This page made possible by the sponsorship of: Cary MacWilliams.

Ghost Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ghost Lake clear sky chart from 2005-11-06 to 2024-01-16.

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%
23386
15%
74785
7%
23338
41%
23338
21%
47886

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%
950
14%
2836
4%
946
29%
946
17%
1940
January11th to 20thNight
23%
886
18%
2736
6%
886
36%
886
21%
1778
January21st to endNight
23%
792
21%
2772
7%
792
40%
792
19%
1720
February1st to 10thNight
26%
720
15%
2520
8%
720
36%
720
16%
1644
February11th to 20thNight
22%
703
13%
2316
5%
700
34%
700
16%
1573
February21st to endNight
28%
592
18%
1785
8%
592
42%
592
20%
1199
March1st to 10thNight
29%
720
15%
2160
8%
720
38%
720
21%
1454
March11th to 20thNight
31%
720
19%
2030
7%
720
42%
720
26%
1309
March21st to endNight
34%
792
13%
2111
5%
792
39%
792
20%
1501
April1st to 10thNight
29%
695
14%
1775
4%
695
35%
695
19%
1296
April11th to 20thNight
27%
533
14%
1601
7%
533
33%
533
18%
1120
April21st to endNight
28%
540
11%
1620
6%
540
34%
540
18%
1108
May1st to 10thNight
39%
414
8%
1486
6%
414
44%
414
16%
1010
May11th to 20thNight
48%
354
13%
1239
15%
354
51%
354
24%
763
May21st to endNight
42%
388
6%
1358
3%
388
44%
388
17%
956
June1st to 10thNight
40%
360
2%
1260
0%
360
41%
360
17%
860
June11th to 20thNight
38%
360
0%
1260
0%
360
38%
360
14%
875
June21st to endNight
58%
360
0%
1260
0%
360
58%
360
24%
755
July1st to 10thNight
62%
350
2%
1225
0%
350
62%
350
27%
716
July11th to 20thNight
52%
348
7%
1218
3%
348
54%
348
28%
717
July21st to endNight
68%
394
14%
1392
16%
372
71%
372
34%
706
August1st to 10thNight
62%
358
14%
1424
19%
356
67%
356
26%
790
August11th to 20thNight
63%
472
17%
1540
19%
472
66%
472
37%
825
August21st to endNight
57%
594
22%
1782
16%
594
61%
594
35%
1001
September1st to 10thNight
49%
666
17%
1746
10%
666
51%
666
35%
1085
September11th to 20thNight
48%
720
18%
1966
10%
720
53%
720
30%
1247
September21st to endNight
39%
720
21%
1980
11%
720
47%
720
30%
1223
October1st to 10thNight
41%
720
19%
2031
10%
720
49%
720
25%
1343
October11th to 20thNight
33%
720
17%
2330
8%
720
45%
720
25%
1417
October21st to endNight
25%
792
18%
2574
6%
792
41%
792
20%
1664
November1st to 10thNight
22%
811
17%
2476
5%
811
35%
811
19%
1670
November11th to 20thNight
18%
950
19%
2770
3%
950
33%
950
21%
1744
November21st to endNight
21%
950
15%
2850
4%
950
31%
950
20%
1840
December1st to 10thNight
24%
950
18%
2850
6%
950
34%
950
20%
1887
December11th to 20thNight
24%
950
14%
3486
6%
949
33%
949
16%
2355
December21st to endNight
22%
1042
11%
5020
4%
1026
34%
1026
13%
2795

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%45%6%6%8%37%
74632
Night
6%8%47%6%35%5%6%9%40%
75169
TransparencyDay
42%9%16%21%10%2
74319
Night
38%9%17%22%11%2
75000
SeeingDay
15%16%32%25%10%2
14164
Night
11%13%35%29%11%1
23391

