MASIL Observatory East
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the MASIL Observatory East 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
28%
14931
18%
47033
8%
14899
39%
14899
20%
30826

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
15%
1618
January16th to endNight
13%
768
18%
2688
4%
768
31%
768
14%
1737
February1st to 15thNight
16%
704
16%
2212
4%
701
31%
701
15%
1509
February16th to endNight
17%
631
21%
1893
6%
631
36%
631
17%
1244
March1st to 15thNight
17%
720
17%
2154
5%
720
31%
720
16%
1477
March16th to endNight
20%
768
22%
2034
7%
768
32%
768
21%
1372
April1st to 15thNight
22%
718
18%
1796
5%
718
30%
718
22%
1270
April16th to endNight
24%
582
18%
1662
5%
582
33%
582
19%
1137
May1st to 15thNight
24%
540
15%
1620
6%
540
32%
540
17%
1123
May16th to endNight
27%
405
11%
1527
7%
404
36%
404
14%
1038
June1st to 15thNight
33%
360
12%
1440
8%
360
45%
360
13%
981
June16th to endNight
38%
360
11%
1440
11%
360
45%
360
20%
906
July1st to 15thNight
46%
340
12%
1360
14%
340
53%
340
20%
831
July16th to endNight
50%
376
15%
1418
16%
354
56%
354
24%
853
August1st to 15thNight
50%
499
16%
1570
13%
497
53%
497
26%
992
August16th to endNight
50%
707
20%
1853
10%
707
54%
707
32%
1205
September1st to 15thNight
40%
720
20%
1863
9%
720
46%
720
34%
1178
September16th to endNight
44%
717
27%
1980
16%
717
53%
717
35%
1196
October1st to 15thNight
35%
684
21%
1913
10%
684
47%
684
25%
1258
October16th to endNight
24%
704
16%
2288
5%
704
37%
704
18%
1489
November1st to 15thNight
30%
700
21%
2277
10%
700
45%
700
22%
1443
November16th to endNight
25%
720
20%
2340
8%
720
40%
720
19%
1509
December1st to 15thNight
20%
720
17%
2511
5%
720
36%
720
16%
1656
December16th to endNight
16%
768
17%
2688
4%
768
32%
768
14%
1804

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%25%434446%39%
48174
Night
17%6%25%424446%40%
47203
Cloud CoverDay
17%6%25%42445%6%39%
48184
Night
17%6%24424446%40%
47208
TransparencyDay
44%6%11%21%14%2
47862
Night
43%5%11%21%15%2
47033
SeeingDay
22%14%30%20%9%3
5949
Night
21%13%32%24%7%
14931

