Nicholas E. Wagman Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Nicholas E. Wagman Observatory clear sky chart from 2005-11-05 to 2017-04-26.

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
35%
14746
15%
45667
10%
14708
41%
14708
18%
32371

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
13%
716
9%
2342
4%
716
20%
716
7%
1932
January16th to endNight
15%
768
8%
2496
3%
768
22%
768
9%
1995
February1st to 15thNight
18%
703
9%
2287
6%
701
24%
701
11%
1800
February16th to endNight
18%
631
12%
1951
4%
631
25%
631
13%
1491
March1st to 15thNight
24%
720
14%
1980
8%
720
30%
720
15%
1506
March16th to endNight
26%
768
18%
2112
9%
768
33%
768
21%
1492
April1st to 15thNight
27%
718
12%
1844
5%
718
31%
718
20%
1370
April16th to endNight
35%
585
18%
1641
7%
585
42%
585
25%
1119
May1st to 15thNight
43%
495
16%
1485
11%
495
48%
495
19%
1050
May16th to endNight
52%
406
17%
1433
15%
406
57%
406
26%
859
June1st to 15thNight
50%
330
17%
1320
18%
330
57%
330
22%
790
June16th to endNight
53%
330
15%
1320
17%
330
59%
330
22%
799
July1st to 15thNight
53%
380
14%
1310
14%
380
57%
380
26%
826
July16th to endNight
67%
522
15%
1469
14%
489
70%
489
32%
896
August1st to 15thNight
67%
494
21%
1474
17%
491
69%
491
34%
879
August16th to endNight
65%
591
22%
1641
16%
591
68%
591
36%
993
September1st to 15thNight
59%
660
26%
1688
17%
660
63%
660
36%
1067
September16th to endNight
51%
657
22%
1821
17%
657
54%
657
29%
1195
October1st to 15thNight
44%
660
18%
1980
17%
660
48%
660
24%
1321
October16th to endNight
30%
704
16%
2112
10%
704
38%
704
18%
1503
November1st to 15thNight
39%
700
20%
2233
16%
700
46%
700
23%
1457
November16th to endNight
25%
720
13%
2520
9%
720
32%
720
13%
1840
December1st to 15thNight
21%
720
8%
2520
6%
720
25%
720
8%
2022
December16th to endNight
16%
768
9%
2688
5%
768
21%
768
8%
2169

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%9%47%5%3445%7%30%
45968
Night
16%9%36%5%34446%33%
45857
Cloud CoverDay
17%9%46%5%3445%7%30%
45978
Night
16%9%36%5%34446%33%
45861
TransparencyDay
52%6%12%18%9%1
45676
Night
50%6%11%18%11%1
45667
SeeingDay
21%10%22%21%15%7%
4878
Night
21%10%26%27%12%1
14753

