Terrarouge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Terrarouge Observatory clear sky chart from 2005-11-05 to 2017-09-19.

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
29%
15091
10%
46659
5%
15046
33%
15046
13%
35563

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
16%
750
9%
2506
1%
746
24%
746
9%
1989
January16th to endNight
21%
784
13%
2592
5%
784
29%
784
11%
1946
February1st to 15thNight
21%
704
9%
2286
3%
701
28%
701
11%
1739
February16th to endNight
22%
631
7%
2010
3%
631
26%
631
10%
1601
March1st to 15thNight
24%
717
12%
2035
5%
717
31%
717
13%
1599
March16th to endNight
27%
738
12%
2082
7%
738
31%
738
14%
1589
April1st to 15thNight
25%
539
10%
1796
7%
539
30%
539
13%
1341
April16th to endNight
32%
540
15%
1662
10%
540
37%
540
19%
1175
May1st to 15thNight
33%
540
10%
1458
6%
540
36%
540
17%
1130
May16th to endNight
35%
561
10%
1496
5%
560
39%
560
18%
1126
June1st to 15thNight
33%
540
5%
1440
3%
540
34%
540
16%
1134
June16th to endNight
44%
380
8%
1280
6%
380
48%
380
17%
901
July1st to 15thNight
53%
440
9%
1290
6%
440
55%
440
27%
823
July16th to endNight
50%
565
10%
1419
8%
532
51%
532
21%
1059
August1st to 15thNight
51%
539
10%
1573
9%
535
51%
535
20%
1123
August16th to endNight
53%
573
12%
1806
10%
573
56%
573
21%
1214
September1st to 15thNight
42%
540
15%
1800
13%
540
47%
540
22%
1165
September16th to endNight
38%
608
18%
1857
14%
608
43%
608
23%
1230
October1st to 15thNight
31%
660
15%
1980
8%
660
38%
660
18%
1431
October16th to endNight
19%
712
8%
2154
3%
712
23%
712
10%
1729
November1st to 15thNight
23%
730
9%
2409
6%
730
27%
730
11%
1887
November16th to endNight
20%
750
6%
2520
3%
750
23%
750
7%
2111
December1st to 15thNight
10%
750
5%
2520
0%
750
16%
750
4%
2178
December16th to endNight
10%
800
5%
2688
0%
800
15%
800
4%
2343

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
19%11%47%5%3445%6%27%
48149
Night
20%10%47%6%34446%26%
46830
TransparencyDay
56%6%12%17%7%
47838
Night
58%6%11%16%6%
46659
SeeingDay
24%8%27%26%11%2
7664
Night
24%10%28%26%8%
15094

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
16%14%7%9%6%3445%5%21%
1432
16th to endDay
14%13%5%11%7%35%45%5%22%
1630
February1st to 15thDay
16%14%5%9%5%35%5%46%24%
1575
16th to endDay
13%14%6%9%7%35%346%24%
1461
March1st to 15thDay
15%12%5%8%6%46%35%5%25%
1912
16th to endDay
16%13%8%8%5%3334428%
2142
April1st to 15thDay
19%12%37%6%3435%6%26%
2153
16th to endDay
21%11%35%5%24346%30%
2295
May1st to 15thDay
24%10%36%5%24446%27%
2494
16th to endDay
21%11%35%43435%7%28%
2618
June1st to 15thDay
25%10%36%5%34446%24%
2520
16th to endDay
22%9%26%5%2445%7%30%
2687
July1st to 15thDay
13%7%25%43445%9%38%
2574
16th to endDay
19%8%45%5%3445%7%30%
2653
August1st to 15thDay
19%6%25%5%245%5%9%33%
2373
16th to endDay
15%7%2443446%8%39%
2396
September1st to 15thDay
17%8%27%5%3345%7%35%
2160
16th to endDay
16%8%25%5%33446%38%
1846
October1st to 15thDay
20%9%37%6%3445%7%28%
1650
16th to endDay
24%13%5%8%6%345%45%17%
1716
November1st to 15thDay
23%15%48%43325%5%20%
1446
16th to endDay
19%18%7%10%6%34446%15%
1440
December1st to 15thDay
24%17%8%10%8%4334410%
1440
16th to endDay
23%15%9%12%8%4422411%
1536
January1st to 15thNight
18%12%5%9%7%34445%23%
2506
16th to endNight
17%12%5%9%6%34446%26%
2592
February1st to 15thNight
19%12%48%6%35%445%25%
2285
16th to endNight
14%17%6%8%7%45%43421%
2010
March1st to 15thNight
17%12%5%9%8%24445%24%
2023
16th to endNight
18%12%7%6%7%33335%29%
2082
April1st to 15thNight
22%12%46%6%33445%26%
1796
16th to endNight
24%9%34323346%34%
1662
May1st to 15thNight
29%7%25%5%24445%28%
1458
16th to endNight
18%10%46%435%5%5%7%28%
1494
June1st to 15thNight
26%9%37%5%24346%25%
1440
16th to endNight
22%6%25%5%2346%6%32%
1280
July1st to 15thNight
11%5%34425%6%6%10%37%
1369
16th to endNight
16%7%345%46%5%8%7%29%
1515
August1st to 15thNight
18%6%25%5%345%48%34%
1584
16th to endNight
15%5%25%5%35%5%6%8%36%
1806
September1st to 15thNight
16%6%25%424447%40%
1800
16th to endNight
17%6%245%245%46%40%
1857
October1st to 15thNight
20%7%26%5%245%46%33%
1980
16th to endNight
27%11%37%5%24445%23%
2154
November1st to 15thNight
22%11%47%6%35%446%23%
2409
16th to endNight
22%14%6%8%6%24446%17%
2520
December1st to 15thNight
24%13%6%8%7%35%5%45%13%
2520
16th to endNight
25%16%5%11%7%35%35%412%
2688

