Teslin
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Teslin clear sky chart from 2005-11-05 to 2017-09-22.

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%
14266
5%
46473
4%
14235
40%
14235
10%
37410

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%
854
3%
3005
3%
850
31%
850
5%
2617
January16th to endNight
32%
800
6%
3072
6%
800
35%
800
7%
2517
February1st to 15thNight
38%
730
7%
2545
6%
727
39%
727
10%
2026
February16th to endNight
49%
655
9%
2144
8%
655
50%
655
15%
1621
March1st to 15thNight
42%
720
11%
2160
9%
720
43%
720
14%
1671
March16th to endNight
47%
634
7%
2017
7%
634
48%
634
13%
1560
April1st to 15thNight
54%
539
7%
1683
6%
539
55%
539
17%
1243
April16th to endNight
48%
513
2%
1413
1%
513
49%
513
16%
1091
May1st to 15thNight
49%
359
0%
1173
0%
359
49%
359
15%
845
May16th to endNight
55%
374
0%
1023
0%
374
55%
374
23%
719
June1st to 15thNight
50%
250
0%
790
0%
250
50%
250
18%
560
June16th to endNight
52%
180
0%
720
0%
180
52%
180
13%
519
July1st to 15thNight
51%
223
0%
742
0%
223
51%
223
14%
552
July16th to endNight
46%
376
0%
1062
0%
354
46%
354
12%
828
August1st to 15thNight
51%
417
0%
1221
0%
415
51%
415
19%
874
August16th to endNight
36%
573
1%
1555
1%
573
37%
573
10%
1299
September1st to 15thNight
42%
540
6%
1746
5%
540
42%
540
12%
1357
September16th to endNight
34%
653
7%
1862
5%
653
35%
653
11%
1510
October1st to 15thNight
39%
660
8%
2065
8%
660
40%
660
13%
1627
October16th to endNight
33%
718
3%
2398
3%
718
35%
718
9%
1961
November1st to 15thNight
33%
730
4%
2626
4%
730
35%
730
6%
2245
November16th to endNight
32%
846
4%
2965
3%
846
33%
846
7%
2497
December1st to 15thNight
28%
930
3%
3060
3%
930
29%
930
6%
2706
December16th to endNight
34%
992
5%
3426
4%
992
36%
992
6%
2965

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%11%5%10%8%46%6%6%7%21%
48487
Night
9%13%6%11%9%5%6%5%6%7%18%
46577
TransparencyDay
59%11%14%12%2
48096
Night
61%9%13%12%2
46473
SeeingDay
16%9%23%26%18%5%
7618
Night
15%5%19%31%23%4
14273

