Widener University
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Widener University 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
31%
14976
20%
46501
10%
14942
43%
14942
22%
29476

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
21%
719
21%
2506
10%
716
37%
716
17%
1583
January16th to endNight
20%
768
22%
2517
6%
768
40%
768
19%
1570
February1st to 15thNight
16%
704
18%
2259
6%
701
31%
701
17%
1451
February16th to endNight
16%
631
26%
1893
7%
631
39%
631
20%
1183
March1st to 15thNight
21%
720
20%
2092
7%
720
36%
720
21%
1327
March16th to endNight
22%
768
22%
2031
8%
768
34%
768
23%
1357
April1st to 15thNight
21%
718
18%
1796
5%
718
28%
718
24%
1197
April16th to endNight
26%
720
18%
1800
4%
720
34%
720
24%
1209
May1st to 15thNight
25%
521
17%
1601
6%
521
35%
521
16%
1086
May16th to endNight
39%
374
15%
1497
11%
374
47%
374
16%
937
June1st to 15thNight
40%
360
15%
1440
15%
360
48%
360
18%
880
June16th to endNight
48%
360
16%
1440
15%
360
57%
360
22%
826
July1st to 15thNight
47%
340
12%
1360
13%
340
50%
340
17%
865
July16th to endNight
50%
415
16%
1454
13%
390
59%
390
25%
836
August1st to 15thNight
57%
569
18%
1617
12%
566
60%
566
28%
1012
August16th to endNight
56%
700
16%
1750
8%
700
58%
700
31%
1162
September1st to 15thNight
49%
660
26%
1650
14%
660
54%
660
33%
1078
September16th to endNight
49%
657
25%
1775
16%
657
57%
657
29%
1140
October1st to 15thNight
40%
660
21%
1980
16%
660
48%
660
26%
1237
October16th to endNight
34%
704
26%
2143
13%
704
50%
704
29%
1265
November1st to 15thNight
30%
700
22%
2277
12%
700
45%
700
24%
1385
November16th to endNight
27%
720
20%
2415
10%
720
41%
720
18%
1530
December1st to 15thNight
22%
720
16%
2520
6%
720
35%
720
14%
1647
December16th to endNight
18%
768
20%
2688
6%
768
36%
768
15%
1713

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
14%5%245%345%5%7%41%
47472
Night
15%5%2442445%7%43%
46675
Cloud CoverDay
14%5%2443445%7%41%
47481
Night
15%5%2442445%7%43%
46681
TransparencyDay
40%6%12%22%15%2
47164
Night
40%5%12%22%17%2
46501
SeeingDay
16%16%23%23%14%5%
5604
Night
16%20%26%25%10%
14978

