Rang Saint-Arthur
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rang Saint-Arthur clear sky chart from 2005-11-05 to 2017-09-22.

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
22%
14673
11%
46888
5%
14641
29%
14641
12%
35005

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
9%
721
9%
2509
3%
717
17%
717
5%
2046
January16th to endNight
15%
768
11%
2688
3%
768
26%
768
9%
2009
February1st to 15thNight
14%
704
9%
2349
2%
701
22%
701
8%
1853
February16th to endNight
13%
631
12%
1893
3%
631
24%
631
10%
1473
March1st to 15thNight
15%
720
14%
2139
6%
720
24%
720
12%
1603
March16th to endNight
26%
768
17%
2055
6%
768
33%
768
17%
1524
April1st to 15thNight
20%
696
15%
1774
4%
696
27%
696
14%
1364
April16th to endNight
24%
540
15%
1620
6%
540
31%
540
16%
1166
May1st to 15thNight
28%
495
11%
1575
8%
495
34%
495
14%
1153
May16th to endNight
26%
375
10%
1428
7%
374
36%
374
12%
1032
June1st to 15thNight
28%
360
6%
1260
4%
360
33%
360
11%
952
June16th to endNight
34%
360
7%
1260
7%
360
38%
360
17%
879
July1st to 15thNight
35%
340
7%
1284
8%
340
39%
340
17%
859
July16th to endNight
41%
376
8%
1418
10%
354
43%
354
17%
941
August1st to 15thNight
41%
446
10%
1517
9%
444
45%
444
19%
1035
August16th to endNight
39%
611
16%
1757
9%
611
44%
611
25%
1154
September1st to 15thNight
32%
720
11%
1869
5%
720
35%
720
23%
1318
September16th to endNight
34%
685
18%
1891
10%
685
40%
685
26%
1249
October1st to 15thNight
25%
660
16%
1899
6%
660
35%
660
17%
1367
October16th to endNight
15%
704
8%
2288
3%
704
21%
704
9%
1813
November1st to 15thNight
21%
700
15%
2277
9%
700
29%
700
11%
1692
November16th to endNight
20%
743
12%
2558
7%
743
27%
743
9%
1972
December1st to 15thNight
10%
750
5%
2700
0%
750
15%
750
5%
2228
December16th to endNight
11%
800
9%
2880
3%
800
19%
800
5%
2323

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%12%48%6%34445%25%
47995
Night
16%11%48%7%35%445%27%
47056
TransparencyDay
59%5%10%16%7%
47681
Night
57%5%11%17%7%
46888
SeeingDay
26%16%28%18%7%1
6233
Night
23%18%28%20%7%
14673

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
14%14%6%12%10%5%5%44417%
1426
16th to endDay
8%14%7%13%7%36%45%5%21%
1536
February1st to 15thDay
9%15%6%11%11%6%6%5%4417%
1509
16th to endDay
12%17%7%10%8%45%43420%
1580
March1st to 15thDay
16%16%6%9%6%3334425%
1811
16th to endDay
14%13%5%8%7%4443428%
2167
April1st to 15thDay
20%14%47%5%24335%28%
2173
16th to endDay
19%14%36%423335%31%
2340
May1st to 15thDay
22%12%47%5%34345%27%
2386
16th to endDay
22%9%47%7%34445%24%
2684
June1st to 15thDay
26%9%36%6%345%47%21%
2700
16th to endDay
24%9%47%6%35%5%46%21%
2700
July1st to 15thDay
18%7%47%7%35%5%6%7%25%
2596
16th to endDay
21%8%37%6%35%6%5%7%23%
2654
August1st to 15thDay
20%9%36%7%445%5%7%22%
2421
16th to endDay
14%8%36%6%36%45%7%32%
2444
September1st to 15thDay
22%9%25%423346%34%
2091
16th to endDay
18%8%35%32345%6%39%
1881
October1st to 15thDay
21%15%47%423335%28%
1729
16th to endDay
24%18%48%6%3433418%
1584
November1st to 15thDay
19%16%48%5%3433326%
1581
16th to endDay
18%17%6%9%7%3333324%
1398
December1st to 15thDay
19%22%7%9%7%3423315%
1260
16th to endDay
20%16%8%11%6%3433318%
1344
January1st to 15thNight
13%13%7%12%10%5%6%43417%
2509
16th to endNight
9%12%6%10%9%46%6%6%6%21%
2688
February1st to 15thNight
7%12%6%10%11%6%7%7%5%420%
2348
16th to endNight
13%14%6%12%7%3444424%
1893
March1st to 15thNight
15%13%5%7%6%35%445%28%
2126
16th to endNight
11%12%5%6%6%45%5%5%432%
2055
April1st to 15thNight
17%14%47%6%34445%27%
1774
16th to endNight
20%9%37%434345%33%
1620
May1st to 15thNight
21%10%36%6%34445%29%
1575
16th to endNight
22%7%37%6%245%35%30%
1426
June1st to 15thNight
24%10%36%6%35%5%45%25%
1260
16th to endNight
16%7%46%6%35%447%32%
1260
July1st to 15thNight
16%7%27%6%345%5%6%33%
1362
16th to endNight
15%6%26%6%35%5%5%7%34%
1514
August1st to 15thNight
16%8%35%5%246%7%7%32%
1527
16th to endNight
14%5%25%5%345%5%7%38%
1757
September1st to 15thNight
18%7%35%5%33445%37%
1869
16th to endNight
17%6%24334345%44%
1891
October1st to 15thNight
19%10%36%434446%32%
1899
16th to endNight
22%15%48%6%35%33323%
2288
November1st to 15thNight
16%12%37%7%35%45%6%26%
2277
16th to endNight
16%13%5%8%7%45%44424%
2558
December1st to 15thNight
18%16%7%12%8%4433316%
2700
16th to endNight
18%16%6%10%8%3434318%
2880

