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 2005-11-06 to 2024-03-01.

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%
22730
11%
81105
7%
22618
42%
22618
17%
54824

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 10thNight
24%
838
9%
4681
4%
816
33%
816
7%
3449
January11th to 20thNight
33%
836
14%
4660
6%
820
39%
820
9%
3121
January21st to endNight
28%
925
7%
5191
5%
902
38%
902
10%
3433
February1st to 10thNight
28%
776
11%
2505
6%
776
35%
776
16%
1787
February11th to 20thNight
30%
740
16%
2404
9%
740
38%
740
19%
1637
February21st to endNight
32%
628
12%
2041
9%
628
36%
628
17%
1426
March1st to 10thNight
28%
722
13%
2130
7%
722
34%
722
19%
1479
March11th to 20thNight
33%
720
18%
1979
7%
720
42%
720
27%
1248
March21st to endNight
34%
792
12%
2160
5%
792
39%
792
20%
1555
April1st to 10thNight
38%
684
10%
1764
4%
684
41%
684
20%
1273
April11th to 20thNight
35%
533
12%
1601
7%
533
39%
533
21%
1111
April21st to endNight
36%
482
13%
1562
8%
482
44%
482
19%
1076
May1st to 10thNight
43%
360
9%
1440
10%
360
46%
360
17%
924
May11th to 20thNight
45%
354
8%
1321
9%
354
47%
354
17%
878
May21st to endNight
36%
388
3%
1358
1%
388
37%
388
14%
992
June1st to 10thNight
35%
360
0%
1260
0%
360
35%
360
17%
858
June11th to 20thNight
38%
360
0%
1260
0%
360
38%
360
17%
865
June21st to endNight
45%
360
0%
1260
0%
360
45%
360
21%
820
July1st to 10thNight
50%
350
0%
1225
0%
350
50%
350
23%
763
July11th to 20thNight
47%
348
5%
1218
2%
348
48%
348
25%
735
July21st to endNight
59%
394
11%
1302
11%
372
63%
372
34%
695
August1st to 10thNight
62%
358
13%
1363
18%
356
65%
356
25%
783
August11th to 20thNight
65%
534
18%
1602
16%
534
68%
534
36%
932
August21st to endNight
49%
594
14%
1782
9%
594
53%
594
24%
1202
September1st to 10thNight
52%
684
16%
1764
7%
684
55%
684
33%
1127
September11th to 20thNight
50%
720
19%
1867
10%
720
53%
720
30%
1246
September21st to endNight
37%
720
18%
2018
9%
720
43%
720
23%
1363
October1st to 10thNight
38%
720
13%
2160
8%
720
44%
720
20%
1482
October11th to 20thNight
35%
720
16%
2160
8%
720
45%
720
21%
1474
October21st to endNight
30%
792
14%
2647
9%
792
39%
792
19%
1751
November1st to 10thNight
24%
740
11%
2590
5%
740
34%
740
13%
1856
November11th to 20thNight
25%
760
14%
2660
7%
760
36%
760
17%
1790
November21st to endNight
27%
807
12%
2759
4%
807
36%
807
17%
1880
December1st to 10thNight
33%
850
11%
2850
6%
850
40%
850
15%
2004
December11th to 20thNight
25%
849
9%
3512
4%
849
33%
849
11%
2668
December21st to endNight
24%
932
9%
5049
4%
905
36%
905
10%
3141

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%8%48%7%47%7%8%9%34%
77820
Night
48%48%7%47%7%8%9%34%
81544
TransparencyDay
43%11%17%19%9%1
77521
Night
42%12%17%19%8%1
81423
SeeingDay
12%18%32%23%12%3
14671
Night
8%11%38%30%12%1
22775

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 10thDay
312%5%9%11%6%8%9%9%8%20%
2219
11th to 20thDay
38%5%8%8%47%8%9%11%30%
2199
21st to endDay
28%410%9%5%9%8%9%11%24%
2442
February1st to 10thDay
