Elachee Nature Science Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Elachee Nature Science Center 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
47%
15524
22%
46918
15%
15481
55%
15481
27%
29261

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
26%
720
23%
2327
9%
716
42%
716
20%
1457
January16th to endNight
24%
768
24%
2475
9%
768
41%
768
21%
1545
February1st to 15thNight
30%
704
26%
2111
10%
701
45%
701
25%
1284
February16th to endNight
24%
631
24%
1893
9%
631
40%
631
24%
1179
March1st to 15thNight
31%
720
24%
2049
11%
720
42%
720
26%
1304
March16th to endNight
38%
768
21%
2112
11%
768
45%
768
29%
1332
April1st to 15thNight
40%
659
24%
1917
14%
659
51%
659
33%
1120
April16th to endNight
48%
540
24%
1682
15%
540
57%
540
31%
1001
May1st to 15thNight
49%
540
19%
1620
10%
540
56%
540
27%
1031
May16th to endNight
60%
561
20%
1683
15%
561
63%
561
30%
1044
June1st to 15thNight
66%
540
15%
1620
13%
540
68%
540
29%
1036
June16th to endNight
71%
540
16%
1620
14%
540
72%
540
31%
991
July1st to 15thNight
69%
510
12%
1530
11%
510
69%
510
25%
1021
July16th to endNight
74%
564
16%
1595
14%
531
77%
531
26%
1066
August1st to 15thNight
67%
539
16%
1609
15%
536
68%
536
26%
1067
August16th to endNight
65%
573
17%
1907
19%
573
66%
573
22%
1291
September1st to 15thNight
61%
717
17%
1977
16%
717
62%
717
26%
1341
September16th to endNight
55%
658
22%
1818
16%
658
61%
658
29%
1175
October1st to 15thNight
53%
660
31%
1837
24%
660
60%
660
35%
1102
October16th to endNight
50%
704
33%
2112
25%
704
63%
704
37%
1170
November1st to 15thNight
50%
700
31%
2248
25%
700
61%
700
36%
1207
November16th to endNight
38%
720
27%
2340
17%
720
52%
720
27%
1349
December1st to 15thNight
35%
720
23%
2340
14%
720
46%
720
22%
1466
December16th to endNight
30%
768
21%
2496
12%
768
41%
768
18%
1682

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
13%5%25%5%35%5%5%7%41%
47819
Night
13%5%2442445%7%45%
47117
TransparencyDay
39%7%12%18%17%4
47520
Night
36%6%11%19%19%6%
46920
SeeingDay
17%6%19%22%21%12%
5398
Night
16%8%22%28%20%3
15526

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 15thDay
17%7%24424335%44%
1611
16th to endDay
19%5%24323346%45%
1748
February1st to 15thDay
17%414424446%44%
1750
16th to endDay
17%5%25%423446%43%
1580
March1st to 15thDay
16%5%14433446%44%
1909
16th to endDay
16%4245%24446%43%
2111
April1st to 15thDay
11%5%15%4245%5%6%44%
2040
16th to endDay
11%4244245%5%6%48%
2277
May1st to 15thDay
12%5%15%435%45%7%44%
2331
16th to endDay
10%425%6%46%5%6%9%38%
2431
June1st to 15thDay
8%426%6%36%8%8%11%33%
2340
16th to endDay
5%3145%46%7%8%10%41%
2340
July1st to 15thDay
9%426%7%48%7%7%10%29%
2340
16th to endDay
7%426%8%5%9%8%8%10%29%
2465
August1st to 15thDay
10%5%35%5%38%6%9%10%32%
2340
16th to endDay
13%6%26%7%47%6%6%9%27%
2283
September1st to 15thDay
12%6%26%6%35%6%5%8%37%
1980
16th to endDay
17%5%25%4345%5%5%41%
1815
October1st to 15thDay
14%412212335%55%
1791
16th to endDay
12%42322223459%
1760
November1st to 15thDay
13%323313345%55%
1609
16th to endDay
16%423423345%47%
1620
December1st to 15thDay
19%6%24413446%41%
1620
16th to endDay
25%6%25%323335%37%
1728
January1st to 15thNight
18%5%34323345%45%
2327
16th to endNight
17%6%2442335%5%44%
2475
February1st to 15thNight
14%5%24323346%48%
2103
16th to endNight
16%5%2442445%6%44%
1893
March1st to 15thNight
15%424424446%46%
2049
16th to endNight
13%5%24323446%48%
2112
April1st to 15thNight
12%41332335%6%52%
1917
16th to endNight
10%424424446%50%
1682
May1st to 15thNight
11%5%15%435%6%6%7%43%
1619
16th to endNight
9%335%33446%10%45%
1682
June1st to 15thNight
7%424435%6%8%12%39%
1620
16th to endNight
5%315%5%35%5%8%12%43%
1620
July1st to 15thNight
7%436%6%45%6%7%11%35%
1620
16th to endNight
6%3245%48%7%9%14%33%
1703
August1st to 15thNight
11%4245%35%6%6%12%36%
1620
16th to endNight
11%425%5%35%6%7%9%35%
1907
September1st to 15thNight
10%5%25%6%345%6%8%39%
1977
16th to endNight
14%4245%3335%6%44%
1818
October1st to 15thNight
13%423322336%54%
1837
16th to endNight
10%32332333359%
2112
November1st to 15thNight
12%323222236%57%
2248
16th to endNight
16%412323345%51%
2340
December1st to 15thNight
16%6%25%424346%44%
2340
16th to endNight
22%7%24424346%37%
2496

