NEFAS Swamp Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the NEFAS Swamp 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
52%
15777
22%
46872
16%
15739
59%
15739
30%
28907

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
35%
716
21%
2327
13%
716
47%
716
24%
1411
January16th to endNight
34%
768
23%
2460
14%
768
47%
768
24%
1534
February1st to 15thNight
35%
701
24%
2108
13%
699
47%
699
29%
1257
February16th to endNight
37%
631
25%
1875
14%
631
48%
631
29%
1143
March1st to 15thNight
40%
720
28%
1980
14%
720
52%
720
35%
1175
March16th to endNight
42%
768
25%
2112
15%
768
51%
768
38%
1225
April1st to 15thNight
44%
718
25%
1976
15%
718
52%
718
37%
1171
April16th to endNight
50%
657
29%
1782
18%
657
57%
657
41%
1023
May1st to 15thNight
60%
539
26%
1619
17%
539
66%
539
41%
892
May16th to endNight
69%
561
23%
1682
16%
561
73%
561
38%
964
June1st to 15thNight
65%
540
14%
1620
10%
540
67%
540
26%
1066
June16th to endNight
73%
540
11%
1620
10%
540
73%
540
28%
1074
July1st to 15thNight
73%
510
10%
1530
9%
510
73%
510
28%
996
July16th to endNight
74%
564
10%
1595
10%
531
75%
531
25%
1094
August1st to 15thNight
74%
539
8%
1609
8%
536
75%
536
25%
1101
August16th to endNight
66%
669
12%
1990
12%
669
66%
669
22%
1392
September1st to 15thNight
61%
707
13%
1944
12%
707
61%
707
21%
1395
September16th to endNight
55%
657
16%
1815
14%
657
58%
657
24%
1261
October1st to 15thNight
60%
660
28%
1866
25%
660
64%
660
35%
1128
October16th to endNight
56%
704
31%
2112
27%
704
64%
704
36%
1194
November1st to 15thNight
51%
700
31%
2101
23%
700
62%
700
39%
1157
November16th to endNight
42%
720
28%
2313
19%
720
56%
720
33%
1306
December1st to 15thNight
44%
720
26%
2340
20%
720
52%
720
28%
1398
December16th to endNight
44%
768
23%
2496
19%
768
53%
768
25%
1550

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
10%6%36%6%45%5%6%7%37%
47771
Night
9%5%25%5%35%46%9%44%
47076
TransparencyDay
43%5%12%17%14%7%
47472
Night
35%5%14%20%15%7%
46879
SeeingDay
11%5%17%22%24%18%
5640
Night
11%5%21%31%24%4
15787

