Coffee Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Coffee Creek Observatory clear sky chart from 2005-11-05 to

2017-09-12
.

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
37%
15862
23%
46929
13%
15815
47%
15815
27%
28294

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
27%
900
23%
2327
8%
895
37%
895
27%
1464
January16th to endNight
25%
960
26%
2496
8%
960
36%
960
27%
1590
February1st to 15thNight
20%
880
17%
2288
6%
876
27%
876
21%
1588
February16th to endNight
21%
663
25%
1925
6%
663
35%
663
24%
1194
March1st to 15thNight
28%
540
22%
1980
11%
540
42%
540
21%
1155
March16th to endNight
23%
576
15%
2112
9%
576
32%
576
16%
1378
April1st to 15thNight
28%
539
21%
1852
13%
539
43%
539
23%
1069
April16th to endNight
24%
540
20%
1715
9%
540
40%
540
19%
1109
May1st to 15thNight
32%
540
20%
1620
12%
540
43%
540
24%
1043
May16th to endNight
39%
563
19%
1661
12%
561
48%
561
26%
1015
June1st to 15thNight
52%
540
20%
1440
11%
540
57%
540
36%
840
June16th to endNight
50%
540
26%
1458
11%
540
59%
540
44%
786
July1st to 15thNight
62%
510
17%
1530
13%
510
65%
510
35%
863
July16th to endNight
63%
564
25%
1594
21%
531
73%
531
39%
848
August1st to 15thNight
73%
539
25%
1610
29%
536
76%
536
39%
876
August16th to endNight
67%
573
27%
1816
29%
573
72%
573
37%
994
September1st to 15thNight
54%
530
25%
1813
25%
530
60%
530
30%
1024
September16th to endNight
58%
492
30%
1815
23%
492
69%
492
31%
944
October1st to 15thNight
44%
654
29%
1974
20%
654
50%
654
32%
1138
October16th to endNight
38%
704
28%
2112
13%
704
50%
704
33%
1179
November1st to 15thNight
35%
755
30%
2155
14%
755
48%
755
33%
1221
November16th to endNight
27%
900
25%
2494
8%
900
40%
900
28%
1520
December1st to 15thNight
23%
900
19%
2520
7%
900
33%
900
20%
1664
December16th to endNight
23%
960
22%
2622
8%
960
34%
960
20%
1792

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
12%6%25%42445%7%44%
47718
Night
10%5%24423446%49%
47124
TransparencyDay
38%5%13%25%14%2
47418
Night
34%5%11%26%17%3
46929
SeeingDay
12%14%22%27%18%4
5886
Night
12%20%25%27%12%1
15862

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
10%7%35%5%34335%47%
1611
16th to endDay
11%8%36%434438%42%
1728
February1st to 15thDay
12%8%5%6%434346%40%
1575
16th to endDay
12%9%35%433346%41%
1557
March1st to 15thDay
11%10%36%5%35%5%5%6%36%
1980
16th to endDay
21%9%45%424335%33%
2110
April1st to 15thDay
15%8%35%324446%41%
2095
16th to endDay
19%8%27%5%34445%34%
2244
May1st to 15thDay
17%8%44425%446%36%
2331
16th to endDay
15%5%25%4345%6%8%37%
2451
June1st to 15thDay
9%5%14425%5%6%9%43%
2520
16th to endDay
5%213425%5%6%9%51%
2498
July1st to 15thDay
8%414425%5%7%10%45%
2340
16th to endDay
6%2135%36%5%7%9%47%
2466
August1st to 15thDay
7%3245%35%5%7%9%46%
2340
16th to endDay
8%415%42445%8%48%
2384
September1st to 15thDay
11%5%25%423446%48%
2064
16th to endDay
8%325%325%46%7%50%
1810
October1st to 15thDay
13%6%24323346%50%
1650
16th to endDay
12%424423345%52%
1760
November1st to 15thDay
9%5%23313347%55%
1701
16th to endDay
15%5%24333326%48%
1464
December1st to 15thDay
14%9%35%5%23346%40%
1440
16th to endDay
13%8%46%4145%46%39%
1599
January1st to 15thNight
9%6%25%434446%50%
2327
16th to endNight
8%7%36%423446%49%
2496
February1st to 15thNight
11%9%46%6%24446%39%
2278
16th to endNight
11%6%36%423246%47%
1925
March1st to 15thNight
11%8%25%423346%47%
1980
16th to endNight
19%7%35%42435%6%37%
2112
April1st to 15thNight
11%7%2441425%6%50%
1852
16th to endNight
17%7%25%423435%43%
1715
May1st to 15thNight
14%43442445%7%43%
1619
16th to endNight
11%5%2341445%8%47%
1659
June1st to 15thNight
5%2134346%5%8%54%
1440
16th to endNight
411232245%12%58%
1458
July1st to 15thNight
7%2133245%7%9%51%
1620
16th to endNight
5%123325%5%6%9%53%
1702
August1st to 15thNight
32133245%6%10%55%
1620
16th to endNight
6%323424445%58%
1816
September1st to 15thNight
9%43442435%6%50%
1813
16th to endNight
6%4134345%5%6%54%
1815
October1st to 15thNight
13%31431334455%
1974
16th to endNight
10%424223335%57%
2112
November1st to 15thNight
8%5%23323337%57%
2155
16th to endNight
14%6%22322335%52%
2494
December1st to 15thNight
15%7%35%42345%5%42%
2520
16th to endNight
14%9%46%423335%40%
2622

