ES Fox Observatory (BAS/BOEC)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the ES Fox Observatory (BAS/BOEC) clear sky chart from 2005-11-05 to 2017-04-25.

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%
14795
10%
45546
8%
14758
36%
14758
14%
34896

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
10%
896
1%
2616
0%
895
11%
895
3%
2438
January16th to endNight
17%
810
4%
2538
3%
810
18%
810
5%
2273
February1st to 15thNight
17%
701
3%
2287
2%
701
19%
701
5%
1986
February16th to endNight
24%
631
8%
1973
3%
631
29%
631
10%
1595
March1st to 15thNight
25%
720
11%
2025
6%
720
29%
720
15%
1571
March16th to endNight
39%
768
19%
2112
12%
768
44%
768
23%
1480
April1st to 15thNight
32%
659
15%
1801
7%
659
38%
659
21%
1283
April16th to endNight
40%
525
17%
1575
10%
525
44%
525
22%
1073
May1st to 15thNight
47%
492
15%
1482
14%
492
50%
492
22%
995
May16th to endNight
57%
342
15%
1369
16%
342
63%
342
23%
785
June1st to 15thNight
50%
330
12%
1174
13%
330
55%
330
21%
750
June16th to endNight
59%
330
12%
1155
15%
330
62%
330
27%
709
July1st to 15thNight
67%
310
18%
1085
22%
310
71%
310
36%
570
July16th to endNight
62%
495
13%
1383
13%
462
62%
462
28%
869
August1st to 15thNight
60%
494
17%
1474
13%
491
64%
491
31%
893
August16th to endNight
58%
525
18%
1575
14%
525
61%
525
29%
984
September1st to 15thNight
54%
654
15%
1715
10%
654
56%
654
28%
1169
September16th to endNight
50%
657
17%
1815
12%
657
52%
657
25%
1242
October1st to 15thNight
36%
660
12%
1963
11%
660
40%
660
16%
1474
October16th to endNight
22%
704
6%
2158
4%
704
25%
704
9%
1800
November1st to 15thNight
26%
700
11%
2359
12%
700
29%
700
11%
1822
November16th to endNight
19%
720
5%
2520
4%
720
21%
720
6%
2147
December1st to 15thNight
11%
720
1%
2520
0%
720
11%
720
2%
2342
December16th to endNight
8%
952
2%
2872
0%
952
10%
952
3%
2646

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
16%10%47%5%34446%32%
46091
Night
17%12%5%8%6%34445%26%
45716
Cloud CoverDay
16%10%47%5%3445%6%32%
46101
Night
17%12%5%8%6%34445%27%
45720
TransparencyDay
52%6%12%18%9%
45779
Night
58%6%10%14%8%
45546
SeeingDay
20%5%22%29%16%5%
5181
Night
22%9%26%26%12%2
14803

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
20%18%11%14%9%343337%
1322
16th to endDay
15%19%9%15%9%4444310%
1685
February1st to 15thDay
13%18%8%15%9%445%3412%
1575
16th to endDay
15%16%7%9%6%47%5%4418%
1497
March1st to 15thDay
15%10%48%6%35%5%5%6%29%
1924
16th to endDay
14%7%46%6%3445%7%35%
2112
April1st to 15thDay
21%9%35%423347%34%
2155
16th to endDay
18%7%25%414347%39%
2273
May1st to 15thDay
17%7%25%433447%40%
2139
16th to endDay
11%5%14434448%47%
2394
June1st to 15thDay
13%6%35%4346%5%8%39%
2453
16th to endDay
12%5%24435%5%5%8%42%
2475
July1st to 15thDay
9%41442446%8%47%
2475
16th to endDay
9%3244245%7%10%45%
2366
August1st to 15thDay
10%5%2342335%9%47%
2145
16th to endDay
11%6%25%43446%7%43%
2270
September1st to 15thDay
16%6%35%434447%38%
1909
16th to endDay
17%5%25%42436%7%38%
1815
October1st to 15thDay
21%9%47%5%23345%31%
1667
16th to endDay
34%10%5%8%5%33335%16%
1713
November1st to 15thDay
21%16%46%6%35%5%45%20%
1498
16th to endDay
25%20%7%9%6%3423412%
1440
December1st to 15thDay
21%24%10%12%7%343236%
1440
16th to endDay
21%25%9%9%8%243345%
1349
January1st to 15thNight
21%20%9%13%8%35%3337%
2616
16th to endNight
16%16%10%15%9%36%33410%
2538
February1st to 15thNight
14%18%9%12%9%4443413%
2285
16th to endNight
15%13%7%12%8%35%345%20%
1973
March1st to 15thNight
16%11%6%8%6%24346%27%
2013
16th to endNight
15%8%46%5%24335%39%
2112
April1st to 15thNight
21%8%35%423446%34%
1801
16th to endNight
19%7%25%42445%6%37%
1575
May1st to 15thNight
14%6%37%6%24448%36%
1482
16th to endNight
10%415%5%35%5%5%7%45%
1367
June1st to 15thNight
14%6%25%6%345%5%7%38%
1174
16th to endNight
10%5%26%5%345%6%9%41%
1155
July1st to 15thNight
8%32342345%9%52%
1155
16th to endNight
7%4235%45%6%7%7%45%
1488
August1st to 15thNight
9%425%42445%9%46%
1485
16th to endNight
10%5%26%5%23447%46%
1575
September1st to 15thNight
14%5%25%3345%5%7%40%
1715
16th to endNight
15%7%36%5%24346%40%
1815
October1st to 15thNight
22%9%36%5%2445%6%29%
1963
16th to endNight
30%11%37%6%24446%18%
2158
November1st to 15thNight
20%14%5%7%6%34446%23%
2359
16th to endNight
26%19%6%7%5%3434414%
2520
December1st to 15thNight
21%25%9%12%5%343327%
2520
16th to endNight
23%22%9%11%7%342337%
2872

