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 2017-12-01.

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%
15804
25%
47834
19%
15758
58%
15758
33%
28148

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
39%
539
25%
1800
17%
539
51%
539
33%
985
April16th to endNight
43%
540
26%
1800
21%
540
54%
540
31%
1024
May1st to 15thNight
46%
540
21%
1800
17%
540
56%
540
29%
1060
May16th to endNight
60%
563
24%
1722
22%
561
66%
561
38%
970
June1st to 15thNight
79%
540
20%
1620
21%
540
82%
540
42%
892
June16th to endNight
73%
540
22%
1620
23%
540
75%
540
36%
931
July1st to 15thNight
77%
510
20%
1530
23%
510
78%
510
38%
862
July16th to endNight
85%
564
22%
1594
27%
531
85%
531
43%
871
August1st to 15thNight
85%
539
23%
1714
28%
536
86%
536
45%
888
August16th to endNight
74%
573
22%
1910
27%
573
75%
573
30%
1136
September1st to 15thNight
72%
540
24%
1800
27%
540
73%
540
33%
1029
September16th to endNight
71%
603
33%
1968
32%
603
73%
603
38%
1064
October1st to 15thNight
65%
720
31%
2160
25%
720
69%
720
42%
1163
October16th to endNight
58%
768
38%
2304
28%
768
66%
768
42%
1232
November1st to 15thNight
52%
760
30%
2280
23%
760
58%
760
37%
1290
November16th to endNight
44%
780
34%
2350
23%
780
55%
780
34%
1375
December1st to 15thNight
38%
844
24%
2376
13%
844
46%
844
28%
1529
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%
48556
Night
11%424323447%50%
48032
TransparencyDay
40%5%10%19%18%5%
48257
Night
33%411%20%21%8%
47836
SeeingDay
12%417%25%28%11%
5802
Night
13%5%23%30%22%3
15804

