Digital Monastery Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Digital Monastery Observatory clear sky chart from 2005-11-05 to

2017-09-12
.

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
40%
15173
20%
46844
12%
15134
49%
15134
25%
29618

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
23%
717
20%
2419
8%
716
39%
716
18%
1546
January16th to endNight
22%
768
21%
2496
7%
768
39%
768
21%
1593
February1st to 15thNight
26%
703
19%
2287
7%
701
41%
701
21%
1413
February16th to endNight
20%
631
21%
1934
6%
631
38%
631
20%
1246
March1st to 15thNight
27%
720
20%
1995
9%
720
39%
720
25%
1314
March16th to endNight
25%
768
21%
2094
8%
768
36%
768
24%
1412
April1st to 15thNight
28%
718
18%
1796
5%
718
35%
718
27%
1215
April16th to endNight
41%
720
18%
1800
7%
720
46%
720
31%
1207
May1st to 15thNight
40%
534
17%
1614
11%
534
46%
534
22%
1097
May16th to endNight
53%
374
17%
1497
18%
374
58%
374
21%
909
June1st to 15thNight
56%
360
19%
1440
20%
360
62%
360
25%
826
June16th to endNight
61%
360
18%
1440
19%
360
68%
360
26%
820
July1st to 15thNight
59%
340
12%
1360
16%
340
61%
340
18%
863
July16th to endNight
73%
547
16%
1578
14%
514
76%
514
34%
917
August1st to 15thNight
68%
539
18%
1609
14%
536
69%
536
31%
994
August16th to endNight
64%
738
21%
1884
14%
738
66%
738
35%
1214
September1st to 15thNight
59%
707
24%
1768
14%
707
63%
707
36%
1138
September16th to endNight
53%
657
22%
1817
18%
657
57%
657
29%
1199
October1st to 15thNight
47%
660
23%
1980
20%
660
55%
660
27%
1274
October16th to endNight
39%
704
27%
2112
16%
704
54%
704
33%
1227
November1st to 15thNight
41%
700
24%
2221
17%
700
52%
700
30%
1325
November16th to endNight
33%
720
20%
2495
12%
720
46%
720
21%
1513
December1st to 15thNight
28%
720
16%
2520
7%
720
40%
720
17%
1655
December16th to endNight
24%
768
20%
2688
7%
768
40%
768
20%
1701

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
14%5%25%5%35%5%5%7%40%
47807
Night
14%5%2442445%7%42%
47026
Cloud CoverDay
14%5%25%5%35%5%5%7%40%
47817
Night
14%5%2442445%7%42%
47030
TransparencyDay
40%6%13%22%15%2
47507
Night
39%6%12%23%15%2
46844
SeeingDay
17%8%21%25%19%7%
5614
Night
17%8%28%31%13%1
15178

