New Glasgow
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the New Glasgow clear sky chart from 2005-11-06 to 2024-01-12.

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
19%
24059
10%
74751
4%
23996
26%
23996
12%
56819

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
9%
850
7%
2649
1%
847
15%
847
7%
2167
January11th to 20thNight
11%
806
6%
2535
1%
806
16%
806
7%
2099
January21st to endNight
14%
811
11%
2618
3%
811
23%
811
9%
2040
February1st to 10thNight
13%
720
9%
2340
3%
720
20%
720
8%
1811
February11th to 20thNight
9%
703
8%
2276
1%
700
18%
700
7%
1811
February21st to endNight
16%
592
13%
1852
3%
592
26%
592
11%
1397
March1st to 10thNight
12%
719
13%
2066
4%
719
21%
719
9%
1666
March11th to 20thNight
20%
720
12%
1980
5%
720
26%
720
13%
1538
March21st to endNight
18%
744
12%
2130
4%
744
26%
744
12%
1653
April1st to 10thNight
16%
540
10%
1800
5%
540
24%
540
9%
1384
April11th to 20thNight
18%
534
14%
1768
6%
534
28%
534
13%
1264
April21st to endNight
19%
540
11%
1620
6%
540
24%
540
13%
1255
May1st to 10thNight
22%
540
13%
1472
7%
540
28%
540
14%
1132
May11th to 20thNight
24%
532
14%
1417
6%
532
31%
532
19%
1042
May21st to endNight
18%
583
10%
1551
3%
582
24%
582
19%
1139
June1st to 10thNight
18%
540
8%
1440
2%
540
22%
540
15%
1121
June11th to 20thNight
23%
540
12%
1440
4%
540
29%
540
22%
1021
June21st to endNight
27%
540
6%
1440
2%
540
30%
540
19%
1084
July1st to 10thNight
30%
526
8%
1401
4%
526
34%
526
26%
977
July11th to 20thNight
34%
522
10%
1392
6%
522
37%
522
26%
970
July21st to endNight
34%
590
11%
1486
8%
558
37%
558
21%
1089
August1st to 10thNight
36%
538
11%
1556
8%
534
40%
534
26%
1036
August11th to 20thNight
34%
532
12%
1596
7%
532
38%
532
19%
1140
August21st to endNight
41%
594
14%
1924
9%
594
47%
594
23%
1237
September1st to 10thNight
32%
540
15%
1800
10%
540
40%
540
23%
1145
September11th to 20thNight
31%
540
20%
1800
13%
540
41%
540
21%
1157
September21st to endNight
26%
702
16%
2071
8%
702
33%
702
20%
1421
October1st to 10thNight
29%
720
15%
2160
7%
720
36%
720
20%
1488
October11th to 20thNight
23%
720
15%
2160
6%
720
30%
720
17%
1517
October21st to endNight
15%
825
12%
2440
4%
825
22%
825
10%
1922
November1st to 10thNight
15%
830
10%
2503
3%
830
21%
830
11%
1934
November11th to 20thNight
15%
850
10%
2660
4%
850
21%
850
8%
2117
November21st to endNight
13%
850
7%
2660
2%
850
18%
850
8%
2157
December1st to 10thNight
9%
850
6%
2660
1%
850
15%
850
7%
2225
December11th to 20thNight
6%
850
5%
3243
0%
849
10%
849
4%
2780
December21st to endNight
7%
926
3%
4845
1%
907
12%
907
2%
3883

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
19%11%5%7%6%35%5%5%6%28%
74704
Night
19%12%48%6%35%45%6%28%
75010
TransparencyDay
57%7%12%17%7%1
74407
Night
58%6%12%17%6%1
74842
SeeingDay
26%21%31%16%41
16328
Night
25%19%31%20%4
24069

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 10thDay
16%16%7%13%7%45%446%18%
1516
11th to 20thDay