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
42%5%8%15%23%4
1612
16th to endDay
40%37%20%21%7%
1748
February1st to 15thDay
39%49%19%23%3
1752
16th to endDay
41%37%21%18%7%
1580
March1st to 15thDay
39%410%17%20%6%
1909
16th to endDay
41%5%11%21%16%3
2112
April1st to 15thDay
38%5%10%19%20%5%
2040
16th to endDay
34%6%9%20%21%5%
2277
May1st to 15thDay
38%6%12%19%18%3
2331
16th to endDay
40%9%13%21%13%2
2435
June1st to 15thDay
39%12%19%19%7%1
2340
16th to endDay
32%10%17%22%14%2
2340
July1st to 15thDay
43%11%18%18%5%1
2201
16th to endDay
43%13%17%16%7%1
2310
August1st to 15thDay
42%11%16%18%8%1
2327
16th to endDay
50%10%14%14%9%1
2283
September1st to 15thDay
43%9%12%16%15%3
1980
16th to endDay
42%6%11%18%17%5%
1815
October1st to 15thDay
31%49%18%27%8%
1791
16th to endDay
29%26%19%29%12%
1760
November1st to 15thDay
31%36%15%32%10%
1609
16th to endDay
38%36%15%27%7%
1620
December1st to 15thDay
43%49%18%16%8%
1620
16th to endDay
50%38%17%14%6%
1728
January1st to 15thNight
42%37%17%23%5%
2327
16th to endNight
41%36%17%23%7%
2475
February1st to 15thNight
37%37%20%21%8%
2112
16th to endNight
38%37%21%22%5%
1893
March1st to 15thNight
38%5%9%19%19%8%
2049
16th to endNight
36%5%10%22%20%4
2112
April1st to 15thNight
31%411%23%22%6%
1917
16th to endNight
33%6%10%21%19%7%
1682
May1st to 15thNight
37%7%14%19%18%2
1620
16th to endNight
33%9%14%27%12%3
1684
June1st to 15thNight
33%11%19%23%9%1
1620
16th to endNight
31%10%17%23%14%2
1620
July1st to 15thNight
37%11%21%20%7%1
1530
16th to endNight
34%14%18%21%8%2
1595
August1st to 15thNight
38%10%18%21%10%1
1609
16th to endNight
40%12%17%17%11%
1907
September1st to 15thNight
39%10%16%16%15%3
1977
16th to endNight
38%6%11%21%15%5%
1818
October1st to 15thNight
32%5%11%16%26%8%
1837
16th to endNight
29%35%18%30%12%
2112
November1st to 15thNight
29%36%17%30%13%
2248
16th to endNight
34%46%19%25%9%
2340
December1st to 15thNight
42%38%19%17%8%
2340
16th to endNight
47%48%15%17%5%
2496

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
23%17%33%20%5%
90
16th to endDay
25%28%34%10%2
96
February1st to 15thDay
21%25%38%14%
90
16th to endDay
25%13%45%12%2
81
March1st to 15thDay
21%15%28%24%9%1
199
16th to endDay
20%11%26%26%12%2
288
April1st to 15thDay
17%10%30%19%19%2
270
16th to endDay
16%6%22%27%21%5%
270
May1st to 15thDay
16%8%29%15%15%13%
288
16th to endDay
16%6%16%22%22%15%
331
June1st to 15thDay
12%111%26%26%20%
315
16th to endDay
9%16%25%24%23%
315
July1st to 15thDay
11%19%25%28%23%
305
16th to endDay
9%7%21%36%24%
326
August1st to 15thDay
20%9%22%26%19%
313
16th to endDay
18%19%21%29%18%
332
September1st to 15thDay
14%313%21%30%16%
315
16th to endDay
22%213%27%22%11%
254
October1st to 15thDay
21%318%25%21%9%
255
16th to endDay
15%5%19%23%29%5%
272
November1st to 15thDay
25%12%22%17%17%3
117
16th to endDay
15%10%23%34%13%3
90
December1st to 15thDay
31%12%31%18%6%
90
16th to endDay
34%16%28%17%21
96
January1st to 15thNight
25%16%27%23%7%
720
16th to endNight
21%16%34%24%2
768
February1st to 15thNight
19%16%30%29%3
704
16th to endNight
17%17%36%23%4
631
March1st to 15thNight
18%13%33%27%5%
720
16th to endNight
18%10%28%29%13%
768
April1st to 15thNight
16%11%29%28%13%1
659
16th to endNight
13%5%27%31%20%1
540
May1st to 15thNight
14%5%25%29%22%3
540
16th to endNight
14%216%28%34%4
563
June1st to 15thNight
10%114%31%32%9%
540
16th to endNight
6%11%35%34%11%
540
July1st to 15thNight
10%7%27%42%11%
510
16th to endNight
7%7%26%47%10%
564
August1st to 15thNight
15%7%26%39%10%
539
16th to endNight
13%28%25%40%10%
573
September1st to 15thNight
13%211%26%37%8%
717
16th to endNight
17%214%37%25%1
658
October1st to 15thNight
15%6%19%28%25%4
660
16th to endNight
13%6%23%30%23%2
704
November1st to 15thNight
14%7%24%31%20%2
700
16th to endNight
17%12%27%27%13%
720
December1st to 15thNight
18%13%26%29%11%
720
16th to endNight
26%12%26%28%6%
768
Page generated at 2017-09-16 17:07:00. Version ac04

Copyright 2017 A. Danko


Elachee Nature Science Center Clear Sky Chart | Charts Home