Abraham Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Abraham Lake clear sky chart from 2005-11-05 to 2017-09-10.

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%
15005
10%
46364
4%
14972
32%
14972
17%
32225

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
12%
900
8%
2685
2%
895
17%
895
10%
2033
January16th to endNight
14%
783
14%
2703
4%
783
26%
783
13%
1865
February1st to 15thNight
19%
700
9%
2464
4%
697
27%
697
12%
1738
February16th to endNight
28%
632
12%
1950
6%
632
36%
632
19%
1367
March1st to 15thNight
15%
720
12%
2160
3%
720
25%
720
15%
1505
March16th to endNight
23%
768
12%
2025
2%
767
29%
767
18%
1443
April1st to 15thNight
27%
671
10%
1751
3%
671
31%
671
16%
1309
April16th to endNight
27%
504
8%
1584
5%
504
31%
504
14%
1154
May1st to 15thNight
44%
359
7%
1398
7%
359
48%
359
18%
897
May16th to endNight
43%
374
3%
1309
1%
374
43%
374
17%
906
June1st to 15thNight
36%
360
0%
1194
0%
360
36%
360
15%
874
June16th to endNight
39%
360
0%
1080
0%
360
39%
360
24%
697
July1st to 15thNight
45%
340
0%
1075
0%
340
45%
340
27%
664
July16th to endNight
55%
376
6%
1319
4%
354
58%
354
27%
741
August1st to 15thNight
61%
360
10%
1432
15%
358
64%
358
25%
802
August16th to endNight
44%
540
17%
1686
14%
540
47%
540
30%
988
September1st to 15thNight
47%
700
14%
1761
8%
700
49%
700
31%
1160
September16th to endNight
31%
656
16%
1815
5%
656
40%
656
27%
1147
October1st to 15thNight
26%
660
10%
1973
6%
660
32%
660
16%
1436
October16th to endNight
18%
704
11%
2288
3%
704
28%
704
13%
1640
November1st to 15thNight
12%
778
10%
2432
3%
778
20%
778
12%
1747
November16th to endNight
14%
900
8%
2700
1%
900
20%
900
12%
2013
December1st to 15thNight
16%
900
11%
2700
4%
900
23%
900
12%
1988
December16th to endNight
16%
960
12%
2880
2%
960
25%
960
12%
2111

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
8%9%48%8%46%6%7%8%26%
48296
Night
47%48%7%47%6%7%10%31%
46515
TransparencyDay
50%10%17%16%5%
47949
Night
43%10%18%18%6%
46367
SeeingDay
17%19%34%20%7%1
6324
Night
10%16%39%22%9%
15011