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
27%48%10%45%5%7%10%38%
1329
11th to 20thDay
27%47%6%45%6%6%11%41%
1349
21st to endDay
29%48%7%46%6%9%8%37%
1584
February1st to 10thDay
27%47%10%5%6%7%7%10%36%
1440
11th to 20thDay
18%6%9%7%6%6%7%7%9%33%
1531
21st to endDay
29%6%13%9%5%5%45%9%34%
1469
March1st to 10thDay
28%5%8%7%5%7%6%7%11%35%
1800
11th to 20thDay
37%5%8%7%45%5%7%10%40%
1928
21st to endDay
414%7%11%7%46%5%5%8%29%
2244
April1st to 10thDay
7%12%5%9%8%46%6%7%9%28%
2184
11th to 20thDay
9%17%7%8%6%35%5%5%7%29%
2310
21st to endDay
12%13%5%7%7%35%5%5%7%32%
2340
May1st to 10thDay
12%13%48%7%46%6%6%7%27%
2473
11th to 20thDay
13%8%36%6%35%6%7%8%34%
2654
21st to endDay
22%10%36%6%45%6%6%7%25%
2917
June1st to 10thDay
18%9%48%6%45%7%7%7%26%
2700
11th to 20thDay
23%9%46%7%46%6%6%7%23%
2700
21st to endDay
11%5%26%7%47%6%6%9%37%
2700
July1st to 10thDay
10%6%36%6%46%7%7%8%38%
2700
11th to 20thDay
11%5%245%35%7%6%9%42%
2700
21st to endDay
7%4245%45%6%7%9%48%
2840
August1st to 10thDay
11%5%245%45%7%7%8%42%
2507
11th to 20thDay
10%325%5%35%47%9%46%
2360
21st to endDay
10%5%245%345%7%9%44%
2574
September1st to 10thDay
12%5%25%5%345%7%6%46%
2212
11th to 20thDay
13%7%35%435%447%46%
1993
21st to endDay
9%8%25%5%346%7%7%45%
1980
October1st to 10thDay
10%11%36%5%25%5%5%7%40%
1928
11th to 20thDay
7%10%47%5%445%7%8%39%
1630
21st to endDay
5%10%5%7%6%45%5%6%9%39%
1782
November1st to 10thDay
5%13%5%6%6%35%7%6%9%36%
1584
11th to 20thDay
39%45%5%45%6%6%7%45%
1406
21st to endDay
29%410%7%345%6%9%41%
1330
December1st to 10thDay
37%411%7%45%5%5%10%39%
1330
11th to 20thDay
29%5%11%8%5%7%6%7%8%33%
1682
21st to endDay
38%47%6%345%5%7%46%
2442
January1st to 10thNight
29%6%10%7%46%6%7%9%34%
2836
11th to 20thNight
37%47%7%46%6%7%11%38%
2736
21st to endNight
37%47%6%46%6%7%9%40%
2772
February1st to 10thNight
37%5%9%7%46%7%7%9%36%
2520
11th to 20thNight
210%6%9%7%46%6%7%9%33%
2315
21st to endNight
17%6%10%10%5%6%5%49%37%
1785
March1st to 10thNight
28%5%8%7%46%7%7%9%35%
2160
11th to 20thNight
28%5%6%5%35%6%7%10%42%
2030
21st to endNight
311%6%9%6%35%5%6%9%35%
2111
April1st to 10thNight
6%13%6%9%7%345%5%7%34%
1775
11th to 20thNight
8%14%5%9%6%3445%7%34%
1601
21st to endNight
10%12%48%5%345%6%8%35%
1620
May1st to 10thNight
11%12%47%6%3447%8%32%
1486
11th to 20thNight
11%6%35%6%45%5%6%9%41%
1239
21st to endNight
20%8%46%5%35%5%48%32%
1358
June1st to 10thNight
17%7%35%5%445%6%9%35%
1260
11th to 20thNight
21%6%36%5%46%5%5%9%31%
1260
21st to endNight
8%427%5%5%5%46%9%44%
1260
July1st to 10thNight
10%5%25%335%47%8%48%
1260
11th to 20thNight
11%5%15%325%6%6%7%48%
1260
21st to endNight
6%42432345%7%60%
1474
August1st to 10thNight
12%5%1343446%8%50%
1432
11th to 20thNight
12%3122235%7%9%53%
1540
21st to endNight
10%5%2433446%7%53%
1782
September1st to 10thNight
11%7%2442445%8%50%
1746
11th to 20thNight
14%8%3442345%6%48%
1966
21st to endNight
10%7%3442445%8%49%
1980
October1st to 10thNight
9%9%35%5%45%46%8%43%
2031
11th to 20thNight
7%9%36%435%47%8%44%
2330
21st to endNight
6%10%47%6%35%5%6%9%40%
2574
