DarkSights Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the DarkSights Observatory clear sky chart from 2005-11-05 to 2019-06-24.

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
65%
17689
26%
54044
24%
17653
68%
17653
37%
30170

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
59%
836
17%
2794
18%
836
62%
836
25%
1740
January16th to endNight
58%
896
21%
2912
23%
896
60%
896
25%
1846
February1st to 15thNight
56%
817
24%
2678
25%
817
60%
817
27%
1665
February16th to endNight
51%
736
22%
2207
19%
736
57%
736
27%
1415
March1st to 15thNight
51%
840
18%
2349
16%
840
54%
840
25%
1583
March16th to endNight
51%
896
19%
2433
15%
896
55%
896
30%
1576
April1st to 15thNight
51%
839
21%
2099
11%
839
54%
839
31%
1387
April16th to endNight
61%
832
25%
2080
13%
832
65%
832
47%
1183
May1st to 15thNight
66%
722
26%
1982
18%
722
68%
722
48%
1048
May16th to endNight
62%
448
21%
1762
22%
448
66%
448
32%
894
June1st to 15thNight
71%
420
27%
1680
30%
420
77%
420
41%
749
June16th to endNight
83%
406
34%
1624
43%
406
85%
406
61%
570
July1st to 15thNight
87%
400
33%
1510
41%
400
88%
400
61%
561
July16th to endNight
78%
612
31%
1737
29%
579
79%
579
53%
808
August1st to 15thNight
74%
597
32%
1742
27%
594
74%
594
54%
833
August16th to endNight
81%
828
35%
2070
22%
828
81%
828
62%
1060
September1st to 15thNight
80%
780
38%
1950
28%
780
81%
780
63%
992
September16th to endNight
78%
776
39%
2123
35%
776
81%
776
62%
1012
October1st to 15thNight
73%
780
31%
2340
32%
780
78%
780
47%
1168
October16th to endNight
72%
832
33%
2496
36%
832
75%
832
46%
1287
November1st to 15thNight
69%
820
29%
2569
30%
820
73%
820
39%
1398
November16th to endNight
62%
840
23%
2831
24%
840
65%
840
30%
1633
December1st to 15thNight
57%
840
22%
2940
21%
840
62%
840
26%
1778
December16th to endNight
50%
896
20%
3136
18%
896
56%
896
22%
1984

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
7%424323346%57%
54776
Night
8%5%24423347%52%
54231
TransparencyDay
26%49%18%23%17%
54462
Night
29%49%18%21%16%
54045
SeeingDay
9%10%24%32%18%4
8261
Night
10%312%35%31%7%
17702

By Month

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
17%6%25%42445%6%40%
1801
16th to endDay
16%7%25%5%34446%39%
2016
February1st to 15thDay
16%8%25%324346%41%
1846
16th to endDay
16%7%35%434347%40%
1839
March1st to 15thDay
15%7%36%5%35%45%8%34%
2268
16th to endDay
12%6%26%5%35%5%6%6%39%
2495
April1st to 15thDay
13%7%35%5%2445%6%41%
2509
16th to endDay
6%413323347%58%
2485
May1st to 15thDay
3313313337%64%
2626
16th to endDay
6%5%35%313347%55%
3050
June1st to 15thDay
3413313346%63%
2940
16th to endDay
1112212235%76%
2844
July1st to 15thDay
212212235%74%
2694
16th to endDay
22212245%75%
2676
August1st to 15thDay
1213312225%74%
2461
16th to endDay
112212235%75%
2484
September1st to 15thDay
1213212235%74%
2340
16th to endDay
2313212236%71%
2165
October1st to 15thDay
4213213336%66%
1950
16th to endDay
6%313224346%60%
2080
November1st to 15thDay
8%4243145%47%52%
1950
16th to endDay
12%7%35%423346%46%
1785
December1st to 15thDay
15%8%35%42443442%
1680
16th to endDay
17%6%34413447%40%
1792
January1st to 15thNight
13%6%25%4245%5%8%40%
2794
16th to endNight
15%7%24424446%43%
2912
February1st to 15thNight
15%7%3442345%5%44%
2666
16th to endNight
15%7%14424347%44%
2207
March1st to 15thNight
16%7%25%433446%39%
2349
16th to endNight
14%5%35%433446%45%
2433
April1st to 15thNight
10%6%245%25%46%8%44%
2099
16th to endNight
6%313224348%58%
2080
May1st to 15thNight
343442335%8%56%
1982
16th to endNight
47%45%433347%49%
1762
June1st to 15thNight
332441335%7%59%
1680
16th to endNight
1213212235%73%
1624
July1st to 15thNight
1212322347%68%
1592
16th to endNight
1326%32445%9%56%
1845
August1st to 15thNight
1435%5%33349%55%
1751
16th to endNight
215%423349%61%
2070
September1st to 15thNight
1423422247%65%
1950
16th to endNight
2213313247%66%
2123
October1st to 15thNight
5%313322346%62%
2340
16th to endNight
5%42432335%7%57%
2496
November1st to 15thNight
7%5%2331335%8%54%
2569
16th to endNight
11%5%2442335%6%49%
2831
December1st to 15thNight
13%7%25%424446%44%
2940
16th to endNight
16%7%34323347%42%
3136

