Meyer-Womble Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Meyer-Womble Observatory clear sky chart from 2005-11-05 to 2018-02-22.

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
31%
16632
26%
48916
9%
16585
48%
16585
28%
26619

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
18%
975
29%
2716
6%
970
40%
970
24%
1404
January16th to endNight
16%
845
33%
2717
8%
845
45%
845
27%
1302
February1st to 15thNight
14%
760
25%
2457
4%
756
38%
756
17%
1249
February16th to endNight
12%
660
33%
1978
3%
660
43%
660
21%
1053
March1st to 15thNight
20%
720
27%
2088
5%
720
39%
720
23%
1148
March16th to endNight
20%
696
25%
2040
6%
696
38%
696
22%
1157
April1st to 15thNight
20%
539
24%
1798
7%
539
41%
539
24%
949
April16th to endNight
24%
540
22%
1800
9%
540
42%
540
22%
1018
May1st to 15thNight
29%
540
18%
1611
5%
540
43%
540
23%
1013
May16th to endNight
40%
563
18%
1498
8%
561
50%
561
31%
912
June1st to 15thNight
48%
540
23%
1440
12%
540
57%
540
45%
759
June16th to endNight
60%
540
26%
1440
17%
540
67%
540
49%
751
July1st to 15thNight
65%
510
17%
1360
13%
510
69%
510
32%
854
July16th to endNight
69%
564
19%
1475
16%
531
71%
531
36%
877
August1st to 15thNight
61%
539
16%
1650
14%
536
64%
536
29%
991
August16th to endNight
63%
573
25%
1910
24%
573
69%
573
31%
1098
September1st to 15thNight
58%
540
27%
1800
20%
540
69%
540
34%
981
September16th to endNight
51%
552
33%
1932
23%
552
67%
552
36%
971
October1st to 15thNight
33%
720
30%
2160
12%
720
48%
720
35%
1121
October16th to endNight
32%
776
34%
2312
11%
776
50%
776
32%
1195
November1st to 15thNight
25%
950
32%
2470
8%
950
42%
950
33%
1313
November16th to endNight
20%
975
33%
2622
7%
975
42%
975
30%
1374
December1st to 15thNight
15%
975
23%
2730
3%
975
33%
975
22%
1462
December16th to endNight
17%
1040
25%
2912
5%
1040
35%
1040
19%
1667

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
5%7%36%5%35%5%5%7%43%
49347
Night
242442445%8%56%
49094
TransparencyDay
37%7%11%22%16%4
49027
Night
24%6%15%28%19%5%
48916
SeeingDay
14%26%27%19%9%2
6316
Night
7%26%28%23%12%1
16636