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
64%7%10%9%7%
1433
16th to endDay
63%5%8%12%9%
1630
February1st to 15thDay
59%5%11%17%4
1578
16th to endDay
59%5%12%13%7%
1461
March1st to 15thDay
58%5%11%16%7%
1923
16th to endDay
59%411%16%7%1
2142
April1st to 15thDay
56%49%15%11%1
2153
16th to endDay
53%5%10%18%11%
2295
May1st to 15thDay
57%5%9%18%8%
2494
16th to endDay
55%6%12%18%6%
2622
June1st to 15thDay
58%7%12%15%6%
2520
16th to endDay
51%6%13%19%7%
2687
July1st to 15thDay
40%8%16%23%10%
2425
16th to endDay
51%7%14%20%6%
2486
August1st to 15thDay
45%9%16%22%6%
2359
16th to endDay
39%7%19%26%7%
2396
September1st to 15thDay
46%6%14%23%8%
2160
16th to endDay
44%6%12%25%10%
1846
October1st to 15thDay
54%413%17%9%
1650
16th to endDay
67%5%11%12%3
1716
November1st to 15thDay
65%5%12%11%4
1446
16th to endDay
70%6%11%8%2
1440
December1st to 15thDay
77%6%8%6%
1440
16th to endDay
79%46%6%2
1536
January1st to 15thNight
63%6%11%11%5%
2506
16th to endNight
58%5%10%18%5%
2592
February1st to 15thNight
60%5%10%14%9%
2286
16th to endNight
65%5%10%12%5%1
2010
March1st to 15thNight
61%5%8%15%7%1
2035
16th to endNight
59%48%17%8%1
2082
April1st to 15thNight
59%410%13%10%1
1796
16th to endNight
50%5%10%17%14%1
1662
May1st to 15thNight
58%5%8%20%6%
1458
16th to endNight
53%7%11%19%6%
1496
June1st to 15thNight
60%5%12%14%7%
1440
16th to endNight
50%7%12%20%7%
1280
July1st to 15thNight
37%8%20%24%8%
1290
16th to endNight
48%9%15%19%5%
1419
August1st to 15thNight
48%8%15%21%6%
1573
16th to endNight
42%9%18%23%6%
1806
September1st to 15thNight
42%7%12%27%9%
1800
16th to endNight
44%6%13%26%9%
1857
October1st to 15thNight
51%5%11%22%8%
1980
16th to endNight
63%6%10%14%5%
2154
November1st to 15thNight
61%6%13%12%5%
2409
16th to endNight
69%7%11%8%2
2520
December1st to 15thNight
73%7%9%8%1
2520
16th to endNight
76%5%8%7%2
2688

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
20%15%41%16%5%
240
16th to endDay
20%14%34%26%4
256
February1st to 15thDay
23%12%35%23%5%
236
16th to endDay
22%8%35%23%8%2
212
March1st to 15thDay
20%16%26%27%8%
261
16th to endDay
27%11%28%21%10%1
288
April1st to 15thDay
30%8%30%22%7%1
270
16th to endDay
21%8%27%27%12%2
270
May1st to 15thDay
33%425%20%10%4
450
16th to endDay
24%5%28%31%9%1
519
June1st to 15thDay
28%5%25%29%10%
495
16th to endDay
27%421%30%13%2
495
July1st to 15thDay
16%220%38%20%2
475
16th to endDay
23%120%33%18%1
514
August1st to 15thDay
23%116%32%21%5%
346
16th to endDay
16%320%34%18%6%
332
September1st to 15thDay
19%5%31%30%12%
315
16th to endDay
19%7%25%32%14%1
254
October1st to 15thDay
23%8%26%24%13%4
225
16th to endDay
27%16%34%14%5%2
240
November1st to 15thDay
26%12%31%18%8%2
235
16th to endDay
29%12%28%22%6%
240
December1st to 15thDay
31%19%27%18%3
240
16th to endDay
28%21%34%13%2
256
January1st to 15thNight
24%15%35%20%4
750
16th to endNight
23%14%33%22%5%
784
February1st to 15thNight
25%10%33%25%4
704
16th to endNight
22%11%31%24%9%
631
March1st to 15thNight
21%9%33%29%6%
720
16th to endNight
24%10%29%23%10%1
738
April1st to 15thNight
29%9%28%24%8%
539
16th to endNight
27%6%27%29%7%1
540
May1st to 15thNight
31%6%23%24%12%3
540
16th to endNight
21%5%30%32%8%
561
June1st to 15thNight
30%5%23%32%8%
540
16th to endNight
23%420%38%11%1
380
July1st to 15thNight
12%121%46%16%
440
16th to endNight
20%119%39%17%1
565
August1st to 15thNight
19%317%38%19%1
539
16th to endNight
17%218%39%20%1
573
September1st to 15thNight
19%5%27%34%12%
540
16th to endNight
22%7%25%31%11%1
608
October1st to 15thNight
23%8%30%24%12%1
660
16th to endNight
30%15%30%19%3
712
November1st to 15thNight
24%13%31%23%5%2
730
16th to endNight
28%15%29%20%5%
750
December1st to 15thNight
30%19%33%12%4
750
16th to endNight
32%18%29%16%3
800
Page generated at 2017-09-20 05:49:47. Version ac04

Copyright 2017 A. Danko


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