Divide
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Divide clear sky chart from 2005-11-05 to 2018-02-14.

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
42%
16570
26%
48812
13%
16525
55%
16525
34%
27003

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%
975
30%
2716
12%
970
51%
970
37%
1402
January16th to endNight
31%
848
34%
2720
16%
848
53%
848
39%
1305
February1st to 15thNight
23%
758
26%
2413
8%
755
43%
755
30%
1256
February16th to endNight
23%
632
34%
1894
7%
632
49%
632
33%
1001
March1st to 15thNight
32%
720
26%
2109
9%
720
47%
720
33%
1165
March16th to endNight
29%
681
27%
2025
10%
681
46%
681
31%
1146
April1st to 15thNight
30%
539
23%
1798
10%
539
48%
539
28%
967
April16th to endNight
28%
540
20%
1800
9%
540
45%
540
23%
1092
May1st to 15thNight
40%
540
18%
1648
12%
540
48%
540
24%
1052
May16th to endNight
41%
562
16%
1498
8%
561
49%
561
31%
943
June1st to 15thNight
58%
540
20%
1440
13%
540
64%
540
44%
788
June16th to endNight
67%
540
23%
1440
18%
540
70%
540
45%
802
July1st to 15thNight
63%
510
15%
1360
13%
510
65%
510
27%
915
July16th to endNight
72%
564
16%
1470
16%
531
73%
531
28%
957
August1st to 15thNight
67%
539
15%
1682
15%
536
68%
536
26%
1041
August16th to endNight
71%
573
21%
1910
23%
573
73%
573
31%
1113
September1st to 15thNight
65%
540
23%
1800
22%
540
70%
540
31%
1024
September16th to endNight
58%
537
32%
1932
25%
537
70%
537
38%
958
October1st to 15thNight
48%
708
29%
2148
15%
708
60%
708
41%
1119
October16th to endNight
50%
784
36%
2320
18%
784
62%
784
43%
1203
November1st to 15thNight
42%
950
32%
2470
15%
950
52%
950
45%
1310
November16th to endNight
37%
975
36%
2577
13%
975
53%
975
46%
1335
December1st to 15thNight
28%
975
25%
2730
7%
975
43%
975
33%
1460
December16th to endNight
24%
1040
28%
2912
9%
1040
41%
1040
29%
1649

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
46%35%5%35%5%5%8%47%
49275
Night
25%2442445%8%55%
48990
Cloud CoverDay
5%6%25%43446%7%49%
49273
Night
342432445%8%57%
48990
TransparencyDay
33%6%12%22%19%6%
48955
Night
26%5%13%26%20%6%
48812
SeeingDay
11%17%30%22%13%4
6267
Night
5%14%31%30%15%2
16573

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
5%24424348%59%
1552
16th to endDay
5%25%313447%60%
1868
February1st to 15thDay
5%37%42236%9%53%
1746
16th to endDay
6%36%42345%8%54%
1580
March1st to 15thDay
27%46%6%2445%8%47%
1850
16th to endDay
39%46%4245%6%9%44%
2198
April1st to 15thDay
49%26%5%35%45%7%44%
2150
16th to endDay
6%12%47%7%25%45%6%37%
2160
May1st to 15thDay
8%10%47%6%35%5%6%7%34%
2301
16th to endDay
6%7%36%5%37%5%6%7%40%
2616
June1st to 15thDay
5%5%25%435%6%6%8%45%
2520
16th to endDay
3325%436%6%6%8%49%
2520
July1st to 15thDay
8%5%26%6%5%7%6%6%9%35%
2520
16th to endDay
7%7%36%7%47%7%7%8%32%
2594
August1st to 15thDay
9%7%37%5%5%7%6%6%7%34%
2268
16th to endDay
7%5%26%6%25%5%7%9%40%
2292
September1st to 15thDay
8%6%26%6%35%5%6%6%44%
2160
16th to endDay
6%413323446%59%
2028
October1st to 15thDay
431332446%6%57%
1809
16th to endDay
36%23213446%61%
1890
November1st to 15thDay
5%2422335%8%61%
1718
16th to endDay
423323447%62%
1711
December1st to 15thDay
425%423349%58%
1560
16th to endDay
14345%335%5%9%53%
1664
January1st to 15thNight
314423447%63%
2716
16th to endNight
325%313237%65%
2720
February1st to 15thNight
5%35%423349%57%
2403
16th to endNight
5%25%41345%6%60%
1894
March1st to 15thNight
2425%32446%8%55%
2109
16th to endNight
36%34413348%55%
2025
April1st to 15thNight
38%23424446%55%
1798
16th to endNight
5%11%46%412338%47%
1800
May1st to 15thNight
6%8%36%5%345%6%8%41%
1647
16th to endNight
46%245%245%6%9%47%
1497
June1st to 15thNight
3313315%5%7%9%57%
1440
16th to endNight
1212325%7%7%8%57%
1440
July1st to 15thNight
5%5%36%6%36%6%6%9%39%
1440
16th to endNight
6%5%136%5%6%7%8%10%37%
1571
August1st to 15thNight
5%425%5%46%5%7%9%42%
1691
16th to endNight
5%424435%5%7%10%44%
1910
September1st to 15thNight
5%424435%6%7%9%46%
1800
16th to endNight
341332345%6%60%
1932
October1st to 15thNight
3312313447%63%
2148
16th to endNight
341331345%6%61%
2320
November1st to 15thNight
323314348%63%
2470
16th to endNight
1413313347%64%
2577
December1st to 15thNight
31442445%10%58%
2730
16th to endNight
5%35%5%2435%8%54%
2912