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
13%5%35%5%2445%5%43%
2110
April1st to 15thDay
13%5%24425%346%45%
2147
16th to endDay
13%435%43446%6%41%
2160
May1st to 15thDay
15%6%35%5%35%45%6%37%
2151
16th to endDay
8%436%5%36%5%6%10%38%
2388
June1st to 15thDay
7%425%5%46%7%8%10%38%
2340
16th to endDay
6%3347%46%8%8%9%36%
2340
July1st to 15thDay
9%325%7%5%7%7%6%10%33%
2340
16th to endDay
9%425%6%5%7%7%8%10%32%
2466
August1st to 15thDay
7%3145%36%6%8%9%41%
2235
16th to endDay
11%425%6%45%6%7%8%36%
2292
September1st to 15thDay
11%5%145%35%5%6%7%42%
2160
16th to endDay
10%3144345%5%7%48%
1977
October1st to 15thDay
8%425%5%23445%53%
1800
16th to endDay
14%413212235%58%
1920
November1st to 15thDay
11%5%13433435%53%
1908
16th to endDay
14%6%24424225%49%
1927
December1st to 15thDay
21%7%3442333439%
1581
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
9%313424348%53%
1800
16th to endNight
11%5%2433345%6%50%
1800
May1st to 15thNight
10%5%245%23449%46%
1799
16th to endNight
7%42342445%9%50%
1722
June1st to 15thNight
5%2143235%7%10%54%
1620
16th to endNight
6%3234346%6%8%51%
1620
July1st to 15thNight
6%325%3246%7%11%47%
1620
16th to endNight
5%211325%6%7%14%49%
1702
August1st to 15thNight
421232448%13%52%
1724
16th to endNight
9%324335%6%7%10%42%
1910
September1st to 15thNight
9%3134345%47%51%
1800
16th to endNight
8%413323345%57%
1968
October1st to 15thNight
7%313433346%58%
2160
16th to endNight
12%21221233461%
2304
November1st to 15thNight
11%313323346%55%
2280
16th to endNight
14%42342322454%
2350
December1st to 15thNight
17%6%25%313236%45%
2376
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
41%410%18%21%2
2112
April1st to 15thDay
40%49%20%18%7%
2147
16th to endDay
40%5%9%20%19%4
2160
May1st to 15thDay
45%410%15%17%5%
2151
16th to endDay
38%7%14%26%11%1
2392
June1st to 15thDay
36%8%13%24%15%
2340
16th to endDay
39%8%14%19%15%2
2340
July1st to 15thDay
41%7%19%21%9%1
2201
16th to endDay
40%8%17%22%10%
2311
August1st to 15thDay
34%7%18%22%14%1
2221
16th to endDay
40%9%16%18%11%2
2292
September1st to 15thDay
39%7%12%18%16%5%
2160
16th to endDay
33%5%10%20%22%7%
1977
October1st to 15thDay
32%37%20%21%14%
1800
16th to endDay
29%25%15%32%14%
1920
November1st to 15thDay
34%47%19%26%7%
1908
16th to endDay
39%25%15%26%10%
1927
December1st to 15thDay
49%26%17%16%7%
1581
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
29%5%11%23%20%10%
1800
16th to endNight
34%49%21%23%6%
1800
May1st to 15thNight
36%5%10%21%18%8%
1800
16th to endNight
29%5%17%27%18%1
1724
June1st to 15thNight
24%7%16%30%20%1
1620
16th to endNight
27%8%14%25%19%3
1620
July1st to 15thNight
26%7%22%28%12%2
1530
16th to endNight
20%10%24%30%12%1
1594
August1st to 15thNight
20%7%23%26%17%3
1714
16th to endNight
32%9%18%22%14%3
1910
September1st to 15thNight
31%6%15%20%17%8%
1800
16th to endNight
28%410%18%26%11%
1968
October1st to 15thNight
27%38%19%24%16%
2160
16th to endNight
26%3415%30%19%
2304
November1st to 15thNight
30%39%20%25%10%
2280
16th to endNight
35%25%14%29%13%
2350
December1st to 15thNight
41%39%21%18%6%
2376
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%20%22%33%8%2
96
April1st to 15thDay
18%12%29%26%12%2
266
16th to endDay
18%8%24%25%19%2
270
May1st to 15thDay
18%6%27%29%13%4
288
16th to endDay
10%325%32%23%5%
475
June1st to 15thDay
9%16%39%33%9%
495
16th to endDay
8%111%30%33%14%
495
July1st to 15thDay
7%8%26%42%14%
475
16th to endDay
6%319%45%23%
515
August1st to 15thDay
10%219%44%21%
388
16th to endDay
14%315%38%26%
332
September1st to 15thDay
9%16%20%35%25%
315
16th to endDay
8%18%25%36%19%
210
October1st to 15thDay
3222%31%32%8%
135
16th to endDay
15%232%20%22%6%
144
November1st to 15thDay
20%231%34%9%
135
16th to endDay
14%7%37%22%13%5%
135
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
11%9%37%28%12%
539
16th to endNight
13%6%32%33%13%
540
May1st to 15thNight
11%431%37%13%1
540
16th to endNight
7%220%37%27%3
563
June1st to 15thNight
5%8%40%39%5%
540
16th to endNight
5%17%27%47%9%
540
July1st to 15thNight
416%28%49%9%
510
16th to endNight
41223%51%16%
564
August1st to 15thNight
4323%51%16%
539
16th to endNight
11%424%46%12%
573
September1st to 15thNight
10%17%31%39%9%
540
16th to endNight
9%18%32%41%5%
603
October1st to 15thNight
8%118%32%33%5%
720
16th to endNight
12%322%31%24%4
768
November1st to 15thNight
12%5%25%32%21%2
760
16th to endNight
14%6%29%30%18%1
780
December1st to 15thNight
21%7%28%31%10%
844
16th to endNight
23%11%27%28%8%
960
Page generated at 2017-12-02 08:14:20. Version ac04

Copyright 2017 A. Danko


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