17%16%8%12%7%45%445%17%
1448
21st to endDay
12%13%7%11%9%5%5%5%45%23%
1737
February1st to 10thDay
16%14%6%10%7%44446%24%
1620
11th to 20thDay
17%15%7%11%7%35%44424%
1573
21st to endDay
10%15%6%9%8%5%6%45%6%27%
1404
March1st to 10thDay
15%17%5%9%7%45%5%5%6%23%
1888
11th to 20thDay
12%11%8%10%9%45%5%45%26%
1980
21st to endDay
18%18%9%9%6%2323426%
2225
April1st to 10thDay
20%16%6%8%5%345%46%25%
2160
11th to 20thDay
23%13%46%5%34345%30%
2139
21st to endDay
23%15%36%6%2445%6%25%
2340
May1st to 10thDay
26%12%46%6%35%45%6%25%
2486
11th to 20thDay
20%11%35%5%35%45%6%31%
2478
21st to endDay
21%10%36%6%35%46%7%31%
2724
June1st to 10thDay
29%8%26%6%35%5%5%8%23%
2520
11th to 20thDay
24%7%36%5%3445%6%32%
2520
21st to endDay
24%8%46%7%35%46%6%27%
2520
July1st to 10thDay
17%6%25%6%46%6%5%8%35%
2520
11th to 20thDay
14%7%37%5%35%6%6%9%35%
2520
21st to endDay
19%7%46%6%46%6%6%8%28%
2745
August1st to 10thDay
17%6%36%5%35%6%6%10%34%
2368
11th to 20thDay
18%7%46%6%45%5%5%7%33%
2304
21st to endDay
16%5%26%5%3446%8%40%
2431
September1st to 10thDay
19%5%36%5%345%5%7%38%
2160
11th to 20thDay
21%7%26%5%35%5%5%6%36%
2160
21st to endDay
20%6%35%6%345%5%6%37%
1884
October1st to 10thDay
20%7%36%6%35%46%7%33%
1800
11th to 20thDay
20%10%37%7%45%46%8%27%
1800
21st to endDay
22%14%38%7%35%45%6%23%
1914
November1st to 10thDay
23%13%47%5%35%5%5%5%24%
1571
11th to 20thDay
17%20%5%9%6%4435%7%21%
1520
21st to endDay
16%16%6%8%7%36%5%5%6%22%
1520
December1st to 10thDay
21%17%6%9%7%445%5%5%19%
1520
11th to 20thDay
24%17%6%11%8%35%445%14%
1906
21st to endDay
20%14%11%11%5%34435%19%
2783
January1st to 10thNight
17%16%7%11%7%45%5%5%5%19%
2649
11th to 20thNight
16%14%6%12%8%45%45%6%20%
2535
21st to endNight
13%12%6%13%8%45%5%5%6%24%
2618
February1st to 10thNight
18%12%5%10%8%46%45%425%
2340
11th to 20thNight
17%15%5%10%9%445%46%22%
2273
21st to endNight
11%16%7%9%7%35%5%45%29%
1852
March1st to 10thNight
14%18%6%12%8%3444423%
2057
11th to 20thNight
14%11%7%11%8%35%446%27%
1979
21st to endNight
18%15%6%8%5%3444427%
2130
April1st to 10thNight
21%13%49%6%35%5%36%25%
1800
11th to 20thNight
20%13%45%5%25%5%45%32%
1768
21st to endNight
23%14%5%6%6%3445%5%26%
1620
May1st to 10thNight
27%11%35%5%34345%28%
1472
11th to 20thNight
24%10%25%5%34445%33%
1416
21st to endNight
17%9%37%5%36%5%410%31%
1550
June1st to 10thNight
25%7%47%6%35%45%8%26%
1440
11th to 20thNight
21%6%36%5%3445%7%37%
1440
21st to endNight
20%6%36%6%5%6%5%5%8%30%
1440
July1st to 10thNight
16%5%35%5%35%6%6%10%35%
1440
11th to 20thNight
14%5%35%6%45%5%7%10%35%
1440
21st to endNight
15%5%37%7%37%5%7%9%31%
1573
August1st to 10thNight
14%6%36%6%345%5%9%39%
1567
11th to 20thNight
17%8%45%5%345%6%7%34%
1596
21st to endNight
15%5%25%6%36%47%9%38%
1924
September1st to 10thNight
13%6%36%5%35%6%6%8%41%
1800
11th to 20thNight
18%8%25%5%23347%42%
1800
21st to endNight
20%6%26%5%3436%6%38%
2071
October1st to 10thNight
20%6%25%6%345%5%7%38%
2160
11th to 20thNight
19%8%36%6%35%5%6%7%33%