38%49%9%6%7%8%8%11%27%
1671
11th to 20thDay
19%5%9%6%5%5%7%8%9%35%
1665
21st to endDay
27%5%10%8%49%6%9%10%30%
1413
March1st to 10thDay
16%49%8%5%7%7%7%11%36%
1834
11th to 20thDay
16%37%7%5%8%9%11%11%33%
1980
21st to endDay
29%410%8%5%8%7%8%10%29%
2195
April1st to 10thDay
310%6%9%9%6%7%7%7%9%28%
2192
11th to 20thDay
49%410%8%5%7%7%8%8%29%
2308
21st to endDay
411%5%8%7%47%7%8%8%30%
2398
May1st to 10thDay
5%10%48%8%5%7%7%7%8%31%
2520
11th to 20thDay
6%10%49%7%5%6%6%8%8%29%
2573
21st to endDay
12%9%48%7%47%6%6%8%29%
2917
June1st to 10thDay
11%8%38%8%47%6%6%8%32%
2700
11th to 20thDay
11%10%48%8%5%6%6%7%8%28%
2700
21st to endDay
9%6%37%8%5%7%5%8%9%34%
2700
July1st to 10thDay
8%6%36%6%47%5%6%7%41%
2700
11th to 20thDay
8%5%36%6%45%6%7%7%42%
2700
21st to endDay
45%35%6%46%5%6%8%47%
2938
August1st to 10thDay
6%5%25%5%45%5%5%8%49%
2564
11th to 20thDay
45%245%45%6%6%7%52%
2298
21st to endDay
6%7%27%7%47%7%7%9%36%
2574
September1st to 10thDay
6%6%26%6%45%5%6%9%45%
2196
11th to 20thDay
8%8%45%6%46%5%5%7%42%
2091
21st to endDay
7%6%26%6%35%6%7%11%41%
1942
October1st to 10thDay
7%10%47%7%46%6%6%8%35%
1800
11th to 20thDay
6%7%35%8%46%6%9%11%35%
1800
21st to endDay
47%48%7%46%5%6%10%40%
1706
November1st to 10thDay
48%5%7%6%5%7%7%9%10%32%
1488
11th to 20thDay
26%38%8%5%8%8%9%11%33%
1520
21st to endDay
28%5%8%7%46%7%8%10%35%
1420
December1st to 10thDay
25%47%8%5%6%9%10%11%34%
1330
11th to 20thDay
411%5%11%7%47%8%10%9%24%
1685
21st to endDay
16%38%6%47%8%10%13%33%
2442
January1st to 10thNight
212%7%12%10%6%8%8%8%8%18%
4726
11th to 20thNight
49%37%9%6%10%7%12%9%24%
4699
21st to endNight
28%5%9%8%5%7%8%8%11%27%
5214
February1st to 10thNight
38%49%8%6%7%7%7%9%32%
2505
11th to 20thNight
28%5%10%8%5%6%5%7%8%37%
2402
21st to endNight
28%6%9%9%5%7%6%7%8%32%
2041
March1st to 10thNight
18%410%8%45%7%8%11%35%
2130
11th to 20thNight
1336%6%5%6%8%9%12%42%
1979
21st to endNight
38%47%6%5%7%7%9%11%33%
2160
April1st to 10thNight
29%49%8%47%7%8%9%32%
1764
11th to 20thNight
48%48%7%46%6%7%10%35%
1601
21st to endNight
49%49%7%46%6%7%8%37%
1562
May1st to 10thNight
38%5%8%7%36%6%6%10%38%
1440
11th to 20thNight
7%9%25%6%47%7%8%10%34%
1321
21st to endNight
14%8%38%7%45%7%7%7%30%
1358
June1st to 10thNight
10%6%27%8%46%7%8%9%33%
1260
11th to 20thNight
10%7%36%6%35%6%8%10%35%
1260
21st to endNight
11%5%36%6%45%6%6%7%42%
1260
July1st to 10thNight
10%5%245%46%6%8%8%43%
1260
11th to 20thNight
8%325%6%36%5%6%10%46%
1260
21st to endNight
5%424426%5%5%10%52%
1379
August1st to 10thNight
8%5%335%35%6%6%8%49%
1370
11th to 20thNight
43145%35%5%6%9%54%
1602
21st to endNight
7%6%46%6%45%7%7%8%41%
1782
September1st to 10thNight
8%6%35%5%3447%8%48%
1764
11th to 20thNight
9%7%35%5%45%45%6%47%
1867
21st to endNight
7%7%38%6%35%5%7%8%40%
2018
October1st to 10thNight
9%10%46%6%35%5%5%8%40%
2160
11th to 20thNight
5%9%37%6%46%6%7%10%38%
2160
21st to endNight
410%46%6%46%5%7%9%39%
2647
November1st to 10thNight
39%49%8%5%6%8%7%10%30%
2590
11th to 20thNight
