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 2024-01-14.

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	18% 9% 4 7% 6% 3 5% 5% 5% 7% 33%	74750
	Night	18% 10% 4 7% 6% 3 4 4 5% 6% 32%	75012
Transparency	Day	51% 7% 11% 19% 10% 1	74455
	Night	53% 6% 11% 19% 10% 1	74841
Seeing	Day	23% 13% 28% 23% 11% 3	13384
	Night	23% 8% 28% 29% 11% 1	22559

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	18% 18% 6% 10% 7% 4 4 4 3 4 21%	1517
	11th to 20th	Day	20% 15% 6% 10% 5% 3 5% 4 4 4 25%	1464
	21st to end	Day	13% 14% 5% 10% 6% 4 6% 5% 6% 5% 25%	1611
February	1st to 10th	Day	13% 16% 5% 11% 8% 3 5% 4 4 6% 24%	1620
	11th to 20th	Day	14% 15% 5% 10% 6% 3 4 5% 4 5% 28%	1605
	21st to end	Day	20% 13% 5% 9% 7% 4 5% 4 4 5% 25%	1480
March	1st to 10th	Day	16% 11% 5% 9% 8% 4 5% 4 5% 5% 29%	1797
	11th to 20th	Day	17% 10% 4 7% 7% 4 6% 4 4 5% 31%	1938
	21st to end	Day	20% 8% 4 6% 5% 3 5% 4 4 5% 37%	2322
April	1st to 10th	Day	21% 11% 4 7% 4 3 4 4 4 5% 33%	2160
	11th to 20th	Day	21% 7% 3 5% 6% 3 4 4 5% 6% 36%	2134
	21st to end	Day	22% 9% 5% 6% 6% 3 4 4 4 5% 31%	2287
May	1st to 10th	Day	20% 8% 3 6% 6% 3 5% 4 5% 6% 34%	2520
	11th to 20th	Day	18% 7% 3 6% 6% 3 4 4 4 7% 39%	2478
	21st to end	Day	18% 6% 3 5% 5% 4 5% 5% 6% 8% 36%	2725
June	1st to 10th	Day	22% 7% 4 6% 6% 3 5% 4 6% 7% 30%	2520
	11th to 20th	Day	14% 6% 2 6% 5% 4 5% 6% 6% 8% 38%	2520
	21st to end	Day	19% 6% 3 6% 5% 4 5% 7% 7% 8% 30%	2520
July	1st to 10th	Day	12% 5% 3 5% 5% 4 6% 6% 7% 8% 40%	2520
	11th to 20th	Day	12% 6% 3 6% 6% 4 5% 5% 7% 9% 37%	2520
	21st to end	Day	12% 6% 3 5% 6% 3 6% 6% 8% 10% 37%	2744
August	1st to 10th	Day	12% 6% 2 6% 6% 4 6% 6% 5% 8% 38%	2506
	11th to 20th	Day	11% 6% 3 5% 5% 3 6% 6% 6% 9% 39%	2263
	21st to end	Day	13% 5% 3 5% 6% 3 5% 5% 6% 8% 43%	2376
September	1st to 10th	Day	15% 5% 2 5% 5% 4 5% 5% 6% 7% 42%	2160
	11th to 20th	Day	14% 4 2 4 4 3 4 5% 5% 7% 47%	2135
	21st to end	Day	18% 6% 3 4 4 3 4 5% 5% 7% 41%	1961
October	1st to 10th	Day	21% 8% 4 5% 5% 3 4 4 5% 7% 35%	1800
	11th to 20th	Day	23% 10% 4 7% 6% 3 5% 5% 5% 5% 28%	1800
	21st to end	Day	26% 8% 4 7% 6% 4 4 4 5% 5% 27%	1800
November	1st to 10th	Day	17% 9% 3 5% 6% 3 5% 5% 5% 7% 35%	1671
	11th to 20th	Day	20% 11% 5% 8% 5% 4 5% 5% 4 6% 27%	1558
	21st to end	Day	22% 12% 5% 8% 7% 3 5% 5% 4 6% 22%	1520
December	1st to 10th	Day	23% 14% 5% 10% 7% 4 5% 5% 4 5% 18%	1520
	11th to 20th	Day	21% 14% 5% 8% 7% 3 5% 3 4 5% 25%	1906
	21st to end	Day	27% 20% 5% 8% 5% 3 3 3 3 3 20%	2772
January	1st to 10th	Night	19% 17% 7% 10% 7% 4 5% 4 4 4 20%	2649
	11th to 20th	Night	20% 17% 6% 9% 7% 3 4 4 4 4 23%	2574
	21st to end	Night	13% 14% 5% 9% 7% 4 5% 4 4 6% 30%	2744
February	1st to 10th	Night	14% 12% 7% 11% 7% 4 6% 5% 5% 6% 24%	2340
	11th to 20th	Night	14% 12% 5% 10% 6% 4 5% 5% 4 5% 29%	2240
	21st to end	Night	17% 12% 5% 9% 6% 4 4 4 5% 5% 29%	1776
