Battlefield Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Battlefield 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
43%
16081
20%
48826
13%
16045
51%
16045
26%
31043

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
28%
776
21%
2583
9%
776
44%
776
21%
1598
January16th to endNight
24%
832
22%
2704
10%
832
40%
832
23%
1701
February1st to 15thNight
24%
757
19%
2424
10%
757
38%
757
23%
1524
February16th to endNight
23%
631
26%
1893
11%
631
42%
631
27%
1134
March1st to 15thNight
31%
720
21%
2028
10%
720
43%
720
27%
1299
March16th to endNight
31%
768
19%
2067
10%
768
39%
768
26%
1401
April1st to 15thNight
33%
718
20%
1796
7%
718
41%
718
31%
1198
April16th to endNight
42%
720
19%
1800
8%
720
45%
720
32%
1197
May1st to 15thNight
40%
690
14%
1770
7%
690
44%
690
26%
1239
May16th to endNight
63%
376
18%
1499
19%
376
66%
376
25%
865
June1st to 15thNight
64%
360
15%
1440
19%
360
67%
360
23%
861
June16th to endNight
66%
360
15%
1440
19%
360
69%
360
22%
855
July1st to 15thNight
69%
363
13%
1383
15%
363
70%
363
22%
846
July16th to endNight
70%
564
16%
1595
14%
531
73%
531
31%
999
August1st to 15thNight
64%
605
13%
1675
9%
602
65%
602
27%
1142
August16th to endNight
62%
764
17%
1910
11%
764
63%
764
27%
1333
September1st to 15thNight
63%
720
23%
1800
16%
720
64%
720
31%
1215
September16th to endNight
51%
717
18%
1950
14%
717
54%
717
25%
1351
October1st to 15thNight
50%
720
22%
2160
19%
720
57%
720
27%
1388
October16th to endNight
45%
768
32%
2304
24%
768
58%
768
33%
1346
November1st to 15thNight
42%
760
20%
2405
14%
760
51%
760
26%
1485
November16th to endNight
41%
780
25%
2558
19%
780
51%
780
26%
1518
December1st to 15thNight
34%
780
19%
2730
12%
780
46%
780
20%
1723
December16th to endNight
30%
832
23%
2912
13%
832
44%
832
22%
1825

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%245%245%5%7%41%
49235
Night
13%5%25%42445%7%44%
49012
Cloud CoverDay
13%5%25%5%3445%7%41%
49245
Night
13%5%25%42445%7%44%
49016
TransparencyDay
40%7%12%21%15%2
48939
Night
39%6%12%21%16%3
48826
SeeingDay
16%6%23%26%19%6%
6320
Night
16%7%26%32%15%1
16089

