Blue Creek
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Blue Creek clear sky chart from 2005-11-06 to 2024-03-28.

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%
24111
18%
80411
13%
24010
46%
24010
20%
53885

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
17%
752
12%
4072
6%
737
27%
737
6%
3095
January11th to 20thNight
14%
760
14%
4042
6%
740
23%
740
6%
3011
January21st to endNight
17%
829
9%
4493
7%
814
28%
814
7%
3407
February1st to 10thNight
20%
760
14%
2428
7%
760
29%
760
13%
1794
February11th to 20thNight
17%
741
15%
2219
6%
740
25%
740
14%
1628
February21st to endNight
15%
628
14%
1884
5%
628
24%
628
13%
1394
March1st to 10thNight
24%
760
20%
2209
10%
760
33%
760
18%
1524
March11th to 20thNight
22%
760
19%
2090
9%
760
32%
760
20%
1455
March21st to endNight
27%
821
16%
2256
8%
821
34%
821
20%
1598
April1st to 10thNight
28%
681
20%
1941
10%
681
37%
681
24%
1276
April11th to 20thNight
33%
533
23%
1678
13%
533
43%
533
24%
1062
April21st to endNight
32%
540
19%
1620
7%
540
42%
540
22%
1101
May1st to 10thNight
36%
540
16%
1620
8%
540
42%
540
22%
1079
May11th to 20thNight
41%
531
16%
1593
9%
531
46%
531
24%
1060
May21st to endNight
59%
583
18%
1745
14%
582
63%
582
31%
1069
June1st to 10thNight
60%
540
18%
1620
15%
540
64%
540
35%
954
June11th to 20thNight
61%
540
18%
1620
15%
540
65%
540
35%
941
June21st to endNight
59%
540
19%
1620
15%
540
63%
540
35%
941
July1st to 10thNight
63%
525
16%
1575
15%
525
64%
525
31%
965
July11th to 20thNight
69%
522
19%
1566
16%
522
71%
522
38%
890
July21st to endNight
66%
591
20%
1672
17%
558
69%
558
34%
998
August1st to 10thNight
71%
537
23%
1600
20%
534
72%
534
34%
938
August11th to 20thNight
67%
534
23%
1598
18%
534
70%
534
31%
977
August21st to endNight
68%
594
26%
1880
23%
594
71%
594
40%
1013
September1st to 10thNight
63%
688
24%
1948
18%
688
67%
688
37%
1152
September11th to 20thNight
64%
720
29%
1980
22%
720
69%
720
38%
1165
September21st to endNight
53%
720
28%
1980
20%
720
60%
720
33%
1228
October1st to 10thNight
55%
720
28%
1999
23%
720
60%
720
37%
1170
October11th to 20thNight
40%
720
25%
2160
18%
720
51%
720
28%
1326
October21st to endNight
34%
792
24%
2422
18%
792
44%
792
22%
1619
November1st to 10thNight
44%
740
26%
2406
21%
740
53%
740
29%
1413
November11th to 20thNight
31%
760
24%
2470
15%
760
44%
760
20%
1603
November21st to endNight
33%
760
20%
2470
15%
760
41%
760
19%
1678
December1st to 10thNight
21%
760
14%
2470
7%
760
30%
760
13%
1816
December11th to 20thNight
24%
759
16%
2979
10%
759
32%
759
13%
2086
December21st to endNight
20%
830
9%
4486
7%
817
28%
817
6%
3459

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
16%9%46%5%35%5%5%7%35%
79132
Night
16%10%46%5%3445%7%37%
80880
TransparencyDay
49%310%22%14%2
78855
Night
49%310%22%15%2
80676
SeeingDay
22%13%27%21%13%5%
13950
Night
20%11%24%27%15%2
24136

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%18%6%9%6%3346%6%23%
2836
11th to 20thDay
