North Point Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the North Point Observatory clear sky chart from 2005-11-06 to 2024-01-16.

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
59%
23640
27%
74839
22%
23592
65%
23592
36%
41444

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
50%
756
18%
2537
16%
756
55%
756
22%
1622
January11th to 20thNight
52%
744
20%
2416
16%
744
59%
744
25%
1498
January21st to endNight
55%
792
24%
2574
24%
792
59%
792
27%
1542
February1st to 10thNight
54%
720
26%
2340
24%
720
61%
720
29%
1370
February11th to 20thNight
49%
700
25%
2221
19%
700
58%
700
28%
1292
February21st to endNight
46%
592
27%
1776
19%
592
57%
592
31%
1027
March1st to 10thNight
42%
720
18%
1995
12%
720
48%
720
24%
1351
March11th to 20thNight
50%
720
24%
1980
18%
720
56%
720
29%
1262
March21st to endNight
44%
792
21%
2160
11%
792
52%
792
34%
1307
April1st to 10thNight
44%
720
25%
1800
12%
720
50%
720
36%
1114
April11th to 20thNight
46%
711
30%
1779
12%
711
55%
711
40%
1035
April21st to endNight
50%
720
31%
1800
12%
720
59%
720
50%
971
May1st to 10thNight
54%
604
29%
1684
15%
604
61%
604
47%
883
May11th to 20thNight
59%
488
28%
1551
21%
488
66%
488
48%
733
May21st to endNight
60%
388
27%
1552
23%
388
71%
388
38%
682
June1st to 10thNight
62%
360
25%
1440
24%
360
72%
360
38%
650
June11th to 20thNight
71%
360
36%
1440
37%
360
83%
360
55%
524
June21st to endNight
76%
360
33%
1440
39%
360
83%
360
54%
557
July1st to 10thNight
81%
350
32%
1400
39%
350
86%
350
55%
527
July11th to 20thNight
80%
509
30%
1553
29%
509
81%
509
50%
720
July21st to endNight
71%
591
31%
1674
29%
558
73%
558
43%
847
August1st to 10thNight
68%
537
29%
1602
24%
534
70%
534
42%
828
August11th to 20thNight
75%
614
34%
1682
22%
614
78%
614
50%
877
August21st to endNight
75%
792
34%
1980
22%
792
76%
792
56%
1063
September1st to 10thNight
81%
720
42%
1800
28%
720
83%
720
67%
874
September11th to 20thNight
68%
720
37%
1800
25%
720
74%
720
54%
988
September21st to endNight
72%
720
38%
2059
33%
720
79%
720
56%
994
October1st to 10thNight
67%
720
32%
2160
28%
720
77%
720
51%
1051
October11th to 20thNight
67%
720
35%
2160
33%
720
74%
720
45%
1113
October21st to endNight
69%
792
36%
2376
35%
792
74%
792
44%
1220
November1st to 10thNight
62%
740
31%
2242
27%
740
69%
740
40%
1215
November11th to 20thNight
62%
760
26%
2474
25%
760
67%
760
34%
1365
November21st to endNight
60%
760
26%
2660
27%
760
66%
760
34%
1405
December1st to 10thNight
52%
760
22%
2660
20%
760
59%
760
25%
1615
December11th to 20thNight
48%
760
18%
3248
19%
759
55%
759
15%
2289
December21st to endNight
43%
828
14%
4824
17%
817
52%
817
13%
3033

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
7%5%24423447%57%
74716
Night
9%5%2442445%8%53%
75103
TransparencyDay
28%48%20%24%16%
74436
Night
30%49%20%22%15%
74905
SeeingDay
9%11%24%31%20%5%
14255
Night
10%6%16%34%29%5%
23657

