Armstrong
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Armstrong clear sky chart from 2005-11-05 to 2017-10-06.

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%
16137
18%
47116
10%
16090
44%
16090
27%
30292

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
28%
900
14%
2461
6%
895
34%
895
20%
1756
January16th to endNight
24%
960
15%
2496
5%
960
31%
960
19%
1813
February1st to 15thNight
26%
879
11%
2288
2%
875
32%
875
20%
1665
February16th to endNight
28%
756
18%
2018
6%
756
37%
756
24%
1377
March1st to 15thNight
33%
540
18%
1980
11%
540
43%
540
24%
1191
March16th to endNight
26%
576
14%
2112
9%
576
35%
576
15%
1451
April1st to 15thNight
28%
539
17%
1821
12%
539
38%
539
21%
1171
April16th to endNight
28%
540
19%
1647
12%
540
38%
540
20%
1145
May1st to 15thNight
37%
540
17%
1581
10%
540
44%
540
28%
1021
May16th to endNight
41%
563
15%
1498
6%
561
46%
561
31%
980
June1st to 15thNight
50%
540
14%
1440
5%
540
54%
540
35%
915
June16th to endNight
54%
540
19%
1440
7%
540
59%
540
46%
809
July1st to 15thNight
64%
510
18%
1360
8%
510
67%
510
51%
719
July16th to endNight
67%
564
23%
1532
16%
531
69%
531
50%
775
August1st to 15thNight
64%
539
23%
1610
21%
536
68%
536
41%
880
August16th to endNight
60%
573
24%
1774
24%
573
65%
573
39%
977
September1st to 15thNight
60%
540
26%
1812
24%
540
68%
540
41%
913
September16th to endNight
46%
549
25%
1992
18%
549
59%
549
32%
1055
October1st to 15thNight
36%
684
25%
2052
14%
684
45%
684
31%
1245
October16th to endNight
35%
704
19%
2112
10%
704
43%
704
27%
1322
November1st to 15thNight
33%
841
24%
2362
10%
841
44%
841
29%
1462
November16th to endNight
28%
900
17%
2520
8%
900
35%
900
23%
1703
December1st to 15thNight
22%
900
11%
2520
3%
900
29%
900
18%
1868
December16th to endNight
22%
960
13%
2688
5%
960
30%
960
15%
2079

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%36%5%3445%7%38%
48078
Night
12%7%35%5%24446%43%
47295
Cloud CoverDay
14%7%36%5%3445%7%38%
48089
Night
12%7%35%424446%43%
47299
Cloud CoverDay
13%7%36%5%3445%7%38%
48087
Night
12%7%35%42445%6%43%
47299
TransparencyDay
44%414%23%11%1
47775
Night
41%414%24%13%1
47116
SeeingDay
16%6%28%29%14%3
6139
Night
15%8%32%31%11%1
16138