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
41%7%12%16%15%6%
1801
16th to endDay
43%7%9%13%18%8%
2016
February1st to 15thDay
42%5%8%17%21%4
1846
16th to endDay
43%6%8%23%14%3
1839
March1st to 15thDay
45%6%10%18%13%4
2268
16th to endDay
41%8%12%17%17%2
2495
April1st to 15thDay
41%6%13%18%17%2
2509
16th to endDay
24%5%12%26%24%6%
2485
May1st to 15thDay
19%410%28%30%7%
2626
16th to endDay
26%5%13%26%21%6%
3054
June1st to 15thDay
20%49%22%26%16%
2940
16th to endDay
11%1416%32%33%
2844
July1st to 15thDay
11%139%24%49%
2547
16th to endDay
11%1411%26%44%
2521
August1st to 15thDay
14%1312%29%39%
2445
16th to endDay
10%15%15%37%30%
2484
September1st to 15thDay
12%15%15%30%35%
2340
16th to endDay
14%26%23%30%22%
2165
October1st to 15thDay
19%49%18%25%23%
1950
16th to endDay
22%410%21%24%15%
2080
November1st to 15thDay
30%6%11%25%18%9%
1950
16th to endDay
37%5%11%18%23%3
1785
December1st to 15thDay
42%6%9%16%17%7%
1680
16th to endDay
43%5%12%16%17%4
1792
January1st to 15thNight
39%6%12%18%15%7%
2794
16th to endNight
40%6%10%12%16%13%
2912
February1st to 15thNight
39%5%9%18%18%8%
2678
16th to endNight
39%6%11%23%16%2
2207
March1st to 15thNight
43%5%11%18%14%5%
2349
16th to endNight
38%6%12%19%18%5%
2433
April1st to 15thNight
36%7%15%19%18%3
2099
16th to endNight
23%412%27%23%8%
2080
May1st to 15thNight
22%311%22%27%11%
1983
16th to endNight
28%5%14%23%21%7%
1762
June1st to 15thNight
22%39%21%24%18%
1680
16th to endNight
11%1314%31%37%
1624
July1st to 15thNight
13%29%22%51%
1510
16th to endNight
19%25%11%19%42%
1737
August1st to 15thNight
21%212%24%38%
1742
16th to endNight
17%1412%30%33%
2070
September1st to 15thNight
16%1412%26%38%
1950
16th to endNight
15%26%20%27%27%
2123
October1st to 15thNight
21%38%19%22%23%
2340
16th to endNight
23%38%21%24%18%
2496
November1st to 15thNight
27%5%12%25%17%11%
2569
16th to endNight
33%5%10%20%22%6%
2831
December1st to 15thNight
38%5%10%15%18%10%
2940
16th to endNight
41%6%11%17%17%6%
3136

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
24%10%24%24%14%1
249
16th to endDay
17%9%19%30%21%1
352
February1st to 15thDay
19%14%21%24%18%1
326
16th to endDay
18%18%28%21%12%1
342
March1st to 15thDay
19%18%27%19%12%2
390
16th to endDay
15%17%31%22%11%1
416
April1st to 15thDay
17%24%25%21%9%1
389
16th to endDay
6%23%26%26%11%4
378
May1st to 15thDay
6%13%36%30%11%1
408
16th to endDay
8%15%29%32%12%2
458
June1st to 15thDay
412%31%33%14%3
435
16th to endDay
1425%42%21%4
408
July1st to 15thDay
121%47%24%3
365
16th to endDay
1118%44%24%9%
391
August1st to 15thDay
2319%44%22%7%
359
16th to endDay
1116%45%26%8%
396
September1st to 15thDay
2417%45%23%6%
375
16th to endDay
26%22%36%23%7%
375
October1st to 15thDay
410%29%33%19%3
375
16th to endDay
8%6%24%27%26%8%
400
November1st to 15thDay
9%5%19%29%29%6%
276
16th to endDay
12%7%22%30%22%4
150
December1st to 15thDay
12%13%20%27%20%5%
120
16th to endDay
16%14%20%24%20%4
128
January1st to 15thNight
15%411%33%27%8%
840
16th to endNight
17%311%34%25%8%
896
February1st to 15thNight
16%5%12%33%26%6%
824
16th to endNight
15%7%17%34%20%4
736
March1st to 15thNight
17%8%15%27%26%5%
840
16th to endNight
15%418%35%21%3
896
April1st to 15thNight
11%8%19%35%21%3
839
16th to endNight
6%5%20%35%25%7%
832
May1st to 15thNight
6%213%42%30%4
723
16th to endNight
6%315%44%26%3
449
June1st to 15thNight
4112%47%30%3
420
16th to endNight
27%47%38%2
406
July1st to 15thNight
1240%50%6%
400
16th to endNight
2227%53%12%
612
August1st to 15thNight
45%34%44%10%
597
16th to endNight
2435%47%9%
828
September1st to 15thNight
35%33%46%10%
780
16th to endNight
319%32%40%13%
776
October1st to 15thNight
7%28%40%31%9%
780
16th to endNight
6%28%31%35%15%
832
November1st to 15thNight
7%113%33%33%9%
820
16th to endNight
13%311%31%30%9%
840
December1st to 15thNight
16%412%32%25%7%
840
16th to endNight
18%6%16%34%21%3
896
Page generated at 2019-06-24 17:41:29. Version ac04

Copyright 2019 A. Danko


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