Eagle Bluff Environmental Learning Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Eagle Bluff Environmental Learning Center 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
34%
16147
17%
47090
9%
16100
41%
16100
24%
31286

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
24%
900
12%
2506
5%
895
31%
895
18%
1826
January16th to endNight
18%
960
13%
2559
3%
960
25%
960
16%
1929
February1st to 15thNight
21%
879
14%
2288
3%
875
28%
875
20%
1658
February16th to endNight
25%
703
18%
1965
6%
703
34%
703
21%
1337
March1st to 15thNight
26%
618
16%
2058
9%
618
34%
618
20%
1329
March16th to endNight
32%
576
14%
2067
11%
576
40%
576
17%
1408
April1st to 15thNight
26%
539
16%
1797
10%
539
37%
539
20%
1220
April16th to endNight
29%
540
17%
1743
10%
540
39%
540
19%
1203
May1st to 15thNight
30%
540
17%
1476
9%
540
37%
540
24%
1016
May16th to endNight
39%
563
17%
1497
6%
561
46%
561
30%
974
June1st to 15thNight
47%
540
13%
1440
6%
540
50%
540
30%
955
June16th to endNight
51%
540
17%
1440
7%
540
55%
540
39%
869
July1st to 15thNight
60%
510
15%
1360
7%
510
62%
510
46%
760
July16th to endNight
65%
564
23%
1417
14%
531
68%
531
46%
797
August1st to 15thNight
62%
539
22%
1608
19%
536
67%
536
37%
926
August16th to endNight
58%
573
22%
1844
22%
573
64%
573
34%
1037
September1st to 15thNight
58%
540
25%
1800
23%
540
66%
540
36%
963
September16th to endNight
46%
615
23%
1962
16%
615
56%
615
32%
1149
October1st to 15thNight
38%
684
23%
2052
14%
684
45%
684
31%
1234
October16th to endNight
33%
704
18%
2147
9%
704
42%
704
23%
1412
November1st to 15thNight
29%
760
23%
2336
12%
760
41%
760
26%
1444
November16th to endNight
22%
900
14%
2520
6%
900
29%
900
19%
1807
December1st to 15thNight
19%
900
11%
2520
3%
900
26%
900
15%
1901
December16th to endNight
18%
960
12%
2688
4%
960
26%
960
12%
2132

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%8%36%5%3445%7%36%
48113
Night
12%8%36%5%2445%6%40%
47259
Cloud CoverDay
26%7%25%5%23446%32%
48124
Night
24%7%25%423345%35%
47263
Cloud CoverDay
14%8%36%5%3445%7%36%
48122
Night
12%8%36%5%24446%40%
47263
TransparencyDay
46%5%13%22%10%
47800
Night
43%412%24%12%1
47091
SeeingDay
18%9%29%25%13%4
6149
Night
17%9%32%28%10%1
16148

