Pont Rouge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pont Rouge Observatory clear sky chart from 2005-11-05 to 2017-08-12.

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
28%
14475
12%
46512
7%
14444
35%
14444
15%
34156

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
14%
720
9%
2506
3%
716
21%
716
8%
1979
January16th to endNight
21%
768
11%
2688
5%
768
30%
768
10%
2051
February1st to 15thNight
20%
703
10%
2359
4%
701
30%
701
11%
1792
February16th to endNight
21%
631
11%
1893
5%
631
29%
631
12%
1477
March1st to 15thNight
21%
720
14%
2160
7%
720
30%
720
14%
1602
March16th to endNight
30%
768
18%
2019
6%
768
38%
768
20%
1448
April1st to 15thNight
25%
718
15%
1796
5%
718
31%
718
18%
1373
April16th to endNight
25%
552
15%
1632
6%
552
33%
552
19%
1140
May1st to 15thNight
28%
439
14%
1519
11%
439
35%
439
16%
1063
May16th to endNight
28%
375
10%
1497
9%
374
37%
374
14%
1044
June1st to 15thNight
35%
360
6%
1272
5%
360
40%
360
14%
921
June16th to endNight
42%
360
7%
1266
9%
360
44%
360
16%
884
July1st to 15thNight
48%
340
7%
1360
10%
340
50%
340
18%
882
July16th to endNight
52%
376
9%
1418
13%
354
54%
354
17%
921
August1st to 15thNight
54%
390
11%
1439
12%
388
57%
388
17%
973
August16th to endNight
44%
603
13%
1653
9%
603
46%
603
24%
1132
September1st to 15thNight
42%
660
10%
1683
6%
660
43%
660
26%
1197
September16th to endNight
40%
657
18%
1815
10%
657
45%
657
26%
1215
October1st to 15thNight
30%
660
18%
1912
9%
660
39%
660
20%
1363
October16th to endNight
23%
704
9%
2288
5%
704
30%
704
13%
1723
November1st to 15thNight
29%
700
15%
2277
9%
700
37%
700
15%
1649
November16th to endNight
26%
732
12%
2543
7%
732
34%
732
12%
1898
December1st to 15thNight
17%
750
6%
2700
2%
750
21%
750
7%
2159
December16th to endNight
14%
789
9%
2817
3%
789
22%
789
7%
2270

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
21%9%36%5%35%446%28%
47459
Night
20%10%36%5%34445%30%
46682
TransparencyDay
55%6%12%16%7%
47147
Night
55%5%11%17%8%
46512
SeeingDay
27%11%26%21%10%2
5820
Night
26%10%27%26%9%
14476

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
20%15%6%8%6%34445%20%
1432
16th to endDay
13%14%7%9%5%35%5%4424%
1536
February1st to 15thDay
10%14%6%12%7%36%33425%
1499
16th to endDay
14%13%6%10%6%35%45%5%23%
1580
March1st to 15thDay
18%11%47%6%3444430%
1790
16th to endDay
14%9%46%5%36%45%434%
2202
April1st to 15thDay
26%8%35%5%3333432%
2152
16th to endDay
23%7%25%5%24435%34%
2328
May1st to 15thDay
25%7%35%424445%31%
2442
16th to endDay
24%7%26%7%35%445%27%
2618
June1st to 15thDay
22%7%36%5%35%46%7%27%
2685
16th to endDay
23%8%37%5%35%5%5%7%24%
2691
July1st to 15thDay
17%6%36%6%45%6%6%7%29%
2520
16th to endDay
19%6%27%5%46%5%7%8%27%
2654
August1st to 15thDay
20%6%26%6%36%5%6%8%25%
2414
16th to endDay
15%6%25%5%35%46%8%36%
2195
September1st to 15thDay
23%5%25%42445%7%36%
1947
16th to endDay
24%424322347%38%
1815
October1st to 15thDay
26%8%24436%435%29%
1715
16th to endDay
28%9%37%7%24345%22%
1584
November1st to 15thDay
22%10%37%6%34345%28%
1581
16th to endDay
24%15%45%5%2434425%
1415
December1st to 15thDay
29%15%35%6%2332324%
1260
16th to endDay
24%17%5%7%5%2343421%
1404
January1st to 15thNight
21%16%5%8%7%33235%22%
2506
16th to endNight
12%14%6%10%7%45%5%5%5%23%
2688
February1st to 15thNight
10%12%5%10%10%45%445%25%
2358
16th to endNight
17%13%6%10%5%35%34425%
1893
March1st to 15thNight
19%10%36%5%34445%30%
2147
16th to endNight
14%9%47%424346%37%
2019
April1st to 15thNight
25%10%35%423445%29%
1796
16th to endNight
21%7%24424347%36%
1632
May1st to 15thNight
25%7%34425%435%34%
1519
16th to endNight
26%6%35%424346%32%
1495
June1st to 15thNight
23%7%25%5%35%446%28%
1272
16th to endNight
22%5%346%3446%7%31%
1266
July1st to 15thNight
18%5%25%3245%6%9%34%
1440
16th to endNight
16%6%35%5%26%46%6%36%
1514
August1st to 15thNight
16%5%25%436%5%6%8%33%
1449
16th to endNight
16%5%246%34447%39%
1653
September1st to 15thNight
21%6%15%32325%6%39%
1683
16th to endNight
24%5%13312326%43%
1815
October1st to 15thNight
22%8%24424446%34%
1912
16th to endNight
28%10%35%333345%28%
2288
November1st to 15thNight
21%9%35%5%24447%31%
2277
16th to endNight
25%12%36%42433429%
2543
December1st to 15thNight
25%16%5%7%7%2333321%
2700
16th to endNight
22%17%6%8%6%2333420%
2817

