Wren Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wren Park clear sky chart from 2005-11-05 to 2017-09-20.

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
38%
14481
8%
46735
7%
14453
40%
14453
14%
35236

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
26%
750
9%
2686
8%
746
30%
746
8%
2186
January16th to endNight
29%
774
8%
2725
7%
774
31%
774
9%
2161
February1st to 15thNight
23%
700
5%
2288
2%
700
26%
700
8%
1903
February16th to endNight
28%
632
13%
2029
7%
632
35%
632
12%
1559
March1st to 15thNight
24%
720
3%
2077
2%
720
25%
720
9%
1751
March16th to endNight
25%
768
5%
2061
2%
768
26%
768
9%
1762
April1st to 15thNight
31%
719
5%
1799
3%
719
31%
719
12%
1506
April16th to endNight
34%
507
7%
1587
6%
507
35%
507
11%
1262
May1st to 15thNight
49%
359
11%
1439
17%
359
51%
359
17%
958
May16th to endNight
52%
374
5%
1490
9%
374
53%
374
14%
1044
June1st to 15thNight
48%
360
2%
1260
1%
360
48%
360
15%
924
June16th to endNight
53%
360
5%
1260
2%
360
53%
360
18%
864
July1st to 15thNight
70%
340
9%
1190
10%
340
70%
340
32%
663
July16th to endNight
77%
376
15%
1350
23%
354
79%
354
38%
650
August1st to 15thNight
79%
411
16%
1483
21%
409
79%
409
38%
723
August16th to endNight
69%
626
18%
1772
16%
626
70%
626
37%
1034
September1st to 15thNight
70%
720
19%
1800
11%
720
70%
720
41%
1096
September16th to endNight
49%
675
16%
1856
14%
675
49%
675
21%
1346
October1st to 15thNight
42%
660
10%
1980
10%
660
45%
660
19%
1426
October16th to endNight
31%
704
5%
2197
5%
704
33%
704
11%
1755
November1st to 15thNight
19%
700
5%
2450
3%
700
22%
700
6%
2102
November16th to endNight
23%
720
5%
2520
4%
720
25%
720
8%
2058
December1st to 15thNight
24%
726
8%
2556
4%
726
30%
726
9%
2071
December16th to endNight
14%
800
5%
2880
3%
800
17%
800
6%
2432

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
30%8%35%42333429%
48128
Night
32%8%2442333428%
46891
Cloud CoverDay
29%9%35%42334428%
48128
Night
31%8%35%423335%28%
46894
TransparencyDay
58%5%12%15%6%1
47787
Night
59%5%13%14%6%1
46736
SeeingDay
29%8%22%25%11%2
6069
Night
35%5%13%23%18%3
14487

By Month

Percentage Cloud Cover NW (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
45%8%25%32323219%
1253
16th to endDay
40%10%34322335%20%
1497
February1st to 15thDay
40%9%36%5%23235%16%
1573
16th to endDay
31%12%35%5%2333423%
1445
March1st to 15thDay
45%12%3442332213%
1881
16th to endDay
37%12%37%6%2433214%
2163
April1st to 15thDay
34%11%46%6%25%33416%
2149
16th to endDay
31%10%47%5%345%5%417%
2373
May1st to 15thDay
27%7%25%5%24335%30%
2511
16th to endDay
28%9%47%5%33445%24%
2618
June1st to 15thDay
33%6%35%5%34345%24%
2700
16th to endDay
27%8%36%5%34445%27%
2700
July1st to 15thDay
14%414323345%50%
2700
16th to endDay
16%423322246%51%
2723
August1st to 15thDay
15%42332345%5%51%
2466
16th to endDay
17%413423447%45%
2429
September1st to 15thDay
16%6%14313225%50%
2160
16th to endDay
30%8%36%41333331%
1871
October1st to 15thDay
31%8%25%423335%28%
1650
16th to endDay
41%7%25%422245%19%
1673
November1st to 15thDay
52%9%2332222213%
1408
16th to endDay
43%9%35%32233320%
1440
December1st to 15thDay
38%12%3431223223%
1401
16th to endDay
45%13%45%42221215%
1344
January1st to 15thNight
45%9%2421123421%
2686
16th to endNight
39%11%3431323422%
2725
February1st to 15thNight
39%10%36%5%22235%18%
2276
16th to endNight
32%10%34433335%27%
2029
March1st to 15thNight
41%10%35%43333317%
2077
16th to endNight
40%10%35%5%3333317%
2057
April1st to 15thNight
29%10%36%7%34445%20%
1799
16th to endNight
33%9%35%5%245%3421%
1587
May1st to 15thNight
21%7%26%3245%46%35%
1439
16th to endNight
22%5%35%6%25%5%5%6%31%
1490
June1st to 15thNight
24%9%36%43444431%
1260
16th to endNight
21%6%37%5%3445%6%32%
1260
July1st to 15thNight
9%424323335%56%
1260
16th to endNight
9%212213345%61%
1444
August1st to 15thNight
10%312212346%60%
1491
16th to endNight
10%42432346%7%49%
1772
September1st to 15thNight
10%413423236%57%
1800
16th to endNight
27%5%245%23436%34%
1856
October1st to 15thNight
27%6%2443443434%
1980
16th to endNight
39%7%25%433345%20%
2197
November1st to 15thNight
49%7%2442232414%
2450
16th to endNight
42%8%25%33332321%
2520
December1st to 15thNight
39%10%2332433421%
2556
16th to endNight
47%12%2431222217%
2880

