Antique Photons Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Antique Photons Observatory clear sky chart from 2005-11-05 to 2017-09-10.

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
41%
15740
26%
46818
15%
15693
51%
15693
34%
26782

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
27%
900
28%
2327
10%
895
40%
895
34%
1408
January16th to endNight
29%
960
30%
2496
10%
960
41%
960
35%
1475
February1st to 15thNight
25%
880
22%
2288
7%
876
34%
876
30%
1422
February16th to endNight
25%
598
27%
1860
8%
598
41%
598
29%
1068
March1st to 15thNight
28%
540
23%
1980
12%
540
42%
540
23%
1167
March16th to endNight
27%
576
20%
2112
13%
576
39%
576
24%
1236
April1st to 15thNight
28%
539
23%
1895
12%
539
45%
539
28%
1064
April16th to endNight
29%
540
22%
1722
12%
540
44%
540
28%
1025
May1st to 15thNight
33%
540
22%
1620
14%
540
45%
540
28%
1014
May16th to endNight
43%
563
20%
1684
14%
561
53%
561
32%
1005
June1st to 15thNight
59%
540
20%
1620
16%
540
65%
540
40%
892
June16th to endNight
62%
540
24%
1620
18%
540
70%
540
49%
821
July1st to 15thNight
66%
510
20%
1530
18%
510
70%
510
40%
845
July16th to endNight
78%
564
30%
1594
33%
531
82%
531
49%
800
August1st to 15thNight
76%
539
27%
1610
30%
536
79%
536
47%
826
August16th to endNight
72%
573
27%
1817
29%
573
75%
573
39%
973
September1st to 15thNight
63%
525
26%
1863
28%
525
67%
525
34%
997
September16th to endNight
63%
492
31%
1815
27%
492
70%
492
38%
892
October1st to 15thNight
46%
624
30%
1944
21%
624
53%
624
36%
1086
October16th to endNight
42%
704
34%
2112
18%
704
54%
704
43%
1089
November1st to 15thNight
37%
733
33%
2133
14%
733
52%
733
40%
1146
November16th to endNight
29%
900
30%
2340
12%
900
41%
900
35%
1412
December1st to 15thNight
30%
900
24%
2340
9%
900
41%
900
30%
1497
December16th to endNight
30%
960
26%
2496
10%
960
41%
960
29%
1622

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
12%5%2442445%7%47%
47805
Night
10%424323346%53%
47014
TransparencyDay
36%5%12%25%17%3
47505
Night
30%411%25%21%5%
46819
SeeingDay
12%8%25%29%20%4
5763
Night
12%10%31%30%13%1
15740

