MIRA Chews Ridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the MIRA Chews Ridge Observatory 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
71%
15399
31%
46551
27%
15363
74%
15363
46%
23724

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
62%
716
23%
2360
23%
716
66%
716
33%
1339
January16th to endNight
62%
768
25%
2496
27%
768
64%
768
30%
1483
February1st to 15thNight
60%
700
25%
2252
26%
700
63%
700
30%
1334
February16th to endNight
55%
632
22%
1895
21%
632
59%
632
30%
1171
March1st to 15thNight
59%
720
20%
2019
19%
720
61%
720
31%
1273
March16th to endNight
59%
768
23%
2076
17%
768
63%
768
36%
1252
April1st to 15thNight
52%
719
25%
1799
14%
719
56%
719
37%
1128
April16th to endNight
63%
720
29%
1800
14%
720
68%
720
53%
967
May1st to 15thNight
70%
683
30%
1763
18%
683
73%
683
61%
886
May16th to endNight
73%
410
34%
1533
30%
410
81%
410
55%
590
June1st to 15thNight
75%
360
33%
1440
34%
360
84%
360
57%
519
June16th to endNight
91%
360
42%
1440
49%
360
96%
360
82%
413
July1st to 15thNight
93%
406
35%
1426
37%
406
94%
406
84%
456
July16th to endNight
94%
564
40%
1593
36%
531
94%
531
78%
619
August1st to 15thNight
91%
585
42%
1634
31%
582
92%
582
84%
650
August16th to endNight
92%
700
43%
1750
28%
700
93%
700
87%
759
September1st to 15thNight
93%
660
46%
1650
34%
660
94%
660
84%
728
September16th to endNight
84%
656
46%
1784
41%
656
87%
656
77%
759
October1st to 15thNight
76%
660
32%
1980
34%
660
79%
660
50%
966
October16th to endNight
78%
704
37%
2112
40%
704
81%
704
52%
1022
November1st to 15thNight
73%
700
34%
2177
34%
700
76%
700
48%
1074
November16th to endNight
70%
720
28%
2364
29%
720
73%
720
39%
1225
December1st to 15thNight
62%
720
25%
2520
25%
720
67%
720
27%
1488
December16th to endNight
52%
768
23%
2688
23%
768
57%
768
23%
1623

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%413313335%63%
47414
Night
4313323346%61%
46742
TransparencyDay
22%37%17%26%22%
47104
Night
23%38%16%24%24%
46552
SeeingDay
8%8%24%34%19%4
5919
Night
8%212%29%34%12%
15409

