East Coast Video Astronomy Rendezvous
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the East Coast Video Astronomy Rendezvous clear sky chart from 2005-11-06 to 2024-01-14.

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
40%
23582
21%
74725
12%
23536
50%
23536
24%
46954

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
22%
757
24%
2478
9%
757
41%
757
20%
1520
January11th to 20thNight
27%
736
23%
2391
11%
736
41%
736
19%
1540
January21st to endNight
22%
792
23%
2574
10%
792
40%
792
21%
1602
February1st to 10thNight
24%
720
18%
2340
8%
720
38%
720
19%
1511
February11th to 20thNight
14%
700
18%
2275
5%
700
31%
700
14%
1498
February21st to endNight
17%
592
23%
1735
7%
592
34%
592
19%
1177
March1st to 10thNight
24%
720
26%
1980
10%
720
40%
720
26%
1227
March11th to 20thNight
24%
720
20%
1980
9%
720
35%
720
20%
1329
March21st to endNight
25%
792
19%
2178
8%
792
34%
792
22%
1448
April1st to 10thNight
27%
720
19%
1826
5%
720
36%
720
24%
1238
April11th to 20thNight
35%
711
20%
1775
7%
711
41%
711
31%
1158
April21st to endNight
35%
694
21%
1774
7%
694
43%
694
27%
1176
May1st to 10thNight
42%
540
17%
1620
9%
540
48%
540
23%
1078
May11th to 20thNight
45%
531
15%
1592
9%
531
49%
531
24%
1070
May21st to endNight
54%
401
15%
1564
15%
401
58%
401
23%
929
June1st to 10thNight
58%
360
19%
1440
20%
360
64%
360
25%
833
June11th to 20thNight
60%
360
15%
1440
19%
360
64%
360
22%
878
June21st to endNight
64%
360
19%
1440
21%
360
69%
360
26%
820
July1st to 10thNight
61%
389
15%
1439
15%
389
64%
389
24%
885
July11th to 20thNight
75%
522
15%
1566
12%
522
76%
522
33%
961
July21st to endNight
70%
591
17%
1672
15%
558
73%
558
33%
1033
August1st to 10thNight
69%
537
16%
1600
13%
534
70%
534
29%
1049
August11th to 20thNight
63%
548
19%
1612
14%
548
65%
548
27%
1051
August21st to endNight
63%
792
18%
1980
12%
792
64%
792
31%
1336
September1st to 10thNight
61%
720
22%
1800
14%
720
64%
720
31%
1197
September11th to 20thNight
62%
720
28%
1859
21%
720
65%
720
36%
1174
September21st to endNight
46%
720
20%
2047
14%
720
52%
720
25%
1362
October1st to 10thNight
51%
720
20%
2160
19%
720
56%
720
29%
1348
October11th to 20thNight
43%
720
26%
2160
17%
720
55%
720
29%
1290
October21st to endNight
40%
792
27%
2376
18%
792
53%
792
28%
1438
November1st to 10thNight
41%
740
28%
2221
18%
740
53%
740
32%
1300
November11th to 20thNight
35%
760
25%
2545
15%
760
49%
760
24%
1492
November21st to endNight
36%
760
22%
2660
15%
760
49%
760
23%
1558
December1st to 10thNight
27%
760
20%
2660
9%
760
42%
760
18%
1702
December11th to 20thNight
31%
760
22%
3175
13%
758
45%
758
18%
1906
December21st to endNight
31%
825
15%
4791
11%
817
46%
817
12%
2840

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
13%6%36%6%35%5%6%8%40%
74632
Night
12%6%35%5%35%5%6%7%43%
75131
TransparencyDay
42%6%12%22%15%3
74350
Night
39%6%12%23%16%3
74932
SeeingDay
19%13%26%23%14%5%
13818
Night
17%11%25%32%14%2
23601