16%16%7%12%7%3433325%
2840
21st to endDay
28%17%7%7%43434419%
3124
February1st to 10thDay
20%13%5%9%5%345%45%29%
1750
11th to 20thDay
18%12%5%10%5%35%445%29%
1848
21st to endDay
22%13%46%5%3335%5%32%
1570
March1st to 10thDay
18%12%45%5%3445%6%35%
1971
11th to 20thDay
20%9%5%6%6%34446%32%
2090
21st to endDay
20%11%46%6%34446%32%
2255
April1st to 10thDay
14%9%47%5%25%45%8%38%
2034
11th to 20thDay
18%8%35%5%24347%40%
2230
21st to endDay
18%8%36%6%45%45%7%34%
2340
May1st to 10thDay
20%8%26%6%35%5%5%6%34%
2340
11th to 20thDay
20%7%47%7%445%5%6%32%
2301
21st to endDay
10%6%36%6%5%5%7%7%9%37%
2531
June1st to 10thDay
12%5%246%46%6%6%9%40%
2340
11th to 20thDay
11%5%25%6%45%6%7%9%40%
2340
21st to endDay
10%5%35%6%46%6%6%10%39%
2340
July1st to 10thDay
13%5%36%5%46%5%6%9%38%
2340
11th to 20thDay
10%6%35%6%37%7%7%9%37%
2340
21st to endDay
12%5%35%5%35%5%7%9%39%
2547
August1st to 10thDay
10%5%26%5%45%6%8%10%39%
2327
11th to 20thDay
9%6%26%6%5%7%6%7%10%36%
2303
21st to endDay
9%4245%45%6%7%9%45%
2472
September1st to 10thDay
15%5%3443445%6%47%
1994
11th to 20thDay
10%4245%35%46%7%49%
1980
21st to endDay
17%6%35%424446%46%
1980
October1st to 10thDay
13%4245%3445%7%47%
1959
11th to 20thDay
16%6%35%434446%46%
1800
21st to endDay
22%8%35%423346%39%
1931
November1st to 10thDay
12%7%24434446%50%
1672
11th to 20thDay
15%12%35%5%2436%6%38%
1710
21st to endDay
18%9%47%433346%38%
1710
December1st to 10thDay
24%13%5%7%5%34445%26%
1710
11th to 20thDay
17%15%6%8%6%34445%28%
2153
21st to endDay
20%18%5%9%7%35%445%19%
3124
January1st to 10thNight
16%20%6%9%7%345%4421%
4109
11th to 20thNight
18%16%6%12%7%3333424%
4120
21st to endNight
26%15%5%7%5%44335%23%
4532
February1st to 10thNight
21%13%5%7%6%33436%28%
2428
11th to 20thNight
21%11%48%5%44445%31%
2218
21st to endNight
23%15%46%5%33345%29%
1884
March1st to 10thNight
18%10%36%434446%37%
2209
11th to 20thNight
19%9%46%5%2445%6%35%
2090
21st to endNight
18%9%46%5%45%45%6%34%
2256
April1st to 10thNight
14%7%35%7%345%5%7%40%
1941
11th to 20thNight
15%7%45%4346%5%7%40%
1678
21st to endNight
18%7%35%5%35%6%47%38%
1620
May1st to 10thNight
19%7%45%5%345%5%9%36%
1620
11th to 20thNight
15%7%36%5%345%6%8%37%
1592
21st to endNight
9%5%245%45%6%7%10%42%
1744
June1st to 10thNight
7%425%5%35%6%7%10%46%
1620
11th to 20thNight
7%425%5%36%5%5%12%46%
1620
21st to endNight
8%4245%35%6%8%10%46%
1620
July1st to 10thNight
9%7%25%5%445%6%9%44%
1620
11th to 20thNight
6%4245%35%5%6%11%48%
1620
21st to endNight
8%4246%35%7%6%10%45%
1771
August1st to 10thNight
7%415%5%36%6%7%9%46%
1611
11th to 20thNight
8%5%345%5%6%5%6%9%43%
1598
21st to endNight
8%41443346%9%53%
1880
September1st to 10thNight
11%5%3343445%8%51%
1948
11th to 20thNight
10%423435%347%53%
1980
21st to endNight
12%5%35%5%245%5%6%48%
1980
October1st to 10thNight
10%5%2443445%8%52%
1999
11th to 20thNight
15%6%34335%46%7%44%
2160
21st to endNight
20%8%345%34445%40%
2422
November1st to 10thNight
13%7%25%5%23345%50%
2406