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
10%9%6%9%8%47%45%6%27%
1432
16th to endDay
11%13%6%12%8%3445%5%22%
1663
February1st to 15thDay
10%13%5%9%6%345%5%6%28%
1575
16th to endDay
16%8%47%6%34446%33%
1506
March1st to 15thDay
15%10%47%424447%35%
1900
16th to endDay
19%10%46%5%24446%30%
2157
April1st to 15thDay
18%11%36%5%34445%31%
2151
16th to endDay
23%11%36%423336%31%
2214
May1st to 15thDay
20%8%36%5%345%5%7%29%
2475
16th to endDay
16%5%35%6%25%447%38%
2617
June1st to 15thDay
14%5%26%435%447%39%
2520
16th to endDay
10%5%346%35%5%6%6%40%
2520
July1st to 15thDay
5%4145%36%5%6%9%46%
2520
16th to endDay
8%5%245%35%5%6%11%42%
2655
August1st to 15thDay
8%425%5%25%5%6%9%42%
2340
16th to endDay
12%425%5%3446%7%43%
2357
September1st to 15thDay
12%5%1442445%8%46%
2160
16th to endDay
13%6%245%24348%42%
1983
October1st to 15thDay
16%6%35%423445%45%
1706
16th to endDay
17%10%45%323345%38%
1724
November1st to 15thDay
12%7%36%42435%7%41%
1522
16th to endDay
14%10%36%5%23337%38%
1440
December1st to 15thDay
17%9%5%8%6%35%5%5%5%26%
1440
16th to endDay
19%15%6%9%7%3334421%
1536
January1st to 15thNight
11%7%5%8%7%45%5%46%32%
2506
16th to endNight
12%11%410%6%4445%7%27%
2559
February1st to 15thNight
8%12%5%8%6%34446%35%
2285
16th to endNight
11%8%36%6%34347%38%
1965
March1st to 15thNight
14%9%36%423347%40%
2046
16th to endNight
16%9%45%5%3445%6%34%
2067
April1st to 15thNight
18%8%36%42445%5%38%
1797
16th to endNight
21%9%35%313346%35%
1743
May1st to 15thNight
19%6%34434445%40%
1476
16th to endNight
12%5%2443446%7%44%
1496
June1st to 15thNight
11%424426%46%9%42%
1440
16th to endNight
7%5%1432436%8%52%
1440
July1st to 15thNight
431342445%9%56%
1440
16th to endNight
5%21241445%9%55%
1513
August1st to 15thNight
6%3135%2446%8%52%
1617
16th to endNight
10%422323346%55%
1844
September1st to 15thNight
10%413323345%57%
1800
16th to endNight
10%5%145%23446%50%
1962
October1st to 15thNight
13%6%2441235%5%49%
2052
16th to endNight
14%7%26%42335%5%42%
2147
November1st to 15thNight
11%7%36%324445%47%
2336
16th to endNight
13%11%47%6%24437%34%
2520
December1st to 15thNight
15%11%49%7%2445%6%27%
2520
16th to endNight
18%14%5%9%6%34445%23%
2688

Percentage Cloud Cover SW (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
23%7%48%7%36%445%24%
1432
16th to endDay
26%11%410%7%2344418%
1663
February1st to 15thDay
24%10%48%5%2235%5%25%
1575
16th to endDay
27%7%36%5%4333429%
1506
March1st to 15thDay
28%8%25%313335%31%
1911
16th to endDay
31%9%35%423345%26%
2157
April1st to 15thDay
31%9%25%43344427%
2151
16th to endDay
36%9%25%422335%24%
2214
May1st to 15thDay
33%7%25%43335%6%24%
2475
16th to endDay
30%4145%24336%31%
2617
June1st to 15thDay
29%5%25%424346%32%
2520
16th to endDay
25%5%245%345%5%433%
2520
July1st to 15thDay
21%4145%345%5%7%37%
2520
16th to endDay
24%41442446%9%35%
2655
August1st to 15thDay
16%425%5%245%5%8%39%
2340
16th to endDay
18%415%5%3345%7%40%
2357
September1st to 15thDay
18%41332445%6%44%
2160
16th to endDay
20%5%14423347%39%
1983
October1st to 15thDay
23%5%3441333442%
1706
16th to endDay
24%9%35%42234436%
1724
November1st to 15thDay
24%6%24423346%37%
1522
16th to endDay
29%8%2441133435%
1440
December1st to 15thDay
31%8%46%5%3434422%
1440
16th to endDay
31%13%5%8%6%3233318%
1536
January1st to 15thNight
24%6%37%6%45%435%28%
2506
16th to endNight
27%10%38%5%33445%23%
2559
February1st to 15thNight
23%10%47%5%23335%30%
2278
16th to endNight
24%6%26%5%34336%33%
1965
March1st to 15thNight
26%8%25%413235%35%
2058
16th to endNight
27%8%25%5%33445%29%
2067
April1st to 15thNight
31%7%1432334432%
1797
16th to endNight
34%8%24312335%28%
1743
May1st to 15thNight
33%5%2332323434%
1475
16th to endNight
27%5%23322445%37%
1496
June1st to 15thNight
26%414425%45%7%33%
1440
16th to endNight
23%31332235%6%43%
1440
July1st to 15thNight
20%213323447%46%
1440
16th to endNight
20%21231335%6%48%
1513
August1st to 15thNight
14%3135%3345%7%48%
1617
16th to endNight
17%312322246%52%
1844
September1st to 15thNight
15%413213345%54%
1800
16th to endNight
16%414423346%48%
1962
October1st to 15thNight
21%6%13412345%46%
2052
16th to endNight
22%6%25%42334439%
2147
November1st to 15thNight
23%6%25%213335%41%
2336
16th to endNight
26%9%35%5%23335%31%
2520
December1st to 15thNight
29%10%28%6%24345%22%
2520
16th to endNight
32%12%48%5%2333420%
2688

