North Jersey Astronomical Group
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the North Jersey Astronomical Group clear sky chart from 2005-11-06 to 2024-01-15.

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
32%
23133
19%
74659
10%
23090
44%
23090
22%
47769

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 10thNight
22%
760
23%
2649
9%
757
40%
757
21%
1589
January11th to 20thNight
23%
740
19%
2588
7%
740
40%
740
16%
1694
January21st to endNight
20%
792
23%
2624
8%
792
39%
792
21%
1588
February1st to 10thNight
21%
720
17%
2340
7%
720
34%
720
19%
1536
February11th to 20thNight
17%
703
21%
2100
5%
700
37%
700
18%
1401
February21st to endNight
19%
592
26%
1776
10%
592
39%
592
20%
1160
March1st to 10thNight
21%
720
21%
2160
7%
720
39%
720
23%
1373
March11th to 20thNight
23%
720
21%
2052
9%
720
36%
720
22%
1353
March21st to endNight
22%
792
22%
2006
6%
792
34%
792
25%
1375
April1st to 10thNight
21%
720
19%
1800
4%
720
31%
720
22%
1255
April11th to 20thNight
27%
711
18%
1775
5%
711
33%
711
25%
1236
April21st to endNight
26%
707
19%
1787
5%
707
35%
707
24%
1233
May1st to 10thNight
23%
540
15%
1620
7%
540
31%
540
17%
1146
May11th to 20thNight
28%
378
19%
1440
11%
378
40%
378
17%
934
May21st to endNight
47%
388
15%
1551
15%
388
53%
388
20%
960
June1st to 10thNight
41%
360
18%
1440
15%
360
52%
360
20%
878
June11th to 20thNight
45%
360
15%
1440
14%
360
54%
360
20%
890
June21st to endNight
53%
360
15%
1440
15%
360
61%
360
25%
827
July1st to 10thNight
51%
350
13%
1400
15%
350
56%
350
20%
866
July11th to 20thNight
55%
348
15%
1392
18%
348
59%
348
21%
851
July21st to endNight
55%
394
18%
1486
17%
372
62%
372
25%
860
August1st to 10thNight
56%
475
16%
1539
12%
473
60%
473
26%
969
August11th to 20thNight
54%
710
14%
1774
9%
710
55%
710
25%
1268
August21st to endNight
53%
792
17%
1980
9%
792
56%
792
29%
1357
September1st to 10thNight
46%
720
20%
1800
10%
720
50%
720
28%
1227
September11th to 20thNight
50%
720
26%
1871
17%
720
54%
720
36%
1163
September21st to endNight
44%
720
24%
1980
15%
720
52%
720
29%
1290
October1st to 10thNight
36%
720
16%
2088
11%
720
42%
720
24%
1395
October11th to 20thNight
38%
720
23%
2160
14%
720
50%
720
28%
1317
October21st to endNight
27%
792
21%
2510
11%
792
42%
792
22%
1618
November1st to 10thNight
36%
740
25%
2407
12%
740
52%
740
27%
1417
November11th to 20thNight
28%
760
25%
2470
12%
760
45%
760
25%
1510
November21st to endNight
29%
760
23%
2555
10%
760
46%
760
23%
1523
December1st to 10thNight
24%
760
19%
2660
8%
760
39%
760
18%
1690
December11th to 20thNight
23%
760
19%
3184
7%
759
38%
759
16%
1954
December21st to endNight
22%
829
13%
4815
7%
817
38%
817
11%
3066

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%6%25%5%35%5%5%7%40%
74779
Night
17%6%35%5%3445%7%42%
75003
TransparencyDay
42%7%12%22%16%2
74484
Night
41%6%12%22%16%3
74832
SeeingDay
20%15%31%22%10%3
13862
Night
20%11%31%28%9%1
23141

