Adams Ranch Dark Sky Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Adams Ranch Dark Sky Site clear sky chart from 2005-11-05 to 2017-09-10.

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
43%
15785
27%
46838
16%
15739
53%
15739
36%
26420

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
33%
899
30%
2327
12%
895
46%
895
38%
1354
January16th to endNight
31%
960
32%
2496
11%
960
45%
960
40%
1454
February1st to 15thNight
29%
854
22%
2262
8%
850
37%
850
30%
1434
February16th to endNight
32%
632
29%
1894
12%
632
44%
632
32%
1064
March1st to 15thNight
35%
543
25%
1983
15%
543
48%
543
27%
1096
March16th to endNight
31%
576
19%
2112
13%
576
39%
576
24%
1247
April1st to 15thNight
28%
539
22%
1926
12%
539
45%
539
28%
1037
April16th to endNight
30%
540
23%
1652
14%
540
44%
540
30%
1000
May1st to 15thNight
35%
539
23%
1620
16%
539
47%
539
31%
976
May16th to endNight
46%
563
22%
1684
18%
561
54%
561
31%
1011
June1st to 15thNight
54%
540
20%
1620
13%
540
61%
540
41%
870
June16th to endNight
56%
540
25%
1620
17%
540
63%
540
51%
795
July1st to 15thNight
66%
510
19%
1530
17%
510
69%
510
41%
838
July16th to endNight
78%
564
28%
1594
31%
531
80%
531
47%
821
August1st to 15thNight
73%
539
26%
1610
28%
536
76%
536
41%
874
August16th to endNight
72%
573
27%
1773
29%
573
75%
573
40%
949
September1st to 15thNight
59%
525
23%
1919
26%
525
63%
525
31%
1045
September16th to endNight
59%
492
32%
1815
27%
492
69%
492
38%
888
October1st to 15thNight
45%
597
30%
1917
22%
597
53%
597
34%
1075
October16th to endNight
42%
704
34%
2112
16%
704
56%
704
47%
1039
November1st to 15thNight
41%
796
32%
2196
14%
796
53%
796
45%
1179
November16th to endNight
34%
900
30%
2340
12%
900
46%
900
38%
1375
December1st to 15thNight
33%
900
26%
2340
10%
900
44%
900
34%
1443
December16th to endNight
33%
960
29%
2496
12%
960
46%
960
33%
1556

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
23%414323345%42%
47791
Night
22%313322345%47%
47034
Cloud CoverDay
10%5%2442445%7%49%
47789
Night
9%423323347%54%
47034
TransparencyDay
34%412%25%18%3
47489
Night
30%411%26%21%5%
46839
SeeingDay
11%7%25%31%20%3
5792
Night
12%8%31%32%13%1
15787

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
24%5%1422222446%
1611
16th to endDay
24%6%14211135%46%
1728
February1st to 15thDay
24%7%2342233441%
1611
16th to endDay
24%6%23312335%43%
1580
March1st to 15thDay
28%5%1432223438%
1975
16th to endDay
31%6%1431223437%
2112
April1st to 15thDay
26%5%13323446%38%
2022
16th to endDay
31%5%2442323434%
2306
May1st to 15thDay
28%414423445%37%
2331
16th to endDay
27%5%245%24446%32%
2430
June1st to 15thDay
22%44423447%40%
2340
16th to endDay
19%1123135%6%7%47%
2340
July1st to 15thDay
23%31342245%8%39%
2340
16th to endDay
20%2133235%7%7%41%
2466
August1st to 15thDay
15%21343346%9%45%
2340
16th to endDay
14%31432345%6%49%
2429
September1st to 15thDay
19%5%14424335%44%
1926
16th to endDay
16%313424446%47%
1815
October1st to 15thDay
19%41322334449%
1702
16th to endDay
15%324312235%55%
1760
November1st to 15thDay
20%31221233453%
1659
16th to endDay
26%4122122449%
1620
December1st to 15thDay
29%5%14312345%37%
1620
16th to endDay
27%6%3442222439%
1728
January1st to 15thNight
24%312212245%48%
2327
16th to endNight
23%31331233349%
2496
February1st to 15thNight
25%6%2432223344%
2252
16th to endNight
23%5%1231223447%
1894
March1st to 15thNight
25%413423335%42%
1983
16th to endNight
27%41432233441%
2112
April1st to 15thNight
27%33312337%43%
1926
16th to endNight
29%5%13322245%39%
1652
May1st to 15thNight
26%32312336%44%
1619
16th to endNight
25%41332345%7%39%
1683
June1st to 15thNight
20%213322346%48%
1620
16th to endNight
18%1221235%9%52%
1620
July1st to 15thNight
21%21332245%7%44%
1620
16th to endNight
19%2123225%5%8%45%
1702
August1st to 15thNight
13%1134335%6%8%49%
1620
16th to endNight
12%31232345%7%53%
1773
September1st to 15thNight
17%413323246%49%
1919
16th to endNight
16%312423346%51%
1815
October1st to 15thNight
20%41332233450%
1917
16th to endNight
15%12212235%61%
2112
November1st to 15thNight
20%21231223455%
2196
16th to endNight
27%41221213448%
2340
December1st to 15thNight
28%414312235%41%
2340
16th to endNight
26%5%2332224443%
2496

