South Baymouth
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the South Baymouth clear sky chart from 2005-11-05 to 2018-01-12.

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
31%
15792
11%
48326
7%
15751
36%
15751
15%
35735

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
14%
955
3%
2778
1%
951
17%
951
6%
2430
January16th to endNight
19%
888
7%
2616
3%
888
22%
888
8%
2180
February1st to 15thNight
16%
702
6%
2287
1%
701
21%
701
8%
1863
February16th to endNight
24%
631
9%
1958
3%
631
31%
631
12%
1499
March1st to 15thNight
25%
720
13%
2049
6%
720
32%
720
19%
1455
March16th to endNight
37%
768
20%
2112
10%
768
44%
768
26%
1414
April1st to 15thNight
29%
621
16%
1777
7%
621
36%
621
22%
1223
April16th to endNight
35%
540
18%
1620
9%
540
41%
540
23%
1096
May1st to 15thNight
42%
540
13%
1620
11%
540
44%
540
22%
1122
May16th to endNight
47%
376
14%
1441
14%
376
54%
376
22%
860
June1st to 15thNight
44%
360
13%
1260
11%
360
50%
360
22%
788
June16th to endNight
55%
360
11%
1260
11%
360
58%
360
26%
778
July1st to 15thNight
63%
340
16%
1190
16%
340
67%
340
33%
657
July16th to endNight
58%
539
16%
1446
14%
506
59%
506
33%
892
August1st to 15thNight
59%
539
18%
1609
14%
536
63%
536
33%
951
August16th to endNight
59%
573
18%
1719
12%
573
64%
573
31%
1038
September1st to 15thNight
50%
687
15%
1869
10%
687
52%
687
29%
1224
September16th to endNight
48%
717
19%
1980
12%
717
51%
717
28%
1314
October1st to 15thNight
32%
720
13%
2124
10%
720
37%
720
17%
1561
October16th to endNight
21%
768
10%
2394
5%
768
28%
768
11%
1886
November1st to 15thNight
25%
760
12%
2549
10%
760
30%
760
10%
1975
November16th to endNight
16%
780
7%
2730
4%
780
19%
780
6%
2259
December1st to 15thNight
10%
868
2%
2818
0%
868
12%
868
4%
2532
December16th to endNight
10%
1040
5%
3120
1%
1040
14%
1040
5%
2738

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%5%3445%7%35%
49020
Night
16%11%47%6%34446%30%
48490
Cloud CoverDay
14%9%36%5%3445%7%35%
49030
Night
15%10%47%6%34446%31%
48494
TransparencyDay
48%6%13%20%10%
48703
Night
55%6%12%17%8%
48326
SeeingDay
18%9%29%27%11%3
6214
Night
21%11%28%24%11%2
15796

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
20%15%6%8%7%45%447%15%
1403
16th to endDay
14%17%8%8%7%35%45%5%18%
1606
February1st to 15thDay
12%15%5%9%8%5%5%5%46%21%
1575
16th to endDay
13%13%5%11%4345%5%6%26%
1514
March1st to 15thDay
14%9%46%5%3445%7%36%
1900
16th to endDay
12%7%35%435%45%6%40%
2112
April1st to 15thDay
19%8%345%2445%6%35%
2180
16th to endDay
16%6%25%42345%7%39%
2340
May1st to 15thDay
18%7%25%424447%38%
2331
16th to endDay
12%42443445%7%45%
2673
June1st to 15thDay
13%425%5%35%6%5%8%39%
2700
16th to endDay
11%6%245%35%5%7%8%38%
2700
July1st to 15thDay
8%415%43446%7%47%
2700
16th to endDay
9%32342446%10%46%
2619
August1st to 15thDay
9%3245%25%46%8%46%
2340
16th to endDay
9%425%6%35%5%6%7%43%
2483
September1st to 15thDay
11%5%25%4245%6%7%44%
2077
16th to endDay
15%5%245%2345%8%41%
1980
October1st to 15thDay
19%9%25%5%3445%5%34%
1836
16th to endDay
26%9%37%8%34436%23%
1829
November1st to 15thDay
21%10%37%5%25%5%5%7%24%
1637
16th to endDay
24%19%5%8%6%43445%14%
1560
December1st to 15thDay
18%20%9%11%7%5%5%33311%
1469
16th to endDay
20%19%6%9%5%45%35%6%12%
1456
January1st to 15thNight
18%16%7%10%8%45%435%14%
2778
16th to endNight
15%15%7%11%8%34445%19%
2616
February1st to 15thNight
11%16%7%11%7%45%5%5%421%
2285
16th to endNight
13%14%5%8%7%3445%5%25%
1958
March1st to 15thNight
14%10%5%6%5%3335%5%36%
2037
16th to endNight
12%7%25%5%34347%41%
2112
April1st to 15thNight
20%7%35%323347%37%
1777
16th to endNight
16%8%35%43445%6%37%
1620
May1st to 15thNight
15%6%37%6%45%445%34%
1620
16th to endNight
11%6%35%5%345%5%8%42%
1439
June1st to 15thNight
12%7%25%435%5%6%7%38%
1260
16th to endNight
9%5%25%5%25%5%6%10%40%
1260
July1st to 15thNight
8%323435%5%5%8%50%
1260
16th to endNight
7%425%5%2445%7%49%
1545
August1st to 15thNight
7%324425%5%6%7%49%
1620
16th to endNight
9%5%25%43435%8%47%
1719
September1st to 15thNight
13%41443345%7%45%
1869
16th to endNight
13%6%25%43435%8%42%
1980
October1st to 15thNight
21%7%36%6%33446%31%
2124
16th to endNight
26%9%35%6%24446%25%
2394
November1st to 15thNight
20%12%36%6%35%5%46%23%
2549
16th to endNight
23%17%5%7%6%34335%17%
2730
December1st to 15thNight
21%19%9%10%7%4444410%
2818
16th to endNight
23%18%6%10%6%44345%12%
3120

