Cuttin' Edge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cuttin' Edge Observatory clear sky chart from 2005-11-05 to 2017-04-30.

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
72%
15221
35%
45625
29%
15182
78%
15182
52%
21874

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
65%
719
33%
2327
28%
716
75%
716
44%
1141
January16th to endNight
61%
768
35%
2496
32%
768
70%
768
40%
1296
February1st to 15thNight
65%
698
35%
2181
29%
698
77%
698
50%
1039
February16th to endNight
61%
632
35%
1895
32%
632
69%
632
46%
971
March1st to 15thNight
63%
720
37%
1992
28%
720
73%
720
54%
995
March16th to endNight
68%
768
36%
2112
27%
768
75%
768
56%
1028
April1st to 15thNight
59%
716
30%
1975
17%
716
69%
716
53%
999
April16th to endNight
61%
537
44%
1646
28%
537
76%
537
68%
654
May1st to 15thNight
69%
494
39%
1484
28%
494
77%
494
58%
651
May16th to endNight
73%
513
36%
1540
28%
513
77%
513
66%
641
June1st to 15thNight
78%
495
35%
1485
31%
495
80%
495
67%
625
June16th to endNight
85%
495
32%
1485
28%
495
86%
495
73%
601
July1st to 15thNight
84%
465
24%
1395
21%
465
84%
465
46%
720
July16th to endNight
83%
522
24%
1467
21%
489
85%
489
41%
808
August1st to 15thNight
89%
494
30%
1476
26%
491
89%
491
48%
740
August16th to endNight
84%
597
31%
1696
26%
597
84%
597
44%
936
September1st to 15thNight
82%
660
31%
1815
26%
660
84%
660
49%
964
September16th to endNight
82%
656
42%
1815
32%
656
87%
656
71%
795
October1st to 15thNight
75%
660
39%
1882
32%
660
79%
660
60%
874
October16th to endNight
77%
704
42%
2112
35%
704
84%
704
62%
928
November1st to 15thNight
75%
700
38%
2173
33%
700
82%
700
59%
957
November16th to endNight
71%
720
39%
2340
36%
720
79%
720
54%
1024
December1st to 15thNight
70%
720
35%
2340
33%
720
77%
720
44%
1140
December16th to endNight
61%
768
33%
2496
29%
768
68%
768
36%
1347

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
3213323446%64%
46101
Night
2212323346%67%
45821
TransparencyDay
18%5%6%15%28%26%
45796
Night
17%46%14%28%28%
45627
SeeingDay
412%28%33%17%3
4914
Night
3315%35%34%7%
15231

