Apache Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Apache Point 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
52%
15485
31%
46925
19%
15441
63%
15441
40%
24533

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
47%
718
29%
2327
20%
716
60%
716
37%
1182
January16th to endNight
43%
768
33%
2496
20%
768
59%
768
35%
1314
February1st to 15thNight
45%
704
33%
2134
19%
699
60%
699
42%
1066
February16th to endNight
29%
632
36%
1894
14%
632
51%
632
36%
971
March1st to 15thNight
43%
720
34%
2031
16%
720
58%
720
38%
1099
March16th to endNight
43%
717
37%
2061
16%
717
60%
717
45%
1019
April1st to 15thNight
31%
539
33%
1798
14%
539
56%
539
32%
894
April16th to endNight
33%
540
39%
1800
18%
540
62%
540
42%
788
May1st to 15thNight
40%
540
30%
1799
18%
539
59%
539
43%
817
May16th to endNight
44%
561
31%
1787
17%
561
63%
561
47%
841
June1st to 15thNight
60%
540
30%
1440
20%
540
67%
540
50%
767
June16th to endNight
65%
540
22%
1497
18%
540
67%
540
41%
856
July1st to 15thNight
68%
510
22%
1530
19%
510
70%
510
37%
874
July16th to endNight
74%
564
20%
1596
18%
531
75%
531
31%
965
August1st to 15thNight
75%
539
18%
1789
21%
536
76%
536
29%
1076
August16th to endNight
72%
573
23%
1910
26%
573
75%
573
30%
1129
September1st to 15thNight
67%
525
22%
1750
22%
525
69%
525
29%
1040
September16th to endNight
67%
492
32%
1757
30%
492
74%
492
41%
847
October1st to 15thNight
57%
656
35%
1976
23%
656
66%
656
48%
974
October16th to endNight
62%
704
39%
2112
25%
704
72%
704
54%
981
November1st to 15thNight
58%
715
39%
2115
22%
715
70%
715
54%
984
November16th to endNight
54%
900
36%
2340
20%
900
62%
900
45%
1266
December1st to 15thNight
45%
900
34%
2370
16%
900
57%
900
40%
1332
December16th to endNight
37%
888
29%
2616
16%
888
50%
888
35%
1451

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
5%42442445%7%55%
47672
Night
5%413323446%58%
47125
Cloud CoverDay
5%42442445%7%55%
47670
Night
5%41332345%6%58%
47125
TransparencyDay
25%5%8%16%25%17%
47370
Night
23%48%17%27%18%
46929
SeeingDay
7%16%26%28%17%4
5244
Night
7%11%24%30%21%4
15489

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
46%24312345%61%
1611
16th to endDay
10%6%22313345%56%
1728
February1st to 15thDay
5%423223235%64%
1724
16th to endDay
5%5%23312235%63%
1580
March1st to 15thDay
6%6%23313337%57%
1926
16th to endDay
4414313235%65%
2163
April1st to 15thDay
4314313346%62%
2150
16th to endDay
3212112235%73%
2160
May1st to 15thDay
3314324436%62%
2151
16th to endDay
3212313347%67%
2317
June1st to 15thDay
221121345%7%65%
2520
16th to endDay
33144346%7%9%51%
2456
July1st to 15thDay
8%426%7%47%6%8%10%32%
2340
16th to endDay
9%5%37%6%47%9%9%9%27%
2461
August1st to 15thDay
8%426%7%6%6%8%9%9%30%
2160
16th to endDay
7%5%27%7%37%6%7%9%34%
2292
September1st to 15thDay
12%5%26%7%35%5%6%7%37%
2097
16th to endDay
6%3134235%5%5%56%
1873
October1st to 15thDay
5%41442225%6%60%
1650
16th to endDay
321221223471%
1760
November1st to 15thDay
2412212346%67%
1729
16th to endDay
6%312223335%63%
1620
December1st to 15thDay
8%5%12312448%58%
1587
16th to endDay
6%10%33322336%53%
1617
January1st to 15thNight
46%2332433461%
2327
16th to endNight
8%5%23323436%57%
2496
February1st to 15thNight
46%12413346%61%
2126
16th to endNight
7%5%12313245%62%
1894
March1st to 15thNight
6%424224345%59%
2031
16th to endNight
5%412213245%67%
2061
April1st to 15thNight
5%413334445%60%
1798
16th to endNight
4312212135%70%
1800
May1st to 15thNight
332223435%66%
1799
16th to endNight
321212435%5%66%
1786
June1st to 15thNight
21135%335%5%7%60%
1440
16th to endNight
2225%5%45%6%6%9%48%
1497
July1st to 15thNight
5%324435%6%6%11%44%
1620
16th to endNight
43245%37%7%8%13%38%
1704
August1st to 15thNight
5%3146%35%9%9%12%36%
1800
16th to endNight
3325%5%45%6%8%10%42%
1910
September1st to 15thNight
8%425%5%45%5%6%7%43%
1750
16th to endNight
6%31232445%6%59%
1757
October1st to 15thNight
5%312222247%63%
1976
16th to endNight
321321232373%
2112
November1st to 15thNight
3312213337%67%
2115
16th to endNight
6%324222235%63%
2340
December1st to 15thNight
8%5%13312345%59%
2370
16th to endNight
7%7%25%423335%55%
2616

