M.A.R.S.Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the M.A.R.S.Observatory 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 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
46%
24180
21%
74372
14%
24129
54%
24129
26%
47217

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
30%
760
23%
2459
10%
757
46%
757
24%
1486
January11th to 20thNight
30%
736
25%
2391
13%
736
45%
736
23%
1503
January21st to endNight
29%
792
27%
2574
12%
792
48%
792
28%
1510
February1st to 10thNight
33%
720
21%
2326
12%
720
44%
720
26%
1415
February11th to 20thNight
21%
700
22%
2098
7%
699
37%
699
23%
1366
February21st to endNight
23%
592
24%
1765
10%
592
38%
592
23%
1158
March1st to 10thNight
35%
720
27%
1980
14%
720
46%
720
29%
1243
March11th to 20thNight
31%
720
21%
1980
11%
720
40%
720
25%
1312
March21st to endNight
33%
792
19%
2178
9%
792
40%
792
25%
1466
April1st to 10thNight
38%
720
23%
1980
11%
720
47%
720
30%
1222
April11th to 20thNight
41%
711
24%
1808
12%
711
49%
711
33%
1137
April21st to endNight
47%
540
26%
1620
15%
540
55%
540
30%
984
May1st to 10thNight
47%
540
17%
1620
9%
540
53%
540
27%
1024
May11th to 20thNight
48%
531
13%
1593
8%
531
51%
531
20%
1117
May21st to endNight
61%
582
17%
1745
14%
582
62%
582
26%
1154
June1st to 10thNight
63%
540
14%
1620
12%
540
65%
540
23%
1100
June11th to 20thNight
61%
540
13%
1620
11%
540
62%
540
25%
1077
June21st to endNight
69%
540
14%
1620
12%
540
70%
540
25%
1083
July1st to 10thNight
66%
525
9%
1575
8%
525
66%
525
20%
1130
July11th to 20thNight
69%
522
11%
1566
10%
522
69%
522
24%
1065
July21st to endNight
71%
591
13%
1672
11%
558
72%
558
22%
1166
August1st to 10thNight
62%
537
9%
1600
9%
534
62%
534
20%
1171
August11th to 20thNight
59%
534
15%
1598
13%
534
60%
534
20%
1145
August21st to endNight
65%
697
15%
1907
12%
697
66%
697
23%
1352
September1st to 10thNight
67%
720
19%
1980
16%
720
68%
720
28%
1319
September11th to 20thNight
57%
720
18%
1980
15%
720
59%
720
25%
1379
September21st to endNight
52%
720
20%
1980
15%
720
57%
720
27%
1338
October1st to 10thNight
55%
720
26%
2060
22%
720
60%
720
33%
1261
October11th to 20thNight
48%
720
28%
2160
20%
720
59%
720
32%
1274
October21st to endNight
51%
792
31%
2376
24%
792
63%
792
36%
1349
November1st to 10thNight
50%
740
28%
2221
22%
740
59%
740
33%
1307
November11th to 20thNight
44%
760
27%
2470
20%
760
55%
760
31%
1388
November21st to endNight
45%
760
27%
2470
20%
760
56%
760
30%
1435
December1st to 10thNight
35%
760
24%
2470
14%
760
48%
760
22%
1607
December11th to 20thNight
40%
759
27%
2908
18%
758
51%
758
24%
1644
December21st to endNight
32%
827
15%
4402
13%
817
43%
817
14%
2530

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
14%5%25%5%35%5%6%8%43%
74928
Night
14%5%25%5%345%5%7%44%
74843
TransparencyDay
38%8%12%20%17%4
74651
Night
38%8%11%19%19%5%
74639
SeeingDay
17%9%22%25%18%9%
14059
Night
16%7%23%31%20%3
24195

