Long Point Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Long Point Observatory clear sky chart from 2005-11-05 to 2017-12-20.

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
36%
15318
15%
48117
10%
15281
42%
15281
19%
33224

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
10%
2398
4%
716
21%
716
8%
1920
January16th to endNight
15%
768
10%
2496
3%
768
23%
768
9%
1966
February1st to 15thNight
18%
702
9%
2287
2%
701
25%
701
9%
1810
February16th to endNight
25%
631
12%
1982
5%
631
32%
631
14%
1480
March1st to 15thNight
27%
720
15%
1986
8%
720
33%
720
17%
1484
March16th to endNight
35%
768
20%
2112
11%
768
42%
768
23%
1468
April1st to 15thNight
30%
718
15%
1848
7%
718
35%
718
22%
1332
April16th to endNight
43%
543
21%
1623
10%
543
50%
543
26%
1034
May1st to 15thNight
43%
540
16%
1620
11%
540
48%
540
24%
1069
May16th to endNight
50%
396
18%
1519
18%
396
58%
396
26%
866
June1st to 15thNight
49%
360
14%
1440
15%
360
56%
360
22%
853
June16th to endNight
57%
360
14%
1440
17%
360
63%
360
24%
843
July1st to 15thNight
66%
351
17%
1371
23%
351
70%
351
32%
702
July16th to endNight
64%
564
16%
1595
14%
531
67%
531
36%
911
August1st to 15thNight
69%
539
18%
1609
15%
536
71%
536
36%
926
August16th to endNight
63%
609
24%
1755
16%
609
67%
609
37%
1016
September1st to 15thNight
57%
720
23%
1854
13%
720
61%
720
34%
1192
September16th to endNight
58%
717
25%
1980
19%
717
62%
717
33%
1216
October1st to 15thNight
46%
720
20%
2158
18%
720
50%
720
25%
1397
October16th to endNight
25%
768
16%
2304
8%
768
34%
768
17%
1658
November1st to 15thNight
36%
760
20%
2525
14%
760
45%
760
20%
1668
November16th to endNight
22%
780
12%
2730
7%
780
29%
780
11%
2004
December1st to 15thNight
14%
780
8%
2730
4%
780
20%
780
8%
2155
December16th to endNight
12%
788
8%
2755
2%
788
19%
788
7%
2254

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%8%36%6%35%5%5%7%33%
48715
Night
15%8%46%5%3445%7%34%
48301
Cloud CoverDay
14%8%36%5%35%5%5%7%34%
48725
Night
16%8%36%5%3445%6%34%
48305
TransparencyDay
48%5%13%21%10%1
48417
Night
49%411%21%11%1
48117
SeeingDay
17%6%23%27%17%7%
5629
Night
20%8%26%28%14%2
15325

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%13%5%9%6%35%45%7%18%
1537
16th to endDay
15%15%6%12%8%46%446%15%
1728
February1st to 15thDay
17%14%6%10%9%45%445%18%
1575
16th to endDay
17%11%6%9%7%35%45%6%20%
1489
March1st to 15thDay
17%12%5%8%7%34447%25%
1963
16th to endDay
16%9%5%6%6%35%346%31%
2112
April1st to 15thDay
18%9%47%5%3435%6%30%
2107
16th to endDay
16%7%35%423447%39%
2340
May1st to 15thDay
15%5%25%7%35%45%7%36%
2331
16th to endDay
11%5%24426%449%42%
2596
June1st to 15thDay
12%5%25%5%25%5%5%8%40%
2520
16th to endDay
10%415%4246%6%10%41%
2520
July1st to 15thDay
7%4245%25%5%6%10%44%
2505
16th to endDay
8%4246%36%6%7%10%39%
2465
August1st to 15thDay
7%4245%36%7%8%9%41%
2340
16th to endDay
9%5%25%425%46%8%44%
2434
September1st to 15thDay
12%5%145%3446%8%41%
2104
16th to endDay
13%415%425%5%5%7%42%
1980
October1st to 15thDay
17%5%27%6%345%46%34%
1801
16th to endDay
21%10%36%6%3445%7%25%
1920
November1st to 15thDay
14%7%36%6%3445%7%37%
1660
16th to endDay
21%11%36%5%345%6%7%23%
1560
December1st to 15thDay
18%15%6%9%6%3445%6%19%
1560
16th to endDay
22%16%6%8%7%345%45%14%
1568
January1st to 15thNight
22%12%5%9%6%34345%21%
2398
16th to endNight
14%14%7%9%7%35%5%5%6%21%
2496
February1st to 15thNight
15%15%6%8%7%35%445%23%
2285
16th to endNight
17%11%5%8%7%2445%7%24%
1982
March1st to 15thNight
18%8%46%6%345%47%28%
1974
16th to endNight
16%8%36%42445%5%37%
2112
April1st to 15thNight
21%7%44435%446%34%
1848
16th to endNight
11%5%25%5%46%45%7%41%
1623
May1st to 15thNight
16%5%36%43447%8%35%
1620
16th to endNight
10%5%25%42446%8%45%
1517
June1st to 15thNight
10%6%26%5%2445%9%41%
1440
16th to endNight
9%425%6%35%5%6%9%40%
1440
July1st to 15thNight
6%313424449%52%
1452
16th to endNight
6%414435%46%8%48%
1703
August1st to 15thNight
6%3135%345%6%10%47%
1620
16th to endNight
9%3145%3335%7%52%
1755
September1st to 15thNight
12%5%34323447%47%
1854
16th to endNight
11%425%43345%6%48%
1980
October1st to 15thNight
17%5%35%32335%6%42%
2158
16th to endNight
20%8%36%5%3445%6%31%
2304
November1st to 15thNight
15%7%35%4345%5%8%36%
2525
16th to endNight
19%12%35%5%35%45%7%27%
2730
December1st to 15thNight
21%15%6%7%5%2345%6%20%
2730
16th to endNight
22%13%7%9%7%34446%17%
2755

