Milford
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Milford clear sky chart from 2005-11-06 to 2024-03-18.

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%
23214
19%
80699
7%
23123
38%
23123
18%
52016

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 10thNight
14%
754
24%
4327
6%
737
34%
737
12%
2290
January11th to 20thNight
13%
758
23%
4344
3%
740
31%
740
8%
2622
January21st to endNight
16%
831
12%
4861
7%
814
35%
814
8%
3394
February1st to 10thNight
15%
760
18%
2389
5%
760
32%
760
17%
1592
February11th to 20thNight
10%
743
20%
2220
3%
740
29%
740
15%
1467
February21st to endNight
14%
628
23%
1884
6%
628
35%
628
16%
1245
March1st to 10thNight
18%
759
22%
2280
7%
759
36%
759
18%
1510
March11th to 20thNight
15%
752
18%
2162
4%
752
30%
752
16%
1485
March21st to endNight
18%
792
22%
2048
6%
792
31%
792
19%
1415
April1st to 10thNight
18%
720
19%
1800
4%
720
27%
720
18%
1279
April11th to 20thNight
22%
711
17%
1775
4%
711
29%
711
22%
1243
April21st to endNight
17%
540
20%
1620
5%
540
29%
540
17%
1104
May1st to 10thNight
20%
540
13%
1620
5%
540
26%
540
15%
1168
May11th to 20thNight
19%
510
16%
1572
7%
510
29%
510
17%
1067
May21st to endNight
27%
389
12%
1551
9%
388
36%
388
16%
1004
June1st to 10thNight
30%
360
13%
1440
8%
360
43%
360
17%
925
June11th to 20thNight
28%
360
13%
1440
10%
360
41%
360
17%
939
June21st to endNight
35%
360
12%
1440
9%
360
46%
360
22%
862
July1st to 10thNight
42%
350
14%
1400
13%
350
51%
350
21%
836
July11th to 20thNight
44%
348
13%
1392
13%
348
50%
348
21%
856
July21st to endNight
41%
394
18%
1486
16%
372
50%
372
22%
886
August1st to 10thNight
40%
488
16%
1552
10%
486
46%
486
28%
942
August11th to 20thNight
44%
576
17%
1640
10%
576
48%
576
25%
1101
August21st to endNight
46%
792
22%
1980
10%
792
50%
792
34%
1273
September1st to 10thNight
38%
720
19%
1800
7%
720
45%
720
28%
1231
September11th to 20thNight
41%
720
24%
1977
13%
720
49%
720
32%
1214
September21st to endNight
38%
720
23%
1980
14%
720
47%
720
27%
1303
October1st to 10thNight
33%
720
19%
1980
9%
720
41%
720
23%
1332
October11th to 20thNight
32%
720
23%
2193
10%
720
46%
720
25%
1351
October21st to endNight
22%
792
17%
2574
6%
792
35%
792
17%
1741
November1st to 10thNight
30%
740
22%
2407
11%
740
44%
740
23%
1474
November11th to 20thNight
20%
760
24%
2470
8%
760
39%
760
20%
1532
November21st to endNight
20%
760
23%
2470
7%
760
40%
760
19%
1513
December1st to 10thNight
17%
760
20%
2622
6%
760
33%
760
15%
1698
December11th to 20thNight
18%
760
18%
3199
4%
759
34%
759
12%
1971
December21st to endNight
14%
827
15%
4804
4%
817
34%
817
9%
3151

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%7%35%5%3445%7%40%
78517
Night
17%7%35%5%3445%6%41%
81260
TransparencyDay
44%5%11%22%15%3
78222
Night
45%5%11%22%15%2
81089
SeeingDay
26%14%32%19%7%2
14157
Night
24%13%33%23%7%1
23237