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
10%9%6%9%8%37%45%6%27%
1432
16th to endDay
11%13%6%12%8%35%45%5%23%
1663
February1st to 15thDay
10%13%5%9%6%345%5%6%28%
1575
16th to endDay
15%8%47%6%43446%33%
1506
March1st to 15thDay
15%10%46%424447%34%
1911
16th to endDay
19%10%46%5%24446%30%
2155
April1st to 15thDay
18%11%36%5%2445%5%32%
2151
16th to endDay
23%10%35%5%23336%31%
2214
May1st to 15thDay
20%8%36%6%345%5%7%29%
2475
16th to endDay
16%5%35%6%34447%37%
2617
June1st to 15thDay
14%5%26%435%45%7%39%
2520
16th to endDay
10%5%346%36%5%6%6%40%
2520
July1st to 15thDay
5%4145%36%6%6%9%46%
2520
16th to endDay
8%5%24435%5%6%12%41%
2655
August1st to 15thDay
8%425%5%345%6%10%42%
2340
16th to endDay
12%415%6%3446%7%42%
2357
September1st to 15thDay
12%5%1442446%7%46%
2160
16th to endDay
13%6%245%33348%42%
1983
October1st to 15thDay
16%6%26%32334445%
1706
16th to endDay
16%11%35%422345%38%
1724
November1st to 15thDay
12%8%35%5%2435%6%42%
1522
16th to endDay
14%10%35%6%13347%38%
1440
December1st to 15thDay
17%9%5%7%7%35%5%46%26%
1440
16th to endDay
19%15%6%10%7%3334421%
1536
January1st to 15thNight
11%7%5%8%6%5%6%5%46%32%
2506
16th to endNight
12%11%5%10%6%445%5%7%26%
2559
February1st to 15thNight
8%12%5%8%6%34345%35%
2278
16th to endNight
12%8%27%6%35%347%38%
1965
March1st to 15thNight
13%9%36%423436%41%
2058
16th to endNight
16%9%35%6%34447%33%
2067
April1st to 15thNight
18%8%45%324445%37%
1797
16th to endNight
22%9%25%414346%35%
1743
May1st to 15thNight
19%6%34434445%40%
1475
16th to endNight
12%5%25%5%25%45%8%44%
1496
June1st to 15thNight
11%5%24426%5%5%9%42%
1440
16th to endNight
7%5%2432346%8%52%
1440
July1st to 15thNight
43134235%5%10%56%
1440
16th to endNight
5%213325%45%9%56%
1513
August1st to 15thNight
5%4135%345%6%7%52%
1617
16th to endNight
10%423323337%54%
1844
September1st to 15thNight
10%413223445%57%
1800
16th to endNight
9%5%24433446%50%
1962
October1st to 15thNight
13%6%1432235%5%49%
2052
16th to endNight
14%7%35%5%2335%5%42%
2147
November1st to 15thNight
11%7%25%324435%47%
2336
16th to endNight
13%11%46%6%24446%34%
2520
December1st to 15thNight
14%11%48%7%25%446%28%
2520
16th to endNight
19%14%5%9%6%34345%23%
2688

