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 2017-04-28.

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%
15212
23%
45614
15%
15169
56%
15169
27%
28328

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%
720
23%
2327
10%
716
45%
716
21%
1426
January16th to endNight
27%
768
24%
2496
12%
768
43%
768
22%
1541
February1st to 15thNight
32%
704
25%
2126
10%
701
48%
701
26%
1298
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%
552
27%
1647
16%
552
57%
552
32%
960
May1st to 15thNight
51%
495
22%
1485
13%
495
58%
495
31%
904
May16th to endNight
61%
513
19%
1538
14%
513
64%
513
29%
963
June1st to 15thNight
64%
495
17%
1485
14%
495
66%
495
28%
963
June16th to endNight
73%
495
17%
1485
14%
495
74%
495
32%
920
July1st to 15thNight
65%
465
12%
1395
10%
465
66%
465
23%
962
July16th to endNight
76%
522
12%
1469
11%
489
77%
489
28%
954
August1st to 15thNight
69%
494
17%
1474
16%
491
69%
491
23%
1005
August16th to endNight
65%
563
13%
1733
13%
563
66%
563
21%
1203
September1st to 15thNight
65%
660
18%
1815
16%
660
66%
660
25%
1244
September16th to endNight
56%
657
20%
1815
15%
657
60%
657
27%
1217
October1st to 15thNight
53%
660
30%
1870
24%
660
61%
660
34%
1126
October16th to endNight
51%
704
34%
2112
27%
704
64%
704
38%
1152
November1st to 15thNight
52%
700
31%
2179
24%
700
63%
700
37%
1182
November16th to endNight
42%
720
26%
2340
17%
720
55%
720
29%
1345
December1st to 15thNight
42%
720
25%
2340
17%
720
53%
720
24%
1433
December16th to endNight
35%
768
22%
2496
15%
768
46%
768
20%
1633

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%
46072
Night
11%5%2442445%7%46%
45814
TransparencyDay
39%7%11%19%17%5%
45773
Night
36%6%11%18%19%7%
45617
SeeingDay
15%6%20%23%23%11%
4954
Night
14%8%22%30%20%3
15214

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%35%433345%44%
1611
16th to endDay
16%5%2431345%5%46%
1728
February1st to 15thDay
15%5%24424445%46%
1732
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%
2269
May1st to 15thDay
10%5%25%435%5%5%8%42%
2136
16th to endDay
10%5%245%37%5%6%8%40%
2223
June1st to 15thDay
9%425%6%46%6%6%9%36%
2145
16th to endDay
42245%47%6%8%12%41%
2145
July1st to 15thDay
9%5%26%9%47%7%8%8%30%
2145
16th to endDay
6%427%7%5%8%7%8%12%28%
2283
August1st to 15thDay
8%5%27%8%5%7%6%8%9%29%
2145
16th to endDay
15%6%36%7%46%6%7%9%26%
2100
September1st to 15thDay
10%6%36%5%346%6%8%36%
1815
16th to endDay
17%6%25%5%33445%40%
1815
October1st to 15thDay
16%413212346%51%
1760
16th to endDay
10%32332323459%
1760
November1st to 15thDay
11%413323235%55%
1676
16th to endDay
14%424323445%50%
1620
December1st to 15thDay
15%6%25%42445%5%42%
1620
16th to endDay
22%6%24423336%38%
1728
January1st to 15thNight
13%6%24424446%45%
2327
16th to endNight
16%6%3432334447%
2496
February1st to 15thNight
16%314334336%47%
2118
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%
1647
May1st to 15thNight
8%4245%25%46%8%47%
1484
16th to endNight
7%415%5%35%5%7%7%44%
1538
June1st to 15thNight
8%5%344446%6%12%37%
1485
16th to endNight
43245%26%7%8%11%43%
1485
July1st to 15thNight
6%5%35%6%36%8%8%11%32%
1485
16th to endNight
5%424445%7%10%14%35%
1577
August1st to 15thNight
7%426%7%5%6%7%7%11%33%
1485
16th to endNight
11%5%26%6%35%7%7%11%32%
1733
September1st to 15thNight
10%5%25%5%45%6%6%10%37%
1815
16th to endNight
16%6%245%23446%42%
1815
October1st to 15thNight
15%41332244453%
1870
16th to endNight
8%313424345%58%
2112
November1st to 15thNight
10%314313336%57%
2179
16th to endNight
12%423424445%51%
2340
December1st to 15thNight
13%6%24424446%46%
2340
16th to endNight
19%6%24424445%40%
2496

