Starlight Hills Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Starlight Hills Observatory clear sky chart from 2005-11-06 to 2024-03-01.

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
52%
24685
28%
79822
18%
24592
62%
24592
41%
40885

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
46%
938
33%
4304
17%
926
61%
926
34%
1946
January11th to 20thNight
43%
903
36%
4204
19%
885
57%
885
38%
1635
January21st to endNight
49%
829
23%
4258
22%
814
64%
814
30%
1890
February1st to 10thNight
36%
760
30%
2450
14%
760
54%
760
41%
1257
February11th to 20thNight
37%
742
29%
2218
15%
740
51%
740
40%
1213
February21st to endNight
33%
628
36%
1884
13%
628
56%
628
47%
935
March1st to 10thNight
41%
722
29%
2166
14%
722
53%
722
46%
1100
March11th to 20thNight
47%
720
26%
2021
15%
720
55%
720
43%
1127
March21st to endNight
38%
645
31%
2031
13%
645
58%
645
38%
1088
April1st to 10thNight
37%
540
27%
1800
14%
540
56%
540
39%
896
April11th to 20thNight
39%
533
23%
1777
15%
533
53%
533
32%
986
April21st to endNight
43%
540
23%
1800
16%
540
55%
540
33%
998
May1st to 10thNight
46%
540
23%
1692
19%
540
54%
540
32%
994
May11th to 20thNight
46%
531
14%
1481
10%
531
50%
531
30%
935
May21st to endNight
47%
583
18%
1552
10%
582
54%
582
37%
929
June1st to 10thNight
62%
540
22%
1440
18%
540
66%
540
45%
787
June11th to 20thNight
62%
540
26%
1440
17%
540
67%
540
51%
755
June21st to endNight
65%
540
23%
1440
19%
540
68%
540
42%
825
July1st to 10thNight
70%
525
18%
1400
16%
525
71%
525
33%
881
July11th to 20thNight
77%
522
26%
1392
23%
522
77%
522
44%
784
July21st to endNight
72%
591
18%
1541
16%
558
72%
558
30%
981
August1st to 10thNight
71%
537
13%
1641
14%
534
72%
534
29%
1001
August11th to 20thNight
74%
534
24%
1778
26%
534
77%
534
37%
952
August21st to endNight
74%
594
24%
1980
26%
594
77%
594
38%
1046
September1st to 10thNight
72%
540
27%
1800
28%
540
77%
540
37%
968
September11th to 20thNight
68%
540
36%
1836
34%
540
75%
540
46%
867
September21st to endNight
64%
540
33%
1980
30%
540
72%
540
43%
929
October1st to 10thNight
56%
671
30%
2111
20%
671
64%
671
42%
1099
October11th to 20thNight
56%
720
38%
2160
19%
720
70%
720
58%
999
October21st to endNight
54%
839
35%
2423
18%
839
65%
839
50%
1230
November1st to 10thNight
56%
925
36%
2405
18%
925
64%
925
59%
1218
November11th to 20thNight
51%
950
39%
2470
19%
950
62%
950
58%
1251
November21st to endNight
49%
950
33%
2503
18%
950
59%
950
51%
1316
December1st to 10thNight
44%
950
30%
2660
14%
950
56%
950
48%
1386
December11th to 20thNight
45%
948
31%
3098
16%
948
57%
948
43%
1562
December21st to endNight
38%
1035
21%
4686
14%
1026
53%
1026
32%
2119

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
4424435%5%6%8%54%
78573
Night
342442445%8%59%
80901
TransparencyDay
25%7%12%23%23%10%
78281
Night
23%6%12%26%24%9%
80715
SeeingDay
7%11%29%29%18%6%
14515
Night
5%6%32%39%16%2
24721

