Woodstock
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Woodstock clear sky chart from 2005-11-05 to 2018-01-12.

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
35%
15375
15%
48124
10%
15337
41%
15337
19%
33455

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
17%
762
10%
2549
5%
761
23%
761
9%
1990
January16th to endNight
15%
768
10%
2496
3%
768
22%
768
9%
1984
February1st to 15thNight
18%
702
7%
2287
2%
701
23%
701
9%
1817
February16th to endNight
24%
631
11%
1973
4%
631
31%
631
13%
1481
March1st to 15thNight
25%
720
14%
2001
7%
720
31%
720
16%
1499
March16th to endNight
33%
768
19%
2112
11%
768
40%
768
22%
1463
April1st to 15thNight
28%
697
16%
1835
7%
697
34%
697
22%
1321
April16th to endNight
40%
540
21%
1620
9%
540
48%
540
26%
1038
May1st to 15thNight
42%
540
17%
1620
11%
540
48%
540
24%
1079
May16th to endNight
46%
399
17%
1522
16%
399
56%
399
25%
877
June1st to 15thNight
49%
360
13%
1428
14%
360
56%
360
22%
838
June16th to endNight
54%
360
16%
1260
17%
360
61%
360
27%
740
July1st to 15thNight
62%
354
18%
1262
22%
354
66%
354
34%
659
July16th to endNight
63%
564
15%
1595
14%
531
65%
531
34%
939
August1st to 15thNight
66%
539
18%
1609
14%
536
69%
536
35%
952
August16th to endNight
63%
594
24%
1740
17%
594
67%
594
37%
1023
September1st to 15thNight
55%
720
21%
1869
13%
720
59%
720
32%
1203
September16th to endNight
57%
717
23%
1980
17%
717
60%
717
33%
1224
October1st to 15thNight
44%
720
17%
2148
16%
720
48%
720
25%
1420
October16th to endNight
26%
768
15%
2309
9%
768
35%
768
16%
1674
November1st to 15thNight
36%
760
18%
2537
16%
760
41%
760
20%
1677
November16th to endNight
24%
780
11%
2730
7%
780
31%
780
12%
2005
December1st to 15thNight
14%
780
6%
2730
2%
780
18%
780
8%
2171
December16th to endNight
12%
832
7%
2912
2%
832
18%
832
7%
2381

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%9%47%6%35%5%5%7%30%
49201
Night
14%8%47%5%3445%7%33%
48303
Cloud CoverDay
14%9%47%6%35%5%5%7%30%
49211
Night
14%8%37%5%3445%7%34%
48307
TransparencyDay
51%6%12%18%9%1
48898
Night
49%5%12%20%11%1
48124
SeeingDay
17%7%27%24%15%7%
5938
Night
18%9%28%28%12%1
15381

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%5%10%6%5%7%446%16%
1631
16th to endDay
13%17%8%14%7%445%45%14%
1728
February1st to 15thDay
14%17%6%10%8%35%5%46%16%
1575
16th to endDay
16%13%6%9%7%46%446%20%
1500
March1st to 15thDay
16%12%5%10%7%34346%24%
1948
16th to endDay
16%9%6%6%6%3445%5%30%
2112
April1st to 15thDay
19%10%5%6%5%25%447%27%
2121
16th to endDay
18%8%35%423437%37%
2340
May1st to 15thDay
17%7%36%5%345%5%7%34%
2331
16th to endDay
13%5%25%5%25%5%5%8%39%
2590
June1st to 15thDay
14%5%35%435%46%9%37%
2527
16th to endDay
12%5%25%5%36%6%7%9%37%
2700
July1st to 15thDay
9%5%25%6%36%6%6%8%40%
2615
16th to endDay
8%6%36%6%46%5%6%9%35%
2465
August1st to 15thDay
8%5%36%6%46%6%7%9%36%
2340
16th to endDay
11%6%25%5%35%5%6%9%38%
2450
September1st to 15thDay
13%5%37%5%35%46%7%36%
2090
16th to endDay
14%5%25%4345%5%7%40%
1980
October1st to 15thDay
18%8%36%6%34446%33%
1811
16th to endDay
23%10%36%6%35%5%46%23%
1914
November1st to 15thDay
13%10%36%6%3445%8%32%
1649
16th to endDay
18%13%6%8%6%35%45%7%20%
1560
December1st to 15thDay
15%16%8%11%7%345%4417%
1560
16th to endDay
20%17%7%11%7%45%5%45%9%
1664
January1st to 15thNight
19%12%5%9%7%4445%6%20%
2549
16th to endNight
14%13%8%11%7%46%45%5%19%
2496
February1st to 15thNight
14%13%6%10%8%45%45%5%20%
2285
16th to endNight
15%11%39%7%35%5%5%7%24%
1973
March1st to 15thNight
17%9%37%6%45%45%6%28%
1989
16th to endNight
15%8%36%5%24445%39%
2112
April1st to 15thNight
19%7%36%5%33347%34%
1835
16th to endNight
11%8%25%6%3445%8%39%
1620
May1st to 15thNight
15%5%36%5%235%6%8%36%
1620
16th to endNight
10%5%244335%5%6%47%
1520
June1st to 15thNight
9%426%4345%7%7%43%
1428
16th to endNight
9%414335%5%5%9%45%
1260
July1st to 15thNight
5%12442345%9%55%
1338
16th to endNight
7%314425%5%6%9%47%
1703
August1st to 15thNight
5%324435%47%9%48%
1620
16th to endNight
7%42442335%7%52%
1740
September1st to 15thNight
12%5%24424347%47%
1869
16th to endNight
12%41442346%7%46%
1980
October1st to 15thNight
17%6%25%42335%7%40%
2148
16th to endNight
21%8%36%5%3445%7%30%
2309
November1st to 15thNight
15%8%25%6%345%6%7%34%
2537
16th to endNight
19%11%5%7%6%345%47%25%
2730
December1st to 15thNight
18%15%6%10%6%35%5%45%18%
2730
16th to endNight
20%15%8%11%7%34445%15%
2912

