Blue Canyon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Blue Canyon clear sky chart from 2005-11-05 to 2017-04-09.

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
58%
14713
27%
45445
22%
14677
65%
14677
36%
25184

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
44%
718
20%
2504
15%
716
53%
716
25%
1477
January16th to endNight
40%
768
25%
2496
16%
768
53%
768
23%
1535
February1st to 15thNight
41%
700
22%
2253
15%
697
53%
697
23%
1423
February16th to endNight
44%
632
24%
1895
19%
632
53%
632
24%
1235
March1st to 15thNight
42%
720
15%
2083
10%
720
48%
720
21%
1434
March16th to endNight
44%
768
18%
2041
11%
768
49%
768
26%
1378
April1st to 15thNight
46%
695
18%
1739
8%
695
50%
695
27%
1213
April16th to endNight
57%
660
22%
1650
11%
660
61%
660
40%
988
May1st to 15thNight
56%
499
27%
1489
19%
499
63%
499
43%
757
May16th to endNight
67%
342
20%
1368
23%
342
69%
342
32%
682
June1st to 15thNight
72%
330
27%
1320
34%
330
77%
330
40%
580
June16th to endNight
82%
330
32%
1320
44%
330
86%
330
59%
473
July1st to 15thNight
93%
310
36%
1240
49%
310
94%
310
69%
399
July16th to endNight
91%
421
37%
1371
41%
393
91%
393
71%
492
August1st to 15thNight
89%
532
39%
1515
32%
529
89%
529
70%
661
August16th to endNight
90%
700
41%
1750
26%
700
90%
700
78%
800
September1st to 15thNight
89%
660
44%
1650
31%
660
91%
660
79%
755
September16th to endNight
78%
656
42%
1772
35%
656
83%
656
64%
836
October1st to 15thNight
63%
660
31%
1980
29%
660
70%
660
45%
1009
October16th to endNight
63%
704
34%
2112
30%
704
72%
704
44%
1094
November1st to 15thNight
59%
700
26%
2275
23%
700
67%
700
34%
1245
November16th to endNight
49%
720
24%
2414
21%
720
56%
720
29%
1388
December1st to 15thNight
41%
720
21%
2520
15%
720
53%
720
21%
1549
December16th to endNight
34%
768
21%
2688
13%
768
46%
768
17%
1781

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%12212335%59%
45833
Night
12%6%12213345%56%
45635
TransparencyDay
28%28%18%24%17%
45512
Night
30%38%18%23%16%
45456
SeeingDay
17%16%33%22%7%2
5178
Night
16%6%13%31%27%5%
14721

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
16%8%14323336%46%
1432
16th to endDay
19%11%22312336%43%
1728
February1st to 15thDay
21%9%12213346%44%
1600
16th to endDay
21%15%3221235%437%
1579
March1st to 15thDay
20%13%33423346%35%
1875
16th to endDay
20%10%23313446%39%
2181
April1st to 15thDay
18%12%13323446%38%
2072
16th to endDay
13%6%23312235%55%
1980
May1st to 15thDay
9%312212347%60%
2127
16th to endDay
13%5%24323447%49%
2391
June1st to 15thDay
9%413214236%60%
2310
16th to endDay
31111122379%
2310
July1st to 15thDay
112122383%
2310
16th to endDay
2111111284%
2385
August1st to 15thDay
211112284%
2104
16th to endDay
111121286%
2100
September1st to 15thDay
2111222381%
1980
16th to endDay
42111112477%
1854
October1st to 15thDay
10%23213345%62%
1650
16th to endDay
11%31331233459%
1760
November1st to 15thDay
11%5%13423346%51%
1584
16th to endDay
15%8%13324335%47%
1545
December1st to 15thDay
21%8%2421345%6%40%
1440
16th to endDay
23%11%23312335%38%
1536
January1st to 15thNight
15%7%13324347%45%
2504
16th to endNight
17%10%12223335%46%
2496
February1st to 15thNight
17%8%2332435%7%40%
2252
16th to endNight
19%12%23113346%41%
1895
March1st to 15thNight
20%11%23323436%36%
2083
16th to endNight
18%10%12313335%44%
2041
April1st to 15thNight
16%10%2432435%6%39%
1739
16th to endNight
11%6%12213345%57%
1650
May1st to 15thNight
9%21331235%5%61%
1489
16th to endNight
10%414313246%56%
1368
June1st to 15thNight
8%311112335%66%
1320
16th to endNight
21211212279%
1320
July1st to 15thNight
12222382%
1320
16th to endNight
121112383%
1473
August1st to 15thNight
21211213378%
1524
16th to endNight
111222383%
1750
September1st to 15thNight
11111112384%
1650
16th to endNight
32111123476%
1772
October1st to 15thNight
8%31331233465%
1980
16th to endNight
11%2121235%5%61%
2112
November1st to 15thNight
12%413213346%54%
2275
16th to endNight
13%7%13323346%50%
2414
December1st to 15thNight
21%7%12323435%43%
2520
16th to endNight
24%10%23212335%39%
2688

