AllSky Camera - Tatla Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the AllSky Camera - Tatla Lake clear sky chart from 2005-11-05 to 2018-01-12.

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
42%
14883
10%
48342
7%
14854
46%
14854
19%
33245

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
35%
805
8%
2852
5%
801
40%
801
12%
2114
January16th to endNight
38%
800
12%
2880
8%
800
44%
800
17%
1972
February1st to 15thNight
36%
699
10%
2310
5%
699
43%
699
17%
1636
February16th to endNight
45%
632
14%
2053
12%
632
49%
632
20%
1386
March1st to 15thNight
29%
720
13%
2076
5%
720
36%
720
20%
1446
March16th to endNight
42%
768
12%
2096
7%
767
45%
767
24%
1435
April1st to 15thNight
42%
635
10%
1715
5%
635
45%
635
20%
1234
April16th to endNight
39%
501
9%
1581
7%
501
43%
501
18%
1136
May1st to 15thNight
45%
359
7%
1434
8%
359
48%
359
17%
933
May16th to endNight
42%
374
3%
1309
1%
374
43%
374
13%
976
June1st to 15thNight
43%
360
0%
1260
0%
360
43%
360
17%
858
June16th to endNight
48%
360
0%
1260
0%
360
48%
360
18%
849
July1st to 15thNight
55%
340
1%
1190
0%
340
55%
340
24%
716
July16th to endNight
56%
376
7%
1239
6%
354
60%
354
29%
715
August1st to 15thNight
70%
420
12%
1452
16%
418
71%
418
26%
869
August16th to endNight
55%
573
14%
1719
10%
573
59%
573
26%
1123
September1st to 15thNight
61%
696
18%
1776
10%
696
63%
696
37%
1116
September16th to endNight
45%
716
16%
1991
10%
716
49%
716
24%
1355
October1st to 15thNight
42%
720
11%
2160
7%
720
47%
720
20%
1490
October16th to endNight
37%
768
13%
2486
7%
768
45%
768
19%
1721
November1st to 15thNight
32%
760
11%
2660
6%
760
39%
760
15%
1861
November16th to endNight
32%
796
12%
2798
6%
796
41%
796
16%
1950
December1st to 15thNight
38%
825
9%
2925
6%
825
43%
825
14%
2128
December16th to endNight
32%
880
13%
3120
6%
880
40%
880
14%
2226

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
5%7%37%7%46%6%7%9%33%
49031
Night
47%37%6%46%6%7%9%35%
48490
TransparencyDay
45%11%17%18%6%
48679
Night
43%11%18%19%6%
48346
SeeingDay
13%17%30%24%11%3
6704
Night
8%7%32%33%15%2
14893