By Month

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 10thDay
18%10%37%5%3445%6%34%
1623
11th to 20thDay
12%7%26%6%34447%45%
1666
21st to endDay
11%6%37%7%445%5%8%39%
1782
February1st to 10thDay
14%6%26%435%5%5%6%45%
1620
11th to 20thDay
12%6%45%4345%48%43%
1626
21st to endDay
14%4244345%5%5%49%
1480
March1st to 10thDay
13%8%36%5%35%5%6%8%38%
1962
11th to 20thDay
14%7%36%5%35%46%7%38%
1980
21st to endDay
11%425%5%35%5%6%9%45%
2195
April1st to 10thDay
10%7%45%5%35%46%8%43%
2160
11th to 20thDay
7%5%24434448%55%
2129
21st to endDay
442443336%9%59%
2160
May1st to 10thDay
45%25%323347%63%
2272
11th to 20thDay
4415%323348%63%
2341
21st to endDay
4425%433447%60%
2723
June1st to 10thDay
5%424323348%60%
2520
11th to 20thDay
121321235%7%73%
2520
21st to endDay
2313313236%73%
2520
July1st to 10thDay
1312322236%73%
2520
11th to 20thDay
1423323346%69%
2350
21st to endDay
1323213237%73%
2546
August1st to 10thDay
1424323348%66%
2328
11th to 20thDay
1423312347%71%
2219
21st to endDay
15%24423346%67%
2376
September1st to 10thDay
1313212236%75%
2160
11th to 20thDay
26%14423447%64%
2160
21st to endDay
2312222335%74%
1896
October1st to 10thDay
3313414337%67%
1800
11th to 20thDay
7%42432335%7%61%
1800
21st to endDay
7%5%24423347%59%
1980
November1st to 10thDay
9%4234245%5%8%54%
1836
11th to 20thDay
8%8%47%5%3345%7%46%
1704
21st to endDay
10%6%234345%5%6%51%
1520
December1st to 10thDay
15%6%45%42446%6%44%
1520
11th to 20thDay
24%10%48%6%3435%5%29%
1928
21st to endDay
22%8%35%5%35%45%8%31%
2794
January1st to 10thNight
15%7%36%5%345%6%9%37%
2537
11th to 20thNight
13%7%46%5%3345%7%44%
2416
21st to endNight
14%6%244345%48%46%
2574
February1st to 10thNight
14%5%25%424447%49%
2340
11th to 20thNight
10%5%44435%5%5%8%48%
2219
21st to endNight
12%5%2442345%6%53%
1776
March1st to 10thNight
14%8%36%5%35%45%6%41%
1995
11th to 20thNight
12%6%25%5%445%6%9%42%
1980
21st to endNight
13%425%423337%53%
2160
April1st to 10thNight
8%5%26%5%25%45%8%51%
1800
11th to 20thNight
7%42432335%7%59%
1779
21st to endNight
432332335%9%63%
1800
May1st to 10thNight
332442345%7%62%
1684
11th to 20thNight
23235%33449%62%
1550
21st to endNight
4424433448%61%
1552
June1st to 10thNight
332433446%9%60%
1440
11th to 20thNight
111232225%8%73%
1440
21st to endNight
1223323347%70%
1440
July1st to 10thNight
1214333338%70%
1440
11th to 20thNight
222342345%9%63%
1606
21st to endNight
15%25%5%345%6%11%52%
1773
August1st to 10thNight
35%25%5%35%45%9%54%
1611
11th to 20thNight
13245%245%6%11%58%
1682
21st to endNight
1425%424448%63%
1980
September1st to 10thNight
1213222449%70%
1800
11th to 20thNight
25%25%5%2345%7%61%
1800
21st to endNight
1223423348%67%
2059
October1st to 10thNight
4423322346%67%
2160
11th to 20thNight
342443445%8%60%
2160
21st to endNight
7%42432345%7%60%
2376
November1st to 10thNight
7%4335%23449%56%
2242
11th to 20thNight
9%5%35%5%235%5%8%50%
2474
21st to endNight
8%4245%33347%56%
2660
December1st to 10thNight
14%6%36%43445%8%44%
2660
11th to 20thNight
27%8%35%43346%7%31%
3276
21st to endNight
18%7%36%6%35%5%6%7%34%
4862