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%16%5%9%6%346%45%19%
1403
16th to endDay
14%17%8%9%7%35%345%20%
1606
February1st to 15thDay
12%14%6%9%8%35%5%5%5%22%
1575
16th to endDay
12%15%6%10%5%35%445%26%
1514
March1st to 15thDay
14%9%47%4235%46%37%
1911
16th to endDay
11%8%36%5%3445%5%40%
2111
April1st to 15thDay
19%8%35%5%24445%35%
2180
16th to endDay
17%8%2442435%6%39%
2340
May1st to 15thDay
18%7%25%424447%39%
2331
16th to endDay
12%424434447%46%
2673
June1st to 15thDay
13%434435%5%6%8%39%
2700
16th to endDay
12%5%25%5%35%5%6%9%38%
2700
July1st to 15thDay
8%5%25%5%245%5%8%47%
2700
16th to endDay
9%323425%5%6%9%46%
2619
August1st to 15thDay
10%5%15%43345%8%46%
2340
16th to endDay
11%436%4346%5%8%42%
2483
September1st to 15thDay
11%5%243335%5%7%44%
2077
16th to endDay
14%6%3442446%8%40%
1980
October1st to 15thDay
19%8%25%5%245%46%35%
1836
16th to endDay
26%9%48%5%33435%24%
1829
November1st to 15thDay
20%10%37%5%35%5%47%26%
1637
16th to endDay
23%19%48%6%35%34416%
1560
December1st to 15thDay
17%22%7%9%6%45%44412%
1469
16th to endDay
19%19%5%10%5%45%445%15%
1456
January1st to 15thNight
17%16%6%10%7%45%345%17%
2778
16th to endNight
14%15%6%9%8%34436%21%
2616
February1st to 15thNight
11%15%6%10%7%45%5%5%5%23%
2278
16th to endNight
13%14%5%8%6%25%46%6%26%
1958
March1st to 15thNight
14%10%47%5%24345%37%
2049
16th to endNight
11%8%35%5%34347%42%
2112
April1st to 15thNight
20%8%25%5%2335%6%37%
1777
16th to endNight
15%8%35%6%3435%7%36%
1620
May1st to 15thNight
15%7%35%7%35%446%34%
1619
16th to endNight
11%6%25%5%245%48%42%
1439
June1st to 15thNight
12%6%36%4245%6%7%38%
1260
16th to endNight
9%5%25%6%26%5%6%9%40%
1260
July1st to 15thNight
9%223435%45%9%49%
1260
16th to endNight
6%425%6%34448%49%
1545
August1st to 15thNight
7%3246%3445%7%49%
1620
16th to endNight
9%5%25%434448%48%
1719
September1st to 15thNight
13%4245%2245%8%46%
1869
16th to endNight
13%5%25%5%24447%44%
1980
October1st to 15thNight
21%6%35%5%345%46%33%
2124
16th to endNight
25%10%36%5%2445%6%26%
2394
November1st to 15thNight
18%11%46%7%35%45%7%26%
2549
16th to endNight
22%15%5%7%6%34446%18%
2730
December1st to 15thNight
20%18%7%10%6%44445%13%
2818
16th to endNight
22%17%6%9%6%34445%16%
3120

