Bridgewater
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bridgewater 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
21%
15551
14%
47828
5%
15508
30%
15508
16%
33925

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
15%
747
11%
2493
4%
743
24%
743
10%
1817
January16th to endNight
13%
768
12%
2496
2%
768
23%
768
11%
1841
February1st to 15thNight
13%
702
9%
2286
1%
701
23%
701
10%
1731
February16th to endNight
16%
631
11%
2024
3%
631
26%
631
11%
1483
March1st to 15thNight
17%
720
15%
1980
4%
720
27%
720
15%
1450
March16th to endNight
16%
768
14%
2112
3%
768
27%
768
15%
1537
April1st to 15thNight
16%
560
14%
1817
5%
560
27%
560
12%
1306
April16th to endNight
18%
540
15%
1620
5%
540
27%
540
16%
1148
May1st to 15thNight
20%
540
11%
1557
4%
540
27%
540
15%
1158
May16th to endNight
19%
561
11%
1496
3%
560
26%
560
18%
1101
June1st to 15thNight
18%
540
7%
1440
2%
540
22%
540
14%
1130
June16th to endNight
24%
360
10%
1260
3%
360
32%
360
15%
889
July1st to 15thNight
32%
415
12%
1265
7%
415
38%
415
24%
826
July16th to endNight
35%
565
11%
1504
8%
532
38%
532
20%
1084
August1st to 15thNight
38%
539
15%
1608
10%
535
41%
535
24%
1071
August16th to endNight
37%
573
20%
1775
12%
573
44%
573
27%
1103
September1st to 15thNight
29%
548
19%
1808
12%
548
39%
548
24%
1137
September16th to endNight
33%
717
23%
2004
13%
717
41%
717
26%
1307
October1st to 15thNight
27%
720
19%
2160
7%
720
37%
720
24%
1399
October16th to endNight
21%
768
18%
2304
6%
768
33%
768
19%
1556
November1st to 15thNight
25%
795
14%
2604
8%
795
34%
795
16%
1822
November16th to endNight
22%
825
13%
2730
4%
825
32%
825
14%
1921
December1st to 15thNight
13%
825
12%
2730
2%
825
24%
825
11%
2011
December16th to endNight
12%
824
11%
2755
2%
824
23%
824
8%
2097

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
21%9%36%5%34446%29%
49007
Night
20%8%36%5%3445%7%30%
48004
TransparencyDay
53%411%19%9%1
48702
Night
52%412%20%9%
47828
SeeingDay
29%14%31%17%6%1
7745
Night
26%14%31%20%6%
15553

