Meadow View Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Meadow View Observatory clear sky chart from 2005-11-05 to 2017-09-20.

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
64%
15156
28%
46917
24%
15117
69%
15117
41%
24964

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
59%
718
19%
2470
19%
716
63%
716
28%
1452
January16th to endNight
55%
768
26%
2496
26%
768
60%
768
28%
1521
February1st to 15thNight
54%
698
24%
2288
22%
697
59%
697
26%
1410
February16th to endNight
51%
632
24%
1915
21%
632
57%
632
30%
1182
March1st to 15thNight
51%
720
15%
2037
13%
720
54%
720
26%
1363
March16th to endNight
46%
768
20%
2073
14%
768
51%
768
30%
1343
April1st to 15thNight
46%
719
22%
1799
9%
719
52%
719
33%
1165
April16th to endNight
59%
720
26%
1800
12%
720
64%
720
46%
1031
May1st to 15thNight
60%
515
28%
1595
20%
515
66%
515
52%
762
May16th to endNight
65%
375
25%
1496
27%
374
72%
374
38%
681
June1st to 15thNight
66%
360
25%
1440
27%
360
74%
360
44%
608
June16th to endNight
79%
360
34%
1440
43%
360
86%
360
63%
492
July1st to 15thNight
89%
340
34%
1360
44%
340
92%
340
76%
415
July16th to endNight
90%
499
41%
1529
40%
467
93%
467
84%
521
August1st to 15thNight
89%
538
40%
1611
32%
535
91%
535
74%
643
August16th to endNight
92%
759
46%
1905
30%
759
93%
759
85%
841
September1st to 15thNight
89%
720
43%
1800
29%
720
91%
720
81%
798
September16th to endNight
80%
675
43%
1845
36%
675
85%
675
73%
801
October1st to 15thNight
69%
660
32%
1980
30%
660
76%
660
52%
953
October16th to endNight
71%
704
34%
2112
34%
704
75%
704
48%
1072
November1st to 15thNight
66%
700
26%
2242
24%
700
72%
700
37%
1223
November16th to endNight
58%
720
22%
2476
23%
720
62%
720
30%
1419
December1st to 15thNight
53%
720
20%
2520
19%
720
59%
720
23%
1558
December16th to endNight
45%
768
21%
2688
18%
768
53%
768
22%
1710

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
9%212212235%64%
47934
Night
11%212212336%60%
47100
TransparencyDay
23%38%18%24%21%
47616
Night
26%48%18%22%19%
46918
SeeingDay
11%6%18%27%26%9%
5872
Night
12%314%34%30%3
15165

