Pedro-Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pedro-Observatory clear sky chart from 2005-11-06 to 2024-01-14.

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%
22515
14%
74728
7%
22474
37%
22474
17%
52126

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 10thNight
16%
760
10%
2649
3%
757
25%
757
9%
2055
January11th to 20thNight
17%
736
11%
2574
4%
736
26%
736
11%
1949
January21st to endNight
21%
792
14%
2772
7%
792
31%
792
15%
1949
February1st to 10thNight
15%
720
12%
2376
3%
720
27%
720
13%
1769
February11th to 20thNight
18%
703
14%
2196
4%
700
31%
700
15%
1574
February21st to endNight
20%
592
17%
1776
7%
592
32%
592
15%
1285
March1st to 10thNight
20%
720
16%
2160
9%
720
30%
720
15%
1591
March11th to 20thNight
22%
720
15%
2082
6%
720
32%
720
16%
1510
March21st to endNight
25%
792
21%
1990
6%
792
35%
792
22%
1425
April1st to 10thNight
23%
720
16%
1800
4%
720
30%
720
20%
1351
April11th to 20thNight
26%
711
17%
1775
4%
711
33%
711
23%
1265
April21st to endNight
23%
578
18%
1658
6%
578
33%
578
19%
1164
May1st to 10thNight
26%
389
15%
1469
10%
389
37%
389
16%
976
May11th to 20thNight
29%
354
19%
1416
15%
354
45%
354
17%
898
May21st to endNight
28%
389
13%
1551
9%
388
40%
388
18%
977
June1st to 10thNight
30%
360
9%
1440
7%
360
41%
360
17%
961
June11th to 20thNight
36%
360
10%
1440
11%
360
44%
360
19%
914
June21st to endNight
40%
360
10%
1440
12%
360
46%
360
17%
945
July1st to 10thNight
44%
350
13%
1400
14%
350
55%
350
24%
804
July11th to 20thNight
49%
348
13%
1392
18%
348
54%
348
23%
824
July21st to endNight
48%
394
13%
1486
14%
372
54%
372
23%
868
August1st to 10thNight
54%
358
16%
1422
15%
356
60%
356
22%
850
August11th to 20thNight
51%
519
17%
1583
11%
519
57%
519
29%
1004
August21st to endNight
45%
792
18%
1980
8%
792
49%
792
32%
1309
September1st to 10thNight
48%
720
15%
1800
6%
720
51%
720
34%
1190
September11th to 20thNight
48%
720
20%
1866
10%
720
53%
720
35%
1185
September21st to endNight
44%
720
23%
1980
14%
720
50%
720
30%
1273
October1st to 10thNight
34%
720
20%
2114
11%
720
44%
720
22%
1428
October11th to 20thNight
27%
720
16%
2193
7%
720
38%
720
20%
1527
October21st to endNight
22%
792
12%
2574
6%
792
32%
792
16%
1848
November1st to 10thNight
25%
740
16%
2407
8%
740
37%
740
16%
1670
November11th to 20thNight
23%
760
18%
2567
10%
760
34%
760
16%
1769
November21st to endNight
18%
760
13%
2660
5%
760
28%
760
12%
1923
December1st to 10thNight
17%
760
10%
2660
3%
760
25%
760
10%
2051
December11th to 20thNight
17%
760
13%
3245
5%
759
28%
759
9%
2383
December21st to endNight
13%
826
8%
4835
3%
817
23%
817
6%
3662

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%9%36%6%35%5%5%7%33%
74765
Night
17%9%47%6%35%45%6%34%
74992
TransparencyDay
50%7%12%19%11%1
74470
Night
50%6%12%20%11%1
74821
SeeingDay
21%16%32%21%8%2
13427
Night
21%11%33%26%8%1
22525

