Easton Woods Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Easton Woods Observatory clear sky chart from 2005-11-06 to 2024-01-15.

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
39%
23912
18%
74586
13%
23865
46%
23865
22%
50188

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 10thNight
18%
760
13%
2459
6%
757
27%
757
11%
1882
January11th to 20thNight
17%
737
12%
2393
5%
737
25%
737
10%
1847
January21st to endNight
20%
792
14%
2574
7%
792
29%
792
13%
1901
February1st to 10thNight
21%
720
12%
2340
6%
720
28%
720
13%
1752
February11th to 20thNight
16%
700
14%
2113
5%
700
25%
700
14%
1576
February21st to endNight
16%
592
15%
1776
5%
592
25%
592
13%
1329
March1st to 10thNight
24%
720
19%
2058
10%
720
33%
720
20%
1411
March11th to 20thNight
24%
720
18%
1980
9%
720
31%
720
19%
1408
March21st to endNight
27%
792
16%
2178
9%
792
33%
792
18%
1564
April1st to 10thNight
27%
720
18%
1980
7%
720
36%
720
23%
1344
April11th to 20thNight
34%
547
23%
1649
13%
547
44%
547
26%
1053
April21st to endNight
28%
540
19%
1620
7%
540
39%
540
21%
1095
May1st to 10thNight
38%
540
15%
1620
8%
540
44%
540
22%
1108
May11th to 20thNight
41%
531
16%
1593
9%
531
46%
531
22%
1083
May21st to endNight
61%
582
17%
1745
13%
582
65%
582
30%
1077
June1st to 10thNight
59%
540
18%
1620
14%
540
63%
540
33%
976
June11th to 20thNight
59%
540
17%
1620
14%
540
63%
540
32%
981
June21st to endNight
59%
540
18%
1620
15%
540
62%
540
33%
970
July1st to 10thNight
62%
525
16%
1575
15%
525
64%
525
32%
963
July11th to 20thNight
66%
522
19%
1566
16%
522
69%
522
36%
908
July21st to endNight
63%
591
19%
1672
16%
558
66%
558
32%
1027
August1st to 10thNight
69%
537
21%
1600
19%
534
70%
534
34%
952
August11th to 20thNight
67%
534
23%
1598
18%
534
70%
534
31%
1004
August21st to endNight
67%
594
26%
1813
22%
594
69%
594
35%
1051
September1st to 10thNight
65%
720
24%
1980
18%
720
67%
720
39%
1184
September11th to 20thNight
64%
720
29%
1980
22%
720
68%
720
38%
1164
September21st to endNight
52%
720
28%
1980
20%
720
58%
720
33%
1235
October1st to 10thNight
54%
720
26%
2038
23%
720
58%
720
36%
1210
October11th to 20thNight
43%
720
24%
2160
18%
720
52%
720
28%
1354
October21st to endNight
36%
792
24%
2380
18%
792
45%
792
23%
1577
November1st to 10thNight
43%
740
25%
2406
21%
740
52%
740
29%
1413
November11th to 20thNight
31%
760
23%
2470
14%
760
44%
760
20%
1620
November21st to endNight
34%
760
20%
2470
15%
760
41%
760
19%
1678
December1st to 10thNight
23%
760
13%
2470
8%
760
30%
760
13%
1851
December11th to 20thNight
25%
759
15%
2996
9%
759
33%
759
13%
2148
December21st to endNight
22%
825
8%
4494
7%
817
29%
817
6%
3492

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%46%6%35%5%5%7%35%
74908
Night
15%9%46%5%3445%7%38%
74876
TransparencyDay
47%5%11%21%13%2
74631
Night
46%5%11%22%14%2
74672
SeeingDay
21%11%27%22%13%6%
13784
Night
20%10%25%29%15%2
23929

