Hanover College
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hanover College clear sky chart from 2005-11-05 to 2017-09-16.

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%
15653
19%
46753
11%
15608
43%
15608
21%
30735

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
14%
900
14%
2506
4%
895
23%
895
13%
1892
January16th to endNight
16%
811
15%
2539
6%
811
26%
811
13%
1847
February1st to 15thNight
16%
704
13%
2115
4%
701
24%
701
14%
1520
February16th to endNight
15%
631
14%
1893
5%
631
23%
631
13%
1385
March1st to 15thNight
18%
720
16%
2121
7%
720
27%
720
16%
1480
March16th to endNight
24%
755
15%
2099
6%
755
32%
755
17%
1478
April1st to 15thNight
27%
539
20%
1797
12%
539
39%
539
21%
1120
April16th to endNight
32%
540
21%
1686
9%
540
44%
540
21%
1104
May1st to 15thNight
29%
540
16%
1620
7%
540
37%
540
17%
1125
May16th to endNight
40%
562
18%
1684
10%
561
48%
561
22%
1083
June1st to 15thNight
51%
540
20%
1505
13%
540
57%
540
32%
902
June16th to endNight
52%
540
20%
1440
10%
540
60%
540
36%
851
July1st to 15thNight
53%
510
17%
1360
12%
510
56%
510
30%
864
July16th to endNight
62%
564
21%
1539
14%
531
71%
531
34%
886
August1st to 15thNight
64%
539
24%
1609
20%
536
69%
536
34%
923
August16th to endNight
71%
573
25%
1902
23%
573
76%
573
36%
1009
September1st to 15thNight
60%
633
26%
1893
24%
633
63%
633
34%
1108
September16th to endNight
53%
661
27%
1826
18%
661
59%
661
31%
1121
October1st to 15thNight
48%
660
31%
1818
22%
660
57%
660
34%
1070
October16th to endNight
33%
704
23%
2230
15%
704
45%
704
24%
1386
November1st to 15thNight
36%
700
27%
2276
19%
700
49%
700
26%
1315
November16th to endNight
28%
720
20%
2340
12%
720
38%
720
17%
1548
December1st to 15thNight
20%
720
13%
2340
7%
720
27%
720
11%
1730
December16th to endNight
15%
887
13%
2615
4%
887
24%
887
11%
1988

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%6%35%5%3445%7%39%
47994
Night
14%7%35%42445%7%40%
46934
Cloud CoverDay
14%7%35%5%3445%7%39%
48003
Night
14%7%35%42445%7%40%
46939
TransparencyDay
44%6%11%21%14%2
47693
Night
42%5%11%22%14%3
46753
SeeingDay
16%16%22%22%15%7%
5698
Night
15%22%22%23%13%2
15654

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%10%48%5%2334430%
1432
16th to endDay
15%11%47%5%34345%34%
1682
February1st to 15thDay
15%11%6%8%5%23336%34%
1744
16th to endDay
15%12%37%5%245%5%5%31%
1580
March1st to 15thDay
23%7%25%42345%6%34%
1827
16th to endDay
18%8%35%6%34446%32%
2135
April1st to 15thDay
17%7%3442445%6%39%
2151
16th to endDay
18%5%3443435%7%38%
2273
May1st to 15thDay
22%7%25%43445%6%33%
2331
16th to endDay
12%5%25%6%36%5%6%8%36%
2431
June1st to 15thDay
10%3246%35%5%6%8%44%
2452
16th to endDay
9%4245%25%46%9%43%
2520
July1st to 15thDay
13%6%26%5%25%47%8%35%
2520
16th to endDay
8%3145%35%7%7%10%41%
2519
August1st to 15thDay
8%325%5%347%6%8%44%
2340
16th to endDay
7%424445%5%6%8%45%
2298
September1st to 15thDay
12%425%5%3445%6%45%
2055
16th to endDay
13%4245%34445%46%
1824
October1st to 15thDay
11%4245%34446%49%
1812
16th to endDay
18%6%14323436%44%
1641
November1st to 15thDay
12%5%2442335%6%49%
1582
16th to endDay
18%8%35%323246%40%
1620
December1st to 15thDay
25%9%5%6%5%23335%30%
1620
16th to endDay
20%13%47%423435%30%
1605
January1st to 15thNight
19%10%49%5%33445%29%
2506
16th to endNight
17%13%47%5%23345%31%
2539
February1st to 15thNight
19%10%45%424435%33%
2113
16th to endNight
16%12%5%8%433445%31%
1893
March1st to 15thNight
18%8%26%5%2435%6%36%
2108
16th to endNight
17%7%35%5%3445%8%34%
2099
April1st to 15thNight
15%5%35%42435%6%43%
1797
16th to endNight
15%6%25%5%35%346%40%
1686
May1st to 15thNight
16%5%37%5%245%5%7%35%
1620
16th to endNight
9%425%6%25%6%6%8%41%
1682
June1st to 15thNight
6%42342445%9%51%
1505
16th to endNight
6%213325%6%7%12%48%
1440
July1st to 15thNight
9%5%25%5%3445%8%46%
1440
16th to endNight
5%3235%246%6%7%51%
1646
August1st to 15thNight
6%31442445%10%51%
1620
16th to endNight
4244245%6%10%52%
1902
September1st to 15thNight
11%32342245%8%51%
1893
16th to endNight
12%425%423346%50%
1826
October1st to 15thNight
7%5%24333447%52%
1818
16th to endNight
16%5%35%433345%44%
2230
November1st to 15thNight
13%424423446%49%
2276
16th to endNight
19%9%34423346%39%
2340
December1st to 15thNight
22%10%46%5%24445%29%
2340
16th to endNight
24%12%35%433445%26%
2615

