South Range
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the South Range clear sky chart from 2005-11-05 to

2017-09-12
.

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
18%
14963
10%
46659
4%
14918
24%
14918
11%
36218

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
9%
740
5%
2617
2%
736
13%
736
3%
2256
January16th to endNight
8%
768
3%
2496
0%
768
11%
768
3%
2246
February1st to 15thNight
6%
704
3%
2286
0%
701
9%
701
3%
2075
February16th to endNight
12%
631
4%
1988
1%
631
16%
631
5%
1682
March1st to 15thNight
13%
720
11%
2010
3%
720
21%
720
10%
1610
March16th to endNight
16%
768
11%
2112
4%
768
22%
768
13%
1617
April1st to 15thNight
15%
593
13%
1799
4%
593
24%
593
12%
1355
April16th to endNight
19%
540
14%
1620
4%
540
26%
540
16%
1156
May1st to 15thNight
19%
540
11%
1605
5%
540
25%
540
14%
1219
May16th to endNight
20%
561
10%
1496
3%
560
27%
560
17%
1135
June1st to 15thNight
20%
424
8%
1324
4%
424
25%
424
12%
1009
June16th to endNight
23%
360
9%
1260
3%
360
32%
360
15%
904
July1st to 15thNight
27%
340
10%
1190
6%
340
35%
340
19%
794
July16th to endNight
28%
539
9%
1529
8%
506
30%
506
17%
1142
August1st to 15thNight
34%
539
13%
1608
9%
535
36%
535
21%
1116
August16th to endNight
32%
573
18%
1739
10%
573
39%
573
24%
1128
September1st to 15thNight
28%
587
17%
1824
9%
587
37%
587
23%
1173
September16th to endNight
34%
657
24%
1815
13%
657
43%
657
25%
1178
October1st to 15thNight
26%
660
17%
1972
7%
660
34%
660
19%
1374
October16th to endNight
16%
704
12%
2139
4%
704
24%
704
12%
1621
November1st to 15thNight
22%
715
10%
2370
7%
715
27%
715
11%
1820
November16th to endNight
19%
750
8%
2520
4%
750
24%
750
8%
1980
December1st to 15thNight
10%
750
5%
2520
1%
750
15%
750
5%
2157
December16th to endNight
7%
800
5%
2820
1%
800
12%
800
3%
2471

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
20%10%47%5%23345%30%
47998
Night
20%12%5%8%6%34345%24%
46832
TransparencyDay
56%5%10%17%9%
47689
Night
60%6%10%15%7%
46659
SeeingDay
29%18%28%15%5%1
7030
Night
28%17%30%17%5%
14963

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
18%20%8%13%10%3432212%
1315
16th to endDay
18%16%8%13%13%5%43339%
1728
February1st to 15thDay
16%18%9%16%14%232239%
1575
16th to endDay
13%17%9%11%8%33335%19%
1485
March1st to 15thDay
18%14%7%10%8%3322424%
1937
16th to endDay
18%12%6%8%5%33335%28%
2112
April1st to 15thDay
19%12%35%423335%33%
2147
16th to endDay
22%9%35%323346%36%
2340
May1st to 15thDay
23%8%45%5%33346%31%
2347
16th to endDay
23%7%35%433347%32%
2618
June1st to 15thDay
26%8%36%423345%29%
2646
16th to endDay
22%6%25%5%24446%34%
2700
July1st to 15thDay
18%5%2432445%7%39%
2700
16th to endDay
19%7%35%5%345%47%34%
2519
August1st to 15thDay
17%5%26%5%2445%6%39%
2340
16th to endDay
14%5%23433446%48%
2462
September1st to 15thDay
18%6%23323236%46%
2054
16th to endDay
18%5%24322246%46%
1815
October1st to 15thDay
21%7%24424346%38%
1658
16th to endDay
25%11%37%423346%26%
1733
November1st to 15thDay
23%13%46%5%33347%24%
1486
16th to endDay
20%17%6%11%6%3333420%
1440
December1st to 15thDay
27%15%7%13%7%2433312%
1440
16th to endDay
24%17%8%14%6%2333310%
1401
January1st to 15thNight
19%18%7%14%10%3323313%
2617
16th to endNight
18%17%8%15%11%443339%
2496
February1st to 15thNight
18%18%8%17%11%343238%
2285
16th to endNight
14%16%7%14%8%35%44414%
1988
March1st to 15thNight
18%13%7%9%6%4434423%
1998
16th to endNight
18%13%8%6%5%23345%26%
2112
April1st to 15thNight
23%12%35%5%24446%26%
1799
16th to endNight
20%10%36%5%2435%6%31%
1620
May1st to 15thNight
22%11%36%5%35%346%28%
1605
16th to endNight
22%7%36%5%25%448%30%
1494
June1st to 15thNight
29%8%35%5%2435%7%25%
1324
16th to endNight
19%8%38%4345%5%8%28%
1260
July1st to 15thNight
15%7%26%5%26%46%9%32%
1260
16th to endNight
18%7%36%6%46%5%6%8%26%
1635
August1st to 15thNight
18%8%25%4345%5%8%34%
1620
16th to endNight
13%6%25%42446%7%40%
1739
September1st to 15thNight
17%5%3442435%7%40%
1824
16th to endNight
17%5%14423436%44%
1815
October1st to 15thNight
19%8%36%5%23446%36%
1972
16th to endNight
26%11%37%422335%29%
2139
November1st to 15thNight
21%13%47%5%2445%5%24%
2370
16th to endNight
21%16%5%8%6%24335%22%
2520
December1st to 15thNight
24%16%7%12%6%2333413%
2520
16th to endNight
25%18%9%11%7%2322412%
2820

