Georgetown
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Georgetown clear sky chart from 2005-11-06 to 2024-03-01.

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%
24800
20%
79725
15%
24708
58%
24708
25%
49810

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 10thNight
35%
752
23%
3998
11%
737
49%
737
15%
2202
January11th to 20thNight
40%
754
24%
3990
14%
740
54%
740
15%
2317
January21st to endNight
31%
826
17%
4439
14%
814
46%
814
15%
2608
February1st to 10thNight
38%
760
21%
2470
14%
760
49%
760
24%
1531
February11th to 20thNight
32%
743
19%
2291
10%
740
45%
740
22%
1503
February21st to endNight
39%
628
21%
1727
12%
628
48%
628
26%
1150
March1st to 10thNight
40%
723
27%
1987
16%
723
50%
723
32%
1249
March11th to 20thNight
43%
720
21%
1980
13%
720
51%
720
27%
1313
March21st to endNight
44%
792
22%
2178
12%
792
52%
792
30%
1393
April1st to 10thNight
46%
720
23%
1913
14%
720
52%
720
34%
1188
April11th to 20thNight
52%
711
24%
1775
14%
711
56%
711
36%
1140
April21st to endNight
55%
720
25%
1800
15%
720
58%
720
40%
1104
May1st to 10thNight
56%
639
21%
1719
11%
639
58%
639
37%
1049
May11th to 20thNight
60%
531
17%
1593
12%
531
61%
531
28%
1006
May21st to endNight
70%
582
18%
1745
15%
582
71%
582
30%
1087
June1st to 10thNight
64%
540
14%
1620
12%
540
64%
540
24%
1078
June11th to 20thNight
69%
540
13%
1620
11%
540
70%
540
29%
1033
June21st to endNight
69%
540
13%
1620
11%
540
70%
540
24%
1061
July1st to 10thNight
69%
525
13%
1575
11%
525
69%
525
23%
1059
July11th to 20thNight
70%
522
10%
1566
9%
522
70%
522
23%
1061
July21st to endNight
74%
591
13%
1672
11%
558
76%
558
29%
1065
August1st to 10thNight
70%
537
11%
1600
10%
534
71%
534
23%
1080
August11th to 20thNight
69%
613
13%
1677
10%
613
69%
613
22%
1184
August21st to endNight
65%
792
13%
1980
9%
792
65%
792
22%
1463
September1st to 10thNight
69%
720
18%
1808
15%
720
70%
720
27%
1284
September11th to 20thNight
64%
720
16%
1980
15%
720
64%
720
23%
1398
September21st to endNight
56%
720
18%
1988
17%
720
58%
720
25%
1373
October1st to 10thNight
58%
720
23%
2160
24%
720
61%
720
30%
1335
October11th to 20thNight
58%
720
29%
2160
26%
720
67%
720
36%
1229
October21st to endNight
56%
792
30%
2376
25%
792
65%
792
36%
1335
November1st to 10thNight
54%
740
27%
2221
22%
740
62%
740
36%
1279
November11th to 20thNight
46%
760
26%
2280
20%
760
55%
760
29%
1404
November21st to endNight
49%
760
26%
2398
19%
760
59%
760
30%
1426
December1st to 10thNight
41%
760
21%
2470
14%
760
51%
760
21%
1617
December11th to 20thNight
41%
759
26%
2939
19%
758
51%
758
23%
1688
December21st to endNight
38%
828
15%
4410
14%
817
47%
817
14%
2518

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
11%5%25%5%35%5%6%9%42%
78930
Night
12%6%25%5%35%5%6%8%44%
80489
TransparencyDay
37%10%14%19%16%5%
78652
Night
37%8%13%19%18%6%
80286
SeeingDay
12%5%19%28%26%10%
14639
Night
13%6%20%31%25%5%
24835

