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 2017-04-01.

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
61%
15371
30%
45365
21%
15331
69%
15331
45%
23802

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
57%
898
32%
2506
22%
895
66%
895
52%
1273
January16th to endNight
56%
780
35%
2508
25%
780
69%
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
56%
720
30%
2121
20%
720
64%
720
49%
1081
March16th to endNight
54%
672
32%
2016
20%
672
65%
672
47%
1026
April1st to 15thNight
44%
497
27%
1658
16%
497
62%
497
40%
836
April16th to endNight
49%
495
24%
1650
19%
495
60%
495
36%
880
May1st to 15thNight
52%
495
24%
1544
20%
495
60%
495
33%
905
May16th to endNight
59%
514
21%
1370
14%
513
65%
513
41%
799
June1st to 15thNight
64%
495
25%
1320
19%
495
67%
495
46%
731
June16th to endNight
74%
495
22%
1320
18%
495
76%
495
45%
743
July1st to 15thNight
69%
465
18%
1240
15%
465
71%
465
34%
794
July16th to endNight
80%
522
21%
1356
20%
489
81%
489
38%
798
August1st to 15thNight
75%
494
17%
1567
19%
491
76%
491
32%
925
August16th to endNight
78%
525
23%
1750
27%
525
79%
525
37%
947
September1st to 15thNight
73%
495
29%
1650
31%
495
78%
495
37%
898
September16th to endNight
75%
492
38%
1782
38%
492
82%
492
51%
754
October1st to 15thNight
63%
630
33%
1950
22%
630
71%
630
47%
967
October16th to endNight
70%
722
38%
2130
26%
722
77%
722
54%
1034
November1st to 15thNight
68%
875
37%
2275
23%
875
74%
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
51%
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%
45752
Night
441332345%7%59%
45543
Cloud CoverDay
331332445%8%58%
45750
Night
441332345%7%59%
45543
TransparencyDay
22%5%11%23%25%12%
45432
Night
23%411%24%25%11%
45365
SeeingDay
7%6%24%31%22%7%
5041
Night
6%223%43%21%2
15380

