Arrakis Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Arrakis Observatory clear sky chart from 2005-11-05 to 2018-03-11.

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
34%
16898
18%
48969
9%
16851
42%
16851
27%
31628

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
25%
975
15%
2779
5%
970
34%
970
21%
1912
January16th to endNight
21%
1040
14%
2704
4%
1040
29%
1040
18%
2004
February1st to 15thNight
24%
954
12%
2483
3%
950
30%
950
21%
1804
February16th to endNight
25%
796
16%
2162
5%
796
33%
796
24%
1484
March1st to 15thNight
28%
601
16%
2129
8%
601
39%
601
21%
1383
March16th to endNight
29%
576
13%
2112
10%
576
36%
576
15%
1448
April1st to 15thNight
29%
539
17%
1818
11%
539
40%
539
22%
1159
April16th to endNight
29%
540
17%
1620
11%
540
39%
540
20%
1129
May1st to 15thNight
32%
540
15%
1613
8%
540
39%
540
27%
1022
May16th to endNight
39%
563
15%
1498
6%
561
44%
561
30%
988
June1st to 15thNight
47%
540
15%
1353
5%
540
50%
540
36%
865
June16th to endNight
54%
540
20%
1260
6%
540
58%
540
52%
736
July1st to 15thNight
63%
510
21%
1190
8%
510
66%
510
58%
666
July16th to endNight
64%
564
21%
1565
14%
531
66%
531
51%
787
August1st to 15thNight
65%
539
22%
1610
19%
536
69%
536
44%
865
August16th to endNight
57%
573
26%
1734
24%
573
65%
573
42%
946
September1st to 15thNight
55%
540
24%
1860
22%
540
65%
540
39%
955
September16th to endNight
42%
537
26%
1980
17%
537
59%
537
31%
1047
October1st to 15thNight
33%
702
25%
2142
14%
702
42%
702
31%
1258
October16th to endNight
31%
789
21%
2325
10%
789
40%
789
27%
1471
November1st to 15thNight
31%
950
22%
2566
9%
950
41%
950
28%
1672
November16th to endNight
27%
975
20%
2730
9%
975
36%
975
26%
1796
December1st to 15thNight
21%
975
11%
2730
3%
975
28%
975
18%
1976
December16th to endNight
19%
1040
15%
3006
4%
1040
30%
1040
16%
2255

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
13%7%35%5%3445%7%39%
49650
Night
11%7%36%5%24447%43%
49138
Cloud CoverDay
13%7%35%5%3445%7%39%
49661
Night
11%7%36%5%24446%43%
49142
Cloud CoverDay
12%7%35%5%3445%7%39%
49659
Night
11%7%36%5%24446%43%
49142
TransparencyDay
43%5%14%23%11%1
49338
Night
40%5%14%24%13%1
48969
SeeingDay
16%8%32%26%12%3
6628
Night
14%9%35%29%9%1
16899

