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 2005-11-06 to 2024-03-23.

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
40%
24738
22%
80497
14%
24632
49%
24632
28%
49180

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
29%
944
18%
4061
8%
926
41%
926
18%
2624
January11th to 20thNight
25%
948
20%
4037
8%
930
34%
930
16%
2706
January21st to endNight
26%
1037
15%
4490
8%
1023
36%
1023
16%
3057
February1st to 10thNight
22%
950
18%
2470
5%
950
31%
950
24%
1713
February11th to 20thNight
23%
929
19%
2404
6%
925
31%
925
27%
1589
February21st to endNight
20%
586
24%
1842
7%
586
33%
586
25%
1138
March1st to 10thNight
26%
570
25%
2090
11%
570
43%
570
26%
1186
March11th to 20thNight
29%
570
20%
2090
13%
570
40%
570
22%
1275
March21st to endNight
23%
600
14%
2200
8%
600
32%
600
15%
1508
April1st to 10thNight
30%
540
22%
1884
12%
540
46%
540
27%
1065
April11th to 20thNight
31%
533
23%
1775
15%
533
44%
533
25%
1075
April21st to endNight
29%
540
20%
1673
11%
540
43%
540
25%
1071
May1st to 10thNight
35%
540
18%
1620
13%
540
44%
540
24%
1077
May11th to 20thNight
44%
531
20%
1594
17%
531
49%
531
31%
974
May21st to endNight
48%
584
19%
1710
13%
582
56%
582
30%
1059
June1st to 10thNight
68%
540
23%
1440
15%
540
72%
540
46%
807
June11th to 20thNight
58%
540
24%
1440
16%
540
62%
540
43%
848
June21st to endNight
59%
540
28%
1466
17%
540
64%
540
52%
774
July1st to 10thNight
73%
525
17%
1575
15%
525
75%
525
40%
884
July11th to 20thNight
76%
522
23%
1566
21%
522
78%
522
49%
792
July21st to endNight
70%
591
24%
1673
25%
558
73%
558
38%
947
August1st to 10thNight
73%
537
23%
1601
24%
534
77%
534
41%
883
August11th to 20thNight
73%
534
28%
1600
32%
534
76%
534
42%
866
August21st to endNight
73%
594
29%
1926
34%
594
75%
594
43%
986
September1st to 10thNight
60%
540
27%
1800
28%
540
65%
540
37%
969
September11th to 20thNight
62%
540
29%
1964
29%
540
69%
540
34%
1046
September21st to endNight
60%
540
31%
1980
29%
540
68%
540
37%
988
October1st to 10thNight
52%
710
27%
2150
20%
710
57%
710
37%
1210
October11th to 20thNight
35%
720
29%
2160
13%
720
46%
720
36%
1225
October21st to endNight
33%
792
26%
2376
13%
792
44%
792
29%
1435
November1st to 10thNight
40%
740
32%
2220
17%
740
53%
740
39%
1192
November11th to 20thNight
34%
943
27%
2518
10%
943
47%
943
36%
1506
November21st to endNight
31%
950
25%
2660
9%
950
43%
950
32%
1620
December1st to 10thNight
29%
950
22%
2660
8%
950
40%
950
29%
1675
December11th to 20thNight
27%
948
23%
3119
8%
948
38%
948
23%
1920
December21st to endNight
23%
1040
15%
4663
8%
1026
36%
1026
12%
3490

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%7%36%5%3445%7%44%
78842
Night
11%7%36%5%3445%6%47%
81086
TransparencyDay
40%6%12%25%16%2
78565
Night
37%5%11%25%18%3
80883
SeeingDay
14%9%28%28%17%4
14697
Night
14%9%33%32%12%1
24761

