Del Oro Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Del Oro Observatory clear sky chart from 2005-11-05 to 2017-10-31.

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
61%
16034
30%
47386
21%
15994
69%
15994
45%
24936

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
58%
898
32%
2506
22%
895
66%
895
52%
1273
January16th to endNight
56%
780
35%
2508
25%
780
70%
780
49%
1185
February1st to 15thNight
52%
698
27%
2209
18%
698
62%
698
39%
1198
February16th to endNight
48%
632
37%
1894
20%
632
65%
632
49%
939
March1st to 15thNight
57%
720
30%
2121
20%
720
65%
720
49%
1081
March16th to endNight
54%
672
32%
2016
20%
672
66%
672
47%
1026
April1st to 15thNight
46%
539
26%
1798
16%
539
62%
539
41%
905
April16th to endNight
49%
540
25%
1800
20%
540
59%
540
35%
977
May1st to 15thNight
54%
540
24%
1684
20%
540
62%
540
34%
983
May16th to endNight
57%
562
21%
1498
14%
561
63%
561
39%
890
June1st to 15thNight
66%
540
24%
1440
18%
540
69%
540
48%
788
June16th to endNight
73%
540
24%
1440
19%
540
75%
540
45%
809
July1st to 15thNight
70%
510
18%
1360
15%
510
71%
510
34%
863
July16th to endNight
81%
564
22%
1473
20%
531
81%
531
37%
875
August1st to 15thNight
74%
539
16%
1710
18%
536
75%
536
31%
1015
August16th to endNight
79%
573
24%
1910
29%
573
79%
573
37%
1031
September1st to 15thNight
75%
540
28%
1800
30%
540
79%
540
37%
975
September16th to endNight
71%
537
38%
1944
37%
537
79%
537
48%
860
October1st to 15thNight
63%
687
32%
2127
21%
687
71%
687
47%
1047
October16th to endNight
70%
788
40%
2324
27%
788
77%
788
54%
1127
November1st to 15thNight
67%
875
37%
2275
23%
875
73%
875
63%
1122
November16th to endNight
63%
900
38%
2341
23%
900
70%
900
58%
1205
December1st to 15thNight
56%
900
29%
2520
16%
900
66%
900
50%
1314
December16th to endNight
52%
960
31%
2688
17%
960
62%
960
45%
1448

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
431332345%8%58%
48376
Night
441332345%7%59%
47564
Cloud CoverDay
431332446%8%57%
48374
Night
441332345%7%59%
47564
TransparencyDay
22%5%11%23%24%12%
48056
Night
23%411%24%24%11%
47386
SeeingDay
7%5%23%31%22%9%
5923
Night
6%223%43%21%2
16043

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
3322113248%66%
1432
16th to endDay
2323312346%65%
1727
February1st to 15thDay
25%24423337%59%
1651
16th to endDay
15%14424437%60%
1580
March1st to 15thDay
231331345%7%61%
1836
16th to endDay
5%5%1332335%9%56%
2208
April1st to 15thDay
5%42222345%9%57%
2150
16th to endDay
9%5%2233435%7%53%
2160
May1st to 15thDay
7%4144245%6%9%48%
2265
16th to endDay
6%2123245%7%9%53%
2614
June1st to 15thDay
5%2122246%7%10%53%
2520
16th to endDay
2123245%6%10%60%
2520
July1st to 15thDay
5%313435%5%7%10%50%
2520
16th to endDay
3213435%7%9%11%48%
2592
August1st to 15thDay
4213336%6%8%11%48%
2241
16th to endDay
42133245%7%10%56%
2292
September1st to 15thDay
5%31342345%9%56%
2160
16th to endDay
5%22223347%66%
2016
October1st to 15thDay
5%2222335%5%66%
1830
16th to endDay
431212235%71%
1886
November1st to 15thDay
2212213247%69%
1583
16th to endDay
2312212336%69%
1617
December1st to 15thDay
2314313447%61%
1440
16th to endDay
35%2331236%8%58%
1536
January1st to 15thNight
1414313336%65%
2506
16th to endNight
2313312335%66%
2508
February1st to 15thNight
46%25%413346%57%
2199
16th to endNight
25%23322345%64%
1894
March1st to 15thNight
45%22213446%62%
2121
16th to endNight
4423213346%63%
2016
April1st to 15thNight
5%5%1322345%6%59%
1798
16th to endNight
11%5%14323347%53%
1800
May1st to 15thNight
12%424214447%50%
1683
16th to endNight
8%3133245%5%8%53%
1497
June1st to 15thNight
411232446%8%60%
1440
16th to endNight
321332447%10%56%
1440
July1st to 15thNight
7%2135%46%6%8%9%45%
1440
16th to endNight
4213436%6%9%11%45%
1574
August1st to 15thNight
4315%5%26%7%8%7%48%
1719
16th to endNight
5%313326%5%6%10%49%
1910
September1st to 15thNight
7%21333446%9%52%
1800
16th to endNight
6%212322346%66%
1944
October1st to 15thNight
6%312212335%65%
2127
16th to endNight
4312212346%67%
2324
November1st to 15thNight
2213212346%69%
2275
16th to endNight
3413212335%69%
2341
December1st to 15thNight
1424423349%58%
2520
16th to endNight
36%2331335%8%58%
2688

