Tusaire Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tusaire Observatory clear sky chart from 2005-11-05 to 2017-12-20.

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
40%
16561
16%
47817
9%
16515
46%
16515
24%
32059

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 15thNight
33%
900
14%
2506
7%
895
39%
895
20%
1798
January16th to endNight
26%
960
12%
2550
4%
960
32%
960
18%
1932
February1st to 15thNight
34%
879
14%
2288
4%
875
41%
875
25%
1600
February16th to endNight
32%
765
15%
2027
4%
765
39%
765
23%
1426
March1st to 15thNight
35%
576
14%
2016
9%
576
41%
576
19%
1346
March16th to endNight
36%
576
16%
2103
13%
576
45%
576
17%
1409
April1st to 15thNight
34%
539
17%
1797
13%
539
44%
539
22%
1181
April16th to endNight
33%
540
16%
1653
11%
540
41%
540
18%
1192
May1st to 15thNight
33%
540
14%
1494
6%
540
39%
540
24%
1038
May16th to endNight
46%
562
15%
1498
6%
561
50%
561
29%
990
June1st to 15thNight
52%
540
12%
1432
4%
540
55%
540
34%
893
June16th to endNight
59%
540
16%
1260
7%
540
62%
540
43%
797
July1st to 15thNight
63%
510
15%
1265
6%
510
65%
510
45%
761
July16th to endNight
67%
564
20%
1430
10%
531
70%
531
46%
798
August1st to 15thNight
67%
539
21%
1610
19%
536
70%
536
37%
914
August16th to endNight
61%
573
22%
1779
21%
573
67%
573
35%
1032
September1st to 15thNight
60%
540
22%
1800
20%
540
67%
540
37%
962
September16th to endNight
46%
576
20%
1984
15%
576
55%
576
29%
1144
October1st to 15thNight
40%
720
23%
2160
14%
720
47%
720
31%
1305
October16th to endNight
35%
768
17%
2319
10%
768
41%
768
22%
1561
November1st to 15thNight
35%
920
18%
2631
10%
920
42%
920
22%
1772
November16th to endNight
31%
975
16%
2730
9%
975
37%
975
20%
1934
December1st to 15thNight
28%
975
10%
2730
4%
975
34%
975
16%
2066
December16th to endNight
24%
984
11%
2755
3%
984
31%
984
12%
2208

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
13%8%36%5%3445%7%36%
49032
Night
12%8%36%5%2445%6%40%
47983
Cloud CoverDay
11%7%25%423445%46%
49043
Night
10%7%25%423345%50%
47987
Cloud CoverDay
13%8%36%5%3445%7%37%
49041
Night
12%8%36%5%2445%6%40%
47987
TransparencyDay
45%6%14%23%9%
48717
Night
43%5%13%24%11%1
47817
SeeingDay
16%6%28%28%15%4
6431
Night
16%7%30%32%12%1
16563

