Gloucester
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gloucester clear sky chart from 2005-11-05 to 2017-09-17.

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%
14886
17%
46810
10%
14853
46%
14853
22%
31033

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
20%
720
15%
2506
6%
716
32%
716
17%
1659
January16th to endNight
16%
768
17%
2688
4%
768
32%
768
15%
1782
February1st to 15thNight
19%
704
14%
2193
3%
701
31%
701
17%
1538
February16th to endNight
23%
631
21%
1893
8%
631
40%
631
21%
1269
March1st to 15thNight
27%
720
16%
2138
8%
720
37%
720
19%
1498
March16th to endNight
29%
768
21%
2058
9%
768
39%
768
24%
1412
April1st to 15thNight
38%
718
18%
1796
7%
718
43%
718
25%
1277
April16th to endNight
42%
567
18%
1647
8%
567
48%
567
23%
1133
May1st to 15thNight
44%
540
14%
1620
9%
540
48%
540
20%
1141
May16th to endNight
50%
440
11%
1562
12%
439
53%
439
18%
1050
June1st to 15thNight
48%
360
12%
1440
16%
360
50%
360
15%
981
June16th to endNight
62%
360
11%
1440
17%
360
63%
360
21%
884
July1st to 15thNight
66%
340
12%
1360
19%
340
67%
340
23%
803
July16th to endNight
67%
376
14%
1418
21%
354
68%
354
21%
900
August1st to 15thNight
66%
530
16%
1600
14%
527
66%
527
29%
1006
August16th to endNight
63%
687
21%
1833
13%
687
65%
687
32%
1176
September1st to 15thNight
60%
720
19%
1880
13%
720
63%
720
35%
1206
September16th to endNight
60%
665
27%
1836
21%
665
64%
665
37%
1101
October1st to 15thNight
42%
660
21%
1840
13%
660
50%
660
27%
1197
October16th to endNight
32%
704
15%
2282
7%
704
43%
704
22%
1482
November1st to 15thNight
36%
700
18%
2277
10%
700
46%
700
22%
1482
November16th to endNight
30%
720
17%
2340
9%
720
41%
720
19%
1530
December1st to 15thNight
21%
720
16%
2475
5%
720
35%
720
17%
1672
December16th to endNight
17%
768
16%
2688
4%
768
31%
768
15%
1854

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%5%2442445%7%41%
47968
Night
17%6%25%424446%39%
46981
Cloud CoverDay
16%6%2442445%7%41%
47978
Night
17%7%25%42445%6%39%
46986
TransparencyDay
41%6%12%22%14%2
47657
Night
44%5%12%20%14%1
46810
SeeingDay
20%318%32%20%4
5936
Night
20%6%27%29%14%2
14886

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
17%7%3331245%7%40%
1432
16th to endDay
16%6%35%423347%41%
1536
February1st to 15thDay
19%6%244245%6%7%34%
1664
16th to endDay
14%8%244245%6%6%39%
1580
March1st to 15thDay
20%7%35%42436%7%34%
1811
16th to endDay
17%6%24424336%43%
2163
April1st to 15thDay
17%5%23435%446%41%
2152
16th to endDay
17%414324447%43%
2312
May1st to 15thDay
24%6%36%423345%35%
2332
16th to endDay
16%5%2442445%7%41%
2562
June1st to 15thDay
23%5%2432446%6%35%
2520
16th to endDay
14%4245%246%6%8%40%
2520
July1st to 15thDay
11%5%24325%46%10%43%
2520
16th to endDay
11%4244346%6%8%42%
2651
August1st to 15thDay
10%4144246%6%9%43%
2340
16th to endDay
11%312425%5%5%8%49%
2366
September1st to 15thDay
12%5%13413347%49%
2079
16th to endDay
13%424323346%53%
1830
October1st to 15thDay
20%5%14423246%44%
1789
16th to endDay
17%6%14424446%42%
1587
November1st to 15thDay
22%7%24323335%41%
1581
16th to endDay
17%7%34323437%41%
1620
December1st to 15thDay
19%7%35%433346%38%
1485
16th to endDay
23%10%24324445%32%
1536
January1st to 15thNight
17%7%35%42345%7%37%
2506
16th to endNight
18%9%3442435%7%35%
2688
February1st to 15thNight
15%9%36%5%24448%34%
2192
16th to endNight
17%8%34423346%40%
1893
March1st to 15thNight
19%7%26%334346%36%
2125
16th to endNight
17%7%25%5%2333443%
2058
April1st to 15thNight
17%8%345%2445%5%38%
1796
16th to endNight
20%426%6%3343438%
1647
May1st to 15thNight
21%7%25%5%34346%34%
1620
16th to endNight
20%6%345%25%36%6%35%
1560
June1st to 15thNight
24%6%25%424337%33%
1440
16th to endNight
15%5%1443446%8%40%
1440
July1st to 15thNight
11%5%35%6%3445%8%41%
1440
16th to endNight
13%435%5%36%5%5%8%39%
1514
August1st to 15thNight
8%5%25%5%36%5%6%8%42%
1611
16th to endNight
12%5%2442445%8%45%
1833
September1st to 15thNight
12%42443345%6%49%
1880
16th to endNight
13%413323345%53%
1836
October1st to 15thNight
19%415%423346%44%
1840
16th to endNight
19%7%24423346%41%
2282
November1st to 15thNight
18%5%25%424436%41%
2277
16th to endNight
17%8%24423446%40%
2340
December1st to 15thNight
19%6%35%4245%5%6%36%
2475
16th to endNight
20%10%34423346%34%
2688

