This page made possible by the sponsorship of: RASC Ottawa Centre.

Fred Lossing Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fred Lossing Observatory 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
29%
14634
13%
46786
8%
14604
35%
14604
16%
33208

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
15%
720
7%
2506
3%
716
19%
716
7%
2023
January16th to endNight
20%
768
12%
2622
7%
768
27%
768
11%
1972
February1st to 15thNight
18%
702
9%
2287
4%
701
25%
701
11%
1735
February16th to endNight
21%
631
13%
1961
6%
631
31%
631
13%
1437
March1st to 15thNight
19%
720
12%
2082
7%
720
26%
720
15%
1541
March16th to endNight
30%
768
19%
2046
9%
768
38%
768
22%
1395
April1st to 15thNight
23%
718
15%
1796
6%
718
28%
718
19%
1324
April16th to endNight
28%
645
17%
1725
7%
645
35%
645
22%
1212
May1st to 15thNight
33%
360
16%
1440
16%
360
42%
360
17%
946
May16th to endNight
33%
375
14%
1497
10%
374
47%
374
19%
942
June1st to 15thNight
34%
360
10%
1440
9%
360
43%
360
15%
953
June16th to endNight
41%
360
8%
1440
11%
360
47%
360
18%
919
July1st to 15thNight
52%
340
15%
1360
22%
340
58%
340
26%
760
July16th to endNight
55%
376
14%
1418
16%
354
60%
354
26%
811
August1st to 15thNight
46%
463
14%
1534
11%
461
51%
461
26%
952
August16th to endNight
46%
699
19%
1845
10%
699
51%
699
36%
1138
September1st to 15thNight
44%
700
15%
1750
7%
700
48%
700
29%
1208
September16th to endNight
46%
657
21%
1800
13%
657
51%
657
31%
1158
October1st to 15thNight
33%
660
18%
1980
11%
660
42%
660
20%
1369
October16th to endNight
24%
704
11%
2186
5%
704
32%
704
12%
1659
November1st to 15thNight
25%
700
16%
2343
12%
700
34%
700
16%
1648
November16th to endNight
20%
720
10%
2520
7%
720
26%
720
9%
1925
December1st to 15thNight
17%
720
6%
2520
3%
720
22%
720
8%
2006
December16th to endNight
14%
768
9%
2688
4%
768
20%
768
7%
2175

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
17%8%36%5%35%446%32%
47849
Night
17%9%47%6%34446%32%
46955
Cloud CoverDay
21%8%36%5%34445%33%
47858
Night
20%8%36%5%24345%35%
46961
TransparencyDay
51%5%11%19%10%1
47536
Night
52%5%11%19%10%
46786
SeeingDay
22%12%29%21%10%3
5431
Night
23%11%29%25%9%
14636

By Month

Percentage Cloud Cover NE (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
19%14%6%9%6%4344421%
1432
16th to endDay
15%13%6%9%8%45%44422%
1599
February1st to 15thDay
13%14%6%12%7%35%43423%
1575
16th to endDay
17%13%48%7%35%435%26%
1512
March1st to 15thDay
17%12%48%7%45%43427%
1865
16th to endDay
14%9%35%5%2244440%
2178
April1st to 15thDay
22%10%36%423435%33%
2152
16th to endDay
21%8%24433436%36%
2242
May1st to 15thDay
19%8%27%5%24446%33%
2511
16th to endDay
16%7%35%5%35%447%35%
2618
June1st to 15thDay
21%6%35%5%35%45%7%31%
2520
16th to endDay
17%5%26%6%36%6%5%7%32%
2520
July1st to 15thDay
12%5%25%5%26%5%6%10%37%
2520
16th to endDay
11%5%25%5%36%5%7%9%36%
2654
August1st to 15thDay
11%6%26%7%45%46%8%37%
2415
16th to endDay
12%425%435%5%6%8%39%
2345
September1st to 15thDay
17%5%25%5%3335%7%39%
2098
16th to endDay
15%4246%235%5%6%43%
1829
October1st to 15thDay
22%7%25%6%25%445%33%
1650
16th to endDay
26%10%38%6%3443424%
1686
November1st to 15thDay
15%9%36%435%446%34%
1512
16th to endDay
20%13%5%7%6%3425%5%24%
1440
December1st to 15thDay
21%15%410%6%35%5%45%16%
1440
16th to endDay
23%15%5%8%5%24445%20%
1536
January1st to 15thNight
16%14%6%10%8%35%445%18%
2506
16th to endNight
12%15%6%9%8%24445%25%
2622
February1st to 15thNight
13%14%6%10%8%34445%24%
2285
16th to endNight
16%11%47%7%24446%29%
1961
March1st to 15thNight
17%12%5%8%6%23345%29%
2069
16th to endNight
14%7%36%5%24445%40%
2046
April1st to 15thNight
22%9%35%5%23335%35%
1796
16th to endNight
17%9%446%23346%36%
1725
May1st to 15thNight
21%8%26%323345%37%
1440
16th to endNight
15%5%36%5%345%5%7%38%
1495
June1st to 15thNight
17%6%36%6%25%46%6%34%
1440
16th to endNight
14%6%25%5%35%46%7%37%
1440
July1st to 15thNight
9%4245%25%5%6%7%46%
1440
16th to endNight
9%2235%345%6%9%46%
1514
August1st to 15thNight
8%5%25%6%3447%9%42%
1544
16th to endNight
10%32443445%7%50%
1845
September1st to 15thNight
16%5%24434446%42%
1750
16th to endNight
15%5%24423345%48%
1800
October1st to 15thNight
20%7%26%5%23446%35%
1980
16th to endNight
23%11%36%5%33346%26%
2186
November1st to 15thNight
19%9%36%5%2444433%
2343
16th to endNight
21%12%49%6%24345%24%
2520
December1st to 15thNight
20%17%48%5%35%44420%
2520
16th to endNight
24%14%5%9%6%3333419%
2688

