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 2017-08-12.

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
21%
15016
13%
46263
5%
14973
30%
14973
16%
32897

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%
528
15%
1575
10%
524
41%
524
24%
1049
August16th to endNight
38%
525
18%
1626
11%
525
44%
525
27%
1006
September1st to 15thNight
29%
502
19%
1657
12%
502
38%
502
23%
1060
September16th to endNight
33%
657
24%
1837
13%
657
42%
657
28%
1179
October1st to 15thNight
26%
660
19%
1980
7%
660
37%
660
23%
1300
October16th to endNight
19%
704
16%
2112
4%
704
30%
704
18%
1454
November1st to 15thNight
26%
723
15%
2398
8%
723
35%
723
17%
1671
November16th to endNight
22%
750
12%
2520
5%
750
32%
750
14%
1780
December1st to 15thNight
14%
750
12%
2520
2%
750
24%
750
11%
1844
December16th to endNight
12%
800
11%
2688
2%
800
22%
800
8%
2053

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%
47704
Night
20%8%36%5%3445%7%30%
46439
TransparencyDay
54%411%19%9%1
47399
Night
52%412%20%9%
46263
SeeingDay
29%14%31%17%6%1
7307
Night
26%14%31%20%6%
15018

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%32%
2288
16th to endDay
14%6%25%5%345%47%40%
2223
September1st to 15thDay
19%6%24325%45%5%40%
1972
16th to endDay
15%7%25%333447%43%
1793
October1st to 15thDay
22%6%145%23347%36%
1650
16th to endDay
21%9%37%6%35%346%29%
1760
November1st to 15thDay
22%10%37%5%33347%27%
1457
16th to endDay
23%9%37%6%345%46%25%
1440
December1st to 15thDay
26%8%37%5%35%5%5%6%21%
1440
16th to endDay
24%11%5%7%7%35%35%6%19%
1536
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%
1587
16th to endNight
14%435%5%23437%44%
1626
September1st to 15thNight
15%7%25%43445%7%41%
1657
16th to endNight
18%6%24323436%45%
1837
October1st to 15thNight
20%5%25%5%23446%40%
1980
16th to endNight
22%7%345%2345%6%35%
2112
November1st to 15thNight
22%8%25%435%45%7%30%
2398
16th to endNight
23%6%26%6%34446%29%
2520
December1st to 15thNight
23%9%37%5%35%45%7%24%
2520
16th to endNight
24%10%46%5%35%5%5%7%21%
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
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
2275
16th to endDay
41%5%14%27%11%
2223
September1st to 15thDay
43%411%23%15%1
1972
16th to endDay
40%46%29%17%1
1793
October1st to 15thDay
47%39%23%13%1
1650
16th to endDay
55%310%20%9%
1760
November1st to 15thDay
55%313%16%8%1
1457
16th to endDay
59%412%15%7%
1440
December1st to 15thDay
60%5%11%18%4
1440
16th to endDay
65%48%15%6%
1536
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%
1575
16th to endNight
39%413%28%13%
1626
September1st to 15thNight
42%6%9%28%12%1
1657
16th to endNight
40%37%29%17%
1837
October1st to 15thNight
44%311%25%13%1
1980
16th to endNight
48%412%22%11%
2112
November1st to 15thNight
51%413%20%9%
2398
16th to endNight
53%415%18%7%
2520
December1st to 15thNight
57%313%20%4
2520
16th to endNight
60%5%11%15%6%
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
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%31%23%11%1
297
16th to endDay
17%7%33%23%14%3
268
September1st to 15thDay
24%7%35%19%9%2
255
16th to endDay
21%11%33%20%8%6%
250
October1st to 15thDay
28%9%32%16%8%4
225
16th to endDay
31%17%30%12%6%2
240
November1st to 15thDay
27%16%25%18%8%3
235
16th to endDay
34%15%27%14%7%1
240
December1st to 15thDay
38%16%27%12%4
240
16th to endDay
35%23%24%14%
256
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%27%30%14%
528
16th to endNight
15%7%32%31%11%1
525
September1st to 15thNight
19%7%37%25%8%
502
16th to endNight
22%9%31%21%12%2
657
October1st to 15thNight
24%10%33%21%8%1
660
16th to endNight
26%16%32%18%5%
704
November1st to 15thNight
26%13%27%22%8%1
723
16th to endNight
28%17%25%20%7%
750
December1st to 15thNight
33%15%30%15%4
750
16th to endNight
34%20%28%14%3
800
Page generated at 2017-08-13 15:16:30. Version ac04

Copyright 2017 A. Danko


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