Gloucester
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gloucester clear sky chart from 2005-11-06 to 2024-01-12.

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
38%
22920
17%
74510
10%
22875
47%
22875
21%
48902

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 10thNight
20%
760
18%
2649
6%
757
34%
757
19%
1673
January11th to 20thNight
19%
728
13%
2546
4%
728
31%
728
13%
1802
January21st to endNight
21%
792
19%
2772
7%
792
36%
792
18%
1775
February1st to 10thNight
20%
720
15%
2283
5%
720
33%
720
16%
1594
February11th to 20thNight
17%
703
19%
2100
5%
700
33%
700
18%
1449
February21st to endNight
23%
592
24%
1776
9%
592
42%
592
23%
1166
March1st to 10thNight
27%
720
20%
2160
10%
720
41%
720
21%
1458
March11th to 20thNight
28%
720
18%
2036
8%
720
38%
720
21%
1432
March21st to endNight
30%
792
21%
2099
8%
792
40%
792
24%
1450
April1st to 10thNight
35%
720
19%
1800
7%
720
41%
720
25%
1291
April11th to 20thNight
41%
665
18%
1729
8%
665
46%
665
27%
1185
April21st to endNight
40%
540
18%
1620
9%
540
46%
540
20%
1124
May1st to 10thNight
42%
540
13%
1620
8%
540
45%
540
18%
1163
May11th to 20thNight
47%
532
15%
1594
11%
532
51%
532
22%
1087
May21st to endNight
54%
404
13%
1566
16%
403
57%
403
18%
1014
June1st to 10thNight
51%
360
13%
1440
18%
360
54%
360
16%
959
June11th to 20thNight
54%
360
13%
1440
20%
360
56%
360
18%
922
June21st to endNight
58%
360
11%
1440
16%
360
60%
360
19%
905
July1st to 10thNight
63%
350
12%
1400
19%
350
64%
350
22%
849
July11th to 20thNight
66%
348
14%
1392
21%
348
66%
348
22%
849
July21st to endNight
66%
394
18%
1486
26%
372
67%
372
24%
892
August1st to 10thNight
69%
524
17%
1587
15%
521
70%
521
31%
970
August11th to 20thNight
63%
532
17%
1596
14%
532
63%
532
23%
1081
August21st to endNight
62%
764
21%
1952
12%
764
64%
764
34%
1253
September1st to 10thNight
60%
720
19%
1829
13%
720
63%
720
35%
1196
September11th to 20thNight
57%
720
24%
1980
17%
720
62%
720
36%
1204
September21st to endNight
55%
720
24%
1980
18%
720
59%
720
32%
1253
October1st to 10thNight
44%
720
17%
1980
11%
720
49%
720
25%
1334
October11th to 20thNight
43%
720
20%
2190
13%
720
52%
720
27%
1373
October21st to endNight
31%
792
15%
2574
8%
792
41%
792
20%
1727
November1st to 10thNight
41%
740
21%
2407
13%
740
51%
740
25%
1496
November11th to 20thNight
29%
760
22%
2470
10%
760
45%
760
24%
1536
November21st to endNight
27%
760
20%
2470
8%
760
41%
760
20%
1567
December1st to 10thNight
20%
760
17%
2588
6%
760
34%
760
17%
1766
December11th to 20thNight
20%
760
16%
3190
4%
758
34%
758
14%
2019
December21st to endNight
20%
828
13%
4769
4%
817
37%
817
10%
3088

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
16%6%25%5%3445%7%42%
74820
Night
17%7%35%5%3445%7%40%
74896
TransparencyDay
41%6%12%23%15%2
74526
Night
44%6%12%21%15%2
74724
SeeingDay
19%419%33%20%5%
13966
Night
20%7%27%30%14%2
22928

