Vulcan
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Vulcan clear sky chart from 2005-11-06 to 2024-01-12.

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
41%
23502
15%
74598
10%
23471
47%
23471
23%
48171

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
34%
947
13%
2836
7%
946
39%
946
17%
2052
January11th to 20thNight
36%
901
15%
2721
10%
901
41%
901
20%
1910
January21st to endNight
35%
792
20%
2772
13%
792
46%
792
19%
1808
February1st to 10thNight
38%
720
13%
2480
12%
720
43%
720
15%
1727
February11th to 20thNight
35%
701
13%
2273
10%
700
41%
700
16%
1642
February21st to endNight
41%
592
15%
1830
12%
592
47%
592
18%
1299
March1st to 10thNight
35%
720
14%
2157
9%
720
41%
720
19%
1530
March11th to 20thNight
35%
720
19%
1980
9%
720
42%
720
23%
1375
March21st to endNight
35%
792
11%
2178
4%
792
39%
792
20%
1580
April1st to 10thNight
31%
653
15%
1738
5%
653
37%
653
20%
1262
April11th to 20thNight
37%
533
15%
1601
10%
533
41%
533
20%
1112
April21st to endNight
38%
540
13%
1620
10%
540
42%
540
20%
1126
May1st to 10thNight
42%
514
10%
1550
9%
514
46%
514
21%
1056
May11th to 20thNight
52%
354
15%
1239
16%
354
55%
354
25%
744
May21st to endNight
46%
388
7%
1358
5%
388
48%
388
17%
939
June1st to 10thNight
44%
360
4%
1260
2%
360
45%
360
19%
824
June11th to 20thNight
38%
360
3%
1260
0%
360
39%
360
18%
850
June21st to endNight
58%
360
4%
1260
0%
360
59%
360
30%
703
July1st to 10thNight
65%
350
5%
1225
2%
350
65%
350
32%
666
July11th to 20thNight
58%
348
9%
1218
8%
348
61%
348
32%
675
July21st to endNight
64%
394
18%
1357
19%
372
72%
372
44%
614
August1st to 10thNight
61%
376
16%
1442
18%
374
67%
374
29%
770
August11th to 20thNight
64%
534
20%
1602
18%
534
67%
534
42%
872
August21st to endNight
56%
594
26%
1782
19%
594
61%
594
40%
962
September1st to 10thNight
54%
606
20%
1728
13%
606
58%
606
34%
1044
September11th to 20thNight
54%
720
21%
1980
14%
720
58%
720
37%
1194
September21st to endNight
46%
720
22%
1980
14%
720
51%
720
35%
1204
October1st to 10thNight
46%
720
20%
2074
12%
720
53%
720
28%
1324
October11th to 20thNight
40%
720
20%
2250
12%
720
51%
720
27%
1394
October21st to endNight
38%
792
20%
2574
12%
792
47%
792
24%
1642
November1st to 10thNight
31%
851
17%
2516
8%
851
39%
851
20%
1754
November11th to 20thNight
32%
950
20%
2664
10%
950
42%
950
25%
1776
November21st to endNight
36%
950
16%
2850
9%
950
43%
950
25%
1855
December1st to 10thNight
39%
950
16%
2850
10%
950
44%
950
21%
1951
December11th to 20thNight
34%
949
14%
3465
9%
949
39%
949
17%
2262
December21st to endNight
33%
1031
11%
4928
8%
1026
39%
1026
13%
2673

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
9%8%47%6%35%5%6%8%39%
74625
Night
7%8%47%6%45%6%6%9%39%
75093
TransparencyDay
40%8%15%24%11%2
74310
Night
40%8%15%22%12%2
74926
SeeingDay
12%9%27%29%18%5%
14229
Night
11%7%30%35%15%2
23524

