Deerlick Astronomy Village
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Deerlick Astronomy Village clear sky chart from 2005-11-05 to 2018-02-14.

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
48%
16253
23%
48785
15%
16210
57%
16210
28%
30258

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
29%
780
23%
2522
10%
776
45%
776
21%
1544
January16th to endNight
29%
832
25%
2704
14%
832
44%
832
23%
1659
February1st to 15thNight
32%
760
24%
2295
11%
757
47%
757
25%
1421
February16th to endNight
25%
631
25%
1893
8%
631
42%
631
26%
1154
March1st to 15thNight
31%
720
25%
2006
10%
720
44%
720
28%
1256
March16th to endNight
37%
768
21%
2112
11%
768
45%
768
29%
1315
April1st to 15thNight
39%
718
25%
1976
14%
718
49%
718
33%
1172
April16th to endNight
48%
558
27%
1665
17%
558
57%
558
32%
971
May1st to 15thNight
51%
540
21%
1620
13%
540
57%
540
31%
981
May16th to endNight
61%
561
20%
1682
15%
561
65%
561
29%
1052
June1st to 15thNight
63%
540
16%
1620
13%
540
65%
540
27%
1059
June16th to endNight
72%
540
17%
1620
14%
540
74%
540
31%
1011
July1st to 15thNight
66%
510
12%
1530
10%
510
67%
510
23%
1058
July16th to endNight
75%
564
12%
1595
11%
531
76%
531
27%
1046
August1st to 15thNight
69%
539
16%
1609
15%
536
69%
536
22%
1107
August16th to endNight
66%
615
15%
1892
14%
615
67%
615
22%
1296
September1st to 15thNight
64%
720
18%
1980
15%
720
65%
720
27%
1334
September16th to endNight
59%
717
22%
1980
18%
717
62%
717
29%
1302
October1st to 15thNight
55%
720
29%
2040
24%
720
62%
720
35%
1217
October16th to endNight
51%
768
36%
2304
27%
768
65%
768
39%
1243
November1st to 15thNight
53%
760
30%
2366
24%
760
63%
760
37%
1295
November16th to endNight
44%
780
28%
2535
18%
780
57%
780
29%
1443
December1st to 15thNight
41%
780
25%
2535
16%
780
54%
780
24%
1547
December16th to endNight
34%
832
22%
2704
14%
832
45%
832
19%
1775

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
12%5%25%5%35%5%5%7%42%
49282
Night
11%5%2442445%7%46%
48985
TransparencyDay
39%7%11%19%17%5%
48983
Night
36%6%11%18%19%7%
48788
SeeingDay
15%6%20%24%22%10%
6017
Night
14%8%22%30%21%3
16255

By Month

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%5%24433345%45%
1746
16th to endDay
16%5%2441335%5%47%
1872
February1st to 15thDay
16%6%24424346%45%
1864
16th to endDay
16%5%14314335%48%
1580
March1st to 15thDay
14%414423446%48%
1953
16th to endDay
15%5%24325%445%46%
2111
April1st to 15thDay
10%42443445%6%48%
1972
16th to endDay
9%324435%5%5%6%49%
2304
May1st to 15thDay
10%5%25%4345%5%8%44%
2331
16th to endDay
10%5%25%5%37%46%8%40%
2431
June1st to 15thDay
9%425%6%46%6%7%9%35%
2340
16th to endDay
5%3245%46%6%8%11%40%
2340
July1st to 15thDay
8%5%26%8%47%7%8%8%31%
2340
16th to endDay
6%427%7%48%7%8%12%28%
2465
August1st to 15thDay
9%6%27%8%5%7%6%8%9%28%
2340
16th to endDay
14%6%26%7%46%6%7%9%27%
2292
September1st to 15thDay
11%6%35%5%346%6%8%37%
1980
16th to endDay
16%5%25%5%3345%5%42%
1980
October1st to 15thDay
16%413212346%51%
1920
16th to endDay
10%31332323460%
1920
November1st to 15thDay
12%413423245%54%
1819
16th to endDay
13%324323445%51%
1755
December1st to 15thDay
16%6%25%42445%5%42%
1755
16th to endDay
21%7%25%423346%37%
1872
January1st to 15thNight
13%6%25%424446%45%
2522
16th to endNight
16%6%3432334447%
2704
February1st to 15thNight
17%424324335%46%
2287
16th to endNight
13%6%14424445%48%
1893
March1st to 15thNight
12%5%24324436%49%
2006
16th to endNight
12%424424437%49%
2112
April1st to 15thNight
11%414423347%52%
1976
16th to endNight
8%414435%347%52%
1665
May1st to 15thNight
8%4245%25%46%8%47%
1619
16th to endNight
7%416%5%35%5%7%8%44%
1682
June1st to 15thNight
8%5%345%5%46%7%13%36%
1620
16th to endNight
43245%26%7%8%11%42%
1620
July1st to 15thNight
6%5%35%6%36%8%8%11%32%
1620
16th to endNight
4425%5%46%7%9%14%35%
1703
August1st to 15thNight
7%426%6%5%6%7%7%11%32%
1620
16th to endNight
10%5%25%6%35%7%7%10%34%
1892
September1st to 15thNight
10%5%25%4446%6%10%39%
1980
16th to endNight
14%5%245%23446%44%
1980
October1st to 15thNight
14%413322445%53%
2040
16th to endNight
8%313323345%59%
2304
November1st to 15thNight
10%414313336%57%
2366
16th to endNight
12%423324445%51%
2535
December1st to 15thNight
14%5%24324446%46%
2535
16th to endNight
18%7%24434446%39%
2704