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
3322112349%65%
1432
16th to endDay
2423212347%65%
1727
February1st to 15thDay
25%24433347%58%
1651
16th to endDay
1425%333446%60%
1580
March1st to 15thDay
231332346%6%61%
1836
16th to endDay
45%2332335%9%55%
2206
April1st to 15thDay
441322346%9%57%
2150
16th to endDay
8%5%2332445%7%52%
2160
May1st to 15thDay
7%4245%245%7%9%47%
2265
16th to endDay
5%2233245%7%10%52%
2614
June1st to 15thDay
42133247%7%10%53%
2520
16th to endDay
2123245%6%9%60%
2520
July1st to 15thDay
4313435%6%7%10%49%
2520
16th to endDay
2213435%7%9%12%47%
2592
August1st to 15thDay
3213435%6%8%11%47%
2241
16th to endDay
32133245%7%10%55%
2292
September1st to 15thDay
5%31341445%9%55%
2160
16th to endDay
5%212222346%65%
2016
October1st to 15thDay
431221335%6%66%
1830
16th to endDay
4312212335%70%
1886
November1st to 15thDay
2213212346%68%
1583
16th to endDay
1413212346%68%
1617
December1st to 15thDay
2314323448%60%
1440
16th to endDay
35%2331326%8%58%
1536
January1st to 15thNight
1423313336%64%
2506
16th to endNight
2314323335%66%
2508
February1st to 15thNight
36%25%41345%6%56%
2199
16th to endNight
25%23312345%64%
1894
March1st to 15thNight
45%22213436%61%
2121
16th to endNight
4413213336%63%
2016
April1st to 15thNight
5%5%12223447%59%
1798
16th to endNight
11%6%14313446%53%
1800
May1st to 15thNight
11%5%1332445%6%50%
1683
16th to endNight
7%31333445%8%54%
1497
June1st to 15thNight
31112245%6%8%61%
1440
16th to endNight
321332447%9%57%
1440
July1st to 15thNight
7%3135%45%6%8%8%45%
1440
16th to endNight
3213436%6%9%11%45%
1574
August1st to 15thNight
4315%5%35%6%8%9%46%
1719
16th to endNight
5%312426%5%6%10%49%
1910
September1st to 15thNight
6%313325%47%9%51%
1800
16th to endNight
6%212212346%65%
1944
October1st to 15thNight
6%312213345%65%
2127
16th to endNight
4312212347%66%
2324
November1st to 15thNight
1313212346%69%
2275
16th to endNight
25%13211335%69%
2341
December1st to 15thNight
142442245%10%57%
2520
16th to endNight
35%2332345%7%59%
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
17%39%32%29%8%
1433
16th to endDay
19%37%28%31%10%
1727
February1st to 15thDay
25%310%29%23%8%
1652
16th to endDay
24%37%24%29%11%
1580
March1st to 15thDay
20%49%24%27%13%
1836
16th to endDay
24%410%22%27%9%
2208
April1st to 15thDay
22%410%24%24%12%
2150
16th to endDay
29%5%10%24%21%9%
2160
May1st to 15thDay
31%6%13%20%21%6%
2265
16th to endDay
23%8%14%23%17%11%
2618
June1st to 15thDay
21%7%13%21%19%17%
2520
16th to endDay
16%5%10%21%26%19%
2520
July1st to 15thDay
24%9%14%19%20%12%
2371
16th to endDay
23%9%16%25%19%5%
2430
August1st to 15thDay
25%10%14%22%14%11%
2226
16th to endDay
21%7%13%22%26%9%
2292
September1st to 15thDay
23%5%12%23%22%13%
2160
16th to endDay
17%37%21%30%18%
2016
October1st to 15thDay
20%49%17%32%15%
1830
16th to endDay
17%26%24%31%18%
1886
November1st to 15thDay
15%38%24%30%18%
1583
16th to endDay
16%26%20%35%18%
1617
December1st to 15thDay
20%412%26%27%7%
1440
16th to endDay
