Mount Chestnut Oak Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mount Chestnut Oak Observing Site 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
44%
16128
21%
49108
15%
16084
50%
16084
25%
31638

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
23%
780
16%
2522
9%
776
32%
776
15%
1781
January16th to endNight
23%
832
20%
2704
11%
832
34%
832
17%
1848
February1st to 15thNight
21%
764
16%
2308
7%
761
30%
761
17%
1652
February16th to endNight
17%
683
17%
2049
7%
683
27%
683
14%
1507
March1st to 15thNight
26%
764
18%
2212
10%
764
33%
764
19%
1549
March16th to endNight
31%
768
15%
2112
9%
768
36%
768
21%
1492
April1st to 15thNight
35%
595
23%
1853
12%
595
48%
595
28%
1134
April16th to endNight
40%
540
22%
1668
13%
540
49%
540
27%
1059
May1st to 15thNight
42%
539
16%
1620
10%
539
48%
539
23%
1091
May16th to endNight
59%
562
19%
1684
14%
561
63%
561
31%
1029
June1st to 15thNight
68%
540
17%
1620
15%
540
71%
540
35%
970
June16th to endNight
69%
540
17%
1620
15%
540
70%
540
33%
972
July1st to 15thNight
64%
510
13%
1530
12%
510
66%
510
30%
948
July16th to endNight
70%
564
18%
1595
16%
531
74%
531
34%
954
August1st to 15thNight
71%
539
22%
1609
21%
536
72%
536
36%
953
August16th to endNight
76%
573
23%
1877
25%
573
76%
573
35%
1032
September1st to 15thNight
63%
678
22%
1938
19%
678
65%
678
32%
1197
September16th to endNight
62%
717
29%
1980
24%
717
65%
717
36%
1199
October1st to 15thNight
57%
720
33%
2007
29%
720
62%
720
39%
1157
October16th to endNight
45%
768
29%
2355
23%
768
55%
768
29%
1414
November1st to 15thNight
45%
760
28%
2471
24%
760
54%
760
29%
1442
November16th to endNight
38%
780
27%
2535
20%
780
49%
780
26%
1544
December1st to 15thNight
30%
780
16%
2535
12%
780
37%
780
17%
1771
December16th to endNight
26%
832
19%
2704
11%
832
36%
832
15%
1943

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
16%6%25%5%3445%7%37%
49523
Night
15%7%35%42445%6%41%
49305
TransparencyDay
46%410%21%15%2
49224
Night
43%310%22%16%3
49108
SeeingDay
19%7%21%21%19%10%
5863
Night
19%7%21%29%19%3
16130

By Month

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
20%10%49%6%23445%28%
1746
16th to endDay
19%10%36%5%23335%35%
1872
February1st to 15thDay
19%10%5%8%5%33435%30%
1884
16th to endDay
20%11%36%5%34436%30%
1710
March1st to 15thDay
23%8%34423345%34%
1985
16th to endDay
20%8%46%424447%32%
2111
April1st to 15thDay
14%6%25%5%3435%7%41%
2105
16th to endDay
16%5%36%5%24445%39%
2292
May1st to 15thDay
19%6%25%6%35%45%7%32%
2331
16th to endDay
12%7%25%5%36%5%5%9%37%
2431
June1st to 15thDay
10%4247%36%7%6%9%37%
2340
16th to endDay
8%425%5%46%6%6%10%38%
2340
July1st to 15thDay
14%5%25%6%47%6%6%8%32%
2340
16th to endDay
11%426%6%46%6%7%10%32%
2465
August1st to 15thDay
10%5%25%6%47%6%7%8%34%
2340
16th to endDay
10%4245%36%6%7%11%36%
2323
September1st to 15thDay
17%5%25%6%3445%7%35%
2010
16th to endDay
15%5%15%424346%46%
1980
October1st to 15thDay
13%313423346%52%
1953
16th to endDay
18%5%24313235%48%
1866
November1st to 15thDay
15%5%23424345%46%
1717
16th to endDay
17%7%13323335%46%
1755
December1st to 15thDay
22%8%35%5%23336%35%
1755
16th to endDay
22%11%36%5%23445%30%
1872
January1st to 15thNight
19%8%48%6%3333433%
2522
16th to endNight
18%10%46%5%23245%35%
2704
February1st to 15thNight
20%9%5%7%424345%32%
2299
16th to endNight
20%12%36%5%35%35%429%
2049
March1st to 15thNight
18%9%35%434445%36%
2212
16th to endNight
16%9%36%5%34446%35%
2112
April1st to 15thNight
14%5%34423347%46%
1853
16th to endNight
15%6%245%3345%7%42%
1668
May1st to 15thNight
17%5%35%5%35%45%7%35%
1619
16th to endNight
7%425%6%35%5%8%9%41%
1682
June1st to 15thNight
6%4245%35%5%8%9%44%
1620
16th to endNight
44245%45%5%7%11%43%
1620
July1st to 15thNight
10%425%5%25%5%7%9%41%
1620
16th to endNight
6%325%5%36%5%6%10%43%
1703
August1st to 15thNight
7%325%5%25%5%6%8%47%
1620
16th to endNight
7%3135%35%5%7%10%47%
1877
September1st to 15thNight
13%42442445%8%45%
1938
16th to endNight
10%5%34423445%50%
1980
October1st to 15thNight
12%413313345%56%
2007
16th to endNight
16%5%24323345%48%
2355
November1st to 15thNight
13%6%24423336%50%
2471
16th to endNight
18%7%23313335%46%
2535
December1st to 15thNight
21%11%35%42335%5%32%
2535
16th to endNight
23%11%35%5%34335%31%
2704

