Tenafly Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tenafly Observatory clear sky chart from 2005-11-06 to 2024-03-18.

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%
23355
19%
80614
10%
23265
44%
23265
21%
51251

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
19%
753
24%
4335
8%
737
38%
737
14%
2318
January11th to 20thNight
22%
758
23%
4335
6%
740
39%
740
11%
2512
January21st to endNight
20%
830
14%
4611
8%
814
37%
814
11%
3105
February1st to 10thNight
21%
760
19%
2456
8%
760
36%
760
20%
1592
February11th to 20thNight
17%
743
20%
2220
5%
740
36%
740
19%
1475
February21st to endNight
20%
628
23%
1884
8%
628
39%
628
20%
1244
March1st to 10thNight
23%
760
21%
2280
8%
760
40%
760
23%
1450
March11th to 20thNight
23%
752
21%
2161
8%
752
37%
752
23%
1419
March21st to endNight
24%
792
22%
1994
6%
792
35%
792
24%
1383
April1st to 10thNight
23%
720
18%
1800
5%
720
32%
720
23%
1267
April11th to 20thNight
30%
711
18%
1775
5%
711
37%
711
26%
1239
April21st to endNight
30%
690
19%
1770
6%
690
37%
690
24%
1226
May1st to 10thNight
25%
540
15%
1620
7%
540
33%
540
17%
1142
May11th to 20thNight
29%
391
19%
1453
11%
391
40%
391
17%
953
May21st to endNight
49%
388
14%
1551
15%
388
54%
388
19%
957
June1st to 10thNight
41%
360
17%
1440
16%
360
51%
360
19%
886
June11th to 20thNight
49%
360
15%
1440
16%
360
57%
360
21%
875
June21st to endNight
56%
360
15%
1440
18%
360
62%
360
25%
842
July1st to 10thNight
55%
350
13%
1400
16%
350
60%
350
20%
874
July11th to 20thNight
58%
348
14%
1392
18%
348
62%
348
20%
854
July21st to endNight
57%
394
18%
1486
20%
372
62%
372
26%
850
August1st to 10thNight
56%
464
16%
1528
13%
462
60%
462
26%
960
August11th to 20thNight
53%
710
15%
1774
9%
710
54%
710
26%
1278
August21st to endNight
54%
792
17%
1980
8%
792
57%
792
31%
1340
September1st to 10thNight
46%
720
20%
1800
11%
720
50%
720
29%
1228
September11th to 20thNight
49%
720
25%
1880
16%
720
54%
720
36%
1162
September21st to endNight
45%
720
24%
1980
16%
720
53%
720
29%
1292
October1st to 10thNight
35%
720
16%
2070
11%
720
40%
720
23%
1394
October11th to 20thNight
37%
720
23%
2160
13%
720
49%
720
28%
1325
October21st to endNight
27%
792
20%
2524
10%
792
40%
792
21%
1655
November1st to 10thNight
34%
740
24%
2407
11%
740
50%
740
27%
1424
November11th to 20thNight
28%
760
26%
2470
13%
760
44%
760
23%
1501
November21st to endNight
28%
760
22%
2541
10%
760
44%
760
23%
1513
December1st to 10thNight
22%
760
18%
2660
7%
760
36%
760
17%
1721
December11th to 20thNight
23%
760
18%
3185
6%
759
37%
759
15%
1951
December21st to endNight
22%
829
13%
4812
7%
817
40%
817
11%
3044

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%6%25%5%345%5%7%40%
78570
Night
18%7%35%5%3445%6%42%
81204
TransparencyDay
42%7%12%22%15%2
78275
Night
42%6%12%23%15%2
81033
SeeingDay
20%12%29%24%12%3
14083
Night
20%11%31%28%10%1
23378

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%3442435%5%48%
2517
11th to 20thDay
15%10%36%7%45%45%7%36%
