Flying Cow Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Flying Cow Observatory clear sky chart from 2005-11-05 to 2017-09-23.

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
65%
16257
18%
46998
15%
16220
68%
16220
29%
30076

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
57%
717
17%
2327
15%
716
63%
716
27%
1437
January16th to endNight
56%
768
24%
2489
21%
768
63%
768
32%
1429
February1st to 15thNight
54%
701
26%
2104
22%
701
60%
701
35%
1237
February16th to endNight
58%
631
28%
1735
18%
631
66%
631
38%
1012
March1st to 15thNight
57%
720
26%
1980
18%
720
65%
720
40%
1159
March16th to endNight
64%
768
26%
2112
21%
768
68%
768
43%
1193
April1st to 15thNight
71%
718
24%
1970
20%
718
73%
718
48%
1062
April16th to endNight
68%
720
24%
1800
15%
720
71%
720
41%
1105
May1st to 15thNight
73%
719
24%
1799
15%
719
75%
719
46%
1067
May16th to endNight
74%
592
16%
1713
15%
592
74%
592
29%
1119
June1st to 15thNight
67%
540
9%
1620
8%
540
67%
540
18%
1191
June16th to endNight
78%
540
10%
1620
8%
540
78%
540
24%
1115
July1st to 15thNight
72%
510
5%
1530
4%
510
72%
510
17%
1124
July16th to endNight
77%
564
9%
1595
9%
531
78%
531
25%
1086
August1st to 15thNight
76%
604
7%
1674
7%
601
77%
601
28%
1128
August16th to endNight
67%
764
5%
1997
5%
764
67%
764
20%
1514
September1st to 15thNight
66%
720
4%
1980
4%
720
66%
720
18%
1495
September16th to endNight
63%
689
5%
1903
5%
689
63%
689
15%
1485
October1st to 15thNight
71%
660
19%
1925
20%
660
71%
660
27%
1256
October16th to endNight
57%
704
19%
2112
19%
704
60%
704
26%
1395
November1st to 15thNight
64%
700
27%
2101
25%
700
69%
700
35%
1247
November16th to endNight
56%
720
25%
2160
21%
720
63%
720
28%
1379
December1st to 15thNight
61%
720
24%
2256
22%
720
66%
720
29%
1389
December16th to endNight
66%
768
22%
2496
23%
768
70%
768
32%
1452

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
9%6%37%8%5%7%7%7%9%28%
47893
Night
6%425%5%35%6%7%10%41%
47201
TransparencyDay
47%10%13%15%9%3
47594
Night
35%9%18%20%12%3
47004
SeeingDay
9%211%21%25%28%
6069
Night
8%213%30%32%12%
16266

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%5%37%6%47%5%7%8%33%
1611
16th to endDay
9%5%25%6%35%5%7%9%38%
1732
February1st to 15thDay
11%6%246%35%5%6%7%38%
1754
16th to endDay
8%435%6%35%45%8%43%
1738
March1st to 15thDay
5%426%6%5%6%7%7%10%37%
1980
16th to endDay
7%5%26%7%46%5%7%8%38%
2111
April1st to 15thDay
6%4246%47%7%7%10%37%
1977
16th to endDay
7%426%7%47%6%6%8%36%
2160
May1st to 15thDay
4435%6%37%6%7%9%41%
2152
16th to endDay
8%6%48%9%6%8%8%7%7%21%
2407
June1st to 15thDay
12%7%410%8%5%9%7%7%9%16%
2340
16th to endDay
9%6%29%9%6%10%8%8%9%18%
2340
July1st to 15thDay
8%8%48%10%5%10%9%8%8%16%
2340
16th to endDay
8%7%49%10%6%9%7%7%9%18%
2465
August1st to 15thDay
8%6%49%9%5%8%9%9%10%19%
2262
16th to endDay
9%7%49%10%6%8%7%8%8%19%
2201
September1st to 15thDay
9%6%5%10%9%6%10%9%8%8%15%
1980
16th to endDay
11%8%410%11%7%9%6%6%8%13%
1894
October1st to 15thDay
7%7%48%8%5%7%8%8%9%24%
1703
16th to endDay
13%6%36%7%5%7%6%7%8%26%
1760
November1st to 15thDay
8%5%36%6%46%6%5%7%38%
1757
16th to endDay
10%5%36%6%46%6%6%8%34%
1800
December1st to 15thDay
11%7%37%5%37%5%6%9%33%
1701
16th to endDay
8%6%25%6%36%6%7%9%37%
1728
January1st to 15thNight
7%5%345%35%5%6%10%41%
2327
16th to endNight
5%425%5%345%6%9%46%
2489
February1st to 15thNight
8%5%25%42345%8%49%
2098
16th to endNight
43244346%6%8%51%
1735
March1st to 15thNight
43145%346%6%9%51%
1980
16th to endNight
43135%245%6%10%52%
2112
April1st to 15thNight
321332446%10%57%
1970
16th to endNight
5%3134345%7%9%49%
1800
May1st to 15thNight
43233245%6%9%55%
1799
16th to endNight
7%5%25%435%6%8%12%37%
1713
June1st to 15thNight
10%6%36%7%37%7%8%12%25%
1620
16th to endNight
45%35%5%47%8%9%12%33%
1620
July1st to 15thNight
6%6%36%6%5%7%7%6%11%31%
1620
16th to endNight
5%5%26%6%46%6%7%10%38%
1703
August1st to 15thNight
4425%6%35%6%7%13%39%
1685
16th to endNight
8%437%7%46%7%8%12%29%
1997
September1st to 15thNight
7%5%37%7%47%8%9%12%26%
1980
16th to endNight
7%6%28%8%48%8%9%10%23%
1903
October1st to 15thNight
6%5%246%46%7%7%12%36%
1925
16th to endNight
12%6%25%5%35%5%6%9%37%
2112
November1st to 15thNight
6%315%5%35%5%6%10%45%
2101
16th to endNight
9%5%25%5%35%45%9%42%
2160
December1st to 15thNight
7%435%5%35%5%6%8%43%
2256
16th to endNight
5%4245%35%5%6%9%47%
2496

