Pictor Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pictor 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
36%
15104
14%
47125
10%
15066
41%
15066
19%
33033

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
14%
717
9%
2387
5%
716
21%
716
8%
1925
January16th to endNight
15%
768
8%
2496
3%
768
21%
768
8%
2013
February1st to 15thNight
16%
702
7%
2287
2%
701
22%
701
9%
1818
February16th to endNight
23%
631
10%
1966
4%
631
30%
631
12%
1494
March1st to 15thNight
24%
720
13%
2004
7%
720
30%
720
16%
1513
March16th to endNight
33%
768
19%
2112
11%
768
39%
768
22%
1474
April1st to 15thNight
28%
694
15%
1838
8%
694
34%
694
21%
1335
April16th to endNight
39%
540
20%
1620
9%
540
47%
540
25%
1044
May1st to 15thNight
41%
540
16%
1620
10%
540
47%
540
24%
1081
May16th to endNight
48%
411
17%
1534
16%
411
57%
411
26%
889
June1st to 15thNight
49%
360
13%
1423
14%
360
55%
360
23%
821
June16th to endNight
52%
360
16%
1260
16%
360
59%
360
27%
737
July1st to 15thNight
62%
366
18%
1271
22%
366
66%
366
35%
675
July16th to endNight
64%
564
15%
1595
14%
531
66%
531
34%
947
August1st to 15thNight
68%
539
18%
1609
15%
536
70%
536
34%
959
August16th to endNight
62%
591
24%
1737
16%
591
67%
591
37%
1014
September1st to 15thNight
55%
720
21%
1875
13%
720
59%
720
33%
1203
September16th to endNight
59%
717
23%
1980
18%
717
62%
717
33%
1242
October1st to 15thNight
44%
720
17%
2145
15%
720
48%
720
24%
1427
October16th to endNight
26%
768
15%
2310
10%
768
35%
768
16%
1700
November1st to 15thNight
36%
700
18%
2328
17%
700
42%
700
21%
1527
November16th to endNight
23%
720
10%
2520
7%
720
29%
720
11%
1898
December1st to 15thNight
14%
720
5%
2520
2%
720
19%
720
7%
2053
December16th to endNight
13%
768
6%
2688
2%
768
17%
768
6%
2244

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
15%9%47%6%35%45%7%30%
48617
Night
15%9%46%5%3445%7%33%
47305
Cloud CoverDay
15%9%47%6%35%45%7%30%
48627
Night
15%8%46%5%3445%7%33%
47309
TransparencyDay
51%7%12%18%9%
48315
Night
49%6%12%19%10%1
47125
SeeingDay
18%7%26%24%15%7%
5785
Night
19%9%28%28%12%1
15110

