Max Ronan Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Max Ronan 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
28%
14892
18%
46853
8%
14860
39%
14860
20%
30621

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
17%
720
19%
2506
6%
716
33%
716
16%
1603
January16th to endNight
14%
768
18%
2688
4%
768
33%
768
14%
1725
February1st to 15thNight
18%
704
17%
2199
4%
701
33%
701
17%
1487
February16th to endNight
18%
631
23%
1893
7%
631
38%
631
19%
1246
March1st to 15thNight
18%
720
17%
2151
6%
720
32%
720
17%
1472
March16th to endNight
21%
768
22%
2037
7%
768
34%
768
21%
1395
April1st to 15thNight
21%
718
18%
1796
4%
718
30%
718
21%
1270
April16th to endNight
24%
582
18%
1662
4%
582
34%
582
20%
1146
May1st to 15thNight
25%
540
15%
1620
7%
540
31%
540
17%
1126
May16th to endNight
26%
417
11%
1539
7%
416
34%
416
16%
1008
June1st to 15thNight
31%
360
12%
1440
9%
360
41%
360
15%
970
June16th to endNight
38%
360
12%
1440
12%
360
45%
360
21%
873
July1st to 15thNight
45%
340
12%
1360
14%
340
51%
340
22%
823
July16th to endNight
47%
376
15%
1418
14%
354
54%
354
21%
874
August1st to 15thNight
46%
509
17%
1580
12%
507
50%
507
27%
994
August16th to endNight
52%
710
21%
1856
11%
710
55%
710
32%
1204
September1st to 15thNight
40%
720
20%
1866
9%
720
47%
720
33%
1201
September16th to endNight
45%
677
27%
1869
17%
677
53%
677
34%
1144
October1st to 15thNight
33%
660
23%
1841
10%
660
45%
660
25%
1208
October16th to endNight
24%
704
17%
2288
6%
704
38%
704
19%
1479
November1st to 15thNight
31%
700
21%
2277
10%
700
45%
700
21%
1437
November16th to endNight
25%
720
20%
2340
8%
720
40%
720
18%
1512
December1st to 15thNight
20%
720
18%
2499
5%
720
36%
720
16%
1631
December16th to endNight
16%
768
18%
2688
4%
768
33%
768
14%
1793

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%2442445%6%39%
47994
Night
17%6%24424446%40%
47023
Cloud CoverDay
17%6%25%42445%7%39%
48004
Night
17%6%25%424446%40%
47028
TransparencyDay
43%5%11%21%14%2
47682
Night
43%5%11%21%15%2
46853
SeeingDay
21%15%31%20%9%2
5907
Night
20%13%32%24%8%
14892

