Photon's End Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Photon's End Observatory clear sky chart from 2005-11-05 to 2018-02-14.

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
33%
15243
14%
48826
9%
15211
40%
15211
18%
34277

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
18%
780
8%
2716
4%
776
24%
776
9%
2165
January16th to endNight
24%
832
11%
2874
7%
832
31%
832
12%
2127
February1st to 15thNight
22%
760
12%
2468
6%
757
29%
757
11%
1877
February16th to endNight
25%
631
15%
1940
8%
631
36%
631
15%
1451
March1st to 15thNight
22%
720
14%
2112
8%
720
30%
720
15%
1570
March16th to endNight
33%
768
21%
2025
10%
768
41%
768
24%
1387
April1st to 15thNight
26%
718
16%
1796
6%
718
32%
718
22%
1318
April16th to endNight
32%
643
18%
1723
8%
643
39%
643
23%
1197
May1st to 15thNight
35%
360
18%
1440
16%
360
44%
360
17%
934
May16th to endNight
38%
375
14%
1497
12%
374
49%
374
20%
934
June1st to 15thNight
40%
360
10%
1440
11%
360
47%
360
17%
950
June16th to endNight
45%
360
9%
1440
13%
360
49%
360
20%
890
July1st to 15thNight
56%
340
14%
1360
21%
340
61%
340
28%
748
July16th to endNight
56%
376
14%
1418
17%
354
61%
354
27%
792
August1st to 15thNight
53%
426
15%
1497
13%
424
58%
424
25%
902
August16th to endNight
56%
717
21%
1863
11%
717
60%
717
37%
1142
September1st to 15thNight
50%
720
16%
1800
8%
720
53%
720
30%
1220
September16th to endNight
51%
717
24%
1953
16%
717
55%
717
33%
1233
October1st to 15thNight
37%
720
18%
2160
12%
720
46%
720
23%
1460
October16th to endNight
29%
768
13%
2411
8%
768
37%
768
16%
1767
November1st to 15thNight
31%
760
17%
2521
12%
760
40%
760
17%
1744
November16th to endNight
22%
780
11%
2730
7%
780
28%
780
11%
2048
December1st to 15thNight
21%
780
8%
2730
4%
780
27%
780
10%
2138
December16th to endNight
17%
832
11%
2912
4%
832
25%
832
9%
2283

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
18%8%36%5%3445%6%33%
49259
Night
18%9%36%5%34445%33%
48995
Cloud CoverDay
18%8%36%5%34446%33%
49268
Night
18%9%36%5%34446%33%
49001
TransparencyDay
51%312%21%10%1
48946
Night
52%311%21%10%1
48826
SeeingDay
22%8%26%24%13%4
5895
Night
23%8%26%29%11%
15243

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
23%14%6%8%6%2343420%
1552
16th to endDay
15%15%49%7%35%445%24%
1700
February1st to 15thDay
14%13%5%11%6%4445%5%24%
1695
16th to endDay
18%13%48%6%345%35%25%
1532
March1st to 15thDay
18%9%47%6%46%44328%
1838
16th to endDay
17%6%35%5%23446%40%
2199
April1st to 15thDay
23%9%35%323335%33%
2152
16th to endDay
21%7%35%5%2434437%
2245
May1st to 15thDay
20%8%36%5%25%446%32%
2511
16th to endDay
18%5%25%6%4445%6%34%
2618
June1st to 15thDay
22%6%25%6%3445%7%30%
2520
16th to endDay
18%6%25%5%35%6%6%7%31%
2520
July1st to 15thDay
13%4245%36%6%7%8%37%
2520
16th to endDay
12%5%26%5%35%5%7%9%36%
2654
August1st to 15thDay
12%6%26%6%35%5%5%7%37%
2451
16th to endDay
10%425%435%5%5%9%43%
2327
September1st to 15thDay
16%4245%24347%42%
2160
16th to endDay
15%5%14423447%46%
2005
October1st to 15thDay
21%7%26%434446%35%
1800
16th to endDay
26%8%36%7%33445%27%
1812
November1st to 15thDay
17%8%35%5%4446%6%33%
1664
16th to endDay
23%11%36%6%24345%25%
1560
December1st to 15thDay
22%13%5%9%6%44445%19%
1560
16th to endDay
24%15%5%7%6%3434421%
1664
January1st to 15thNight
19%16%6%9%7%4434420%
2716
16th to endNight
15%15%5%8%6%35%345%26%
2874
February1st to 15thNight
13%13%6%11%6%45%5%45%23%
2466
16th to endNight
17%11%5%7%7%35%435%28%
1940
March1st to 15thNight
19%12%47%6%2334429%
2099
16th to endNight
16%8%36%5%3333441%
2025
April1st to 15thNight
25%7%34424335%35%
1796
16th to endNight
19%7%26%423345%38%
1723
May1st to 15thNight
22%7%35%423445%36%
1440
16th to endNight
17%6%35%425%45%6%37%
1495
June1st to 15thNight
19%6%25%6%345%6%6%32%
1440
16th to endNight
17%5%25%4245%6%7%37%
1440
July1st to 15thNight
10%3245%345%5%8%46%
1440
16th to endNight
8%5%24435%5%6%8%45%
1514
August1st to 15thNight
10%6%34425%6%6%9%40%
1507
16th to endNight
9%31443436%7%48%
1863
September1st to 15thNight
15%5%25%5%34346%42%
1800
16th to endNight
16%424313336%49%
1953
October1st to 15thNight
19%6%35%5%33445%38%
2160
16th to endNight
24%9%35%5%25%446%28%
2411
November1st to 15thNight
22%7%36%5%24346%33%
2521
16th to endNight
23%11%47%6%3444425%
2730
December1st to 15thNight
22%16%46%6%4443421%
2730
16th to endNight
23%15%5%7%6%2444420%
2912