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
37%37%11%6%7%6%10%10%25%
1330
16th to endDay
16%25%5%37%7%9%13%35%
1344
February1st to 15thDay
28%37%6%5%7%7%8%12%29%
1550
16th to endDay
16%49%6%38%7%8%9%33%
1421
March1st to 15thDay
15%37%7%47%7%9%11%34%
1882
16th to endDay
17%39%8%5%8%7%9%10%28%
2124
April1st to 15thDay
39%5%9%9%47%7%7%9%26%
2230
16th to endDay
412%5%9%8%47%7%7%8%24%
2379
May1st to 15thDay
5%9%48%7%5%7%7%7%8%28%
2517
16th to endDay
12%10%48%6%47%6%7%7%24%
2804
June1st to 15thDay
11%8%38%7%46%6%6%8%28%
2700
16th to endDay
10%7%36%8%47%5%8%8%28%
2700
July1st to 15thDay
8%5%35%5%36%5%6%7%42%
2700
16th to endDay
5%5%36%6%46%5%5%7%43%
2846
August1st to 15thDay
5%5%25%6%45%5%5%7%45%
2496
16th to endDay
46%26%6%46%7%7%8%38%
2483
September1st to 15thDay
7%6%25%5%34448%47%
2183
16th to endDay
6%5%25%5%35%7%6%10%40%
1966
October1st to 15thDay
6%8%36%7%46%5%7%8%36%
1800
16th to endDay
36%36%7%46%6%7%11%36%
1735
November1st to 15thDay
36%45%6%36%6%9%11%34%
1528
16th to endDay
27%47%7%37%8%7%8%36%
1492
December1st to 15thDay
26%47%7%46%8%8%9%32%
1365
16th to endDay
7%39%7%37%7%8%14%29%
1456
January1st to 15thNight
28%48%8%5%10%8%8%10%25%
2852
16th to endNight
26%46%6%5%7%7%8%12%32%
2880
February1st to 15thNight
38%47%6%5%6%7%7%9%33%
2298
16th to endNight
18%5%8%7%46%5%7%8%36%
2053
March1st to 15thNight
16%38%6%45%7%8%11%36%
2076
16th to endNight
25%26%5%46%8%9%13%35%
2096
April1st to 15thNight
39%36%7%36%6%7%9%33%
1715
16th to endNight
49%48%6%36%5%6%10%33%
1581
May1st to 15thNight
5%8%46%6%35%7%6%11%35%
1433
16th to endNight
14%7%26%7%46%6%7%8%28%
1309
June1st to 15thNight
12%436%6%26%6%8%9%34%
1260
16th to endNight
10%6%35%5%346%6%8%39%
1260
July1st to 15thNight
7%313447%5%6%8%46%
1260
16th to endNight
5%424426%46%9%49%
1323
August1st to 15thNight
6%4335%25%5%6%8%48%
1459
16th to endNight
6%5%35%6%35%6%6%8%43%
1719
September1st to 15thNight
7%5%2442336%6%52%
1776
16th to endNight
7%6%36%5%35%5%7%7%42%
1991
October1st to 15thNight
6%9%35%5%35%46%9%39%
2160
16th to endNight
49%36%5%46%5%7%9%35%
2486
November1st to 15thNight
27%37%7%47%7%8%10%32%
2660
16th to endNight
28%5%8%7%46%7%6%9%34%
2798
December1st to 15thNight
28%5%7%6%48%7%8%10%28%
2925
16th to endNight
17%5%9%7%47%7%9%10%28%
3120

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
53%11%16%15%3
1330
16th to endDay
37%13%22%18%6%2
1344
February1st to 15thDay
46%13%18%15%5%
1550
16th to endDay
45%10%16%20%7%
1421
March1st to 15thDay
40%11%20%20%7%
1882
16th to endDay
47%11%19%17%4
2124
April1st to 15thDay
52%11%15%14%6%
2230
16th to endDay
56%11%14%12%4
2379
May1st to 15thDay
52%10%15%14%6%
2517
16th to endDay
58%10%13%13%3
2808
June1st to 15thDay
51%10%16%15%5%1
2700
16th to endDay
51%10%14%16%5%
2700
July1st to 15thDay
40%9%14%22%11%1
2541
16th to endDay
37%9%19%23%10%
2667
August1st to 15thDay
34%10%20%25%7%
2478
16th to endDay
39%11%20%19%6%1
2483
September1st to 15thDay
35%7%19%25%10%1
2183
16th to endDay
37%11%18%23%7%1
1966
October1st to 15thDay
45%9%19%20%6%
1800
16th to endDay
41%12%19%19%6%
1735
November1st to 15thDay
41%12%19%21%5%
1528
16th to endDay
42%12%18%18%6%1
1492
December1st to 15thDay
46%13%19%17%3
1365
16th to endDay
43%12%17%18%7%
1456
January1st to 15thNight
52%11%17%15%3
2852
16th to endNight
43%12%20%15%6%2
2880
February1st to 15thNight
46%10%19%15%8%
2310
16th to endNight
45%7%16%24%5%
2053
March1st to 15thNight
40%12%19%20%6%
2076
16th to endNight
36%13%23%20%5%
2100
April1st to 15thNight
44%11%19%18%5%
1715
16th to endNight
48%10%19%17%4
1581
May1st to 15thNight
42%10%22%16%6%
1434
16th to endNight
52%12%17%14%3
1309
June1st to 15thNight
43%11%17%18%6%1
1260
16th to endNight
41%12%16%21%6%
1260
July1st to 15thNight
33%11%20%21%11%1
1190
16th to endNight
32%8%23%26%9%
1239
August1st to 15thNight
32%10%19%28%7%
1452
16th to endNight
36%11%20%24%5%1
1719
September1st to 15thNight
31%7%18%29%11%1
1776
16th to endNight
40%10%18%22%7%1
1991
October1st to 15thNight
40%12%18%21%7%
2160
16th to endNight
43%12%19%20%5%
2486
November1st to 15thNight
46%11%19%18%4
2660
16th to endNight
45%11%18%16%5%2
2798
December1st to 15thNight
49%12%17%16%3
2925
16th to endNight
48%11%16%15%7%
3120

