Pedro-Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pedro-Observatory clear sky chart from 2005-11-05 to 2019-06-24.

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
28%
16839
14%
53992
7%
16807
37%
16807
18%
37725

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
17%
840
11%
2926
3%
836
26%
836
10%
2237
January16th to endNight
18%
896
12%
3136
4%
896
28%
896
12%
2297
February1st to 15thNight
18%
824
11%
2705
3%
821
29%
821
13%
2031
February16th to endNight
21%
735
14%
2213
6%
735
32%
735
16%
1593
March1st to 15thNight
19%
840
14%
2520
8%
840
27%
840
14%
1906
March16th to endNight
30%
896
20%
2327
8%
896
39%
896
24%
1602
April1st to 15thNight
23%
838
17%
2096
5%
838
30%
838
20%
1558
April16th to endNight
26%
720
16%
1966
5%
720
34%
720
20%
1393
May1st to 15thNight
26%
442
17%
1702
11%
442
38%
442
16%
1140
May16th to endNight
27%
439
13%
1753
10%
438
39%
438
16%
1137
June1st to 15thNight
29%
420
9%
1680
7%
420
40%
420
15%
1151
June16th to endNight
39%
406
8%
1625
10%
406
44%
406
18%
1045
July1st to 15thNight
48%
370
14%
1480
17%
370
56%
370
26%
821
July16th to endNight
52%
408
12%
1546
14%
386
57%
386
24%
906
August1st to 15thNight
51%
383
14%
1524
14%
381
57%
381
19%
958
August16th to endNight
51%
817
19%
2059
10%
817
55%
817
37%
1297
September1st to 15thNight
48%
780
16%
1950
8%
780
51%
780
32%
1309
September16th to endNight
46%
777
21%
2129
13%
777
52%
777
33%
1329
October1st to 15thNight
31%
780
18%
2307
9%
780
42%
780
22%
1565
October16th to endNight
23%
832
13%
2664
6%
832
33%
832
16%
1910
November1st to 15thNight
25%
820
18%
2668
9%
820
37%
820
16%
1860
November16th to endNight
21%
840
13%
2940
7%
840
30%
840
12%
2127
December1st to 15thNight
19%
840
12%
2940
4%
840
29%
840
12%
2186
December16th to endNight
16%
896
12%
3136
4%
896
26%
896
10%
2367

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
17%8%36%6%35%45%6%32%
54835
Night
17%8%36%5%34446%34%
54161
Cloud CoverDay
17%8%36%5%35%45%6%33%
54844
Night
17%9%36%5%34446%34%
54167
TransparencyDay
50%6%12%19%10%1
54522
Night
50%5%11%20%10%1
53992
SeeingDay
22%13%30%22%9%2
7708
Night
22%10%32%25%9%
16839

By Month

Percentage Cloud Cover NE (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
18%14%5%8%6%3445%424%
1672
16th to endDay
12%14%48%7%2445%428%
1792
February1st to 15thDay
13%13%5%9%8%36%446%25%
1816
16th to endDay
15%13%49%7%35%345%27%
1830
March1st to 15thDay
16%12%5%9%7%4434426%
2090
16th to endDay
15%8%35%5%34346%39%
2599
April1st to 15thDay
21%10%35%433445%32%
2512
16th to endDay
22%7%35%5%2344435%
2598
May1st to 15thDay
21%6%36%6%34446%31%
2920
16th to endDay
21%6%25%5%35%45%6%32%
3066
June1st to 15thDay
22%6%245%35%45%7%31%
2940
16th to endDay
18%6%35%5%46%6%6%6%29%
2842
July1st to 15thDay
12%4346%35%6%6%8%38%
2730
16th to endDay
12%5%25%5%36%6%7%8%35%
2878
August1st to 15thDay
12%6%26%7%46%7%6%7%30%
2673
16th to endDay
10%4246%35%5%6%8%44%
2484
September1st to 15thDay
16%5%245%245%5%8%39%
2340
16th to endDay
13%42442335%6%49%
2161
October1st to 15thDay
22%7%25%5%24446%33%
1981
16th to endDay
21%9%36%8%3435%6%27%
1911
November1st to 15thDay
17%8%35%6%35%46%7%31%
1848
16th to endDay
22%10%36%4245%46%29%
1680
December1st to 15thDay
21%13%5%7%6%2444425%
1680
16th to endDay
21%13%5%8%6%2444424%
1792
January1st to 15thNight
16%14%6%8%6%34445%24%
2926
16th to endNight
11%12%5%9%7%36%5%45%28%
3136
February1st to 15thNight
12%12%5%9%8%36%5%5%6%25%
2703
16th to endNight
15%10%48%6%35%445%32%
2213
March1st to 15thNight
17%11%5%7%5%35%5%45%28%
2507
16th to endNight
14%8%25%6%2434442%
2327
April1st to 15thNight
23%7%36%423345%33%
2096
16th to endNight
23%7%24424346%37%
1966
May1st to 15thNight
20%6%36%5%33445%36%
1702
16th to endNight
20%6%25%5%2445%6%38%
1751
June1st to 15thNight
22%7%26%32345%7%33%
1680
16th to endNight
17%425%5%25%447%38%
1625
July1st to 15thNight
8%434435%5%6%9%45%
1560
16th to endNight
10%434435%5%6%7%44%
1642
August1st to 15thNight
11%6%26%6%345%5%8%39%
1534
16th to endNight
11%42342435%7%49%
2059
September1st to 15thNight
13%3245%2445%7%43%
1950
16th to endNight
16%42322335%6%49%
2129
October1st to 15thNight
18%6%35%424446%39%
2307
16th to endNight
22%8%36%5%3345%6%32%
2664
November1st to 15thNight
20%8%25%433446%34%
2668
16th to endNight
21%11%47%5%23435%30%
2940
December1st to 15thNight
19%13%46%5%34345%27%
2940
16th to endNight
20%14%5%7%5%33335%25%
3136

