Dark Ridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dark Ridge Observatory clear sky chart from 2005-11-05 to 2017-12-02.

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%
15838
34%
47874
17%
15794
64%
15794
42%
23099

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
37%
720
34%
2327
15%
716
59%
716
37%
1088
January16th to endNight
34%
768
38%
2496
17%
768
59%
768
37%
1113
February1st to 15thNight
34%
703
38%
2112
13%
700
59%
700
44%
960
February16th to endNight
21%
632
41%
1894
10%
632
52%
632
37%
839
March1st to 15thNight
34%
720
37%
2052
14%
720
54%
720
40%
989
March16th to endNight
33%
705
40%
2049
14%
705
57%
705
48%
936
April1st to 15thNight
28%
539
37%
1798
10%
539
59%
539
37%
790
April16th to endNight
29%
540
41%
1800
15%
540
65%
540
46%
706
May1st to 15thNight
34%
540
31%
1800
14%
540
59%
540
45%
787
May16th to endNight
43%
562
32%
1772
15%
561
64%
561
48%
814
June1st to 15thNight
62%
540
30%
1440
18%
540
71%
540
57%
717
June16th to endNight
68%
540
23%
1448
18%
540
71%
540
44%
820
July1st to 15thNight
76%
510
21%
1530
20%
510
77%
510
40%
842
July16th to endNight
81%
564
20%
1616
21%
531
82%
531
39%
898
August1st to 15thNight
80%
539
20%
1789
24%
536
80%
536
34%
1008
August16th to endNight
79%
573
20%
1910
24%
573
80%
573
34%
1070
September1st to 15thNight
73%
540
23%
1800
24%
540
75%
540
34%
1004
September16th to endNight
68%
537
35%
1929
33%
537
75%
537
42%
921
October1st to 15thNight
56%
692
35%
2132
21%
692
67%
692
47%
1020
October16th to endNight
57%
768
41%
2304
24%
768
70%
768
55%
1031
November1st to 15thNight
47%
806
41%
2326
18%
806
64%
806
53%
1040
November16th to endNight
44%
975
41%
2535
17%
975
59%
975
47%
1270
December1st to 15thNight
36%
910
39%
2372
13%
910
56%
910
44%
1173
December16th to endNight
29%
915
36%
2643
13%
915
50%
915
36%
1263

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
421332445%7%59%
48551
Night
3212223347%65%
48073
Cloud CoverDay
431332445%7%58%
48549
Night
321222335%7%64%
48073
TransparencyDay
22%5%8%18%26%19%
48251
Night
18%39%18%28%21%
47875
SeeingDay
8%15%24%28%17%5%
5564
Night
5%17%25%26%20%5%
15840

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
1212223346%68%
1611
16th to endDay
4312212348%64%
1728
February1st to 15thDay
2212223245%70%
1747
16th to endDay
1212213245%72%
1580
March1st to 15thDay
2312334346%64%
1905
16th to endDay
1212313347%67%
2175
April1st to 15thDay
2212213338%67%
2150
16th to endDay
211111223478%
2160
May1st to 15thDay
323323446%64%
2151
16th to endDay
4112223447%65%
2336
June1st to 15thDay
1123245%6%9%63%
2520
16th to endDay
4313425%6%8%8%48%
2506
July1st to 15thDay
9%425%6%47%7%7%10%34%
2340
16th to endDay
8%425%5%47%8%9%11%32%
2440
August1st to 15thDay
9%326%6%47%9%8%9%30%
2160
16th to endDay
7%425%7%47%7%8%9%35%
2292
September1st to 15thDay
13%5%25%5%345%6%8%40%
2160
16th to endDay
8%313323337%57%
2031
October1st to 15thDay
5%32223345%66%
1825
16th to endDay
112212225%76%
1920
November1st to 15thDay
111212245%75%
1847
16th to endDay
3211212235%72%
1755
December1st to 15thDay
22221245%8%66%
1622
16th to endDay
2312213348%65%
1590
January1st to 15thNight
1323213335%67%
2327
16th to endNight
3212212237%69%
2496
February1st to 15thNight
121121335%6%69%
2102
16th to endNight
221112246%73%
1894
March1st to 15thNight
1212223447%67%
2052
16th to endNight
2212212235%73%
2049
April1st to 15thNight
32121345%7%66%
1798
16th to endNight
112112235%77%
1800
May1st to 15thNight
3212212236%70%
1799
16th to endNight
5%2121335%7%67%
1771
June1st to 15thNight
1112245%6%9%64%
1440
16th to endNight
2113436%7%6%9%52%
1448
July1st to 15thNight
7%323315%5%5%12%48%
1620
16th to endNight
42233346%8%14%44%
1726
August1st to 15thNight
6%2135%35%6%9%14%41%
1800
16th to endNight
4323435%6%6%12%47%
1910
September1st to 15thNight
9%32333347%10%47%
1800
16th to endNight
8%312212336%63%
1929
October1st to 15thNight
3212313336%67%
2132
16th to endNight
221111222475%
2304
November1st to 15thNight
2112211236%73%
2326
16th to endNight
22231233472%
2535
December1st to 15thNight
322212348%68%
2372
16th to endNight
221222235%6%68%
2643

