Hall's Harbour Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hall's Harbour Observatory clear sky chart from 2005-11-05 to 2017-09-20.

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
21%
15005
10%
46687
4%
14960
26%
14960
12%
35958

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%
750
5%
2613
1%
746
14%
746
4%
2215
January16th to endNight
10%
769
6%
2505
2%
769
15%
769
6%
2122
February1st to 15thNight
10%
704
4%
2286
1%
701
13%
701
4%
1992
February16th to endNight
15%
631
6%
2036
1%
631
21%
631
7%
1647
March1st to 15thNight
14%
720
12%
1983
4%
720
22%
720
12%
1553
March16th to endNight
17%
768
12%
2112
4%
768
24%
768
13%
1617
April1st to 15thNight
15%
559
12%
1801
5%
559
24%
559
11%
1368
April16th to endNight
23%
540
13%
1620
6%
540
29%
540
16%
1181
May1st to 15thNight
26%
540
9%
1539
4%
540
30%
540
14%
1194
May16th to endNight
23%
561
9%
1496
3%
560
29%
560
18%
1133
June1st to 15thNight
25%
462
6%
1362
3%
462
28%
462
12%
1052
June16th to endNight
31%
360
8%
1260
4%
360
36%
360
15%
900
July1st to 15thNight
40%
350
8%
1200
5%
350
44%
350
22%
768
July16th to endNight
33%
565
8%
1480
5%
532
35%
532
19%
1104
August1st to 15thNight
39%
539
11%
1608
8%
535
40%
535
20%
1128
August16th to endNight
39%
573
16%
1764
9%
573
45%
573
24%
1159
September1st to 15thNight
34%
548
16%
1808
10%
548
42%
548
23%
1148
September16th to endNight
32%
677
20%
1891
11%
677
40%
677
25%
1260
October1st to 15thNight
26%
660
17%
1980
7%
660
34%
660
19%
1353
October16th to endNight
18%
704
12%
2112
4%
704
24%
704
12%
1586
November1st to 15thNight
21%
725
11%
2428
7%
725
26%
725
11%
1862
November16th to endNight
18%
750
8%
2520
4%
750
22%
750
8%
2039
December1st to 15thNight
8%
750
6%
2520
0%
750
14%
750
5%
2143
December16th to endNight
7%
800
4%
2763
1%
800
11%
800
3%
2434

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%10%47%6%34346%29%
48148
Night
20%11%5%7%6%34445%25%
46855
TransparencyDay
56%6%11%17%8%
47835
Night
59%6%11%15%6%
46687
SeeingDay
25%16%30%19%7%1
7312
Night
25%17%30%20%5%
15005

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
16%17%6%12%10%6%5%23413%
1320
16th to endDay
15%14%7%8%12%6%7%34414%
1718
February1st to 15thDay
17%14%5%14%12%5%6%44410%
1575
16th to endDay
12%15%7%12%7%45%43422%
1436
March1st to 15thDay
16%12%6%9%7%45%33426%
1965
16th to endDay
16%11%7%9%5%23335%30%
2112
April1st to 15thDay
18%10%46%5%35%445%30%
2144
16th to endDay
21%9%245%2435%6%33%
2340
May1st to 15thDay
24%9%35%424446%28%
2413
16th to endDay
21%9%36%5%33447%29%
2618
June1st to 15thDay
27%8%35%434446%26%
2607
16th to endDay
20%8%35%5%35%46%7%29%
2700
July1st to 15thDay
15%5%25%42446%8%39%
2676
16th to endDay
19%7%36%5%35%45%6%31%
2585
August1st to 15thDay
17%6%35%5%24447%39%
2340
16th to endDay
13%6%13323347%48%
2438
September1st to 15thDay
18%6%24424346%42%
2151
16th to endDay
16%6%25%423246%47%
1838
October1st to 15thDay
19%8%24423446%39%
1650
16th to endDay
22%12%36%5%24446%26%
1757
November1st to 15thDay
23%12%46%6%33235%27%
1430
16th to endDay
20%15%7%11%7%3433418%
1440
December1st to 15thDay
23%15%7%12%7%4423314%
1440
16th to endDay
23%17%8%13%8%2324311%
1455
January1st to 15thNight
17%17%8%11%10%33335%14%
2613
16th to endNight
17%13%7%11%11%5%6%435%14%
2505
February1st to 15thNight
18%14%7%13%12%5%5%23411%
2285
16th to endNight
15%15%7%10%8%35%44420%
2036
March1st to 15thNight
18%12%5%9%7%34435%26%
1971
16th to endNight
19%12%7%7%423245%28%
2112
April1st to 15thNight
22%13%47%5%24435%26%
1801
16th to endNight
22%10%35%5%3434432%
1620
May1st to 15thNight
24%9%36%5%35%346%25%
1539
16th to endNight
20%9%36%5%245%5%7%28%
1494
June1st to 15thNight
28%7%46%7%43445%24%
1362
16th to endNight
20%8%45%6%345%5%7%29%
1260
July1st to 15thNight
14%7%25%4246%6%10%34%
1270
16th to endNight
17%11%46%5%35%5%5%8%25%
1581
August1st to 15thNight
19%9%35%5%2345%6%33%
1620
16th to endNight
14%6%35%5%4346%7%38%
1764
September1st to 15thNight
16%6%3433445%6%40%
1808
16th to endNight
15%7%25%42435%5%42%
1891
October1st to 15thNight
18%7%245%3345%6%37%
1980
16th to endNight
25%12%36%42235%6%27%
2112
November1st to 15thNight
23%11%46%6%34345%25%
2428
16th to endNight
21%16%6%7%5%34435%20%
2520
December1st to 15thNight
23%14%6%11%8%34345%14%
2520
16th to endNight
26%16%7%9%9%3433411%
2763