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 10thDay
17%7%46%42345%6%42%
1517
11th to 20thDay
20%9%45%32345%7%37%
1454
21st to endDay
15%7%36%5%345%5%7%41%
1584
February1st to 10thDay
21%8%35%5%35%5%6%6%33%
1672
11th to 20thDay
14%8%26%4345%6%8%39%
1748
21st to endDay
17%9%25%5%345%6%6%37%
1480
March1st to 10thDay
17%7%35%43445%9%38%
1797
11th to 20thDay
16%6%36%6%335%5%7%40%
1922
21st to endDay
19%8%25%5%34346%43%
2254
April1st to 10thDay
19%7%35%43445%6%40%
2160
11th to 20thDay
16%7%245%35%45%7%42%
2179
21st to endDay
20%6%25%435%5%5%7%38%
2340
May1st to 10thDay
23%6%35%5%24447%35%
2340
11th to 20thDay
17%6%26%5%3435%6%42%
2301
21st to endDay
14%5%35%4345%49%44%
2724
June1st to 10thDay
19%5%35%5%35%5%6%8%36%
2520
11th to 20thDay
15%6%35%5%345%5%8%41%
2520
21st to endDay
16%5%25%5%35%6%6%9%38%
2520
July1st to 10thDay
12%5%344345%6%9%45%
2520
11th to 20thDay
9%6%35%5%36%6%7%9%43%
2520
21st to endDay
10%425%5%35%5%7%8%45%
2740
August1st to 10thDay
9%4245%36%7%7%9%44%
2327
11th to 20thDay
11%6%25%6%346%6%8%44%
2304
21st to endDay
13%413425%5%6%9%48%
2401
September1st to 10thDay
13%5%25%4245%47%49%
2130
11th to 20thDay
14%6%2233335%5%54%
1980
21st to endDay
16%6%2442435%6%47%
1980
October1st to 10thDay
22%5%24433345%44%
1980
11th to 20thDay
15%6%2443445%8%46%
1764
21st to endDay
22%6%25%4245%45%41%
1782
November1st to 10thDay
17%7%24433346%47%
1671
11th to 20thDay
18%8%24323447%44%
1710
21st to endDay
18%7%24434447%43%
1710
December1st to 10thDay
19%8%45%5%34346%39%
1591
11th to 20thDay
22%7%25%33345%5%40%
1906
21st to endDay
22%10%36%5%24446%32%
2772
January1st to 10thNight
17%8%25%43445%8%39%
2649
11th to 20thNight
21%10%45%5%35%45%6%32%
2546
21st to endNight
15%9%35%5%35%45%8%37%
2772
February1st to 10thNight
18%10%36%5%345%5%7%34%
2283
11th to 20thNight
16%10%35%5%3445%6%38%
2098
21st to endNight
19%8%35%43345%6%42%
1776
March1st to 10thNight
16%9%36%43435%6%39%
2150
11th to 20thNight
17%9%36%5%35%446%37%
2036
21st to endNight
19%8%36%5%33345%42%
2099
April1st to 10thNight
19%8%36%5%345%6%6%36%
1800
11th to 20thNight
20%7%25%5%33446%40%
1729
21st to endNight
20%6%27%6%46%45%5%35%
1620
May1st to 10thNight
22%8%36%6%35%35%6%33%
1620
11th to 20thNight
18%7%25%435%5%6%7%36%
1593
21st to endNight
18%7%46%5%3445%7%38%
1565
June1st to 10thNight
20%7%37%5%35%446%37%
1440
11th to 20thNight
17%8%35%43445%9%37%
1440
21st to endNight
16%6%25%5%3447%9%38%
1440
July1st to 10thNight
14%5%35%6%35%46%8%41%
1440
11th to 20thNight
11%6%27%6%5%5%6%6%9%38%
1440
21st to endNight
14%5%35%5%35%46%8%43%
1574
August1st to 10thNight
8%5%26%6%36%5%7%10%44%
1598
11th to 20thNight
11%7%36%6%36%6%7%9%37%
1596
21st to endNight
13%5%2442445%8%47%
1952
September1st to 10thNight
12%6%345%3345%8%46%
1829
11th to 20thNight
14%5%24423445%54%
1980
21st to endNight
16%5%2442445%7%46%
1980
October1st to 10thNight
21%5%26%433446%41%
1980
11th to 20thNight
15%7%25%43445%7%44%
2190
21st to endNight
23%8%35%5%2345%6%38%
2574
November1st to 10thNight
16%5%25%5%34446%46%
2407
11th to 20thNight
18%7%25%424447%45%
2470
21st to endNight
17%7%344345%5%7%43%
2470
December1st to 10thNight
21%8%35%5%345%5%5%37%
2588
11th to 20thNight
19%8%2443446%7%39%
3288
21st to endNight
21%10%35%5%23446%36%
4884