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
14%6%24434448%40%
1432
16th to endDay
14%7%24325%45%6%43%
1704
February1st to 15thDay
16%5%25%5%246%46%40%
1600
16th to endDay
13%6%37%435%45%6%39%
1580
March1st to 15thDay
15%435%5%25%5%46%40%
1856
16th to endDay
20%424434446%41%
2193
April1st to 15thDay
17%5%2342435%7%43%
2152
16th to endDay
15%4245%2445%7%43%
2160
May1st to 15thDay
18%6%245%345%5%6%36%
2360
16th to endDay
15%5%235%25%46%8%38%
2618
June1st to 15thDay
13%5%235%35%6%6%9%36%
2520
16th to endDay
10%325%5%36%5%6%10%39%
2520
July1st to 15thDay
9%5%26%6%45%6%6%8%37%
2520
16th to endDay
7%425%6%37%6%7%10%37%
2612
August1st to 15thDay
12%325%6%35%5%6%8%39%
2235
16th to endDay
11%5%235%25%5%6%8%42%
2100
September1st to 15thDay
13%42443445%7%46%
1980
16th to endDay
15%6%15%4335%47%42%
1852
October1st to 15thDay
17%4233235%5%7%45%
1650
16th to endDay
18%41332435%7%46%
1727
November1st to 15thDay
16%5%23423345%47%
1581
16th to endDay
17%433423346%45%
1544
December1st to 15thDay
17%424425%45%7%40%
1440
16th to endDay
19%6%25%5%2445%6%38%
1536
January1st to 15thNight
17%5%24434446%41%
2506
16th to endNight
16%7%2343345%6%42%
2517
February1st to 15thNight
14%7%36%42345%6%41%
2258
16th to endNight
16%5%2442345%5%46%
1893
March1st to 15thNight
17%5%2432335%7%45%
2079
16th to endNight
16%6%25%5%23335%44%
2031
April1st to 15thNight
16%5%244235%5%6%43%
1796
16th to endNight
17%42432445%7%43%
1800
May1st to 15thNight
18%6%3443445%6%38%
1601
16th to endNight
14%6%245%335%6%6%41%
1495
June1st to 15thNight
15%5%25%42345%10%41%
1440
16th to endNight
9%5%15%4345%6%10%42%
1440
July1st to 15thNight
10%5%345%36%6%7%9%36%
1440
16th to endNight
6%5%24435%5%7%9%43%
1553
August1st to 15thNight
8%424425%46%10%45%
1628
16th to endNight
12%5%245%34448%44%
1750
September1st to 15thNight
14%424413447%48%
1650
16th to endNight
13%5%2442445%7%45%
1775
October1st to 15thNight
18%414313346%46%
1980
16th to endNight
16%413322237%50%
2143
November1st to 15thNight
14%6%25%42423449%
2277
16th to endNight
16%6%2442445%6%40%
2415
December1st to 15thNight
19%6%25%4345%46%38%
2520
16th to endNight
18%5%25%42445%6%40%
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
14%5%345%245%37%41%
1432
16th to endDay
15%6%23434446%45%
1704
February1st to 15thDay
15%6%25%4245%5%6%41%
1600
16th to endDay
13%6%46%43446%5%40%
1580
March1st to 15thDay
15%5%26%5%3445%6%41%
1866
16th to endDay
19%42442445%6%41%
2192
April1st to 15thDay
17%5%24414446%44%
2152
16th to endDay
15%4145%2446%6%43%
2160
May1st to 15thDay
18%6%145%25%5%5%6%37%
2360
16th to endDay
16%424435%45%8%39%
2618
June1st to 15thDay
12%5%25%5%25%6%7%8%37%
2520
16th to endDay
10%425%446%5%5%10%40%
2520
July1st to 15thDay
9%5%25%6%36%6%6%9%38%
2520
16th to endDay
7%425%5%47%6%6%10%38%
2612
August1st to 15thDay
11%425%6%345%6%7%41%
2235
16th to endDay
10%5%24435%46%8%43%
2100
September1st to 15thDay
12%42443435%7%46%
1980
16th to endDay
14%6%25%5%24447%42%
1852
October1st to 15thDay
17%41332345%7%45%
1650
16th to endDay
18%41332445%5%47%
1727
November1st to 15thDay
16%5%13423346%46%
1581
16th to endDay
17%42342335%5%46%
1544
December1st to 15thDay
17%42442445%7%41%
1440
16th to endDay
19%5%2442445%7%38%
1536
January1st to 15thNight
17%5%2442445%5%42%
2506
16th to endNight
16%6%24424446%43%
2517
February1st to 15thNight
14%7%35%424346%42%
2251
16th to endNight
15%5%24423346%45%
1893
March1st to 15thNight
17%5%24423347%44%
2092
16th to endNight
16%6%25%5%34335%44%
2031
April1st to 15thNight
16%5%2432445%6%44%
1796
16th to endNight
17%43442345%7%43%
1800
May1st to 15thNight
17%7%25%424447%38%
1601
16th to endNight
15%5%244345%5%7%40%
1495
June1st to 15thNight
15%5%25%42445%9%42%
1440
16th to endNight
9%5%24435%5%7%11%42%
1440
July1st to 15thNight
10%435%5%36%6%7%8%36%
1440
16th to endNight
6%4245%35%5%7%9%43%
1553
August1st to 15thNight
8%325%435%5%6%7%46%
1628
16th to endNight
12%4244245%48%45%
1750
September1st to 15thNight
14%415%423446%49%
1650
16th to endNight
13%6%24423448%45%
1775
October1st to 15thNight
18%41432335%6%46%
1980
16th to endNight
16%5%13323246%50%
2143
November1st to 15thNight
