New Haven
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the New Haven clear sky chart from 2005-11-05 to 2017-08-12.

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
27%
14836
19%
46465
8%
14804
39%
14804
19%
30216

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
16%
720
21%
2506
8%
716
33%
716
15%
1575
January16th to endNight
15%
768
21%
2650
5%
768
35%
768
15%
1649
February1st to 15thNight
16%
704
18%
2189
5%
701
31%
701
15%
1451
February16th to endNight
16%
631
24%
1893
7%
631
38%
631
18%
1225
March1st to 15thNight
17%
720
17%
2160
6%
720
31%
720
16%
1442
March16th to endNight
19%
768
23%
2004
6%
768
33%
768
22%
1329
April1st to 15thNight
19%
718
17%
1796
4%
718
27%
718
20%
1274
April16th to endNight
23%
657
17%
1737
3%
657
32%
657
20%
1193
May1st to 15thNight
24%
540
16%
1620
6%
540
33%
540
15%
1145
May16th to endNight
31%
377
13%
1499
9%
376
39%
376
15%
961
June1st to 15thNight
33%
360
14%
1440
11%
360
44%
360
16%
951
June16th to endNight
43%
360
14%
1440
13%
360
52%
360
22%
834
July1st to 15thNight
45%
340
11%
1360
15%
340
49%
340
19%
859
July16th to endNight
47%
376
15%
1418
14%
354
56%
354
20%
859
August1st to 15thNight
48%
508
17%
1557
10%
506
54%
506
25%
967
August16th to endNight
52%
700
17%
1750
8%
700
55%
700
30%
1174
September1st to 15thNight
43%
660
23%
1670
12%
660
47%
660
29%
1099
September16th to endNight
44%
657
24%
1815
15%
657
51%
657
27%
1157
October1st to 15thNight
31%
660
21%
1886
12%
660
42%
660
23%
1240
October16th to endNight
24%
704
18%
2238
5%
704
39%
704
20%
1450
November1st to 15thNight
25%
700
21%
2277
10%
700
41%
700
20%
1431
November16th to endNight
22%
720
20%
2352
9%
720
36%
720
17%
1511
December1st to 15thNight
21%
720
16%
2520
6%
720
35%
720
13%
1650
December16th to endNight
13%
768
19%
2688
4%
768
30%
768
12%
1790

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%2442445%7%41%
47514
Night
17%6%24424446%42%
46635
Cloud CoverDay
16%5%2442445%7%41%
47524
Night
17%6%24424446%42%
46640
TransparencyDay
41%6%12%21%15%2
47202
Night
42%5%11%21%15%2
46465
SeeingDay
18%19%26%22%9%2
5697
Night
18%23%26%22%7%
14836

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
17%5%2432346%442%
1432
16th to endDay
16%6%25%423447%41%
1572
February1st to 15thDay
16%6%245%3445%7%39%
1672
16th to endDay
17%5%2443346%7%39%
1580
March1st to 15thDay
18%7%24434447%38%
1790
16th to endDay
17%6%35%424435%42%
2218
April1st to 15thDay
20%6%24324346%41%
2152
16th to endDay
17%424424346%44%
2223
May1st to 15thDay
23%6%2432335%7%35%
2338
16th to endDay
17%5%25%42345%8%40%
2618
June1st to 15thDay
22%5%245%245%5%7%34%
2520
16th to endDay
12%5%245%345%6%10%39%
2520
July1st to 15thDay
12%5%25%5%36%47%8%38%
2520
16th to endDay
12%5%245%25%5%6%8%39%
2654
August1st to 15thDay
13%424435%5%6%8%42%
2292
16th to endDay
11%5%25%6%2345%8%43%
2100
September1st to 15thDay
13%414444446%46%
1959
16th to endDay
15%413424346%47%
1815
October1st to 15thDay
17%6%24423346%42%
1743
16th to endDay
17%4135%24447%43%
1634
November1st to 15thDay
19%6%23323336%44%
1581
16th to endDay
17%5%23323347%44%
1605
December1st to 15thDay
19%5%245%33447%40%
1440
16th to endDay
21%9%23323346%37%
1536
January1st to 15thNight
19%6%14423346%43%
2506
16th to endNight
16%8%24323337%43%
2650
February1st to 15thNight
15%8%45%423446%40%
2188
16th to endNight
17%6%23423336%44%
1893
March1st to 15thNight
20%6%1342445%6%40%
2147
16th to endNight
16%6%34423345%45%
2004
April1st to 15thNight
18%6%25%424447%39%
1796
16th to endNight
20%5%35%423335%42%
1737
May1st to 15thNight
21%7%245%34446%35%
1620
16th to endNight
20%5%25%334448%37%
1497
June1st to 15thNight
22%5%2442345%6%37%
1440
16th to endNight
13%424424449%45%
1440
July1st to 15thNight
13%5%15%435%5%7%9%38%
1440
16th to endNight
11%4245%36%6%7%8%38%
1514
August1st to 15thNight
10%424425%6%6%7%44%
1567
16th to endNight
12%325%43445%8%43%
1750
September1st to 15thNight
15%5%23424347%46%
1670
16th to endNight
15%5%2442433449%
1815
October1st to 15thNight
16%5%26%423335%44%
1886
16th to endNight
18%5%2442435%6%42%
2238
November1st to 15thNight
17%6%34323345%45%
2277
16th to endNight
19%5%24424346%41%
2352
December1st to 15thNight
21%5%2432435%6%38%
2520
16th to endNight
21%6%24434346%38%
2688