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
8%11%7%8%8%35%5%5%7%27%
1474
16th to endDay
11%11%7%10%7%45%5%5%6%23%
1728
February1st to 15thDay
10%13%5%11%8%3445%5%26%
1575
16th to endDay
12%8%48%7%445%5%6%31%
1464
March1st to 15thDay
14%9%6%9%5%23445%33%
1969
16th to endDay
19%9%46%5%3445%7%29%
2112
April1st to 15thDay
16%8%37%5%2445%7%34%
2127
16th to endDay
26%10%35%423345%28%
2310
May1st to 15thDay
21%7%35%5%34447%33%
2370
16th to endDay
16%5%25%5%4445%6%38%
2617
June1st to 15thDay
15%5%25%5%3445%8%39%
2520
16th to endDay
8%4245%25%5%6%8%45%
2520
July1st to 15thDay
6%214445%5%6%9%49%
2520
16th to endDay
6%423425%5%7%10%48%
2528
August1st to 15thDay
9%5%25%6%35%5%5%8%42%
2340
16th to endDay
12%42443445%6%45%
2427
September1st to 15thDay
12%32442435%7%50%
2146
16th to endDay
13%423414346%50%
1956
October1st to 15thDay
15%5%24433345%47%
1706
16th to endDay
15%9%34433346%42%
1760
November1st to 15thDay
10%7%25%31445%7%46%
1493
16th to endDay
14%8%5%5%433348%38%
1440
December1st to 15thDay
15%9%5%11%10%45%435%25%
1440
16th to endDay
17%15%5%9%6%23436%23%
1536
January1st to 15thNight
8%7%47%8%36%5%7%8%31%
2461
16th to endNight
11%11%48%5%35%45%7%31%
2496
February1st to 15thNight
11%12%5%8%5%3445%6%33%
2285
16th to endNight
10%8%46%6%34447%39%
2018
March1st to 15thNight
12%7%35%324447%43%
1968
16th to endNight
16%9%5%7%5%24435%35%
2112
April1st to 15thNight
16%6%35%5%25%35%5%40%
1821
16th to endNight
21%9%25%424335%36%
1647
May1st to 15thNight
16%5%1332445%6%44%
1581
16th to endNight
14%415%42445%8%42%
1496
June1st to 15thNight
10%2145%345%6%10%43%
1440
16th to endNight
7%21342335%8%57%
1440
July1st to 15thNight
321232445%7%61%
1440
16th to endNight
311331345%10%59%
1638
August1st to 15thNight
5%3145%245%5%8%55%
1620
16th to endNight
9%414424235%58%
1774
September1st to 15thNight
9%412323347%58%
1812
16th to endNight
10%41322345%7%52%
1992
October1st to 15thNight
14%5%14424335%50%
2052
16th to endNight
17%7%14423346%45%
2112
November1st to 15thNight
11%6%25%433446%47%
2362
16th to endNight
12%9%36%424447%40%
2520
December1st to 15thNight
14%10%5%9%7%34435%30%
2520
16th to endNight
18%12%5%7%7%3444427%
2688

