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 2017-10-31.

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
25%
14929
14%
47304
6%
14894
33%
14894
16%
33451

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%
738
12%
2613
3%
734
28%
734
10%
1896
January16th to endNight
18%
768
14%
2661
4%
768
30%
768
12%
1902
February1st to 15thNight
17%
704
11%
2286
4%
701
27%
701
12%
1695
February16th to endNight
15%
631
12%
1946
3%
631
26%
631
11%
1486
March1st to 15thNight
19%
720
16%
2067
6%
720
30%
720
16%
1508
March16th to endNight
22%
768
17%
2112
6%
768
31%
768
17%
1521
April1st to 15thNight
18%
629
15%
1752
4%
629
27%
629
15%
1279
April16th to endNight
21%
540
17%
1620
6%
540
31%
540
17%
1128
May1st to 15thNight
23%
540
11%
1620
5%
540
30%
540
16%
1184
May16th to endNight
20%
453
10%
1395
5%
452
27%
452
13%
1034
June1st to 15thNight
26%
360
8%
1260
5%
360
32%
360
14%
928
June16th to endNight
31%
360
7%
1260
6%
360
35%
360
16%
889
July1st to 15thNight
37%
340
11%
1190
9%
340
44%
340
22%
775
July16th to endNight
43%
393
10%
1411
11%
370
47%
370
18%
928
August1st to 15thNight
45%
539
11%
1608
9%
535
47%
535
25%
1063
August16th to endNight
43%
573
20%
1719
12%
573
49%
573
29%
1053
September1st to 15thNight
33%
657
15%
1878
8%
657
38%
657
26%
1218
September16th to endNight
40%
717
24%
1980
14%
717
48%
717
33%
1200
October1st to 15thNight
31%
720
19%
2112
8%
720
41%
720
24%
1384
October16th to endNight
22%
768
14%
2419
5%
768
33%
768
15%
1746
November1st to 15thNight
22%
711
16%
2343
8%
711
32%
711
15%
1651
November16th to endNight
24%
750
15%
2520
6%
750
35%
750
12%
1780
December1st to 15thNight
15%
750
10%
2652
3%
750
24%
750
9%
1990
December16th to endNight
14%
800
11%
2880
3%
800
24%
800
7%
2213

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
20%8%36%5%34446%31%
48454
Night
19%8%36%5%34446%32%
47467
TransparencyDay
53%411%20%9%
48135
Night
52%411%21%9%
47304
SeeingDay
27%12%28%20%8%2
6813
Night
25%13%30%23%7%
14929

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
16%14%5%7%6%35%347%25%
1325
16th to endDay
16%10%48%7%35%446%27%
1563
February1st to 15thDay
11%12%5%8%8%5%6%5%5%6%25%
1575
16th to endDay
16%11%48%8%4444425%
1524
March1st to 15thDay
21%12%46%434435%28%
1882
16th to endDay
15%11%6%8%5%24245%32%
2112
April1st to 15thDay
24%11%35%5%33346%29%
2194
16th to endDay
25%6%35%5%2344434%
2340
May1st to 15thDay
26%7%25%6%34345%29%
2332
16th to endDay
26%7%35%5%2445%6%28%
2727
June1st to 15thDay
28%8%36%5%2435%6%26%
2700
16th to endDay
24%6%35%6%35%46%6%25%
2700
July1st to 15thDay
15%5%25%6%36%5%6%8%33%
2700
16th to endDay
17%7%35%6%45%6%5%8%30%
2645
August1st to 15thDay
18%5%26%5%35%6%5%8%31%
2340
16th to endDay
14%5%25%6%345%5%7%39%
2483
September1st to 15thDay
17%6%25%5%2344442%
2079
16th to endDay
17%414423237%46%
1980
October1st to 15thDay
21%8%24423336%39%
1848
16th to endDay
26%9%25%5%33345%31%
1801
November1st to 15thDay
21%9%35%6%35%346%30%
1515
16th to endDay
22%9%45%5%34347%29%
1440
December1st to 15thDay
25%9%47%435%335%25%
1305
16th to endDay
22%13%5%6%7%33435%22%
1344
January1st to 15thNight
15%12%5%8%5%35%45%6%28%
2613
16th to endNight
13%9%5%8%6%46%6%5%6%27%
2661
February1st to 15thNight
10%14%48%7%46%446%27%
2285
16th to endNight
17%15%47%6%2444427%
1946
March1st to 15thNight
19%9%36%6%34445%31%
2055
16th to endNight
16%10%46%5%33445%34%
2112
April1st to 15thNight
23%9%35%434336%30%
1752
16th to endNight
26%6%2433344436%
1620
May1st to 15thNight
22%7%46%5%35%35%8%28%
1620
16th to endNight
24%8%36%5%3445%6%27%
1393
June1st to 15thNight
24%6%36%6%35%5%47%26%
1260
16th to endNight
20%7%35%5%35%45%7%30%
1260
July1st to 15thNight
14%5%45%5%246%7%8%34%
1260
16th to endNight
16%425%6%35%5%6%9%34%
1507
August1st to 15thNight
14%5%35%5%25%5%6%6%38%
1620
16th to endNight
13%5%2443345%8%45%
1719
September1st to 15thNight
17%6%245%23447%42%
1878
16th to endNight
13%313323445%51%
1980
October1st to 15thNight
20%5%245%2345%5%40%
2112
16th to endNight
24%9%36%423345%32%
2419
November1st to 15thNight
22%7%35%5%24445%32%
2343
16th to endNight
20%8%36%5%24446%32%
2520
December1st to 15thNight
26%10%36%6%24435%26%
2652
16th to endNight
24%13%47%5%3444423%
2880