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
40%48%15%25%4
1747
16th to endDay
38%36%19%23%9%
1872
February1st to 15thDay
40%38%21%20%6%
1866
16th to endDay
39%35%20%23%7%
1580
March1st to 15thDay
37%5%8%20%19%9%
1953
16th to endDay
38%5%10%21%17%5%
2112
April1st to 15thDay
34%5%10%20%22%7%
1972
16th to endDay
32%6%10%19%23%6%
2304
May1st to 15thDay
36%6%13%20%18%4
2331
16th to endDay
39%8%14%22%13%2
2435
June1st to 15thDay
41%9%16%21%9%1
2340
16th to endDay
33%10%18%21%13%3
2340
July1st to 15thDay
41%12%17%18%7%2
2201
16th to endDay
40%13%19%17%6%2
2310
August1st to 15thDay
47%11%14%17%8%1
2327
16th to endDay
48%11%15%13%9%
2292
September1st to 15thDay
42%9%11%17%16%2
1980
16th to endDay
42%6%10%18%17%4
1980
October1st to 15thDay
33%410%20%24%7%
1920
16th to endDay
28%3418%30%13%
1920
November1st to 15thDay
32%37%18%25%11%
1819
16th to endDay
34%46%18%26%8%
1755
December1st to 15thDay
42%5%9%16%17%8%
1755
16th to endDay
48%5%8%17%14%6%
1872
January1st to 15thNight
39%47%16%25%7%
2522
16th to endNight
40%35%17%22%10%
2704
February1st to 15thNight
40%27%18%20%10%
2296
16th to endNight
36%47%18%24%8%
1893
March1st to 15thNight
35%5%9%17%21%9%
2006
16th to endNight
34%5%11%18%21%7%
2112
April1st to 15thNight
31%48%23%22%8%
1976
16th to endNight
30%6%9%21%21%10%
1665
May1st to 15thNight
33%7%13%21%18%5%
1620
16th to endNight
33%10%14%24%14%2
1684
June1st to 15thNight
36%10%18%22%10%1
1620
16th to endNight
30%12%17%23%13%3
1620
July1st to 15thNight
37%15%18%18%6%3
1530
16th to endNight
33%13%25%17%7%2
1595
August1st to 15thNight
41%11%16%21%8%1
1609
16th to endNight
40%12%19%16%9%
1892
September1st to 15thNight
38%10%14%15%15%4
1980
16th to endNight
40%6%12%17%18%5%
1980
October1st to 15thNight
32%5%9%18%25%8%
2040
16th to endNight
27%36%17%31%14%
2304
November1st to 15thNight
29%47%18%26%14%
2366
16th to endNight
33%47%15%26%12%
2535
December1st to 15thNight
38%5%9%19%19%8%
2535
16th to endNight
45%5%8%18%16%6%
2704

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
20%19%37%18%4
135
16th to endDay
18%25%34%14%6%
144
February1st to 15thDay
25%20%39%14%
130
16th to endDay
20%14%45%13%4
81
March1st to 15thDay
16%14%30%29%7%
243
16th to endDay
15%9%32%26%14%
288
April1st to 15thDay
14%15%25%20%20%4
270
16th to endDay
10%5%28%27%25%4
270
May1st to 15thDay
12%8%30%22%15%10%
288
16th to endDay
13%5%16%23%26%14%
331
June1st to 15thDay
11%213%23%28%20%
315
16th to endDay
7%16%27%26%22%
315
July1st to 15thDay
10%10%23%34%21%
305
16th to endDay
7%7%24%39%21%
326
August1st to 15thDay
16%12%25%26%18%
313
16th to endDay
14%10%24%30%18%
332
September1st to 15thDay
16%113%21%34%13%
315
16th to endDay
20%213%30%21%11%
314
October1st to 15thDay
22%218%27%18%10%
315
16th to endDay
12%7%21%27%24%6%
336
November1st to 15thDay
22%5%23%24%21%3
237
16th to endDay
8%8%29%28%22%2
135
December1st to 15thDay
25%12%34%22%5%
135
16th to endDay
31%16%29%17%41
144
January1st to 15thNight
18%17%30%25%8%
780
16th to endNight
19%15%31%27%5%
832
February1st to 15thNight
19%14%29%31%4
760
16th to endNight
17%17%36%24%3
631
March1st to 15thNight
14%14%34%29%6%
720
16th to endNight
14%11%31%28%13%
768
April1st to 15thNight
14%13%29%26%14%
718
16th to endNight
12%8%26%35%15%1
558
May1st to 15thNight
10%5%27%33%20%2
540
16th to endNight
10%217%33%32%4
563
June1st to 15thNight
10%213%34%31%7%
540
16th to endNight
6%11%35%36%9%
540
July1st to 15thNight
8%9%33%36%10%
510
16th to endNight
6%17%29%47%6%
564
August1st to 15thNight
10%5%33%42%7%
539
16th to endNight
13%8%29%39%8%
615
September1st to 15thNight
12%111%30%38%6%
720
16th to endNight
19%112%30%31%4
717
October1st to 15thNight
16%320%28%25%6%
720
16th to endNight
10%7%24%29%24%2
768
November1st to 15thNight
13%5%23%32%21%4
760
16th to endNight
13%11%26%28%17%1
780
December1st to 15thNight
18%11%24%31%12%1
780
16th to endNight
21%13%26%30%7%
832
Page generated at 2018-02-15 10:58:46. Version ac04

Copyright 2018 A. Danko


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