Skyfall Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Skyfall Observatory clear sky chart from 2005-11-05 to 2017-09-20.

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
53%
15593
23%
46974
17%
15551
60%
15551
29%
29024

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
33%
718
23%
2327
13%
716
47%
716
24%
1420
January16th to endNight
32%
768
25%
2428
14%
768
45%
768
25%
1518
February1st to 15thNight
36%
704
26%
2108
13%
700
50%
700
29%
1269
February16th to endNight
35%
631
26%
1893
12%
631
48%
631
30%
1144
March1st to 15thNight
40%
720
27%
2037
14%
720
51%
720
33%
1218
March16th to endNight
43%
768
23%
2112
12%
768
50%
768
33%
1275
April1st to 15thNight
49%
691
25%
1949
18%
691
56%
691
36%
1161
April16th to endNight
56%
540
30%
1707
21%
540
66%
540
38%
942
May1st to 15thNight
57%
539
25%
1620
17%
539
64%
539
33%
959
May16th to endNight
67%
561
22%
1682
17%
561
69%
561
34%
1003
June1st to 15thNight
68%
540
15%
1620
13%
540
68%
540
26%
1087
June16th to endNight
71%
540
16%
1620
15%
540
72%
540
26%
1061
July1st to 15thNight
74%
510
11%
1530
9%
510
74%
510
25%
1063
July16th to endNight
73%
564
13%
1595
12%
531
73%
531
25%
1075
August1st to 15thNight
75%
539
14%
1654
14%
536
75%
536
25%
1090
August16th to endNight
66%
591
16%
1928
18%
591
67%
591
20%
1325
September1st to 15thNight
65%
720
17%
1980
16%
720
65%
720
26%
1338
September16th to endNight
58%
677
20%
1870
16%
677
61%
677
24%
1288
October1st to 15thNight
59%
660
31%
1823
25%
660
64%
660
38%
1083
October16th to endNight
60%
704
33%
2112
30%
704
67%
704
39%
1156
November1st to 15thNight
57%
700
31%
2203
26%
700
65%
700
37%
1200
November16th to endNight
44%
720
28%
2340
21%
720
57%
720
32%
1329
December1st to 15thNight
44%
720
25%
2340
20%
720
53%
720
28%
1395
December16th to endNight
40%
768
23%
2496
19%
768
48%
768
22%
1625

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
11%5%25%5%35%45%8%42%
47854
Night
10%4244245%5%7%46%
47177
TransparencyDay
38%7%12%17%17%6%
47555
Night
35%6%11%17%19%9%
46980
SeeingDay
12%415%23%25%18%
5471
Night
12%5%21%31%24%4
15598

