Flushing Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Flushing Observatory clear sky chart from 2005-11-05 to 2018-03-21.

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
36%
16549
15%
49298
9%
16507
41%
16507
20%
34632

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
19%
975
9%
2716
3%
970
23%
970
13%
2169
January16th to endNight
21%
968
8%
2840
3%
968
27%
968
12%
2260
February1st to 15thNight
17%
761
9%
2450
3%
761
24%
761
11%
1902
February16th to endNight
24%
683
14%
2049
6%
683
31%
683
14%
1551
March1st to 15thNight
29%
780
16%
2262
10%
780
34%
780
18%
1642
March16th to endNight
34%
792
19%
2178
10%
792
41%
792
22%
1531
April1st to 15thNight
29%
570
13%
1798
9%
570
34%
570
19%
1249
April16th to endNight
34%
540
20%
1620
9%
540
44%
540
26%
1052
May1st to 15thNight
35%
540
14%
1620
7%
540
42%
540
22%
1105
May16th to endNight
45%
562
16%
1638
11%
561
51%
561
28%
1044
June1st to 15thNight
54%
444
16%
1344
14%
444
58%
444
30%
825
June16th to endNight
55%
463
16%
1363
12%
463
60%
463
33%
826
July1st to 15thNight
63%
510
16%
1360
14%
510
65%
510
40%
818
July16th to endNight
64%
564
18%
1471
15%
531
67%
531
39%
878
August1st to 15thNight
66%
539
19%
1609
16%
536
69%
536
34%
962
August16th to endNight
60%
573
22%
1746
17%
573
65%
573
34%
1021
September1st to 15thNight
59%
655
23%
1915
18%
655
63%
655
33%
1152
September16th to endNight
59%
717
24%
1980
18%
717
63%
717
33%
1235
October1st to 15thNight
45%
720
19%
2064
15%
720
49%
720
24%
1406
October16th to endNight
26%
768
15%
2425
8%
768
35%
768
16%
1744
November1st to 15thNight
34%
760
18%
2471
15%
760
41%
760
20%
1652
November16th to endNight
25%
780
13%
2594
8%
780
32%
780
14%
1885
December1st to 15thNight
17%
845
6%
2795
2%
845
21%
845
9%
2223
December16th to endNight
15%
1040
8%
2990
1%
1040
21%
1040
9%
2500

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
14%8%36%6%3445%7%33%
49533
Night
15%9%46%5%34446%35%
49473
Cloud CoverDay
14%9%36%6%3445%7%33%
49543
Night
15%9%46%5%34446%35%
49477
TransparencyDay
49%6%12%20%10%1
49227
Night
49%5%11%20%11%1
49298
SeeingDay
18%7%26%23%15%7%
6454
Night
19%7%28%30%11%1
16553

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
16%15%6%10%8%45%43417%
1552
16th to endDay
16%16%9%11%7%35%34417%
1735
February1st to 15thDay
14%16%6%9%8%34445%20%
1742
16th to endDay
13%13%6%10%8%45%45%423%
1710
March1st to 15thDay
15%10%49%7%3345%6%28%
2017
16th to endDay
16%9%48%6%35%345%31%
2174
April1st to 15thDay
20%10%35%6%24347%30%
2160
16th to endDay
16%8%25%5%34447%37%
2340
May1st to 15thDay
20%7%35%42445%7%34%
2331
16th to endDay
13%6%35%5%35%5%6%7%39%
2475
June1st to 15thDay
11%6%25%5%35%5%6%8%40%
2610
16th to endDay
9%5%26%436%6%7%10%37%
2589
July1st to 15thDay
7%5%235%36%5%6%8%44%
2520
16th to endDay
9%5%145%45%6%7%8%40%
2595
August1st to 15thDay
9%5%25%6%46%6%7%8%38%
2340
16th to endDay
12%435%5%35%5%5%7%41%
2454
September1st to 15thDay
12%5%245%35%5%6%9%40%
2031
16th to endDay
12%5%25%4345%5%9%41%
1980
October1st to 15thDay
15%7%26%6%3445%6%37%
1896
16th to endDay
22%9%36%5%33446%30%
1797
November1st to 15thDay
17%8%35%6%2435%7%35%
1717
16th to endDay
16%13%48%6%3445%5%26%
1693
December1st to 15thDay
16%14%7%10%7%33445%21%
1492
16th to endDay
20%17%6%10%5%2335%6%17%
1583
January1st to 15thNight
22%11%6%8%6%3345%422%
2716
16th to endNight
13%13%8%10%7%4445%5%20%
2840
February1st to 15thNight
14%15%5%9%7%35%44425%
2448
16th to endNight
16%12%48%8%25%445%26%
2049
March1st to 15thNight
15%10%5%7%5%3444433%
2250
16th to endNight
16%7%35%5%345%46%36%
2178
April1st to 15thNight
20%8%45%5%2445%6%33%
1798
16th to endNight
15%7%25%42345%7%40%
1620
May1st to 15thNight
16%6%36%5%345%46%37%
1620
16th to endNight
13%4244345%5%7%43%
1636
June1st to 15thNight
11%325%4246%49%44%
1344
16th to endNight
9%434425%45%9%45%
1363
July1st to 15thNight
6%42442446%8%51%
1440
16th to endNight
7%314425%5%5%9%50%
1571
August1st to 15thNight
6%3145%345%6%8%49%
1620
16th to endNight
9%5%23423447%52%
1746
September1st to 15thNight
11%5%133235%47%50%
1915
16th to endNight
10%425%42345%7%48%
1980
October1st to 15thNight
18%7%24434346%40%
2064
16th to endNight
21%8%26%5%33445%32%
2425
November1st to 15thNight
16%8%35%5%2445%6%36%
2471
16th to endNight
20%11%36%6%2445%5%28%
2594
December1st to 15thNight
19%14%7%9%5%34335%21%
2795
16th to endNight
20%15%8%9%6%24435%18%
2990