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
58%36%16%13%1
1747
16th to endDay
52%28%25%10%1
1872
February1st to 15thDay
57%27%20%10%1
1886
16th to endDay
56%39%18%10%1
1710
March1st to 15thDay
52%27%18%15%2
1985
16th to endDay
52%310%21%10%
2112
April1st to 15thDay
42%310%23%16%3
2105
16th to endDay
46%29%22%15%3
2292
May1st to 15thDay
49%5%11%20%11%1
2331
16th to endDay
42%5%14%23%11%2
2435
June1st to 15thDay
41%6%13%22%13%1
2340
16th to endDay
39%6%12%19%19%2
2340
July1st to 15thDay
46%5%15%16%12%2
2201
16th to endDay
43%5%14%20%12%2
2310
August1st to 15thDay
43%5%14%20%13%1
2327
16th to endDay
39%5%14%22%16%2
2323
September1st to 15thDay
49%310%17%14%4
2010
16th to endDay
39%29%20%24%2
1980
October1st to 15thDay
32%39%24%24%5%
1953
16th to endDay
39%26%24%23%3
1866
November1st to 15thDay
39%26%23%21%5%
1717
16th to endDay
41%25%26%21%3
1755
December1st to 15thDay
52%29%21%11%2
1755
16th to endDay
56%312%18%8%
1872
January1st to 15thNight
55%28%16%14%3
2522
16th to endNight
52%27%22%13%1
2704
February1st to 15thNight
54%29%20%10%1
2308
16th to endNight
57%38%17%10%2
2049
March1st to 15thNight
50%38%18%15%3
2212
16th to endNight
49%410%24%10%1
2112
April1st to 15thNight
39%29%23%20%4
1853
16th to endNight
42%39%23%15%4
1668
May1st to 15thNight
47%313%21%12%2
1620
16th to endNight
35%5%16%25%13%2
1684
June1st to 15thNight
33%5%17%25%15%2
1620
16th to endNight
33%6%15%24%15%4
1620
July1st to 15thNight
36%6%17%20%16%2
1530
16th to endNight
33%5%18%23%15%3
1595
August1st to 15thNight
32%416%23%19%2
1609
16th to endNight
30%416%27%17%3
1877
September1st to 15thNight
36%5%14%22%15%5%
1938
16th to endNight
35%38%20%29%2
1980
October1st to 15thNight
31%28%24%25%6%
2007
16th to endNight
38%2423%24%4
2355
November1st to 15thNight
37%15%22%25%6%
2471
16th to endNight
41%25%24%22%2
2535
December1st to 15thNight
54%19%20%11%2
2535
16th to endNight
57%18%18%12%1
2704

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
28%22%32%10%5%
135
16th to endDay
28%22%35%9%4
144
February1st to 15thDay
34%20%34%9%1
135
16th to endDay
35%13%42%8%
120
March1st to 15thDay
32%14%35%12%3
201
16th to endDay
20%12%30%22%11%1
288
April1st to 15thDay
22%12%24%22%15%2
270
16th to endDay
23%5%27%20%17%5%
270
May1st to 15thDay
21%11%23%19%14%9%
288
16th to endDay
19%320%25%18%12%
331
June1st to 15thDay
11%212%32%24%16%
315
16th to endDay
12%321%25%24%13%
315
July1st to 15thDay
18%216%24%21%16%
305
16th to endDay
10%19%23%30%25%
326
August1st to 15thDay
14%9%21%29%24%
313
16th to endDay
12%17%26%32%19%
332
September1st to 15thDay
18%210%18%30%19%
315
16th to endDay
15%210%23%31%15%
314
October1st to 15thDay
12%420%24%28%8%
315
16th to endDay
20%7%23%24%17%6%
282
November1st to 15thDay
21%10%25%27%12%2
135
16th to endDay
22%8%34%21%11%1
135
December1st to 15thDay
21%17%38%14%7%
135
16th to endDay
25%25%37%11%1
144
January1st to 15thNight
27%14%29%22%6%
780
16th to endNight
24%14%30%26%3
832
February1st to 15thNight
27%11%32%25%2
764
16th to endNight
28%14%34%19%3
683
March1st to 15thNight
26%10%29%26%5%
764
16th to endNight
20%9%30%28%10%
768
April1st to 15thNight
17%11%31%27%11%
595
16th to endNight
17%431%29%14%1
540
May1st to 15thNight
18%324%34%16%2
540
16th to endNight
9%117%34%29%7%
563
June1st to 15thNight
7%111%41%32%6%
540
16th to endNight
6%12%37%36%6%
540
July1st to 15thNight
14%10%33%36%4
510
16th to endNight
6%27%27%43%11%
564
August1st to 15thNight
9%5%31%44%8%
539
16th to endNight
8%437%38%10%
573
September1st to 15thNight
15%110%29%35%7%
678
16th to endNight
12%114%29%34%6%
717
October1st to 15thNight
16%416%28%28%5%
720
16th to endNight
20%5%24%29%17%2
768
November1st to 15thNight
17%7%23%30%17%3
760
16th to endNight
21%10%24%30%11%
780
December1st to 15thNight
28%12%21%28%7%
780
16th to endNight
31%11%25%26%4
832
Page generated at 2018-03-12 13:28:06. Version ac04

Copyright 2018 A. Danko


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