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 2005-11-05 to

2017-09-12
.

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
54%
15886
28%
46816
18%
15844
63%
15844
42%
25223

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 15thNight
50%
898
31%
2506
19%
895
61%
895
49%
1302
January16th to endNight
50%
800
35%
2528
22%
800
65%
800
46%
1243
February1st to 15thNight
40%
701
26%
2220
15%
699
53%
699
40%
1179
February16th to endNight
39%
632
36%
1894
15%
632
60%
632
46%
971
March1st to 15thNight
46%
720
28%
2127
16%
720
57%
720
45%
1121
March16th to endNight
45%
669
28%
2013
15%
669
58%
669
40%
1095
April1st to 15thNight
40%
539
24%
1798
14%
539
57%
539
38%
925
April16th to endNight
44%
540
23%
1800
18%
540
56%
540
32%
1021
May1st to 15thNight
49%
539
20%
1650
17%
539
54%
539
31%
992
May16th to endNight
50%
562
18%
1498
11%
561
56%
561
37%
901
June1st to 15thNight
62%
540
22%
1440
15%
540
67%
540
48%
761
June16th to endNight
70%
540
24%
1440
18%
540
74%
540
47%
783
July1st to 15thNight
69%
510
17%
1360
15%
510
69%
510
32%
872
July16th to endNight
75%
564
20%
1451
18%
531
75%
531
35%
895
August1st to 15thNight
72%
539
15%
1698
16%
536
73%
536
30%
1027
August16th to endNight
77%
573
24%
1910
26%
573
79%
573
37%
1022
September1st to 15thNight
69%
530
25%
1766
25%
530
73%
530
35%
982
September16th to endNight
73%
492
35%
1782
36%
492
79%
492
46%
809
October1st to 15thNight
55%
630
31%
1950
20%
630
64%
630
42%
1027
October16th to endNight
62%
733
36%
2141
22%
733
71%
733
52%
1066
November1st to 15thNight
58%
875
35%
2275
19%
875
66%
875
58%
1160
November16th to endNight
54%
900
37%
2361
21%
900
63%
900
56%
1207
December1st to 15thNight
43%
900
26%
2520
12%
900
55%
900
45%
1358
December16th to endNight
42%
960
29%
2688
13%
960
55%
960
42%
1504

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
44234245%6%8%53%
47861
Night
341332445%7%58%
46992
Cloud CoverDay
44244345%6%8%52%
47859
Night
342342445%8%57%
46992
TransparencyDay
26%6%12%24%21%8%
47539
Night
23%6%12%26%22%8%
46816
SeeingDay
8%10%29%27%16%6%
5803
Night
5%429%38%18%3
15893

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 15thDay
231321345%8%63%
1432
16th to endDay
1414323246%63%
1707
February1st to 15thDay
14345%13448%57%
1642
16th to endDay
15%25%42335%7%58%
1580
March1st to 15thDay
34245%1345%9%55%
1830
16th to endDay
47%2332436%9%52%
2210
April1st to 15thDay
45%243235%5%9%53%
2150
16th to endDay
8%7%24335%5%5%7%47%
2160
May1st to 15thDay
9%7%35%5%35%6%6%7%40%
2298
16th to endDay
7%5%23435%5%7%8%44%
2616
June1st to 15thDay
5%3134245%8%9%50%
2520
16th to endDay
32133246%8%9%53%
2520
July1st to 15thDay
6%4145%37%5%8%9%43%
2520
16th to endDay
5%3245%46%7%8%10%42%
2616
August1st to 15thDay
6%4245%36%7%8%10%41%
2253
16th to endDay
5%323435%6%7%8%49%
2292
September1st to 15thDay
7%3133346%7%8%51%
2113
16th to endDay
323323446%65%
1848
October1st to 15thDay
5%31322335%6%63%
1678
16th to endDay
433211335%69%
1719
November1st to 15thDay
121242335%8%64%
1583
16th to endDay
323312346%68%
1598
December1st to 15thDay
13245%24437%59%
1440
16th to endDay
35%34324448%56%
1536
January1st to 15thNight
1224323345%66%
2506
16th to endNight
132332343466%
2528
February1st to 15thNight
2425%42335%8%57%
2210
16th to endNight
15%1442335%463%
1894
March1st to 15thNight
141442446%7%60%
2127
16th to endNight
35%23324447%58%
2013
April1st to 15thNight
5%42322345%6%58%
1798
16th to endNight
8%7%23323347%52%
1800
May1st to 15thNight
8%6%2332446%8%48%
1649
16th to endNight
8%6%1242445%9%51%
1497
June1st to 15thNight
431222245%10%60%
1440
16th to endNight
22132245%7%9%58%
1440
July1st to 15thNight
5%3245%36%6%6%10%45%
1440
16th to endNight
5%4143346%8%10%47%
1550
August1st to 15thNight
6%315%5%26%5%7%8%46%
1707
16th to endNight
5%31343447%10%51%
1910
September1st to 15thNight
6%414435%46%9%49%
1766
16th to endNight
3212313346%66%
1782
October1st to 15thNight
6%5%12313336%61%
1950
16th to endNight
3311322346%66%
2141
November1st to 15thNight
221232235%8%66%
2275
16th to endNight
1223212346%68%
2361
December1st to 15thNight
1325%42335%8%59%
2520
16th to endNight
2424424347%57%
2688