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
10%8%47%6%445%5%7%41%
1682
11th to 20thDay
14%8%38%5%3445%6%39%
1647
21st to endDay
13%9%46%5%35%45%6%41%
1782
February1st to 10thDay
11%9%5%7%5%35%6%6%7%35%
1620
11th to 20thDay
15%8%36%5%35%45%7%38%
1573
21st to endDay
15%9%36%5%3445%5%40%
1518
March1st to 10thDay
12%8%25%4345%45%48%
1980
11th to 20thDay
15%8%36%5%36%5%5%6%39%
1980
21st to endDay
15%9%36%6%35%5%5%6%36%
2178
April1st to 10thDay
10%6%37%5%35%5%6%7%43%
2133
11th to 20thDay
13%6%35%5%34446%46%
2134
21st to endDay
16%7%36%5%36%45%7%38%
2200
May1st to 10thDay
16%7%25%5%45%6%6%8%36%
2340
11th to 20thDay
17%7%27%5%45%6%6%7%34%
2301
21st to endDay
12%6%26%6%35%6%6%9%37%
2712
June1st to 10thDay
12%435%6%36%5%7%8%40%
2520
11th to 20thDay
10%5%26%7%36%7%7%10%36%
2520
21st to endDay
9%5%35%6%46%7%7%11%40%
2520
July1st to 10thDay
10%5%36%6%46%6%6%9%39%
2475
11th to 20thDay
7%426%7%5%7%7%7%11%38%
2340
21st to endDay
11%6%36%6%46%7%7%10%34%
2547
August1st to 10thDay
9%5%37%8%6%7%7%9%9%32%
2327
11th to 20thDay
12%5%35%8%45%7%7%8%35%
2268
21st to endDay
11%6%36%6%45%6%7%9%38%
2376
September1st to 10thDay
13%7%35%6%45%45%6%43%
2160
11th to 20thDay
11%6%26%5%35%5%6%7%45%
2098
21st to endDay
18%6%36%5%35%5%5%7%36%
1913
October1st to 10thDay
16%7%2443445%8%44%
1800
11th to 20thDay
14%6%25%5%34445%47%
1800
21st to endDay
14%6%3442445%6%47%
1980
November1st to 10thDay
11%5%35%43445%6%52%
1857
11th to 20thDay
12%5%35%435%5%47%47%
1629
21st to endDay
13%5%244345%47%48%
1520
December1st to 10thDay
15%8%26%5%35%5%5%7%37%
1520
11th to 20thDay
13%6%35%5%3445%8%45%
1910
21st to endDay
16%8%35%6%45%6%6%8%35%
2772
January1st to 10thNight
10%8%36%435%5%5%7%44%
2478
11th to 20thNight
14%8%36%5%345%7%6%40%
2391
21st to endNight
11%9%35%5%35%46%6%42%
2574
February1st to 10thNight
13%7%36%6%35%6%5%7%39%
2340
11th to 20thNight
17%9%35%5%345%46%38%
2273
21st to endNight
14%8%38%5%35%5%5%6%38%
1735
March1st to 10thNight
11%6%245%35%5%5%6%48%
1980
11th to 20thNight
16%7%35%5%345%5%6%42%
1980
21st to endNight
15%7%36%5%3445%7%41%
2178
April1st to 10thNight
11%6%36%6%45%5%6%7%41%
1826
11th to 20thNight
11%5%26%5%345%7%7%45%
1775
21st to endNight
14%6%25%5%345%5%7%43%
1774
May1st to 10thNight
15%6%35%5%445%5%8%40%
1620
11th to 20thNight
14%6%37%5%445%5%7%40%
1592
21st to endNight
11%5%25%6%3446%10%42%
1563
June1st to 10thNight
10%5%25%6%346%6%10%44%
1440
11th to 20thNight
10%5%247%36%5%7%9%41%
1440
21st to endNight
9%425%445%6%8%10%44%
1440
July1st to 10thNight
10%5%346%45%6%7%9%42%
1481
11th to 20thNight
7%3245%5%5%5%7%11%46%
1620
21st to endNight
6%435%5%45%5%8%12%42%
1771
August1st to 10thNight
7%5%26%7%45%7%8%10%40%
1611
11th to 20thNight
10%6%36%6%45%6%5%9%41%
1612
21st to endNight
8%6%36%5%36%7%7%11%39%
1980
September1st to 10thNight
13%6%25%4245%6%8%45%
1800
11th to 20thNight
10%5%35%5%44447%50%
1859
21st to endNight
16%8%35%5%25%446%43%
2047
October1st to 10thNight
16%5%24434447%47%
2160
11th to 20thNight
12%6%35%33446%5%50%
2160
21st to endNight
14%6%2443435%6%49%
2376
November1st to 10thNight
10%7%35%5%2345%6%51%
2221
11th to 20thNight
12%6%35%5%3445%7%48%
2545
21st to endNight
12%6%25%5%345%6%7%46%
2660
December1st to 10thNight
14%8%36%5%35%45%6%40%
2660
11th to 20thNight
15%6%35%5%35%5%5%7%42%
3285
21st to endNight
14%7%37%6%45%6%6%7%36%
4884