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
16%6%3342345%5%44%
1682
16th to endDay
15%5%342245%46%45%
1872
February1st to 15thDay
15%7%26%423446%43%
1737
16th to endDay
14%5%244235%5%7%43%
1580
March1st to 15thDay
14%5%24323346%49%
1918
16th to endDay
18%5%24324445%43%
2157
April1st to 15thDay
12%5%23422347%50%
2152
16th to endDay
13%5%15%5%2445%6%45%
2160
May1st to 15thDay
15%5%25%4245%6%7%39%
2192
16th to endDay
12%425%5%245%6%8%42%
2614
June1st to 15thDay
10%424426%6%7%9%41%
2520
16th to endDay
7%5%25%5%36%6%7%11%37%
2520
July1st to 15thDay
8%325%6%36%7%8%11%36%
2492
16th to endDay
7%5%346%37%6%8%11%34%
2465
August1st to 15thDay
10%6%26%7%46%6%7%9%32%
2262
16th to endDay
10%7%25%6%46%7%7%10%32%
2292
September1st to 15thDay
13%5%25%6%35%45%9%38%
2160
16th to endDay
21%6%35%6%25%45%6%31%
2007
October1st to 15thDay
18%7%34424336%42%
1800
16th to endDay
11%324423436%52%
1920
November1st to 15thDay
18%5%24313445%45%
1780
16th to endDay
13%31432425%5%52%
1729
December1st to 15thDay
15%6%235%25%35%7%43%
1560
16th to endDay
19%6%24324346%41%
1664
January1st to 15thNight
13%6%25%42445%7%44%
2583
16th to endNight
17%5%24424336%44%
2704
February1st to 15thNight
17%6%14423345%43%
2423
16th to endNight
12%6%24423345%49%
1893
March1st to 15thNight
14%414424446%47%
2016
16th to endNight
18%5%25%434445%42%
2067
April1st to 15thNight
11%6%25%43445%8%44%
1796
16th to endNight
16%5%2342335%7%46%
1800
May1st to 15thNight
14%6%25%43445%7%40%
1770
16th to endNight
10%5%134235%5%8%47%
1497
June1st to 15thNight
9%4245%35%5%7%10%40%
1440
16th to endNight
5%325%5%35%7%7%9%43%
1440
July1st to 15thNight
6%425%6%35%7%6%12%38%
1465
16th to endNight
8%4245%35%5%8%10%40%
1703
August1st to 15thNight
8%426%6%35%5%6%10%37%
1686
16th to endNight
10%5%26%6%35%5%6%10%37%
1910
September1st to 15thNight
12%5%25%5%3445%7%43%
1800
16th to endNight
17%6%36%5%24447%38%
1950
October1st to 15thNight
16%5%25%324435%46%
2160
16th to endNight
13%414323445%53%
2304
November1st to 15thNight
16%5%24323447%45%
2405
16th to endNight
14%424423446%48%
2558
December1st to 15thNight
14%6%25%434346%42%
2730
16th to endNight
17%7%25%424346%42%
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
16%6%243235%45%43%
1682
16th to endDay
15%6%24324446%46%
1872
February1st to 15thDay
15%7%25%423445%43%
1737
16th to endDay
13%5%25%4245%48%42%
1580
March1st to 15thDay
14%5%23323345%49%
1929
16th to endDay
18%5%24325%445%43%
2156
April1st to 15thDay
12%424432346%51%
2152
16th to endDay
13%425%5%2435%6%45%
2160
May1st to 15thDay
15%5%25%425%5%5%8%39%
2192
16th to endDay
12%425%5%35%5%5%8%42%
2614
June1st to 15thDay
10%414426%6%7%9%40%
2520
16th to endDay
8%5%25%6%46%6%7%12%36%
2520
July1st to 15thDay
8%325%6%36%7%8%10%36%
2492
16th to endDay
7%5%26%7%46%6%8%12%33%
2465
August1st to 15thDay
11%5%36%7%36%5%7%9%32%
2262
16th to endDay
11%6%26%5%46%6%6%10%30%
2292
September1st to 15thDay
13%5%25%5%345%6%8%38%
2160
16th to endDay
21%7%26%5%35%35%6%31%
2007
October1st to 15thDay
19%6%245%23345%42%
1800
16th to endDay
11%324423346%52%
1920
November1st to 15thDay
19%5%24323435%45%
1780
16th to endDay
13%324423345%52%
1729
December1st to 15thDay
14%6%25%434346%44%
1560
16th to endDay
19%6%24423445%41%
1664
January1st to 15thNight
13%6%2442445%7%43%
2583
16th to endNight
17%5%25%434326%44%
2704
February1st to 15thNight
18%6%24313445%44%
2416
16th to endNight
12%6%24423346%49%
1893
March1st to 15thNight
14%414424346%47%
2028
16th to endNight
18%5%25%324345%42%
2067
April1st to 15thNight
11%6%25%42445%7%45%
1796
16th to endNight
17%414423347%46%
1800
May1st to 15thNight
15%6%25%5%35%45%7%39%
1769
16th to endNight
10%5%144245%5%8%47%
1497
June1st to 15thNight
8%4344345%7%10%41%
1440
16th to endNight
6%335%5%35%6%7%9%43%
1440
July1st to 15thNight
7%425%5%36%6%7%11%38%
1465
16th to endNight
7%5%245%346%9%9%40%
1703
August1st to 15thNight
8%5%26%6%346%6%9%38%
1686
16th to endNight
11%5%26%6%35%46%9%37%
1910
September1st to 15thNight
12%5%25%5%25%35%7%44%
1800
16th to endNight
17%5%36%5%24347%38%
1950
October1st to 15thNight
16%5%25%424435%46%
2160
16th to endNight
13%413322345%53%
2304
