Darling Hill Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Darling Hill Observatory clear sky chart from 2005-11-05 to 2017-09-19.

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
27%
14869
11%
46889
8%
14838
31%
14838
13%
35227

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
10%
720
5%
2506
3%
716
13%
716
5%
2154
January16th to endNight
11%
768
6%
2565
3%
768
15%
768
5%
2193
February1st to 15thNight
8%
704
6%
2287
1%
701
14%
701
5%
1970
February16th to endNight
13%
631
9%
1931
4%
631
19%
631
8%
1590
March1st to 15thNight
16%
720
10%
2073
4%
720
22%
720
11%
1649
March16th to endNight
21%
768
14%
2049
6%
768
26%
768
14%
1572
April1st to 15thNight
19%
718
10%
1796
3%
718
22%
718
14%
1399
April16th to endNight
30%
717
17%
1797
7%
717
35%
717
23%
1270
May1st to 15thNight
37%
386
17%
1466
15%
386
44%
386
17%
984
May16th to endNight
40%
374
15%
1497
15%
374
47%
374
19%
945
June1st to 15thNight
38%
360
12%
1440
12%
360
46%
360
15%
965
June16th to endNight
46%
360
13%
1440
17%
360
53%
360
21%
882
July1st to 15thNight
53%
340
13%
1360
18%
340
57%
340
23%
798
July16th to endNight
57%
376
15%
1418
18%
354
60%
354
25%
823
August1st to 15thNight
50%
527
14%
1598
10%
525
54%
525
27%
1013
August16th to endNight
54%
735
18%
1881
11%
735
55%
735
33%
1222
September1st to 15thNight
45%
720
17%
1800
9%
720
48%
720
29%
1228
September16th to endNight
47%
673
21%
1836
16%
673
51%
673
27%
1233
October1st to 15thNight
33%
660
15%
1980
12%
660
37%
660
17%
1435
October16th to endNight
17%
704
7%
2158
4%
704
22%
704
9%
1746
November1st to 15thNight
20%
700
14%
2283
9%
700
27%
700
13%
1684
November16th to endNight
19%
720
11%
2520
8%
720
26%
720
9%
1940
December1st to 15thNight
11%
720
4%
2520
1%
720
14%
720
5%
2143
December16th to endNight
9%
768
3%
2688
1%
768
12%
768
3%
2389

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
17%11%48%6%3445%6%27%
47935
Night
16%12%5%8%6%34445%28%
47059
Cloud CoverDay
17%11%47%6%3445%6%27%
47945
Night
16%11%5%8%6%34445%28%
47064
TransparencyDay
57%5%10%16%8%
47623
Night
58%5%10%16%8%
46889
SeeingDay
25%14%27%18%10%4
5568
Night
25%17%25%22%9%1
14870