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
11%7%2432323453%
1611
16th to endDay
13%6%24323335%52%
1728
February1st to 15thDay
12%8%35%422245%46%
1578
16th to endDay
13%6%24324346%47%
1618
March1st to 15thDay
15%8%24323346%44%
1980
16th to endDay
21%6%35%424346%38%
2110
April1st to 15thDay
14%5%25%32435%6%44%
2052
16th to endDay
19%6%36%423345%39%
2237
May1st to 15thDay
18%6%25%434345%40%
2331
16th to endDay
11%5%26%5%35%5%5%8%38%
2430
June1st to 15thDay
8%425%5%36%5%47%47%
2340
16th to endDay
6%2135%3447%9%49%
2340
July1st to 15thDay
8%4245%37%6%8%8%40%
2340
16th to endDay
5%324435%5%6%9%49%
2466
August1st to 15thDay
5%3135%346%7%11%47%
2340
16th to endDay
6%324435%5%5%8%49%
2384
September1st to 15thDay
12%4245%3445%7%45%
1981
16th to endDay
9%31332445%7%53%
1815
October1st to 15thDay
14%5%13312335%53%
1674
16th to endDay
12%313212346%59%
1760
November1st to 15thDay
11%313323347%57%
1722
16th to endDay
16%6%12212336%54%
1620
December1st to 15thDay
17%5%25%423345%46%
1620
16th to endDay
15%7%35%323236%45%
1728
January1st to 15thNight
12%5%23412345%54%
2327
16th to endNight
9%423323345%56%
2496
February1st to 15thNight
12%7%24312246%50%
2278
16th to endNight
11%5%2442334452%
1860
March1st to 15thNight
13%6%24324445%47%
1980
16th to endNight
16%42442335%6%47%
2112
April1st to 15thNight
12%5%24323345%53%
1895
16th to endNight
13%6%25%322346%48%
1722
May1st to 15thNight
13%425%424346%47%
1619
16th to endNight
10%425%43437%10%44%
1683
June1st to 15thNight
5%31432445%7%56%
1620
16th to endNight
411222345%10%61%
1620
July1st to 15thNight
5%223425%5%6%11%50%
1620
16th to endNight
421332335%10%59%
1702
August1st to 15thNight
32123245%7%10%56%
1620
16th to endNight
5%314425%5%5%8%53%
1817
September1st to 15thNight
10%424323337%54%
1863
16th to endNight
8%213333446%58%
1815
October1st to 15thNight
10%414423336%55%
1944
16th to endNight
8%312213235%63%
2112
November1st to 15thNight
9%31321333461%
2133
16th to endNight
12%43421223456%
2340
December1st to 15thNight
15%5%24313337%47%
2340
16th to endNight
15%7%24323335%47%
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
35%29%29%20%1
1612
16th to endDay
35%211%29%18%2
1728
February1st to 15thDay
40%412%25%13%3
1579
16th to endDay
38%39%28%15%4
1618
March1st to 15thDay
40%410%21%17%5%
1980
16th to endDay
47%411%21%13%1
2112
April1st to 15thDay
40%5%13%22%15%3
2052
16th to endDay
45%410%20%16%2
2237
May1st to 15thDay
46%410%19%16%1
2331
16th to endDay
41%8%14%22%12%
2434
June1st to 15thDay
35%7%12%26%17%1
2340
16th to endDay
29%6%15%25%19%4
2340
July1st to 15thDay
34%8%14%27%13%
2201
16th to endDay
27%6%15%31%16%1
2311
August1st to 15thDay
27%8%15%24%19%4
2326
16th to endDay
30%7%13%26%16%5%
2384
September1st to 15thDay
36%5%12%20%15%8%
1981
16th to endDay
27%5%11%25%23%5%
1815
October1st to 15thDay
32%411%23%23%5%
1674
16th to endDay
27%39%29%24%6%
1760
November1st to 15thDay
27%49%27%23%6%
1722
16th to endDay
33%38%25%24%4
1620
December1st to 15thDay
40%311%27%16%1
1620
16th to endDay
41%310%24%16%4
1728
January1st to 15thNight
31%48%27%24%3
2327
16th to endNight
29%410%27%22%5%
2496
February1st to 15thNight
36%310%27%18%4
2288
16th to endNight
34%39%27%20%5%
1860
March1st to 15thNight
38%410%19%19%6%
1980
16th to endNight
37%5%12%25%17%2
2112
April1st to 15thNight
33%5%10%21%22%6%
1895
16th to endNight
36%410%23%19%5%
1722
May1st to 15thNight
38%5%10%20%20%4
1620
16th to endNight
32%7%17%25%15%1
1685
June1st to 15thNight
24%7%12%31%21%2
1620
16th to endNight
19%5%14%30%23%5%
1620
July1st to 15thNight
26%6%12%32%20%2
1530
16th to endNight
19%5%11%34%24%3
1594
August1st to 15thNight
19%7%15%29%22%5%
1610
16th to endNight
26%5%13%27%20%7%
1817
September1st to 15thNight
29%5%10%24%19%10%
1863
16th to endNight
25%410%25%27%6%
1815
October1st to 15thNight
30%410%20%24%9%
1944
16th to endNight
24%38%26%29%8%
2112
November1st to 15thNight
25%38%25%27%9%
2133
16th to endNight
33%27%23%27%6%
2340
December1st to 15thNight
36%411%25%19%2
2340
16th to endNight
39%310%22%18%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
25%18%34%15%5%
90
16th to endDay
10%32%30%19%7%
96
February1st to 15thDay
10%20%48%16%4
90
16th to endDay
12%27%41%17%1
81
March1st to 15thDay
21%25%43%8%1
90
16th to endDay
15%23%28%26%6%
96
April1st to 15thDay
14%16%41%16%9%
171
16th to endDay
26%14%34%15%8%1
347
May1st to 15thDay
17%15%34%23%7%1
468
16th to endDay
15%10%37%23%10%2
517
June1st to 15thDay
8%427%33%21%3
495
16th to endDay
6%423%38%22%4
495
July1st to 15thDay
9%218%43%22%4
475
16th to endDay
5%7%33%40%12%
515
August1st to 15thDay
6%110%39%35%6%
493
16th to endDay
8%114%36%32%6%
424
September1st to 15thDay
7%310%33%38%7%
178
16th to endDay
4122%31%28%12%
90
October1st to 15thDay
6%6%40%18%22%5%
90
16th to endDay
11%5%38%31%11%2
96
November1st to 15thDay
13%430%25%23%3
90
16th to endDay
34%17%27%16%21
90
December1st to 15thDay
20%15%41%12%7%3
90
16th to endDay
21%16%43%13%4
96
January1st to 15thNight
14%16%38%24%5%
900
16th to endNight
11%17%38%27%4
960
February1st to 15thNight
16%17%37%25%3
880
16th to endNight
13%17%41%24%3
598
March1st to 15thNight
17%12%39%26%4
540
16th to endNight
16%13%41%24%4
576
April1st to 15thNight
15%12%41%24%5%
539
16th to endNight
15%11%40%23%8%
540
May1st to 15thNight
13%10%39%28%8%1
540
16th to endNight
13%433%29%17%1
563
June1st to 15thNight
5%425%41%21%1
540
16th to endNight
2227%41%23%1
540
July1st to 15thNight
5%20%46%24%2
510
16th to endNight
5%9%41%40%3
564
August1st to 15thNight
3112%45%33%3
539
16th to endNight
6%113%43%31%4
573
September1st to 15thNight
12%216%40%27%1
525
16th to endNight
9%219%35%28%4
492
October1st to 15thNight
13%433%27%19%3
624
16th to endNight
10%10%34%29%12%
704
November1st to 15thNight
11%12%35%26%12%
733
16th to endNight
15%16%36%23%7%
900
December1st to 15thNight
19%14%32%27%5%
900
16th to endNight
18%14%34%28%4
960
Page generated at 2017-09-11 18:35:17. Version ac04

Copyright 2017 A. Danko


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