Elk Creek
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Elk Creek clear sky chart from 2005-11-05 to 2017-09-24.

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%
15743
20%
46978
11%
15704
48%
15704
22%
30211

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%
719
21%
2327
7%
716
33%
716
14%
1484
January16th to endNight
17%
768
22%
2496
6%
768
35%
768
14%
1585
February1st to 15thNight
18%
701
22%
2261
7%
701
37%
701
15%
1380
February16th to endNight
12%
631
21%
1882
5%
631
29%
631
14%
1260
March1st to 15thNight
22%
720
21%
1980
10%
720
32%
720
19%
1347
March16th to endNight
26%
768
15%
2112
8%
768
33%
768
19%
1458
April1st to 15thNight
28%
718
19%
1913
6%
718
39%
718
23%
1247
April16th to endNight
37%
597
19%
1677
9%
597
44%
597
23%
1106
May1st to 15thNight
39%
540
15%
1620
6%
540
46%
540
22%
1073
May16th to endNight
52%
561
14%
1684
9%
561
56%
561
25%
1097
June1st to 15thNight
65%
540
13%
1620
12%
540
66%
540
28%
1043
June16th to endNight
62%
540
17%
1620
12%
540
66%
540
31%
1014
July1st to 15thNight
65%
510
11%
1530
9%
510
67%
510
28%
994
July16th to endNight
74%
564
14%
1595
11%
531
76%
531
33%
962
August1st to 15thNight
63%
539
17%
1609
14%
536
63%
536
26%
1089
August16th to endNight
67%
642
19%
1788
16%
642
67%
642
29%
1193
September1st to 15thNight
59%
720
22%
1953
16%
720
62%
720
30%
1265
September16th to endNight
51%
693
20%
1914
16%
693
55%
693
26%
1278
October1st to 15thNight
46%
660
28%
1936
22%
660
55%
660
28%
1206
October16th to endNight
39%
704
30%
2112
18%
704
54%
704
29%
1230
November1st to 15thNight
42%
700
26%
2173
18%
700
54%
700
28%
1260
November16th to endNight
32%
720
26%
2340
15%
720
47%
720
22%
1374
December1st to 15thNight
27%
720
22%
2340
11%
720
41%
720
16%
1525
December16th to endNight
20%
768
19%
2496
7%
768
35%
768
12%
1741

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%7%36%6%35%5%6%7%34%
47933
Night
10%6%25%5%35%5%6%8%40%
47171
Cloud CoverDay
13%6%36%6%35%5%5%7%34%
47943
Night
11%5%25%5%35%5%6%8%41%
47175
TransparencyDay
47%5%11%19%13%2
47644
Night
40%5%13%22%15%3
46978
SeeingDay
21%11%21%19%16%10%
5584
Night
19%13%21%25%17%2
15749

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
13%6%48%5%35%45%7%35%
1611
16th to endDay
11%7%47%5%345%5%5%39%
1728
February1st to 15thDay
10%10%5%8%434445%38%
1599
16th to endDay
12%7%37%7%34447%37%
1589
March1st to 15thDay
13%6%35%5%345%5%5%41%
1969
16th to endDay
16%9%37%6%35%446%34%
2112
April1st to 15thDay
12%6%15%434447%43%
2033
16th to endDay
15%6%26%5%45%46%6%35%
2292
May1st to 15thDay
16%7%36%6%5%6%5%6%7%29%
2331
16th to endDay
13%6%36%7%46%5%7%7%29%
2431
June1st to 15thDay
10%5%37%8%47%6%7%8%30%
2340
16th to endDay
9%5%47%7%46%6%8%8%32%
2340
July1st to 15thDay
12%6%37%7%47%7%7%9%24%
2340
16th to endDay
11%7%38%8%48%6%7%9%24%
2465
August1st to 15thDay
13%6%38%8%5%7%7%7%8%23%
2340
16th to endDay
12%6%26%7%36%6%7%10%28%
2402
September1st to 15thDay
15%7%37%5%45%46%8%31%
2004
16th to endDay
21%6%25%5%35%5%5%6%31%
1905
October1st to 15thDay
17%6%23424446%42%
1692
16th to endDay
14%7%25%5%24335%45%
1760
November1st to 15thDay
10%6%24423447%48%
1682
16th to endDay
14%5%36%43435%5%43%
1620
December1st to 15thDay
12%8%25%5%335%6%7%38%
1620
16th to endDay
15%10%36%6%235%5%6%33%
1728
January1st to 15thNight
10%6%36%6%46%46%6%37%
2327
16th to endNight
13%6%35%5%35%5%6%6%37%
2496
February1st to 15thNight
10%7%35%5%3445%7%41%
2259
16th to endNight
9%7%37%7%45%5%6%8%34%
1882
March1st to 15thNight
12%6%36%5%346%5%7%38%
1968
16th to endNight
11%7%35%6%36%5%6%8%36%
2112
April1st to 15thNight
9%6%36%5%345%6%7%41%
1913
16th to endNight
12%6%25%5%25%5%5%8%39%
1677
May1st to 15thNight
13%6%345%35%46%10%37%
1620
16th to endNight
9%5%35%435%5%7%11%38%
1682
June1st to 15thNight
7%3145%36%6%7%12%40%
1620
16th to endNight
5%2246%35%5%6%10%45%
1620
July1st to 15thNight
8%325%435%6%8%12%39%
1620
16th to endNight
43145%36%5%8%14%41%
1703
August1st to 15thNight
9%5%25%5%46%6%6%9%38%
1620
16th to endNight
8%5%245%25%6%8%10%38%
1788
September1st to 15thNight
11%5%25%4345%46%46%
1953
16th to endNight
15%5%15%43445%7%41%
1914
October1st to 15thNight
14%5%15%323345%48%
1936
16th to endNight
10%6%15%424346%49%
2112
November1st to 15thNight
10%6%24424346%51%
2173
16th to endNight
11%6%25%5%2445%6%45%
2340
December1st to 15thNight
12%7%37%5%35%46%7%36%
2340
16th to endNight
14%9%37%6%35%6%5%6%31%
2496