23%411%30%22%6%
1536
January1st to 15thNight
20%29%29%28%8%
2506
16th to endNight
20%39%26%30%9%
2508
February1st to 15thNight
27%5%8%30%22%5%
2209
16th to endNight
22%17%26%30%11%
1894
March1st to 15thNight
22%29%24%30%9%
2121
16th to endNight
21%410%23%28%11%
2016
April1st to 15thNight
24%411%23%22%13%
1798
16th to endNight
31%313%22%20%9%
1800
May1st to 15thNight
32%5%12%21%19%8%
1684
16th to endNight
27%7%16%19%16%11%
1498
June1st to 15thNight
20%7%13%25%16%16%
1440
16th to endNight
21%9%11%18%19%19%
1440
July1st to 15thNight
33%8%14%19%16%7%
1360
16th to endNight
27%9%17%24%17%3
1473
August1st to 15thNight
29%10%16%21%12%9%
1710
16th to endNight
25%7%15%24%18%6%
1910
September1st to 15thNight
27%6%13%23%18%11%
1800
16th to endNight
19%38%22%30%15%
1944
October1st to 15thNight
21%310%17%31%14%
2127
16th to endNight
17%46%20%32%18%
2324
November1st to 15thNight
15%29%23%31%17%
2275
16th to endNight
19%16%23%32%16%
2341
December1st to 15thNight
22%312%30%24%6%
2520
16th to endNight
24%412%26%25%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
13%6%21%27%24%6%
90
16th to endDay
8%322%44%17%3
96
February1st to 15thDay
5%334%37%17%1
90
16th to endDay
38%29%35%22%
81
March1st to 15thDay
314%28%34%17%1
126
16th to endDay
10%15%34%28%8%2
288
April1st to 15thDay
7%16%39%21%10%4
269
16th to endDay
16%12%38%24%5%2
270
May1st to 15thDay
9%9%28%32%16%2
402
16th to endDay
10%5%23%33%20%6%
517
June1st to 15thDay
5%6%22%28%29%7%
495
16th to endDay
4420%29%29%12%
495
July1st to 15thDay
8%216%24%34%13%
475
16th to endDay
39%26%39%19%
451
August1st to 15thDay
6%119%34%22%16%
315
16th to endDay
6%218%34%26%12%
332
September1st to 15thDay
5%326%33%20%12%
315
16th to endDay
12%216%33%19%14%
171
October1st to 15thDay
6%120%37%20%14%
135
16th to endDay
6%18%29%31%13%
144
November1st to 15thDay
112%35%37%13%
90
16th to endDay
7%8%23%43%15%1
90
December1st to 15thDay
36%33%50%5%1
90
16th to endDay
7%34%48%7%2
96
January1st to 15thNight
4227%45%17%2
900
16th to endNight
5%32%44%15%1
780
February1st to 15thNight
5%130%49%12%
704
16th to endNight
5%436%44%8%
632
March1st to 15thNight
6%229%45%13%1
720
16th to endNight
6%330%47%11%
672
April1st to 15thNight
7%6%36%36%11%
539
16th to endNight
13%329%38%12%
540
May1st to 15thNight
12%324%42%15%
540
16th to endNight
8%225%40%21%1
563
June1st to 15thNight
4123%45%23%1
540
16th to endNight
417%43%33%
540
July1st to 15thNight
8%210%36%38%4
510
16th to endNight
46%31%50%6%
564
August1st to 15thNight
6%6%38%43%3
539
16th to endNight
6%25%37%43%4
573
September1st to 15thNight
7%9%42%33%6%
540
16th to endNight
7%213%41%29%4
537
October1st to 15thNight
8%121%41%22%4
687
16th to endNight
6%117%42%27%4
788
November1st to 15thNight
3221%50%20%2
875
16th to endNight
5%225%47%17%1
900
December1st to 15thNight
3130%52%10%1
900
16th to endNight
6%332%44%11%1
960
Page generated at 2017-11-01 15:23:34. Version ac04

Copyright 2017 A. Danko


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