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
8%9%5%9%7%45%6%6%7%28%
1482
16th to endDay
8%11%5%10%9%5%6%5%5%6%25%
1872
February1st to 15thDay
10%9%5%10%8%445%6%6%28%
1710
16th to endDay
10%9%48%7%35%5%5%7%31%
1610
March1st to 15thDay
16%10%5%8%5%24446%31%
2055
16th to endDay
15%12%5%6%6%34446%30%
2112
April1st to 15thDay
16%8%35%5%2445%7%37%
2127
16th to endDay
24%10%25%433345%32%
2340
May1st to 15thDay
21%6%25%5%34446%33%
2337
16th to endDay
16%6%25%4345%5%7%37%
2617
June1st to 15thDay
16%6%25%425%5%5%7%38%
2604
16th to endDay
8%4134345%6%9%48%
2700
July1st to 15thDay
6%2134245%5%9%53%
2700
16th to endDay
5%3133345%6%9%53%
2493
August1st to 15thDay
10%425%6%45%6%6%8%41%
2340
16th to endDay
9%42433345%8%50%
2468
September1st to 15thDay
11%5%23433347%49%
2097
16th to endDay
11%5%2432335%6%50%
1980
October1st to 15thDay
15%6%23414436%46%
1806
16th to endDay
14%8%35%423345%44%
1897
November1st to 15thDay
10%8%36%5%23446%44%
1620
16th to endDay
11%10%36%43446%7%35%
1560
December1st to 15thDay
13%11%49%8%35%446%27%
1560
16th to endDay
15%10%5%7%7%45%448%25%
1563
January1st to 15thNight
7%7%5%8%6%37%6%6%8%33%
2779
16th to endNight
8%11%49%6%46%5%6%7%27%
2704
February1st to 15thNight
9%11%5%8%6%35%5%36%34%
2480
16th to endNight
8%7%48%8%35%448%36%
2162
March1st to 15thNight
11%9%37%5%34346%40%
2117
16th to endNight
16%10%46%5%24436%34%
2112
April1st to 15thNight
15%8%245%24436%41%
1818
16th to endNight
20%7%25%425%346%36%
1620
May1st to 15thNight
16%6%24423245%46%
1613
16th to endNight
12%415%5%35%46%9%41%
1496
June1st to 15thNight
10%5%23325%35%8%48%
1353
16th to endNight
5%21232345%8%60%
1260
July1st to 15thNight
311331345%7%65%
1260
16th to endNight
321231336%9%61%
1671
August1st to 15thNight
5%3333346%8%57%
1620
16th to endNight
8%413313346%59%
1734
September1st to 15thNight
8%313323336%59%
1860
16th to endNight
9%413323446%55%
1980
October1st to 15thNight
14%6%24312335%52%
2142
16th to endNight
15%8%24413346%45%
2325
November1st to 15thNight
10%7%36%5%24445%46%
2566
16th to endNight
10%8%36%43445%6%42%
2730
December1st to 15thNight
11%10%38%7%35%447%32%
2730
16th to endNight
16%10%5%8%6%45%5%5%6%27%
3006

Percentage Cloud Cover SW (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
8%10%5%9%7%45%6%6%8%28%
1482
16th to endDay
8%11%5%10%9%5%7%6%5%6%25%
1872
February1st to 15thDay
10%10%49%8%35%5%5%7%27%
1710
16th to endDay
11%9%48%7%36%5%5%6%31%
1610
March1st to 15thDay
16%10%5%8%5%24346%31%
2066
16th to endDay
16%11%5%6%6%34446%30%
2112
April1st to 15thDay
16%7%35%5%24447%36%
2127
16th to endDay
24%10%35%423345%32%
2340
May1st to 15thDay
21%6%246%34346%33%
2337
16th to endDay
16%6%25%425%5%5%7%36%
2617
June1st to 15thDay
16%5%345%25%5%5%7%38%
2604
16th to endDay
8%413425%5%5%9%49%
2700
July1st to 15thDay
6%2134235%6%9%53%
2700
16th to endDay
5%213325%5%6%8%53%
2493
August1st to 15thDay
10%5%25%5%35%5%6%8%40%
2340
16th to endDay
10%41442345%7%50%
2468
September1st to 15thDay
11%5%23424346%50%
2097
16th to endDay
11%5%2343335%6%50%
1980
October1st to 15thDay
15%6%24413336%46%
1806
16th to endDay
14%9%34424336%43%
1897
November1st to 15thDay
10%8%27%5%2345%6%44%
1620
16th to endDay
11%10%36%5%2437%7%36%
1560
December1st to 15thDay
13%11%5%9%7%445%46%27%
1560
16th to endDay
15%10%6%7%7%35%45%7%26%
1563
January1st to 15thNight
7%7%5%8%6%46%6%5%7%34%
2779
16th to endNight
8%11%410%6%46%6%6%7%27%
2704
February1st to 15thNight
9%11%49%6%445%46%33%
2473
16th to endNight
8%6%48%8%35%448%37%
2162
March1st to 15thNight
11%10%36%424446%39%
2129
16th to endNight
16%9%5%6%5%24437%33%
2112
April1st to 15thNight
16%8%24424346%41%
1818
16th to endNight
20%7%35%424346%36%
1620
May1st to 15thNight
16%6%24413246%46%
1612
16th to endNight
12%4145%345%6%8%41%
1496
June1st to 15thNight
10%5%2432435%8%48%
1353
16th to endNight
5%312323348%61%
1260
July1st to 15thNight
311231435%7%65%
1260
16th to endNight
321232336%9%61%
1671
August1st to 15thNight
5%31233346%8%56%
1620
16th to endNight
9%314322336%59%
1734
September1st to 15thNight
9%313223346%59%
1860
16th to endNight
9%413324347%54%
1980
October1st to 15thNight
15%5%24212235%52%
2142
16th to endNight
16%8%24413245%45%
2325
November1st to 15thNight
11%7%36%424445%45%
2566
16th to endNight
10%8%36%5%34446%43%
2730
December1st to 15thNight
11%10%48%8%35%5%47%32%
2730
16th to endNight
16%10%5%8%6%3445%6%27%
3006