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
17%6%2432346%443%
1432
16th to endDay
16%6%26%32346%6%42%
1572
February1st to 15thDay
16%5%25%435%447%40%
1672
16th to endDay
17%5%244335%5%7%40%
1580
March1st to 15thDay
18%6%25%434447%38%
1800
16th to endDay
17%7%24424445%42%
2218
April1st to 15thDay
19%6%23424347%41%
2152
16th to endDay
17%5%14424446%44%
2223
May1st to 15thDay
22%7%2432345%6%36%
2338
16th to endDay
16%425%42445%8%40%
2618
June1st to 15thDay
22%5%2442445%8%35%
2520
16th to endDay
11%5%244345%5%10%41%
2520
July1st to 15thDay
11%5%25%5%35%5%6%10%39%
2520
16th to endDay
12%5%245%25%5%6%8%41%
2654
August1st to 15thDay
13%3244346%6%8%43%
2292
16th to endDay
11%5%25%5%3345%7%45%
2100
September1st to 15thDay
13%314434446%47%
1959
16th to endDay
15%413424346%47%
1815
October1st to 15thDay
17%6%14424446%43%
1743
16th to endDay
16%4144245%47%43%
1634
November1st to 15thDay
19%6%14423335%44%
1581
16th to endDay
17%42332435%7%44%
1605
December1st to 15thDay
19%4245%2435%6%41%
1440
16th to endDay
22%7%2432435%6%37%
1536
January1st to 15thNight
19%5%24323346%43%
2506
16th to endNight
17%8%24314336%43%
2650
February1st to 15thNight
14%8%35%424445%41%
2181
16th to endNight
17%6%23433346%44%
1893
March1st to 15thNight
20%6%23324446%40%
2160
16th to endNight
16%6%33323346%46%
2003
April1st to 15thNight
18%6%25%423446%39%
1796
16th to endNight
20%5%245%23345%42%
1737
May1st to 15thNight
20%7%25%43435%6%35%
1620
16th to endNight
20%6%24434449%36%
1497
June1st to 15thNight
22%5%2442435%7%37%
1440
16th to endNight
13%324434349%46%
1440
July1st to 15thNight
13%425%425%5%7%8%39%
1440
16th to endNight
11%425%5%35%6%7%9%38%
1514
August1st to 15thNight
10%4244345%7%7%44%
1567
16th to endNight
12%425%5%2445%8%43%
1750
September1st to 15thNight
15%5%235%23447%45%
1670
16th to endNight
15%5%24335%235%49%
1815
October1st to 15thNight
16%5%25%5%23336%44%
1886
16th to endNight
18%5%24424346%42%
2238
November1st to 15thNight
17%6%2432235%445%
2277
16th to endNight
20%5%24424346%41%
2352
December1st to 15thNight
21%6%2432435%6%38%
2520
16th to endNight
21%6%24434345%38%
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
42%5%14%21%12%3
1433
16th to endDay
42%5%10%24%14%2
1572
February1st to 15thDay
44%6%13%20%14%1
1675
16th to endDay
42%6%11%23%14%2
1580
March1st to 15thDay
46%414%21%10%2
1800
16th to endDay
44%410%17%18%3
2218
April1st to 15thDay
43%5%10%21%16%3
2152
16th to endDay
40%5%9%22%18%3
2223
May1st to 15thDay
48%5%9%19%14%2
2338
16th to endDay
41%8%14%20%13%2
2622
June1st to 15thDay
47%7%12%20%10%1
2520
16th to endDay
37%9%14%23%13%1
2520
July1st to 15thDay
39%8%11%22%16%1
2371
16th to endDay
37%8%15%22%13%2
2487
August1st to 15thDay
35%10%14%22%16%
2278
16th to endDay
37%7%9%25%18%1
2100
September1st to 15thDay
37%7%12%20%20%1
1959
16th to endDay
36%5%7%22%24%2
1815
October1st to 15thDay
42%411%22%16%2
1743
16th to endDay
39%6%11%24%15%2
1634
November1st to 15thDay
43%313%18%18%2
1581
16th to endDay
40%412%25%14%2
1605
December1st to 15thDay
44%416%19%14%1
