Stardust Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stardust Observatory clear sky chart from 2005-11-05 to 2017-09-22.

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%
15923
20%
46914
13%
15878
47%
15878
26%
30169

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%
900
17%
2506
7%
895
32%
895
21%
1763
January16th to endNight
21%
960
15%
2550
4%
960
29%
960
19%
1871
February1st to 15thNight
25%
829
13%
2238
3%
827
32%
827
19%
1605
February16th to endNight
25%
631
20%
1893
8%
631
35%
631
23%
1244
March1st to 15thNight
29%
695
16%
2135
9%
695
35%
695
20%
1470
March16th to endNight
30%
576
15%
2010
8%
576
39%
576
17%
1350
April1st to 15thNight
32%
539
19%
1797
13%
539
43%
539
23%
1118
April16th to endNight
36%
540
20%
1800
16%
540
44%
540
23%
1166
May1st to 15thNight
38%
540
17%
1594
10%
540
45%
540
23%
1105
May16th to endNight
50%
563
20%
1497
13%
561
56%
561
32%
984
June1st to 15thNight
62%
540
20%
1440
12%
540
65%
540
41%
839
June16th to endNight
57%
540
20%
1440
12%
540
61%
540
37%
882
July1st to 15thNight
70%
510
19%
1360
14%
510
71%
510
40%
808
July16th to endNight
75%
564
26%
1417
20%
531
78%
531
47%
800
August1st to 15thNight
77%
539
23%
1674
25%
536
79%
536
43%
862
August16th to endNight
73%
573
23%
1910
25%
573
76%
573
36%
1047
September1st to 15thNight
63%
540
29%
1800
31%
540
66%
540
35%
973
September16th to endNight
62%
649
32%
1856
23%
649
67%
649
39%
1067
October1st to 15thNight
51%
660
29%
1952
21%
660
58%
660
36%
1139
October16th to endNight
34%
704
23%
2170
14%
704
44%
704
28%
1320
November1st to 15thNight
35%
700
26%
2276
16%
700
48%
700
29%
1302
November16th to endNight
29%
771
20%
2391
12%
771
39%
771
24%
1524
December1st to 15thNight
23%
900
13%
2520
5%
900
30%
900
19%
1852
December16th to endNight
20%
960
13%
2688
4%
960
28%
960
14%
2078

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%38%
47973
Night
13%7%35%424347%42%
47083
Cloud CoverDay
13%7%35%5%3445%7%38%
47981
Night
13%7%35%424447%42%
47088
TransparencyDay
44%5%12%23%13%2
47660
Night
41%411%23%15%2
46915
SeeingDay
14%5%23%27%21%7%
5943
Night
16%8%27%31%14%1
15924

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%12%5%9%6%35%346%26%
1432
16th to endDay
14%13%48%7%34345%29%
1671
February1st to 15thDay
13%11%5%8%7%35%336%30%
1624
16th to endDay
12%10%48%6%34447%31%
1580
March1st to 15thDay
15%10%37%6%35%346%33%
1826
16th to endDay
16%11%47%6%35%5%47%29%
2213
April1st to 15thDay
17%7%45%42435%6%38%
2151
16th to endDay
18%8%25%6%35%446%36%
2160
May1st to 15thDay
19%8%35%5%25%46%7%32%
2352
16th to endDay
13%5%36%6%35%5%5%7%37%
2617
June1st to 15thDay
9%5%25%5%345%6%8%44%
2520
16th to endDay
8%425%5%35%5%6%9%42%
2520
July1st to 15thDay
8%3145%35%6%6%9%44%
2520
16th to endDay
5%324425%6%8%11%46%
2655
August1st to 15thDay
7%4144346%7%10%44%
2274
16th to endDay
8%425%435%5%6%9%44%
2292
September1st to 15thDay
12%4145%24447%47%
2160
16th to endDay
8%5%25%43445%7%48%
1905
October1st to 15thDay
14%5%23423436%47%
1675
16th to endDay
16%8%24313445%44%
1702
November1st to 15thDay
16%6%23413445%47%
1582
16th to endDay
17%9%5%5%42334438%
1566
December1st to 15thDay
18%10%6%7%5%2445%6%26%
1440
16th to endDay
18%11%6%7%5%3445%5%26%
1536
January1st to 15thNight
13%9%37%6%34445%36%
2506
16th to endNight
13%12%5%7%6%34345%32%
2550
February1st to 15thNight
14%9%5%7%6%34346%34%
2236
16th to endNight
14%9%36%5%24345%40%
1893
March1st to 15thNight
17%9%36%434445%37%
2122
16th to endNight
16%8%46%6%2445%7%33%
2010
April1st to 15thNight
13%5%36%5%3445%5%43%
1797
16th to endNight
18%6%25%5%33346%39%
1800
May1st to 15thNight
18%5%35%5%24447%37%
1594
16th to endNight
10%5%245%3445%9%44%
1496
June1st to 15thNight
9%31342445%9%51%
1440
16th to endNight
7%426%42436%11%45%
1440
July1st to 15thNight
7%414335%46%9%48%
1440
16th to endNight
3214335%46%10%53%
1513
August1st to 15thNight
421332346%11%55%
1683
16th to endNight
6%3234245%5%7%53%
1910
September1st to 15thNight
10%424422336%55%
1800
16th to endNight
7%42442335%8%51%
1856
October1st to 15thNight
12%313423347%52%
1952
16th to endNight
16%6%13323335%48%
2170
November1st to 15thNight
11%6%24423235%51%
2276
16th to endNight
17%7%25%424347%41%
2391
December1st to 15thNight
20%11%46%434336%31%
2520
16th to endNight
20%13%5%8%5%24335%26%
2688

