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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 2020-06-03.

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%
18538
19%
57798
10%
18507
44%
18507
22%
37509

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%
900
20%
3136
8%
896
38%
896
18%
1970
January16th to endNight
21%
960
22%
3259
8%
960
39%
960
20%
2006
February1st to 15thNight
17%
884
17%
2774
5%
881
33%
881
18%
1873
February16th to endNight
20%
791
25%
2373
9%
791
40%
791
21%
1534
March1st to 15thNight
22%
900
19%
2700
8%
900
37%
900
22%
1775
March16th to endNight
25%
960
23%
2489
9%
960
36%
960
26%
1691
April1st to 15thNight
27%
898
17%
2246
6%
898
33%
898
24%
1584
April16th to endNight
30%
857
18%
2193
6%
857
37%
857
25%
1530
May1st to 15thNight
28%
653
16%
2003
7%
653
36%
653
17%
1402
May16th to endNight
41%
470
14%
1881
13%
470
47%
470
16%
1224
June1st to 15thNight
44%
425
16%
1701
15%
425
54%
425
18%
1091
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
52%
837
23%
2310
18%
837
57%
837
31%
1482
October1st to 15thNight
39%
840
18%
2436
13%
840
46%
840
23%
1628
October16th to endNight
30%
896
21%
2812
11%
896
43%
896
24%
1770
November1st to 15thNight
31%
880
21%
2862
10%
880
46%
880
23%
1793
November16th to endNight
28%
900
22%
2960
11%
900
42%
900
21%
1851
December1st to 15thNight
24%
900
16%
3150
7%
900
36%
900
17%
2080
December16th to endNight
19%
960
20%
3360
6%
960
36%
960
17%
2159

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
16%5%25%42445%7%41%
58616
Night
16%6%25%424446%42%
57968
Cloud CoverDay
16%6%2442445%7%40%
58625
Night
17%6%25%424446%41%
57974
TransparencyDay
41%6%12%21%15%2
58304
Night
42%5%11%21%15%2
57798
SeeingDay
20%9%29%25%11%2
9249
Night
20%9%31%27%10%1
18539

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%25%43445%7%41%
1792
16th to endDay
15%7%25%42445%6%42%
2017
February1st to 15thDay
17%7%35%424446%38%
2076
16th to endDay
17%5%25%5%34446%41%
1980
March1st to 15thDay
15%6%25%42445%7%40%
2240
16th to endDay
17%7%35%42435%5%41%
2786
April1st to 15thDay
19%6%35%324347%38%
2692
16th to endDay
18%5%15%424446%41%
2702
May1st to 15thDay
21%6%25%43335%9%35%
2950
16th to endDay
18%5%234245%5%8%38%
3290
June1st to 15thDay
18%6%2442345%8%36%
2968
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
14%5%244245%5%6%44%
2310
October1st to 15thDay
18%6%25%42445%6%39%
2181
16th to endDay
18%425%323346%44%
2114
November1st to 15thDay
18%6%2432334445%
1986
16th to endDay
14%6%24323346%45%
1988
December1st to 15thDay
18%7%35%423446%39%
1800
16th to endDay
20%7%2432335%6%38%
1920
January1st to 15thNight
18%5%2442345%5%42%
3136
16th to endNight
16%7%24323446%43%
3259
February1st to 15thNight
18%7%36%5%23335%39%
2773
16th to endNight
18%7%24423435%43%
2373
March1st to 15thNight
18%6%24423446%41%
2687
16th to endNight
17%8%34423445%42%
2489
April1st to 15thNight
18%6%35%4245%46%38%
2246
16th to endNight
19%6%25%423446%40%
2193
May1st to 15thNight
20%7%36%424445%36%
2003
16th to endNight
19%8%24424347%36%
1879
June1st to 15thNight
19%6%2332445%8%38%
1701
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
12%5%25%423346%48%
2310
October1st to 15thNight
18%6%25%5%23335%43%
2436
16th to endNight
18%6%24322335%45%
2812
November1st to 15thNight
17%5%25%423335%46%
2862
16th to endNight
16%5%2443345%6%43%
2960
December1st to 15thNight
21%6%25%5%2445%6%37%
3150
16th to endNight
19%6%2442445%5%40%
3360