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
14%6%35%5%26%5%6%6%38%
1516
16th to endDay
14%8%25%5%34446%40%
1728
February1st to 15thDay
13%7%35%5%35%5%46%37%
1575
16th to endDay
12%7%35%5%45%46%5%39%
1539
March1st to 15thDay
14%5%25%5%35%347%41%
1951
16th to endDay
16%6%25%5%3445%6%37%
2128
April1st to 15thDay
15%425%5%2445%7%41%
2152
16th to endDay
17%6%24424346%42%
2160
May1st to 15thDay
17%5%25%435%5%5%9%35%
2346
16th to endDay
16%5%25%5%3445%7%38%
2618
June1st to 15thDay
12%324425%6%7%9%40%
2520
16th to endDay
10%415%426%5%6%9%43%
2520
July1st to 15thDay
9%5%25%6%36%6%7%8%38%
2520
16th to endDay
7%425%5%47%7%7%9%37%
2480
August1st to 15thDay
11%426%6%46%7%6%8%36%
2340
16th to endDay
11%4245%346%6%8%41%
2304
September1st to 15thDay
15%42442335%7%45%
2112
16th to endDay
17%5%2443445%7%39%
1811
October1st to 15thDay
19%413423346%45%
1650
16th to endDay
14%415%434446%45%
1760
November1st to 15thDay
13%5%2442435%6%47%
1637
16th to endDay
18%415%43345%7%40%
1464
December1st to 15thDay
16%5%25%5%25%46%7%35%
1440
16th to endDay
17%5%25%5%4446%5%38%
1536
January1st to 15thNight
16%5%35%42445%7%39%
2419
16th to endNight
15%7%25%424446%41%
2496
February1st to 15thNight
13%5%25%4245%5%7%43%
2285
16th to endNight
12%7%25%5%35%5%5%6%40%
1934
March1st to 15thNight
15%6%24424446%42%
1983
16th to endNight
15%6%2442445%7%41%
2094
April1st to 15thNight
12%5%35%5%35%45%7%40%
1796
16th to endNight
16%5%2432446%7%43%
1800
May1st to 15thNight
19%6%2442445%7%37%
1614
16th to endNight
12%5%245%345%48%42%
1495
June1st to 15thNight
10%4244235%8%8%44%
1440
16th to endNight
8%3244345%6%10%43%
1440
July1st to 15thNight
10%425%5%46%5%7%9%38%
1440
16th to endNight
6%314425%5%8%12%45%
1685
August1st to 15thNight
9%4145%25%5%6%9%44%
1620
16th to endNight
10%3234345%6%9%45%
1884
September1st to 15thNight
13%42342345%7%47%
1768
16th to endNight
15%5%245%24445%45%
1817
October1st to 15thNight
19%5%24324345%44%
1980
16th to endNight
14%313323346%51%
2112
November1st to 15thNight
13%5%24423345%50%
2221
16th to endNight
16%42442445%8%42%
2495
December1st to 15thNight
16%5%35%6%35%5%5%5%37%
2520
16th to endNight
16%5%25%42445%8%38%
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
15%6%34436%5%6%6%38%
1516
16th to endDay
14%8%345%2445%5%40%
1728
February1st to 15thDay
13%7%36%5%45%5%5%6%38%
1575
16th to endDay
12%7%46%5%3445%6%39%
1539
March1st to 15thDay
14%6%345%35%346%41%
1962
16th to endDay
17%6%25%6%245%46%38%
2127
April1st to 15thDay
15%435%5%2445%7%41%
2152
16th to endDay
18%5%25%424346%42%
2160
May1st to 15thDay
18%5%245%25%5%6%8%35%
2346
16th to endDay
16%5%25%5%3445%7%38%
2618
June1st to 15thDay
12%414325%6%7%9%41%
2520
16th to endDay
10%425%435%5%6%9%43%
2520
July1st to 15thDay
9%425%6%45%7%6%8%39%
2520
16th to endDay
7%3245%47%7%7%11%37%
2480
August1st to 15thDay
11%436%5%46%6%6%8%36%
2340
16th to endDay
10%5%245%345%6%8%42%
2304
September1st to 15thDay
15%423423447%45%
2112
16th to endDay
16%5%25%5%3445%7%39%
1811
October1st to 15thDay
20%313324336%45%
1650
16th to endDay
14%4245%24446%45%
1760
November1st to 15thDay
13%5%1442345%7%47%
1637
16th to endDay
18%42443336%6%41%
1464
December1st to 15thDay
16%5%26%5%25%5%6%7%36%
1440
16th to endDay
17%6%25%6%2445%5%38%
1536
January1st to 15thNight
16%6%35%43445%7%39%
2419
16th to endNight
15%7%25%42445%6%40%
2496
February1st to 15thNight
14%5%25%4245%5%6%44%
2278
16th to endNight
12%7%26%5%25%5%5%6%40%
1934
March1st to 15thNight
16%6%24425%446%42%
1995
16th to endNight
14%6%35%434447%41%
2094
April1st to 15thNight
13%5%36%5%36%46%6%40%
1796
16th to endNight
16%5%2442446%6%43%
1800
May1st to 15thNight
18%7%245%245%47%37%
1613
16th to endNight
12%5%25%4345%5%7%43%
1495
June1st to 15thNight
10%5%244245%7%8%44%
1440
16th to endNight
8%325%425%46%11%44%
1440
July1st to 15thNight
10%425%5%47%5%8%9%36%
1440
16th to endNight
6%314325%6%8%11%45%
1685
August1st to 15thNight
9%4145%25%5%7%8%44%
1620
16th to endNight
10%4134345%5%9%45%
1884
September1st to 15thNight
13%41343336%7%47%
1768
16th to endNight
15%5%25%5%24436%44%
1817
October1st to 15thNight
19%424423345%44%
1980
16th to endNight
14%423323346%52%
2112
