Blue Creek Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Blue Creek Observing Site clear sky chart from 2005-11-05 to 2017-10-06.

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%
15754
18%
46964
12%
15710
46%
15710
23%
31356

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%
900
13%
2506
5%
895
23%
895
13%
1963
January16th to endNight
20%
807
13%
2535
7%
807
27%
807
13%
1896
February1st to 15thNight
19%
703
13%
2145
5%
701
26%
701
15%
1543
February16th to endNight
20%
631
14%
1893
5%
631
28%
631
15%
1396
March1st to 15thNight
24%
720
15%
2111
8%
720
30%
720
18%
1488
March16th to endNight
29%
768
16%
2112
7%
768
37%
768
21%
1487
April1st to 15thNight
30%
542
18%
1800
11%
542
41%
542
22%
1171
April16th to endNight
37%
540
19%
1665
9%
540
46%
540
24%
1078
May1st to 15thNight
32%
540
15%
1620
9%
540
39%
540
19%
1146
May16th to endNight
53%
562
18%
1684
14%
561
57%
561
28%
1058
June1st to 15thNight
61%
540
19%
1503
15%
540
65%
540
37%
901
June16th to endNight
60%
540
18%
1440
11%
540
66%
540
37%
877
July1st to 15thNight
59%
510
17%
1360
13%
510
61%
510
34%
859
July16th to endNight
69%
564
22%
1542
18%
531
73%
531
38%
906
August1st to 15thNight
70%
539
24%
1609
21%
536
72%
536
37%
943
August16th to endNight
74%
573
23%
1866
24%
573
76%
573
37%
1025
September1st to 15thNight
64%
642
27%
1902
22%
642
68%
642
35%
1098
September16th to endNight
58%
717
28%
1980
22%
717
62%
717
34%
1211
October1st to 15thNight
53%
684
28%
1900
22%
684
59%
684
36%
1133
October16th to endNight
34%
704
21%
2219
16%
704
43%
704
24%
1427
November1st to 15thNight
40%
700
25%
2276
19%
700
51%
700
29%
1340
November16th to endNight
30%
720
17%
2340
12%
720
38%
720
18%
1603
December1st to 15thNight
22%
720
11%
2340
7%
720
28%
720
13%
1768
December16th to endNight
17%
888
12%
2616
4%
888
25%
888
12%
2039

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
14%7%36%5%3445%7%37%
48219
Night
14%7%35%5%3445%6%39%
47145
Cloud CoverDay
14%7%36%5%3445%7%37%
48228
Night
14%7%35%5%3445%7%39%
47150
TransparencyDay
45%5%11%20%13%2
47918
Night
44%5%11%21%14%2
46964
SeeingDay
16%9%24%23%16%9%
5798
Night
17%9%27%27%15%2
15756

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
19%11%5%8%5%34445%27%
1432
16th to endDay
13%12%7%8%7%34445%29%
1686
February1st to 15thDay
15%12%5%7%5%24446%30%
1717
16th to endDay
15%12%6%8%5%24336%30%
1580
March1st to 15thDay
22%9%36%42435%5%31%
1838
16th to endDay
18%9%46%5%3345%6%31%
2118
April1st to 15thDay
16%7%45%42445%6%37%
2151
16th to endDay
18%6%25%42445%7%37%
2295
May1st to 15thDay
22%8%35%5%3445%6%31%
2331
16th to endDay
12%5%26%6%35%5%6%7%36%
2431
June1st to 15thDay
10%425%5%25%5%5%7%42%
2454
16th to endDay
8%425%5%45%5%6%9%41%
2520
July1st to 15thDay
11%5%35%6%35%5%6%9%36%
2520
16th to endDay
7%3246%46%5%7%10%39%
2517
August1st to 15thDay
7%436%5%346%5%10%41%
2340
16th to endDay
7%425%6%35%5%6%9%43%
2333
September1st to 15thDay
12%5%24435%5%5%6%43%
2045
16th to endDay
12%5%25%424345%48%
1980
October1st to 15thDay
10%5%26%5%3445%6%45%
1857
16th to endDay
17%7%2442335%6%40%
1650
November1st to 15thDay
9%6%35%425%34449%
1582
16th to endDay
18%9%36%6%23345%36%
1620
December1st to 15thDay
24%11%47%5%23335%27%
1620
16th to endDay
19%14%6%8%5%33336%26%
1602
January1st to 15thNight
19%10%5%9%7%35%34426%
2506
16th to endNight
16%14%5%7%5%34345%28%
2535
February1st to 15thNight
18%10%46%5%23446%31%
2143
16th to endNight
16%12%5%6%6%3445%5%29%
1893
March1st to 15thNight
17%8%37%5%345%46%34%
2098
16th to endNight
15%9%45%5%24447%35%
2112
April1st to 15thNight
15%7%35%5%2446%6%39%
1800
16th to endNight
13%6%25%435%45%7%41%
1665
May1st to 15thNight
18%6%36%5%3445%7%33%
1620
16th to endNight
9%5%25%435%5%6%9%42%
1682
June1st to 15thNight
6%4235%245%6%9%48%
1503
16th to endNight
6%22343448%10%48%
1440
July1st to 15thNight
8%5%24425%5%5%7%48%
1440
16th to endNight
6%42443446%9%49%
1649
August1st to 15thNight
5%414435%5%6%9%50%
1620
16th to endNight
432443446%9%51%
1866
September1st to 15thNight
10%5%2332335%6%52%
1902
16th to endNight
11%424424337%50%
1980
October1st to 15thNight
10%424423447%51%
1900
16th to endNight
15%6%26%6%23345%43%
2219
November1st to 15thNight
12%5%24423446%48%
2276
16th to endNight
17%9%46%5%23446%34%
2340
December1st to 15thNight
22%10%5%8%5%24445%26%
2340
16th to endNight
23%12%47%5%345%45%24%
2616