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
16%15%7%9%8%5%5%44417%
1552
16th to endDay
16%16%9%11%9%35%335%16%
1735
February1st to 15thDay
14%16%6%9%8%44445%20%
1742
16th to endDay
13%14%5%10%9%3445%423%
1710
March1st to 15thDay
15%10%49%7%34446%28%
2028
16th to endDay
16%10%48%7%34345%31%
2173
April1st to 15thDay
20%10%35%6%34347%31%
2160
16th to endDay
15%8%25%5%33446%37%
2340
May1st to 15thDay
19%7%3442445%7%34%
2331
16th to endDay
12%6%25%5%35%5%5%8%39%
2475
June1st to 15thDay
10%6%35%5%345%6%8%40%
2610
16th to endDay
9%5%26%436%6%7%10%36%
2589
July1st to 15thDay
7%424435%5%6%9%44%
2520
16th to endDay
9%5%245%36%6%7%8%40%
2595
August1st to 15thDay
9%5%26%6%46%6%6%9%37%
2340
16th to endDay
12%435%445%5%5%7%41%
2454
September1st to 15thDay
11%5%245%35%5%6%8%40%
2031
16th to endDay
12%5%25%5%345%5%9%41%
1980
October1st to 15thDay
15%7%27%5%3445%6%37%
1896
16th to endDay
21%9%36%5%34446%30%
1797
November1st to 15thDay
17%9%35%6%3335%7%34%
1717
16th to endDay
16%12%5%7%6%34446%26%
1693
December1st to 15thDay
16%14%7%11%7%3335%5%21%
1492
16th to endDay
21%16%6%10%5%23446%17%
1583
January1st to 15thNight
22%11%6%9%6%34445%22%
2716
16th to endNight
14%13%8%10%8%4445%5%21%
2840
February1st to 15thNight
14%14%6%9%7%3444425%
2441
16th to endNight
16%12%48%7%35%446%26%
2049
March1st to 15thNight
16%10%47%5%34345%33%
2262
16th to endNight
16%7%35%5%35%5%45%36%
2178
April1st to 15thNight
20%8%45%42345%6%33%
1798
16th to endNight
15%7%35%42446%6%40%
1620
May1st to 15thNight
16%6%36%5%3345%6%37%
1619
16th to endNight
13%425%4245%6%7%44%
1636
June1st to 15thNight
11%3245%246%49%45%
1344
16th to endNight
9%424426%46%9%45%
1363
July1st to 15thNight
6%3345%1437%7%52%
1440
16th to endNight
7%3144345%5%9%50%
1571
August1st to 15thNight
6%3145%346%6%7%49%
1620
16th to endNight
10%423423447%51%
1746
September1st to 15thNight
11%5%133245%47%50%
1915
16th to endNight
10%435%424447%48%
1980
October1st to 15thNight
18%7%15%434346%40%
2064
16th to endNight
21%9%26%5%34445%32%
2425
November1st to 15thNight
16%9%35%5%3445%5%36%
2471
16th to endNight
20%12%46%5%345%46%28%
2594
December1st to 15thNight
19%14%7%9%5%34335%21%
2795
16th to endNight
20%16%8%10%6%23435%18%
2990