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
46%1441334461%
1611
16th to endDay
9%6%22313245%57%
1728
February1st to 15thDay
5%423213235%64%
1724
16th to endDay
5%5%14312235%63%
1580
March1st to 15thDay
6%5%24313236%58%
1926
16th to endDay
4423313235%65%
2161
April1st to 15thDay
4414323346%63%
2150
16th to endDay
3212112235%73%
2160
May1st to 15thDay
2313324446%63%
2151
16th to endDay
3212223347%68%
2317
June1st to 15thDay
221122345%6%67%
2520
16th to endDay
3224435%6%7%8%53%
2456
July1st to 15thDay
7%426%7%48%7%9%9%33%
2340
16th to endDay
8%5%26%7%47%9%10%9%27%
2461
August1st to 15thDay
7%5%36%7%47%8%9%10%30%
2160
16th to endDay
6%5%36%6%46%7%7%9%35%
2292
September1st to 15thDay
10%6%26%6%35%6%6%7%37%
2097
16th to endDay
6%3133235%5%7%57%
1873
October1st to 15thDay
5%314323246%62%
1650
16th to endDay
321121223472%
1760
November1st to 15thDay
3313212345%68%
1729
16th to endDay
6%412223335%63%
1620
December1st to 15thDay
7%5%12213348%59%
1587
16th to endDay
7%9%24323346%53%
1617
January1st to 15thNight
45%2332443461%
2327
16th to endNight
9%423313346%57%
2496
February1st to 15thNight
5%5%12313346%62%
2126
16th to endNight
7%5%13313235%62%
1894
March1st to 15thNight
7%41332434459%
2031
16th to endNight
7%31211333467%
2061
April1st to 15thNight
5%313424346%60%
1798
16th to endNight
5%31221223470%
1800
May1st to 15thNight
3312214435%67%
1799
16th to endNight
321221345%6%66%
1786
June1st to 15thNight
21134245%6%6%60%
1440
16th to endNight
22245%45%5%6%8%50%
1497
July1st to 15thNight
44145%36%5%7%10%45%
1620
16th to endNight
42245%36%7%9%13%40%
1704
August1st to 15thNight
5%315%5%36%8%10%12%37%
1800
16th to endNight
2415%5%45%6%8%10%42%
1910
September1st to 15thNight
7%5%25%5%35%5%7%8%43%
1750
16th to endNight
6%213423446%60%
1757
October1st to 15thNight
431322225%7%64%
1976
16th to endNight
311331122473%
2112
November1st to 15thNight
3312212337%68%
2115
16th to endNight
6%423213235%63%
2340
December1st to 15thNight
8%413312346%59%
2370
16th to endNight
8%6%24423236%54%
2616