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
18%6%23433346%48%
1706
11th to 20thDay
18%7%25%424346%45%
1647
21st to endDay
17%5%24324446%50%
1782
February1st to 10thDay
16%6%144346%6%8%42%
1633
11th to 20thDay
20%6%2443335%5%45%
1748
21st to endDay
19%7%35%5%3445%6%40%
1489
March1st to 10thDay
16%5%2232345%6%51%
1980
11th to 20thDay
17%6%25%4345%5%8%40%
1980
21st to endDay
17%5%25%5%3445%6%42%
2178
April1st to 10thDay
11%42443445%9%50%
1980
11th to 20thDay
15%43442445%8%48%
2112
21st to endDay
13%5%244345%5%7%48%
2340
May1st to 10thDay
10%5%25%5%35%5%6%9%45%
2340
11th to 20thDay
15%5%26%6%35%5%7%8%38%
2301
21st to endDay
11%6%25%5%35%6%7%10%40%
2531
June1st to 10thDay
10%6%26%5%36%7%8%11%35%
2340
11th to 20thDay
7%5%25%6%46%7%7%10%41%
2340
21st to endDay
8%4247%46%7%8%11%39%
2340
July1st to 10thDay
9%5%37%7%46%8%8%11%32%
2340
11th to 20thDay
9%5%37%6%46%9%9%11%32%
2340
21st to endDay
8%427%6%5%7%8%8%11%34%
2547
August1st to 10thDay
11%5%37%6%5%7%7%8%10%31%
2327
11th to 20thDay
12%6%36%7%47%8%7%10%28%
2303
21st to endDay
10%5%35%7%5%5%6%6%11%37%
2425
September1st to 10thDay
10%426%5%35%6%7%8%43%
1980
11th to 20thDay
12%7%26%5%35%5%6%7%42%
1980
21st to endDay
17%6%26%5%35%5%45%42%
1980
October1st to 10thDay
14%425%322436%55%
1899
11th to 20thDay
14%5%23423335%57%
1800
21st to endDay
15%5%13423335%57%
1980
November1st to 10thDay
13%5%24323345%56%
1853
11th to 20thDay
14%423324446%53%
1710
21st to endDay
16%42432335%7%50%
1710
December1st to 10thDay
20%6%2442445%5%43%
1710
11th to 20thDay
17%424312346%52%
2153
21st to endDay
20%6%2442435%7%43%
3124
January1st to 10thNight
18%5%2442435%6%48%
2459
11th to 20thNight
17%5%35%434445%45%
2391
21st to endNight
16%5%24423445%50%
2574
February1st to 10thNight
16%6%244235%5%6%47%
2326
11th to 20thNight
19%6%35%43335%5%45%
2098
21st to endNight
17%7%35%43445%6%42%
1765
March1st to 10thNight
13%6%34424447%49%
1980
11th to 20thNight
16%5%35%43445%8%42%
1980
21st to endNight
16%5%35%5%3445%6%43%
2178
April1st to 10thNight
13%5%245%245%5%7%49%
1980
11th to 20thNight
14%6%2442345%7%50%
1808
21st to endNight
12%5%25%5%34347%50%
1620
May1st to 10thNight
12%5%35%5%345%5%7%46%
1620
11th to 20thNight
13%7%26%8%46%45%9%36%
1592
21st to endNight
13%6%26%5%346%6%8%41%
1744
June1st to 10thNight
11%5%35%5%46%7%7%13%33%
1620
11th to 20thNight
11%6%25%7%35%7%7%10%38%
1620
21st to endNight
6%5%26%6%47%7%9%11%36%
1620
July1st to 10thNight
8%6%37%8%48%7%9%10%29%
1620
11th to 20thNight
8%6%36%6%47%7%7%13%34%
1620
21st to endNight
6%5%26%7%5%8%7%10%13%32%
1771
August1st to 10thNight
11%6%39%6%46%7%8%11%29%
1611
11th to 20thNight
11%7%37%7%36%6%7%12%31%
1598
21st to endNight
9%7%36%6%46%7%8%11%33%
1907
September1st to 10thNight
10%5%25%6%36%6%7%8%41%
1980
11th to 20thNight
14%5%36%6%35%6%7%7%38%
1980
21st to endNight
16%6%36%5%3445%7%42%
1980
October1st to 10thNight
17%424423346%50%
2060
11th to 20thNight
14%5%2442335%6%52%
2160
21st to endNight
14%42432333458%
2376
November1st to 10thNight
14%5%25%433335%55%
2221
11th to 20thNight
13%5%33324346%54%
2470
21st to endNight
15%42342446%7%49%
2470
December1st to 10thNight
21%6%25%423445%43%
2470
11th to 20thNight
17%5%24323345%51%
3042
21st to endNight
21%5%24335%45%7%41%
4532

