White Rock
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the White Rock clear sky chart from 2005-11-05 to 2018-08-29.

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
67%
16981
32%
50659
24%
16939
74%
16939
49%
25325

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
68%
818
35%
2561
30%
815
76%
815
59%
1124
January16th to endNight
64%
832
37%
2704
30%
832
75%
832
53%
1222
February1st to 15thNight
60%
761
29%
2415
22%
760
69%
760
49%
1149
February16th to endNight
56%
684
38%
2050
27%
684
69%
684
51%
1007
March1st to 15thNight
59%
780
34%
2204
24%
780
66%
780
50%
1142
March16th to endNight
62%
782
36%
2238
23%
782
72%
782
54%
1082
April1st to 15thNight
49%
584
33%
1948
22%
584
66%
584
45%
923
April16th to endNight
52%
579
35%
1929
25%
579
70%
579
47%
889
May1st to 15thNight
62%
585
28%
1949
24%
584
72%
584
43%
964
May16th to endNight
63%
610
32%
1659
23%
609
71%
609
52%
857
June1st to 15thNight
71%
585
29%
1560
22%
585
76%
585
57%
790
June16th to endNight
79%
585
27%
1560
22%
585
81%
585
55%
803
July1st to 15thNight
77%
555
17%
1549
15%
555
77%
555
37%
916
July16th to endNight
80%
612
15%
1737
14%
579
80%
579
31%
1041
August1st to 15thNight
83%
575
16%
1811
18%
572
83%
572
35%
1021
August16th to endNight
80%
615
22%
2050
27%
615
81%
615
34%
1140
September1st to 15thNight
77%
540
25%
1800
27%
540
79%
540
34%
999
September16th to endNight
75%
570
36%
1935
33%
570
81%
570
49%
894
October1st to 15thNight
69%
720
34%
2160
25%
720
74%
720
53%
1055
October16th to endNight
75%
768
42%
2304
30%
768
82%
768
61%
1033
November1st to 15thNight
73%
851
40%
2371
27%
851
79%
851
69%
1054
November16th to endNight
70%
975
42%
2535
27%
975
76%
975
62%
1260
December1st to 15thNight
62%
975
32%
2718
21%
975
70%
975
53%
1388
December16th to endNight
58%
1040
32%
2912
22%
1040
66%
1040
48%
1572

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
22123245%6%8%60%
51586
Night
221232345%7%63%
50851
TransparencyDay
20%410%24%27%13%
51278
Night
20%310%24%27%12%
50661
SeeingDay
46%21%33%25%7%
6821
Night
4219%47%23%2
16986

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
121221335%8%69%
1717
16th to endDay
2222222346%69%
1872
February1st to 15thDay
1313423447%63%
1774
16th to endDay
31242445%9%62%
1710
March1st to 15thDay
131342435%7%62%
2083
16th to endDay
111231345%7%64%
2337
April1st to 15thDay
121322445%8%63%
2330
16th to endDay
1212324448%63%
2306
May1st to 15thDay
2113225%45%8%61%
2331
16th to endDay
22222345%8%66%
2804
June1st to 15thDay
112245%6%8%66%
2730
16th to endDay
11221446%9%64%
2730
July1st to 15thDay
3214436%8%9%11%43%
2652
16th to endDay
32145%38%8%10%14%37%
2675
August1st to 15thDay
2214437%7%9%11%44%
2392
16th to endDay
32135%36%7%9%12%44%
2449
September1st to 15thDay
5%413435%6%6%8%48%
2160
16th to endDay
22222345%6%67%
2022
October1st to 15thDay
412313446%66%
1800
16th to endDay
111221223475%
1920
November1st to 15thDay
111211346%73%
1803
16th to endDay
1212212235%72%
1755
December1st to 15thDay
1212222447%68%
1570
16th to endDay
141332445%8%59%
1664
January1st to 15thNight
1211113346%71%
2561
16th to endNight
2212112346%69%
2704
February1st to 15thNight
2313323246%66%
2405
16th to endNight
1312323346%67%
2050
March1st to 15thNight
2413324246%64%
2204
16th to endNight
2212213336%69%
2238
April1st to 15thNight
2213323448%63%
1948
16th to endNight
3213214335%68%
1929
May1st to 15thNight
2313333346%62%
1949
16th to endNight
3113313346%68%
1659
June1st to 15thNight
11122145%5%7%66%
1560
16th to endNight
1133146%6%8%62%
1560
July1st to 15thNight
32135%47%6%9%11%42%
1634
16th to endNight
21237%47%8%10%13%37%
1845
August1st to 15thNight
3214435%7%10%13%43%
1820
16th to endNight
4214435%7%10%12%43%
2050
September1st to 15thNight
42135%26%6%9%11%46%
1800
16th to endNight
4212313347%65%
1935
October1st to 15thNight
4212212336%68%
2160
16th to endNight
3111212235%73%
2304
November1st to 15thNight
111111335%77%
2371
16th to endNight
221211324473%
2535
December1st to 15thNight
3312223246%67%
2718
16th to endNight
2313323346%62%
2912

