Milford
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Milford clear sky chart from 2005-11-05 to 2017-08-12.

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
25%
14779
18%
46456
7%
14747
37%
14747
20%
30338

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
14%
720
19%
2506
5%
716
32%
716
15%
1612
January16th to endNight
14%
768
19%
2688
4%
768
34%
768
14%
1728
February1st to 15thNight
15%
704
17%
2180
4%
701
31%
701
16%
1465
February16th to endNight
14%
631
23%
1893
5%
631
35%
631
18%
1239
March1st to 15thNight
16%
720
17%
2160
6%
720
30%
720
17%
1482
March16th to endNight
18%
768
23%
2025
7%
768
32%
768
20%
1375
April1st to 15thNight
18%
718
18%
1796
3%
718
27%
718
19%
1288
April16th to endNight
21%
600
18%
1680
4%
600
31%
600
20%
1143
May1st to 15thNight
20%
540
15%
1620
6%
540
28%
540
17%
1128
May16th to endNight
22%
417
11%
1539
7%
416
30%
416
15%
1029
June1st to 15thNight
28%
360
12%
1440
7%
360
39%
360
15%
961
June16th to endNight
32%
360
12%
1440
10%
360
42%
360
22%
877
July1st to 15thNight
39%
340
12%
1360
12%
340
46%
340
22%
810
July16th to endNight
42%
376
15%
1418
13%
354
51%
354
21%
867
August1st to 15thNight
41%
495
17%
1544
10%
493
47%
493
27%
957
August16th to endNight
48%
673
19%
1723
10%
673
51%
673
33%
1114
September1st to 15thNight
38%
660
20%
1704
8%
660
46%
660
28%
1140
September16th to endNight
43%
657
24%
1815
15%
657
51%
657
33%
1114
October1st to 15thNight
32%
660
23%
1837
10%
660
44%
660
25%
1195
October16th to endNight
23%
704
17%
2287
5%
704
38%
704
20%
1479
November1st to 15thNight
27%
700
20%
2277
9%
700
41%
700
22%
1438
November16th to endNight
23%
720
21%
2340
8%
720
39%
720
18%
1491
December1st to 15thNight
18%
720
18%
2496
6%
720
33%
720
15%
1620
December16th to endNight
13%
768
19%
2688
4%
768
32%
768
14%
1786

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
17%6%24424446%39%
47521
Night
17%6%24424446%41%
46626
Cloud CoverDay
17%6%25%43445%6%39%
47531
Night
17%6%25%424446%40%
46631
TransparencyDay
44%411%21%15%2
47209
Night
44%411%21%15%2
46456
SeeingDay
23%14%30%19%8%2
5755
Night
22%14%33%22%6%
14779