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%13%5%9%7%36%45%6%19%
1537
16th to endDay
14%15%5%12%8%45%6%46%15%
1728
February1st to 15thDay
17%15%5%10%7%45%445%18%
1575
16th to endDay
17%10%7%9%7%35%45%6%21%
1489
March1st to 15thDay
17%12%48%6%44446%26%
1974
16th to endDay
17%8%5%6%6%36%435%31%
2111
April1st to 15thDay
18%9%46%5%3445%6%31%
2107
16th to endDay
16%7%25%433446%40%
2340
May1st to 15thDay
15%5%25%6%35%45%7%37%
2331
16th to endDay
11%5%24435%45%8%43%
2596
June1st to 15thDay
12%5%25%5%3445%9%41%
2520
16th to endDay
10%4244345%7%9%42%
2520
July1st to 15thDay
8%4144345%6%9%47%
2505
16th to endDay
8%4135%36%6%8%10%41%
2465
August1st to 15thDay
8%314446%6%7%10%42%
2340
16th to endDay
9%425%4235%6%8%47%
2434
September1st to 15thDay
12%5%245%345%5%8%41%
2104
16th to endDay
14%5%24435%45%6%43%
1980
October1st to 15thDay
17%6%25%6%445%47%34%
1801
16th to endDay
23%9%37%5%3445%7%24%
1920
November1st to 15thDay
14%7%26%6%3435%8%36%
1660
16th to endDay
22%11%37%5%35%5%5%7%23%
1560
December1st to 15thDay
18%15%6%8%6%26%5%46%17%
1560
16th to endDay
22%16%6%8%7%35%44415%
1568
January1st to 15thNight
23%12%5%8%6%4444421%
2398
16th to endNight
14%15%7%9%8%35%5%5%5%21%
2496
February1st to 15thNight
15%15%5%9%7%35%445%22%
2278
16th to endNight
17%10%5%9%6%35%45%7%24%
1982
March1st to 15thNight
19%8%47%5%345%47%28%
1986
16th to endNight
16%8%46%424445%37%
2112
April1st to 15thNight
21%8%34434436%34%
1848
16th to endNight
12%425%5%36%45%7%41%
1623
May1st to 15thNight
17%5%36%4435%6%8%35%
1619
16th to endNight
10%5%25%5%2436%8%45%
1517
June1st to 15thNight
11%5%25%5%25%45%9%41%
1440
16th to endNight
9%5%25%6%445%6%9%41%
1440
July1st to 15thNight
6%412435%45%9%52%
1452
16th to endNight
6%315%4345%6%8%48%
1703
August1st to 15thNight
7%2144346%7%9%47%
1620
16th to endNight
9%32343435%7%52%
1755
September1st to 15thNight
13%5%24323446%48%
1854
16th to endNight
12%425%42336%6%48%
1980
October1st to 15thNight
18%5%15%42335%6%41%
2158
16th to endNight
21%7%35%43445%6%31%
2304
November1st to 15thNight
16%7%26%435%5%5%7%36%
2525
16th to endNight
20%12%35%6%35%45%7%26%
2730
December1st to 15thNight
22%16%6%6%5%3445%6%19%
2730
16th to endNight
22%14%7%9%7%34346%17%
2755