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
14%11%5%10%6%35%446%26%
1432
16th to endDay
13%13%5%8%7%34345%29%
1671
February1st to 15thDay
13%11%48%7%35%436%30%
1624
16th to endDay
12%10%5%8%5%4445%6%31%
1580
March1st to 15thDay
15%11%47%6%34346%32%
1836
16th to endDay
16%10%47%6%25%5%47%29%
2211
April1st to 15thDay
17%7%45%5%2435%6%38%
2151
16th to endDay
18%8%25%6%25%446%35%
2160
May1st to 15thDay
18%8%35%5%35%45%7%31%
2352
16th to endDay
13%5%26%6%35%5%5%7%37%
2617
June1st to 15thDay
9%425%5%345%6%8%44%
2520
16th to endDay
8%425%5%35%5%6%9%42%
2520
July1st to 15thDay
7%3145%45%6%6%9%44%
2520
16th to endDay
5%315%425%6%8%11%46%
2655
August1st to 15thDay
7%4145%346%7%10%44%
2274
16th to endDay
8%425%5%345%6%8%45%
2292
September1st to 15thDay
12%4145%24447%47%
2160
16th to endDay
9%425%43445%7%48%
1905
October1st to 15thDay
14%5%24423336%47%
1675
16th to endDay
16%8%25%323445%44%
1702
November1st to 15thDay
16%5%23413445%47%
1582
16th to endDay
18%9%5%5%42334438%
1566
December1st to 15thDay
18%10%6%7%5%25%45%6%26%
1440
16th to endDay
18%11%6%7%5%3445%5%26%
1536
January1st to 15thNight
13%9%36%6%35%345%36%
2506
16th to endNight
13%11%5%7%6%34435%33%
2550
February1st to 15thNight
14%9%5%6%6%34346%34%
2229
16th to endNight
14%10%26%5%24345%40%
1893
March1st to 15thNight
16%9%36%434445%37%
2135
16th to endNight
16%8%45%6%3445%6%33%
2010
April1st to 15thNight
13%5%35%5%3445%5%43%
1797
16th to endNight
17%6%25%5%34346%39%
1800
May1st to 15thNight
18%5%35%425%45%7%36%
1593
16th to endNight
10%5%245%345%6%8%44%
1496
June1st to 15thNight
9%31342435%9%51%
1440
16th to endNight
7%416%425%46%10%46%
1440
July1st to 15thNight
6%415%435%46%9%48%
1440
16th to endNight
3214336%45%10%53%
1513
August1st to 15thNight
421342346%10%55%
1683
16th to endNight
6%3134245%5%7%53%
1910
September1st to 15thNight
10%424423336%55%
1800
16th to endNight
7%42442345%8%52%
1856
October1st to 15thNight
12%314423347%52%
1952
16th to endNight
16%6%13324345%48%
2170
November1st to 15thNight
11%6%25%423336%51%
2276
16th to endNight
16%7%35%414447%41%
2391
December1st to 15thNight
20%11%46%5%33336%31%
2520
16th to endNight
20%13%48%434335%27%
2688