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%15%6%10%8%5%5%5%45%15%
1549
16th to endDay
14%18%7%12%9%45%335%14%
1728
February1st to 15thDay
15%17%7%10%7%45%436%17%
1575
16th to endDay
16%14%6%10%7%45%5%46%17%
1506
March1st to 15thDay
17%12%5%9%6%35%45%5%23%
1945
16th to endDay
16%10%5%8%5%3445%6%29%
2112
April1st to 15thDay
19%10%5%6%6%2445%6%27%
2121
16th to endDay
17%9%35%433347%37%
2340
May1st to 15thDay
18%6%35%6%3345%7%34%
2331
16th to endDay
12%6%35%5%345%6%7%38%
2581
June1st to 15thDay
13%6%26%435%46%8%38%
2532
16th to endDay
12%434436%6%6%9%37%
2700
July1st to 15thDay
9%425%5%35%5%6%10%41%
2607
16th to endDay
9%5%25%6%46%5%5%10%37%
2465
August1st to 15thDay
9%6%25%6%5%6%6%7%8%36%
2340
16th to endDay
12%6%25%5%35%5%5%9%37%
2453
September1st to 15thDay
13%5%37%6%345%6%7%36%
2082
16th to endDay
14%5%15%5%3446%8%39%
1980
October1st to 15thDay
20%6%35%7%3445%6%33%
1815
16th to endDay
24%9%47%6%35%45%5%23%
1911
November1st to 15thDay
15%9%36%5%35%447%34%
1528
16th to endDay
20%13%5%8%6%3445%7%20%
1440
December1st to 15thDay
18%16%7%11%6%33446%16%
1440
16th to endDay
21%18%8%11%8%3445%49%
1536
January1st to 15thNight
21%13%6%9%6%35%445%19%
2387
16th to endNight
14%15%8%11%8%34445%17%
2496
February1st to 15thNight
15%14%6%10%7%35%445%20%
2285
16th to endNight
16%11%5%9%7%45%5%5%7%23%
1966
March1st to 15thNight
17%10%47%6%25%5%5%7%27%
1992
16th to endNight
16%8%46%5%23445%38%
2112
April1st to 15thNight
20%8%36%434347%33%
1838
16th to endNight
12%7%25%5%345%6%7%39%
1620
May1st to 15thNight
15%6%36%4245%5%8%35%
1620
16th to endNight
9%5%25%425%46%6%46%
1532
June1st to 15thNight
10%5%25%5%245%7%9%42%
1423
16th to endNight
8%5%243345%6%10%44%
1260
July1st to 15thNight
5%41442336%8%55%
1348
16th to endNight
7%315%425%5%6%9%47%
1703
August1st to 15thNight
6%323426%5%7%9%48%
1620
16th to endNight
8%42442445%7%53%
1737
September1st to 15thNight
11%5%25%42345%6%47%
1875
16th to endNight
11%424425%36%8%46%
1980
October1st to 15thNight
17%5%25%42445%7%39%
2145
16th to endNight
22%8%35%6%2445%6%29%
2310
November1st to 15thNight
14%7%25%5%345%6%8%36%
2328
16th to endNight
21%13%46%5%3445%7%23%
2520
December1st to 15thNight
20%16%6%8%6%35%45%5%18%
2520
16th to endNight
21%14%7%10%7%35%445%15%
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
18%14%5%10%7%45%5%5%6%15%
1549
16th to endDay
14%17%8%13%8%45%34414%
1728
February1st to 15thDay
15%17%7%10%8%45%436%18%
1575
16th to endDay
16%14%5%10%7%45%5%46%18%
1506
March1st to 15thDay
18%12%5%9%6%25%45%6%23%
1956
16th to endDay
17%9%6%7%5%25%45%5%30%
2111
April1st to 15thDay
19%10%5%6%5%3435%7%27%
2121
16th to endDay
18%8%35%5%23346%36%
2340
May1st to 15thDay
17%6%46%5%3445%7%34%
2331
16th to endDay
12%6%35%5%35%5%5%8%38%
2581
June1st to 15thDay
13%5%35%5%25%5%5%9%38%
2532
16th to endDay
12%425%5%36%5%7%9%37%
2700
July1st to 15thDay
9%5%25%5%35%6%6%10%40%
2607
16th to endDay
9%6%26%6%36%5%6%9%36%
2465
August1st to 15thDay
9%5%26%6%45%7%7%8%36%
2340
16th to endDay
12%5%25%5%35%5%6%9%38%
2453
September1st to 15thDay
13%6%26%5%35%5%6%7%36%
2082
16th to endDay
14%5%246%245%6%7%39%
1980
October1st to 15thDay
18%7%37%6%3445%5%33%
1815
16th to endDay
23%10%47%6%3445%5%23%
1911
November1st to 15thDay
14%10%36%6%2445%7%34%
1528
16th to endDay
19%12%5%9%6%3445%7%20%
1440
December1st to 15thDay
18%15%8%10%6%34346%17%
1440
16th to endDay
20%17%7%12%7%35%345%10%
1536
January1st to 15thNight
21%13%5%9%6%3445%5%20%
2387
16th to endNight
14%14%8%11%8%35%446%18%
2496
February1st to 15thNight
14%13%7%10%7%36%45%5%21%
2278
16th to endNight
16%10%5%9%6%35%5%47%24%
1966
March1st to 15thNight
18%9%48%5%35%5%5%7%27%
2004
16th to endNight
15%9%47%4235%36%38%
2112
April1st to 15thNight
19%8%46%5%24347%33%
1838
16th to endNight
12%7%25%5%35%5%5%7%39%
1620
May1st to 15thNight
16%6%25%5%345%5%8%35%
1619
16th to endNight
9%435%5%245%5%6%47%
1532
June1st to 15thNight
10%425%5%25%5%6%9%41%
1423
16th to endNight
9%5%244345%6%10%45%
1260
July1st to 15thNight
5%31443345%8%54%
1348
16th to endNight
7%31443445%10%47%
1703
August1st to 15thNight
5%3245%25%5%7%9%48%
1620
16th to endNight
8%42442445%7%53%
1737
September1st to 15thNight
11%5%2442345%6%46%
1875
16th to endNight
11%5%1432446%8%46%
