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Great Neck South High Big Blue Rebel Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Great Neck South High Big Blue Rebel Observatory clear sky chart from 2005-11-05 to 2019-09-17.

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
34%
17554
19%
54738
10%
17523
45%
17523
22%
35463

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
22%
840
21%
2926
8%
836
39%
836
18%
1828
January16th to endNight
20%
896
20%
3041
7%
896
37%
896
20%
1886
February1st to 15thNight
18%
824
18%
2586
5%
821
35%
821
19%
1715
February16th to endNight
20%
735
24%
2205
8%
735
39%
735
21%
1429
March1st to 15thNight
22%
840
19%
2520
8%
840
37%
840
22%
1662
March16th to endNight
27%
896
22%
2324
9%
896
37%
896
27%
1558
April1st to 15thNight
28%
838
18%
2096
6%
838
34%
838
25%
1475
April16th to endNight
31%
800
17%
2046
6%
800
37%
800
25%
1427
May1st to 15thNight
30%
610
16%
1870
8%
610
37%
610
17%
1316
May16th to endNight
43%
438
14%
1753
13%
438
49%
438
17%
1123
June1st to 15thNight
45%
420
16%
1680
15%
420
54%
420
18%
1080
June16th to endNight
61%
420
15%
1680
19%
420
66%
420
24%
991
July1st to 15thNight
57%
400
13%
1600
17%
400
59%
400
21%
964
July16th to endNight
59%
440
16%
1674
18%
418
65%
418
22%
996
August1st to 15thNight
56%
635
17%
1866
13%
633
58%
633
30%
1179
August16th to endNight
60%
892
17%
2230
9%
892
62%
892
33%
1487
September1st to 15thNight
50%
840
21%
2103
12%
840
53%
840
29%
1449
September16th to endNight
51%
782
23%
2159
17%
782
56%
782
30%
1400
October1st to 15thNight
41%
780
19%
2262
14%
780
48%
780
24%
1487
October16th to endNight
30%
832
21%
2611
12%
832
43%
832
25%
1631
November1st to 15thNight
32%
820
21%
2667
10%
820
46%
820
22%
1686
November16th to endNight
29%
840
21%
2763
11%
840
42%
840
21%
1733
December1st to 15thNight
25%
840
16%
2940
7%
840
38%
840
17%
1933
December16th to endNight
18%
896
18%
3136
5%
896
34%
896
17%
2028

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
15%5%25%42445%7%41%
55955
Night
16%6%24424446%42%
54908
Cloud CoverDay
16%6%2442445%7%41%
55964
Night
16%6%25%424446%42%
54914
TransparencyDay
41%6%12%21%15%1
55643
Night
42%5%12%21%15%2
54738
SeeingDay
20%8%29%26%12%3
8377
Night
20%9%30%28%10%1
17555

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%6%2442445%7%41%
1672
16th to endDay
15%7%25%32445%6%41%
1883
February1st to 15thDay
16%6%35%424446%40%
1935
16th to endDay
17%5%25%5%24446%42%
1840
March1st to 15thDay
16%6%25%42445%7%39%
2090
16th to endDay
16%7%35%42435%6%42%
2600
April1st to 15thDay
19%6%35%323347%39%
2512
16th to endDay
17%5%14424447%42%
2519
May1st to 15thDay
22%6%25%42335%9%34%
2752
16th to endDay
19%5%2342445%8%39%
3066
June1st to 15thDay
18%6%2442345%8%36%
2940
16th to endDay
11%5%25%435%5%6%8%42%
2940
July1st to 15thDay
9%4245%36%6%6%8%42%
2940
16th to endDay
11%5%35%5%35%6%6%8%39%
3102
August1st to 15thDay
11%425%5%35%6%7%8%40%
2649
16th to endDay
11%4245%335%6%9%44%
2676
September1st to 15thDay
14%5%1433445%7%44%
2517
16th to endDay
15%5%244245%5%6%43%
2156
October1st to 15thDay
18%6%15%42445%6%40%
2025
16th to endDay
17%425%323346%45%
1963
November1st to 15thDay
18%6%2432334445%
1851
16th to endDay
14%6%24324346%45%
1855
December1st to 15thDay
16%7%35%424446%41%
1680
16th to endDay
21%8%2432335%6%38%
1792
January1st to 15thNight
18%5%24423445%43%
2926
16th to endNight
17%7%23323446%43%
3041
February1st to 15thNight
16%6%36%5%33336%40%
2585
16th to endNight
18%7%24423335%44%
2205
March1st to 15thNight
18%6%24423347%41%
2507
16th to endNight
16%8%34423445%43%
2324
April1st to 15thNight
18%6%25%4245%46%39%
2096
16th to endNight
19%6%25%423446%40%
2046
May1st to 15thNight
20%7%36%5%24445%36%
1870
16th to endNight
19%7%24424347%37%
1751
June1st to 15thNight
20%6%2332445%8%38%
1680
16th to endNight
10%5%25%43446%10%42%
1680
July1st to 15thNight
11%4245%35%6%5%9%41%
1680
16th to endNight
10%5%24435%6%6%9%41%
1770
August1st to 15thNight
10%5%25%5%35%5%6%8%44%
1876
16th to endNight
11%5%24425%46%6%44%
2230
September1st to 15thNight
15%425%43445%6%43%
2103
16th to endNight
13%5%26%423346%47%
2159
October1st to 15thNight
17%5%25%5%23336%44%
2262
16th to endNight
18%5%24422335%46%
2611
November1st to 15thNight
18%5%25%423235%46%
2667
16th to endNight
16%5%2443335%6%43%
2763
December1st to 15thNight
20%6%25%5%2445%6%37%
2940
16th to endNight
19%6%25%42445%5%39%
3136

