Del Valle
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Del Valle clear sky chart from 2005-11-05 to 2017-04-01.

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
69%
14869
29%
45389
26%
14833
72%
14833
41%
24463

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
62%
716
19%
2403
19%
716
66%
716
28%
1427
January16th to endNight
58%
768
24%
2496
26%
768
61%
768
27%
1534
February1st to 15thNight
57%
699
24%
2275
25%
699
62%
699
26%
1410
February16th to endNight
56%
632
24%
1895
22%
632
61%
632
27%
1210
March1st to 15thNight
53%
720
19%
2025
18%
720
56%
720
28%
1327
March16th to endNight
52%
768
21%
2076
15%
768
57%
768
30%
1338
April1st to 15thNight
50%
663
23%
1659
12%
663
54%
663
31%
1090
April16th to endNight
60%
660
25%
1650
12%
660
64%
660
47%
940
May1st to 15thNight
69%
582
31%
1572
20%
582
74%
582
57%
786
May16th to endNight
75%
342
26%
1368
25%
342
82%
342
44%
584
June1st to 15thNight
72%
330
31%
1320
32%
330
81%
330
48%
538
June16th to endNight
87%
330
36%
1320
45%
330
91%
330
71%
421
July1st to 15thNight
93%
325
38%
1255
47%
325
95%
325
75%
402
July16th to endNight
92%
522
36%
1467
33%
489
93%
489
72%
592
August1st to 15thNight
91%
524
41%
1507
31%
521
92%
521
72%
628
August16th to endNight
92%
700
41%
1750
27%
700
93%
700
79%
800
September1st to 15thNight
92%
660
44%
1650
33%
660
92%
660
79%
756
September16th to endNight
85%
656
43%
1790
38%
656
88%
656
67%
824
October1st to 15thNight
75%
660
31%
1980
32%
660
81%
660
48%
985
October16th to endNight
76%
704
35%
2112
37%
704
80%
704
47%
1091
November1st to 15thNight
70%
700
28%
2202
28%
700
74%
700
40%
1174
November16th to endNight
67%
720
26%
2409
27%
720
70%
720
33%
1344
December1st to 15thNight
57%
720
21%
2520
21%
720
62%
720
24%
1559
December16th to endNight
50%
768
21%
2688
20%
768
56%
768
22%
1703

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
6%313313345%62%
45713
Night
7%31332335%6%59%
45575
TransparencyDay
24%37%18%25%20%
45398
Night
26%47%17%22%20%
45390
SeeingDay
9%12%27%33%14%2
5317
Night
8%5%11%32%32%10%
14880