By Month

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 10thDay
17%13%7%9%8%44445%24%
1706
11th to 20thDay
19%16%7%9%7%34345%22%
1656
21st to endDay
19%14%6%9%7%345%3426%
1782
February1st to 10thDay
23%11%6%8%6%23345%27%
1620
11th to 20thDay
19%13%6%9%5%3445%6%25%
1731
21st to endDay
21%13%5%6%6%23445%31%
1480
March1st to 10thDay
18%9%46%5%35%446%36%
1900
11th to 20thDay
20%10%48%6%3445%6%31%
1980
21st to endDay
21%10%5%7%5%35%446%32%
2178
April1st to 10thDay
15%8%47%5%45%45%6%37%
1981
11th to 20thDay
17%9%35%5%2445%6%39%
2272
21st to endDay
20%8%36%7%345%47%34%
2340
May1st to 10thDay
19%7%46%7%35%5%48%32%
2340
11th to 20thDay
19%7%46%6%45%5%5%7%32%
2301
21st to endDay
9%6%26%5%47%6%6%10%40%
2531
June1st to 10thDay
12%5%35%6%35%7%7%9%39%
2340
11th to 20thDay
9%6%36%7%5%6%5%7%9%39%
2340
21st to endDay
10%5%35%6%46%7%8%10%37%
2340
July1st to 10thDay
12%6%35%6%36%6%7%8%38%
2340
11th to 20thDay
10%5%35%6%36%7%7%9%37%
2340
21st to endDay
12%435%6%47%6%7%8%38%
2547
August1st to 10thDay
9%425%6%46%7%8%11%37%
2327
11th to 20thDay
9%6%27%6%46%6%7%10%38%
2303
21st to endDay
9%425%5%36%5%6%8%45%
2520
September1st to 10thDay
14%5%345%35%46%6%45%
1980
11th to 20thDay
10%5%245%35%45%8%49%
1980
21st to endDay
17%6%245%3345%6%45%
1980
October1st to 10thDay
13%5%25%5%3446%7%46%
1922
11th to 20thDay
15%7%25%5%4345%5%44%
1800
21st to endDay
20%8%36%5%33346%39%
1972
November1st to 10thDay
11%6%345%25%445%50%
1672
11th to 20thDay
16%11%46%43445%6%38%
1710
21st to endDay
17%9%46%5%35%45%6%36%
1710
December1st to 10thDay
23%14%5%9%5%34345%25%
1710
11th to 20thDay
18%15%5%9%6%3435%6%27%
2153
21st to endDay
20%19%6%10%8%445%5%5%17%
3124
January1st to 10thNight
17%14%6%10%7%45%445%25%
2459
11th to 20thNight
20%13%6%9%6%34445%24%
2393
21st to endNight
18%14%6%9%6%3445%5%29%
2574
February1st to 10thNight
22%13%47%5%3445%5%27%
2340
11th to 20thNight
20%12%48%6%34445%29%
2112
21st to endNight
22%15%5%6%5%34335%29%
1776
March1st to 10thNight
17%8%36%5%25%45%6%37%
2058
11th to 20thNight
19%9%5%6%5%3445%7%33%
1980
21st to endNight
19%9%47%6%35%446%34%
2178
April1st to 10thNight
14%8%46%5%3445%7%39%
1980
11th to 20thNight
13%7%36%5%35%47%7%40%
1649
21st to endNight
16%8%37%5%445%5%6%38%
1620
May1st to 10thNight
18%8%25%5%35%5%5%7%36%
1620
11th to 20thNight
16%8%46%5%25%5%6%8%37%
1592
21st to endNight
8%5%25%446%6%8%11%42%
1744
June1st to 10thNight
8%4245%35%5%8%9%45%
1620
11th to 20thNight
7%5%345%35%6%8%10%44%
1620
21st to endNight
9%425%5%35%6%7%10%45%
1620
July1st to 10thNight
10%6%245%35%5%8%8%46%
1620
11th to 20thNight
7%425%435%5%6%10%49%
1620
21st to endNight
8%425%5%46%6%7%10%43%
1771
August1st to 10thNight
7%5%245%45%6%7%8%46%
1611
11th to 20thNight
7%5%36%6%36%6%6%8%44%
1598
21st to endNight
8%415%5%45%5%5%7%51%
1813
September1st to 10thNight
12%415%3335%6%7%52%
1980
11th to 20thNight
9%425%43445%7%53%
1980
21st to endNight
13%6%25%43435%6%49%
1980
October1st to 10thNight
11%5%2443245%7%52%
2038
11th to 20thNight
14%6%35%32446%8%44%
2160
21st to endNight
19%7%35%5%2445%5%41%
2380
November1st to 10thNight
14%6%25%434446%49%
2406
11th to 20thNight
16%9%35%5%35%45%6%40%
2470
21st to endNight
19%11%36%5%33446%36%
2470
December1st to 10thNight
21%13%48%5%3445%5%27%
2470
11th to 20thNight
17%13%7%8%6%34347%29%
3042
21st to endNight
19%17%5%8%8%46%45%6%19%
4532

