Braidwood Dark Sky Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Braidwood Dark Sky Site 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
38%
15828
18%
46474
11%
15785
45%
15785
25%
30774

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%
900
14%
2506
4%
895
29%
895
19%
1814
January16th to endNight
21%
960
13%
2637
5%
960
27%
960
16%
1982
February1st to 15thNight
23%
788
13%
2199
4%
788
30%
788
20%
1569
February16th to endNight
28%
631
18%
1893
8%
631
37%
631
18%
1321
March1st to 15thNight
27%
720
14%
2160
9%
720
32%
720
18%
1511
March16th to endNight
29%
618
15%
2010
9%
618
37%
618
20%
1382
April1st to 15thNight
30%
539
15%
1797
10%
539
39%
539
21%
1192
April16th to endNight
35%
540
18%
1749
12%
540
44%
540
23%
1174
May1st to 15thNight
37%
540
16%
1611
9%
540
43%
540
24%
1092
May16th to endNight
50%
563
19%
1498
11%
561
55%
561
34%
949
June1st to 15thNight
53%
540
17%
1440
11%
540
57%
540
37%
882
June16th to endNight
53%
540
18%
1440
11%
540
57%
540
35%
903
July1st to 15thNight
65%
510
17%
1360
12%
510
68%
510
37%
831
July16th to endNight
71%
564
24%
1417
19%
531
74%
531
46%
805
August1st to 15thNight
78%
527
22%
1565
22%
524
78%
524
42%
856
August16th to endNight
68%
525
20%
1750
20%
525
72%
525
35%
983
September1st to 15thNight
64%
498
30%
1653
30%
498
70%
498
36%
889
September16th to endNight
59%
657
26%
1815
20%
657
63%
657
36%
1092
October1st to 15thNight
50%
660
29%
1897
21%
660
57%
660
35%
1109
October16th to endNight
29%
704
20%
2229
11%
704
40%
704
23%
1420
November1st to 15thNight
32%
700
25%
2276
16%
700
44%
700
25%
1378
November16th to endNight
29%
744
17%
2364
11%
744
37%
744
20%
1567
December1st to 15thNight
21%
900
12%
2520
4%
900
28%
900
17%
1876
December16th to endNight
16%
960
11%
2688
3%
960
23%
960
11%
2197

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%7%35%5%3445%7%37%
47507
Night
14%7%35%5%24446%40%
46642
Cloud CoverDay
14%7%35%5%3445%7%37%
47516
Night
14%7%35%5%24446%40%
46647
TransparencyDay
45%412%22%12%1
47193
Night
44%412%22%14%2
46474
SeeingDay
15%6%25%26%18%7%
5802
Night
18%7%28%30%13%1
15831