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 10thDay
43%5%11%26%12%2
1518
11th to 20thDay
47%7%14%20%9%2
1454
21st to endDay
42%5%15%24%13%1
1584
February1st to 10thDay
50%6%14%17%12%2
1672
11th to 20thDay
44%6%14%22%12%2
1757
21st to endDay
46%6%13%19%14%3
1480
March1st to 10thDay
44%6%13%20%13%4
1800
11th to 20thDay
42%5%11%22%16%4
1922
21st to endDay
44%5%10%20%16%5%
2254
April1st to 10thDay
44%5%9%20%18%4
2160
11th to 20thDay
41%6%10%24%15%3
2179
21st to endDay
43%6%10%21%16%3
2340
May1st to 10thDay
49%5%10%21%14%2
2340
11th to 20thDay
43%6%10%21%18%3
2305
21st to endDay
39%7%15%24%13%2
2724
June1st to 10thDay
46%7%13%22%12%1
2520
11th to 20thDay
41%6%13%20%17%2
2520
21st to endDay
41%8%15%23%13%1
2520
July1st to 10thDay
36%7%13%25%16%2
2450
11th to 20thDay
36%8%14%27%13%2
2445
21st to endDay
34%8%15%25%14%3
2587
August1st to 10thDay
32%10%17%28%12%1
2314
11th to 20thDay
37%9%14%25%14%1
2304
21st to endDay
33%7%12%25%20%2
2401
September1st to 10thDay
35%6%12%27%19%1
2130
11th to 20thDay
34%410%27%23%2
1980
21st to endDay
38%410%23%22%2
1980
October1st to 10thDay
43%6%10%24%15%3
1980
11th to 20thDay
37%6%12%30%14%2
1764
21st to endDay
44%5%12%21%14%3
1782
November1st to 10thDay
40%414%24%16%2
1671
11th to 20thDay
41%410%23%20%2
1710
21st to endDay
42%6%16%22%13%1
1710
December1st to 10thDay
48%5%15%15%16%1
1591
11th to 20thDay
47%6%13%16%15%4
1906
21st to endDay
53%5%11%20%10%1
2772
January1st to 10thNight
44%5%15%21%14%2
2649
11th to 20thNight
53%6%14%19%7%2
2546
21st to endNight
45%5%13%19%16%2
2772
February1st to 10thNight
49%7%13%18%11%2
2283
11th to 20thNight
48%5%11%20%13%3
2100
21st to endNight
45%311%24%14%4
1776
March1st to 10thNight
45%6%10%21%15%3
2160
11th to 20thNight
48%6%10%16%16%3
2037
21st to endNight
46%48%18%18%5%
2099
April1st to 10thNight
48%5%10%16%17%3
1800
11th to 20thNight
45%49%21%18%3
1729
21st to endNight
49%6%9%17%16%3
1620
May1st to 10thNight
54%5%9%16%13%3
1620
11th to 20thNight
46%7%12%17%14%4
1594
21st to endNight
46%6%13%19%14%1
1566
June1st to 10thNight
49%7%11%20%12%
1440
11th to 20thNight
45%7%12%19%15%1
1440
21st to endNight
40%10%13%22%13%1
1440
July1st to 10thNight
40%7%14%22%16%1
1400
11th to 20thNight
41%7%14%28%10%1
1392
21st to endNight
38%7%14%27%12%2
1486
August1st to 10thNight
34%8%16%26%14%2
1587
11th to 20thNight
40%11%14%20%14%
1596
21st to endNight
35%7%11%27%20%1
1952
September1st to 10thNight
36%6%13%25%18%1
1829
11th to 20thNight
33%6%10%24%25%2
1980
21st to endNight
36%6%9%26%21%2
1980
October1st to 10thNight
45%5%12%22%14%3
1980
11th to 20thNight
39%6%15%28%12%1
2190
21st to endNight
47%5%12%20%14%2
2574
November1st to 10thNight
40%6%12%22%17%3
2407
11th to 20thNight
41%412%22%18%3
2470
21st to endNight
42%5%15%24%12%2
2470
December1st to 10thNight
49%6%13%20%11%1
2588
11th to 20thNight
45%6%16%16%17%1
3288
21st to endNight
50%6%11%24%10%
4884