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
13%8%46%6%25%45%6%36%
1611
16th to endDay
11%7%36%5%35%45%6%40%
1728
February1st to 15thDay
9%10%47%5%33445%39%
1599
16th to endDay
12%6%47%7%34347%38%
1589
March1st to 15thDay
13%6%25%5%245%5%6%42%
1980
16th to endDay
16%8%37%5%35%345%35%
2111
April1st to 15thDay
12%5%35%5%24447%43%
2033
16th to endDay
16%6%25%7%35%5%5%7%35%
2292
May1st to 15thDay
16%7%26%6%46%5%6%7%29%
2331
16th to endDay
13%6%37%6%36%5%8%7%29%
2431
June1st to 15thDay
10%5%26%8%5%7%6%7%9%30%
2340
16th to endDay
9%5%36%6%46%7%7%8%33%
2340
July1st to 15thDay
12%7%38%7%47%7%6%9%24%
2340
16th to endDay
11%6%48%8%5%8%6%7%8%24%
2465
August1st to 15thDay
13%6%38%9%6%7%7%7%8%22%
2340
16th to endDay
12%6%36%7%37%6%8%9%28%
2402
September1st to 15thDay
15%7%27%6%35%5%5%7%32%
2004
16th to endDay
21%7%25%6%25%45%6%31%
1905
October1st to 15thDay
17%42442435%6%43%
1692
16th to endDay
14%5%25%434335%46%
1760
November1st to 15thDay
10%5%24324346%50%
1682
16th to endDay
15%5%26%5%2335%6%43%
1620
December1st to 15thDay
12%8%245%3445%8%39%
1620
16th to endDay
16%9%27%5%3446%5%34%
1728
January1st to 15thNight
11%6%26%5%36%46%8%39%
2327
16th to endNight
13%7%246%35%5%5%5%40%
2496
February1st to 15thNight
11%7%245%35%35%7%42%
2252
16th to endNight
10%6%26%6%46%6%6%7%36%
1882
March1st to 15thNight
12%5%35%5%445%5%7%39%
1980
16th to endNight
11%6%35%6%35%5%6%7%37%
2112
April1st to 15thNight
10%5%25%445%5%6%7%42%
1913
16th to endNight
13%426%5%345%6%7%40%
1677
May1st to 15thNight
13%6%345%25%46%9%38%
1619
16th to endNight
10%5%246%245%7%11%38%
1682
June1st to 15thNight
7%3145%36%6%8%12%39%
1620
16th to endNight
6%3246%25%5%7%9%45%
1620
July1st to 15thNight
8%4245%36%5%7%11%40%
1620
16th to endNight
5%324435%5%9%14%40%
1703
August1st to 15thNight
10%5%25%6%35%5%7%9%38%
1620
16th to endNight
9%5%245%35%5%7%10%39%
1788
September1st to 15thNight
11%5%35%32445%7%45%
1953
16th to endNight
16%5%25%5%24446%41%
1914
October1st to 15thNight
14%5%24323436%49%
1936
16th to endNight
10%5%25%324347%50%
2112
November1st to 15thNight
11%5%14324345%52%
2173
16th to endNight
11%6%2442445%6%46%
2340
December1st to 15thNight
12%6%36%5%35%45%7%38%
2340
16th to endNight
14%9%36%6%35%5%46%32%
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
47%311%21%13%3
1612
16th to endDay
43%38%26%15%2
1728
February1st to 15thDay
46%38%21%17%3
1601
16th to endDay
46%214%20%13%2
1589
March1st to 15thDay
42%411%21%16%3
1980
16th to endDay
50%49%21%11%2
2112
April1st to 15thDay
40%312%25%13%5%
2033
16th to endDay
47%5%9%19%14%3
2292
May1st to 15thDay
51%7%13%16%9%1
2331
16th to endDay
50%6%13%20%7%1
2435
June1st to 15thDay
48%8%14%18%8%
2340
16th to endDay
45%9%13%16%13%1
2340
July1st to 15thDay
52%10%12%12%10%1
2201
16th to endDay
52%9%14%14%7%1
2310
August1st to 15thDay
55%8%12%15%7%
2327
16th to endDay
49%8%14%17%9%1
2402
September1st to 15thDay
49%6%9%16%14%3
2004
16th to endDay
52%48%17%15%1
1905
October1st to 15thDay
41%310%23%15%5%
1692
16th to endDay
40%26%25%18%6%
1760
November1st to 15thDay
34%39%17%27%7%
1682
16th to endDay
41%36%22%21%3
1620