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 10thDay
13%7%26%5%35%5%5%7%43%
1517
11th to 20thDay
16%8%35%6%45%5%5%6%37%
1478
21st to endDay
14%8%25%5%245%5%7%43%
1728
February1st to 10thDay
19%8%35%5%25%45%6%38%
1620
11th to 20thDay
15%6%35%6%34446%44%
1748
21st to endDay
21%7%3444445%6%38%
1480
March1st to 10thDay
14%7%36%5%3445%7%44%
1797
11th to 20thDay
16%6%25%6%35%5%6%8%38%
1905
21st to endDay
19%7%35%5%3445%6%40%
2348
April1st to 10thDay
18%8%36%4245%5%6%40%
2160
11th to 20thDay
17%5%246%2445%8%42%
2134
21st to endDay
21%5%245%3436%7%40%
2173
May1st to 10thDay
24%7%245%35%45%7%35%
2340
11th to 20thDay
21%5%35%5%345%5%7%37%
2468
21st to endDay
16%6%25%43446%8%41%
2725
June1st to 10thDay
17%5%25%5%35%6%7%9%37%
2520
11th to 20thDay
16%6%36%5%36%5%6%8%35%
2520
21st to endDay
12%5%35%6%35%6%6%10%40%
2520
July1st to 10thDay
11%5%25%7%46%5%7%10%37%
2520
11th to 20thDay
10%5%25%5%35%7%7%11%40%
2520
21st to endDay
12%6%36%7%47%6%6%9%36%
2744
August1st to 10thDay
10%6%25%6%46%7%7%9%38%
2366
11th to 20thDay
12%6%36%5%45%5%7%9%39%
2126
21st to endDay
14%5%26%5%35%5%6%7%42%
2376
September1st to 10thDay
14%5%345%35%5%5%7%42%
2160
11th to 20thDay
14%5%25%32345%8%49%
2088
21st to endDay
17%5%26%6%35%445%42%
1980
October1st to 10thDay
21%6%2443345%7%40%
1870
11th to 20thDay
17%5%2443445%6%47%
1800
21st to endDay
22%5%2442445%5%42%
1846
November1st to 10thDay
14%6%24423345%52%
1671
11th to 20thDay
18%5%24423446%47%
1710
21st to endDay
16%5%24425%45%7%45%
1623
December1st to 10thDay
18%8%35%5%34448%39%
1520
11th to 20thDay
22%5%24323446%44%
1906
21st to endDay
18%8%37%6%35%6%5%8%31%
2772
January1st to 10thNight
16%6%3442435%6%46%
2649
11th to 20thNight
19%7%25%435%45%6%39%
2588
21st to endNight
14%8%35%42445%7%44%
2624
February1st to 10thNight
17%9%35%5%34445%41%
2340
11th to 20thNight
17%8%36%5%3445%5%41%
2098
21st to endNight
20%7%345%3435%5%42%
1776
March1st to 10thNight
16%7%25%5%24446%45%
2150
11th to 20thNight
17%7%25%42445%6%43%
2051
21st to endNight
18%6%35%43445%7%42%
2006
April1st to 10thNight
19%7%35%43446%6%39%
1800
11th to 20thNight
18%7%245%35%45%7%41%
1775
21st to endNight
20%6%35%433347%42%
1787
May1st to 10thNight
22%7%46%6%3445%5%36%
1620
11th to 20thNight
19%8%35%5%2445%7%38%
1439
21st to endNight
17%6%25%5%3446%8%41%
1550
June1st to 10thNight
17%5%34445%46%8%41%
1440
11th to 20thNight
14%5%35%5%345%6%9%40%
1440
21st to endNight
11%325%5%345%7%10%45%
1440
July1st to 10thNight
12%5%35%6%35%6%6%9%40%
1440
11th to 20thNight
12%5%25%5%46%6%8%9%39%
1440
21st to endNight
10%5%245%35%6%7%11%42%
1574
August1st to 10thNight
9%5%25%5%35%5%6%9%44%
1549
11th to 20thNight
12%5%27%7%46%6%6%8%36%
1774
21st to endNight
14%5%36%5%3445%9%42%
1980
September1st to 10thNight
16%435%6%435%5%6%44%
1800
11th to 20thNight
15%5%24323347%52%
1871
21st to endNight
17%6%24434347%45%
1980
October1st to 10thNight
20%6%35%434446%42%
2088
11th to 20thNight
16%5%245%23446%49%
2160
21st to endNight
21%7%25%423445%44%
2510
November1st to 10thNight
13%5%25%3245%45%52%
2407
11th to 20thNight
20%6%24423345%48%
2470
21st to endNight
15%5%35%4345%5%7%47%
2555
December1st to 10thNight
19%7%35%5%235%5%6%40%
2660
11th to 20thNight
20%7%2443445%6%42%
3288
21st to endNight
20%9%36%5%34446%36%
4884

