Humble ISD Astronomical Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Humble ISD Astronomical Observatory clear sky chart from 2005-11-06 to 2024-01-15.

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
51%
23698
23%
74269
17%
23639
57%
23639
29%
44859

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
34%
950
25%
2458
10%
946
43%
946
30%
1607
January11th to 20thNight
35%
923
24%
2399
10%
923
43%
923
29%
1577
January21st to endNight
34%
990
25%
2574
10%
990
41%
990
27%
1735
February1st to 10thNight
28%
843
20%
2283
8%
843
35%
843
23%
1572
February11th to 20thNight
31%
674
19%
2068
9%
670
38%
670
23%
1350
February21st to endNight
23%
444
23%
1628
10%
444
36%
444
16%
1078
March1st to 10thNight
32%
540
22%
1980
14%
540
43%
540
21%
1242
March11th to 20thNight
35%
540
20%
1980
14%
540
44%
540
20%
1244
March21st to endNight
37%
594
23%
2178
16%
594
48%
594
25%
1261
April1st to 10thNight
34%
540
20%
1980
15%
540
44%
540
20%
1247
April11th to 20thNight
34%
533
23%
1804
15%
533
47%
533
23%
1116
April21st to endNight
38%
540
24%
1800
19%
540
49%
540
25%
1096
May1st to 10thNight
41%
540
20%
1769
17%
540
48%
540
23%
1102
May11th to 20thNight
49%
531
22%
1594
21%
531
54%
531
31%
978
May21st to endNight
59%
583
21%
1745
20%
582
64%
582
32%
1061
June1st to 10thNight
75%
540
23%
1620
25%
540
77%
540
44%
861
June11th to 20thNight
77%
540
22%
1620
23%
540
81%
540
45%
857
June21st to endNight
70%
540
17%
1620
20%
540
70%
540
32%
989
July1st to 10thNight
78%
525
14%
1575
18%
525
79%
525
31%
971
July11th to 20thNight
84%
522
22%
1566
26%
522
85%
522
43%
845
July21st to endNight
83%
591
18%
1673
22%
558
84%
558
38%
943
August1st to 10thNight
89%
537
24%
1601
27%
534
90%
534
57%
754
August11th to 20thNight
85%
534
22%
1695
26%
534
85%
534
41%
901
August21st to endNight
78%
594
17%
1994
21%
594
79%
594
31%
1186
September1st to 10thNight
75%
540
17%
1980
21%
540
76%
540
30%
1118
September11th to 20thNight
66%
540
21%
1980
24%
540
67%
540
25%
1197
September21st to endNight
71%
540
27%
1980
31%
540
73%
540
32%
1070
October1st to 10thNight
73%
638
30%
2078
28%
638
74%
638
41%
1085
October11th to 20thNight
61%
720
33%
2160
23%
720
67%
720
40%
1196
October21st to endNight
54%
792
33%
2376
24%
792
60%
792
38%
1323
November1st to 10thNight
58%
740
27%
2220
22%
740
62%
740
36%
1270
November11th to 20thNight
49%
760
28%
2280
19%
760
56%
760
32%
1354
November21st to endNight
41%
802
27%
2322
17%
802
48%
802
28%
1484
December1st to 10thNight
40%
950
25%
2470
14%
950
46%
950
27%
1692
December11th to 20thNight
35%
949
22%
2882
10%
948
40%
948
21%
1940
December21st to endNight
33%
1039
14%
4337
10%
1026
39%
1026
18%
2557

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%6%36%6%45%6%6%8%40%
74977
Night
12%6%2443445%8%48%
74825
TransparencyDay
41%8%12%17%15%7%
74702
Night
35%6%13%20%17%9%
74620
SeeingDay
12%7%20%27%24%10%
13728
Night
15%6%22%33%22%2
23706

