Stone Bridge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stone Bridge clear sky chart from 2005-11-05 to 2017-09-19.

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
44%
15889
28%
46904
13%
15844
58%
15844
41%
24375

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
34%
863
31%
2469
12%
858
53%
858
48%
1140
January16th to endNight
32%
768
35%
2496
16%
768
56%
768
48%
1081
February1st to 15thNight
25%
701
26%
2267
8%
698
46%
698
41%
1081
February16th to endNight
23%
632
35%
1894
6%
632
52%
632
44%
901
March1st to 15thNight
34%
720
29%
2064
10%
720
51%
720
43%
1047
March16th to endNight
33%
711
29%
2055
11%
711
50%
711
41%
1065
April1st to 15thNight
34%
539
25%
1798
12%
539
52%
539
37%
875
April16th to endNight
34%
540
25%
1800
12%
540
51%
540
30%
973
May1st to 15thNight
38%
539
21%
1659
12%
539
50%
539
29%
991
May16th to endNight
48%
562
19%
1498
9%
561
58%
561
38%
880
June1st to 15thNight
60%
540
25%
1440
15%
540
67%
540
50%
748
June16th to endNight
69%
540
27%
1440
20%
540
74%
540
52%
749
July1st to 15thNight
70%
510
15%
1360
14%
510
71%
510
30%
889
July16th to endNight
76%
564
14%
1529
14%
531
78%
531
27%
1002
August1st to 15thNight
73%
539
15%
1652
14%
536
74%
536
29%
998
August16th to endNight
73%
573
23%
1910
24%
573
76%
573
28%
1149
September1st to 15thNight
69%
540
25%
1800
23%
540
76%
540
32%
1031
September16th to endNight
64%
534
35%
1814
27%
534
74%
534
44%
870
October1st to 15thNight
50%
660
32%
1980
17%
660
62%
660
47%
995
October16th to endNight
48%
704
37%
2112
16%
704
64%
704
51%
995
November1st to 15thNight
42%
850
35%
2250
15%
850
56%
850
56%
1085
November16th to endNight
36%
900
38%
2409
13%
900
54%
900
54%
1147
December1st to 15thNight
26%
900
25%
2520
5%
900
44%
900
42%
1255
December16th to endNight
28%
960
27%
2688
8%
960
45%
960
39%
1428

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
23244345%6%8%54%
47921
Night
231232345%8%63%
47087
TransparencyDay
26%8%13%24%20%6%
47606
Night
20%7%16%28%21%5%
46904
SeeingDay
8%16%31%24%14%3
5779
Night
311%35%30%16%1
15894

