Quetican Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Quetican Observatory clear sky chart from 2005-11-05 to

2017-09-12
.

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
30%
15167
10%
46686
7%
15126
33%
15126
13%
35590

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
7%
899
1%
2623
0%
895
8%
895
2%
2440
January16th to endNight
14%
823
4%
2551
2%
823
16%
823
4%
2297
February1st to 15thNight
15%
702
4%
2287
2%
701
18%
701
6%
1966
February16th to endNight
23%
631
8%
1976
4%
631
27%
631
9%
1601
March1st to 15thNight
23%
720
12%
2025
6%
720
29%
720
14%
1546
March16th to endNight
34%
768
18%
2112
10%
768
40%
768
19%
1470
April1st to 15thNight
30%
656
15%
1797
6%
656
35%
656
20%
1259
April16th to endNight
32%
540
18%
1620
7%
540
41%
540
19%
1096
May1st to 15thNight
44%
528
14%
1608
12%
528
47%
528
18%
1080
May16th to endNight
44%
374
14%
1497
13%
374
53%
374
19%
864
June1st to 15thNight
44%
360
13%
1267
11%
360
51%
360
19%
797
June16th to endNight
53%
360
13%
1260
13%
360
58%
360
22%
768
July1st to 15thNight
64%
340
17%
1190
21%
340
67%
340
32%
629
July16th to endNight
52%
525
15%
1482
14%
492
59%
492
29%
907
August1st to 15thNight
56%
539
17%
1609
14%
536
60%
536
28%
966
August16th to endNight
57%
573
18%
1719
12%
573
61%
573
28%
1058
September1st to 15thNight
50%
699
15%
1831
9%
699
52%
699
28%
1242
September16th to endNight
49%
657
17%
1815
12%
657
51%
657
26%
1229
October1st to 15thNight
31%
660
12%
1963
10%
660
35%
660
14%
1472
October16th to endNight
18%
704
6%
2161
3%
704
22%
704
7%
1823
November1st to 15thNight
26%
700
11%
2364
11%
700
28%
700
10%
1859
November16th to endNight
16%
720
4%
2520
3%
720
18%
720
5%
2187
December1st to 15thNight
8%
729
1%
2529
0%
729
10%
729
2%
2342
December16th to endNight
6%
960
2%
2880
0%
960
8%
960
2%
2692

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%47%6%3445%6%33%
47966
Night
16%11%48%6%35%446%27%
46855
Cloud CoverDay
14%9%47%6%3445%6%33%
47976
Night
16%11%5%8%7%34446%27%
46859
TransparencyDay
50%7%12%19%9%
47653
Night
58%6%10%15%8%
46686
SeeingDay
18%12%19%28%16%5%
5795
Night
19%21%21%22%12%2
15171

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
18%18%8%15%10%46%4326%
1313
16th to endDay
13%18%9%16%11%6%5%3328%
1671
February1st to 15thDay
13%15%9%13%9%5%5%43414%
1575
16th to endDay
13%14%6%9%9%6%5%445%18%
1494
March1st to 15thDay
12%9%5%8%7%35%45%6%30%
1923
16th to endDay
12%7%37%7%3445%5%36%
2112
April1st to 15thDay
19%8%36%5%33446%34%
2160
16th to endDay
17%7%24423348%40%
2340
May1st to 15thDay
17%6%35%42435%6%41%
2342
16th to endDay
11%42432445%8%48%
2618
June1st to 15thDay
13%5%244345%5%8%42%
2690
16th to endDay
11%5%245%245%6%9%43%
2700
July1st to 15thDay
8%42433445%8%50%
2700
16th to endDay
8%414425%46%9%48%
2578
August1st to 15thDay
10%41442445%7%49%
2340
16th to endDay
11%5%26%43445%7%43%
2478
September1st to 15thDay
14%5%26%5%2345%8%41%
2038
16th to endDay
17%6%244235%5%7%40%
1815
October1st to 15thDay
21%9%25%5%33446%31%
1667
16th to endDay
29%12%5%7%6%34445%16%
1708
November1st to 15thDay
18%13%47%7%36%5%5%5%23%
1492
16th to endDay
19%21%7%10%7%35%335%12%
1440
December1st to 15thDay
19%20%8%12%10%5%5%5%226%
1428
16th to endDay
21%21%9%15%7%343345%
1344
January1st to 15thNight
19%18%7%14%10%46%4446%
2623
16th to endNight
14%16%9%14%11%5%5%43310%
2551
February1st to 15thNight
11%18%9%12%9%45%5%4413%
2285
16th to endNight
14%11%7%11%9%37%5%46%20%
1976
March1st to 15thNight
14%11%5%8%6%35%445%29%
2013
16th to endNight
13%7%46%5%34445%38%
2112
April1st to 15thNight
21%7%34424446%36%
1797
16th to endNight
18%6%25%42445%6%38%
1620
May1st to 15thNight
16%6%35%6%35%35%6%37%
1608
16th to endNight
12%5%25%5%3445%6%44%
1495
June1st to 15thNight
13%5%25%6%3445%8%39%
1267
16th to endNight
9%4245%36%5%5%8%43%
1260
July1st to 15thNight
6%4134335%5%10%50%
1260
16th to endNight
7%425%435%5%5%8%48%
1586
August1st to 15thNight
9%4235%235%6%8%49%
1620
16th to endNight
9%5%25%43445%8%47%
1719
September1st to 15thNight
13%425%5%3446%8%42%
1831
16th to endNight
16%5%25%434448%40%
1815
October1st to 15thNight
22%8%26%6%35%45%6%29%
1963
16th to endNight
26%12%47%6%5%4446%17%
2161
November1st to 15thNight
18%12%47%8%45%446%22%
2364
16th to endNight
23%17%5%9%8%34435%14%
2520
December1st to 15thNight
21%21%7%12%8%343337%
2529
16th to endNight
23%21%9%14%6%343336%
2880