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 10thDay
41%411%26%14%4
1518
11th to 20thDay
46%7%13%19%12%3
1478
21st to endDay
40%5%11%26%15%3
1728
February1st to 10thDay
46%5%13%22%11%2
1620
11th to 20thDay
43%5%9%24%16%3
1757
21st to endDay
46%5%11%21%14%3
1480
March1st to 10thDay
40%5%13%24%15%3
1800
11th to 20thDay
43%6%12%22%15%2
1905
21st to endDay
46%5%10%18%17%5%
2348
April1st to 10thDay
43%6%10%20%16%5%
2160
11th to 20thDay
41%5%12%22%17%3
2134
21st to endDay
44%5%10%20%17%4
2173
May1st to 10thDay
49%6%9%18%16%2
2340
11th to 20thDay
44%8%10%20%15%3
2472
21st to endDay
40%8%14%22%14%2
2725
June1st to 10thDay
41%9%14%20%15%2
2520
11th to 20thDay
44%9%12%22%12%2
2520
21st to endDay
39%9%13%23%16%1
2520
July1st to 10thDay
40%10%12%21%16%1
2450
11th to 20thDay
34%10%15%24%15%2
2445
21st to endDay
41%10%12%18%16%3
2591
August1st to 10thDay
38%11%14%22%14%1
2352
11th to 20thDay
39%10%14%22%13%1
2126
21st to endDay
40%7%11%21%18%3
2376
September1st to 10thDay
40%8%11%21%18%3
2160
11th to 20thDay
34%5%11%22%25%3
2088
21st to endDay
43%6%9%19%20%4
1980
October1st to 10thDay
43%5%11%22%16%2
1870
11th to 20thDay
38%5%12%25%18%2
1800
21st to endDay
43%5%10%22%17%2
1846
November1st to 10thDay
35%411%24%22%3
1671
11th to 20thDay
39%410%23%21%4
1710
21st to endDay
38%5%13%30%12%2
1623
December1st to 10thDay
45%5%14%21%14%1
1520
11th to 20thDay
41%5%15%24%13%3
1906
21st to endDay
50%8%11%23%8%
2772
January1st to 10thNight
39%5%11%24%16%4
2649
11th to 20thNight
45%7%13%23%11%2
2588
21st to endNight
40%311%23%19%3
2624
February1st to 10thNight
45%5%12%23%12%2
2340
11th to 20thNight
45%410%19%17%5%
2100
21st to endNight
44%47%25%16%3
1776
March1st to 10thNight
40%5%12%23%15%5%
2160
11th to 20thNight
42%6%11%21%17%4
2052
21st to endNight
43%5%11%17%18%6%
2006
April1st to 10thNight
44%5%10%20%17%4
1800
11th to 20thNight
44%5%10%20%19%2
1775
21st to endNight
43%6%9%20%18%4
1787
May1st to 10thNight
50%6%10%17%15%2
1620
11th to 20thNight
46%6%11%15%18%3
1440
21st to endNight
42%7%15%20%13%3
1551
June1st to 10thNight
41%7%11%21%19%2
1440
11th to 20thNight
40%8%13%25%12%1
1440
21st to endNight
34%9%15%25%16%1
1440
July1st to 10thNight
40%9%14%19%16%2
1400
11th to 20thNight
38%10%13%25%12%2
1392
21st to endNight
32%11%17%21%16%3
1486
August1st to 10thNight
35%12%15%22%15%2
1539
11th to 20thNight
42%11%14%22%11%1
1774
21st to endNight
39%8%12%19%19%2
1980
September1st to 10thNight
41%7%11%23%17%1
1800
11th to 20thNight
34%5%11%23%24%3
1871
21st to endNight
41%5%8%22%22%2
1980
October1st to 10thNight
44%5%12%22%14%2
2088
11th to 20thNight
36%5%13%27%17%2
2160
21st to endNight
43%5%11%23%17%1
2510
November1st to 10thNight
35%5%11%23%22%4
2407
11th to 20thNight
40%49%24%19%5%
2470
21st to endNight
37%5%13%28%15%1
2555
December1st to 10thNight
44%5%13%22%14%2
2660
11th to 20thNight
43%5%12%20%16%4
3288
21st to endNight
47%7%13%20%12%1
4884