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
57%5%11%16%7%
1326
16th to endDay
57%39%21%9%
1563
February1st to 15thDay
57%411%19%6%
1578
16th to endDay
60%410%14%7%1
1524
March1st to 15thDay
58%49%14%12%1
1893
16th to endDay
55%38%19%11%1
2112
April1st to 15thDay
56%28%18%11%2
2194
16th to endDay
53%38%18%12%3
2340
May1st to 15thDay
57%27%19%10%1
2332
16th to endDay
56%5%11%19%6%
2731
June1st to 15thDay
58%412%15%7%1
2700
16th to endDay
57%412%17%8%
2700
July1st to 15thDay
44%6%16%21%10%
2541
16th to endDay
51%6%14%20%6%
2479
August1st to 15thDay
50%5%14%24%5%
2327
16th to endDay
43%5%15%27%8%
2483
September1st to 15thDay
45%411%26%11%
2079
16th to endDay
39%310%30%14%1
1980
October1st to 15thDay
48%311%26%9%
1848
16th to endDay
56%311%19%8%
1801
November1st to 15thDay
54%5%12%16%10%
1515
16th to endDay
56%312%19%7%
1440
December1st to 15thDay
62%411%15%5%
1305
16th to endDay
64%37%15%8%
1344
January1st to 15thNight
55%6%11%17%9%
2613
16th to endNight
55%410%20%8%
2661
February1st to 15thNight
56%5%10%19%6%
2286
16th to endNight
60%48%14%10%1
1946
March1st to 15thNight
54%39%19%11%1
2067
16th to endNight
52%37%21%13%1
2112
April1st to 15thNight
54%37%16%13%3
1752
16th to endNight
50%38%18%15%3
1620
May1st to 15thNight
55%49%19%10%1
1620
16th to endNight
57%5%11%17%8%
1395
June1st to 15thNight
56%5%10%19%6%1
1260
16th to endNight
53%5%13%18%9%
1260
July1st to 15thNight
42%7%16%24%8%
1190
16th to endNight
46%6%15%20%10%
1411
August1st to 15thNight
43%5%17%25%7%
1608
16th to endNight
37%417%31%9%
1719
September1st to 15thNight
41%413%27%12%
1878
16th to endNight
34%314%31%14%1
1980
October1st to 15thNight
43%312%27%11%
2112
16th to endNight
54%310%21%9%
2419
November1st to 15thNight
52%413%19%9%
2343
16th to endNight
53%5%12%20%8%
2520
December1st to 15thNight
61%39%20%4
2652
16th to endNight
63%48%16%6%
2880

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%23%35%18%1
60
16th to endDay
27%15%34%14%8%
91
February1st to 15thDay
21%14%35%21%6%
236
16th to endDay
21%19%30%20%8%
230
March1st to 15thDay
29%18%33%12%41
270
16th to endDay
27%17%27%16%7%4
288
April1st to 15thDay
37%16%22%15%5%1
270
16th to endDay
28%14%32%14%8%2
270
May1st to 15thDay
34%12%31%15%41
288
16th to endDay
33%14%29%15%6%
511
June1st to 15thDay
33%11%25%21%7%1
495
16th to endDay
30%8%29%21%8%2
495
July1st to 15thDay
20%8%29%25%14%
475
16th to endDay
18%6%28%33%11%1
346
August1st to 15thDay
19%7%27%29%12%3
313
16th to endDay
19%10%25%26%12%3
332
September1st to 15thDay
19%6%33%25%12%2
315
16th to endDay
19%10%24%28%11%6%
314
October1st to 15thDay
25%12%27%15%13%6%
282
16th to endDay
34%17%25%15%6%1
288
November1st to 15thDay
30%11%27%19%10%1
235
16th to endDay
29%17%28%17%7%
240
December1st to 15thDay
36%14%30%14%3
105
16th to endDay
39%12%39%9%
64
January1st to 15thNight
25%17%33%20%2
738
16th to endNight
22%17%33%21%4
768
February1st to 15thNight
20%18%36%19%5%
704
16th to endNight
27%19%30%17%4
631
March1st to 15thNight
27%13%35%21%1
720
16th to endNight
26%15%29%20%7%
768
April1st to 15thNight
30%16%29%18%4
629
16th to endNight
31%14%29%19%5%
540
May1st to 15thNight
27%12%31%22%5%
540
16th to endNight
29%10%33%20%5%
453
June1st to 15thNight
26%7%32%26%7%
360
16th to endNight
24%6%32%28%8%
360
July1st to 15thNight
16%334%32%12%
340
16th to endNight
18%425%37%12%
393
August1st to 15thNight
17%225%37%15%
539
16th to endNight
16%428%34%15%
573
September1st to 15thNight
20%5%33%29%10%
657
16th to endNight
16%9%29%30%12%
717
October1st to 15thNight
23%9%30%25%10%
720
16th to endNight
30%17%25%21%5%
768
November1st to 15thNight
27%15%28%19%7%
711
16th to endNight
27%16%25%21%7%
750
December1st to 15thNight
33%17%28%17%3
750
16th to endNight
34%17%26%16%3
800
Page generated at 2017-11-01 18:23:29. Version ac04

Copyright 2017 A. Danko


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