Mark Ice Station
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mark Ice Station clear sky chart from 2005-11-06 to 2024-02-10.

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 TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(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

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
24%
22962
17%
80326
7%
22867
37%
22867
16%
52078

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 10thNight
11%
751
21%
4337
4%
737
30%
737
9%
2400
January11th to 20thNight
13%
758
18%
4353
3%
740
28%
740
7%
2652
January21st to endNight
14%
832
11%
4866
5%
814
32%
814
7%
3454
February1st to 10thNight
12%
759
16%
2439
3%
759
29%
759
13%
1651
February11th to 20thNight
10%
703
19%
2100
3%
700
30%
700
14%
1391
February21st to endNight
12%
592
21%
1776
4%
592
32%
592
14%
1191
March1st to 10thNight
15%
720
21%
2160
7%
720
33%
720
17%
1420
March11th to 20thNight
16%
720
17%
2091
5%
720
29%
720
14%
1443
March21st to endNight
19%
792
21%
2017
5%
792
31%
792
19%
1389
April1st to 10thNight
18%
720
18%
1800
3%
720
27%
720
19%
1274
April11th to 20thNight
22%
711
16%
1775
4%
711
29%
711
21%
1230
April21st to endNight
19%
545
18%
1625
4%
545
30%
545
16%
1115
May1st to 10thNight
21%
540
13%
1620
5%
540
28%
540
15%
1165
May11th to 20thNight
23%
444
16%
1506
9%
444
34%
444
17%
995
May21st to endNight
34%
389
13%
1551
11%
388
43%
388
16%
991
June1st to 10thNight
31%
360
13%
1440
10%
360
44%
360
16%
932
June11th to 20thNight
32%
360
12%
1440
11%
360
40%
360
15%
936
June21st to endNight
39%
360
11%
1440
11%
360
48%
360
20%
894
July1st to 10thNight
41%
350
13%
1400
13%
350
50%
350
22%
851
July11th to 20thNight
48%
348
13%
1392
15%
348
51%
348
22%
849
July21st to endNight
47%
394
19%
1486
17%
372
56%
372
26%
841
August1st to 10thNight
45%
435
17%
1499
11%
433
51%
433
24%
898
August11th to 20thNight
40%
582
16%
1646
9%
582
44%
582
22%
1108
August21st to endNight
45%
792
21%
1980
9%
792
50%
792
33%
1283
September1st to 10thNight
40%
720
21%
1800
7%
720
47%
720
33%
1171
September11th to 20thNight
41%
720
25%
1955
13%
720
49%
720
34%
1194
September21st to endNight
38%
720
24%
1980
15%
720
46%
720
29%
1261
October1st to 10thNight
32%
720
16%
1980
9%
720
39%
720
20%
1362
October11th to 20thNight
28%
720
20%
2222
8%
720
42%
720
24%
1405
October21st to endNight
21%
792
14%
2574
5%
792
33%
792
14%
1772
November1st to 10thNight
26%
740
22%
2407
10%
740
41%
740
21%
1494
November11th to 20thNight
22%
760
22%
2470
8%
760
39%
760
18%
1547
November21st to endNight
19%
760
20%
2503
6%
760
36%
760
17%
1565
December1st to 10thNight
15%
760
17%
2660
4%
760
31%
760
13%
1767
December11th to 20thNight
15%
760
16%
3208
3%
759
31%
759
11%
2031
December21st to endNight
12%
833
13%
4828
3%
817
30%
817
7%
3156

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 ForecastData
Points
Cloud CoverDay
16%7%36%6%35%5%5%7%37%
78126
Night
16%8%36%5%35%5%5%7%39%
80830
TransparencyDay
44%7%12%21%13%2
77831
Night
43%7%13%22%13%2
80659
SeeingDay
23%20%30%18%7%2
