Shaw Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Shaw Lake clear sky chart from 2005-11-05 to 2017-10-16.

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
39%
15356
10%
46844
6%
15331
43%
15331
18%
33567

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
30%
895
7%
2685
4%
895
33%
895
12%
2130
January16th to endNight
30%
960
13%
2880
7%
960
37%
960
15%
2104
February1st to 15thNight
38%
715
10%
2430
8%
714
42%
714
15%
1746
February16th to endNight
43%
632
13%
2052
11%
632
47%
632
18%
1453
March1st to 15thNight
35%
720
14%
2106
9%
720
40%
720
19%
1545
March16th to endNight
36%
767
11%
2112
7%
767
38%
767
16%
1612
April1st to 15thNight
40%
554
14%
1652
9%
554
44%
554
22%
1138
April16th to endNight
37%
540
12%
1578
10%
540
40%
540
19%
1129
May1st to 15thNight
47%
395
6%
1295
4%
395
48%
395
25%
805
May16th to endNight
45%
374
0%
1309
0%
374
45%
374
18%
886
June1st to 15thNight
47%
360
0%
1107
0%
360
47%
360
18%
794
June16th to endNight
49%
360
0%
900
0%
360
49%
360
23%
658
July1st to 15thNight
55%
340
0%
1130
0%
340
55%
340
26%
698
July16th to endNight
58%
376
1%
1239
0%
354
59%
354
26%
743
August1st to 15thNight
65%
387
6%
1330
5%
385
66%
385
25%
818
August16th to endNight
54%
573
12%
1719
10%
573
57%
573
27%
1117
September1st to 15thNight
52%
569
13%
1745
11%
569
54%
569
28%
1087
September16th to endNight
47%
716
18%
1980
10%
716
54%
716
32%
1243
October1st to 15thNight
40%
720
14%
2158
8%
720
44%
720
20%
1514
October16th to endNight
33%
768
13%
2361
7%
768
39%
768
18%
1689
November1st to 15thNight
31%
875
14%
2472
9%
875
36%
875
17%
1844
November16th to endNight
31%
900
8%
2706
3%
900
36%
900
13%
2101
December1st to 15thNight
28%
900
6%
2880
3%
900
31%
900
10%
2315
December16th to endNight
33%
960
9%
3018
4%
960
37%
960
11%
2398

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
11%9%47%6%45%5%6%7%30%
48595
Night
9%10%48%7%45%5%6%7%30%
47001
TransparencyDay
51%6%17%18%5%
48245
Night
51%6%15%19%5%
46855
SeeingDay
18%7%26%26%16%4
6489
Night
15%5%26%33%16%2
15371