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
43%5%9%22%17%4
1683
11th to 20thDay
45%5%10%23%16%1
1647
21st to endDay
45%49%21%17%4
1782
February1st to 10thDay
47%5%11%21%13%3
1620
11th to 20thDay
46%5%8%21%17%3
1582
21st to endDay
45%412%18%17%4
1518
March1st to 10thDay
38%410%23%21%3
1980
11th to 20thDay
45%5%9%18%17%5%
1980
21st to endDay
47%6%11%18%14%4
2178
April1st to 10thDay
39%5%12%20%18%6%
2133
11th to 20thDay
38%5%10%20%20%6%
2134
21st to endDay
46%6%10%21%14%4
2200
May1st to 10thDay
44%7%13%20%13%2
2340
11th to 20thDay
47%8%12%19%11%2
2305
21st to endDay
42%7%15%24%10%1
2712
June1st to 10thDay
40%7%12%24%15%1
2520
11th to 20thDay
42%9%14%21%13%2
2520
21st to endDay
36%9%14%25%14%2
2520
July1st to 10thDay
41%9%13%21%15%2
2407
11th to 20thDay
38%10%15%23%13%1
2271
21st to endDay
43%8%12%20%15%1
2405
August1st to 10thDay
44%10%15%22%9%
2314
11th to 20thDay
44%9%14%21%11%1
2268
21st to endDay
41%8%15%23%11%2
2376
September1st to 10thDay
41%7%13%18%18%4
2160
11th to 20thDay
38%6%8%26%18%3
2098
21st to endDay
47%6%9%20%17%2
1913
October1st to 10thDay
39%5%10%26%16%4
1800
11th to 20thDay
39%5%9%23%21%3
1800
21st to endDay
36%5%8%24%22%4
1980
November1st to 10thDay
33%49%25%24%4
1857
11th to 20thDay
38%410%21%22%6%
1629
21st to endDay
36%411%26%21%2
1520
December1st to 10thDay
45%5%11%22%13%3
1520
11th to 20thDay
37%5%12%29%13%5%
1906
21st to endDay
44%7%13%24%10%1
2772
January1st to 10thNight
38%7%10%21%20%5%
2478
11th to 20thNight
42%6%11%22%16%2
2391
21st to endNight
42%410%23%19%2
2574
February1st to 10thNight
43%5%12%24%14%2
2340
11th to 20thNight
46%5%8%21%15%5%
2275
21st to endNight
45%6%10%21%14%4
1735
March1st to 10thNight
36%5%10%28%18%3
1980
11th to 20thNight
43%6%10%21%17%3
1980
21st to endNight
43%5%13%19%16%4
2178
April1st to 10thNight
41%6%10%21%17%4
1826
11th to 20thNight
37%5%13%21%20%5%
1775
21st to endNight
40%5%12%27%13%4
1774
May1st to 10thNight
41%8%13%22%12%4
1620
11th to 20thNight
43%7%13%21%14%1
1593
21st to endNight
38%7%20%24%10%1
1564
June1st to 10thNight
34%8%14%29%13%1
1440
11th to 20thNight
37%10%16%23%13%1
1440
21st to endNight
34%8%17%22%17%2
1440
July1st to 10thNight
37%10%17%20%14%3
1439
11th to 20thNight
30%11%18%26%13%2
1566
21st to endNight
31%9%20%25%13%1
1672
August1st to 10thNight
36%10%18%24%11%1
1600
11th to 20thNight
40%7%15%26%12%1
1612
21st to endNight
37%9%17%24%10%2
1980
September1st to 10thNight
37%8%13%22%16%4
1800
11th to 20thNight
35%5%11%28%19%2
1859
21st to endNight
43%5%10%22%17%2
2047
October1st to 10thNight
39%5%12%25%17%3
2160
11th to 20thNight
33%6%9%27%22%3
2160
21st to endNight
35%6%9%24%23%3
2376
November1st to 10thNight
34%411%23%22%6%
2221
11th to 20thNight
37%47%24%22%5%
2545
21st to endNight
37%5%11%24%20%4
2660
December1st to 10thNight
44%5%11%24%13%3
2660
11th to 20thNight
39%6%9%23%19%3
3288
21st to endNight
41%8%14%22%13%1
4884