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
45%7%25%32332419%
1253
16th to endDay
40%10%25%32233421%
1497
February1st to 15thDay
38%10%36%5%33235%17%
1573
16th to endDay
30%12%46%5%2334422%
1445
March1st to 15thDay
44%12%35%42333213%
1881
16th to endDay
36%12%47%6%3333313%
2163
April1st to 15thDay
33%12%48%5%3433415%
2149
16th to endDay
31%11%47%6%345%5%5%15%
2373
May1st to 15thDay
26%7%36%425%335%30%
2511
16th to endDay
28%10%36%6%3325%6%23%
2618
June1st to 15thDay
32%8%35%433445%23%
2700
16th to endDay
26%8%36%5%34445%26%
2700
July1st to 15thDay
14%5%24323345%50%
2700
16th to endDay
15%5%24312245%52%
2723
August1st to 15thDay
14%41332345%6%50%
2466
16th to endDay
15%5%24323348%45%
2429
September1st to 15thDay
16%6%24422325%50%
2160
16th to endDay
29%9%36%42232331%
1871
October1st to 15thDay
29%9%3441345%428%
1650
16th to endDay
40%8%26%422345%19%
1673
November1st to 15thDay
51%9%4431323312%
1408
16th to endDay
42%9%25%31432319%
1440
December1st to 15thDay
36%14%35%31222223%
1401
16th to endDay
44%13%46%42322214%
1344
January1st to 15thNight
44%8%3431123421%
2685
16th to endNight
38%12%34322235%21%
2725
February1st to 15thNight
38%10%36%43323418%
2276
16th to endNight
31%10%345%23335%26%
2029
March1st to 15thNight
40%10%45%42433416%
2077
16th to endNight
38%11%36%5%2323316%
2061
April1st to 15thNight
30%11%45%7%34435%19%
1799
16th to endNight
32%10%5%6%433435%20%
1587
May1st to 15thNight
22%7%36%4245%46%33%
1439
16th to endNight
21%7%25%6%345%5%6%31%
1490
June1st to 15thNight
23%9%36%5%34435%30%
1260
16th to endNight
20%7%46%5%3445%6%32%
1260
July1st to 15thNight
9%423413336%56%
1260
16th to endNight
10%212222446%60%
1444
August1st to 15thNight
10%313212347%59%
1491
16th to endNight
9%425%42346%7%49%
1772
September1st to 15thNight
11%313323335%57%
1800
16th to endNight
26%6%25%5%23336%34%
1856
October1st to 15thNight
26%7%24423435%33%
1980
16th to endNight
37%9%35%323336%20%
2197
November1st to 15thNight
48%9%2442233414%
2450
16th to endNight
42%7%35%41322321%
2520
December1st to 15thNight
38%11%3432333421%
2556
16th to endNight
46%13%35%31222316%
2880

