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 2017-04-08.

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
27%
14412
18%
45415
8%
14380
39%
14380
20%
29791

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
21%
690
19%
1726
5%
690
30%
690
21%
1229
April16th to endNight
24%
534
18%
1524
5%
534
33%
534
20%
1032
May1st to 15thNight
24%
495
16%
1485
7%
495
32%
495
18%
1022
May16th to endNight
28%
370
11%
1396
7%
369
37%
369
15%
939
June1st to 15thNight
33%
330
12%
1320
8%
330
45%
330
12%
918
June16th to endNight
38%
330
10%
1320
11%
330
44%
330
20%
824
July1st to 15thNight
47%
310
12%
1240
14%
310
54%
310
20%
761
July16th to endNight
50%
348
14%
1306
14%
326
56%
326
24%
784
August1st to 15thNight
50%
457
17%
1438
13%
455
53%
455
26%
915
August16th to endNight
49%
648
18%
1698
9%
648
52%
648
31%
1111
September1st to 15thNight
42%
660
21%
1708
9%
660
48%
660
34%
1085
September16th to endNight
45%
657
27%
1815
16%
657
53%
657
37%
1082
October1st to 15thNight
34%
660
22%
1848
10%
660
46%
660
24%
1231
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%38%
45852
Night
17%6%25%424446%40%
45585
Cloud CoverDay
17%6%25%42445%6%39%
45862
Night
17%6%2442445%6%40%
45590
TransparencyDay
44%6%11%21%14%2
45540
Night
43%5%11%21%14%2
45415
SeeingDay
22%14%29%21%9%3
5232
Night
21%13%32%24%7%
14412