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
20%10%5%8%42334430%
1432
16th to endDay
14%12%47%5%33345%34%
1682
February1st to 15thDay
15%10%5%9%434236%34%
1744
16th to endDay
14%12%47%5%345%5%5%30%
1580
March1st to 15thDay
23%8%26%42335%5%33%
1837
16th to endDay
17%8%36%6%3445%6%33%
2134
April1st to 15thDay
17%7%3443445%5%39%
2151
16th to endDay
17%5%34434448%37%
2273
May1st to 15thDay
21%7%25%42445%6%33%
2331
16th to endDay
12%5%26%5%46%6%6%8%36%
2431
June1st to 15thDay
9%425%6%35%5%6%8%43%
2452
16th to endDay
9%4245%35%46%9%43%
2520
July1st to 15thDay
12%6%36%435%5%7%9%35%
2520
16th to endDay
8%325%435%7%7%10%41%
2519
August1st to 15thDay
7%325%5%346%6%9%44%
2340
16th to endDay
7%415%435%5%6%9%44%
2298
September1st to 15thDay
12%426%5%3445%6%45%
2055
16th to endDay
14%4245%34346%46%
1824
October1st to 15thDay
11%5%145%33445%49%
1812
16th to endDay
17%7%24323446%44%
1641
November1st to 15thDay
11%6%24324346%49%
1582
16th to endDay
18%8%35%423346%40%
1620
December1st to 15thDay
25%10%5%6%5%22235%30%
1620
16th to endDay
20%13%5%6%5%23335%29%
1605
January1st to 15thNight
19%10%48%6%33345%29%
2506
16th to endNight
17%13%47%5%23345%31%
2539
February1st to 15thNight
18%11%36%424445%32%
2106
16th to endNight
16%12%5%7%5%24445%31%
1893
March1st to 15thNight
18%8%36%5%3445%5%36%
2121
16th to endNight
17%7%35%5%2445%7%34%
2099
April1st to 15thNight
15%5%35%42435%6%43%
1797
16th to endNight
14%6%345%35%35%6%40%
1686
May1st to 15thNight
15%5%37%5%345%5%7%35%
1619
16th to endNight
10%425%6%346%6%9%40%
1682
June1st to 15thNight
6%42342445%9%51%
1505
16th to endNight
5%213425%5%7%12%48%
1440
July1st to 15thNight
9%5%25%425%45%8%46%
1440
16th to endNight
6%2234345%6%8%50%
1646
August1st to 15thNight
6%315%42446%10%50%
1620
16th to endNight
42144345%6%10%51%
1902
September1st to 15thNight
11%41342335%8%51%
1893
16th to endNight
12%415%432346%50%
1826
October1st to 15thNight
8%4243245%46%53%
1818
16th to endNight
16%5%25%423345%44%
2230
November1st to 15thNight
13%42432345%6%49%
2276
16th to endNight
19%9%34423346%39%
2340
December1st to 15thNight
21%11%46%5%23445%29%
2340
16th to endNight
24%12%36%423445%27%
2615