2160
21st to endNight
26%10%47%5%445%45%25%
2440
November1st to 10thNight
19%14%47%6%45%446%27%
2503
11th to 20thNight
19%14%5%7%7%35%5%5%6%23%
2660
21st to endNight
19%17%6%8%6%345%5%6%21%
2660
December1st to 10thNight
20%19%5%10%6%45%45%6%17%
2660
11th to 20thNight
25%16%5%11%7%3433418%
3293
21st to endNight
26%15%6%12%5%2343420%
4884

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
70%7%9%10%4
1517
11th to 20thDay
72%6%10%9%4
1448
21st to endDay
64%5%9%13%8%
1737
February1st to 10thDay
64%410%14%7%1
1620
11th to 20thDay
65%6%9%15%5%
1581
21st to endDay
56%7%11%16%8%1
1404
March1st to 10thDay
62%5%8%16%8%
1892
11th to 20thDay
61%7%10%15%7%2
1980
21st to endDay
64%47%15%8%2
2225
April1st to 10thDay
60%7%8%13%10%3
2160
11th to 20thDay
56%5%8%18%11%1
2139
21st to endDay
60%7%10%15%8%1
2340
May1st to 10thDay
60%7%8%16%8%1
2486
11th to 20thDay
53%7%10%20%10%
2482
21st to endDay
52%8%11%19%9%1
2724
June1st to 10thDay
59%7%12%17%5%1
2520
11th to 20thDay
52%7%11%21%9%1
2520
21st to endDay
57%9%10%15%10%1
2520
July1st to 10thDay
44%9%16%21%9%
2450
11th to 20thDay
44%9%15%23%8%1
2444
21st to endDay
53%9%13%19%7%
2592
August1st to 10thDay
44%10%15%24%7%
2354
11th to 20thDay
49%9%15%20%8%
2304
21st to endDay
41%7%16%26%10%
2431
September1st to 10thDay
45%7%13%24%10%1
2160
11th to 20thDay
48%7%12%21%12%1
2160
21st to endDay
47%6%10%24%12%
1884
October1st to 10thDay
49%7%12%22%10%
1800
11th to 20thDay
56%6%17%16%5%
1800
21st to endDay
63%6%12%14%5%1
1914
November1st to 10thDay
63%6%10%15%5%
1571
11th to 20thDay
65%6%14%11%4
1520
21st to endDay
65%7%16%10%2
1520
December1st to 10thDay
70%6%14%8%2
1520
11th to 20thDay
75%411%7%21
1905
21st to endDay
69%5%16%7%2
2783
January1st to 10thNight
69%5%12%12%3
2649
11th to 20thNight
69%6%11%11%3
2535
21st to endNight
62%6%10%16%6%
2618
February1st to 10thNight
64%410%13%8%1
2340
11th to 20thNight
66%5%10%13%5%1
2276
21st to endNight
58%6%10%17%9%1
1852
March1st to 10thNight
65%5%7%14%8%1
2066
11th to 20thNight
59%6%10%16%8%2
1980
21st to endNight
60%6%8%16%9%2
2130
April1st to 10thNight
62%6%9%13%8%2
1800
11th to 20thNight
54%5%9%18%11%2
1768
21st to endNight
59%7%9%14%10%
1620
May1st to 10thNight
59%5%8%19%8%1
1472
11th to 20thNight
53%5%10%23%9%1
1417
21st to endNight
50%7%15%20%7%1
1551
June1st to 10thNight
57%8%10%20%5%
1440
11th to 20thNight
47%6%12%20%14%
1440
21st to endNight
52%8%13%17%8%1
1440
July1st to 10thNight
42%9%21%21%8%
1401
11th to 20thNight
42%9%18%22%9%1
1392
21st to endNight
48%9%18%19%6%1
1486
August1st to 10thNight
41%7%19%27%5%
1556
11th to 20thNight
48%9%15%22%5%
1596
21st to endNight
40%8%19%25%8%
1924
September1st to 10thNight
40%8%14%28%10%1
1800
11th to 20thNight
44%5%12%27%12%1
1800
21st to endNight
46%7%12%25%10%1
2071
October1st to 10thNight
45%8%13%22%11%
2160
11th to 20thNight
50%5%16%25%4
2160
21st to endNight
61%7%10%15%7%
2440
November1st to 10thNight
59%6%12%16%6%
2503
11th to 20thNight
