Sproat Lake (east)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sproat Lake (east) 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
35%
14634
8%
47095
6%
14605
37%
14605
12%
36729

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%
750
6%
2686
5%
746
22%
746
5%
2378
January16th to endNight
23%
793
7%
2769
7%
793
24%
793
6%
2360
February1st to 15thNight
24%
700
6%
2288
4%
700
26%
700
7%
1947
February16th to endNight
32%
632
12%
2053
11%
632
36%
632
12%
1591
March1st to 15thNight
21%
720
4%
2038
3%
720
23%
720
8%
1743
March16th to endNight
23%
768
5%
2112
3%
768
25%
768
8%
1816
April1st to 15thNight
32%
653
7%
1739
4%
653
33%
653
13%
1403
April16th to endNight
32%
540
7%
1620
6%
540
33%
540
11%
1314
May1st to 15thNight
51%
377
11%
1458
16%
377
53%
377
14%
1017
May16th to endNight
48%
375
5%
1378
6%
374
51%
374
14%
1000
June1st to 15thNight
46%
360
2%
1260
2%
360
46%
360
16%
888
June16th to endNight
44%
360
3%
1260
2%
360
44%
360
14%
921
July1st to 15thNight
65%
340
7%
1190
6%
340
65%
340
28%
684
July16th to endNight
69%
376
12%
1259
16%
354
71%
354
35%
669
August1st to 15thNight
75%
496
13%
1570
15%
494
75%
494
35%
877
August16th to endNight
62%
573
15%
1719
13%
573
64%
573
30%
1054
September1st to 15thNight
67%
711
19%
1796
12%
711
68%
711
38%
1119
September16th to endNight
39%
716
13%
1994
10%
716
42%
716
19%
1479
October1st to 15thNight
42%
720
8%
2160
7%
720
44%
720
18%
1570
October16th to endNight
25%
708
6%
2220
4%
708
28%
708
8%
1877
November1st to 15thNight
15%
700
5%
2450
3%
700
17%
700
5%
2131
November16th to endNight
21%
720
5%
2520
2%
720
24%
720
6%
2117
December1st to 15thNight
20%
746
5%
2676
3%
746
23%
746
6%
2262
December16th to endNight
14%
800
5%
2880
2%
800
17%
800
5%
2512

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
24%11%47%6%34445%24%
48365
Night
25%10%36%5%34445%25%
47241
Cloud CoverDay
21%12%48%6%34445%24%
48365
Night
22%11%47%6%34445%25%
47244
TransparencyDay
62%6%12%12%5%
48015
Night
61%6%12%13%5%
47095
SeeingDay
27%11%24%22%10%2
6499
Night
29%5%21%25%15%2
14639

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
38%13%49%7%3332311%
1253
16th to endDay
35%17%5%7%5%3323410%
1452
February1st to 15thDay
35%14%5%9%5%2332412%
1576
16th to endDay
25%14%37%6%34445%18%
1421
March1st to 15thDay
33%18%48%8%3422310%
1920
16th to endDay
33%16%5%7%7%2422412%
2112
April1st to 15thDay
27%14%5%9%6%4443414%
2206
16th to endDay
28%13%49%7%25%43415%
2340
May1st to 15thDay
21%10%47%6%35%5%5%6%24%
2493
16th to endDay
21%10%49%8%35%5%45%19%
2732
June1st to 15thDay
22%10%48%6%35%45%6%22%
2700
16th to endDay
23%10%49%6%345%5%5%22%
2700
July1st to 15thDay
12%5%25%5%34347%44%
2700
16th to endDay
9%5%3443346%7%49%
2823
August1st to 15thDay
9%5%35%42445%7%45%
2380
16th to endDay
12%6%26%5%2445%9%39%
2483
September1st to 15thDay
12%7%15%42345%5%45%
2163
16th to endDay
22%9%47%6%33335%28%
1965
October1st to 15thDay
27%11%46%5%3433424%
1800
16th to endDay
38%11%37%5%3434414%
1670
November1st to 15thDay
39%13%48%6%243339%
1408
16th to endDay
37%10%5%7%6%3434312%
1440
December1st to 15thDay
31%14%7%8%5%2434313%
1284
16th to endDay
40%14%48%42323310%
1344
January1st to 15thNight
38%13%49%5%2333311%
2686
16th to endNight
33%13%48%6%24445%11%
2769
February1st to 15thNight
32%15%46%5%23335%15%
2276
16th to endNight
24%13%36%5%3434426%
2053
March1st to 15thNight
30%13%46%7%35%43415%
2038
16th to endNight
29%13%37%5%35%435%16%
2108
April1st to 15thNight
22%9%47%6%4445%7%22%
1739
16th to endNight
25%9%37%6%46%35%5%20%
1620
May1st to 15thNight
15%7%37%7%35%45%6%34%
1457
16th to endNight
16%7%37%6%35%5%6%8%28%
1378
June1st to 15thNight
17%8%36%435%5%47%33%
1260
16th to endNight
15%7%36%7%36%6%6%7%28%
1260
July1st to 15thNight
10%424324446%51%
1260
16th to endNight
8%423323347%56%
1344
August1st to 15thNight
5%41342445%7%56%
1578
16th to endNight
10%5%145%245%5%8%47%
1719
September1st to 15thNight
8%3134246%5%7%53%
1796
16th to endNight
22%8%37%5%33445%32%
1994
October1st to 15thNight
22%8%26%5%24435%33%
2160
16th to endNight
36%10%36%6%2334415%
2220
November1st to 15thNight
40%10%48%6%2323313%
2450
16th to endNight
34%11%5%6%6%34435%15%
2520
December1st to 15thNight
30%14%6%6%5%35%44416%
2676
16th to endNight
37%14%5%8%424335%10%
2880