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 10thDay
15%16%6%10%8%4445%424%
1517
11th to 20thDay
17%16%5%9%6%24445%29%
1464
21st to endDay
11%14%49%8%36%6%6%5%30%
1584
February1st to 10thDay
14%15%5%9%8%45%446%26%
1583
11th to 20thDay
12%13%5%10%7%45%5%47%27%
1650
21st to endDay
17%14%5%10%8%35%44427%
1480
March1st to 10thDay
15%12%5%9%8%45%45%430%
1797
11th to 20thDay
15%11%5%7%6%45%45%6%33%
1876
21st to endDay
18%9%47%6%3445%6%35%
2365
April1st to 10thDay
21%11%46%5%35%445%32%
2160
11th to 20thDay
21%7%35%5%3445%6%36%
2134
21st to endDay
21%10%47%6%3445%5%32%
2300
May1st to 10thDay
20%7%37%7%35%5%5%7%33%
2506
11th to 20thDay
20%7%35%5%3445%8%35%
2478
21st to endDay
18%6%36%5%46%5%5%7%35%
2725
June1st to 10thDay
22%7%35%7%45%5%6%7%30%
2520
11th to 20thDay
15%6%36%5%46%6%7%7%36%
2520
21st to endDay
19%8%46%6%5%6%6%6%6%29%
2520
July1st to 10thDay
12%435%7%46%6%6%8%39%
2520
11th to 20thDay
13%5%35%6%47%6%7%10%34%
2520
21st to endDay
12%6%36%6%46%6%7%9%37%
2744
August1st to 10thDay
12%6%26%7%5%6%7%6%8%35%
2506
11th to 20thDay
10%6%36%6%47%6%7%9%37%
2296
21st to endDay
13%425%6%3446%7%43%
2376
September1st to 10thDay
14%5%245%345%6%9%41%
2160
11th to 20thDay
14%425%42446%7%48%
2093
21st to endDay
17%7%25%5%3446%6%42%
1980
October1st to 10thDay
21%7%25%5%3445%7%36%
1844
11th to 20thDay
20%8%37%8%45%5%5%6%28%
1765
21st to endDay
24%10%46%7%3445%5%30%
1782
November1st to 10thDay
15%8%45%6%46%5%5%8%35%
1671
11th to 20thDay
18%10%47%7%45%5%5%7%30%
1611
21st to endDay
20%12%37%6%45%6%5%7%26%
1520
December1st to 10thDay
22%14%5%9%8%35%44423%
1520
11th to 20thDay
19%15%5%8%5%34445%28%
1906
21st to endDay
26%16%5%9%5%3343422%
2772
January1st to 10thNight
15%15%6%10%8%35%5%5%5%23%
2649
11th to 20thNight
15%15%6%10%6%35%345%27%
2574
21st to endNight
10%11%5%9%8%45%5%46%33%
2772
February1st to 10thNight
12%12%5%10%9%36%5%5%6%26%
2376
11th to 20thNight
13%10%5%8%7%36%5%5%6%32%
2194
21st to endNight
15%12%49%7%35%445%33%
1776
March1st to 10thNight
16%11%6%9%6%35%5%46%31%
2150
11th to 20thNight
15%13%46%6%35%45%6%32%
2082
21st to endNight
16%8%27%7%35%44441%
1990
April1st to 10thNight
23%8%37%6%3445%6%32%
1800
11th to 20thNight
19%6%36%6%3445%6%38%
1775
21st to endNight
21%8%45%435%45%6%35%
1658
May1st to 10thNight
21%7%36%6%34446%36%
1469
11th to 20thNight
19%7%36%4245%6%5%40%
1415
21st to endNight
17%6%25%6%25%45%6%41%
1550
June1st to 10thNight
21%6%36%5%345%6%8%33%
1440
11th to 20thNight
17%8%26%4345%5%7%39%
1440
21st to endNight
18%6%26%5%35%5%5%7%37%
1440
July1st to 10thNight
9%5%35%5%35%6%7%8%45%
1440
11th to 20thNight
11%6%35%5%45%6%6%9%41%
1440
21st to endNight
11%445%5%35%5%6%8%43%
1574
August1st to 10thNight
11%6%26%5%35%5%6%9%43%
1432
11th to 20thNight
11%6%36%435%5%5%7%45%
1583
21st to endNight
14%4245%3446%8%45%
1980
September1st to 10thNight
11%435%5%35%5%6%7%46%
1800
11th to 20thNight
14%5%24424448%49%
1866
21st to endNight
17%5%2443346%6%47%
1980
October1st to 10thNight
18%7%35%5%34445%41%
2114
11th to 20thNight
20%7%46%5%35%45%6%36%
2193
21st to endNight
22%8%37%6%3445%6%31%
2574
November1st to 10thNight
18%9%36%6%4445%8%34%
2407
11th to 20thNight
18%8%47%6%35%5%5%6%35%
2567
21st to endNight
20%12%47%6%33446%30%
2660
December1st to 10thNight
19%13%6%8%6%45%45%6%23%
2660
11th to 20thNight
22%13%5%7%6%35%435%28%
3288
21st to endNight
25%17%5%8%5%2334423%
4884