11th to 20thNight
16%9%36%6%34436%40%
2470
21st to endNight
19%11%35%5%34446%36%
2470
December1st to 10thNight
22%13%47%5%34446%27%
2470
11th to 20thNight
18%12%7%8%5%34346%31%
3042
21st to endNight
20%18%7%8%7%44445%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
63%111%15%9%
2837
11th to 20thDay
67%27%17%7%1
2840
21st to endDay
70%16%17%41
3124
February1st to 10thDay
59%39%17%10%1
1750
11th to 20thDay
58%28%19%11%1
1858
21st to endDay
56%27%22%11%2
1570
March1st to 10thDay
52%27%27%11%1
1971
11th to 20thDay
54%28%21%13%2
2090
21st to endDay
55%38%21%11%2
2255
April1st to 10thDay
47%29%25%13%3
2034
11th to 20thDay
47%28%22%17%4
2230
21st to endDay
51%311%21%11%3
2340
May1st to 10thDay
51%311%23%10%2
2340
11th to 20thDay
53%412%19%12%2
2305
21st to endDay
42%5%15%23%13%1
2531
June1st to 10thDay
41%411%26%16%2
2340
11th to 20thDay
40%5%14%23%16%2
2340
21st to endDay
40%5%14%23%14%3
2340
July1st to 10thDay
45%5%12%20%17%2
2275
11th to 20thDay
40%5%13%23%16%2
2271
21st to endDay
39%414%26%14%2
2405
August1st to 10thDay
39%5%13%28%14%1
2314
11th to 20thDay
42%5%11%27%13%1
2303
21st to endDay
35%415%24%18%5%
2472
September1st to 10thDay
38%311%23%19%6%
1994
11th to 20thDay
36%210%25%24%2
1980
21st to endDay
41%26%26%22%2
1980
October1st to 10thDay
35%311%26%23%2
1959
11th to 20thDay
41%27%28%19%2
1800
21st to endDay
48%29%24%16%2
1931
November1st to 10thDay
37%29%28%20%3
1672
11th to 20thDay
47%27%22%18%4
1710
21st to endDay
49%29%23%16%2
1710
December1st to 10thDay
62%29%19%7%1
1710
11th to 20thDay
60%28%18%12%1
2150
21st to endDay
69%28%14%6%1
3124
January1st to 10thNight
67%27%16%8%
4109
11th to 20thNight
66%18%16%8%1
4120
21st to endNight
67%16%19%6%1
4532
February1st to 10thNight
60%38%19%9%1
2428
11th to 20thNight
58%27%20%12%1
2219
21st to endNight
59%29%16%10%3
1884
March1st to 10thNight
50%26%24%16%2
2209
11th to 20thNight
50%29%24%13%1
2090
21st to endNight
51%39%24%11%2
2256
April1st to 10thNight
44%39%25%16%2
1941
11th to 20thNight
44%310%19%18%7%
1678
21st to endNight
47%410%22%15%2
1620
May1st to 10thNight
47%412%23%12%3
1620
11th to 20thNight
45%5%15%20%13%2
1593
21st to endNight
36%6%16%23%17%2
1745
June1st to 10thNight
34%5%15%25%19%3
1620
11th to 20thNight
32%5%16%21%22%3
1620
21st to endNight
32%5%17%26%17%3
1620
July1st to 10thNight
38%412%24%18%4
1575
11th to 20thNight
30%417%24%21%3
1566
21st to endNight
33%5%14%30%15%2
1672
August1st to 10thNight
33%6%14%30%16%2
1600
11th to 20thNight
36%5%12%27%18%1
1598
21st to endNight
29%414%28%20%6%
1880
September1st to 10thNight
33%314%25%18%7%
1948
11th to 20thNight
33%39%26%26%3
1980
21st to endNight
37%37%23%28%2
1980
October1st to 10thNight
33%310%27%23%4
1999
11th to 20thNight
39%38%26%21%3
2160
21st to endNight
48%37%22%17%3
2422
November1st to 10thNight
38%38%24%24%4
2406
11th to 20thNight
48%26%20%20%4
2470
21st to endNight
51%29%23%14%2
2470
December1st to 10thNight
60%28%20%9%1
2470
11th to 20thNight
57%19%23%9%1