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
71%8%10%8%1
1404
16th to endDay
70%5%12%8%2
1606
February1st to 15thDay
64%8%12%11%3
1577
16th to endDay
57%7%15%14%5%
1514
March1st to 15thDay
47%5%14%20%10%
1911
16th to endDay
42%6%14%20%13%2
2112
April1st to 15thDay
48%5%11%21%12%1
2180
16th to endDay
43%412%23%13%2
2340
May1st to 15thDay
45%410%21%15%2
2331
16th to endDay
37%6%16%22%17%
2677
June1st to 15thDay
40%6%14%25%11%1
2700
16th to endDay
40%8%13%24%12%
2700
July1st to 15thDay
31%7%13%30%15%1
2541
16th to endDay
32%8%16%27%14%
2456
August1st to 15thDay
32%7%20%26%13%
2327
16th to endDay
35%9%16%27%9%
2483
September1st to 15thDay
36%8%17%28%8%
2077
16th to endDay
40%8%16%26%8%
1980
October1st to 15thDay
51%5%11%18%12%
1836
16th to endDay
64%5%12%11%5%
1829
November1st to 15thDay
58%8%12%15%5%
1637
16th to endDay
73%5%10%7%3
1560
December1st to 15thDay
80%48%32
1469
16th to endDay
75%7%8%8%
1456
January1st to 15thNight
73%7%9%7%1
2778
16th to endNight
69%5%12%9%3
2616
February1st to 15thNight
67%6%10%12%3
2287
16th to endNight
58%7%14%12%6%
1958
March1st to 15thNight
50%5%14%20%8%1
2049
16th to endNight
42%5%11%20%16%3
2112
April1st to 15thNight
47%49%21%14%1
1777
16th to endNight
45%5%8%19%18%2
1620
May1st to 15thNight
49%410%19%13%2
1620
16th to endNight
39%6%13%21%16%2
1441
June1st to 15thNight
41%6%10%24%15%1
1260
16th to endNight
37%8%16%23%14%
1260
July1st to 15thNight
29%7%13%28%19%2
1190
16th to endNight
34%6%14%26%18%
1446
August1st to 15thNight
31%8%16%29%12%2
1609
16th to endNight
34%6%17%28%11%1
1719
September1st to 15thNight
38%7%15%26%10%1
1869
16th to endNight
39%7%15%28%9%
1980
October1st to 15thNight
55%410%19%10%
2124
16th to endNight
61%6%12%14%4
2394
November1st to 15thNight
61%6%11%15%4
2549
16th to endNight
70%5%12%9%2
2730
December1st to 15thNight
78%6%7%41
2818
16th to endNight
76%5%8%7%1
3120

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
27%17%38%15%1
96
16th to endDay
36%8%29%16%9%
96
February1st to 15thDay
28%25%33%12%
90
16th to endDay
29%18%38%12%1
81
March1st to 15thDay
23%13%34%20%5%
201
16th to endDay
20%11%30%25%8%3
288
April1st to 15thDay
24%10%26%28%9%1
270
16th to endDay
23%8%36%16%10%4
270
May1st to 15thDay
23%7%28%26%11%2
288
16th to endDay
14%6%31%29%14%2
388
June1st to 15thDay
15%7%32%28%14%1
495
16th to endDay
14%5%30%34%12%2
495
July1st to 15thDay
9%429%37%15%3
475
16th to endDay
9%330%38%12%4
455
August1st to 15thDay
10%220%40%17%7%
313
16th to endDay
14%5%23%31%19%5%
332
September1st to 15thDay
13%422%30%19%9%
315
16th to endDay
18%5%25%28%16%5%
314
October1st to 15thDay
21%13%27%25%10%1
315
16th to endDay
25%19%35%14%4
245
November1st to 15thDay
27%18%29%21%2
116
16th to endDay
27%24%36%8%2
90
December1st to 15thDay
25%32%31%8%2
90
16th to endDay
30%30%35%31
96
January1st to 15thNight
25%20%30%18%3
956
16th to endNight
24%13%30%24%6%1
888
February1st to 15thNight
19%17%35%20%5%
704
16th to endNight
20%11%35%24%7%
631
March1st to 15thNight
20%15%33%23%6%
720
16th to endNight
16%8%31%29%12%1
768
April1st to 15thNight
24%9%33%24%7%1
621
16th to endNight
21%6%31%24%14%2
540
May1st to 15thNight
18%425%30%18%3
540
16th to endNight
15%5%23%33%19%1
377
June1st to 15thNight
15%426%34%16%2
360
16th to endNight
10%320%39%23%2
360
July1st to 15thNight
10%120%40%23%3
340
16th to endNight
8%123%35%28%3
539
August1st to 15thNight
8%219%38%26%4
539
16th to endNight
12%219%32%27%5%
573
September1st to 15thNight
15%5%23%26%17%11%
687
16th to endNight
16%5%25%27%18%6%
717
October1st to 15thNight
24%10%26%24%13%1
720
16th to endNight
30%14%27%20%5%
768
November1st to 15thNight
26%16%27%20%7%
760
16th to endNight
32%17%25%18%6%
780
December1st to 15thNight
30%20%31%12%4
868
16th to endNight
32%17%31%13%4
1040
Page generated at 2018-01-12 22:01:27. Version ac04

Copyright 2018 A. Danko


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