By Month

Percentage Cloud Cover NW (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
410%5%9%8%36%48%8%35%
1329
11th to 20thDay
6%9%5%9%7%46%6%7%9%33%
1294
21st to endDay
5%8%411%8%47%6%7%10%30%
1584
February1st to 10thDay
6%9%5%10%8%5%8%7%6%7%29%
1478
11th to 20thDay
6%13%5%9%9%46%6%6%8%28%
1575
21st to endDay
412%8%11%8%5%6%5%5%8%30%
1422
March1st to 10thDay
411%5%9%7%46%6%6%8%32%
1802
11th to 20thDay
7%8%5%8%7%45%5%6%10%36%
1979
21st to endDay
8%12%6%9%6%46%6%7%8%29%
2178
April1st to 10thDay
9%11%6%8%7%46%6%5%8%30%
2218
11th to 20thDay
10%12%48%7%36%6%6%8%31%
2310
21st to endDay
10%9%48%7%45%5%6%7%34%
2340
May1st to 10thDay
12%10%47%6%46%6%6%7%32%
2406
11th to 20thDay
11%6%36%6%46%5%6%9%37%
2654
21st to endDay
19%8%36%6%45%6%5%7%31%
2917
June1st to 10thDay
13%7%36%6%45%6%8%9%32%
2700
11th to 20thDay
17%8%46%6%45%6%6%8%29%
2700
21st to endDay
8%4245%36%5%7%11%45%
2700
July1st to 10thDay
7%425%435%6%7%9%48%
2700
11th to 20thDay
7%5%24435%5%7%9%50%
2700
21st to endDay
432333447%9%58%
2878
August1st to 10thDay
8%42443447%11%49%
2488
11th to 20thDay
7%424425%5%6%9%52%
2299
21st to endDay
8%42442447%9%52%
2574
September1st to 10thDay
10%5%25%4245%5%7%51%
2229
11th to 20thDay
13%7%3442445%7%47%
1980
21st to endDay
9%6%35%43446%8%47%
1980
October1st to 10thDay
13%9%36%6%35%45%7%39%
1886
11th to 20thDay
10%8%37%7%345%6%9%40%
1706
21st to endDay
6%11%37%6%35%5%7%9%37%
1782
November1st to 10thDay
10%13%5%8%4446%6%8%32%
1542
11th to 20thDay
6%9%48%5%4446%9%39%
1511
21st to endDay
49%6%8%6%25%6%8%10%36%
1330
December1st to 10thDay
5%11%5%10%7%46%5%47%35%
1330
11th to 20thDay
310%5%10%10%5%6%6%6%6%31%
1682
21st to endDay
47%37%5%45%6%6%10%43%
2442
January1st to 10thNight
410%5%9%8%5%7%7%7%10%28%
2836
11th to 20thNight
5%9%49%7%5%6%6%7%9%32%
2721
21st to endNight
5%10%48%7%45%7%7%10%34%
2772
February1st to 10thNight
5%10%5%9%9%5%6%6%6%8%31%
2480
11th to 20thNight
5%12%5%10%8%5%6%6%6%8%28%
2272
21st to endNight
5%10%6%10%9%46%5%6%7%32%
1830
March1st to 10thNight
410%5%10%9%46%6%7%8%32%
2157
11th to 20thNight
6%11%48%6%46%6%6%10%34%
1980
21st to endNight
6%12%5%8%8%36%5%7%9%30%
2178
April1st to 10thNight
8%11%5%9%7%46%5%5%9%31%
1738
11th to 20thNight
9%10%5%9%7%45%6%6%8%32%
1601
21st to endNight
10%10%48%6%45%5%6%9%33%
1620
May1st to 10thNight
11%11%46%5%45%5%6%8%36%
1550
11th to 20thNight
9%6%45%436%5%6%8%44%
1239
21st to endNight
17%6%36%6%45%6%6%8%32%
1358
June1st to 10thNight
12%8%26%5%45%7%7%8%36%
1260
11th to 20thNight
16%7%36%6%36%5%7%8%32%
1260
21st to endNight
5%426%445%6%9%10%46%
1260
July1st to 10thNight
5%425%6%346%7%9%49%
1260
11th to 20thNight
6%425%4335%7%9%52%
1260
21st to endNight
43133235%7%9%60%
1437
August1st to 10thNight
6%425%5%445%5%9%50%
1450
11th to 20thNight
5%42432446%12%54%
1602
21st to endNight
8%413433449%55%
1782
September1st to 10thNight
10%425%5%345%5%8%49%
1728
11th to 20thNight
12%6%2433335%7%52%
1980
21st to endNight
8%6%25%5%345%5%8%47%
1980
October1st to 10thNight
12%8%25%5%245%6%6%43%
2074
11th to 20thNight
9%7%36%435%5%6%8%43%
2250
21st to endNight
7%8%47%6%35%5%6%9%39%
2574
November1st to 10thNight
9%11%48%6%45%6%6%8%34%
2516
11th to 20thNight
5%8%48%6%447%7%9%39%
2664
21st to endNight
5%10%46%5%445%7%11%39%
2850
December1st to 10thNight
410%5%8%7%5%6%5%7%8%35%
2850
11th to 20thNight
38%310%7%5%5%7%7%10%34%
3510
21st to endNight
48%47%7%35%5%6%8%44%
5214

