Valemount
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Valemount clear sky chart from 2005-11-05 to 2017-10-31.

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
26%
15138
5%
47211
3%
15107
28%
15107
11%
38061

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
11%
883
4%
2820
2%
880
13%
880
5%
2519
January16th to endNight
14%
779
6%
2754
4%
779
18%
779
5%
2394
February1st to 15thNight
15%
700
4%
2442
4%
696
17%
696
6%
2086
February16th to endNight
25%
632
8%
1990
6%
632
31%
632
12%
1584
March1st to 15thNight
12%
720
6%
2160
2%
720
16%
720
7%
1871
March16th to endNight
20%
768
4%
2007
1%
768
22%
768
10%
1698
April1st to 15thNight
31%
719
7%
1799
3%
719
33%
719
15%
1444
April16th to endNight
30%
420
7%
1500
5%
420
35%
420
12%
1133
May1st to 15thNight
37%
360
5%
1440
4%
360
39%
360
14%
1036
May16th to endNight
42%
374
2%
1277
0%
374
42%
374
17%
914
June1st to 15thNight
40%
360
0%
1080
0%
360
40%
360
17%
799
June16th to endNight
42%
360
0%
1080
0%
360
42%
360
17%
794
July1st to 15thNight
50%
340
0%
1020
0%
340
50%
340
25%
676
July16th to endNight
55%
376
4%
1293
2%
354
58%
354
24%
782
August1st to 15thNight
61%
360
7%
1432
11%
358
63%
358
21%
865
August16th to endNight
44%
542
13%
1688
11%
542
47%
542
23%
1104
September1st to 15thNight
45%
720
12%
1800
7%
720
45%
720
26%
1267
September16th to endNight
35%
716
12%
1945
7%
716
38%
716
20%
1430
October1st to 15thNight
29%
720
7%
2169
4%
720
32%
720
15%
1647
October16th to endNight
17%
768
4%
2496
2%
768
20%
768
7%
2104
November1st to 15thNight
10%
712
4%
2448
2%
712
13%
712
4%
2173
November16th to endNight
13%
900
3%
2700
1%
900
15%
900
5%
2433
December1st to 15thNight
16%
917
4%
2799
2%
917
18%
917
5%
2501
December16th to endNight
14%
992
3%
3072
1%
992
16%
992
4%
2807

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%13%6%11%9%5%6%5%5%6%19%
48578
Night
8%13%6%11%9%5%6%5%5%6%18%
47353
TransparencyDay
66%313%12%3
48224
Night
67%412%12%3
47211
SeeingDay
22%14%28%23%9%1
6778
Night
22%10%32%24%10%
15145

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
6%21%9%14%10%45%5%5%6%10%
1129
16th to endDay
413%9%14%14%5%7%5%47%12%
1470
February1st to 15thDay
5%15%7%13%10%5%6%7%5%6%16%
1421
16th to endDay
210%7%12%12%6%8%7%6%5%20%
1484
March1st to 15thDay
316%8%12%12%6%6%7%6%5%13%
1800
16th to endDay
415%8%17%11%5%7%6%5%413%
2214
April1st to 15thDay
6%17%9%14%11%5%6%6%6%411%
2149
16th to endDay
9%15%8%12%9%46%5%6%6%15%
2459
May1st to 15thDay
9%15%7%11%7%45%5%46%22%
2511
16th to endDay
17%12%5%10%7%45%6%5%6%19%
2831
June1st to 15thDay
21%13%410%8%46%445%16%
2880
16th to endDay
17%10%6%9%9%47%5%5%5%17%
2880
July1st to 15thDay
13%8%37%7%35%5%6%7%31%
2880
16th to endDay
11%7%37%7%46%5%6%7%32%
2784
August1st to 15thDay
10%7%48%8%5%6%6%7%8%29%
2520
16th to endDay
11%9%49%8%46%5%6%7%25%
2512
September1st to 15thDay
10%11%47%7%3445%6%32%
2160
16th to endDay
13%10%6%8%9%5%6%5%5%5%23%
2013
October1st to 15thDay
11%13%6%11%8%5%5%5%6%5%20%
1791
16th to endDay
14%14%5%12%11%5%6%5%4415%
1726
November1st to 15thDay
9%17%8%14%10%5%7%5%4411%
1394
16th to endDay
416%9%14%12%7%7%6%5%410%
1260
December1st to 15thDay
7%17%6%14%12%5%7%5%5%5%11%
1158
16th to endDay
6%16%6%16%11%6%10%6%45%8%
1152
January1st to 15thNight
11%21%9%15%10%46%4447%
2820
16th to endNight
5%15%10%16%13%6%8%6%5%5%7%
2754
February1st to 15thNight
7%16%7%14%11%6%6%5%5%5%11%
2430
16th to endNight
311%5%13%11%6%8%7%7%7%17%
1990
March1st to 15thNight
417%9%14%11%5%8%6%45%13%
2160
16th to endNight
314%7%14%12%5%7%6%6%7%15%
2003
April1st to 15thNight
314%6%10%9%5%7%7%5%8%21%
1799
16th to endNight
9%10%5%10%8%5%7%7%5%8%21%
1500
May1st to 15thNight
8%11%47%7%5%7%6%6%8%27%
1439
16th to endNight
13%8%35%6%5%5%5%7%8%29%
1277
June1st to 15thNight
17%8%37%6%45%5%5%7%27%
1080
16th to endNight
9%8%37%8%5%7%7%7%8%26%
1080
July1st to 15thNight
13%6%26%5%335%6%8%38%
1080
16th to endNight
8%5%25%6%36%5%6%8%40%
1384
August1st to 15thNight
7%5%25%7%46%5%7%10%37%
1440
16th to endNight
9%6%26%6%46%6%6%9%35%
1688
September1st to 15thNight
7%9%48%6%345%46%37%
1800
16th to endNight
15%8%47%6%35%5%5%6%30%
1945
October1st to 15thNight
11%12%5%9%7%36%446%26%
2169
16th to endNight
12%15%6%11%9%46%5%5%6%14%
2496
November1st to 15thNight
12%20%8%13%9%46%5%5%310%
2448
16th to endNight
7%18%10%17%11%5%8%45%37%
2700
December1st to 15thNight
8%17%7%13%12%7%7%6%45%8%
2799
16th to endNight
5%18%11%17%12%7%7%5%444
3072