By Month

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
4212324335%65%
1611
16th to endDay
6%5%1221345%5%61%
1728
February1st to 15thDay
26%13323336%62%
1680
16th to endDay
5%32342245%7%58%
1579
March1st to 15thDay
3212323346%65%
1968
16th to endDay
221331335%5%66%
2112
April1st to 15thDay
222423346%66%
1973
16th to endDay
1112112346%73%
2292
May1st to 15thDay
2112312336%69%
2136
16th to endDay
221321233470%
2221
June1st to 15thDay
112222479%
2145
16th to endDay
1111222381%
2145
July1st to 15thDay
2213446%6%6%8%54%
2145
16th to endDay
4425%6%47%8%9%10%37%
2285
August1st to 15thDay
33135%36%5%7%9%50%
2145
16th to endDay
4314435%6%7%8%50%
2148
September1st to 15thDay
42134345%6%8%55%
1815
16th to endDay
212211235%75%
1815
October1st to 15thDay
2112322435%71%
1746
16th to endDay
112212345%74%
1760
November1st to 15thDay
122223445%70%
1684
16th to endDay
4211212335%71%
1620
December1st to 15thDay
46%13324246%60%
1620
16th to endDay
6%5%24323346%56%
1728
January1st to 15thNight
3312323345%64%
2327
16th to endNight
6%41332433461%
2496
February1st to 15thNight
2413222345%68%
2170
16th to endNight
5%21242345%6%62%
1895
March1st to 15thNight
3212223246%66%
1992
16th to endNight
211131235%6%69%
2112
April1st to 15thNight
3113323336%67%
1975
16th to endNight
1112235%79%
1646
May1st to 15thNight
111212245%74%
1484
16th to endNight
21211112480%
1540
June1st to 15thNight
1121223379%
1485
16th to endNight
121222382%
1485
July1st to 15thNight
11134245%7%8%58%
1485
16th to endNight
1324436%6%9%11%47%
1575
August1st to 15thNight
1123245%7%11%57%
1485
16th to endNight
1213426%6%6%9%55%
1696
September1st to 15thNight
221342336%8%60%
1815
16th to endNight
21111123479%
1815
October1st to 15thNight
212312346%72%
1882
16th to endNight
1112211225%76%
2112
November1st to 15thNight
112212445%72%
2173
16th to endNight
412212225%72%
2340
December1st to 15thNight
431222335%5%65%
2340
16th to endNight
7%423414446%57%
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
21%45%15%33%19%
1612
16th to endDay
24%46%16%30%17%
1728
February1st to 15thDay
23%36%17%25%22%
1680
16th to endDay
25%5%5%18%29%16%
1579
March1st to 15thDay
19%4413%35%22%
1968
16th to endDay
18%45%16%36%17%
2112
April1st to 15thDay
18%27%15%33%23%
1973
16th to endDay
12%3413%34%30%
2292
May1st to 15thDay
13%45%13%30%31%
2136
16th to endDay
14%4410%34%32%
2224
June1st to 15thDay
9%135%25%54%
2145
16th to endDay
8%135%19%60%
2145
July1st to 15thDay
22%9%9%15%16%26%
2006
16th to endDay
31%12%13%18%16%6%
2130
August1st to 15thDay
24%7%10%18%19%19%
2130
16th to endDay
24%9%9%18%23%13%
2148
September1st to 15thDay
22%7%10%16%22%20%
1815
16th to endDay
11%35%9%33%37%
1815
October1st to 15thDay
15%4315%27%34%
1746
16th to endDay
11%35%12%34%32%
1760
November1st to 15thDay
14%36%17%32%26%
1684
16th to endDay
16%3317%28%30%
1620
December1st to 15thDay
25%5%7%21%24%15%
1620
16th to endDay
29%46%21%26%10%
1728
January1st to 15thNight
21%45%15%32%20%
2327
16th to endNight
26%3415%28%21%
2496
February1st to 15thNight
19%37%17%27%24%
2181
16th to endNight
22%46%18%29%18%
1895
March1st to 15thNight
17%35%12%34%25%
1992
16th to endNight
14%47%16%33%22%
2112
April1st to 15thNight
18%35%13%33%26%
1975
16th to endNight
8%25%13%35%35%
1646
May1st to 15thNight
11%4313%30%36%
1485
16th to endNight
10%2310%36%36%
1541
June1st to 15thNight
10%31420%59%
1485
16th to endNight
9%13314%67%
1485
July1st to 15thNight
19%7%12%13%19%27%
1395
16th to endNight
22%9%16%21%20%9%
1467
August1st to 15thNight
17%8%13%17%20%23%
1476
16th to endNight
23%7%9%19%23%17%
1696
September1st to 15thNight
19%6%12%17%19%24%
1815
16th to endNight
9%248%37%37%
1815
October1st to 15thNight
14%2416%27%33%
1882
16th to endNight
12%26%10%25%41%
2112
November1st to 15thNight
14%35%15%34%26%
2173
16th to endNight
15%3414%28%34%
2340
December1st to 15thNight
20%5%6%18%27%20%
2340
16th to endNight
28%5%7%19%28%11%
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
24%5%23%32%13%1
90
16th to endDay
10%14%23%20%21%8%
96
February1st to 15thDay
413%32%29%16%2
195
16th to endDay
8%27%29%23%9%1
238
March1st to 15thDay
5%20%31%24%12%5%
270
16th to endDay
324%32%24%12%1
288
April1st to 15thDay
7%21%34%23%8%4
269
16th to endDay
330%38%19%6%1
267
May1st to 15thDay
420%43%22%7%1
228
16th to endDay
5%15%36%28%12%3
266
June1st to 15thDay
213%41%25%12%3
255
16th to endDay
228%43%18%5%
255
July1st to 15thDay
1227%49%17%1
245
16th to endDay
312%48%24%9%
271
August1st to 15thDay
2115%47%27%7%
255
16th to endDay
414%46%29%5%
268
September1st to 15thDay
6%125%43%18%3
255
16th to endDay
5%7%24%40%18%2
255
October1st to 15thDay
312%35%24%18%4
186
16th to endDay
3416%40%30%5%
96
November1st to 15thDay
17%15%34%32%8%
90
16th to endDay
313%33%31%17%1
90
December1st to 15thDay
37%14%37%35%1
90
16th to endDay
8%20%17%30%20%2
96
January1st to 15thNight
5%420%40%22%7%
720
16th to endNight
7%5%20%36%25%4
768
February1st to 15thNight
4419%43%25%2
704
16th to endNight
6%5%22%42%18%3
632
March1st to 15thNight
5%5%23%37%25%4
720
16th to endNight
27%18%39%28%4
768
April1st to 15thNight
45%24%37%23%3
716
16th to endNight
8%27%35%24%3
537
May1st to 15thNight
26%18%41%28%3
495
16th to endNight
1316%39%33%4
515
June1st to 15thNight
2115%44%31%4
495
16th to endNight
19%35%46%6%
495
July1st to 15thNight
2427%53%11%
465
16th to endNight
11318%56%18%
522
August1st to 15thNight
2216%62%16%
494
16th to endNight
2318%54%21%
597
September1st to 15thNight
26%24%51%13%
660
16th to endNight
2111%29%44%10%
656
October1st to 15thNight
3313%37%36%5%
660
16th to endNight
1213%32%39%9%
704
November1st to 15thNight
3116%37%33%7%
700
16th to endNight
5%416%35%30%7%
720
December1st to 15thNight
7%414%39%31%2
720
16th to endNight
9%416%42%21%4
768
Page generated at 2017-04-30 17:40:04. Version ac04

Copyright 2017 A. Danko


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