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 2024-12-06.

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%
24171
18%
97305
10%
23910
44%
23910
18%
61154

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%
753
25%
4333
9%
737
40%
737
14%
2322
January11th to 20thNight
22%
759
23%
4343
7%
740
39%
740
10%
2550
January21st to endNight
19%
828
14%
4577
8%
814
38%
814
11%
3051
February1st to 10thNight
21%
760
19%
2470
8%
760
36%
760
20%
1596
February11th to 20thNight
16%
743
21%
2220
4%
740
36%
740
19%
1471
February21st to endNight
20%
628
24%
1884
9%
628
38%
628
20%
1233
March1st to 10thNight
21%
756
18%
3696
7%
744
38%
744
13%
2458
March11th to 20thNight
22%
756
21%
3583
9%
740
35%
740
16%
1890
March21st to endNight
21%
836
14%
3406
6%
814
33%
814
16%
2134
April1st to 10thNight
21%
760
19%
1900
4%
760
31%
760
22%
1333
April11th to 20thNight
26%
751
18%
1875
5%
751
32%
751
25%
1309
April21st to endNight
27%
746
18%
1886
5%
746
35%
746
25%
1290
May1st to 10thNight
23%
569
13%
2803
6%
566
30%
566
10%
2009
May11th to 20thNight
27%
396
12%
2526
11%
389
39%
389
9%
1697
May21st to endNight
46%
405
10%
2726
15%
399
52%
399
13%
1488
June1st to 10thNight
41%
380
18%
1520
16%
380
53%
380
21%
917
June11th to 20thNight
45%
380
15%
1520
15%
380
54%
380
21%
918
June21st to endNight
51%
380
15%
1520
14%
380
59%
380
24%
882
July1st to 10thNight
50%
362
13%
2374
14%
360
55%
360
12%
1425
July11th to 20thNight
53%
364
11%
2256
18%
358
58%
358
12%
1425
July21st to endNight
53%
413
12%
2482
17%
383
62%
383
13%
1605
August1st to 10thNight
54%
496
11%
2647
12%
485
58%
485
14%
1825
August11th to 20thNight
53%
739
14%
2841
8%
729
55%
729
17%
1902
August21st to endNight
52%
823
16%
3066
8%
814
55%
814
24%
1739
September1st to 10thNight
45%
760
22%
1900
10%
760
50%
760
30%
1279
September11th to 20thNight
51%
760
25%
1975
16%
760
55%
760
36%
1223
September21st to endNight
43%
760
23%
2090
14%
760
51%
760
28%
1380
October1st to 10thNight
37%
760
12%
2851
11%
740
42%
740
17%
1972
October11th to 20thNight
38%
760
21%
2429
14%
740
50%
740
26%
1507
October21st to endNight
29%
836
17%
3043
11%
814
43%
814
20%
1917
November1st to 10thNight
36%
780
26%
2537
13%
780
54%
780
28%
1471
November11th to 20thNight
27%
800
24%
2600
12%
800
44%
800
25%
1582
November21st to endNight
28%
800
23%
2690
10%
800
45%
800
23%
1610
December1st to 10thNight
25%
783
20%
2737
9%
783
40%
783
18%
1724
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
17%7%26%44446%7%39%
101585
Night
18%7%26%44435%6%41%
98136
TransparencyDay
42%7%12%22%16%2
105117
Night
41%6%12%23%16%2
102680
SeeingDay
20%15%31%22%10%3
15075
Night
20%11%31%28%9%1
24257

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
15%7%26%334346%47%
2517
11th to 20thDay
15%9%37%6%6%435%6%36%
2520
21st to endDay
22%12%47%43434433%
3028
February1st to 10thDay
18%8%37%43435%6%40%