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
19%7%35%42445%6%42%
1707
11th to 20thDay
18%7%35%423345%44%
1656
21st to endDay
18%7%35%6%24346%42%
1782
February1st to 10thDay
23%9%35%434345%36%
1692
11th to 20thDay
21%9%36%5%33445%37%
1776
21st to endDay
19%9%36%5%24346%38%
1628
March1st to 10thDay
20%9%36%5%35%447%34%
1980
11th to 20thDay
18%8%36%5%35%5%5%5%38%
1980
21st to endDay
16%6%36%6%3445%6%41%
2178
April1st to 10thDay
16%7%27%6%45%5%46%37%
1980
11th to 20thDay
18%8%35%5%35%35%7%38%
2102
21st to endDay
9%6%27%6%45%5%6%7%43%
2160
May1st to 10thDay
10%5%37%8%46%5%7%7%39%
2186
11th to 20thDay
9%6%26%6%45%5%6%9%40%
2302
21st to endDay
9%6%36%7%48%8%8%10%30%
2531
June1st to 10thDay
6%5%36%7%47%7%7%10%41%
2340
11th to 20thDay
5%325%6%5%7%8%9%11%39%
2340
21st to endDay
7%6%37%9%6%9%9%7%8%29%
2340
July1st to 10thDay
10%5%36%7%5%8%8%9%11%29%
2340
11th to 20thDay
5%436%6%5%7%8%9%12%34%
2340
21st to endDay
4436%7%47%8%9%13%35%
2546
August1st to 10thDay
32246%5%7%7%10%13%40%
2328
11th to 20thDay
5%425%6%5%7%8%9%10%39%
2204
21st to endDay
8%436%7%47%7%8%11%34%
2357
September1st to 10thDay
6%437%7%46%7%8%10%38%
1980
11th to 20thDay
14%6%36%7%46%6%6%7%36%
1980
21st to endDay
8%6%35%6%35%5%6%8%46%
1980
October1st to 10thDay
7%4145%35%45%8%54%
1863
11th to 20thDay
10%425%6%35%5%47%49%
1800
21st to endDay
14%424423346%53%
1980
November1st to 10thDay
10%6%36%5%445%5%7%47%
1858
11th to 20thDay
11%6%36%5%3445%6%47%
1900
21st to endDay
16%7%37%6%34447%41%
1855
December1st to 10thDay
15%8%46%5%45%447%39%
1710
11th to 20thDay
14%7%45%435%6%5%6%41%
2161
21st to endDay
17%7%25%434446%44%
3135
January1st to 10thNight
19%7%24423346%46%
2458
11th to 20thNight
20%6%34423335%48%
2399
21st to endNight
19%7%35%433436%43%
2574
February1st to 10thNight
19%9%36%5%23347%39%
2283
11th to 20thNight
21%8%34423335%43%
2068
21st to endNight
22%8%35%42445%438%
1628
March1st to 10thNight
20%8%35%32336%7%40%
1980
11th to 20thNight
17%7%36%5%3445%7%40%
1980
21st to endNight
15%7%25%433346%48%
2178
April1st to 10thNight
14%6%36%6%345%6%8%39%
1980
11th to 20thNight
19%6%24424447%44%
1804
21st to endNight
14%6%36%5%35%447%46%
1800
May1st to 10thNight
12%7%36%5%35%5%5%9%41%
1769
11th to 20thNight
9%7%246%3445%9%46%
1593
21st to endNight
7%5%245%25%6%7%10%46%
1745
June1st to 10thNight
5%31332446%10%57%
1620
11th to 20thNight
42133345%7%11%57%
1620
21st to endNight
5%435%5%45%6%9%11%43%
1620
July1st to 10thNight
6%4245%45%6%8%12%45%
1620
11th to 20thNight
3313325%47%12%57%
1620
21st to endNight
32235%25%6%7%12%52%
1772
August1st to 10thNight
221232336%12%65%
1611
11th to 20thNight
43124245%7%14%53%
1695
21st to endNight
5%325%6%45%6%8%11%45%
1994
September1st to 10thNight
5%435%4346%7%10%48%
1980
11th to 20thNight
11%6%36%5%3446%8%45%
1980
21st to endNight
8%5%24425%45%8%54%
1980
October1st to 10thNight
5%3244245%5%7%60%
2078
11th to 20thNight
10%42332345%6%57%
2160
21st to endNight
12%5%24323335%59%
2376
November1st to 10thNight
10%5%24434446%55%
2220
11th to 20thNight
12%5%244345%47%50%
2280
21st to endNight
17%6%345%2445%6%45%
2322
December1st to 10thNight
18%7%345%34446%42%
2470
11th to 20thNight
17%7%36%5%34445%43%
3036
21st to endNight
16%7%25%5%2435%5%45%
4532