March	1st to 10th	Night	16% 12% 5% 8% 8% 4 5% 4 4 5% 28%	2150
	11th to 20th	Night	18% 12% 5% 6% 6% 3 4 4 3 5% 33%	2020
	21st to end	Night	18% 9% 3 7% 5% 3 3 3 4 5% 40%	2034
April	1st to 10th	Night	22% 9% 4 6% 5% 3 5% 3 4 6% 32%	1800
	11th to 20th	Night	19% 8% 4 6% 6% 3 4 4 4 6% 36%	1775
	21st to end	Night	21% 9% 3 6% 5% 2 4 4 5% 6% 34%	1689
May	1st to 10th	Night	21% 6% 3 6% 4 2 5% 4 5% 6% 37%	1440
	11th to 20th	Night	20% 6% 2 6% 4 2 3 4 5% 6% 42%	1415
	21st to end	Night	14% 7% 3 4 6% 3 5% 5% 6% 6% 42%	1550
June	1st to 10th	Night	17% 6% 3 6% 5% 3 6% 5% 7% 10% 32%	1440
	11th to 20th	Night	14% 7% 3 6% 4 2 5% 6% 6% 6% 41%	1440
	21st to end	Night	17% 8% 2 5% 5% 2 6% 5% 6% 8% 36%	1440
July	1st to 10th	Night	11% 4 2 5% 4 4 5% 5% 7% 8% 45%	1440
	11th to 20th	Night	11% 6% 3 5% 5% 3 4 5% 6% 9% 43%	1440
	21st to end	Night	10% 5% 3 6% 5% 3 6% 6% 6% 9% 42%	1574
August	1st to 10th	Night	11% 5% 2 5% 5% 4 4 7% 6% 8% 42%	1432
	11th to 20th	Night	11% 6% 3 4 5% 3 4 5% 6% 7% 45%	1615
	21st to end	Night	11% 5% 2 6% 4 3 5% 5% 6% 7% 44%	1980
September	1st to 10th	Night	11% 6% 2 5% 6% 4 5% 5% 5% 7% 44%	1800
	11th to 20th	Night	15% 5% 2 4 4 2 4 5% 5% 6% 48%	1824
	21st to end	Night	17% 5% 2 5% 5% 4 4 3 4 7% 44%	1997
October	1st to 10th	Night	19% 7% 3 6% 4 3 5% 4 5% 6% 38%	2160
	11th to 20th	Night	21% 8% 3 6% 6% 3 4 5% 4 6% 33%	2160
	21st to end	Night	23% 9% 3 7% 7% 3 4 4 4 6% 29%	2556
November	1st to 10th	Night	20% 9% 3 6% 6% 3 4 4 5% 6% 33%	2407
	11th to 20th	Night	19% 10% 4 7% 7% 4 5% 5% 5% 5% 30%	2619
	21st to end	Night	22% 12% 5% 8% 6% 4 4 4 5% 6% 23%	2660
December	1st to 10th	Night	21% 15% 7% 9% 6% 4 5% 4 4 4 19%	2660
	11th to 20th	Night	23% 14% 5% 7% 6% 3 4 3 4 4 26%	3288
	21st to end	Night	31% 18% 4 8% 5% 3 3 3 3 3 19%	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	68% 6% 7% 14% 5%	1518
	11th to 20th	Day	64% 4 9% 12% 10% 1	1464
	21st to end	Day	60% 6% 10% 15% 9% 1	1611
February	1st to 10th	Day	62% 5% 9% 16% 6% 2	1620
	11th to 20th	Day	59% 5% 11% 15% 9% 1	1614
	21st to end	Day	62% 4 9% 14% 10% 1	1480
March	1st to 10th	Day	58% 5% 9% 17% 10% 2	1800
	11th to 20th	Day	55% 5% 12% 14% 12% 3	1938
	21st to end	Day	51% 5% 8% 17% 14% 5%	2322
April	1st to 10th	Day	55% 4 9% 18% 12% 3	2160
	11th to 20th	Day	50% 5% 8% 20% 15% 2	2134
	21st to end	Day	56% 6% 8% 14% 13% 4	2287
May	1st to 10th	Day	52% 5% 7% 19% 15% 3	2520
	11th to 20th	Day	46% 5% 10% 20% 16% 3	2482
	21st to end	Day	45% 8% 11% 19% 14% 2	2725
June	1st to 10th	Day	53% 7% 11% 18% 11% 1	2520
	11th to 20th	Day	42% 8% 12% 22% 13% 3	2520
	21st to end	Day	49% 10% 12% 18% 10% 1	2520
July	1st to 10th	Day	40% 9% 13% 25% 13% 1	2450
	11th to 20th	Day	41% 9% 14% 25% 11%	2445
	21st to end	Day	41% 10% 14% 25% 10%	2591
August	1st to 10th	Day	42% 10% 16% 24% 9%	2492