Percentage Cloud Cover SW (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
32%17%7%10%6%2332210%
1253
16th to endDay
31%16%7%11%7%232339%
1452
February1st to 15thDay
31%15%5%10%5%3333412%
1576
16th to endDay
22%14%5%7%7%45%5%5%5%18%
1421
March1st to 15thDay
30%18%7%9%6%3433310%
1920
16th to endDay
28%19%5%9%7%3333312%
2112
April1st to 15thDay
23%15%6%10%8%45%43414%
2206
16th to endDay
27%13%5%9%7%35%43316%
2340
May1st to 15thDay
19%11%47%6%35%45%7%25%
2493
16th to endDay
19%12%48%7%45%5%5%6%19%
2732
June1st to 15thDay
19%12%5%8%6%35%446%22%
2700
16th to endDay
19%11%5%9%7%3446%6%22%
2700
July1st to 15thDay
12%6%25%434446%45%
2700
16th to endDay
9%5%3443435%6%50%
2823
August1st to 15thDay
8%6%36%42345%7%47%
2380
16th to endDay
10%7%36%5%3445%9%40%
2483
September1st to 15thDay
11%6%25%42435%6%47%
2163
16th to endDay
20%10%48%5%34445%28%
1965
October1st to 15thDay
24%11%38%6%3444424%
1800
16th to endDay
32%12%48%6%34336%13%
1670
November1st to 15thDay
34%17%5%8%5%2433310%
1408
16th to endDay
32%14%6%9%6%3434311%
1440
December1st to 15thDay
27%17%6%8%6%2444413%
1284
16th to endDay
35%15%7%8%4342349%
1344
January1st to 15thNight
31%15%7%8%6%2333311%
2685
16th to endNight
28%14%6%9%6%23346%12%
2769
February1st to 15thNight
28%16%5%7%5%2435%415%
2276
16th to endNight
19%13%46%6%35%44426%
2053
March1st to 15thNight
25%13%6%8%6%45%34415%
2038
16th to endNight
24%15%5%8%7%35%445%16%
2112
April1st to 15thNight
18%11%47%8%45%45%6%22%
1739
16th to endNight
23%10%5%7%6%45%45%6%20%
1620
May1st to 15thNight
15%6%35%6%36%5%47%33%
1457
16th to endNight
13%7%47%6%36%6%6%8%28%
1378
June1st to 15thNight
15%8%36%5%36%5%47%33%
1260
16th to endNight
13%7%37%7%45%6%6%8%29%
1260
July1st to 15thNight
9%5%23324447%52%
1260
16th to endNight
7%41331435%6%57%
1344
August1st to 15thNight
442343445%6%56%
1578
16th to endNight
8%6%15%5%245%5%8%47%
1719
September1st to 15thNight
7%4134235%5%7%53%
1796
16th to endNight
20%8%37%6%23346%32%
1994
October1st to 15thNight
19%9%37%5%34345%33%
2160
16th to endNight
30%12%48%6%2345%5%16%
2220
November1st to 15thNight
34%15%48%6%2333313%
2450
16th to endNight
30%12%5%7%6%3445%415%
2520
December1st to 15thNight
25%15%7%9%6%3434415%
2676
16th to endNight
31%16%5%8%5%3433410%
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
81%435%3
1253
16th to endDay
80%35%431
1452
February1st to 15thDay
77%47%6%31
1576
16th to endDay
67%6%10%11%3
1421
March1st to 15thDay
80%37%6%1
1920
16th to endDay
78%48%7%
2112
April1st to 15thDay
74%6%7%9%1
2206
16th to endDay
72%410%9%3
2340
May1st to 15thDay
59%7%14%13%5%
2493
16th to endDay
65%9%12%11%1
2736
June1st to 15thDay
62%8%14%9%3
2700
16th to endDay
62%7%14%12%3
2700
July1st to 15thDay
40%7%19%21%10%
2541
16th to endDay
33%8%20%26%10%
2645
August1st to 15thDay
36%9%18%24%10%1
2363
16th to endDay
42%7%21%21%6%
2483
September1st to 15thDay
38%7%13%23%15%
2163
16th to endDay
58%5%12%13%8%
1965
October1st to 15thDay
63%6%10%11%7%
1800
16th to endDay
73%5%10%7%2
1670
November1st to 15thDay
80%5%5%5%2
1408
16th to endDay