1710
11th to 20thDay
15%7%36%5%4435%6%44%
1848
21st to endDay
20%8%3444436%6%38%
1570
March1st to 10thDay
27%8%26%334345%35%
3116
11th to 20thDay
10%5%15%6%45%47%8%44%
3349
21st to endDay
21%7%25%33325%6%43%
4124
April1st to 10thDay
18%8%26%44445%7%39%
2280
11th to 20thDay
18%5%25%5%4435%7%41%
2254
21st to endDay
20%6%25%44336%7%40%
2294
May1st to 10thDay
28%8%25%43435%7%30%
4106
11th to 20thDay
24%8%37%5%4445%6%31%
4388
21st to endDay
14%5%25%44446%8%45%
4837
June1st to 10thDay
16%5%25%5%45%48%9%37%
2660
11th to 20thDay
15%7%27%45%6%47%8%36%
2660
21st to endDay
12%5%26%6%5%5%5%7%9%39%
2660
July1st to 10thDay
9%6%37%6%6%6%5%8%11%35%
4440
11th to 20thDay
11%6%26%5%5%5%5%7%10%38%
4440
21st to endDay
13%8%38%6%5%6%46%8%31%
4814
August1st to 10thDay
20%7%26%5%5%6%46%8%31%
4158
11th to 20thDay
12%6%26%44446%8%43%
3730
21st to endDay
11%6%26%445%45%8%46%
4180
September1st to 10thDay
14%5%35%5%45%35%7%43%
2280
11th to 20thDay
14%5%15%34435%8%48%
2204
21st to endDay
18%6%26%5%5%4345%40%
2090
October1st to 10thDay
20%6%25%34335%7%41%
1973
11th to 20thDay
16%5%25%44335%6%49%
1900
21st to endDay
20%5%25%33435%5%44%
1948
November1st to 10thDay
14%6%24333245%52%
1761
11th to 20thDay
17%5%2442335%6%48%
1800
21st to endDay
16%6%25%435%35%6%45%
1708
December1st to 10thDay
18%8%26%44335%8%39%
1560
11th to 20thDay
22%5%2433345%6%44%
1906
21st to endDay
18%8%38%5%5%5%45%7%31%
2772
January1st to 10thNight
16%7%2433335%6%47%
4429
11th to 20thNight
16%8%36%444345%42%
4440
21st to endNight
25%10%35%434345%34%
4624
February1st to 10thNight
17%9%25%44335%5%43%
2470
11th to 20thNight
17%8%36%44335%5%42%
2218
21st to endNight
19%8%25%443346%41%
1884
March1st to 10thNight
24%10%26%433345%37%
3724
11th to 20thNight
12%7%26%44445%6%47%
3607
21st to endNight
19%9%36%333345%43%
3506
April1st to 10thNight
19%7%25%5%4436%6%39%
1900
11th to 20thNight
18%7%25%44435%7%41%
1875
21st to endNight
19%7%36%34335%7%42%
1886
May1st to 10thNight
26%10%37%43435%6%29%
2834
11th to 20thNight
26%9%37%5%33346%33%
2533
21st to endNight
16%7%26%43436%8%41%
2738
June1st to 10thNight
16%6%3445%436%8%41%
1520
11th to 20thNight
13%6%25%445%46%9%42%
1520
21st to endNight
11%316%5%4447%10%43%
1520
July1st to 10thNight
10%6%37%5%5%5%47%9%39%
2520
11th to 20thNight
13%6%26%45%5%48%9%37%
2520
21st to endNight
17%9%26%445%47%9%35%
2739
August1st to 10thNight
22%7%26%445%46%7%33%
2721
11th to 20thNight
14%7%27%5%5%5%46%7%39%
3097
21st to endNight
10%5%26%34435%8%52%
3476
September1st to 10thNight
15%5%36%5%5%445%6%45%
1900
11th to 20thNight
15%5%24334347%52%
1975
21st to endNight
19%6%25%443246%44%
2090
October1st to 10thNight
19%6%36%343346%42%
2204
11th to 20thNight
15%5%25%333346%51%
2280
21st to endNight
20%7%25%333345%45%
2650
November1st to 10thNight
12%5%25%334345%53%
2537
11th to 20thNight
20%6%24333345%48%
2600
21st to endNight
15%5%25%43445%7%46%
