Vincent Court Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Vincent Court Observatory clear sky chart from 2005-11-06 to 2024-02-15.

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
33%
23344
21%
80142
11%
23249
45%
23249
22%
49458

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
19%
754
26%
4331
9%
737
40%
737
13%
2306
January11th to 20thNight
22%
760
25%
4326
7%
740
40%
740
12%
2475
January21st to endNight
20%
831
15%
4481
7%
814
39%
814
11%
2921
February1st to 10thNight
22%
760
19%
2470
7%
760
38%
760
20%
1564
February11th to 20thNight
13%
722
21%
2163
5%
718
33%
718
18%
1412
February21st to endNight
16%
592
26%
1776
9%
592
37%
592
19%
1140
March1st to 10thNight
22%
720
24%
2160
9%
720
40%
720
24%
1312
March11th to 20thNight
21%
720
22%
2016
8%
720
35%
720
21%
1335
March21st to endNight
22%
792
23%
2027
7%
792
34%
792
26%
1369
April1st to 10thNight
19%
720
21%
1800
5%
720
30%
720
25%
1208
April11th to 20thNight
27%
711
20%
1775
7%
711
33%
711
28%
1189
April21st to endNight
28%
720
21%
1800
6%
720
36%
720
28%
1194
May1st to 10thNight
25%
572
17%
1652
7%
572
33%
572
21%
1141
May11th to 20thNight
25%
372
19%
1434
9%
372
38%
372
19%
894
May21st to endNight
47%
388
15%
1551
14%
388
53%
388
19%
958
June1st to 10thNight
43%
360
18%
1440
16%
360
54%
360
22%
859
June11th to 20thNight
48%
360
16%
1440
17%
360
55%
360
21%
857
June21st to endNight
53%
360
16%
1440
16%
360
60%
360
26%
803
July1st to 10thNight
54%
350
14%
1400
16%
350
58%
350
21%
852
July11th to 20thNight
60%
348
18%
1392
21%
348
64%
348
28%
773
July21st to endNight
57%
394
21%
1486
20%
372
65%
372
27%
814
August1st to 10thNight
59%
535
17%
1599
11%
533
61%
533
30%
991
August11th to 20thNight
55%
710
17%
1774
10%
710
58%
710
30%
1203
August21st to endNight
55%
792
17%
1980
8%
792
58%
792
32%
1311
September1st to 10thNight
48%
720
21%
1800
10%
720
53%
720
32%
1208
September11th to 20thNight
55%
720
29%
1853
19%
720
60%
720
40%
1113
September21st to endNight
46%
720
25%
1980
19%
720
53%
720
29%
1295
October1st to 10thNight
40%
720
19%
2114
13%
720
48%
720
27%
1351
October11th to 20thNight
41%
720
25%
2160
16%
720
53%
720
31%
1287
October21st to endNight
30%
792
25%
2470
13%
792
45%
792
25%
1530
November1st to 10thNight
36%
740
26%
2407
14%
740
53%
740
31%
1358
November11th to 20thNight
31%
760
26%
2470
14%
760
46%
760
22%
1508
November21st to endNight
29%
760
24%
2553
10%
760
46%
760
25%
1491
December1st to 10thNight
21%
760
20%
2660
7%
760
37%
760
17%
1683
December11th to 20thNight
23%
760
21%
3184
7%
759
41%
759
17%
1899
December21st to endNight
23%
829
15%
4778
9%
817
40%
817
12%
2854

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%35%5%5%7%41%
78283
Night
16%6%25%5%3445%7%43%
80784
TransparencyDay
43%311%24%16%3
77988
Night
42%311%24%17%3
80613
SeeingDay
21%14%29%22%11%3
13987
Night
19%11%31%28%9%1
23363

