Niagara Centre Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Niagara Centre Observatory clear sky chart from 2005-11-05 to 2017-04-07.

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
36%
14439
13%
45484
9%
14401
41%
14401
17%
32586

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
13%
716
8%
2449
3%
716
18%
716
7%
1991
January16th to endNight
15%
768
8%
2496
3%
768
21%
768
8%
2029
February1st to 15thNight
16%
703
6%
2287
2%
701
22%
701
9%
1862
February16th to endNight
24%
631
9%
2001
4%
631
30%
631
12%
1560
March1st to 15thNight
25%
720
12%
1980
6%
720
29%
720
14%
1547
March16th to endNight
34%
768
19%
2112
10%
768
41%
768
23%
1500
April1st to 15thNight
31%
686
14%
1743
6%
686
35%
686
20%
1307
April16th to endNight
44%
525
19%
1515
10%
525
50%
525
25%
1012
May1st to 15thNight
50%
470
17%
1460
13%
470
55%
470
24%
968
May16th to endNight
55%
342
16%
1369
18%
342
61%
342
23%
810
June1st to 15thNight
47%
330
13%
1320
14%
330
55%
330
19%
826
June16th to endNight
58%
330
12%
1320
17%
330
62%
330
22%
791
July1st to 15thNight
65%
310
17%
1240
26%
310
67%
310
31%
647
July16th to endNight
64%
479
13%
1426
14%
446
66%
446
31%
848
August1st to 15thNight
68%
494
16%
1474
13%
491
69%
491
32%
896
August16th to endNight
66%
578
21%
1628
14%
578
68%
578
36%
988
September1st to 15thNight
58%
660
21%
1664
11%
660
61%
660
31%
1112
September16th to endNight
55%
657
20%
1834
14%
657
58%
657
30%
1185
October1st to 15thNight
44%
660
17%
1980
15%
660
48%
660
23%
1338
October16th to endNight
25%
704
10%
2112
6%
704
31%
704
15%
1580
November1st to 15thNight
34%
700
18%
2346
16%
700
40%
700
21%
1569
November16th to endNight
24%
720
10%
2520
7%
720
30%
720
11%
1868
December1st to 15thNight
16%
720
5%
2520
2%
720
20%
720
7%
2074
December16th to endNight
13%
768
4%
2688
1%
768
17%
768
5%
2278

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
14%9%36%6%35%45%7%32%
45747
Night
16%9%46%5%3445%6%33%
45666
Cloud CoverDay
15%9%36%6%35%45%7%32%
45757
Night
16%9%36%5%34446%33%
45670
TransparencyDay
49%7%13%18%9%
45447
Night
50%7%12%17%9%1
45484
SeeingDay
18%6%22%26%18%7%
4725
Night
20%8%27%28%13%1
14445

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
19%14%6%9%8%36%445%17%
1488
16th to endDay
14%16%6%11%11%5%6%5%4414%
1728
February1st to 15thDay
16%17%6%11%8%45%44416%
1575
16th to endDay
17%13%5%11%8%3445%6%20%
1470
March1st to 15thDay
16%13%49%7%45%45%5%23%
1969
16th to endDay
15%11%47%6%3435%6%33%
2112
April1st to 15thDay
21%11%36%5%24345%31%
2021
16th to endDay
17%7%36%5%23445%39%
2123
May1st to 15thDay
12%8%26%6%3446%7%36%
2161
16th to endDay
11%5%245%345%5%7%44%
2394
June1st to 15thDay
14%7%35%5%2446%7%38%
2310
16th to endDay
11%4244346%7%10%40%
2310
July1st to 15thDay
7%424435%5%6%10%44%
2310
16th to endDay
10%5%246%36%6%6%10%37%
2324
August1st to 15thDay
8%4246%36%6%7%10%38%
2145
16th to endDay
11%5%2443345%9%44%
2210
September1st to 15thDay
13%6%25%5%345%6%7%38%
1966
16th to endDay
14%5%25%5%35%45%8%38%
1795
October1st to 15thDay
19%7%36%424446%36%
1650
16th to endDay
23%11%37%6%2445%5%24%
1760
November1st to 15thDay
12%8%36%5%45%5%5%7%34%
1510
16th to endDay
20%12%38%6%24446%26%
1440
December1st to 15thDay
17%16%6%8%6%35%45%5%20%
1440
16th to endDay
22%16%7%8%7%35%45%5%12%
1536
January1st to 15thNight
20%16%6%8%6%34445%20%
2449
16th to endNight
15%15%6%9%7%35%45%5%20%
2496
February1st to 15thNight
16%14%5%10%7%45%445%21%
2285
16th to endNight
16%13%5%8%6%34446%24%
2001
March1st to 15thNight
21%10%37%7%35%446%26%
1968
16th to endNight
15%9%36%5%33345%38%
2112
April1st to 15thNight
20%8%36%5%3435%5%33%
1743
16th to endNight
12%7%26%43445%5%42%
1515
May1st to 15thNight
14%6%36%5%2445%9%37%
1460
16th to endNight
12%4245%345%6%6%45%
1367
June1st to 15thNight
12%426%6%345%6%7%38%
1320
16th to endNight
9%4147%35%45%8%43%
1320
July1st to 15thNight
6%3143245%6%8%52%
1320
16th to endNight
7%3245%25%5%5%8%49%
1533
August1st to 15thNight
7%423435%6%7%10%44%
1485
16th to endNight
7%42343445%7%50%
1628
September1st to 15thNight
14%5%24323447%45%
1664
16th to endNight
12%6%26%434337%46%
1834
October1st to 15thNight
18%6%35%424446%40%
1980
16th to endNight
22%9%35%5%25%5%46%28%
2112
November1st to 15thNight
14%7%35%43445%8%37%
2346
16th to endNight
20%10%46%5%34447%28%
2520
December1st to 15thNight
22%15%5%7%5%2435%5%21%
2520
16th to endNight
21%14%7%9%7%35%445%15%
2688