By Month

Percentage Cloud Cover NE (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
12%17%9%13%9%5%5%44412%
1432
16th to endDay
12%17%8%14%10%5%5%5%4313%
1659
February1st to 15thDay
13%16%10%16%11%4443211%
1575
16th to endDay
16%16%6%14%11%4432316%
1542
March1st to 15thDay
16%17%6%11%7%2443419%
1874
16th to endDay
17%13%6%8%6%14345%28%
2175
April1st to 15thDay
18%14%5%6%5%23435%29%
2152
16th to endDay
16%12%35%42325%6%36%
2174
May1st to 15thDay
18%9%36%5%34445%32%
2484
16th to endDay
16%7%25%5%35%5%6%8%32%
2618
June1st to 15thDay
24%7%25%42446%7%29%
2520
16th to endDay
16%6%25%5%45%5%6%10%31%
2520
July1st to 15thDay
12%5%35%6%36%6%6%8%33%
2520
16th to endDay
14%6%26%6%45%6%6%8%32%
2654
August1st to 15thDay
14%6%26%6%46%6%6%8%29%
2349
16th to endDay
14%7%36%5%35%5%6%7%33%
2309
September1st to 15thDay
20%6%25%5%34446%35%
2160
16th to endDay
16%7%25%5%24346%40%
1867
October1st to 15thDay
22%10%24424347%31%
1650
16th to endDay
26%15%36%5%3444420%
1713
November1st to 15thDay
14%15%36%5%25%446%30%
1572
16th to endDay
19%16%5%10%7%3424421%
1440
December1st to 15thDay
15%24%8%10%6%3433415%
1440
16th to endDay
17%20%11%13%8%3334310%
1536
January1st to 15thNight
15%17%7%14%9%4443313%
2506
16th to endNight
12%16%8%13%11%5%6%44412%
2565
February1st to 15thNight
12%17%8%16%10%45%43413%
2285
16th to endNight
15%13%7%15%9%35%335%18%
1931
March1st to 15thNight
16%14%6%10%8%34335%22%
2061
16th to endNight
17%14%6%8%5%23345%28%
2049
April1st to 15thNight
19%12%47%5%44345%27%
1796
16th to endNight
17%10%35%42334440%
1797
May1st to 15thNight
18%6%36%434446%36%
1466
16th to endNight
13%5%35%5%25%5%6%7%38%
1495
June1st to 15thNight
20%6%35%42446%6%34%
1440
16th to endNight
14%425%42445%9%40%
1440
July1st to 15thNight
7%325%6%36%5%6%9%42%
1440
16th to endNight
11%425%42446%9%44%
1514
August1st to 15thNight
10%426%5%25%5%6%7%43%
1608
16th to endNight
10%6%25%4235%47%46%
1881
September1st to 15thNight
16%4345%24447%41%
1800
16th to endNight
15%7%1342446%6%42%
1836
October1st to 15thNight
23%8%25%5%24446%32%
1980
16th to endNight
27%13%36%6%24445%21%
2158
November1st to 15thNight
16%16%38%5%23446%29%
2283
16th to endNight
17%17%6%8%6%24245%24%
2520
December1st to 15thNight
20%19%7%11%6%25%43414%
2520
16th to endNight
18%20%10%14%7%3333310%
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
13%16%9%14%9%5%5%44412%
1432
16th to endDay
11%17%9%13%10%5%5%43313%
1659
February1st to 15thDay
14%16%9%16%10%45%33311%
1575
16th to endDay
15%16%6%14%11%45%32316%
1542
March1st to 15thDay
17%16%6%12%6%3444419%
1885
16th to endDay
17%13%6%8%6%23345%28%
2174
April1st to 15thDay
18%14%5%6%5%23336%29%
2152
16th to endDay
17%12%25%423346%36%
2174
May1st to 15thDay
18%9%36%6%34445%32%
2484
16th to endDay
16%7%35%6%35%5%6%8%32%
2618
June1st to 15thDay
24%7%25%5%3446%7%29%
2520
16th to endDay
16%6%35%5%45%5%6%9%31%
2520
July1st to 15thDay
12%6%26%6%36%6%7%8%33%
2520
16th to endDay
14%6%25%6%45%6%6%8%32%
2654
August1st to 15thDay
15%6%26%6%47%5%6%8%29%
2349
16th to endDay
14%7%26%6%45%5%6%7%32%
2309
September1st to 15thDay
20%5%25%5%34446%35%
2160
16th to endDay
16%6%25%5%34345%40%
1867
October1st to 15thDay
22%11%24424346%32%
1650
16th to endDay
26%16%35%5%2444420%
1713
November1st to 15thDay
14%15%45%5%34446%30%
1572
16th to endDay
19%15%5%10%7%33345%21%
1440
December1st to 15thDay
15%24%8%10%6%2433315%
1440
16th to endDay
17%19%12%12%8%2334310%
1536
January1st to 15thNight
15%17%7%14%10%45%44313%
2506
16th to endNight
12%16%8%13%11%5%7%43413%
2565
February1st to 15thNight
11%16%9%15%10%4443313%
2278
16th to endNight
14%13%7%14%10%25%435%18%
1931
March1st to 15thNight
16%14%7%10%8%34335%22%
2073
16th to endNight
16%14%6%8%424345%28%
2049
April1st to 15thNight
19%13%46%6%3444427%
1796
16th to endNight
17%10%25%5%2334439%
1797
May1st to 15thNight
18%7%36%43435%7%35%
1466
16th to endNight
12%5%35%5%35%5%5%8%38%
1495
June1st to 15thNight
20%6%35%42346%6%34%
1440
16th to endNight
15%425%43445%9%40%
1440
July1st to 15thNight
7%425%6%36%5%7%8%42%
1440
16th to endNight
11%32442446%8%44%
1514
August1st to 15thNight
10%415%435%5%6%8%43%
1608
16th to endNight
11%5%25%42445%8%45%
1881
September1st to 15thNight
15%5%345%2445%7%40%