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
5%2442335%8%59%
1552
16th to endDay
1425%22235%8%60%
1868
February1st to 15thDay
15%36%4233410%54%
1746
16th to endDay
6%35%32345%7%56%
1580
March1st to 15thDay
37%35%5%2445%6%50%
1850
16th to endDay
48%35%42446%9%45%
2196
April1st to 15thDay
49%244345%5%7%46%
2150
16th to endDay
6%12%5%6%5%2445%6%39%
2160
May1st to 15thDay
8%10%37%5%35%5%6%7%36%
2301
16th to endDay
7%7%25%435%6%6%8%41%
2616
June1st to 15thDay
6%4145%345%7%9%47%
2520
16th to endDay
43145%35%6%6%8%51%
2520
July1st to 15thDay
9%5%25%5%5%6%7%6%8%37%
2520
16th to endDay
9%6%26%7%37%6%7%8%34%
2594
August1st to 15thDay
11%5%26%6%36%6%6%7%36%
2268
16th to endDay
8%5%25%5%35%5%7%9%42%
2292
September1st to 15thDay
9%5%245%345%6%6%46%
2160
16th to endDay
6%41332335%5%60%
2028
October1st to 15thDay
5%31232436%6%59%
1809
16th to endDay
46%13213445%62%
1890
November1st to 15thDay
141431335%8%62%
1718
16th to endDay
42321335%7%63%
1711
December1st to 15thDay
425%413449%58%
1560
16th to endDay
426%42446%8%54%
1664
January1st to 15thNight
31431235%7%64%
2716
16th to endNight
1324313236%66%
2720
February1st to 15thNight
5%35%313349%58%
2403
16th to endNight
5%3431345%6%62%
1894
March1st to 15thNight
242432445%8%56%
2109
16th to endNight
37%24423347%57%
2025
April1st to 15thNight
38%23313347%56%
1798
16th to endNight
6%11%35%412246%49%
1800
May1st to 15thNight
7%8%25%435%5%5%8%43%
1647
16th to endNight
5%5%2442446%9%49%
1497
June1st to 15thNight
32122245%6%8%60%
1440
16th to endNight
2212235%5%6%9%58%
1440
July1st to 15thNight
5%426%437%6%7%8%42%
1440
16th to endNight
7%3235%47%7%7%10%40%
1571
August1st to 15thNight
6%5%145%35%5%7%8%45%
1691
16th to endNight
6%4234245%8%9%46%
1910
September1st to 15thNight
6%424325%7%6%9%48%
1800
16th to endNight
441432335%6%61%
1932
October1st to 15thNight
431221325%6%64%
2148
16th to endNight
341421345%6%62%
2320
November1st to 15thNight
42322335%8%64%
2470
16th to endNight
1414313246%65%
2577
December1st to 15thNight
131431345%10%59%
2730
16th to endNight
1435%424447%56%
2912