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 15thDay
9%10%6%9%7%36%6%5%6%28%
1432
16th to endDay
9%13%6%10%6%36%6%5%6%24%
1673
February1st to 15thDay
7%11%7%8%6%35%45%6%32%
1575
16th to endDay
10%10%5%9%8%345%46%30%
1446
March1st to 15thDay
13%10%5%7%6%24347%33%
1945
16th to endDay
18%10%46%6%34446%31%
2121
April1st to 15thDay
16%8%45%5%33436%37%
2151
16th to endDay
22%11%36%5%34345%28%
2304
May1st to 15thDay
19%8%36%6%35%446%31%
2457
16th to endDay
14%7%35%5%35%45%8%35%
2617
June1st to 15thDay
15%6%3442446%8%37%
2523
16th to endDay
9%4246%35%6%6%9%40%
2700
July1st to 15thDay
7%4144245%5%8%50%
2616
16th to endDay
6%414425%5%7%9%47%
2639
August1st to 15thDay
8%5%25%5%45%6%6%8%40%
2340
16th to endDay
13%42342445%7%47%
2422
September1st to 15thDay
8%415%435%5%5%7%48%
2160
16th to endDay
16%5%15%4245%5%7%42%
1961
October1st to 15thDay
17%7%35%423435%42%
1800
16th to endDay
19%9%36%413345%37%
1905
November1st to 15thDay
13%10%5%7%423445%36%
1557
16th to endDay
14%10%36%5%2446%7%31%
1560
December1st to 15thDay
14%13%5%8%8%45%445%24%
1560
16th to endDay
16%17%7%11%6%3423421%
1568
January1st to 15thNight
10%9%5%8%6%35%5%5%7%33%
2506
16th to endNight
11%13%5%10%5%2445%6%29%
2550
February1st to 15thNight
7%11%5%7%5%34347%38%
2285
16th to endNight
8%9%46%7%35%5%5%5%38%
2027
March1st to 15thNight
11%10%46%5%34445%39%
2004
16th to endNight
17%8%36%434447%35%
2103
April1st to 15thNight
16%9%35%423446%40%
1797
16th to endNight
23%9%35%423446%32%
1653
May1st to 15thNight
18%6%35%5%13347%39%
1494
16th to endNight
11%5%245%345%6%8%41%
1496
June1st to 15thNight
11%42433445%9%46%
1432
16th to endNight
7%2234145%6%9%52%
1260
July1st to 15thNight
431343445%8%55%
1341
16th to endNight
431432346%8%56%
1527
August1st to 15thNight
8%31332435%7%54%
1620
16th to endNight
9%41432345%7%53%
1779
September1st to 15thNight
8%32342345%7%54%
1800
16th to endNight
13%41432445%6%49%
1984
October1st to 15thNight
12%7%3332235%6%49%
2160
16th to endNight
18%10%24423345%39%
2319
November1st to 15thNight
14%8%36%5%2344441%
2631
16th to endNight
14%9%35%5%35%447%35%
2730
December1st to 15thNight
12%12%5%9%7%45%346%29%
2730
16th to endNight
16%16%5%10%7%34345%22%
2755

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
6%7%38%6%35%5%5%5%42%
1432
16th to endDay
7%12%48%6%245%5%6%36%
1673
February1st to 15thDay
6%10%47%5%24445%43%
1575
16th to endDay
7%9%49%7%34435%42%
1446
March1st to 15thDay
9%9%36%5%23346%46%
1956
16th to endDay
13%9%35%424235%43%
2121
April1st to 15thDay
13%8%25%422325%48%
2151
16th to endDay
19%10%25%42334439%
2304
May1st to 15thDay
15%7%25%6%3433442%
2457
16th to endDay
12%6%2442445%6%46%
2617
June1st to 15thDay
13%6%2432335%5%48%
2523
16th to endDay
8%3144345%5%7%50%
2700
July1st to 15thDay
7%31332345%6%59%
2616
16th to endDay
6%3134235%6%7%55%
2639
August1st to 15thDay
6%415%5%45%5%7%7%46%
2340
16th to endDay
11%413424346%52%
2422
September1st to 15thDay
7%41443445%7%53%
2160
16th to endDay
13%41442435%6%49%
1961
October1st to 15thDay
16%7%2442334447%
1800
16th to endDay
17%8%15%5%12345%44%
1905
November1st to 15thDay
11%8%35%42333447%
1557
16th to endDay
12%9%35%5%24346%42%
1560
December1st to 15thDay
11%11%48%8%33335%35%
1560
16th to endDay
10%16%6%9%5%3322335%
1568
January1st to 15thNight
6%8%37%5%33446%46%
2506
16th to endNight
9%12%48%423345%41%
2550
February1st to 15thNight
6%11%45%423346%49%
2278
16th to endNight
5%8%26%6%34345%48%
2027
March1st to 15thNight
8%8%35%5%2334451%
2016
16th to endNight
13%7%24422335%48%
2103
April1st to 15thNight
13%7%2432234451%
1797
16th to endNight
20%7%24322335%43%
1653
May1st to 15thNight
15%6%24423236%49%
1493
16th to endNight
11%413423447%52%
1496
June1st to 15thNight
9%423223347%57%
1432
16th to endNight
6%2133125%47%62%
1260
July1st to 15thNight
5%212423446%62%
1341
16th to endNight
3213222447%64%
1527
August1st to 15thNight
7%313324346%59%
1620
16th to endNight
8%31431325%6%59%
1779
September1st to 15thNight
6%41342245%6%59%
1800
16th to endNight
10%31332335%6%56%
1984
October1st to 15thNight
11%7%2322235%454%
2160
16th to endNight
16%8%24323245%45%
2319
November1st to 15thNight
12%7%16%42333451%
2631
16th to endNight
10%8%245%24346%46%
2730
December1st to 15thNight
10%10%38%6%3333440%
2730
16th to endNight
12%13%5%9%6%2323436%
2755