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
16%6%3442445%5%41%
1432
16th to endDay
16%5%24425%345%43%
1536
February1st to 15thDay
16%6%35%435%7%5%6%35%
1660
16th to endDay
14%9%35%424445%40%
1580
March1st to 15thDay
20%8%3442445%6%35%
1798
16th to endDay
18%7%35%423445%39%
2184
April1st to 15thDay
18%7%35%5%2345%6%38%
2152
16th to endDay
19%5%25%434347%39%
2297
May1st to 15thDay
24%8%345%34446%32%
2332
16th to endDay
17%5%2443435%7%40%
2584
June1st to 15thDay
25%5%235%2445%6%33%
2520
16th to endDay
16%5%25%5%25%5%6%7%35%
2520
July1st to 15thDay
12%5%25%5%345%7%9%37%
2520
16th to endDay
12%5%25%5%36%5%6%8%39%
2654
August1st to 15thDay
11%5%25%5%35%6%7%9%37%
2358
16th to endDay
11%314436%5%5%8%45%
2345
September1st to 15thDay
13%5%24434445%47%
2094
16th to endDay
15%5%24322345%49%
1860
October1st to 15thDay
20%5%14423446%40%
1786
16th to endDay
16%6%2442445%5%42%
1584
November1st to 15thDay
20%6%2442234443%
1581
16th to endDay
18%5%35%323345%43%
1620
December1st to 15thDay
19%6%35%5%24245%39%
1461
16th to endDay
22%9%24334446%34%
1536
January1st to 15thNight
16%8%25%434435%41%
2506
16th to endNight
15%9%35%5%24435%40%
2688
February1st to 15thNight
14%9%35%5%345%5%7%36%
2198
16th to endNight
16%9%24423346%41%
1893
March1st to 15thNight
18%7%35%435%345%37%
2138
16th to endNight
16%8%3433433444%
2037
April1st to 15thNight
17%7%35%5%24446%38%
1796
16th to endNight
22%4245%3433440%
1662
May1st to 15thNight
21%6%245%35%45%6%35%
1620
16th to endNight
19%6%25%42445%8%34%
1537
June1st to 15thNight
23%7%15%425%446%34%
1440
16th to endNight
16%434425%45%8%40%
1440
July1st to 15thNight
12%6%25%5%25%46%8%40%
1440
16th to endNight
13%435%436%45%8%39%
1514
August1st to 15thNight
9%4245%35%5%6%6%43%
1590
16th to endNight
12%4245%3445%7%45%
1856
September1st to 15thNight
13%5%24413347%47%
1866
16th to endNight
14%5%13312336%52%
1869
October1st to 15thNight
19%6%14323445%44%
1841
16th to endNight
19%6%2442345%6%40%
2288
November1st to 15thNight
16%5%25%323446%44%
2277
16th to endNight
17%6%35%5%24346%41%
2340
December1st to 15thNight
20%6%34424446%38%
2499
16th to endNight
19%8%35%424446%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
16%7%25%3245%46%40%
1432
16th to endDay
16%5%25%43335%5%44%
1536
February1st to 15thDay
17%7%35%425%5%6%7%34%
1660
16th to endDay
14%8%344245%46%39%
1580
March1st to 15thDay
21%6%35%32445%6%34%
1808
16th to endDay
18%6%35%42345%5%39%
2184
April1st to 15thDay
18%7%35%5%2345%6%37%
2152
16th to endDay
19%5%2442435%6%40%
2297
May1st to 15thDay
23%8%25%5%33446%32%
2332
16th to endDay
17%6%25%433348%40%
2584
June1st to 15thDay
25%5%24425%45%7%32%
2520
16th to endDay
15%6%25%5%36%5%6%8%34%
2520
July1st to 15thDay
11%5%25%6%35%5%7%9%37%
2520
16th to endDay
12%425%5%35%5%6%8%39%
2654
August1st to 15thDay
11%5%25%5%36%6%7%9%37%
2358
16th to endDay
11%413425%5%6%8%45%
2345
September1st to 15thDay
13%424434346%47%
2094
16th to endDay
15%6%2432235%5%49%
1860
October1st to 15thDay
20%5%15%424346%40%
1786
16th to endDay
16%6%25%424446%42%
1584
November1st to 15thDay
20%7%24413335%43%
1581
16th to endDay
18%5%35%333336%43%
1620
December1st to 15thDay
18%6%345%33346%39%
1461
16th to endDay
22%8%34425%445%35%
1536
January1st to 15thNight
16%7%26%424345%41%
2506
16th to endNight
15%9%345%34335%40%
2688
February1st to 15thNight
14%9%25%5%345%5%6%37%
2191
16th to endNight
17%8%34423346%41%
1893
March1st to 15thNight
19%6%35%425%345%37%
2151
16th to endNight
16%8%3433443443%
2036
April1st to 15thNight
18%6%35%5%24346%37%
1796
16th to endNight
22%425%434335%39%
1662
May1st to 15thNight
21%6%25%5%3445%5%35%
1620
16th to endNight
19%6%25%425%45%9%34%
1537
June1st to 15thNight
23%6%25%424436%34%
1440
16th to endNight
15%424435%35%8%40%
1440
July1st to 15thNight
12%6%25%5%2447%8%40%
1440
16th to endNight
12%5%25%5%36%46%8%39%
1514
August1st to 15thNight
10%415%5%36%5%6%7%42%
1590
16th to endNight
12%3145%35%45%8%44%
1856
September1st to 15thNight
13%5%14423446%48%
1866
16th to endNight
14%414323336%52%
1869
October1st to 15thNight
19%5%23424445%44%
1841
16th to endNight
19%6%245%2345%7%40%