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
17%8%4332346%7%39%
1432
16th to endDay
16%7%25%43335%6%41%
1536
February1st to 15thDay
19%7%244345%5%7%34%
1664
16th to endDay
14%8%24425%45%7%39%
1580
March1st to 15thDay
21%7%25%43346%7%34%
1821
16th to endDay
17%6%25%424345%43%
2163
April1st to 15thDay
17%5%24435%35%6%40%
2152
16th to endDay
17%41432435%7%43%
2312
May1st to 15thDay
23%6%25%423436%35%
2332
16th to endDay
16%5%25%42445%8%40%
2562
June1st to 15thDay
23%43342445%7%34%
2520
16th to endDay
14%4245%25%5%6%8%40%
2520
July1st to 15thDay
10%5%234345%6%9%43%
2520
16th to endDay
10%434425%5%7%9%42%
2651
August1st to 15thDay
10%4244345%7%9%43%
2340
16th to endDay
11%312425%5%5%8%49%
2366
September1st to 15thDay
12%5%23423347%49%
2079
16th to endDay
13%414323345%52%
1830
October1st to 15thDay
19%5%24323346%43%
1789
16th to endDay
17%5%2442445%6%42%
1587
November1st to 15thDay
21%8%23323245%41%
1581
16th to endDay
17%7%24323437%42%
1620
December1st to 15thDay
19%7%35%433346%38%
1485
16th to endDay
23%10%343245%45%32%
1536
January1st to 15thNight
17%7%35%42335%8%37%
2506
16th to endNight
17%9%3442435%7%36%
2688
February1st to 15thNight
15%8%46%6%2445%7%34%
2185
16th to endNight
17%8%2343335%6%40%
1893
March1st to 15thNight
19%7%35%425%346%36%
2138
16th to endNight
17%7%345%2343442%
2057
April1st to 15thNight
17%8%35%5%34445%37%
1796
16th to endNight
19%5%26%6%3434438%
1647
May1st to 15thNight
20%7%25%5%4435%5%34%
1620
16th to endNight
20%6%25%42446%6%35%
1560
June1st to 15thNight
24%7%25%424347%33%
1440
16th to endNight
15%5%25%5%2446%9%40%
1440
July1st to 15thNight
10%5%26%5%345%5%8%41%
1440
16th to endNight
12%426%6%36%5%6%8%37%
1514
August1st to 15thNight
8%5%25%5%36%5%6%8%42%
1611
16th to endNight
11%5%245%2445%8%45%
1833
September1st to 15thNight
13%41442445%6%48%
1880
16th to endNight
13%412323446%53%
1836
October1st to 15thNight
19%415%423346%43%
1840
16th to endNight
18%7%24423446%40%
2282
November1st to 15thNight
17%5%25%424446%41%
2277
16th to endNight
17%7%34433347%40%
2340
December1st to 15thNight
19%7%35%42445%6%37%
2475
16th to endNight
20%10%34434346%34%
2688

