Maple-Brook Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Maple-Brook Observatory clear sky chart from 2005-11-05 to 2017-09-24.

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
21%
15228
12%
46800
5%
15183
28%
15183
14%
34456

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
11%
750
10%
2506
2%
746
20%
746
8%
1953
January16th to endNight
13%
775
11%
2535
3%
775
23%
775
8%
1984
February1st to 15thNight
14%
704
7%
2286
2%
701
20%
701
8%
1810
February16th to endNight
17%
631
9%
2024
3%
631
23%
631
9%
1582
March1st to 15thNight
18%
720
13%
1998
4%
720
26%
720
13%
1509
March16th to endNight
18%
762
15%
2106
4%
762
27%
762
15%
1565
April1st to 15thNight
15%
539
13%
1796
5%
539
25%
539
11%
1318
April16th to endNight
17%
540
14%
1650
6%
540
25%
540
16%
1192
May1st to 15thNight
21%
540
11%
1506
5%
540
27%
540
15%
1153
May16th to endNight
19%
561
10%
1496
2%
560
25%
560
17%
1110
June1st to 15thNight
17%
540
7%
1440
2%
540
21%
540
14%
1124
June16th to endNight
24%
420
8%
1320
2%
420
29%
420
17%
970
July1st to 15thNight
34%
474
9%
1324
5%
474
37%
474
25%
896
July16th to endNight
35%
565
10%
1447
8%
532
37%
532
20%
1055
August1st to 15thNight
38%
539
12%
1608
9%
535
40%
535
21%
1118
August16th to endNight
38%
573
17%
1796
11%
573
43%
573
24%
1149
September1st to 15thNight
32%
540
17%
1800
10%
540
42%
540
24%
1117
September16th to endNight
33%
660
23%
1925
13%
660
42%
660
24%
1261
October1st to 15thNight
27%
660
20%
1980
8%
660
37%
660
21%
1324
October16th to endNight
16%
705
15%
2115
4%
705
25%
705
15%
1520
November1st to 15thNight
25%
730
13%
2414
8%
730
30%
730
14%
1756
November16th to endNight
22%
750
13%
2520
5%
750
30%
750
12%
1842
December1st to 15thNight
11%
750
10%
2520
1%
750
22%
750
8%
1980
December16th to endNight
11%
800
9%
2688
3%
800
19%
800
7%
2168

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
21%10%46%5%34446%27%
48114
Night
20%9%47%6%34446%28%
46975
TransparencyDay
58%310%18%8%
47807
Night
56%411%19%7%
46800
SeeingDay
29%15%29%17%6%1
7578
Night
27%14%30%20%5%
15228

