Newton/Godin Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Newton/Godin Observatory clear sky chart from 2005-11-05 to 2017-10-06.

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
45%
14607
11%
46945
9%
14582
48%
14582
19%
32479

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
33%
746
9%
2686
7%
746
38%
746
10%
2144
January16th to endNight
37%
778
9%
2694
8%
778
40%
778
10%
2078
February1st to 15thNight
34%
696
6%
2288
4%
696
38%
696
11%
1802
February16th to endNight
37%
632
11%
2050
10%
632
40%
632
14%
1518
March1st to 15thNight
34%
720
7%
2036
4%
720
36%
720
14%
1605
March16th to endNight
35%
768
9%
2091
5%
768
37%
768
15%
1626
April1st to 15thNight
40%
710
9%
1790
4%
710
42%
710
21%
1315
April16th to endNight
41%
536
13%
1616
7%
536
46%
536
21%
1097
May1st to 15thNight
48%
359
13%
1439
15%
359
54%
359
22%
836
May16th to endNight
55%
375
8%
1475
10%
374
59%
374
22%
895
June1st to 15thNight
48%
360
6%
1260
5%
360
50%
360
27%
755
June16th to endNight
51%
360
8%
1260
5%
360
53%
360
31%
709
July1st to 15thNight
66%
340
13%
1190
11%
340
69%
340
47%
548
July16th to endNight
74%
376
18%
1337
23%
354
81%
354
51%
546
August1st to 15thNight
79%
472
18%
1546
20%
470
82%
470
51%
703
August16th to endNight
70%
606
24%
1752
18%
606
73%
606
49%
886
September1st to 15thNight
74%
720
24%
1800
14%
720
76%
720
56%
969
September16th to endNight
56%
716
19%
1984
14%
716
59%
716
28%
1301
October1st to 15thNight
52%
684
13%
2052
12%
684
55%
684
25%
1355
October16th to endNight
41%
704
10%
2178
7%
704
44%
704
16%
1618
November1st to 15thNight
30%
700
8%
2450
6%
700
34%
700
10%
1933
November16th to endNight
33%
720
7%
2520
4%
720
38%
720
10%
1958
December1st to 15thNight
34%
729
7%
2571
4%
729
38%
729
10%
1992
December16th to endNight
27%
800
6%
2880
3%
800
32%
800
9%
2290

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
13%7%36%5%35%5%5%7%34%
48283
Night
16%8%36%5%35%5%5%7%32%
47100
Cloud CoverDay
13%8%36%5%35%5%5%7%34%
48283
Night
16%8%36%5%35%5%5%7%32%
47103
TransparencyDay
47%5%20%20%6%
47941
Night
49%5%17%19%6%1
46946
SeeingDay
14%6%18%30%22%7%
6251
Night
19%6%17%29%21%6%
14620

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
22%14%6%10%7%35%5%26%15%
1253
16th to endDay
23%11%6%11%7%47%5%45%11%
1527
February1st to 15thDay
27%11%47%7%46%446%14%
1576
16th to endDay
16%11%48%6%48%45%6%22%
1424
March1st to 15thDay
18%12%6%8%7%46%6%6%5%16%
1923
16th to endDay
15%12%5%9%7%47%5%5%6%17%
2133
April1st to 15thDay
14%8%46%6%46%7%7%8%23%
2158
16th to endDay
12%8%47%6%36%6%7%8%28%
2343
May1st to 15thDay
11%5%35%5%46%6%6%8%37%
2511
16th to endDay
11%7%36%5%36%5%5%9%34%
2633
June1st to 15thDay
9%5%26%5%35%5%6%9%40%
2700
16th to endDay
9%5%25%436%6%6%8%41%
2700
July1st to 15thDay
5%313313348%60%
2700
16th to endDay
5%11112235%8%65%
2739
August1st to 15thDay
5%313323348%61%
2405
16th to endDay
6%31432446%9%53%
2450
September1st to 15thDay
6%31432345%8%54%
2160
16th to endDay
13%8%25%5%35%45%8%36%
1974
October1st to 15thDay
17%8%36%6%45%6%5%6%29%
1705
16th to endDay
20%11%47%7%35%5%6%7%19%
1691
November1st to 15thDay
27%11%48%5%35%445%17%
1408
16th to endDay
23%13%6%8%7%45%5%4416%
1440
December1st to 15thDay
22%11%48%7%46%45%5%19%
1386
16th to endDay
21%14%5%10%7%36%435%15%
1344
January1st to 15thNight
24%10%48%6%36%45%5%20%
2686
16th to endNight
23%9%48%6%46%5%5%7%19%
2694
February1st to 15thNight
22%11%47%6%35%5%45%21%
2276
16th to endNight
19%9%47%6%35%5%5%6%25%
2050
March1st to 15thNight
20%10%46%6%46%6%7%6%18%
2036
16th to endNight
15%10%49%7%46%6%6%7%21%
2087
April1st to 15thNight
15%8%36%6%35%6%7%7%28%
1790
16th to endNight
15%6%36%5%35%5%7%9%31%
1616
May1st to 15thNight
9%6%35%5%36%5%6%8%39%
1439
16th to endNight
8%5%35%5%45%6%6%11%37%
1475
June1st to 15thNight
10%6%35%6%2446%8%42%
1260
16th to endNight
8%425%4246%6%10%44%
1260
July1st to 15thNight
43133224310%62%
1260
16th to endNight
31112132410%67%
1430
August1st to 15thNight
111232336%8%64%
1554
16th to endNight
5%31221346%9%58%
1752
September1st to 15thNight
5%212213248%63%
1800
16th to endNight
12%6%35%6%3445%8%39%
1984
October1st to 15thNight
14%7%36%7%33346%39%
2052
16th to endNight
23%9%37%5%35%45%8%24%
2178
November1st to 15thNight
27%9%47%6%45%5%45%19%
2450
16th to endNight
20%10%5%9%7%46%5%5%5%19%
2520
December1st to 15thNight
23%10%37%7%36%5%46%20%
2571
16th to endNight
22%11%5%7%7%45%6%5%6%18%
2880