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
78%39%6%1
1129
16th to endDay
71%39%9%41
1470
February1st to 15thDay
71%311%8%5%
1421
16th to endDay
65%314%9%5%
1484
March1st to 15thDay
74%211%9%1
1800
16th to endDay
74%311%8%1
2214
April1st to 15thDay
77%210%8%1
2149
16th to endDay
69%5%12%10%2
2459
May1st to 15thDay
63%414%13%3
2511
16th to endDay
66%414%12%2
2835
June1st to 15thDay
72%39%10%3
2880
16th to endDay
69%311%11%3
2880
July1st to 15thDay
55%411%19%8%
2711
16th to endDay
52%416%21%5%
2612
August1st to 15thDay
51%5%19%16%5%1
2503
16th to endDay
57%316%17%5%
2512
September1st to 15thDay
51%218%20%5%
2160
16th to endDay
60%413%14%5%
2013
October1st to 15thDay
64%217%11%3
1791
16th to endDay
73%313%9%
1726
November1st to 15thDay
77%38%6%2
1394
16th to endDay
76%36%6%5%
1260
December1st to 15thDay
75%37%10%3
1158
16th to endDay
79%36%7%2
1152
January1st to 15thNight
81%26%6%2
2820
16th to endNight
77%35%6%41
2754
February1st to 15thNight
75%38%6%4
2442
16th to endNight
64%5%11%13%5%
1990
March1st to 15thNight
77%27%8%3
2160
16th to endNight
70%5%13%9%1
2007
April1st to 15thNight
63%415%14%3
1799
16th to endNight
62%317%13%3
1500
May1st to 15thNight
56%5%16%16%5%
1440
16th to endNight
53%6%18%18%3
1277
June1st to 15thNight
57%317%16%4
1080
16th to endNight
55%419%16%3
1080
July1st to 15thNight
45%419%23%7%
1020
16th to endNight
41%420%26%6%
1293
August1st to 15thNight
41%6%25%21%5%
1432
16th to endNight
44%422%21%6%
1688
September1st to 15thNight
47%318%22%6%1
1800
16th to endNight
53%417%18%6%
1945
October1st to 15thNight
58%417%15%3
2169
16th to endNight
71%6%11%10%
2496
November1st to 15thNight
81%26%5%3
2448
16th to endNight
81%345%3
2700
December1st to 15thNight
78%449%2
2799
16th to endNight
83%346%2
3072

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
5%133%38%13%8%
60
16th to endDay
21%6%34%20%10%6%
64
February1st to 15thDay
14%18%41%20%21
81
16th to endDay
9%16%39%19%11%3
222
March1st to 15thDay
22%27%34%12%2
270
16th to endDay
22%17%37%16%4
288
April1st to 15thDay
24%17%30%20%6%
269
16th to endDay
25%22%27%15%6%2
270
May1st to 15thDay
25%18%26%19%10%1
288
16th to endDay
25%10%19%28%12%3
546
June1st to 15thDay
29%14%24%22%8%
675
16th to endDay
24%12%25%26%9%1
675
July1st to 15thDay
21%11%24%30%10%1
645
16th to endDay
17%13%31%26%8%1
452
August1st to 15thDay
16%7%21%33%15%4
315
16th to endDay
18%15%35%22%7%
332
September1st to 15thDay
27%14%24%22%9%1
315
16th to endDay
25%15%26%23%8%
315
October1st to 15thDay
26%14%33%15%10%
306
16th to endDay
24%11%29%25%6%2
144
November1st to 15thDay
24%14%51%6%3
62
16th to endDay
13%11%33%21%11%8%
60
December1st to 15thDay
11%8%23%33%16%6%
60
16th to endDay
1154%15%23%3
64
January1st to 15thNight
30%13%34%15%5%
885
16th to endNight
22%12%39%19%6%
779
February1st to 15thNight
24%12%33%21%6%
704
16th to endNight
14%9%37%28%9%
632
March1st to 15thNight
20%14%43%15%6%
720
16th to endNight
18%10%39%24%7%
768
April1st to 15thNight
15%10%32%28%12%
719
16th to endNight
18%9%33%29%9%
420
May1st to 15thNight
16%6%30%32%13%
360
16th to endNight
18%425%32%17%
375
June1st to 15thNight
25%6%20%32%13%
360
16th to endNight
15%6%25%32%17%1
360
July1st to 15thNight
20%317%38%18%
340
16th to endNight
13%6%18%38%21%
376
August1st to 15thNight
11%315%40%28%1
360
16th to endNight
15%5%28%36%14%
542
September1st to 15thNight
18%7%23%32%17%1
720
16th to endNight
27%7%23%28%12%
716
October1st to 15thNight
25%7%29%28%8%
720
16th to endNight
31%8%33%19%5%
768
November1st to 15thNight
33%14%34%13%3
712
16th to endNight
25%13%36%18%41
900
December1st to 15thNight
25%11%37%17%7%
917
16th to endNight
20%13%36%20%8%
992
Page generated at 2017-11-01 14:23:40. Version ac04

Copyright 2017 A. Danko


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