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
39%5%8%21%21%6%
1707
11th to 20thDay
43%47%18%22%6%
1647
21st to endDay
36%36%24%22%7%
1782
February1st to 10thDay
38%6%12%20%18%6%
1633
11th to 20thDay
41%6%8%20%21%5%
1758
21st to endDay
45%6%8%15%18%8%
1489
March1st to 10thDay
35%5%8%20%24%8%
1980
11th to 20thDay
43%7%11%17%16%7%
1980
21st to endDay
42%7%12%19%18%3
2178
April1st to 10thDay
32%5%12%21%24%6%
1980
11th to 20thDay
35%6%10%20%21%9%
2112
21st to endDay
35%6%13%24%18%4
2340
May1st to 10thDay
34%9%16%21%17%3
2340
11th to 20thDay
41%11%15%19%12%2
2305
21st to endDay
36%10%16%24%13%1
2531
June1st to 10thDay
38%11%17%22%11%1
2340
11th to 20thDay
35%12%18%21%13%1
2340
21st to endDay
35%14%17%20%13%2
2340
July1st to 10thDay
42%13%17%15%11%3
2275
11th to 20thDay
38%17%20%15%9%1
2271
21st to endDay
38%14%20%19%9%1
2405
August1st to 10thDay
43%13%17%19%7%
2314
11th to 20thDay
45%15%15%16%8%1
2303
21st to endDay
39%11%17%21%8%3
2425
September1st to 10thDay
37%10%13%20%17%4
1980
11th to 20thDay
39%8%13%17%19%3
1980
21st to endDay
43%7%9%20%16%5%
1980
October1st to 10thDay
31%6%9%21%27%5%
1899
11th to 20thDay
30%5%9%24%24%8%
1800
21st to endDay
32%46%22%25%10%
1980
November1st to 10thDay
32%38%18%30%8%
1853
11th to 20thDay
33%48%22%25%8%
1710
21st to endDay
35%48%22%24%7%
1710
December1st to 10thDay
43%6%9%21%16%5%
1710
11th to 20thDay
34%48%21%23%11%
2150
21st to endDay
39%5%8%25%19%3
3124
January1st to 10thNight
38%5%10%17%24%7%
2459
11th to 20thNight
42%5%7%16%25%6%
2391
21st to endNight
37%37%21%27%5%
2574
February1st to 10thNight
38%5%12%19%20%6%
2326
11th to 20thNight
43%48%17%22%6%
2099
21st to endNight
42%6%10%15%20%7%
1765
March1st to 10thNight
36%5%7%18%23%11%
1980
11th to 20thNight
40%7%9%18%19%7%
1980
21st to endNight
42%7%10%20%17%4
2178
April1st to 10thNight
34%6%10%20%24%5%
1980
11th to 20thNight
33%6%8%22%22%8%
1808
21st to endNight
35%6%11%23%21%4
1620
May1st to 10thNight
37%8%14%21%17%3
1620
11th to 20thNight
44%11%11%17%15%1
1593
21st to endNight
38%10%12%26%12%2
1745
June1st to 10thNight
40%12%16%20%11%1
1620
11th to 20thNight
39%11%19%21%9%1
1620
21st to endNight
36%14%18%16%12%4
1620
July1st to 10thNight
43%14%19%13%8%3
1575
11th to 20thNight
36%15%22%18%6%2
1566
21st to endNight
36%18%20%19%7%1
1672
August1st to 10thNight
42%16%20%14%8%
1600
11th to 20thNight
42%15%18%15%9%1
1598
21st to endNight
41%13%18%19%8%2
1907
September1st to 10thNight
36%11%14%19%14%4
1980
11th to 20thNight
42%10%14%15%18%2
1980
21st to endNight
42%7%12%17%18%4
1980
October1st to 10thNight
35%6%10%21%23%5%
2060
11th to 20thNight
33%5%9%24%20%8%
2160
21st to endNight
31%46%20%28%11%
2376
November1st to 10thNight
34%47%18%26%11%
2221
11th to 20thNight
33%48%17%26%11%
2470
21st to endNight
35%5%6%22%26%7%
2470
December1st to 10thNight
44%6%8%18%19%6%
2470
11th to 20thNight
36%49%16%26%10%
3044
21st to endNight
41%6%9%21%19%3
4532