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
9%10%6%10%7%4446%7%27%
1474
16th to endDay
11%12%6%10%8%35%5%5%6%24%
1728
February1st to 15thDay
10%13%6%10%8%25%445%27%
1575
16th to endDay
12%8%48%7%345%5%6%31%
1464
March1st to 15thDay
15%9%6%9%5%23445%33%
1980
16th to endDay
19%10%46%5%34447%29%
2112
April1st to 15thDay
16%8%36%5%2445%7%34%
2127
16th to endDay
26%10%35%423346%28%
2310
May1st to 15thDay
21%7%35%5%2435%7%34%
2370
16th to endDay
17%5%25%445%45%6%38%
2617
June1st to 15thDay
15%5%25%5%2445%8%40%
2520
16th to endDay
8%424435%5%5%8%46%
2520
July1st to 15thDay
6%214435%5%6%9%49%
2520
16th to endDay
6%423425%5%7%10%49%
2528
August1st to 15thDay
9%425%6%35%5%5%8%42%
2340
16th to endDay
12%5%1443446%7%45%
2427
September1st to 15thDay
12%323323348%51%
2146
16th to endDay
13%423424346%50%
1956
October1st to 15thDay
16%5%24433335%47%
1706
16th to endDay
16%8%35%323246%42%
1760
November1st to 15thDay
10%7%25%3245%47%47%
1493
16th to endDay
14%8%45%433347%38%
1440
December1st to 15thDay
15%9%5%10%9%45%435%25%
1440
16th to endDay
17%15%5%8%7%23446%23%
1536
January1st to 15thNight
9%8%47%7%35%5%7%8%32%
2461
16th to endNight
12%10%49%5%3445%7%31%
2496
February1st to 15thNight
11%12%5%7%6%2445%6%33%
2278
16th to endNight
10%8%46%6%34447%39%
2018
March1st to 15thNight
13%7%35%323447%43%
1980
16th to endNight
17%9%47%5%34445%34%
2112
April1st to 15thNight
16%6%26%42444441%
1821
16th to endNight
21%8%35%424335%36%
1647
May1st to 15thNight
17%42332445%6%44%
1580
16th to endNight
14%5%1443445%8%42%
1496
June1st to 15thNight
10%3246%246%6%10%43%
1440
16th to endNight
7%21342345%7%58%
1440
July1st to 15thNight
32231445%8%62%
1440
16th to endNight
321332445%10%59%
1638
August1st to 15thNight
5%413424448%55%
1620
16th to endNight
9%414423335%58%
1774
September1st to 15thNight
9%312222347%58%
1812
16th to endNight
11%41332435%7%53%
1992
October1st to 15thNight
14%6%1442323451%
2052
16th to endNight
17%7%14423336%45%
2112
November1st to 15thNight
11%6%25%433345%48%
2362
16th to endNight
12%9%36%424446%40%
2520
December1st to 15thNight
14%11%5%9%7%34345%30%
2520
16th to endNight
18%12%48%6%3344427%
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
8%11%6%9%8%35%5%5%7%27%
1474
16th to endDay
11%12%6%10%8%36%46%5%24%
1728
February1st to 15thDay
10%13%6%10%8%35%5%5%5%26%
1575
16th to endDay
13%7%49%8%3445%7%31%
1464
March1st to 15thDay
14%10%6%10%5%23445%33%
1980
16th to endDay
19%10%36%5%3445%7%28%
2110
April1st to 15thDay
17%8%37%4235%5%6%34%
2127
16th to endDay
26%10%35%423345%28%
2310
May1st to 15thDay
21%7%345%34347%33%
2370
16th to endDay
16%5%25%5%35%5%5%6%37%
2617
June1st to 15thDay
15%5%25%6%2445%8%40%
2520
16th to endDay
8%4145%35%5%6%8%45%
2520
July1st to 15thDay
5%214435%5%6%9%49%
2520
16th to endDay
5%4144245%7%10%47%
2528
August1st to 15thDay
8%5%25%6%35%5%5%7%42%
2340
16th to endDay
11%5%2442446%6%45%
2427
September1st to 15thDay
11%424324448%50%
2146
16th to endDay
12%424323446%50%
1956
October1st to 15thDay
15%5%24423345%47%
1706
16th to endDay
16%8%34423346%42%
1760
November1st to 15thDay
10%6%25%324447%47%
1493
16th to endDay
14%9%45%5%33347%38%
1440
December1st to 15thDay
16%9%411%9%5%4335%25%
1440
16th to endDay
18%15%5%8%6%23437%23%
1536
January1st to 15thNight
8%8%47%7%36%5%7%7%31%
2461
16th to endNight
11%11%48%6%4445%7%31%
2496
February1st to 15thNight
11%13%46%5%34446%33%
2278
16th to endNight
9%8%47%5%35%45%6%39%
2018
March1st to 15thNight
12%8%35%324447%43%
1980
16th to endNight
16%10%47%424445%34%
2112
April1st to 15thNight
16%6%26%425%445%40%
1821
16th to endNight
21%9%35%424335%36%
1647
May1st to 15thNight
16%5%243245%5%6%44%
1580
16th to endNight
14%42443445%9%41%
1496
June1st to 15thNight
10%3145%245%6%10%42%
1440
16th to endNight
7%21242345%8%57%
1440
July1st to 15thNight
311232445%8%61%
1440
16th to endNight
321332445%10%59%
1638
August1st to 15thNight
5%32432345%8%55%
1620
16th to endNight
9%313413345%58%
1774
September1st to 15thNight
9%312323346%58%
1812
16th to endNight
11%41232445%7%52%
1992
October1st to 15thNight
14%5%2432333450%
2052
16th to endNight