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
8%13%6%9%8%5%5%5%7%6%22%
1253
16th to endDay
8%10%5%12%8%47%348%26%
1344
February1st to 15thDay
6%11%5%10%9%37%6%6%7%25%
1435
16th to endDay
6%12%7%9%9%47%5%6%5%22%
1422
March1st to 15thDay
8%11%5%9%8%5%6%5%5%8%23%
1854
16th to endDay
9%12%6%9%7%35%6%5%7%25%
2111
April1st to 15thDay
11%13%47%7%35%45%7%27%
2292
16th to endDay
16%11%48%5%35%45%7%26%
2382
May1st to 15thDay
11%7%26%5%46%6%6%8%33%
2653
16th to endDay
16%6%36%5%35%45%7%34%
2802
June1st to 15thDay
16%8%36%6%46%5%6%6%27%
2850
16th to endDay
15%7%46%7%46%5%6%8%27%
3058
July1st to 15thDay
12%425%6%35%45%8%39%
2754
16th to endDay
12%6%35%5%36%6%7%9%34%
2846
August1st to 15thDay
11%6%25%5%35%6%7%10%36%
2622
16th to endDay
9%5%27%5%35%6%7%9%36%
2483
September1st to 15thDay
13%6%25%6%3445%7%39%
2214
16th to endDay
13%6%35%435%46%8%38%
1980
October1st to 15thDay
13%13%5%7%5%335%5%6%30%
1799
16th to endDay
10%16%47%5%35%446%30%
1520
November1st to 15thDay
11%9%6%8%7%45%5%6%5%28%
1384
16th to endDay
6%11%7%10%9%5%6%5%5%7%23%
1254
December1st to 15thDay
7%12%8%13%7%5%6%6%6%7%17%
1080
16th to endDay
6%12%6%12%11%5%6%7%7%7%17%
1203
January1st to 15thNight
7%12%6%10%9%6%7%6%5%5%21%
2685
16th to endNight
6%9%410%8%5%6%5%6%7%29%
2880
February1st to 15thNight
7%10%5%9%9%45%5%6%5%29%
2429
16th to endNight
5%11%49%8%46%7%8%8%26%
2052
March1st to 15thNight
8%10%5%9%7%46%5%6%9%26%
2106
16th to endNight
10%14%6%8%6%35%5%5%7%25%
2109
April1st to 15thNight
10%9%36%5%36%5%6%7%33%
1652
16th to endNight
13%13%46%6%33446%32%
1578
May1st to 15thNight
9%6%37%6%4445%7%40%
1295
16th to endNight
15%8%36%435%46%6%34%
1309
June1st to 15thNight
13%7%39%5%46%7%6%7%28%
1107
16th to endNight
14%7%46%6%45%5%5%8%32%
900
July1st to 15thNight
9%6%245%345%7%8%41%
1200
16th to endNight
9%424426%6%7%8%42%
1323
August1st to 15thNight
7%326%6%46%6%6%9%40%
1337
16th to endNight
9%6%25%5%46%5%6%8%39%
1719
September1st to 15thNight
12%7%25%43345%6%45%
1745
16th to endNight
11%5%243245%7%9%43%
1980
October1st to 15thNight
13%11%35%5%4446%7%33%
2158
16th to endNight
10%12%47%7%345%5%7%30%
2361
November1st to 15thNight
11%12%5%8%6%35%5%6%5%29%
2472
16th to endNight
6%12%5%10%8%5%6%5%5%7%25%
2706
December1st to 15thNight
9%13%7%11%9%5%6%6%5%6%19%
2880
16th to endNight
412%6%11%10%6%8%7%7%7%17%
3018

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
59%6%16%12%4
1253
16th to endDay
56%5%14%15%6%1
1344
February1st to 15thDay
56%7%16%14%5%
1435
16th to endDay
60%5%12%16%4
1422
March1st to 15thDay
57%6%17%13%3
1854
16th to endDay
57%6%14%16%4
2112
April1st to 15thDay
54%5%16%15%7%
2292
16th to endDay
56%5%12%15%8%
2382
May1st to 15thDay
45%5%12%24%11%
2653
16th to endDay
48%6%13%20%11%
2807
June1st to 15thDay
54%6%14%19%5%
2850
16th to endDay
53%6%15%18%4
3058
July1st to 15thDay
43%7%20%24%4
2595
16th to endDay
43%8%28%18%1
2667
August1st to 15thDay
41%9%27%19%1
2604
16th to endDay
40%9%27%18%2
2483
September1st to 15thDay
43%6%22%21%6%
2214
16th to endDay
42%7%20%23%6%
1980
October1st to 15thDay
54%5%18%19%2
1799
16th to endDay
53%6%17%20%2
1520
November1st to 15thDay
54%7%15%18%3
1384
16th to endDay
58%8%14%15%2
1254
December1st to 15thDay
64%7%11%15%1
1080
16th to endDay
63%7%12%12%3
1203
January1st to 15thNight
61%7%14%13%2
2685
16th to endNight
52%7%14%18%5%1
2880
February1st to 15thNight
54%5%14%18%7%
2440
16th to endNight
51%6%16%18%6%
2052
March1st to 15thNight
52%6%14%20%5%
2106
16th to endNight
57%5%12%17%7%
2112
April1st to 15thNight
47%5%15%21%8%1
1652
16th to endNight
52%49%18%12%2
1578
May1st to 15thNight
41%312%23%16%1
1296
16th to endNight
49%5%12%20%10%1
1309
June1st to 15thNight
51%6%15%19%7%
1107
16th to endNight
48%7%16%20%5%1
900
July1st to 15thNight
37%7%21%27%6%
1130
16th to endNight
35%8%25%28%2
1239
August1st to 15thNight
36%9%26%25%2
1330
16th to endNight
40%6%22%25%4
1719
September1st to 15thNight
38%5%20%26%7%1
1745
16th to endNight
34%6%20%27%9%1
1980
October1st to 15thNight
50%415%23%5%
2158
16th to endNight
51%5%17%21%3
2361
November1st to 15thNight
54%6%13%20%5%
2472
16th to endNight
57%8%17%13%3
2706
December1st to 15thNight
63%7%12%13%2
2880
16th to endNight
62%7%13%13%3
3018