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
13%6%243235%47%45%
1534
16th to endDay
15%6%26%434345%44%
1728
February1st to 15thDay
13%8%245%24346%43%
1589
16th to endDay
16%6%35%5%2445%7%38%
1579
March1st to 15thDay
11%6%26%6%345%7%8%36%
1932
16th to endDay
12%6%36%435%5%46%41%
2148
April1st to 15thDay
13%6%3443445%8%42%
1974
16th to endDay
5%312313348%61%
1980
May1st to 15thDay
432212346%67%
2042
16th to endDay
431331335%7%63%
2391
June1st to 15thDay
2212313346%68%
2310
16th to endDay
11113383%
2310
July1st to 15thDay
112387%
2292
16th to endDay
1122385%
2286
August1st to 15thDay
11111386%
2112
16th to endDay
11112486%
2100
September1st to 15thDay
11112287%
1980
16th to endDay
31121234475%
1837
October1st to 15thDay
3213312237%67%
1650
16th to endDay
6%32312446%63%
1760
November1st to 15thDay
8%32332446%7%51%
1655
16th to endDay
10%5%2442335%7%50%
1548
December1st to 15thDay
14%7%46%5%23446%41%
1440
16th to endDay
15%8%25%5%14346%40%
1536
January1st to 15thNight
11%424335%46%8%44%
2403
16th to endNight
13%5%24423446%47%
2496
February1st to 15thNight
12%5%244245%5%7%43%
2263
16th to endNight
12%6%2442447%7%43%
1895
March1st to 15thNight
13%6%345%24347%44%
2025
16th to endNight
10%6%25%4235%5%7%45%
2076
April1st to 15thNight
8%425%5%35%5%6%7%45%
1659
16th to endNight
5%22222435%8%60%
1650
May1st to 15thNight
321221225%8%66%
1572
16th to endNight
21121346%8%66%
1368
June1st to 15thNight
211231335%6%68%
1320
16th to endNight
111112384%
1320
July1st to 15thNight
11125%84%
1336
16th to endNight
1111245%79%
1575
August1st to 15thNight
11124482%
1516
16th to endNight
11114384%
1750
September1st to 15thNight
123385%
1650
16th to endNight
211111245%77%
1790
October1st to 15thNight
421222345%7%64%
1980
16th to endNight
4212323346%64%
2112
November1st to 15thNight
7%3222145%5%9%56%
2202
16th to endNight
8%424424448%51%
2409
December1st to 15thNight
12%7%25%5%2435%7%43%
2520
16th to endNight
16%6%2442445%6%42%
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
38%410%20%16%8%
1534
16th to endDay
43%5%6%13%19%11%
1728
February1st to 15thDay
42%47%18%21%5%
1589
16th to endDay
45%47%24%14%2
1579
March1st to 15thDay
43%5%10%18%15%6%
1932
16th to endDay
42%6%11%18%16%4
2148
April1st to 15thDay
40%411%19%20%3
1974
16th to endDay
22%412%25%26%7%
1980
May1st to 15thDay
19%37%26%33%10%
2042
16th to endDay
22%411%26%25%8%
2395
June1st to 15thDay
18%48%21%24%21%
2310
16th to endDay
7%1315%32%39%
2310
July1st to 15thDay
5%227%26%56%
2144
16th to endDay
6%139%27%51%
2131
August1st to 15thDay
6%2111%29%49%
2096
16th to endDay
5%229%40%39%
2100
September1st to 15thDay
6%2212%33%43%
1980
16th to endDay
11%3322%34%24%
1837
October1st to 15thDay
20%27%22%25%20%
1650
16th to endDay
22%47%22%25%15%
1760
November1st to 15thDay
31%410%23%21%8%
1655
16th to endDay
35%48%20%27%4
1548
December1st to 15thDay
44%49%16%20%4
1440
16th to endDay
44%410%16%17%5%
1536
January1st to 15thNight
36%5%10%20%17%9%
2403
16th to endNight
39%49%12%17%16%
2496
February1st to 15thNight
39%5%7%20%19%7%
2275
16th to endNight
39%6%9%24%15%4
1895
March1st to 15thNight
41%410%19%15%8%
2025
16th to endNight
37%6%11%18%17%8%
2076
April1st to 15thNight
37%5%13%20%19%4
1659
16th to endNight
22%5%12%26%23%10%
1650
May1st to 15thNight
16%47%20%33%17%
1573
16th to endNight
16%6%10%23%30%11%
1368
June1st to 15thNight
16%48%18%21%29%
1320
16th to endNight
8%1312%26%48%
1320
July1st to 15thNight
5%216%17%65%
1255
16th to endNight
7%35%9%19%55%
1467
August1st to 15thNight
7%419%26%51%
1507
16th to endNight
5%319%34%45%
1750
September1st to 15thNight
6%328%27%52%
1650
16th to endNight
11%3218%32%30%
1790
October1st to 15thNight
21%38%20%24%21%
1980
16th to endNight
21%5%421%28%18%
2112
November1st to 15thNight
25%5%10%23%23%10%
2202
16th to endNight
32%47%21%24%9%
2409
December1st to 15thNight
41%48%16%20%8%
2520
16th to endNight
43%49%15%18%7%
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
19%17%23%30%7%1
162
16th to endDay
17%11%26%27%15%1
256
February1st to 15thDay
19%15%22%30%12%
239
16th to endDay
22%15%26%23%10%
238
March1st to 15thDay
16%20%25%21%12%2
270
16th to endDay
18%19%30%24%6%1
288
April1st to 15thDay
20%27%27%16%7%
211
16th to endDay
10%28%30%22%6%
210
May1st to 15thDay
11%16%38%25%7%
228
16th to endDay
6%15%31%32%11%2
266
June1st to 15thDay
7%14%34%34%7%1
255
16th to endDay
35%34%36%14%5%
255
July1st to 15thDay
126%49%19%3
245
16th to endDay
220%51%19%5%
271
August1st to 15thDay
1324%47%16%6%
255
16th to endDay
222%48%18%6%
268
September1st to 15thDay
321%45%23%6%
255
16th to endDay
5%7%20%41%20%4
255
October1st to 15thDay
6%11%29%33%16%2
255
16th to endDay
9%10%28%32%18%
272
November1st to 15thDay
11%6%20%25%29%6%
161
16th to endDay
8%14%28%26%20%1
78
December1st to 15thDay
21%15%33%23%6%
60
16th to endDay
20%10%15%34%15%3
64
January1st to 15thNight
13%5%10%30%27%12%
720
16th to endNight
16%6%10%29%25%11%
768
February1st to 15thNight
15%6%10%30%26%9%
704
16th to endNight
14%11%12%34%20%6%
632
March1st to 15thNight
14%10%13%27%28%6%
720
16th to endNight
11%9%17%32%24%4
768
April1st to 15thNight
8%12%19%33%20%5%
663
16th to endNight
6%8%21%29%25%8%
660
May1st to 15thNight
3317%38%27%8%
583
16th to endNight
2414%38%33%6%
343
June1st to 15thNight
2317%38%32%5%
330
16th to endNight
18%48%35%5%
330
July1st to 15thNight
333%50%11%
325
16th to endNight
1224%56%15%
522
August1st to 15thNight
432%50%11%
524
16th to endNight
5%30%52%10%
700
September1st to 15thNight
1426%51%14%
660
16th to endNight
27%30%42%16%
656
October1st to 15thNight
6%49%33%31%14%
660
16th to endNight
6%28%32%32%17%
704
November1st to 15thNight
8%412%29%32%12%
700
16th to endNight
10%49%33%31%10%
720
December1st to 15thNight
14%8%10%33%25%8%
720
16th to endNight
16%10%14%31%22%5%
768
Page generated at 2017-04-02 04:39:05. Version ac04

Copyright 2017 A. Danko


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