MileOak Corner
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the MileOak Corner clear sky chart from 2005-11-05 to 2017-04-02.

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
26%
14443
18%
45360
8%
14412
37%
14412
18%
29980

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
17%
720
19%
2506
7%
716
33%
716
16%
1613
January16th to endNight
16%
768
19%
2686
6%
768
33%
768
15%
1749
February1st to 15thNight
14%
703
15%
2184
4%
701
28%
701
15%
1498
February16th to endNight
17%
631
21%
1893
6%
631
34%
631
16%
1279
March1st to 15thNight
16%
720
16%
2160
6%
720
28%
720
14%
1495
March16th to endNight
19%
768
22%
2013
7%
768
32%
768
21%
1359
April1st to 15thNight
17%
666
16%
1666
3%
666
26%
666
16%
1224
April16th to endNight
23%
578
17%
1568
3%
578
32%
578
19%
1068
May1st to 15thNight
18%
495
17%
1485
6%
495
29%
495
15%
1029
May16th to endNight
29%
344
12%
1370
10%
343
36%
343
14%
882
June1st to 15thNight
28%
330
13%
1320
9%
330
40%
330
14%
884
June16th to endNight
39%
330
11%
1320
10%
330
47%
330
19%
798
July1st to 15thNight
43%
310
13%
1240
14%
310
49%
310
20%
758
July16th to endNight
44%
348
12%
1306
13%
326
53%
326
20%
788
August1st to 15thNight
45%
443
17%
1424
12%
441
50%
441
24%
873
August16th to endNight
51%
700
18%
1750
9%
700
54%
700
30%
1153
September1st to 15thNight
40%
660
20%
1680
10%
660
46%
660
27%
1135
September16th to endNight
45%
657
25%
1815
15%
657
53%
657
30%
1120
October1st to 15thNight
34%
660
22%
1873
13%
660
43%
660
23%
1235
October16th to endNight
25%
704
15%
2260
6%
704
36%
704
18%
1510
November1st to 15thNight
26%
700
21%
2277
10%
700
41%
700
21%
1445
November16th to endNight
22%
720
19%
2356
7%
720
36%
720
16%
1565
December1st to 15thNight
19%
720
16%
2520
5%
720
32%
720
14%
1682
December16th to endNight
15%
768
17%
2688
5%
768
29%
768
12%
1838

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%6%25%43445%7%38%
45770
Night
17%6%25%42445%6%39%
45530
Cloud CoverDay
17%6%25%42445%7%39%
45780
Night
17%6%35%42445%6%39%
45535
TransparencyDay
44%6%12%21%13%2
45458
Night
44%5%12%21%14%1
45360
SeeingDay
19%19%25%21%9%4
5167
Night
18%23%27%23%6%
14444

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%7%24425%5%6%7%38%
1432
16th to endDay
14%8%25%42346%6%39%
1536
February1st to 15thDay
16%7%37%5%35%5%47%33%
1675
16th to endDay
15%8%37%5%24437%37%
1580
March1st to 15thDay
19%7%25%424447%34%
1790
16th to endDay
18%6%34424346%41%
2210
April1st to 15thDay
19%7%25%433346%37%
1984
16th to endDay
17%5%24334347%43%
2062
May1st to 15thDay
23%7%25%43345%6%33%
2145
16th to endDay
16%5%35%5%245%5%7%38%
2394
June1st to 15thDay
22%7%3442445%7%32%
2310
16th to endDay
13%5%25%5%35%6%7%9%34%
2310
July1st to 15thDay
11%5%26%6%36%5%6%9%36%
2310
16th to endDay
12%436%5%36%5%6%8%37%
2458
August1st to 15thDay
12%435%5%46%46%7%39%
2183
16th to endDay
11%425%6%345%5%7%43%
2100
September1st to 15thDay
14%5%25%5%23446%45%
1950
16th to endDay
15%423413445%50%
1815
October1st to 15thDay
19%6%25%323346%41%
1755
16th to endDay
16%7%36%433445%40%
1612
November1st to 15thDay
18%8%34333236%42%
1581
16th to endDay
18%6%233245%46%42%
1602
December1st to 15thDay
20%5%35%325%447%37%
1440
16th to endDay
22%8%245%2445%6%33%
1536
January1st to 15thNight
18%8%25%433346%39%
2506
16th to endNight
15%9%35%5%2336%5%38%
2686
February1st to 15thNight
15%7%36%6%35%45%5%36%
2183
16th to endNight
16%8%345%25%345%38%
1893
March1st to 15thNight
19%7%345%2445%6%35%
2147
16th to endNight
17%6%35%323346%42%
2013
April1st to 15thNight
19%9%35%5%24336%34%
1666
16th to endNight
21%5%25%423336%40%
1568
May1st to 15thNight
18%6%36%5%3435%5%37%
1485
16th to endNight
18%5%245%3445%8%37%
1368
June1st to 15thNight
22%5%25%42445%6%35%
1320
16th to endNight
14%5%25%32445%9%42%
1320
July1st to 15thNight
12%425%5%35%5%6%7%41%
1320
16th to endNight
10%5%25%5%35%6%7%10%38%
1402
August1st to 15thNight
9%5%15%4345%5%9%43%
1434
16th to endNight
11%415%4345%6%8%43%
1750
September1st to 15thNight
13%5%25%43445%5%44%
1680
16th to endNight
14%5%24314335%52%
1815
October1st to 15thNight
17%6%25%324445%43%
1873
16th to endNight
19%7%35%41345%5%38%
2260
November1st to 15thNight
17%6%24413345%44%
2277
16th to endNight
18%7%36%42444439%
2356
December1st to 15thNight
20%7%3442445%5%36%
2520
16th to endNight
21%7%25%42445%6%33%
2688