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 10thDay
14%5%244345%5%8%46%
2836
11th to 20thDay
10%436%5%3435%9%47%
2840
21st to endDay
13%8%35%5%34446%45%
3124
February1st to 10thDay
14%6%35%5%35%46%8%40%
1710
11th to 20thDay
18%6%25%433445%46%
1772
21st to endDay
16%6%36%5%2445%7%43%
1727
March1st to 10thDay
14%5%3442335%6%52%
1980
11th to 20thDay
13%6%25%6%45%5%5%7%41%
1980
21st to endDay
13%435%5%35%5%6%8%43%
2178
April1st to 10thDay
10%3244245%5%8%52%
2046
11th to 20thDay
10%3235%35%46%8%51%
2134
21st to endDay
7%42333446%8%54%
2160
May1st to 10thDay
7%425%4345%7%9%50%
2255
11th to 20thDay
10%6%35%6%346%7%9%41%
2301
21st to endDay
10%6%25%5%35%6%8%11%37%
2531
June1st to 10thDay
10%7%37%7%47%7%8%11%30%
2340
11th to 20thDay
9%325%6%47%7%8%12%38%
2340
21st to endDay
7%5%35%6%5%6%8%9%13%33%
2340
July1st to 10thDay
8%6%25%6%5%7%8%8%12%31%
2340
11th to 20thDay
8%5%36%7%47%7%10%12%31%
2340
21st to endDay
7%5%35%7%48%8%8%13%32%
2547
August1st to 10thDay
10%5%25%7%47%8%9%12%29%
2327
11th to 20thDay
10%6%37%6%47%8%9%12%28%
2206
21st to endDay
13%8%37%6%5%6%7%8%9%28%
2376
September1st to 10thDay
10%5%345%35%7%9%11%38%
2147
11th to 20thDay
14%7%36%7%36%6%5%9%36%
1980
21st to endDay
16%6%35%5%35%5%6%7%38%
1972
October1st to 10thDay
14%5%26%6%335%46%46%
1800
11th to 20thDay
10%5%244335%47%54%
1800
21st to endDay
10%5%15%43345%5%55%
1980
November1st to 10thDay
12%5%13433446%56%
1857
11th to 20thDay
14%6%35%423346%49%
1900
21st to endDay
12%5%25%5%23347%51%
1777
December1st to 10thDay
13%6%46%6%35%5%6%7%39%
1710
11th to 20thDay
14%424323335%55%
2153
21st to endDay
17%8%35%424445%42%
3124
January1st to 10thNight
15%6%245%35%46%7%43%
4109
11th to 20thNight
10%7%36%6%35%6%6%7%41%
4120
21st to endNight
12%7%37%5%3445%6%44%
4532
February1st to 10thNight
15%5%35%5%2445%7%43%
2470
11th to 20thNight
17%8%25%5%245%46%42%
2289
21st to endNight
14%7%36%4445%5%7%43%
1727
March1st to 10thNight
11%5%345%3445%7%48%
1987
11th to 20thNight
12%5%26%6%35%5%6%7%44%
1980
21st to endNight
12%6%26%435%45%8%46%
2178
April1st to 10thNight
9%5%345%3445%8%50%
1913
11th to 20thNight
12%3345%3445%7%50%
1775
21st to endNight
7%4244345%5%8%54%
1800
May1st to 10thNight
7%5%15%5%25%46%8%52%
1719
11th to 20thNight
11%435%4345%6%10%46%
1592
21st to endNight
9%425%4446%7%11%45%
1744
June1st to 10thNight
10%6%35%6%46%6%8%13%35%
1620
11th to 20thNight
8%5%25%5%26%6%7%11%43%
1620
21st to endNight
6%436%6%46%7%10%15%34%
1620
July1st to 10thNight
7%5%36%6%46%6%8%13%36%
1620
11th to 20thNight
7%6%36%6%46%5%8%13%35%
1620
21st to endNight
5%326%6%45%7%9%12%41%
1771
August1st to 10thNight
7%5%26%5%37%7%9%14%33%
1611
11th to 20thNight
8%6%26%8%47%7%8%13%32%
1677
21st to endNight
11%6%36%6%46%6%7%11%33%
1980
September1st to 10thNight
8%436%7%46%6%6%9%40%
1808
11th to 20thNight
10%8%35%6%447%6%9%38%
1980
21st to endNight
16%7%35%6%245%5%8%38%
1988
October1st to 10thNight
13%6%25%4345%46%48%
2160
11th to 20thNight
9%424424346%56%
2160
21st to endNight
9%5%24424446%55%
2376
November1st to 10thNight
11%424434446%56%
2221
11th to 20thNight
13%7%35%42345%6%49%
2280
21st to endNight
10%5%25%5%25%46%7%49%
2398
December1st to 10thNight
16%6%35%5%345%6%7%41%
2470
11th to 20thNight
17%6%25%433336%50%
3042
21st to endNight
17%6%35%4245%6%6%41%
4532