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
14%10%38%5%3445%6%38%
2847
11th to 20thDay
10%10%5%7%7%47%335%38%
2850
21st to endDay
14%15%6%7%433336%35%
3135
February1st to 10thDay
15%10%5%6%5%43346%39%
1710
11th to 20thDay
12%8%47%5%3445%6%42%
1664
21st to endDay
12%9%36%434446%45%
1626
March1st to 10thDay
11%9%37%5%35%5%5%6%42%
2090
11th to 20thDay
19%10%36%434446%38%
2090
21st to endDay
19%12%46%6%35%35%6%31%
2200
April1st to 10thDay
13%8%35%5%2445%7%44%
2074
11th to 20thDay
15%8%36%435%446%40%
2134
21st to endDay
19%7%27%6%35%446%37%
2284
May1st to 10thDay
17%9%45%5%36%45%6%35%
2340
11th to 20thDay
15%8%35%5%35%5%5%7%39%
2302
21st to endDay
14%7%36%5%45%6%6%8%35%
2562
June1st to 10thDay
7%415%436%6%6%10%49%
2520
11th to 20thDay
7%425%5%35%5%6%10%47%
2520
21st to endDay
7%324435%46%9%53%
2486
July1st to 10thDay
9%5%24435%5%7%10%44%
2340
11th to 20thDay
4214435%6%7%9%55%
2340
21st to endDay
8%425%5%46%7%7%9%44%
2546
August1st to 10thDay
8%325%5%35%6%7%10%45%
2328
11th to 20thDay
7%425%435%5%6%9%50%
2301
21st to endDay
8%414435%46%8%52%
2428
September1st to 10thDay
13%5%25%32445%7%52%
2160
11th to 20thDay
9%5%246%35%5%5%7%50%
1993
21st to endDay
9%325%42446%6%55%
1971
October1st to 10thDay
12%6%2432435%7%51%
1800
11th to 20thDay
12%6%24323345%56%
1800
21st to endDay
16%6%35%423346%47%
1980
November1st to 10thDay
9%5%24423347%55%
1858
11th to 20thDay
14%6%24323338%50%
1658
21st to endDay
15%6%36%5%23335%48%
1520
December1st to 10thDay
9%9%35%6%2335%7%46%
1520
11th to 20thDay
11%9%5%7%5%34446%42%
1918
21st to endDay
15%14%8%12%6%24445%26%
2947
January1st to 10thNight
10%9%313%6%44335%41%
4108
11th to 20thNight
10%9%47%7%48%5%45%38%
4120
21st to endNight
16%12%5%10%5%23335%36%
4532
February1st to 10thNight
12%10%46%6%3445%7%39%
2470
11th to 20thNight
12%8%37%5%2445%7%43%
2403
21st to endNight
12%7%37%5%34345%47%
1842
March1st to 10thNight
11%7%34423446%50%
2090
11th to 20thNight
15%8%35%43445%6%43%
2090
21st to endNight
20%9%46%6%24447%34%
2200
April1st to 10thNight
10%6%35%42445%7%50%
1884
11th to 20thNight
14%7%36%42325%7%47%
1775
21st to endNight
16%7%26%5%2344445%
1673
May1st to 10thNight
15%6%35%5%345%6%8%40%
1620
11th to 20thNight
14%5%245%23446%50%
1593
21st to endNight
10%5%35%5%245%7%9%44%
1709
June1st to 10thNight
5%213435%6%6%9%56%
1440
11th to 20thNight
6%3245%335%7%11%52%
1440
21st to endNight
5%21332345%10%61%
1466
July1st to 10thNight
7%314425%5%8%10%52%
1620
11th to 20thNight
321343346%10%60%
1620
21st to endNight
7%334326%5%7%10%49%
1772
August1st to 10thNight
4223435%6%6%10%54%
1611
11th to 20thNight
7%42432445%7%58%
1600
21st to endNight
5%32343335%7%61%
1926
September1st to 10thNight
10%43442335%5%56%
1800
11th to 20thNight
9%4234245%6%7%53%
1964
21st to endNight
6%4244345%5%5%59%
1980
October1st to 10thNight
10%424424445%57%
2150
11th to 20thNight
13%425%323345%56%
2160
21st to endNight
16%7%34423335%51%
2376
November1st to 10thNight
8%5%24332336%61%
2220
11th to 20thNight
10%6%23424448%54%
2518
21st to endNight
15%6%33423335%53%
2660
December1st to 10thNight
12%8%344345%6%6%46%
2660
11th to 20thNight
11%8%36%5%33447%45%
3279
21st to endNight
18%16%7%8%5%3333430%
4715