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
7%10%5%9%8%446%6%8%28%
1482
16th to endDay
8%11%5%10%8%5%6%6%5%6%24%
1872
February1st to 15thDay
10%10%49%9%35%5%5%7%27%
1710
16th to endDay
10%10%48%7%36%6%5%5%30%
1610
March1st to 15thDay
16%10%5%7%5%34446%30%
2066
16th to endDay
15%11%5%6%6%34446%30%
2110
April1st to 15thDay
16%7%35%434347%36%
2127
16th to endDay
23%10%35%433345%32%
2340
May1st to 15thDay
21%7%246%35%346%33%
2337
16th to endDay
15%6%35%435%5%5%7%36%
2617
June1st to 15thDay
16%5%25%5%25%45%8%38%
2604
16th to endDay
8%4143345%5%9%48%
2700
July1st to 15thDay
5%2134245%6%9%53%
2700
16th to endDay
4313325%5%6%8%53%
2493
August1st to 15thDay
9%5%25%5%35%5%6%9%39%
2340
16th to endDay
10%42442345%8%50%
2468
September1st to 15thDay
11%5%2342435%6%50%
2097
16th to endDay
11%5%2443245%7%49%
1980
October1st to 15thDay
15%6%34423435%46%
1806
16th to endDay
15%8%35%323337%43%
1897
November1st to 15thDay
9%8%36%423446%43%
1620
16th to endDay
11%10%36%5%3446%7%35%
1560
December1st to 15thDay
12%12%410%7%45%446%27%
1560
16th to endDay
15%10%7%7%7%35%5%47%25%
1563
January1st to 15thNight
7%7%5%8%6%47%6%5%7%34%
2779
16th to endNight
9%11%49%6%45%6%6%7%27%
2704
February1st to 15thNight
9%11%49%7%35%5%36%33%
2473
16th to endNight
8%6%48%8%46%447%36%
2162
March1st to 15thNight
11%9%46%5%24346%39%
2129
16th to endNight
15%9%5%7%5%24446%33%
2112
April1st to 15thNight
15%8%24425%346%41%
1818
16th to endNight
20%8%35%5%24345%36%
1620
May1st to 15thNight
16%7%24423245%46%
1612
16th to endNight
12%425%5%445%6%8%41%
1496
June1st to 15thNight
10%5%2442435%8%48%
1353
16th to endNight
5%31132335%8%60%
1260
July1st to 15thNight
32321435%6%64%
1260
16th to endNight
321222346%8%61%
1671
August1st to 15thNight
431332346%8%56%
1620
16th to endNight
8%313313345%59%
1734
September1st to 15thNight
8%312313446%59%
1860
16th to endNight
9%41332435%7%54%
1980
October1st to 15thNight
15%5%24312235%52%
2142
16th to endNight
16%8%24413246%45%
2325
November1st to 15thNight
10%8%26%5%24436%45%
2566
16th to endNight
10%8%36%5%3445%6%42%
2730
December1st to 15thNight
11%10%48%7%35%446%31%
2730
16th to endNight
16%10%48%6%35%5%45%27%
3006

