Hodgson Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hodgson Observatory clear sky chart from 2005-11-06 to 2024-01-17.

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
38%
24767
20%
74598
11%
24709
46%
24709
28%
46498

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
32%
950
17%
2671
7%
946
40%
946
23%
1824
January11th to 20thNight
30%
935
17%
2476
8%
935
35%
935
22%
1771
January21st to endNight
25%
990
17%
2574
6%
990
33%
990
21%
1857
February1st to 10thNight
28%
900
14%
2340
5%
900
34%
900
24%
1634
February11th to 20thNight
27%
867
16%
2262
6%
863
32%
863
26%
1533
February21st to endNight
34%
592
21%
1776
8%
592
45%
592
25%
1164
March1st to 10thNight
31%
612
18%
2052
9%
612
41%
612
24%
1274
March11th to 20thNight
31%
540
19%
1980
13%
540
40%
540
21%
1235
March21st to endNight
26%
594
13%
2178
8%
594
35%
594
16%
1467
April1st to 10thNight
26%
540
15%
1935
9%
540
37%
540
21%
1214
April11th to 20thNight
26%
533
22%
1599
11%
533
40%
533
23%
1032
April21st to endNight
33%
540
19%
1620
12%
540
44%
540
25%
1056
May1st to 10thNight
36%
540
17%
1620
11%
540
44%
540
28%
1017
May11th to 20thNight
40%
531
19%
1594
10%
531
48%
531
29%
997
May21st to endNight
40%
583
14%
1594
5%
582
44%
582
28%
1049
June1st to 10thNight
56%
540
21%
1393
8%
540
59%
540
43%
824
June11th to 20thNight
47%
540
22%
1260
7%
540
51%
540
47%
760
June21st to endNight
58%
540
21%
1260
8%
540
61%
540
48%
761
July1st to 10thNight
67%
525
19%
1261
9%
525
68%
525
50%
741
July11th to 20thNight
66%
522
24%
1464
13%
522
70%
522
52%
753
July21st to endNight
68%
591
23%
1673
17%
558
70%
558
49%
836
August1st to 10thNight
61%
537
21%
1601
18%
534
64%
534
34%
926
August11th to 20thNight
61%
534
26%
1600
25%
534
68%
534
43%
857
August21st to endNight
60%
594
28%
1782
27%
594
67%
594
46%
929
September1st to 10thNight
54%
540
23%
1870
22%
540
62%
540
36%
978
September11th to 20thNight
51%
540
28%
1980
23%
540
64%
540
37%
990
September21st to endNight
44%
540
29%
1980
20%
540
59%
540
37%
984
October1st to 10thNight
37%
643
26%
2083
17%
643
46%
643
30%
1223
October11th to 20thNight
35%
720
26%
2160
13%
720
45%
720
32%
1264
October21st to endNight
36%
851
25%
2435
11%
851
45%
851
30%
1482
November1st to 10thNight
37%
925
26%
2405
11%
925
47%
925
38%
1427
November11th to 20thNight
31%
950
24%
2579
9%
950
42%
950
31%
1619
November21st to endNight
36%
950
23%
2660
12%
950
43%
950
33%
1617
December1st to 10thNight
29%
950
16%
2660
6%
950
37%
950
26%
1767
December11th to 20thNight
33%
949
16%
3172
7%
949
40%
949
21%
1993
December21st to endNight
24%
1039
10%
5049
7%
1026
35%
1026
10%
3643

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
12%7%36%5%3445%7%43%
74853
Night
11%7%36%5%3445%7%46%
74962
TransparencyDay
41%6%13%25%13%2
74562
Night
38%6%14%26%15%2
74773
SeeingDay
15%9%30%29%13%3
14740
Night
14%8%34%34%10%1
24775