November1st to 15thNight
13%5%24422445%50%
2221
16th to endNight
16%42432445%7%42%
2495
December1st to 15thNight
16%5%25%5%35%5%5%5%38%
2520
16th to endNight
16%5%25%42445%8%39%
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%13%21%12%2
1517
16th to endDay
43%414%23%11%2
1728
February1st to 15thDay
46%5%13%21%11%2
1577
16th to endDay
44%5%12%24%11%1
1539
March1st to 15thDay
43%5%11%23%14%2
1962
16th to endDay
46%5%11%18%15%2
2128
April1st to 15thDay
41%5%11%21%16%3
2152
16th to endDay
42%48%19%19%5%
2160
May1st to 15thDay
44%7%12%19%14%1
2346
16th to endDay
42%7%14%21%12%1
2622
June1st to 15thDay
34%10%14%24%14%
2520
16th to endDay
35%9%15%22%15%1
2520
July1st to 15thDay
38%9%14%19%14%2
2371
16th to endDay
35%9%15%22%15%2
2324
August1st to 15thDay
42%8%14%19%14%1
2327
16th to endDay
36%6%14%24%14%2
2304
September1st to 15thDay
37%6%12%19%22%2
2112
16th to endDay
42%5%8%22%18%2
1811
October1st to 15thDay
40%410%23%17%2
1650
16th to endDay
38%411%26%18%
1760
November1st to 15thDay
37%413%21%17%5%
1637
16th to endDay
42%411%26%13%1
1464
December1st to 15thDay
44%6%15%21%9%1
1440
16th to endDay
45%6%12%23%11%
1536
January1st to 15thNight
43%5%12%20%14%3
2419
16th to endNight
42%413%26%12%1
2496
February1st to 15thNight
39%5%15%23%14%2
2287
16th to endNight
42%5%12%24%14%1
1934
March1st to 15thNight
41%412%27%11%1
1995
16th to endNight
42%5%10%21%16%2
2094
April1st to 15thNight
41%5%11%21%16%3
1796
16th to endNight
39%5%10%21%17%6%
1800
May1st to 15thNight
44%6%9%22%14%2
1614
16th to endNight
39%8%14%21%14%2
1497
June1st to 15thNight
33%8%12%27%16%1
1440
16th to endNight
33%8%13%24%17%2
1440
July1st to 15thNight
41%10%14%18%11%4
1360
16th to endNight
27%10%19%23%17%2
1578
August1st to 15thNight
34%8%15%22%17%2
1609
16th to endNight
33%7%13%23%18%3
1884
September1st to 15thNight
34%5%13%20%21%3
1768
16th to endNight
41%5%8%21%20%3
1817
October1st to 15thNight
41%49%23%18%2
1980
16th to endNight
32%410%30%20%1
2112
November1st to 15thNight
37%38%24%18%6%
2221
16th to endNight
39%5%12%22%17%3
2495
December1st to 15thNight
45%6%12%22%10%1
2520
16th to endNight
43%5%16%22%10%1
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
25%31%20%14%6%1
74
16th to endDay
28%26%30%13%2
96
February1st to 15thDay
21%23%43%11%1
90
16th to endDay
19%16%40%21%2
198
March1st to 15thDay
17%17%27%29%7%
270
16th to endDay
20%11%32%26%6%2
288
April1st to 15thDay
17%15%25%25%13%2
270
16th to endDay
24%426%17%20%7%
270
May1st to 15thDay
26%14%22%19%11%6%
288
16th to endDay
19%416%25%25%8%
331
June1st to 15thDay
16%323%23%23%9%
315
16th to endDay
12%424%28%24%6%
315
July1st to 15thDay
13%217%30%27%8%
305
16th to endDay
8%18%33%32%14%
326
August1st to 15thDay
13%115%25%29%14%
313
16th to endDay
10%18%31%26%21%
332
September1st to 15thDay
16%414%20%25%19%
299
16th to endDay
24%113%26%20%12%
254
October1st to 15thDay
21%5%13%30%21%7%
255
16th to endDay
12%14%25%30%15%1
272
November1st to 15thDay
15%8%26%24%22%2
245
16th to endDay
23%13%27%21%10%3
84
December1st to 15thDay
16%31%21%13%11%5%
60
16th to endDay
25%12%37%21%3
64
January1st to 15thNight
20%14%37%24%3
720
16th to endNight
19%13%40%24%1
768
February1st to 15thNight
18%15%33%29%2
704
16th to endNight
18%17%37%24%1
631
March1st to 15thNight
21%11%34%27%4
720
16th to endNight
17%12%38%24%5%1
768
April1st to 15thNight
15%13%39%27%4
718
16th to endNight
18%7%28%32%12%
720
May1st to 15thNight
23%5%24%33%12%
534
16th to endNight
16%218%40%21%1
375
June1st to 15thNight
10%223%37%24%1
360
16th to endNight
9%218%48%20%
360
July1st to 15thNight
12%116%42%26%1
340
16th to endNight
6%19%45%32%4
547
August1st to 15thNight
12%9%46%28%2
539
16th to endNight
12%112%38%30%4
738
September1st to 15thNight
14%117%33%29%1
707
16th to endNight
17%218%31%28%2
657
October1st to 15thNight
20%421%29%20%2
660
16th to endNight
16%8%32%32%9%
704
November1st to 15thNight
14%6%31%34%11%1
700
16th to endNight
18%14%29%28%8%
720
December1st to 15thNight
20%9%35%26%7%
720
16th to endNight
20%8%40%27%2
768
Page generated at 2017-09-13 07:39:06. Version ac04

Copyright 2017 A. Danko


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