	11th to 20th	Day	40% 10% 15% 25% 9% 1	2263
	21st to end	Day	38% 9% 14% 26% 12% 1	2376
September	1st to 10th	Day	40% 8% 13% 26% 13%	2160
	11th to 20th	Day	36% 7% 14% 30% 13% 1	2135
	21st to end	Day	42% 7% 14% 27% 9%	1961
October	1st to 10th	Day	49% 6% 10% 22% 12% 1	1800
	11th to 20th	Day	57% 8% 13% 16% 6% 1	1800
	21st to end	Day	60% 5% 12% 16% 7% 1	1800
November	1st to 10th	Day	49% 7% 14% 22% 7% 1	1671
	11th to 20th	Day	59% 4 13% 14% 9%	1558
	21st to end	Day	63% 6% 12% 12% 6% 1	1520
December	1st to 10th	Day	68% 7% 11% 10% 3	1520
	11th to 20th	Day	63% 6% 13% 14% 5%	1906
	21st to end	Day	71% 4 7% 14% 4	2772
January	1st to 10th	Night	68% 6% 10% 11% 5%	2649
	11th to 20th	Night	66% 6% 9% 10% 8% 1	2574
	21st to end	Night	57% 5% 10% 16% 11% 1	2744
February	1st to 10th	Night	61% 5% 10% 16% 7% 1	2340
	11th to 20th	Night	57% 5% 10% 19% 8% 1	2242
	21st to end	Night	55% 5% 9% 17% 12% 1	1776
March	1st to 10th	Night	57% 5% 9% 16% 10% 2	2160
	11th to 20th	Night	54% 3 11% 17% 11% 3	2021
	21st to end	Night	49% 4 8% 20% 16% 4	2034
April	1st to 10th	Night	54% 5% 10% 15% 15% 2	1800
	11th to 20th	Night	49% 5% 8% 21% 17% 2	1775
	21st to end	Night	51% 5% 9% 17% 15% 4	1689
May	1st to 10th	Night	48% 6% 7% 18% 16% 5%	1440
	11th to 20th	Night	44% 5% 8% 21% 19% 4	1416
	21st to end	Night	40% 10% 11% 19% 17% 3	1551
June	1st to 10th	Night	46% 9% 12% 23% 11%	1440
	11th to 20th	Night	42% 9% 10% 22% 16% 2	1440
	21st to end	Night	45% 10% 12% 19% 14% 1	1440
July	1st to 10th	Night	34% 10% 12% 27% 16% 1	1400
	11th to 20th	Night	36% 7% 13% 31% 12%	1392
	21st to end	Night	38% 9% 15% 24% 14%	1486
August	1st to 10th	Night	37% 10% 17% 25% 10% 1	1422
	11th to 20th	Night	36% 8% 16% 28% 11%	1615
	21st to end	Night	37% 8% 16% 28% 11%	1980
September	1st to 10th	Night	39% 8% 12% 26% 15% 1	1800
	11th to 20th	Night	36% 8% 12% 34% 10% 1	1824
	21st to end	Night	41% 6% 11% 31% 11%	1997
October	1st to 10th	Night	46% 8% 10% 23% 12% 1	2160
	11th to 20th	Night	52% 7% 11% 20% 9%	2160
	21st to end	Night	57% 7% 12% 16% 8% 1	2556
November	1st to 10th	Night	52% 5% 14% 20% 9%	2407
	11th to 20th	Night	56% 6% 12% 17% 9% 1	2619
	21st to end	Night	61% 7% 12% 15% 5%	2660
December	1st to 10th	Night	67% 6% 10% 12% 4	2660
	11th to 20th	Night	62% 5% 9% 17% 7% 1	3288
	21st to end	Night	70% 5% 7% 13% 4	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	27% 13% 30% 25% 4 1	180
	11th to 20th	Day	29% 13% 35% 16% 6% 1	166
	21st to end	Day	19% 12% 36% 25% 7% 1	188
February	1st to 10th	Day	32% 24% 32% 11% 1	240
	11th to 20th	Day	28% 20% 38% 14% 1	272
	21st to end	Day	28% 17% 32% 21% 2	346
March	1st to 10th	Day	26% 15% 31% 23% 5%	420
	11th to 20th	Day	24% 19% 32% 20% 5% 1	420
	21st to end	Day	30% 13% 29% 17% 9% 2	462
April	1st to 10th	Day	28% 16% 30% 17% 8% 2	420
	11th to 20th	Day	29% 17% 20% 21% 11% 2	412
