Machias
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Machias clear sky chart from 2005-11-05 to 2017-05-01.

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
24%
14500
14%
45631
6%
14461
33%
14461
14%
32198

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
13%
729
13%
2561
3%
725
25%
725
10%
1771
January16th to endNight
11%
768
11%
2609
1%
768
23%
768
10%
1846
February1st to 15thNight
13%
704
10%
2286
2%
701
23%
701
9%
1657
February16th to endNight
15%
631
15%
1931
3%
631
29%
631
12%
1366
March1st to 15thNight
16%
720
15%
2058
5%
720
26%
720
13%
1514
March16th to endNight
21%
768
17%
2112
6%
768
29%
768
16%
1505
April1st to 15thNight
17%
637
15%
1777
3%
637
27%
637
15%
1321
April16th to endNight
26%
540
13%
1620
5%
540
33%
540
17%
1152
May1st to 15thNight
24%
498
13%
1494
7%
498
31%
498
15%
1107
May16th to endNight
27%
472
10%
1374
6%
471
33%
471
14%
1045
June1st to 15thNight
26%
330
8%
1155
5%
330
31%
330
11%
889
June16th to endNight
31%
330
7%
1155
6%
330
35%
330
12%
860
July1st to 15thNight
41%
310
9%
1115
11%
310
44%
310
15%
781
July16th to endNight
34%
408
8%
1361
7%
381
39%
381
11%
999
August1st to 15thNight
44%
494
10%
1473
8%
490
45%
490
16%
1080
August16th to endNight
48%
525
15%
1575
9%
525
51%
525
22%
1055
September1st to 15thNight
40%
610
16%
1740
9%
610
45%
610
24%
1155
September16th to endNight
39%
657
25%
1815
13%
657
49%
657
32%
1101
October1st to 15thNight
30%
660
20%
1933
9%
660
40%
660
21%
1280
October16th to endNight
22%
704
16%
2197
6%
704
33%
704
18%
1480
November1st to 15thNight
29%
705
16%
2307
9%
705
38%
705
17%
1564
November16th to endNight
18%
750
15%
2520
5%
750
31%
750
13%
1745
December1st to 15thNight
12%
750
11%
2583
3%
750
22%
750
10%
1861
December16th to endNight
11%
800
11%
2880
2%
800
23%
800
9%
2064

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
20%7%35%424447%35%
46127
Night
21%8%35%424446%35%
45802
TransparencyDay
49%6%12%19%10%1
45816
Night
51%5%12%19%10%
45631
SeeingDay
24%18%24%21%9%1
6081
Night
23%23%24%20%7%
14500

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
17%7%345%23445%39%
1376
16th to endDay
18%9%45%423345%37%
1614
February1st to 15thDay
17%10%35%5%36%448%31%
1575
16th to endDay
15%9%36%43445%8%33%
1539
March1st to 15thDay
21%10%35%424335%34%
1891
16th to endDay
18%9%35%5%33236%38%
2112
April1st to 15thDay
22%9%35%323346%34%
2170
16th to endDay
23%7%25%423346%35%
2340
May1st to 15thDay
25%7%35%5%2435%6%29%
2140
16th to endDay
25%7%3442345%7%29%
2394
June1st to 15thDay
29%7%35%5%1445%6%26%
2475
16th to endDay
24%7%35%5%24347%30%
2475
July1st to 15thDay
17%5%2443446%11%34%
2439
16th to endDay
18%7%25%445%5%5%8%31%
2385
August1st to 15thDay
17%7%25%42445%8%36%
2145
16th to endDay
13%4234345%6%9%41%
2275
September1st to 15thDay
15%5%2332335%7%46%
1887
16th to endDay
18%414423236%48%
1815
October1st to 15thDay
19%6%24433447%39%
1697
16th to endDay
23%5%2442335%5%37%
1674
November1st to 15thDay
23%6%25%32335%7%37%
1551
16th to endDay
22%8%34314335%37%
1440
December1st to 15thDay
27%8%23423436%33%
1374
16th to endDay
27%8%25%423245%34%
1344
January1st to 15thNight
17%8%35%424346%37%
2561
16th to endNight
15%11%36%325%45%7%33%
2609
February1st to 15thNight
16%9%35%5%35%446%34%
2285
16th to endNight
17%9%35%5%24446%36%
1931
March1st to 15thNight
19%11%37%424336%33%
2046
16th to endNight
17%8%35%5%24445%36%
2112
April1st to 15thNight
25%7%35%42445%5%30%
1777
16th to endNight
23%8%35%424346%32%
1620
May1st to 15thNight
23%9%35%5%23446%30%
1494
16th to endNight
27%8%25%5%3446%5%27%
1372
June1st to 15thNight
33%9%35%414246%23%
1155
16th to endNight
26%9%35%42426%7%28%
1155
July1st to 15thNight
20%9%25%43446%8%30%
1188
16th to endNight
23%8%45%436%45%5%28%
1462
August1st to 15thNight
19%8%24435%5%6%8%31%
1485
16th to endNight
17%5%3343445%8%40%
1575
September1st to 15thNight
19%6%25%323337%42%
1740
16th to endNight
14%5%14322346%51%
1815
October1st to 15thNight
21%5%24433446%40%
1933
16th to endNight
22%6%24422336%40%
2197
November1st to 15thNight
20%6%25%43445%5%38%
2307
16th to endNight
21%7%25%424346%37%
2520
December1st to 15thNight
25%9%35%322335%34%
2583
16th to endNight
24%8%34424435%34%
2880