By Month

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 10thDay
8%9%5%9%7%5%7%5%5%6%34%
1489
11th to 20thDay
8%12%5%9%7%45%46%7%32%
1623
21st to endDay
9%12%414%8%47%6%5%7%24%
1782
February1st to 10thDay
11%9%49%9%6%7%447%30%
1620
11th to 20thDay
10%10%47%7%35%46%6%37%
1601
21st to endDay
13%10%47%8%5%5%45%7%33%
1480
March1st to 10thDay
14%9%5%9%424436%39%
1908
11th to 20thDay
13%9%47%7%345%48%34%
1980
21st to endDay
19%13%37%6%35%446%30%
2178
April1st to 10thDay
15%8%46%6%2446%6%38%
2024
11th to 20thDay
19%9%36%434446%37%
2311
21st to endDay
22%7%35%433446%39%
2340
May1st to 10thDay
17%7%25%5%45%45%6%39%
2340
11th to 20thDay
15%7%35%5%45%5%5%7%39%
2302
21st to endDay
18%6%26%5%35%46%8%37%
2681
June1st to 10thDay
12%42442446%9%49%
2562
11th to 20thDay
13%424435%5%5%7%46%
2700
21st to endDay
9%42443446%9%50%
2700
July1st to 10thDay
7%3244345%6%11%52%
2658
11th to 20thDay
7%32332345%7%60%
2444
21st to endDay
6%3243245%6%9%55%
2546
August1st to 10thDay
10%5%25%6%35%5%6%8%44%
2328
11th to 20thDay
10%425%43446%9%50%
2301
21st to endDay
8%42342435%7%57%
2574
September1st to 10thDay
15%424434445%51%
2085
11th to 20thDay
10%424434447%54%
1980
21st to endDay
11%42442346%5%54%
1980
October1st to 10thDay
16%5%25%434345%49%
1859
11th to 20thDay
14%6%24323446%53%
1800
21st to endDay
16%7%36%423345%47%
1918
November1st to 10thDay
10%5%35%42446%6%50%
1673
11th to 20thDay
8%9%39%7%34446%43%
1597
21st to endDay
12%8%36%5%335%5%7%42%
1520
December1st to 10thDay
8%9%39%6%445%6%7%39%
1520
11th to 20thDay
7%11%5%9%7%5%46%6%6%34%
1918
21st to endDay
15%9%5%13%6%45%5%5%7%26%
2531
January1st to 10thNight
7%7%38%7%6%6%6%5%8%36%
2671
11th to 20thNight
8%10%49%8%4446%7%35%
2476
21st to endNight
9%12%48%5%35%45%7%35%
2574
February1st to 10thNight
10%10%47%6%35%45%7%38%
2340
11th to 20thNight
9%10%47%5%345%5%7%42%
2261
21st to endNight
10%9%36%5%35%5%5%6%44%
1776
March1st to 10thNight
11%6%36%6%4445%6%44%
2052
11th to 20thNight
13%9%45%5%3445%6%43%
1980
21st to endNight
16%10%47%5%45%45%7%36%
2178
April1st to 10thNight
15%6%36%5%345%5%7%41%
1935
11th to 20thNight
16%8%36%42345%7%42%
1599
21st to endNight
19%6%25%425%45%7%41%
1620
May1st to 10thNight
15%6%2443446%8%44%
1620
11th to 20thNight
14%5%25%5%3445%8%46%
1593
21st to endNight
14%5%35%6%35%5%5%8%41%
1593
June1st to 10thNight
8%42343346%9%54%
1393
11th to 20thNight
9%3243235%7%9%53%
1260
21st to endNight
7%2133345%6%9%57%
1260
July1st to 10thNight
5%22343346%8%60%
1298
11th to 20thNight
421242436%7%65%
1512
21st to endNight
32133245%7%9%60%
1772
August1st to 10thNight
7%4245%346%6%8%50%
1611
11th to 20thNight
7%32332345%8%60%
1600
21st to endNight
5%32342336%9%60%
1782
September1st to 10thNight
9%42433335%6%58%
1870
11th to 20thNight
10%32332346%7%58%
1980
21st to endNight
10%323323447%60%
1980
October1st to 10thNight
17%41443235%452%
2083
11th to 20thNight
12%6%34323446%54%
2160
21st to endNight
14%6%24423445%52%
2435
November1st to 10thNight
8%5%245%245%6%7%54%
2405
11th to 20thNight
10%6%27%5%3445%7%48%
2579
21st to endNight
9%7%25%43445%7%49%
2660
December1st to 10thNight
8%8%47%6%345%5%7%41%
2660
11th to 20thNight
10%8%37%7%35%45%7%41%
3279
21st to endNight
16%10%5%13%7%3445%5%28%
5115