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%7%12%6%
1433
16th to endDay
60%5%8%16%7%
1536
February1st to 15thDay
61%413%12%6%
1502
16th to endDay
61%6%8%13%8%1
1580
March1st to 15thDay
56%5%10%14%11%1
1800
16th to endDay
50%6%8%17%12%3
2202
April1st to 15thDay
55%5%9%14%9%4
2152
16th to endDay
52%49%17%13%2
2328
May1st to 15thDay
53%5%10%16%11%1
2442
16th to endDay
57%7%10%15%9%
2622
June1st to 15thDay
53%7%13%15%8%1
2685
16th to endDay
57%7%12%14%8%
2691
July1st to 15thDay
48%9%17%18%5%
2371
16th to endDay
53%9%15%16%5%
2487
August1st to 15thDay
52%10%19%13%3
2400
16th to endDay
42%9%18%22%6%
2195
September1st to 15thDay
47%5%16%20%8%
1947
16th to endDay
44%5%16%24%7%
1815
October1st to 15thDay
55%6%12%17%7%
1715
16th to endDay
63%5%11%15%3
1584
November1st to 15thDay
58%6%10%17%6%
1581
16th to endDay
62%410%16%4
1415
December1st to 15thDay
65%5%10%14%4
1260
16th to endDay
66%6%7%11%7%
1404
January1st to 15thNight
66%49%14%4
2506
16th to endNight
60%5%9%16%7%
2688
February1st to 15thNight
60%49%16%7%
2359
16th to endNight
62%5%8%13%9%1
1893
March1st to 15thNight
55%5%9%15%11%2
2160
16th to endNight
48%5%10%18%14%3
2019
April1st to 15thNight
56%47%17%11%2
1796
16th to endNight
47%6%10%18%14%3
1632
May1st to 15thNight
52%410%16%12%2
1519
16th to endNight
53%6%11%17%10%1
1497
June1st to 15thNight
55%6%13%16%6%1
1272
16th to endNight
51%6%12%17%11%
1266
July1st to 15thNight
44%8%19%19%7%
1360
16th to endNight
44%8%17%19%8%
1418
August1st to 15thNight
45%10%18%21%4
1439
16th to endNight
43%7%18%23%6%
1653
September1st to 15thNight
45%6%15%22%9%
1683
16th to endNight
43%414%27%9%
1815
October1st to 15thNight
50%5%11%23%8%
1912
16th to endNight
58%5%13%17%5%
2288
November1st to 15thNight
52%7%13%16%9%
2277
16th to endNight
59%411%17%6%
2543
December1st to 15thNight
67%411%11%4
2700
16th to endNight
68%47%11%6%
2817

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
30%15%35%18%1
60
16th to endDay
28%25%26%14%6%
64
February1st to 15thDay
19%20%35%18%5%
112
16th to endDay
24%13%32%23%5%
239
March1st to 15thDay
27%20%26%18%6%
270
16th to endDay
20%15%25%23%12%2
288
April1st to 15thDay
35%14%22%21%41
270
16th to endDay
31%14%25%17%8%2
270
May1st to 15thDay
34%12%27%16%7%1
288
16th to endDay
25%16%29%21%6%
331
June1st to 15thDay
27%9%29%23%10%
480
16th to endDay
26%8%29%24%9%1
486
July1st to 15thDay
23%8%32%19%12%2
305
16th to endDay
23%8%23%29%12%2
326
August1st to 15thDay
23%424%27%15%4
297
16th to endDay
26%5%23%20%16%6%
268
September1st to 15thDay
24%8%21%23%16%5%
255
16th to endDay
23%12%23%18%14%7%
254
October1st to 15thDay
28%10%29%17%12%2
250
16th to endDay
35%10%25%19%8%
240
November1st to 15thDay
29%14%22%20%11%
235
16th to endDay
34%12%20%21%8%2
108
December1st to 15thDay
40%13%31%11%3
60
16th to endDay
43%20%28%7%
64
January1st to 15thNight
27%13%32%22%4
720
16th to endNight
19%13%31%26%7%
768
February1st to 15thNight
16%13%36%26%7%
704
16th to endNight
23%14%31%23%5%
631
March1st to 15thNight
25%12%35%21%5%
720
16th to endNight
20%14%28%26%8%1
768
April1st to 15thNight
31%11%25%25%5%
718
16th to endNight
26%13%29%21%8%
552
May1st to 15thNight
25%9%32%23%8%
439
16th to endNight
31%5%28%26%7%
375
June1st to 15thNight
28%424%34%7%
360
16th to endNight
24%322%35%13%
360
July1st to 15thNight
20%320%37%16%1
340
16th to endNight
19%218%43%15%
376
August1st to 15thNight
20%215%34%26%
390
16th to endNight
19%423%35%16%
603
September1st to 15thNight
25%322%31%13%1
660
16th to endNight
26%6%23%26%16%1
657
October1st to 15thNight
26%10%28%23%11%
660
16th to endNight
35%10%26%21%6%
704
November1st to 15thNight
27%11%26%24%9%1
700
16th to endNight
32%14%20%21%9%1
732
December1st to 15thNight
33%14%24%22%5%
750
16th to endNight
33%14%26%20%41
789
Page generated at 2017-08-13 14:16:32. Version ac04

Copyright 2017 A. Danko


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