Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Point clear sky chart from 2005-11-05 to 2017-03-31.

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
51%
15007
25%
45342
19%
14961
57%
14961
33%
26813

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
34%
900
25%
2327
10%
895
43%
895
30%
1497
January16th to endNight
29%
960
26%
2496
9%
960
39%
960
29%
1648
February1st to 15thNight
33%
812
24%
2220
8%
809
43%
809
30%
1416
February16th to endNight
24%
593
27%
1855
10%
593
38%
593
25%
1155
March1st to 15thNight
33%
540
24%
1980
15%
540
45%
540
24%
1197
March16th to endNight
40%
576
22%
2112
16%
576
49%
576
26%
1226
April1st to 15thNight
37%
494
26%
1650
17%
494
51%
494
32%
916
April16th to endNight
43%
495
25%
1650
20%
495
53%
495
31%
930
May1st to 15thNight
45%
495
22%
1650
17%
495
55%
495
28%
988
May16th to endNight
63%
515
24%
1575
23%
513
67%
513
38%
881
June1st to 15thNight
79%
495
21%
1485
22%
495
82%
495
43%
811
June16th to endNight
75%
495
22%
1485
23%
495
77%
495
38%
840
July1st to 15thNight
75%
465
21%
1395
24%
465
76%
465
37%
794
July16th to endNight
85%
522
21%
1468
25%
489
85%
489
42%
808
August1st to 15thNight
86%
494
24%
1570
30%
491
87%
491
48%
793
August16th to endNight
76%
525
21%
1750
27%
525
76%
525
31%
1029
September1st to 15thNight
71%
495
24%
1650
28%
495
72%
495
31%
961
September16th to endNight
69%
552
31%
1803
29%
552
71%
552
36%
998
October1st to 15thNight
63%
660
31%
1980
25%
660
67%
660
41%
1081
October16th to endNight
59%
704
35%
2112
27%
704
65%
704
41%
1147
November1st to 15thNight
53%
700
31%
2100
23%
700
59%
700
38%
1173
November16th to endNight
42%
720
32%
2169
21%
720
53%
720
32%
1291
December1st to 15thNight
37%
840
24%
2364
13%
840
45%
840
28%
1525
December16th to endNight
33%
960
21%
2496
10%
960
40%
960
26%
1708

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
13%5%25%5%35%45%7%42%
45707
Night
12%424323447%50%
45540
TransparencyDay
40%5%10%19%18%5%
45408
Night
33%410%20%21%8%
45344
SeeingDay
12%417%25%28%11%
4825
Night
14%5%23%30%22%3
15007

By Month

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
20%425%41325%444%
1611
16th to endDay
21%6%3432223345%
1728
February1st to 15thDay
18%6%2442333444%
1639
16th to endDay
19%6%35%423335%43%
1628
March1st to 15thDay
19%7%25%435%34439%
1980
16th to endDay
14%5%35%5%2445%5%43%
2104
April1st to 15thDay
14%5%24425%347%44%
1967
16th to endDay
14%5%35%5%3436%6%42%
1980
May1st to 15thDay
16%6%35%5%35%45%6%35%
1971
16th to endDay
8%436%5%36%5%6%10%39%
2184
June1st to 15thDay
7%325%5%46%7%8%10%38%
2145
16th to endDay
6%3347%47%8%7%9%36%
2145
July1st to 15thDay
10%325%7%5%7%7%6%10%33%
2145
16th to endDay
9%5%25%6%5%7%7%9%10%31%
2284
August1st to 15thDay
6%2145%46%6%8%9%43%
2049
16th to endDay
10%425%6%45%6%7%9%37%
2100
September1st to 15thDay
11%5%146%46%5%6%7%40%
1980
16th to endDay
10%415%4345%5%7%47%
1813
October1st to 15thDay
8%5%15%5%23445%53%
1650
16th to endDay
15%413212235%58%
1760
November1st to 15thDay
11%5%13323335%55%
1758
16th to endDay
16%6%24424225%48%
1779
December1st to 15thDay
21%7%35%42333439%
1579
16th to endDay
18%8%35%433346%39%
1728
January1st to 15thNight
16%5%24313335%48%
2327
16th to endNight
20%5%2431333446%
2496
February1st to 15thNight
15%6%25%323335%47%
2211
16th to endNight
17%6%25%323336%46%
1855
March1st to 15thNight
16%424423446%44%
1980
16th to endNight
13%5%24423336%48%
2112
April1st to 15thNight
10%42332445%8%52%
1650
16th to endNight
11%424323446%51%
1650
May1st to 15thNight
10%5%25%5%23449%44%
1649
16th to endNight
6%42442445%9%51%
1575
June1st to 15thNight
42132245%7%10%54%
1485
16th to endNight
5%2233346%7%8%52%
1485
July1st to 15thNight
7%325%3246%7%10%46%
1485
16th to endNight
5%211325%6%7%14%48%
1576
August1st to 15thNight
311232448%13%53%
1580
16th to endNight
8%324335%6%7%11%43%
1750
September1st to 15thNight
9%3144345%47%50%
1650
16th to endNight
9%413324335%55%
1803
October1st to 15thNight
8%313433346%57%
1980
16th to endNight
12%21332233460%
2112
November1st to 15thNight
11%313323346%56%
2100
16th to endNight
15%42341332453%
2169
December1st to 15thNight
17%6%35%313236%45%
2364
16th to endNight
17%8%35%42333443%
2496