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
43%5%6%15%21%10%
1708
11th to 20thDay
43%5%5%15%20%11%
1656
21st to endDay
45%36%15%18%13%
1782
February1st to 10thDay
52%45%12%15%11%
1692
11th to 20thDay
50%47%12%17%9%
1786
21st to endDay
47%6%9%14%14%11%
1628
March1st to 10thDay
50%8%7%12%17%6%
1980
11th to 20thDay
47%5%9%11%18%9%
1980
21st to endDay
43%5%8%15%21%7%
2178
April1st to 10thDay
47%7%7%16%15%8%
1980
11th to 20thDay
46%5%8%14%17%9%
2102
21st to endDay
39%7%9%18%20%6%
2160
May1st to 10thDay
43%7%10%16%17%7%
2186
11th to 20thDay
39%9%10%22%17%4
2306
21st to endDay
44%10%14%19%12%1
2531
June1st to 10thDay
35%10%16%22%15%1
2340
11th to 20thDay
34%11%17%23%14%2
2340
21st to endDay
48%12%15%18%8%1
2340
July1st to 10thDay
42%13%20%20%5%
2276
11th to 20thDay
37%14%21%20%7%
2271
21st to endDay
35%14%22%24%41
2405
August1st to 10thDay
29%13%21%27%9%
2314
11th to 20thDay
36%12%19%23%8%1
2204
21st to endDay
40%14%18%19%7%2
2357
September1st to 10thDay
38%12%16%16%13%5%
1980
11th to 20thDay
46%8%14%15%14%4
1980
21st to endDay
35%7%13%18%17%10%
1980
October1st to 10thDay
29%6%10%22%19%14%
1863
11th to 20thDay
34%6%8%16%20%15%
1800
21st to endDay
33%5%6%14%25%17%
1980
November1st to 10thDay
36%5%10%18%21%10%
1858
11th to 20thDay
38%6%9%12%22%12%
1900
21st to endDay
45%5%7%15%18%11%
1855
December1st to 10thDay
46%48%17%17%7%
1710
11th to 20thDay
42%6%9%13%21%9%
2159
21st to endDay
41%5%6%16%21%11%
3135
January1st to 10thNight
40%47%17%21%12%
2458
11th to 20thNight
41%36%17%20%13%
2399
21st to endNight
44%45%16%18%14%
2574
February1st to 10thNight
47%47%12%17%13%
2283
11th to 20thNight
45%48%13%18%12%
2068
21st to endNight
49%5%5%14%14%13%
1628
March1st to 10thNight
44%5%10%16%17%9%
1980
11th to 20thNight
43%6%11%13%19%8%
1980
21st to endNight
38%412%16%19%10%
2178
April1st to 10thNight
42%7%10%17%15%9%
1980
11th to 20thNight
41%5%10%16%15%13%
1804
21st to endNight
39%6%9%20%19%7%
1800
May1st to 10thNight
40%7%11%18%16%8%
1769
11th to 20thNight
34%8%12%22%19%4
1594
21st to endNight
31%10%19%27%12%1
1746
June1st to 10thNight
21%8%20%32%18%
1620
11th to 20thNight
21%8%18%31%19%3
1620
21st to endNight
30%11%21%26%11%1
1620
July1st to 10thNight
31%11%27%25%6%
1575
11th to 20thNight
19%11%31%30%9%
1566
21st to endNight
21%13%29%31%5%1
1673
August1st to 10thNight
13%6%32%37%11%1
1601
11th to 20thNight
20%11%31%30%7%1
1695
21st to endNight
28%13%23%27%7%2
1994
September1st to 10thNight
27%12%23%21%12%4
1980
11th to 20thNight
37%8%14%21%15%4
1980
21st to endNight
29%7%14%21%18%10%
1980
October1st to 10thNight
24%6%11%27%19%13%
2078
11th to 20thNight
27%6%8%22%23%14%
2160
21st to endNight
30%37%17%23%20%
2376
November1st to 10thNight
30%6%11%21%22%10%
2220
11th to 20thNight
33%6%10%19%20%12%
2280
21st to endNight
40%5%8%19%18%10%
2322
December1st to 10thNight
43%6%8%19%14%10%
2470
11th to 20thNight
45%5%7%10%19%14%
3037
21st to endNight
41%48%12%27%8%
4532