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%7%245%35%35%6%39%
1432
16th to endDay
16%7%25%4235%6%6%39%
1536
February1st to 15thDay
16%7%36%6%35%45%7%32%
1675
16th to endDay
16%8%36%5%24346%37%
1580
March1st to 15thDay
20%8%35%434347%35%
1800
16th to endDay
18%7%24423335%42%
2210
April1st to 15thDay
20%7%35%6%23435%37%
1984
16th to endDay
17%5%1443435%6%44%
2062
May1st to 15thDay
24%7%24423446%33%
2145
16th to endDay
17%5%3443445%7%40%
2394
June1st to 15thDay
23%7%34425%35%7%32%
2310
16th to endDay
14%5%25%5%35%6%7%9%35%
2310
July1st to 15thDay
11%5%25%7%45%5%6%8%36%
2310
16th to endDay
13%435%6%36%5%5%9%37%
2458
August1st to 15thDay
13%5%25%5%45%5%5%7%38%
2183
16th to endDay
11%5%25%5%25%5%5%7%42%
2100
September1st to 15thDay
14%6%345%24335%45%
1950
16th to endDay
16%314423345%50%
1815
October1st to 15thDay
18%6%24413346%41%
1755
16th to endDay
16%7%26%424445%41%
1612
November1st to 15thDay
19%7%33333236%42%
1581
16th to endDay
18%5%23324445%42%
1602
December1st to 15thDay
19%6%35%324437%37%
1440
16th to endDay
23%8%2442445%6%33%
1536
January1st to 15thNight
18%8%25%333345%39%
2506
16th to endNight
15%9%45%5%2345%6%38%
2686
February1st to 15thNight
15%7%36%5%35%45%5%36%
2176
16th to endNight
17%8%345%34445%38%
1893
March1st to 15thNight
20%6%35%5%2435%7%35%
2160
16th to endNight
18%6%25%423337%42%
2012
April1st to 15thNight
20%8%45%434345%35%
1666
16th to endNight
22%6%24423345%40%
1568
May1st to 15thNight
18%7%35%5%3435%5%37%
1485
16th to endNight
18%5%245%245%5%8%36%
1368
June1st to 15thNight
21%6%245%24347%36%
1320
16th to endNight
14%5%2442345%8%43%
1320
July1st to 15thNight
12%4245%35%5%6%8%41%
1320
16th to endNight
10%5%35%4346%7%8%38%
1402
August1st to 15thNight
10%425%435%5%5%9%44%
1434
16th to endNight
12%5%144345%6%8%43%
1750
September1st to 15thNight
14%5%25%334446%45%
1680
16th to endNight
15%42431324451%
1815
October1st to 15thNight
17%5%24423446%43%
1873
16th to endNight
19%7%35%5%23346%38%
2260
November1st to 15thNight
18%6%24323346%44%
2277
16th to endNight
18%7%35%424445%39%
2356
December1st to 15thNight
20%7%35%43345%5%37%
2520
16th to endNight
21%7%3442445%6%33%
2688

