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 2018-03-11.

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%
16234
31%
49165
20%
16190
63%
16190
40%
25663

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
49%
778
30%
2522
21%
776
61%
776
37%
1287
January16th to endNight
45%
832
34%
2704
22%
832
61%
832
36%
1397
February1st to 15thNight
46%
764
34%
2316
20%
759
61%
759
42%
1150
February16th to endNight
28%
684
34%
2050
13%
684
50%
684
34%
1076
March1st to 15thNight
43%
764
33%
2156
15%
764
58%
764
39%
1162
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%
540
22%
1800
23%
540
70%
540
30%
1057
September16th to endNight
66%
537
33%
1917
31%
537
74%
537
40%
937
October1st to 15thNight
57%
716
33%
2156
22%
716
65%
716
49%
1057
October16th to endNight
63%
768
41%
2304
25%
768
73%
768
54%
1069
November1st to 15thNight
57%
776
38%
2296
22%
776
69%
776
53%
1072
November16th to endNight
55%
975
37%
2535
21%
975
64%
975
46%
1361
December1st to 15thNight
45%
975
33%
2568
16%
975
56%
975
40%
1450
December16th to endNight
38%
962
31%
2834
17%
962
51%
962
36%
1562

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%
49432
Night
5%413323446%58%
49365
Cloud CoverDay
5%42432445%6%56%
49430
Night
5%41332345%6%59%
49365
TransparencyDay
24%5%8%16%26%17%
49130
Night
23%48%16%27%18%
49169
SeeingDay
7%16%26%28%16%3
5806
Night
7%11%24%31%21%4
16238

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%60%
1746
16th to endDay
9%6%23313345%57%
1872
February1st to 15thDay
5%423223235%64%
1872
16th to endDay
6%6%23312235%61%
1710
March1st to 15thDay
6%6%23313336%57%
2037
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
11%5%26%7%35%5%6%7%38%
2160
16th to endDay
6%3134235%5%5%56%
2043
October1st to 15thDay
5%41442225%6%61%
1800
16th to endDay
321221223472%
1920
November1st to 15thDay
25%12212346%66%
1876
16th to endDay
6%312223345%64%
1755
December1st to 15thDay
8%5%12313347%58%
1719
16th to endDay
5%9%33312446%54%
1752
January1st to 15thNight
46%2332433460%
2522
16th to endNight
8%423322336%59%
2704
February1st to 15thNight
46%12313346%62%
2308
16th to endNight
8%5%12313345%60%
2050
March1st to 15thNight
6%424224336%59%
2156
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%44%
1800
16th to endNight
6%31342445%6%58%
1917
October1st to 15thNight
4313222347%64%
2156
16th to endNight
321321232373%
2304
November1st to 15thNight
3212213247%67%
2296
16th to endNight
6%324222235%64%
2535
December1st to 15thNight
8%5%13322445%58%
2568
16th to endNight
7%6%14423335%56%
2834

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%1331345%460%
1746
16th to endDay
8%6%22313245%58%
1872
February1st to 15thDay
5%423213236%64%
1872
16th to endDay
6%6%14312335%62%
1710
March1st to 15thDay
6%5%24314236%58%
2037
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%25%6%35%6%6%7%38%
2160
16th to endDay
6%313424447%57%
2043
October1st to 15thDay
5%314313246%63%
1800
16th to endDay
321121223473%
1920
November1st to 15thDay
3313212345%67%
1876
16th to endDay
5%412223335%64%
1755
December1st to 15thDay
7%6%12212347%59%
1719
16th to endDay
6%9%23323346%54%
1752
January1st to 15thNight
5%5%2332443461%
2522
16th to endNight
8%423313346%59%
2704
February1st to 15thNight
5%5%12313346%62%
2308
16th to endNight
9%5%1321324460%
2050
March1st to 15thNight
6%413313345%59%
2156
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%44%
1800
16th to endNight
5%213424446%59%
1917
October1st to 15thNight
331322225%6%65%
2156
16th to endNight
411231122473%
2304
November1st to 15thNight
3312212337%68%
2296
16th to endNight
6%423213235%64%
2535
December1st to 15thNight
8%5%13312346%58%
2568
16th to endNight
7%6%24423236%55%
2834

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%30%17%
1747
16th to endDay
26%45%15%32%15%
1872
February1st to 15thDay
22%25%17%28%22%
1873
16th to endDay
24%1413%33%22%
1710
March1st to 15thDay
25%35%13%31%19%
2037
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
38%7%11%18%18%5%
2160
16th to endDay
24%5%8%20%28%12%
2043
October1st to 15thDay
22%38%19%28%19%
1800
16th to endDay
15%3419%33%24%
1920
November1st to 15thDay
17%26%21%31%20%
1876
16th to endDay
20%4417%31%21%
1755
December1st to 15thDay
23%38%20%32%10%
1719
16th to endDay
28%47%21%27%10%
1752
January1st to 15thNight
25%46%15%31%16%
2522
16th to endNight
26%4415%32%17%
2704
February1st to 15thNight
21%36%14%28%24%
2318
16th to endNight
25%2312%34%20%
2050
March1st to 15thNight
24%3413%31%21%
2156
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
33%7%15%18%17%8%
1800
16th to endNight
23%5%10%19%29%12%
1917
October1st to 15thNight
19%37%18%30%20%
2156
16th to endNight
16%2318%28%30%
2304
November1st to 15thNight
15%35%19%35%20%
2296
16th to endNight
22%2413%31%25%
2535
December1st to 15thNight
25%37%17%29%16%
2568
16th to endNight
28%39%18%27%12%
2834

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%25%22%25%7%1
135
16th to endDay
7%30%21%20%17%2
144
February1st to 15thDay
9%15%34%25%11%2
135
16th to endDay
15%39%21%17%5%1
120
March1st to 15thDay
11%24%43%16%31
254
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
12%218%40%20%5%
315
16th to endDay
9%436%39%9%1
198
October1st to 15thDay
9%8%31%31%13%5%
135
16th to endDay
6%6%25%32%19%9%
144
November1st to 15thDay
8%28%25%22%11%2
135
16th to endDay
9%28%21%27%12%
135
December1st to 15thDay
11%25%25%26%9%1
135
16th to endDay
17%29%24%21%7%
144
January1st to 15thNight
7%11%27%31%16%4
780
16th to endNight
9%14%26%29%16%3
832
February1st to 15thNight
8%13%28%30%15%3
764
16th to endNight
10%22%35%23%6%1
684
March1st to 15thNight
7%19%25%31%13%1
764
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
7%211%33%36%8%
540
16th to endNight
6%5%16%37%28%5%
537
October1st to 15thNight
6%6%26%32%24%5%
716
16th to endNight
47%21%29%28%8%
768
November1st to 15thNight
5%10%24%27%25%6%
776
16th to endNight
8%12%18%31%22%5%
975
December1st to 15thNight
11%14%24%31%16%2
975
16th to endNight
12%14%30%27%13%1
962
Page generated at 2018-03-12 11:28:12. Version ac04

Copyright 2018 A. Danko


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