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
20%14%5%9%7%35%5%45%17%
1488
16th to endDay
14%16%6%11%10%5%6%44414%
1728
February1st to 15thDay
17%17%5%12%7%4444416%
1575
16th to endDay
17%13%7%9%8%35%345%20%
1470
March1st to 15thDay
17%12%49%7%36%445%23%
1980
16th to endDay
16%11%36%6%34346%32%
2111
April1st to 15thDay
21%11%36%5%23345%31%
2021
16th to endDay
18%7%35%5%24446%39%
2123
May1st to 15thDay
13%7%26%5%35%5%5%7%37%
2161
16th to endDay
11%5%2443445%7%44%
2394
June1st to 15thDay
14%6%25%5%35%45%8%38%
2310
16th to endDay
12%414435%6%6%9%40%
2310
July1st to 15thDay
7%4235%35%5%6%9%44%
2310
16th to endDay
11%4245%46%6%6%10%37%
2324
August1st to 15thDay
9%4236%36%6%7%10%40%
2145
16th to endDay
11%5%244335%5%8%44%
2210
September1st to 15thDay
14%5%345%345%6%7%39%
1966
16th to endDay
15%5%25%5%35%45%7%38%
1795
October1st to 15thDay
20%7%36%424345%36%
1650
16th to endDay
24%10%37%6%4445%5%23%
1760
November1st to 15thDay
12%8%36%6%36%45%7%35%
1510
16th to endDay
21%12%45%6%33446%26%
1440
December1st to 15thDay
18%17%5%8%7%25%44420%
1440
16th to endDay
22%17%6%9%7%4445%5%13%
1536
January1st to 15thNight
21%15%6%8%6%33445%20%
2449
16th to endNight
15%17%6%9%7%35%445%20%
2496
February1st to 15thNight
16%14%6%11%7%35%335%21%
2278
16th to endNight
17%13%48%7%34445%24%
2001
March1st to 15thNight
21%10%47%6%35%445%27%
1980
16th to endNight
16%9%36%5%2335%5%37%
2112
April1st to 15thNight
21%8%36%5%34345%32%
1743
16th to endNight
12%7%26%5%345%45%41%
1515
May1st to 15thNight
14%6%25%5%3446%9%37%
1459
16th to endNight
11%4234345%5%7%45%
1367
June1st to 15thNight
13%426%6%35%5%6%7%39%
1320
16th to endNight
9%4146%445%5%9%42%
1320
July1st to 15thNight
6%315%325%46%9%51%
1320
16th to endNight
8%3235%25%6%5%9%47%
1533
August1st to 15thNight
7%414435%6%6%10%45%
1485
16th to endNight
8%4234345%5%7%50%
1628
September1st to 15thNight
15%424333447%45%
1664
16th to endNight
13%5%15%5%24346%46%
1834
October1st to 15thNight
18%7%26%423446%39%
1980
16th to endNight
23%9%36%5%35%446%28%
2112
November1st to 15thNight
15%7%26%5%2445%8%37%
2346
16th to endNight
20%10%46%5%34446%28%
2520
December1st to 15thNight
22%15%5%7%5%34445%21%
2520
16th to endNight
22%14%7%8%7%34445%15%
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
67%7%11%10%3
1489
16th to endDay
71%6%10%7%2
1728
February1st to 15thDay
70%6%10%9%2
1577
16th to endDay
64%6%12%11%4
1470
March1st to 15thDay
60%8%12%13%4
1980
16th to endDay
52%5%10%20%9%1
2112
April1st to 15thDay
55%412%16%10%
2021
16th to endDay
46%410%19%15%3
2123
May1st to 15thDay
44%7%12%22%12%
2161
16th to endDay
38%8%14%23%14%1
2398
June1st to 15thDay
41%8%15%22%10%1
2310
16th to endDay
35%10%16%22%13%
2310
July1st to 15thDay
32%8%15%23%19%1
2161
16th to endDay
39%9%17%20%11%1
2168
August1st to 15thDay
35%9%19%20%13%1
2132
16th to endDay
36%6%14%27%12%1
2210
September1st to 15thDay
40%8%15%22%11%
1966
16th to endDay
42%7%15%22%11%
1795
October1st to 15thDay
48%6%14%17%11%1
1650
16th to endDay
61%7%15%12%3
1760
November1st to 15thDay
46%9%17%16%8%1
1510
16th to endDay
