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 2018-01-20.

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%
15568
10%
48313
4%
15523
26%
15523
12%
37267

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%
825
5%
2832
1%
821
13%
821
4%
2418
January16th to endNight
10%
790
6%
2569
2%
790
16%
790
6%
2176
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
33%
717
20%
2004
11%
717
40%
717
25%
1337
October1st to 15thNight
27%
720
17%
2160
7%
720
35%
720
20%
1465
October16th to endNight
20%
768
13%
2304
5%
768
27%
768
13%
1696
November1st to 15thNight
20%
798
11%
2636
7%
798
25%
798
11%
2031
November16th to endNight
17%
825
8%
2730
4%
825
22%
825
8%
2210
December1st to 15thNight
7%
825
5%
2730
0%
825
13%
825
5%
2338
December16th to endNight
6%
880
4%
2993
1%
880
10%
880
3%
2652

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%
49210
Night
20%11%5%8%7%34445%25%
48481
TransparencyDay
56%6%11%17%8%
48897
Night
59%6%11%15%6%
48313
SeeingDay
25%17%29%18%7%1
7673
Night
25%17%30%20%5%
15568

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%16%7%12%10%6%5%23412%
1431
16th to endDay
15%14%7%9%12%6%7%34414%
1758
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
15%5%24423347%46%
1956
October1st to 15thDay
18%8%23423446%40%
1800
16th to endDay
20%12%36%5%2435%7%28%
1917
November1st to 15thDay
22%13%46%6%34235%26%
1552
16th to endDay
20%16%7%10%7%3434419%
1560
December1st to 15thDay
23%16%7%12%7%3423313%
1560
16th to endDay
23%16%8%13%10%2333311%
1576
January1st to 15thNight
17%16%8%11%11%43335%14%
2832
16th to endNight
17%13%7%11%11%5%6%435%14%
2569
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%26%42435%6%42%
2004
October1st to 15thNight
17%7%25%5%34446%38%
2160
16th to endNight
23%11%36%42335%6%29%
2304
November1st to 15thNight
23%11%46%6%24345%25%
2636
16th to endNight
21%16%6%7%5%34435%20%
2730
December1st to 15thNight
24%15%6%11%7%34335%14%
2730
16th to endNight
25%16%7%10%10%3333310%
2993

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
1432
16th to endDay
74%5%7%8%3
1758
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
1956
October1st to 15thDay
45%5%12%25%10%
1800
16th to endDay
55%5%11%20%6%
1917
November1st to 15thDay
60%5%12%13%6%
1552
16th to endDay
69%7%10%9%2
1560
December1st to 15thDay
76%48%8%2
1560
16th to endDay
79%49%43
1576
January1st to 15thNight
73%6%9%8%2
2832
16th to endNight
72%5%9%10%1
2569
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%6%12%25%12%
2004
October1st to 15thNight
45%6%12%25%10%
2160
16th to endNight
55%5%11%20%7%
2304
November1st to 15thNight
59%7%11%15%6%
2636
16th to endNight
66%6%12%11%3
2730
December1st to 15thNight
72%6%8%9%2
2730
16th to endNight
77%6%6%7%2
2993

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
18%34%33%13%
163
16th to endDay
24%24%37%10%2
270
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%13%2
308
October1st to 15thDay
23%14%28%21%7%4
270
16th to endDay
26%26%23%15%7%
288
November1st to 15thDay
28%21%25%17%5%2
280
16th to endDay
27%25%28%13%4
285
December1st to 15thDay
34%28%23%12%1
285
16th to endDay
29%33%25%8%1
216
January1st to 15thNight
23%29%32%13%1
825
16th to endNight
23%28%31%13%2
790
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%10%33%27%9%1
717
October1st to 15thNight
21%12%34%21%8%1
720
16th to endNight
29%20%26%18%4
768
November1st to 15thNight
29%17%28%17%5%1
798
16th to endNight
27%22%27%18%4
825
December1st to 15thNight
32%24%30%11%1
825
16th to endNight
32%26%26%10%2
880
Page generated at 2018-01-21 13:19:29. Version ac04

Copyright 2018 A. Danko


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