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
19%414313346%46%
1465
16th to endDay
22%313313336%46%
1728
February1st to 15thDay
21%412323336%47%
1576
16th to endDay
20%5%13213248%44%
1559
March1st to 15thDay
22%414413447%41%
1921
16th to endDay
18%5%13323348%44%
2151
April1st to 15thDay
15%42442345%7%46%
2149
16th to endDay
7%313223345%62%
2160
May1st to 15thDay
4212212336%68%
2352
16th to endDay
5%212313347%63%
2615
June1st to 15thDay
4312213346%67%
2520
16th to endDay
21112383%
2520
July1st to 15thDay
11112386%
2520
16th to endDay
111289%
2533
August1st to 15thDay
11112286%
2340
16th to endDay
111389%
2298
September1st to 15thDay
11122484%
2160
16th to endDay
31111122478%
1882
October1st to 15thDay
6%21222224469%
1650
16th to endDay
11%213222336%59%
1760
November1st to 15thDay
12%3432345%6%52%
1617
16th to endDay
18%413313345%51%
1482
December1st to 15thDay
22%5%2331333445%
1440
16th to endDay
25%5%14323235%41%
1536
January1st to 15thNight
17%423312347%49%
2470
16th to endNight
20%414322235%49%
2496
February1st to 15thNight
19%413323447%44%
2276
16th to endNight
19%413223446%46%
1915
March1st to 15thNight
20%424423448%40%
2037
16th to endNight
17%324412447%46%
2073
April1st to 15thNight
11%43442445%8%46%
1799
16th to endNight
7%223213346%61%
1800
May1st to 15thNight
5%22212246%67%
1595
16th to endNight
431232345%7%61%
1496
June1st to 15thNight
4213212238%67%
1440
16th to endNight
211213380%
1440
July1st to 15thNight
111111286%
1440
16th to endNight
11289%
1635
August1st to 15thNight
1111112285%
1620
16th to endNight
112387%
1905
September1st to 15thNight
11111485%
1800
16th to endNight
2111123480%
1845
October1st to 15thNight
7%2121234370%
1980
16th to endNight
8%23212346%63%
2112
November1st to 15thNight
11%2222345%7%55%
2242
16th to endNight
15%413313346%51%
2476
December1st to 15thNight
23%313313346%44%
2520
16th to endNight
26%322313435%43%
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
40%411%19%17%7%
1465
16th to endDay
40%5%8%14%17%13%
1728
February1st to 15thDay
37%5%13%16%21%5%
1576
16th to endDay
39%410%28%14%2
1559
March1st to 15thDay
42%5%12%18%12%7%
1921
16th to endDay
38%6%14%18%17%4
2151
April1st to 15thDay
37%5%11%20%20%4
2149
16th to endDay
24%5%11%25%24%9%
2160
May1st to 15thDay
17%310%23%32%12%
2352
16th to endDay
20%5%14%26%23%10%
2619
June1st to 15thDay
18%5%11%20%22%22%
2520
16th to endDay
7%15%15%34%35%
2520
July1st to 15thDay
41310%29%50%
2371
16th to endDay
5%1210%23%56%
2376
August1st to 15thDay
5%1311%32%44%
2324
16th to endDay
3214%34%43%
2298
September1st to 15thDay
6%1412%32%41%
2160
16th to endDay
10%26%23%32%25%
1882
October1st to 15thDay
18%47%22%27%19%
1650
16th to endDay
26%48%22%25%13%
1760
November1st to 15thDay
30%6%11%25%15%8%
1617
16th to endDay
35%5%9%20%19%8%
1482
December1st to 15thDay
43%39%17%20%5%
1440
16th to endDay
47%47%16%17%6%
1536
January1st to 15thNight
35%6%12%19%17%8%
2470
16th to endNight
39%37%15%18%15%
2496
February1st to 15thNight
39%49%19%17%9%
2288
16th to endNight
37%5%11%23%18%4
1915
March1st to 15thNight
42%6%12%15%15%7%
2037
16th to endNight
38%6%10%20%17%6%
2073
April1st to 15thNight
34%6%13%21%16%7%
1799
16th to endNight
23%5%11%22%27%10%
1800
May1st to 15thNight
18%410%21%30%15%
1596
16th to endNight
20%6%13%25%23%10%
1496
June1st to 15thNight
17%5%12%21%22%20%
1440
16th to endNight
10%25%14%30%36%
1440
July1st to 15thNight
6%211%24%53%
1360
16th to endNight
4311%19%60%
1529
August1st to 15thNight
8%1213%30%42%
1611
16th to endNight
41213%33%44%
1905
September1st to 15thNight
6%1410%33%45%
1800
16th to endNight
8%25%17%35%29%
1845
October1st to 15thNight
18%46%19%29%21%
1980
16th to endNight
21%49%22%23%19%
2112
November1st to 15thNight
26%7%13%25%17%9%
2242
16th to endNight
33%6%7%21%20%10%
2476
December1st to 15thNight
41%5%9%15%20%7%
2520
16th to endNight
44%48%14%19%8%
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
33%8%18%26%10%2
93
16th to endDay
23%7%19%21%17%9%
256
February1st to 15thDay
26%5%19%25%19%4
236
16th to endDay
23%11%18%25%14%6%
235
March1st to 15thDay
27%10%23%18%15%5%
270
16th to endDay
22%15%21%21%14%3
288
April1st to 15thDay
18%13%26%24%12%4
269
16th to endDay
11%18%22%28%15%3
270
May1st to 15thDay
6%7%34%25%22%3
288
16th to endDay
6%7%16%25%32%12%
330
June1st to 15thDay
6%8%20%32%25%6%
315
16th to endDay
2315%35%31%12%
315
July1st to 15thDay
118%36%40%11%
305
16th to endDay
10%36%40%12%
327
August1st to 15thDay
115%29%41%11%
315
16th to endDay
11%27%42%17%
332
September1st to 15thDay
213%29%35%18%
315
16th to endDay
45%18%29%27%14%
272
October1st to 15thDay
7%7%24%27%20%14%
255
16th to endDay
17%5%17%30%22%6%
272
November1st to 15thDay
17%313%18%36%9%
123
16th to endDay
16%428%29%20%
67
December1st to 15thDay
45%128%16%8%
60
16th to endDay
17%120%29%28%3
64
January1st to 15thNight
18%312%40%23%2
720
16th to endNight
21%413%36%21%4
768
February1st to 15thNight
20%5%13%36%23%1
704
16th to endNight
21%5%19%31%20%2
632
March1st to 15thNight
20%7%15%30%23%3
720
16th to endNight
18%6%22%29%21%
768
April1st to 15thNight
12%8%26%30%19%2
719
16th to endNight
9%6%20%35%22%5%
720
May1st to 15thNight
6%425%34%28%1
516
16th to endNight
46%18%37%30%2
375
June1st to 15thNight
5%220%41%28%1
360
16th to endNight
2115%42%36%2
360
July1st to 15thNight
16%42%45%3
340
16th to endNight
7%33%53%4
499
August1st to 15thNight
16%34%52%4
538
16th to endNight
5%34%54%4
759
September1st to 15thNight
116%30%53%7%
720
16th to endNight
4211%29%40%11%
675
October1st to 15thNight
7%316%31%33%6%
660
16th to endNight
9%311%34%33%7%
704
November1st to 15thNight
12%314%33%32%4
700
16th to endNight
15%416%39%21%3
720
December1st to 15thNight
24%312%35%21%2
720
16th to endNight
25%418%31%19%1
768
Page generated at 2017-09-21 04:18:22. Version ac04

Copyright 2017 A. Danko


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