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
51%7%14%15%10%
1483
16th to endDay
57%5%15%16%5%
1872
February1st to 15thDay
53%5%15%18%6%
1711
16th to endDay
51%8%12%16%10%1
1610
March1st to 15thDay
54%413%20%6%
2066
16th to endDay
54%6%14%20%4
2112
April1st to 15thDay
46%5%14%24%8%1
2127
16th to endDay
54%412%19%8%
2340
May1st to 15thDay
50%6%11%22%8%
2337
16th to endDay
45%7%13%22%10%
2621
June1st to 15thDay
44%6%15%23%9%
2604
16th to endDay
31%7%16%29%13%2
2700
July1st to 15thDay
25%7%17%32%14%3
2541
16th to endDay
25%6%16%29%19%2
2337
August1st to 15thDay
38%7%15%24%11%2
2326
16th to endDay
31%6%14%31%13%3
2468
September1st to 15thDay
34%5%14%27%17%
2097
16th to endDay
34%413%30%15%
1980
October1st to 15thDay
38%5%12%24%16%1
1806
16th to endDay
42%314%24%13%1
1897
November1st to 15thDay
39%5%13%22%17%1
1620
16th to endDay
45%5%18%19%10%1
1560
December1st to 15thDay
57%5%12%14%9%1
1560
16th to endDay
57%412%14%7%1
1563
January1st to 15thNight
46%5%13%22%11%
2779
16th to endNight
52%5%15%19%7%
2704
February1st to 15thNight
50%5%13%19%10%1
2483
16th to endNight
44%5%13%20%14%2
2162
March1st to 15thNight
45%413%25%9%1
2129
16th to endNight
51%5%14%21%6%
2112
April1st to 15thNight
43%411%26%13%
1818
16th to endNight
48%5%10%21%10%2
1620
May1st to 15thNight
40%414%24%14%2
1613
16th to endNight
37%7%16%22%14%1
1498
June1st to 15thNight
33%6%17%27%13%1
1353
16th to endNight
21%5%15%30%22%3
1260
July1st to 15thNight
17%5%17%36%18%4
1190
16th to endNight
18%5%18%32%19%4
1565
August1st to 15thNight
23%6%16%32%18%2
1610
16th to endNight
26%414%31%18%4
1734
September1st to 15thNight
26%413%32%20%2
1860
16th to endNight
29%5%11%34%18%1
1980
October1st to 15thNight
35%310%27%20%2
2142
16th to endNight
40%314%24%15%1
2325
November1st to 15thNight
39%412%22%17%2
2566
16th to endNight
41%416%23%12%1
2730
December1st to 15thNight
51%5%15%18%8%
2730
16th to endNight
55%5%12%16%8%
3006

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
15%10%43%22%6%
135
16th to endDay
17%9%36%29%5%
144
February1st to 15thDay
14%17%48%19%
135
16th to endDay
22%17%32%21%5%
120
March1st to 15thDay
28%15%33%20%2
121
16th to endDay
28%7%31%23%8%1
96
April1st to 15thDay
19%11%41%17%7%2
246
16th to endDay
30%13%27%19%7%2
450
May1st to 15thDay
23%10%32%25%7%1
468
16th to endDay
22%7%33%22%11%1
517
June1st to 15thDay
16%7%33%24%13%3
495
16th to endDay
8%6%40%28%14%2
495
July1st to 15thDay
6%5%29%36%17%5%
475
16th to endDay
6%328%37%19%4
515
August1st to 15thDay
9%423%33%24%4
493
16th to endDay
13%326%31%18%6%
508
September1st to 15thDay
13%325%36%14%4
252
16th to endDay
19%5%35%26%6%5%
135
October1st to 15thDay
14%11%41%20%9%2
135
16th to endDay
18%13%38%18%9%2
144
November1st to 15thDay
11%11%36%30%8%1
135
16th to endDay
25%16%36%18%3
135
December1st to 15thDay
20%19%38%15%5%
135
16th to endDay
22%20%40%13%2
144
January1st to 15thNight
11%15%40%25%5%1
975
16th to endNight
14%13%42%26%3
1040
February1st to 15thNight
15%13%38%24%6%
955
16th to endNight
11%12%41%23%8%2
796
March1st to 15thNight
15%10%38%27%6%
601
16th to endNight
20%10%33%26%8%
576
April1st to 15thNight
20%10%35%25%7%
539
16th to endNight
25%9%32%20%9%1
540
May1st to 15thNight
18%9%36%24%9%
540
16th to endNight
16%5%32%33%11%
563
June1st to 15thNight
14%5%29%36%14%
540
16th to endNight
6%233%44%12%
540
July1st to 15thNight
5%225%44%20%1
510
16th to endNight
4125%47%19%1
564
August1st to 15thNight
6%22%46%22%1
539
16th to endNight
10%125%38%21%3
573
September1st to 15thNight
10%228%37%17%3
540
16th to endNight
10%7%36%29%13%2
537
October1st to 15thNight
17%10%35%26%9%
702
16th to endNight
20%9%33%27%8%
789
November1st to 15thNight
15%11%36%26%8%
950
16th to endNight
14%15%39%23%6%
975
December1st to 15thNight
17%12%42%24%3
975
16th to endNight
22%11%38%21%5%
1040
Page generated at 2018-03-12 12:28:10. Version ac04

Copyright 2018 A. Danko


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