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
52%417%18%9%
1490
11th to 20thDay
51%6%14%20%8%
1623
21st to endDay
59%7%13%16%5%1
1782
February1st to 10thDay
55%5%14%16%9%
1620
11th to 20thDay
48%5%14%21%12%1
1610
21st to endDay
51%6%12%20%10%2
1480
March1st to 10thDay
47%5%12%24%10%1
1908
11th to 20thDay
50%6%11%23%10%
1980
21st to endDay
55%7%14%17%5%1
2178
April1st to 10thDay
46%5%13%25%10%1
2024
11th to 20thDay
48%5%11%21%14%2
2311
21st to endDay
47%5%12%24%12%1
2340
May1st to 10thDay
46%6%12%23%13%1
2340
11th to 20thDay
44%6%13%24%11%1
2306
21st to endDay
45%7%13%21%13%1
2681
June1st to 10thDay
33%7%15%29%14%2
2562
11th to 20thDay
36%7%13%24%16%3
2700
21st to endDay
30%7%15%31%14%3
2700
July1st to 10thDay
27%8%17%32%15%1
2586
11th to 20thDay
24%6%12%31%20%7%
2369
21st to endDay
25%7%14%34%18%3
2405
August1st to 10thDay
36%7%16%27%12%2
2314
11th to 20thDay
31%7%14%34%13%1
2301
21st to endDay
27%7%12%30%19%5%
2574
September1st to 10thDay
36%5%9%28%19%2
2085
11th to 20thDay
30%6%14%32%16%2
1980
21st to endDay
30%7%12%30%21%1
1980
October1st to 10thDay
39%410%27%18%2
1859
11th to 20thDay
33%411%31%18%4
1800
21st to endDay
41%411%24%17%2
1918
November1st to 10thDay
34%5%18%26%16%2
1673
11th to 20thDay
41%5%15%24%14%1
1597
21st to endDay
41%5%15%24%14%1
1520
December1st to 10thDay
44%5%17%22%10%2
1520
11th to 20thDay
50%6%17%22%5%
1915
21st to endDay
57%6%12%18%6%1
2531
January1st to 10thNight
45%6%14%23%12%1
2671
11th to 20thNight
48%6%16%22%7%1
2476
21st to endNight
48%7%15%20%9%1
2574
February1st to 10thNight
47%5%13%24%11%1
2340
11th to 20thNight
43%5%13%23%13%3
2262
21st to endNight
42%5%12%24%13%3
1776
March1st to 10thNight
41%5%15%28%9%2
2052
11th to 20thNight
42%6%11%25%14%2
1980
21st to endNight
49%6%13%22%8%1
2178
April1st to 10thNight
42%6%13%22%15%1
1935
11th to 20thNight
42%5%9%25%17%2
1599
21st to endNight
43%5%12%24%14%2
1620
May1st to 10thNight
38%6%14%26%15%2
1620
11th to 20thNight
38%6%13%25%18%1
1594
21st to endNight
40%6%14%23%14%3
1594
June1st to 10thNight
26%7%16%29%19%3
1393
11th to 20thNight
26%6%18%25%21%5%
1260
21st to endNight
23%7%16%30%21%3
1260
July1st to 10thNight
22%7%16%33%19%4
1261
11th to 20thNight
19%6%14%32%22%7%
1464
21st to endNight
19%6%17%31%22%5%
1673
August1st to 10thNight
30%7%15%29%16%3
1601
11th to 20thNight
24%6%14%34%19%3
1600
21st to endNight
22%6%15%27%24%6%
1782
September1st to 10thNight
27%5%13%27%22%5%
1870
11th to 20thNight
25%6%13%34%20%2
1980
21st to endNight
25%6%10%35%22%3
1980
October1st to 10thNight
35%5%11%27%21%1
2083
11th to 20thNight
33%49%28%22%4
2160
21st to endNight
36%413%24%21%1
2435
November1st to 10thNight
29%5%15%24%22%4
2405
11th to 20thNight
36%6%14%26%17%2
2579
21st to endNight
34%5%14%29%17%1
2660
December1st to 10thNight
42%5%16%27%10%
2660
11th to 20thNight
42%5%20%26%7%
3281
21st to endNight
58%5%10%19%7%
5115