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
50%5%12%19%10%4
1623
11th to 20thDay
42%5%9%16%18%10%
1666
21st to endDay
44%5%9%16%19%7%
1782
February1st to 10thDay
41%37%21%20%8%
1620
11th to 20thDay
38%5%9%21%20%7%
1635
21st to endDay
38%48%25%17%8%
1480
March1st to 10thDay
45%412%20%16%3
1962
11th to 20thDay
44%5%10%22%15%5%
1980
21st to endDay
36%7%14%22%17%4
2195
April1st to 10thDay
38%5%14%20%18%4
2160
11th to 20thDay
29%5%14%25%21%5%
2132
21st to endDay
23%414%31%25%4
2160
May1st to 10thDay
22%49%29%29%7%
2272
11th to 20thDay
21%38%34%25%9%
2344
21st to endDay
25%414%29%24%4
2724
June1st to 10thDay
24%311%27%28%7%
2520
11th to 20thDay
13%210%22%36%17%
2520
21st to endDay
14%3316%36%29%
2520
July1st to 10thDay
13%3311%27%44%
2451
11th to 20thDay
16%4411%26%39%
2280
21st to endDay
14%3210%27%44%
2405
August1st to 10thDay
18%4314%31%30%
2312
11th to 20thDay
15%3212%36%33%
2219
21st to endDay
18%4214%32%30%
2376
September1st to 10thDay
13%2211%32%40%
2160
11th to 20thDay
21%3424%34%14%
2160
21st to endDay
14%2423%33%23%
1896
October1st to 10thDay
20%45%17%31%23%
1800
11th to 20thDay
25%48%19%24%21%
1800
21st to endDay
27%47%22%24%17%
1980
November1st to 10thDay
29%5%9%27%19%11%
1836
11th to 20thDay
39%5%9%22%18%7%
1704
21st to endDay
33%410%21%21%11%
1520
December1st to 10thDay
41%49%21%18%8%
1520
11th to 20thDay
59%37%12%15%3
1928
21st to endDay
51%414%19%9%3
2794
January1st to 10thNight
44%414%22%11%5%
2537
11th to 20thNight
41%411%18%14%12%
2416
21st to endNight
37%5%12%15%20%10%
2574
February1st to 10thNight
37%48%21%20%11%
2340
11th to 20thNight
35%410%21%21%9%
2221
21st to endNight
33%411%27%20%6%
1776
March1st to 10thNight
44%5%11%19%17%5%
1995
11th to 20thNight
40%48%23%20%6%
1980
21st to endNight
34%414%23%19%6%
2160
April1st to 10thNight
33%414%22%21%6%
1800
11th to 20thNight
27%412%28%20%10%
1779
21st to endNight
20%311%32%26%7%
1800
May1st to 10thNight
23%310%23%30%11%
1684
11th to 20thNight
20%412%27%28%8%
1551
21st to endNight
22%316%29%24%6%
1552
June1st to 10thNight
22%5%10%22%32%9%
1440
11th to 20thNight
12%38%23%34%20%
1440
21st to endNight
15%2314%35%31%
1440
July1st to 10thNight
14%3210%28%43%
1400
11th to 20thNight
19%45%10%22%41%
1553
21st to endNight
25%4310%19%39%
1674
August1st to 10thNight
26%4215%25%28%
1602
11th to 20thNight
20%5%210%27%34%
1682
21st to endNight
19%4414%26%33%
1980
September1st to 10thNight
13%229%32%41%
1800
11th to 20thNight
21%45%21%31%18%
1800
21st to endNight
16%3420%29%27%
2059
October1st to 10thNight
19%46%17%28%26%
2160
11th to 20thNight
23%46%21%21%25%
2160
21st to endNight
24%36%21%25%20%
2376
November1st to 10thNight
28%49%28%18%12%
2242
11th to 20thNight
32%412%26%18%8%
2474
21st to endNight
29%5%9%22%23%12%
2660
December1st to 10thNight
40%5%8%18%18%11%
2660
11th to 20thNight
54%49%15%15%4
3276
21st to endNight
51%314%18%11%3
4862