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 10thDay
34%7%9%20%24%6%
2837
11th to 20thDay
34%5%7%19%25%9%
2840
21st to endDay
41%6%8%19%18%8%
3124
February1st to 10thDay
41%7%9%19%19%4
1710
11th to 20thDay
41%6%7%17%22%7%
1781
21st to endDay
40%6%11%18%17%9%
1727
March1st to 10thDay
34%5%10%20%21%10%
1980
11th to 20thDay
42%8%11%18%14%7%
1980
21st to endDay
37%9%13%18%18%5%
2178
April1st to 10thDay
30%7%14%20%24%6%
2046
11th to 20thDay
31%7%12%24%17%10%
2134
21st to endDay
25%10%13%25%22%4
2160
May1st to 10thDay
27%10%15%26%18%4
2255
11th to 20thDay
37%9%18%21%14%1
2305
21st to endDay
35%12%17%22%13%
2531
June1st to 10thDay
42%13%17%19%10%
2340
11th to 20thDay
34%13%21%24%8%
2340
21st to endDay
36%15%23%20%7%1
2340
July1st to 10thDay
38%16%20%18%7%1
2275
11th to 20thDay
38%17%22%16%6%1
2271
21st to endDay
36%16%23%21%31
2405
August1st to 10thDay
39%16%24%18%3
2314
11th to 20thDay
43%17%20%15%5%
2206
21st to endDay
47%14%18%14%6%1
2376
September1st to 10thDay
34%16%19%16%14%2
2147
11th to 20thDay
43%12%13%15%14%4
1980
21st to endDay
44%9%12%19%14%3
1972
October1st to 10thDay
38%7%10%18%23%4
1800
11th to 20thDay
30%7%10%23%23%8%
1800
21st to endDay
29%5%9%17%30%10%
1980
November1st to 10thDay
31%5%9%17%27%10%
1857
11th to 20thDay
38%5%8%16%23%10%
1900
21st to endDay
35%5%9%20%23%8%
1777
December1st to 10thDay
42%9%12%17%14%6%
1710
11th to 20thDay
32%47%25%25%7%
2150
21st to endDay
43%6%8%18%21%4
3124
January1st to 10thNight
37%7%9%18%20%9%
4109
11th to 20thNight
39%7%8%17%24%5%
4120
21st to endNight
40%7%6%13%27%6%
4532
February1st to 10thNight
40%5%9%18%19%8%
2470
11th to 20thNight
43%6%8%15%19%9%
2291
21st to endNight
41%7%10%17%16%10%
1727
March1st to 10thNight
35%7%9%19%20%11%
1987
11th to 20thNight
39%8%12%18%16%6%
1980
21st to endNight
37%7%14%20%17%6%
2178
April1st to 10thNight
34%6%12%19%21%8%
1913
11th to 20thNight
33%7%11%20%19%10%
1775
21st to endNight
28%8%14%24%21%5%
1800
May1st to 10thNight
29%9%13%25%20%5%
1719
11th to 20thNight
35%10%17%23%15%1
1593
21st to endNight
31%13%18%26%12%1
1745
June1st to 10thNight
39%11%19%21%9%
1620
11th to 20thNight
35%11%21%25%9%
1620
21st to endNight
35%14%22%22%6%
1620
July1st to 10thNight
37%15%22%17%9%1
1575
11th to 20thNight
37%15%25%15%7%
1566
21st to endNight
32%13%25%26%4
1672
August1st to 10thNight
36%15%25%19%4
1600
11th to 20thNight
39%16%21%20%4
1677
21st to endNight
42%15%20%18%41
1980
September1st to 10thNight
38%14%15%18%13%3
1808
11th to 20thNight
40%13%14%17%14%2
1980
21st to endNight
44%7%13%20%12%4
1988
October1st to 10thNight
37%6%11%20%21%5%
2160
11th to 20thNight
30%6%10%21%25%8%
2160
21st to endNight
30%5%8%19%26%12%
2376
November1st to 10thNight
31%410%16%26%12%
2221
11th to 20thNight
37%6%9%15%22%11%
2280
21st to endNight
34%6%10%19%22%8%
2398
December1st to 10thNight
41%9%12%15%17%6%
2470
11th to 20thNight
37%48%19%25%6%
3044
21st to endNight
41%6%9%20%19%4
4532