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
15%5%25%42445%7%41%
1672
16th to endDay
15%7%25%42335%6%41%
1883
February1st to 15thDay
16%7%35%424446%40%
1935
16th to endDay
17%5%25%424346%41%
1840
March1st to 15thDay
17%6%35%42445%8%39%
2100
16th to endDay
16%7%3442345%5%42%
2599
April1st to 15thDay
19%7%34423347%39%
2512
16th to endDay
17%5%2442435%7%42%
2519
May1st to 15thDay
22%5%25%42345%8%34%
2752
16th to endDay
19%5%1343445%8%39%
3066
June1st to 15thDay
20%6%25%42445%8%36%
2940
16th to endDay
12%5%25%5%345%5%9%41%
2940
July1st to 15thDay
10%5%245%35%6%7%8%41%
2940
16th to endDay
11%5%245%35%5%6%8%39%
3102
August1st to 15thDay
11%5%24435%5%7%8%40%
2649
16th to endDay
11%5%245%3445%9%43%
2676
September1st to 15thDay
14%5%1442345%7%44%
2517
16th to endDay
15%5%245%25%446%42%
2156
October1st to 15thDay
18%6%245%24447%40%
2025
16th to endDay
17%5%25%32335%6%45%
1963
November1st to 15thDay
19%5%24323335%45%
1851
16th to endDay
14%5%2442435%6%46%
1855
December1st to 15thDay
16%7%35%423446%41%
1680
16th to endDay
21%9%24323446%38%
1792
January1st to 15thNight
18%5%24424345%43%
2926
16th to endNight
17%7%24323446%43%
3041
February1st to 15thNight
16%6%36%424346%40%
2578
16th to endNight
18%6%2442333444%
2205
March1st to 15thNight
19%5%245%23446%41%
2520
16th to endNight
17%7%24423445%44%
2324
April1st to 15thNight
19%6%25%424446%39%
2096
16th to endNight
19%6%34423446%40%
2046
May1st to 15thNight
20%6%36%5%24345%36%
1870
16th to endNight
20%6%25%424348%37%
1751
June1st to 15thNight
20%6%24335%35%8%37%
1680
16th to endNight
10%5%25%435%5%6%10%41%
1680
July1st to 15thNight
10%335%435%5%5%9%41%
1680
16th to endNight
10%5%25%435%5%6%9%40%
1770
August1st to 15thNight
10%415%5%35%46%8%43%
1876
16th to endNight
11%425%425%5%6%7%43%
2230
September1st to 15thNight
14%5%15%43445%6%43%
2103
16th to endNight
13%5%25%5%23246%47%
2159
October1st to 15thNight
18%5%245%22335%44%
2262
16th to endNight
18%5%24422345%46%
2611
November1st to 15thNight
17%5%25%423335%45%
2667
16th to endNight
17%5%25%423346%43%
2763
December1st to 15thNight
20%6%2442435%7%37%
2940
16th to endNight
19%7%25%42445%5%39%
3136

