Long Island Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Long Island Lake clear sky chart from 2005-11-05 to 2017-09-20.

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
43%
15197
10%
46589
7%
15170
46%
15170
18%
33328

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
35%
906
7%
2752
4%
906
38%
906
13%
2127
January16th to endNight
33%
921
13%
2841
8%
921
38%
921
16%
2086
February1st to 15thNight
41%
700
9%
2458
9%
698
44%
698
15%
1770
February16th to endNight
46%
632
12%
2022
12%
632
49%
632
18%
1427
March1st to 15thNight
40%
720
14%
2121
10%
720
44%
720
20%
1528
March16th to endNight
42%
767
11%
2079
6%
767
44%
767
17%
1580
April1st to 15thNight
43%
599
13%
1679
8%
599
47%
599
20%
1227
April16th to endNight
40%
528
12%
1608
10%
528
44%
528
19%
1152
May1st to 15thNight
49%
359
6%
1272
6%
359
50%
359
22%
819
May16th to endNight
42%
375
0%
1309
0%
374
43%
374
15%
931
June1st to 15thNight
46%
360
0%
1158
0%
360
46%
360
15%
835
June16th to endNight
57%
360
0%
1080
0%
360
57%
360
21%
766
July1st to 15thNight
65%
340
0%
1053
0%
340
65%
340
27%
669
July16th to endNight
59%
376
1%
1239
0%
354
59%
354
24%
756
August1st to 15thNight
68%
360
5%
1367
7%
358
69%
358
23%
825
August16th to endNight
55%
559
13%
1705
11%
559
58%
559
26%
1100
September1st to 15thNight
59%
627
15%
1764
11%
627
60%
627
32%
1113
September16th to endNight
50%
675
19%
1869
11%
675
56%
675
34%
1171
October1st to 15thNight
44%
660
14%
1985
10%
660
48%
660
21%
1387
October16th to endNight
39%
716
14%
2300
10%
716
46%
716
18%
1609
November1st to 15thNight
33%
875
13%
2516
8%
875
38%
875
17%
1898
November16th to endNight
32%
900
9%
2700
5%
900
36%
900
14%
2084
December1st to 15thNight
32%
900
8%
2700
5%
900
34%
900
11%
2150
December16th to endNight
39%
982
11%
3012
5%
982
44%
982
14%
2318

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
11%8%47%6%45%5%6%8%30%
48291
Night
9%9%47%6%45%5%6%7%31%
46730
TransparencyDay
49%8%17%18%5%
47934
Night
49%7%15%19%6%
46592
SeeingDay
15%423%29%20%6%
6552
Night
13%325%35%17%2
15208

