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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 2015-05-26.

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
47%
12642
23%
37894
15%
12599
55%
12599
27%
23683

By Month

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
JanuaryNight
29%
1240
23%
4017
12%
1236
44%
1236
22%
2476
FebruaryNight
28%
1107
24%
3332
9%
1104
43%
1104
25%
2063
MarchNight
33%
1240
22%
3432
10%
1240
44%
1240
27%
2162
AprilNight
42%
1064
26%
3035
15%
1064
51%
1064
32%
1805
MayNight
58%
900
21%
2699
14%
900
62%
900
30%
1655
JuneNight
67%
810
17%
2430
14%
810
69%
810
29%
1565
JulyNight
67%
801
11%
2306
10%
768
67%
768
23%
1597
AugustNight
66%
867
17%
2629
15%
864
66%
864
22%
1822
SeptemberNight
59%
1077
18%
2970
15%
1077
61%
1077
25%
2034
OctoberNight
51%
1116
32%
3258
24%
1116
61%
1116
35%
1888
NovemberNight
46%
1180
29%
3756
20%
1180
59%
1180
33%
2083
DecemberNight
38%
1240
23%
4030
15%
1240
49%
1240
22%
2533

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%41%
38356
Night
12%5%2442445%7%45%
38094
TransparencyDay
39%7%11%18%17%5%
38057
Night
36%6%10%18%19%7%
37897
SeeingDay
15%317%22%25%14%
2376
Night
14%8%23%30%19%2
12644

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
MonthOccurrence of each ForecastData
Points
JanuaryDay
17%5%24323345%46%
2781
Night
15%6%3432343447%
4017
FebruaryDay
16%5%14424435%45%
2745
Night
16%5%14424446%46%
3324
MarchDay
16%425%424445%46%
3386
Night
13%5%24424436%49%
3432
AprilDay
10%4244345%5%6%48%
3561
Night
10%414424347%51%
3035
MayDay
10%5%25%436%46%8%41%
3888
Night
7%425%5%25%5%7%8%45%
2698
JuneDay
7%3246%47%6%7%10%37%
3510
Night
6%3245%36%7%7%12%39%
2430
JulyDay
9%5%37%8%5%8%7%8%9%26%
3622
Night
7%6%36%6%36%7%9%11%32%
2504
AugustDay
13%6%26%7%46%6%7%9%28%
3484
Night
10%5%26%6%46%7%7%10%32%
2640
SeptemberDay
13%6%36%5%345%6%6%37%
2970
Night
13%6%25%5%345%5%7%38%
2970
OctoberDay
13%423323335%54%
2880
Night
11%413324345%54%
3258
NovemberDay
12%424323335%54%
2739
Night
11%423323336%55%
3756
DecemberDay
18%5%24424446%40%
2790
Night
16%6%24424346%44%
4030

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthOccurrence of each ForecastData
Points
JanuaryDay
39%47%16%25%6%
2782
Night
40%45%17%24%8%
4017
FebruaryDay
40%37%19%23%5%
2747
Night
39%37%17%21%9%
3333
MarchDay
39%5%9%20%17%7%
3387
Night
36%6%10%17%21%8%
3432
AprilDay
34%5%10%19%23%5%
3561
Night
31%5%8%22%22%8%
3035
MayDay
37%7%15%22%14%3
3892
Night
32%9%15%22%15%3
2701
JuneDay
36%10%17%20%12%2
3510
Night
33%11%17%21%12%2
2430
JulyDay
46%12%15%14%7%3
3328
Night
39%13%19%15%7%3
2306
AugustDay
48%10%14%15%9%1
3471
Night
43%10%16%17%10%1
2629
SeptemberDay
44%7%11%17%15%3
2970
Night
42%8%12%15%15%4
2970
OctoberDay
31%47%18%27%10%
2880
Night
31%48%16%27%12%
3258
NovemberDay
33%36%19%26%10%
2739
Night
31%36%16%27%14%
3756
DecemberDay
43%5%9%16%16%7%
2790
Night
41%5%8%18%19%7%
4030

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
MonthOccurrence of each ForecastData
Points
JanuaryNight
18%16%31%26%6%
1240
FebruaryNight
19%15%33%27%3
1107
MarchDay
17%10%26%28%15%
287
Night
15%13%32%28%9%
1240
AprilDay
13%8%29%18%26%3
300
Night
13%10%30%30%14%
1064
MayDay
11%320%23%24%17%
350
Night
9%322%33%28%3
902
JuneDay
11%11%21%28%26%
270
Night
7%114%36%33%6%
810
JulyDay
13%8%18%35%23%
267
Night
9%19%31%40%7%
801
AugustDay
22%10%18%26%23%
277
Night
12%8%31%39%7%
867
SeptemberDay
20%112%22%29%13%
269
Night
17%211%31%32%4
1077
OctoberDay
17%5%17%28%22%8%
279
Night
13%6%24%29%22%4
1116
NovemberDay
12%329%22%24%6%
77
Night
13%9%27%29%17%2
1180
DecemberNight
18%13%24%30%10%
1240
Page generated at 2015-05-27 12:02:44. Version ac04

Copyright 2015 A. Danko


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