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
121332345%5%67%
1611
16th to endDay
431321245%7%64%
1728
February1st to 15thDay
1313223245%69%
1747
16th to endDay
1212213235%72%
1580
March1st to 15thDay
2312334446%63%
1905
16th to endDay
1212323347%67%
2173
April1st to 15thDay
2213213347%68%
2150
16th to endDay
211111235%77%
2160
May1st to 15thDay
4212324346%63%
2151
16th to endDay
4212213447%65%
2336
June1st to 15thDay
1123145%6%9%62%
2520
16th to endDay
4323336%6%8%8%48%
2506
July1st to 15thDay
10%325%7%47%6%7%9%34%
2340
16th to endDay
9%435%6%47%8%9%11%30%
2440
August1st to 15thDay
9%426%7%47%9%8%9%30%
2160
16th to endDay
8%426%7%47%7%8%9%34%
2292
September1st to 15thDay
13%5%25%6%25%5%5%8%39%
2160
16th to endDay
7%413323446%56%
2031
October1st to 15thDay
4312222346%66%
1825
16th to endDay
11222235%75%
1920
November1st to 15thDay
211213245%74%
1847
16th to endDay
3211211346%72%
1755
December1st to 15thDay
22131245%9%65%
1622
16th to endDay
131221345%7%65%
1590
January1st to 15thNight
132231335%5%66%
2327
16th to endNight
3212212337%68%
2496
February1st to 15thNight
121122325%6%69%
2102
16th to endNight
2211112347%71%
1894
March1st to 15thNight
121222345%6%67%
2052
16th to endNight
1212213235%73%
2049
April1st to 15thNight
32122445%7%66%
1798
16th to endNight
112112235%76%
1800
May1st to 15thNight
3212212336%70%
1799
16th to endNight
42121335%7%67%
1771
June1st to 15thNight
11112245%6%8%63%
1440
16th to endNight
2213437%6%6%9%52%
1448
July1st to 15thNight
7%323325%47%11%48%
1620
16th to endNight
5%213335%7%8%14%44%
1726
August1st to 15thNight
6%3135%35%5%10%14%40%
1800
16th to endNight
4224435%5%6%12%47%
1910
September1st to 15thNight
9%31343447%9%47%
1800
16th to endNight
8%312212336%63%
1929
October1st to 15thNight
3312313336%67%
2132
16th to endNight
22211223475%
2304
November1st to 15thNight
2112211246%73%
2326
16th to endNight
221231233472%
2535
December1st to 15thNight
222222348%67%
2372
16th to endNight
22232235%6%67%
2643