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
48%7%17%17%7%1
1377
16th to endDay
51%5%17%18%6%
1614
February1st to 15thDay
53%7%15%15%6%
1578
16th to endDay
47%7%15%19%7%1
1539
March1st to 15thDay
52%5%11%17%10%2
1902
16th to endDay
46%5%11%17%15%3
2112
April1st to 15thDay
47%5%10%18%14%2
2170
16th to endDay
48%6%10%17%14%2
2340
May1st to 15thDay
54%5%10%15%13%1
2140
16th to endDay
53%7%11%20%7%
2398
June1st to 15thDay
59%6%11%13%7%1
2475
16th to endDay
55%5%9%17%10%1
2475
July1st to 15thDay
49%6%14%20%8%
2283
16th to endDay
52%7%15%17%7%
2224
August1st to 15thDay
49%6%11%21%9%
2132
16th to endDay
41%6%15%24%12%
2275
September1st to 15thDay
38%6%12%23%16%2
1887
16th to endDay
37%48%31%16%
1815
October1st to 15thDay
42%5%12%24%14%
1697
16th to endDay
46%5%12%23%10%
1674
November1st to 15thDay
46%6%14%19%12%
1551
16th to endDay
50%6%13%18%9%1
1440
December1st to 15thDay
54%6%16%17%6%
1374
16th to endDay
55%5%12%17%8%
1344
January1st to 15thNight
52%415%19%7%
2561
16th to endNight
52%6%16%17%6%
2609
February1st to 15thNight
53%6%15%16%6%
2286
16th to endNight
50%6%12%18%10%1
1931
March1st to 15thNight
54%410%16%12%1
2058
16th to endNight
50%410%19%14%1
2112
April1st to 15thNight
54%5%8%15%12%2
1777
16th to endNight
52%411%15%13%2
1620
May1st to 15thNight
55%5%8%16%12%1
1494
16th to endNight
58%411%17%7%
1374
June1st to 15thNight
63%311%13%5%1
1155
16th to endNight
59%49%17%9%
1155
July1st to 15thNight
51%6%13%16%12%
1115
16th to endNight
57%6%12%15%7%
1361
August1st to 15thNight
51%7%13%19%7%
1473
16th to endNight
44%5%14%22%12%
1575
September1st to 15thNight
43%5%11%23%15%
1740
16th to endNight
34%39%30%20%
1815
October1st to 15thNight
43%5%10%23%14%2
1933
16th to endNight
46%5%11%24%11%
2197
November1st to 15thNight
47%5%14%20%11%
2307
16th to endNight
49%6%13%18%10%
2520
December1st to 15thNight
55%414%18%6%
2583
16th to endNight
56%415%15%8%
2880

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%23%41%16%1
60
16th to endDay
23%23%34%16%2
142
February1st to 15thDay
23%28%30%14%2
236
16th to endDay
19%24%31%20%3
232
March1st to 15thDay
22%30%28%13%4
270
16th to endDay
23%26%26%16%5%1
288
April1st to 15thDay
27%19%32%13%5%1
270
16th to endDay
24%16%34%17%5%2
270
May1st to 15thDay
28%19%24%19%6%1
229
16th to endDay
28%20%20%18%10%1
390
June1st to 15thDay
27%16%20%27%8%
420
16th to endDay
29%15%15%23%14%1
420
July1st to 15thDay
29%11%15%24%17%2
367
16th to endDay
25%12%18%28%13%1
270
August1st to 15thDay
22%7%19%31%16%2
253
16th to endDay
19%7%17%31%19%3
268
September1st to 15thDay
20%8%20%31%16%3
255
16th to endDay
18%9%22%31%13%5%
254
October1st to 15thDay
21%17%24%19%13%2
234
16th to endDay
25%15%34%19%5%
240
November1st to 15thDay
21%22%22%22%8%2
235
16th to endDay
22%29%25%16%5%
240
December1st to 15thDay
29%23%27%15%2
174
16th to endDay
37%20%31%9%1
64
January1st to 15thNight
19%33%29%13%3
729
16th to endNight
20%33%29%13%2
768
February1st to 15thNight
20%33%28%14%2
704
16th to endNight
20%31%27%15%3
631
March1st to 15thNight
23%30%25%16%3
720
16th to endNight
19%29%26%18%6%
768
April1st to 15thNight
24%22%32%15%4
637
16th to endNight
22%19%25%25%6%
540
May1st to 15thNight
23%20%25%23%6%2
498
16th to endNight
27%21%18%24%7%1
472
June1st to 15thNight
30%20%15%23%8%
330
16th to endNight
28%19%13%27%11%1
330
July1st to 15thNight
28%13%11%28%16%
310
16th to endNight
27%18%11%28%14%
408
August1st to 15thNight
25%11%11%31%18%1
494
16th to endNight
20%10%14%33%19%2
525
September1st to 15thNight
21%10%18%31%15%1
610
16th to endNight
19%11%24%25%15%3
657
October1st to 15thNight
23%13%26%23%11%2
660
16th to endNight
23%18%32%18%5%
704
November1st to 15thNight
19%22%23%23%8%1
705
16th to endNight
20%29%26%14%7%
750
December1st to 15thNight
30%27%26%12%3
750
16th to endNight
29%31%25%11%1
800
Page generated at 2017-05-02 08:43:27. Version ac04

Copyright 2017 A. Danko


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