27%48%7%47%8%9%10%34%
2660
21st to endNight
27%48%7%5%6%7%9%10%32%
2759
December1st to 10thNight
37%5%7%8%5%9%9%9%10%29%
2850
11th to 20thNight
312%6%12%8%5%7%6%8%8%23%
3520
21st to endNight
17%48%8%5%7%9%10%10%29%
5214

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 10thDay
49%16%15%14%5%1
2219
11th to 20thDay
45%9%18%16%5%8%
2220
21st to endDay
41%20%17%16%6%1
2442
February1st to 10thDay
48%13%15%14%8%1
1671
11th to 20thDay
43%11%15%19%11%1
1674
21st to endDay
44%11%15%21%8%1
1413
March1st to 10thDay
40%11%17%22%9%1
1834
11th to 20thDay
38%12%20%22%7%1
1980
21st to endDay
47%13%17%17%5%
2195
April1st to 10thDay
50%12%16%13%8%1
2192
11th to 20thDay
49%12%11%17%11%
2308
21st to endDay
49%12%14%17%8%1
2398
May1st to 10thDay
48%11%16%16%9%
2520
11th to 20thDay
50%11%15%17%6%1
2576
21st to endDay
52%11%13%17%7%1
2918
June1st to 10thDay
48%10%14%15%9%3
2700
11th to 20thDay
52%10%15%17%6%1
2700
21st to endDay
45%11%14%19%8%2
2700
July1st to 10thDay
41%10%14%21%11%2
2626
11th to 20thDay
38%9%17%22%12%1
2619
21st to endDay
33%9%18%24%15%2
2775
August1st to 10thDay
32%9%19%28%9%1
2546
11th to 20thDay
28%10%19%27%14%2
2298
21st to endDay
41%12%21%19%7%1
2574
September1st to 10thDay
35%9%20%26%8%2
2196
11th to 20thDay
40%8%16%24%9%3
2091
21st to endDay
36%12%17%23%10%1
1942
October1st to 10thDay
46%9%18%21%7%
1800
11th to 20thDay
41%12%17%23%7%
1800
21st to endDay
40%11%17%20%11%1
1706
November1st to 10thDay
42%13%18%21%6%
1488
11th to 20thDay
42%13%19%15%11%
1520
21st to endDay
42%11%18%20%7%2
1420
December1st to 10thDay
41%14%17%20%7%2
1330
11th to 20thDay
48%12%20%13%6%
1688
21st to endDay
33%17%19%23%7%2
2442
January1st to 10thNight
53%13%15%14%4
4726
11th to 20thNight
46%12%16%13%6%6%
4740
21st to endNight
41%17%22%13%7%1
5214
February1st to 10thNight
47%11%17%14%10%1
2505
11th to 20thNight
44%9%15%20%11%1
2404
21st to endNight
47%9%13%21%8%1
2041
March1st to 10thNight
40%13%18%18%10%
2130
11th to 20thNight
31%12%21%26%9%1
1980
21st to endNight
41%14%20%18%7%
2160
April1st to 10thNight
42%13%21%17%7%
1764
11th to 20thNight
41%12%17%21%8%
1601
21st to endNight
45%10%14%23%9%
1562
May1st to 10thNight
40%12%19%19%9%
1440
11th to 20thNight
42%12%19%20%5%1
1321
21st to endNight
50%12%15%16%6%
1358
June1st to 10thNight
44%12%16%17%8%3
1260
11th to 20thNight
44%12%14%24%7%
1260
21st to endNight
39%12%16%22%10%2
1260
July1st to 10thNight
36%12%18%20%11%3
1225
11th to 20thNight
33%11%20%24%11%
1218
21st to endNight
27%8%21%28%14%2
1302
August1st to 10thNight
33%10%16%31%9%1
1363
11th to 20thNight
26%11%20%29%11%3
1602
21st to endNight
38%12%20%24%5%1
1782
September1st to 10thNight
32%9%19%28%10%2
1764
11th to 20thNight
37%9%16%24%11%3
1867
21st to endNight
39%11%19%24%7%1
2018
October1st to 10thNight
43%10%17%23%7%
2160
11th to 20thNight
40%13%18%21%9%
2160
21st to endNight
40%12%17%23%8%
2647
November1st to 10thNight
47%13%16%17%6%1
2590
11th to 20thNight
43%11%19%18%9%
2660
21st to endNight
43%12%19%17%7%3
2759