2690
December1st to 10thNight
18%7%35%43445%6%40%
2737
11th to 20thNight
20%7%25%44435%6%42%
3288
21st to endNight
20%9%36%5%34346%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
38%311%32%13%3
2518
11th to 20thDay
47%6%12%21%13%2
2520
21st to endDay
54%6%8%20%10%2
3028
February1st to 10thDay
45%5%13%23%12%2
1710
11th to 20thDay
42%5%9%24%17%3
1857
21st to endDay
46%5%11%21%14%3
1570
March1st to 10thDay
50%5%11%23%9%2
3119
11th to 20thDay
33%9%13%29%14%2
3349
21st to endDay
43%48%16%24%5%
4124
April1st to 10thDay
44%6%10%20%16%4
2280
11th to 20thDay
42%5%12%21%17%3
2254
21st to endDay
43%6%10%20%18%4
2294
May1st to 10thDay
52%7%12%15%12%1
4120
11th to 20thDay
51%9%12%18%9%1
4392
21st to endDay
35%8%11%26%18%2
4837
June1st to 10thDay
40%9%13%20%15%2
2660
11th to 20thDay
42%9%13%23%11%2
2660
21st to endDay
39%9%13%22%16%1
2660
July1st to 10thDay
41%10%12%21%15%1
4370
11th to 20thDay
39%8%16%22%14%1
4365
21st to endDay
48%8%11%16%15%2
4661
August1st to 10thDay
48%8%14%20%9%
4144
11th to 20thDay
37%7%14%28%13%1
3766
21st to endDay
35%6%10%28%19%2
4180
September1st to 10thDay
39%8%10%21%19%3
2280
11th to 20thDay
34%5%11%23%25%3
2204
21st to endDay
45%6%8%19%19%3
2090
October1st to 10thDay
39%5%10%18%23%6%
3272
11th to 20thDay
26%411%24%31%5%
3140
21st to endDay
27%414%25%26%4
3186
November1st to 10thDay
35%412%23%24%3
1761
11th to 20thDay
38%410%24%21%4
1800
21st to endDay
39%5%13%29%11%2
1708
December1st to 10thDay
45%5%14%21%14%1
1560
11th to 20thDay
41%5%15%24%13%3
1906
21st to endDay
50%8%11%23%8%
2772
January1st to 10thNight
38%5%11%31%12%4
4429
11th to 20thNight
44%5%12%25%12%2
4440
21st to endNight
51%5%9%22%12%2
4624
February1st to 10thNight
44%5%12%24%12%2
2470
11th to 20thNight
45%49%19%18%5%
2220
21st to endNight
44%48%24%16%4
1884
March1st to 10thNight
50%5%10%21%11%3
3734
11th to 20thNight
35%7%14%25%16%3
3608
21st to endNight
45%48%15%22%7%
3506
April1st to 10thNight
45%6%10%19%16%4
1900
11th to 20thNight
44%5%10%20%19%2
1875
21st to endNight
42%6%9%21%19%4
1886
May1st to 10thNight
55%7%10%17%10%1
2840
11th to 20thNight
53%7%14%14%10%2
2534
21st to endNight
39%8%14%24%13%3
2739
June1st to 10thNight
40%7%11%21%19%2
1520
11th to 20thNight
39%8%13%27%12%1
1520
21st to endNight
35%9%15%25%16%1
1520
July1st to 10thNight
41%9%15%18%14%2
2480
11th to 20thNight
41%9%14%23%12%1
2472
21st to endNight
44%8%14%15%17%2
2651
August1st to 10thNight
49%9%16%16%9%1
2711
11th to 20thNight
42%8%13%27%10%1
3127
21st to endNight
31%6%10%32%19%1
3476
September1st to 10thNight
40%7%10%23%19%1
1900
11th to 20thNight
33%5%11%23%24%3
1975
21st to endNight
42%5%9%22%21%2
2090
October1st to 10thNight
39%5%12%22%20%2
3672
11th to 20thNight
24%49%28%30%4
3779
21st to endNight
30%411%30%22%2
4362
November1st to 10thNight
34%5%11%24%22%4
2537
11th to 20thNight
39%49%24%20%4
2600
21st to endNight
38%5%13%28%15%1