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
23%14%6%9%5%3333420%
1552
16th to endDay
14%15%5%9%6%35%445%24%
1700
February1st to 15thDay
14%13%411%7%35%445%24%
1695
16th to endDay
19%12%5%7%6%35%445%25%
1532
March1st to 15thDay
18%9%38%6%36%44430%
1848
16th to endDay
17%6%345%23446%41%
2198
April1st to 15thDay
23%10%35%423235%33%
2152
16th to endDay
21%7%35%424335%36%
2245
May1st to 15thDay
19%7%36%5%33445%36%
2511
16th to endDay
17%5%25%6%34446%38%
2618
June1st to 15thDay
22%6%25%6%345%47%30%
2520
16th to endDay
18%6%25%5%36%6%5%8%31%
2520
July1st to 15thDay
13%5%245%36%5%7%9%37%
2520
16th to endDay
12%5%26%5%35%5%7%9%36%
2654
August1st to 15thDay
17%5%26%5%35%5%6%6%35%
2451
16th to endDay
14%424425%5%5%8%41%
2327
September1st to 15thDay
16%4245%34448%41%
2160
16th to endDay
14%5%23423346%47%
2005
October1st to 15thDay
21%6%35%5%33446%34%
1800
16th to endDay
26%8%36%6%34345%26%
1812
November1st to 15thDay
17%8%35%6%3445%7%32%
1664
16th to endDay
24%11%46%6%2345%5%25%
1560
December1st to 15thDay
23%14%48%6%35%445%19%
1560
16th to endDay
24%15%5%8%5%35%33321%
1664
January1st to 15thNight
20%15%6%9%6%4433420%
2716
16th to endNight
15%15%5%8%6%25%445%25%
2874
February1st to 15thNight
13%13%6%10%7%46%445%23%
2459
16th to endNight
18%11%47%7%25%44428%
1940
March1st to 15thNight
19%11%46%6%2334432%
2112
16th to endNight
15%8%35%5%2334344%
2025
April1st to 15thNight
25%9%2442333435%
1796
16th to endNight
19%8%26%423346%38%
1723
May1st to 15thNight
22%7%26%423346%37%
1440
16th to endNight
17%6%2443445%6%39%
1495
June1st to 15thNight
19%7%25%5%345%5%8%31%
1440
16th to endNight
17%5%25%4245%6%7%37%
1440
July1st to 15thNight
10%3245%345%6%8%45%
1440
16th to endNight
8%4245%346%5%9%44%
1514
August1st to 15thNight
13%6%25%4245%6%9%39%
1507
16th to endNight
13%32433346%6%47%
1863
September1st to 15thNight
14%5%25%5%34346%42%
1800
16th to endNight
16%5%23323335%49%
1953
October1st to 15thNight
18%7%25%434446%38%
2160
16th to endNight
25%9%35%5%33346%27%
2411
November1st to 15thNight
22%8%26%5%34346%33%
2521
16th to endNight
23%10%48%5%35%44425%
2730
December1st to 15thNight
23%15%46%5%4444421%
2730
16th to endNight
24%15%5%7%5%2444420%
2912