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%8%34424446%41%
1432
16th to endDay
15%6%3442346%6%43%
1536
February1st to 15thDay
17%7%24435%6%5%6%35%
1679
16th to endDay
15%9%25%43434441%
1580
March1st to 15thDay
20%8%24423446%37%
1790
16th to endDay
17%6%34422436%42%
2198
April1st to 15thDay
19%6%26%434446%38%
2152
16th to endDay
18%4145%24437%41%
2280
May1st to 15thDay
25%7%35%424345%32%
2332
16th to endDay
18%5%25%42435%8%39%
2584
June1st to 15thDay
25%5%24424446%34%
2520
16th to endDay
15%425%6%35%5%6%8%35%
2520
July1st to 15thDay
13%435%6%35%6%48%37%
2520
16th to endDay
13%5%26%5%36%5%6%8%37%
2654
August1st to 15thDay
13%5%25%6%35%46%8%38%
2308
16th to endDay
12%4245%35%5%6%8%41%
2124
September1st to 15thDay
15%5%24423348%46%
1925
16th to endDay
15%5%23323345%51%
1815
October1st to 15thDay
21%5%14422336%44%
1790
16th to endDay
17%5%24433437%43%
1584
November1st to 15thDay
21%6%2342243344%
1581
16th to endDay
17%5%2342445%5%43%
1620
December1st to 15thDay
18%6%34414346%40%
1461
16th to endDay
22%7%24334446%35%
1536
January1st to 15thNight
18%8%35%423335%41%
2506
16th to endNight
16%9%34423345%41%
2688
February1st to 15thNight
14%8%35%4245%45%38%
2179
16th to endNight
16%8%35%324445%41%
1893
March1st to 15thNight
17%8%245%25%5%46%37%
2147
16th to endNight
16%7%45%424235%43%
2025
April1st to 15thNight
16%8%26%5%245%45%37%
1796
16th to endNight
22%5%235%33335%41%
1680
May1st to 15thNight
23%6%25%334335%36%
1620
16th to endNight
19%5%346%34447%36%
1537
June1st to 15thNight
23%5%24424447%35%
1440
16th to endNight
15%425%325%5%6%8%40%
1440
July1st to 15thNight
12%6%34425%46%9%40%
1440
16th to endNight
12%425%5%36%5%5%7%40%
1514
August1st to 15thNight
10%425%5%35%5%6%9%43%
1554
16th to endNight
12%5%23335%45%7%46%
1723
September1st to 15thNight
14%415%425%446%43%
1704
16th to endNight
13%6%24322336%51%
1815
October1st to 15thNight
21%423313435%45%
1837
16th to endNight
18%6%15%5%24446%40%
2287
November1st to 15thNight
17%6%24423345%45%
2277
16th to endNight
19%6%24324445%41%
2340
December1st to 15thNight
19%7%245%13445%40%
2496
16th to endNight
18%9%25%423447%36%
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
15%9%34424445%42%
1432
16th to endDay
15%5%244235%46%43%
1536
February1st to 15thDay
17%7%245%45%46%6%35%
1679
16th to endDay
15%9%26%33434441%
1580
March1st to 15thDay
21%8%24424346%36%
1800
16th to endDay
17%6%35%333436%42%
2198
April1st to 15thDay
18%7%25%42335%6%37%
2152
16th to endDay
18%415%434447%41%
2280
May1st to 15thDay
25%7%25%42435%6%32%
2332
16th to endDay
18%42443345%8%39%
2584
June1st to 15thDay
25%6%24423447%33%
2520
16th to endDay
15%5%25%6%35%5%6%8%35%
2520
July1st to 15thDay
13%5%26%6%35%5%48%37%
2520
16th to endDay
13%5%25%5%36%5%6%8%37%
2654
August1st to 15thDay
12%6%25%5%345%6%7%38%
2308
16th to endDay
12%425%5%35%5%5%8%41%
2124
September1st to 15thDay
14%42443335%7%46%
1925
16th to endDay
15%5%14323335%51%
1815
October1st to 15thDay
22%5%24322245%44%
1790
16th to endDay
17%5%2442335%6%42%
1584
November1st to 15thDay
21%6%2432334343%
1581
16th to endDay
16%5%2442446%6%42%
1620
December1st to 15thDay
18%7%34324446%40%
1461
16th to endDay
22%8%34425%445%36%
1536
January1st to 15thNight
17%8%35%424345%40%
2506
16th to endNight
16%9%35%423345%40%
2688
February1st to 15thNight
15%8%35%5%245%46%38%
2172
16th to endNight
16%8%34414435%42%
1893
March1st to 15thNight
17%8%25%5%34446%37%
2160
16th to endNight
16%8%45%424235%43%
2024
April1st to 15thNight
17%8%26%5%345%5%5%37%
1796
16th to endNight
21%5%245%23336%40%
1680
May1st to 15thNight
23%6%35%423445%36%
1620
16th to endNight
18%6%347%335%47%35%
1537
June1st to 15thNight
22%6%15%42445%6%35%
1440
16th to endNight
14%5%245%245%5%9%40%
1440
July1st to 15thNight
12%5%35%5%25%46%9%40%
1440
16th to endNight
12%435%5%45%5%5%9%38%
1514
August1st to 15thNight
9%415%5%35%5%6%8%43%
1554
16th to endNight
12%423325%5%5%7%46%
1723
September1st to 15thNight
14%415%435%5%46%43%
1704
16th to endNight
15%424312346%51%
1815
October1st to 15thNight
21%5%14314335%45%
1837
16th to endNight
18%6%15%5%24346%40%
2287