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
8%6%245%35%45%8%45%
1575
16th to endDay
12%7%35%42345%5%45%
1728
February1st to 15thDay
10%7%36%424446%44%
1611
16th to endDay
15%9%35%434446%37%
1579
March1st to 15thDay
8%7%36%5%25%5%5%9%38%
1938
16th to endDay
9%8%36%425%45%8%43%
2148
April1st to 15thDay
10%8%34423446%45%
2149
16th to endDay
5%313314438%59%
2160
May1st to 15thDay
2212213348%67%
2184
16th to endDay
3212212446%66%
2578
June1st to 15thDay
222212346%70%
2520
16th to endDay
111387%
2520
July1st to 15thDay
1112387%
2444
16th to endDay
111112384%
2468
August1st to 15thDay
112387%
2230
16th to endDay
1111288%
2100
September1st to 15thDay
111112386%
1980
16th to endDay
111212235%77%
1842
October1st to 15thDay
421332335%7%62%
1650
16th to endDay
3312323345%65%
1760
November1st to 15thDay
7%434423335%57%
1681
16th to endDay
6%6%24434447%51%
1593
December1st to 15thDay
10%7%46%6%35%46%5%40%
1440
16th to endDay
11%11%35%424346%40%
1536
January1st to 15thNight
7%6%25%6%2445%7%47%
2360
16th to endNight
11%6%35%4345%46%45%
2496
February1st to 15thNight
8%5%26%5%35%5%5%8%42%
2241
16th to endNight
9%8%35%5%35%45%6%44%
1895
March1st to 15thNight
7%6%35%5%36%5%47%43%
2019
16th to endNight
6%5%244346%6%8%46%
2076
April1st to 15thNight
6%6%34435%5%5%6%48%
1799
16th to endNight
221332345%8%61%
1800
May1st to 15thNight
212312347%69%
1763
16th to endNight
112213347%71%
1532
June1st to 15thNight
12213437%72%
1440
16th to endNight
111390%
1440
July1st to 15thNight
1112487%
1512
16th to endNight
1112385%
1701
August1st to 15thNight
1111387%
1643
16th to endNight
1111388%
1750
September1st to 15thNight
11122385%
1650
16th to endNight
11111111482%
1784
October1st to 15thNight
3312323346%63%
1980
16th to endNight
322323347%64%
2112
November1st to 15thNight
4313323348%60%
2177
16th to endNight
44144245%5%8%52%
2364
December1st to 15thNight
7%7%35%5%345%5%6%45%
2520
16th to endNight
10%8%45%5%3345%6%42%
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
36%38%20%19%11%
1575
16th to endDay
38%5%7%13%19%15%
1728
February1st to 15thDay
38%46%18%23%8%
1611
16th to endDay
46%5%8%20%14%5%
1579
March1st to 15thDay
39%5%10%19%15%9%
1938
16th to endDay
39%411%20%18%5%
2148
April1st to 15thDay
37%310%23%19%4
2149
16th to endDay
22%5%11%26%26%7%
2160
May1st to 15thDay
15%28%26%35%11%
2184
16th to endDay
16%411%25%30%10%
2582
June1st to 15thDay
14%39%20%28%23%
2520
16th to endDay
5%1213%33%44%
2520
July1st to 15thDay
5%126%24%59%
2301
16th to endDay
7%2410%26%50%
2313
August1st to 15thDay
6%210%29%49%
2214
16th to endDay
4211%36%43%
2100
September1st to 15thDay
6%1410%29%47%
1980
16th to endDay
10%1417%37%28%
1842
October1st to 15thDay
20%37%21%26%20%
1650
16th to endDay
21%26%22%26%20%
1760
November1st to 15thDay
28%38%18%28%12%
1681
16th to endDay
31%38%18%27%10%
1593
December1st to 15thDay
41%48%16%18%9%
1440
16th to endDay
42%411%16%16%8%
1536
January1st to 15thNight
34%28%20%22%10%
2360
16th to endNight
36%410%11%18%18%
2496
February1st to 15thNight
37%38%18%21%10%
2252
16th to endNight
38%311%20%18%6%
1895
March1st to 15thNight
36%6%11%16%17%11%
2019
16th to endNight
32%414%18%19%10%
2076
April1st to 15thNight
34%311%23%20%6%
1799
16th to endNight
18%413%25%27%10%
1800
May1st to 15thNight
15%36%21%35%17%
1764
16th to endNight
12%310%24%33%15%
1533
June1st to 15thNight
11%210%17%26%31%
1440
16th to endNight
31210%26%56%
1440
July1st to 15thNight
425%19%67%
1426
16th to endNight
6%238%21%57%
1593
August1st to 15thNight
6%17%25%58%
1634
16th to endNight
417%31%53%
1750
September1st to 15thNight
5%129%20%60%
1650
16th to endNight
8%217%34%35%
1784
October1st to 15thNight
20%26%20%27%21%
1980
16th to endNight
19%26%18%30%21%
2112
November1st to 15thNight
21%39%20%29%15%
2177
16th to endNight
27%39%18%26%13%
2364
December1st to 15thNight
38%47%16%21%12%
2520
16th to endNight
40%410%17%16%10%
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
19%10%23%25%19%2
204
16th to endDay
17%9%27%22%17%5%
256
February1st to 15thDay
15%12%25%22%20%3
243
16th to endDay
19%14%26%25%12%1
238
March1st to 15thDay
16%12%27%24%17%1
270
16th to endDay
14%10%38%25%10%1
288
April1st to 15thDay
19%18%30%19%11%1
269
16th to endDay
10%18%37%25%7%1
270
May1st to 15thDay
9%9%35%29%13%2
288
16th to endDay
6%11%22%37%16%5%
330
June1st to 15thDay
5%7%32%35%13%5%
315
16th to endDay
323%42%21%7%
315
July1st to 15thDay
117%44%28%6%
305
16th to endDay
1112%44%30%9%
327
August1st to 15thDay
2118%47%23%7%
300
16th to endDay
213%52%22%9%
268
September1st to 15thDay
2214%46%28%5%
255
16th to endDay
5%6%14%42%26%4
255
October1st to 15thDay
47%25%40%18%3
255
16th to endDay
8%5%32%29%20%3
272
November1st to 15thDay
9%8%15%23%35%7%
187
16th to endDay
10%10%27%34%15%2
85
December1st to 15thDay
20%11%35%25%8%
60
16th to endDay
17%10%17%28%23%3
64
January1st to 15thNight
13%212%28%30%12%
720
16th to endNight
15%311%30%28%9%
768
February1st to 15thNight
14%315%30%27%9%
704
16th to endNight
15%5%17%29%25%6%
632
March1st to 15thNight
13%415%31%26%8%
720
16th to endNight
11%420%30%28%5%
768
April1st to 15thNight
12%5%21%32%22%4
719
16th to endNight
5%7%20%30%26%10%
720
May1st to 15thNight
2218%36%28%11%
684
16th to endNight
3314%32%35%10%
411
June1st to 15thNight
1216%34%36%7%
360
16th to endNight
6%32%48%10%
360
July1st to 15thNight
1320%51%22%
406
16th to endNight
1114%51%31%
564
August1st to 15thNight
324%49%22%
585
16th to endNight
421%56%16%
700
September1st to 15thNight
423%51%20%
660
16th to endNight
29%21%46%19%
656
October1st to 15thNight
6%210%31%32%16%
660
16th to endNight
6%19%27%34%19%
704
November1st to 15thNight
6%211%33%31%14%
700
16th to endNight
7%312%32%30%12%
720
December1st to 15thNight
12%312%34%28%8%
720
16th to endNight
18%6%16%30%21%6%
768
Page generated at 2017-08-13 11:16:48. Version ac04

Copyright 2017 A. Danko


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