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
23%38%17%29%18%
1612
16th to endDay
28%35%16%30%15%
1728
February1st to 15thDay
22%25%17%27%24%
1725
16th to endDay
22%1414%34%21%
1580
March1st to 15thDay
25%35%13%32%18%
1926
16th to endDay
20%3412%36%22%
2163
April1st to 15thDay
21%3415%32%22%
2150
16th to endDay
14%1411%32%34%
2160
May1st to 15thDay
19%5%8%11%29%26%
2151
16th to endDay
15%4416%29%28%
2320
June1st to 15thDay
15%48%15%24%32%
2520
16th to endDay
23%7%9%16%20%21%
2456
July1st to 15thDay
36%11%15%16%12%7%
2201
16th to endDay
38%14%19%18%9%
2306
August1st to 15thDay
39%11%17%20%8%2
2147
16th to endDay
36%12%14%18%14%2
2292
September1st to 15thDay
39%7%12%18%16%5%
2097
16th to endDay
23%5%9%20%28%12%
1873
October1st to 15thDay
22%38%19%27%19%
1650
16th to endDay
16%3318%34%24%
1760
November1st to 15thDay
17%26%19%32%21%
1729
16th to endDay
21%4417%30%21%
1620
December1st to 15thDay
22%48%21%33%10%
1587
16th to endDay
29%47%21%28%8%
1617
January1st to 15thNight
25%46%15%30%17%
2327
16th to endNight
27%4415%31%15%
2496
February1st to 15thNight
22%36%14%27%25%
2136
16th to endNight
23%2313%35%20%
1894
March1st to 15thNight
24%35%14%31%20%
2031
16th to endNight
19%3413%37%21%
2061
April1st to 15thNight
23%45%12%36%18%
1798
16th to endNight
16%3412%32%30%
1800
May1st to 15thNight
17%35%15%31%25%
1800
16th to endNight
17%47%16%28%25%
1788
June1st to 15thNight
20%5%7%12%22%32%
1440
16th to endNight
25%7%12%16%15%22%
1497
July1st to 15thNight
28%7%14%24%18%7%
1530
16th to endNight
30%11%21%24%11%1
1596
August1st to 15thNight
30%12%19%24%11%2
1789
16th to endNight
30%10%15%23%17%2
1910
September1st to 15thNight
34%7%16%17%15%8%
1750
16th to endNight
22%5%10%19%29%12%
1757
October1st to 15thNight
20%37%18%29%20%
1976
16th to endNight
16%2318%28%30%
2112
November1st to 15thNight
15%2417%36%22%
2115
16th to endNight
23%2413%30%25%
2340
December1st to 15thNight
25%37%17%29%16%
2370
16th to endNight
29%39%18%28%10%
2616

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%28%23%23%5%1
90
16th to endDay
11%36%27%11%12%1
96
February1st to 15thDay
7%16%32%27%13%2
90
16th to endDay
7%34%25%22%7%2
81
March1st to 15thDay
11%25%42%16%31
216
16th to endDay
7%32%35%17%5%1
288
April1st to 15thDay
9%41%33%12%21
269
16th to endDay
10%40%33%12%2
270
May1st to 15thDay
432%42%17%2
288
16th to endDay
324%44%21%6%
357
June1st to 15thDay
37%26%35%22%4
495
16th to endDay
3223%34%31%4
431
July1st to 15thDay
6%215%42%26%6%
305
16th to endDay
9%9%32%37%11%
327
August1st to 15thDay
5%110%38%33%10%
315
16th to endDay
7%214%36%31%7%
332
September1st to 15thDay
13%217%40%21%5%
294
16th to endDay
10%229%43%12%2
148
October1st to 15thDay
11%7%27%32%14%6%
90
16th to endDay
10%6%25%32%16%9%
96
November1st to 15thDay
11%26%23%20%14%4
90
16th to endDay
14%34%17%23%10%
90
December1st to 15thDay
7%26%31%25%6%2
90
16th to endDay
25%29%22%18%4
96
January1st to 15thNight
7%12%28%30%16%4
720
16th to endNight
10%14%28%29%14%2
768
February1st to 15thNight
9%14%29%28%15%3
704
16th to endNight
8%23%36%23%6%1
632
March1st to 15thNight
7%20%25%30%13%1
720
16th to endNight
6%16%31%31%12%1
717
April1st to 15thNight
6%25%33%26%7%
539
16th to endNight
6%21%36%26%8%
540
May1st to 15thNight
419%34%32%9%
540
16th to endNight
310%38%34%11%1
563
June1st to 15thNight
2427%40%22%1
540
16th to endNight
2320%44%24%4
540
July1st to 15thNight
4115%37%36%4
510
16th to endNight
6%18%31%39%12%
564
August1st to 15thNight
5%17%23%46%15%
539
16th to endNight
3110%27%44%12%
573
September1st to 15thNight
8%212%33%35%8%
525
16th to endNight
7%415%36%30%5%
492
October1st to 15thNight
6%6%25%32%23%5%
656
16th to endNight
37%21%30%27%8%
704
November1st to 15thNight
5%11%23%27%25%6%
715
16th to endNight
9%12%19%31%21%5%
900
December1st to 15thNight
11%15%24%32%14%2
900
16th to endNight
12%15%30%27%12%2
888
Page generated at 2017-09-11 17:35:31. Version ac04

Copyright 2017 A. Danko


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