By Month

Percentage Cloud Cover NW (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
8%11%7%11%9%47%45%7%21%
1185
16th to endDay
8%12%5%10%6%36%45%8%27%
1395
February1st to 15thDay
8%9%49%8%5%6%5%6%7%26%
1403
16th to endDay
6%11%7%10%7%5%5%7%6%8%21%
1451
March1st to 15thDay
7%14%6%11%8%47%5%5%6%21%
1838
16th to endDay
11%12%6%9%7%45%6%6%6%23%
2142
April1st to 15thDay
9%12%5%6%6%35%6%5%7%29%
2269
16th to endDay
14%11%37%7%35%5%6%7%26%
2349
May1st to 15thDay
11%7%45%6%35%5%6%8%33%
2679
16th to endDay
16%7%36%6%35%5%6%8%30%
2802
June1st to 15thDay
17%9%37%6%45%5%6%7%26%
2799
16th to endDay
14%6%35%6%45%6%6%9%30%
2880
July1st to 15thDay
11%425%5%36%5%6%10%37%
2843
16th to endDay
12%5%25%5%35%6%8%9%36%
2846
August1st to 15thDay
9%5%25%5%46%6%7%10%35%
2583
16th to endDay
8%5%26%6%36%5%7%9%36%
2497
September1st to 15thDay
12%6%26%5%345%5%7%37%
2195
16th to endDay
12%5%244345%5%9%42%
1860
October1st to 15thDay
14%8%47%5%26%447%34%
1644
16th to endDay
11%10%46%5%45%45%7%33%
1560
November1st to 15thDay
10%11%6%7%7%45%5%5%6%28%
1342
16th to endDay
6%11%6%10%9%35%5%5%6%28%
1260
December1st to 15thDay
7%15%49%10%5%7%6%5%7%19%
1260
16th to endDay
410%7%11%9%6%8%6%7%7%21%
1209
January1st to 15thNight
8%13%6%9%8%5%6%5%5%6%24%
2752
16th to endNight
7%11%5%9%6%45%5%5%7%30%
2841
February1st to 15thNight
7%10%6%9%9%45%45%7%28%
2449
16th to endNight
6%11%6%7%7%45%5%6%9%29%
2022
March1st to 15thNight
8%10%48%7%45%5%5%9%30%
2121
16th to endNight
10%12%5%8%6%36%6%7%7%25%
2076
April1st to 15thNight
10%10%47%6%35%6%6%6%32%
1679
16th to endNight
12%11%47%6%36%45%7%31%
1608
May1st to 15thNight
9%7%46%6%35%5%5%7%38%
1271
16th to endNight
20%8%25%6%25%45%7%29%
1309
June1st to 15thNight
13%6%49%7%47%6%6%7%28%
1158
16th to endNight
10%7%36%6%36%5%7%8%31%
1080
July1st to 15thNight
8%5%13445%6%8%11%39%
1116
16th to endNight
9%4246%36%6%7%8%40%
1323
August1st to 15thNight
6%3245%37%6%7%10%41%
1374
16th to endNight
11%5%25%6%345%6%8%40%
1705
September1st to 15thNight
10%5%244245%5%7%46%
1764
16th to endNight
10%6%2432345%8%48%
1869
October1st to 15thNight
12%8%37%6%35%45%8%33%
1985
16th to endNight
10%9%5%8%5%345%6%7%32%
2300
November1st to 15thNight
12%11%5%8%6%345%6%5%28%
2516
16th to endNight
6%12%6%11%8%35%46%7%26%
2700
December1st to 15thNight
10%12%6%10%8%5%6%6%5%6%21%
2700
16th to endNight
6%11%6%10%7%5%7%6%6%7%23%
3012

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
62%8%14%9%4
1185
16th to endDay
54%6%12%17%7%1
1395
February1st to 15thDay
53%7%17%15%5%
1403
16th to endDay
58%7%14%15%4
1451
March1st to 15thDay
60%7%12%14%4
1838
16th to endDay
57%9%13%14%4
2143
April1st to 15thDay
51%7%17%17%6%
2269
16th to endDay
55%6%12%17%6%1
2349
May1st to 15thDay
45%7%14%22%9%
2679
16th to endDay
50%7%11%20%9%
2807
June1st to 15thDay
54%9%14%17%3
2799
16th to endDay
48%10%17%18%4
2880
July1st to 15thDay
40%11%21%22%3
2677
16th to endDay
40%12%25%20%1
2667
August1st to 15thDay
41%11%28%16%1
2565
16th to endDay
39%9%26%19%4
2497
September1st to 15thDay
43%8%22%19%5%
2195
16th to endDay
36%8%19%25%7%1
1860
October1st to 15thDay
49%6%17%23%3
1644
16th to endDay
49%7%15%25%2
1560
November1st to 15thDay
54%7%17%15%5%
1342
16th to endDay
55%8%14%17%31
1260
December1st to 15thDay
62%8%12%14%2
1260
16th to endDay
57%9%13%14%5%
1209
January1st to 15thNight
58%7%15%13%4
2752
16th to endNight
52%7%15%16%7%1
2841
February1st to 15thNight
54%6%15%16%6%
2461
16th to endNight
50%6%16%18%7%
2022
March1st to 15thNight
49%7%13%20%7%
2121
16th to endNight
54%8%13%17%7%
2079
April1st to 15thNight
49%8%10%20%9%1
1679
16th to endNight
51%5%9%19%12%1
1608
May1st to 15thNight
44%5%12%22%14%1
1272
16th to endNight
52%7%10%18%9%1
1309
June1st to 15thNight
51%8%14%18%5%
1158
16th to endNight
46%8%16%22%4
1080
July1st to 15thNight
35%11%23%25%5%
1053
16th to endNight
35%10%23%26%3
1239
August1st to 15thNight
33%12%27%24%1
1367
16th to endNight
39%8%21%25%6%
1705
September1st to 15thNight
35%7%18%29%7%1
1764
16th to endNight
33%6%17%30%10%1
1869
October1st to 15thNight
47%7%13%26%5%
1985
16th to endNight
48%7%15%23%4
2300
November1st to 15thNight
55%6%12%20%4
2516
16th to endNight
56%9%15%14%4
2700
December1st to 15thNight
62%7%12%13%3
2700
16th to endNight
56%8%13%16%4
3012