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
21%14%7%11%6%33335%19%
1593
16th to endDay
17%18%8%10%9%3333417%
1728
February1st to 15thDay
19%16%7%10%7%4443418%
1575
16th to endDay
17%15%5%11%6%24345%23%
1518
March1st to 15thDay
20%12%5%8%5%25%445%25%
1969
16th to endDay
18%10%36%6%345%47%28%
2112
April1st to 15thDay
19%10%47%5%24346%31%
2103
16th to endDay
21%7%35%324346%35%
2239
May1st to 15thDay
18%7%37%6%35%5%6%7%27%
2136
16th to endDay
14%5%35%5%35%6%6%8%35%
2327
June1st to 15thDay
15%5%25%435%5%6%8%35%
2310
16th to endDay
15%7%25%6%35%46%8%32%
2310
July1st to 15thDay
13%8%26%6%345%6%7%35%
2230
16th to endDay
11%5%35%7%36%5%6%9%33%
2283
August1st to 15thDay
12%5%27%7%46%6%7%9%30%
2145
16th to endDay
13%5%245%25%5%6%9%39%
2196
September1st to 15thDay
15%6%25%5%245%5%7%40%
1939
16th to endDay
18%6%35%43345%6%38%
1808
October1st to 15thDay
20%6%26%435%45%5%36%
1650
16th to endDay
22%8%35%5%24445%32%
1760
November1st to 15thDay
13%10%35%5%34447%38%
1621
16th to endDay
23%12%37%6%24345%25%
1440
December1st to 15thDay
22%16%10%9%5%2332417%
1440
16th to endDay
23%18%7%9%5%23335%17%
1536
January1st to 15thNight
23%14%6%11%6%3442319%
2342
16th to endNight
18%14%5%9%7%4444422%
2496
February1st to 15thNight
18%12%5%11%6%3444423%
2285
16th to endNight
17%12%410%6%34445%26%
1951
March1st to 15thNight
21%10%47%5%24446%27%
1968
16th to endNight
17%8%36%424346%37%
2112
April1st to 15thNight
19%9%36%435%336%32%
1844
16th to endNight
13%6%37%6%34347%39%
1641
May1st to 15thNight
16%7%36%6%3445%6%35%
1485
16th to endNight
10%6%245%3445%8%44%
1431
June1st to 15thNight
11%425%4235%5%10%43%
1320
16th to endNight
9%425%5%35%46%9%41%
1320
July1st to 15thNight
8%5%36%5%35%5%48%42%
1397
16th to endNight
9%225%435%5%6%10%43%
1577
August1st to 15thNight
7%314425%5%7%9%47%
1485
16th to endNight
9%4233245%5%8%48%
1641
September1st to 15thNight
11%5%1342336%7%48%
1688
16th to endNight
13%6%35%42445%6%43%
1821
October1st to 15thNight
16%5%26%5%3445%6%41%
1980
16th to endNight
22%8%245%345%45%34%
2112
November1st to 15thNight
16%7%2442435%7%40%
2233
16th to endNight
21%12%37%5%24446%28%
2520
December1st to 15thNight
21%15%7%9%6%34435%20%
2520
16th to endNight
21%16%7%7%6%24345%19%
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
21%14%8%10%7%24335%19%
1593
16th to endDay
17%19%7%11%8%33335%16%
1728
February1st to 15thDay
19%17%7%9%6%44335%17%
1575
16th to endDay
18%14%5%11%7%23245%23%
1518
March1st to 15thDay
21%11%5%8%5%34445%25%
1980
16th to endDay
19%9%47%5%25%35%7%29%
2111
April1st to 15thDay
19%9%46%5%34345%31%
2103
16th to endDay
21%7%35%424336%35%
2239
May1st to 15thDay
19%7%37%6%35%5%6%7%28%
2136
16th to endDay
14%5%35%6%35%5%6%8%36%
2327
June1st to 15thDay
15%5%25%5%35%5%5%8%35%
2310
16th to endDay
16%7%25%6%35%46%9%32%
2310
July1st to 15thDay
13%7%36%6%345%5%8%35%
2230
16th to endDay
12%5%25%6%36%6%6%9%33%
2283
August1st to 15thDay
12%426%6%46%6%7%9%31%
2145
16th to endDay
14%5%244245%6%10%39%
2196
September1st to 15thDay
16%5%25%5%3445%6%40%
1939
16th to endDay
18%6%35%443446%38%
1808
October1st to 15thDay
20%6%25%435%445%36%
1650
16th to endDay
21%9%35%5%24445%32%
1760
November1st to 15thDay
13%9%35%5%34447%38%
1621
16th to endDay
23%12%46%6%34345%26%
1440
December1st to 15thDay
22%16%9%9%5%3342418%
1440
16th to endDay
23%19%6%9%5%23335%17%
1536
January1st to 15thNight
23%14%6%11%6%3442319%
2342
16th to endNight
18%15%6%9%7%4444422%
2496
February1st to 15thNight
18%12%5%11%6%3444423%
2278
16th to endNight
17%12%49%6%35%44426%
1951
March1st to 15thNight
21%9%5%7%5%2445%6%27%
1980
16th to endNight
17%8%36%424436%37%
2112
April1st to 15thNight
20%9%35%425%336%33%
1844
16th to endNight
13%6%36%6%23347%40%
1641
May1st to 15thNight
16%6%37%5%345%5%6%35%
1484
16th to endNight
10%6%245%245%5%8%45%
1431
June1st to 15thNight
11%425%5%2446%10%42%
1320
16th to endNight
10%5%25%5%35%46%8%41%
1320
July1st to 15thNight
8%436%6%35%46%8%41%
1397
16th to endNight
9%216%3346%6%10%43%
1577
August1st to 15thNight
7%314425%47%9%46%
1485
16th to endNight
10%4234245%5%8%49%
1641
September1st to 15thNight
12%5%1442345%7%49%
1688
16th to endNight
14%5%25%5%2445%6%43%
1821
October1st to 15thNight