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
19%12%48%6%35%345%24%
1672
16th to endDay
12%14%48%6%35%46%5%29%
1792
February1st to 15thDay
13%14%48%6%46%5%4425%
1816
16th to endDay
16%12%49%6%35%44428%
1830
March1st to 15thDay
17%12%47%8%45%345%26%
2100
16th to endDay
15%8%35%5%23445%39%
2598
April1st to 15thDay
20%9%36%5%3444432%
2512
16th to endDay
22%7%25%5%33445%35%
2598
May1st to 15thDay
21%6%35%6%34346%32%
2920
16th to endDay
20%5%25%435%45%7%32%
3066
June1st to 15thDay
21%6%25%5%35%45%8%31%
2940
16th to endDay
17%6%26%6%45%5%6%7%30%
2842
July1st to 15thDay
11%425%446%6%6%8%39%
2730
16th to endDay
12%5%25%5%35%6%7%9%35%
2878
August1st to 15thDay
12%6%27%7%46%6%6%8%32%
2673
16th to endDay
9%4145%35%5%6%8%45%
2484
September1st to 15thDay
15%5%245%245%5%7%41%
2340
16th to endDay
13%424423346%49%
2161
October1st to 15thDay
22%7%25%5%34446%34%
1981
16th to endDay
21%8%46%6%35%445%29%
1911
November1st to 15thDay
16%9%45%5%35%45%7%32%
1848
16th to endDay
22%8%35%6%24446%29%
1680
December1st to 15thDay
22%12%5%7%5%25%345%24%
1680
16th to endDay
22%13%5%6%6%34445%24%
1792
January1st to 15thNight
16%15%5%8%6%3445%5%23%
2926
16th to endNight
12%12%5%9%6%45%446%28%
3136
February1st to 15thNight
13%11%5%10%7%35%5%5%5%25%
2696
16th to endNight
16%10%47%5%35%35%5%31%
2213
March1st to 15thNight
18%11%5%7%5%34445%28%
2520
16th to endNight
15%8%35%5%3333442%
2327
April1st to 15thNight
23%7%45%5%33346%33%
2096
16th to endNight
23%6%24423345%37%
1966
May1st to 15thNight
20%6%36%5%34345%35%
1702
16th to endNight
20%6%15%424446%37%
1751
June1st to 15thNight
23%6%35%42445%6%33%
1680
16th to endNight
17%5%25%5%345%6%7%38%
1625
July1st to 15thNight
9%415%425%5%7%9%44%
1560
16th to endNight
10%435%425%5%6%9%43%
1642
August1st to 15thNight
11%426%6%25%45%8%39%
1534
16th to endNight
11%32442435%7%49%
2059
September1st to 15thNight
13%4245%3445%7%43%
1950
16th to endNight
16%414322346%49%
2129
October1st to 15thNight
18%5%35%5%24345%39%
2307
16th to endNight
22%8%36%5%23346%32%
2664
November1st to 15thNight
20%8%25%5%25%437%33%
2668
16th to endNight
21%12%36%5%24345%30%
2940
December1st to 15thNight
20%13%46%6%24446%27%
2940
16th to endNight
20%15%5%7%5%3433426%
3136