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
59%49%16%9%
1433
16th to endDay
57%313%18%6%
1671
February1st to 15thDay
55%313%19%6%
1626
16th to endDay
52%412%21%9%
1580
March1st to 15thDay
53%413%21%6%
1836
16th to endDay
55%412%21%5%1
2213
April1st to 15thDay
46%310%24%12%1
2151
16th to endDay
49%5%11%19%12%1
2160
May1st to 15thDay
50%5%14%20%9%
2352
16th to endDay
44%7%12%17%15%2
2621
June1st to 15thDay
36%5%12%25%17%2
2520
16th to endDay
37%6%12%22%17%3
2520
July1st to 15thDay
33%7%13%27%14%3
2371
16th to endDay
29%7%16%30%16%
2488
August1st to 15thDay
32%6%15%27%15%1
2260
16th to endDay
33%7%12%24%17%4
2292
September1st to 15thDay
36%47%24%20%6%
2160
16th to endDay
34%38%31%18%2
1905
October1st to 15thDay
38%39%25%19%2
1675
16th to endDay
41%311%24%15%2
1702
November1st to 15thDay
38%311%24%18%3
1582
16th to endDay
50%211%24%10%1
1566
December1st to 15thDay
57%5%12%16%7%
1440
16th to endDay
58%411%17%7%1
1536
January1st to 15thNight
49%410%21%13%
2506
16th to endNight
53%314%20%8%
2550
February1st to 15thNight
52%312%19%10%1
2238
16th to endNight
45%312%26%11%
1893
March1st to 15thNight
49%411%22%10%1
2135
16th to endNight
49%413%21%9%1
2010
April1st to 15thNight
41%310%26%15%2
1797
16th to endNight
46%310%20%15%4
1800
May1st to 15thNight
46%6%10%21%14%
1594
16th to endNight
36%7%14%19%19%3
1498
June1st to 15thNight
29%414%28%19%4
1440
16th to endNight
32%5%14%23%19%4
1440
July1st to 15thNight
30%412%29%18%4
1360
16th to endNight
25%416%31%19%2
1417
August1st to 15thNight
23%5%15%31%21%3
1674
16th to endNight
28%6%12%26%19%6%
1910
September1st to 15thNight
31%37%26%23%7%
1800
16th to endNight
29%49%29%23%4
1856
October1st to 15thNight
32%39%26%22%5%
1952
16th to endNight
39%29%26%19%2
2170
November1st to 15thNight
35%210%24%20%5%
2276
16th to endNight
42%311%26%15%
2391
December1st to 15thNight
55%312%18%9%
2520
16th to endNight
61%39%16%7%1
2688

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
28%10%37%15%7%
90
16th to endDay
11%21%34%25%7%
96
February1st to 15thDay
15%16%40%22%5%
90
16th to endDay
14%14%29%29%11%
81
March1st to 15thDay
27%17%30%18%5%
90
16th to endDay
25%12%30%21%8%1
197
April1st to 15thDay
20%10%31%27%8%1
270
16th to endDay
21%6%27%28%12%3
270
May1st to 15thDay
24%8%27%26%11%3
333
16th to endDay
15%7%31%26%14%4
517
June1st to 15thDay
11%320%31%26%7%
495
16th to endDay
10%429%26%22%6%
495
July1st to 15thDay
12%116%32%25%12%
475
16th to endDay
6%14%31%34%12%
515
August1st to 15thDay
8%110%30%34%14%
427
16th to endDay
7%114%28%35%12%
332
September1st to 15thDay
13%212%28%31%11%
315
16th to endDay
9%5%12%26%32%12%
278
October1st to 15thDay
9%10%21%29%21%6%
115
16th to endDay
22%236%31%7%
96
November1st to 15thDay
5%6%26%28%20%12%
90
16th to endDay
38%14%24%16%41
90
December1st to 15thDay
22%16%31%22%6%1
90
16th to endDay
28%13%45%10%2
96
January1st to 15thNight
17%14%37%24%5%
900
16th to endNight
19%14%35%26%3
960
February1st to 15thNight
20%12%34%27%4
830
16th to endNight
19%12%36%28%3
631
March1st to 15thNight
21%12%31%27%6%
695
16th to endNight
19%9%35%27%8%
576
April1st to 15thNight
16%12%33%28%8%
539
16th to endNight
21%5%31%31%10%
540
May1st to 15thNight
20%5%27%36%8%1
540
16th to endNight
11%426%36%20%1
563
June1st to 15thNight
10%219%48%18%
540
16th to endNight
10%123%40%22%1
540
July1st to 15thNight
7%212%44%30%2
510
16th to endNight
4111%42%36%3
564
August1st to 15thNight
6%16%46%35%4
539
16th to endNight
7%110%36%40%3
573
September1st to 15thNight
11%313%36%29%6%
540
16th to endNight
8%5%16%36%28%5%
649
October1st to 15thNight
13%425%33%20%2
660
16th to endNight
20%8%32%28%9%
704
November1st to 15thNight
14%9%36%26%12%1
700
16th to endNight
20%10%34%26%7%
771
December1st to 15thNight
27%9%33%25%4
900
16th to endNight
27%11%31%24%4
960
Page generated at 2017-09-23 05:43:37. Version ac04

Copyright 2017 A. Danko


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