Brooklyn Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Brooklyn Lake clear sky chart from 2005-11-05 to 2017-09-16.

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
29%
16000
22%
46853
9%
15957
41%
15957
25%
26369

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
14%
900
21%
2506
5%
895
29%
895
16%
1441
January16th to endNight
11%
805
24%
2533
4%
805
34%
805
17%
1396
February1st to 15thNight
11%
696
15%
2288
3%
696
25%
696
11%
1370
February16th to endNight
9%
632
18%
1914
1%
632
27%
632
12%
1140
March1st to 15thNight
19%
720
21%
2073
4%
720
35%
720
21%
1144
March16th to endNight
21%
708
20%
2052
7%
708
34%
708
20%
1225
April1st to 15thNight
19%
539
17%
1798
7%
539
32%
539
19%
1036
April16th to endNight
25%
540
19%
1800
9%
540
38%
540
20%
1071
May1st to 15thNight
30%
540
19%
1521
9%
540
39%
540
25%
942
May16th to endNight
45%
563
20%
1498
13%
561
50%
561
32%
894
June1st to 15thNight
46%
540
20%
1440
10%
540
52%
540
42%
770
June16th to endNight
55%
540
29%
1440
18%
540
63%
540
55%
711
July1st to 15thNight
64%
510
18%
1360
13%
510
68%
510
44%
763
July16th to endNight
68%
564
25%
1450
20%
531
70%
531
48%
776
August1st to 15thNight
61%
539
23%
1611
17%
536
66%
536
42%
849
August16th to endNight
69%
573
33%
1898
31%
573
77%
573
45%
923
September1st to 15thNight
52%
540
30%
1800
20%
540
68%
540
42%
893
September16th to endNight
51%
538
32%
1788
24%
538
61%
538
42%
830
October1st to 15thNight
30%
660
28%
1980
11%
660
45%
660
27%
1118
October16th to endNight
21%
718
28%
2126
7%
718
39%
718
28%
1151
November1st to 15thNight
15%
875
26%
2275
5%
875
29%
875
22%
1282
November16th to endNight
11%
900
26%
2494
3%
900
30%
900
18%
1396
December1st to 15thNight
9%
900
15%
2520
2%
900
20%
900
12%
1561
December16th to endNight
10%
960
17%
2688
2%
960
24%
960
11%
1687

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
46%36%6%35%5%7%8%41%
47905
Night
2424425%6%8%10%47%
47028
TransparencyDay
37%414%22%15%4
47582
Night
28%5%18%27%15%4
46853
SeeingDay
12%25%30%18%10%1
5907
Night
9%32%25%19%11%1
16008