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
17%14%49%7%46%5%5%7%17%
1631
16th to endDay
13%17%7%13%9%445%45%14%
1728
February1st to 15thDay
15%16%6%11%7%445%46%17%
1575
16th to endDay
16%13%5%11%7%45%446%20%
1500
March1st to 15thDay
16%12%410%8%34346%23%
1959
16th to endDay
15%10%5%7%6%44346%30%
2111
April1st to 15thDay
18%10%46%5%35%5%46%27%
2121
16th to endDay
18%8%35%423346%37%
2340
May1st to 15thDay
17%6%36%5%3445%6%35%
2331
16th to endDay
12%6%345%345%5%8%39%
2590
June1st to 15thDay
13%5%36%5%25%5%5%10%37%
2527
16th to endDay
11%5%15%6%35%6%7%9%37%
2700
July1st to 15thDay
8%435%6%36%6%6%8%40%
2615
16th to endDay
8%6%35%7%36%6%6%9%36%
2465
August1st to 15thDay
9%5%26%6%45%6%7%9%36%
2340
16th to endDay
11%6%25%6%35%47%8%38%
2450
September1st to 15thDay
13%6%37%5%36%5%6%7%36%
2090
16th to endDay
13%5%25%5%3446%8%39%
1980
October1st to 15thDay
17%7%48%6%34346%33%
1811
16th to endDay
22%10%37%6%445%5%6%23%
1914
November1st to 15thDay
13%10%37%6%2446%7%32%
1649
16th to endDay
18%12%5%8%6%35%447%21%
1560
December1st to 15thDay
15%16%7%11%7%3445%5%17%
1560
16th to endDay
19%15%8%11%7%45%6%45%10%
1664
January1st to 15thNight
19%11%5%8%7%45%45%6%20%
2549
16th to endNight
14%13%8%11%8%35%447%19%
2496
February1st to 15thNight
14%13%6%9%8%45%445%21%
2278
16th to endNight
15%10%5%9%7%45%45%7%25%
1973
March1st to 15thNight
18%9%37%6%35%5%5%7%27%
2001
16th to endNight
15%9%37%424345%39%
2112
April1st to 15thNight
20%7%36%434337%34%
1835
16th to endNight
11%6%36%5%3445%7%40%
1620
May1st to 15thNight
15%6%25%5%2445%8%37%
1619
16th to endNight
10%5%2443445%6%48%
1520
June1st to 15thNight
9%5%35%5%25%5%6%8%42%
1428
16th to endNight
9%425%5%35%45%9%45%
1260
July1st to 15thNight
5%21432446%7%55%
1338
16th to endNight
7%315%4345%6%10%47%
1703
August1st to 15thNight
5%315%3445%7%10%48%
1620
16th to endNight
7%42442435%7%52%
1740
September1st to 15thNight
11%6%24424347%47%
1869
16th to endNight
11%4145%2437%7%46%
1980
October1st to 15thNight
16%7%25%424347%41%
2148
16th to endNight
20%7%27%5%3445%7%30%
2309
November1st to 15thNight
14%8%25%5%345%6%7%35%
2537
16th to endNight
19%10%47%6%345%5%7%25%
2730
December1st to 15thNight
18%14%6%9%6%3445%6%19%
2730
16th to endNight
19%14%7%11%7%34445%16%
2912