November1st to 15thNight
16%5%14323347%46%
2405
16th to endNight
14%414423445%49%
2558
December1st to 15thNight
14%6%35%5%3435%6%42%
2730
16th to endNight
16%6%24424346%42%
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
41%5%10%21%17%3
1683
16th to endDay
39%410%23%17%4
1872
February1st to 15thDay
42%49%23%16%4
1740
16th to endDay
37%6%11%22%17%3
1580
March1st to 15thDay
37%5%10%22%18%4
1929
16th to endDay
42%5%10%19%17%3
2157
April1st to 15thDay
35%411%24%19%4
2152
16th to endDay
38%6%11%18%18%6%
2160
May1st to 15thDay
42%7%14%21%12%1
2192
16th to endDay
38%8%14%24%13%1
2618
June1st to 15thDay
34%10%16%23%13%
2520
16th to endDay
37%9%17%20%13%2
2520
July1st to 15thDay
36%13%16%21%10%1
2345
16th to endDay
37%10%17%21%11%1
2310
August1st to 15thDay
43%10%14%19%11%
2249
16th to endDay
44%9%14%17%11%2
2292
September1st to 15thDay
42%8%11%18%16%2
2160
16th to endDay
51%7%10%16%14%
2007
October1st to 15thDay
44%47%22%18%2
1800
16th to endDay
33%5%7%24%23%5%
1920
November1st to 15thDay
41%412%19%17%3
1780
16th to endDay
34%410%24%20%4
1729
December1st to 15thDay
42%412%22%15%3
1560
16th to endDay
44%410%23%12%3
1664
January1st to 15thNight
39%6%10%20%17%5%
2583
16th to endNight
42%49%21%17%5%
2704
February1st to 15thNight
41%48%23%18%3
2424
16th to endNight
36%310%25%18%5%
1893
March1st to 15thNight
38%6%11%23%16%4
2028
16th to endNight
43%5%10%20%17%3
2067
April1st to 15thNight
37%6%12%19%20%3
1796
16th to endNight
38%5%10%20%19%5%
1800
May1st to 15thNight
42%8%13%23%10%1
1770
16th to endNight
32%11%17%24%13%2
1499
June1st to 15thNight
36%9%16%25%11%1
1440
16th to endNight
34%11%18%19%14%1
1440
July1st to 15thNight
35%12%19%21%10%1
1383
16th to endNight
31%11%18%24%11%1
1595
August1st to 15thNight
40%9%18%20%11%
1675
16th to endNight
42%8%14%23%10%1
1910
September1st to 15thNight
39%7%14%20%15%3
1800
16th to endNight
45%6%12%16%17%1
1950
October1st to 15thNight
40%5%9%21%19%2
2160
16th to endNight
32%5%7%25%24%5%
2304
November1st to 15thNight
39%5%11%18%20%4
2405
16th to endNight
36%5%8%23%19%6%
2558
December1st to 15thNight
43%5%11%20%15%3
2730
16th to endNight
42%412%21%14%4
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
20%20%32%20%5%
120
16th to endDay
18%20%31%22%5%1
144
February1st to 15thDay
23%18%38%15%4
173
16th to endDay
12%13%42%26%4
239
March1st to 15thDay
12%14%38%25%8%1
270
16th to endDay
17%10%31%29%7%2
288
April1st to 15thDay
14%12%32%23%13%3
270
16th to endDay
18%7%25%28%17%3
270
May1st to 15thDay
23%5%36%20%12%2
288
16th to endDay
16%418%26%25%9%
331
June1st to 15thDay
15%316%27%28%8%
315
16th to endDay
11%120%33%27%4
315
July1st to 15thDay
11%9%34%35%8%
305
16th to endDay
8%8%31%35%14%
326
August1st to 15thDay
11%9%34%29%14%
313
16th to endDay
13%19%28%30%16%
332
September1st to 15thDay
16%315%26%20%17%
315
16th to endDay
26%314%23%23%7%
314
October1st to 15thDay
25%318%26%20%5%
315
16th to endDay
13%6%28%26%19%6%
336
November1st to 15thDay
21%5%28%23%15%5%
296
16th to endDay
13%13%27%25%17%2
259
December1st to 15thDay
23%12%33%17%11%2
90
16th to endDay
22%17%28%27%4
96
January1st to 15thNight
16%15%34%25%7%
780
16th to endNight
19%12%38%25%3
832
February1st to 15thNight
20%13%37%25%2
760
16th to endNight
14%16%41%22%3
631
March1st to 15thNight
16%10%37%27%7%
720
16th to endNight
20%7%35%27%8%
768
April1st to 15thNight
15%8%38%27%9%
718
16th to endNight
19%5%30%34%9%1
720
May1st to 15thNight
17%5%30%36%9%
690
16th to endNight
12%215%43%23%2
377
June1st to 15thNight
7%216%43%24%4
360
16th to endNight
7%16%46%27%1
360
July1st to 15thNight
8%11%46%29%2
363
16th to endNight
8%110%41%33%4
564
August1st to 15thNight
10%111%41%31%4
605
16th to endNight
12%18%37%35%4
764
September1st to 15thNight
14%11%38%29%5%
720
16th to endNight
20%214%31%28%1
717
October1st to 15thNight
18%419%32%22%3
720
16th to endNight
16%8%26%28%16%3
768
November1st to 15thNight
18%6%26%30%15%2
760
16th to endNight
15%10%29%28%14%1
780
December1st to 15thNight
18%10%31%27%11%
780
16th to endNight
20%9%34%29%6%
832
Page generated at 2018-02-15 10:58:45. Version ac04

Copyright 2018 A. Danko


Battlefield Observatory Clear Sky Chart |Charts Home