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
16%14%5%7%6%4444425%
1432
16th to endDay
14%14%7%8%6%34445%25%
1587
February1st to 15thDay
15%12%6%6%5%25%446%28%
1662
16th to endDay
16%9%48%6%34346%31%
1580
March1st to 15thDay
17%12%46%425%446%29%
1790
16th to endDay
17%10%36%5%245%47%29%
2223
April1st to 15thDay
18%9%45%5%24346%34%
2151
16th to endDay
20%6%25%5%335%46%35%
2211
May1st to 15thDay
20%8%36%42445%8%30%
2337
16th to endDay
15%5%35%5%25%46%7%39%
2617
June1st to 15thDay
11%425%435%5%5%8%43%
2520
16th to endDay
10%425%5%36%6%6%9%37%
2520
July1st to 15thDay
8%4245%45%5%6%8%44%
2520
16th to endDay
6%3245%46%6%7%9%43%
2655
August1st to 15thDay
7%425%5%35%47%10%44%
2295
16th to endDay
9%5%246%35%5%5%7%43%
2100
September1st to 15thDay
13%424434346%48%
1966
16th to endDay
9%6%25%42445%7%46%
1815
October1st to 15thDay
14%6%24324447%43%
1730
16th to endDay
17%7%25%5%2445%5%37%
1642
November1st to 15thDay
15%6%2443345%6%43%
1582
16th to endDay
19%9%46%413336%36%
1596
December1st to 15thDay
19%13%47%6%35%33427%
1440
16th to endDay
22%15%6%6%5%34335%22%
1536
January1st to 15thNight
16%11%47%5%33345%33%
2506
16th to endNight
14%13%6%8%6%25%445%29%
2637
February1st to 15thNight
16%12%45%5%24346%34%
2197
16th to endNight
16%9%46%5%25%445%34%
1893
March1st to 15thNight
17%10%45%43435%5%34%
2147
16th to endNight
16%8%35%6%3445%6%33%
2010
April1st to 15thNight
15%7%46%5%145%46%38%
1797
16th to endNight
20%6%24434447%37%
1749
May1st to 15thNight
19%6%25%6%2345%9%34%
1611
16th to endNight
10%4245%25%47%9%44%
1496
June1st to 15thNight
10%5%2442435%6%49%
1440
16th to endNight
8%5%25%5%3446%9%44%
1440
July1st to 15thNight
7%314425%5%6%8%50%
1440
16th to endNight
4215%42446%9%54%
1513
August1st to 15thNight
43143345%5%9%53%
1574
16th to endNight
9%32342446%7%51%
1750
September1st to 15thNight
12%313223337%54%
1653
16th to endNight
8%4135%35%5%6%8%47%
1815
October1st to 15thNight
11%414423346%53%
1897
16th to endNight
19%7%25%413335%42%
2229
November1st to 15thNight
14%6%25%423435%47%
2276
16th to endNight
18%7%35%5%34346%37%
2364
December1st to 15thNight
19%11%48%5%33335%30%
2520
16th to endNight
23%15%5%8%6%3433421%
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
16%14%5%7%6%5%444425%
1432
16th to endDay
15%14%6%8%6%34346%25%
1587
February1st to 15thDay
15%12%6%7%5%25%446%28%
1662
16th to endDay
16%9%48%7%34346%31%
1580
March1st to 15thDay
17%12%46%5%24446%29%
1800
16th to endDay
17%10%46%6%245%47%29%
2222
April1st to 15thDay
18%9%35%5%24346%34%
2151
16th to endDay
19%7%25%5%335%46%35%
2211
May1st to 15thDay
19%8%45%43445%7%30%
2337
16th to endDay
14%6%35%5%25%45%7%39%
2617
June1st to 15thDay
11%425%5%35%46%8%43%
2520
16th to endDay
9%425%6%36%6%6%9%37%
2520
July1st to 15thDay
8%4245%35%5%6%8%45%
2520
16th to endDay
6%3145%46%5%7%9%43%
2655
August1st to 15thDay
6%425%5%3447%10%44%
2295
16th to endDay
9%5%245%36%5%5%8%43%
2100
September1st to 15thDay
12%424434446%48%
1966
16th to endDay
8%6%25%42446%7%46%
1815
October1st to 15thDay
14%6%24324447%43%
1730
16th to endDay
17%7%25%5%245%5%5%37%
1642
November1st to 15thDay
15%6%3443336%6%43%
1582
16th to endDay
19%9%47%413336%36%
1596
December1st to 15thDay
19%12%47%6%45%34427%
1440
16th to endDay
22%15%7%7%5%33335%22%
1536
January1st to 15thNight
16%11%46%6%24335%34%
2506
16th to endNight
14%12%6%8%6%25%435%29%
2637
February1st to 15thNight
16%12%45%5%24246%34%
2190
16th to endNight
16%9%45%5%25%445%34%
1893
March1st to 15thNight
18%10%45%5%3435%5%34%
2160
16th to endNight
16%8%35%6%3445%7%33%
2010
April1st to 15thNight
15%7%36%5%245%46%38%
1797
16th to endNight
20%6%25%42445%7%37%
1749
May1st to 15thNight
19%6%25%5%2435%9%34%
1610
16th to endNight
10%424425%46%9%44%
1496
June1st to 15thNight
10%5%3442435%6%49%
1440
16th to endNight
8%5%25%5%3446%9%44%
1440
July1st to 15thNight
7%324425%5%6%8%50%
1440
16th to endNight
4215%4235%6%9%54%
1513
August1st to 15thNight
44143445%5%9%53%
1574
16th to endNight
9%42342446%7%50%
1750
September1st to 15thNight
12%313322347%54%
1653
16th to endNight
7%4135%35%5%6%8%47%
1815
October1st to 15thNight
11%424413346%53%
1897
