Milagro Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Milagro Observatory clear sky chart from 2005-11-05 to 2017-10-06.

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
62%
15808
28%
47204
23%
15769
68%
15769
39%
25901

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
64%
717
29%
2327
29%
716
68%
716
41%
1198
January16th to endNight
58%
768
32%
2496
30%
768
65%
768
37%
1347
February1st to 15thNight
58%
701
26%
2288
23%
700
66%
700
37%
1221
February16th to endNight
49%
632
30%
1902
22%
632
59%
632
37%
1062
March1st to 15thNight
56%
720
31%
1980
21%
720
64%
720
41%
1134
March16th to endNight
55%
768
26%
2112
19%
768
61%
768
36%
1259
April1st to 15thNight
46%
569
25%
1828
16%
569
58%
569
30%
1042
April16th to endNight
46%
540
30%
1795
20%
540
60%
540
34%
924
May1st to 15thNight
55%
539
26%
1619
19%
539
62%
539
38%
888
May16th to endNight
57%
562
26%
1655
19%
561
62%
561
38%
897
June1st to 15thNight
70%
540
32%
1440
24%
540
74%
540
56%
721
June16th to endNight
78%
540
32%
1464
27%
540
82%
540
61%
713
July1st to 15thNight
72%
510
16%
1530
13%
510
74%
510
31%
926
July16th to endNight
75%
564
17%
1593
16%
531
76%
531
27%
1030
August1st to 15thNight
77%
539
21%
1611
19%
536
78%
536
32%
973
August16th to endNight
77%
573
27%
1869
28%
573
78%
573
36%
1030
September1st to 15thNight
72%
543
26%
1803
27%
543
75%
543
33%
1026
September16th to endNight
73%
716
39%
2003
29%
716
79%
716
53%
1003
October1st to 15thNight
65%
684
32%
2052
23%
684
72%
684
48%
1028
October16th to endNight
68%
704
38%
2112
28%
704
76%
704
51%
1030
November1st to 15thNight
69%
700
35%
2100
28%
700
74%
700
47%
1061
November16th to endNight
62%
876
34%
2474
24%
876
68%
876
48%
1265
December1st to 15thNight
59%
900
24%
2520
18%
900
63%
900
39%
1469
December16th to endNight
52%
903
22%
2631
18%
903
56%
903
29%
1654

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
5%41342445%6%55%
47980
Night
5%424424446%57%
47399
TransparencyDay
27%49%20%24%13%
47675
Night
27%48%21%24%13%
47205
SeeingDay
8%12%25%33%17%3
5565
Night
8%5%17%36%26%4
15816

By Month

Percentage Cloud Cover SW (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
7%6%1332334459%
1611
16th to endDay
7%10%23313236%54%
1728
February1st to 15thDay
5%8%245%24346%52%
1575
16th to endDay
7%9%25%5%24435%48%
1568
March1st to 15thDay
6%6%23323446%55%
1980
16th to endDay
5%5%25%3145%5%6%53%
2112
April1st to 15thDay
6%6%25%424445%52%
2120
16th to endDay
441342445%7%55%
2163
May1st to 15thDay
45%23435%5%6%6%52%
2331
16th to endDay
431342335%7%59%
2456
June1st to 15thDay
3212313346%67%
2520
16th to endDay
12312345%73%
2491
July1st to 15thDay
32235%35%7%7%10%48%
2340
16th to endDay
6%4245%36%7%8%11%38%
2467
August1st to 15thDay
6%416%5%45%6%7%7%43%
2340
16th to endDay
23145%46%6%7%9%48%
2332
September1st to 15thDay
6%3135%346%6%7%49%
2154
16th to endDay
421332333468%
1956
October1st to 15thDay
7%212323347%61%
1705
16th to endDay
4312322335%68%
1760
November1st to 15thDay
4313322246%64%
1759
16th to endDay
45%1321233467%
1470
December1st to 15thDay
9%8%24323345%52%
1440
16th to endDay
9%10%26%423346%47%
1602
January1st to 15thNight
6%6%2322233462%
2327
16th to endNight
8%7%2332222459%
2496
February1st to 15thNight
47%25%313335%58%
2277
16th to endNight
7%7%23323336%55%
1902
March1st to 15thNight
5%5%24423445%57%
1980
16th to endNight
6%5%244345%45%52%
2112
April1st to 15thNight
8%6%144345%47%50%
1828
16th to endNight
5%42343433461%
1795
May1st to 15thNight
5%424433347%56%
1619
16th to endNight
6%314423336%58%
1654
June1st to 15thNight
3211313345%70%
1440
16th to endNight
111221345%6%69%
1464
July1st to 15thNight
22246%47%7%7%7%46%
1620
16th to endNight
3326%7%48%7%8%11%35%
1701
August1st to 15thNight
3315%5%35%6%6%9%48%
1620
16th to endNight
33145%35%7%7%10%48%
1869
September1st to 15thNight
43245%36%47%7%49%
1803
16th to endNight
4212412235%68%
2003
October1st to 15thNight
421231335%5%64%
2052
16th to endNight
321322233469%
2112
November1st to 15thNight
5%413213345%63%
2100
16th to endNight
5%41321323466%
2474
December1st to 15thNight
8%7%24323235%55%
2520
16th to endNight
9%10%25%423345%47%
2631