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 10thDay
62%47%17%9%
1707
11th to 20thDay
66%310%16%4
1656
21st to endDay
62%49%17%7%1
1782
February1st to 10thDay
60%411%17%7%1
1620
11th to 20thDay
59%5%10%17%9%1
1741
21st to endDay
56%47%21%10%2
1480
March1st to 10thDay
49%39%28%9%1
1900
11th to 20thDay
55%49%18%12%1
1980
21st to endDay
54%5%9%19%11%2
2178
April1st to 10thDay
47%6%10%23%11%3
1981
11th to 20thDay
45%5%10%19%17%4
2272
21st to endDay
50%5%11%19%12%3
2340
May1st to 10thDay
51%411%22%9%2
2340
11th to 20thDay
52%6%12%19%11%2
2305
21st to endDay
38%8%17%23%14%1
2531
June1st to 10thDay
39%8%13%24%14%2
2340
11th to 20thDay
40%7%14%21%16%2
2340
21st to endDay
39%8%15%21%14%2
2340
July1st to 10thDay
42%8%13%20%16%2
2275
11th to 20thDay
39%8%14%22%15%2
2271
21st to endDay
39%7%14%25%13%3
2405
August1st to 10thDay
37%8%16%26%13%1
2314
11th to 20thDay
39%7%13%28%12%1
2303
21st to endDay
35%7%14%23%18%4
2520
September1st to 10thDay
38%5%11%22%19%6%
1980
11th to 20thDay
34%6%11%27%21%2
1980
21st to endDay
40%5%8%26%20%1
1980
October1st to 10thDay
36%5%11%24%22%1
1922
11th to 20thDay
41%49%27%18%2
1800
21st to endDay
47%49%23%15%1
1972
November1st to 10thDay
36%410%28%19%3
1672
11th to 20thDay
48%47%21%17%3
1710
21st to endDay
49%49%23%14%1
1710
December1st to 10thDay
63%39%18%6%1
1710
11th to 20thDay
58%6%9%18%9%
2150
21st to endDay
69%5%9%12%5%
3124
January1st to 10thNight
62%48%15%9%1
2459
11th to 20thNight
63%410%16%6%1
2393
21st to endNight
58%410%20%7%2
2574
February1st to 10thNight
59%410%19%7%1
2340
11th to 20thNight
58%48%18%11%1
2113
21st to endNight
58%410%17%8%3
1776
March1st to 10thNight
47%5%8%23%15%2
2058
11th to 20thNight
51%410%22%11%2
1980
21st to endNight
52%49%21%12%2
2178
April1st to 10thNight
44%6%8%23%16%3
1980
11th to 20thNight
41%411%19%18%7%
1649
21st to endNight
46%6%10%21%15%2
1620
May1st to 10thNight
46%6%12%20%12%3
1620
11th to 20thNight
45%7%12%20%13%3
1593
21st to endNight
34%8%18%23%15%2
1745
June1st to 10thNight
33%7%12%26%19%3
1620
11th to 20thNight
32%8%17%21%20%3
1620
21st to endNight
32%8%15%24%18%3
1620
July1st to 10thNight
35%7%14%24%18%3
1575
11th to 20thNight
30%7%16%26%18%2
1566
21st to endNight
33%8%14%28%15%2
1672
August1st to 10thNight
32%7%16%28%15%2
1600
11th to 20thNight
35%8%13%26%18%
1598
21st to endNight
31%6%11%27%20%5%
1813
September1st to 10thNight
31%5%15%24%18%7%
1980
11th to 20thNight
31%5%11%26%25%3
1980
21st to endNight
37%410%22%26%2
1980
October1st to 10thNight
32%5%11%28%20%4
2038
11th to 20thNight
38%5%10%26%19%2
2160
21st to endNight
45%48%24%16%3
2380
November1st to 10thNight
37%410%24%21%4
2406
11th to 20thNight
46%47%22%18%3
2470
21st to endNight
50%410%22%13%1
2470
December1st to 10thNight
59%5%9%19%7%
2470
11th to 20thNight
57%410%21%8%1
3044
21st to endNight
66%5%9%15%5%
4532