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%
1975
16th to endDay
9%5%2232435%7%54%
1980
May1st to 15thDay
8%4144245%6%9%48%
2075
16th to endDay
6%2123245%7%9%53%
2390
June1st to 15thDay
5%2122246%7%10%52%
2310
16th to endDay
1123245%6%10%60%
2310
July1st to 15thDay
5%313435%5%7%10%49%
2310
16th to endDay
32134247%9%11%49%
2402
August1st to 15thDay
4113335%6%9%10%49%
2054
16th to endDay
42133245%6%10%56%
2100
September1st to 15thDay
5%31342345%9%56%
1980
16th to endDay
312223347%69%
1848
October1st to 15thDay
5%2222335%6%66%
1678
16th to endDay
5%31211235%71%
1730
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%1322335%7%59%
1658
16th to endNight
10%5%1332335%7%54%
1650
May1st to 15thNight
13%5%24214447%50%
1543
16th to endNight
8%31332445%8%55%
1369
June1st to 15thNight
411232446%7%60%
1320
16th to endNight
22133245%8%10%56%
1320
July1st to 15thNight
7%2135%46%6%8%9%43%
1320
16th to endNight
3213437%5%9%12%46%
1457
August1st to 15thNight
3315%5%36%7%7%7%48%
1576
16th to endNight
6%313326%5%6%10%49%
1750
September1st to 15thNight
7%31333446%9%52%
1650
16th to endNight
3112322346%68%
1782
October1st to 15thNight
6%313212336%64%
1950
16th to endNight
4312212346%67%
2130
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
45%1322346%9%56%
1975
16th to endDay
8%5%2332435%7%53%
1980
May1st to 15thDay
7%4245%245%6%9%46%
2075
16th to endDay
5%2233245%7%10%52%
2390
June1st to 15thDay
4213325%7%7%10%52%
2310
16th to endDay
1123245%6%9%61%
2310
July1st to 15thDay
4312435%6%7%11%49%
2310
16th to endDay
3213435%7%9%12%47%
2402
August1st to 15thDay
3113435%6%8%11%48%
2054
16th to endDay
32133245%6%10%56%
2100
September1st to 15thDay
5%31341445%9%55%
1980
16th to endDay
212222346%69%
1848
October1st to 15thDay
431221335%6%66%
1678
16th to endDay
4312212325%70%
1730
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%13223447%58%
1658
16th to endNight
10%6%14313446%54%
1650
May1st to 15thNight
12%6%23224446%50%
1543
16th to endNight
7%31323445%8%55%
1369
June1st to 15thNight
41113245%5%7%60%
1320
16th to endNight
2213325%48%9%57%
1320
July1st to 15thNight
7%2135%46%7%8%8%43%
1320
16th to endNight
3213436%5%9%12%46%
1457
August1st to 15thNight
3315%5%36%6%7%9%47%
1576
16th to endNight
5%312426%5%6%10%49%
1750
September1st to 15thNight
6%31332447%9%51%
1650
16th to endNight
3212213346%68%
1782
October1st to 15thNight
5%412213346%64%
1950
16th to endNight
4312212346%66%
2130
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
23%411%24%24%12%
1975
16th to endDay
28%410%24%21%10%
1980
May1st to 15thDay
32%6%13%19%21%6%
2075
16th to endDay
23%9%14%23%16%12%
2394
June1st to 15thDay
22%7%12%21%19%15%
2310
16th to endDay
15%5%10%21%26%20%
2310
July1st to 15thDay
25%9%14%19%18%12%
2161
16th to endDay
23%9%15%25%20%5%
2240
August1st to 15thDay
25%10%15%22%14%12%
2039
16th to endDay
21%7%13%22%25%9%
2100
September1st to 15thDay
23%5%12%21%22%13%
1980
16th to endDay
13%38%22%32%19%
1848
October1st to 15thDay
19%410%17%33%14%
1678
16th to endDay
16%26%24%32%17%
1730
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%
1658
16th to endNight
30%313%22%21%9%
1650
May1st to 15thNight
33%5%12%20%19%8%
1544
16th to endNight
26%7%16%20%17%11%
1370
June1st to 15thNight
21%7%12%25%16%15%
1320
16th to endNight
20%9%12%18%19%19%
1320
July1st to 15thNight
34%8%15%18%14%8%
1240
16th to endNight
26%9%17%24%17%3
1356
August1st to 15thNight
29%11%16%21%12%9%
1567
16th to endNight
25%8%16%25%17%7%
1750
September1st to 15thNight
28%5%13%22%18%11%
1650
16th to endNight
16%38%23%31%15%
1782
October1st to 15thNight
22%310%17%31%13%
1950
16th to endNight
17%46%20%32%17%
2130
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%18%43%18%8%3
211
16th to endDay
17%13%40%22%41
210
May1st to 15thDay
10%10%30%30%15%1
332
16th to endDay
10%5%23%33%21%5%
437
June1st to 15thDay
5%7%24%26%28%7%
420
16th to endDay
4320%28%30%12%
420
July1st to 15thDay
9%318%25%34%10%
400
16th to endDay
411%28%40%14%
387
August1st to 15thDay
5%121%34%20%16%
255
16th to endDay
5%320%34%26%9%
268
September1st to 15thDay
4330%36%20%4
255
16th to endDay
2117%35%24%18%
123
October1st to 15thDay
1122%35%23%16%
90
16th to endDay
7%14%29%35%13%
96
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
8%6%37%36%11%
497
16th to endNight
12%430%38%13%
495
May1st to 15thNight
13%325%42%15%
495
16th to endNight
7%224%41%21%2
515
June1st to 15thNight
4124%46%22%1
495
16th to endNight
4116%43%34%1
495
July1st to 15thNight
7%211%37%38%2
465
16th to endNight
46%33%50%5%
522
August1st to 15thNight
5%16%38%44%4
494
16th to endNight
6%2437%43%4
525
September1st to 15thNight
8%9%44%32%4
495
16th to endNight
4213%42%31%5%
492
October1st to 15thNight
8%120%40%23%4
630
16th to endNight
6%117%43%26%4
722
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 2017-04-02 05:39:08. Version ac04

Copyright 2017 A. Danko


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