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 15thDay
1313323448%62%
1432
16th to endDay
141442325%7%62%
1707
February1st to 15thDay
1425%5%2445%7%56%
1642
16th to endDay
5%244235%5%6%58%
1580
March1st to 15thDay
35%15%42446%8%54%
1830
16th to endDay
46%2432445%9%50%
2208
April1st to 15thDay
45%25%4245%6%9%50%
2150
16th to endDay
8%6%25%425%5%5%8%44%
2160
May1st to 15thDay
8%7%36%5%36%5%7%7%37%
2298
16th to endDay
7%415%437%5%7%8%43%
2616
June1st to 15thDay
4314435%5%7%9%50%
2520
16th to endDay
3213435%6%8%9%52%
2520
July1st to 15thDay
6%424446%6%8%9%42%
2520
16th to endDay
5%3246%46%7%8%10%40%
2616
August1st to 15thDay
6%325%5%47%7%7%10%39%
2253
16th to endDay
5%323325%6%7%9%48%
2292
September1st to 15thDay
6%3133345%6%8%51%
2113
16th to endDay
324323446%64%
1848
October1st to 15thDay
5%214323347%61%
1678
16th to endDay
4313211335%68%
1719
November1st to 15thDay
121241336%9%62%
1583
16th to endDay
323213347%67%
1598
December1st to 15thDay
13245%2445%6%59%
1440
16th to endDay
25%3433445%8%55%
1536
January1st to 15thNight
224323346%65%
2506
16th to endNight
1313324336%65%
2528
February1st to 15thNight
15%25%42346%8%55%
2210
16th to endNight
1424424345%62%
1894
March1st to 15thNight
13135%335%6%7%58%
2127
16th to endNight
3423424348%57%
2013
April1st to 15thNight
442342345%7%57%
1798
16th to endNight
8%8%2432335%8%50%
1800
May1st to 15thNight
8%6%23425%5%6%8%45%
1649
16th to endNight
6%5%2432445%9%49%
1497
June1st to 15thNight
331322335%10%60%
1440
16th to endNight
23122245%8%10%57%
1440
July1st to 15thNight
5%325%6%36%7%6%9%44%
1440
16th to endNight
5%424435%6%8%10%45%
1550
August1st to 15thNight
5%4245%45%6%7%9%44%
1707
16th to endNight
43134345%7%10%50%
1910
September1st to 15thNight
6%3145%35%5%6%9%48%
1766
16th to endNight
3212323446%65%
1782
October1st to 15thNight
5%6%1321235%6%59%
1950
16th to endNight
3312313346%66%
2141
November1st to 15thNight
112231335%7%65%
2275
16th to endNight
121331335%6%67%
2361
December1st to 15thNight
1325%42335%9%58%
2520
16th to endNight
242443435%7%57%
2688