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
46%8%14%23%8%2
1329
11th to 20thDay
45%9%14%22%8%2
1294
21st to endDay
46%9%15%17%10%2
1584
February1st to 10thDay
53%8%13%16%8%2
1478
11th to 20thDay
51%7%15%18%7%1
1584
21st to endDay
53%6%11%18%11%1
1422
March1st to 10thDay
48%9%15%18%10%1
1802
11th to 20thDay
43%8%14%22%11%1
1980
21st to endDay
49%9%16%19%7%
2178
April1st to 10thDay
51%7%14%21%7%
2218
11th to 20thDay
48%8%12%20%9%2
2310
21st to endDay
46%9%14%21%10%1
2340
May1st to 10thDay
47%9%13%21%9%
2406
11th to 20thDay
41%9%14%24%11%1
2658
21st to endDay
50%7%12%21%8%1
2918
June1st to 10thDay
44%9%17%20%9%1
2700
11th to 20thDay
48%9%14%19%9%1
2700
21st to endDay
31%8%19%28%12%2
2700
July1st to 10thDay
28%9%17%31%12%3
2626
11th to 20thDay
27%9%17%28%15%3
2619
21st to endDay
21%7%16%31%22%4
2718
August1st to 10thDay
27%8%17%31%13%3
2471
11th to 20thDay
26%8%20%31%11%3
2299
21st to endDay
27%6%17%30%17%3
2574
September1st to 10thDay
31%6%14%26%17%6%
2229
11th to 20thDay
37%7%11%29%13%3
1980
21st to endDay
34%7%14%29%13%3
1980
October1st to 10thDay
44%8%12%24%10%1
1886
11th to 20thDay
40%7%17%24%10%2
1706
21st to endDay
41%8%15%23%11%2
1782
November1st to 10thDay
49%8%13%19%9%1
1542
11th to 20thDay
40%7%18%24%10%1
1511
21st to endDay
39%8%17%23%10%3
1330
December1st to 10thDay
48%9%11%18%11%3
1330
11th to 20thDay
49%7%15%23%5%1
1684
21st to endDay
34%8%13%24%19%3
2442
January1st to 10thNight
48%10%13%17%9%2
2836
11th to 20thNight
45%9%15%20%8%2
2721
21st to endNight
43%8%15%18%14%2
2772
February1st to 10thNight
49%8%12%17%11%2
2480
11th to 20thNight
51%8%12%19%9%1
2273
21st to endNight
50%7%11%19%10%3
1830
March1st to 10thNight
47%9%13%21%8%1
2157
11th to 20thNight
44%8%14%22%11%1
1980
21st to endNight
47%10%17%18%8%1
2178
April1st to 10thNight
48%9%12%19%12%
1738
11th to 20thNight
48%7%13%21%9%1
1601
21st to endNight
45%9%14%22%8%2
1620
May1st to 10thNight
44%8%13%23%11%1
1550
11th to 20thNight
35%9%14%29%10%2
1239
21st to endNight
48%9%14%20%8%2
1358
June1st to 10thNight
42%10%15%22%11%1
1260
11th to 20thNight
46%8%16%20%9%2
1260
21st to endNight
29%9%20%25%15%2
1260
July1st to 10thNight
28%9%18%30%13%2
1225
11th to 20thNight
28%9%17%24%17%5%
1218
21st to endNight
18%6%18%28%25%5%
1357
August1st to 10thNight
30%7%17%28%14%4
1442
11th to 20thNight
24%7%18%32%16%3
1602
21st to endNight
25%7%12%31%20%5%
1782
September1st to 10thNight
32%7%13%25%17%6%
1728
11th to 20thNight
32%6%13%28%17%5%
1980
21st to endNight
32%6%16%27%15%4
1980
October1st to 10thNight
38%7%15%24%15%1
2074
11th to 20thNight
37%7%15%24%14%3
2250
21st to endNight
40%8%15%25%13%1
2574
November1st to 10thNight
47%7%11%22%11%2
2516
11th to 20thNight
39%8%16%20%15%1
2664
21st to endNight
38%9%19%20%11%3
2850
December1st to 10thNight
45%7%15%20%10%3
2850
11th to 20thNight
42%10%21%21%6%1
3507
21st to endNight
37%6%13%25%14%5%
5214