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 10thDay
12%13%34%37%3
270
11th to 20thDay
7%9%34%38%11%1
270
21st to endDay
19%9%40%28%31
297
February1st to 10thDay
13%11%27%40%9%
270
11th to 20thDay
24%8%35%27%6%
300
21st to endDay
14%12%34%32%8%1
382
March1st to 10thDay
15%8%33%30%14%1
420
11th to 20thDay
15%8%34%31%9%2
420
21st to endDay
13%6%36%30%13%2
462
April1st to 10thDay
12%9%31%31%16%1
420
11th to 20thDay
9%5%26%28%25%7%
412
21st to endDay
9%6%22%34%22%8%
420
May1st to 10thDay
6%429%34%22%5%
423
11th to 20thDay
12%217%30%30%9%
447
21st to endDay
15%29%28%32%15%
485
June1st to 10thDay
10%410%30%36%11%
450
11th to 20thDay
12%19%26%32%21%
450
21st to endDay
7%16%26%45%15%
450
July1st to 10thDay
8%3416%45%23%
445
11th to 20thDay
7%16%18%45%25%
444
21st to endDay
5%15%25%44%19%
488
August1st to 10thDay
12%27%21%38%20%
446
11th to 20thDay
11%15%17%40%26%
439
21st to endDay
14%28%16%38%23%
495
September1st to 10thDay
9%27%22%40%20%
450
11th to 20thDay
14%311%25%34%12%
450
21st to endDay
18%38%22%38%11%
450
October1st to 10thDay
18%414%28%24%12%
450
11th to 20thDay
11%218%30%29%10%
450
21st to endDay
9%419%32%28%7%
495
November1st to 10thDay
16%7%19%29%22%8%
455
11th to 20thDay
17%5%24%40%11%3
460
21st to endDay
12%8%23%39%15%2
337
December1st to 10thDay
20%5%22%39%14%
270
11th to 20thDay
19%6%25%38%9%3
270
21st to endDay
18%8%26%32%15%2
297
January1st to 10thNight
14%14%29%33%9%1
760
11th to 20thNight
13%12%28%34%13%
760
21st to endNight
17%11%34%33%4
836
February1st to 10thNight
17%9%30%34%9%
760
11th to 20thNight
21%11%30%34%4
743
21st to endNight
17%8%29%35%11%
628
March1st to 10thNight
13%8%33%34%12%
723
11th to 20thNight
14%7%28%39%12%
720
21st to endNight
15%7%29%33%15%1
792
April1st to 10thNight
11%9%30%34%16%1
720
11th to 20thNight
11%7%24%33%22%3
711
21st to endNight
9%5%26%36%21%3
720
May1st to 10thNight
7%6%25%37%24%1
639
11th to 20thNight
12%416%36%28%5%
531
21st to endNight
10%27%27%41%12%
584
June1st to 10thNight
11%211%36%35%6%
540
11th to 20thNight
10%19%25%42%13%
540
21st to endNight
7%27%32%41%11%
540
July1st to 10thNight
10%26%25%47%10%
525
11th to 20thNight
10%5%21%49%15%
522
21st to endNight
5%16%30%48%11%
591
August1st to 10thNight
8%15%26%45%15%
537
11th to 20thNight
9%26%21%45%16%
613
21st to endNight
12%26%18%43%18%
792
September1st to 10thNight
9%27%23%48%11%
720
11th to 20thNight
13%47%31%35%11%
720
21st to endNight
22%38%24%35%8%
720
October1st to 10thNight
15%5%14%29%29%8%
720
11th to 20thNight
11%421%30%28%5%
720
21st to endNight
12%5%21%30%27%6%
792
November1st to 10thNight
12%5%22%33%22%5%
740
11th to 20thNight
15%9%25%32%17%2
760
21st to endNight
11%9%25%33%20%3
760
December1st to 10thNight
17%8%25%35%14%1
760
11th to 20thNight
19%8%27%29%16%2
760
21st to endNight
19%8%28%30%14%
836
Page generated at 2024-02-27 06:30:14. Version ac07

Copyright © 2024 Attilla Danko.


Georgetown Clear Sky Chart |Charts Home