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
14%13%33%25%12%3
270
11th to 20thDay
19%10%35%28%7%1
258
21st to endDay
15%10%39%27%8%1
264
February1st to 10thDay
12%19%37%29%3
240
11th to 20thDay
15%15%41%24%41
240
21st to endDay
21%13%40%20%6%
198
March1st to 10thDay
17%16%35%28%32
240
11th to 20thDay
21%10%38%22%8%1
240
21st to endDay
29%13%36%17%5%1
264
April1st to 10thDay
24%14%38%19%5%
284
11th to 20thDay
24%14%32%22%7%1
589
21st to endDay
24%13%32%20%9%2
600
May1st to 10thDay
21%12%29%28%9%2
603
11th to 20thDay
21%10%29%26%12%3
625
21st to endDay
21%7%30%28%11%2
679
June1st to 10thDay
10%7%21%37%21%5%
630
11th to 20thDay
12%5%34%31%15%3
630
21st to endDay
9%7%30%35%17%2
630
July1st to 10thDay
6%318%40%26%6%
621
11th to 20thDay
8%429%34%20%4
618
21st to endDay
5%327%40%22%4
684
August1st to 10thDay
11%321%40%21%4
626
11th to 20thDay
11%422%35%23%5%
615
21st to endDay
8%427%34%22%4
693
September1st to 10thDay
18%5%27%31%15%5%
375
11th to 20thDay
9%437%30%16%4
270
21st to endDay
16%12%35%24%11%2
270
October1st to 10thDay
20%8%26%29%13%4
270
11th to 20thDay
16%17%34%22%9%1
270
21st to endDay
21%15%37%19%7%
297
November1st to 10thDay
18%11%33%26%8%4
270
11th to 20thDay
13%19%40%21%7%
270
21st to endDay
20%15%31%24%9%1
270
December1st to 10thDay
11%11%39%26%11%1
270
11th to 20thDay
14%14%41%23%7%
270
21st to endDay
23%14%36%24%3
297
January1st to 10thNight
13%10%37%31%9%1
950
11th to 20thNight
13%12%34%33%7%1
935
21st to endNight
16%11%39%28%6%1
990
February1st to 10thNight
15%10%39%30%6%
900
11th to 20thNight
15%12%39%28%6%
867
21st to endNight
14%9%37%31%8%1
592
March1st to 10thNight
13%10%38%31%7%
612
11th to 20thNight
18%10%36%31%5%
540
21st to endNight
20%12%36%24%8%1
594
April1st to 10thNight
19%12%40%26%3
540
11th to 20thNight
20%13%36%25%5%1
533
21st to endNight
22%10%33%26%9%1
540
May1st to 10thNight
18%8%34%31%8%1
540
11th to 20thNight
17%9%31%32%12%
531
21st to endNight
16%7%32%35%10%
584
June1st to 10thNight
8%5%26%44%16%1
540
11th to 20thNight
10%336%38%13%
540
21st to endNight
6%427%46%17%
540
July1st to 10thNight
6%219%45%27%
525
11th to 20thNight
4223%53%17%1
522
21st to endNight
4221%55%17%1
591
August1st to 10thNight
8%320%45%22%1
537
11th to 20thNight
7%423%42%23%1
534
21st to endNight
6%227%43%19%2
594
September1st to 10thNight
10%5%26%41%17%1
540
11th to 20thNight
10%6%30%39%14%2
540
21st to endNight
11%5%38%34%12%1
540
October1st to 10thNight
19%7%32%31%11%1
643
11th to 20thNight
16%12%35%31%7%1
720
21st to endNight
18%12%31%30%10%
851
November1st to 10thNight
11%10%38%32%10%1
925
11th to 20thNight
13%11%40%29%6%
950
21st to endNight
13%9%37%33%8%
950
December1st to 10thNight
14%11%38%32%6%
950
11th to 20thNight
17%6%35%33%8%1
950
21st to endNight
21%11%34%27%6%
1045
Page generated at 2024-01-14 08:55:03. Version ac07

Copyright 2024 Attilla Danko


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