Tillsonburg
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tillsonburg clear sky chart from 2005-11-05 to 2017-10-06.

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
36%
15012
15%
46889
10%
14975
42%
14975
19%
32408

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
16%
717
10%
2389
5%
716
23%
716
8%
1893
January16th to endNight
16%
768
10%
2496
3%
768
23%
768
9%
1974
February1st to 15thNight
17%
701
8%
2287
2%
701
24%
701
9%
1790
February16th to endNight
24%
631
11%
1970
4%
631
31%
631
13%
1480
March1st to 15thNight
25%
720
14%
1998
7%
720
32%
720
17%
1497
March16th to endNight
33%
768
20%
2112
11%
768
40%
768
22%
1466
April1st to 15thNight
27%
701
15%
1842
7%
701
33%
701
21%
1337
April16th to endNight
40%
540
21%
1620
9%
540
49%
540
26%
1047
May1st to 15thNight
41%
540
17%
1620
11%
540
47%
540
23%
1094
May16th to endNight
50%
408
17%
1531
17%
408
57%
408
25%
889
June1st to 15thNight
47%
360
13%
1440
14%
360
54%
360
23%
838
June16th to endNight
52%
360
17%
1278
16%
360
60%
360
27%
750
July1st to 15thNight
66%
365
18%
1301
22%
365
69%
365
35%
684
July16th to endNight
62%
564
16%
1595
15%
531
63%
531
35%
925
August1st to 15thNight
70%
539
18%
1609
15%
536
72%
536
36%
931
August16th to endNight
63%
597
24%
1743
17%
597
68%
597
37%
1017
September1st to 15thNight
57%
720
22%
1869
14%
720
60%
720
33%
1199
September16th to endNight
60%
717
23%
1980
17%
717
63%
717
33%
1223
October1st to 15thNight
46%
684
19%
2039
18%
684
50%
684
26%
1314
October16th to endNight
25%
704
15%
2112
8%
704
35%
704
16%
1534
November1st to 15thNight
37%
700
20%
2330
17%
700
43%
700
22%
1495
November16th to endNight
23%
720
11%
2520
7%
720
29%
720
12%
1857
December1st to 15thNight
15%
720
7%
2520
2%
720
20%
720
9%
1979
December16th to endNight
15%
768
7%
2688
2%
768
20%
768
7%
2195

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
15%8%37%6%35%5%5%7%31%
48295
Night
15%8%36%5%3445%7%34%
47071
Cloud CoverDay
15%8%37%5%35%45%7%32%
48305
Night
15%8%36%5%3445%7%34%
47075
TransparencyDay
50%6%13%19%9%1
47996
Night
48%6%12%20%11%1
46889
SeeingDay
17%7%26%24%16%7%
5632
Night
19%9%28%28%13%1
15019