75%7%6%6%4
1440
December1st to 15thDay
74%5%6%7%4
1284
16th to endDay
79%46%6%21
1344
January1st to 15thNight
78%5%46%4
2686
16th to endNight
74%45%8%42
2769
February1st to 15thNight
72%5%7%9%31
2288
16th to endNight
62%410%16%5%
2053
March1st to 15thNight
73%410%8%2
2038
16th to endNight
71%6%10%9%2
2112
April1st to 15thNight
62%7%13%13%3
1739
16th to endNight
63%8%11%12%4
1620
May1st to 15thNight
51%7%14%18%7%
1458
16th to endNight
51%10%19%15%2
1378
June1st to 15thNight
50%7%25%10%3
1260
16th to endNight
52%9%18%15%3
1260
July1st to 15thNight
32%8%22%24%11%1
1190
16th to endNight
26%8%24%31%8%1
1259
August1st to 15thNight
28%7%24%27%9%2
1570
16th to endNight
34%7%24%24%6%1
1719
September1st to 15thNight
29%8%14%27%16%2
1796
16th to endNight
54%5%13%16%7%2
1994
October1st to 15thNight
52%6%14%14%11%
2160
16th to endNight
71%5%9%9%3
2220
November1st to 15thNight
77%47%6%21
2450
16th to endNight
72%5%8%8%5%
2520
December1st to 15thNight
73%5%8%7%4
2676
16th to endNight
77%5%6%6%4
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
21%6%15%21%28%6%
60
16th to endDay
51%9%15%16%7%
133
February1st to 15thDay
45%11%21%15%5%
236
16th to endDay
33%13%27%18%7%1
211
March1st to 15thDay
50%18%18%11%2
264
16th to endDay
44%14%25%9%32
288
April1st to 15thDay
38%18%21%15%31
269
16th to endDay
37%18%23%12%6%1
270
May1st to 15thDay
26%15%22%27%7%1
288
16th to endDay
23%8%27%23%11%5%
447
June1st to 15thDay
22%13%29%21%9%2
495
16th to endDay
23%14%27%23%8%2
495
July1st to 15thDay
15%9%23%35%14%1
475
16th to endDay
10%7%25%35%18%2
492
August1st to 15thDay
12%7%18%30%23%6%
315
16th to endDay
15%7%24%29%17%6%
332
September1st to 15thDay
19%5%26%27%15%5%
315
16th to endDay
27%10%27%20%11%2
315
October1st to 15thDay
28%12%23%21%10%2
315
16th to endDay
43%9%23%14%6%2
240
November1st to 15thDay
48%15%15%13%8%
60
16th to endDay
45%18%18%10%16%
60
December1st to 15thDay
43%10%20%16%8%1
60
16th to endDay
42%420%17%14%1
64
January1st to 15thNight
42%5%18%21%11%1
750
16th to endNight
37%5%21%20%12%2
793
February1st to 15thNight
40%7%17%26%7%
704
16th to endNight
29%6%23%27%13%1
632
March1st to 15thNight
35%9%27%18%8%1
720
16th to endNight
33%9%24%21%8%1
768
April1st to 15thNight
25%6%25%28%12%1
653
16th to endNight
26%427%32%8%1
540
May1st to 15thNight
16%419%35%22%1
378
16th to endNight
16%220%38%20%1
375
June1st to 15thNight
18%5%21%31%22%
360
16th to endNight
18%425%34%15%1
360
July1st to 15thNight
9%315%40%28%2
340
16th to endNight
8%214%33%36%3
376
August1st to 15thNight
8%19%34%36%10%
496
16th to endNight
13%215%30%31%6%
573
September1st to 15thNight
11%114%30%31%11%
711
16th to endNight
25%5%21%23%19%5%
716
October1st to 15thNight
28%318%28%18%2
720
16th to endNight
39%421%21%10%2
708
November1st to 15thNight
44%9%24%19%3
700
16th to endNight
37%6%23%18%11%2
720
December1st to 15thNight
34%7%22%24%10%
746
16th to endNight
42%7%27%17%5%
800
Page generated at 2017-10-17 13:35:29. Version ac04

Copyright 2017 A. Danko


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