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
45%8%11%15%14%4
1612
16th to endDay
41%6%10%19%15%6%
1732
February1st to 15thDay
41%6%8%21%15%7%
1756
16th to endDay
36%6%11%23%15%6%
1738
March1st to 15thDay
37%7%13%22%15%3
1980
16th to endDay
40%5%14%19%14%5%
2112
April1st to 15thDay
35%8%14%22%15%3
1977
16th to endDay
40%8%10%19%17%3
2160
May1st to 15thDay
34%7%12%24%15%6%
2152
16th to endDay
53%10%11%15%7%
2411
June1st to 15thDay
59%12%13%10%3
2340
16th to endDay
54%15%19%10%
2340
July1st to 15thDay
56%18%17%7%
2201
16th to endDay
55%14%20%9%
2310
August1st to 15thDay
51%16%21%9%
2249
16th to endDay
56%15%19%8%
2201
September1st to 15thDay
57%16%18%6%
1980
16th to endDay
64%13%12%6%2
1894
October1st to 15thDay
50%10%12%15%9%1
1703
16th to endDay
50%8%9%14%11%5%
1760
November1st to 15thDay
41%7%9%19%15%6%
1757
16th to endDay
45%6%9%14%16%8%
1800
December1st to 15thDay
46%7%10%16%14%3
1701
16th to endDay
40%6%13%18%16%4
1728
January1st to 15thNight
36%7%17%22%12%3
2327
16th to endNight
31%6%14%26%15%6%
2489
February1st to 15thNight
33%410%24%19%7%
2107
16th to endNight
28%6%14%25%19%5%
1735
March1st to 15thNight
27%6%14%27%17%5%
1980
16th to endNight
25%6%16%26%19%5%
2112
April1st to 15thNight
21%6%21%29%17%3
1970
16th to endNight
28%7%15%23%20%4
1800
May1st to 15thNight
24%7%13%33%15%5%
1800
16th to endNight
35%10%19%26%8%
1715
June1st to 15thNight
45%13%21%15%4
1620
16th to endNight
37%14%31%14%1
1620
July1st to 15thNight
44%16%27%11%
1530
16th to endNight
35%15%32%15%1
1595
August1st to 15thNight
32%15%34%16%
1674
16th to endNight
42%17%27%10%1
1997
September1st to 15thNight
43%18%27%9%1
1980
16th to endNight
48%17%20%10%2
1903
October1st to 15thNight
37%9%18%18%14%1
1925
16th to endNight
42%6%12%20%15%4
2112
November1st to 15thNight
32%5%12%22%21%6%
2101
16th to endNight
40%5%10%18%17%8%
2160
December1st to 15thNight
36%7%14%21%17%3
2256
16th to endNight
32%6%15%23%17%4
2496

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
14%8%30%28%15%2
90
16th to endDay
12%12%29%27%14%4
96
February1st to 15thDay
9%325%38%14%8%
94
16th to endDay
9%425%38%21%2
239
March1st to 15thDay
5%228%34%23%4
270
16th to endDay
45%21%33%26%8%
288
April1st to 15thDay
5%222%27%28%14%
270
16th to endDay
9%112%30%29%16%
270
May1st to 15thDay
4114%23%33%23%
288
16th to endDay
7%25%20%32%31%
331
June1st to 15thDay
11%16%18%25%36%
315
16th to endDay
7%28%26%54%
315
July1st to 15thDay
418%23%61%
305
16th to endDay
6%28%24%56%
326
August1st to 15thDay
7%37%23%57%
313
16th to endDay
13%49%23%48%
332
September1st to 15thDay
8%1412%20%52%
315
16th to endDay
12%29%29%45%
283
October1st to 15thDay
9%25%21%41%18%
255
16th to endDay
15%217%27%22%13%
272
November1st to 15thDay
10%112%33%26%14%
265
16th to endDay
9%323%33%25%4
270
December1st to 15thDay
16%416%33%25%4
171
16th to endDay
9%212%46%23%5%
96
January1st to 15thNight
11%5%17%36%26%2
720
16th to endNight
7%5%24%43%18%1
768
February1st to 15thNight
9%5%23%40%20%1
704
16th to endNight
6%325%43%19%
631
March1st to 15thNight
6%226%41%20%1
720
16th to endNight
5%320%46%23%1
768
April1st to 15thNight
2217%46%27%3
718
16th to endNight
6%216%44%27%1
720
May1st to 15thNight
3112%45%32%2
720
16th to endNight
7%25%31%42%9%
594
June1st to 15thNight
12%1318%43%20%
540
16th to endNight
3310%46%34%
540
July1st to 15thNight
6%137%44%35%
510
16th to endNight
6%15%42%43%
564
August1st to 15thNight
6%26%47%35%
604
16th to endNight
9%412%40%32%
764
September1st to 15thNight
9%149%40%34%
720
16th to endNight
12%213%39%31%
689
October1st to 15thNight
9%5%31%40%12%
660
16th to endNight
14%113%29%31%8%
704
November1st to 15thNight
8%116%35%33%4
700
16th to endNight
10%319%35%27%2
720
December1st to 15thNight
8%416%38%30%2
720
16th to endNight
7%316%36%32%3
768
Page generated at 2017-09-24 09:15:53. Version ac04

Copyright 2017 A. Danko


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