1440
16th to endDay
48%5%14%18%12%
1536
January1st to 15thNight
43%411%23%14%2
2506
16th to endNight
42%410%23%16%2
2650
February1st to 15thNight
44%6%11%21%12%2
2189
16th to endNight
42%49%23%17%2
1893
March1st to 15thNight
45%5%13%19%13%3
2160
16th to endNight
40%49%21%19%4
2004
April1st to 15thNight
45%5%10%20%15%2
1796
16th to endNight
45%38%20%17%3
1737
May1st to 15thNight
49%6%9%16%15%2
1620
16th to endNight
45%6%17%16%12%1
1499
June1st to 15thNight
47%6%11%19%13%2
1440
16th to endNight
36%6%14%25%15%
1440
July1st to 15thNight
41%8%12%21%14%1
1360
16th to endNight
38%8%16%22%11%2
1418
August1st to 15thNight
34%9%14%24%15%2
1557
16th to endNight
38%6%11%25%16%1
1750
September1st to 15thNight
38%6%10%26%17%
1670
16th to endNight
39%46%21%26%1
1815
October1st to 15thNight
42%5%10%22%16%3
1886
16th to endNight
43%5%13%21%15%
2238
November1st to 15thNight
41%411%20%18%3
2277
16th to endNight
44%411%24%12%2
2352
December1st to 15thNight
46%5%14%19%14%
2520
16th to endNight
47%5%12%20%13%1
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
15%31%35%18%
60
16th to endDay
25%21%38%14%
70
February1st to 15thDay
21%27%37%12%1
188
16th to endDay
15%28%33%18%4
239
March1st to 15thDay
21%31%27%16%3
270
16th to endDay
20%28%33%12%31
288
April1st to 15thDay
22%25%29%15%6%
270
16th to endDay
20%19%29%20%7%2
270
May1st to 15thDay
28%26%21%14%6%1
288
16th to endDay
20%17%26%24%9%1
331
June1st to 15thDay
20%17%25%22%12%2
315
16th to endDay
15%15%30%25%12%1
315
July1st to 15thDay
16%9%23%33%14%2
305
16th to endDay
11%12%26%31%14%3
326
August1st to 15thDay
12%8%21%34%17%5%
297
16th to endDay
12%9%20%28%17%10%
268
September1st to 15thDay
13%12%24%24%15%9%
255
16th to endDay
18%9%25%20%16%8%
254
October1st to 15thDay
21%12%21%27%11%4
255
16th to endDay
15%22%30%22%7%1
249
November1st to 15thDay
20%22%22%20%11%2
235
16th to endDay
16%29%25%20%8%
225
December1st to 15thDay
20%25%30%18%6%
60
16th to endDay
35%17%37%7%1
64
January1st to 15thNight
18%32%29%16%3
720
16th to endNight
19%31%30%17%1
768
February1st to 15thNight
16%29%32%18%1
704
16th to endNight
19%29%31%17%2
631
March1st to 15thNight
23%28%26%18%3
720
16th to endNight
18%27%31%17%4
768
April1st to 15thNight
19%27%31%18%3
718
16th to endNight
18%26%27%21%5%
657
May1st to 15thNight
20%24%27%18%8%
540
16th to endNight
20%19%21%30%7%
377
June1st to 15thNight
20%19%22%28%8%
360
16th to endNight
14%18%20%35%10%
360
July1st to 15thNight
12%14%20%35%15%1
340
16th to endNight
11%17%15%38%14%1
376
August1st to 15thNight
14%10%20%39%14%
508
16th to endNight
12%10%16%36%20%3
700
September1st to 15thNight
16%12%21%30%16%2
660
16th to endNight
17%12%18%27%20%3
657
October1st to 15thNight
18%16%26%25%11%1
660
16th to endNight
20%19%33%20%6%
704
November1st to 15thNight
18%26%26%18%9%1
700
16th to endNight
18%28%26%19%5%
720
December1st to 15thNight
24%27%22%19%5%
720
16th to endNight
23%32%27%14%2
768
Page generated at 2017-08-13 14:16:27. Version ac04

Copyright 2017 A. Danko


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