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
68%47%11%6%
1427
16th to endDay
62%48%16%8%
1536
February1st to 15thDay
68%48%11%5%
1512
16th to endDay
66%35%14%7%1
1580
March1st to 15thDay
62%37%13%11%1
1821
16th to endDay
58%47%16%10%1
2167
April1st to 15thDay
59%37%16%9%3
2173
16th to endDay
55%37%18%12%2
2340
May1st to 15thDay
58%310%17%9%
2386
16th to endDay
60%6%10%16%6%
2688
June1st to 15thDay
60%6%10%16%5%
2700
16th to endDay
62%5%10%15%5%
2700
July1st to 15thDay
53%7%15%17%5%
2445
16th to endDay
60%6%12%16%4
2487
August1st to 15thDay
58%7%16%13%3
2407
16th to endDay
48%6%15%23%6%
2444
September1st to 15thDay
50%413%19%10%
2091
16th to endDay
45%5%13%25%10%
1881
October1st to 15thDay
58%410%19%6%
1729
16th to endDay
69%38%14%4
1584
November1st to 15thDay
61%5%10%14%7%
1581
16th to endDay
64%5%8%16%5%
1398
December1st to 15thDay
73%38%11%2
1260
16th to endDay
71%36%10%7%
1344
January1st to 15thNight
68%5%7%12%5%
2509
16th to endNight
59%5%9%17%6%
2688
February1st to 15thNight
62%7%8%14%6%1
2349
16th to endNight
63%47%14%10%
1893
March1st to 15thNight
56%5%7%17%10%2
2139
16th to endNight
52%6%9%18%12%1
2055
April1st to 15thNight
56%5%5%18%11%2
1774
16th to endNight
53%48%17%13%2
1620
May1st to 15thNight
56%410%16%11%
1575
16th to endNight
56%6%11%17%9%
1428
June1st to 15thNight
60%6%9%16%6%
1260
16th to endNight
50%6%16%18%8%
1260
July1st to 15thNight
47%6%18%19%6%
1284
16th to endNight
46%8%18%18%7%
1418
August1st to 15thNight
46%8%19%23%2
1517
16th to endNight
40%7%18%27%5%
1757
September1st to 15thNight
46%6%13%24%7%1
1869
16th to endNight
41%5%16%26%9%
1891
October1st to 15thNight
51%5%11%23%8%
1899
16th to endNight
63%5%10%15%4
2288
November1st to 15thNight
55%7%13%15%7%
2277
16th to endNight
61%6%9%17%5%
2558
December1st to 15thNight
71%48%12%2
2700
16th to endNight
69%47%12%6%
2880

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
21%33%40%5%
60
16th to endDay
20%31%34%9%31
64
February1st to 15thDay
30%13%30%17%6%
152
16th to endDay
23%18%35%17%4
239
March1st to 15thDay
26%25%29%13%4
270
16th to endDay
22%21%20%19%12%2
288
April1st to 15thDay
31%22%25%14%5%1
270
16th to endDay
28%19%28%15%6%2
270
May1st to 15thDay
33%10%32%15%41
288
16th to endDay
26%18%30%18%4
397
June1st to 15thDay
29%14%26%20%8%
495
16th to endDay
28%10%29%22%8%
495
July1st to 15thDay
21%14%34%20%8%
379
16th to endDay
23%10%33%27%41
326
August1st to 15thDay
23%11%31%22%7%2
313
16th to endDay
21%14%27%20%12%3
332
September1st to 15thDay
22%13%29%20%10%4
315
16th to endDay
19%16%29%16%13%5%
278
October1st to 15thDay
25%18%24%20%9%3
244
16th to endDay
36%22%21%13%6%
240
November1st to 15thDay
27%21%24%19%6%
235
16th to endDay
25%20%26%16%10%
159
December1st to 15thDay
43%16%28%8%3
60
16th to endDay
39%37%20%3
64
January1st to 15thNight
23%28%31%13%2
721
16th to endNight
18%23%35%17%3
768
February1st to 15thNight
15%26%35%17%4
704
16th to endNight
24%20%34%14%5%
631
March1st to 15thNight
25%20%34%14%4
720
16th to endNight
18%21%27%22%8%
768
April1st to 15thNight
26%19%28%18%6%
696
16th to endNight
28%12%28%21%7%1
540
May1st to 15thNight
25%13%26%23%10%
495
16th to endNight
26%12%26%25%9%1
375
June1st to 15thNight
28%8%25%26%11%
360
16th to endNight
21%9%26%32%9%
360
July1st to 15thNight
18%8%32%25%15%
340
16th to endNight
19%5%24%38%11%
376
August1st to 15thNight
21%5%23%29%19%1
446
16th to endNight
17%8%28%30%12%2
611
September1st to 15thNight
22%10%28%25%11%1
720
16th to endNight
19%12%30%23%12%1
685
October1st to 15thNight
24%16%27%21%7%1
660
16th to endNight
32%20%25%15%6%
704
November1st to 15thNight
25%22%25%20%5%
700
16th to endNight
27%21%25%17%6%2
743
December1st to 15thNight
27%26%28%13%3
750
16th to endNight
31%25%22%15%4
800
Page generated at 2017-09-23 06:43:45. Version ac04

Copyright 2017 A. Danko


Rang Saint-Arthur Clear Sky Chart | Charts Home