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
18%14%49%8%46%5%36%17%
1549
16th to endDay
14%17%8%11%8%45%45%415%
1728
February1st to 15thDay
16%17%6%9%7%45%445%18%
1575
16th to endDay
16%13%5%11%6%46%447%19%
1502
March1st to 15thDay
17%13%5%10%6%35%346%24%
1950
16th to endDay
17%9%5%7%5%44346%30%
2112
April1st to 15thDay
19%10%47%6%2445%6%27%
2116
16th to endDay
18%8%35%423448%36%
2340
May1st to 15thDay
17%6%36%6%345%5%8%33%
2331
16th to endDay
12%5%35%5%35%5%5%8%39%
2581
June1st to 15thDay
12%6%36%5%25%5%6%9%38%
2520
16th to endDay
12%5%25%425%6%6%10%38%
2676
July1st to 15thDay
8%4345%445%7%10%41%
2574
16th to endDay
10%5%25%6%45%5%7%10%36%
2465
August1st to 15thDay
8%5%25%6%46%7%7%8%37%
2340
16th to endDay
11%5%25%5%35%6%5%8%39%
2447
September1st to 15thDay
13%5%25%5%35%5%6%8%37%
2088
16th to endDay
13%5%24435%46%9%39%
1980
October1st to 15thDay
16%7%46%6%35%445%35%
1719
16th to endDay
24%10%37%6%33446%24%
1760
November1st to 15thDay
14%8%26%5%35%45%7%35%
1526
16th to endDay
22%10%47%6%35%447%22%
1440
December1st to 15thDay
19%15%6%10%5%4434421%
1440
16th to endDay
20%17%6%10%7%35%5%35%13%
1536
January1st to 15thNight
20%13%6%9%6%3444421%
2389
16th to endNight
14%14%7%9%7%45%45%6%20%
2496
February1st to 15thNight
15%14%5%9%6%45%5%5%5%22%
2285
16th to endNight
17%9%5%8%7%35%45%5%25%
1970
March1st to 15thNight
18%8%47%5%35%46%7%27%
1986
16th to endNight
15%9%35%5%33445%37%
2112
April1st to 15thNight
19%7%35%5%35%437%33%
1842
16th to endNight
11%5%26%5%35%5%6%7%40%
1620
May1st to 15thNight
16%6%35%5%345%6%8%35%
1620
16th to endNight
10%424435%5%5%6%46%
1529
June1st to 15thNight
10%415%6%25%5%7%9%41%
1440
16th to endNight
9%4145%245%5%9%45%
1278
July1st to 15thNight
5%31342446%8%54%
1380
16th to endNight
7%3235%35%5%5%8%49%
1703
August1st to 15thNight
5%4145%35%5%6%10%47%
1620
16th to endNight
8%32442445%7%52%
1743
September1st to 15thNight
11%5%2443445%6%46%
1869
16th to endNight
12%31442446%7%47%
1980
October1st to 15thNight
15%5%35%424446%43%
2039
16th to endNight
21%8%26%5%25%45%6%30%
2112
November1st to 15thNight
15%6%25%4345%5%8%38%
2330
16th to endNight
21%11%46%6%2445%7%26%
2520
December1st to 15thNight
20%13%7%8%5%23446%21%
2520
16th to endNight
21%13%5%9%6%45%45%5%17%
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
19%13%5%9%7%45%5%45%18%
1549
16th to endDay
14%17%7%11%8%45%44416%
1728
February1st to 15thDay
17%16%6%9%7%5%5%445%19%
1575
16th to endDay
17%13%6%10%7%35%447%19%
1502
March1st to 15thDay
18%12%5%9%6%34346%25%
1961
16th to endDay
17%9%5%7%6%25%346%31%
2111
April1st to 15thDay
19%10%36%6%3445%6%28%
2116
16th to endDay
18%8%35%42435%7%37%
2340
May1st to 15thDay
17%6%26%5%35%35%8%34%
2331
16th to endDay
12%5%25%5%3446%8%39%
2581
June1st to 15thDay
12%6%36%435%5%5%9%38%
2520
16th to endDay
12%5%24435%6%6%10%38%
2676
July1st to 15thDay
8%425%435%5%6%10%42%
2574
16th to endDay
10%5%25%5%35%6%7%10%36%
2465
August1st to 15thDay
8%425%6%45%6%7%9%37%
2340
16th to endDay
11%5%25%5%35%5%6%8%40%
2447
September1st to 15thDay
13%5%25%5%445%6%8%37%
2088
16th to endDay
14%5%25%43446%7%40%
1980
October1st to 15thDay
16%7%36%5%35%5%45%36%
1719
16th to endDay
24%10%27%6%34445%25%
1760
November1st to 15thDay
14%7%36%6%35%5%47%36%
1526
16th to endDay
22%10%38%6%345%5%6%22%
1440
December1st to 15thDay
19%15%6%9%6%3444421%
1440
16th to endDay
20%18%7%10%7%25%445%13%
1536
January1st to 15thNight
21%13%6%8%6%3444422%
2389
16th to endNight
15%14%7%10%7%3445%6%20%
2496
February1st to 15thNight
15%14%5%9%7%35%5%5%5%22%
2278
16th to endNight
17%10%5%8%6%45%45%5%26%
1970
March1st to 15thNight
19%8%47%5%3445%8%27%
1998
16th to endNight
15%9%35%433446%37%
2112
April1st to 15thNight
20%7%35%5%25%447%33%
1842
16th to endNight
11%5%26%5%345%6%7%40%
1620
May1st to 15thNight
16%5%35%5%25%5%5%7%35%
1619
16th to endNight
10%325%43445%7%46%
1529
June1st to 15thNight
10%425%5%35%5%7%9%41%
1440
16th to endNight
10%4245%435%6%9%44%
1278
July1st to 15thNight
5%31432345%8%54%
1380
16th to endNight
7%4135%245%6%8%48%
1703
August1st to 15thNight
5%4145%346%6%10%48%
1620
16th to endNight
8%414433447%52%
1743
September1st to 15thNight
12%425%4335%5%6%46%
1869
16th to endNight
11%41443346%6%48%