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 15thDay
9%10%6%9%7%45%5%5%6%28%
1432
16th to endDay
10%13%6%9%6%35%6%6%7%23%
1673
February1st to 15thDay
7%11%6%9%6%35%45%6%32%
1575
16th to endDay
10%10%5%9%8%34447%29%
1446
March1st to 15thDay
12%10%5%7%6%34347%33%
1956
16th to endDay
18%10%46%5%25%446%31%
2119
April1st to 15thDay
16%9%36%423445%37%
2151
16th to endDay
23%10%35%5%3435%429%
2304
May1st to 15thDay
19%8%36%6%35%345%31%
2457
16th to endDay
15%6%26%5%345%5%8%36%
2617
June1st to 15thDay
16%6%25%4245%5%8%38%
2523
16th to endDay
10%4245%35%5%6%10%40%
2700
July1st to 15thDay
7%323425%45%8%50%
2616
16th to endDay
7%4234345%7%9%48%
2639
August1st to 15thDay
8%5%25%5%35%5%7%8%41%
2340
16th to endDay
14%42443435%7%46%
2422
September1st to 15thDay
8%424435%45%8%47%
2160
16th to endDay
16%42442445%7%41%
1961
October1st to 15thDay
17%7%25%5%13345%41%
1800
16th to endDay
20%9%35%5%2234437%
1905
November1st to 15thDay
13%10%5%7%424445%36%
1557
16th to endDay
15%10%36%5%345%6%8%31%
1560
December1st to 15thDay
14%13%6%9%8%4445%5%24%
1560
16th to endDay
16%17%7%12%5%34325%21%
1568
January1st to 15thNight
10%9%5%8%5%35%46%6%33%
2506
16th to endNight
12%12%6%10%5%2445%6%29%
2550
February1st to 15thNight
7%12%47%5%2435%7%39%
2278
16th to endNight
8%9%36%6%45%446%38%
2027
March1st to 15thNight
12%9%45%6%25%335%39%
2016
16th to endNight
17%8%36%424447%35%
2103
April1st to 15thNight
16%9%35%323346%40%
1797
16th to endNight
23%8%35%423446%33%
1653
May1st to 15thNight
18%6%35%433347%39%
1493
16th to endNight
12%5%245%25%5%5%8%41%
1496
June1st to 15thNight
11%425%33435%9%46%
1432
16th to endNight
7%3243235%6%9%52%
1260
July1st to 15thNight
5%31342345%9%55%
1341
16th to endNight
42233245%5%10%55%
1527
August1st to 15thNight
9%31443346%7%53%
1620
16th to endNight
9%32432345%7%53%
1779
September1st to 15thNight
8%41442346%6%55%
1800
16th to endNight
13%41442335%6%49%
1984
October1st to 15thNight
13%7%23223346%49%
2160
16th to endNight
18%9%25%423245%39%
2319
November1st to 15thNight
15%8%27%423445%40%
2631
16th to endNight
14%9%35%6%34447%35%
2730
December1st to 15thNight
12%12%5%10%7%45%345%29%
2730
16th to endNight
16%15%6%10%7%34345%23%
2755