1800
16th to endNight
15%6%233345%5%6%42%
1836
October1st to 15thNight
23%8%26%5%33446%32%
1980
16th to endNight
27%12%37%6%24335%21%
2158
November1st to 15thNight
15%16%47%5%23436%29%
2283
16th to endNight
17%16%6%8%5%24345%24%
2520
December1st to 15thNight
20%18%8%10%7%2433415%
2520
16th to endNight
17%20%10%15%7%2333311%
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
76%46%7%4
1433
16th to endDay
75%310%7%3
1659
February1st to 15thDay
79%36%8%2
1577
16th to endDay
74%37%9%4
1542
March1st to 15thDay
68%410%10%4
1885
16th to endDay
58%48%15%11%
2175
April1st to 15thDay
58%39%18%8%1
2152
16th to endDay
48%39%20%15%1
2174
May1st to 15thDay
52%5%10%19%10%
2484
16th to endDay
48%7%13%18%11%
2622
June1st to 15thDay
53%5%10%19%9%
2520
16th to endDay
48%7%13%19%10%
2520
July1st to 15thDay
46%7%9%24%10%
2371
16th to endDay
47%7%15%20%9%
2487
August1st to 15thDay
50%6%13%20%8%
2335
16th to endDay
47%6%11%22%10%
2309
September1st to 15thDay
49%410%22%11%1
2160
16th to endDay
46%5%8%23%14%1
1867
October1st to 15thDay
53%5%8%20%11%1
1650
16th to endDay
66%411%11%4
1713
November1st to 15thDay
54%413%15%8%2
1572
16th to endDay
65%5%12%12%4
1440
December1st to 15thDay
72%5%10%7%3
1440
16th to endDay
79%48%5%1
1536
January1st to 15thNight
75%47%7%4
2506
16th to endNight
74%48%8%3
2565
February1st to 15thNight
75%46%9%3
2287
16th to endNight
69%39%11%4
1931
March1st to 15thNight
65%311%13%5%
2073
16th to endNight
59%39%15%10%1
2049
April1st to 15thNight
58%5%9%15%9%1
1796
16th to endNight
47%39%20%16%1
1797
May1st to 15thNight
48%6%10%20%13%1
1466
16th to endNight
43%6%13%21%12%1
1497
June1st to 15thNight
49%5%11%22%9%
1440
16th to endNight
40%6%12%24%14%
1440
July1st to 15thNight
36%7%13%26%14%1
1360
16th to endNight
37%6%14%25%13%2
1418
August1st to 15thNight
37%8%16%27%9%
1598
16th to endNight
36%6%14%28%13%1
1881
September1st to 15thNight
42%413%23%14%1
1800
16th to endNight
40%6%9%27%13%1
1836
October1st to 15thNight
53%5%10%16%13%
1980
16th to endNight
65%5%11%11%5%
2158
November1st to 15thNight
56%410%14%9%3
2283
16th to endNight
63%411%15%5%
2520
December1st to 15thNight
74%5%10%8%2
2520
16th to endNight
79%47%6%1
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
26%31%30%5%6%
60
16th to endDay
30%30%30%8%
85
February1st to 15thDay
34%37%24%3
90
16th to endDay
32%26%27%10%2
201
March1st to 15thDay
32%22%25%14%4
270
16th to endDay
30%21%25%15%5%1
288
April1st to 15thDay
31%20%28%10%7%1
270
16th to endDay
27%11%27%17%11%4
270
May1st to 15thDay
34%12%24%15%10%2
288
16th to endDay
19%12%35%16%12%2
331
June1st to 15thDay
29%8%26%22%9%1
315
16th to endDay
19%16%31%23%6%2
315
July1st to 15thDay
18%6%31%27%11%4
305
16th to endDay
15%6%31%27%15%4
326
August1st to 15thDay
16%10%28%20%16%8%
313
16th to endDay
15%7%25%22%14%14%
332
September1st to 15thDay
21%8%19%23%16%10%
315
16th to endDay
17%12%24%20%14%11%
266
October1st to 15thDay
26%11%24%16%16%4
255
16th to endDay
44%16%22%12%4
263
November1st to 15thDay
27%16%25%23%6%1
226
16th to endDay
33%26%28%11%
60
December1st to 15thDay
31%28%23%13%11
60
16th to endDay
37%26%32%3
64
January1st to 15thNight
28%29%27%11%3
720
16th to endNight
26%24%29%16%2
768
February1st to 15thNight
25%25%33%13%1
704
16th to endNight
28%24%27%15%3
631
March1st to 15thNight
29%22%27%17%2
720
16th to endNight
27%22%24%18%6%
768
April1st to 15thNight
31%18%26%20%2
718
16th to endNight
26%15%23%24%8%
717
May1st to 15thNight
23%11%24%30%10%
386
16th to endNight
13%7%32%30%15%
375
June1st to 15thNight
21%9%22%31%13%
360
16th to endNight
16%5%25%38%13%
360
July1st to 15thNight
10%225%42%17%1
340
16th to endNight
14%220%42%18%1
376
August1st to 15thNight
14%5%23%32%21%2
527
16th to endNight
14%322%32%24%2
735
September1st to 15thNight
18%8%20%31%17%2
720
16th to endNight
18%9%20%24%21%5%
673
October1st to 15thNight
29%13%20%20%15%
660
16th to endNight
37%17%24%17%3
704
November1st to 15thNight
27%19%28%16%7%
700
16th to endNight
30%21%24%17%5%1
720
December1st to 15thNight
34%25%23%13%2
720
16th to endNight
32%27%25%12%1
768
Page generated at 2017-09-20 04:49:46. Version ac04

Copyright 2017 A. Danko


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