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
19%18%10%16%8%343337%
1322
16th to endDay
14%19%9%14%10%45%33410%
1685
February1st to 15thDay
13%18%8%14%9%45%44412%
1575
16th to endDay
15%17%6%9%7%37%5%45%17%
1497
March1st to 15thDay
14%10%49%6%35%5%5%5%29%
1935
16th to endDay
14%7%46%6%345%46%35%
2111
April1st to 15thDay
21%10%26%423346%33%
2155
16th to endDay
18%7%35%42335%6%39%
2273
May1st to 15thDay
17%6%34424437%40%
2139
16th to endDay
11%5%2433445%9%46%
2394
June1st to 15thDay
13%7%244345%5%8%39%
2453
16th to endDay
12%5%24435%46%8%41%
2475
July1st to 15thDay
9%42442446%7%47%
2475
16th to endDay
9%4244245%7%10%44%
2366
August1st to 15thDay
12%5%1432435%8%47%
2145
16th to endDay
12%5%35%43446%8%42%
2270
September1st to 15thDay
16%6%35%434447%38%
1909
16th to endDay
18%6%25%5%3436%7%37%
1815
October1st to 15thDay
22%9%37%5%24335%31%
1667
16th to endDay
32%12%5%7%5%3333416%
1713
November1st to 15thDay
20%15%5%7%6%25%5%46%21%
1498
16th to endDay
24%20%6%8%6%345%3313%
1440
December1st to 15thDay
20%24%9%13%7%243346%
1440
16th to endDay
20%24%9%12%6%343347%
1349
January1st to 15thNight
21%18%8%13%9%344437%
2616
16th to endNight
15%18%8%14%8%35%44411%
2538
February1st to 15thNight
14%17%9%11%9%45%34414%
2278
16th to endNight
16%12%7%11%7%35%346%20%
1973
March1st to 15thNight
15%12%5%8%7%34445%27%
2025
16th to endNight
15%8%47%42333440%
2112
April1st to 15thNight
20%9%35%41435%7%34%
1801
16th to endNight
19%7%25%5%23446%37%
1575
May1st to 15thNight
14%6%46%6%2445%7%36%
1481
16th to endNight
10%425%435%5%6%6%45%
1367
June1st to 15thNight
13%6%25%5%35%5%5%7%38%
1174
16th to endNight
11%5%246%245%6%8%42%
1155
July1st to 15thNight
8%41332445%10%52%
1155
16th to endNight
7%4235%46%6%6%7%46%
1488
August1st to 15thNight
10%43443346%9%45%
1485
16th to endNight
10%5%26%5%33447%46%
1575
September1st to 15thNight
13%5%26%3245%6%7%41%
1715
16th to endNight
14%6%35%6%33436%41%
1815
October1st to 15thNight
21%8%37%6%2445%6%30%
1963
16th to endNight
28%11%37%6%34335%20%
2158
November1st to 15thNight
19%13%47%6%35%445%24%
2359
16th to endNight
24%18%6%7%5%24345%16%
2520
December1st to 15thNight
20%24%9%12%6%243338%
2520
16th to endNight
22%22%9%12%7%343239%
2872