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
47%5%9%25%13%1
2848
11th to 20thDay
50%411%22%12%1
2850
21st to endDay
52%411%17%16%1
3135
February1st to 10thDay
48%412%23%11%3
1710
11th to 20thDay
44%5%13%22%15%2
1673
21st to endDay
41%411%23%16%4
1626
March1st to 10thDay
44%5%10%22%15%4
2090
11th to 20thDay
48%6%9%22%13%2
2090
21st to endDay
53%6%13%19%8%1
2200
April1st to 10thDay
40%413%24%17%2
2074
11th to 20thDay
44%5%12%23%15%1
2134
21st to endDay
50%411%24%11%1
2284
May1st to 10thDay
50%6%10%20%13%1
2340
11th to 20thDay
44%6%13%24%13%
2306
21st to endDay
47%7%14%21%9%2
2562
June1st to 10thDay
28%8%18%29%15%2
2520
11th to 20thDay
31%8%14%28%17%2
2520
21st to endDay
27%7%14%30%18%3
2486
July1st to 10thDay
33%9%15%24%16%3
2276
11th to 20thDay
22%8%19%29%18%4
2271
21st to endDay
32%8%15%31%14%1
2405
August1st to 10thDay
31%10%17%27%13%2
2314
11th to 20thDay
30%7%14%31%16%2
2301
21st to endDay
28%7%13%25%20%7%
2428
September1st to 10thDay
33%413%27%17%6%
2160
11th to 20thDay
32%7%10%25%24%3
1993
21st to endDay
29%411%28%25%3
1971
October1st to 10thDay
33%411%28%21%3
1800
11th to 20thDay
32%47%27%25%5%
1800
21st to endDay
39%410%22%19%5%
1980
November1st to 10thDay
31%5%11%30%19%5%
1858
11th to 20thDay
35%310%26%22%3
1658
21st to endDay
40%48%27%20%1
1520
December1st to 10thDay
37%413%30%13%1
1520
11th to 20thDay
44%5%11%26%12%2
1915
21st to endDay
60%49%17%8%2
2947
January1st to 10thNight
46%5%14%22%12%2
4108
11th to 20thNight
49%5%11%21%13%1
4120
21st to endNight
51%412%20%11%2
4532
February1st to 10thNight
46%5%11%21%15%3
2470
11th to 20thNight
41%411%24%17%3
2404
21st to endNight
40%49%22%19%7%
1842
March1st to 10thNight
36%410%25%20%5%
2090
11th to 20thNight
41%5%10%23%16%4
2090
21st to endNight
51%5%11%21%10%2
2200
April1st to 10thNight
34%5%10%24%22%4
1884
11th to 20thNight
40%38%28%17%3
1775
21st to endNight
42%412%26%15%1
1673
May1st to 10thNight
42%7%12%22%15%1
1620
11th to 20thNight
36%6%14%26%17%1
1594
21st to endNight
35%8%16%28%12%2
1710
June1st to 10thNight
22%8%18%33%16%3
1440
11th to 20thNight
26%7%14%31%20%2
1440
21st to endNight
20%5%13%35%23%4
1466
July1st to 10thNight
25%8%16%30%17%4
1575
11th to 20thNight
19%6%16%33%22%4
1566
21st to endNight
28%7%13%31%20%2
1673
August1st to 10thNight
23%9%17%33%15%3
1601
11th to 20thNight
25%6%12%32%23%2
1600
21st to endNight
24%5%12%27%25%7%
1926
September1st to 10thNight
30%411%29%19%8%
1800
11th to 20thNight
29%6%10%26%25%4
1964
21st to endNight
26%5%8%28%29%5%
1980
October1st to 10thNight
30%5%8%26%26%6%
2150
11th to 20thNight
32%36%28%23%8%
2160
21st to endNight
37%48%23%24%4
2376
November1st to 10thNight
27%312%28%24%6%
2220
11th to 20thNight
31%49%26%25%4
2518
21st to endNight
36%39%29%20%3
2660
December1st to 10thNight
37%5%12%28%16%1
2660
11th to 20thNight
39%5%10%28%17%2
3281
21st to endNight
58%5%7%18%9%2
4715