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
9%5%14323335%55%
1611
16th to endDay
10%6%24313236%53%
1728
February1st to 15thDay
10%7%445%23335%48%
1611
16th to endDay
9%6%24423346%50%
1580
March1st to 15thDay
14%6%25%433345%45%
1975
16th to endDay
19%8%35%41333442%
2110
April1st to 15thDay
11%5%2433445%7%46%
2022
16th to endDay
17%5%35%5%3434443%
2306
May1st to 15thDay
15%5%35%43435%5%41%
2331
16th to endDay
13%5%25%6%25%45%8%38%
2430
June1st to 15thDay
7%4145%345%5%8%48%
2340
16th to endDay
5%2134245%7%9%53%
2340
July1st to 15thDay
9%3234236%7%10%44%
2340
16th to endDay
43244346%8%10%48%
2466
August1st to 15thDay
6%3135%35%5%7%10%47%
2340
16th to endDay
6%3244245%5%7%51%
2429
September1st to 15thDay
12%5%25%435%436%47%
1926
16th to endDay
8%314324447%54%
1815
October1st to 15thDay
11%423323345%54%
1702
16th to endDay
8%323313245%60%
1760
November1st to 15thDay
6%413223346%60%
1659
16th to endDay
12%422312336%58%
1620
December1st to 15thDay
14%5%2442335%6%47%
1620
16th to endDay
14%7%35%423436%45%
1728
January1st to 15thNight
10%413422346%56%
2327
16th to endNight
7%42432334459%
2496
February1st to 15thNight
11%7%3442333450%
2252
16th to endNight
9%5%2332335%6%54%
1894
March1st to 15thNight
10%414433446%50%
1983
16th to endNight
15%5%24324346%46%
2112
April1st to 15thNight
12%313413448%51%
1926
16th to endNight
14%5%24322345%49%
1652
May1st to 15thNight
14%414424347%49%
1619
16th to endNight
10%4133245%5%9%46%
1683
June1st to 15thNight
5%21442335%8%57%
1620
16th to endNight
411222336%10%60%
1620
July1st to 15thNight
6%2134245%6%10%51%
1620
16th to endNight
42133245%6%11%55%
1702
August1st to 15thNight
42234345%7%9%51%
1620
16th to endNight
43233335%5%8%55%
1773
September1st to 15thNight
10%414424346%52%
1919
16th to endNight
7%31242335%6%57%
1815
October1st to 15thNight
12%42332333455%
1917
16th to endNight
7%212212335%67%
2112
November1st to 15thNight
7%313323245%62%
2196
16th to endNight
12%423313235%58%
2340
December1st to 15thNight
13%5%24313347%51%
2340
16th to endNight
13%6%34323346%50%
2496