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
12%6%35%5%3445%8%40%
1611
16th to endDay
14%6%25%425%445%44%
1761
February1st to 15thDay
15%6%2442334446%
1750
16th to endDay
13%6%25%5%3333448%
1595
March1st to 15thDay
9%4233245%5%7%51%
1980
16th to endDay
9%426%6%34446%47%
2111
April1st to 15thDay
9%5%36%5%3445%5%47%
1972
16th to endDay
6%425%5%36%5%5%7%46%
2185
May1st to 15thDay
6%325%5%35%5%5%8%47%
2331
16th to endDay
9%5%26%7%45%6%6%7%38%
2431
June1st to 15thDay
10%5%27%8%5%7%7%7%9%28%
2340
16th to endDay
8%5%35%8%6%7%7%8%10%26%
2340
July1st to 15thDay
6%6%49%10%47%7%8%10%24%
2340
16th to endDay
8%6%48%9%6%9%7%7%10%22%
2465
August1st to 15thDay
11%6%39%10%6%8%7%8%10%18%
2340
16th to endDay
12%8%49%9%5%7%7%7%8%20%
2196
September1st to 15thDay
11%7%39%9%5%8%6%8%8%22%
1936
16th to endDay
15%9%38%7%46%6%47%25%
1815
October1st to 15thDay
10%7%35%5%45%446%42%
1763
16th to endDay
9%416%5%23445%51%
1760
November1st to 15thDay
8%42443335%8%50%
1757
16th to endDay
10%4245%2436%6%50%
1644
December1st to 15thDay
13%6%15%6%3446%6%42%
1620
16th to endDay
10%6%36%5%35%45%8%40%
1728
January1st to 15thNight
12%5%245%2445%7%44%
2327
16th to endNight
14%6%25%42435%5%44%
2460
February1st to 15thNight
13%5%35%42334450%
2103
16th to endNight
12%6%25%424347%47%
1875
March1st to 15thNight
7%5%245%23448%50%
1980
16th to endNight
9%414423336%55%
2112
April1st to 15thNight
8%42342335%7%52%
1976
16th to endNight
6%41342435%7%56%
1782
May1st to 15thNight
5%213435%5%6%9%52%
1619
16th to endNight
6%415%325%46%11%49%
1682
June1st to 15thNight
9%425%6%47%6%9%11%33%
1620
16th to endNight
7%3247%46%7%7%12%35%
1620
July1st to 15thNight
5%425%6%37%7%8%13%35%
1620
16th to endNight
35%26%6%48%7%9%13%32%
1703
August1st to 15thNight
5%425%7%47%7%9%13%31%
1620
16th to endNight
8%6%36%5%36%7%8%11%31%
1990
September1st to 15thNight
9%6%37%7%46%6%8%12%28%
1944
16th to endNight
11%9%36%5%345%7%9%32%
1815
October1st to 15thNight
9%5%15%42336%7%48%
1866
16th to endNight
7%42443445%6%51%
2112
November1st to 15thNight
8%32432435%8%53%
2101
16th to endNight
9%5%23424447%50%
2313
December1st to 15thNight
12%6%24424348%44%
2340
16th to endNight
12%5%35%5%34447%42%
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
42%37%17%18%10%
1612
16th to endDay
41%25%18%20%11%
1761
February1st to 15thDay
41%26%13%20%15%
1752
16th to endDay
40%17%13%22%13%
1595
March1st to 15thDay
30%39%22%23%10%
1980
16th to endDay
36%310%18%20%10%
2112
April1st to 15thDay
37%37%17%23%10%
1972
16th to endDay
35%49%21%19%10%
2185
May1st to 15thDay
34%410%21%19%9%
2331
16th to endDay
41%5%11%21%15%4
2435
June1st to 15thDay
50%7%16%15%8%
2340
16th to endDay
48%10%18%17%5%
2340
July1st to 15thDay
50%8%23%15%1
2201
16th to endDay
52%9%21%13%3
2310
August1st to 15thDay
56%8%21%11%2
2327
16th to endDay
57%8%18%11%2
2196
September1st to 15thDay
55%8%15%13%5%1
1936
16th to endDay
56%5%10%13%9%3
1815
October1st to 15thDay
41%47%17%17%12%
1763
16th to endDay
35%36%15%23%15%
1760
November1st to 15thDay
32%37%22%22%12%
1757
16th to endDay
34%37%17%23%14%
1644
December1st to 15thDay
41%48%22%16%6%
1620
16th to endDay
40%410%21%14%8%
1728
January1st to 15thNight
39%39%19%17%10%
2327
16th to endNight
41%36%14%21%12%
2460
February1st to 15thNight
36%28%15%20%16%
2112
16th to endNight
37%38%18%19%12%
1875
March1st to 15thNight
32%310%24%18%9%
1980
16th to endNight
30%312%20%20%11%
2112
April1st to 15thNight
31%410%20%23%9%
1976
16th to endNight
27%413%23%21%9%
1782
May1st to 15thNight
26%5%14%26%19%8%
1620
16th to endNight
28%5%18%27%16%3
1684
June1st to 15thNight
39%8%21%22%7%
1620
16th to endNight
37%10%24%20%6%
1620
July1st to 15thNight
36%10%29%20%2
1530
16th to endNight
36%14%27%17%3
1595
August1st to 15thNight
37%13%32%14%2
1609
16th to endNight
42%11%25%15%4
1990
September1st to 15thNight
44%11%20%15%6%1
1944
16th to endNight
46%6%15%20%8%3
1815
October1st to 15thNight
34%411%20%18%10%
1866
16th to endNight
31%37%19%23%14%
2112
November1st to 15thNight
29%29%23%22%12%
2101
16th to endNight
32%38%19%20%15%
2313
December1st to 15thNight
38%311%23%16%6%
2340
16th to endNight
40%410%21%14%8%
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
18%16%38%8%10%6%
90
16th to endDay
20%17%38%17%5%
96
February1st to 15thDay
24%15%30%21%7%1
90
16th to endDay
10%13%39%32%31
96
March1st to 15thDay
12%11%31%30%11%2
270
16th to endDay
13%7%28%23%21%4
288
April1st to 15thDay
10%10%27%23%22%5%
270
16th to endDay
7%5%21%30%20%13%
270
May1st to 15thDay
7%6%23%25%20%16%
288
16th to endDay
8%29%25%31%22%
331
June1st to 15thDay
13%29%18%30%26%
315
16th to endDay
10%5%13%36%33%
315
July1st to 15thDay
5%316%30%42%
305
16th to endDay
8%417%35%32%
326
August1st to 15thDay
13%17%15%28%32%
313
16th to endDay
11%1416%29%35%
332
September1st to 15thDay
16%19%22%23%26%
299
16th to endDay
24%16%17%29%20%
254
October1st to 15thDay
13%417%30%26%7%
255
16th to endDay
8%5%21%31%26%5%
272
November1st to 15thDay
11%327%27%25%5%
265
16th to endDay
10%8%35%22%17%4
114
December1st to 15thDay
5%14%41%25%12%1
90
16th to endDay
16%9%30%31%8%4
96
January1st to 15thNight
16%11%30%28%11%1
720
16th to endNight
17%12%29%31%8%
768
February1st to 15thNight
16%12%29%31%9%
704
16th to endNight
14%10%32%35%6%
631
March1st to 15thNight
10%10%34%33%10%
720
16th to endNight
11%7%33%32%14%
768
April1st to 15thNight
10%9%31%35%12%
718
16th to endNight
9%5%28%37%17%1
657
May1st to 15thNight
6%224%44%18%2
540
16th to endNight
8%212%36%34%5%
563
June1st to 15thNight
10%110%34%35%8%
540
16th to endNight
8%5%25%44%14%
540
July1st to 15thNight
7%323%46%19%
510
16th to endNight
41324%50%16%
564
August1st to 15thNight
6%1320%52%15%
539
16th to endNight
12%16%21%41%16%
669
September1st to 15thNight
13%17%27%38%11%
707
16th to endNight
17%211%28%32%6%
657
October1st to 15thNight
11%217%37%28%2
660
16th to endNight
9%423%35%25%1
704
November1st to 15thNight
9%329%38%18%1
700
16th to endNight
10%6%35%29%17%1
720
December1st to 15thNight
14%7%28%32%16%
720
16th to endNight
14%8%24%35%16%
768
Page generated at 2017-09-13 07:39:23. Version ac04

Copyright 2017 A. Danko


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