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
71%5%5%10%6%1
1253
16th to endDay
65%6%9%13%32
1497
February1st to 15thDay
71%5%8%6%6%1
1573
16th to endDay
65%39%14%5%1
1445
March1st to 15thDay
76%48%8%1
1881
16th to endDay
75%48%9%1
2163
April1st to 15thDay
72%5%11%9%1
2149
16th to endDay
68%5%12%9%4
2373
May1st to 15thDay
56%5%14%15%7%
2511
16th to endDay
61%6%16%12%2
2622
June1st to 15thDay
62%415%11%41
2700
16th to endDay
58%5%15%15%5%
2700
July1st to 15thDay
36%5%15%27%12%3
2541
16th to endDay
33%417%30%11%2
2554
August1st to 15thDay
34%5%19%29%9%1
2449
16th to endDay
37%5%21%26%7%1
2429
September1st to 15thDay
37%413%21%18%3
2160
16th to endDay
57%5%10%15%9%1
1871
October1st to 15thDay
56%414%14%8%1
1650
16th to endDay
66%5%13%11%3
1673
November1st to 15thDay
78%28%7%11
1408
16th to endDay
70%37%9%7%
1440
December1st to 15thDay
69%47%9%8%
1401
16th to endDay
77%35%8%31
1344
January1st to 15thNight
68%5%6%13%5%
2686
16th to endNight
65%5%9%12%42
2725
February1st to 15thNight
71%49%9%32
2288
16th to endNight
62%310%16%6%1
2029
March1st to 15thNight
70%5%12%8%3
2077
16th to endNight
71%411%9%1
2061
April1st to 15thNight
66%5%12%12%2
1799
16th to endNight
65%412%12%4
1587
May1st to 15thNight
49%5%17%17%8%1
1440
16th to endNight
52%7%21%14%3
1490
June1st to 15thNight
56%419%11%5%1
1260
16th to endNight
50%6%19%18%42
1260
July1st to 15thNight
31%6%13%29%15%3
1190
16th to endNight
23%5%18%32%16%3
1350
August1st to 15thNight
24%5%21%32%11%3
1483
16th to endNight
31%421%27%10%2
1772
September1st to 15thNight
29%6%17%22%20%4
1800
16th to endNight
50%5%13%19%7%2
1856
October1st to 15thNight
52%5%14%17%8%1
1980
16th to endNight
65%5%14%10%4
2197
November1st to 15thNight
74%5%8%6%22
2450
16th to endNight
69%49%7%7%1
2520
December1st to 15thNight
67%5%8%11%5%
2556
16th to endNight
75%38%7%41
2880

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%13%18%21%25%6%
60
16th to endDay
48%6%12%20%9%3
64
February1st to 15thDay
44%10%18%16%7%2
233
16th to endDay
37%10%23%17%9%1
215
March1st to 15thDay
55%10%20%13%1
270
16th to endDay
45%12%21%15%4
288
April1st to 15thDay
37%11%21%15%11%1
269
16th to endDay
30%15%27%18%6%1
270
May1st to 15thDay
28%9%28%23%7%1
288
16th to endDay
33%8%15%23%13%4
333
June1st to 15thDay
26%8%25%27%9%2
495
16th to endDay
23%9%28%27%9%1
495
July1st to 15thDay
15%424%38%13%2
475
16th to endDay
11%6%25%36%15%4
392
August1st to 15thDay
15%320%33%19%7%
315
16th to endDay
12%7%21%37%15%5%
332
September1st to 15thDay
19%9%20%27%17%4
315
16th to endDay
27%419%30%13%3
272
October1st to 15thDay
35%6%20%23%12%
255
16th to endDay
42%6%17%23%7%2
189
November1st to 15thDay
66%6%18%6%1
60
16th to endDay
51%116%6%15%8%
60
December1st to 15thDay
55%10%18%13%3
60
16th to endDay
51%20%20%6%1
64
January1st to 15thNight
48%8%12%18%12%
750
16th to endNight
44%6%12%23%12%
774
February1st to 15thNight
44%6%16%23%7%
704
16th to endNight
35%9%19%21%12%1
632
March1st to 15thNight
43%8%17%18%11%
720
16th to endNight
43%6%16%23%8%2
768
April1st to 15thNight
35%6%15%26%14%1
719
16th to endNight
38%5%12%27%14%1
507
May1st to 15thNight
24%311%32%25%2
360
16th to endNight
24%28%28%31%4
375
June1st to 15thNight
24%411%26%26%6%
360
16th to endNight
24%19%31%28%4
360
July1st to 15thNight
11%37%28%42%5%
340
16th to endNight
11%6%25%47%9%
376
August1st to 15thNight
12%220%47%16%
411
16th to endNight
12%26%25%44%9%
626
September1st to 15thNight
13%27%32%34%10%
720
16th to endNight
29%39%26%26%4
675
October1st to 15thNight
29%316%26%21%2
660
16th to endNight
42%5%14%23%12%2
704
November1st to 15thNight
53%5%16%20%4
700
16th to endNight
47%7%15%16%11%2
720
December1st to 15thNight
43%7%18%23%6%
726
16th to endNight
52%8%19%17%3
800
Page generated at 2017-09-21 04:18:23. Version ac04

Copyright 2017 A. Danko


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