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
78%38%7%1
1316
16th to endDay
78%5%7%6%1
1728
February1st to 15thDay
81%5%7%41
1578
16th to endDay
68%5%10%11%3
1485
March1st to 15thDay
65%49%12%6%
1948
16th to endDay
59%5%8%17%8%1
2112
April1st to 15thDay
55%48%16%13%1
2147
16th to endDay
49%411%19%14%1
2340
May1st to 15thDay
55%5%8%17%11%1
2347
16th to endDay
52%6%11%20%8%
2622
June1st to 15thDay
57%5%9%17%9%1
2646
16th to endDay
50%7%10%19%11%
2700
July1st to 15thDay
43%7%13%23%11%1
2541
16th to endDay
49%7%12%20%9%
2363
August1st to 15thDay
45%8%11%21%12%
2327
16th to endDay
38%6%11%27%14%
2462
September1st to 15thDay
41%411%24%16%1
2054
16th to endDay
39%48%29%16%1
1815
October1st to 15thDay
47%5%10%23%11%1
1658
16th to endDay
59%5%10%17%8%
1733
November1st to 15thDay
60%5%10%16%6%
1486
16th to endDay
68%5%9%11%4
1440
December1st to 15thDay
75%6%8%7%2
1440
16th to endDay
79%47%6%2
1401
January1st to 15thNight
75%5%9%8%1
2617
16th to endNight
79%6%6%6%1
2496
February1st to 15thNight
80%5%6%5%1
2286
16th to endNight
71%6%10%8%3
1988
March1st to 15thNight
63%410%13%7%
2010
16th to endNight
58%5%11%15%9%
2112
April1st to 15thNight
57%5%8%15%11%1
1799
16th to endNight
52%410%19%11%1
1620
May1st to 15thNight
56%5%9%18%8%
1605
16th to endNight
52%7%12%19%6%
1496
June1st to 15thNight
58%7%11%17%41
1324
16th to endNight
53%6%11%17%9%
1260
July1st to 15thNight
44%8%17%17%10%
1190
16th to endNight
51%10%11%19%6%
1529
August1st to 15thNight
46%6%12%24%8%
1608
16th to endNight
39%8%14%25%12%
1739
September1st to 15thNight
42%5%10%27%13%
1824
16th to endNight
40%47%28%17%
1815
October1st to 15thNight
49%5%11%19%12%1
1972
16th to endNight
58%49%19%7%
2139
November1st to 15thNight
59%7%12%14%5%
2370
16th to endNight
63%6%13%11%4
2520
December1st to 15thNight
73%5%10%9%1
2520
16th to endNight
77%5%7%6%2
2820

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
36%26%30%6%
65
16th to endDay
32%27%27%11%
256
February1st to 15thDay
28%26%35%8%1
236
16th to endDay
24%24%30%16%3
223
March1st to 15thDay
31%27%28%9%3
270
16th to endDay
32%25%22%12%42
288
April1st to 15thDay
32%27%25%10%3
270
16th to endDay
26%23%29%14%5%1
270
May1st to 15thDay
33%23%27%11%31
303
16th to endDay
31%16%29%16%41
519
June1st to 15thDay
34%15%28%17%3
495
16th to endDay
31%12%31%17%5%1
495
July1st to 15thDay
26%9%31%19%10%1
475
16th to endDay
25%11%32%21%7%1
365
August1st to 15thDay
23%11%33%21%8%1
313
16th to endDay
22%11%27%22%14%1
332
September1st to 15thDay
23%14%36%16%7%1
299
16th to endDay
24%11%31%20%7%5%
254
October1st to 15thDay
29%11%26%19%8%3
226
16th to endDay
35%22%23%11%6%
240
November1st to 15thDay
31%18%25%17%42
235
16th to endDay
31%23%25%12%6%
240
December1st to 15thDay
38%25%20%14%
240
16th to endDay
42%31%17%8%
121
January1st to 15thNight
34%21%28%13%1
740
16th to endNight
33%24%27%12%1
768
February1st to 15thNight
31%25%30%10%1
704
16th to endNight
27%24%30%12%3
631
March1st to 15thNight
29%20%30%16%2
720
16th to endNight
27%21%28%15%5%
768
April1st to 15thNight
34%18%29%14%3
593
16th to endNight
27%15%35%17%4
540
May1st to 15thNight
30%13%32%18%4
540
16th to endNight
27%13%34%20%3
561
June1st to 15thNight
32%12%29%21%3
424
16th to endNight
24%8%39%20%7%
360
July1st to 15thNight
20%5%42%24%7%
340
16th to endNight
20%7%38%28%4
539
August1st to 15thNight
19%7%33%28%9%
539
16th to endNight
16%8%37%26%9%
573
September1st to 15thNight
21%10%36%22%8%
587
16th to endNight
20%12%29%24%11%1
657
October1st to 15thNight
26%13%29%20%9%1
660
16th to endNight
33%19%27%15%3
704
November1st to 15thNight
28%16%27%19%6%
715
16th to endNight
32%19%25%16%6%
750
December1st to 15thNight
37%22%25%12%2
750
16th to endNight
38%24%25%9%2
800
Page generated at 2017-09-13 08:39:25. Version ac04

Copyright 2017 A. Danko


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