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 10thDay
62%5%10%16%7%
1518
11th to 20thDay
58%5%11%14%11%1
1464
21st to endDay
53%7%10%18%11%1
1584
February1st to 10thDay
60%5%8%17%8%2
1583
11th to 20thDay
57%5%13%15%10%1
1659
21st to endDay
61%48%16%9%3
1480
March1st to 10thDay
57%410%16%11%2
1800
11th to 20thDay
52%412%15%13%3
1876
21st to endDay
50%5%10%18%13%4
2365
April1st to 10thDay
55%5%9%18%11%3
2160
11th to 20thDay
47%5%9%22%13%2
2134
21st to endDay
54%6%8%17%12%4
2300
May1st to 10thDay
50%6%8%20%13%3
2506
11th to 20thDay
47%6%10%18%16%3
2482
21st to endDay
46%8%12%18%14%2
2725
June1st to 10thDay
51%7%11%18%11%2
2520
11th to 20thDay
44%9%11%21%12%3
2520
21st to endDay
53%8%12%16%9%1
2520
July1st to 10thDay
39%9%14%26%11%1
2450
11th to 20thDay
41%10%15%24%10%
2445
21st to endDay
41%10%17%23%9%
2591
August1st to 10thDay
43%9%17%22%8%
2492
11th to 20thDay
40%10%18%23%9%
2296
21st to endDay
38%7%16%24%13%1
2376
September1st to 10thDay
37%8%16%26%13%
2160
11th to 20thDay
35%6%14%30%13%1
2093
21st to endDay
42%6%15%26%11%
1980
October1st to 10thDay
47%6%13%22%12%1
1844
11th to 20thDay
55%7%13%19%6%
1765
21st to endDay
56%5%13%16%8%1
1782
November1st to 10thDay
47%8%15%20%10%1
1671
11th to 20thDay
52%7%13%17%10%1
1611
21st to endDay
56%8%16%14%6%1
1520
December1st to 10thDay
65%6%10%13%5%
1520
11th to 20thDay
59%5%11%17%8%
1906
21st to endDay
66%6%10%13%6%
2772
January1st to 10thNight
62%7%9%16%6%1
2649
11th to 20thNight
60%6%11%14%8%2
2574
21st to endNight
52%6%10%17%13%2
2772
February1st to 10thNight
58%5%11%18%8%1
2376
11th to 20thNight
53%6%11%20%10%1
2196
21st to endNight
54%5%9%17%14%1
1776
March1st to 10thNight
55%6%8%18%10%2
2160
11th to 20thNight
52%6%10%16%13%3
2083
21st to endNight
48%5%8%20%14%4
1990
April1st to 10thNight
52%5%8%19%14%2
1800
11th to 20thNight
47%5%9%22%15%2
1775
21st to endNight
50%5%8%20%14%4
1658
May1st to 10thNight
49%5%8%18%14%5%
1469
11th to 20thNight
44%7%9%19%17%4
1416
21st to endNight
42%8%11%20%16%3
1551
June1st to 10thNight
48%7%12%21%12%1
1440
11th to 20thNight
44%7%11%21%14%3
1440
21st to endNight
46%8%12%20%13%
1440
July1st to 10thNight
34%9%16%26%15%1
1400
11th to 20thNight
38%7%16%29%10%
1392
21st to endNight
36%8%19%24%12%
1486
August1st to 10thNight
37%9%18%25%11%
1422
11th to 20thNight
37%7%19%25%12%
1583
21st to endNight
36%8%16%27%12%
1980
September1st to 10thNight
35%8%16%25%15%1
1800
11th to 20thNight
35%6%14%32%12%1
1866
21st to endNight
38%6%13%29%14%
1980
October1st to 10thNight
46%6%10%24%14%1
2114
11th to 20thNight
48%6%14%23%8%
2193
21st to endNight
53%6%13%18%9%1
2574
November1st to 10thNight
49%7%13%21%8%1
2407
11th to 20thNight
50%6%14%19%10%2
2567
21st to endNight
56%5%12%18%8%1
2660
December1st to 10thNight
62%6%12%15%5%
2660
11th to 20thNight
58%5%10%19%7%1
3288
21st to endNight
65%5%9%16%6%
4884