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 10thDay
30%20%35%10%4
270
11th to 20thDay
35%18%33%13%2
252
21st to endDay
27%28%31%11%3
264
February1st to 10thDay
36%22%26%13%3
240
11th to 20thDay
42%28%26%5%
240
21st to endDay
33%22%37%8%1
198
March1st to 10thDay
27%21%34%15%3
340
11th to 20thDay
28%19%33%14%5%1
420
21st to endDay
33%16%29%18%3
462
April1st to 10thDay
23%17%30%19%10%1
420
11th to 20thDay
25%15%30%20%8%2
412
21st to endDay
27%14%33%17%6%2
420
May1st to 10thDay
27%14%30%17%10%3
423
11th to 20thDay
21%11%28%24%10%5%
447
21st to endDay
14%6%25%29%18%8%
485
June1st to 10thDay
16%5%23%29%19%7%
450
11th to 20thDay
14%8%25%28%17%8%
450
21st to endDay
13%6%30%24%18%9%
450
July1st to 10thDay
14%219%23%19%22%
445
11th to 20thDay
10%420%32%22%12%
444
21st to endDay
13%417%29%22%14%
488
August1st to 10thDay
12%316%29%27%12%
446
11th to 20thDay
12%220%34%20%12%
439
21st to endDay
10%318%31%24%13%
495
September1st to 10thDay
14%416%26%26%13%
450
11th to 20thDay
10%315%28%32%13%
450
21st to endDay
19%8%20%26%22%6%
450
October1st to 10thDay
14%7%26%29%18%7%
450
11th to 20thDay
18%12%32%23%12%3
450
21st to endDay
26%12%31%23%8%
487
November1st to 10thDay
16%17%34%24%7%1
270
11th to 20thDay
29%14%31%20%5%2
270
21st to endDay
21%19%37%18%5%
270
December1st to 10thDay
32%18%30%14%41
270
11th to 20thDay
26%20%37%12%41
270
21st to endDay
32%18%32%13%5%1
297
January1st to 10thNight
28%17%31%19%5%
760
11th to 20thNight
30%16%30%20%3
737
21st to endNight
25%17%33%23%3
792
February1st to 10thNight
31%14%29%24%2
720
11th to 20thNight
29%18%33%19%1
703
21st to endNight
30%15%34%19%2
592
March1st to 10thNight
25%14%31%27%4
720
11th to 20thNight
25%14%32%20%8%1
720
21st to endNight
25%12%30%24%8%
792
April1st to 10thNight
20%14%33%24%8%
720
11th to 20thNight
17%12%33%25%12%1
547
21st to endNight
19%8%38%27%7%1
540
May1st to 10thNight
22%8%27%30%11%2
540
11th to 20thNight
20%5%26%30%18%1
531
21st to endNight
10%418%35%29%5%
584
June1st to 10thNight
9%321%41%25%2
540
11th to 20thNight
9%319%41%27%2
540
21st to endNight
10%321%37%28%3
540
July1st to 10thNight
13%312%33%31%9%
525
11th to 20thNight
8%214%36%36%5%
522
21st to endNight
10%115%32%39%4
591
August1st to 10thNight
8%210%39%37%4
537
11th to 20thNight
11%111%37%32%7%
534
21st to endNight
9%215%30%35%9%
594
September1st to 10thNight
13%212%34%34%6%
720
11th to 20thNight
11%312%33%33%7%
720
21st to endNight
17%6%18%33%23%3
720
October1st to 10thNight
14%5%21%33%24%4
720
11th to 20thNight
18%10%24%33%14%1
720
21st to endNight
23%10%26%29%11%1
792
November1st to 10thNight
17%10%25%30%16%2
740
11th to 20thNight
21%16%27%26%10%1
760
21st to endNight
25%12%24%30%8%1
760
December1st to 10thNight
32%13%28%23%5%
760
11th to 20thNight
24%13%32%25%6%
760
21st to endNight
27%16%28%27%3
836
Page generated at 2024-01-11 22:33:49. Version ac07

Copyright 2024 Attilla Danko


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