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 15thDay
55%6%11%19%7%
1433
16th to endDay
57%6%16%15%3
1673
February1st to 15thDay
51%5%14%20%6%1
1576
16th to endDay
53%5%12%21%6%
1446
March1st to 15thDay
51%415%19%6%
1956
16th to endDay
53%5%13%23%3
2121
April1st to 15thDay
47%5%11%21%12%1
2151
16th to endDay
56%5%11%16%9%
2304
May1st to 15thDay
53%6%11%20%7%
2457
16th to endDay
45%6%12%22%11%1
2621
June1st to 15thDay
42%8%14%27%7%
2523
16th to endDay
36%7%17%27%10%1
2700
July1st to 15thDay
29%7%15%29%16%1
2464
16th to endDay
30%9%18%25%15%1
2473
August1st to 15thDay
37%8%13%28%9%2
2326
16th to endDay
35%5%15%28%13%1
2422
September1st to 15thDay
32%7%15%33%9%
2160
16th to endDay
40%7%13%32%6%
1961
October1st to 15thDay
44%5%12%24%12%
1800
16th to endDay
48%414%22%8%
1905
November1st to 15thDay
48%5%12%20%11%
1557
16th to endDay
49%7%18%15%7%1
1560
December1st to 15thDay
60%5%15%13%4
1560
16th to endDay
68%410%11%4
1568
January1st to 15thNight
49%6%12%22%8%
2506
16th to endNight
55%5%14%17%6%
2550
February1st to 15thNight
46%416%23%8%
2288
16th to endNight
45%6%14%23%9%
2027
March1st to 15thNight
46%6%15%21%9%
2016
16th to endNight
48%5%14%24%5%
2103
April1st to 15thNight
45%49%24%14%1
1797
16th to endNight
51%6%8%18%12%2
1653
May1st to 15thNight
45%5%13%21%12%1
1494
16th to endNight
38%7%13%23%15%2
1498
June1st to 15thNight
34%5%17%28%12%1
1432
16th to endNight
27%7%14%30%15%4
1260
July1st to 15thNight
26%5%15%31%17%2
1265
16th to endNight
22%6%16%29%19%4
1430
August1st to 15thNight
28%6%13%31%15%4
1610
16th to endNight
30%6%14%29%16%3
1779
September1st to 15thNight
28%5%14%34%17%
1800
16th to endNight
33%6%15%31%13%
1984
October1st to 15thNight
36%410%30%15%2
2160
16th to endNight
46%414%21%11%
2319
November1st to 15thNight
45%5%11%24%12%
2631
16th to endNight
48%6%17%18%8%1
2730
December1st to 15thNight
56%5%13%18%5%
2730
16th to endNight
64%5%12%13%4
2755

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 15thDay
17%8%32%27%11%2
90
16th to endDay
21%8%33%26%9%1
96
February1st to 15thDay
15%18%40%21%4
90
16th to endDay
22%12%37%20%6%1
81
March1st to 15thDay
17%5%35%33%5%2
90
16th to endDay
26%15%23%24%9%
105
April1st to 15thDay
21%10%28%27%11%
270
16th to endDay
29%8%29%21%9%2
414
May1st to 15thDay
20%10%31%24%9%2
468
16th to endDay
19%7%30%24%13%4
517
June1st to 15thDay
14%5%30%30%15%3
495
16th to endDay
9%5%32%32%15%5%
495
July1st to 15thDay
9%423%28%23%10%
475
16th to endDay
8%322%35%23%6%
515
August1st to 15thDay
9%322%32%26%6%
493
16th to endDay
17%419%32%20%6%
462
September1st to 15thDay
9%327%31%22%5%
315
16th to endDay
22%327%29%10%5%
168
October1st to 15thDay
12%8%37%20%14%7%
135
16th to endDay
25%6%38%17%12%
144
November1st to 15thDay
15%8%31%29%13%1
135
16th to endDay
29%11%35%19%3
135
December1st to 15thDay
22%8%34%28%6%
135
16th to endDay
33%12%36%17%
108
January1st to 15thNight
14%9%34%29%10%1
900
16th to endNight
18%8%37%29%5%
960
February1st to 15thNight
12%9%35%32%9%
880
16th to endNight
13%8%38%28%10%1
765
March1st to 15thNight
15%8%35%30%9%
576
16th to endNight
20%7%30%28%11%2
576
April1st to 15thNight
20%9%32%29%7%
539
16th to endNight
28%5%28%26%9%1
540
May1st to 15thNight
20%8%33%28%8%
540
16th to endNight
13%429%35%15%
563
June1st to 15thNight
13%425%42%12%
540
16th to endNight
9%325%44%17%
540
July1st to 15thNight
7%122%42%24%1
510
16th to endNight
6%119%46%24%1
564
August1st to 15thNight
9%215%44%25%2
539
16th to endNight
10%120%39%25%2
573
September1st to 15thNight
8%222%40%21%4
540
16th to endNight
14%6%29%28%18%2
576
October1st to 15thNight
19%6%30%29%12%1
720
16th to endNight
24%7%28%31%7%
768
November1st to 15thNight
19%8%31%30%9%
920
16th to endNight
18%11%33%27%9%
975
December1st to 15thNight
17%9%35%29%6%
975
16th to endNight
23%8%30%28%7%
984
Page generated at 2017-12-21 06:04:48. Version ac04

Copyright 2017 A. Danko


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