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
69%5%9%11%4
1553
16th to endDay
71%5%9%9%4
1735
February1st to 15thDay
65%6%10%13%5%
1744
16th to endDay
62%5%9%14%7%
1710
March1st to 15thDay
56%6%12%16%8%
2028
16th to endDay
54%5%10%20%8%1
2174
April1st to 15thDay
53%410%20%10%
2160
16th to endDay
46%5%13%16%14%2
2340
May1st to 15thDay
48%5%11%20%10%2
2331
16th to endDay
42%6%12%23%12%1
2479
June1st to 15thDay
40%7%11%24%14%1
2610
16th to endDay
40%8%12%22%15%
2589
July1st to 15thDay
35%6%11%26%18%2
2371
16th to endDay
37%9%13%21%15%2
2433
August1st to 15thDay
39%8%12%24%12%2
2327
16th to endDay
39%7%11%24%15%1
2454
September1st to 15thDay
39%7%12%26%12%1
2031
16th to endDay
39%6%12%28%13%
1980
October1st to 15thDay
46%5%11%21%12%1
1896
16th to endDay
54%5%16%17%6%
1797
November1st to 15thDay
49%5%11%23%9%
1717
16th to endDay
57%6%13%15%5%
1693
December1st to 15thDay
64%5%12%13%3
1492
16th to endDay
68%412%9%4
1583
January1st to 15thNight
63%411%12%7%
2716
16th to endNight
63%5%13%13%3
2840
February1st to 15thNight
62%5%10%14%7%
2450
16th to endNight
59%411%16%7%
2049
March1st to 15thNight
53%49%19%11%1
2262
16th to endNight
48%5%11%22%11%1
2178
April1st to 15thNight
49%411%19%13%
1798
16th to endNight
41%5%11%20%17%3
1620
May1st to 15thNight
46%5%10%21%11%3
1620
16th to endNight
38%6%11%24%15%4
1638
June1st to 15thNight
34%7%11%27%17%1
1344
16th to endNight
34%6%15%25%17%1
1363
July1st to 15thNight
29%6%9%29%21%2
1360
16th to endNight
28%7%17%22%22%2
1471
August1st to 15thNight
29%9%11%31%15%2
1609
16th to endNight
31%6%12%29%17%2
1746
September1st to 15thNight
33%5%10%29%18%1
1915
16th to endNight
34%6%12%29%16%
1980
October1st to 15thNight
45%5%9%23%15%1
2064
16th to endNight
53%5%12%20%7%
2425
November1st to 15thNight
47%5%13%21%11%1
2471
16th to endNight
56%414%17%6%
2594
December1st to 15thNight
65%5%11%11%5%
2795
16th to endNight
69%5%10%10%4
2990

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
14%12%41%24%6%
135
16th to endDay
32%10%34%20%2
144
February1st to 15thDay
30%17%37%12%2
135
16th to endDay
21%15%40%17%5%
120
March1st to 15thDay
30%8%30%23%7%
213
16th to endDay
24%6%29%24%12%2
311
April1st to 15thDay
28%7%28%24%8%2
270
16th to endDay
21%8%30%20%14%5%
270
May1st to 15thDay
26%6%28%20%14%4
288
16th to endDay
17%6%27%24%15%8%
375
June1st to 15thDay
13%6%30%29%13%5%
495
16th to endDay
11%8%29%25%18%6%
495
July1st to 15thDay
10%6%23%27%21%11%
475
16th to endDay
10%225%29%20%11%
455
August1st to 15thDay
10%215%24%25%20%
313
16th to endDay
15%318%19%24%18%
332
September1st to 15thDay
11%319%22%26%17%
315
16th to endDay
15%415%21%28%14%
314
October1st to 15thDay
18%8%22%26%19%4
315
16th to endDay
30%9%26%25%7%
213
November1st to 15thDay
20%12%25%27%9%3
135
16th to endDay
28%16%34%14%5%
121
December1st to 15thDay
26%16%37%13%5%
90
16th to endDay
26%20%36%12%2
125
January1st to 15thNight
26%12%32%22%5%
975
16th to endNight
20%9%35%28%5%
968
February1st to 15thNight
22%10%39%23%3
764
16th to endNight
23%11%32%27%4
683
March1st to 15thNight
21%10%31%29%7%
780
16th to endNight
19%9%29%30%9%1
792
April1st to 15thNight
22%11%32%26%6%
570
16th to endNight
21%6%33%27%9%1
540
May1st to 15thNight
19%433%32%8%1
540
16th to endNight
15%329%33%15%2
563
June1st to 15thNight
13%323%46%13%
444
16th to endNight
9%226%42%17%1
463
July1st to 15thNight
10%117%42%25%2
510
16th to endNight
8%119%45%22%2
564
August1st to 15thNight
8%115%41%28%3
539
16th to endNight
12%217%34%28%4
573
September1st to 15thNight
14%318%32%24%6%
655
16th to endNight
13%416%33%27%5%
717
October1st to 15thNight
20%5%22%32%16%1
720
16th to endNight
26%9%31%26%5%
768
November1st to 15thNight
21%9%30%26%11%
760
16th to endNight
25%13%31%21%7%
780
December1st to 15thNight
26%11%34%21%3
845
16th to endNight
28%12%35%21%2
1040
Page generated at 2018-03-22 11:34:22. Version ac04

Copyright 2018 A. Danko


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