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
16%39%11%6%7%7%9%10%25%
1253
16th to endDay
16%5%6%8%6%7%6%9%11%29%
1532
February1st to 15thDay
16%5%9%10%48%6%9%10%28%
1400
16th to endDay
16%5%10%11%6%7%9%7%9%23%
1521
March1st to 15thDay
5%310%10%6%9%8%9%10%26%
1800
16th to endDay
210%7%13%10%5%8%8%8%8%16%
2195
April1st to 15thDay
414%8%11%9%5%7%6%7%8%15%
2197
16th to endDay
6%14%7%14%8%46%5%5%6%19%
2375
May1st to 15thDay
7%16%5%9%7%45%5%6%8%24%
2553
16th to endDay
17%14%47%6%46%5%5%7%20%
2802
June1st to 15thDay
20%11%49%6%46%6%6%7%16%
2763
16th to endDay
16%9%48%8%36%5%6%7%24%
2880
July1st to 15thDay
12%6%37%7%36%5%6%8%32%
2817
16th to endDay
10%6%35%7%47%6%6%8%34%
2757
August1st to 15thDay
13%7%37%7%45%6%6%7%29%
2520
16th to endDay
10%7%36%6%446%7%9%33%
2514
September1st to 15thDay
12%11%36%5%2446%7%36%
2086
16th to endDay
10%7%26%6%46%6%6%8%34%
1815
October1st to 15thDay
6%11%5%7%7%46%6%7%9%27%
1655
16th to endDay
310%48%6%46%6%8%8%31%
1584
November1st to 15thDay
6%46%8%5%7%7%10%12%30%
1413
16th to endDay
16%48%9%5%6%8%8%9%30%
1260
December1st to 15thDay
15%311%9%5%8%6%7%11%28%
1260
16th to endDay
6%5%8%7%46%8%7%11%32%
1344
January1st to 15thNight
6%411%10%5%8%7%9%13%22%
2685
16th to endNight
16%39%8%5%8%7%7%11%30%
2703
February1st to 15thNight
27%39%9%6%8%7%8%9%27%
2452
16th to endNight
5%48%9%6%9%8%9%11%27%
1950
March1st to 15thNight
448%7%5%8%9%8%11%30%
2160
16th to endNight
19%5%10%8%37%7%9%10%26%
2025
April1st to 15thNight
310%6%9%7%35%6%8%9%27%
1751
16th to endNight
412%410%7%36%6%6%8%29%
1584
May1st to 15thNight
5%13%36%5%25%5%6%9%35%
1397
16th to endNight
15%13%244345%7%9%28%
1309
June1st to 15thNight
16%10%46%5%36%5%5%7%28%
1194
16th to endNight
10%6%35%6%3446%9%40%
1080
July1st to 15thNight
8%5%25%425%5%6%9%45%
1140
16th to endNight
6%314426%6%8%10%44%
1410
August1st to 15thNight
9%6%145%235%6%10%44%
1440
16th to endNight
8%5%243235%6%9%47%
1686
September1st to 15thNight
9%8%2442445%8%45%
1761
16th to endNight
8%6%244245%6%10%44%
1815
October1st to 15thNight
5%10%5%9%7%45%46%8%33%
1973
16th to endNight
37%410%9%5%6%7%7%8%28%
2288
November1st to 15thNight
6%37%9%5%10%7%8%10%28%
2432
16th to endNight
16%5%11%9%5%8%7%7%9%27%
2700
December1st to 15thNight
15%412%9%47%7%8%12%25%
2700
16th to endNight
3310%11%6%10%9%7%11%24%
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
49%10%18%15%41
1253
16th to endDay
44%13%15%16%7%2
1532
February1st to 15thDay
44%10%18%17%6%1
1400
16th to endDay
51%9%14%15%7%
1521
March1st to 15thDay
43%15%20%16%4
1800
16th to endDay
56%14%15%10%3
2196
April1st to 15thDay
61%11%13%10%2
2197
16th to endDay
61%10%14%10%2
2375
May1st to 15thDay
54%9%16%13%5%
2553
16th to endDay
63%8%15%10%3
2807
June1st to 15thDay
63%8%13%11%3
2763
16th to endDay
54%9%16%14%4
2880
July1st to 15thDay
47%8%16%19%7%
2653
16th to endDay
44%9%18%20%6%
2585
August1st to 15thDay
49%9%18%16%5%
2503
16th to endDay
41%9%17%22%6%1
2514
September1st to 15thDay
44%7%17%20%8%1
2086
16th to endDay
42%9%16%21%7%1
1815
October1st to 15thDay
48%11%14%19%5%
1655
16th to endDay
41%12%23%19%3
1584
November1st to 15thDay
38%14%23%17%5%
1413
16th to endDay
41%12%23%15%5%2
1260
December1st to 15thDay
50%10%16%16%6%
1260
16th to endDay
40%11%19%19%8%1
1344
January1st to 15thNight
51%12%18%11%41
2685
16th to endNight
44%11%17%16%7%3
2703
February1st to 15thNight
48%10%16%16%6%2
2464
16th to endNight
45%9%15%19%8%1
1950
March1st to 15thNight
39%14%21%17%6%
2160
16th to endNight
45%9%18%20%6%
2028
April1st to 15thNight
47%11%17%16%6%
1751
16th to endNight
49%10%21%14%3
1584
May1st to 15thNight
42%8%21%20%6%
1398
16th to endNight
48%7%18%19%5%
1309
June1st to 15thNight
53%7%16%18%3
1194
16th to endNight
37%9%24%22%4
1080
July1st to 15thNight
34%9%20%26%8%
1075
16th to endNight
31%8%24%26%8%
1319
August1st to 15thNight
33%7%26%28%4
1432
16th to endNight
30%8%22%29%8%
1686
September1st to 15thNight
34%8%20%25%9%1
1761
16th to endNight
33%8%22%26%10%
1815
October1st to 15thNight
47%10%16%19%5%
1973
16th to endNight
46%12%18%18%3
2288
November1st to 15thNight
43%15%17%16%7%
2432
16th to endNight
47%14%16%13%6%2
2700
December1st to 15thNight
49%11%16%16%7%
2700
16th to endNight
49%11%15%16%5%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%340%31%13%3
60
16th to endDay
12%18%39%18%7%3
64
February1st to 15thDay
16%18%48%10%6%
60
16th to endDay
7%19%43%24%5%
200
March1st to 15thDay
13%38%31%14%2
270
16th to endDay
14%26%41%15%1
288
April1st to 15thDay
17%30%33%14%3
269
16th to endDay
17%27%29%17%6%1
270
May1st to 15thDay
18%14%36%23%5%
330
16th to endDay
26%9%24%22%13%3
517
June1st to 15thDay
23%17%30%19%7%1
558
16th to endDay
18%17%33%20%7%2
675
July1st to 15thDay
16%13%32%25%10%1
587
16th to endDay
14%14%39%23%7%1
426
August1st to 15thDay
16%12%31%27%8%2
315
16th to endDay
16%21%38%18%3
332
September1st to 15thDay
21%22%28%21%6%1
294
16th to endDay
18%27%36%12%4
255
October1st to 15thDay
19%26%30%17%5%
197
16th to endDay
416%37%27%13%1
96
November1st to 15thDay
5%29%46%10%6%1
77
16th to endDay
6%13%40%18%10%11%
60
December1st to 15thDay
8%20%26%20%18%6%
60
16th to endDay
9%14%46%25%4
64
January1st to 15thNight
8%22%51%12%4
900
16th to endNight
7%28%43%14%6%
783
February1st to 15thNight
7%20%42%19%8%
704
16th to endNight
311%49%25%9%
632
March1st to 15thNight
424%47%18%4
720
16th to endNight
7%13%45%24%8%
768
April1st to 15thNight
8%13%36%27%12%
671
16th to endNight
13%12%38%27%8%
504
May1st to 15thNight
12%6%30%35%14%
360
16th to endNight
24%6%22%29%16%1
375
June1st to 15thNight
20%5%30%29%12%1
360
16th to endNight
14%8%30%28%16%1
360
July1st to 15thNight
13%5%29%32%18%
340
16th to endNight
8%5%25%45%14%
376
August1st to 15thNight
13%315%34%30%2
360
16th to endNight
14%9%27%33%13%
540
September1st to 15thNight
14%7%26%31%15%3
700
16th to endNight
14%16%33%21%10%1
656
October1st to 15thNight
12%13%39%24%8%
660
16th to endNight
10%19%45%20%4
704
November1st to 15thNight
8%26%48%12%2
778
16th to endNight
9%22%46%15%6%
900
December1st to 15thNight
7%24%43%17%6%
900
16th to endNight
323%46%18%7%
960
Page generated at 2017-09-11 17:35:25. Version ac04

Copyright 2017 A. Danko


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