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

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
44%
15407
21%
46881
15%
15363
51%
15363
25%
30159

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
21%
720
17%
2327
9%
716
31%
716
15%
1648
January16th to endNight
22%
768
19%
2496
10%
768
33%
768
16%
1713
February1st to 15thNight
21%
704
16%
2127
7%
701
31%
701
17%
1507
February16th to endNight
18%
631
18%
1893
7%
631
28%
631
15%
1378
March1st to 15thNight
27%
720
19%
2082
10%
720
34%
720
20%
1455
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
64%
665
22%
1902
20%
665
66%
665
33%
1167
September16th to endNight
59%
657
27%
1815
22%
657
62%
657
33%
1129
October1st to 15thNight
56%
660
34%
1840
30%
660
62%
660
38%
1063
October16th to endNight
45%
704
28%
2159
22%
704
54%
704
29%
1300
November1st to 15thNight
47%
700
29%
2276
25%
700
56%
700
31%
1289
November16th to endNight
36%
720
25%
2340
18%
720
47%
720
25%
1451
December1st to 15thNight
30%
720
16%
2340
13%
720
36%
720
17%
1645
December16th to endNight
27%
768
19%
2496
11%
768
37%
768
15%
1780

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
15%6%35%5%3445%7%37%
47782
Night
14%7%35%42445%6%41%
47078
TransparencyDay
46%410%21%15%2
47483
Night
43%310%22%16%3
46881
SeeingDay
18%6%20%22%20%11%
5275
Night
19%7%21%29%19%3
15409

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%11%5%9%6%23345%27%
1611
16th to endDay
19%10%36%5%23335%36%
1728
February1st to 15thDay
17%11%5%8%5%33335%31%
1735
16th to endDay
18%11%46%5%345%36%30%
1580
March1st to 15thDay
23%8%34423346%34%
1878
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%
1966
16th to endDay
16%5%15%424346%44%
1815
October1st to 15thDay
13%314423336%52%
1790
16th to endDay
19%5%24313235%47%
1711
November1st to 15thDay
14%5%23424345%48%
1582
16th to endDay
18%7%13323336%44%
1620
December1st to 15thDay
23%8%35%5%23336%33%
1620
16th to endDay
21%11%25%5%23445%31%
1728
January1st to 15thNight
20%9%47%6%3333432%
2327
16th to endNight
18%10%46%5%23345%35%
2496
February1st to 15thNight
18%9%5%7%5%24345%33%
2118
16th to endNight
20%11%46%435%35%431%
1893
March1st to 15thNight
17%10%35%434445%36%
2082
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%424424448%46%
1902
16th to endNight
11%5%34424445%48%
1815
October1st to 15thNight
12%413323345%55%
1840
16th to endNight
17%5%24323335%48%
2159
November1st to 15thNight
13%5%23323336%52%
2276
16th to endNight
18%7%23313335%44%
2340
December1st to 15thNight
23%10%35%423345%32%
2340
16th to endNight
23%11%35%5%24335%31%
2496

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
59%36%16%12%1
1612
16th to endDay
52%29%25%9%1
1728
February1st to 15thDay
57%17%21%10%2
1737
16th to endDay
55%39%19%10%1
1580
March1st to 15thDay
52%37%19%14%2
1878
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
48%311%17%14%4
1966
16th to endDay
42%27%19%25%2
1815
October1st to 15thDay
33%38%23%24%6%
1790
16th to endDay
40%26%24%22%3
1711
November1st to 15thDay
37%26%23%23%6%
1582
16th to endDay
42%25%26%20%3
1620
December1st to 15thDay
53%29%20%12%2
1620
16th to endDay
54%312%19%8%
1728
January1st to 15thNight
55%28%16%14%2
2327
16th to endNight
52%28%22%12%1
2496
February1st to 15thNight
53%210%20%11%1
2127
16th to endNight
55%38%19%11%1
1893
March1st to 15thNight
50%38%19%14%3
2082
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
35%5%14%22%16%5%
1902
16th to endNight
37%36%19%29%3
1815
October1st to 15thNight
31%38%24%25%7%
1840
16th to endNight
38%2424%24%5%
2159
November1st to 15thNight
35%15%22%27%7%
2276
16th to endNight
42%26%25%20%3
2340
December1st to 15thNight
55%19%19%11%2
2340
16th to endNight
56%19%18%12%1
2496

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
35%22%31%5%41
90
16th to endDay
29%25%38%43
96
February1st to 15thDay
28%23%38%6%2
90
16th to endDay
28%16%43%11%1
81
March1st to 15thDay
32%14%32%15%4
168
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
17%111%18%31%19%
299
16th to endDay
19%29%24%31%12%
254
October1st to 15thDay
13%322%24%27%9%
255
16th to endDay
21%7%21%26%18%5%
223
November1st to 15thDay
16%12%24%25%17%3
90
16th to endDay
28%10%36%18%5%
90
December1st to 15thDay
22%16%37%16%5%1
90
16th to endDay
22%25%41%8%2
96
January1st to 15thNight
28%15%29%21%5%
720
16th to endNight
25%14%31%26%2
768
February1st to 15thNight
26%12%33%25%2
704
16th to endNight
28%14%34%19%3
631
March1st to 15thNight
26%10%28%27%5%
720
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
14%9%29%36%8%
665
16th to endNight
14%115%30%32%5%
657
October1st to 15thNight
16%416%29%26%5%
660
16th to endNight
20%5%24%29%17%2
704
November1st to 15thNight
16%7%23%30%18%3
700
16th to endNight
22%11%24%30%10%
720
December1st to 15thNight
30%12%21%27%7%
720
16th to endNight
30%11%25%27%5%
768
Page generated at 2017-09-13 07:39:19. Version ac04

Copyright 2017 A. Danko


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