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%7%244345%46%40%
1432
16th to endDay
15%6%245%25%445%43%
1536
February1st to 15thDay
16%6%36%436%5%5%6%34%
1648
16th to endDay
13%10%36%425%35%5%38%
1580
March1st to 15thDay
20%9%36%425%347%34%
1796
16th to endDay
17%6%345%23436%40%
2187
April1st to 15thDay
18%6%25%5%33446%39%
2152
16th to endDay
18%6%25%424347%40%
2298
May1st to 15thDay
24%8%25%4245%46%32%
2332
16th to endDay
18%5%25%5%2445%7%37%
2597
June1st to 15thDay
24%5%25%434447%31%
2520
16th to endDay
18%5%25%6%35%5%5%8%33%
2520
July1st to 15thDay
13%5%35%5%35%6%6%7%36%
2520
16th to endDay
13%5%35%6%36%5%6%7%36%
2654
August1st to 15thDay
13%5%25%5%36%6%6%7%36%
2367
16th to endDay
12%314435%6%6%7%44%
2348
September1st to 15thDay
14%425%42445%5%46%
2097
16th to endDay
14%5%23323335%52%
1980
October1st to 15thDay
20%4245%34335%42%
1843
16th to endDay
18%5%25%434445%41%
1584
November1st to 15thDay
19%6%25%323346%43%
1581
16th to endDay
19%5%34422345%44%
1620
December1st to 15thDay
19%6%36%5%24346%37%
1446
16th to endDay
22%8%25%424436%34%
1536
January1st to 15thNight
15%8%35%434446%40%
2506
16th to endNight
15%9%25%424445%39%
2688
February1st to 15thNight
14%8%36%6%25%45%6%36%
2211
16th to endNight
17%8%25%424446%40%
1893
March1st to 15thNight
19%8%244245%5%6%37%
2141
16th to endNight
17%6%3432344444%
2034
April1st to 15thNight
18%8%25%5%24346%38%
1796
16th to endNight
22%5%24414335%40%
1662
May1st to 15thNight
20%6%26%43345%5%36%
1620
16th to endNight
20%5%25%5%3445%6%34%
1525
June1st to 15thNight
24%6%34425%247%33%
1440
16th to endNight
16%5%35%4245%5%8%39%
1440
July1st to 15thNight
13%5%345%346%48%39%
1440
16th to endNight
13%4234345%7%9%40%
1514
August1st to 15thNight
10%5%245%25%6%6%7%42%
1580
16th to endNight
12%4245%3445%7%44%
1853
September1st to 15thNight
14%5%1442245%6%49%
1863
16th to endNight
13%5%13322246%52%
1980
October1st to 15thNight
19%5%23433345%44%
1913
16th to endNight
19%6%245%2345%6%39%
2288
November1st to 15thNight
17%6%24424336%43%
2277
16th to endNight
17%5%26%434346%41%
2340
December1st to 15thNight
19%7%245%23346%38%
2511
16th to endNight
19%8%26%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%6%25%42445%5%41%
1432
16th to endDay
14%6%24425%35%5%43%
1536
February1st to 15thDay
16%7%26%5%25%5%5%6%35%
1648
16th to endDay
14%9%46%5%2435%5%39%
1580
March1st to 15thDay
20%9%26%42435%6%33%
1806
16th to endDay
18%6%25%5%2334441%
2187
April1st to 15thDay
18%6%26%424346%39%
2152
16th to endDay
19%5%25%423446%40%
2298
May1st to 15thDay
24%7%25%434446%32%
2332
16th to endDay
18%435%43445%8%37%
2597
June1st to 15thDay
24%5%245%25%45%6%32%
2520
16th to endDay
17%5%245%45%5%5%8%35%
2520
July1st to 15thDay
13%4345%35%5%6%8%37%
2520
16th to endDay
13%5%26%5%36%5%6%8%37%
2654
August1st to 15thDay
13%5%25%5%36%6%6%8%36%
2367
16th to endDay
12%313425%5%5%8%44%
2348
September1st to 15thDay
13%5%2442435%5%46%
2097
16th to endDay
15%5%1332333451%
1980
October1st to 15thDay
20%6%235%24335%42%
1843
16th to endDay
17%5%25%334446%41%
1584
November1st to 15thDay
20%6%24323245%43%
1581
16th to endDay
18%5%34423345%44%
1620
December1st to 15thDay
19%6%36%424346%38%
1446
16th to endDay
23%8%2432345%435%
1536
January1st to 15thNight
16%7%35%424445%40%
2506
16th to endNight
16%9%34424445%39%
2688
February1st to 15thNight
14%8%35%6%345%5%6%36%
2204
16th to endNight
17%7%3442335%6%40%
1893
March1st to 15thNight
20%7%2442445%5%37%
2154
16th to endNight
16%7%35%313345%43%
2033
April1st to 15thNight
18%8%35%424345%39%
1796
16th to endNight
21%6%14424345%40%
1662
May1st to 15thNight
20%6%26%4345%46%36%
1620
16th to endNight
20%425%5%245%6%6%34%
1525
June1st to 15thNight
23%6%25%434347%34%
1440
16th to endNight
16%5%3342436%7%40%
1440
July1st to 15thNight
13%5%245%35%5%5%8%39%
1440
16th to endNight
13%4145%3446%9%40%
1514
August1st to 15thNight
10%425%435%6%5%8%43%
1580
16th to endNight
12%42443445%8%44%
1853
September1st to 15thNight
14%41431345%7%48%
1863
16th to endNight
14%423323346%52%
1980
October1st to 15thNight
18%5%14423335%44%
1913
16th to endNight
19%5%25%43345%5%41%
2288