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
13%17%8%14%13%5%5%446%6%
944
16th to endDay
8%16%6%11%11%5%6%7%7%7%10%
1152
February1st to 15thDay
7%15%6%11%9%45%8%7%6%18%
1318
16th to endDay
410%7%9%11%6%7%7%8%8%17%
1329
March1st to 15thDay
212%7%12%11%7%8%6%5%7%19%
1800
16th to endDay
310%7%13%9%46%5%6%7%23%
2205
April1st to 15thDay
411%6%12%10%5%7%5%6%7%20%
2262
16th to endDay
5%12%6%11%8%5%7%5%5%7%23%
2547
May1st to 15thDay
12%14%6%10%8%35%5%5%5%22%
2778
16th to endDay
9%8%36%7%46%5%6%8%32%
3090
June1st to 15thDay
12%8%48%8%37%6%6%7%25%
3168
16th to endDay
12%8%410%8%46%6%6%8%20%
3240
July1st to 15thDay
14%8%38%8%47%6%8%8%21%
3174
16th to endDay
14%7%48%8%46%6%7%8%23%
3035
August1st to 15thDay
10%6%37%7%45%6%6%8%33%
2732
16th to endDay
23%10%38%7%36%5%5%6%19%
2647
September1st to 15thDay
18%11%5%8%6%36%5%5%6%21%
2212
16th to endDay
19%10%410%9%45%5%5%5%20%
1910
October1st to 15thDay
12%13%5%9%10%445%5%6%22%
1565
16th to endDay
11%16%7%11%7%45%6%5%7%15%
1471
November1st to 15thDay
9%18%9%11%9%6%6%5%6%5%10%
1232
16th to endDay
6%13%9%14%8%6%7%8%8%7%9%
981
December1st to 15thDay
7%19%8%15%8%6%7%5%6%9%5%
900
16th to endDay
6%16%8%11%14%7%8%5%7%7%5%
795
January1st to 15thNight
9%17%8%13%11%6%8%44411%
3005
16th to endNight
9%15%7%12%10%47%6%6%6%11%
3072
February1st to 15thNight
6%13%6%13%9%5%8%6%6%6%16%
2533
16th to endNight
310%7%11%10%5%5%5%6%8%24%
2144
March1st to 15thNight
313%7%12%9%5%6%5%5%5%25%
2160
16th to endNight
311%8%12%10%5%7%6%5%6%22%
2012
April1st to 15thNight
5%11%5%8%7%46%6%6%8%29%
1683
16th to endNight
7%11%5%8%7%46%6%7%8%27%
1413
May1st to 15thNight
9%9%48%6%45%6%6%8%29%
1172
16th to endNight
8%7%45%5%46%5%6%9%35%
1023
June1st to 15thNight
9%6%29%6%47%5%5%9%33%
790
16th to endNight
13%6%35%8%45%8%8%8%27%
720
July1st to 15thNight
11%7%27%7%36%6%10%10%24%
786
16th to endNight
13%9%36%6%47%6%8%7%25%
1134
August1st to 15thNight
10%7%36%6%335%10%11%32%
1227
16th to endNight
19%11%48%7%36%5%5%5%21%
1555
September1st to 15thNight
16%10%38%7%35%5%5%6%26%
1746
16th to endNight
16%12%48%9%44446%24%
1862
October1st to 15thNight
15%14%48%5%2445%6%27%
2065
16th to endNight
11%18%5%9%6%45%5%5%7%19%
2398
November1st to 15thNight
8%17%8%12%10%6%6%5%6%7%10%
2626
16th to endNight
8%14%7%14%10%5%8%6%6%8%8%
2965
December1st to 15thNight
9%19%8%15%11%5%6%5%6%5%6%
3060
16th to endNight
7%16%8%12%12%7%8%6%6%7%6%
3426

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%47%43
944
16th to endDay
65%9%12%8%3
1152
February1st to 15thDay
59%10%10%15%4
1318
16th to endDay
57%9%15%13%4
1329
March1st to 15thDay
60%9%8%15%41
1800
16th to endDay
57%9%14%11%6%
2205
April1st to 15thDay
60%11%13%12%2
2262
16th to endDay
58%11%15%12%2
2547
May1st to 15thDay
61%8%13%12%3
2778
16th to endDay
47%10%17%20%3
3094
June1st to 15thDay
54%12%13%15%3
3168
16th to endDay
58%11%15%11%1
3240
July1st to 15thDay
56%12%17%11%1
2989
16th to endDay
55%14%19%10%
2844
August1st to 15thDay
47%12%21%16%2
2713
16th to endDay
64%12%15%6%
2647
September1st to 15thDay
62%12%11%11%2
2212
16th to endDay
63%10%12%12%1
1910
October1st to 15thDay
61%9%15%12%1
1565
16th to endDay
64%11%15%8%
1471
November1st to 15thDay
70%8%12%8%
1232
16th to endDay
65%10%12%9%2
981
December1st to 15thDay
73%8%10%5%1
900
16th to endDay
72%7%7%9%2
795
January1st to 15thNight
73%8%8%5%4
3005
16th to endNight
66%8%12%10%1
3072
February1st to 15thNight
62%8%10%15%3
2545
16th to endNight
54%9%17%13%5%
2144
March1st to 15thNight
58%7%11%14%6%1
2160
16th to endNight
59%7%13%11%7%
2017
April1st to 15thNight
49%11%16%19%2
1683
16th to endNight
53%10%17%15%2
1413
May1st to 15thNight
51%9%18%17%3
1173
16th to endNight
43%9%16%25%3
1023
June1st to 15thNight
47%10%17%21%3
790
16th to endNight
49%12%20%15%1
720
July1st to 15thNight
49%13%20%15%
742
16th to endNight
51%16%17%14%
1062
August1st to 15thNight
43%13%22%17%2
1221
16th to endNight
63%11%14%10%
1555
September1st to 15thNight
55%11%15%15%1
1746
16th to endNight
60%10%13%14%
1862
October1st to 15thNight
56%11%15%14%2
2065
16th to endNight
62%11%16%8%
2398
November1st to 15thNight
68%11%11%8%
2626
16th to endNight
68%9%10%9%1
2965
December1st to 15thNight
75%7%8%7%1
3060
16th to endNight
73%7%8%7%3
3426