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
19%11%5%8%5%34445%27%
1432
16th to endDay
13%12%6%8%7%34445%29%
1686
February1st to 15thDay
15%13%5%7%5%23446%30%
1717
16th to endDay
15%12%5%8%5%24345%30%
1580
March1st to 15thDay
23%8%36%43345%5%31%
1848
16th to endDay
18%9%46%6%33446%31%
2117
April1st to 15thDay
16%8%35%42445%6%37%
2151
16th to endDay
18%6%25%5%2345%7%37%
2295
May1st to 15thDay
22%8%36%435%446%31%
2331
16th to endDay
12%6%26%6%35%6%6%7%36%
2431
June1st to 15thDay
10%425%5%36%46%7%42%
2454
16th to endDay
8%435%5%36%5%6%9%41%
2520
July1st to 15thDay
11%5%35%6%35%5%7%9%35%
2520
16th to endDay
7%425%6%47%6%7%10%39%
2517
August1st to 15thDay
7%436%5%35%5%6%11%41%
2340
16th to endDay
6%4346%45%6%6%9%43%
2333
September1st to 15thDay
12%6%245%35%5%5%6%43%
2045
16th to endDay
13%5%25%5%23345%47%
1980
October1st to 15thDay
10%5%26%5%3445%6%45%
1857
16th to endDay
17%8%2442335%6%40%
1650
November1st to 15thDay
9%6%35%424345%49%
1582
16th to endDay
17%9%45%6%22446%36%
1620
December1st to 15thDay
24%11%5%7%5%2334427%
1620
16th to endDay
19%14%5%8%5%24236%26%
1602
January1st to 15thNight
19%9%5%9%7%35%34426%
2506
16th to endNight
16%13%6%7%5%34445%28%
2535
February1st to 15thNight
17%10%47%5%23445%31%
2136
16th to endNight
16%11%5%6%5%35%35%6%29%
1893
March1st to 15thNight
17%8%37%5%345%5%6%33%
2111
16th to endNight
15%9%45%5%2445%7%34%
2112
April1st to 15thNight
15%7%35%5%2446%6%38%
1800
16th to endNight
13%6%25%435%45%7%40%
1665
May1st to 15thNight
18%6%36%6%2435%7%33%
1619
16th to endNight
9%5%25%435%5%6%8%42%
1682
June1st to 15thNight
6%4245%245%6%9%48%
1503
16th to endNight
5%3135%3448%10%48%
1440
July1st to 15thNight
8%5%145%25%45%8%48%
1440
16th to endNight
6%4244245%5%9%50%
1649
August1st to 15thNight
5%4135%3447%9%49%
1620
16th to endNight
43235%35%46%9%51%
1866
September1st to 15thNight
10%5%2332245%6%52%
1902
16th to endNight
11%424424337%50%
1980
October1st to 15thNight
10%424433447%51%
1900
16th to endNight
15%6%26%6%23345%43%
2219
November1st to 15thNight
12%5%24423446%47%
2276
16th to endNight
17%9%46%5%23447%33%
2340
December1st to 15thNight
22%11%5%8%5%3444426%
2340
16th to endNight
22%12%47%5%345%45%24%
2616