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
15%211%36%30%2
1718
16th to endDay
18%29%31%32%6%
1872
February1st to 15thDay
20%312%32%21%8%
1775
16th to endDay
21%25%27%31%10%
1710
March1st to 15thDay
22%25%25%33%10%
2083
16th to endDay
18%36%26%33%10%
2337
April1st to 15thDay
19%46%25%31%13%
2330
16th to endDay
19%35%21%33%16%
2306
May1st to 15thDay
20%47%21%32%14%
2331
16th to endDay
16%38%20%26%24%
2807
June1st to 15thDay
14%37%17%22%33%
2730
16th to endDay
15%46%17%27%30%
2730
July1st to 15thDay
28%8%16%19%15%12%
2509
16th to endDay
27%10%22%27%10%1
2520
August1st to 15thDay
26%8%18%23%17%6%
2377
16th to endDay
26%7%15%27%17%6%
2449
September1st to 15thDay
29%5%14%23%18%8%
2160
16th to endDay
17%35%22%33%17%
2022
October1st to 15thDay
19%36%19%35%16%
1800
16th to endDay
15%16%23%38%15%
1920
November1st to 15thDay
12%26%29%35%12%
1803
16th to endDay
17%15%27%36%11%
1755
December1st to 15thDay
18%215%35%24%4
1570
16th to endDay
25%413%29%24%2
1664
January1st to 15thNight
15%210%37%28%5%
2561
16th to endNight
18%29%28%35%6%
2704
February1st to 15thNight
20%312%30%23%9%
2415
16th to endNight
21%25%24%34%12%
2050
March1st to 15thNight
23%2427%32%10%
2204
16th to endNight
18%2423%36%14%
2238
April1st to 15thNight
21%37%22%29%15%
1948
16th to endNight
19%35%20%34%16%
1929
May1st to 15thNight
24%37%18%29%16%
1950
16th to endNight
18%5%9%18%21%26%
1660
June1st to 15thNight
17%310%17%22%29%
1560
16th to endNight
17%411%14%20%31%
1560
July1st to 15thNight
27%8%21%15%11%13%
1549
16th to endNight
30%10%26%21%9%1
1737
August1st to 15thNight
27%8%23%20%11%7%
1811
16th to endNight
28%8%17%25%13%7%
2050
September1st to 15thNight
28%7%19%20%14%10%
1800
16th to endNight
19%311%17%28%20%
1935
October1st to 15thNight
19%27%17%31%20%
2160
16th to endNight
15%15%19%38%19%
2304
November1st to 15thNight
12%16%28%38%12%
2371
16th to endNight
17%1426%35%15%
2535
December1st to 15thNight
21%210%34%25%5%
2718
16th to endNight
24%212%32%24%2
2912

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
7%5%29%40%14%2
135
16th to endDay
4222%42%23%5%
144
February1st to 15thDay
25%22%46%21%
135
16th to endDay
9%10%32%29%15%3
120
March1st to 15thDay
49%28%35%17%2
268
16th to endDay
6%19%34%24%14%1
352
April1st to 15thDay
8%18%37%24%8%3
329
16th to endDay
8%17%37%24%9%1
318
May1st to 15thDay
5%11%35%32%12%2
348
16th to endDay
39%28%35%20%2
563
June1st to 15thDay
26%19%36%31%3
570
16th to endDay
2114%32%37%10%
570
July1st to 15thDay
47%32%43%11%
478
16th to endDay
31429%34%25%
391
August1st to 15thDay
5%18%27%39%17%
359
16th to endDay
5%19%35%35%13%
385
September1st to 15thDay
5%214%39%26%11%
315
16th to endDay
5%324%38%23%4
213
October1st to 15thDay
2231%31%28%4
135
16th to endDay
35%16%29%31%13%
144
November1st to 15thDay
6%420%38%25%4
135
16th to endDay
5%5%31%33%19%4
135
December1st to 15thDay
1228%40%25%2
135
16th to endDay
9%6%22%47%12%
144
January1st to 15thNight
2122%54%17%1
819
16th to endNight
5%125%50%15%1
832
February1st to 15thNight
5%224%55%12%
764
16th to endNight
3432%52%6%
684
March1st to 15thNight
5%326%51%12%
780
16th to endNight
36%25%51%14%
782
April1st to 15thNight
46%34%43%10%
584
16th to endNight
5%434%44%10%
579
May1st to 15thNight
5%322%51%16%
585
16th to endNight
3322%49%20%
611
June1st to 15thNight
1218%48%27%1
585
16th to endNight
2112%50%32%1
585
July1st to 15thNight
416%36%47%4
555
16th to endNight
4127%57%8%
612
August1st to 15thNight
41127%57%7%
575
16th to endNight
5%333%49%6%
615
September1st to 15thNight
6%6%43%40%3
540
16th to endNight
6%11%44%34%2
570
October1st to 15thNight
4218%49%22%2
720
16th to endNight
415%45%30%4
768
November1st to 15thNight
3119%49%25%
851
16th to endNight
5%220%47%22%2
975
December1st to 15thNight
5%224%53%12%1
975
16th to endNight
6%326%51%11%
1040
Page generated at 2018-08-30 03:34:20. Version ac04

Copyright 2018 A. Danko


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