November1st to 10thNight
412%5%7%6%35%6%7%8%37%
2476
11th to 20thNight
37%47%5%35%5%7%10%44%
2770
21st to endNight
29%5%9%7%35%47%9%40%
2850
December1st to 10thNight
29%5%8%7%47%6%6%9%38%
2850
11th to 20thNight
19%49%8%5%6%7%8%9%34%
3510
21st to endNight
28%48%7%45%6%6%8%42%
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
40%8%16%23%9%4
1329
11th to 20thDay
36%9%18%23%10%3
1349
21st to endDay
40%8%18%19%12%2
1584
February1st to 10thDay
41%8%18%19%10%4
1440
11th to 20thDay
44%9%17%20%9%1
1540
21st to endDay
48%7%13%18%12%2
1469
March1st to 10thDay
41%10%19%21%8%1
1800
11th to 20thDay
38%9%16%24%11%2
1929
21st to endDay
52%10%17%14%6%1
2244
April1st to 10thDay
50%10%18%15%7%
2184
11th to 20thDay
52%9%12%18%8%1
2310
21st to endDay
52%8%14%18%7%1
2340
May1st to 10thDay
53%10%16%16%6%
2473
11th to 20thDay
45%9%14%23%8%
2658
21st to endDay
55%9%13%17%5%
2918
June1st to 10thDay
54%11%14%14%7%1
2700
11th to 20thDay
58%10%13%13%6%1
2700
21st to endDay
40%11%17%22%8%2
2700
July1st to 10thDay
39%11%16%20%11%2
2626
11th to 20thDay
36%11%16%23%12%2
2619
21st to endDay
29%10%15%29%15%2
2682
August1st to 10thDay
36%12%17%24%10%1
2490
11th to 20thDay
32%9%21%26%10%2
2360
21st to endDay
33%10%16%27%11%2
2574
September1st to 10thDay
35%8%17%24%14%3
2212
11th to 20thDay
38%8%16%24%12%2
1993
21st to endDay
35%9%17%25%12%2
1980
October1st to 10thDay
42%8%14%24%10%2
1928
11th to 20thDay
41%8%17%21%10%3
1630
21st to endDay
41%9%16%20%13%1
1782
November1st to 10thDay
43%11%14%20%11%1
1584
11th to 20thDay
36%8%19%24%11%1
1406
21st to endDay
37%10%19%22%9%3
1330
December1st to 10thDay
41%8%17%18%14%2
1330
11th to 20thDay
42%12%16%19%10%1
1684
21st to endDay
33%8%12%24%18%5%
2442
January1st to 10thNight
42%10%17%17%10%3
2836
11th to 20thNight
38%9%18%22%8%4
2736
21st to endNight
38%8%15%20%15%2
2772
February1st to 10thNight
41%10%14%20%11%3
2520
11th to 20thNight
45%9%17%17%10%1
2316
21st to endNight
44%6%12%22%13%3
1785
March1st to 10thNight
39%11%18%22%8%1
2160
11th to 20thNight
34%10%20%22%13%1
2030
21st to endNight
44%9%18%19%9%1
2111
April1st to 10thNight
48%8%14%19%10%1
1775
11th to 20thNight
48%8%14%20%9%1
1601
21st to endNight
45%9%17%20%7%2
1620
May1st to 10thNight
48%7%16%19%9%1
1486
11th to 20thNight
39%8%17%28%8%1
1239
21st to endNight
49%9%14%22%5%1
1358
June1st to 10thNight
45%10%16%20%8%1
1260
11th to 20thNight
48%10%16%15%9%1
1260
21st to endNight
34%10%20%26%9%1
1260
July1st to 10thNight
30%11%19%25%13%1
1225
11th to 20thNight
33%9%19%26%12%1
1218
21st to endNight
24%8%17%30%19%1
1392
August1st to 10thNight
31%9%19%30%10%1
1424
11th to 20thNight
25%8%25%30%12%1
1540
21st to endNight
27%8%17%30%16%2
1782
September1st to 10thNight
32%6%20%26%13%2
1746
11th to 20thNight
36%7%16%25%12%4
1966
21st to endNight
33%7%19%24%14%3
1980
October1st to 10thNight
40%8%15%24%12%1
2031
11th to 20thNight
35%9%19%24%11%2
2330
21st to endNight
38%10%17%24%10%1
2574
November1st to 10thNight
42%9%15%20%11%2
2476
11th to 20thNight
35%9%18%22%14%1
2770
21st to endNight
38%9%18%21%10%4
2850