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
56%5%12%15%9%
1433
16th to endDay
62%314%14%5%
1663
February1st to 15thDay
53%413%19%8%
1576
16th to endDay
51%5%10%22%8%
1506
March1st to 15thDay
50%414%21%8%
1911
16th to endDay
54%5%13%20%4
2157
April1st to 15thDay
53%410%19%9%1
2151
16th to endDay
54%412%17%9%
2214
May1st to 15thDay
53%6%12%19%7%
2475
16th to endDay
46%5%11%21%13%1
2621
June1st to 15thDay
43%5%11%25%12%1
2520
16th to endDay
40%7%12%24%13%
2520
July1st to 15thDay
34%6%15%27%13%1
2371
16th to endDay
34%8%14%24%15%1
2488
August1st to 15thDay
36%7%12%29%12%1
2326
16th to endDay
38%6%14%25%12%1
2357
September1st to 15thDay
36%5%13%29%14%
2160
16th to endDay
40%5%13%30%9%
1983
October1st to 15thDay
42%310%26%15%
1706
16th to endDay
47%314%24%8%
1724
November1st to 15thDay
42%413%23%14%1
1522
16th to endDay
47%5%18%20%6%
1440
December1st to 15thDay
58%414%15%5%
1440
16th to endDay
67%49%12%5%
1536
January1st to 15thNight
52%412%20%9%
2506
16th to endNight
55%5%13%16%8%
2559
February1st to 15thNight
51%313%21%9%
2288
16th to endNight
46%312%26%9%1
1965
March1st to 15thNight
44%413%23%11%1
2058
16th to endNight
50%5%14%23%6%
2067
April1st to 15thNight
48%49%21%14%2
1797
16th to endNight
50%410%19%12%2
1743
May1st to 15thNight
45%410%24%12%
1476
16th to endNight
38%5%13%25%15%1
1498
June1st to 15thNight
37%7%13%26%13%1
1440
16th to endNight
29%6%14%28%18%3
1440
July1st to 15thNight
24%5%16%33%18%2
1360
16th to endNight
24%5%16%31%17%4
1417
August1st to 15thNight
29%6%12%30%19%2
1608
16th to endNight
31%413%31%14%4
1844
September1st to 15thNight
28%410%30%24%
1800
16th to endNight
34%412%30%17%1
1962
October1st to 15thNight
35%410%28%18%2
2052
16th to endNight
43%412%23%14%1
2147
November1st to 15thNight
39%312%24%17%2
2336
16th to endNight
51%413%22%6%1
2520
December1st to 15thNight
57%412%18%6%
2520
16th to endNight
62%411%13%6%
2688

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
21%16%40%16%5%
90
16th to endDay
25%14%34%20%5%
96
February1st to 15thDay
16%25%35%16%5%
90
16th to endDay
34%13%29%18%21
81
March1st to 15thDay
25%15%38%15%4
90
16th to endDay
31%10%26%20%9%2
141
April1st to 15thDay
25%12%30%22%8%
270
16th to endDay
29%15%26%19%8%1
324
May1st to 15thDay
25%13%31%21%5%2
468
16th to endDay
20%11%32%22%10%3
517
June1st to 15thDay
15%8%30%28%13%3
495
16th to endDay
10%9%38%23%13%4
495
July1st to 15thDay
8%428%32%17%9%
475
16th to endDay
11%327%29%20%6%
515
August1st to 15thDay
10%224%35%21%5%
493
16th to endDay
19%5%17%28%21%8%
397
September1st to 15thDay
13%6%23%30%17%8%
315
16th to endDay
17%8%35%22%13%3
228
October1st to 15thDay
10%14%30%24%15%3
107
16th to endDay
30%12%29%19%8%
96
November1st to 15thDay
7%10%33%37%7%3
90
16th to endDay
36%10%33%12%7%
90
December1st to 15thDay
20%14%45%17%2
90
16th to endDay
35%19%35%8%1
96
January1st to 15thNight
16%15%37%23%7%
900
16th to endNight
20%12%39%22%4
960
February1st to 15thNight
15%15%37%24%5%1
880
16th to endNight
15%14%39%23%7%
703
March1st to 15thNight
19%11%36%23%7%
618
16th to endNight
19%10%31%27%9%1
576
April1st to 15thNight
23%10%35%23%6%
539
16th to endNight
25%8%32%25%7%
540
May1st to 15thNight
23%8%32%27%5%1
540
16th to endNight
15%6%33%31%11%1
563
June1st to 15thNight
15%5%26%42%11%
540
16th to endNight
10%430%40%13%
540
July1st to 15thNight
6%226%35%26%1
510
16th to endNight
7%19%47%21%2
564
August1st to 15thNight
7%120%42%24%3
539
16th to endNight
14%122%34%22%4
573
September1st to 15thNight
13%221%37%17%7%
540
16th to endNight
10%7%28%34%17%1
615
October1st to 15thNight
16%7%35%23%15%1
684
16th to endNight
21%9%29%31%8%
704
November1st to 15thNight
17%11%37%24%8%
760
16th to endNight
20%15%36%20%6%
900
December1st to 15thNight
22%11%39%21%5%
900
16th to endNight
26%11%32%23%5%
960
Page generated at 2017-10-07 13:07:55. Version ac04

Copyright 2017 A. Danko


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