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 2017-04-30.

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
35%
14547
14%
45416
10%
14509
40%
14509
18%
32002

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%
537
20%
1612
9%
537
47%
537
25%
1038
May1st to 15thNight
43%
495
17%
1485
11%
495
49%
495
24%
987
May16th to endNight
49%
376
17%
1403
16%
376
57%
376
26%
807
June1st to 15thNight
48%
330
14%
1305
15%
330
55%
330
23%
756
June16th to endNight
52%
330
15%
1155
15%
330
59%
330
28%
673
July1st to 15thNight
63%
333
19%
1158
23%
333
66%
333
35%
607
July16th to endNight
64%
522
13%
1469
12%
489
66%
489
34%
877
August1st to 15thNight
67%
494
18%
1474
15%
491
70%
491
34%
881
August16th to endNight
63%
541
22%
1591
15%
541
67%
541
36%
936
September1st to 15thNight
55%
660
22%
1719
14%
660
59%
660
32%
1114
September16th to endNight
58%
657
20%
1815
15%
657
61%
657
32%
1150
October1st to 15thNight
44%
660
17%
1966
16%
660
48%
660
24%
1304
October16th to endNight
25%
704
13%
2118
8%
704
33%
704
16%
1578
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%
46305
Night
15%9%46%5%3445%7%32%
45596
Cloud CoverDay
15%9%47%6%35%45%7%30%
46315
Night
15%9%46%5%3445%7%33%
45600
TransparencyDay
51%7%12%18%9%
46003
Night
49%6%12%19%10%1
45416
SeeingDay
18%8%26%24%15%7%
5028
Night
19%9%28%28%12%1
14553