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
41%5%13%24%12%3
1673
16th to endDay
42%413%24%13%2
1883
February1st to 15thDay
44%5%13%21%13%1
1938
16th to endDay
43%411%25%13%1
1840
March1st to 15thDay
42%6%14%23%10%1
2100
16th to endDay
43%5%10%21%16%3
2600
April1st to 15thDay
44%411%20%14%3
2512
16th to endDay
40%6%10%20%18%3
2519
May1st to 15thDay
47%6%11%19%13%1
2752
16th to endDay
42%8%14%20%12%1
3070
June1st to 15thDay
45%7%12%20%12%1
2940
16th to endDay
37%9%13%22%15%1
2940
July1st to 15thDay
36%9%13%21%17%1
2791
16th to endDay
37%9%14%22%13%2
2935
August1st to 15thDay
36%8%15%23%13%
2635
16th to endDay
36%7%12%23%18%2
2676
September1st to 15thDay
37%7%14%20%19%1
2517
16th to endDay
41%5%9%19%21%2
2156
October1st to 15thDay
43%5%12%19%16%1
2025
16th to endDay
38%411%25%17%1
1963
November1st to 15thDay
42%5%12%20%17%1
1851
16th to endDay
38%413%25%14%2
1855
December1st to 15thDay
44%5%16%18%13%1
1680
16th to endDay
46%5%14%20%11%
1792
January1st to 15thNight
41%5%11%23%14%3
2926
16th to endNight
41%412%23%16%2
3041
February1st to 15thNight
45%412%21%13%2
2586
16th to endNight
43%48%23%17%3
2205
March1st to 15thNight
44%413%21%13%3
2520
16th to endNight
42%410%20%17%4
2324
April1st to 15thNight
44%6%10%20%15%3
2096
16th to endNight
44%6%8%16%21%2
2046
May1st to 15thNight
50%6%10%16%13%2
1870
16th to endNight
46%6%15%17%13%1
1753
June1st to 15thNight
44%7%10%19%16%
1680
16th to endNight
36%7%14%25%14%1
1680
July1st to 15thNight
38%9%13%21%16%1
1600
16th to endNight
36%9%14%24%12%2
1674
August1st to 15thNight
35%8%15%24%14%1
1866
16th to endNight
36%7%15%21%17%1
2230
September1st to 15thNight
40%8%10%23%15%1
2103
16th to endNight
38%5%8%21%23%2
2159
October1st to 15thNight
43%5%11%21%15%2
2262
16th to endNight
40%411%25%17%1
2611
November1st to 15thNight
42%410%20%17%3
2667
16th to endNight
40%5%11%25%14%2
2763
December1st to 15thNight
46%5%14%20%11%1
2940
16th to endNight
45%412%22%12%1
3136

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
15%25%37%16%5%
120
16th to endDay
22%12%44%16%3
154
February1st to 15thDay
22%18%37%19%2
271
16th to endDay
22%13%39%20%4
343
March1st to 15thDay
20%15%37%21%5%
390
16th to endDay
20%12%38%20%6%1
416
April1st to 15thDay
23%11%36%18%8%1
390
16th to endDay
24%8%33%21%9%1
379
May1st to 15thDay
31%10%26%23%6%1
408
16th to endDay
23%5%26%28%14%1
459
June1st to 15thDay
20%7%28%27%12%3
435
16th to endDay
16%229%34%15%1
435
July1st to 15thDay
12%20%38%23%4
425
16th to endDay
14%118%37%22%5%
454
August1st to 15thDay
15%119%35%21%6%
418
16th to endDay
12%218%39%19%7%
460
September1st to 15thDay
20%326%24%18%7%
435
16th to endDay
21%420%24%16%12%
378
October1st to 15thDay
25%5%19%29%16%4
375
16th to endDay
15%12%37%24%9%1
364
November1st to 15thDay
22%10%28%25%10%1
325
16th to endDay
15%16%32%26%7%
295
December1st to 15thDay
20%15%39%16%9%
120
16th to endDay
31%20%36%10%1
128
January1st to 15thNight
20%15%37%22%3
840
16th to endNight
22%15%39%21%2
896
February1st to 15thNight
20%13%41%22%1
824
16th to endNight
22%15%38%21%2
735
March1st to 15thNight
22%11%39%21%4
840
16th to endNight
21%9%37%25%4
896
April1st to 15thNight
22%10%35%25%5%
838
16th to endNight
21%8%35%28%6%
800
May1st to 15thNight
22%8%31%28%8%
610
16th to endNight
23%322%35%14%1
439
June1st to 15thNight
22%323%35%16%
420
16th to endNight
11%217%51%16%
420
July1st to 15thNight
11%219%44%20%1
400
16th to endNight
12%117%44%22%2
440
August1st to 15thNight
14%119%42%21%1
635
16th to endNight
15%114%36%29%3
892
September1st to 15thNight
18%322%35%17%3
840
16th to endNight
16%321%30%23%5%
782
October1st to 15thNight
20%8%23%27%17%2
780
16th to endNight
20%11%33%25%8%
832
November1st to 15thNight
20%10%32%23%11%1
820
16th to endNight
19%13%33%26%7%
840
December1st to 15thNight
24%10%34%22%6%1
840
16th to endNight
24%14%40%19%2
896
Page generated at 2019-09-17 21:12:19. Version ac04

Copyright 2019 A. Danko


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