By Month

Percentage Cloud Cover SW (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
21221435%8%66%
1480
16th to endDay
213323447%66%
1728
February1st to 15thDay
31431335%10%63%
1595
16th to endDay
21432335%9%63%
1580
March1st to 15thDay
132342445%9%59%
1895
16th to endDay
1434325%5%6%8%54%
2169
April1st to 15thDay
15%2332445%8%56%
2150
16th to endDay
36%25%445%5%6%8%47%
2160
May1st to 15thDay
47%345%35%5%6%9%43%
2287
16th to endDay
43145%35%6%7%9%47%
2616
June1st to 15thDay
2214436%6%6%9%53%
2520
16th to endDay
2213436%5%7%7%55%
2520
July1st to 15thDay
6%326%6%46%6%6%9%40%
2520
16th to endDay
4436%7%5%7%8%9%9%34%
2532
August1st to 15thDay
6%426%6%46%6%7%9%37%
2298
16th to endDay
5%325%5%36%6%6%9%44%
2292
September1st to 15thDay
4315%6%36%5%8%7%45%
2160
16th to endDay
231342345%6%62%
1888
October1st to 15thDay
31134235%5%6%61%
1650
16th to endDay
2312223247%67%
1760
November1st to 15thDay
21212238%74%
1597
16th to endDay
112212236%74%
1548
December1st to 15thDay
213322148%67%
1440
16th to endDay
131322245%9%62%
1536
January1st to 15thNight
111112247%73%
2469
16th to endNight
212211336%74%
2496
February1st to 15thNight
213312436%68%
2257
16th to endNight
212323348%68%
1894
March1st to 15thNight
1312313347%67%
2064
16th to endNight
141221336%7%66%
2055
April1st to 15thNight
1312213349%64%
1798
16th to endNight
46%2432245%6%57%
1800
May1st to 15thNight
46%35%5%2435%6%52%
1658
16th to endNight
342332437%8%55%
1497
June1st to 15thNight
12113125%5%8%67%
1440
16th to endNight
11222346%8%65%
1440
July1st to 15thNight
5%5%246%25%6%7%9%44%
1440
16th to endNight
4323437%7%8%10%43%
1635
August1st to 15thNight
3414435%5%6%9%49%
1661
16th to endNight
4314435%6%8%10%46%
1910
September1st to 15thNight
4323335%6%7%11%48%
1800
16th to endNight
321232335%6%65%
1814
October1st to 15thNight
32231235%7%65%
1980
16th to endNight
1212212347%70%
2112
November1st to 15thNight
111212248%74%
2250
16th to endNight
1212112245%75%
2409
December1st to 15thNight
22313347%68%
2520
16th to endNight
1323313348%65%
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
16%6%20%35%18%2
1481
16th to endDay
18%5%16%33%21%4
1728
February1st to 15thDay
19%7%19%34%15%4
1596
16th to endDay
19%6%13%32%23%3
1580
March1st to 15thDay
23%6%13%28%24%3
1895
16th to endDay
26%6%12%30%19%4
2169
April1st to 15thDay
26%7%13%28%18%6%
2150
16th to endDay
33%7%11%24%19%3
2160
May1st to 15thDay
37%9%12%22%16%1
2287
16th to endDay
30%10%14%20%18%4
2620
June1st to 15thDay
25%8%13%18%22%12%
2520
16th to endDay
23%7%8%17%28%13%
2520
July1st to 15thDay
38%10%13%15%15%7%
2371
16th to endDay
38%14%17%18%8%3
2375
August1st to 15thDay
39%13%13%13%13%6%
2283
16th to endDay
33%10%13%22%15%3
2292
September1st to 15thDay
33%10%12%16%18%7%
2160
16th to endDay
22%7%10%24%27%8%
1888
October1st to 15thDay
23%6%9%24%28%7%
1650
16th to endDay
18%49%29%30%7%
1760
November1st to 15thDay
11%6%13%26%32%10%
1597
16th to endDay
13%39%36%28%8%
1548
December1st to 15thDay
17%6%20%35%17%2
1440
16th to endDay
20%9%21%29%14%4
1536
January1st to 15thNight
12%422%36%21%2
2469
16th to endNight
13%416%35%24%5%
2496
February1st to 15thNight
18%419%37%16%3
2267
16th to endNight
15%415%33%25%4
1894
March1st to 15thNight
18%5%15%32%25%3
2064
16th to endNight
18%7%14%36%21%1
2055
April1st to 15thNight
19%7%15%29%23%4
1798
16th to endNight
27%6%15%28%18%3
1800
May1st to 15thNight
33%6%13%26%17%3
1659
16th to endNight
25%8%19%23%19%4
1498
June1st to 15thNight
15%8%15%21%22%16%
1440
16th to endNight
16%7%11%23%25%15%
1440
July1st to 15thNight
34%10%17%16%12%7%
1360
16th to endNight
30%17%23%17%8%3
1529
August1st to 15thNight
29%13%19%18%12%6%
1652
16th to endNight
29%13%15%22%14%4
1910
September1st to 15thNight
27%11%16%20%15%8%
1800
16th to endNight
18%6%11%29%26%6%
1814
October1st to 15thNight
18%6%12%26%28%7%
1980
16th to endNight
15%5%10%29%33%6%
2112
November1st to 15thNight
10%6%15%29%29%8%
2250
16th to endNight
12%310%36%29%7%
2409
December1st to 15thNight
16%5%23%31%20%1
2520
16th to endNight
19%7%20%30%18%3
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
422%30%22%21%
90
16th to endDay
8%10%34%37%9%
96
February1st to 15thDay
8%25%42%18%4
90
16th to endDay
333%32%18%8%3
81
March1st to 15thDay
9%30%34%18%6%
185
16th to endDay
13%37%36%10%1
288
April1st to 15thDay
11%36%33%13%41
269
16th to endDay
12%43%30%8%3
270
May1st to 15thDay
12%22%33%21%7%1
351
16th to endDay
9%17%29%26%13%2
517
June1st to 15thDay
412%32%28%18%3
495
16th to endDay
27%30%30%24%5%
495
July1st to 15thDay
9%5%21%27%28%8%
475
16th to endDay
7%322%33%26%6%
391
August1st to 15thDay
10%439%31%10%3
315
16th to endDay
12%5%31%31%16%3
332
September1st to 15thDay
9%11%40%23%11%4
315
16th to endDay
5%7%41%26%14%4
172
October1st to 15thDay
116%22%30%24%5%
90
16th to endDay
12%13%23%27%20%2
96
November1st to 15thDay
414%22%25%28%4
90
16th to endDay
8%30%34%23%3
90
December1st to 15thDay
240%40%16%1
90
16th to endDay
323%41%26%41
96
January1st to 15thNight
220%40%24%10%2
863
16th to endNight
116%46%25%9%
768
February1st to 15thNight
214%52%25%5%
704
16th to endNight
118%53%22%3
632
March1st to 15thNight
216%43%29%7%
720
16th to endNight
316%45%27%7%
711
April1st to 15thNight
317%42%28%7%
539
16th to endNight
7%16%37%29%7%
540
May1st to 15thNight
6%10%37%32%11%
540
16th to endNight
7%7%31%34%17%1
563
June1st to 15thNight
25%28%41%20%1
540
16th to endNight
1321%39%32%2
540
July1st to 15thNight
8%19%37%38%5%
510
16th to endNight
6%6%27%53%4
564
August1st to 15thNight
5%11%35%42%4
539
16th to endNight
5%210%35%40%5%
573
September1st to 15thNight
7%116%43%26%4
540
16th to endNight
4322%38%25%5%
534
October1st to 15thNight
37%35%33%17%2
660
16th to endNight
37%37%32%15%3
704
November1st to 15thNight
213%40%29%13%
850
16th to endNight
315%42%28%9%1
900
December1st to 15thNight
321%48%21%4
900
16th to endNight
219%46%23%8%
960
Page generated at 2017-09-20 02:49:46. Version ac04

Copyright 2017 A. Danko


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