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
15%15%6%10%10%45%446%16%
1432
16th to endDay
16%13%49%9%46%45%5%20%
1687
February1st to 15thDay
16%14%5%10%8%5%6%445%17%
1575
16th to endDay
13%17%8%9%5%34336%23%
1449
March1st to 15thDay
18%15%5%8%6%45%33425%
1948
16th to endDay
17%13%6%8%6%3333329%
2118
April1st to 15thDay
22%14%47%6%3433424%
2153
16th to endDay
25%11%36%5%2344428%
2309
May1st to 15thDay
28%11%35%43445%5%24%
2444
16th to endDay
24%10%37%424446%26%
2618
June1st to 15thDay
30%10%36%434445%22%
2520
16th to endDay
26%9%35%424446%26%
2644
July1st to 15thDay
18%7%345%35%5%5%9%32%
2538
16th to endDay
21%9%46%6%35%45%7%25%
2620
August1st to 15thDay
21%7%36%5%3445%7%28%
2340
16th to endDay
16%5%25%433448%40%
2405
September1st to 15thDay
21%6%245%2435%7%36%
2160
16th to endDay
17%7%24413346%42%
1890
October1st to 15thDay
20%7%335%2345%7%35%
1650
16th to endDay
23%10%46%6%34445%25%
1757
November1st to 15thDay
26%11%47%424335%26%
1441
16th to endDay
21%12%6%7%5%35%35%5%22%
1440
December1st to 15thDay
24%12%6%11%5%34345%19%
1440
16th to endDay
24%15%7%10%7%2433417%
1536
January1st to 15thNight
16%13%5%10%9%3445%421%
2506
16th to endNight
17%11%5%9%8%5%6%5%45%20%
2535
February1st to 15thNight
18%12%49%9%5%5%5%5%7%16%
2285
16th to endNight
15%14%6%10%7%34445%22%
2024
March1st to 15thNight
19%12%45%7%3435%6%26%
1986
16th to endNight
20%10%5%7%5%24335%30%
2106
April1st to 15thNight
23%12%36%424345%28%
1796
16th to endNight
24%9%46%42435%5%30%
1650
May1st to 15thNight
27%10%35%42445%6%25%
1506
16th to endNight
20%7%46%6%345%5%7%28%
1494
June1st to 15thNight
29%10%36%5%23235%25%
1440
16th to endNight
24%7%35%5%34447%28%
1320
July1st to 15thNight
14%5%36%435%46%9%35%
1404
16th to endNight
17%8%36%5%345%6%8%29%
1545
August1st to 15thNight
19%7%26%4345%5%6%34%
1620
16th to endNight
15%5%25%5%34447%41%
1796
September1st to 15thNight
16%6%2442445%7%41%
1800
16th to endNight
19%6%24413436%43%
1925
October1st to 15thNight
20%6%24433337%37%
1980
16th to endNight
25%7%26%5%23446%30%
2115
November1st to 15thNight
23%11%36%434345%29%
2414
16th to endNight
22%9%46%5%44446%27%
2520
December1st to 15thNight
23%11%49%7%34445%21%
2520
16th to endNight
25%12%7%9%6%35%44418%
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
65%5%11%12%3
1433
16th to endDay
63%46%17%7%
1687
February1st to 15thDay
67%48%12%5%
1578
16th to endDay
63%310%15%7%
1449
March1st to 15thDay
64%27%15%8%1
1959
16th to endDay
60%27%18%10%1
2118
April1st to 15thDay
63%36%14%11%1
2153
16th to endDay
58%37%17%11%1
2309
May1st to 15thDay
61%28%18%7%
2444
16th to endDay
59%310%18%7%1
2622
June1st to 15thDay
64%410%14%6%1
2520
16th to endDay
59%412%17%7%
2644
July1st to 15thDay
47%5%14%22%9%
2390
16th to endDay
57%412%18%5%
2455
August1st to 15thDay
53%413%20%7%
2327
16th to endDay
42%316%27%9%
2405
September1st to 15thDay
47%311%24%11%1
2160
16th to endDay
42%39%28%15%
1890
October1st to 15thDay
47%310%25%12%
1650
16th to endDay
59%310%20%5%
1757
November1st to 15thDay
60%310%16%8%
1441
16th to endDay
62%5%10%13%7%
1440
December1st to 15thDay
67%39%16%3
1440
16th to endDay
70%27%12%6%
1536
January1st to 15thNight
63%410%16%3
2506
16th to endNight
63%5%7%18%4
2535
February1st to 15thNight
66%310%13%5%
2286
16th to endNight
64%311%14%6%
2024
March1st to 15thNight
57%311%17%8%
1998
16th to endNight
56%28%20%9%1
2106
April1st to 15thNight
58%37%17%10%2
1796
16th to endNight
55%29%17%12%1
1650
May1st to 15thNight
59%310%19%6%
1506
16th to endNight
54%414%19%6%1
1496
June1st to 15thNight
62%210%17%5%
1440
16th to endNight
56%311%19%7%
1320
July1st to 15thNight
43%6%18%21%9%
1324
16th to endNight
52%5%15%19%6%
1447
August1st to 15thNight
50%314%24%6%
1608
16th to endNight
42%416%25%10%
1796
September1st to 15thNight
42%311%29%12%1
1800
16th to endNight
43%39%29%12%
1925
October1st to 15thNight
47%310%27%11%
1980
16th to endNight
54%310%22%9%
2115
November1st to 15thNight
56%411%19%7%
2414
16th to endNight
57%413%17%7%
2520
December1st to 15thNight
64%49%17%4
2520
16th to endNight
68%47%14%5%
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
22%24%33%19%
240
16th to endDay
26%21%36%12%3
256
February1st to 15thDay
27%19%33%16%2
236
16th to endDay
25%23%29%16%5%
212
March1st to 15thDay
26%27%28%13%4
267
16th to endDay
29%25%27%11%41
288
April1st to 15thDay
34%22%29%10%2
270
16th to endDay
25%21%34%12%31
270
May1st to 15thDay
39%14%24%13%5%1
400
16th to endDay
31%14%31%17%4
519
June1st to 15thDay
37%12%25%19%4
495
16th to endDay
32%10%30%18%5%2
495
July1st to 15thDay
23%7%32%25%9%1
475
16th to endDay
29%5%29%24%9%1
481
August1st to 15thDay
24%7%33%22%8%2
313
16th to endDay
22%10%28%23%11%3
332
September1st to 15thDay
23%12%32%21%8%1
315
16th to endDay
21%11%28%23%11%3
278
October1st to 15thDay
25%12%29%16%11%3
225
16th to endDay
32%19%25%14%5%2
240
November1st to 15thDay
28%13%27%19%8%2
235
16th to endDay
31%18%25%16%7%1
240
December1st to 15thDay
35%22%24%14%3
240
16th to endDay
34%21%31%10%1
256
January1st to 15thNight
26%21%33%17%1
750
16th to endNight
29%20%31%16%2
775
February1st to 15thNight
29%17%32%18%1
704
16th to endNight
27%21%28%18%4
631
March1st to 15thNight
27%20%29%17%4
720
16th to endNight
28%19%27%19%4
762
April1st to 15thNight
31%17%30%16%4
539
16th to endNight
31%14%32%18%2
540
May1st to 15thNight
32%13%28%18%6%
540
16th to endNight
23%12%39%20%4
561
June1st to 15thNight
35%10%31%18%4
540
16th to endNight
25%6%35%24%6%
420
July1st to 15thNight
16%241%31%8%
474
16th to endNight
22%429%32%10%
565
August1st to 15thNight
22%428%31%11%
539
16th to endNight
18%7%30%31%11%
573
September1st to 15thNight
19%8%33%29%8%
540
16th to endNight
24%8%28%25%11%1
660
October1st to 15thNight
24%12%29%21%9%1
660
16th to endNight
31%17%30%15%5%
705
November1st to 15thNight
30%11%27%22%6%1
730
16th to endNight
29%17%25%20%6%
750
December1st to 15thNight
34%17%31%13%3
750
16th to endNight
32%21%29%14%2
800
Page generated at 2017-09-25 10:02:22. Version ac04

Copyright 2017 A. Danko


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