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
3218%35%25%14%
82
16th to endDay
328%37%26%4
64
February1st to 15thDay
8%13%37%30%8%1
233
16th to endDay
9%17%35%24%12%
211
March1st to 15thDay
11%31%34%16%4
263
16th to endDay
11%25%34%21%5%1
288
April1st to 15thDay
16%23%30%18%8%2
269
16th to endDay
19%27%27%19%4
270
May1st to 15thDay
15%21%28%25%7%1
294
16th to endDay
20%16%28%20%10%3
518
June1st to 15thDay
17%23%30%19%8%1
495
16th to endDay
15%18%33%20%10%2
495
July1st to 15thDay
12%16%32%27%8%2
475
16th to endDay
9%14%30%30%12%2
515
August1st to 15thDay
9%6%25%31%20%7%
354
16th to endDay
10%16%28%31%10%2
332
September1st to 15thDay
13%11%28%25%15%5%
315
16th to endDay
14%15%26%26%12%3
315
October1st to 15thDay
14%18%32%18%12%3
315
16th to endDay
10%16%38%20%12%2
235
November1st to 15thDay
5%13%35%36%7%1
90
16th to endDay
7%333%32%12%11%
90
December1st to 15thDay
6%221%30%26%13%
90
16th to endDay
10%5%31%29%19%4
96
January1st to 15thNight
8%8%36%31%13%3
805
16th to endNight
6%8%36%33%12%2
800
February1st to 15thNight
7%7%36%31%15%1
707
16th to endNight
6%6%30%39%15%2
632
March1st to 15thNight
311%47%30%5%
720
16th to endNight
49%34%33%16%1
768
April1st to 15thNight
8%8%28%38%15%
635
16th to endNight
7%7%38%34%10%
501
May1st to 15thNight
8%6%30%39%15%
360
16th to endNight
18%5%24%37%13%1
375
June1st to 15thNight
12%7%30%36%11%
360
16th to endNight
13%6%25%38%16%
360
July1st to 15thNight
10%5%24%40%18%
340
16th to endNight
7%325%37%25%1
376
August1st to 15thNight
7%11%40%34%4
420
16th to endNight
9%422%35%26%1
573
September1st to 15thNight
11%418%30%29%5%
696
16th to endNight
12%9%27%28%18%3
716
October1st to 15thNight
11%8%29%31%15%2
720
16th to endNight
10%8%35%29%13%2
768
November1st to 15thNight
6%11%39%33%7%
760
16th to endNight
7%7%42%30%10%2
796
December1st to 15thNight
6%7%34%35%12%2
825
16th to endNight
7%6%39%32%12%1
880
Page generated at 2018-01-12 19:01:24. Version ac04

Copyright 2018 A. Danko


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