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
28%10%31%18%11%2
284
11th to 20thDay
19%13%21%27%17%3
356
21st to endDay
13%10%25%31%19%3
374
February1st to 10thDay
18%12%21%26%19%4
340
11th to 20thDay
17%16%27%24%14%3
358
21st to endDay
13%19%25%25%17%2
346
March1st to 10thDay
19%16%30%22%10%2
420
11th to 20thDay
20%13%29%20%13%5%
420
21st to endDay
12%21%32%22%12%2
462
April1st to 10thDay
13%17%31%25%11%3
420
11th to 20thDay
11%20%31%21%13%4
412
21st to endDay
5%21%28%27%13%6%
420
May1st to 10thDay
6%19%29%28%17%1
423
11th to 20thDay
7%17%30%26%15%5%
448
21st to endDay
6%13%27%30%18%5%
485
June1st to 10thDay
8%11%29%29%17%6%
450
11th to 20thDay
410%31%38%14%3
450
21st to endDay
5%26%41%24%4
450
July1st to 10thDay
3323%48%20%3
446
11th to 20thDay
217%45%30%7%
444
21st to endDay
1117%50%24%6%
487
August1st to 10thDay
3422%44%23%4
447
11th to 20thDay
2123%40%25%8%
437
21st to endDay
3219%44%26%7%
495
September1st to 10thDay
1418%38%28%10%
450
11th to 20thDay
48%22%35%24%7%
450
21st to endDay
38%23%31%29%7%
450
October1st to 10thDay
48%24%29%22%12%
450
11th to 20thDay
6%9%21%22%32%11%
450
21st to endDay
11%7%21%26%25%10%
495
November1st to 10thDay
11%10%18%21%33%8%
432
11th to 20thDay
7%12%15%32%26%8%
266
21st to endDay
11%9%23%34%21%3
180
December1st to 10thDay
19%13%18%27%15%7%
180
11th to 20thDay
18%18%21%24%16%3
180
21st to endDay
20%14%23%30%12%1
198
January1st to 10thNight
19%9%13%30%24%5%
760
11th to 20thNight
17%7%14%34%23%5%
744
21st to endNight
16%7%14%34%25%4
792
February1st to 10thNight
16%8%14%34%24%4
720
11th to 20thNight
12%11%19%30%23%5%
704
21st to endNight
15%12%21%29%21%3
592
March1st to 10thNight
17%11%21%28%20%3
720
11th to 20thNight
15%9%18%31%23%4
720
21st to endNight
14%9%26%32%18%2
792
April1st to 10thNight
11%9%26%32%19%3
720
11th to 20thNight
10%14%24%26%21%5%
711
21st to endNight
6%12%28%28%24%3
720
May1st to 10thNight
5%6%26%31%27%4
604
11th to 20thNight
3423%33%33%3
488
21st to endNight
5%8%18%36%30%3
389
June1st to 10thNight
35%23%39%28%1
360
11th to 20thNight
15%18%51%23%2
360
21st to endNight
2116%45%35%1
360
July1st to 10thNight
2110%44%40%3
350
11th to 20thNight
31440%43%10%
509
21st to endNight
216%42%44%5%
591
August1st to 10thNight
419%38%41%6%
537
11th to 20thNight
211%41%39%7%
614
21st to endNight
318%39%42%8%
792
September1st to 10thNight
119%38%43%8%
720
11th to 20thNight
4313%37%36%7%
720
21st to endNight
35%13%34%38%8%
720
October1st to 10thNight
5%417%31%34%9%
720
11th to 20thNight
5%415%32%35%8%
720
21st to endNight
9%411%30%34%12%
792
November1st to 10thNight
7%6%16%27%35%9%
740
11th to 20thNight
12%413%34%31%7%
760
21st to endNight
11%5%16%36%26%6%
760
December1st to 10thNight
17%6%17%31%24%6%
760
11th to 20thNight
23%8%14%31%20%4
760
21st to endNight
19%9%20%31%19%1
836
Page generated at 2024-01-13 06:37:56. Version ac07

Copyright 2024 Attilla Danko


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