Greencastle
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Greencastle clear sky chart from 2005-11-05 to 2017-09-21.

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
41%
15834
18%
46860
13%
15792
47%
15792
24%
31267

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%
900
15%
2506
6%
895
28%
895
16%
1898
January16th to endNight
21%
945
13%
2640
5%
945
28%
945
17%
1972
February1st to 15thNight
22%
702
12%
2112
5%
701
29%
701
16%
1536
February16th to endNight
23%
631
16%
1893
7%
631
31%
631
17%
1360
March1st to 15thNight
24%
720
15%
2160
9%
720
29%
720
18%
1532
March16th to endNight
31%
682
16%
2032
8%
682
39%
682
21%
1423
April1st to 15thNight
34%
539
18%
1797
11%
539
44%
539
22%
1167
April16th to endNight
37%
540
20%
1724
12%
540
46%
540
25%
1112
May1st to 15thNight
38%
540
14%
1620
9%
540
45%
540
20%
1156
May16th to endNight
53%
561
17%
1611
12%
561
56%
561
27%
1057
June1st to 15thNight
58%
540
18%
1440
14%
540
60%
540
38%
885
June16th to endNight
65%
540
19%
1440
15%
540
68%
540
36%
904
July1st to 15thNight
68%
510
17%
1360
14%
510
69%
510
38%
835
July16th to endNight
75%
564
26%
1435
21%
531
78%
531
46%
806
August1st to 15thNight
71%
539
22%
1651
21%
536
73%
536
37%
946
August16th to endNight
73%
573
24%
1910
25%
573
76%
573
36%
1032
September1st to 15thNight
64%
588
25%
1848
23%
588
68%
588
33%
1081
September16th to endNight
62%
681
26%
1881
21%
681
65%
681
35%
1143
October1st to 15thNight
54%
660
30%
1826
23%
660
59%
660
36%
1094
October16th to endNight
34%
704
20%
2255
15%
704
42%
704
24%
1422
November1st to 15thNight
40%
700
26%
2276
19%
700
52%
700
28%
1342
November16th to endNight
31%
720
18%
2340
13%
720
39%
720
19%
1588
December1st to 15thNight
23%
795
11%
2415
6%
795
29%
795
15%
1834
December16th to endNight
18%
960
12%
2688
4%
960
26%
960
13%
2142

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%7%36%5%3445%7%37%
48003
Night
14%7%35%424446%40%
47031
Cloud CoverDay
14%7%36%5%3445%7%37%
48012
Night
14%7%35%5%24446%40%
47036
TransparencyDay
44%6%12%21%13%2
47692
Night
44%5%11%21%14%2
46860
SeeingDay
16%6%23%24%19%8%
5856
Night
18%7%27%29%15%1
15838