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%14%26%5%
1612
16th to endDay
38%37%18%23%8%
1728
February1st to 15thDay
38%38%21%20%6%
1734
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%
2269
May1st to 15thDay
36%7%14%20%16%4
2136
16th to endDay
38%8%15%22%12%2
2227
June1st to 15thDay
40%9%16%22%9%1
2145
16th to endDay
31%10%18%21%14%3
2145
July1st to 15thDay
43%12%15%17%7%3
2006
16th to endDay
41%14%20%16%6%1
2128
August1st to 15thDay
45%11%14%17%8%1
2132
16th to endDay
49%12%15%12%9%
2100
September1st to 15thDay
42%9%12%17%15%2
1815
16th to endDay
44%6%10%17%16%4
1815
October1st to 15thDay
33%49%20%24%7%
1760
16th to endDay
29%3419%30%12%
1760
November1st to 15thDay
32%36%18%26%12%
1676
16th to endDay
35%46%19%25%8%
1620
December1st to 15thDay
41%5%10%17%16%8%
1620
16th to endDay
47%5%8%16%14%7%
1728
January1st to 15thNight
39%47%16%24%7%
2327
16th to endNight
40%35%17%22%10%
2496
February1st to 15thNight
38%27%18%20%10%
2127
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%
1647
May1st to 15thNight
33%7%14%21%18%4
1485
16th to endNight
33%10%14%24%14%2
1540
June1st to 15thNight
35%10%18%22%11%1
1485
16th to endNight
29%12%17%22%14%3
1485
July1st to 15thNight
38%13%19%17%7%3
1395
16th to endNight
32%13%25%18%7%1
1469
August1st to 15thNight
40%11%16%21%8%1
1474
16th to endNight
42%12%19%14%10%1
1733
September1st to 15thNight
39%11%15%15%13%4
1815
16th to endNight
42%6%11%16%17%5%
1815
October1st to 15thNight
33%5%9%18%24%8%
1870
16th to endNight
27%36%17%29%14%
2112
November1st to 15thNight
28%36%17%27%15%
2179
16th to endNight
34%47%15%26%12%
2340
December1st to 15thNight
38%5%8%19%19%8%
2340
16th to endNight
44%5%8%17%17%7%
2496

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
18%14%43%16%6%
90
16th to endDay
18%30%34%11%5%
96
February1st to 15thDay
16%25%41%16%
90
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%427%27%26%4
259
May1st to 15thDay
10%6%29%25%15%11%
228
16th to endDay
13%214%21%30%16%
267
June1st to 15thDay
12%113%21%28%22%
255
16th to endDay
412%28%28%26%
255
July1st to 15thDay
11%12%22%32%20%
245
16th to endDay
5%5%21%42%24%
270
August1st to 15thDay
15%9%26%27%19%
253
16th to endDay
17%7%22%32%20%
268
September1st to 15thDay
15%10%21%36%14%
255
16th to endDay
24%214%29%19%8%
254
October1st to 15thDay
23%219%26%18%8%
255
16th to endDay
12%5%19%27%26%8%
272
November1st to 15thDay
25%5%22%21%21%4
184
16th to endDay
11%8%27%27%22%2
90
December1st to 15thDay
20%15%35%22%6%
90
16th to endDay
37%14%21%17%6%2
96
January1st to 15thNight
18%17%30%25%8%
720
16th to endNight
19%16%33%27%4
768
February1st to 15thNight
18%14%30%31%4
704
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
552
May1st to 15thNight
10%426%34%21%2
495
16th to endNight
10%216%31%34%4
515
June1st to 15thNight
10%214%35%30%6%
495
16th to endNight
411%35%37%9%
495
July1st to 15thNight
9%10%34%34%9%
465
16th to endNight
6%17%30%48%6%
522
August1st to 15thNight
9%5%34%42%7%
494
16th to endNight
13%9%28%39%9%
563
September1st to 15thNight
12%19%29%39%6%
660
16th to endNight
20%113%31%28%3
657
October1st to 15thNight
17%321%27%25%5%
660
16th to endNight
10%7%25%30%23%2
704
November1st to 15thNight
13%5%24%32%20%3
700
16th to endNight
14%11%27%27%16%1
720
December1st to 15thNight
17%10%25%31%12%1
720
16th to endNight
20%14%25%31%8%
768
Page generated at 2017-04-29 09:45:00. Version ac04

Copyright 2017 A. Danko


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