December1st to 10thNight
46%12%17%17%7%1
2850
11th to 20thNight
51%15%15%14%5%
3516
21st to endNight
37%16%16%18%12%1
5214

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 10thDay
413%42%28%7%6%
180
11th to 20thDay
216%36%30%13%3
180
21st to endDay
5%11%43%25%14%3
198
February1st to 10thDay
9%23%40%22%6%
367
11th to 20thDay
8%17%40%25%9%1
365
21st to endDay
11%22%42%17%8%1
307
March1st to 10thDay
7%24%31%23%13%2
391
11th to 20thDay
8%25%34%21%10%1
420
21st to endDay
14%24%32%18%10%1
462
April1st to 10thDay
14%25%32%20%7%1
420
11th to 20thDay
11%25%29%20%11%4
412
21st to endDay
17%22%27%20%10%4
420
May1st to 10thDay
11%21%28%29%9%1
423
11th to 20thDay
14%15%30%25%12%4
542
21st to endDay
17%19%31%19%12%3
680
June1st to 10thDay
15%22%35%19%7%1
630
11th to 20thDay
17%22%31%19%10%1
630
21st to endDay
12%16%33%23%12%3
630
July1st to 10thDay
13%15%30%24%15%4
621
11th to 20thDay
11%16%30%25%14%3
618
21st to endDay
7%15%31%25%17%5%
684
August1st to 10thDay
10%10%25%31%18%7%
507
11th to 20thDay
6%13%24%32%18%5%
437
21st to endDay
9%16%32%26%14%3
495
September1st to 10thDay
11%15%31%26%13%3
450
11th to 20thDay
15%13%27%26%15%4
450
21st to endDay
16%21%30%21%10%2
450
October1st to 10thDay
18%18%25%22%14%4
450
11th to 20thDay
12%21%32%22%10%3
450
21st to endDay
16%19%38%14%11%3
304
November1st to 10thDay
13%21%35%22%8%1
180
11th to 20thDay
416%32%32%12%3
180
21st to endDay
9%21%31%21%9%8%
180
December1st to 10thDay
411%36%29%13%6%
180
11th to 20thDay
5%17%38%24%11%6%
180
21st to endDay
7%15%38%29%11%1
198
January1st to 10thNight
6%13%45%25%8%2
850
11th to 20thNight
6%11%41%34%6%2
850
21st to endNight
413%43%26%11%2
935
February1st to 10thNight
8%14%41%26%10%1
776
11th to 20thNight
6%9%42%30%13%1
744
21st to endNight
7%13%38%32%9%2
628
March1st to 10thNight
314%44%26%12%1
722
11th to 20thNight
213%43%30%11%
720
21st to endNight
7%13%36%29%14%1
792
April1st to 10thNight
7%11%34%36%12%1
684
11th to 20thNight
8%9%40%31%12%
533
21st to endNight
7%11%39%32%10%1
482
May1st to 10thNight
39%37%38%12%
360
11th to 20thNight
10%9%29%43%8%1
354
21st to endNight
17%7%31%35%10%
389
June1st to 10thNight
12%9%37%35%7%
360
11th to 20thNight
13%9%35%32%11%1
360
21st to endNight
12%5%29%41%13%
360
July1st to 10thNight
11%5%29%39%16%
350
11th to 20thNight
11%6%30%38%16%
348
21st to endNight
6%228%40%23%2
394
August1st to 10thNight
11%218%38%30%2
358
11th to 20thNight
5%421%38%30%2
534
21st to endNight
8%8%29%36%19%1
594
September1st to 10thNight
12%6%25%36%20%1
684
11th to 20thNight
13%8%25%27%24%4
720
21st to endNight
11%14%33%28%13%1
720
October1st to 10thNight
14%11%29%29%14%2
720
11th to 20thNight
9%11%39%25%14%2
720
21st to endNight
12%12%40%25%9%2
792
November1st to 10thNight
5%17%43%26%7%1
740
11th to 20thNight
5%15%47%25%7%1
760
21st to endNight
5%13%47%25%7%2
807
December1st to 10thNight
5%11%40%29%14%2
850
11th to 20thNight
6%11%43%29%9%2
850
21st to endNight
6%10%48%28%8%1
935
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