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
55%5%9%17%11%
1433
16th to endDay
52%411%24%6%
1682
February1st to 15thDay
53%310%22%9%
1746
16th to endDay
53%5%11%21%8%
1580
March1st to 15thDay
51%5%11%18%12%
1837
16th to endDay
52%5%9%21%9%
2135
April1st to 15thDay
43%6%9%22%16%1
2151
16th to endDay
44%5%10%21%13%3
2273
May1st to 15thDay
51%7%11%18%10%
2331
16th to endDay
43%8%14%17%14%1
2435
June1st to 15thDay
36%8%12%23%17%2
2452
16th to endDay
35%8%12%20%18%3
2520
July1st to 15thDay
44%7%12%16%16%3
2371
16th to endDay
34%9%16%23%13%3
2363
August1st to 15thDay
34%9%11%23%18%2
2327
16th to endDay
33%8%13%22%17%5%
2298
September1st to 15thDay
39%5%11%17%19%6%
2055
16th to endDay
39%5%8%19%25%2
1824
October1st to 15thDay
36%48%26%21%3
1812
16th to endDay
41%5%8%26%16%2
1641
November1st to 15thDay
35%39%25%19%6%
1582
16th to endDay
46%38%23%16%1
1620
December1st to 15thDay
58%310%17%9%
1620
16th to endDay
58%49%19%7%
1605
January1st to 15thNight
57%48%17%10%
2506
16th to endNight
55%410%20%8%1
2539
February1st to 15thNight
54%411%21%6%1
2115
16th to endNight
55%411%19%9%
1893
March1st to 15thNight
49%5%8%22%12%2
2121
16th to endNight
47%6%13%22%7%1
2099
April1st to 15thNight
40%411%21%18%2
1797
16th to endNight
43%5%9%21%13%6%
1686
May1st to 15thNight
46%7%12%21%10%1
1620
16th to endNight
37%8%13%20%15%4
1684
June1st to 15thNight
28%8%12%25%20%3
1505
16th to endNight
25%9%19%19%21%4
1440
July1st to 15thNight
35%6%12%22%17%5%
1360
16th to endNight
27%7%14%29%17%3
1539
August1st to 15thNight
28%7%15%26%18%4
1609
16th to endNight
25%6%14%29%19%4
1902
September1st to 15thNight
31%5%11%23%20%7%
1893
16th to endNight
35%47%21%26%4
1826
October1st to 15thNight
30%49%26%22%5%
1818
16th to endNight
41%39%25%17%3
2230
November1st to 15thNight
34%49%22%22%5%
2276
16th to endNight
47%39%21%16%1
2340
December1st to 15thNight
56%6%9%17%8%1
2340
16th to endNight
59%411%16%7%
2615

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
35%21%30%10%21
90
16th to endDay
25%36%27%10%1
96
February1st to 15thDay
22%46%18%12%
90
16th to endDay
13%23%51%8%2
81
March1st to 15thDay
26%26%29%16%
127
16th to endDay
23%24%29%14%6%1
288
April1st to 15thDay
19%23%27%20%7%1
270
16th to endDay
19%19%27%18%12%3
270
May1st to 15thDay
22%22%28%15%7%4
288
16th to endDay
19%16%23%20%11%8%
331
June1st to 15thDay
10%15%16%32%18%6%
427
16th to endDay
9%19%22%25%16%5%
495
July1st to 15thDay
17%11%20%23%17%9%
475
16th to endDay
7%11%13%26%22%17%
379
August1st to 15thDay
11%6%12%23%27%19%
313
16th to endDay
10%6%14%25%26%15%
332
September1st to 15thDay
11%8%15%24%26%13%
315
16th to endDay
14%8%15%26%24%9%
257
October1st to 15thDay
12%14%20%28%18%6%
255
16th to endDay
15%13%36%24%9%
153
November1st to 15thDay
14%12%25%27%14%5%
90
16th to endDay
30%15%31%18%4
90
December1st to 15thDay
30%14%36%13%23
90
16th to endDay
26%28%39%42
96
January1st to 15thNight
18%31%31%16%3
900
16th to endNight
21%29%27%19%1
811
February1st to 15thNight
22%28%30%18%
704
16th to endNight
20%28%32%16%1
631
March1st to 15thNight
20%27%30%18%3
720
16th to endNight
17%27%26%21%6%
755
April1st to 15thNight
15%25%28%22%7%
539
16th to endNight
17%23%23%25%9%
540
May1st to 15thNight
16%22%26%22%10%
540
16th to endNight
10%19%21%28%15%4
563
June1st to 15thNight
7%18%17%34%19%2
540
16th to endNight
6%17%18%32%22%1
540
July1st to 15thNight
9%13%14%30%27%3
510
16th to endNight
6%17%8%30%30%7%
564
August1st to 15thNight
7%9%10%32%33%6%
539
16th to endNight
49%9%32%39%5%
573
September1st to 15thNight
10%9%12%30%29%6%
633
16th to endNight
13%12%14%27%27%4
661
October1st to 15thNight
11%14%21%26%21%4
660
16th to endNight
16%17%28%24%11%
704
November1st to 15thNight
12%23%25%22%15%1
700
16th to endNight
22%27%20%21%7%
720
December1st to 15thNight
24%27%23%16%6%1
720
16th to endNight
24%31%25%15%2
887
Page generated at 2017-09-17 12:05:40. Version ac04

Copyright 2017 A. Danko


Hanover College Clear Sky Chart | Charts Home