13885
Night
22%18%31%22%6%1
22980

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
12%8%37%5%345%5%7%40%
2517
11th to 20thDay
15%8%48%6%445%5%6%35%
2520
21st to endDay
16%14%46%6%345%5%6%30%
2772
February1st to 10thDay
16%7%37%6%47%6%6%6%32%
1723
11th to 20thDay
12%7%38%7%45%46%8%36%
1748
21st to endDay
16%11%47%6%35%5%5%434%
1480
March1st to 10thDay
13%9%28%6%35%46%7%36%
1797
11th to 20thDay
16%8%45%6%35%5%5%7%36%
1868
21st to endDay
17%8%46%5%34446%39%
2335
April1st to 10thDay
16%10%45%6%45%446%36%
2160
11th to 20thDay
15%6%36%5%45%5%6%6%38%
2134
21st to endDay
21%8%37%7%345%46%32%
2333
May1st to 10thDay
22%9%46%5%34446%32%
2340
11th to 20thDay
18%6%35%7%3445%6%39%
2403
21st to endDay
15%6%35%6%3445%8%41%
2725
June1st to 10thDay
19%6%26%7%45%5%5%9%32%
2520
11th to 20thDay
17%6%36%6%45%5%5%9%36%
2520
21st to endDay
18%7%36%5%45%5%6%8%32%
2520
July1st to 10thDay
14%5%26%5%46%6%6%7%39%
2520
11th to 20thDay
12%6%36%6%45%5%7%9%38%
2520
21st to endDay
13%5%25%6%46%5%7%8%38%
2744
August1st to 10thDay
11%6%25%6%45%6%7%9%37%
2409
11th to 20thDay
12%6%26%6%46%6%7%8%35%
2250
21st to endDay
12%5%25%6%35%6%6%8%42%
2376
September1st to 10thDay
12%5%36%5%445%6%6%44%
2160
11th to 20thDay
14%6%24434346%49%
2004
21st to endDay
16%6%25%43445%7%44%
1980
October1st to 10thDay
22%8%25%6%34445%37%
1980
11th to 20thDay
12%7%35%435%5%5%7%42%
1735
21st to endDay
22%7%36%5%35%446%35%
1782
November1st to 10thDay
12%7%46%5%23446%47%
1671
11th to 20thDay
18%6%345%3445%6%43%
1710
21st to endDay
18%8%25%5%345%47%39%
1672
December1st to 10thDay
16%9%47%8%35%5%5%6%33%
1520
11th to 20thDay
21%7%35%5%35%44440%
1906
21st to endDay
19%12%36%5%3445%6%30%
2772
January1st to 10thNight
16%7%35%5%3445%6%42%
4429
11th to 20thNight
13%7%39%7%45%5%6%8%34%
4440
21st to endNight
20%12%5%8%6%445%45%29%
4884
February1st to 10thNight
14%9%36%5%35%5%6%7%37%
2439
11th to 20thNight
12%7%36%6%46%6%5%7%38%
2098
21st to endNight
14%9%46%5%35%6%5%5%38%
1776
March1st to 10thNight
13%8%36%5%345%5%6%40%
2150
11th to 20thNight
15%7%37%5%35%6%6%7%36%
2090
21st to endNight
16%7%35%425%5%5%7%40%
2017
April1st to 10thNight
16%8%37%6%35%45%6%37%
1800
11th to 20thNight
17%7%25%5%35%5%5%7%40%
1775
21st to endNight
20%8%37%433446%37%
1625
May1st to 10thNight
20%9%47%5%445%5%6%31%
1620
11th to 20thNight
17%8%36%6%245%5%8%37%
1505
21st to endNight
15%7%37%6%3446%8%38%
1550
June1st to 10thNight
18%7%46%5%245%37%38%
1440
11th to 20thNight
19%6%35%5%35%45%7%36%
1440
21st to endNight
15%6%36%4345%6%8%40%
1440
July1st to 10thNight
13%6%35%435%5%6%7%43%
1440
11th to 20thNight
13%5%25%435%5%7%10%39%
1440
21st to endNight
12%5%24425%5%6%8%47%
1574
August1st to 10thNight
8%7%27%425%5%6%8%46%
1509
11th to 20thNight
12%8%26%6%45%46%7%38%
1646
21st to endNight
15%5%2442345%7%48%
1980
September1st to 10thNight
13%5%25%42346%6%49%
1800
11th to 20thNight
13%6%25%323447%52%
1955
21st to endNight
13%5%26%5%3445%6%48%
1980
October1st to 10thNight
21%6%26%6%24445%40%
1980
11th to 20thNight
15%6%345%245%6%7%42%
2222
21st to endNight