November1st to 15thNight
17%6%24424347%43%
2277
16th to endNight
17%5%345%2435%6%41%
2340
December1st to 15thNight
19%6%35%424345%39%
2511
16th to endNight
19%8%34423446%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
44%6%10%23%12%2
1433
16th to endDay
41%5%13%26%12%1
1536
February1st to 15thDay
48%6%12%20%11%
1651
16th to endDay
47%410%20%13%3
1580
March1st to 15thDay
50%5%11%16%12%3
1806
16th to endDay
44%5%7%20%15%6%
2187
April1st to 15thDay
46%39%19%15%3
2152
16th to endDay
44%5%7%20%19%3
2298
May1st to 15thDay
51%5%8%16%14%2
2332
16th to endDay
44%7%12%20%12%2
2601
June1st to 15thDay
51%6%11%18%10%1
2520
16th to endDay
45%7%12%19%13%1
2520
July1st to 15thDay
41%8%11%22%14%1
2371
16th to endDay
42%7%12%22%12%2
2487
August1st to 15thDay
42%8%13%21%12%1
2353
16th to endDay
33%7%13%25%16%2
2348
September1st to 15thDay
37%6%10%21%21%2
2097
16th to endDay
36%47%22%25%2
1980
October1st to 15thDay
45%38%24%14%3
1843
16th to endDay
42%6%11%23%14%1
1584
November1st to 15thDay
43%412%23%14%1
1581
16th to endDay
43%412%21%16%1
1620
December1st to 15thDay
47%5%14%18%15%
1446
16th to endDay
50%6%12%18%11%
1536
January1st to 15thNight
44%5%12%21%13%2
2506
16th to endNight
45%410%20%15%2
2688
February1st to 15thNight
46%6%12%20%12%2
2212
16th to endNight
44%411%22%13%3
1893
March1st to 15thNight
46%6%10%19%14%2
2154
16th to endNight
42%410%16%19%5%
2034
April1st to 15thNight
46%49%18%17%2
1796
16th to endNight
46%5%8%19%16%4
1662
May1st to 15thNight
48%6%9%17%15%3
1620
16th to endNight
48%8%12%18%11%1
1527
June1st to 15thNight
51%6%10%21%10%
1440
16th to endNight
41%8%12%21%14%1
1440
July1st to 15thNight
40%8%13%24%13%
1360
16th to endNight
38%7%15%26%10%1
1418
August1st to 15thNight
36%9%14%23%14%1
1570
16th to endNight
37%6%12%25%18%
1853
September1st to 15thNight
34%5%12%26%20%
1863
16th to endNight
33%38%26%26%1
1980
October1st to 15thNight
41%410%24%14%3
1913
16th to endNight
44%5%13%23%13%
2288
November1st to 15thNight
41%5%11%21%17%2
2277
16th to endNight
44%312%22%13%2
2340
December1st to 15thNight
46%5%13%21%12%
2511
16th to endNight
47%5%12%20%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
30%20%28%18%3
60
16th to endDay
29%18%37%14%
64
February1st to 15thDay
27%21%29%17%3
214
16th to endDay
18%24%30%19%5%
239
March1st to 15thDay
30%19%30%14%5%
270
16th to endDay
23%23%32%12%5%2
288
April1st to 15thDay
24%19%32%13%8%1
270
16th to endDay
22%15%32%18%7%2
270
May1st to 15thDay
37%14%25%12%6%3
288
16th to endDay
21%14%32%24%5%1
331
June1st to 15thDay
24%12%33%19%8%
315
16th to endDay
17%13%39%23%42
315
July1st to 15thDay
18%6%33%26%13%1
305
16th to endDay
14%8%29%32%11%3
326
August1st to 15thDay
17%9%27%25%16%3
313
16th to endDay
13%8%27%27%16%6%
332
September1st to 15thDay
18%8%29%22%13%6%
315
16th to endDay
21%8%24%16%15%13%
314
October1st to 15thDay
23%11%22%23%14%4
275
16th to endDay
22%14%33%21%7%
240
November1st to 15thDay
26%14%24%22%8%2
235
16th to endDay
26%14%27%18%10%1
240
December1st to 15thDay
21%25%34%12%6%
66
16th to endDay
35%20%29%14%
64
January1st to 15thNight
20%20%36%19%2
720
16th to endNight
25%18%35%17%2
768
February1st to 15thNight
21%19%36%20%1
704
16th to endNight
22%18%35%17%5%
631
March1st to 15thNight
24%19%34%17%3
720
16th to endNight
21%20%33%18%6%
768
April1st to 15thNight
22%16%35%20%3
718
16th to endNight
23%17%32%19%6%
582
May1st to 15thNight
23%14%32%23%5%
540
16th to endNight
22%8%35%27%5%
405
June1st to 15thNight
25%9%27%30%6%1
360
16th to endNight
18%5%34%33%8%
360
July1st to 15thNight
14%326%41%12%1
340
16th to endNight
14%126%40%16%
376
August1st to 15thNight
12%428%40%13%
499
16th to endNight
14%325%35%18%2
707
September1st to 15thNight
16%5%32%29%15%
720
16th to endNight
17%5%28%25%20%3
717
October1st to 15thNight
22%9%27%26%12%1
684
16th to endNight
24%15%30%22%6%
704
November1st to 15thNight
20%12%31%24%9%1
700
16th to endNight
21%17%29%21%8%
720
December1st to 15thNight
24%17%34%20%4
720
16th to endNight
25%19%35%17%1
768
Page generated at 2017-10-07 14:07:51. Version ac04

Copyright 2017 A. Danko


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