14%6%25%42333449%
2277
16th to endNight
17%5%244245%47%40%
2415
December1st to 15thNight
19%6%25%42445%5%38%
2520
16th to endNight
17%6%244245%5%6%40%
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%414%21%12%3
1433
16th to endDay
39%5%12%24%14%2
1704
February1st to 15thDay
42%412%24%12%2
1603
16th to endDay
42%5%12%25%12%2
1580
March1st to 15thDay
43%413%23%12%2
1866
16th to endDay
43%410%21%17%2
2193
April1st to 15thDay
41%5%10%23%15%4
2152
16th to endDay
39%5%10%17%21%4
2160
May1st to 15thDay
46%7%11%18%14%2
2360
16th to endDay
42%7%13%22%13%1
2622
June1st to 15thDay
41%9%12%24%11%1
2520
16th to endDay
38%8%14%22%14%1
2520
July1st to 15thDay
40%8%12%20%14%3
2371
16th to endDay
37%7%14%24%14%1
2448
August1st to 15thDay
39%7%12%21%16%1
2222
16th to endDay
37%7%11%20%19%3
2100
September1st to 15thDay
36%5%12%19%23%2
1980
16th to endDay
40%48%19%23%2
1852
October1st to 15thDay
37%413%24%17%2
1650
16th to endDay
38%411%26%18%1
1727
November1st to 15thDay
38%413%21%18%3
1581
16th to endDay
39%410%28%15%2
1544
December1st to 15thDay
41%5%16%23%11%1
1440
16th to endDay
45%414%21%12%
1536
January1st to 15thNight
43%5%11%21%15%3
2506
16th to endNight
42%411%25%15%1
2517
February1st to 15thNight
43%412%22%14%2
2259
16th to endNight
39%49%24%18%3
1893
March1st to 15thNight
39%412%23%16%2
2092
16th to endNight
42%310%20%18%3
2031
April1st to 15thNight
40%412%21%17%4
1796
16th to endNight
39%5%10%17%21%4
1800
May1st to 15thNight
46%6%8%18%17%2
1601
16th to endNight
41%8%14%15%16%3
1497
June1st to 15thNight
41%7%12%20%18%
1440
16th to endNight
34%7%14%26%15%1
1440
July1st to 15thNight
40%11%14%17%13%2
1360
16th to endNight
32%8%18%24%14%1
1454
August1st to 15thNight
33%7%14%22%19%1
1617
16th to endNight
37%6%12%20%19%2
1750
September1st to 15thNight
35%6%10%21%23%2
1650
16th to endNight
37%5%7%21%25%2
1775
October1st to 15thNight
39%412%23%16%2
1980
16th to endNight
35%310%28%19%2
2143
November1st to 15thNight
38%411%20%17%7%
2277
16th to endNight
43%410%23%15%2
2415
December1st to 15thNight
45%5%13%20%12%1
2520
16th to endNight
44%5%13%22%12%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
21%26%38%8%31
60
16th to endDay
23%17%32%22%3
92
February1st to 15thDay
21%31%30%13%2
117
16th to endDay
14%25%40%16%2
239
March1st to 15thDay
17%28%25%22%5%
270
16th to endDay
19%23%31%18%42
288
April1st to 15thDay
21%21%29%16%8%2
270
16th to endDay
18%19%24%21%12%2
270
May1st to 15thDay
29%23%20%14%9%3
288
16th to endDay
20%14%16%26%19%2
331
June1st to 15thDay
13%16%25%22%17%3
315
16th to endDay
12%13%26%29%15%3
315
July1st to 15thDay
14%7%19%31%20%6%
305
16th to endDay
7%11%15%32%23%9%
326
August1st to 15thDay
12%7%15%30%23%9%
297
16th to endDay
9%6%11%27%27%17%
268
September1st to 15thDay
12%10%20%23%21%11%
255
16th to endDay
20%7%14%28%14%14%
254
October1st to 15thDay
21%9%18%25%19%6%
255
16th to endDay
14%15%30%24%13%
266
November1st to 15thDay
16%17%24%25%14%1
235
16th to endDay
17%21%33%15%10%1
164
December1st to 15thDay
20%23%31%11%13%
60
16th to endDay
35%10%39%12%1
64
January1st to 15thNight
15%26%29%23%3
720
16th to endNight
18%24%33%22%1
768
February1st to 15thNight
17%26%34%20%1
704
16th to endNight
17%27%34%17%2
631
March1st to 15thNight
20%24%31%19%4
720
16th to endNight
17%23%32%18%7%
768
April1st to 15thNight
16%28%31%19%4
718
16th to endNight
15%22%30%23%7%
720
May1st to 15thNight
21%21%26%24%5%
521
16th to endNight
16%19%18%33%10%
375
June1st to 15thNight
16%18%19%34%10%
360
16th to endNight
6%17%21%40%13%
360
July1st to 15thNight
9%14%21%36%17%
340
16th to endNight
7%18%16%35%20%2
415
August1st to 15thNight
11%10%11%41%21%2
569
16th to endNight
13%10%13%33%26%2
700
September1st to 15thNight
13%11%20%33%20%2
660
16th to endNight
15%11%16%29%23%3
657
October1st to 15thNight
19%14%20%27%17%1
660
16th to endNight
18%15%29%27%9%
704
November1st to 15thNight
15%20%28%23%10%1
700
16th to endNight
16%25%26%22%8%
720
December1st to 15thNight
21%23%26%19%7%1
720
16th to endNight
17%28%31%20%2
768
Page generated at 2017-08-13 14:16:34. Version ac04

Copyright 2017 A. Danko


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