16th to endNight
19%7%35%413335%42%
2229
November1st to 15thNight
14%6%35%423435%46%
2276
16th to endNight
18%7%35%5%34346%37%
2364
December1st to 15thNight
19%10%48%5%23335%30%
2520
16th to endNight
23%14%5%8%6%3433322%
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
60%412%13%8%
1433
16th to endDay
61%411%15%7%
1587
February1st to 15thDay
56%413%16%6%1
1664
16th to endDay
53%412%22%5%1
1580
March1st to 15thDay
54%414%19%6%
1800
16th to endDay
52%5%14%20%5%1
2223
April1st to 15thDay
51%311%21%12%
2151
16th to endDay
49%413%17%10%3
2211
May1st to 15thDay
51%5%12%22%7%
2337
16th to endDay
42%6%12%20%15%2
2621
June1st to 15thDay
37%5%11%26%17%1
2520
16th to endDay
39%7%13%21%16%1
2520
July1st to 15thDay
35%6%12%26%15%3
2371
16th to endDay
32%6%17%25%14%2
2488
August1st to 15thDay
32%5%15%27%17%1
2280
16th to endDay
37%5%11%24%17%3
2100
September1st to 15thDay
36%410%24%19%4
1966
16th to endDay
35%39%28%19%1
1815
October1st to 15thDay
39%411%27%15%1
1730
16th to endDay
46%312%23%11%1
1642
November1st to 15thDay
40%412%24%15%2
1582
16th to endDay
50%212%23%8%
1596
December1st to 15thDay
60%310%19%6%
1440
16th to endDay
64%410%12%6%
1536
January1st to 15thNight
52%412%18%11%
2506
16th to endNight
57%314%16%7%
2637
February1st to 15thNight
51%312%21%9%1
2199
16th to endNight
51%411%22%9%
1893
March1st to 15thNight
51%412%20%9%1
2160
16th to endNight
49%414%20%9%1
2010
April1st to 15thNight
46%411%20%14%2
1797
16th to endNight
46%410%21%12%4
1749
May1st to 15thNight
46%413%23%12%
1611
16th to endNight
34%7%15%21%18%3
1498
June1st to 15thNight
34%412%26%19%3
1440
16th to endNight
35%5%15%23%17%3
1440
July1st to 15thNight
30%7%12%27%18%3
1360
16th to endNight
24%5%15%30%18%4
1417
August1st to 15thNight
26%5%16%29%19%3
1565
16th to endNight
29%6%12%26%19%5%
1750
September1st to 15thNight
29%39%26%24%5%
1653
16th to endNight
32%5%10%26%21%3
1815
October1st to 15thNight
32%410%27%23%2
1897
16th to endNight
44%210%25%15%1
2229
November1st to 15thNight
39%38%25%17%5%
2276
16th to endNight
47%313%23%11%
2364
December1st to 15thNight
57%211%18%8%
2520
16th to endNight
67%38%14%5%
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
31%10%28%20%7%2
90
16th to endDay
19%13%31%27%8%
96
February1st to 15thDay
17%20%42%17%2
90
16th to endDay
16%11%35%24%11%1
81
March1st to 15thDay
31%18%30%16%3
90
16th to endDay
27%8%31%20%10%2
240
April1st to 15thDay
21%12%30%22%12%
270
16th to endDay
20%9%28%24%10%5%
270
May1st to 15thDay
23%9%26%24%10%4
294
16th to endDay
19%8%29%21%16%5%
517
June1st to 15thDay
11%425%32%20%5%
495
16th to endDay
10%7%31%28%16%5%
495
July1st to 15thDay
11%222%28%21%11%
475
16th to endDay
6%117%33%27%12%
515
August1st to 15thDay
8%213%30%25%18%
375
16th to endDay
11%212%30%27%15%
268
September1st to 15thDay
14%312%25%34%10%
255
16th to endDay
11%316%27%31%9%
254
October1st to 15thDay
14%425%22%27%4
170
16th to endDay
22%6%35%29%6%
96
November1st to 15thDay
7%10%24%26%21%10%
90
16th to endDay
41%7%30%11%10%
90
December1st to 15thDay
22%18%31%17%7%2
90
16th to endDay
27%20%43%44
96
January1st to 15thNight
22%13%37%20%5%
900
16th to endNight
20%13%34%27%3
960
February1st to 15thNight
22%12%34%27%4
791
16th to endNight
21%9%35%26%6%
631
March1st to 15thNight
23%13%32%25%5%
720
16th to endNight
20%7%36%26%8%
618
April1st to 15thNight
20%11%33%27%6%
539
16th to endNight
23%432%28%9%
540
May1st to 15thNight
23%428%32%10%
540
16th to endNight
11%329%36%17%
563
June1st to 15thNight
14%223%45%13%
540
16th to endNight
9%224%44%18%1
540
July1st to 15thNight
9%117%42%26%2
510
16th to endNight
4113%46%31%2
564
August1st to 15thNight
6%8%46%33%4
527
16th to endNight
9%214%34%35%3
525
September1st to 15thNight
13%312%36%28%4
498
16th to endNight
9%417%35%29%3
657
October1st to 15thNight
15%6%24%32%21%1
660
16th to endNight
23%10%32%24%9%
704
November1st to 15thNight
17%10%34%27%10%
700
16th to endNight
21%12%31%26%7%
744
December1st to 15thNight
26%11%32%23%6%
900
16th to endNight
30%10%32%21%4
960
Page generated at 2017-08-13 13:16:30. Version ac04

Copyright 2017 A. Danko


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