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 2018-02-22.

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
37%
16516
24%
48889
14%
16470
46%
16470
36%
27602

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
30%
974
26%
2522
11%
970
40%
970
38%
1481
January16th to endNight
28%
1040
29%
2704
9%
1040
40%
1040
41%
1547
February1st to 15thNight
25%
926
21%
2454
8%
922
33%
922
31%
1540
February16th to endNight
26%
660
23%
1978
9%
660
37%
660
31%
1138
March1st to 15thNight
30%
543
23%
1983
14%
543
41%
543
27%
1096
March16th to endNight
27%
576
16%
2112
11%
576
34%
576
24%
1247
April1st to 15thNight
24%
539
20%
1926
11%
539
38%
539
28%
1037
April16th to endNight
23%
540
18%
1652
10%
540
35%
540
30%
1000
May1st to 15thNight
30%
539
21%
1620
14%
539
42%
539
31%
976
May16th to endNight
37%
563
18%
1684
14%
561
44%
561
31%
1011
June1st to 15thNight
45%
540
18%
1620
12%
540
51%
540
41%
870
June16th to endNight
47%
540
20%
1620
14%
540
53%
540
51%
795
July1st to 15thNight
57%
510
17%
1530
15%
510
60%
510
41%
838
July16th to endNight
65%
564
23%
1594
26%
531
70%
531
47%
821
August1st to 15thNight
66%
539
25%
1610
28%
536
70%
536
41%
874
August16th to endNight
67%
573
26%
1773
27%
573
69%
573
40%
949
September1st to 15thNight
56%
540
23%
1974
26%
540
60%
540
32%
1066
September16th to endNight
54%
537
28%
1980
25%
537
62%
537
37%
974
October1st to 15thNight
39%
651
28%
2091
20%
651
46%
651
33%
1180
October16th to endNight
40%
768
32%
2304
15%
768
53%
768
48%
1126
November1st to 15thNight
34%
864
28%
2384
13%
864
45%
864
43%
1304
November16th to endNight
30%
975
27%
2535
11%
975
39%
975
39%
1485
December1st to 15thNight
29%
975
23%
2535
10%
975
38%
975
36%
1543
December16th to endNight
28%
1040
24%
2704
10%
1040
38%
1040
32%
1704

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
22%414323346%43%
49365
Night
22%313322345%47%
49085
Cloud CoverDay
10%5%2442445%7%49%
49363
Night
9%423323347%54%
49085
TransparencyDay
34%412%25%18%3
49063
Night
30%411%26%21%5%
48890
SeeingDay
11%7%26%30%19%3
6286
Night
12%8%32%32%13%1
16518

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
23%5%1432222447%
1746
16th to endDay
22%6%14211125%49%
1872
February1st to 15thDay
22%7%2442234441%
1750
16th to endDay
24%6%24312335%42%
1642
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%14424336%45%
1984
16th to endDay
16%313424446%46%
1980
October1st to 15thDay
18%413323345%50%
1857
16th to endDay
14%213312235%57%
1920
November1st to 15thDay
20%41221233452%
1801
16th to endDay
25%41221122450%
1755
December1st to 15thDay
27%5%13313345%39%
1755
16th to endDay
26%6%3442222439%
1872
January1st to 15thNight
23%413312245%47%
2522
16th to endNight
21%31321233352%
2704
February1st to 15thNight
23%6%2332223345%
2444
16th to endNight
24%5%1231223445%
1978
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%50%
1974
16th to endNight
15%31242335%6%50%
1980
October1st to 15thNight
20%41332233450%
2091
16th to endNight
14%12212235%62%
2304
November1st to 15thNight
20%31331223454%
2384
16th to endNight
26%31221213449%
2535
December1st to 15thNight
25%414312235%43%
2535
16th to endNight
25%6%2432223442%
2704

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
10%5%24323335%54%
1746
16th to endDay
9%6%24312236%55%
1872
February1st to 15thDay
9%8%45%423345%47%
1750
16th to endDay
10%6%24423446%49%
1642
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
11%5%25%434436%48%
1984
16th to endDay
9%314324447%52%
1980
October1st to 15thDay
10%423323345%55%
1857
16th to endDay
7%323313245%61%
1920
November1st to 15thDay
7%5%13223346%58%
1801
16th to endDay
11%422312336%58%
1755
December1st to 15thDay
13%5%2442335%6%49%
1755
16th to endDay
13%7%35%423436%45%
1872
January1st to 15thNight
10%413422347%55%
2522
16th to endNight
7%42432333461%
2704
February1st to 15thNight
11%6%33423335%51%
2444
16th to endNight
10%5%2332335%6%52%
1978
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%413424346%53%
1974
16th to endNight
8%31242335%7%57%
1980
October1st to 15thNight
12%42332333455%
2091
16th to endNight
6%212212335%67%
2304
November1st to 15thNight
8%313323245%60%
2384
16th to endNight
12%423313235%58%
2535
December1st to 15thNight
12%424313346%53%
2535
16th to endNight
13%6%34323346%49%
2704

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
33%210%30%20%2
1747
16th to endDay
31%211%28%22%2
1872
February1st to 15thDay
39%314%26%12%3
1751
16th to endDay
35%210%28%17%4
1642
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
36%5%10%23%16%7%
1984
16th to endDay
29%5%9%26%22%5%
1980
October1st to 15thDay
30%311%23%24%5%
1857
16th to endDay
26%210%27%25%7%
1920
November1st to 15thDay
26%311%27%23%6%
1801
16th to endDay
28%29%26%28%4
1755
December1st to 15thDay
36%310%30%16%1
1755
16th to endDay
42%211%22%16%4
1872
January1st to 15thNight
29%39%30%23%4
2522
16th to endNight
27%29%29%23%6%
2704
February1st to 15thNight
36%312%25%16%4
2454
16th to endNight
32%411%26%18%6%
1978
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
31%410%24%18%9%
1974
16th to endNight
26%310%28%25%5%
1980
October1st to 15thNight
33%39%19%22%10%
2091
16th to endNight
20%37%27%33%8%
2304
November1st to 15thNight
26%210%25%25%8%
2384
16th to endNight
30%28%25%27%6%
2535
December1st to 15thNight
32%311%28%21%2
2535
16th to endNight
36%312%24%17%6%
2704

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
22%11%34%22%9%
135
16th to endDay
10%14%40%27%5%1
144
February1st to 15thDay
5%22%44%23%3
135
16th to endDay
13%27%37%19%4
100
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%35%34%10%
139
16th to endDay
11%227%30%17%10%
135
October1st to 15thDay
5%11%37%25%14%5%
135
16th to endDay
410%36%36%9%3
144
November1st to 15thDay
15%5%33%17%24%2
135
16th to endDay
21%20%31%21%4
135
December1st to 15thDay
11%9%50%21%5%1
135
16th to endDay
19%20%36%19%4
144
January1st to 15thNight
12%13%36%29%6%
975
16th to endNight
10%11%41%29%5%
1040
February1st to 15thNight
15%13%38%28%4
926
16th to endNight
14%14%36%29%4
660
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
11%217%35%28%3
540
16th to endNight
11%322%35%22%4
537
October1st to 15thNight
15%5%31%26%19%2
651
16th to endNight
8%8%38%30%14%
768
November1st to 15thNight
11%8%36%29%12%1
864
16th to endNight
16%12%33%29%8%
975
December1st to 15thNight
16%12%34%30%6%
975
16th to endNight
16%12%34%30%5%
1040
Page generated at 2018-02-23 10:21:32. Version ac04

Copyright 2018 A. Danko


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