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
18%17%8%15%11%46%4326%
1313
16th to endDay
13%18%10%15%12%6%6%3327%
1671
February1st to 15thDay
13%15%8%14%10%5%5%6%3413%
1575
16th to endDay
14%13%6%10%9%5%6%445%18%
1494
March1st to 15thDay
12%8%5%8%7%445%5%6%30%
1934
16th to endDay
12%6%47%6%35%45%6%36%
2111
April1st to 15thDay
19%8%35%5%33446%34%
2160
16th to endDay
16%7%25%324348%40%
2340
May1st to 15thDay
16%6%35%424347%40%
2342
16th to endDay
11%42442435%8%48%
2618
June1st to 15thDay
12%5%244346%5%8%41%
2690
16th to endDay
11%4245%25%5%6%9%42%
2700
July1st to 15thDay
7%42433446%8%50%
2700
16th to endDay
8%41442446%9%48%
2578
August1st to 15thDay
9%4144245%5%7%49%
2340
16th to endDay
10%5%25%43445%8%42%
2478
September1st to 15thDay
13%6%26%43446%7%41%
2038
16th to endDay
16%6%345%335%46%40%
1815
October1st to 15thDay
20%9%36%6%34436%31%
1667
16th to endDay
28%13%49%5%34435%16%
1708
November1st to 15thDay
18%12%46%7%46%5%4423%
1492
16th to endDay
19%19%8%10%7%45%336%11%
1440
December1st to 15thDay
19%20%9%12%10%46%3226%
1428
16th to endDay
21%20%9%15%8%333335%
1344
January1st to 15thNight
19%17%7%14%11%45%435%6%
2623
16th to endNight
14%16%8%14%12%46%43310%
2551
February1st to 15thNight
11%17%9%12%10%45%5%4413%
2278
16th to endNight
13%11%7%11%9%36%445%20%
1976
March1st to 15thNight
14%11%5%8%7%34445%28%
2025
16th to endNight
13%8%46%6%24445%38%
2112
April1st to 15thNight
21%7%35%324446%36%
1797
16th to endNight
18%6%26%4245%5%6%37%
1620
May1st to 15thNight
16%6%35%5%35%45%6%37%
1607
16th to endNight
11%5%16%43445%6%44%
1495
June1st to 15thNight
12%6%26%6%3445%8%38%
1267
16th to endNight
8%5%245%347%5%8%43%
1260
July1st to 15thNight
6%41343346%9%51%
1260
16th to endNight
7%424425%6%5%8%48%
1586
August1st to 15thNight
8%4234335%6%8%48%
1620
16th to endNight
8%5%25%4345%5%8%46%
1719
September1st to 15thNight
13%415%5%3447%7%42%
1831
16th to endNight
14%7%25%5%34447%40%
1815
October1st to 15thNight
20%9%36%5%35%45%6%28%
1963
16th to endNight
25%13%49%6%44446%16%
2161
November1st to 15thNight
17%13%48%7%45%446%22%
2364
16th to endNight
22%16%6%10%7%3444413%
2520
December1st to 15thNight
20%21%7%13%8%443437%
2529
16th to endNight
22%21%9%14%7%344336%
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
84%46%3
1314
16th to endDay
83%5%5%31
1671
February1st to 15thDay
73%6%8%9%1
1577
16th to endDay
67%6%9%11%5%
1494
March1st to 15thDay
53%6%13%18%8%
1934
16th to endDay
46%6%11%18%13%2
2112
April1st to 15thDay
49%6%9%20%11%1
2160
16th to endDay
42%5%12%22%14%2
2340
May1st to 15thDay
43%5%10%23%15%2
2342
16th to endDay
34%6%15%25%16%1
2622
June1st to 15thDay
38%7%13%26%13%
2690
16th to endDay
36%9%14%26%12%
2700
July1st to 15thDay
30%7%15%29%16%2
2541
16th to endDay
31%9%13%29%13%1
2419
August1st to 15thDay
32%8%17%26%14%
2327
16th to endDay
37%9%16%25%10%
2478
September1st to 15thDay
40%7%16%25%9%
2038
16th to endDay
42%8%14%25%8%
1815
October1st to 15thDay
54%5%11%18%9%
1667
16th to endDay
70%6%11%8%2
1708
November1st to 15thDay
62%7%10%12%6%
1492
16th to endDay
76%6%9%5%1