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
32%210%29%22%2
1612
16th to endDay
33%211%28%21%2
1728
February1st to 15thDay
39%213%26%13%4
1612
16th to endDay
34%210%30%18%4
1580
March1st to 15thDay
41%39%23%16%5%
1975
16th to endDay
47%39%22%14%1
2112
April1st to 15thDay
36%415%24%16%3
2022
16th to endDay
45%48%23%15%2
2306
May1st to 15thDay
43%5%9%20%18%1
2331
16th to endDay
42%6%14%22%12%1
2434
June1st to 15thDay
33%5%14%25%18%2
2340
16th to endDay
25%7%13%27%23%4
2340
July1st to 15thDay
30%7%14%28%15%2
2201
16th to endDay
26%6%13%31%18%2
2311
August1st to 15thDay
28%6%18%23%19%3
2326
16th to endDay
29%5%13%26%18%6%
2429
September1st to 15thDay
37%5%10%23%15%7%
1926
16th to endDay
29%5%9%25%24%5%
1815
October1st to 15thDay
30%310%24%25%4
1702
16th to endDay
28%29%27%25%6%
1760
November1st to 15thDay
24%311%27%25%7%
1659
16th to endDay
29%29%25%27%5%
1620
December1st to 15thDay
37%311%31%15%
1620
16th to endDay
41%210%23%17%4
1728
January1st to 15thNight
28%38%29%24%4
2327
16th to endNight
29%210%29%22%6%
2496
February1st to 15thNight
37%310%25%17%4
2262
16th to endNight
30%411%27%19%6%
1894
March1st to 15thNight
34%410%23%20%7%
1983
16th to endNight
38%412%24%16%2
2112
April1st to 15thNight
31%412%23%22%5%
1926
16th to endNight
36%311%23%18%5%
1652
May1st to 15thNight
35%412%22%20%3
1620
16th to endNight
32%7%16%26%15%1
1685
June1st to 15thNight
24%5%15%31%19%3
1620
16th to endNight
19%416%30%23%5%
1620
July1st to 15thNight
26%5%12%30%21%3
1530
16th to endNight
21%5%12%32%23%3
1594
August1st to 15thNight
25%6%12%31%18%5%
1610
16th to endNight
25%6%11%26%23%6%
1773
September1st to 15thNight
32%410%24%17%9%
1919
16th to endNight
26%310%26%26%6%
1815
October1st to 15thNight
32%39%20%22%10%
1917
16th to endNight
20%37%28%32%7%
2112
November1st to 15thNight
24%210%25%27%9%
2196
16th to endNight
30%28%25%26%6%
2340
December1st to 15thNight
34%311%28%20%1
2340
16th to endNight
35%211%24%18%7%
2496

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
25%11%30%25%7%
90
16th to endDay
13%16%40%23%41
96
February1st to 15thDay
5%22%46%21%4
90
16th to endDay
8%25%37%23%4
81
March1st to 15thDay
20%26%41%12%
90
16th to endDay
25%13%35%20%32
96
April1st to 15thDay
16%16%36%24%5%
141
16th to endDay
21%14%37%18%6%1
416
May1st to 15thDay
16%13%33%25%9%1
468
16th to endDay
16%9%34%24%12%2
517
June1st to 15thDay
8%327%35%21%2
495
16th to endDay
5%322%42%23%2
495
July1st to 15thDay
11%115%39%29%3
475
16th to endDay
5%9%36%39%8%
515
August1st to 15thDay
6%110%39%35%6%
493
16th to endDay
7%112%35%37%6%
469
September1st to 15thDay
4213%39%34%6%
123
16th to endDay
8%325%25%21%15%
90
October1st to 15thDay
313%28%26%18%8%
90
16th to endDay
47%34%42%7%4
96
November1st to 15thDay
10%233%18%33%2
90
16th to endDay
26%25%26%15%41
90
December1st to 15thDay
13%8%51%18%5%2
90
16th to endDay
18%17%34%22%6%
96
January1st to 15thNight
12%13%36%30%6%
900
16th to endNight
11%11%41%29%5%
960
February1st to 15thNight
15%13%37%28%4
854
16th to endNight
12%14%38%30%4
632
March1st to 15thNight
13%11%36%32%5%
543
16th to endNight
18%11%37%27%5%
576
April1st to 15thNight
13%15%38%26%5%
539
16th to endNight
18%8%40%23%8%
540
May1st to 15thNight
15%6%38%27%10%
540
16th to endNight
12%6%30%33%15%1
563
June1st to 15thNight
6%429%38%20%
540
16th to endNight
5%232%41%17%
540
July1st to 15thNight
5%119%47%22%1
510
16th to endNight
49%44%37%3
564
August1st to 15thNight
6%13%45%32%2
539
16th to endNight
5%13%39%38%2
573
September1st to 15thNight
12%317%35%28%3
525
16th to endNight
10%322%35%23%4
492
October1st to 15thNight
14%5%31%26%19%2
597
16th to endNight
8%7%39%29%15%
704
November1st to 15thNight
10%9%36%29%12%1
796
16th to endNight
16%13%33%28%7%
900
December1st to 15thNight
17%12%34%29%5%
900
16th to endNight
16%12%34%30%6%
960
Page generated at 2017-09-11 18:35:19. Version ac04

Copyright 2017 A. Danko


Adams Ranch Dark Sky Site Clear Sky Chart | Charts Home