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 2018-01-12.

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%
15659
20%
48398
12%
15620
50%
15620
25%
30517

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
24%
762
20%
2572
8%
761
40%
761
20%
1620
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
21%
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
17%
1796
5%
718
34%
718
27%
1215
April16th to endNight
41%
720
18%
1800
7%
720
45%
720
31%
1207
May1st to 15thNight
40%
534
17%
1614
11%
534
46%
534
22%
1097
May16th to endNight
52%
374
17%
1497
18%
374
57%
374
21%
909
June1st to 15thNight
55%
360
19%
1440
20%
360
61%
360
25%
826
June16th to endNight
62%
360
18%
1440
19%
360
68%
360
26%
820
July1st to 15thNight
58%
340
12%
1360
16%
340
60%
340
18%
863
July16th to endNight
73%
547
16%
1578
14%
514
76%
514
34%
917
August1st to 15thNight
69%
539
18%
1609
14%
536
69%
536
31%
994
August16th to endNight
65%
738
21%
1884
14%
738
66%
738
35%
1214
September1st to 15thNight
58%
720
24%
1800
14%
720
62%
720
36%
1155
September16th to endNight
55%
717
25%
1982
21%
717
59%
717
31%
1284
October1st to 15thNight
47%
720
22%
2160
19%
720
55%
720
26%
1393
October16th to endNight
39%
768
28%
2304
18%
768
54%
768
34%
1330
November1st to 15thNight
41%
760
24%
2411
16%
760
52%
760
30%
1442
November16th to endNight
34%
780
21%
2703
14%
780
47%
780
23%
1614
December1st to 15thNight
28%
780
16%
2730
7%
780
41%
780
17%
1795
December16th to endNight
25%
832
19%
2912
7%
832
41%
832
20%
1844

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%
48931
Night
14%5%2442445%7%43%
48580
Cloud CoverDay
14%5%25%5%35%5%5%7%40%
48941
Night
14%5%2442445%7%43%
48584
TransparencyDay
40%6%12%22%15%2
48631
Night
39%6%12%23%15%2
48398
SeeingDay
17%8%21%25%19%7%
5983
Night
16%8%28%31%13%1
15664

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%5%35%425%5%6%6%38%
1607
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%42442435%7%45%
2160
16th to endDay
15%5%2443445%7%41%
1976
October1st to 15thDay
20%413423346%44%
1800
16th to endDay
13%415%433446%47%
1920
November1st to 15thDay
14%5%1443435%7%45%
1777
16th to endDay
17%414433447%43%
1586
December1st to 15thDay
16%5%25%5%25%5%6%7%36%
1560
16th to endDay
16%5%35%5%4446%5%37%
1664
January1st to 15thNight
15%5%2442445%7%40%
2572
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%42342446%7%47%
1800
16th to endNight
14%5%245%24435%47%
1982
October1st to 15thNight
19%5%24324345%43%
2160
16th to endNight
14%41322335%6%51%
2304
November1st to 15thNight
13%5%24423345%49%
2411
16th to endNight
15%42442445%8%43%
2703
December1st to 15thNight
15%5%35%6%35%6%5%6%37%
2730
16th to endNight
15%6%25%42446%8%38%
2912

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%24435%5%6%7%38%
1607
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%4235%2345%7%45%
2160
16th to endDay
14%5%25%5%3445%7%41%
1976
October1st to 15thDay
21%413324336%45%
1800
16th to endDay
13%4245%24446%47%
1920
November1st to 15thDay
14%5%1442435%7%45%
1777
16th to endDay
17%42443336%6%43%
1586
December1st to 15thDay
16%5%26%5%25%5%6%7%36%
1560
16th to endDay
16%6%25%6%2446%6%38%
1664
January1st to 15thNight
16%6%2443445%7%40%
2572
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
12%41343346%7%47%
1800
16th to endNight
13%5%245%23436%46%
1982
October1st to 15thNight
19%424424345%43%
2160
16th to endNight
14%423323346%52%
2304
November1st to 15thNight
13%5%24422445%49%
2411
16th to endNight
15%42432445%7%44%
2703
December1st to 15thNight
16%5%26%6%35%5%5%5%37%
2730
16th to endNight
16%6%25%42445%8%39%
2912

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%6%13%21%12%2
1608
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
2160
16th to endDay
41%5%8%23%18%2
1976
October1st to 15thDay
40%5%10%23%17%2
1800
16th to endDay
37%410%26%19%1
1920
November1st to 15thDay
38%413%21%16%5%
1777
16th to endDay
39%411%28%14%1
1586
December1st to 15thDay
44%6%15%22%9%1
1560
16th to endDay
45%6%12%23%11%
1664
January1st to 15thNight
42%5%12%21%14%4
2572
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%14%20%22%3
1800
16th to endNight
39%48%23%20%3
1982
October1st to 15thNight
42%49%22%17%2
2160
16th to endNight
32%310%30%20%1
2304
November1st to 15thNight
37%39%24%18%6%
2411
16th to endNight
37%5%11%23%18%3
2703
December1st to 15thNight
45%6%12%22%10%1
2730
16th to endNight
42%5%16%23%10%1
2912

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
24%26%25%16%6%2
99
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%
315
16th to endDay
20%213%26%22%14%
314
October1st to 15thDay
23%412%29%22%8%
315
16th to endDay
11%15%25%27%17%2
336
November1st to 15thDay
16%7%25%27%21%2
295
16th to endDay
18%14%31%22%10%2
116
December1st to 15thDay
16%28%22%17%11%3
90
16th to endDay
20%13%43%16%5%
96
January1st to 15thNight
19%13%37%25%3
765
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
720
16th to endNight
16%217%30%29%3
717
October1st to 15thNight
21%421%29%21%2
720
16th to endNight
16%8%32%30%11%
768
November1st to 15thNight
14%6%31%35%11%1
760
16th to endNight
17%13%30%29%8%
780
December1st to 15thNight
19%9%36%26%7%
780
16th to endNight
20%7%41%27%2
832
Page generated at 2018-01-12 22:01:37. Version ac04

Copyright 2018 A. Danko


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