By Month

Percentage Cloud Cover NE (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
15%8%245%33445%47%
2517
11th to 20thDay
15%9%38%6%34446%38%
2523
21st to endDay
23%8%36%5%34345%36%
3124
February1st to 10thDay
16%7%36%6%34447%40%
1710
11th to 20thDay
17%7%36%5%35%436%41%
1777
21st to endDay
19%8%36%5%3445%5%37%
1480
March1st to 10thDay
13%6%35%5%34346%47%
1797
11th to 20thDay
16%6%25%6%35%5%5%6%41%
1939
21st to endDay
21%7%25%4345%45%40%
2328
April1st to 10thDay
16%8%45%435%45%7%41%
2160
11th to 20thDay
15%425%4445%6%8%42%
2134
21st to endDay
17%5%26%6%45%5%6%6%39%
2160
May1st to 10thDay
21%6%36%6%3445%8%35%
2305
11th to 20thDay
18%6%345%36%5%5%8%37%
2473
21st to endDay
14%7%25%5%35%5%5%8%41%
2725
June1st to 10thDay
14%5%25%6%35%6%8%10%37%
2520
11th to 20thDay
13%5%35%6%35%5%7%9%38%
2520
21st to endDay
11%5%35%5%36%5%6%9%41%
2520
July1st to 10thDay
9%5%35%6%46%7%7%9%39%
2520
11th to 20thDay
8%5%35%6%46%6%7%12%40%
2520
21st to endDay
11%5%37%6%45%6%6%9%38%
2744
August1st to 10thDay
10%5%27%6%46%7%6%9%39%
2307
11th to 20thDay
12%6%26%6%35%6%6%9%39%
2126
21st to endDay
13%5%36%5%45%5%6%9%39%
2376
September1st to 10thDay
13%7%26%5%3446%7%43%
2160
11th to 20thDay
11%5%25%5%3445%8%50%
2106
21st to endDay
16%7%26%5%3445%7%40%
1980
October1st to 10thDay
18%7%25%42345%7%43%
1843
11th to 20thDay
15%6%235%3445%6%48%
1800
21st to endDay
18%6%35%433446%45%
1885
November1st to 10thDay
13%5%2442335%7%51%
1671
11th to 20thDay
16%5%25%33435%6%47%
1710
21st to endDay
14%6%25%6%2345%6%47%
1625
December1st to 10thDay
18%7%35%42445%7%39%
1520
11th to 20thDay
19%7%34334445%44%
1906
21st to endDay
17%7%26%445%6%7%7%37%
2772
January1st to 10thNight
17%6%2442435%6%47%
4429
11th to 20thNight
18%8%35%433345%44%
4436
21st to endNight
23%10%25%5%34445%36%
4532
February1st to 10thNight
16%8%46%43435%7%41%
2470
11th to 20thNight
18%8%35%42445%6%41%
2163
21st to endNight
19%7%36%43335%5%43%
1776
March1st to 10thNight
16%5%25%42445%7%47%
2150
11th to 20thNight
17%6%36%434445%44%
2015
21st to endNight
18%6%36%5%24446%42%
2027
April1st to 10thNight
16%7%26%425%5%5%6%42%
1800
11th to 20thNight
16%5%36%5%35%45%6%42%
1775
21st to endNight
19%5%244245%5%7%43%
1800
May1st to 10thNight
18%8%37%5%345%5%6%37%
1652
11th to 20thNight
18%6%36%6%245%6%7%38%
1433
21st to endNight
14%7%35%435%5%5%9%40%
1550
June1st to 10thNight
14%6%245%35%5%7%8%42%
1440
11th to 20thNight
11%6%37%5%36%5%6%7%41%
1440
21st to endNight
9%5%25%5%45%6%7%11%42%
1440
July1st to 10thNight
9%6%26%7%45%6%7%9%39%
1440
11th to 20thNight
7%5%25%6%46%6%7%10%43%
1440
21st to endNight
8%435%5%35%6%8%10%43%
1574
August1st to 10thNight
9%6%26%5%35%6%7%9%42%
1609
11th to 20thNight
10%6%27%5%46%6%6%9%38%
1774
21st to endNight
12%6%26%5%345%6%9%41%
1980
September1st to 10thNight
14%6%35%5%445%5%6%44%
1800
11th to 20thNight
11%5%243335%5%6%53%
1853
21st to endNight
17%7%25%42445%7%42%
1980
October1st to 10thNight
18%7%25%434346%44%
2114
11th to 20thNight
14%5%24434446%50%
2160
21st to endNight