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
38%412%25%17%1
1612
16th to endDay
41%415%25%11%1
1728
February1st to 15thDay
45%415%23%9%1
1576
16th to endDay
43%413%24%12%2
1557
March1st to 15thDay
47%6%10%22%11%1
1980
16th to endDay
52%5%11%19%9%1
2112
April1st to 15thDay
43%311%24%15%
2095
16th to endDay
52%411%20%11%
2244
May1st to 15thDay
49%5%10%22%12%
2331
16th to endDay
45%6%15%21%10%
2455
June1st to 15thDay
34%8%15%26%14%1
2520
16th to endDay
26%7%16%29%17%2
2498
July1st to 15thDay
32%7%18%27%12%2
2201
16th to endDay
27%8%15%33%13%1
2311
August1st to 15thDay
31%8%15%27%16%1
2326
16th to endDay
32%6%12%26%15%6%
2384
September1st to 15thDay
36%411%24%17%5%
2064
16th to endDay
30%5%11%28%21%1
1810
October1st to 15thDay
35%49%25%20%4
1650
16th to endDay
33%311%26%19%4
1760
November1st to 15thDay
29%411%27%21%5%
1701
16th to endDay
38%39%27%19%
1464
December1st to 15thDay
44%413%26%9%
1440
16th to endDay
45%413%21%11%2
1599
January1st to 15thNight
35%414%25%18%2
2327
16th to endNight
36%412%27%16%2
2496
February1st to 15thNight
45%5%11%23%12%1
2288
16th to endNight
37%411%25%18%2
1925
March1st to 15thNight
38%411%24%16%4
1980
16th to endNight
46%412%23%10%1
2112
April1st to 15thNight
35%48%26%20%2
1852
16th to endNight
43%410%24%15%1
1715
May1st to 15thNight
40%5%12%23%16%1
1620
16th to endNight
33%7%17%26%13%2
1661
June1st to 15thNight
26%6%16%31%16%2
1440
16th to endNight
19%5%14%32%23%3
1458
July1st to 15thNight
26%6%14%31%15%3
1530
16th to endNight
23%6%13%32%20%2
1594
August1st to 15thNight
23%7%13%33%18%3
1610
16th to endNight
27%5%8%25%25%6%
1816
September1st to 15thNight
32%5%11%23%19%7%
1813
16th to endNight
27%6%8%29%24%3
1815
October1st to 15thNight
32%38%25%23%6%
1974
16th to endNight
30%48%29%22%4
2112
November1st to 15thNight
29%311%24%23%8%
2155
16th to endNight
35%38%30%19%2
2494
December1st to 15thNight
41%5%13%26%11%
2520
16th to endNight
45%5%11%22%12%3
2622

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
17%21%38%20%2
90
16th to endDay
19%12%43%18%41
96
February1st to 15thDay
8%23%37%25%4
90
16th to endDay
11%22%43%14%8%
81
March1st to 15thDay
14%20%50%12%3
90
16th to endDay
26%14%32%21%5%
96
April1st to 15thDay
19%19%32%18%9%
214
16th to endDay
22%24%28%17%6%1
354
May1st to 15thDay
18%20%28%21%9%1
468
16th to endDay
17%18%28%21%9%4
517
June1st to 15thDay
10%16%20%29%18%5%
495
16th to endDay
6%15%25%30%18%3
495
July1st to 15thDay
13%9%13%32%25%6%
475
16th to endDay
6%12%8%31%33%7%
515
August1st to 15thDay
7%8%6%37%35%4
493
16th to endDay
9%6%12%30%32%8%
424
September1st to 15thDay
10%5%13%34%26%8%
251
16th to endDay
3223%38%18%13%
90
October1st to 15thDay
7%5%31%32%13%10%
90
16th to endDay
7%6%37%39%8%1
96
November1st to 15thDay
8%6%23%35%14%11%
90
16th to endDay
34%15%27%17%31
90
December1st to 15thDay
17%16%40%17%43
90
16th to endDay
23%17%37%17%3
96
January1st to 15thNight
10%26%32%23%6%
900
16th to endNight
11%24%34%25%4
960
February1st to 15thNight
13%25%33%23%3
880
16th to endNight
14%25%35%20%3
663
March1st to 15thNight
15%23%29%24%6%1
540
16th to endNight
18%24%29%22%4
576
April1st to 15thNight
13%23%31%25%5%
539
16th to endNight
18%23%30%21%6%
540
May1st to 15thNight
14%21%27%25%10%
540
16th to endNight
12%21%22%27%13%2
563
June1st to 15thNight
5%18%18%38%17%1
540
16th to endNight
218%25%37%14%1
540
July1st to 15thNight
7%12%11%40%24%2
510
16th to endNight
5%16%7%35%32%2
564
August1st to 15thNight
410%7%40%36%1
539
16th to endNight
7%9%9%36%33%4
573
September1st to 15thNight
11%10%18%34%21%3
530
16th to endNight
7%10%16%36%22%6%
492
October1st to 15thNight
14%14%23%28%16%2
654
16th to endNight
10%17%31%27%13%
704
November1st to 15thNight
9%22%30%24%12%
755
16th to endNight
16%26%29%21%6%
900
December1st to 15thNight
18%24%30%21%4
900
16th to endNight
16%25%29%24%3
960
Page generated at 2017-09-13 06:39:14. Version ac04

Copyright 2017 A. Danko


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