22%8%26%5%25%45%6%35%
2574
November1st to 10thNight
14%7%36%5%34445%46%
2407
11th to 20thNight
16%6%345%35%446%43%
2470
21st to endNight
14%6%35%5%345%5%7%42%
2503
December1st to 10thNight
17%9%47%5%35%46%6%36%
2660
11th to 20thNight
19%7%35%5%35%5%5%6%38%
3288
21st to endNight
19%11%47%5%445%5%6%30%
4884

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
41%6%10%33%9%1
2518
11th to 20thDay
46%7%13%22%10%2
2520
21st to endDay
52%7%10%21%9%1
2772
February1st to 10thDay
49%7%14%18%11%2
1723
11th to 20thDay
45%8%11%20%14%3
1757
21st to endDay
51%5%10%18%13%3
1480
March1st to 10thDay
45%6%13%19%13%4
1800
11th to 20thDay
45%6%12%17%15%4
1868
21st to endDay
47%6%7%19%16%6%
2335
April1st to 10thDay
48%5%9%20%15%3
2160
11th to 20thDay
43%7%12%19%16%2
2134
21st to endDay
51%6%9%16%15%3
2333
May1st to 10thDay
52%5%9%18%12%2
2340
11th to 20thDay
45%6%9%20%17%3
2407
21st to endDay
41%9%13%22%13%2
2725
June1st to 10thDay
47%8%13%20%10%1
2520
11th to 20thDay
44%8%13%19%15%2
2520
21st to endDay
48%9%13%19%11%1
2520
July1st to 10thDay
41%8%12%21%16%2
2450
11th to 20thDay
41%9%15%23%12%1
2445
21st to endDay
40%8%15%23%13%2
2591
August1st to 10thDay
40%9%16%22%12%1
2395
11th to 20thDay
41%9%14%22%11%2
2250
21st to endDay
36%9%14%24%16%2
2376
September1st to 10thDay
38%6%13%24%17%1
2160
11th to 20thDay
35%5%9%25%23%2
2004
21st to endDay
38%6%10%23%19%3
1980
October1st to 10thDay
49%5%9%20%13%3
1980
11th to 20thDay
37%7%13%29%11%2
1735
21st to endDay
49%6%11%19%12%3
1782
November1st to 10thDay
39%5%13%25%16%3
1671
11th to 20thDay
40%7%11%22%17%3
1710
21st to endDay
44%5%16%22%10%2
1672
December1st to 10thDay
48%7%14%16%13%1
1520
11th to 20thDay
44%5%13%19%16%2
1906
21st to endDay
52%6%13%18%10%1
2772
January1st to 10thNight
39%6%14%26%11%3
4429
11th to 20thNight
44%8%15%20%10%3
4440
21st to endNight
56%6%11%15%10%2
4884
February1st to 10thNight
45%8%14%19%12%2
2439
11th to 20thNight
43%7%13%20%14%3
2100
21st to endNight
44%6%12%23%12%3
1776
March1st to 10thNight
44%5%11%24%13%3
2160
11th to 20thNight
44%9%12%17%15%3
2091
21st to endNight
43%6%10%17%19%5%
2017
April1st to 10thNight
45%7%11%19%16%2
1800
11th to 20thNight
43%6%12%21%17%1
1775
21st to endNight
47%7%11%18%14%4
1625
May1st to 10thNight
52%6%10%18%12%3
1620
11th to 20thNight
45%7%13%17%15%3
1506
21st to endNight
44%8%13%22%11%1
1551
June1st to 10thNight
46%7%13%22%11%1
1440
11th to 20thNight
45%9%13%19%13%2
1440
21st to endNight
40%9%16%21%13%1
1440
July1st to 10thNight
38%9%16%22%14%1
1400
11th to 20thNight
37%10%17%25%11%
1392
21st to endNight
33%9%17%27%13%2
1486
August1st to 10thNight
34%11%15%25%15%1
1499
11th to 20thNight
42%9%15%21%12%1
1646
21st to endNight
35%7%12%28%18%1
1980
September1st to 10thNight
35%7%13%26%18%1
1800
11th to 20thNight
32%6%11%26%23%2
1955
21st to endNight
36%7%10%27%18%2
1980
October1st to 10thNight
45%6%12%22%12%3
1980
11th to 20thNight
38%7%15%26%13%1
2222
21st to endNight
49%6%12%20%11%2
2574
November1st to 10thNight
39%7%11%22%19%3
2407
11th to 20thNight
41%5%12%22%17%3
