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 2018-03-21.

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
59%
15921
27%
49217
22%
15885
65%
15885
36%
27178

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%
778
20%
2714
16%
776
53%
776
24%
1629
January16th to endNight
41%
832
24%
2704
16%
832
53%
832
23%
1678
February1st to 15thNight
43%
760
24%
2445
17%
757
55%
757
25%
1495
February16th to endNight
46%
684
25%
2051
20%
684
54%
684
25%
1318
March1st to 15thNight
42%
780
15%
2257
10%
780
47%
780
21%
1573
March16th to endNight
43%
792
18%
2107
11%
792
49%
792
25%
1435
April1st to 15thNight
45%
719
18%
1799
8%
719
50%
719
27%
1260
April16th to endNight
56%
720
23%
1800
11%
720
60%
720
38%
1097
May1st to 15thNight
58%
545
26%
1625
18%
545
63%
545
43%
828
May16th to endNight
68%
374
23%
1496
28%
374
71%
374
33%
733
June1st to 15thNight
72%
360
26%
1440
33%
360
77%
360
40%
633
June16th to endNight
83%
360
34%
1440
46%
360
87%
360
60%
509
July1st to 15thNight
93%
340
34%
1360
47%
340
94%
340
71%
431
July16th to endNight
91%
456
40%
1490
44%
428
92%
428
72%
532
August1st to 15thNight
88%
581
37%
1654
30%
578
89%
578
68%
731
August16th to endNight
90%
764
42%
1910
27%
764
91%
764
77%
880
September1st to 15thNight
89%
720
42%
1800
30%
720
90%
720
77%
829
September16th to endNight
76%
716
44%
1934
35%
716
82%
716
64%
910
October1st to 15thNight
65%
720
31%
2160
29%
720
71%
720
47%
1069
October16th to endNight
65%
768
37%
2304
33%
768
74%
768
46%
1171
November1st to 15thNight
58%
760
25%
2470
22%
760
65%
760
33%
1388
November16th to endNight
49%
780
24%
2615
22%
780
56%
780
28%
1520
December1st to 15thNight
44%
780
23%
2730
17%
780
54%
780
23%
1627
December16th to endNight
35%
832
22%
2912
14%
832
47%
832
17%
1902

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%
49629
Night
12%6%12213335%56%
49407
TransparencyDay
28%27%18%24%17%
49308
Night
30%37%18%22%16%
49228
SeeingDay
17%15%32%23%9%3
6398
Night
16%5%13%31%27%5%
15929

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
17%8%14323336%44%
1552
16th to endDay
19%11%22312346%41%
1872
February1st to 15thDay
19%8%12213346%45%
1738
16th to endDay
19%16%3321235%438%
1709
March1st to 15thDay
20%13%33423345%34%
2031
16th to endDay
20%11%23313346%38%
2242
April1st to 15thDay
19%12%13323446%38%
2149
16th to endDay
14%6%13313335%53%
2160
May1st to 15thDay
8%312212347%61%
2321
16th to endDay
13%5%23313446%51%
2615
June1st to 15thDay
9%413213235%60%
2520
16th to endDay
3111122381%
2520
July1st to 15thDay
111112284%
2520
16th to endDay
11111111284%
2574
August1st to 15thDay
211112283%
2295
16th to endDay
1121286%
2292
September1st to 15thDay
2111223479%
2160
16th to endDay
5%2211112475%
2022
October1st to 15thDay
9%22213345%64%
1800
16th to endDay
10%31331223460%
1920
November1st to 15thDay
14%6%13423346%49%
1719
16th to endDay
15%8%13323345%46%
1674
December1st to 15thDay
19%8%2421245%6%42%
1560
16th to endDay
22%10%23313436%39%
1664
January1st to 15thNight
16%7%1332435%7%43%
2714
16th to endNight
17%10%12223336%44%
2704
February1st to 15thNight
16%7%24323346%44%
2444
16th to endNight
18%12%23113346%43%
2051
March1st to 15thNight
20%12%23323446%34%
2257
16th to endNight
18%11%12313335%43%
2107
April1st to 15thNight
17%10%2432335%6%39%
1799
16th to endNight
12%6%13213345%56%
1800
May1st to 15thNight
8%21331335%5%61%
1625
16th to endNight
10%313313246%57%
1496
June1st to 15thNight
8%311112335%65%
1440
16th to endNight
21211212280%
1440
July1st to 15thNight
2222383%
1440
16th to endNight
121112383%
1592
August1st to 15thNight
21221213377%
1663
16th to endNight
111222382%
1910
September1st to 15thNight
11111122383%
1800
16th to endNight
32111123476%
1934
October1st to 15thNight
7%21221222467%
2160
16th to endNight
10%2121235%5%63%
2304
November1st to 15thNight
14%413213346%52%
2470
16th to endNight
13%7%13324346%49%
2615
December1st to 15thNight
20%6%12323335%46%
2730
16th to endNight
23%10%23313336%39%
2912