November1st to 15thNight
17%6%34423235%45%
2277
16th to endNight
19%5%2432435%5%41%
2340
December1st to 15thNight
19%7%25%423445%40%
2496
16th to endNight
18%9%35%42445%6%36%
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
42%6%10%23%12%3
1433
16th to endDay
41%311%27%14%1
1536
February1st to 15thDay
47%5%12%19%13%1
1682
16th to endDay
46%310%22%14%3
1580
March1st to 15thDay
48%311%22%10%3
1800
16th to endDay
44%39%21%15%5%
2198
April1st to 15thDay
47%211%19%16%2
2152
16th to endDay
43%48%21%18%3
2280
May1st to 15thDay
53%37%17%14%2
2332
16th to endDay
43%6%13%21%13%2
2588
June1st to 15thDay
51%411%20%10%1
2520
16th to endDay
43%7%12%20%14%
2520
July1st to 15thDay
45%6%11%21%13%1
2371
16th to endDay
42%6%14%21%11%3
2487
August1st to 15thDay
42%6%13%21%13%1
2294
16th to endDay
39%5%10%24%17%2
2124
September1st to 15thDay
37%5%12%21%20%1
1925
16th to endDay
36%36%24%25%3
1815
October1st to 15thDay
43%38%25%15%3
1790
16th to endDay
41%412%22%16%2
1584
November1st to 15thDay
44%312%21%16%1
1581
16th to endDay
40%5%11%24%15%2
1620
December1st to 15thDay
44%415%18%16%
1461
16th to endDay
50%5%13%18%11%1
1536
January1st to 15thNight
46%311%21%14%2
2506
16th to endNight
46%310%20%15%2
2688
February1st to 15thNight
46%413%21%12%2
2180
16th to endNight
44%39%21%17%2
1893
March1st to 15thNight
48%410%20%13%3
2160
16th to endNight
45%28%18%19%5%
2025
April1st to 15thNight
48%48%19%16%2
1796
16th to endNight
46%39%20%15%4
1680
May1st to 15thNight
49%410%17%14%3
1620
16th to endNight
48%6%14%19%8%2
1539
June1st to 15thNight
49%6%13%18%11%1
1440
16th to endNight
40%7%12%23%15%1
1440
July1st to 15thNight
40%5%14%24%14%
1360
16th to endNight
41%6%14%25%10%2
1418
August1st to 15thNight
37%6%14%23%15%2
1544
16th to endNight
36%6%12%27%16%
1723
September1st to 15thNight
40%6%11%22%18%
1704
16th to endNight
36%38%21%27%2
1815
October1st to 15thNight
41%411%22%16%3
1837
16th to endNight
44%312%22%15%
2287
November1st to 15thNight
42%311%21%16%3
2277
16th to endNight
44%312%22%15%2
2340
December1st to 15thNight
46%414%21%12%
2496
16th to endNight
48%412%21%12%
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
28%26%30%13%1
60
16th to endDay
32%17%37%12%
64
February1st to 15thDay
30%20%31%13%4
225
16th to endDay
24%24%29%17%2
239
March1st to 15thDay
35%15%30%11%5%
270
16th to endDay
25%22%32%11%6%2
288
April1st to 15thDay
27%16%36%12%6%
270
16th to endDay
25%15%32%18%33
270
May1st to 15thDay
39%17%21%15%5%1
288
16th to endDay
22%12%38%19%7%
331
June1st to 15thDay
26%13%31%20%7%
315
16th to endDay
17%13%37%22%6%2
315
July1st to 15thDay
20%8%31%29%8%
305
16th to endDay
12%8%34%29%13%2
326
August1st to 15thDay
15%7%29%32%12%3
297
16th to endDay
14%425%26%21%6%
268
September1st to 15thDay
18%9%23%27%17%4
255
16th to endDay
21%430%18%12%12%
254
October1st to 15thDay
23%11%26%18%12%7%
255
16th to endDay
19%16%33%20%8%
240
November1st to 15thDay
27%11%30%18%8%2
235
16th to endDay
23%20%28%15%9%1
240
December1st to 15thDay
29%25%27%13%3
81
16th to endDay
37%29%23%7%1
64
January1st to 15thNight
24%19%37%16%2
720
16th to endNight
26%19%33%17%2
768
February1st to 15thNight
22%20%36%18%2
704
16th to endNight
25%20%34%16%2
631
March1st to 15thNight
23%20%36%16%2
720
16th to endNight
24%21%31%18%4
768
April1st to 15thNight
23%19%36%17%3
718
16th to endNight
25%17%33%18%5%
600
May1st to 15thNight
28%14%30%22%3
540
16th to endNight
20%10%40%23%5%
417
June1st to 15thNight
24%7%33%29%5%
360
16th to endNight
16%441%30%6%
360
July1st to 15thNight
12%434%37%11%
340
16th to endNight
12%432%39%10%
376
August1st to 15thNight
11%435%38%9%
495
16th to endNight
15%226%38%15%1
673
September1st to 15thNight
16%5%32%31%13%
660
16th to endNight
17%6%25%28%17%3
657
October1st to 15thNight
24%9%28%24%11%1
660
16th to endNight
24%15%32%21%6%
704
November1st to 15thNight
21%14%32%20%11%1
700
16th to endNight
25%17%28%20%7%1
720
December1st to 15thNight
26%18%32%17%4
720
16th to endNight
27%19%35%15%1
768
Page generated at 2017-08-13 14:16:45. Version ac04

Copyright 2017 A. Danko


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