2520
21st to endDay
22%11%46%5%34445%33%
2996
February1st to 10thDay
18%7%25%6%245%46%40%
1722
11th to 20thDay
15%6%35%435%446%45%
1848
21st to endDay
20%7%35%4245%5%5%39%
1570
March1st to 10thDay
15%7%36%5%235%5%6%44%
1897
11th to 20thDay
15%6%25%5%45%6%6%7%40%
1963
21st to endDay
20%8%35%5%3445%6%39%
2361
April1st to 10thDay
19%7%36%5%2345%6%41%
2160
11th to 20thDay
17%5%25%43445%8%42%
2134
21st to endDay
21%4245%3445%8%39%
2187
May1st to 10thDay
24%7%245%3445%7%34%
2340
11th to 20thDay
20%5%35%5%35%5%5%8%36%
2455
21st to endDay
16%5%25%435%6%5%8%42%
2725
June1st to 10thDay
17%5%245%35%5%8%9%37%
2520
11th to 20thDay
16%6%35%5%35%6%6%8%37%
2520
21st to endDay
12%5%25%6%45%5%7%9%39%
2520
July1st to 10thDay
11%5%36%7%46%6%6%8%38%
2520
11th to 20thDay
10%5%25%6%35%6%8%10%41%
2520
21st to endDay
12%6%36%7%46%6%7%9%35%
2744
August1st to 10thDay
10%5%26%6%46%7%7%9%38%
2379
11th to 20thDay
12%6%25%7%35%5%7%9%39%
2126
21st to endDay
13%5%26%6%35%6%6%8%40%
2376
September1st to 10thDay
14%5%245%45%5%5%7%43%
2160
11th to 20thDay
14%5%24423447%50%
2080
21st to endDay
17%5%25%6%35%5%5%6%42%
1980
October1st to 10thDay
22%6%24433348%41%
1886
11th to 20thDay
16%5%25%433447%47%
1800
21st to endDay
22%5%23434446%42%
1831
November1st to 10thDay
15%5%24433346%51%
1671
11th to 20thDay
19%5%2343335%6%47%
1710
21st to endDay
15%6%34435%45%7%45%
1634
December1st to 10thDay
19%7%25%5%24448%39%
1520
11th to 20thDay
23%5%24223446%45%
1906
21st to endDay
19%8%38%6%45%5%5%7%31%
2772
January1st to 10thNight
17%6%24424445%48%
4429
11th to 20thNight
17%8%36%434445%42%
4440
21st to endNight
25%10%34424445%34%
4656
February1st to 10thNight
17%8%345%34446%42%
2456
11th to 20thNight
17%7%35%5%34446%42%
2218
21st to endNight
20%6%345%34445%41%
1884
March1st to 10thNight
18%6%2433445%6%45%
2270
11th to 20thNight
16%8%25%43445%7%43%
2160
21st to endNight
19%7%25%5%245%46%41%
1994
April1st to 10thNight
19%6%35%5%3345%7%39%
1800
11th to 20thNight
18%7%245%25%45%7%41%
1775
21st to endNight
21%6%25%434446%42%
1770
May1st to 10thNight
22%6%47%5%34445%36%
1620
11th to 20thNight
19%8%35%5%34447%38%
1452
21st to endNight
18%6%2443446%9%41%
1550
June1st to 10thNight
18%5%245%35%45%8%41%
1440
11th to 20thNight
14%5%35%5%36%46%9%40%
1440
21st to endNight
11%325%6%35%5%6%9%44%
1440
July1st to 10thNight
11%5%37%6%45%5%6%9%40%
1440
11th to 20thNight
12%6%25%6%36%5%8%9%39%
1440
21st to endNight
12%5%245%35%6%7%9%42%
1574
August1st to 10thNight
9%5%35%6%36%6%6%8%44%
1538
11th to 20thNight
11%6%37%7%5%47%7%8%36%
1774
21st to endNight
14%5%25%5%35%45%8%43%
1980
September1st to 10thNight
16%5%35%5%3445%7%43%
1800
11th to 20thNight
15%5%24323347%52%
1880
21st to endNight
17%6%35%433446%45%
1980
October1st to 10thNight
20%7%35%5%34346%41%
2070
11th to 20thNight
16%5%245%23447%48%
2160
21st to endNight
21%7%35%33335%5%43%
2524
November1st to 10thNight
14%5%244235%5%5%51%
2407
11th to 20thNight
20%5%34323345%48%
2470
21st to endNight
15%5%244245%5%6%47%