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
65%410%12%5%
1538
16th to endDay
69%5%9%11%3
1728
February1st to 15thDay
67%410%13%4
1577
16th to endDay
62%410%16%5%
1489
March1st to 15thDay
60%412%17%4
1974
16th to endDay
54%48%21%8%1
2112
April1st to 15thDay
53%411%19%10%
2107
16th to endDay
44%411%21%15%2
2340
May1st to 15thDay
45%412%23%13%
2331
16th to endDay
38%5%14%25%14%1
2600
June1st to 15thDay
40%6%13%25%12%1
2520
16th to endDay
35%7%16%24%15%
2520
July1st to 15thDay
32%5%13%28%18%2
2357
16th to endDay
36%7%18%24%12%1
2310
August1st to 15thDay
33%7%17%26%12%1
2327
16th to endDay
34%416%28%13%2
2434
September1st to 15thDay
39%5%14%27%12%
2104
16th to endDay
40%5%14%26%13%
1980
October1st to 15thDay
49%412%19%12%1
1801
16th to endDay
57%5%14%15%5%
1920
November1st to 15thDay
46%5%14%22%9%1
1660
16th to endDay
58%6%13%15%5%
1560
December1st to 15thDay
66%6%12%12%2
1560
16th to endDay
72%49%11%1
1568
January1st to 15thNight
67%47%10%8%
2398
16th to endNight
64%5%9%14%5%
2496
February1st to 15thNight
64%5%9%13%6%
2287
16th to endNight
59%311%19%6%
1982
March1st to 15thNight
55%410%20%7%1
1986
16th to endNight
48%49%22%13%2
2112
April1st to 15thNight
51%39%20%13%
1848
16th to endNight
41%49%21%19%4
1623
May1st to 15thNight
45%311%25%12%2
1620
16th to endNight
36%412%24%17%3
1519
June1st to 15thNight
40%5%10%26%14%1
1440
16th to endNight
38%5%12%23%17%1
1440
July1st to 15thNight
29%410%28%23%3
1371
16th to endNight
31%5%15%27%17%3
1595
August1st to 15thNight
29%6%16%31%14%1
1609
16th to endNight
31%412%31%17%2
1755
September1st to 15thNight
35%5%11%28%16%2
1854
16th to endNight
35%411%30%17%1
1980
October1st to 15thNight
42%49%24%17%
2158
16th to endNight
53%412%20%9%
2304
November1st to 15thNight
45%5%11%22%12%1
2525
16th to endNight
57%5%12%18%6%
2730
December1st to 15thNight
65%5%11%12%5%
2730
16th to endNight
69%5%10%11%3
2755

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
24%18%38%7%9%1
77
16th to endDay
29%14%35%18%2
96
February1st to 15thDay
18%12%53%14%1
90
16th to endDay
18%16%35%27%2
81
March1st to 15thDay
26%7%26%29%9%
264
16th to endDay
22%5%34%26%11%
288
April1st to 15thDay
21%10%32%24%8%2
270
16th to endDay
17%433%25%12%7%
270
May1st to 15thDay
21%6%22%27%15%5%
288
16th to endDay
13%325%32%18%6%
331
June1st to 15thDay
14%220%39%18%4
315
16th to endDay
15%224%33%19%5%
315
July1st to 15thDay
11%315%31%26%10%
305
16th to endDay
9%117%34%25%11%
326
August1st to 15thDay
8%114%33%30%11%
313
16th to endDay
13%413%26%26%16%
332
September1st to 15thDay
9%216%26%30%13%
315
16th to endDay
15%214%22%24%19%
314
October1st to 15thDay
19%6%20%26%19%8%
315
16th to endDay
25%12%29%23%8%1
336
November1st to 15thDay
19%8%28%25%13%2
136
16th to endDay
25%14%31%20%7%1
90
December1st to 15thDay
18%28%24%20%7%
90
16th to endDay
30%29%27%12%
72
January1st to 15thNight
30%15%31%17%4
720
16th to endNight
23%13%35%22%5%
768
February1st to 15thNight
24%13%33%24%4
704
16th to endNight
23%9%30%30%6%
631
March1st to 15thNight
23%8%30%28%8%
720
16th to endNight
21%5%31%29%11%1
768
April1st to 15thNight
24%7%31%27%8%
718
16th to endNight
15%6%28%34%12%2
543
May1st to 15thNight
20%422%34%16%2
540
16th to endNight
13%223%33%21%4
397
June1st to 15thNight
14%123%38%20%
360
16th to endNight
10%318%43%23%
360
July1st to 15thNight
7%118%38%28%4
351
16th to endNight
10%15%41%26%5%
564
August1st to 15thNight
8%112%38%31%6%
539
16th to endNight
11%115%32%32%7%
609
September1st to 15thNight
15%315%31%27%6%
720
16th to endNight
14%415%27%29%9%
717
October1st to 15thNight
20%6%19%27%20%3
720
16th to endNight
25%10%32%24%5%
768
November1st to 15thNight
20%9%27%28%12%1
760
16th to endNight
27%16%28%18%8%1
780
December1st to 15thNight
33%15%30%16%4
780
16th to endNight
29%13%34%19%2
788
Page generated at 2017-12-21 07:04:47. Version ac04

Copyright 2017 A. Danko


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