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
18%9%35%433347%37%
2327
May1st to 15thDay
16%6%45%6%3445%8%33%
2136
16th to endDay
12%6%35%5%245%6%7%40%
2360
June1st to 15thDay
14%6%26%435%45%9%37%
2321
16th to endDay
12%434436%6%6%9%37%
2475
July1st to 15thDay
9%4245%35%5%6%10%40%
2390
16th to endDay
9%5%25%6%46%5%5%10%36%
2283
August1st to 15thDay
9%6%25%6%5%6%6%7%8%36%
2145
16th to endDay
11%6%25%5%25%5%5%10%37%
2248
September1st to 15thDay
14%6%37%5%345%6%7%35%
1909
16th to endDay
15%5%15%5%3446%9%37%
1815
October1st to 15thDay
19%6%35%7%3445%6%33%
1664
16th to endDay
26%10%47%6%35%35%5%22%
1752
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%
1612
May1st to 15thNight
14%7%35%435%5%6%8%36%
1485
16th to endNight
9%425%42446%6%47%
1401
June1st to 15thNight
10%5%25%5%235%7%8%42%
1305
16th to endNight
8%5%144345%5%10%45%
1155
July1st to 15thNight
431442336%8%56%
1235
16th to endNight
7%315%425%5%6%9%46%
1577
August1st to 15thNight
6%324436%5%7%8%48%
1485
16th to endNight
8%32442435%7%53%
1591
September1st to 15thNight
11%5%35%5%24446%46%
1719
16th to endNight
12%424425%46%8%45%
1815
October1st to 15thNight
16%6%35%42445%7%40%
1966
16th to endNight
23%9%35%5%2445%6%28%
2118
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%23347%37%
2327
May1st to 15thDay
16%6%46%5%3445%7%33%
2136
16th to endDay
12%6%35%5%25%5%5%7%40%
2360
June1st to 15thDay
14%6%35%5%25%5%5%9%37%
2321
16th to endDay
12%425%5%36%5%7%9%37%
2475
July1st to 15thDay
8%5%25%5%35%6%6%10%40%
2390
16th to endDay
9%6%26%6%36%5%6%9%36%
2283
August1st to 15thDay
9%6%26%6%46%7%6%7%36%
2145
16th to endDay
12%5%25%5%35%5%6%9%37%
2248
September1st to 15thDay
14%6%27%5%36%5%6%7%35%
1909
16th to endDay
15%5%25%6%245%6%7%38%
1815
October1st to 15thDay
17%7%37%6%34446%34%
1664
16th to endDay
25%10%47%6%3445%5%22%
1752
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%6%25%6%35%5%5%7%39%
1612
May1st to 15thNight
15%6%35%5%35%5%6%8%35%
1484
16th to endNight
9%4345%245%46%48%
1401
June1st to 15thNight
10%425%5%245%6%8%41%
1305
16th to endNight
9%4234345%6%10%45%
1155
July1st to 15thNight
431443345%8%55%
1235
16th to endNight
7%3245%345%6%10%47%
1577
August1st to 15thNight
5%325%425%5%7%9%48%
1485
16th to endNight
8%424423447%53%
1591
September1st to 15thNight
11%5%34423446%46%
1719
16th to endNight
12%5%1432446%8%44%
1815
October1st to 15thNight
16%6%25%424447%40%
1966
16th to endNight
23%8%35%43445%7%28%
2118
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
2327
May1st to 15thDay
47%7%13%20%9%
2136
16th to endDay
41%7%13%21%14%2
2364
June1st to 15thDay
42%7%14%22%11%1
2321
16th to endDay
40%8%14%22%13%
2475
July1st to 15thDay
36%8%12%26%15%1
2238
16th to endDay
42%8%14%20%11%2
2128
August1st to 15thDay
40%10%15%19%12%1
2132
16th to endDay
40%8%14%22%11%1
2248
September1st to 15thDay
45%7%14%21%10%
1909
16th to endDay
41%7%15%24%10%
1815
October1st to 15thDay
51%5%12%16%12%1
1664
16th to endDay
62%6%13%12%4
1752
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
1612
May1st to 15thNight
43%5%11%24%12%2
1485
16th to endNight
35%6%12%25%15%3
1403
June1st to 15thNight
36%7%13%25%14%1
1305
16th to endNight
34%7%15%23%18%
1155
July1st to 15thNight
26%6%10%29%22%3
1158
16th to endNight
31%8%16%23%17%3
1469
August1st to 15thNight
30%9%15%29%14%1
1474
16th to endNight
30%6%12%30%17%3
1591
September1st to 15thNight
36%6%12%27%15%1
1719
16th to endNight
35%7%13%29%13%
1815
October1st to 15thNight
42%6%12%20%16%
1966
16th to endNight
54%6%13%18%6%
2118
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%8%29%22%10%7%
266
May1st to 15thDay
17%8%29%22%16%5%
228
16th to endDay
14%328%28%16%7%
267
June1st to 15thDay
18%5%22%31%16%4
266
16th to endDay
12%5%29%32%15%5%
420
July1st to 15thDay
11%323%31%20%8%
347
16th to endDay
9%320%27%26%12%
270
August1st to 15thDay
9%117%28%24%16%
253
16th to endDay
12%414%23%23%22%
268
September1st to 15thDay
14%315%22%28%15%
255
16th to endDay
18%5%15%27%20%12%
254
October1st to 15thDay
18%8%22%27%18%5%
255
16th to endDay
30%9%31%22%5%
264
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%32%32%10%1
537
May1st to 15thNight
17%5%25%34%16%1
495
16th to endNight
12%427%34%18%1
377
June1st to 15thNight
13%229%41%13%
330
16th to endNight
11%324%44%14%
330
July1st to 15thNight
5%222%45%22%2
333
16th to endNight
9%117%47%22%2
522
August1st to 15thNight
8%115%41%29%3
494
16th to endNight
9%117%36%29%4
541
September1st to 15thNight
13%5%18%32%24%5%
660
16th to endNight
14%416%33%25%5%
657
October1st to 15thNight
20%5%24%29%17%2
660
16th to endNight
27%9%32%23%6%
704
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 2017-04-30 20:39:59. Version ac04

Copyright 2017 A. Danko


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