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%5%25%447%41%
1792
16th to endDay
15%7%25%42445%6%42%
2017
February1st to 15thDay
17%8%35%424446%38%
2076
16th to endDay
16%5%25%424346%41%
1980
March1st to 15thDay
16%6%25%42445%8%40%
2250
16th to endDay
17%7%3442345%5%41%
2785
April1st to 15thDay
19%6%34423347%39%
2692
16th to endDay
18%5%24424347%41%
2702
May1st to 15thDay
21%5%25%42345%8%35%
2950
16th to endDay
19%5%1342445%8%38%
3290
June1st to 15thDay
19%6%25%42445%8%36%
2968
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
14%5%14424446%44%
2310
October1st to 15thDay
18%6%14424446%39%
2181
16th to endDay
18%5%25%32335%6%44%
2114
November1st to 15thDay
18%5%24323335%46%
1986
16th to endDay
15%5%2442435%6%45%
1988
December1st to 15thDay
18%6%35%5%23446%40%
1800
16th to endDay
20%8%24323446%38%
1920
January1st to 15thNight
18%5%25%424445%42%
3136
16th to endNight
16%7%24323446%44%
3259
February1st to 15thNight
18%6%36%5%24345%39%
2766
16th to endNight
18%6%24423335%44%
2373
March1st to 15thNight
18%6%245%23446%41%
2700
16th to endNight
17%7%24423345%43%
2489
April1st to 15thNight
18%6%25%4245%46%38%
2246
16th to endNight
19%6%34423446%40%
2193
May1st to 15thNight
20%6%36%434345%36%
2003
16th to endNight
19%7%25%424347%35%
1879
June1st to 15thNight
19%6%24335%35%8%38%
1701
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%425%423246%48%
2310
October1st to 15thNight
18%5%35%5%22335%43%
2436
16th to endNight
18%6%24422345%45%
2812
November1st to 15thNight
17%5%25%423335%46%
2862
16th to endNight
17%5%25%423446%43%
2960
December1st to 15thNight
20%6%2442435%6%37%
3150
16th to endNight
19%7%2442445%5%40%
3360

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%12%24%12%3
1793
16th to endDay
41%412%24%13%2
2017
February1st to 15thDay
46%412%21%12%1
2079
16th to endDay
43%411%24%14%1
1980
March1st to 15thDay
41%6%14%23%12%1
2250
16th to endDay
44%410%21%16%2
2786
April1st to 15thDay
44%5%11%20%14%3
2692
16th to endDay
42%5%10%20%17%2
2702
May1st to 15thDay
46%6%11%18%14%2
2950
16th to endDay
42%8%14%19%12%1
3294
June1st to 15thDay
45%8%12%20%12%1
2968
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
38%5%10%21%22%2
2310
October1st to 15thDay
44%5%12%19%15%2
2181
16th to endDay
40%410%24%18%2
2114
November1st to 15thDay
41%5%12%20%18%2
1986
16th to endDay
39%412%26%14%2
1988
December1st to 15thDay
45%5%15%19%13%1
1800
16th to endDay
46%5%13%22%11%
1920
January1st to 15thNight
42%5%11%23%13%3
3136
16th to endNight
40%411%23%16%2
3259
February1st to 15thNight
47%412%20%12%2
2774
16th to endNight
43%48%22%17%3
2373
March1st to 15thNight
43%413%21%13%3
2700
16th to endNight
43%410%20%17%4
2489
April1st to 15thNight
44%6%10%20%14%2
2246
16th to endNight
44%5%8%17%20%3
2193
May1st to 15thNight
49%6%9%16%14%2
2003
16th to endNight
47%6%15%16%12%1
1881
June1st to 15thNight
44%7%10%19%16%
1701
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
37%5%8%21%23%2
2310
October1st to 15thNight
44%5%11%21%14%2
2436
16th to endNight
40%411%25%17%1
2812
November1st to 15thNight
41%410%21%18%3
2862
16th to endNight
40%5%11%25%14%2
2960
December1st to 15thNight
47%5%14%20%11%1
3150
16th to endNight
45%412%23%12%1
3360

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
16%28%34%15%4
150
16th to endDay
20%12%44%16%42
192
February1st to 15thDay
25%18%36%17%2
322
16th to endDay
22%15%38%20%4
399
March1st to 15thDay
18%16%39%20%5%
450
16th to endDay
22%12%38%20%5%1
480
April1st to 15thDay
23%12%36%17%8%1
450
16th to endDay
27%10%32%20%7%1
439
May1st to 15thDay
29%12%28%21%6%1
468
16th to endDay
22%427%28%14%2
523
June1st to 15thDay
19%7%29%27%12%3
443
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
19%421%27%16%11%
434
October1st to 15thDay
25%6%21%27%15%3
435
16th to endDay
18%12%35%23%9%
419
November1st to 15thDay
21%12%29%25%10%1
370
16th to endDay
16%15%35%25%6%
338
December1st to 15thDay
23%14%38%15%8%
150
16th to endDay
28%18%39%11%2
160
January1st to 15thNight
20%16%37%21%3
900
16th to endNight
21%15%38%21%2
960
February1st to 15thNight
22%13%41%21%1
884
16th to endNight
22%15%38%21%2
791
March1st to 15thNight
22%12%39%21%4
900
16th to endNight
21%10%38%24%4
960
April1st to 15thNight
22%11%35%25%5%
898
16th to endNight
22%8%35%28%5%
857
May1st to 15thNight
22%10%32%27%7%
653
16th to endNight
23%422%33%14%1
471
June1st to 15thNight
21%323%34%16%
425
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%31%22%4
837
October1st to 15thNight
20%8%25%26%16%2
840
16th to endNight
21%11%32%25%8%
896
November1st to 15thNight
19%10%33%24%11%1
880
16th to endNight
19%13%34%25%7%
900
December1st to 15thNight
25%11%34%21%6%1
900
16th to endNight
23%14%40%19%2
960
Page generated at 2020-06-04 03:18:57. Version ac04

Copyright 2020 A. Danko


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