to 20th	Night	13% 3 19% 46% 19% 1	388
	21st to end	Night	13% 3 21% 44% 18% 1	438
August	1st to 10th	Night	13% 4 14% 47% 22% 1	398
	11th to 20th	Night	15% 2 17% 34% 29% 2	614
	21st to end	Night	15% 5% 21% 37% 21% 2	880
September	1st to 10th	Night	14% 4 25% 36% 20% 1	800
	11th to 20th	Night	17% 4 17% 33% 26% 3	800
	21st to end	Night	19% 6% 23% 30% 20% 2	800
October	1st to 10th	Night	22% 5% 26% 30% 17% 1	800
	11th to 20th	Night	25% 8% 27% 31% 9% 1	800
	21st to end	Night	26% 10% 28% 30% 6%	880
November	1st to 10th	Night	28% 8% 26% 28% 9% 1	820
	11th to 20th	Night	25% 11% 32% 23% 10%	840
	21st to end	Night	28% 13% 29% 23% 8%	840
December	1st to 10th	Night	30% 11% 30% 24% 5%	840
	11th to 20th	Night	30% 12% 29% 23% 5% 1	840
	21st to end	Night	35% 10% 30% 19% 5%	924

Page generated at 2026-01-29 01:21:46. Version ac07

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