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 10thDay
14%8%46%5%24445%45%
2517
11th to 20thDay
16%8%46%5%3445%5%40%
2520
21st to endDay
21%11%45%5%3445%5%34%
2772
February1st to 10thDay
19%7%35%5%35%6%5%6%36%
1788
11th to 20thDay
13%8%36%5%35%447%41%
1848
21st to endDay
19%11%26%5%44345%38%
1570
March1st to 10thDay
18%9%25%43445%6%39%
1897
11th to 20thDay
16%6%35%6%445%47%40%
1962
21st to endDay
19%9%36%5%33445%41%
2305
April1st to 10thDay
19%8%26%434447%38%
2160
11th to 20thDay
17%5%25%5%3445%8%40%
2134
21st to endDay
22%5%26%6%35%5%46%35%
2340
May1st to 10thDay
25%8%35%425%447%32%
2340
11th to 20thDay
19%6%25%5%2445%6%41%
2336
21st to endDay
15%5%25%435%45%8%44%
2725
June1st to 10thDay
20%6%35%5%36%5%5%8%35%
2520
11th to 20thDay
18%6%25%6%35%5%6%7%37%
2520
21st to endDay
17%5%35%6%45%5%6%8%36%
2520
July1st to 10thDay
13%5%35%6%36%6%5%8%41%
2520
11th to 20thDay
14%5%26%5%35%5%6%9%39%
2520
21st to endDay
12%5%25%6%45%5%7%9%39%
2744
August1st to 10thDay
10%6%36%6%45%5%7%9%38%
2359
11th to 20thDay
14%5%25%6%45%5%6%8%40%
2257
21st to endDay
12%4245%35%6%6%9%43%
2376
September1st to 10thDay
15%5%245%2445%8%45%
2160
11th to 20thDay
15%5%23433346%51%
1981
21st to endDay
18%5%25%43435%6%45%
1980
October1st to 10thDay
24%5%35%5%23345%42%
1980
11th to 20thDay
16%6%2443345%7%47%
1761
21st to endDay
21%7%25%433446%40%
1782
November1st to 10thDay
16%6%25%5%2344449%
1671
11th to 20thDay
19%6%24324445%46%
1710
21st to endDay
17%6%2443446%5%43%
1710
December1st to 10thDay
18%8%445%35%45%6%38%
1554
11th to 20thDay
21%7%34423335%45%
1906
21st to endDay
21%11%36%5%34446%33%
2772
January1st to 10thNight
17%8%34323336%48%
4429
11th to 20thNight
16%9%47%6%34445%40%
4440
21st to endNight
22%13%46%5%34445%30%
4884
February1st to 10thNight
17%8%36%5%345%5%5%39%
2389
11th to 20thNight
14%8%36%5%345%5%6%40%
2218
21st to endNight
19%9%25%5%24445%41%
1884
March1st to 10thNight
17%8%25%5%34446%41%
2270
11th to 20thNight
15%9%45%5%35%446%39%
2161
21st to endNight
17%9%45%434346%41%
2048
April1st to 10thNight
18%7%26%5%35%5%5%6%37%
1800
11th to 20thNight
18%6%35%5%345%5%6%39%
1775
21st to endNight
22%8%35%5%33336%39%
1620
May1st to 10thNight
25%9%35%434446%33%
1620
11th to 20thNight
19%6%346%345%5%7%38%
1571
21st to endNight
16%7%5%5%6%34447%39%
1550
June1st to 10thNight
18%6%36%5%35%45%8%38%
1440
11th to 20thNight
20%6%35%5%35%5%5%8%36%
1440
21st to endNight
14%6%25%3245%7%10%41%
1440
July1st to 10thNight
13%6%35%436%5%6%10%40%
1440
11th to 20thNight
14%7%346%35%5%7%10%36%
1440
21st to endNight
13%5%35%435%6%5%8%43%
1574
August1st to 10thNight
9%425%6%36%5%7%9%43%
1562
11th to 20thNight
11%6%26%5%47%6%7%9%38%
1640
21st to endNight
13%5%2443445%7%49%
1980
September1st to 10thNight
14%6%26%6%35%45%6%44%
1800
11th to 20thNight
14%5%24333347%51%
1977
21st to endNight
16%6%25%4335%5%6%45%
1980
October1st to 10thNight
23%5%34423446%42%
1980
11th to 20thNight
16%5%245%25%45%7%46%
2193
21st to endNight
22%8%35%424446%38%
2574
November1st to 10thNight
15%5%25%5%34345%49%
2407
11th to 20thNight
19%7%34324345%46%
2470
21st to endNight
17%6%245%3445%7%45%
2470
December1st to 10thNight
20%7%25%5%2445%5%40%
2622
11th to 20thNight
20%6%244245%5%6%41%
3288
21st to endNight
20%11%36%5%3345%6%34%
4884