2470
21st to endNight
40%6%17%24%12%1
2503
December1st to 10thNight
47%6%15%20%11%1
2660
11th to 20thNight
44%7%15%17%16%2
3288
21st to endNight
50%7%12%22%9%1
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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
31%24%29%13%3
180
11th to 20thDay
32%26%31%9%11
180
21st to endDay
25%28%34%10%3
198
February1st to 10thDay
32%31%27%9%2
318
11th to 20thDay
33%27%27%12%1
416
21st to endDay
30%27%29%12%2
346
March1st to 10thDay
30%22%36%10%3
420
11th to 20thDay
29%29%29%10%31
420
21st to endDay
29%25%30%10%5%2
462
April1st to 10thDay
31%25%25%10%6%1
420
11th to 20thDay
27%27%28%10%6%1
412
21st to endDay
31%21%30%12%5%1
420
May1st to 10thDay
32%24%26%12%5%1
423
11th to 20thDay
20%21%39%15%42
447
21st to endDay
18%17%33%24%6%1
485
June1st to 10thDay
20%16%38%17%9%1
450
11th to 20thDay
18%17%36%22%7%1
450
21st to endDay
19%17%35%18%8%2
450
July1st to 10thDay
17%10%31%29%11%2
445
11th to 20thDay
16%10%33%29%11%2
444
21st to endDay
13%13%36%27%9%2
488
August1st to 10thDay
12%11%31%33%11%3
446
11th to 20thDay
14%10%32%27%13%4
439
21st to endDay
13%14%32%27%11%4
495
September1st to 10thDay
18%13%27%22%15%4
450
11th to 20thDay
18%17%26%19%12%7%
450
21st to endDay
18%16%31%21%8%6%
450
October1st to 10thDay
28%16%24%18%10%4
450
11th to 20thDay
20%19%31%22%6%2
410
21st to endDay
32%17%27%19%41
396
November1st to 10thDay
22%22%26%19%9%1
365
11th to 20thDay
31%22%24%18%31
370
21st to endDay
31%20%30%13%5%1
332
December1st to 10thDay
24%34%27%11%4
180
11th to 20thDay
37%22%33%6%2
180
21st to endDay
32%26%29%10%31
198
January1st to 10thNight
23%26%35%15%2
760
11th to 20thNight
26%26%30%15%2
760
21st to endNight
20%25%36%17%3
836
February1st to 10thNight
24%23%36%16%2
759
11th to 20thNight
22%27%36%14%1
703
21st to endNight
27%27%31%14%1
592
March1st to 10thNight
25%22%34%17%2
720
11th to 20thNight
25%24%31%17%3
720
21st to endNight
25%21%32%17%5%
792
April1st to 10thNight
26%20%32%19%4
720
11th to 20thNight
22%23%31%19%5%
711
21st to endNight
28%18%32%20%3
545
May1st to 10thNight
26%17%33%20%4
540
11th to 20thNight
22%14%35%23%5%
444
21st to endNight
20%8%33%31%7%1
389
June1st to 10thNight
19%11%35%27%9%
360
11th to 20thNight
20%11%33%29%7%1
360
21st to endNight
15%8%34%37%6%
360
July1st to 10thNight
16%7%31%37%9%
350
11th to 20thNight
14%428%40%12%2
348
21st to endNight
12%5%34%38%11%
394
August1st to 10thNight
11%8%28%39%14%
435
11th to 20thNight
14%8%30%33%13%2
582
21st to endNight
15%9%26%35%15%1
792
September1st to 10thNight
16%8%32%29%14%1
720
11th to 20thNight
16%10%29%27%16%2
720
21st to endNight
16%12%30%28%13%2
720
October1st to 10thNight
24%14%24%25%11%2
720
11th to 20thNight
19%15%33%22%10%1
720
21st to endNight
27%20%27%21%5%
792
November1st to 10thNight
19%19%31%23%7%1
740
11th to 20thNight
22%25%28%18%5%1
760
21st to endNight
23%22%32%18%4
760
December1st to 10thNight
24%24%33%15%3
760
11th to 20thNight
26%23%33%15%3
760
21st to endNight
27%25%31%14%2
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