1440
December1st to 15thDay
85%6%5%2
1428
16th to endDay
85%46%2
1344
January1st to 15thNight
83%6%6%3
2623
16th to endNight
78%6%8%41
2551
February1st to 15thNight
73%5%8%8%2
2287
16th to endNight
64%7%10%11%5%
1976
March1st to 15thNight
56%5%11%17%7%
2025
16th to endNight
46%5%9%19%15%2
2112
April1st to 15thNight
49%410%21%12%1
1797
16th to endNight
45%5%9%18%19%2
1620
May1st to 15thNight
46%5%10%19%16%2
1608
16th to endNight
37%5%13%24%16%1
1497
June1st to 15thNight
41%6%11%22%16%1
1267
16th to endNight
36%7%13%27%14%
1260
July1st to 15thNight
27%5%14%29%20%2
1190
16th to endNight
33%8%13%26%17%
1482
August1st to 15thNight
32%8%16%26%14%1
1609
16th to endNight
35%7%16%26%12%1
1719
September1st to 15thNight
38%8%14%26%10%
1831
16th to endNight
42%6%15%25%9%
1815
October1st to 15thNight
55%6%10%17%9%
1963
16th to endNight
69%7%10%9%3
2161
November1st to 15thNight
62%6%12%13%3
2364
16th to endNight
74%6%11%5%
2520
December1st to 15thNight
83%5%6%2
2529
16th to endNight
85%5%5%3
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
22%12%37%22%4
70
16th to endDay
31%10%30%20%7%
96
February1st to 15thDay
26%18%33%18%2
90
16th to endDay
22%12%43%20%1
81
March1st to 15thDay
17%19%27%29%5%
224
16th to endDay
23%14%23%25%8%4
288
April1st to 15thDay
20%14%25%27%8%2
270
16th to endDay
22%14%22%24%11%4
270
May1st to 15thDay
19%11%18%26%17%6%
288
16th to endDay
13%10%16%34%18%6%
331
June1st to 15thDay
14%13%18%32%17%3
485
16th to endDay
14%13%13%32%19%5%
495
July1st to 15thDay
9%9%14%33%25%7%
475
16th to endDay
11%11%14%31%25%6%
400
August1st to 15thDay
13%6%11%29%27%11%
313
16th to endDay
16%6%12%31%24%9%
332
September1st to 15thDay
19%6%16%24%22%11%
299
16th to endDay
18%9%18%22%23%8%
254
October1st to 15thDay
24%13%20%26%12%2
255
16th to endDay
34%16%24%17%6%
220
November1st to 15thDay
14%9%28%33%12%2
75
16th to endDay
25%18%40%13%3
60
December1st to 15thDay
31%21%28%13%5%
60
16th to endDay
31%29%34%4
64
January1st to 15thNight
22%29%29%13%4
900
16th to endNight
18%26%26%21%6%1
823
February1st to 15thNight
18%25%29%20%4
704
16th to endNight
17%20%27%25%8%
631
March1st to 15thNight
17%24%26%22%7%1
720
16th to endNight
17%20%22%26%11%2
768
April1st to 15thNight
20%21%22%26%7%1
656
16th to endNight
19%20%22%20%15%1
540
May1st to 15thNight
18%17%12%29%18%2
528
16th to endNight
12%19%16%29%20%1
375
June1st to 15thNight
13%18%14%35%15%2
360
16th to endNight
9%17%12%32%25%1
360
July1st to 15thNight
9%13%7%41%23%5%
340
16th to endNight
9%17%14%33%23%2
525
August1st to 15thNight
13%11%13%29%27%5%
539
16th to endNight
11%11%15%27%29%5%
573
September1st to 15thNight
14%13%17%26%17%10%
699
16th to endNight
18%13%15%24%21%7%
657
October1st to 15thNight
26%14%21%20%13%3
660
16th to endNight
34%19%23%19%4
704
November1st to 15thNight
23%22%22%20%10%1
700
16th to endNight
25%28%22%16%6%
720
December1st to 15thNight
30%31%23%11%2
729
16th to endNight
28%30%24%13%3
960
Page generated at 2017-09-13 07:39:18. Version ac04

Copyright 2017 A. Danko


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