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 10thDay
42%48%32%13%2
2518
11th to 20thDay
47%49%25%13%2
2520
21st to endDay
53%49%22%11%2
2772
February1st to 10thDay
48%5%12%19%14%3
1788
11th to 20thDay
44%6%9%22%16%3
1857
21st to endDay
50%310%20%14%3
1570
March1st to 10thDay
46%411%21%13%5%
1900
11th to 20thDay
44%5%9%22%16%4
1962
21st to endDay
47%49%18%17%6%
2305
April1st to 10thDay
47%310%20%16%4
2160
11th to 20thDay
42%5%10%21%19%3
2134
21st to endDay
49%5%8%18%16%4
2340
May1st to 10thDay
53%38%19%14%2
2340
11th to 20thDay
44%5%9%20%18%3
2340
21st to endDay
39%6%13%25%14%2
2725
June1st to 10thDay
47%6%13%23%11%1
2520
11th to 20thDay
45%6%11%20%15%2
2520
21st to endDay
44%7%12%22%13%1
2520
July1st to 10thDay
42%6%10%24%14%3
2450
11th to 20thDay
42%6%14%25%12%2
2445
21st to endDay
41%7%13%22%14%4
2591
August1st to 10thDay
41%7%14%24%13%1
2345
11th to 20thDay
43%6%13%23%14%1
2257
21st to endDay
38%5%11%24%19%2
2376
September1st to 10thDay
38%6%11%25%19%2
2160
11th to 20thDay
36%49%25%24%3
1981
21st to endDay
41%39%21%23%3
1980
October1st to 10thDay
47%48%23%14%4
1980
11th to 20thDay
37%411%29%17%2
1761
21st to endDay
45%413%19%15%4
1782
November1st to 10thDay
40%312%24%18%3
1671
11th to 20thDay
40%410%22%21%2
1710
21st to endDay
41%5%12%27%12%3
1710
December1st to 10thDay
47%5%13%16%17%2
1554
11th to 20thDay
44%312%18%17%5%
1906
21st to endDay
52%5%10%21%11%1
2772
January1st to 10thNight
39%311%30%13%3
4429
11th to 20thNight
47%411%23%12%3
4440
21st to endNight
57%49%17%11%2
4884
February1st to 10thNight
46%5%13%21%14%2
2389
11th to 20thNight
45%410%19%18%4
2220
21st to endNight
46%47%24%16%4
1884
March1st to 10thNight
45%49%23%15%4
2280
11th to 20thNight
47%5%11%17%17%4
2162
21st to endNight
47%37%19%19%5%
2048
April1st to 10thNight
48%49%19%16%3
1800
11th to 20thNight
46%49%20%18%3
1775
21st to endNight
48%410%20%14%4
1620
May1st to 10thNight
53%5%10%16%13%3
1620
11th to 20thNight
46%7%11%20%13%4
1572
21st to endNight
47%6%13%20%12%1
1551
June1st to 10thNight
46%6%14%21%12%1
1440
11th to 20thNight
47%6%11%21%14%1
1440
21st to endNight
38%8%16%24%13%1
1440
July1st to 10thNight
40%6%15%22%16%1
1400
11th to 20thNight
42%7%16%26%9%1
1392
21st to endNight
39%6%15%25%12%2
1486
August1st to 10thNight
36%7%18%24%13%2
1552
11th to 20thNight
42%8%15%22%13%
1640
21st to endNight
35%6%11%27%20%1
1980
September1st to 10thNight
41%7%10%23%18%1
1800
11th to 20thNight
35%5%10%22%26%2
1977
21st to endNight
42%48%22%20%3
1980
October1st to 10thNight
45%411%23%13%4
1980
11th to 20thNight
38%5%12%28%15%1
2193
21st to endNight
49%411%20%15%2
2574
November1st to 10thNight
39%5%11%22%19%4
2407
11th to 20thNight
42%310%22%20%3
2470
21st to endNight
40%413%27%14%2
2470
December1st to 10thNight
47%412%22%14%1
2622
11th to 20thNight
43%5%14%18%17%2
3288
21st to endNight
51%5%8%25%11%1
4884