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
20%11%49%5%33445%26%
1432
16th to endDay
12%14%7%7%6%24446%29%
1581
February1st to 15thDay
14%12%5%8%7%34345%29%
1750
16th to endDay
14%12%49%6%34347%29%
1580
March1st to 15thDay
20%9%46%5%3335%6%30%
1790
16th to endDay
17%10%46%5%35%348%30%
2202
April1st to 15thDay
17%9%2442335%6%38%
2151
16th to endDay
18%6%26%5%34447%35%
2235
May1st to 15thDay
21%8%36%5%34436%32%
2331
16th to endDay
12%5%36%6%45%5%5%8%36%
2502
June1st to 15thDay
10%4245%345%5%8%44%
2520
16th to endDay
9%5%25%5%35%5%7%9%41%
2520
July1st to 15thDay
10%425%5%35%5%6%9%39%
2520
16th to endDay
5%3345%37%6%8%10%41%
2634
August1st to 15thDay
8%414435%48%11%42%
2295
16th to endDay
7%415%5%45%5%5%8%44%
2292
September1st to 15thDay
12%6%24435%5%5%7%42%
2100
16th to endDay
12%5%2443445%5%47%
1872
October1st to 15thDay
14%5%144245%46%45%
1801
16th to endDay
16%7%26%42345%6%40%
1615
November1st to 15thDay
12%5%245%34345%48%
1582
16th to endDay
19%8%47%424336%35%
1620
December1st to 15thDay
21%12%47%42434428%
1542
16th to endDay
21%14%5%8%5%23345%26%
1536
January1st to 15thNight
18%10%38%6%34445%30%
2506
16th to endNight
15%12%6%7%5%34445%30%
2640
February1st to 15thNight
16%12%5%7%5%33346%30%
2110
16th to endNight
15%10%47%5%25%346%32%
1893
March1st to 15thNight
18%9%46%425%445%34%
2147
16th to endNight
17%8%35%5%34347%35%
2032
April1st to 15thNight
15%7%35%5%3335%7%40%
1797
16th to endNight
16%7%3442445%6%40%
1724
May1st to 15thNight
18%5%35%6%335%48%34%
1620
16th to endNight
11%5%25%5%25%5%5%7%41%
1609
June1st to 15thNight
8%5%25%32335%8%50%
1440
16th to endNight
6%424435%5%6%11%46%
1440
July1st to 15thNight
9%3134245%6%10%49%
1440
16th to endNight
5%31342345%10%55%
1532
August1st to 15thNight
6%2244246%6%9%51%
1662
16th to endNight
6%314335%45%8%54%
1910
September1st to 15thNight
10%5%2332445%7%50%
1848
16th to endNight
11%41442345%7%50%
1881
October1st to 15thNight
10%323433346%52%
1826
16th to endNight
17%7%24324345%43%
2255
November1st to 15thNight
12%6%23423446%48%
2276
16th to endNight
18%10%45%423345%37%
2340
December1st to 15thNight
20%11%6%9%5%2334427%
2415
16th to endNight
24%11%5%7%5%2434425%
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
20%11%49%6%33445%26%
1432
16th to endDay
12%14%7%7%5%34346%29%
1581
February1st to 15thDay
14%12%5%8%7%3445%5%29%
1750
16th to endDay
14%12%5%8%6%24447%29%
1580
March1st to 15thDay
21%9%46%6%3335%6%30%
1800
16th to endDay
17%10%46%5%35%348%30%
2201
April1st to 15thDay
17%9%3442435%6%38%
2151
16th to endDay
18%6%26%5%33446%36%
2235
May1st to 15thDay
21%8%36%5%34436%32%
2331
16th to endDay
12%5%36%6%45%6%48%36%
2502
June1st to 15thDay
10%4245%345%5%8%44%
2520
16th to endDay
8%5%25%5%35%5%7%9%41%
2520
July1st to 15thDay
10%5%25%5%35%5%6%9%39%
2520
16th to endDay
5%334437%7%8%10%41%
2634
August1st to 15thDay
7%424436%47%11%42%
2295
16th to endDay
7%415%5%45%5%6%8%44%
2292
September1st to 15thDay
12%6%24435%5%5%8%42%
2100
16th to endDay
12%5%2443445%6%47%
1872
October1st to 15thDay
14%5%24424446%45%
1801
16th to endDay
16%7%26%42345%6%40%
1615
November1st to 15thDay
12%5%345%24345%48%
1582
16th to endDay
19%8%47%424336%35%
1620
December1st to 15thDay
21%12%47%5%2444428%
1542
16th to endDay
20%14%5%8%5%23345%26%
1536
January1st to 15thNight
18%10%48%6%34445%30%
2506
16th to endNight
14%12%6%7%6%34346%29%
2640
February1st to 15thNight
16%12%5%7%5%33346%30%
2103
16th to endNight
15%10%47%6%25%446%32%
1893
March1st to 15thNight
19%9%46%425%5%45%34%
2160
16th to endNight
17%8%36%5%34347%35%
2032
April1st to 15thNight
15%7%35%5%3335%7%40%
1797
16th to endNight
16%7%35%42445%6%40%
1724
May1st to 15thNight
18%5%45%6%33448%34%
1619
16th to endNight
11%5%25%5%25%5%6%7%41%
1609
June1st to 15thNight
8%5%25%32235%8%50%
1440
16th to endNight
6%4244345%6%11%45%
1440
July1st to 15thNight
8%3143245%6%10%49%
1440
16th to endNight
5%31342345%10%55%
1532
August1st to 15thNight
5%3144245%6%9%50%
1662
16th to endNight
6%314325%45%8%53%
1910
September1st to 15thNight
9%6%2432445%7%49%
1848
16th to endNight
11%41442345%7%50%
1881
October1st to 15thNight
10%32433435%6%52%
1826
16th to endNight