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
61%5%10%14%7%
1673
16th to endDay
55%6%10%17%8%1
1792
February1st to 15thDay
60%410%17%6%
1818
16th to endDay
58%310%16%8%1
1830
March1st to 15thDay
61%310%14%8%1
2100
16th to endDay
46%310%18%15%4
2599
April1st to 15thDay
54%48%18%11%2
2512
16th to endDay
50%5%7%18%13%3
2598
May1st to 15thDay
52%5%8%18%13%2
2920
16th to endDay
49%7%11%18%11%1
3070
June1st to 15thDay
51%6%10%17%11%2
2940
16th to endDay
50%8%10%18%9%1
2842
July1st to 15thDay
38%8%14%25%11%
2581
16th to endDay
42%9%16%21%8%
2711
August1st to 15thDay
48%9%16%19%6%
2659
16th to endDay
35%7%18%25%11%
2484
September1st to 15thDay
40%7%13%24%12%
2340
16th to endDay
36%415%30%11%
2161
October1st to 15thDay
50%6%11%21%9%
1981
16th to endDay
57%5%13%16%6%
1911
November1st to 15thDay
50%7%14%17%9%1
1848
16th to endDay
55%6%13%16%7%
1680
December1st to 15thDay
61%5%11%15%5%
1680
16th to endDay
63%49%12%9%
1792
January1st to 15thNight
61%6%9%15%6%
2926
16th to endNight
56%6%10%16%8%1
3136
February1st to 15thNight
58%5%11%17%6%
2705
16th to endNight
53%49%19%12%
2213
March1st to 15thNight
57%6%9%17%8%1
2520
16th to endNight
45%410%18%17%3
2327
April1st to 15thNight
52%46%20%14%1
2096
16th to endNight
49%48%18%15%3
1966
May1st to 15thNight
49%5%8%18%14%3
1702
16th to endNight
45%7%10%20%13%1
1753
June1st to 15thNight
50%6%10%18%12%
1680
16th to endNight
44%7%11%20%14%1
1625
July1st to 15thNight
32%7%15%27%15%
1480
16th to endNight
35%8%18%24%12%
1546
August1st to 15thNight
41%9%17%22%9%
1524
16th to endNight
32%6%17%29%13%
2059
September1st to 15thNight
38%6%14%25%13%1
1950
16th to endNight
35%5%14%31%12%
2129
October1st to 15thNight
45%5%11%24%11%
2307
16th to endNight
52%6%13%19%8%
2664
November1st to 15thNight
50%5%12%20%8%2
2668
16th to endNight
57%411%18%7%
2940
December1st to 15thNight
58%413%17%5%
2940
16th to endNight
61%410%14%8%
3136

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%22%29%24%5%
120
16th to endDay
25%21%37%12%2
128
February1st to 15thDay
29%27%37%5%
172
16th to endDay
25%16%32%21%3
333
March1st to 15thDay
25%18%30%20%4
390
16th to endDay
22%15%31%18%9%2
416
April1st to 15thDay
26%18%33%13%7%1
390
16th to endDay
26%17%28%18%7%1
379
May1st to 15thDay
27%14%31%18%5%1
408
16th to endDay
22%16%34%18%6%
459
June1st to 15thDay
24%14%30%22%7%
435
16th to endDay
23%9%30%27%7%1
407
July1st to 15thDay
12%8%34%27%13%3
365
16th to endDay
17%425%35%15%2
390
August1st to 15thDay
14%5%25%33%17%2
358
16th to endDay
13%5%23%30%16%10%
396
September1st to 15thDay
17%5%28%25%17%7%
375
16th to endDay
16%11%23%26%14%7%
374
October1st to 15thDay
26%11%29%19%11%1
375
16th to endDay
27%16%30%20%5%
348
November1st to 15thDay
24%18%29%18%9%
322
16th to endDay
31%17%26%19%4
120
December1st to 15thDay
24%15%33%23%4
120
16th to endDay
27%22%33%11%4
128
January1st to 15thNight
23%15%34%22%5%
840
16th to endNight
17%14%40%21%5%
896
February1st to 15thNight
18%11%42%22%4
824
16th to endNight
21%12%37%24%4
735
March1st to 15thNight
24%13%36%21%4
840
16th to endNight
18%11%34%27%8%
896
April1st to 15thNight
26%12%32%24%4
838
16th to endNight
28%11%30%21%6%
720
May1st to 15thNight
22%9%35%24%7%1
442
16th to endNight
23%7%37%24%7%
439
June1st to 15thNight
28%6%30%25%9%
420
16th to endNight
20%330%30%13%
406
July1st to 15thNight
9%433%33%17%
370
16th to endNight
12%225%41%15%1
408
August1st to 15thNight
15%321%37%20%1
383
16th to endNight
14%326%32%20%2
817
September1st to 15thNight
16%425%36%14%1
780
16th to endNight
19%6%25%26%19%2
777
October1st to 15thNight
21%7%32%26%10%1
780
16th to endNight
28%10%31%22%6%
832
November1st to 15thNight
25%11%31%22%8%
820
16th to endNight
27%12%30%18%8%1
840
December1st to 15thNight
27%12%33%21%5%
840
16th to endNight
29%13%32%20%4
896
Page generated at 2019-06-24 20:41:28. Version ac04

Copyright 2019 A. Danko


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