Percentage Cloud Cover SW (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
22%13%5%11%7%35%5%35%16%
1253
16th to endDay
23%11%5%12%8%5%5%5%5%5%11%
1527
February1st to 15thDay
26%12%5%7%7%45%446%15%
1576
16th to endDay
14%13%48%6%46%5%6%6%21%
1424
March1st to 15thDay
19%12%6%8%7%46%6%6%5%16%
1923
16th to endDay
16%11%6%9%7%46%5%6%7%17%
2133
April1st to 15thDay
14%9%46%6%46%6%6%9%22%
2158
16th to endDay
13%8%46%6%35%7%6%8%28%
2343
May1st to 15thDay
11%6%25%6%35%6%5%8%37%
2511
16th to endDay
11%7%36%5%36%6%5%9%34%
2633
June1st to 15thDay
9%5%26%5%35%46%10%40%
2700
16th to endDay
9%6%245%36%5%6%8%41%
2700
July1st to 15thDay
5%31331325%8%61%
2700
16th to endDay
5%112213348%66%
2739
August1st to 15thDay
4313323348%61%
2405
16th to endDay
6%31432446%9%53%
2450
September1st to 15thDay
6%32342345%8%55%
2160
16th to endDay
13%7%35%5%35%35%9%36%
1974
October1st to 15thDay
17%8%37%6%45%5%6%6%28%
1705
16th to endDay
20%11%38%8%35%5%6%8%18%
1691
November1st to 15thDay
27%12%48%6%25%445%17%
1408
16th to endDay
23%12%6%8%7%46%43416%
1440
December1st to 15thDay
21%12%5%8%7%36%5%4419%
1386
16th to endDay
21%14%6%9%8%35%5%46%14%
1344
January1st to 15thNight
24%10%5%7%6%35%445%20%
2685
16th to endNight
23%9%47%7%346%6%6%19%
2694
February1st to 15thNight
21%11%48%6%45%45%6%21%
2276
16th to endNight
18%9%48%6%35%5%6%6%26%
2050
March1st to 15thNight
20%11%47%7%37%6%6%6%19%
2036
16th to endNight
15%11%5%8%7%46%6%6%7%21%
2091
April1st to 15thNight
15%9%36%5%35%6%6%8%28%
1790
16th to endNight
16%7%36%5%345%7%8%32%
1616
May1st to 15thNight
9%6%25%445%6%5%8%40%
1439
16th to endNight
8%5%25%6%36%5%6%11%37%
1475
June1st to 15thNight
10%6%36%6%245%5%7%42%
1260
16th to endNight
9%4244245%6%10%45%
1260
July1st to 15thNight
4212322339%63%
1260
16th to endNight
321213337%70%
1430
August1st to 15thNight
121231245%7%66%
1554
16th to endNight
5%31221336%9%59%
1752
September1st to 15thNight
5%212312347%64%
1800
16th to endNight
12%6%25%6%3345%8%39%
1984
October1st to 15thNight
14%8%26%6%34345%40%
2052
16th to endNight
23%9%36%5%3445%7%24%
2178
November1st to 15thNight
27%10%37%6%45%5%45%19%
2450
16th to endNight
19%11%5%8%6%46%5%5%5%20%
2520
December1st to 15thNight
22%11%46%6%36%6%5%5%20%
2571
16th to endNight
21%12%5%8%6%45%5%5%6%17%
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
70%49%10%3
1253
16th to endDay
74%412%7%1
1527
February1st to 15thDay
68%6%11%8%3
1576
16th to endDay
59%416%15%3
1424
March1st to 15thDay
64%5%15%12%1
1923
16th to endDay
62%5%16%14%1
2133
April1st to 15thDay
52%7%20%17%2
2158
16th to endDay
47%6%18%21%4
2343
May1st to 15thDay
41%6%21%22%8%
2511
16th to endDay
45%5%26%18%2
2637
June1st to 15thDay
37%6%27%20%6%
2700
16th to endDay
37%5%28%22%5%
2700
July1st to 15thDay
22%424%32%13%2
2541
16th to endDay
17%328%34%13%1
2569
August1st to 15thDay
22%425%34%10%1
2388
16th to endDay
26%5%26%32%7%1
2450
September1st to 15thDay
28%421%27%17%1
2160
16th to endDay
46%5%18%20%8%
1974
October1st to 15thDay
54%416%19%6%
1705
16th to endDay
60%6%18%11%3
1691
November1st to 15thDay
68%313%10%21
1408
16th to endDay