62%8%13%12%5%
2660
21st to endNight
64%8%15%11%2
2660
December1st to 10thNight
70%5%13%9%2
2660
11th to 20thNight
74%410%9%3
3295
21st to endNight
71%413%10%2
4884

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
30%26%31%11%2
370
11th to 20thDay
28%28%27%12%4
343
21st to endDay
23%31%33%12%1
374
February1st to 10thDay
29%29%31%10%1
340
11th to 20thDay
31%30%27%11%1
336
21st to endDay
22%25%37%12%41
280
March1st to 10thDay
23%27%34%13%2
382
11th to 20thDay
25%30%30%12%3
420
21st to endDay
32%30%24%11%2
462
April1st to 10thDay
35%30%25%8%2
420
11th to 20thDay
32%30%25%10%3
412
21st to endDay
29%21%32%14%3
420
May1st to 10thDay
34%23%26%12%32
569
11th to 20thDay
25%20%33%17%5%1
624
21st to endDay
26%20%35%16%3
680
June1st to 10thDay
34%17%28%17%4
630
11th to 20thDay
24%17%36%18%41
630
21st to endDay
24%13%34%21%6%1
630
July1st to 10thDay
19%12%39%25%5%1
620
11th to 20thDay
15%12%39%25%8%
618
21st to endDay
21%9%35%27%6%1
685
August1st to 10thDay
15%8%39%29%7%2
487
11th to 20thDay
23%12%32%21%10%1
439
21st to endDay
17%11%34%27%9%1
495
September1st to 10thDay
19%17%37%20%6%1
450
11th to 20thDay
28%16%30%21%41
450
21st to endDay
23%19%32%18%7%2
394
October1st to 10thDay
23%16%30%21%8%2
360
11th to 20thDay
25%24%28%15%7%1
360
21st to endDay
28%28%27%12%5%1
396
November1st to 10thDay
30%27%27%12%41
365
11th to 20thDay
36%25%24%12%21
370
21st to endDay
35%30%22%10%21
370
December1st to 10thDay
35%26%29%9%1
370
11th to 20thDay
39%30%24%7%
370
21st to endDay
28%31%27%12%2
407
January1st to 10thNight
27%26%31%15%2
850
11th to 20thNight
26%26%32%14%2
806
21st to endNight
22%27%32%16%3
811
February1st to 10thNight
27%23%32%17%1
720
11th to 20thNight
29%30%26%13%2
703
21st to endNight
22%22%33%18%5%
592
March1st to 10thNight
24%24%33%17%2
720
11th to 20thNight
21%24%27%22%6%
720
21st to endNight
26%22%28%20%3
744
April1st to 10thNight
31%21%28%17%3
540
11th to 20thNight
27%20%30%18%5%
534
21st to endNight
30%17%29%19%5%
540
May1st to 10thNight
33%16%26%18%6%1
540
11th to 20thNight
27%14%30%24%41
532
21st to endNight
22%15%40%19%3
583
June1st to 10thNight
30%12%35%19%4
540
11th to 20thNight
24%11%38%22%4
540
21st to endNight
21%11%36%27%5%
540
July1st to 10thNight
17%8%41%29%6%
526
11th to 20thNight
15%8%38%32%7%
522
21st to endNight
19%7%34%34%6%
590
August1st to 10thNight
15%8%36%33%9%1
538
11th to 20thNight
21%9%30%30%9%1
532
21st to endNight
15%8%31%37%8%1
594
September1st to 10thNight
16%8%40%29%7%
540
11th to 20thNight
23%11%30%28%8%
540
21st to endNight
22%16%32%24%6%1
702
October1st to 10thNight
24%13%29%25%8%
720
11th to 20thNight
22%18%33%20%7%1
720
21st to endNight
33%23%27%14%3
825
November1st to 10thNight
29%23%28%16%31
830
11th to 20thNight
30%25%26%15%41
850
21st to endNight
32%25%26%16%2
850
December1st to 10thNight
30%26%29%12%2
850
11th to 20thNight
33%29%26%9%2
850
21st to endNight
32%28%24%13%21
935
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