Percentage Cloud Cover SE (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
19%13%6%9%8%3234424%
1432
16th to endDay
13%13%5%9%8%445%4424%
1599
February1st to 15thDay
14%13%6%12%7%4443424%
1575
16th to endDay
19%12%48%7%35%43426%
1512
March1st to 15thDay
26%9%36%5%3433331%
1875
16th to endDay
25%7%2431233340%
2177
April1st to 15thDay
25%9%35%41323434%
2152
16th to endDay
24%7%33423335%38%
2242
May1st to 15thDay
32%6%25%42333431%
2511
16th to endDay
28%5%24423335%34%
2618
June1st to 15thDay
24%6%345%24445%34%
2520
16th to endDay
21%425%5%25%45%6%35%
2520
July1st to 15thDay
12%5%25%4345%6%9%38%
2520
16th to endDay
11%5%25%5%36%6%7%9%36%
2654
August1st to 15thDay
28%4145%34347%31%
2415
16th to endDay
28%41342345%6%35%
2345
September1st to 15thDay
16%5%245%24346%43%
2098
16th to endDay
15%425%5%23446%45%
1829
October1st to 15thDay
20%7%25%5%35%446%35%
1650
16th to endDay
26%9%37%7%3443427%
1686
November1st to 15thDay
19%7%36%434446%34%
1512
16th to endDay
23%11%6%7%5%2434425%
1440
December1st to 15thDay
21%15%5%9%6%45%34420%
1440
16th to endDay
22%15%5%8%5%2434422%
1536
January1st to 15thNight
16%14%6%10%7%35%43423%
2506
16th to endNight
12%14%6%8%7%34345%30%
2622
February1st to 15thNight
15%13%5%11%6%34345%25%
2278
16th to endNight
18%11%38%6%24445%29%
1961
March1st to 15thNight
28%8%36%42323432%
2082
16th to endNight
25%5%2443332341%
2046
April1st to 15thNight
24%8%3442332436%
1796
16th to endNight
19%8%35%423346%38%
1725
May1st to 15thNight
27%6%24412235%39%
1440
16th to endNight
20%424324447%42%
1495
June1st to 15thNight
19%5%36%43445%6%35%
1440
16th to endNight
17%6%25%5%2446%6%38%
1440
July1st to 15thNight
9%424435%5%5%7%47%
1440
16th to endNight
9%324435%6%5%8%46%
1514
August1st to 15thNight
22%415%42445%7%37%
1544
16th to endNight
24%313323346%42%
1845
September1st to 15thNight
15%5%14434445%45%
1750
16th to endNight
15%424322235%51%
1800
October1st to 15thNight
19%7%25%42335%5%38%
1980
16th to endNight
24%10%36%5%33346%29%
2186
November1st to 15thNight
24%9%25%43333436%
2343
16th to endNight
26%11%36%42333429%
2520
December1st to 15thNight
22%14%36%5%24345%26%
2520
16th to endNight
25%13%5%8%6%3333424%
2688