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
75%5%9%7%1
1321
16th to endDay
73%6%7%8%3
1718
February1st to 15thDay
76%5%8%5%2
1578
16th to endDay
65%6%10%12%4
1436
March1st to 15thDay
63%48%14%7%
1976
16th to endDay
58%48%18%8%1
2112
April1st to 15thDay
57%6%8%15%12%1
2144
16th to endDay
52%5%9%18%12%1
2340
May1st to 15thDay
57%5%9%17%9%
2413
16th to endDay
56%7%10%18%6%
2622
June1st to 15thDay
58%6%10%15%6%
2607
16th to endDay
54%7%12%16%8%
2700
July1st to 15thDay
41%7%15%23%11%
2519
16th to endDay
51%7%12%21%6%
2423
August1st to 15thDay
46%8%13%20%11%
2327
16th to endDay
36%5%15%29%11%
2438
September1st to 15thDay
43%5%13%24%12%1
2151
16th to endDay
40%311%28%15%1
1838
October1st to 15thDay
47%5%12%24%10%
1650
16th to endDay
58%5%11%17%6%
1757
November1st to 15thDay
61%413%13%6%
1430
16th to endDay
70%7%10%9%2
1440
December1st to 15thDay
75%49%8%2
1440
16th to endDay
78%49%42
1455
January1st to 15thNight
72%6%9%8%2
2613
16th to endNight
72%5%9%10%1
2505
February1st to 15thNight
75%5%8%7%2
2286
16th to endNight
65%6%11%10%4
2036
March1st to 15thNight
60%5%10%15%7%1
1983
16th to endNight
58%410%16%9%
2112
April1st to 15thNight
60%48%13%10%2
1801
16th to endNight
53%5%10%15%12%1
1620
May1st to 15thNight
59%6%10%17%5%1
1539
16th to endNight
52%8%13%18%6%1
1496
June1st to 15thNight
60%6%12%16%4
1362
16th to endNight
50%9%13%19%6%
1260
July1st to 15thNight
38%10%19%21%8%
1200
16th to endNight
50%9%16%17%5%
1480
August1st to 15thNight
47%7%14%22%8%
1608
16th to endNight
41%7%17%26%7%
1764
September1st to 15thNight
40%7%13%27%11%
1808
16th to endNight
41%5%12%26%12%
1891
October1st to 15thNight
46%6%12%24%9%
1980
16th to endNight
57%5%10%18%7%
2112
November1st to 15thNight
59%6%10%15%6%
2428
16th to endNight
66%5%11%12%3
2520
December1st to 15thNight
71%6%8%10%2
2520
16th to endNight
76%6%6%7%2
2763

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
17%33%33%14%
127
16th to endDay
24%24%37%10%2
256
February1st to 15thDay
21%27%34%13%2
236
16th to endDay
23%23%30%16%5%
215
March1st to 15thDay
20%30%32%12%3
270
16th to endDay
25%26%28%13%41
288
April1st to 15thDay
27%25%29%13%3
270
16th to endDay
21%22%29%17%8%
270
May1st to 15thDay
33%15%26%17%5%1
369
16th to endDay
29%13%30%19%5%
519
June1st to 15thDay
34%11%26%20%6%
495
16th to endDay
25%10%33%22%6%2
495
July1st to 15thDay
18%5%33%27%12%1
475
16th to endDay
25%432%22%13%
446
August1st to 15thDay
21%6%31%25%13%1
313
16th to endDay
18%9%29%26%15%
332
September1st to 15thDay
24%9%33%23%9%
315
16th to endDay
20%9%29%25%12%2
266
October1st to 15thDay
26%12%27%20%8%4
225
16th to endDay
30%24%24%15%5%
240
November1st to 15thDay
30%20%24%17%42
235
16th to endDay
28%25%25%13%5%
240
December1st to 15thDay
31%28%23%14%2
240
16th to endDay
30%30%26%9%21
175
January1st to 15thNight
24%27%32%14%1
750
16th to endNight
23%29%30%13%2
769
February1st to 15thNight
27%25%30%15%1
704
16th to endNight
23%25%29%15%4
631
March1st to 15thNight
23%22%33%15%4
720
16th to endNight
24%22%30%16%5%
768
April1st to 15thNight
29%18%31%16%5%
559
16th to endNight
26%13%32%22%3
540
May1st to 15thNight
30%10%27%22%7%
540
16th to endNight
22%10%36%23%6%
561
June1st to 15thNight
29%8%29%25%6%
462
16th to endNight
23%5%29%33%6%1
360
July1st to 15thNight
14%432%38%9%
350
16th to endNight
18%431%34%10%
565
August1st to 15thNight
22%5%22%36%13%
539
16th to endNight
15%5%32%31%13%
573
September1st to 15thNight
18%8%33%29%10%
548
16th to endNight
18%9%33%26%9%1
677
October1st to 15thNight
23%12%33%19%8%1
660
16th to endNight
30%20%27%17%3
704
November1st to 15thNight
29%16%28%17%5%1
725
16th to endNight
27%22%26%18%4
750
December1st to 15thNight
31%25%30%11%2
750
16th to endNight
33%25%26%10%3
800
Page generated at 2017-09-21 08:18:17. Version ac04

Copyright 2017 A. Danko


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