Starsearch Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Starsearch Observatory clear sky chart from 2005-11-05 to 2017-04-28.

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%
15097
19%
45557
15%
15058
54%
15058
26%
29267

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
40%
716
11%
2503
9%
716
43%
716
14%
1858
January16th to endNight
43%
768
13%
2496
11%
768
45%
768
16%
1807
February1st to 15thNight
39%
700
9%
2288
8%
698
42%
698
16%
1688
February16th to endNight
38%
632
13%
1926
10%
632
44%
632
19%
1349
March1st to 15thNight
43%
720
14%
2040
10%
720
48%
720
21%
1454
March16th to endNight
40%
768
15%
2112
9%
768
45%
768
22%
1479
April1st to 15thNight
42%
641
16%
1823
9%
641
45%
641
25%
1205
April16th to endNight
43%
534
21%
1602
14%
534
48%
534
27%
1002
May1st to 15thNight
52%
494
20%
1484
17%
494
54%
494
30%
903
May16th to endNight
55%
514
14%
1481
13%
513
57%
513
27%
973
June1st to 15thNight
57%
393
19%
1218
17%
393
63%
393
33%
715
June16th to endNight
70%
330
28%
1155
32%
330
77%
330
50%
494
July1st to 15thNight
78%
310
24%
1193
33%
310
82%
310
44%
523
July16th to endNight
79%
497
27%
1442
29%
464
79%
464
55%
664
August1st to 15thNight
74%
494
30%
1476
26%
491
76%
491
49%
750
August16th to endNight
73%
525
35%
1575
28%
525
76%
525
51%
777
September1st to 15thNight
68%
620
31%
1761
24%
620
74%
620
48%
917
September16th to endNight
69%
656
34%
1815
28%
656
73%
656
48%
958
October1st to 15thNight
60%
660
24%
1922
19%
660
64%
660
37%
1113
October16th to endNight
58%
704
25%
2161
22%
704
63%
704
32%
1290
November1st to 15thNight
50%
700
20%
2275
18%
700
53%
700
23%
1458
November16th to endNight
45%
867
15%
2487
11%
867
49%
867
23%
1716
December1st to 15thNight
36%
900
8%
2520
5%
900
38%
900
16%
1924
December16th to endNight
29%
954
9%
2802
6%
954
32%
954
12%
2250

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
9%9%35%424446%44%
46137
Night
9%9%36%42445%6%43%
45741
TransparencyDay
39%5%10%19%16%7%
45820
Night
39%6%12%20%14%6%
45558
SeeingDay
12%17%30%25%11%2
5110
Night
12%8%20%36%20%3
15107

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
10%17%5%8%6%34336%29%
1433
16th to endDay
13%18%5%7%5%3334429%
1728
February1st to 15thDay
13%17%6%9%5%23336%28%
1575
16th to endDay
10%18%6%9%5%24346%27%
1545
March1st to 15thDay
9%15%6%7%6%3445%6%31%
1920
16th to endDay
12%16%6%8%42445%6%28%
2112
April1st to 15thDay
11%11%47%7%35%5%47%31%
2122
16th to endDay
10%11%45%42445%6%38%
2305
May1st to 15thDay
9%7%345%35%46%7%41%
2136
16th to endDay
13%9%37%6%35%45%7%33%
2279
June1st to 15thDay
10%6%25%4346%5%6%44%
2409
16th to endDay
3312223346%67%
2475
July1st to 15thDay
321321335%7%63%
2353
16th to endDay
331232335%5%64%
2310
August1st to 15thDay
4313423347%61%
2145
16th to endDay
4313333446%63%
2275
September1st to 15thDay
4413423447%60%
1868
16th to endDay
7%413323245%61%
1815
October1st to 15thDay
11%8%245%24336%46%
1708
16th to endDay
8%8%25%44435%7%44%
1710
November1st to 15thDay
15%10%45%413445%40%
1584
16th to endDay
9%12%46%5%3345%5%39%
1461
December1st to 15thDay
13%17%6%9%7%24445%24%
1440
16th to endDay
14%13%6%10%7%3445%424%
1429
January1st to 15thNight
13%15%48%5%24447%29%
2503
16th to endNight
12%16%6%7%5%23345%32%
2496
February1st to 15thNight
10%15%6%9%6%2445%5%29%
2277
16th to endNight
8%12%6%7%43446%6%34%
1926
March1st to 15thNight
7%10%5%7%7%35%5%5%7%34%
2040
16th to endNight
10%11%36%4245%6%8%35%
2112
April1st to 15thNight
8%9%46%5%2446%6%41%
1823
16th to endNight
11%7%2442445%5%46%
1602
May1st to 15thNight
6%6%26%43445%6%48%
1484
16th to endNight
12%6%245%36%5%5%6%41%
1480
June1st to 15thNight
7%5%144245%5%9%47%
1218
16th to endNight
321231233469%
1155
July1st to 15thNight
12123245%7%8%59%
1273
16th to endNight
2113223347%66%
1549
August1st to 15thNight
3324235%7%8%57%
1485
16th to endNight
331231235%6%64%
1575
September1st to 15thNight
431432344464%
1761
16th to endNight
7%213212345%63%
1815
October1st to 15thNight
9%6%24323245%55%
1922
16th to endNight
10%6%2442445%7%47%
2161
November1st to 15thNight
10%11%35%42435%6%42%
2275
16th to endNight
7%9%46%6%3445%6%39%
2487
December1st to 15thNight
14%13%5%8%5%3445%5%28%
2520
16th to endNight
15%17%6%10%6%3433424%
2802