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
10%325%35%20%6%
60
16th to endDay
10%131%34%18%3
64
February1st to 15thDay
11%16%29%25%16%1
68
16th to endDay
14%8%23%35%13%3
81
March1st to 15thDay
16%14%40%20%7%
246
16th to endDay
16%12%37%24%6%1
288
April1st to 15thDay
19%15%35%19%9%
269
16th to endDay
22%14%27%23%10%1
312
May1st to 15thDay
14%11%22%29%17%5%
468
16th to endDay
20%5%21%28%19%5%
517
June1st to 15thDay
23%9%25%21%15%4
495
16th to endDay
18%422%29%19%5%
673
July1st to 15thDay
14%325%31%20%4
517
16th to endDay
13%5%26%26%20%6%
515
August1st to 15thDay
17%317%26%23%11%
442
16th to endDay
12%7%30%31%15%1
332
September1st to 15thDay
22%9%23%27%12%4
315
16th to endDay
19%9%27%26%14%2
315
October1st to 15thDay
27%8%26%19%14%3
143
16th to endDay
34%7%24%20%13%1
99
November1st to 15thDay
25%5%31%27%8%1
86
16th to endDay
10%8%35%15%16%15%
60
December1st to 15thDay
341%30%18%6%
60
16th to endDay
9%335%29%15%6%
64
January1st to 15thNight
12%8%28%36%12%2
900
16th to endNight
12%9%31%35%8%1
960
February1st to 15thNight
13%5%25%36%16%1
722
16th to endNight
9%428%37%17%2
632
March1st to 15thNight
14%5%31%31%12%2
720
16th to endNight
16%7%26%29%16%2
768
April1st to 15thNight
14%8%29%32%15%1
554
16th to endNight
19%5%28%29%16%1
540
May1st to 15thNight
13%7%20%35%20%3
396
16th to endNight
18%5%19%29%24%2
375
June1st to 15thNight
18%418%34%21%2
360
16th to endNight
18%119%29%28%2
360
July1st to 15thNight
12%219%37%26%
340
16th to endNight
12%217%36%26%4
376
August1st to 15thNight
9%115%35%31%5%
387
16th to endNight
13%220%38%23%
573
September1st to 15thNight
16%320%32%24%2
569
16th to endNight
14%5%25%36%16%1
716
October1st to 15thNight
20%326%31%13%3
720
16th to endNight
18%7%28%32%11%1
768
November1st to 15thNight
19%5%33%28%9%3
875
16th to endNight
13%8%31%32%12%2
900
December1st to 15thNight
17%7%28%30%12%3
900
16th to endNight
9%5%30%33%16%4
960
Page generated at 2017-10-17 14:35:27. Version ac04

Copyright 2017 A. Danko


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