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
42%35%18%23%7%
1612
16th to endDay
44%2317%23%8%
1728
February1st to 15thDay
43%26%19%19%7%
1641
16th to endDay
45%26%17%21%7%
1628
March1st to 15thDay
47%47%16%18%5%
1980
16th to endDay
42%410%18%21%2
2106
April1st to 15thDay
41%48%19%18%7%
1967
16th to endDay
41%49%20%20%3
1980
May1st to 15thDay
47%5%11%15%14%5%
1971
16th to endDay
38%6%14%26%11%1
2188
June1st to 15thDay
36%8%14%25%14%1
2145
16th to endDay
38%8%14%19%15%2
2145
July1st to 15thDay
42%6%18%20%10%1
2006
16th to endDay
41%8%17%21%9%
2129
August1st to 15thDay
32%7%18%23%15%1
2035
16th to endDay
39%9%16%18%12%2
2100
September1st to 15thDay
40%7%12%18%13%6%
1980
16th to endDay
34%5%8%19%22%8%
1813
October1st to 15thDay
32%36%18%22%15%
1650
16th to endDay
30%15%16%31%14%
1760
November1st to 15thDay
33%37%19%27%8%
1758
16th to endDay
40%25%15%26%9%
1779
December1st to 15thDay
49%26%17%16%7%
1579
16th to endDay
46%38%18%18%4
1728
January1st to 15thNight
39%37%15%26%8%
2327
16th to endNight
41%36%16%22%9%
2496
February1st to 15thNight
39%26%19%23%8%
2220
16th to endNight
40%35%19%19%10%
1855
March1st to 15thNight
40%39%16%21%7%
1980
16th to endNight
37%49%20%22%5%
2112
April1st to 15thNight
30%5%11%22%19%10%
1650
16th to endNight
34%38%21%24%7%
1650
May1st to 15thNight
37%5%11%22%17%6%
1650
16th to endNight
29%416%27%19%2
1577
June1st to 15thNight
23%7%17%30%20%1
1485
16th to endNight
26%8%14%26%19%4
1485
July1st to 15thNight
27%7%22%26%13%2
1395
16th to endNight
21%10%25%29%11%2
1468
August1st to 15thNight
19%6%24%26%18%3
1570
16th to endNight
31%9%18%21%15%3
1750
September1st to 15thNight
32%7%15%19%16%8%
1650
16th to endNight
31%38%17%26%12%
1803
October1st to 15thNight
28%38%16%24%18%
1980
16th to endNight
27%3415%29%18%
2112
November1st to 15thNight
29%48%19%26%11%
2100
16th to endNight
36%15%13%28%13%
2169
December1st to 15thNight
41%39%21%18%6%
2364
16th to endNight
45%36%18%20%5%
2496

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
18%10%42%20%8%
90
16th to endDay
19%26%39%11%3
96
February1st to 15thDay
17%15%43%20%3
90
16th to endDay
12%20%45%17%3
81
March1st to 15thDay
24%13%45%16%
90
16th to endDay
12%21%23%30%9%2
94
April1st to 15thDay
18%13%30%26%11%
206
16th to endDay
20%7%22%28%18%2
210
May1st to 15thDay
20%6%26%31%13%2
228
16th to endDay
10%222%32%25%6%
399
June1st to 15thDay
8%16%40%33%9%
420
16th to endDay
6%10%27%36%17%
420
July1st to 15thDay
7%10%27%42%11%
400
16th to endDay
6%1319%45%23%
445
August1st to 15thDay
8%120%43%25%
322
16th to endDay
10%416%41%27%
268
September1st to 15thDay
9%25%20%36%25%
255
16th to endDay
11%17%22%38%17%
159
October1st to 15thDay
1127%34%30%5%
90
16th to endDay
18%126%16%29%8%
96
November1st to 15thDay
24%331%33%6%1
90
16th to endDay
22%6%41%15%10%4
90
December1st to 15thDay
24%5%43%14%10%2
90
16th to endDay
18%14%41%16%6%2
96
January1st to 15thNight
20%10%30%29%8%
900
16th to endNight
21%9%35%29%3
960
February1st to 15thNight
18%9%34%31%5%
812
16th to endNight
20%13%37%26%2
593
March1st to 15thNight
17%10%33%33%4
540
16th to endNight
17%6%32%29%13%
576
April1st to 15thNight
12%9%38%28%11%
494
16th to endNight
13%5%32%34%12%
495
May1st to 15thNight
12%430%39%12%1
495
16th to endNight
7%218%38%29%4
515
June1st to 15thNight
5%8%41%38%5%
495
16th to endNight
427%26%48%10%
495
July1st to 15thNight
5%16%29%48%9%
465
16th to endNight
5%1223%50%16%
522
August1st to 15thNight
3323%51%17%
494
16th to endNight
9%425%47%12%
525
September1st to 15thNight
11%17%31%40%8%
495
16th to endNight
10%19%32%40%5%
552
October1st to 15thNight
8%119%31%33%5%
660
16th to endNight
12%321%32%25%4
704
November1st to 15thNight
11%5%25%32%22%2
700
16th to endNight
15%7%30%28%16%
720
December1st to 15thNight
21%7%28%30%10%
840
16th to endNight
23%11%27%28%8%
960
Page generated at 2017-04-01 07:23:14. Version ac04

Copyright 2017 A. Danko


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