December1st to 15thDay
41%5%10%19%18%4
1620
16th to endDay
49%410%16%14%3
1728
January1st to 15thNight
42%411%18%17%5%
2327
16th to endNight
43%310%22%17%2
2496
February1st to 15thNight
40%210%25%17%3
2261
16th to endNight
44%5%11%24%12%1
1882
March1st to 15thNight
43%6%9%23%14%2
1980
16th to endNight
44%6%13%22%11%1
2112
April1st to 15thNight
39%5%13%24%13%4
1913
16th to endNight
41%6%13%20%15%3
1677
May1st to 15thNight
42%7%17%21%11%
1620
16th to endNight
38%8%21%23%6%1
1684
June1st to 15thNight
34%10%22%22%9%
1620
16th to endNight
32%9%18%23%13%1
1620
July1st to 15thNight
36%9%18%20%11%2
1530
16th to endNight
29%10%25%22%10%1
1595
August1st to 15thNight
40%9%15%21%12%
1609
16th to endNight
37%9%16%25%8%1
1788
September1st to 15thNight
38%6%13%21%16%3
1953
16th to endNight
42%5%10%22%17%1
1914
October1st to 15thNight
37%49%24%20%3
1936
16th to endNight
35%28%27%19%6%
2112
November1st to 15thNight
33%49%17%26%8%
2173
16th to endNight
37%27%25%21%4
2340
December1st to 15thNight
44%5%9%19%16%5%
2340
16th to endNight
51%410%15%15%2
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
42%20%23%10%22
90
16th to endDay
42%23%22%8%2
96
February1st to 15thDay
34%37%22%41
90
16th to endDay
38%31%21%6%2
90
March1st to 15thDay
28%21%23%18%8%
270
16th to endDay
21%25%24%18%8%1
288
April1st to 15thDay
24%15%23%21%12%2
270
16th to endDay
22%11%22%19%17%6%
270
May1st to 15thDay
25%15%30%12%10%6%
288
16th to endDay
18%9%21%19%16%15%
331
June1st to 15thDay
11%6%22%24%22%13%
315
16th to endDay
14%8%29%19%15%11%
315
July1st to 15thDay
17%5%22%25%14%14%
305
16th to endDay
11%212%28%24%20%
326
August1st to 15thDay
17%119%19%23%18%
313
16th to endDay
14%15%21%20%27%
332
September1st to 15thDay
17%414%17%27%18%
315
16th to endDay
25%415%20%20%13%
287
October1st to 15thDay
21%10%18%20%21%7%
255
16th to endDay
18%15%20%23%16%5%
272
November1st to 15thDay
22%12%18%24%17%4
190
16th to endDay
24%24%21%21%7%1
90
December1st to 15thDay
37%21%21%14%5%
90
16th to endDay
39%19%25%14%1
96
January1st to 15thNight
28%23%25%17%4
720
16th to endNight
26%25%27%18%1
768
February1st to 15thNight
30%21%25%22%
704
16th to endNight
25%29%30%12%1
631
March1st to 15thNight
25%18%30%21%3
720
16th to endNight
20%16%30%21%9%
768
April1st to 15thNight
21%19%27%24%7%
718
16th to endNight
19%13%21%31%12%1
597
May1st to 15thNight
18%10%24%29%13%2
540
16th to endNight
13%5%19%26%27%7%
563
June1st to 15thNight
9%215%37%30%4
540
16th to endNight
7%318%30%35%5%
540
July1st to 15thNight
10%113%34%35%4
510
16th to endNight
5%210%30%41%10%
564
August1st to 15thNight
14%110%33%35%5%
539
16th to endNight
13%7%28%42%7%
642
September1st to 15thNight
14%314%26%35%6%
720
16th to endNight
19%5%15%26%28%4
693
October1st to 15thNight
18%9%20%25%19%6%
660
16th to endNight
17%14%24%26%13%2
704
November1st to 15thNight
18%13%21%27%16%2
700
16th to endNight
25%17%20%25%10%
720
December1st to 15thNight
23%20%24%24%7%
720
16th to endNight
27%19%27%20%4
768
Page generated at 2017-09-25 09:02:24. Version ac04

Copyright 2017 A. Danko


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