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
8%318%36%30%3
60
16th to endDay
9%123%39%18%7%
64
February1st to 15thDay
19%124%31%18%4
61
16th to endDay
11%415%39%21%7%
110
March1st to 15thDay
15%5%34%28%13%2
270
16th to endDay
19%229%27%19%2
288
April1st to 15thDay
14%7%32%29%13%1
269
16th to endDay
23%8%26%25%12%2
270
May1st to 15thDay
13%8%23%28%19%5%
456
16th to endDay
19%317%28%24%6%
517
June1st to 15thDay
20%420%31%17%5%
594
16th to endDay
13%5%20%28%24%8%
675
July1st to 15thDay
9%219%32%30%5%
611
16th to endDay
13%319%30%25%7%
515
August1st to 15thDay
10%217%26%23%19%
378
16th to endDay
9%6%32%29%20%1
332
September1st to 15thDay
19%7%24%27%15%5%
315
16th to endDay
15%10%28%26%16%2
272
October1st to 15thDay
27%324%22%18%4
136
16th to endDay
22%5%19%21%23%6%
96
November1st to 15thDay
27%5%25%35%6%
79
16th to endDay
6%128%31%10%21%
60
December1st to 15thDay
16%130%31%8%11%
60
16th to endDay
4420%37%21%10%
64
January1st to 15thNight
13%428%37%13%2
911
16th to endNight
14%7%32%33%10%2
921
February1st to 15thNight
11%326%36%20%2
704
16th to endNight
9%325%36%21%3
632
March1st to 15thNight
11%330%37%13%3
720
16th to endNight
17%325%33%18%2
768
April1st to 15thNight
14%326%34%17%2
599
16th to endNight
17%6%24%32%17%2
528
May1st to 15thNight
11%5%21%38%20%3
360
16th to endNight
25%221%26%21%2
375
June1st to 15thNight
16%320%35%20%3
360
16th to endNight
12%214%37%30%2
360
July1st to 15thNight
10%115%46%24%1
340
16th to endNight
11%18%36%28%4
376
August1st to 15thNight
9%12%38%33%6%
360
16th to endNight
13%216%40%24%2
559
September1st to 15thNight
14%118%37%25%3
627
16th to endNight
12%228%38%15%2
675
October1st to 15thNight
16%124%39%14%2
660
16th to endNight
16%5%27%33%16%1
716
November1st to 15thNight
18%5%31%31%11%1
875
16th to endNight
10%5%33%33%14%2
900
December1st to 15thNight
16%5%29%31%12%4
900
16th to endNight
10%326%37%16%5%
982
Page generated at 2017-09-21 05:18:16. Version ac04

Copyright 2017 A. Danko


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