3044
21st to endNight
69%27%16%7%
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%22%31%14%3
270
11th to 20thDay
38%23%31%7%1
270
21st to endDay
33%27%27%12%2
297
February1st to 10thDay
33%24%29%11%3
270
11th to 20thDay
38%27%29%42
270
21st to endDay
38%23%34%5%
225
March1st to 10thDay
33%21%31%11%4
341
11th to 20thDay
28%21%32%14%5%
460
21st to endDay
35%18%27%16%4
490
April1st to 10thDay
24%19%28%19%9%1
420
11th to 20thDay
28%18%24%18%9%3
412
21st to endDay
28%16%34%14%6%2
420
May1st to 10thDay
27%17%30%16%8%2
423
11th to 20thDay
23%10%33%20%9%4
447
21st to endDay
14%9%25%29%16%7%
485
June1st to 10thDay
15%7%23%33%15%7%
450
11th to 20thDay
13%8%28%29%16%7%
450
21st to endDay
13%8%30%23%17%9%
450
July1st to 10thDay
15%317%22%20%22%
445
11th to 20thDay
10%6%23%29%21%11%
444
21st to endDay
14%321%28%22%13%
488
August1st to 10thDay
12%5%18%27%23%14%
446
11th to 20thDay
12%5%20%32%23%9%
439
21st to endDay
8%5%20%31%24%12%
495
September1st to 10thDay
14%419%26%26%10%
450
11th to 20thDay
9%418%26%31%12%
450
21st to endDay
18%10%20%26%21%5%
450
October1st to 10thDay
13%7%26%29%18%6%
450
11th to 20thDay
18%16%31%22%11%3
450
21st to endDay
28%13%31%22%7%
446
November1st to 10thDay
17%19%30%25%7%1
270
11th to 20thDay
29%17%29%17%6%1
270
21st to endDay
24%21%34%15%41
270
December1st to 10thDay
31%22%30%13%5%
270
11th to 20thDay
28%20%33%13%41
270
21st to endDay
32%22%32%10%4
297
January1st to 10thNight
31%19%28%18%5%
760
11th to 20thNight
32%18%30%17%2
760
21st to endNight
26%21%30%21%2
836
February1st to 10thNight
31%16%28%23%2
760
11th to 20thNight
32%19%28%20%1
743
21st to endNight
31%18%31%18%1
628
March1st to 10thNight
25%18%28%23%5%
760
11th to 20thNight
26%18%31%18%7%
760
21st to endNight
26%13%29%25%7%
821
April1st to 10thNight
22%15%30%24%9%
681
11th to 20thNight
19%12%30%25%12%2
533
21st to endNight
22%9%32%30%7%
540
May1st to 10thNight
20%10%29%29%11%1
540
11th to 20thNight
18%7%26%32%17%1
531
21st to endNight
9%6%20%32%28%5%
584
June1st to 10thNight
9%321%42%24%2
540
11th to 20thNight
9%319%37%27%4
540
21st to endNight
9%422%34%28%3
540
July1st to 10thNight
13%313%31%31%10%
525
11th to 20thNight
7%214%36%38%5%
522
21st to endNight
9%312%38%33%4
591
August1st to 10thNight
8%29%38%37%5%
537
11th to 20thNight
8%212%37%33%7%
534
21st to endNight
8%213%34%36%7%
594
September1st to 10thNight
14%212%32%34%6%
688
11th to 20thNight
10%415%29%34%8%
720
21st to endNight
14%6%20%34%24%3
720
October1st to 10thNight
12%6%22%31%25%4
720
11th to 20thNight
18%11%26%30%14%1
720
21st to endNight
24%12%26%26%11%1
792
November1st to 10thNight
18%10%24%29%18%1
740
11th to 20thNight
23%15%27%23%11%1
760
21st to endNight
27%12%23%29%8%1
760
December1st to 10thNight
31%16%25%21%6%
760
11th to 20thNight
27%13%31%23%6%1
760
21st to endNight
30%16%28%23%4
836
Page generated at 2024-03-24 23:37:00. Version ac07

Copyright © 2024 Attilla Danko.


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