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
19%7%25%5%33446%38%
2062
16th to endDay
18%6%25%424347%40%
2106
May1st to 15thDay
23%7%2442445%6%34%
2137
16th to endDay
17%5%35%5%2445%7%38%
2375
June1st to 15thDay
25%6%25%434447%30%
2310
16th to endDay
18%5%25%5%35%5%5%8%34%
2310
July1st to 15thDay
12%6%35%5%35%6%6%8%36%
2310
16th to endDay
12%5%35%6%45%5%6%7%36%
2458
August1st to 15thDay
13%5%25%5%36%6%6%8%36%
2170
16th to endDay
12%315%435%6%6%7%43%
2151
September1st to 15thDay
14%425%4245%5%5%46%
1922
16th to endDay
14%5%2332433452%
1815
October1st to 15thDay
21%4245%34335%41%
1780
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
19%8%25%5%24346%38%
1726
16th to endNight
21%5%24424335%41%
1524
May1st to 15thNight
19%6%26%43445%5%37%
1485
16th to endNight
20%5%25%5%345%5%6%35%
1394
June1st to 15thNight
25%6%34425%347%32%
1320
16th to endNight
16%5%3441445%8%40%
1320
July1st to 15thNight
13%4345%35%6%49%38%
1320
16th to endNight
13%4234345%7%10%40%
1402
August1st to 15thNight
10%5%245%26%5%5%7%43%
1448
16th to endNight
12%425%5%3446%8%43%
1698
September1st to 15thNight
14%41442245%6%48%
1708
16th to endNight
13%5%12322247%53%
1815
October1st to 15thNight
20%5%23433345%43%
1848
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
19%6%26%424346%39%
2062
16th to endDay
18%5%25%423446%41%
2106
May1st to 15thDay
23%6%24334446%34%
2137
16th to endDay
17%435%43445%8%37%
2375
June1st to 15thDay
25%5%35%425%45%6%30%
2310
16th to endDay
17%5%245%35%5%5%7%35%
2310
July1st to 15thDay
13%435%5%35%5%6%8%37%
2310
16th to endDay
12%5%26%5%36%6%6%8%37%
2458
August1st to 15thDay
13%5%25%5%36%6%6%8%36%
2170
16th to endDay
12%313436%6%5%8%43%
2151
September1st to 15thDay
13%5%2442435%5%46%
1922
16th to endDay
14%5%2332333452%
1815
October1st to 15thDay
20%6%235%24335%40%
1780
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
19%8%35%424345%38%
1726
16th to endNight
21%5%14424345%41%
1524
May1st to 15thNight
18%6%26%4345%46%37%
1485
16th to endNight
20%425%5%35%5%6%6%35%
1394
June1st to 15thNight
24%6%25%435%347%32%
1320
16th to endNight
16%5%3342436%8%40%
1320
July1st to 15thNight
13%5%145%36%5%5%8%38%
1320
16th to endNight
14%41442446%9%40%
1402
August1st to 15thNight
10%5%25%435%6%5%7%43%
1448
16th to endNight
12%42443446%8%43%
1698
September1st to 15thNight
14%41431345%7%47%
1708
16th to endNight
14%422323346%53%
1815
October1st to 15thNight
19%5%24424435%43%
1848
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
47%39%18%16%3
2062
16th to endDay
43%5%6%20%19%3
2106
May1st to 15thDay
49%5%9%16%15%2
2137
16th to endDay
44%7%13%20%12%2
2379
June1st to 15thDay
53%6%12%18%8%1
2310
16th to endDay
45%7%12%19%13%1
2310
July1st to 15thDay
41%8%11%23%14%1
2161
16th to endDay
42%7%13%22%11%2
2291
August1st to 15thDay
42%8%13%21%12%1
2156
16th to endDay
35%8%13%25%15%2
2151
September1st to 15thDay
37%7%10%22%20%1
1922
16th to endDay
36%47%23%25%2
1815
October1st to 15thDay
46%39%23%13%3
1780
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
47%49%18%17%2
1726
16th to endNight
45%5%8%19%16%4
1524
May1st to 15thNight
47%6%9%17%15%3
1485
16th to endNight
47%8%12%17%11%1
1396
June1st to 15thNight
52%6%10%20%8%1
1320
16th to endNight
41%8%13%21%14%1
1320
July1st to 15thNight
40%8%13%24%13%
1240
16th to endNight
37%7%15%27%9%1
1306
August1st to 15thNight
37%9%13%23%14%2
1438
16th to endNight
37%6%13%25%16%
1698
September1st to 15thNight
34%6%12%26%19%
1708
16th to endNight
32%38%26%26%1
1815
October1st to 15thNight
43%410%22%14%3
1848
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
27%18%30%14%8%1
240
16th to endDay
20%15%32%19%8%3
210
May1st to 15thDay
32%15%25%14%8%3
228
16th to endDay
18%14%32%27%5%1
267
June1st to 15thDay
25%13%30%18%10%1
255
16th to endDay
16%9%39%26%5%3
255
July1st to 15thDay
15%6%33%26%15%2
245
16th to endDay
12%8%31%33%12%1
270
August1st to 15thDay
16%9%28%25%15%3
253
16th to endDay
13%7%22%28%19%8%
268
September1st to 15thDay
18%7%25%25%15%8%
255
16th to endDay
19%9%24%17%14%13%
254
October1st to 15thDay
25%12%22%21%13%4
252
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
23%17%35%20%3
690
16th to endNight
23%17%32%20%6%
534
May1st to 15thNight
22%13%33%23%5%
495
16th to endNight
22%8%35%27%5%
370
June1st to 15thNight
25%9%26%29%7%1
330
16th to endNight
18%434%33%9%
330
July1st to 15thNight
15%424%40%13%1
310
16th to endNight
14%227%40%16%
348
August1st to 15thNight
12%427%41%13%
457
16th to endNight
14%325%35%17%2
648
September1st to 15thNight
16%431%30%16%
660
16th to endNight
16%5%28%26%19%2
657
October1st to 15thNight
23%10%27%26%11%1
660
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 2017-04-09 06:54:12. Version ac04

Copyright 2017 A. Danko


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