Cégep de Thetford
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cégep de Thetford clear sky chart from 2005-11-05 to 2017-09-23.

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
24%
14681
11%
46953
6%
14649
30%
14649
12%
35525

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
10%
720
8%
2506
3%
716
16%
716
5%
2094
January16th to endNight
14%
768
8%
2688
2%
768
21%
768
7%
2180
February1st to 15thNight
14%
704
8%
2334
2%
701
21%
701
7%
1903
February16th to endNight
14%
631
10%
1893
4%
631
24%
631
10%
1505
March1st to 15thNight
15%
720
13%
2160
6%
720
23%
720
11%
1668
March16th to endNight
26%
768
16%
2023
6%
768
35%
768
17%
1508
April1st to 15thNight
22%
718
14%
1796
4%
718
28%
718
16%
1389
April16th to endNight
24%
549
15%
1629
6%
549
31%
549
17%
1142
May1st to 15thNight
26%
473
13%
1553
10%
473
33%
473
15%
1120
May16th to endNight
26%
375
10%
1497
9%
374
34%
374
11%
1057
June1st to 15thNight
28%
360
7%
1302
6%
360
33%
360
12%
969
June16th to endNight
39%
360
8%
1302
8%
360
43%
360
17%
897
July1st to 15thNight
41%
340
9%
1360
12%
340
46%
340
17%
900
July16th to endNight
43%
376
10%
1418
12%
354
46%
354
17%
927
August1st to 15thNight
45%
426
11%
1497
10%
424
48%
424
17%
1035
August16th to endNight
42%
656
16%
1802
9%
656
46%
656
25%
1214
September1st to 15thNight
39%
720
12%
1848
5%
720
41%
720
25%
1303
September16th to endNight
41%
689
19%
1902
11%
689
46%
689
27%
1243
October1st to 15thNight
28%
660
16%
1898
8%
660
37%
660
17%
1401
October16th to endNight
18%
704
9%
2288
4%
704
24%
704
10%
1791
November1st to 15thNight
21%
700
13%
2277
8%
700
29%
700
12%
1714
November16th to endNight
21%
729
12%
2489
8%
729
27%
729
9%
1925
December1st to 15thNight
11%
750
5%
2700
1%
750
16%
750
5%
2262
December16th to endNight
10%
785
7%
2791
3%
785
15%
785
4%
2378

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%11%47%6%34445%25%
47949
Night
18%11%48%6%34445%27%
47123
TransparencyDay
60%5%9%16%7%
47637
Night
58%5%10%16%7%
46953
SeeingDay
29%13%27%18%8%2
5977
Night
26%14%28%21%8%
14681

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
17%17%8%12%10%35%33314%
1432
16th to endDay
11%15%9%11%10%45%5%25%19%
1536
February1st to 15thDay
12%19%8%11%9%45%5%3315%
1525
16th to endDay
13%20%6%10%8%35%5%4318%
1580
March1st to 15thDay
17%16%6%8%6%3434425%
1790
16th to endDay
17%12%5%7%7%25%43330%
2198
April1st to 15thDay
23%13%36%5%2433428%
2152
16th to endDay
22%12%36%5%23335%31%
2331
May1st to 15thDay
25%9%46%5%24345%27%
2409
16th to endDay
24%8%37%5%345%5%6%23%
2618
June1st to 15thDay
28%7%25%5%35%5%47%24%
2655
16th to endDay
24%7%36%6%345%5%6%24%
2653
July1st to 15thDay
18%7%36%6%35%5%5%8%28%
2520
16th to endDay
23%7%36%5%35%5%6%7%25%
2654
August1st to 15thDay
23%7%26%7%45%5%5%8%23%
2439
16th to endDay
17%6%25%5%4445%7%35%
2399
September1st to 15thDay
24%7%25%333446%34%
2112
16th to endDay
19%6%25%42335%8%38%
1895
October1st to 15thDay
25%12%25%423335%28%
1730
16th to endDay
26%20%37%5%2433418%
1584
November1st to 15thDay
21%17%37%5%3433425%
1581
16th to endDay
21%16%6%9%5%23235%23%
1466
December1st to 15thDay
23%21%7%10%6%3223316%
1260
16th to endDay
22%19%8%10%6%4432214%
1430
January1st to 15thNight
16%16%7%14%7%35%33417%
2506
16th to endNight
11%15%8%11%9%46%5%5%417%
2688
February1st to 15thNight
10%14%7%11%11%47%44319%
2333
16th to endNight
14%18%5%10%7%35%43325%
1893
March1st to 15thNight
19%12%5%7%6%35%44427%
2147
16th to endNight
14%10%37%6%35%5%4433%
2023
April1st to 15thNight
22%11%37%5%24445%27%
1796
16th to endNight
21%9%25%42435%5%35%
1629
May1st to 15thNight
23%8%36%5%24345%31%
1553
16th to endNight
22%8%26%7%24446%29%
1495
June1st to 15thNight
26%8%26%5%25%445%27%
1302
16th to endNight
19%5%36%5%35%5%5%8%31%
1302
July1st to 15thNight
16%5%35%5%26%5%6%5%36%
1440
16th to endNight
16%6%25%5%25%5%5%7%36%
1514
August1st to 15thNight
17%8%25%5%3445%7%34%
1507
16th to endNight
15%5%25%5%2335%7%41%
1802
September1st to 15thNight
23%6%24313445%39%
1848
16th to endNight
18%5%14314436%45%
1902
October1st to 15thNight
20%8%36%5%34446%31%
1898
16th to endNight
26%12%46%5%34345%23%
2288
November1st to 15thNight
20%12%46%6%3444427%
2277
16th to endNight
20%16%5%8%5%2333325%
2489
December1st to 15thNight
21%18%8%12%7%2323315%
2700
16th to endNight
20%18%8%10%8%3433314%
2791