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
29%417%34%14%1
1612
16th to endDay
34%311%27%20%3
1728
February1st to 15thDay
33%415%24%17%3
1575
16th to endDay
38%38%20%26%2
1568
March1st to 15thDay
29%36%28%26%4
1980
16th to endDay
30%38%21%29%6%
2112
April1st to 15thDay
33%46%19%24%12%
2120
16th to endDay
26%47%21%27%12%
2163
May1st to 15thDay
29%48%17%30%9%
2331
16th to endDay
23%38%15%32%16%
2459
June1st to 15thDay
18%2410%27%36%
2520
16th to endDay
12%349%23%47%
2491
July1st to 15thDay
26%7%14%13%16%21%
2201
16th to endDay
32%9%17%19%11%9%
2312
August1st to 15thDay
33%9%10%14%15%15%
2325
16th to endDay
27%6%11%20%20%13%
2332
September1st to 15thDay
29%6%10%14%20%17%
2154
16th to endDay
19%45%15%31%23%
1956
October1st to 15thDay
23%35%22%34%10%
1705
16th to endDay
19%36%20%39%10%
1760
November1st to 15thDay
21%28%24%34%8%
1759
16th to endDay
22%27%31%27%7%
1470
December1st to 15thDay
34%314%30%15%
1440
16th to endDay
40%419%23%11%
1602
January1st to 15thNight
26%311%33%22%2
2327
16th to endNight
31%28%30%24%3
2496
February1st to 15thNight
28%413%27%19%6%
2288
16th to endNight
31%29%20%31%4
1902
March1st to 15thNight
28%45%28%26%6%
1980
16th to endNight
32%47%19%29%7%
2112
April1st to 15thNight
33%35%19%23%14%
1828
16th to endNight
28%2418%30%15%
1795
May1st to 15thNight
28%47%17%30%11%
1620
16th to endNight
27%48%15%26%17%
1655
June1st to 15thNight
17%3211%26%39%
1440
16th to endNight
14%349%20%46%
1464
July1st to 15thNight
31%10%12%10%12%22%
1530
16th to endNight
37%9%15%14%11%11%
1593
August1st to 15thNight
29%11%11%14%15%18%
1611
16th to endNight
27%7%11%18%19%14%
1869
September1st to 15thNight
31%6%8%16%15%21%
1803
16th to endNight
19%25%15%30%26%
2003
October1st to 15thNight
21%36%19%29%19%
2052
16th to endNight
19%3418%39%14%
2112
November1st to 15thNight
23%27%21%32%12%
2100
16th to endNight
22%17%26%31%11%
2474
December1st to 15thNight
31%312%29%20%3
2520
16th to endNight
39%314%25%14%1
2631

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
34%426%22%10%2
90
16th to endDay
13%6%22%35%17%4
96
February1st to 15thDay
11%11%20%35%22%
90
16th to endDay
11%22%31%21%11%
132
March1st to 15thDay
9%21%30%28%9%
270
16th to endDay
9%28%36%19%6%
288
April1st to 15thDay
9%25%32%20%9%2
269
16th to endDay
12%30%34%17%4
270
May1st to 15thDay
10%18%38%22%10%1
288
16th to endDay
8%17%28%27%15%3
357
June1st to 15thDay
48%24%37%21%4
495
16th to endDay
1321%41%25%6%
466
July1st to 15thDay
5%311%48%26%3
305
16th to endDay
7%111%45%24%8%
327
August1st to 15thDay
7%315%47%22%3
315
16th to endDay
5%322%37%26%3
332
September1st to 15thDay
6%423%45%15%4
315
16th to endDay
6%11%27%29%19%5%
291
October1st to 15thDay
315%26%28%18%7%
107
16th to endDay
8%11%35%26%14%4
96
November1st to 15thDay
6%10%20%32%27%3
90
16th to endDay
11%20%34%26%7%
90
December1st to 15thDay
12%8%35%33%10%
90
16th to endDay
18%15%16%30%16%2
96
January1st to 15thNight
10%315%40%24%5%
720
16th to endNight
12%419%37%21%5%
768
February1st to 15thNight
8%422%40%20%2
704
16th to endNight
12%6%25%37%15%2
632
March1st to 15thNight
8%7%23%34%24%2
720
16th to endNight
7%10%20%37%20%2
768
April1st to 15thNight
13%12%23%34%14%2
569
16th to endNight
9%13%25%32%16%1
540
May1st to 15thNight
7%6%24%40%17%3
540
16th to endNight
8%7%22%34%23%3
563
June1st to 15thNight
4418%38%31%2
540
16th to endNight
2214%36%39%5%
540
July1st to 15thNight
5%19%34%43%5%
510
16th to endNight
5%7%29%48%8%
564
August1st to 15thNight
45%32%46%10%
539
16th to endNight
48%30%45%9%
573
September1st to 15thNight
4113%38%35%6%
543
16th to endNight
6%213%34%33%9%
716
October1st to 15thNight
6%420%41%21%4
684
16th to endNight
5%316%36%30%7%
704
November1st to 15thNight
6%5%13%41%27%5%
700
16th to endNight
8%8%18%33%24%6%
876
December1st to 15thNight
12%419%41%19%3
900
16th to endNight
14%7%16%39%19%2
903
Page generated at 2017-10-07 12:07:45. Version ac04

Copyright 2017 A. Danko


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