2541
December1st to 10thNight
20%6%35%5%2445%6%40%
2660
11th to 20thNight
20%7%24435%446%42%
3288
21st to endNight
20%9%35%5%35%45%6%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
37%411%32%13%3
2518
11th to 20thDay
47%6%12%23%11%2
2520
21st to endDay
54%6%9%21%9%2
2996
February1st to 10thDay
45%5%13%22%13%2
1722
11th to 20thDay
42%5%10%25%17%2
1857
21st to endDay
45%5%12%21%14%3
1570
March1st to 10thDay
40%5%14%24%14%3
1900
11th to 20thDay
40%7%13%24%14%2
1963
21st to endDay
46%5%8%18%17%5%
2361
April1st to 10thDay
44%5%11%19%16%5%
2160
11th to 20thDay
41%5%12%21%18%3
2134
21st to endDay
43%7%11%20%16%4
2187
May1st to 10thDay
47%6%10%19%16%2
2340
11th to 20thDay
44%7%11%20%14%3
2459
21st to endDay
40%8%15%22%14%2
2725
June1st to 10thDay
41%9%14%21%14%1
2520
11th to 20thDay
44%8%12%22%12%2
2520
21st to endDay
39%8%15%22%15%1
2520
July1st to 10thDay
41%9%12%22%15%1
2450
11th to 20thDay
35%8%18%23%13%2
2445
21st to endDay
42%9%13%18%15%3
2591
August1st to 10thDay
38%11%15%22%13%1
2365
11th to 20thDay
40%7%16%23%13%1
2126
21st to endDay
38%8%11%23%18%3
2376
September1st to 10thDay
39%7%13%22%17%2
2160
11th to 20thDay
33%6%12%23%24%2
2080
21st to endDay
42%6%10%19%19%3
1980
October1st to 10thDay
43%6%10%23%16%2
1886
11th to 20thDay
37%6%12%25%18%2
1800
21st to endDay
44%6%9%22%16%3
1831
November1st to 10thDay
35%5%11%24%22%3
1671
11th to 20thDay
39%410%23%20%3
1710
21st to endDay
39%5%14%28%12%2
1634
December1st to 10thDay
45%6%15%20%13%1
1520
11th to 20thDay
41%415%24%14%2
1906
21st to endDay
50%9%10%23%8%
2772
January1st to 10thNight
39%412%30%12%4
4429
11th to 20thNight
43%5%13%25%12%2
4440
21st to endNight
51%6%9%21%11%2
4656
February1st to 10thNight
44%5%12%24%13%2
2456
11th to 20thNight
44%6%9%19%17%5%
2220
21st to endNight
43%5%8%23%16%4
1884
March1st to 10thNight
40%5%12%24%15%4
2280
11th to 20thNight
41%6%11%22%16%3
2161
21st to endNight
43%6%10%18%18%5%
1994
April1st to 10thNight
45%6%10%20%16%3
1800
11th to 20thNight
42%7%9%20%20%2
1775
21st to endNight
44%6%8%21%17%4
1770
May1st to 10thNight
50%6%10%18%14%2
1620
11th to 20thNight
46%7%10%17%18%2
1453
21st to endNight
42%7%17%20%12%2
1551
June1st to 10thNight
42%7%10%21%18%2
1440
11th to 20thNight
40%7%16%25%11%1
1440
21st to endNight
34%9%16%24%15%1
1440
July1st to 10thNight
40%9%13%20%15%3
1400
11th to 20thNight
38%10%13%25%12%1
1392
21st to endNight
33%8%18%22%16%3
1486
August1st to 10thNight
35%11%15%21%16%2
1528
11th to 20thNight
42%10%14%23%10%1
1774
21st to endNight
38%8%13%20%19%2
1980
September1st to 10thNight
41%7%11%24%16%1
1800
11th to 20thNight
33%6%11%23%24%3
1880
21st to endNight
40%5%8%22%22%2
1980
October1st to 10thNight
44%6%12%22%14%3
2070
11th to 20thNight
36%6%14%27%16%2
2160
21st to endNight
45%5%11%22%16%1
2524
November1st to 10thNight
35%6%11%22%21%4
2407
11th to 20thNight
40%49%24%19%5%
2470
21st to endNight
37%5%13%29%14%2
2541
December1st to 10thNight
45%6%12%22%14%1
2660
11th to 20thNight