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
13%5%345%24436%46%
1611
16th to endDay
14%5%24324346%45%
1794
February1st to 15thDay
13%5%25%424446%44%
1750
16th to endDay
15%5%24324346%47%
1580
March1st to 15thDay
12%5%2442445%6%47%
1923
16th to endDay
13%323424346%48%
2111
April1st to 15thDay
11%5%2442435%6%49%
2008
16th to endDay
8%21342345%7%54%
2253
May1st to 15thDay
8%415%5%3445%8%48%
2331
16th to endDay
6%415%5%46%5%6%9%43%
2431
June1st to 15thDay
10%425%6%46%7%6%10%34%
2340
16th to endDay
5%4246%47%7%7%12%38%
2340
July1st to 15thDay
9%5%37%7%5%8%7%7%10%28%
2340
16th to endDay
8%5%27%7%47%7%8%10%29%
2465
August1st to 15thDay
11%5%27%6%47%6%9%12%25%
2291
16th to endDay
14%6%27%7%46%6%6%8%28%
2262
September1st to 15thDay
11%427%5%45%6%7%9%36%
1980
16th to endDay
14%7%16%7%45%446%37%
1859
October1st to 15thDay
14%5%14313236%52%
1805
16th to endDay
10%313313345%59%
1760
November1st to 15thDay
10%413314346%55%
1652
16th to endDay
14%4145%23346%50%
1620
December1st to 15thDay
14%5%25%423346%46%
1620
16th to endDay
21%7%35%5%13346%37%
1728
January1st to 15thNight
13%7%24424445%46%
2327
16th to endNight
18%5%2442323447%
2428
February1st to 15thNight
14%5%23414336%49%
2103
16th to endNight
13%5%2442345%5%48%
1893
March1st to 15thNight
10%42442335%7%50%
2037
16th to endNight
12%424313346%52%
2112
April1st to 15thNight
11%22432435%8%51%
1949
16th to endNight
6%3133245%6%8%53%
1707
May1st to 15thNight
7%3244245%5%6%51%
1619
16th to endNight
6%415%4345%6%9%47%
1682
June1st to 15thNight
7%5%26%5%36%7%8%11%34%
1620
16th to endNight
4425%5%47%7%9%9%38%
1620
July1st to 15thNight
6%5%25%6%46%8%8%12%33%
1620
16th to endNight
6%5%25%5%46%7%8%13%33%
1703
August1st to 15thNight
7%4246%46%6%9%13%35%
1665
16th to endNight
10%5%26%6%45%8%7%10%32%
1928
September1st to 15thNight
11%5%35%6%35%5%6%8%39%
1980
16th to endNight
9%7%37%6%346%6%7%37%
1870
October1st to 15thNight
12%414323335%54%
1823
16th to endNight
10%41331333459%
2112
November1st to 15thNight
9%313323335%57%
2203
16th to endNight
12%423423335%55%
2340
December1st to 15thNight
13%5%2442445%6%47%
2340
16th to endNight
17%5%345%34446%39%
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
38%47%14%25%8%
1612
16th to endDay
38%47%16%22%10%
1794
February1st to 15thDay
40%36%16%22%10%
1752
16th to endDay
37%46%16%24%9%
1580
March1st to 15thDay
36%5%9%19%20%9%
1923
16th to endDay
36%5%11%15%23%6%
2112
April1st to 15thDay
35%47%20%21%9%
2008
16th to endDay
28%5%9%24%22%9%
2253
May1st to 15thDay
33%6%12%20%21%6%
2331
16th to endDay
34%7%14%24%14%3
2435
June1st to 15thDay
40%10%17%18%11%1
2340
16th to endDay
34%12%16%19%14%2
2340
July1st to 15thDay
44%11%20%15%5%1
2201
16th to endDay
43%12%17%18%6%
2310
August1st to 15thDay
45%11%21%14%6%
2278
16th to endDay
50%10%15%14%8%1
2262
September1st to 15thDay
41%10%15%14%16%2
1980
16th to endDay
47%7%8%16%15%5%
1859
October1st to 15thDay
34%39%19%22%10%
1805
16th to endDay
26%36%15%28%18%
1760
November1st to 15thDay
29%37%17%25%16%
1652
16th to endDay
35%47%14%24%14%
1620
December1st to 15thDay
39%49%17%19%9%
1620
16th to endDay
47%47%17%15%6%
1728
January1st to 15thNight
39%46%16%25%8%
2327
16th to endNight
41%3413%25%11%
2428
February1st to 15thNight
37%36%16%22%13%
2112
16th to endNight
36%47%15%22%14%
1893
March1st to 15thNight
32%5%8%20%22%10%
2037
16th to endNight
33%5%10%17%23%10%
2112
April1st to 15thNight
32%47%20%22%12%
1949
16th to endNight
27%6%10%23%21%11%
1707
May1st to 15thNight
31%7%11%18%22%8%
1620
16th to endNight
31%7%14%25%16%5%
1684
June1st to 15thNight
38%10%17%22%11%
1620
16th to endNight
36%11%16%18%13%3
1620
July1st to 15thNight
37%14%23%16%6%1
1530
16th to endNight
35%14%22%18%7%1
1595
August1st to 15thNight
36%12%24%19%7%
1654
16th to endNight
42%12%17%16%9%1
1928
September1st to 15thNight
39%9%14%16%15%3
1980
16th to endNight
42%8%11%15%17%4
1870
October1st to 15thNight
32%49%20%19%14%
1823
16th to endNight
28%37%15%26%18%
2112
November1st to 15thNight
29%36%15%28%16%
2203
16th to endNight
33%36%16%23%16%
2340
December1st to 15thNight
36%5%9%18%21%8%
2340
16th to endNight
44%5%6%19%16%8%
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
10%13%36%23%11%5%
90
16th to endDay
14%19%46%9%9%
96
February1st to 15thDay
12%24%30%26%6%
90
16th to endDay
17%8%41%30%1
81
March1st to 15thDay
13%12%27%31%14%1
213
16th to endDay
12%5%28%34%18%1
288
April1st to 15thDay
14%12%18%30%20%4
270
16th to endDay
7%421%28%28%10%
270
May1st to 15thDay
9%6%19%27%23%13%
288
16th to endDay
6%210%22%34%22%
331
June1st to 15thDay
13%5%20%28%32%
315
16th to endDay
7%5%18%31%35%
315
July1st to 15thDay
6%416%32%40%
305
16th to endDay
6%1315%34%38%
326
August1st to 15thDay
14%417%30%31%
313
16th to endDay
12%5%16%34%31%
332
September1st to 15thDay
14%110%20%28%24%
315
16th to endDay
17%18%28%29%13%
270
October1st to 15thDay
18%313%28%26%9%
255
16th to endDay
9%419%29%28%8%
272
November1st to 15thDay
17%5%25%28%19%3
160
16th to endDay
5%12%27%26%23%4
90
December1st to 15thDay
18%440%24%5%6%
90
16th to endDay
33%9%19%23%11%2
96
January1st to 15thNight
15%13%31%28%9%1
720
16th to endNight
18%10%32%31%6%
768
February1st to 15thNight
16%9%32%32%9%
704
16th to endNight
15%7%38%34%4
631
March1st to 15thNight
10%10%33%34%9%
720
16th to endNight
13%7%30%31%16%
768
April1st to 15thNight
13%6%27%33%18%
691
16th to endNight
8%227%35%23%1
540
May1st to 15thNight
7%423%35%26%3
540
16th to endNight
7%114%36%34%5%
563
June1st to 15thNight
8%19%35%36%8%
540
16th to endNight
5%6%28%46%11%
540
July1st to 15thNight
8%5%28%39%18%
510
16th to endNight
8%425%50%10%
564
August1st to 15thNight
7%5%22%50%13%
539
16th to endNight
12%16%20%43%15%
591
September1st to 15thNight
11%17%25%42%11%
720
16th to endNight
14%111%36%33%2
677
October1st to 15thNight
15%116%32%28%4
660
16th to endNight
11%319%34%27%2
704
November1st to 15thNight
12%420%39%21%2
700
16th to endNight
14%7%28%30%17%1
720
December1st to 15thNight
14%7%27%32%16%1
720
16th to endNight
20%7%25%34%11%1
768
Page generated at 2017-09-21 07:18:11. Version ac04

Copyright 2017 A. Danko


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