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
43%5%15%23%10%2
1433
16th to endDay
42%5%14%24%11%1
1536
February1st to 15thDay
48%6%13%19%10%
1678
16th to endDay
47%5%10%21%13%2
1580
March1st to 15thDay
49%413%21%9%2
1800
16th to endDay
43%5%9%20%15%4
2210
April1st to 15thDay
48%311%17%15%2
1984
16th to endDay
40%49%21%19%3
2062
May1st to 15thDay
50%5%9%18%13%2
2145
16th to endDay
43%7%13%20%13%2
2398
June1st to 15thDay
50%7%13%18%9%1
2310
16th to endDay
41%10%14%20%11%
2310
July1st to 15thDay
44%7%11%22%13%1
2161
16th to endDay
41%7%16%19%12%2
2291
August1st to 15thDay
42%8%13%22%13%1
2169
16th to endDay
37%7%9%27%15%1
2100
September1st to 15thDay
40%5%11%22%18%1
1950
16th to endDay
35%48%24%25%2
1815
October1st to 15thDay
43%6%9%23%13%3
1755
16th to endDay
43%5%13%21%12%2
1612
November1st to 15thDay
44%413%20%14%2
1581
16th to endDay
42%5%11%24%14%2
1602
December1st to 15thDay
45%5%17%18%12%
1440
16th to endDay
50%6%15%17%9%
1536
January1st to 15thNight
46%314%21%11%2
2506
16th to endNight
45%5%11%22%12%2
2686
February1st to 15thNight
47%5%13%20%11%1
2184
16th to endNight
46%5%10%21%14%2
1893
March1st to 15thNight
48%5%11%19%12%2
2160
16th to endNight
42%410%20%16%5%
2013
April1st to 15thNight
50%49%17%15%1
1666
16th to endNight
45%48%19%17%4
1568
May1st to 15thNight
48%5%10%17%14%3
1485
16th to endNight
44%7%17%18%10%1
1370
June1st to 15thNight
48%6%14%19%10%
1320
16th to endNight
38%8%14%24%14%
1320
July1st to 15thNight
37%9%13%25%12%
1240
16th to endNight
38%8%16%23%10%2
1306
August1st to 15thNight
35%8%15%23%14%2
1424
16th to endNight
36%8%12%26%15%
1750
September1st to 15thNight
39%7%11%22%18%
1680
16th to endNight
36%47%23%26%2
1815
October1st to 15thNight
43%411%21%15%3
1873
16th to endNight
46%5%13%22%11%
2260
November1st to 15thNight
41%412%20%17%2
2277
16th to endNight
46%5%12%20%12%1
2356
December1st to 15thNight
47%6%14%20%10%
2520
16th to endNight
49%5%12%20%10%
2688

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
16%31%31%16%3
60
16th to endDay
26%18%37%15%1
64
February1st to 15thDay
24%27%27%18%1
191
16th to endDay
18%28%33%15%2
239
March1st to 15thDay
30%25%24%18%2
270
16th to endDay
22%29%25%12%6%2
288
April1st to 15thDay
23%26%26%15%7%
214
16th to endDay
17%25%24%21%7%4
210
May1st to 15thDay
30%22%21%14%8%2
228
16th to endDay
16%20%28%20%10%2
267
June1st to 15thDay
22%23%21%18%10%2
255
16th to endDay
13%17%28%26%10%3
255
July1st to 15thDay
15%14%26%24%14%4
245
16th to endDay
14%16%23%28%15%2
270
August1st to 15thDay
12%11%23%30%14%7%
253
16th to endDay
12%10%17%27%21%10%
268
September1st to 15thDay
16%13%19%25%13%10%
255
16th to endDay
17%8%25%19%13%14%
254
October1st to 15thDay
23%11%20%23%12%7%
255
16th to endDay
16%23%29%22%7%
245
November1st to 15thDay
22%18%22%25%7%2
235
16th to endDay
22%20%28%17%8%2
222
December1st to 15thDay
15%30%33%13%8%
60
16th to endDay
32%23%31%12%
64
January1st to 15thNight
18%28%31%19%2
720
16th to endNight
18%26%32%19%1
768
February1st to 15thNight
18%25%35%18%1
704
16th to endNight
20%29%30%17%2
631
March1st to 15thNight
23%30%26%17%1
720
16th to endNight
19%26%30%18%4
768
April1st to 15thNight
22%29%27%18%2
666
16th to endNight
18%29%24%20%6%
578
May1st to 15thNight
17%28%30%17%5%
495
16th to endNight
18%24%24%27%4
344
June1st to 15thNight
19%22%26%26%6%
330
16th to endNight
13%20%23%34%7%
330
July1st to 15thNight
11%15%22%37%13%
310
16th to endNight
12%18%19%38%10%1
348
August1st to 15thNight
11%13%22%39%12%
443
16th to endNight
11%11%18%35%20%2
700
September1st to 15thNight
15%13%24%31%13%
660
16th to endNight
15%14%18%29%17%3
657
October1st to 15thNight
21%15%25%28%8%1
660
16th to endNight
20%20%30%23%5%
704
November1st to 15thNight
18%23%27%21%8%
700
16th to endNight
16%28%27%19%7%
720
December1st to 15thNight
22%23%31%17%4
720
16th to endNight
23%29%28%17%1
768
Page generated at 2017-04-03 01:35:07. Version ac04

Copyright 2017 A. Danko


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