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
65%410%12%6%1
1433
16th to endDay
63%5%9%11%8%
1599
February1st to 15thDay
63%410%15%4
1577
16th to endDay
60%311%13%9%1
1512
March1st to 15thDay
60%5%11%15%7%
1875
16th to endDay
45%49%19%15%5%
2178
April1st to 15thDay
54%45%18%14%2
2152
16th to endDay
49%47%19%16%3
2242
May1st to 15thDay
50%5%7%19%14%2
2511
16th to endDay
47%6%11%20%12%2
2622
June1st to 15thDay
52%6%9%20%10%
2520
16th to endDay
49%6%11%20%11%
2520
July1st to 15thDay
37%7%14%27%12%
2371
16th to endDay
40%9%15%23%10%
2487
August1st to 15thDay
44%7%14%22%10%
2401
16th to endDay
39%7%14%27%11%
2345
September1st to 15thDay
42%5%12%27%11%
2098
16th to endDay
40%6%12%31%9%
1829
October1st to 15thDay
51%5%11%20%9%
1650
16th to endDay
62%5%11%14%5%
1686
November1st to 15thDay
48%7%14%20%9%
1512
16th to endDay
62%5%11%12%6%1
1440
December1st to 15thDay
68%6%11%11%2
1440
16th to endDay
66%6%10%10%6%
1536
January1st to 15thNight
67%5%10%11%5%
2506
16th to endNight
59%5%8%17%8%
2622
February1st to 15thNight
62%312%15%5%
2287
16th to endNight
56%411%18%9%
1961
March1st to 15thNight
56%410%19%8%
2082
16th to endNight
45%410%20%16%3
2046
April1st to 15thNight
53%37%19%15%1
1796
16th to endNight
47%5%7%19%17%3
1725
May1st to 15thNight
48%5%7%19%14%4
1440
16th to endNight
43%6%12%20%14%2
1497
June1st to 15thNight
49%5%11%21%10%1
1440
16th to endNight
43%7%12%21%14%
1440
July1st to 15thNight
33%7%12%30%15%1
1360
16th to endNight
33%8%14%27%15%
1418
August1st to 15thNight
38%7%17%23%12%
1534
16th to endNight
32%5%15%33%12%
1845
September1st to 15thNight
42%6%11%28%11%
1750
16th to endNight
38%5%12%33%10%
1800
October1st to 15thNight
48%5%10%22%13%
1980
16th to endNight
58%5%13%15%6%
2186
November1st to 15thNight
52%5%12%17%10%1
2343
16th to endNight
61%5%11%16%4
2520
December1st to 15thNight
65%6%13%12%3
2520
16th to endNight
68%5%8%11%5%
2688

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
30%25%23%16%5%
60
16th to endDay
33%18%33%13%1
75
February1st to 15thDay
31%25%34%8%
90
16th to endDay
32%22%25%15%4
171
March1st to 15thDay
24%16%32%21%4
270
16th to endDay
22%19%29%17%9%2
288
April1st to 15thDay
29%20%27%15%7%
270
16th to endDay
26%17%24%14%12%4
270
May1st to 15thDay
30%11%28%19%6%4
288
16th to endDay
22%11%37%17%9%2
331
June1st to 15thDay
28%8%28%23%8%2
315
16th to endDay
17%9%33%25%11%1
315
July1st to 15thDay
15%5%28%29%14%5%
305
16th to endDay
15%5%30%27%15%5%
326
August1st to 15thDay
12%7%25%33%13%7%
313
16th to endDay
11%5%27%28%14%11%
332
September1st to 15thDay
19%7%25%19%15%11%
294
16th to endDay
17%9%30%20%14%7%
254
October1st to 15thDay
23%12%25%23%12%2
255
16th to endDay
33%15%26%17%7%
259
November1st to 15thDay
21%11%30%24%10%1
166
16th to endDay
36%13%33%13%3
60
December1st to 15thDay
18%23%43%11%3
60
16th to endDay
42%23%29%31
64
January1st to 15thNight
25%17%33%18%4
720
16th to endNight
22%14%33%23%4
768
February1st to 15thNight
20%17%36%21%3
704
16th to endNight
22%17%32%20%5%
631
March1st to 15thNight
26%14%33%23%2
720
16th to endNight
20%16%26%25%9%
768
April1st to 15thNight
27%15%28%23%4
718
16th to endNight
23%14%28%23%8%
645
May1st to 15thNight
26%6%25%29%9%1
360
16th to endNight
17%7%37%23%14%
375
June1st to 15thNight
22%6%29%32%9%
360
16th to endNight
18%429%35%11%
360
July1st to 15thNight
10%227%43%15%1
340
16th to endNight
10%127%45%14%1
376
August1st to 15thNight
12%324%36%20%1
463
16th to endNight
11%5%24%34%22%2
699
September1st to 15thNight
20%5%26%26%18%2
700
16th to endNight
19%8%23%25%21%2
657
October1st to 15thNight
24%9%27%24%12%1
660
16th to endNight
31%13%25%22%6%
704
November1st to 15thNight
26%10%31%20%10%
700
16th to endNight
32%15%24%19%6%
720
December1st to 15thNight
30%16%30%18%3
720
16th to endNight
35%13%28%17%21
768
Page generated at 2017-09-11 19:35:24. Version ac04

Copyright 2017 A. Danko


Fred Lossing Observatory Clear Sky Chart | Charts Home