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 10thDay
31%22%27%16%4
180
11th to 20thDay
34%21%32%9%3
180
21st to endDay
29%20%35%13%31
198
February1st to 10thDay
37%18%30%14%2
378
11th to 20thDay
33%25%31%9%2
456
21st to endDay
35%17%30%14%3
382
March1st to 10thDay
34%17%33%12%4
460
11th to 20thDay
30%24%30%12%41
449
21st to endDay
31%18%34%11%5%3
462
April1st to 10thDay
35%20%26%12%5%1
420
11th to 20thDay
29%19%34%12%41
412
21st to endDay
33%15%32%16%32
420
May1st to 10thDay
37%19%26%13%41
423
11th to 20thDay
25%15%39%15%41
447
21st to endDay
21%14%34%22%8%2
485
June1st to 10thDay
22%11%35%22%8%2
450
11th to 20thDay
20%12%40%20%6%2
450
21st to endDay
18%10%35%26%9%2
450
July1st to 10thDay
18%7%31%29%12%3
445
11th to 20thDay
18%430%33%12%3
444
21st to endDay
14%7%39%31%9%1
488
August1st to 10thDay
12%7%33%35%11%2
446
11th to 20thDay
19%6%31%28%13%4
439
21st to endDay
13%7%33%27%13%6%
495
September1st to 10thDay
20%10%25%24%16%4
450
11th to 20thDay
21%8%30%21%11%9%
450
21st to endDay
23%8%33%22%9%5%
450
October1st to 10thDay
29%10%26%19%11%5%
450
11th to 20thDay
21%13%34%20%10%2
405
21st to endDay
29%13%33%17%8%1
396
November1st to 10thDay
25%14%30%19%9%3
365
11th to 20thDay
31%16%30%18%5%
370
21st to endDay
29%18%30%16%7%
370
December1st to 10thDay
27%26%29%13%5%
214
11th to 20thDay
39%19%31%8%2
180
21st to endDay
32%20%31%11%33
198
January1st to 10thNight
25%18%37%17%3
760
11th to 20thNight
31%17%34%16%2
760
21st to endNight
24%20%33%20%3
836
February1st to 10thNight
26%17%36%19%3
760
11th to 20thNight
25%23%36%15%1
743
21st to endNight
32%18%31%16%3
628
March1st to 10thNight
27%18%33%18%4
760
11th to 20thNight
24%22%35%16%3
752
21st to endNight
28%18%32%18%4
792
April1st to 10thNight
26%20%32%18%3
720
11th to 20thNight
24%17%34%20%5%
711
21st to endNight
26%18%34%19%3
540
May1st to 10thNight
32%12%30%22%41
540
11th to 20thNight
23%15%38%20%4
510
21st to endNight
19%6%41%28%6%
389
June1st to 10thNight
22%5%34%30%9%
360
11th to 20thNight
22%5%38%29%6%1
360
21st to endNight
14%5%39%34%8%
360
July1st to 10thNight
16%431%36%13%
350
11th to 20thNight
14%130%41%14%
348
21st to endNight
15%434%38%9%
394
August1st to 10thNight
11%336%39%11%
488
11th to 20thNight
15%328%41%13%
576
21st to endNight
17%424%38%14%3
792
September1st to 10thNight
17%5%32%33%12%1
720
11th to 20thNight
18%6%29%28%17%3
720
21st to endNight
21%7%27%31%11%3
720
October1st to 10thNight
27%8%28%26%11%2
720
11th to 20thNight
20%11%32%23%12%1
720
21st to endNight
29%13%31%20%7%
792
November1st to 10thNight
19%12%34%25%10%1
740
11th to 20thNight
26%16%33%17%7%1
760
21st to endNight
25%18%32%19%5%1
760
December1st to 10thNight
28%16%34%17%5%
760
11th to 20thNight
27%18%32%20%3
760
21st to endNight
28%17%35%17%3
836
Page generated at 2024-03-15 14:01:39. Version ac07

Copyright © 2024 Attilla Danko.


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