17%7%24423345%43%
2255
November1st to 15thNight
11%6%23423446%48%
2276
16th to endNight
18%10%45%423345%37%
2340
December1st to 15thNight
20%11%6%8%5%2334427%
2415
16th to endNight
24%11%6%7%6%2434425%
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
59%49%16%9%
1433
16th to endDay
55%414%18%6%
1581
February1st to 15thDay
56%412%16%7%1
1752
16th to endDay
54%412%20%6%
1580
March1st to 15thDay
54%5%13%19%7%
1800
16th to endDay
52%6%12%20%6%
2202
April1st to 15thDay
45%5%10%24%13%1
2151
16th to endDay
47%6%11%20%9%4
2235
May1st to 15thDay
52%6%11%19%10%
2331
16th to endDay
44%9%10%18%15%2
2506
June1st to 15thDay
35%7%12%25%16%3
2520
16th to endDay
36%7%14%20%16%3
2520
July1st to 15thDay
39%7%12%21%15%2
2371
16th to endDay
33%11%15%24%12%1
2468
August1st to 15thDay
33%7%14%24%17%1
2282
16th to endDay
34%8%12%22%15%6%
2292
September1st to 15thDay
38%7%10%20%18%4
2100
16th to endDay
36%5%8%24%21%2
1872
October1st to 15thDay
38%5%10%25%18%2
1801
16th to endDay
43%413%23%14%
1615
November1st to 15thDay
38%312%21%18%6%
1582
16th to endDay
50%310%21%13%1
1620
December1st to 15thDay
58%5%10%17%7%
1542
16th to endDay
60%5%12%16%4
1536
January1st to 15thNight
55%5%8%19%9%
2506
16th to endNight
55%5%12%18%7%
2640
February1st to 15thNight
55%413%17%8%
2112
16th to endNight
52%5%12%20%9%
1893
March1st to 15thNight
52%410%20%9%1
2160
16th to endNight
49%413%22%8%1
2032
April1st to 15thNight
44%5%9%23%15%2
1797
16th to endNight
43%410%21%14%6%
1724
May1st to 15thNight
48%7%11%19%12%
1620
16th to endNight
39%8%13%17%16%4
1611
June1st to 15thNight
31%6%11%27%20%2
1440
16th to endNight
31%8%14%21%20%4
1440
July1st to 15thNight
28%8%15%22%19%4
1360
16th to endNight
24%5%13%35%18%2
1435
August1st to 15thNight
28%7%15%24%22%3
1651
16th to endNight
28%5%12%25%20%6%
1910
September1st to 15thNight
33%5%10%22%20%6%
1848
16th to endNight
32%6%10%21%24%5%
1881
October1st to 15thNight
33%410%25%22%4
1826
16th to endNight
42%310%24%15%2
2255
November1st to 15thNight
36%48%22%21%6%
2276
16th to endNight
50%310%21%13%
2340
December1st to 15thNight
59%49%16%8%
2415
16th to endNight
61%6%8%15%7%
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
34%11%33%14%5%1
90
16th to endDay
15%20%44%17%1
96
February1st to 15thDay
18%23%41%12%4
90
16th to endDay
19%11%38%24%6%
81
March1st to 15thDay
32%20%34%12%1
90
16th to endDay
23%12%32%21%8%1
282
April1st to 15thDay
21%10%30%22%12%1
270
16th to endDay
23%7%29%22%12%4
270
May1st to 15thDay
23%10%26%22%11%4
288
16th to endDay
16%430%21%17%9%
402
June1st to 15thDay
13%222%34%20%6%
495
16th to endDay
13%429%26%18%7%
495
July1st to 15thDay
13%221%27%22%12%
475
16th to endDay
5%214%27%32%18%
494
August1st to 15thDay
13%16%21%34%22%
313
16th to endDay
9%111%27%34%15%
332
September1st to 15thDay
12%313%25%30%15%
315
16th to endDay
17%410%22%30%13%
275
October1st to 15thDay
12%5%24%26%24%6%
241
16th to endDay
20%11%32%32%3
96
November1st to 15thDay
5%13%18%30%24%7%
90
16th to endDay
27%18%30%15%6%1
90
December1st to 15thDay
18%15%40%20%41
90
16th to endDay
28%11%47%12%
96
January1st to 15thNight
24%13%36%23%3
900
16th to endNight
21%15%35%24%3
945
February1st to 15thNight
21%12%37%26%2
704
16th to endNight
22%10%39%24%3
631
March1st to 15thNight
24%11%35%24%4
720
16th to endNight
21%8%33%27%7%1
682
April1st to 15thNight
19%10%32%28%9%
539
16th to endNight
19%7%31%30%10%
540
May1st to 15thNight
19%5%30%32%11%
540
16th to endNight
14%221%36%21%4
563
June1st to 15thNight
11%219%44%21%
540
16th to endNight
9%218%43%25%1
540
July1st to 15thNight
8%114%40%31%1
510
16th to endNight
6%18%38%39%6%
564
August1st to 15thNight
7%110%39%35%5%
539
16th to endNight
7%19%32%44%5%
573
September1st to 15thNight
12%314%36%28%5%
588
16th to endNight
13%412%31%34%4
681
October1st to 15thNight
12%5%21%34%20%5%
660
16th to endNight
22%9%30%26%9%
704
November1st to 15thNight
15%8%32%29%13%1
700
16th to endNight
23%11%28%26%9%
720
December1st to 15thNight
27%10%32%21%6%1
795
16th to endNight
30%9%35%18%5%
960
Page generated at 2017-09-22 07:35:39. Version ac04

Copyright 2017 A. Danko


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