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
132332445%10%63%
2538
11th to 20thDay
1214436%5%6%8%60%
2640
21st to endDay
15%25%5%3445%6%60%
3146
February1st to 10thDay
25%345%2445%7%59%
1729
11th to 20thDay
1325%43446%8%58%
1849
21st to endDay
1427%5%2445%7%58%
1570
March1st to 10thDay
2426%5%235%5%8%57%
1800
11th to 20thDay
5%6%25%42445%9%54%
1935
21st to endDay
37%34435%46%9%52%
2324
April1st to 10thDay
35%244246%5%9%55%
2160
11th to 20thDay
7%5%35%4346%6%8%49%
2131
21st to endDay
6%8%25%335%5%5%9%49%
2160
May1st to 10thDay
9%8%25%5%36%6%7%7%41%
2266
11th to 20thDay
8%7%35%6%36%7%7%9%39%
2410
21st to endDay
7%424446%6%9%9%45%
2724
June1st to 10thDay
44245%35%7%8%10%48%
2520
11th to 20thDay
5%314425%6%8%9%53%
2520
21st to endDay
33245%46%7%9%9%48%
2520
July1st to 10thDay
6%4245%37%7%8%10%44%
2520
11th to 20thDay
43245%37%7%7%9%50%
2520
21st to endDay
5%426%6%46%8%9%11%37%
2683
August1st to 10thDay
6%4246%47%8%9%11%39%
2289
11th to 20thDay
5%424436%6%7%9%50%
2123
21st to endDay
5%324435%6%8%9%52%
2376
September1st to 10thDay
5%323335%6%7%7%56%
2160
11th to 20thDay
6%3133345%6%7%58%
2124
21st to endDay
5%414323446%65%
1980
October1st to 10thDay
5%42322345%7%63%
1846
11th to 20thDay
2313323335%72%
1800
21st to endDay
5%414212346%67%
1913
November1st to 10thDay
131332336%8%68%
1673
11th to 20thDay
1313413347%68%
1710
21st to endDay
1425%423447%64%
1674
December1st to 10thDay
133442345%8%62%
1520
11th to 20thDay
24245%245%37%61%
1926
21st to endDay
25%244345%47%61%
2794
January1st to 10thNight
15%36%5%2346%8%58%
4417
11th to 20thNight
121343445%7%65%
4359
21st to endNight
1424434446%62%
4521
February1st to 10thNight
25%26%5%2445%8%59%
2450
11th to 20thNight
15%46%42446%7%55%
2218
21st to endNight
1425%42335%466%
1884
March1st to 10thNight
1425%42445%8%61%
2166
11th to 20thNight
45%245%2446%7%57%
2021
21st to endNight
36%23435%45%7%57%
2031
April1st to 10thNight
4423334447%61%
1800
11th to 20thNight
7%9%25%33346%7%52%
1777
21st to endNight
7%6%3443445%8%54%
1800
May1st to 10thNight
9%6%24435%5%6%8%50%
1692
11th to 20thNight
8%9%3442446%9%46%
1481
21st to endNight
9%5%234345%5%8%51%
1552
June1st to 10thNight
5%3233235%7%11%57%
1440
11th to 20thNight
431323346%9%63%
1440
21st to endNight
4414435%6%6%9%54%
1440
July1st to 10thNight
6%315%5%47%7%6%9%48%
1440
11th to 20thNight
33335%245%7%10%54%
1440
21st to endNight
6%5%15%436%7%9%11%43%
1632
August1st to 10thNight
6%425%5%47%6%8%10%44%
1650
11th to 20thNight
6%3145%35%5%7%9%52%
1778
21st to endNight
4315%5%35%6%8%10%51%
1980
September1st to 10thNight
44145%46%5%6%9%52%
1800
11th to 20thNight
7%41322335%8%62%
1836
21st to endNight
5%413323446%65%
1980
October1st to 10thNight
8%5%12323347%61%
2111
11th to 20thNight
2312322336%72%
2160
21st to endNight
4423323436%66%
2423
November1st to 10thNight
132332335%8%68%
2405
11th to 20thNight
122331345%6%70%
2470
21st to endNight
242432335%6%65%
2503
December1st to 10thNight
1325%5%3435%7%64%
2660
11th to 20thNight
13244245%6%9%60%
3271
21st to endNight
2425%42445%8%60%
4873