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
18%5%9%26%32%7%
53
16th to endDay
20%7%10%25%32%3
64
February1st to 15thDay
11%5%25%27%22%6%
212
16th to endDay
8%325%29%20%12%
211
March1st to 15thDay
8%10%31%27%16%6%
240
16th to endDay
8%9%21%28%24%7%
282
April1st to 15thDay
10%12%27%22%20%5%
287
16th to endDay
14%12%31%25%13%2
450
May1st to 15thDay
22%14%25%23%10%3
468
16th to endDay
12%10%23%28%18%7%
617
June1st to 15thDay
14%7%22%28%21%4
675
16th to endDay
14%8%21%28%22%4
675
July1st to 15thDay
17%7%17%29%21%5%
636
16th to endDay
19%10%21%26%18%4
515
August1st to 15thDay
13%6%20%28%21%9%
494
16th to endDay
28%13%21%23%9%4
496
September1st to 15thDay
25%13%25%18%12%5%
315
16th to endDay
23%12%26%17%14%5%
279
October1st to 15thDay
19%14%28%24%9%4
225
16th to endDay
16%12%23%26%16%5%
207
November1st to 15thDay
20%330%30%10%6%
60
16th to endDay
13%16%33%20%16%
60
December1st to 15thDay
8%118%23%25%23%
60
16th to endDay
8%216%35%24%13%
37
January1st to 15thNight
18%417%32%23%4
855
16th to endNight
16%7%23%30%20%2
800
February1st to 15thNight
11%5%22%38%19%3
734
16th to endNight
8%217%41%24%5%
655
March1st to 15thNight
7%6%25%35%21%3
720
16th to endNight
5%415%31%32%9%
634
April1st to 15thNight
8%415%32%33%6%
539
16th to endNight
10%6%16%32%28%5%
513
May1st to 15thNight
12%5%18%28%29%5%
360
16th to endNight
11%417%28%34%3
375
June1st to 15thNight
12%422%32%24%4
250
16th to endNight
14%317%35%26%2
180
July1st to 15thNight
14%5%18%29%28%3
223
16th to endNight
17%421%30%22%3
376
August1st to 15thNight
13%220%31%24%7%
417
16th to endNight
24%5%21%26%18%3
573
September1st to 15thNight
22%6%16%28%22%3
540
16th to endNight
23%10%21%24%18%2
653
October1st to 15thNight
22%6%20%30%15%3
660
16th to endNight
21%7%21%26%16%5%
718
November1st to 15thNight
15%421%32%21%4
730
16th to endNight
12%5%19%33%25%3
846
December1st to 15thNight
17%6%17%33%22%2
930
16th to endNight
13%416%34%23%7%
992
Page generated at 2017-09-23 03:43:45. Version ac04

Copyright 2017 A. Danko


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