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
236%335%5%6%9%52%
1552
16th to endDay
335%5%3445%8%54%
1869
February1st to 15thDay
337%5%25%5%6%11%47%
1733
16th to endDay
348%5%35%5%48%50%
1642
March1st to 15thDay
16%35%6%45%35%8%46%
1869
16th to endDay
29%47%5%36%47%9%38%
2184
April1st to 15thDay
310%36%6%36%46%7%41%
2150
16th to endDay
6%16%5%8%6%345%45%33%
2160
May1st to 15thDay
8%14%5%7%6%35%5%5%7%31%
2337
16th to endDay
10%11%47%6%45%45%6%32%
2616
June1st to 15thDay
7%5%36%5%45%5%5%7%42%
2520
16th to endDay
5%435%5%36%6%6%7%46%
2520
July1st to 15thDay
11%6%38%7%46%6%5%6%33%
2520
16th to endDay
11%7%48%7%46%6%6%7%28%
2591
August1st to 15thDay
14%8%48%7%45%5%5%6%29%
2299
16th to endDay
11%7%47%6%36%45%6%35%
2292
September1st to 15thDay
11%7%26%434345%45%
2160
16th to endDay
7%6%25%5%23445%51%
2025
October1st to 15thDay
7%6%36%5%24345%51%
1800
16th to endDay
36%243235%48%53%
1899
November1st to 15thDay
142332345%8%59%
1718
16th to endDay
315%32346%8%59%
1667
December1st to 15thDay
326%6%4445%8%54%
1560
16th to endDay
325%6%35%46%9%51%
1664
January1st to 15thNight
11243346%10%60%
2716
16th to endNight
2243224410%62%
2717
February1st to 15thNight
22432436%10%58%
2447
16th to endNight
32442345%10%57%
1978
March1st to 15thNight
4244245%6%8%55%
2088
16th to endNight
35%3431435%8%54%
2040
April1st to 15thNight
16%1432446%9%56%
1798
16th to endNight
49%35%323448%49%
1800
May1st to 15thNight
7%9%25%3345%6%8%43%
1610
16th to endNight
6%5%24435%46%9%47%
1497
June1st to 15thNight
32112235%5%10%59%
1440
16th to endNight
2233235%6%8%61%
1440
July1st to 15thNight
45%245%37%5%6%10%43%
1440
16th to endNight
5%4245%35%47%10%45%
1576
August1st to 15thNight
6%5%25%6%25%5%6%8%46%
1659
16th to endNight
7%325%5%345%5%7%48%
1910
September1st to 15thNight
6%5%14325%46%8%50%
1800
16th to endNight
431332345%5%61%
1932
October1st to 15thNight
4313313447%62%
2160
16th to endNight
25%24313347%61%
2312
November1st to 15thNight
312323349%63%
2470
16th to endNight
31232445%9%61%
2622
December1st to 15thNight
41442335%8%60%
2730
16th to endNight
325%5%3445%9%55%
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
27%6%20%25%15%4
1553
16th to endDay
26%6%16%27%17%5%
1869
February1st to 15thDay
28%8%20%26%12%3
1734
16th to endDay
29%7%10%27%19%4
1642
March1st to 15thDay
34%5%12%28%16%2
1869
16th to endDay
38%7%10%28%11%3
2184
April1st to 15thDay
39%6%11%21%14%4
2150
16th to endDay
50%5%8%21%11%2
2160
May1st to 15thDay
50%6%10%20%11%
2337
16th to endDay
50%6%9%20%10%2
2620
June1st to 15thDay
38%7%10%15%20%7%
2520
16th to endDay
33%6%7%22%22%7%
2520
July1st to 15thDay
47%8%9%14%13%6%
2371
16th to endDay
48%10%11%16%8%3
2429
August1st to 15thDay
52%9%8%11%12%5%
2284
16th to endDay
45%7%8%20%14%3
2292
September1st to 15thDay
39%6%6%18%20%8%
2160
16th to endDay
31%7%7%24%26%3
2025
October1st to 15thDay
34%46%22%26%5%
1800
16th to endDay
26%7%9%26%24%5%
1899
November1st to 15thDay
21%5%13%24%26%7%
1718
16th to endDay
21%5%12%30%22%6%
1667
December1st to 15thDay
26%8%16%29%15%2
1560
16th to endDay
27%9%15%25%17%4
1664
January1st to 15thNight
18%6%19%31%18%4
2716
16th to endNight
19%415%32%21%7%
2717
February1st to 15thNight
20%7%18%34%15%3
2457
16th to endNight
22%5%12%32%21%5%
1978
March1st to 15thNight
23%6%13%32%20%4
2088
16th to endNight
26%7%13%32%16%3
2040
April1st to 15thNight
24%7%12%31%18%4
1798
16th to endNight
32%5%15%29%15%1
1800
May1st to 15thNight
37%6%15%24%14%1
1611
16th to endNight
31%6%18%27%13%2
1498
June1st to 15thNight
17%8%16%26%21%9%
1440
16th to endNight
18%6%11%27%24%11%
1440
July1st to 15thNight
33%9%14%20%15%7%
1360
16th to endNight
30%7%20%24%12%4
1475
August1st to 15thNight
33%9%16%19%15%6%
1650
16th to endNight
31%7%13%25%19%2
1910
September1st to 15thNight
29%6%13%22%19%9%
1800
16th to endNight
23%5%9%32%25%3
1932
October1st to 15thNight
21%5%11%28%25%7%
2160
16th to endNight
22%411%28%27%5%
2312
November1st to 15thNight
17%5%12%27%26%9%
2470
16th to endNight
19%5%12%31%24%6%
2622
December1st to 15thNight
21%6%21%28%17%4
2730
16th to endNight
24%8%18%26%17%4
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
6%47%21%14%9%
135
16th to endDay
6%43%29%18%2
144
February1st to 15thDay
13%61%19%5%
135
16th to endDay
9%50%23%15%3
100
March1st to 15thDay
15%44%24%13%1
159
16th to endDay
16%46%27%9%
288
April1st to 15thDay
20%36%28%11%2
269
16th to endDay
26%41%21%8%1
270
May1st to 15thDay
17%26%31%17%5%
396
16th to endDay
19%20%28%18%10%2
517
June1st to 15thDay
9%21%29%24%12%2
495
16th to endDay
5%12%35%26%17%3
495
July1st to 15thDay
15%8%22%26%19%6%
475
16th to endDay
13%9%20%29%19%8%
450
August1st to 15thDay
20%12%30%25%9%1
315
16th to endDay
18%11%28%29%10%1
332
September1st to 15thDay
15%24%32%18%7%1
315
16th to endDay
12%21%34%20%8%3
198
October1st to 15thDay
8%36%25%14%12%1
135
16th to endDay
14%34%29%14%5%1
144
November1st to 15thDay
5%40%20%20%10%2
135
16th to endDay
10%48%33%5%2
135
December1st to 15thDay
11%54%22%8%2
135
16th to endDay
7%54%24%11%1
144
January1st to 15thNight
9%41%27%13%6%1
975
16th to endNight
9%35%35%14%5%
845
February1st to 15thNight
8%43%30%13%3
764
16th to endNight
5%43%33%14%3
660
March1st to 15thNight
5%37%31%16%7%
720
16th to endNight
8%34%34%19%3
696
April1st to 15thNight
8%27%39%18%4
539
16th to endNight
10%28%32%22%6%
540
May1st to 15thNight
13%16%35%24%9%1
540
16th to endNight
10%13%28%29%16%1
563
June1st to 15thNight
7%10%32%34%14%1
540
16th to endNight
35%24%40%23%2
540
July1st to 15thNight
8%213%36%35%4
510
16th to endNight
7%28%35%39%6%
564
August1st to 15thNight
8%212%43%30%2
539
16th to endNight
6%314%38%29%6%
573
September1st to 15thNight
7%322%36%22%6%
540
16th to endNight
6%10%25%32%21%3
552
October1st to 15thNight
7%24%32%20%13%1
720
16th to endNight
6%29%27%23%9%2
776
November1st to 15thNight
6%34%30%18%7%1
950
16th to endNight
438%34%17%5%
975
December1st to 15thNight
9%40%32%14%3
975
16th to endNight
7%42%28%16%5%
1040
Page generated at 2018-02-23 09:21:32. Version ac04

Copyright 2018 A. Danko


Meyer-Womble Observatory Clear Sky Chart |Charts Home