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
43%6%13%24%9%2
1433
16th to endDay
44%414%24%11%
1536
February1st to 15thDay
48%7%13%18%10%
1667
16th to endDay
42%5%14%21%13%1
1580
March1st to 15thDay
47%6%13%18%11%2
1821
16th to endDay
41%411%22%14%4
2163
April1st to 15thDay
42%410%22%16%3
2152
16th to endDay
39%5%9%24%16%3
2312
May1st to 15thDay
50%48%18%15%2
2332
16th to endDay
41%7%14%22%12%1
2566
June1st to 15thDay
48%6%13%19%10%1
2520
16th to endDay
39%7%14%21%15%1
2520
July1st to 15thDay
35%7%14%25%15%1
2371
16th to endDay
35%8%14%24%13%2
2484
August1st to 15thDay
33%9%16%26%13%1
2327
16th to endDay
31%7%12%27%19%1
2366
September1st to 15thDay
34%6%12%23%22%1
2079
16th to endDay
33%39%26%24%2
1830
October1st to 15thDay
41%5%10%24%15%2
1789
16th to endDay
42%411%25%14%2
1587
November1st to 15thDay
46%312%22%14%1
1581
16th to endDay
43%6%12%21%14%1
1620
December1st to 15thDay
48%415%15%15%
1485
16th to endDay
54%5%12%17%9%
1536
January1st to 15thNight
46%6%16%18%10%1
2506
16th to endNight
48%412%19%12%1
2688
February1st to 15thNight
48%7%14%18%9%1
2193
16th to endNight
45%411%22%13%2
1893
March1st to 15thNight
48%6%10%19%13%2
2138
16th to endNight
44%5%8%18%18%4
2058
April1st to 15thNight
47%49%18%17%2
1796
16th to endNight
48%48%18%16%3
1647
May1st to 15thNight
51%411%15%14%3
1620
16th to endNight
47%7%13%18%10%1
1562
June1st to 15thNight
51%5%11%18%11%
1440
16th to endNight
39%9%12%21%15%1
1440
July1st to 15thNight
38%6%14%25%14%
1360
16th to endNight
41%8%13%24%10%2
1418
August1st to 15thNight
36%7%13%24%15%2
1600
16th to endNight
35%7%10%26%18%
1833
September1st to 15thNight
34%6%12%24%20%1
1880
16th to endNight
32%5%7%26%26%2
1836
October1st to 15thNight
42%412%23%15%3
1840
16th to endNight
44%5%13%22%13%
2282
November1st to 15thNight
44%5%13%20%14%2
2277
16th to endNight
45%5%14%20%12%2
2340
December1st to 15thNight
47%6%15%19%10%
2475
16th to endNight
49%6%13%19%10%
2688

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
16%10%33%35%5%
60
16th to endDay
25%6%32%29%6%
64
February1st to 15thDay
26%9%36%24%2
242
16th to endDay
15%7%39%28%8%
239
March1st to 15thDay
22%6%36%27%7%
270
16th to endDay
21%6%31%28%11%1
288
April1st to 15thDay
22%425%32%14%
270
16th to endDay
21%217%40%13%4
270
May1st to 15thDay
30%219%27%14%5%
288
16th to endDay
20%110%37%24%4
331
June1st to 15thDay
24%18%36%25%3
315
16th to endDay
15%9%44%26%3
315
July1st to 15thDay
17%6%33%34%8%
305
16th to endDay
12%5%34%39%6%
326
August1st to 15thDay
13%7%33%38%6%
313
16th to endDay
13%5%34%29%15%
332
September1st to 15thDay
17%13%32%26%10%
315
16th to endDay
19%12%33%20%13%
259
October1st to 15thDay
24%120%26%22%6%
250
16th to endDay
19%5%30%31%11%
240
November1st to 15thDay
26%5%21%29%14%1
235
16th to endDay
25%8%25%27%10%2
240
December1st to 15thDay
21%6%35%26%8%
105
16th to endDay
29%135%29%3
64
January1st to 15thNight
23%11%40%20%3
720
16th to endNight
22%14%40%20%2
768
February1st to 15thNight
20%11%42%24%2
704
16th to endNight
22%10%39%21%6%
631
March1st to 15thNight
24%6%37%25%6%
720
16th to endNight
21%6%34%24%11%1
768
April1st to 15thNight
22%229%34%10%
718
16th to endNight
21%223%33%17%1
567
May1st to 15thNight
23%119%37%14%3
540
16th to endNight
25%113%40%17%1
440
June1st to 15thNight
25%212%36%20%3
360
16th to endNight
17%8%46%25%1
360
July1st to 15thNight
11%6%45%32%4
340
16th to endNight
14%6%38%36%3
376
August1st to 15thNight
10%11%42%32%3
530
16th to endNight
14%110%32%33%8%
687
September1st to 15thNight
14%114%38%26%4
720
16th to endNight
16%214%29%28%8%
665
October1st to 15thNight
21%421%31%16%4
660
16th to endNight
22%6%33%28%8%
704
November1st to 15thNight
20%6%29%28%12%2
700
16th to endNight
21%10%31%26%9%1
720
December1st to 15thNight
22%10%38%22%5%
720
16th to endNight
26%12%39%18%2
768
Page generated at 2017-09-18 08:38:26. Version ac04

Copyright 2017 A. Danko


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