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
22%17%34%23%4
270
11th to 20thDay
27%19%29%21%4
249
21st to endDay
20%20%39%16%5%
264
February1st to 10thDay
22%22%34%18%5%
240
11th to 20thDay
36%17%35%10%2
240
21st to endDay
27%27%28%15%2
207
March1st to 10thDay
21%14%32%25%8%
420
11th to 20thDay
22%14%38%20%5%1
420
21st to endDay
23%15%32%23%6%
462
April1st to 10thDay
17%15%31%23%13%1
420
11th to 20thDay
17%15%26%24%16%2
412
21st to endDay
18%11%25%26%14%6%
420
May1st to 10thDay
11%13%32%24%15%5%
423
11th to 20thDay
15%6%19%30%21%9%
447
21st to endDay
16%415%24%26%15%
485
June1st to 10thDay
13%315%34%22%13%
450
11th to 20thDay
9%416%27%24%20%
450
21st to endDay
10%217%29%26%15%
450
July1st to 10thDay
11%18%25%30%25%
445
11th to 20thDay
9%28%30%29%22%
444
21st to endDay
7%29%30%31%21%
488
August1st to 10thDay
16%213%28%22%19%
446
11th to 20thDay
12%48%28%29%18%
439
21st to endDay
12%212%25%27%23%
495
September1st to 10thDay
13%310%24%31%19%
450
11th to 20thDay
16%312%23%31%15%
450
21st to endDay
23%318%26%24%6%
450
October1st to 10thDay
18%5%20%24%22%10%
450
11th to 20thDay
14%6%23%30%20%6%
450
21st to endDay
18%7%21%35%15%4
495
November1st to 10thDay
21%8%24%26%16%4
451
11th to 20thDay
17%13%36%24%7%2
270
21st to endDay
12%11%35%29%11%2
270
December1st to 10thDay
25%14%31%24%6%
270
11th to 20thDay
21%13%33%23%9%
270
21st to endDay
27%14%33%18%7%1
297
January1st to 10thNight
20%12%33%28%7%
760
11th to 20thNight
20%11%33%32%4
736
21st to endNight
18%10%40%30%3
792
February1st to 10thNight
18%11%34%34%3
720
11th to 20thNight
22%13%39%25%2
703
21st to endNight
20%13%39%25%3
592
March1st to 10thNight
17%12%31%36%3
720
11th to 20thNight
19%11%35%26%9%1
720
21st to endNight
20%8%33%31%7%
792
April1st to 10thNight
16%11%32%31%10%
720
11th to 20thNight
15%12%27%30%14%1
711
21st to endNight
15%6%27%34%17%
540
May1st to 10thNight
13%7%26%35%19%
540
11th to 20thNight
15%5%21%33%24%2
531
21st to endNight
16%211%31%36%5%
584
June1st to 10thNight
12%211%38%32%4
540
11th to 20thNight
13%314%28%32%11%
540
21st to endNight
8%19%36%40%6%
540
July1st to 10thNight
10%37%26%46%9%
525
11th to 20thNight
11%17%26%43%12%
522
21st to endNight
7%17%30%47%8%
591
August1st to 10thNight
15%18%26%42%8%
537
11th to 20thNight
13%38%28%40%9%
534
21st to endNight
11%29%26%44%7%
697
September1st to 10thNight
11%29%29%40%9%
720
11th to 20thNight
17%313%23%38%6%
720
21st to endNight
19%418%28%29%3
720
October1st to 10thNight
17%418%28%27%6%
720
11th to 20thNight
17%6%25%28%22%2
720
21st to endNight
15%5%23%34%19%3
792
November1st to 10thNight
17%424%35%17%3
740
11th to 20thNight
15%8%28%36%11%1
760
21st to endNight
17%5%29%34%14%1
760
December1st to 10thNight
22%9%28%33%7%
760
11th to 20thNight
20%7%29%35%9%1
760
21st to endNight
26%8%28%31%7%
836
Page generated at 2024-01-11 13:32:01. Version ac07

Copyright 2024 Attilla Danko


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