2690
December1st to 10thNight
43%5%13%23%14%2
2737
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
23%31%34%10%2
180
21st to endDay
19%24%38%13%42
270
February1st to 10thDay
27%23%37%11%2
270
11th to 20thDay
24%21%37%16%2
456
21st to endDay
27%19%34%16%4
382
March1st to 10thDay
23%24%29%20%4
460
11th to 20thDay
22%22%34%16%41
460
21st to endDay
27%21%32%13%6%1
506
April1st to 10thDay
27%22%31%13%7%1
460
11th to 20thDay
23%21%32%15%7%2
452
21st to endDay
28%17%34%16%32
460
May1st to 10thDay
32%18%27%16%5%2
463
11th to 20thDay
23%13%33%23%8%1
487
21st to endDay
19%8%29%27%14%2
529
June1st to 10thDay
16%11%32%25%12%2
490
11th to 20thDay
16%15%31%25%12%1
490
21st to endDay
14%12%33%24%15%2
490
July1st to 10thDay
13%6%26%31%19%5%
485
11th to 20thDay
10%430%31%20%4
484
21st to endDay
14%8%28%33%14%2
532
August1st to 10thDay
13%6%24%34%16%7%
486
11th to 20thDay
15%6%22%33%20%4
479
21st to endDay
12%8%28%30%16%7%
539
September1st to 10thDay
18%10%26%23%17%7%
490
11th to 20thDay
16%7%28%25%14%11%
490
21st to endDay
22%12%30%21%10%5%
490
October1st to 10thDay
25%9%28%20%13%5%
490
11th to 20thDay
18%16%30%22%11%2
490
21st to endDay
24%14%32%19%9%2
464
November1st to 10thDay
16%14%34%22%11%3
395
11th to 20thDay
22%19%33%22%41
400
21st to endDay
19%21%34%19%6%1
308
December1st to 10thDay
22%26%28%17%7%
190
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%15%33%24%3
760
21st to endNight
20%16%38%24%2
836
February1st to 10thNight
22%12%38%26%2
760
11th to 20thNight
22%16%42%18%1
743
21st to endNight
23%17%35%21%3
628
March1st to 10thNight
22%15%38%21%5%
760
11th to 20thNight
22%15%37%21%41
760
21st to endNight
22%15%37%21%5%1
836
April1st to 10thNight
23%16%35%21%5%
760
11th to 20thNight
22%15%34%24%5%
751
21st to endNight
22%13%34%26%5%1
746
May1st to 10thNight
23%14%35%22%7%
570
11th to 20thNight
23%12%32%27%7%
399
21st to endNight
20%6%21%39%13%1
411
June1st to 10thNight
18%6%30%35%11%
380
11th to 20thNight
15%429%38%13%
380
21st to endNight
10%5%26%49%10%
380
July1st to 10thNight
12%5%24%39%20%1
370
11th to 20thNight
13%421%42%19%1
368
21st to endNight
15%422%45%13%1
416
August1st to 10thNight
12%221%43%20%2
502
11th to 20thNight
17%317%39%23%1
750
21st to endNight
15%418%40%21%2
836
September1st to 10thNight
15%425%35%18%3
760
11th to 20thNight
17%5%21%34%20%4
760
21st to endNight
21%425%33%15%1
760
October1st to 10thNight
23%8%26%26%15%3
760
11th to 20thNight
18%9%30%31%11%1
760
21st to endNight
23%10%33%25%8%
836
November1st to 10thNight
15%10%33%28%12%1
780
11th to 20thNight
22%11%35%24%7%1
800
21st to endNight
18%15%35%26%6%1
800
December1st to 10thNight
24%13%33%24%5%1
783
11th to 20thNight
22%12%36%27%3
760
21st to endNight
23%13%36%25%2
836
Page generated at 2024-12-03 06:45:13. Version ac07

Copyright © 2024 Attilla Danko.


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