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 10thDay
17%21%36%22%4
180
11th to 20thDay
25%16%38%15%5%1
166
21st to endDay
18%19%38%20%5%1
176
February1st to 10thDay
29%27%37%5%1
224
11th to 20thDay
21%23%41%13%2
317
21st to endDay
28%20%32%18%2
346
March1st to 10thDay
25%18%35%19%4
420
11th to 20thDay
23%22%34%17%41
420
21st to endDay
28%18%29%16%7%1
462
April1st to 10thDay
26%16%33%17%6%1
420
11th to 20thDay
29%20%25%17%8%1
412
21st to endDay
26%20%31%16%5%1
420
May1st to 10thDay
24%17%36%17%5%1
423
11th to 20thDay
22%16%34%21%6%1
447
21st to endDay
19%20%33%21%6%1
485
June1st to 10thDay
24%16%32%20%7%1
450
11th to 20thDay
18%16%30%24%10%2
450
21st to endDay
24%11%29%24%9%2
450
July1st to 10thDay
12%10%33%28%13%3
445
11th to 20thDay
15%9%33%29%12%2
444
21st to endDay
14%8%32%31%13%2
488
August1st to 10thDay
13%10%27%33%15%2
446
11th to 20thDay
12%6%28%32%15%8%
439
21st to endDay
16%12%27%25%14%6%
495
September1st to 10thDay
16%6%36%23%13%6%
450
11th to 20thDay
13%11%28%27%15%6%
450
21st to endDay
20%12%26%24%12%5%
450
October1st to 10thDay
25%15%28%19%12%1
450
11th to 20thDay
22%16%33%21%8%1
432
21st to endDay
29%16%31%19%5%
396
November1st to 10thDay
24%20%30%20%6%1
365
11th to 20thDay
23%20%33%17%6%
271
21st to endDay
26%21%32%17%41
180
December1st to 10thDay
26%18%28%22%6%1
180
11th to 20thDay
24%23%37%13%11
180
21st to endDay
31%24%26%12%6%1
198
January1st to 10thNight
23%14%34%23%5%
760
11th to 20thNight
22%15%35%23%4
736
21st to endNight
15%13%42%24%6%1
792
February1st to 10thNight
19%13%43%22%41
720
11th to 20thNight
20%14%42%20%5%
703
21st to endNight
22%13%35%26%3
592
March1st to 10thNight
22%16%35%24%4
720
11th to 20thNight
23%16%35%20%6%
720
21st to endNight
20%12%36%26%6%
792
April1st to 10thNight
26%13%33%23%5%
720
11th to 20thNight
23%13%34%25%5%1
711
21st to endNight
27%12%32%21%7%
578
May1st to 10thNight
22%12%34%25%6%2
389
11th to 20thNight
23%10%31%29%7%
354
21st to endNight
20%7%40%25%8%
389
June1st to 10thNight
24%8%33%26%8%
360
11th to 20thNight
22%5%32%29%12%
360
21st to endNight
21%7%27%31%14%1
360
July1st to 10thNight
10%6%36%33%14%1
350
11th to 20thNight
11%427%43%14%
348
21st to endNight
13%427%42%13%2
394
August1st to 10thNight
15%420%43%17%1
358
11th to 20thNight
13%426%32%23%2
519
21st to endNight
15%5%28%32%18%2
792
September1st to 10thNight
13%6%28%38%13%1
720
11th to 20thNight
16%6%26%33%18%2
720
21st to endNight
19%8%26%30%15%2
720
October1st to 10thNight
21%10%29%29%10%1
720
11th to 20thNight
23%9%33%26%8%1
720
21st to endNight
27%11%33%24%5%
792
November1st to 10thNight
22%13%33%24%7%1
740
11th to 20thNight
23%13%34%21%9%1
760
21st to endNight
27%15%32%19%6%1
760
December1st to 10thNight
26%13%35%20%6%
760
11th to 20thNight
27%16%32%21%41
760
21st to endNight
32%15%32%17%4
836
Page generated at 2024-01-11 13:32:00. Version ac07

Copyright 2024 Attilla Danko


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