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
48%34%29%13%12%
180
11th to 20thDay
8%10%33%26%15%8%
163
21st to endDay
7%8%33%34%15%3
176
February1st to 10thDay
10%10%37%33%8%3
178
11th to 20thDay
9%9%36%29%13%3
240
21st to endDay
11%10%27%31%17%3
288
March1st to 10thDay
8%14%36%25%13%3
420
11th to 20thDay
10%11%32%30%14%3
420
21st to endDay
12%15%29%25%13%5%
462
April1st to 10thDay
14%14%31%27%12%2
420
11th to 20thDay
14%13%26%28%16%3
412
21st to endDay
16%12%28%27%14%3
420
May1st to 10thDay
15%11%25%26%17%7%
467
11th to 20thDay
17%6%21%29%22%4
625
21st to endDay
19%8%18%29%18%8%
679
June1st to 10thDay
14%8%27%31%17%3
630
11th to 20thDay
19%9%27%28%15%2
630
21st to endDay
10%324%33%22%7%
630
July1st to 10thDay
7%421%35%27%5%
621
11th to 20thDay
11%5%24%35%20%6%
618
21st to endDay
5%425%35%24%7%
624
August1st to 10thDay
10%423%33%23%6%
447
11th to 20thDay
10%5%19%32%24%10%
437
21st to endDay
8%8%24%31%18%10%
495
September1st to 10thDay
13%7%29%26%20%5%
450
11th to 20thDay
19%6%24%29%16%6%
450
21st to endDay
17%13%28%24%14%4
450
October1st to 10thDay
17%8%21%25%23%6%
356
11th to 20thDay
11%14%30%23%16%7%
270
21st to endDay
15%14%30%25%13%2
297
November1st to 10thDay
19%11%29%27%12%3
270
11th to 20thDay
11%15%33%26%14%1
266
21st to endDay
417%31%24%15%9%
180
December1st to 10thDay
8%11%29%32%16%4
180
11th to 20thDay
11%9%41%24%12%3
180
21st to endDay
10%7%25%30%23%6%
198
January1st to 10thNight
8%11%34%31%13%1
950
11th to 20thNight
8%9%36%34%12%1
901
21st to endNight
11%8%35%32%12%2
792
February1st to 10thNight
10%10%29%33%15%3
720
11th to 20thNight
10%7%33%37%12%2
704
21st to endNight
10%6%24%36%21%3
592
March1st to 10thNight
10%7%33%34%14%2
720
11th to 20thNight
11%7%36%31%13%2
720
21st to endNight
12%8%31%33%12%4
792
April1st to 10thNight
13%7%34%31%13%2
653
11th to 20thNight
15%6%33%33%12%1
533
21st to endNight
15%9%29%34%13%1
540
May1st to 10thNight
17%8%22%34%18%1
514
11th to 20thNight
14%6%23%34%22%1
354
21st to endNight
19%6%23%30%20%2
389
June1st to 10thNight
15%5%28%34%16%1
360
11th to 20thNight
19%8%27%32%14%
360
21st to endNight
9%323%41%23%2
360
July1st to 10thNight
7%318%45%26%1
350
11th to 20thNight
8%322%47%19%1
348
21st to endNight
6%223%43%23%2
394
August1st to 10thNight
8%417%43%26%2
376
11th to 20thNight
8%320%45%22%2
534
21st to endNight
11%422%43%19%1
594
September1st to 10thNight
13%324%38%21%2
606
11th to 20thNight
15%5%20%38%19%2
720
21st to endNight
12%6%29%35%15%3
720
October1st to 10thNight
15%6%25%34%19%2
720
11th to 20thNight
12%7%31%32%15%3
720
21st to endNight
11%8%35%33%12%1
792
November1st to 10thNight
15%8%39%30%8%1
851
11th to 20thNight
10%12%39%28%10%1
950
21st to endNight
10%9%36%33%10%2
950
December1st to 10thNight
9%8%32%34%14%2
950
11th to 20thNight
8%9%34%36%11%1
950
21st to endNight
11%8%33%34%12%2
1045
Page generated at 2024-01-09 14:24:27. Version ac07

Copyright 2024 Attilla Danko


Vulcan Clear Sky Chart |Charts Home