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
325%45%5%6%11%15%39%
1432
16th to endDay
327%6%46%6%10%11%38%
1701
February1st to 15thDay
347%8%5%6%7%10%10%35%
1575
16th to endDay
5%49%9%48%6%10%9%32%
1559
March1st to 15thDay
16%46%6%35%37%10%42%
1885
16th to endDay
27%37%7%5%6%6%6%10%35%
2170
April1st to 15thDay
310%47%7%45%5%6%8%36%
2150
16th to endDay
5%14%5%8%6%36%5%6%7%29%
2160
May1st to 15thDay
9%11%47%6%45%5%5%7%32%
2427
16th to endDay
8%9%47%7%46%6%6%8%30%
2616
June1st to 15thDay
6%5%26%5%35%5%6%8%44%
2520
16th to endDay
22134245%5%8%59%
2520
July1st to 15thDay
6%5%25%5%35%5%6%7%44%
2520
16th to endDay
6%5%37%6%36%6%7%7%39%
2617
August1st to 15thDay
6%6%38%8%36%5%5%7%36%
2340
16th to endDay
6%5%35%6%35%45%5%47%
2302
September1st to 15thDay
7%6%35%434446%51%
2160
16th to endDay
5%5%24323345%58%
1843
October1st to 15thDay
5%6%27%5%35%45%6%48%
1650
16th to endDay
26%344346%7%7%49%
1735
November1st to 15thDay
1335%436%6%7%10%47%
1583
16th to endDay
1237%6%26%47%11%47%
1464
December1st to 15thDay
5%26%9%45%7%9%12%35%
1440
16th to endDay
337%7%5%7%8%10%13%31%
1536
January1st to 15thNight
212425%10%13%16%39%
2506
16th to endNight
223436%8%12%10%45%
2533
February1st to 15thNight
325%5%36%8%15%13%35%
2277
16th to endNight
336%6%36%7%12%10%39%
1914
March1st to 15thNight
324325%6%8%11%48%
2073
16th to endNight
16%345%245%7%12%43%
2052
April1st to 15thNight
17%26%5%35%6%7%9%43%
1798
16th to endNight
6%10%36%32446%8%42%
1800
May1st to 15thNight
7%8%25%5%345%6%8%42%
1520
16th to endNight
5%5%235%45%6%7%9%44%
1497
June1st to 15thNight
32123245%7%8%57%
1440
16th to endNight
121321335%6%68%
1440
July1st to 15thNight
33135%345%6%11%52%
1440
16th to endNight
2213425%5%6%9%54%
1549
August1st to 15thNight
242442347%10%52%
1620
16th to endNight
321332446%8%59%
1898
September1st to 15thNight
6%31332345%7%58%
1800
16th to endNight
4312313347%64%
1788
October1st to 15thNight
45%245%246%6%7%50%
1980
16th to endNight
36%134235%6%9%53%
2126
November1st to 15thNight
14234346%8%10%52%
2275
16th to endNight
224425%6%9%11%50%
2494
December1st to 15thNight
15%24426%8%11%15%38%
2520
16th to endNight
1425%5%46%8%12%14%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
28%11%28%20%8%2
1433
16th to endDay
36%423%23%10%1
1701
February1st to 15thDay
38%8%25%17%7%1
1575
16th to endDay
44%5%18%21%8%1
1559
March1st to 15thDay
35%422%25%10%1
1885
16th to endDay
45%316%24%8%1
2170
April1st to 15thDay
45%315%21%12%1
2150
16th to endDay
50%313%25%6%
2160
May1st to 15thDay
49%312%23%10%
2427
16th to endDay
48%412%24%9%
2620
June1st to 15thDay
34%412%21%20%6%
2520
16th to endDay
21%36%22%33%12%
2520
July1st to 15thDay
36%5%8%17%17%14%
2371
16th to endDay
39%5%8%20%14%11%
2453
August1st to 15thDay
42%410%14%18%9%
2325
16th to endDay
35%47%21%23%7%
2302
September1st to 15thDay
33%37%19%25%10%
2160
16th to endDay
27%39%32%25%2
1843
October1st to 15thDay
36%312%30%14%2
1650
16th to endDay
31%316%31%14%2
1735
November1st to 15thDay
29%6%17%23%19%3
1583
16th to endDay
29%422%28%13%1
1464
December1st to 15thDay
38%8%26%20%6%
1440
16th to endDay
40%9%18%20%8%2
1536
January1st to 15thNight
25%8%26%26%9%3
2506
16th to endNight
28%5%21%27%14%2
2533
February1st to 15thNight
32%8%26%21%9%1
2288
16th to endNight
35%322%25%10%2
1914
March1st to 15thNight
26%424%29%12%2
2073
16th to endNight
33%321%29%9%1
2052
April1st to 15thNight
35%419%24%14%2
1798
16th to endNight
38%316%30%10%
1800
May1st to 15thNight
37%415%30%11%
1521
16th to endNight
32%417%32%11%
1498
June1st to 15thNight
21%417%28%22%5%
1440
16th to endNight
16%27%26%31%16%
1440
July1st to 15thNight
25%415%20%21%12%
1360
16th to endNight
22%415%22%20%14%
1450
August1st to 15thNight
24%5%14%25%18%11%
1611
16th to endNight
20%49%26%29%9%
1898
September1st to 15thNight
23%312%22%28%10%
1800
16th to endNight
19%311%32%29%3
1788
October1st to 15thNight
28%5%11%33%17%4
1980
16th to endNight
26%315%35%17%2
2126
November1st to 15thNight
24%419%27%18%4
2275
16th to endNight
25%5%20%32%13%2
2494
December1st to 15thNight
31%9%25%22%9%
2520
16th to endNight
35%7%21%25%7%2
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
13%37%18%20%7%2
90
16th to endDay
6%55%26%6%6%
96
February1st to 15thDay
25%50%13%11%
90
16th to endDay
19%46%24%7%1
81
March1st to 15thDay
21%41%28%7%2
175
16th to endDay
14%40%36%6%1
288
April1st to 15thDay
16%44%30%8%1
269
16th to endDay
25%36%27%8%2
270
May1st to 15thDay
18%24%29%16%9%1
411
16th to endDay
15%20%29%19%11%2
517
June1st to 15thDay
8%20%27%24%16%2
495
16th to endDay
319%34%24%15%2
495
July1st to 15thDay
10%8%32%23%21%3
475
16th to endDay
9%8%29%28%19%4
476
August1st to 15thDay
9%13%41%29%5%
315
16th to endDay
9%12%34%32%9%2
332
September1st to 15thDay
13%24%32%21%7%1
315
16th to endDay
13%18%38%15%10%4
165
October1st to 15thDay
428%43%15%43
90
16th to endDay
18%34%31%10%32
96
November1st to 15thDay
333%33%12%17%
90
16th to endDay
20%55%21%3
90
December1st to 15thDay
25%51%18%4
90
16th to endDay
11%60%17%7%3
96
January1st to 15thNight
15%45%22%9%5%2
900
16th to endNight
10%47%26%10%3
805
February1st to 15thNight
12%47%22%10%5%
704
16th to endNight
11%50%24%9%3
632
March1st to 15thNight
8%43%25%15%5%1
720
16th to endNight
7%37%28%19%6%
708
April1st to 15thNight
7%33%34%17%5%
539
16th to endNight
14%29%28%20%7%
540
May1st to 15thNight
13%19%30%20%15%
540
16th to endNight
8%15%24%31%17%1
563
June1st to 15thNight
5%15%29%31%17%1
540
16th to endNight
210%27%39%18%1
540
July1st to 15thNight
45%17%37%33%1
510
16th to endNight
3217%36%34%5%
564
August1st to 15thNight
5%322%40%25%1
539
16th to endNight
35%14%37%33%4
573
September1st to 15thNight
8%7%26%31%20%4
540
16th to endNight
6%14%25%27%19%6%
538
October1st to 15thNight
10%28%26%21%12%1
660
16th to endNight
10%33%31%13%7%2
718
November1st to 15thNight
11%45%25%10%5%1
875
16th to endNight
9%49%28%8%3
900
December1st to 15thNight
14%52%22%8%2
900
16th to endNight
12%50%21%10%2
960
Page generated at 2017-09-16 15:06:59. Version ac04

Copyright 2017 A. Danko


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