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 10thDay
21%29%29%18%3
180
11th to 20thDay
22%30%35%11%2
170
21st to endDay
18%26%38%13%32
240
February1st to 10thDay
29%23%35%10%2
240
11th to 20thDay
25%20%37%17%2
416
21st to endDay
29%19%34%16%3
346
March1st to 10thDay
22%25%30%20%3
420
11th to 20thDay
22%22%35%17%41
420
21st to endDay
27%21%32%13%7%1
462
April1st to 10thDay
25%22%32%13%7%1
420
11th to 20thDay
22%20%33%16%8%2
412
21st to endDay
30%17%34%15%32
420
May1st to 10thDay
32%18%27%16%5%2
423
11th to 20thDay
22%14%35%21%7%1
447
21st to endDay
20%7%27%28%15%3
485
June1st to 10thDay
16%12%32%25%13%3
450
11th to 20thDay
17%16%31%24%11%1
450
21st to endDay
14%12%33%25%15%2
450
July1st to 10thDay
13%6%25%31%19%5%
445
11th to 20thDay
11%429%31%21%4
444
21st to endDay
14%8%27%34%14%3
488
August1st to 10thDay
11%7%24%36%16%7%
446
11th to 20thDay
15%5%21%34%21%4
439
21st to endDay
13%7%29%28%16%7%
495
September1st to 10thDay
18%10%26%23%16%7%
450
11th to 20thDay
16%7%29%24%13%10%
450
21st to endDay
20%12%31%21%11%6%
450
October1st to 10thDay
27%8%27%20%13%4
450
11th to 20thDay
19%16%29%23%12%1
450
21st to endDay
26%14%32%18%9%2
428
November1st to 10thDay
16%14%32%23%12%3
365
11th to 20thDay
23%19%32%21%41
370
21st to endDay
17%21%34%20%6%1
283
December1st to 10thDay
22%27%29%15%7%
180
11th to 20thDay
29%22%35%12%2
180
21st to endDay
27%18%35%14%6%1
198
January1st to 10thNight
18%16%40%21%4
760
11th to 20thNight
25%14%33%25%3
740
21st to endNight
19%16%39%23%2
792
February1st to 10thNight
23%13%37%26%2
720
11th to 20thNight
23%16%40%19%1
703
21st to endNight
23%18%35%21%3
592
March1st to 10thNight
22%15%38%21%5%
720
11th to 20thNight
23%14%37%21%41
720
21st to endNight
21%14%38%22%5%1
792
April1st to 10thNight
23%16%35%21%5%
720
11th to 20thNight
22%15%34%24%5%
711
21st to endNight
23%13%33%25%5%1
707
May1st to 10thNight
23%13%35%22%7%
540
11th to 20thNight
22%12%32%28%6%
378
21st to endNight
20%6%20%39%13%1
389
June1st to 10thNight
18%6%29%34%12%
360
11th to 20thNight
15%5%29%38%13%
360
21st to endNight
9%426%50%10%
360
July1st to 10thNight
12%5%24%38%20%1
350
11th to 20thNight
13%320%43%20%1
348
21st to endNight
14%322%46%14%1
394
August1st to 10thNight
10%321%44%20%2
475
11th to 20thNight
16%316%40%23%1
710
21st to endNight
16%418%40%21%2
792
September1st to 10thNight
16%424%35%18%3
720
11th to 20thNight
18%5%21%34%19%4
720
21st to endNight
20%5%25%33%16%2
720
October1st to 10thNight
24%8%26%25%15%3
720
11th to 20thNight
19%10%29%31%11%
720
21st to endNight
24%11%34%23%8%
792
November1st to 10thNight
16%10%32%28%13%1
740
11th to 20thNight
22%11%34%24%7%1
760
21st to endNight
17%15%34%27%6%1
760
December1st to 10thNight
24%13%33%24%5%1
760
11th to 20thNight
22%12%36%27%3
760
21st to endNight
23%13%36%25%2
836
Page generated at 2024-01-12 16:17:46. Version ac07

Copyright 2024 Attilla Danko


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