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
17%36%17%33%21%
1612
16th to endDay
18%36%14%34%21%
1728
February1st to 15thDay
17%25%17%28%29%
1748
16th to endDay
14%3315%36%27%
1580
March1st to 15thDay
19%46%18%30%21%
1905
16th to endDay
17%2315%33%26%
2175
April1st to 15thDay
16%35%15%35%24%
2150
16th to endDay
10%2312%35%34%
2160
May1st to 15thDay
20%36%13%28%27%
2151
16th to endDay
17%46%17%26%28%
2339
June1st to 15thDay
15%5%9%14%25%29%
2520
16th to endDay
26%7%10%18%17%19%
2506
July1st to 15thDay
37%10%14%16%14%6%
2201
16th to endDay
36%10%22%20%10%
2287
August1st to 15thDay
40%11%17%21%7%2
2147
16th to endDay
38%10%15%21%12%2
2292
September1st to 15thDay
37%7%11%19%17%6%
2160
16th to endDay
25%5%7%22%27%12%
2031
October1st to 15thDay
20%28%17%27%22%
1825
16th to endDay
12%1420%34%25%
1920
November1st to 15thDay
12%26%23%32%22%
1847
16th to endDay
15%25%17%32%28%
1755
December1st to 15thDay
16%37%23%36%12%
1622
16th to endDay
17%311%19%34%13%
1590
January1st to 15thNight
19%37%15%31%22%
2327
16th to endNight
17%26%17%34%22%
2496
February1st to 15thNight
16%26%16%27%31%
2112
16th to endNight
13%2416%36%27%
1894
March1st to 15thNight
16%36%16%32%23%
2052
16th to endNight
14%2414%37%26%
2049
April1st to 15thNight
16%36%13%38%22%
1798
16th to endNight
11%15%13%34%33%
1800
May1st to 15thNight
16%25%16%29%28%
1800
16th to endNight
16%36%19%26%27%
1773
June1st to 15thNight
15%5%9%16%22%31%
1440
16th to endNight
24%7%13%18%15%20%
1448
July1st to 15thNight
26%6%17%24%18%6%
1530
16th to endNight
24%8%27%24%13%1
1616
August1st to 15thNight
28%8%22%26%10%2
1789
16th to endNight
27%9%21%23%15%2
1910
September1st to 15thNight
29%6%18%21%15%8%
1800
16th to endNight
24%210%21%29%11%
1929
October1st to 15thNight
19%38%17%29%22%
2132
16th to endNight
14%1418%28%31%
2304
November1st to 15thNight
13%2421%34%24%
2326
16th to endNight
17%1415%31%29%
2535
December1st to 15thNight
16%18%21%31%20%
2372
16th to endNight
16%38%22%33%15%
2643

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
6%33%30%20%7%2
90
16th to endDay
10%39%17%21%9%1
96
February1st to 15thDay
10%17%32%25%14%
90
16th to endDay
6%32%32%16%7%6%
81
March1st to 15thDay
8%28%43%13%5%1
195
16th to endDay
9%35%35%14%42
288
April1st to 15thDay
11%35%31%17%2
269
16th to endDay
9%38%35%12%21
270
May1st to 15thDay
6%30%44%13%4
288
16th to endDay
5%24%35%22%9%1
402
June1st to 15thDay
26%30%34%21%4
495
16th to endDay
5%217%36%30%7%
481
July1st to 15thDay
8%10%44%26%8%
305
16th to endDay
337%29%38%17%
327
August1st to 15thDay
6%26%31%34%16%
315
16th to endDay
11%36%39%28%11%
332
September1st to 15thDay
13%311%44%18%8%
315
16th to endDay
10%227%40%16%3
186
October1st to 15thDay
17%6%28%29%14%2
135
16th to endDay
411%25%30%18%11%
144
November1st to 15thDay
11%21%28%21%12%4
135
16th to endDay
8%25%31%17%14%1
135
December1st to 15thDay
7%20%39%22%7%3
94
16th to endDay
14%32%33%15%31
96
January1st to 15thNight
425%27%25%12%4
720
16th to endNight
5%29%29%21%11%2
768
February1st to 15thNight
422%37%22%9%4
704
16th to endNight
5%34%36%17%4
632
March1st to 15thNight
5%27%29%25%9%1
720
16th to endNight
421%38%24%9%
705
April1st to 15thNight
5%27%37%24%5%
539
16th to endNight
227%37%24%7%
540
May1st to 15thNight
5%17%40%29%5%
540
16th to endNight
5%12%35%28%15%2
563
June1st to 15thNight
2329%40%23%1
540
16th to endNight
3219%37%33%3
540
July1st to 15thNight
6%25%32%46%6%
510
16th to endNight
5%1319%55%14%
564
August1st to 15thNight
7%2119%48%20%
539
16th to endNight
41421%51%16%
573
September1st to 15thNight
9%3429%43%9%
540
16th to endNight
10%212%36%32%4
537
October1st to 15thNight
5%8%25%32%21%6%
692
16th to endNight
5%11%23%29%20%8%
768
November1st to 15thNight
317%28%26%16%6%
806
16th to endNight
5%20%26%26%15%4
975
December1st to 15thNight
7%24%28%26%10%2
910
16th to endNight
6%32%29%22%6%2
915
Page generated at 2017-12-03 09:16:43. Version ac04

Copyright 2017 A. Danko


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