58%7%13%14%5%
1440
December1st to 15thDay
65%8%14%9%1
1440
16th to endDay
73%8%9%7%1
1536
January1st to 15thNight
65%7%11%10%4
2449
16th to endNight
65%7%11%11%3
2496
February1st to 15thNight
66%6%11%12%3
2287
16th to endNight
60%6%13%13%5%
2001
March1st to 15thNight
59%6%11%16%5%
1980
16th to endNight
48%6%8%21%13%1
2112
April1st to 15thNight
53%5%10%17%12%
1743
16th to endNight
42%5%10%19%17%4
1515
May1st to 15thNight
42%7%12%24%10%2
1460
16th to endNight
36%8%12%22%16%3
1369
June1st to 15thNight
40%9%12%20%14%1
1320
16th to endNight
38%7%13%23%14%1
1320
July1st to 15thNight
27%8%13%23%24%2
1240
16th to endNight
31%8%17%21%16%3
1426
August1st to 15thNight
31%9%18%24%14%1
1474
16th to endNight
31%7%12%31%16%1
1628
September1st to 15thNight
37%7%14%23%15%1
1664
16th to endNight
39%5%11%28%14%1
1834
October1st to 15thNight
45%5%13%20%13%
1980
16th to endNight
55%6%16%14%5%
2112
November1st to 15thNight
44%7%14%20%11%1
2346
16th to endNight
55%8%15%16%4
2520
December1st to 15thNight
65%9%12%9%3
2520
16th to endNight
70%8%11%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
23%20%36%8%10%1
69
16th to endDay
25%15%34%20%4
96
February1st to 15thDay
20%16%50%13%
90
16th to endDay
18%13%32%31%4
96
March1st to 15thDay
24%10%32%25%7%
270
16th to endDay
23%6%29%28%9%2
288
April1st to 15thDay
28%8%25%24%9%3
235
16th to endDay
20%5%20%31%15%7%
210
May1st to 15thDay
18%321%27%21%7%
228
16th to endDay
11%220%31%23%8%
267
June1st to 15thDay
18%420%32%19%4
255
16th to endDay
16%118%32%24%6%
255
July1st to 15thDay
11%314%30%29%11%
245
16th to endDay
11%221%28%24%11%
270
August1st to 15thDay
9%115%28%26%18%
253
16th to endDay
13%114%24%28%18%
268
September1st to 15thDay
12%315%21%31%14%
255
16th to endDay
18%6%12%23%24%13%
254
October1st to 15thDay
19%5%25%19%23%7%
255
16th to endDay
31%9%27%22%8%
272
November1st to 15thDay
10%13%30%29%12%3
110
16th to endDay
23%15%23%25%13%
60
December1st to 15thDay
20%28%30%15%6%
60
16th to endDay
29%25%35%7%1
64
January1st to 15thNight
28%17%30%17%4
720
16th to endNight
24%14%36%20%4
768
February1st to 15thNight
22%16%35%23%3
704
16th to endNight
19%13%32%29%4
631
March1st to 15thNight
26%10%30%24%7%
720
16th to endNight
19%5%32%29%12%
768
April1st to 15thNight
23%9%29%30%6%
686
16th to endNight
13%6%28%35%13%1
525
May1st to 15thNight
16%322%34%21%2
470
16th to endNight
13%323%35%21%2
343
June1st to 15thNight
16%127%33%20%
330
16th to endNight
10%119%46%21%
330
July1st to 15thNight
6%118%43%27%2
310
16th to endNight
9%116%43%24%3
479
August1st to 15thNight
9%113%39%29%5%
494
16th to endNight
10%14%35%33%4
578
September1st to 15thNight
15%5%15%31%26%6%
660
16th to endNight
15%318%28%27%6%
657
October1st to 15thNight
21%7%22%26%20%2
660
16th to endNight
28%9%31%24%5%
704
November1st to 15thNight
16%8%34%25%13%2
700
16th to endNight
25%14%31%19%9%
720
December1st to 15thNight
31%14%30%18%3
720
16th to endNight
26%14%35%20%3
768
Page generated at 2017-04-08 05:35:19. Version ac04

Copyright 2017 A. Danko


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