19%7%25%42335%446%
2470
November1st to 10thNight
11%5%24434446%52%
2407
11th to 20thNight
17%5%25%5%24335%47%
2470
21st to endNight
13%5%25%5%35%5%5%7%46%
2553
December1st to 10thNight
20%7%25%43345%6%40%
2660
11th to 20thNight
18%5%25%5%3445%7%41%
3288
21st to endNight
18%8%36%5%3445%6%39%
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
41%211%26%15%4
2518
11th to 20thDay
49%29%23%14%2
2523
21st to endDay
53%210%23%10%2
3124
February1st to 10thDay
46%311%27%12%2
1710
11th to 20thDay
46%38%25%15%3
1786
21st to endDay
48%38%22%14%4
1480
March1st to 10thDay
40%312%27%15%4
1800
11th to 20thDay
44%310%23%17%4
1939
21st to endDay
48%37%21%18%4
2328
April1st to 10thDay
45%48%22%16%5%
2160
11th to 20thDay
40%312%24%18%4
2134
21st to endDay
44%49%20%19%4
2160
May1st to 10thDay
48%39%21%16%3
2305
11th to 20thDay
46%311%23%15%2
2477
21st to endDay
42%5%14%23%13%3
2725
June1st to 10thDay
41%5%13%23%15%2
2520
11th to 20thDay
42%413%25%13%3
2520
21st to endDay
40%5%12%25%17%1
2520
July1st to 10thDay
41%5%12%24%15%2
2450
11th to 20thDay
36%5%14%27%16%2
2445
21st to endDay
42%5%10%23%17%2
2591
August1st to 10thDay
42%5%12%24%16%1
2293
11th to 20thDay
42%5%14%22%16%2
2126
21st to endDay
41%411%22%18%4
2376
September1st to 10thDay
41%312%20%20%3
2160
11th to 20thDay
35%38%24%26%4
2106
21st to endDay
45%28%20%22%3
1980
October1st to 10thDay
42%311%24%19%2
1843
11th to 20thDay
38%29%26%23%2
1800
21st to endDay
41%38%25%20%2
1885
November1st to 10thDay
36%111%28%21%2
1671
11th to 20thDay
40%38%24%23%3
1710
21st to endDay
39%212%32%13%3
1625
December1st to 10thDay
46%214%23%15%1
1520
11th to 20thDay
44%211%27%13%2
1906
21st to endDay
47%312%24%13%1
2772
January1st to 10thNight
41%29%31%13%4
4429
11th to 20thNight
45%210%26%14%2
4436
21st to endNight
52%26%24%13%2
4532
February1st to 10thNight
45%213%25%13%2
2470
11th to 20thNight
46%28%21%18%5%
2165
21st to endNight
45%26%25%18%4
1776
March1st to 10thNight
39%210%26%18%5%
2160
11th to 20thNight
45%29%22%19%4
2016
21st to endNight
45%28%20%19%6%
2027
April1st to 10thNight
44%210%21%19%5%
1800
11th to 20thNight
43%39%22%21%3
1775
21st to endNight
42%39%21%20%5%
1800
May1st to 10thNight
49%39%20%18%2
1652
11th to 20thNight
45%412%17%18%4
1434
21st to endNight
43%6%15%20%14%2
1551
June1st to 10thNight
41%5%12%22%19%2
1440
11th to 20thNight
41%5%14%25%13%1
1440
21st to endNight
36%5%15%26%16%2
1440
July1st to 10thNight
41%6%16%21%14%2
1400
11th to 20thNight
35%5%15%28%15%2
1392
21st to endNight
34%5%15%28%14%3
1486
August1st to 10thNight
38%6%18%22%16%1
1599
11th to 20thNight
43%414%23%15%1
1774
21st to endNight
40%414%19%19%3
1980
September1st to 10thNight
41%411%22%19%2
1800
11th to 20thNight
32%310%25%26%4
1853
21st to endNight
42%36%24%22%2
1980
October1st to 10thNight
43%310%25%17%3
2114
11th to 20thNight
37%311%29%18%3
2160
21st to endNight
42%28%26%20%2
2470
November1st to 10thNight
34%311%25%22%5%
2407
11th to 20thNight
41%38%23%20%5%
2470
21st to endNight
38%212%28%17%2
2553
December1st to 10thNight