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 10thDay
25%7%31%29%7%1
180
11th to 20thDay
18%12%31%29%9%1
164
21st to endDay
20%437%27%11%1
176
February1st to 10thDay
28%10%32%25%5%
354
11th to 20thDay
22%7%43%23%5%
416
21st to endDay
19%8%31%36%6%1
346
March1st to 10thDay
20%8%30%33%10%
420
11th to 20thDay
17%9%31%36%7%
420
21st to endDay
23%5%27%31%10%3
462
April1st to 10thDay
23%6%27%29%13%2
420
11th to 20thDay
20%420%42%13%1
412
21st to endDay
24%317%40%14%2
420
May1st to 10thDay
27%319%35%13%3
423
11th to 20thDay
16%117%41%19%5%
447
21st to endDay
17%211%34%30%7%
485
June1st to 10thDay
19%28%38%27%6%
450
11th to 20thDay
16%39%40%26%6%
450
21st to endDay
15%28%40%29%6%
450
July1st to 10thDay
16%25%31%37%10%
445
11th to 20thDay
11%27%32%38%10%
444
21st to endDay
11%15%36%42%4
488
August1st to 10thDay
10%27%33%41%8%
446
11th to 20thDay
13%26%35%31%13%
439
21st to endDay
13%17%33%36%9%
495
September1st to 10thDay
18%111%29%28%13%
450
11th to 20thDay
20%213%30%26%10%
450
21st to endDay
20%114%35%23%7%
450
October1st to 10thDay
25%118%27%23%6%
450
11th to 20thDay
15%425%28%24%3
384
21st to endDay
26%424%31%13%1
396
November1st to 10thDay
16%6%23%35%18%3
365
11th to 20thDay
23%9%28%29%11%
370
21st to endDay
23%7%30%26%12%2
370
December1st to 10thDay
21%7%38%26%8%
251
11th to 20thDay
21%6%38%29%6%
180
21st to endDay
24%8%31%28%8%1
198
January1st to 10thNight
22%12%41%21%4
760
11th to 20thNight
27%11%37%21%4
728
21st to endNight
18%13%41%23%5%
792
February1st to 10thNight
23%12%37%25%2
720
11th to 20thNight
22%12%44%19%4
703
21st to endNight
22%10%39%23%5%
592
March1st to 10thNight
22%9%38%26%6%
720
11th to 20thNight
22%7%36%27%8%1
720
21st to endNight
22%7%32%26%11%1
792
April1st to 10thNight
24%5%29%32%10%
720
11th to 20thNight
20%327%36%13%
665
21st to endNight
23%324%35%15%1
540
May1st to 10thNight
25%319%38%12%2
540
11th to 20thNight
23%118%39%16%2
532
21st to endNight
22%211%41%21%2
404
June1st to 10thNight
23%212%38%22%4
360
11th to 20thNight
18%411%42%25%1
360
21st to endNight
19%19%43%25%2
360
July1st to 10thNight
15%26%40%33%4
350
11th to 20thNight
14%26%38%36%4
348
21st to endNight
14%27%39%36%3
394
August1st to 10thNight
9%28%41%36%4
524
11th to 20thNight
13%29%41%31%5%
532
21st to endNight
15%112%29%36%7%
764
September1st to 10thNight
14%113%38%29%5%
720
11th to 20thNight
16%416%32%26%7%
720
21st to endNight
18%216%33%25%6%
720
October1st to 10thNight
23%419%29%19%5%
720
11th to 20thNight
18%5%27%33%16%2
720
21st to endNight
25%6%30%29%8%1
792
November1st to 10thNight
18%5%29%33%13%2
740
11th to 20thNight
20%11%34%25%8%1
760
21st to endNight
19%14%34%26%7%1
760
December1st to 10thNight
24%11%38%22%5%
760
11th to 20thNight
23%13%38%22%4
760
21st to endNight
24%13%37%22%3
836
Page generated at 2024-01-09 16:24:25. Version ac07

Copyright 2024 Attilla Danko


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