71%49%12%2
1440
December1st to 15thDay
66%411%12%4
1386
16th to endDay
70%5%10%9%2
1344
January1st to 15thNight
65%5%11%11%4
2686
16th to endNight
62%5%12%14%31
2694
February1st to 15thNight
62%6%14%11%5%
2288
16th to endNight
57%416%16%5%
2050
March1st to 15thNight
61%5%15%15%2
2036
16th to endNight
58%5%17%16%1
2091
April1st to 15thNight
50%6%18%19%4
1790
16th to endNight
46%5%18%22%6%
1616
May1st to 15thNight
39%5%19%23%10%1
1440
16th to endNight
39%7%28%19%4
1475
June1st to 15thNight
39%427%22%41
1260
16th to endNight
32%5%29%24%5%1
1260
July1st to 15thNight
20%323%33%16%3
1190
16th to endNight
14%5%24%35%17%3
1337
August1st to 15thNight
17%426%33%14%4
1546
16th to endNight
20%424%36%10%2
1752
September1st to 15thNight
19%321%26%21%6%
1800
16th to endNight
41%5%16%23%11%1
1984
October1st to 15thNight
46%216%23%10%
2052
16th to endNight
57%417%15%4
2178
November1st to 15thNight
64%5%12%12%21
2450
16th to endNight
62%5%13%12%5%
2520
December1st to 15thNight
64%414%12%3
2571
16th to endNight
65%5%14%10%3
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
13%5%20%38%21%1
60
16th to endDay
32%6%20%20%15%4
115
February1st to 15thDay
32%11%16%25%13%1
236
16th to endDay
21%13%15%31%16%1
212
March1st to 15thDay
31%12%24%20%9%1
270
16th to endDay
20%11%21%34%9%2
288
April1st to 15thDay
20%8%19%24%22%5%
269
16th to endDay
16%6%22%35%15%3
270
May1st to 15thDay
19%9%13%27%28%2
288
16th to endDay
10%320%29%27%8%
348
June1st to 15thDay
9%5%25%34%21%4
495
16th to endDay
10%6%26%33%16%6%
495
July1st to 15thDay
5%319%34%31%6%
475
16th to endDay
2219%32%27%15%
408
August1st to 15thDay
5%112%28%32%19%
315
16th to endDay
5%411%29%32%17%
332
September1st to 15thDay
9%210%30%33%13%
315
16th to endDay
15%312%30%30%7%
315
October1st to 15thDay
20%6%13%32%23%4
278
16th to endDay
23%8%13%32%18%3
223
November1st to 15thDay
36%10%16%30%6%
60
16th to endDay
20%8%18%23%20%10%
60
December1st to 15thDay
28%11%25%26%8%
60
16th to endDay
34%10%25%18%10%
64
January1st to 15thNight
27%9%16%27%18%1
750
16th to endNight
27%6%12%27%22%3
778
February1st to 15thNight
25%7%16%27%18%3
704
16th to endNight
24%8%15%26%19%5%
632
March1st to 15thNight
22%11%20%25%15%4
720
16th to endNight
17%9%20%30%17%4
768
April1st to 15thNight
17%7%22%27%22%3
710
16th to endNight
17%5%24%32%16%3
536
May1st to 15thNight
13%424%28%24%5%
360
16th to endNight
10%218%37%27%3
375
June1st to 15thNight
13%224%34%21%3
360
16th to endNight
9%128%32%20%6%
360
July1st to 15thNight
5%118%39%30%4
340
16th to endNight
415%40%32%5%
376
August1st to 15thNight
39%33%39%13%
472
16th to endNight
6%314%31%32%11%
606
September1st to 15thNight
7%10%27%32%22%
720
16th to endNight
15%211%30%27%12%
716
October1st to 15thNight
18%310%30%25%12%
684
16th to endNight
25%5%12%27%20%8%
704
November1st to 15thNight
31%7%19%27%13%1
700
16th to endNight
21%9%19%26%17%5%
720
December1st to 15thNight
26%9%16%29%15%2
729
16th to endNight
27%9%21%29%11%1
800
Page generated at 2017-10-07 11:07:53. Version ac04

Copyright 2017 A. Danko


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