46%211%24%14%2
2660
11th to 20thNight
43%312%20%18%4
3288
21st to endNight
47%212%26%12%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
28%20%32%15%41
180
11th to 20thDay
37%24%25%12%1
182
21st to endDay
26%23%32%14%41
297
February1st to 10thDay
29%26%31%11%2
270
11th to 20thDay
29%23%34%11%2
421
21st to endDay
30%21%33%15%2
346
March1st to 10thDay
27%19%31%19%4
420
11th to 20thDay
27%22%32%13%5%1
420
21st to endDay
29%20%31%16%41
462
April1st to 10thDay
25%24%32%12%6%1
420
11th to 20thDay
23%16%33%16%9%2
412
21st to endDay
28%20%31%15%42
420
May1st to 10thDay
29%17%28%16%8%2
423
11th to 20thDay
22%14%34%21%8%1
447
21st to endDay
20%9%21%30%17%4
485
June1st to 10thDay
16%11%30%26%13%4
450
11th to 20thDay
18%12%29%26%11%4
450
21st to endDay
14%8%30%30%14%3
450
July1st to 10thDay
11%6%24%31%21%6%
445
11th to 20thDay
9%5%24%32%23%7%
444
21st to endDay
11%8%31%30%16%4
488
August1st to 10thDay
11%5%25%35%16%8%
446
11th to 20thDay
13%5%21%33%21%7%
439
21st to endDay
13%6%25%28%17%11%
495
September1st to 10thDay
17%8%25%23%18%9%
450
11th to 20thDay
13%7%29%28%14%9%
450
21st to endDay
21%13%26%24%10%6%
450
October1st to 10thDay
27%7%23%23%13%7%
450
11th to 20thDay
18%14%27%28%11%2
450
21st to endDay
21%16%32%20%9%2
447
November1st to 10thDay
19%11%33%22%12%3
365
11th to 20thDay
24%17%31%21%6%1
370
21st to endDay
20%15%38%19%8%1
285
December1st to 10thDay
24%28%31%11%7%
180
11th to 20thDay
38%18%27%12%5%
180
21st to endDay
31%14%33%17%41
198
January1st to 10thNight
20%19%37%22%3
760
11th to 20thNight
24%15%35%22%4
760
21st to endNight
19%19%38%23%1
836
February1st to 10thNight
21%15%36%26%2
760
11th to 20thNight
25%21%37%17%1
722
21st to endNight
24%20%37%17%2
592
March1st to 10thNight
22%17%35%21%3
720
11th to 20thNight
24%17%35%19%5%
720
21st to endNight
20%13%40%21%5%
792
April1st to 10thNight
21%18%38%18%5%
720
11th to 20thNight
18%14%37%26%4
711
21st to endNight
22%11%36%26%5%
720
May1st to 10thNight
21%15%33%25%5%
572
11th to 20thNight
20%9%40%26%6%
372
21st to endNight
17%7%23%39%13%2
389
June1st to 10thNight
17%5%30%35%12%
360
11th to 20thNight
11%6%28%42%13%
360
21st to endNight
11%228%46%13%
360
July1st to 10thNight
10%6%20%44%18%1
350
11th to 20thNight
7%421%48%20%1
348
21st to endNight
8%324%47%18%
394
August1st to 10thNight
10%319%46%20%3
535
11th to 20thNight
13%417%40%24%3
710
21st to endNight
14%416%40%23%2
792
September1st to 10thNight
17%424%36%18%3
720
11th to 20thNight
15%421%33%22%4
720
21st to endNight
20%5%22%35%17%1
720
October1st to 10thNight
21%7%26%26%16%3
720
11th to 20thNight
17%10%28%34%12%
720
21st to endNight
22%10%33%26%8%
792
November1st to 10thNight
14%8%37%28%11%1
740
11th to 20thNight
20%16%29%26%9%
760
21st to endNight
17%14%35%26%8%
760
December1st to 10thNight
27%15%32%19%7%1
760
11th to 20thNight
20%14%36%25%5%
760
21st to endNight
22%14%34%27%3
836
Page generated at 2024-02-12 06:35:34. Version ac07

Copyright 2024 Attilla Danko


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