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
20%16%37%22%4
270
11th to 20thDay
23%17%39%18%3
270
21st to endDay
15%11%48%23%3
297
February1st to 10thDay
23%16%39%19%3
270
11th to 20thDay
18%17%43%17%41
270
21st to endDay
16%24%46%12%3
225
March1st to 10thDay
17%17%45%19%3
270
11th to 20thDay
24%13%37%20%5%
270
21st to endDay
29%20%31%18%2
270
April1st to 10thDay
19%17%36%19%7%1
334
11th to 20thDay
20%14%38%20%6%
412
21st to endDay
20%15%36%21%8%1
544
May1st to 10thDay
20%11%38%22%9%1
603
11th to 20thDay
21%9%29%26%12%3
625
21st to endDay
17%6%30%25%15%6%
679
June1st to 10thDay
7%420%33%28%9%
630
11th to 20thDay
9%425%34%23%5%
630
21st to endDay
7%5%33%35%19%3
630
July1st to 10thDay
12%311%30%31%13%
621
11th to 20thDay
5%114%39%31%8%
618
21st to endDay
9%213%37%31%8%
684
August1st to 10thDay
8%312%41%31%5%
626
11th to 20thDay
7%216%37%31%7%
615
21st to endDay
9%213%30%36%11%
547
September1st to 10thDay
16%215%34%26%8%
450
11th to 20thDay
5%318%40%26%8%
283
21st to endDay
10%424%38%19%5%
270
October1st to 10thDay
14%5%31%26%16%7%
270
11th to 20thDay
13%14%42%23%7%1
270
21st to endDay
24%12%35%23%5%1
297
November1st to 10thDay
16%11%34%29%7%3
270
11th to 20thDay
19%16%33%23%8%2
270
21st to endDay
20%13%37%22%8%
270
December1st to 10thDay
10%15%40%28%43
270
11th to 20thDay
19%16%35%20%9%1
270
21st to endDay
22%23%36%18%1
297
January1st to 10thNight
13%12%41%27%6%
950
11th to 20thNight
15%14%40%26%5%
950
21st to endNight
14%12%41%29%3
1045
February1st to 10thNight
17%12%43%24%4
950
11th to 20thNight
17%13%41%26%2
929
21st to endNight
18%14%45%19%31
586
March1st to 10thNight
15%11%45%24%5%
570
11th to 20thNight
19%11%35%28%6%1
570
21st to endNight
25%11%36%24%4
600
April1st to 10thNight
15%10%41%28%5%
540
11th to 20thNight
18%11%36%29%6%
533
21st to endNight
20%9%38%26%6%
540
May1st to 10thNight
17%7%36%30%9%
540
11th to 20thNight
17%5%30%35%13%1
531
21st to endNight
12%6%27%36%17%2
584
June1st to 10thNight
6%318%45%26%3
540
11th to 20thNight
6%424%45%20%1
540
21st to endNight
5%231%47%14%1
540
July1st to 10thNight
9%210%41%35%4
525
11th to 20thNight
2214%48%31%3
522
21st to endNight
8%112%44%33%2
591
August1st to 10thNight
4114%45%34%1
537
11th to 20thNight
7%311%45%32%3
534
21st to endNight
7%212%39%38%3
594
September1st to 10thNight
11%319%40%22%4
540
11th to 20thNight
10%219%39%26%4
540
21st to endNight
7%423%43%20%4
540
October1st to 10thNight
11%5%28%35%18%3
710
11th to 20thNight
14%9%39%30%7%
720
21st to endNight
19%11%33%27%9%
792
November1st to 10thNight
10%9%37%32%11%1
740
11th to 20thNight
13%12%39%28%8%
943
21st to endNight
19%11%36%28%5%
950
December1st to 10thNight
17%11%39%27%5%1
950
11th to 20thNight
18%9%41%27%5%
950
21st to endNight
18%15%38%25%4
1045
Page generated at 2024-03-19 22:31:03. Version ac07

Copyright © 2024 Attilla Danko.


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