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
83%5%6%4
1323
16th to endDay
79%6%6%42
1685
February1st to 15thDay
75%6%8%7%
1577
16th to endDay
67%8%10%9%4
1497
March1st to 15thDay
55%7%12%17%7%
1935
16th to endDay
47%6%13%17%13%1
2112
April1st to 15thDay
51%5%9%20%11%
2155
16th to endDay
45%5%10%22%14%2
2273
May1st to 15thDay
43%6%9%23%14%1
2139
16th to endDay
35%7%14%24%16%2
2398
June1st to 15thDay
41%7%13%23%13%
2453
16th to endDay
39%8%14%23%13%
2475
July1st to 15thDay
31%7%15%26%16%2
2316
16th to endDay
33%8%17%26%13%
2208
August1st to 15thDay
33%7%16%25%15%1
2132
16th to endDay
39%7%15%25%11%1
2270
September1st to 15thDay
44%7%14%24%9%
1909
16th to endDay
44%8%14%24%8%
1815
October1st to 15thDay
56%5%10%17%8%
1667
16th to endDay
72%5%10%9%2
1713
November1st to 15thDay
64%7%10%11%5%
1498
16th to endDay
76%5%9%6%1
1440
December1st to 15thDay
84%6%5%2
1440
16th to endDay
83%5%6%3
1349
January1st to 15thNight
82%7%6%31
2616
16th to endNight
77%6%8%5%1
2538
February1st to 15thNight
75%6%9%8%1
2287
16th to endNight
65%6%11%10%5%
1973
March1st to 15thNight
58%6%11%16%6%
2025
16th to endNight
48%410%19%15%2
2112
April1st to 15thNight
50%410%21%12%1
1801
16th to endNight
46%5%9%17%18%2
1575
May1st to 15thNight
46%5%9%21%14%1
1482
16th to endNight
37%6%12%25%15%2
1369
June1st to 15thNight
43%6%11%22%14%1
1174
16th to endNight
38%6%12%25%16%
1155
July1st to 15thNight
27%5%13%29%20%3
1085
16th to endNight
34%9%13%24%16%1
1383
August1st to 15thNight
34%7%17%24%15%2
1474
16th to endNight
37%6%13%27%13%1
1575
September1st to 15thNight
40%8%13%26%10%
1715
16th to endNight
44%6%14%24%10%
1815
October1st to 15thNight
55%6%9%17%9%
1963
16th to endNight
68%6%11%9%3
2158
November1st to 15thNight
62%5%13%13%41
2359
16th to endNight
72%6%12%7%
2520
December1st to 15thNight
82%7%6%2
2520
16th to endNight
83%5%7%3
2872

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
23%14%36%21%4
71
16th to endDay
34%5%31%23%5%
96
February1st to 15thDay
30%15%35%18%
90
16th to endDay
24%19%29%24%1
81
March1st to 15thDay
22%11%28%29%6%1
225
16th to endDay
23%6%23%30%11%3
288
April1st to 15thDay
25%6%29%25%9%2
270
16th to endDay
27%422%23%16%6%
250
May1st to 15thDay
21%324%26%18%6%
228
16th to endDay
15%220%30%24%7%
267
June1st to 15thDay
16%323%33%19%4
398
16th to endDay
14%220%36%21%4
420
July1st to 15thDay
11%219%37%22%7%
400
16th to endDay
10%119%39%20%7%
327
August1st to 15thDay
15%112%32%25%12%
253
16th to endDay
20%111%31%23%11%
268
September1st to 15thDay
15%320%28%20%11%
255
16th to endDay
19%420%24%22%9%
254
October1st to 15thDay
20%7%27%29%11%3
255
16th to endDay
39%9%24%20%5%
225
November1st to 15thDay
27%6%25%27%10%2
76
16th to endDay
30%13%31%21%3
60
December1st to 15thDay
31%20%28%15%5%
60
16th to endDay
43%26%25%4
64
January1st to 15thNight
27%17%32%17%4
900
16th to endNight
23%10%33%24%6%1
810
February1st to 15thNight
23%11%35%23%5%
704
16th to endNight
21%9%32%28%8%
631
March1st to 15thNight
22%9%35%23%8%
720
16th to endNight
19%5%28%29%14%2
768
April1st to 15thNight
23%9%29%28%7%1
659
16th to endNight
24%424%28%16%1
525
May1st to 15thNight
18%319%36%19%2
492
16th to endNight
13%220%37%23%2
343
June1st to 15thNight
15%420%37%19%2
330
16th to endNight
13%216%40%27%
330
July1st to 15thNight
10%115%41%27%3
310
16th to endNight
9%119%38%28%2
495
August1st to 15thNight
11%216%37%28%3
494
16th to endNight
12%317%31%30%4
525
September1st to 15thNight
16%420%31%18%8%
654
16th to endNight
17%5%19%29%21%6%
657
October1st to 15thNight
25%9%22%26%13%2
660
16th to endNight
36%11%25%22%4
704
November1st to 15thNight
26%12%28%20%10%1
700
16th to endNight
35%13%24%20%5%
720
December1st to 15thNight
33%19%29%13%3
720
16th to endNight
32%13%33%15%3
952
Page generated at 2017-04-26 17:21:43. Version ac04

Copyright 2017 A. Danko


ES Fox Observatory (BAS/BOEC) Clear Sky Chart | Charts Home