2288
November1st to 15thNight
17%5%26%323445%44%
2277
16th to endNight
17%6%25%434346%41%
2340
December1st to 15thNight
19%6%35%424446%38%
2499
16th to endNight
19%8%35%423446%37%
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
43%411%24%12%3
1433
16th to endDay
41%312%27%13%1
1536
February1st to 15thDay
47%5%13%19%12%
1663
16th to endDay
45%412%20%14%2
1580
March1st to 15thDay
49%411%18%12%3
1808
16th to endDay
44%38%21%15%5%
2184
April1st to 15thDay
46%410%19%15%3
2152
16th to endDay
43%47%21%18%3
2297
May1st to 15thDay
53%47%17%14%2
2332
16th to endDay
43%6%13%21%12%2
2588
June1st to 15thDay
50%6%12%19%10%1
2520
16th to endDay
44%7%12%19%14%
2520
July1st to 15thDay
40%8%11%23%15%1
2371
16th to endDay
40%6%15%22%12%2
2487
August1st to 15thDay
40%7%14%23%12%1
2344
16th to endDay
34%7%12%26%17%1
2345
September1st to 15thDay
36%5%11%22%22%1
2094
16th to endDay
36%47%24%23%2
1860
October1st to 15thDay
44%49%23%14%3
1786
16th to endDay
42%5%11%24%14%1
1584
November1st to 15thDay
44%311%23%14%1
1581
16th to endDay
43%412%20%16%1
1620
December1st to 15thDay
46%414%17%16%
1461
16th to endDay
51%412%19%11%
1536
January1st to 15thNight
45%412%21%13%2
2506
16th to endNight
46%310%20%15%2
2688
February1st to 15thNight
47%412%20%12%2
2199
16th to endNight
44%49%23%15%3
1893
March1st to 15thNight
48%49%20%14%3
2151
16th to endNight
44%47%18%19%5%
2037
April1st to 15thNight
47%49%18%17%2
1796
16th to endNight
47%48%18%16%4
1662
May1st to 15thNight
48%5%9%16%15%3
1620
16th to endNight
46%6%15%18%10%1
1539
June1st to 15thNight
50%6%11%20%10%
1440
16th to endNight
40%6%13%22%15%1
1440
July1st to 15thNight
38%7%13%25%14%
1360
16th to endNight
41%6%12%26%10%1
1418
August1st to 15thNight
37%7%12%24%15%2
1580
16th to endNight
36%6%10%26%19%
1856
September1st to 15thNight
36%5%11%25%19%1
1866
16th to endNight
34%46%24%27%1
1869
October1st to 15thNight
42%411%22%15%4
1841
16th to endNight
43%5%12%24%13%
2288
November1st to 15thNight
41%5%11%22%16%3
2277
16th to endNight
44%411%22%14%2
2340
December1st to 15thNight
46%413%21%12%
2499
16th to endNight
48%411%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
15%35%21%25%3
60
16th to endDay
26%26%34%12%
64
February1st to 15thDay
25%20%35%16%2
224
16th to endDay
18%23%31%21%4
239
March1st to 15thDay
22%27%31%14%4
270
16th to endDay
21%23%31%14%6%1
288
April1st to 15thDay
24%18%31%15%9%
270
16th to endDay
22%17%33%18%5%2
270
May1st to 15thDay
34%17%25%14%5%2
288
16th to endDay
19%14%35%22%6%
331
June1st to 15thDay
24%12%36%16%9%
315
16th to endDay
18%14%38%21%32
315
July1st to 15thDay
17%8%32%26%13%1
305
16th to endDay
14%7%32%30%13%2
326
August1st to 15thDay
13%9%31%26%14%3
313
16th to endDay
12%6%28%31%15%5%
332
September1st to 15thDay
18%9%29%23%13%4
315
16th to endDay
20%7%27%16%13%14%
270
October1st to 15thDay
26%11%21%21%13%5%
252
16th to endDay
20%17%30%24%7%
240
November1st to 15thDay
25%11%30%19%10%2
235
16th to endDay
23%17%30%15%10%1
240
December1st to 15thDay
22%30%30%11%4
81
16th to endDay
29%23%34%12%
64
January1st to 15thNight
20%20%37%18%2
720
16th to endNight
23%18%36%17%2
768
February1st to 15thNight
20%19%37%21%1
704
16th to endNight
23%18%35%18%4
631
March1st to 15thNight
24%18%35%18%3
720
16th to endNight
21%18%34%18%7%
768
April1st to 15thNight
21%19%34%20%4
718
16th to endNight
23%15%32%22%5%
582
May1st to 15thNight
25%14%30%22%5%
540
16th to endNight
22%11%35%23%6%
417
June1st to 15thNight
24%8%31%25%8%1
360
16th to endNight
18%5%32%33%9%
360
July1st to 15thNight
13%329%40%12%1
340
16th to endNight
13%328%38%15%
376
August1st to 15thNight
13%429%38%14%
509
16th to endNight
14%423%37%18%1
710
September1st to 15thNight
16%5%31%29%14%1
720
16th to endNight
17%5%25%26%21%3
677
October1st to 15thNight
22%10%27%25%11%1
660
16th to endNight
23%15%31%22%7%
704
November1st to 15thNight
18%15%29%24%10%1
700
16th to endNight
21%18%28%22%7%
720
December1st to 15thNight
24%16%34%20%3
720
16th to endNight
24%19%35%17%2
768
Page generated at 2017-09-21 07:18:22. Version ac04

Copyright 2017 A. Danko


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