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
68%27%15%5%
1553
16th to endDay
61%411%14%7%
1700
February1st to 15thDay
61%211%18%4
1697
16th to endDay
60%39%16%9%1
1532
March1st to 15thDay
59%311%16%7%1
1848
16th to endDay
46%29%19%16%5%
2199
April1st to 15thDay
53%27%20%13%2
2152
16th to endDay
50%26%21%14%4
2245
May1st to 15thDay
52%37%21%13%2
2511
16th to endDay
49%411%20%11%1
2622
June1st to 15thDay
53%411%21%8%
2520
16th to endDay
48%5%14%21%10%
2520
July1st to 15thDay
39%415%28%12%
2371
16th to endDay
43%5%17%23%10%
2487
August1st to 15thDay
44%416%24%9%
2437
16th to endDay
36%416%30%11%
2327
September1st to 15thDay
42%312%29%12%
2160
16th to endDay
37%413%33%10%
2005
October1st to 15thDay
50%212%22%10%
1800
16th to endDay
60%313%15%6%
1812
November1st to 15thDay
50%414%20%8%1
1664
16th to endDay
60%313%15%6%
1560
December1st to 15thDay
67%311%13%3
1560
16th to endDay
67%39%13%6%
1664
January1st to 15thNight
68%39%12%5%
2716
16th to endNight
60%39%17%7%
2874
February1st to 15thNight
62%39%18%5%
2468
16th to endNight
58%38%19%9%
1940
March1st to 15thNight
58%29%19%8%1
2112
16th to endNight
47%29%20%16%4
2025
April1st to 15thNight
52%37%19%16%1
1796
16th to endNight
48%38%19%18%3
1723
May1st to 15thNight
49%37%19%15%4
1440
16th to endNight
45%311%22%14%2
1497
June1st to 15thNight
49%411%23%9%1
1440
16th to endNight
43%5%13%21%15%
1440
July1st to 15thNight
33%5%13%30%15%1
1360
16th to endNight
35%415%27%15%
1418
August1st to 15thNight
37%6%18%24%11%
1497
16th to endNight
33%316%34%11%
1863
September1st to 15thNight
43%312%27%11%1
1800
16th to endNight
37%310%36%11%
1953
October1st to 15thNight
47%310%26%11%
2160
16th to endNight
57%213%20%5%
2411
November1st to 15thNight
52%313%19%10%
2521
16th to endNight
61%311%17%4
2730
December1st to 15thNight
65%312%13%4
2730
16th to endNight
66%39%13%6%
2912

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
30%6%30%26%5%1
90
16th to endDay
28%8%34%24%2
104
February1st to 15thDay
33%13%35%16%
130
16th to endDay
34%12%26%20%6%
191
March1st to 15thDay
25%10%33%21%8%
270
16th to endDay
22%11%28%23%10%3
288
April1st to 15thDay
27%16%27%20%8%
270
16th to endDay
24%11%25%22%12%3
270
May1st to 15thDay
29%7%27%20%10%4
288
16th to endDay
21%11%30%19%14%2
331
June1st to 15thDay
27%5%27%25%11%2
315
16th to endDay
23%6%25%26%16%2
315
July1st to 15thDay
13%328%30%17%5%
305
16th to endDay
12%223%34%20%6%
326
August1st to 15thDay
13%5%20%32%20%7%
313
16th to endDay
10%6%19%29%20%12%
332
September1st to 15thDay
19%420%19%20%15%
315
16th to endDay
17%6%18%22%23%11%
314
October1st to 15thDay
22%8%25%23%16%2
315
16th to endDay
32%10%23%24%9%
309
November1st to 15thDay
21%9%27%28%10%1
228
16th to endDay
31%16%25%21%5%
90
December1st to 15thDay
25%12%33%22%6%
90
16th to endDay
39%15%33%11%
96
January1st to 15thNight
29%11%29%22%5%
780
16th to endNight
23%9%31%27%7%
832
February1st to 15thNight
20%12%33%27%6%
760
16th to endNight
25%9%30%28%4
631
March1st to 15thNight
26%12%30%27%3
720
16th to endNight
21%11%28%28%10%
768
April1st to 15thNight
29%7%30%26%5%
718
16th to endNight
25%11%26%27%8%
643
May1st to 15thNight
27%6%23%31%9%1
360
16th to endNight
20%5%28%33%10%1
375
June1st to 15thNight
21%325%37%11%
360
16th to endNight
18%322%38%14%1
360
July1st to 15thNight
9%324%45%17%
340
16th to endNight
9%221%43%21%1
376
August1st to 15thNight
16%315%36%24%2
426
16th to endNight
11%419%37%25%2
717
September1st to 15thNight
18%220%35%20%2
720
16th to endNight
20%420%28%24%2
717
October1st to 15thNight
22%8%24%29%14%1
720
16th to endNight
31%8%23%27%8%
768
November1st to 15thNight
27%8%25%24%13%
760
16th to endNight
29%13%24%22%9%
780
December1st to 15thNight
31%11%28%23%3
780
16th to endNight
32%8%30%21%5%1
832
Page generated at 2018-02-15 10:58:42. Version ac04

Copyright 2018 A. Danko


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