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
24%416%28%20%5%
1553
16th to endDay
22%414%31%20%7%
1868
February1st to 15thDay
26%418%29%16%4
1747
16th to endDay
27%49%28%24%5%
1580
March1st to 15thDay
33%410%24%21%5%
1850
16th to endDay
34%6%10%25%18%3
2198
April1st to 15thDay
37%5%11%23%15%6%
2150
16th to endDay
46%5%10%19%16%3
2160
May1st to 15thDay
47%8%11%18%14%1
2301
16th to endDay
39%9%13%19%13%5%
2620
June1st to 15thDay
32%8%13%16%19%10%
2520
16th to endDay
28%7%10%19%23%10%
2520
July1st to 15thDay
42%7%11%16%14%7%
2371
16th to endDay
45%8%15%18%9%2
2432
August1st to 15thDay
45%8%12%13%12%5%
2253
16th to endDay
38%7%13%20%17%3
2292
September1st to 15thDay
38%5%10%18%18%8%
2160
16th to endDay
26%49%23%30%5%
2028
October1st to 15thDay
25%5%10%23%27%7%
1809
16th to endDay
23%48%26%28%8%
1890
November1st to 15thDay
21%311%24%27%11%
1718
16th to endDay
20%37%28%29%9%
1711
December1st to 15thDay
24%5%16%28%20%6%
1560
16th to endDay
26%7%14%25%19%6%
1664
January1st to 15thNight
19%415%31%23%4
2716
16th to endNight
19%312%30%25%7%
2720
February1st to 15thNight
25%416%34%15%3
2413
16th to endNight
23%49%29%25%7%
1894
March1st to 15thNight
26%5%11%27%25%4
2109
16th to endNight
28%5%10%29%21%4
2025
April1st to 15thNight
28%5%12%28%19%5%
1798
16th to endNight
38%5%12%25%14%3
1800
May1st to 15thNight
40%6%13%23%13%2
1648
16th to endNight
33%7%17%22%13%5%
1498
June1st to 15thNight
21%7%19%22%15%14%
1440
16th to endNight
21%8%13%22%21%12%
1440
July1st to 15thNight
39%8%14%18%11%6%
1360
16th to endNight
35%10%19%22%10%1
1470
August1st to 15thNight
36%9%17%19%12%5%
1682
16th to endNight
32%7%16%24%15%3
1910
September1st to 15thNight
31%7%15%21%16%7%
1800
16th to endNight
24%410%28%25%5%
1932
October1st to 15thNight
21%6%13%22%27%8%
2148
16th to endNight
21%5%8%28%28%7%
2320
November1st to 15thNight
19%411%26%26%12%
2470
16th to endNight
19%310%27%29%8%
2577
December1st to 15thNight
21%6%17%27%20%5%
2730
16th to endNight
27%416%23%22%5%
2912

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
11%20%31%23%12%
135
16th to endDay
425%36%25%7%1
144
February1st to 15thDay
8%50%30%9%2
130
16th to endDay
11%28%32%19%6%2
81
March1st to 15thDay
17%24%37%15%4
140
16th to endDay
19%32%35%10%1
288
April1st to 15thDay
15%37%29%11%41
269
16th to endDay
29%33%23%10%2
270
May1st to 15thDay
13%19%35%23%6%1
402
16th to endDay
12%17%31%23%12%2
517
June1st to 15thDay
8%14%28%25%19%4
495
16th to endDay
49%31%26%21%6%
495
July1st to 15thDay
11%422%27%24%9%
475
16th to endDay
11%319%30%26%9%
453
August1st to 15thDay
16%8%27%30%12%4
315
16th to endDay
13%433%27%17%3
332
September1st to 15thDay
8%16%33%26%10%4
315
16th to endDay
8%15%40%20%10%4
183
October1st to 15thDay
5%21%26%25%14%6%
135
16th to endDay
8%17%30%27%11%4
144
November1st to 15thDay
8%19%28%22%17%4
135
16th to endDay
11%25%42%14%6%
135
December1st to 15thDay
8%34%36%15%5%
135
16th to endDay
6%31%36%20%4
144
January1st to 15thNight
5%21%35%25%10%2
975
16th to endNight
318%41%27%7%1
848
February1st to 15thNight
421%44%24%4
760
16th to endNight
323%44%23%4
632
March1st to 15thNight
418%40%27%8%
720
16th to endNight
7%17%41%26%7%
681
April1st to 15thNight
7%23%34%26%6%
539
16th to endNight
11%17%35%26%8%1
540
May1st to 15thNight
10%8%34%32%11%1
540
16th to endNight
7%9%32%33%15%1
563
June1st to 15thNight
5%5%25%41%17%3
540
16th to endNight
2120%46%24%3
540
July1st to 15thNight
7%112%37%37%4
510
16th to endNight
7%18%32%44%6%
564
August1st to 15thNight
8%112%37%34%5%
539
16th to endNight
7%19%35%38%6%
573
September1st to 15thNight
7%118%36%30%6%
540
16th to endNight
45%25%37%21%4
537
October1st to 15thNight
5%12%30%33%14%3
708
16th to endNight
5%9%30%33%17%3
784
November1st to 15thNight
415%33%31%13%2
950
16th to endNight
417%38%29%8%1
975
December1st to 15thNight
325%38%24%6%
975
16th to endNight
5%24%38%22%8%
1040
Page generated at 2018-02-15 08:58:52. Version ac04

Copyright 2018 A. Danko


Divide Clear Sky Chart |Charts Home