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
74%37%9%4
1433
16th to endDay
67%37%15%5%
1536
February1st to 15thDay
73%36%10%4
1528
16th to endDay
70%36%11%6%1
1580
March1st to 15thDay
63%39%12%9%1
1800
16th to endDay
59%47%16%10%1
2198
April1st to 15thDay
59%37%16%9%2
2152
16th to endDay
55%38%16%11%2
2331
May1st to 15thDay
58%49%16%9%1
2409
16th to endDay
60%6%9%14%8%
2622
June1st to 15thDay
59%6%10%15%6%
2655
16th to endDay
58%6%9%17%6%
2653
July1st to 15thDay
51%8%14%19%6%
2371
16th to endDay
57%7%12%17%5%
2487
August1st to 15thDay
57%7%15%15%2
2425
16th to endDay
47%5%13%24%8%
2399
September1st to 15thDay
50%5%11%21%9%
2112
16th to endDay
44%6%12%26%10%
1895
October1st to 15thDay
58%411%19%5%
1730
16th to endDay
71%36%14%3
1584
November1st to 15thDay
62%49%14%7%
1581
16th to endDay
65%5%8%14%5%
1466
December1st to 15thDay
74%37%11%2
1260
16th to endDay
77%45%7%5%
1430
January1st to 15thNight
72%46%11%4
2506
16th to endNight
68%5%7%12%4
2688
February1st to 15thNight
68%47%13%5%
2334
16th to endNight
65%38%11%9%1
1893
March1st to 15thNight
60%5%7%16%8%1
2160
16th to endNight
53%5%9%16%12%2
2023
April1st to 15thNight
57%47%16%10%2
1796
16th to endNight
49%410%17%13%3
1629
May1st to 15thNight
54%5%8%17%13%1
1553
16th to endNight
55%6%10%17%9%
1497
June1st to 15thNight
57%6%10%17%6%
1302
16th to endNight
50%6%13%21%8%
1302
July1st to 15thNight
46%8%14%21%8%
1360
16th to endNight
45%8%17%19%9%
1418
August1st to 15thNight
47%9%15%23%4
1497
16th to endNight
41%7%15%26%8%
1802
September1st to 15thNight
46%413%26%8%
1848
16th to endNight
39%6%13%28%12%
1902
October1st to 15thNight
52%6%10%20%9%
1898
16th to endNight
63%5%10%14%5%
2288
November1st to 15thNight
59%413%14%6%1
2277
16th to endNight
63%38%16%6%
2489
December1st to 15thNight
73%38%10%3
2700
16th to endNight
75%37%8%4
2791

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
25%20%41%13%
60
16th to endDay
25%29%31%12%1
64
February1st to 15thDay
33%17%26%16%4
136
16th to endDay
24%20%33%17%3
239
March1st to 15thDay
31%19%29%15%3
270
16th to endDay
25%19%27%13%11%2
288
April1st to 15thDay
37%15%28%11%5%1
270
16th to endDay
34%15%27%13%6%2
270
May1st to 15thDay
37%10%30%11%7%2
288
16th to endDay
29%16%31%16%5%1
331
June1st to 15thDay
33%10%25%21%8%
450
16th to endDay
27%8%32%22%8%
448
July1st to 15thDay
22%11%33%23%8%
305
16th to endDay
25%7%27%28%9%1
326
August1st to 15thDay
28%7%27%22%12%1
313
16th to endDay
25%10%21%21%13%6%
332
September1st to 15thDay
24%10%25%22%12%5%
315
16th to endDay
20%12%24%22%12%8%
283
October1st to 15thDay
28%13%28%14%11%3
249
16th to endDay
40%13%20%17%5%1
240
November1st to 15thDay
29%17%24%19%7%1
235
16th to endDay
37%17%19%14%9%1
141
December1st to 15thDay
45%18%26%8%1
60
16th to endDay
46%20%28%4
64
January1st to 15thNight
28%22%30%14%3
720
16th to endNight
24%19%33%17%5%
768
February1st to 15thNight
19%21%36%18%4
704
16th to endNight
26%15%34%17%5%
631
March1st to 15thNight
29%16%33%16%2
720
16th to endNight
21%17%29%24%6%1
768
April1st to 15thNight
30%13%29%21%5%
718
16th to endNight
27%15%28%19%8%
549
May1st to 15thNight
27%10%30%23%6%1
473
16th to endNight
26%7%32%26%6%
375
June1st to 15thNight
30%9%24%26%8%
360
16th to endNight
21%5%28%34%9%
360
July1st to 15thNight
16%430%34%13%
340
16th to endNight
18%425%39%11%
376
August1st to 15thNight
21%421%33%18%
426
16th to endNight
19%5%24%28%17%3
656
September1st to 15thNight
25%7%23%29%12%1
720
16th to endNight
21%7%28%24%17%1
689
October1st to 15thNight
25%13%27%21%9%1
660
16th to endNight
36%15%24%18%5%
704
November1st to 15thNight
27%17%26%21%7%
700
16th to endNight
32%17%23%17%9%
729
December1st to 15thNight
34%20%27%15%3
750
16th to endNight
36%19%24%14%4
785
Page generated at 2017-09-24 09:15:55. Version ac04

Copyright 2017 A. Danko


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