43%5%13%19%17%3
3288
21st to endNight
46%8%13%22%11%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%25%32%17%41
180
11th to 20thDay
24%24%37%12%21
180
21st to endDay
19%19%41%13%5%2
261
February1st to 10thDay
27%16%38%17%2
282
11th to 20thDay
23%19%38%18%2
456
21st to endDay
25%18%34%19%4
382
March1st to 10thDay
20%21%33%21%4
460
11th to 20thDay
18%20%37%19%5%1
449
21st to endDay
26%19%31%18%6%1
462
April1st to 10thDay
24%18%33%17%7%1
420
11th to 20thDay
20%16%33%19%10%2
412
21st to endDay
27%15%34%17%5%1
420
May1st to 10thDay
31%13%30%17%7%2
423
11th to 20thDay
20%11%35%23%10%2
447
21st to endDay
19%8%24%28%16%4
485
June1st to 10thDay
18%8%28%28%15%4
450
11th to 20thDay
17%11%28%32%11%2
450
21st to endDay
15%8%28%27%18%4
450
July1st to 10thDay
13%322%35%20%7%
445
11th to 20thDay
12%321%34%25%5%
444
21st to endDay
14%6%23%35%20%2
488
August1st to 10thDay
11%5%20%37%19%8%
446
11th to 20thDay
15%420%34%22%5%
439
21st to endDay
13%5%25%32%18%8%
495
September1st to 10thDay
18%5%28%22%20%8%
450
11th to 20thDay
16%5%28%24%16%11%
450
21st to endDay
19%9%27%26%13%5%
450
October1st to 10thDay
28%8%24%21%16%4
450
11th to 20thDay
18%12%28%25%14%2
450
21st to endDay
25%13%30%21%9%1
420
November1st to 10thDay
17%13%29%27%11%3
365
11th to 20thDay
21%16%34%22%6%1
370
21st to endDay
17%19%33%25%5%1
294
December1st to 10thDay
22%22%33%17%42
180
11th to 20thDay
28%21%36%12%3
180
21st to endDay
28%14%36%14%8%1
198
January1st to 10thNight
20%14%43%20%4
760
11th to 20thNight
23%16%34%23%4
760
21st to endNight
20%15%40%22%2
836
February1st to 10thNight
23%12%37%26%2
760
11th to 20thNight
22%17%40%20%1
743
21st to endNight
25%15%35%21%4
628
March1st to 10thNight
23%15%36%22%5%
760
11th to 20thNight
22%13%38%22%41
752
21st to endNight
22%14%36%23%5%
792
April1st to 10thNight
21%16%35%23%5%
720
11th to 20thNight
21%12%33%27%6%
711
21st to endNight
23%11%32%27%6%1
690
May1st to 10thNight
24%11%33%24%7%1
540
11th to 20thNight
21%10%33%28%7%
391
21st to endNight
20%5%17%41%15%2
389
June1st to 10thNight
20%5%26%34%14%1
360
11th to 20thNight
14%426%39%17%
360
21st to endNight
10%223%51%14%1
360
July1st to 10thNight
11%322%43%20%
350
11th to 20thNight
11%419%43%21%2
348
21st to endNight
14%418%46%17%2
394
August1st to 10thNight
12%220%44%21%2
464
11th to 20thNight
15%416%37%25%3
710
21st to endNight
15%417%37%24%2
792
September1st to 10thNight
17%423%35%19%2
720
11th to 20thNight
18%5%23%32%19%4
720
21st to endNight
20%5%24%32%17%2
720
October1st to 10thNight
23%9%27%23%14%2
720
11th to 20thNight
18%11%28%32%10%1
720
21st to endNight
26%12%32%23%7%
792
November1st to 10thNight
16%10%34%26%12%1
740
11th to 20thNight
23%13%32%24%8%1
760
21st to endNight
19%13%35%25%7%1
760
December1st to 10thNight
24%14%36%20%5%1
760
11th to 20thNight
23%14%35%24%4
760
21st to endNight
25%13%36%24%3
836
Page generated at 2024-03-15 14:01:40. Version ac07

Copyright © 2024 Attilla Danko.


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