Ghost Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ghost Lake clear sky chart from 2005-11-05 to 2017-09-21.

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
34%
15149
13%
46839
6%
15116
42%
15116
21%
30782

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 15thNight
19%
900
12%
2685
3%
895
27%
895
16%
1877
January16th to endNight
22%
801
18%
2721
8%
801
36%
801
18%
1751
February1st to 15thNight
28%
699
13%
2438
7%
696
38%
696
18%
1581
February16th to endNight
28%
632
15%
1959
7%
632
38%
632
21%
1322
March1st to 15thNight
25%
720
13%
2133
5%
720
35%
720
20%
1428
March16th to endNight
33%
768
14%
2064
4%
767
40%
767
20%
1479
April1st to 15thNight
30%
641
10%
1721
4%
641
34%
641
17%
1265
April16th to endNight
32%
540
11%
1620
7%
540
36%
540
17%
1152
May1st to 15thNight
43%
394
10%
1409
9%
394
47%
394
19%
907
May16th to endNight
45%
374
5%
1309
4%
374
45%
374
16%
940
June1st to 15thNight
40%
360
0%
1260
0%
360
40%
360
14%
896
June16th to endNight
52%
360
0%
1260
0%
360
52%
360
21%
800
July1st to 15thNight
59%
340
2%
1190
0%
340
59%
340
26%
716
July16th to endNight
65%
376
9%
1297
9%
354
67%
354
30%
717
August1st to 15thNight
66%
378
12%
1450
18%
376
69%
376
27%
815
August16th to endNight
61%
573
20%
1719
16%
573
65%
573
39%
916
September1st to 15thNight
54%
684
17%
1816
10%
684
56%
684
36%
1108
September16th to endNight
47%
680
20%
1881
10%
680
54%
680
33%
1140
October1st to 15thNight
36%
660
16%
1950
8%
660
44%
660
20%
1346
October16th to endNight
33%
704
19%
2288
8%
704
47%
704
24%
1427
November1st to 15thNight
20%
805
17%
2389
5%
805
33%
805
22%
1509
November16th to endNight
23%
900
13%
2700
3%
900
32%
900
19%
1803
December1st to 15thNight
25%
900
14%
2700
6%
900
33%
900
17%
1925
December16th to endNight
23%
960
16%
2880
4%
960
34%
960
19%
1962

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
10%8%36%6%35%5%6%8%34%
48058
Night
6%7%46%5%35%5%6%8%39%
46994
TransparencyDay
45%9%16%19%7%1
47714
Night
40%8%18%21%9%1
46842
SeeingDay
16%14%32%24%10%2
6018
Night
11%11%34%28%12%1
15156

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 15thDay
27%37%7%25%5%7%9%39%
1253
16th to endDay
210%47%7%45%5%7%7%37%
1512
February1st to 15thDay
17%47%8%46%5%6%9%37%
1426
16th to endDay
29%6%10%7%45%6%6%9%31%
1513
March1st to 15thDay
27%47%6%5%7%5%7%9%36%
1827
16th to endDay
412%7%10%6%36%5%6%9%26%
2156
April1st to 15thDay
9%15%5%7%6%35%5%5%8%25%
2227
16th to endDay
13%14%46%7%25%45%6%28%
2340
May1st to 15thDay
10%10%36%6%35%5%6%7%32%
2541
16th to endDay
22%9%36%6%45%6%6%7%21%
2802
June1st to 15thDay
22%9%47%6%45%6%5%5%22%
2700
16th to endDay
15%6%26%6%46%5%6%8%31%
2700
July1st to 15thDay
12%5%245%36%6%7%8%36%
2700
16th to endDay
8%4245%45%6%7%9%42%
2781
August1st to 15thDay
13%415%5%35%6%7%9%37%
2502
16th to endDay
10%3145%3446%8%45%
2483
September1st to 15thDay
14%5%2442345%5%47%
2142
16th to endDay
10%6%135%345%6%8%45%
1871
October1st to 15thDay
11%11%36%5%345%6%7%34%
1679
16th to endDay
7%8%45%5%35%5%7%8%37%
1584
November1st to 15thDay
38%445%45%7%6%8%40%
1455
16th to endDay
210%37%6%345%5%7%43%
1260
December1st to 15thDay
37%311%7%46%6%7%8%33%
1260
16th to endDay
29%47%6%345%6%8%38%
1344
January1st to 15thNight
28%5%9%6%36%5%6%10%33%
2685
16th to endNight
38%47%6%35%5%6%9%38%
2721
February1st to 15thNight
37%5%8%6%36%5%6%8%37%
2427
16th to endNight
28%6%8%8%45%45%8%36%
1959
March1st to 15thNight
17%46%5%46%7%7%10%36%
2133
16th to endNight
39%6%8%5%35%5%6%8%36%
2064
April1st to 15thNight
9%13%6%8%5%3345%8%31%
1721
16th to endNight
10%13%47%4345%5%8%33%
1620
May1st to 15thNight
9%9%37%5%3447%8%37%
1408
16th to endNight
20%7%35%5%25%5%5%8%30%
1309
June1st to 15thNight
19%6%36%5%34448%31%
1260
16th to endNight
13%5%26%43446%9%39%
1260
July1st to 15thNight
9%5%15%325%47%7%47%
1260
16th to endNight
7%323325%45%8%53%
1386
August1st to 15thNight
13%41231346%8%48%
1458
16th to endNight
9%31222345%8%56%
1719
September1st to 15thNight
13%5%13312446%53%
1816
16th to endNight
9%5%2332345%8%49%
1881
October1st to 15thNight
11%8%36%5%35%46%7%37%
1950
16th to endNight
6%9%25%425%5%6%9%42%
2288
November1st to 15thNight
38%444246%7%10%43%
2389
16th to endNight
39%5%8%6%25%46%10%37%
2700
December1st to 15thNight
28%5%8%7%47%6%6%8%33%
2700
16th to endNight
18%5%8%8%36%6%7%9%34%
2880