1980
October1st to 15thNight
15%5%25%5%23446%44%
2039
16th to endNight
22%8%25%5%2445%6%31%
2112
November1st to 15thNight
15%6%35%5%2445%8%39%
2330
16th to endNight
21%10%36%6%24447%27%
2520
December1st to 15thNight
21%13%6%8%6%23446%22%
2520
16th to endNight
22%12%6%8%6%35%45%6%17%
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
67%5%10%11%4
1550
16th to endDay
71%5%9%9%3
1728
February1st to 15thDay
67%5%10%12%4
1577
16th to endDay
64%6%11%12%4
1502
March1st to 15thDay
61%5%11%15%5%
1961
16th to endDay
54%411%19%9%1
2112
April1st to 15thDay
55%411%18%9%
2116
16th to endDay
46%411%20%14%1
2340
May1st to 15thDay
47%6%13%20%11%
2331
16th to endDay
41%7%13%21%13%1
2585
June1st to 15thDay
41%6%14%23%12%1
2520
16th to endDay
39%8%15%22%13%
2676
July1st to 15thDay
35%7%13%25%16%2
2425
16th to endDay
39%8%15%22%11%2
2310
August1st to 15thDay
39%9%15%22%12%1
2327
16th to endDay
39%6%14%24%12%1
2447
September1st to 15thDay
41%7%15%23%11%
2088
16th to endDay
39%6%14%26%12%
1980
October1st to 15thDay
49%5%13%18%12%1
1719
16th to endDay
59%5%15%14%5%
1760
November1st to 15thDay
47%6%13%21%9%1
1526
16th to endDay
61%5%13%14%4
1440
December1st to 15thDay
65%6%14%10%2
1440
16th to endDay
72%5%9%9%1
1536
January1st to 15thNight
64%6%9%11%7%
2389
16th to endNight
64%5%10%14%4
2496
February1st to 15thNight
63%5%11%13%5%
2287
16th to endNight
58%413%16%6%
1970
March1st to 15thNight
54%6%11%19%6%1
1998
16th to endNight
48%410%21%13%2
2112
April1st to 15thNight
50%5%9%20%13%1
1842
16th to endNight
40%6%9%21%18%3
1620
May1st to 15thNight
44%6%9%24%12%2
1620
16th to endNight
36%5%12%24%16%3
1531
June1st to 15thNight
37%6%13%26%14%1
1440
16th to endNight
34%7%13%24%18%1
1278
July1st to 15thNight
27%6%10%28%22%3
1301
16th to endNight
31%6%16%24%18%3
1595
August1st to 15thNight
29%6%16%31%14%1
1609
16th to endNight
30%6%12%30%17%2
1743
September1st to 15thNight
36%5%12%27%16%2
1869
16th to endNight
33%6%11%30%16%
1980
October1st to 15thNight
41%5%10%24%17%
2039
16th to endNight
52%5%12%20%7%
2112
November1st to 15thNight
42%6%14%21%13%1
2330
16th to endNight
56%5%14%16%5%
2520
December1st to 15thNight
63%6%13%12%3
2520
16th to endNight
66%7%12%10%3
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
18%18%43%7%10%1
79
16th to endDay
33%19%33%11%2
96
February1st to 15thDay
26%20%44%8%
90
16th to endDay
19%19%43%16%1
81
March1st to 15thDay
24%10%33%22%8%
251
16th to endDay
25%8%34%21%9%1
288
April1st to 15thDay
24%13%28%21%10%1
270
16th to endDay
20%7%30%21%12%7%
270
May1st to 15thDay
22%9%26%21%14%5%
288
16th to endDay
15%7%27%28%12%8%
331
June1st to 15thDay
17%424%33%17%3
315
16th to endDay
13%6%28%31%15%4
471
July1st to 15thDay
12%322%29%22%9%
387
16th to endDay
9%318%29%27%11%
326
August1st to 15thDay
9%18%30%23%16%
313
16th to endDay
13%216%23%24%18%
332
September1st to 15thDay
11%118%24%28%15%
315
16th to endDay
15%414%24%22%18%
314
October1st to 15thDay
17%6%24%23%21%6%
278
16th to endDay
27%8%31%24%5%1
272
November1st to 15thDay
13%16%30%24%9%4
81
16th to endDay
28%18%31%11%8%1
60
December1st to 15thDay
28%28%26%11%5%
60
16th to endDay
29%28%29%10%1
64
January1st to 15thNight
26%16%34%16%5%
720
16th to endNight
22%14%36%21%4
768
February1st to 15thNight
23%15%35%22%3
704
16th to endNight
23%12%30%27%5%
631
March1st to 15thNight
23%12%32%25%6%
720
16th to endNight
20%8%31%27%10%
768
April1st to 15thNight
24%12%30%25%6%
701
16th to endNight
14%6%34%32%11%1
540
May1st to 15thNight
17%6%25%33%15%1
540
16th to endNight
11%428%35%18%1
409
June1st to 15thNight
12%328%39%15%
360
16th to endNight
10%226%43%15%
360
July1st to 15thNight
7%121%42%25%2
365
16th to endNight
8%117%45%23%2
564
August1st to 15thNight
7%212%43%29%3
539
16th to endNight
9%217%32%34%3
597
September1st to 15thNight
13%5%15%34%26%4
720
16th to endNight
12%316%31%28%7%
717
October1st to 15thNight
17%6%21%32%19%2
684
16th to endNight
26%9%31%25%6%
704
November1st to 15thNight
18%9%30%29%12%1
700
16th to endNight
27%12%30%19%9%
720
December1st to 15thNight
29%14%35%16%3
720
16th to endNight
26%13%36%20%3
768
Page generated at 2017-10-07 14:07:56. Version ac04

Copyright 2017 A. Danko


Tillsonburg Clear Sky Chart | Charts Home