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
66%6%10%11%4
1632
16th to endDay
72%49%8%4
1728
February1st to 15thDay
67%6%9%12%3
1577
16th to endDay
64%411%12%5%
1500
March1st to 15thDay
61%5%11%15%5%
1959
16th to endDay
53%411%17%10%1
2112
April1st to 15thDay
56%5%11%17%9%
2121
16th to endDay
48%410%21%13%1
2340
May1st to 15thDay
47%7%11%21%11%
2331
16th to endDay
42%7%12%22%13%2
2594
June1st to 15thDay
42%7%13%23%12%1
2527
16th to endDay
41%7%14%22%13%
2700
July1st to 15thDay
36%8%11%25%15%2
2462
16th to endDay
41%8%14%20%11%2
2310
August1st to 15thDay
41%8%15%19%12%1
2327
16th to endDay
40%7%13%23%12%1
2450
September1st to 15thDay
44%6%14%22%12%
2090
16th to endDay
41%7%13%26%11%
1980
October1st to 15thDay
52%412%16%12%1
1811
16th to endDay
60%6%13%13%5%
1914
November1st to 15thDay
48%7%13%20%8%
1649
16th to endDay
61%5%15%13%4
1560
December1st to 15thDay
65%7%14%8%3
1560
16th to endDay
74%7%8%7%2
1664
January1st to 15thNight
63%5%11%11%7%
2549
16th to endNight
65%5%10%14%3
2496
February1st to 15thNight
65%5%10%13%5%
2287
16th to endNight
58%5%12%15%7%
1973
March1st to 15thNight
54%6%11%19%6%
2001
16th to endNight
47%5%9%22%12%2
2112
April1st to 15thNight
50%310%20%13%
1835
16th to endNight
41%410%20%19%3
1620
May1st to 15thNight
44%5%10%24%13%2
1620
16th to endNight
35%7%12%25%15%3
1522
June1st to 15thNight
37%7%12%25%15%1
1428
16th to endNight
35%6%14%23%18%
1260
July1st to 15thNight
26%6%10%29%22%3
1262
16th to endNight
31%7%15%24%17%3
1595
August1st to 15thNight
29%8%14%31%13%1
1609
16th to endNight
30%5%11%31%17%2
1740
September1st to 15thNight
36%5%11%27%15%2
1869
16th to endNight
34%6%12%30%15%
1980
October1st to 15thNight
43%5%11%23%16%
2148
16th to endNight
52%5%13%18%8%
2309
November1st to 15thNight
45%6%14%20%12%1
2537
16th to endNight
56%5%15%15%6%
2730
December1st to 15thNight
65%6%13%10%4
2730
16th to endNight
69%5%11%10%3
2912

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%19%41%15%4
105
16th to endDay
39%15%30%13%1
96
February1st to 15thDay
20%18%47%13%
90
16th to endDay
23%16%45%12%2
81
March1st to 15thDay
25%8%36%22%7%
249
16th to endDay
27%5%32%22%9%1
288
April1st to 15thDay
22%13%29%20%11%2
270
16th to endDay
21%8%28%22%12%6%
270
May1st to 15thDay
21%6%29%21%14%6%
288
16th to endDay
16%7%26%26%15%7%
331
June1st to 15thDay
16%423%34%16%3
322
16th to endDay
12%7%31%31%12%4
495
July1st to 15thDay
11%424%28%21%8%
413
16th to endDay
7%420%28%27%10%
326
August1st to 15thDay
9%118%27%26%16%
313
16th to endDay
13%217%22%24%20%
332
September1st to 15thDay
11%5%14%25%27%15%
315
16th to endDay
15%316%23%23%17%
314
October1st to 15thDay
19%5%26%24%18%6%
315
16th to endDay
26%7%34%23%6%1
330
November1st to 15thDay
21%12%33%17%10%5%
119
16th to endDay
22%17%38%13%7%
90
December1st to 15thDay
26%21%31%16%4
90
16th to endDay
26%27%35%7%4
96
January1st to 15thNight
24%16%34%17%6%
765
16th to endNight
21%13%36%23%4
768
February1st to 15thNight
21%16%33%24%3
704
16th to endNight
23%12%30%27%6%
631
March1st to 15thNight
22%10%35%24%6%
720
16th to endNight
19%9%32%26%11%
768
April1st to 15thNight
24%11%29%28%6%
697
16th to endNight
14%8%32%33%11%1
540
May1st to 15thNight
18%5%25%33%15%1
540
16th to endNight
12%429%34%18%1
400
June1st to 15thNight
12%327%41%14%
360
16th to endNight
10%226%46%14%
360
July1st to 15thNight
5%121%48%20%2
354
16th to endNight
8%20%44%23%3
564
August1st to 15thNight
6%116%41%30%3
539
16th to endNight
9%117%35%31%4
594
September1st to 15thNight
13%419%32%25%5%
720
16th to endNight
13%417%30%27%6%
717
October1st to 15thNight
20%5%23%30%17%3
720
16th to endNight
25%11%31%24%7%
768
November1st to 15thNight
18%10%28%29%11%1
760
16th to endNight
24%14%30%21%8%
780
December1st to 15thNight
27%17%33%17%4
780
16th to endNight
26%15%35%17%4
832
Page generated at 2018-01-12 22:01:25. Version ac04

Copyright 2018 A. Danko


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