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
17%5%11%33%25%8%
2539
11th to 20thDay
20%6%13%29%24%8%
2640
21st to endDay
24%5%11%28%26%6%
3146
February1st to 10thDay
24%5%12%26%23%10%
1729
11th to 20thDay
21%7%8%26%29%8%
1859
21st to endDay
25%5%7%22%25%17%
1570
March1st to 10thDay
23%6%11%23%26%11%
1800
11th to 20thDay
26%6%12%25%26%6%
1935
21st to endDay
27%7%13%25%21%8%
2324
April1st to 10thDay
23%7%14%23%22%10%
2160
11th to 20thDay
31%6%13%23%18%9%
2134
21st to endDay
31%7%14%24%20%4
2160
May1st to 10thDay
36%9%11%24%16%4
2266
11th to 20thDay
37%10%16%20%14%3
2414
21st to endDay
29%11%15%22%16%8%
2724
June1st to 10thDay
26%9%16%22%17%10%
2520
11th to 20thDay
21%8%12%18%24%16%
2520
21st to endDay
27%9%12%20%22%11%
2520
July1st to 10thDay
30%10%13%18%20%10%
2451
11th to 20thDay
26%9%13%25%19%8%
2445
21st to endDay
34%12%19%20%13%3
2534
August1st to 10thDay
33%11%19%19%12%7%
2274
11th to 20thDay
26%9%11%22%21%11%
2123
21st to endDay
24%7%13%23%24%8%
2376
September1st to 10thDay
22%7%11%22%23%14%
2160
11th to 20thDay
22%7%9%17%29%16%
2124
21st to endDay
20%5%8%21%33%14%
1980
October1st to 10thDay
22%6%11%21%29%11%
1846
11th to 20thDay
16%48%21%33%18%
1800
21st to endDay
21%38%27%26%16%
1913
November1st to 10thDay
15%410%24%28%19%
1673
11th to 20thDay
15%5%6%31%33%10%
1710
21st to endDay
20%5%7%22%29%17%
1674
December1st to 10thDay
20%7%11%28%26%8%
1520
11th to 20thDay
23%5%8%24%30%9%
1924
21st to endDay
21%6%12%26%24%12%
2794
January1st to 10thNight
24%5%9%30%28%5%
4417
11th to 20thNight
15%7%13%29%26%10%
4359
21st to endNight
22%7%12%32%22%5%
4521
February1st to 10thNight
24%5%9%28%24%9%
2450
11th to 20thNight
26%6%9%29%22%8%
2218
21st to endNight
20%47%26%28%16%
1884
March1st to 10thNight
21%5%10%24%30%10%
2166
11th to 20thNight
24%6%13%24%27%6%
2021
21st to endNight
24%7%11%24%28%7%
2031
April1st to 10thNight
22%6%14%23%25%11%
1800
11th to 20thNight
29%7%12%25%18%8%
1777
21st to endNight
29%7%15%26%18%6%
1800
May1st to 10thNight
31%8%13%25%19%4
1692
11th to 20thNight
33%10%20%20%12%5%
1482
21st to endNight
29%8%18%21%16%8%
1552
June1st to 10thNight
22%7%22%25%14%10%
1440
11th to 20thNight
17%7%15%23%20%17%
1440
21st to endNight
24%9%11%22%23%11%
1440
July1st to 10thNight
31%11%15%21%17%6%
1400
11th to 20thNight
24%8%13%32%17%6%
1392
21st to endNight
30%14%21%21%13%1
1541
August1st to 10thNight
32%11%21%19%11%7%
1641
11th to 20thNight
26%8%15%27%19%6%
1778
21st to endNight
23%9%16%27%18%6%
1980
September1st to 10thNight
26%7%11%23%22%11%
1800
11th to 20thNight
20%5%11%23%26%15%
1836
21st to endNight
21%6%8%24%32%10%
1980
October1st to 10thNight
23%6%11%23%25%12%
2111
11th to 20thNight
15%48%23%32%17%
2160
21st to endNight
20%49%26%27%14%
2423
November1st to 10thNight
15%5%10%25%29%17%
2405
11th to 20thNight
15%49%29%32%11%
2470
21st to endNight
20%49%23%30%13%
2503
December1st to 10thNight
19%6%13%26%26%10%
2660
11th to 20thNight
20%6%10%26%31%7%
3272
21st to endNight
23%5%13%23%25%11%
4873