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
41%38%21%18%6%
1552
16th to endDay
44%28%14%18%11%
1872
February1st to 15thDay
39%211%17%21%6%
1738
16th to endDay
48%27%24%13%2
1709
March1st to 15thDay
51%310%13%15%5%
2031
16th to endDay
46%415%17%12%3
2242
April1st to 15thDay
46%312%19%14%2
2149
16th to endDay
32%313%23%21%5%
2160
May1st to 15thDay
22%311%31%24%6%
2321
16th to endDay
32%312%27%19%5%
2619
June1st to 15thDay
26%211%18%23%17%
2520
16th to endDay
10%1317%40%26%
2520
July1st to 15thDay
7%129%29%49%
2371
16th to endDay
9%1211%24%51%
2414
August1st to 15thDay
8%1211%32%42%
2279
16th to endDay
6%1114%39%36%
2292
September1st to 15thDay
9%2312%36%35%
2160
16th to endDay
15%15%24%33%19%
2022
October1st to 15thDay
22%26%24%27%17%
1800
16th to endDay
28%27%19%24%16%
1920
November1st to 15thDay
36%310%21%18%8%
1719
16th to endDay
39%37%21%21%6%
1674
December1st to 15thDay
42%37%18%18%8%
1560
16th to endDay
47%38%13%18%8%
1664
January1st to 15thNight
39%39%19%19%8%
2714
16th to endNight
42%37%13%19%14%
2704
February1st to 15thNight
40%27%20%19%9%
2455
16th to endNight
43%38%23%17%4
2051
March1st to 15thNight
49%39%15%14%6%
2257
16th to endNight
43%411%20%13%5%
2107
April1st to 15thNight
45%412%21%11%4
1799
16th to endNight
30%412%26%21%4
1800
May1st to 15thNight
23%312%26%26%8%
1626
16th to endNight
27%414%29%18%5%
1496
June1st to 15thNight
20%410%22%23%17%
1440
16th to endNight
12%1416%33%31%
1440
July1st to 15thNight
6%228%25%54%
1360
16th to endNight
8%1311%22%53%
1490
August1st to 15thNight
12%1211%27%44%
1654
16th to endNight
8%1213%33%40%
1910
September1st to 15thNight
8%1313%36%36%
1800
16th to endNight
13%2421%37%20%
1934
October1st to 15thNight
21%25%22%27%20%
2160
16th to endNight
22%36%21%27%18%
2304
November1st to 15thNight
32%411%21%20%10%
2470
16th to endNight
36%37%20%22%8%
2615
December1st to 15thNight
39%37%18%19%11%
2730
16th to endNight
47%37%11%21%8%
2912

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
45%8%18%15%8%2
90
16th to endDay
31%11%23%22%9%1
304
February1st to 15thDay
25%14%28%20%9%
289
16th to endDay
34%13%28%18%3
290
March1st to 15thDay
38%19%18%14%7%2
330
16th to endDay
32%18%28%15%4
311
April1st to 15thDay
31%24%26%13%4
269
16th to endDay
24%23%31%15%4
270
May1st to 15thDay
15%26%32%17%5%1
288
16th to endDay
19%17%28%19%8%5%
330
June1st to 15thDay
15%20%33%20%6%3
315
16th to endDay
5%12%42%25%7%6%
315
July1st to 15thDay
17%44%29%6%9%
305
16th to endDay
11%43%28%11%5%
327
August1st to 15thDay
212%40%29%9%5%
315
16th to endDay
10%39%30%13%6%
332
September1st to 15thDay
29%43%27%13%3
315
16th to endDay
8%13%38%30%7%1
315
October1st to 15thDay
7%21%33%24%10%1
315
16th to endDay
17%10%27%29%13%1
336
November1st to 15thDay
22%8%15%22%25%3
135
16th to endDay
27%10%17%29%14%
116
December1st to 15thDay
26%15%21%15%14%6%
90
16th to endDay
21%323%27%20%3
96
January1st to 15thNight
23%5%19%29%17%4
780
16th to endNight
25%10%16%27%17%2
832
February1st to 15thNight
22%7%19%31%16%2
764
16th to endNight
26%9%14%30%16%3
684
March1st to 15thNight
28%7%15%27%19%2
780
16th to endNight
26%8%16%26%20%2
792
April1st to 15thNight
23%5%17%32%18%2
719
16th to endNight
16%7%14%34%21%5%
720
May1st to 15thNight
9%8%17%33%26%3
546
16th to endNight
13%28%32%36%6%
375
June1st to 15thNight
8%5%10%35%36%4
360
16th to endNight
317%38%45%4
360
July1st to 15thNight
230%60%6%
340
16th to endNight
228%57%10%
456
August1st to 15thNight
2337%46%8%
581
16th to endNight
1437%46%8%
764
September1st to 15thNight
2436%45%10%
720
16th to endNight
4311%34%32%12%
716
October1st to 15thNight
9%5%14%33%29%7%
720
16th to endNight
12%5%12%29%31%7%
768
November1st to 15thNight
16%5%14%31%26%5%
760
16th to endNight
18%7%19%30%20%3
780
December1st to 15thNight
24%9%16%31%15%2
780
16th to endNight
30%10%18%25%14%1
832
Page generated at 2018-03-22 08:34:20. Version ac04

Copyright 2018 A. Danko


Blue Canyon Clear Sky Chart |Charts Home