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
27%13%33%21%6%1
270
11th to 20thDay
25%9%33%27%42
252
21st to endDay
21%17%34%22%5%
264
February1st to 10thDay
31%15%29%20%5%
240
11th to 20thDay
27%19%33%16%5%
240
21st to endDay
25%21%41%12%2
198
March1st to 10thDay
28%15%36%16%5%
240
11th to 20thDay
20%21%38%13%6%2
240
21st to endDay
21%18%36%18%8%
264
April1st to 10thDay
18%19%34%24%5%
240
11th to 20thDay
26%15%25%20%13%1
380
21st to endDay
12%13%36%26%12%1
420
May1st to 10thDay
15%12%29%28%14%
449
11th to 20thDay
12%7%28%33%18%2
625
21st to endDay
10%6%25%36%19%3
679
June1st to 10thDay
7%212%36%31%11%
630
11th to 20thDay
6%213%40%29%11%
630
21st to endDay
7%410%31%31%16%
630
July1st to 10thDay
7%210%25%37%19%
621
11th to 20thDay
5%1425%42%24%
618
21st to endDay
315%24%44%22%
684
August1st to 10thDay
2423%46%24%
626
11th to 20thDay
41319%46%27%
518
21st to endDay
10%16%19%33%31%
476
September1st to 10thDay
7%1328%39%23%
270
11th to 20thDay
10%38%29%34%16%
270
21st to endDay
10%18%30%40%10%
270
October1st to 10thDay
6%411%43%29%6%
270
11th to 20thDay
10%5%20%34%22%8%
270
21st to endDay
21%10%23%25%17%4
297
November1st to 10thDay
12%6%24%36%18%4
270
11th to 20thDay
16%11%26%35%11%3
270
21st to endDay
21%16%30%21%10%3
270
December1st to 10thDay
17%7%38%24%10%4
270
11th to 20thDay
21%16%32%25%6%1
270
21st to endDay
18%11%40%23%6%2
297
January1st to 10thNight
22%9%32%28%9%
950
11th to 20thNight
24%10%26%33%7%
923
21st to endNight
22%8%30%33%7%
990
February1st to 10thNight
26%10%31%28%5%
843
11th to 20thNight
27%8%31%28%6%
674
21st to endNight
25%12%35%24%3
444
March1st to 10thNight
24%7%33%31%5%
540
11th to 20thNight
19%9%33%32%7%
540
21st to endNight
17%9%34%30%9%
594
April1st to 10thNight
16%8%37%33%6%
540
11th to 20thNight
22%8%31%30%9%
533
21st to endNight
17%8%34%31%10%
540
May1st to 10thNight
15%11%29%37%8%
540
11th to 20thNight
11%5%28%38%15%2
531
21st to endNight
7%424%39%23%2
584
June1st to 10thNight
5%312%43%34%3
540
11th to 20thNight
4112%50%30%3
540
21st to endNight
6%212%34%41%5%
540
July1st to 10thNight
5%16%36%44%8%
525
11th to 20thNight
31434%50%7%
522
21st to endNight
21336%50%7%
591
August1st to 10thNight
21334%54%7%
537
11th to 20thNight
5%1233%52%7%
534
21st to endNight
6%1226%55%9%
594
September1st to 10thNight
6%16%25%53%9%
540
11th to 20thNight
13%17%28%46%5%
540
21st to endNight
8%19%33%44%4
540
October1st to 10thNight
6%212%36%39%5%
638
11th to 20thNight
10%320%37%27%2
720
21st to endNight
13%7%21%36%20%2
792
November1st to 10thNight
11%421%39%24%2
740
11th to 20thNight
14%7%26%35%18%1
760
21st to endNight
19%7%28%31%14%1
802
December1st to 10thNight
19%8%27%31%13%1
950
11th to 20thNight
23%9%26%33%8%1
950
21st to endNight
21%9%32%30%7%
1045
Page generated at 2024-01-12 06:31:47. Version ac07

Copyright 2024 Attilla Danko


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