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
6%7%34%37%13%4
270
11th to 20thDay
7%11%35%36%9%2
270
21st to endDay
313%35%34%13%3
297
February1st to 10thDay
416%47%26%6%2
270
11th to 20thDay
315%45%26%10%1
270
21st to endDay
120%47%26%5%1
225
March1st to 10thDay
413%41%30%9%3
240
11th to 20thDay
10%18%40%21%9%2
375
21st to endDay
11%23%39%20%6%1
462
April1st to 10thDay
10%18%39%23%8%1
420
11th to 20thDay
13%25%34%20%6%2
412
21st to endDay
15%18%34%24%7%2
420
May1st to 10thDay
14%16%33%26%9%2
529
11th to 20thDay
14%11%28%29%14%4
625
21st to endDay
9%11%30%25%20%4
679
June1st to 10thDay
7%9%23%31%22%8%
630
11th to 20thDay
6%10%27%33%19%5%
630
21st to endDay
5%7%23%34%24%7%
630
July1st to 10thDay
7%5%16%31%31%10%
621
11th to 20thDay
5%314%33%33%11%
618
21st to endDay
7%413%28%34%14%
625
August1st to 10thDay
10%218%34%28%8%
447
11th to 20thDay
5%6%21%33%22%13%
437
21st to endDay
6%323%38%21%9%
495
September1st to 10thDay
7%427%33%19%10%
450
11th to 20thDay
6%6%29%28%22%9%
414
21st to endDay
10%7%19%26%26%12%
270
October1st to 10thDay
10%13%19%24%23%11%
270
11th to 20thDay
29%34%32%17%6%
270
21st to endDay
7%12%33%28%17%3
297
November1st to 10thDay
412%35%28%15%6%
270
11th to 20thDay
47%39%32%15%3
270
21st to endDay
6%11%35%31%12%4
270
December1st to 10thDay
314%41%26%14%3
270
11th to 20thDay
5%7%41%30%15%1
270
21st to endDay
314%44%29%9%2
297
January1st to 10thNight
37%39%36%13%4
950
11th to 20thNight
37%42%36%9%2
905
21st to endNight
25%37%43%11%1
836
February1st to 10thNight
36%51%33%6%1
760
11th to 20thNight
37%49%33%8%1
744
21st to endNight
39%50%34%4
628
March1st to 10thNight
37%46%34%9%2
722
11th to 20thNight
7%7%34%40%11%1
720
21st to endNight
5%10%43%35%7%
645
April1st to 10thNight
7%11%42%35%5%
540
11th to 20thNight
14%9%35%33%7%1
533
21st to endNight
12%10%33%35%9%1
540
May1st to 10thNight
11%8%30%38%12%1
540
11th to 20thNight
13%7%27%38%14%2
531
21st to endNight
11%6%30%34%17%2
584
June1st to 10thNight
5%6%21%43%21%3
540
11th to 20thNight
45%25%51%15%1
540
21st to endNight
5%319%48%24%2
540
July1st to 10thNight
7%312%41%34%3
525
11th to 20thNight
427%46%36%5%
522
21st to endNight
9%36%35%43%4
591
August1st to 10thNight
8%38%40%37%4
537
11th to 20thNight
7%19%49%31%4
534
21st to endNight
5%210%44%35%5%
594
September1st to 10thNight
6%312%46%28%6%
540
11th to 20thNight
8%315%46%23%4
540
21st to endNight
7%321%43%22%4
540
October1st to 10thNight
11%5%25%39%18%3
671
11th to 20thNight
4432%38%18%4
720
21st to endNight
6%5%31%37%17%3
839
November1st to 10thNight
3434%42%15%2
925
11th to 20thNight
36%36%42%10%2
950
21st to endNight
5%6%35%39%13%2
950
December1st to 10thNight
27%42%38%9%1
950
11th to 20thNight
37%39%38%12%1
950
21st to endNight
5%8%44%34%8%1
1045
Page generated at 2024-02-27 04:30:16. Version ac07

Copyright © 2024 Attilla Danko.


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