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
40%29%21%19%6%
1432
16th to endDay
43%27%15%18%11%
1728
February1st to 15thDay
41%311%17%20%5%
1600
16th to endDay
48%28%25%12%2
1579
March1st to 15thDay
50%310%12%17%5%
1875
16th to endDay
45%415%17%13%3
2181
April1st to 15thDay
46%312%19%15%2
2072
16th to endDay
31%313%24%21%5%
1980
May1st to 15thDay
22%410%30%24%6%
2127
16th to endDay
33%313%26%17%5%
2395
June1st to 15thDay
25%211%17%23%18%
2310
16th to endDay
11%1317%42%23%
2310
July1st to 15thDay
8%1210%30%45%
2161
16th to endDay
10%1211%25%48%
2225
August1st to 15thDay
7%1210%31%45%
2088
16th to endDay
6%1114%39%36%
2100
September1st to 15thDay
9%1310%37%36%
1980
16th to endDay
13%15%24%33%21%
1854
October1st to 15thDay
23%26%25%27%13%
1650
16th to endDay
29%28%20%25%14%
1760
November1st to 15thDay
33%311%21%19%9%
1584
16th to endDay
39%37%20%21%7%
1545
December1st to 15thDay
44%38%19%19%4
1440
16th to endDay
49%39%12%17%7%
1536
January1st to 15thNight
38%39%19%19%9%
2504
16th to endNight
41%27%13%19%15%
2496
February1st to 15thNight
43%37%20%17%8%
2263
16th to endNight
44%38%23%16%4
1895
March1st to 15thNight
48%39%15%14%7%
2083
16th to endNight
42%5%11%20%14%5%
2041
April1st to 15thNight
44%5%12%21%12%4
1739
16th to endNight
29%413%26%22%4
1650
May1st to 15thNight
23%312%25%26%8%
1490
16th to endNight
28%415%29%15%6%
1368
June1st to 15thNight
20%5%10%21%23%18%
1320
16th to endNight
12%1416%36%28%
1320
July1st to 15thNight
7%229%26%50%
1240
16th to endNight
8%1311%23%50%
1371
August1st to 15thNight
11%1211%27%45%
1515
16th to endNight
8%1213%34%40%
1750
September1st to 15thNight
7%1311%38%37%
1650
16th to endNight
13%2421%36%21%
1772
October1st to 15thNight
23%26%23%28%15%
1980
16th to endNight
23%36%22%28%14%
2112
November1st to 15thNight
29%411%21%21%11%
2275
16th to endNight
35%38%21%22%9%
2414
December1st to 15thNight
42%38%18%20%6%
2520
16th to endNight
48%37%11%20%8%
2688

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
53%8%20%10%6%1
60
16th to endDay
32%13%22%21%8%1
256
February1st to 15thDay
29%14%27%18%8%
241
16th to endDay
36%12%28%19%3
238
March1st to 15thDay
38%20%17%14%7%1
270
16th to endDay
30%19%28%15%4
288
April1st to 15thDay
30%25%25%13%4
244
16th to endDay
22%24%31%16%3
210
May1st to 15thDay
17%28%33%14%41
228
16th to endDay
20%19%28%18%6%5%
266
June1st to 15thDay
12%22%35%21%33
255
16th to endDay
6%14%47%21%45%
255
July1st to 15thDay
29%47%28%47%
245
16th to endDay
19%47%29%8%4
271
August1st to 15thDay
214%41%29%6%4
255
16th to endDay
12%44%28%9%5%
268
September1st to 15thDay
310%46%27%9%3
255
16th to endDay
6%12%38%32%7%1
255
October1st to 15thDay
9%21%33%23%9%2
255
16th to endDay
19%12%31%27%8%
272
November1st to 15thDay
12%6%17%24%33%5%
90
16th to endDay
27%15%18%27%10%1
77
December1st to 15thDay
36%20%20%16%6%
60
16th to endDay
28%125%26%15%3
64
January1st to 15thNight
22%6%20%29%16%5%
720
16th to endNight
24%11%17%26%17%2
768
February1st to 15thNight
23%7%19%30%16%1
704
16th to endNight
27%9%14%28%16%3
632
March1st to 15thNight
27%7%15%27%19%2
720
16th to endNight
25%8%17%26%20%2
768
April1st to 15thNight
22%5%17%32%18%2
695
16th to endNight
15%7%13%33%22%6%
660
May1st to 15thNight
9%9%18%31%27%3
500
16th to endNight
13%39%32%35%6%
343
June1st to 15thNight
7%410%36%35%4
330
16th to endNight
318%39%42%4
330
July1st to 15thNight
331%59%5%
310
16th to endNight
228%57%9%
421
August1st to 15thNight
2338%45%8%
532
16th to endNight
15%38%46%7%
700
September1st to 15thNight
21435%45%10%
660
16th to endNight
4310%35%33%12%
656
October1st to 15thNight
10%5%14%32%30%7%
660
16th to endNight
13%5%13%30%29%7%
704
November1st to 15thNight
13%5%15%32%26%6%
700
16th to endNight
17%7%20%29%20%4
720
December1st to 15thNight
25%9%16%31%14%2
720
16th to endNight
31%10%18%24%13%1
768
Page generated at 2017-04-10 06:00:37. Version ac04

Copyright 2017 A. Danko


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