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 15thDay
17%5%12%33%25%5%
1433
16th to endDay
20%48%31%25%9%
1707
February1st to 15thDay
25%5%13%32%17%5%
1643
16th to endDay
24%48%28%26%8%
1580
March1st to 15thDay
25%412%24%24%8%
1830
16th to endDay
27%7%11%24%22%5%
2210
April1st to 15thDay
26%6%13%25%19%7%
2150
16th to endDay
36%5%13%22%16%5%
2160
May1st to 15thDay
40%7%11%21%16%2
2298
16th to endDay
32%9%16%21%13%6%
2620
June1st to 15thDay
26%7%15%19%19%11%
2520
16th to endDay
21%7%11%20%25%12%
2520
July1st to 15thDay
33%7%13%20%15%9%
2371
16th to endDay
31%10%17%22%14%3
2452
August1st to 15thDay
34%10%14%19%12%8%
2238
16th to endDay
27%7%13%23%22%5%
2292
September1st to 15thDay
25%7%12%23%19%10%
2113
16th to endDay
18%5%9%23%33%9%
1848
October1st to 15thDay
22%5%11%22%29%8%
1678
16th to endDay
18%39%26%30%12%
1719
November1st to 15thDay
18%410%25%27%14%
1583
16th to endDay
15%36%27%32%13%
1598
December1st to 15thDay
23%6%11%30%23%4
1440
16th to endDay
26%6%13%27%19%7%
1536
January1st to 15thNight
20%411%30%26%6%
2506
16th to endNight
20%5%9%28%26%10%
2528
February1st to 15thNight
25%6%12%32%19%4
2220
16th to endNight
21%47%31%25%9%
1894
March1st to 15thNight
21%5%10%27%28%6%
2127
16th to endNight
23%7%12%23%27%5%
2013
April1st to 15thNight
23%6%14%25%21%8%
1798
16th to endNight
31%5%13%26%16%5%
1800
May1st to 15thNight
33%7%15%22%16%4
1650
16th to endNight
28%8%18%23%13%7%
1498
June1st to 15thNight
20%6%19%24%14%14%
1440
16th to endNight
20%8%14%22%21%14%
1440
July1st to 15thNight
33%9%15%21%12%7%
1360
16th to endNight
28%11%18%25%13%2
1451
August1st to 15thNight
32%9%17%21%11%7%
1698
16th to endNight
25%7%16%28%16%4
1910
September1st to 15thNight
29%6%13%24%17%9%
1766
16th to endNight
18%5%9%27%30%8%
1782
October1st to 15thNight
23%6%11%21%28%9%
1950
16th to endNight
18%48%27%29%11%
2141
November1st to 15thNight
16%410%26%27%15%
2275
16th to endNight
16%38%27%32%11%
2361
December1st to 15thNight
21%6%14%30%20%5%
2520
16th to endNight
25%5%14%26%22%5%
2688

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 15thDay
15%7%25%31%15%4
90
16th to endDay
8%5%29%38%18%
96
February1st to 15thDay
8%8%50%26%5%
90
16th to endDay
116%46%25%7%2
81
March1st to 15thDay
216%45%26%8%
120
16th to endDay
10%26%43%13%31
288
April1st to 15thDay
10%20%43%18%42
269
16th to endDay
19%26%33%17%21
270
May1st to 15thDay
12%14%31%29%8%3
420
16th to endDay
13%12%26%27%16%4
517
June1st to 15thDay
6%10%26%30%20%6%
495
16th to endDay
46%25%29%25%8%
495
July1st to 15thDay
9%220%27%29%10%
475
16th to endDay
7%214%30%30%14%
475
August1st to 15thDay
12%423%35%17%7%
315
16th to endDay
7%324%42%13%8%
332
September1st to 15thDay
8%442%24%14%7%
300
16th to endDay
37%30%22%22%13%
123
October1st to 15thDay
46%22%35%22%8%
90
16th to endDay
5%9%33%25%19%7%
96
November1st to 15thDay
16%26%32%22%11%
90
16th to endDay
8%10%46%23%10%1
90
December1st to 15thDay
6%8%57%20%5%1
90
16th to endDay
6%8%40%33%10%1
96
January1st to 15thNight
25%37%35%13%5%
900
16th to endNight
35%37%39%12%2
800
February1st to 15thNight
3447%36%7%
704
16th to endNight
27%45%35%7%
632
March1st to 15thNight
35%41%35%13%2
720
16th to endNight
5%8%37%38%9%
669
April1st to 15thNight
8%11%37%33%8%
539
16th to endNight
13%9%29%36%9%1
540
May1st to 15thNight
12%7%26%37%15%
540
16th to endNight
9%429%37%17%2
563
June1st to 15thNight
4324%43%20%2
540
16th to endNight
3217%47%26%2
540
July1st to 15thNight
7%110%39%37%4
510
16th to endNight
6%6%35%44%6%
564
August1st to 15thNight
7%18%37%39%5%
539
16th to endNight
6%7%40%38%6%
573
September1st to 15thNight
8%112%41%29%7%
530
16th to endNight
4215%42%28%6%
492
October1st to 15thNight
10%327%35%17%5%
630
16th to endNight
4424%37%23%5%
733
November1st to 15thNight
2330%41%16%4
875
16th to endNight
35%33%40%13%3
900
December1st to 15thNight
26%42%37%9%2
900
16th to endNight
37%41%34%10%2
960
Page generated at 2017-09-13 05:39:09. Version ac04

Copyright 2017 A. Danko


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