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 15thDay
39%8%19%24%6%2
1253
16th to endDay
43%7%16%18%10%3
1512
February1st to 15thDay
41%8%18%21%8%2
1426
16th to endDay
47%7%17%18%7%
1513
March1st to 15thDay
41%10%19%20%6%
1827
16th to endDay
54%8%17%14%4
2157
April1st to 15thDay
54%9%15%13%6%
2227
16th to endDay
55%7%14%16%5%1
2340
May1st to 15thDay
48%8%15%19%7%
2541
16th to endDay
60%8%13%12%4
2807
June1st to 15thDay
60%9%12%10%41
2700
16th to endDay
48%10%16%17%5%1
2700
July1st to 15thDay
41%10%19%20%6%1
2541
16th to endDay
34%12%16%25%10%1
2607
August1st to 15thDay
40%11%20%20%6%
2485
16th to endDay
34%7%18%28%9%1
2483
September1st to 15thDay
36%6%15%23%15%2
2142
16th to endDay
36%8%16%26%10%2
1871
October1st to 15thDay
47%8%15%18%9%
1679
16th to endDay
40%10%16%22%9%
1584
November1st to 15thDay
39%11%17%21%9%
1455
16th to endDay
38%8%19%22%8%2
1260
December1st to 15thDay
46%8%17%17%8%
1260
16th to endDay
39%8%18%21%11%1
1344
January1st to 15thNight
44%10%18%17%6%2
2685
16th to endNight
41%7%16%19%11%3
2721
February1st to 15thNight
41%9%16%21%9%1
2438
16th to endNight
44%7%14%19%12%1
1959
March1st to 15thNight
38%11%23%20%6%
2133
16th to endNight
44%9%17%19%7%
2067
April1st to 15thNight
50%7%16%16%8%
1721
16th to endNight
47%9%15%20%5%1
1620
May1st to 15thNight
44%6%16%23%8%
1409
16th to endNight
51%7%16%17%41
1309
June1st to 15thNight
50%9%15%16%7%
1260
16th to endNight
39%9%18%23%7%1
1260
July1st to 15thNight
33%10%17%27%10%
1190
16th to endNight
29%8%18%31%11%
1297
August1st to 15thNight
31%9%21%28%8%
1450
16th to endNight
23%7%21%32%14%1
1719
September1st to 15thNight
33%419%23%16%2
1816
16th to endNight
31%7%20%25%12%3
1881
October1st to 15thNight
44%8%14%20%9%1
1950
16th to endNight
35%9%20%25%8%
2288
November1st to 15thNight
34%9%18%24%11%
2389
16th to endNight
41%8%20%17%8%3
2700
December1st to 15thNight
46%10%16%19%6%
2700
16th to endNight
42%9%17%20%8%1
2880

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 15thDay
8%335%25%20%8%
60
16th to endDay
9%12%31%31%9%6%
64
February1st to 15thDay
12%16%49%10%7%3
65
16th to endDay
6%16%31%36%7%
172
March1st to 15thDay
8%30%41%18%1
270
16th to endDay
13%29%37%14%4
288
April1st to 15thDay
24%24%31%15%3
269
16th to endDay
26%20%28%17%5%
270
May1st to 15thDay
17%16%31%22%10%1
354
16th to endDay
24%9%23%26%12%3
517
June1st to 15thDay
25%13%26%21%10%1
495
16th to endDay
16%11%34%21%12%2
495
July1st to 15thDay
17%6%27%27%18%2
475
16th to endDay
11%11%33%28%13%2
450
August1st to 15thDay
14%6%32%30%12%3
315
16th to endDay
12%12%36%25%10%3
332
September1st to 15thDay
19%13%34%23%5%3
315
16th to endDay
14%22%31%24%6%1
276
October1st to 15thDay
17%14%35%25%6%
168
16th to endDay
7%431%40%14%2
96
November1st to 15thDay
14%10%43%27%4
88
16th to endDay
11%13%28%23%13%10%
60
December1st to 15thDay
111%30%41%13%1
60
16th to endDay
10%18%31%26%7%4
64
January1st to 15thNight
10%17%45%20%5%
900
16th to endNight
9%18%41%22%6%
801
February1st to 15thNight
7%12%40%23%14%1
704
16th to endNight
6%7%43%28%13%
632
March1st to 15thNight
6%14%46%24%6%
720
16th to endNight
8%10%36%34%9%
768
April1st to 15thNight
14%12%31%31%8%1
641
16th to endNight
18%11%29%29%11%
540
May1st to 15thNight
15%6%27%36%12%
395
16th to endNight
23%6%17%30%21%1
375
June1st to 15thNight
23%6%21%29%16%2
360
16th to endNight
14%5%19%34%23%1
360
July1st to 15thNight
13%317%36%27%1
340
16th to endNight
6%418%45%23%2
376
August1st to 15thNight
15%29%33%35%3
378
16th to endNight
10%5%17%41%22%1
573
September1st to 15thNight
19%5%16%32%23%3
684
16th to endNight
13%8%26%34%14%2
680
October1st to 15thNight
16%9%30%31%11%1
660
16th to endNight
10%12%36%32%6%1
704
November1st to 15thNight
10%18%47%18%41
805
16th to endNight
8%16%44%24%5%
900
December1st to 15thNight
6%16%42%24%10%
900
16th to endNight
6%16%42%23%8%1
960
Page generated at 2017-09-22 05:35:29. Version ac04

Copyright 2017 A. Danko


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