16%5%26%5%345%47%40%
1980
16th to endNight
22%7%25%5%34445%34%
2112
November1st to 15thNight
16%7%24424347%40%
2233
16th to endNight
21%11%36%5%25%346%28%
2520
December1st to 15thNight
21%15%6%8%6%33435%20%
2520
16th to endNight
20%16%7%7%6%34345%19%
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
69%49%12%4
1594
16th to endDay
71%311%10%2
1728
February1st to 15thDay
69%5%8%11%3
1577
16th to endDay
63%413%12%6%
1518
March1st to 15thDay
60%6%11%15%5%
1980
16th to endDay
54%5%11%18%8%
2112
April1st to 15thDay
53%5%10%18%11%
2103
16th to endDay
48%6%10%17%14%3
2239
May1st to 15thDay
52%8%12%17%8%
2136
16th to endDay
43%9%15%19%9%2
2331
June1st to 15thDay
43%9%13%22%10%
2310
16th to endDay
47%8%13%19%10%
2310
July1st to 15thDay
46%7%11%18%13%3
2088
16th to endDay
44%8%13%20%12%
2128
August1st to 15thDay
45%8%14%21%9%
2132
16th to endDay
39%7%13%24%12%3
2196
September1st to 15thDay
41%6%11%21%16%2
1939
16th to endDay
45%49%23%15%
1808
October1st to 15thDay
47%6%11%20%13%
1650
16th to endDay
51%5%14%19%8%
1760
November1st to 15thDay
45%411%20%13%3
1621
16th to endDay
59%412%16%6%
1440
December1st to 15thDay
71%49%11%3
1440
16th to endDay
70%410%10%3
1536
January1st to 15thNight
70%48%12%4
2342
16th to endNight
65%5%11%12%4
2496
February1st to 15thNight
63%410%14%6%
2287
16th to endNight
59%5%10%17%7%
1951
March1st to 15thNight
55%6%11%17%8%
1980
16th to endNight
48%5%11%20%11%2
2112
April1st to 15thNight
51%5%9%17%13%
1844
16th to endNight
44%5%10%19%14%5%
1641
May1st to 15thNight
48%7%8%20%13%1
1485
16th to endNight
36%7%15%22%15%2
1433
June1st to 15thNight
36%9%13%27%13%
1320
16th to endNight
37%9%14%18%17%2
1320
July1st to 15thNight
38%7%12%19%17%3
1310
16th to endNight
32%8%15%22%15%4
1469
August1st to 15thNight
30%8%16%25%18%1
1474
16th to endNight
31%6%12%27%16%4
1641
September1st to 15thNight
33%6%12%22%21%3
1688
16th to endNight
40%5%9%24%18%1
1821
October1st to 15thNight
42%7%11%22%13%1
1980
16th to endNight
50%5%11%22%9%
2112
November1st to 15thNight
44%411%18%15%5%
2233
16th to endNight
56%5%9%17%9%
2520
December1st to 15thNight
66%5%10%11%4
2520
16th to endNight
66%6%11%13%2
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
26%27%29%5%5%4
87
16th to endDay
31%30%27%8%3
96
February1st to 15thDay
32%30%33%4
90
16th to endDay
24%20%40%12%1
105
March1st to 15thDay
30%14%29%17%8%
270
16th to endDay
22%19%33%15%6%2
288
April1st to 15thDay
27%14%27%19%9%1
270
16th to endDay
20%12%27%18%12%8%
254
May1st to 15thDay
28%14%19%17%13%6%
228
16th to endDay
18%5%20%26%16%11%
267
June1st to 15thDay
16%7%21%30%19%3
255
16th to endDay
20%7%18%29%18%7%
255
July1st to 15thDay
20%322%26%15%11%
245
16th to endDay
12%217%28%28%11%
270
August1st to 15thDay
14%316%24%26%13%
253
16th to endDay
16%113%21%27%20%
268
September1st to 15thDay
14%115%27%23%16%
255
16th to endDay
20%6%14%24%22%11%
254
October1st to 15thDay
20%5%21%27%21%3
255
16th to endDay
22%15%31%20%7%1
272
November1st to 15thDay
20%11%18%28%17%4
157
16th to endDay
28%21%31%10%5%3
60
December1st to 15thDay
35%23%20%11%6%3
60
16th to endDay
42%21%28%7%
64
January1st to 15thNight
30%18%29%17%3
720
16th to endNight
27%16%34%19%2
768
February1st to 15thNight
25%17%32%23%1
704
16th to endNight
24%15%37%20%2
631
March1st to 15thNight
26%16%28%24%4
720
16th to endNight
21%13%34%22%7%1
768
April1st to 15thNight
25%14%30%22%6%
718
16th to endNight
16%7%34%29%11%1
585
May1st to 15thNight
18%8%24%37%9%1
495
16th to endNight
12%325%30%23%3
408
June1st to 15thNight
11%326%39%19%
330
16th to endNight
12%127%35%22%
330
July1st to 15thNight
12%122%37%22%3
380
16th to endNight
9%112%42%29%4
522
August1st to 15thNight
10%113%43%27%3
494
16th to endNight
11%114%33%34%5%
591
September1st to 15thNight
13%415%34%27%4
660
16th to endNight
17%5%19%25%27%4
657
October1st to 15thNight
18%7%23%28%19%1
660
16th to endNight
25%13%27%27%6%
704
November1st to 15thNight
20%7%28%29%12%1
700
16th to endNight
28%15%25%20%8%
720
December1st to 15thNight
30%16%25%21%5%
720
16th to endNight
29%15%32%20%1
768
Page generated at 2017-04-27 17:48:54. Version ac04

Copyright 2017 A. Danko


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