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
56%7%17%13%5%
1433
16th to endDay
58%5%11%16%6%1
1728
February1st to 15thDay
57%6%13%16%5%
1575
16th to endDay
57%6%13%16%41
1545
March1st to 15thDay
52%7%13%18%6%1
1920
16th to endDay
54%7%12%17%7%
2112
April1st to 15thDay
51%6%13%18%9%
2122
16th to endDay
44%6%10%25%13%
2305
May1st to 15thDay
40%5%8%26%17%1
2136
16th to endDay
48%6%10%21%11%1
2282
June1st to 15thDay
38%5%12%23%17%3
2409
16th to endDay
17%45%19%35%17%
2475
July1st to 15thDay
19%46%18%30%21%
2204
16th to endDay
19%35%14%21%34%
2154
August1st to 15thDay
21%37%14%29%24%
2130
16th to endDay
22%35%17%31%19%
2275
September1st to 15thDay
23%47%17%31%14%
1868
16th to endDay
23%48%24%29%8%
1815
October1st to 15thDay
38%5%11%27%12%3
1708
16th to endDay
37%6%15%24%15%
1710
November1st to 15thDay
44%6%13%21%10%1
1584
16th to endDay
44%7%18%18%8%1
1461
December1st to 15thDay
61%8%13%13%2
1440
16th to endDay
60%7%15%11%4
1429
January1st to 15thNight
53%9%14%16%41
2503
16th to endNight
54%5%12%19%5%2
2496
February1st to 15thNight
54%7%15%16%6%
2288
16th to endNight
48%6%17%20%5%1
1926
March1st to 15thNight
47%8%12%22%8%
2040
16th to endNight
44%8%14%23%8%
2112
April1st to 15thNight
40%7%16%22%11%2
1823
16th to endNight
38%5%12%23%18%
1602
May1st to 15thNight
33%7%10%27%18%2
1485
16th to endNight
39%7%12%24%13%2
1481
June1st to 15thNight
31%7%11%23%20%5%
1218
16th to endNight
17%35%16%31%25%
1155
July1st to 15thNight
19%45%19%26%23%
1193
16th to endNight
17%2413%24%36%
1442
August1st to 15thNight
20%46%16%23%27%
1476
16th to endNight
19%35%16%30%24%
1575
September1st to 15thNight
22%48%13%31%20%
1761
16th to endNight
22%46%26%30%10%
1815
October1st to 15thNight
31%314%27%16%5%
1922
16th to endNight
33%6%11%29%18%1
2161
November1st to 15thNight
42%6%12%22%13%3
2275
16th to endNight
43%8%14%21%9%1
2487
December1st to 15thNight
54%8%17%14%4
2520
16th to endNight
62%6%11%13%3
2802

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
24%334%21%9%6%
61
16th to endDay
26%9%21%29%13%
96
February1st to 15thDay
21%15%25%24%11%2
90
16th to endDay
19%26%31%14%6%
204
March1st to 15thDay
17%32%28%18%3
270
16th to endDay
20%34%30%12%2
288
April1st to 15thDay
18%28%27%19%41
269
16th to endDay
21%28%28%15%5%
259
May1st to 15thDay
12%20%42%19%3
228
16th to endDay
15%14%27%25%13%4
324
June1st to 15thDay
12%12%22%31%16%4
420
16th to endDay
411%26%31%22%3
420
July1st to 15thDay
48%26%37%20%2
288
16th to endDay
310%40%32%12%
271
August1st to 15thDay
6%10%43%27%11%1
255
16th to endDay
411%33%31%13%5%
268
September1st to 15thDay
420%35%23%12%3
255
16th to endDay
7%14%27%30%13%5%
255
October1st to 15thDay
16%16%24%24%12%6%
148
16th to endDay
20%10%30%20%15%2
96
November1st to 15thDay
10%7%22%22%21%16%
90
16th to endDay
14%25%41%14%4
90
December1st to 15thDay
18%16%35%26%2
90
16th to endDay
17%14%38%18%8%2
75
January1st to 15thNight
18%7%20%35%15%2
720
16th to endNight
20%7%19%32%18%2
768
February1st to 15thNight
15%10%20%37%13%1
704
16th to endNight
11%12%28%32%12%1
632
March1st to 15thNight
9%9%26%38%13%2
720
16th to endNight
14%12%25%33%12%
768
April1st to 15thNight
11%13%24%31%16%2
641
16th to endNight
12%11%26%30%17%1
534
May1st to 15thNight
10%8%22%35%20%2
495
16th to endNight
14%6%17%33%23%4
515
June1st to 15thNight
8%5%23%37%22%2
393
16th to endNight
5%314%40%30%5%
330
July1st to 15thNight
1111%45%36%4
310
16th to endNight
319%47%35%3
497
August1st to 15thNight
413%45%33%1
494
16th to endNight
3313%43%31%4
525
September1st to 15thNight
6%315%37%30%6%
620
16th to endNight
8%411%35%29%9%
656
October1st to 15thNight
11%5%16%35%25%4
660
16th to endNight
13%6%15%37%24%3
704
November1st to 15thNight
15%8%18%35%19%2
700
16th to endNight
9%11%24%35%14%4
867
December1st to 15thNight
19%10%23%35%10%
900
16th to endNight
22%13%23%28%11%1
954
Page generated at 2017-04-29 07:45:08. Version ac04

Copyright 2017 A. Danko


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