December1st to 10thNight
41%8%16%22%10%4
2850
11th to 20thNight
40%14%19%19%8%1
3507
21st to endNight
35%10%15%23%13%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
7%14%38%27%10%4
180
11th to 20thDay
8%11%42%29%7%2
170
21st to endDay
10%16%43%20%7%3
176
February1st to 10thDay
16%21%39%18%44
160
11th to 20thDay
9%22%39%23%7%
221
21st to endDay
8%20%33%28%9%1
335
March1st to 10thDay
11%21%37%24%5%3
420
11th to 20thDay
10%25%32%23%6%3
420
21st to endDay
13%24%35%17%8%2
462
April1st to 10thDay
16%21%36%19%6%1
420
11th to 20thDay
18%23%28%21%8%1
412
21st to endDay
23%23%27%20%7%
420
May1st to 10thDay
20%19%26%22%10%2
431
11th to 20thDay
18%12%28%28%12%2
625
21st to endDay
22%9%24%29%13%2
679
June1st to 10thDay
19%17%30%23%10%2
630
11th to 20thDay
26%15%29%20%9%2
630
21st to endDay
14%12%30%25%15%3
630
July1st to 10thDay
15%7%29%28%18%3
621
11th to 20thDay
15%12%28%30%13%3
618
21st to endDay
9%11%32%31%14%3
586
August1st to 10thDay
12%9%33%30%11%3
447
11th to 20thDay
11%8%34%32%13%2
437
21st to endDay
11%13%34%26%13%3
495
September1st to 10thDay
15%17%34%23%9%2
450
11th to 20thDay
18%13%33%26%8%2
450
21st to endDay
16%23%29%23%7%2
450
October1st to 10thDay
15%17%32%22%12%2
398
11th to 20thDay
14%18%31%27%9%1
270
21st to endDay
17%21%34%20%7%1
297
November1st to 10thDay
17%17%39%22%41
270
11th to 20thDay
15%20%42%20%3
216
21st to endDay
9%23%34%19%11%4
180
December1st to 10thDay
5%18%42%27%7%1
180
11th to 20thDay
7%19%41%27%6%1
180
21st to endDay
6%14%43%26%8%3
198
January1st to 10thNight
10%18%46%21%5%1
950
11th to 20thNight
9%16%46%24%5%1
886
21st to endNight
9%22%39%23%7%
792
February1st to 10thNight
7%14%42%23%13%1
720
11th to 20thNight
9%14%41%27%8%1
704
21st to endNight
6%12%38%28%15%1
592
March1st to 10thNight
7%13%44%27%9%1
720
11th to 20thNight
8%15%39%29%8%1
720
21st to endNight
9%12%32%35%10%2
792
April1st to 10thNight
12%12%34%31%9%1
695
11th to 20thNight
16%11%36%28%9%
533
21st to endNight
16%15%32%27%10%
540
May1st to 10thNight
18%10%25%36%10%1
414
11th to 20thNight
13%5%26%38%16%1
354
21st to endNight
23%7%20%30%19%1
389
June1st to 10thNight
21%8%25%32%13%1
360
11th to 20thNight
23%8%25%27%16%1
360
21st to endNight
10%6%19%36%27%2
360
July1st to 10thNight
13%5%15%40%26%1
350
11th to 20thNight
14%324%41%16%1
348
21st to endNight
6%7%15%45%25%2
394
August1st to 10thNight
13%315%37%30%2
358
11th to 20thNight
12%317%42%24%2
472
21st to endNight
11%6%20%44%18%2
594
September1st to 10thNight
17%6%23%35%17%3
666
11th to 20thNight
19%7%19%34%18%2
720
21st to endNight
14%12%31%30%12%2
720
October1st to 10thNight
14%9%29%36%12%1
720
11th to 20thNight
13%10%37%31%8%1
720
21st to endNight
10%18%39%27%6%1
792
November1st to 10thNight
14%14%44%21%6%
811
11th to 20thNight
9%23%46%19%21
950
21st to endNight
8%19%43%23%6%1
950
December1st to 10thNight
7%18%44%23%8%
950
11th to 20thNight
5%18%44%26%7%
950
21st to endNight
6%17%44%23%9%1
1045
Page generated at 2024-01-12 23:38:15. Version ac07

Copyright 2024 Attilla Danko


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