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
59%49%15%11%
1433
16th to endDay
56%413%19%5%
1686
February1st to 15thDay
54%411%18%10%
1719
16th to endDay
56%411%21%7%
1580
March1st to 15thDay
53%5%12%20%7%
1848
16th to endDay
53%5%12%19%8%
2118
April1st to 15thDay
45%5%11%22%13%1
2151
16th to endDay
45%5%10%21%13%4
2295
May1st to 15thDay
52%6%11%17%10%1
2331
16th to endDay
43%8%14%19%13%1
2435
June1st to 15thDay
37%7%11%22%17%1
2454
16th to endDay
38%7%13%20%17%3
2520
July1st to 15thDay
43%6%12%17%17%2
2371
16th to endDay
36%9%15%23%12%2
2361
August1st to 15thDay
35%7%13%24%17%2
2327
16th to endDay
35%7%13%22%16%5%
2333
September1st to 15thDay
39%5%10%20%18%5%
2045
16th to endDay
37%49%22%24%1
1980
October1st to 15thDay
38%49%25%19%2
1857
16th to endDay
43%411%24%13%1
1650
November1st to 15thDay
37%48%24%20%5%
1582
16th to endDay
50%310%21%13%1
1620
December1st to 15thDay
60%410%15%8%
1620
16th to endDay
61%410%17%5%
1602
January1st to 15thNight
61%47%17%8%
2506
16th to endNight
58%5%10%18%7%
2535
February1st to 15thNight
54%412%20%7%1
2145
16th to endNight
55%5%11%19%8%
1893
March1st to 15thNight
50%5%10%21%10%1
2111
16th to endNight
48%5%12%24%8%1
2112
April1st to 15thNight
44%49%22%16%1
1800
16th to endNight
41%6%11%19%15%7%
1665
May1st to 15thNight
49%6%10%23%9%1
1620
16th to endNight
36%8%13%22%15%4
1684
June1st to 15thNight
29%8%12%27%20%2
1503
16th to endNight
29%8%17%19%21%3
1440
July1st to 15thNight
34%6%12%22%18%5%
1360
16th to endNight
27%7%13%30%17%2
1542
August1st to 15thNight
29%7%13%26%20%2
1609
16th to endNight
26%7%13%27%19%4
1866
September1st to 15thNight
31%5%11%23%22%6%
1902
16th to endNight
34%47%24%26%2
1980
October1st to 15thNight
32%49%27%21%4
1900
16th to endNight
43%39%25%15%2
2219
November1st to 15thNight
36%310%21%22%5%
2276
16th to endNight
50%310%20%13%
2340
December1st to 15thNight
60%310%15%8%1
2340
16th to endNight
61%5%10%15%7%
2616

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
34%21%31%11%11
90
16th to endDay
22%33%35%6%2
96
February1st to 15thDay
22%40%27%8%1
90
16th to endDay
18%20%46%13%
81
March1st to 15thDay
30%18%33%17%
138
16th to endDay
22%16%33%18%7%1
288
April1st to 15thDay
19%15%30%22%10%2
270
16th to endDay
21%10%28%17%14%7%
270
May1st to 15thDay
27%12%26%17%9%6%
288
16th to endDay
20%8%25%18%12%13%
331
June1st to 15thDay
9%324%34%20%7%
429
16th to endDay
13%6%26%32%13%7%
495
July1st to 15thDay
15%421%28%18%11%
475
16th to endDay
7%116%28%27%19%
377
August1st to 15thDay
13%114%23%23%23%
313
16th to endDay
9%314%23%33%15%
332
September1st to 15thDay
11%416%23%28%15%
315
16th to endDay
15%317%19%29%14%
314
October1st to 15thDay
11%5%26%27%20%8%
278
16th to endDay
15%9%41%25%8%
162
November1st to 15thDay
8%14%25%23%20%7%
90
16th to endDay
30%15%32%17%4
90
December1st to 15thDay
30%20%30%14%41
90
16th to endDay
30%30%29%9%1
96
January1st to 15thNight
23%17%36%18%3
900
16th to endNight
23%17%34%22%2
807
February1st to 15thNight
23%15%36%23%1
704
16th to endNight
21%17%35%23%2
631
March1st to 15thNight
22%15%33%24%4
720
16th to endNight
19%12%33%26%8%
768
April1st to 15thNight
18%12%33%26%8%
542
16th to endNight
16%9%33%25%12%1
540
May1st to 15thNight
21%7%31%25%13%
540
16th to endNight
12%324%30%23%5%
563
June1st to 15thNight
8%220%44%22%1
540
16th to endNight
7%125%37%25%2
540
July1st to 15thNight
12%118%35%29%3
510
16th to endNight
7%111%35%35%6%
564
August1st to 15thNight
7%113%34%36%6%
539
16th to endNight
4111%34%41%6%
573
September1st to 15thNight
13%312%31%32%6%
642
16th to endNight
12%416%27%31%5%
717
October1st to 15thNight
13%6%21%30%22%5%
684
16th to endNight
19%10%32%25%11%
704
November1st to 15thNight
15%9%30%25%17%1
700
16th to endNight
22%14%26%26%8%
720
December1st to 15thNight
28%14%28%21%5%1
720
16th to endNight
28%15%33%18%4
888
Page generated at 2017-10-07 14:07:50. Version ac04

Copyright 2017 A. Danko


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