	21st to end	Day	30% 14% 31% 17% 8% 1	420
May	1st to 10th	Day	24% 13% 33% 22% 6% 3	423
	11th to 20th	Day	20% 17% 28% 22% 9% 3	447
	21st to end	Day	19% 12% 34% 23% 9% 2	485
June	1st to 10th	Day	25% 10% 28% 24% 11% 2	450
	11th to 20th	Day	16% 13% 28% 26% 14% 3	450
	21st to end	Day	21% 12% 25% 26% 14% 2	450
July	1st to 10th	Day	13% 8% 24% 32% 16% 7%	445
	11th to 20th	Day	13% 7% 30% 29% 18% 4	444
	21st to end	Day	14% 7% 26% 32% 18% 3	488
August	1st to 10th	Day	13% 7% 25% 31% 20% 4	446
	11th to 20th	Day	14% 5% 21% 32% 19% 8%	439
	21st to end	Day	15% 9% 25% 26% 16% 8%	495
September	1st to 10th	Day	18% 7% 27% 22% 17% 9%	450
	11th to 20th	Day	14% 8% 22% 22% 20% 13%	450
	21st to end	Day	19% 12% 26% 20% 15% 7%	450
October	1st to 10th	Day	26% 12% 22% 20% 16% 4	450
	11th to 20th	Day	28% 16% 26% 19% 10% 1	450
	21st to end	Day	32% 11% 28% 22% 7%	405
November	1st to 10th	Day	27% 16% 23% 24% 10% 1	365
	11th to 20th	Day	28% 17% 34% 15% 4 2	218
	21st to end	Day	28% 19% 26% 20% 7%	180
December	1st to 10th	Day	32% 12% 30% 19% 7%	180
	11th to 20th	Day	26% 18% 37% 16% 2 1	180
	21st to end	Day	34% 18% 32% 13% 3 1	198
January	1st to 10th	Night	28% 11% 33% 22% 5%	760
	11th to 20th	Night	29% 10% 29% 25% 6% 1	736
	21st to end	Night	20% 9% 33% 30% 8% 1	792
February	1st to 10th	Night	21% 11% 38% 25% 5%	720
	11th to 20th	Night	22% 11% 37% 25% 5%	703
	21st to end	Night	24% 11% 30% 30% 4 1	592
March	1st to 10th	Night	24% 12% 32% 27% 5%	720
	11th to 20th	Night	25% 11% 34% 24% 6% 1	720
	21st to end	Night	23% 9% 32% 27% 9%	792
April	1st to 10th	Night	27% 11% 28% 28% 6%	720
	11th to 20th	Night	24% 11% 31% 26% 7% 1	711
	21st to end	Night	26% 10% 29% 27% 8% 1	609
May	1st to 10th	Night	26% 6% 28% 29% 9% 2	360
	11th to 20th	Night	24% 6% 26% 34% 9%	354
	21st to end	Night	17% 5% 33% 31% 13% 1	389
June	1st to 10th	Night	18% 3 27% 43% 10%	360
	11th to 20th	Night	17% 4 28% 36% 14% 1	360
	21st to end	Night	17% 4 26% 34% 18% 1	360
July	1st to 10th	Night	11% 4 24% 42% 19%	350
	11th to 20th	Night	13% 2 19% 45% 20% 1	348
	21st to end	Night	13% 3 21% 43% 19% 1	394
August	1st to 10th	Night	13% 4 15% 46% 22% 1	358
	11th to 20th	Night	14% 2 17% 36% 29% 2	551
	21st to end	Night	15% 5% 21% 37% 20% 2	792
September	1st to 10th	Night	15% 4 25% 36% 20% 1	720
	11th to 20th	Night	19% 5% 18% 33% 22% 3	720
	21st to end	Night	19% 6% 23% 30% 20% 2	720
October	1st to 10th	Night	23% 6% 27% 29% 15%	720
	11th to 20th	Night	26% 8% 27% 30% 9% 1	720
	21st to end	Night	27% 10% 28% 29% 6%	792
November	1st to 10th	Night	27% 7% 27% 28% 9% 1	740
	11th to 20th	Night	25% 11% 33% 21% 10%	760
	21st to end	Night	28% 12% 29% 23% 8%	760
December	1st to 10th	Night	30% 11% 30% 23% 5%	760
	11th to 20th	Night	29% 12% 29% 23% 5% 1	760
	21st to end	Night	36% 10% 31% 18% 4	836

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