1980
October1st to 15thNight
16%6%25%424447%40%
2145
16th to endNight
21%8%35%43445%6%30%
2310
November1st to 15thNight
13%8%25%4345%6%7%36%
2328
16th to endNight
21%11%5%5%5%34448%24%
2520
December1st to 15thNight
20%14%6%8%5%25%5%46%18%
2520
16th to endNight
21%14%6%10%7%35%446%15%
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
69%6%9%10%3
1550
16th to endDay
73%6%7%9%3
1728
February1st to 15thDay
68%6%9%12%3
1577
16th to endDay
64%7%9%12%4
1506
March1st to 15thDay
61%6%11%14%5%
1956
16th to endDay
54%5%12%17%9%
2112
April1st to 15thDay
56%5%11%17%9%
2121
16th to endDay
47%410%20%14%1
2340
May1st to 15thDay
47%6%13%20%10%
2331
16th to endDay
42%7%13%21%13%1
2585
June1st to 15thDay
41%7%14%23%12%1
2532
16th to endDay
40%8%14%22%12%
2700
July1st to 15thDay
36%8%11%26%15%1
2455
16th to endDay
41%9%13%21%11%2
2310
August1st to 15thDay
40%10%15%20%11%1
2327
16th to endDay
41%7%14%23%11%1
2453
September1st to 15thDay
44%7%14%21%11%
2082
16th to endDay
40%7%14%25%11%
1980
October1st to 15thDay
51%5%12%17%12%1
1815
16th to endDay
60%7%13%12%5%
1911
November1st to 15thDay
48%7%13%20%9%1
1528
16th to endDay
61%7%13%13%2
1440
December1st to 15thDay
67%8%13%8%1
1440
16th to endDay
76%6%8%7%1
1536
January1st to 15thNight
65%6%9%10%6%
2387
16th to endNight
66%6%10%13%3
2496
February1st to 15thNight
64%6%11%12%4
2287
16th to endNight
58%6%13%14%6%
1966
March1st to 15thNight
55%6%11%19%6%
2004
16th to endNight
47%5%10%21%12%2
2112
April1st to 15thNight
51%39%20%12%
1838
16th to endNight
41%6%10%19%18%3
1620
May1st to 15thNight
44%5%11%23%12%2
1620
16th to endNight
35%6%13%25%14%3
1534
June1st to 15thNight
36%7%14%25%14%1
1423
16th to endNight
34%7%14%23%18%
1260
July1st to 15thNight
27%7%10%29%22%3
1271
16th to endNight
30%8%15%24%18%3
1595
August1st to 15thNight
29%9%14%30%13%1
1609
16th to endNight
30%6%12%30%17%2
1737
September1st to 15thNight
36%6%12%27%15%1
1875
16th to endNight
34%7%12%30%14%
1980
October1st to 15thNight
42%6%11%21%16%
2145
16th to endNight
53%6%13%18%7%
2310
November1st to 15thNight
43%6%14%20%12%1
2328
16th to endNight
59%6%14%15%4
2520
December1st to 15thNight
66%8%12%9%3
2520
16th to endNight
69%7%11%8%2
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
21%18%40%11%6%1
79
16th to endDay
38%14%34%12%
96
February1st to 15thDay
21%20%48%10%
90
16th to endDay
18%19%48%11%2
81
March1st to 15thDay
25%10%34%20%8%
246
16th to endDay
26%7%33%21%9%1
288
April1st to 15thDay
23%13%27%22%9%2
270
16th to endDay
21%9%29%22%10%7%
270
May1st to 15thDay
21%8%29%21%13%4
288
16th to endDay
16%6%29%26%14%6%
331
June1st to 15thDay
16%423%34%16%4
327
16th to endDay
12%6%31%30%13%4
495
July1st to 15thDay
11%323%31%21%8%
417
16th to endDay
9%319%29%26%11%
326
August1st to 15thDay
10%117%29%25%16%
313
16th to endDay
12%416%21%25%19%
332
September1st to 15thDay
13%416%23%27%14%
315
16th to endDay
16%5%16%23%21%16%
314
October1st to 15thDay
21%7%21%26%17%5%
315
16th to endDay
27%9%33%21%6%1
327
November1st to 15thDay
16%17%28%23%9%4
81
16th to endDay
26%15%40%10%8%
60
December1st to 15thDay
30%30%26%8%5%
60
16th to endDay
31%25%37%6%
64
January1st to 15thNight
25%16%35%16%4
720
16th to endNight
22%12%36%23%4
768
February1st to 15thNight
21%16%35%22%3
704
16th to endNight
23%12%31%27%5%
631
March1st to 15thNight
21%12%34%24%6%
720
16th to endNight
19%10%32%26%11%
768
April1st to 15thNight
24%11%30%27%5%
694
16th to endNight
15%7%33%32%10%1
540
May1st to 15thNight
18%5%25%33%15%1
540
16th to endNight
12%428%34%17%1
412
June1st to 15thNight
12%230%42%12%
360
16th to endNight
11%325%45%13%
360
July1st to 15thNight
6%121%45%22%1
366
16th to endNight
8%117%46%23%2
564
August1st to 15thNight
7%114%41%30%3
539
16th to endNight
8%118%35%30%5%
591
September1st to 15thNight
13%5%18%31%25%5%
720
16th to endNight
13%416%32%27%6%
717
October1st to 15thNight
20%5%23%29%17%2
720
16th to endNight
26%10%31%24%7%
768
November1st to 15thNight
18%10%30%28%11%1
700
16th to endNight
27%12%29%21%8%
720
December1st to 15thNight
29%14%35%17%2
720
16th to endNight
26%14%36%18%3
768
Page generated at 2017-11-01 17:23:39. Version ac04

Copyright 2017 A. Danko


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