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
25%29%29%13%5%
258
11th to 20thDay
27%26%31%14%3
249
21st to endDay
28%30%26%13%21
264
February1st to 10thDay
28%31%31%8%3
240
11th to 20thDay
40%25%30%4
240
21st to endDay
33%20%27%17%3
332
March1st to 10thDay
25%22%28%21%3
420
11th to 20thDay
26%25%27%15%6%1
420
21st to endDay
25%20%30%18%6%1
462
April1st to 10thDay
22%24%26%19%7%2
420
11th to 20thDay
21%18%25%22%11%3
412
21st to endDay
28%14%31%16%9%1
420
May1st to 10thDay
23%19%28%15%12%3
423
11th to 20thDay
22%14%28%23%10%3
447
21st to endDay
18%6%27%26%17%7%
485
June1st to 10thDay
14%10%26%27%20%3
450
11th to 20thDay
17%9%27%28%15%5%
450
21st to endDay
12%9%27%30%19%3
450
July1st to 10thDay
12%420%31%23%11%
445
11th to 20thDay
7%120%33%28%10%
444
21st to endDay
12%222%31%25%9%
488
August1st to 10thDay
11%7%17%27%26%12%
446
11th to 20thDay
13%319%30%23%11%
439
21st to endDay
10%419%29%23%15%
495
September1st to 10thDay
17%6%18%23%24%13%
450
11th to 20thDay
14%418%31%22%11%
450
21st to endDay
25%9%21%26%15%5%
450
October1st to 10thDay
21%5%20%28%21%6%
450
11th to 20thDay
18%14%25%25%15%2
450
21st to endDay
19%16%32%21%9%3
495
November1st to 10thDay
15%15%30%26%12%3
455
11th to 20thDay
18%16%32%22%10%1
281
21st to endDay
21%19%36%18%5%1
180
December1st to 10thDay
21%27%33%14%6%1
180
11th to 20thDay
22%24%28%19%7%
180
21st to endDay
25%14%36%18%7%1
198
January1st to 10thNight
18%21%34%24%4
760
11th to 20thNight
22%16%27%30%4
736
21st to endNight
19%16%38%26%2
792
February1st to 10thNight
17%20%33%27%3
720
11th to 20thNight
27%22%32%16%2
703
21st to endNight
23%20%35%20%2
592
March1st to 10thNight
18%18%36%25%3
720
11th to 20thNight
23%18%30%22%5%1
720
21st to endNight
19%18%34%24%5%1
792
April1st to 10thNight
16%21%30%26%6%
720
11th to 20thNight
15%14%31%29%10%1
711
21st to endNight
18%12%29%33%9%
694
May1st to 10thNight
21%8%23%31%16%2
540
11th to 20thNight
16%5%24%38%15%2
531
21st to endNight
13%218%42%21%2
403
June1st to 10thNight
13%419%40%24%1
360
11th to 20thNight
13%312%46%24%2
360
21st to endNight
7%316%49%24%1
360
July1st to 10thNight
14%214%37%28%5%
389
11th to 20thNight
7%29%38%40%4
522
21st to endNight
7%211%41%34%5%
591
August1st to 10thNight
10%18%45%32%3
537
11th to 20thNight
11%310%41%32%3
548
21st to endNight
11%312%37%33%4
792
September1st to 10thNight
15%311%35%30%6%
720
11th to 20thNight
12%313%36%31%5%
720
21st to endNight
21%419%32%22%2
720
October1st to 10thNight
19%7%17%30%24%4
720
11th to 20thNight
16%10%25%33%14%1
720
21st to endNight
17%11%26%32%12%1
792
November1st to 10thNight
14%12%27%34%12%1
740
11th to 20thNight
16%15%28%30%9%1
760
21st to endNight
16%14%28%32%9%1
760
December1st to 10thNight
21%15%30%27%6%1
760
11th to 20thNight
17%11%33%34%4
760
21st to endNight
17%16%29%36%3
836
Page generated at 2024-01-11 13:31:57. Version ac07

Copyright 2024 Attilla Danko


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