17%6%23423446%44%
2112
November1st to 15thNight
11%6%25%433446%47%
2362
16th to endNight
12%9%36%5%24446%40%
2520
December1st to 15thNight
14%10%5%9%7%35%345%30%
2520
16th to endNight
18%12%47%7%3444427%
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
54%5%14%17%9%
1475
16th to endDay
59%415%16%4
1728
February1st to 15thDay
58%412%17%6%
1576
16th to endDay
51%6%13%19%8%1
1464
March1st to 15thDay
53%315%20%6%
1980
16th to endDay
53%5%14%20%5%
2112
April1st to 15thDay
48%314%22%8%1
2127
16th to endDay
58%311%19%7%
2310
May1st to 15thDay
50%413%22%8%
2370
16th to endDay
45%5%13%21%12%1
2621
June1st to 15thDay
42%415%24%11%1
2520
16th to endDay
34%5%15%28%14%1
2520
July1st to 15thDay
30%5%17%29%13%3
2371
16th to endDay
28%6%16%29%15%2
2371
August1st to 15thDay
37%6%15%27%11%1
2326
16th to endDay
36%5%13%28%13%2
2427
September1st to 15thDay
32%415%29%16%
2146
16th to endDay
35%312%33%13%
1956
October1st to 15thDay
39%212%24%19%1
1706
16th to endDay
43%215%25%12%
1760
November1st to 15thDay
36%414%24%18%1
1493
16th to endDay
46%5%18%20%9%
1440
December1st to 15thDay
62%412%12%7%1
1440
16th to endDay
61%313%14%6%
1536
January1st to 15thNight
48%6%13%21%10%
2461
16th to endNight
52%316%18%8%
2496
February1st to 15thNight
51%413%20%9%
2288
16th to endNight
44%313%24%11%2
2018
March1st to 15thNight
40%316%25%11%1
1980
16th to endNight
51%5%12%23%6%
2112
April1st to 15thNight
44%310%26%13%1
1821
16th to endNight
51%39%20%12%2
1647
May1st to 15thNight
39%6%13%24%14%1
1581
16th to endNight
39%415%24%13%2
1498
June1st to 15thNight
33%6%18%26%13%1
1440
16th to endNight
24%5%16%29%22%3
1440
July1st to 15thNight
19%5%17%34%17%4
1360
16th to endNight
20%417%34%19%4
1532
August1st to 15thNight
26%5%14%32%18%2
1610
16th to endNight
29%313%31%17%4
1774
September1st to 15thNight
25%314%32%22%1
1812
16th to endNight
30%413%32%18%1
1992
October1st to 15thNight
37%39%26%20%2
2052
16th to endNight
40%314%24%15%1
2112
November1st to 15thNight
37%312%24%20%1
2362
16th to endNight
45%416%22%10%1
2520
December1st to 15thNight
55%314%18%6%
2520
16th to endNight
59%411%15%9%
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
17%6%34%30%10%1
90
16th to endDay
19%10%32%30%5%2
96
February1st to 15thDay
15%21%35%24%3
90
16th to endDay
24%8%28%27%11%
81
March1st to 15thDay
24%11%36%27%
90
16th to endDay
39%7%25%20%7%
96
April1st to 15thDay
21%10%30%28%9%
246
16th to endDay
33%12%24%19%8%2
420
May1st to 15thDay
24%11%28%27%6%1
468
16th to endDay
19%6%31%26%12%2
517
June1st to 15thDay
14%429%32%15%3
495
16th to endDay
7%5%35%35%11%4
495
July1st to 15thDay
6%227%33%22%7%
475
16th to endDay
9%323%36%22%5%
515
August1st to 15thDay
8%321%34%27%4
493
16th to endDay
17%420%29%21%6%
467
September1st to 15thDay
11%324%35%21%4
301
16th to endDay
13%5%35%25%14%4
135
October1st to 15thDay
13%10%32%25%14%4
107
16th to endDay
21%8%37%19%11%1
96
November1st to 15thDay
27%34%38%12%4
90
16th to endDay
37%10%30%17%4
90
December1st to 15thDay
17%15%40%17%7%1
90
16th to endDay
32%15%33%14%4
96
January1st to 15thNight
13%11%38%27%7%1
900
16th to endNight
18%11%34%28%5%
960
February1st to 15thNight
17%10%35%28%6%1
880
16th to endNight
13%10%38%26%8%1
756
March1st to 15thNight
15%8%36%28%10%
540
16th to endNight
21%8%35%25%8%
576
April1st to 15thNight
20%9%35%28%5%
539
16th to endNight
25%8%32%23%8%1
540
May1st to 15thNight
19%7%32%30%9%
540
16th to endNight
16%5%30%33%12%
563
June1st to 15thNight
11%427%42%14%
540
16th to endNight
8%229%43%15%
540
July1st to 15thNight
4223%43%24%2
510
16th to endNight
3121%46%24%2
564
August1st to 15thNight
6%119%42%26%3
539
16th to endNight
11%119%40%21%4
573
September1st to 15thNight
11%222%40%21%2
540
16th to endNight
10%7%30%34%15%1
549
October1st to 15thNight
17%7%34%27%12%1
684
16th to endNight
21%8%30%30%9%
704
November1st to 15thNight
14%11%36%26%11%
841
16th to endNight
16%14%36%25%7%
900
December1st to 15thNight
19%10%37%28%4
900
16th to endNight
24%9%34%24%6%
960
Page generated at 2017-10-07 13:07:53. Version ac04

Copyright 2017 A. Danko


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