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
15%11%6%8%6%36%5%6%8%20%
1444
16th to endDay
18%11%47%6%45%6%5%6%22%
1728
February1st to 15thDay
17%13%5%9%8%45%445%20%
1575
16th to endDay
14%11%6%9%8%34346%27%
1445
March1st to 15thDay
21%11%47%6%24445%27%
1969
16th to endDay
17%11%5%8%5%23345%33%
2112
April1st to 15thDay
22%13%46%5%3434428%
2132
16th to endDay
23%8%34313346%34%
2337
May1st to 15thDay
27%9%36%434346%26%
2395
16th to endDay
24%10%35%323447%29%
2618
June1st to 15thDay
29%9%46%5%23335%25%
2527
16th to endDay
22%9%36%6%34447%27%
2700
July1st to 15thDay
19%7%345%3446%8%32%
2604
16th to endDay
20%10%36%5%35%5%5%6%28%
2559
August1st to 15thDay
18%7%35%5%345%6%8%31%
2340
16th to endDay
14%6%25%5%345%47%41%
2426
September1st to 15thDay
18%6%24325%45%6%40%
2151
16th to endDay
16%7%25%333447%42%
1956
October1st to 15thDay
20%6%245%23347%37%
1800
16th to endDay
20%8%36%5%25%346%32%
1920
November1st to 15thDay
21%11%37%5%3335%7%27%
1581
16th to endDay
22%9%37%6%345%46%26%
1560
December1st to 15thDay
27%8%37%5%35%5%5%5%20%
1560
16th to endDay
24%11%5%7%7%35%35%5%19%
1568
January1st to 15thNight
16%9%48%7%36%5%5%8%24%
2493
16th to endNight
17%11%48%6%45%5%48%21%
2496
February1st to 15thNight
18%10%5%8%6%46%6%6%6%20%
2285
16th to endNight
15%10%5%8%8%45%5%6%6%25%
2024
March1st to 15thNight
21%9%45%5%35%446%30%
1968
16th to endNight
17%11%36%5%25%35%5%31%
2112
April1st to 15thNight
25%9%25%434446%28%
1817
16th to endNight
24%8%25%5%14346%32%
1620
May1st to 15thNight
26%8%45%434346%28%
1557
16th to endNight
21%8%46%5%23447%31%
1494
June1st to 15thNight
28%9%35%5%34245%25%
1440
16th to endNight
25%7%25%33335%6%31%
1260
July1st to 15thNight
15%6%25%5%25%45%8%37%
1341
16th to endNight
18%7%45%5%3446%7%30%
1607
August1st to 15thNight
17%7%25%42345%6%40%
1620
16th to endNight
14%4345%23437%44%
1775
September1st to 15thNight
15%6%25%43335%6%43%
1808
16th to endNight
18%6%14323436%44%
2004
October1st to 15thNight
19%5%25%5%23446%41%
2160
16th to endNight
21%6%245%23446%37%
2304
November1st to 15thNight
21%8%25%435%45%7%30%
2604
16th to endNight
22%6%26%6%3445%7%29%
2730
December1st to 15thNight
23%9%37%5%35%45%7%23%
2730
16th to endNight
24%10%46%5%35%5%5%7%21%
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
58%415%15%5%
1445
16th to endDay
57%49%20%7%
1728
February1st to 15thDay
63%312%13%5%1
1578
16th to endDay
58%312%18%6%1
1445
March1st to 15thDay
58%38%17%9%1
1980
16th to endDay
53%39%19%12%1
2112
April1st to 15thDay
58%46%15%13%1
2132
16th to endDay
51%310%19%12%2
2337
May1st to 15thDay
59%48%16%10%1
2395
16th to endDay
53%412%20%7%1
2622
June1st to 15thDay
61%49%15%7%1
2527
16th to endDay
55%5%11%17%10%
2700
July1st to 15thDay
46%5%15%20%10%1
2453
16th to endDay
53%6%12%20%6%
2399
August1st to 15thDay
48%5%13%20%10%1
2327
16th to endDay
40%413%27%12%
2426
September1st to 15thDay
41%411%24%15%1
2151
16th to endDay
42%37%28%16%1
1956
October1st to 15thDay
46%310%25%13%1
1800
16th to endDay
52%310%23%9%
1920
November1st to 15thDay
55%313%16%8%1
1581
16th to endDay
57%412%17%7%
1560
December1st to 15thDay
61%5%11%18%4
1560
16th to endDay
65%48%15%6%
1568
January1st to 15thNight
55%6%14%17%5%
2493
16th to endNight
57%413%20%3
2496
February1st to 15thNight
59%413%16%5%
2286
16th to endNight
56%315%17%6%
2024
March1st to 15thNight
55%212%18%10%1
1980
16th to endNight
53%310%18%12%1
2112
April1st to 15thNight
55%48%17%12%2
1817
16th to endNight
52%39%20%11%1
1620
May1st to 15thNight
57%49%20%7%
1557
16th to endNight
52%5%13%19%8%1
1496
June1st to 15thNight
61%39%17%7%
1440
16th to endNight
54%411%19%9%
1260
July1st to 15thNight
42%6%15%25%10%
1265
16th to endNight
50%6%13%21%6%1
1504
August1st to 15thNight
43%5%13%24%11%
1608
16th to endNight
40%412%28%13%
1775
September1st to 15thNight
40%5%9%29%13%1
1808
16th to endNight
41%47%28%16%
2004
October1st to 15thNight
43%311%26%14%1
2160
16th to endNight
46%412%23%11%
2304
November1st to 15thNight
51%413%20%9%
2604
16th to endNight
52%415%18%7%
2730
December1st to 15thNight
58%313%20%4
2730
16th to endNight
60%5%11%16%6%
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
25%17%39%15%2
240
16th to endDay
28%19%35%13%2
256
February1st to 15thDay
25%20%34%17%2
236
16th to endDay
23%18%33%18%5%1
216
March1st to 15thDay
31%24%26%11%4
270
16th to endDay
34%16%28%13%5%2
288
April1st to 15thDay
33%20%30%10%4
270
16th to endDay
28%14%39%12%41
270
May1st to 15thDay
35%17%26%13%41
351
16th to endDay
33%11%32%15%41
519
June1st to 15thDay
34%13%30%16%4
495
16th to endDay
30%12%29%20%5%1
495
July1st to 15thDay
23%6%35%24%9%1
475
16th to endDay
28%7%28%25%10%1
420
August1st to 15thDay
21%11%32%22%10%1
313
16th to endDay
17%7%34%24%13%2
332
September1st to 15thDay
22%10%36%19%8%2
315
16th to endDay
25%10%30%18%8%5%
308
October1st to 15thDay
25%10%32%18%8%4
270
16th to endDay
29%17%30%11%7%2
288
November1st to 15thDay
26%17%26%17%9%2
280
16th to endDay
32%16%30%12%6%1
285
December1st to 15thDay
40%17%25%12%3
285
16th to endDay
36%23%23%14%
268
January1st to 15thNight
28%17%34%17%2
747
16th to endNight
28%20%32%14%3
768
February1st to 15thNight
27%19%34%17%1
704
16th to endNight
25%19%33%17%4
631
March1st to 15thNight
26%20%30%19%3
720
16th to endNight
26%20%31%16%4
768
April1st to 15thNight
32%15%31%16%4
560
16th to endNight
29%17%29%19%3
540
May1st to 15thNight
32%11%31%18%5%
540
16th to endNight
25%13%35%19%5%1
561
June1st to 15thNight
33%12%30%19%5%
540
16th to endNight
28%8%33%20%8%
360
July1st to 15thNight
16%5%40%25%11%
415
16th to endNight
21%6%30%31%10%
565
August1st to 15thNight
20%5%28%30%14%
539
16th to endNight
16%6%32%30%11%1
573
September1st to 15thNight
18%8%37%26%8%
548
16th to endNight
23%9%30%21%12%2
717
October1st to 15thNight
23%10%34%22%9%1
720
16th to endNight
25%16%32%18%6%
768
November1st to 15thNight
25%14%28%22%7%1
795
16th to endNight
27%18%26%19%7%
825
December1st to 15thNight
34%16%30%15%3
825
16th to endNight
34%20%27%14%3
824
Page generated at 2017-12-21 08:04:45. Version ac04

Copyright 2017 A. Danko


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