Robinson Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Robinson Creek Observatory clear sky chart from 2005-11-05 to 2017-10-31.

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
59%
15433
26%
47436
22%
15396
63%
15396
35%
26897

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
53%
716
16%
2375
16%
716
55%
716
21%
1563
January16th to endNight
51%
768
25%
2496
26%
768
54%
768
24%
1592
February1st to 15thNight
45%
699
20%
2288
19%
699
49%
699
20%
1538
February16th to endNight
43%
632
20%
1945
16%
632
49%
632
23%
1274
March1st to 15thNight
45%
720
12%
1980
9%
720
48%
720
20%
1424
March16th to endNight
41%
768
17%
2112
12%
768
46%
768
24%
1433
April1st to 15thNight
41%
719
19%
1807
8%
719
46%
719
25%
1242
April16th to endNight
49%
699
23%
1779
11%
699
55%
699
39%
1037
May1st to 15thNight
57%
539
28%
1619
19%
539
64%
539
46%
821
May16th to endNight
57%
412
25%
1534
21%
411
66%
411
39%
715
June1st to 15thNight
56%
360
24%
1440
24%
360
68%
360
37%
668
June16th to endNight
71%
360
35%
1440
43%
360
79%
360
60%
518
July1st to 15thNight
84%
390
33%
1410
38%
390
88%
390
75%
471
July16th to endNight
86%
564
39%
1593
35%
531
89%
531
73%
636
August1st to 15thNight
88%
538
40%
1611
33%
535
90%
535
76%
631
August16th to endNight
85%
717
44%
1863
30%
717
87%
717
76%
828
September1st to 15thNight
85%
720
42%
1800
28%
720
87%
720
76%
821
September16th to endNight
74%
716
39%
1990
33%
716
79%
716
61%
930
October1st to 15thNight
68%
720
29%
2160
28%
720
74%
720
47%
1086
October16th to endNight
65%
768
32%
2304
32%
768
70%
768
38%
1289
November1st to 15thNight
56%
700
23%
2162
21%
700
60%
700
28%
1339
November16th to endNight
53%
720
19%
2520
20%
720
56%
720
24%
1525
December1st to 15thNight
47%
720
19%
2520
19%
720
51%
720
19%
1674
December16th to endNight
41%
768
18%
2688
17%
768
45%
768
17%
1842

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
11%5%23313336%56%
48314
Night
12%5%24323346%52%
47624
TransparencyDay
29%27%20%23%15%
48002
Night
32%38%19%21%14%
47437
SeeingDay
15%11%26%26%14%5%
6198
Night
14%413%30%26%8%
15443

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
18%7%36%5%23436%37%
1561
16th to endDay
22%7%24323235%42%
1728
February1st to 15thDay
23%6%35%325%346%37%
1576
16th to endDay
22%7%25%313447%35%
1526
March1st to 15thDay
24%9%45%424436%31%
1980
16th to endDay
20%7%25%434348%33%
2112
April1st to 15thDay
18%7%35%5%2445%7%35%
2140
16th to endDay
11%5%24323347%50%
2178
May1st to 15thDay
7%41221335%8%58%
2331
16th to endDay
8%5%24323347%54%
2578
June1st to 15thDay
7%424323246%57%
2520
16th to endDay
322112225%74%
2520
July1st to 15thDay
1111112482%
2463
16th to endDay
1111112483%
2468
August1st to 15thDay
111111112481%
2340
16th to endDay
111122483%
2339
September1st to 15thDay
11112135%78%
2160
16th to endDay
332212135%72%
1967
October1st to 15thDay
9%312223235%63%
1800
16th to endDay
10%5%24313247%54%
1918
November1st to 15thDay
11%6%25%42345%8%44%
1693
16th to endDay
17%6%245%23336%43%
1440
December1st to 15thDay
20%10%34424335%39%
1440
16th to endDay
26%8%35%323345%33%
1536
January1st to 15thNight
17%6%36%5%345%5%6%35%
2375
16th to endNight
20%7%35%322336%41%
2496
February1st to 15thNight
20%7%36%5%35%35%5%35%
2276
16th to endNight
20%6%25%32445%6%37%
1945
March1st to 15thNight
21%8%25%425%5%5%7%31%
1980
16th to endNight
19%7%26%324446%38%
2112
April1st to 15thNight
15%7%35%434447%38%
1807
16th to endNight
9%423323348%53%
1779
May1st to 15thNight
4323323248%60%
1619
16th to endNight
5%414323347%59%
1533
June1st to 15thNight
5%424313346%60%
1440
16th to endNight
3211223476%
1440
July1st to 15thNight
111122383%
1494
16th to endNight
111111235%78%
1701
August1st to 15thNight
12111235%79%
1620
16th to endNight
1111125%81%
1863
September1st to 15thNight
2121122481%
1800
16th to endNight
3212212247%68%
1990
October1st to 15thNight
6%423222235%64%
2160
16th to endNight
9%5%25%324346%52%
2304
November1st to 15thNight
13%5%25%425%5%6%7%41%
2162
16th to endNight
16%6%25%42345%6%42%
2520
December1st to 15thNight
22%7%25%423345%37%
2520
16th to endNight
25%7%35%423346%33%
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
47%29%16%12%11%
1561
16th to endDay
46%26%13%17%13%
1728
February1st to 15thDay
47%36%17%18%5%
1576
16th to endDay
48%410%22%11%3
1526
March1st to 15thDay
55%38%13%14%4
1980
16th to endDay
50%311%18%12%2
2112
April1st to 15thDay
46%313%24%11%1
2140
16th to endDay
33%314%26%16%4
2178
May1st to 15thDay
23%210%33%23%6%
2331
16th to endDay
29%310%35%17%4
2582
June1st to 15thDay
26%210%23%25%11%
2520
16th to endDay
13%1420%39%21%
2520
July1st to 15thDay
8%1213%38%36%
2318
16th to endDay
8%39%28%47%
2313
August1st to 15thDay
8%1221%34%31%
2324
16th to endDay
6%1418%37%30%
2339
September1st to 15thDay
10%1218%34%32%
2160
16th to endDay
15%26%24%31%19%
1967
October1st to 15thDay
24%25%21%27%18%
1800
16th to endDay
29%37%22%23%13%
1918
November1st to 15thDay
37%410%25%12%9%
1693
16th to endDay
43%29%17%19%7%
1440
December1st to 15thDay
50%36%15%19%4
1440
16th to endDay
53%37%15%13%7%
1536
January1st to 15thNight
46%410%15%13%9%
2375
16th to endNight
44%27%15%16%14%
2496
February1st to 15thNight
49%38%16%15%6%
2288
16th to endNight
45%311%23%13%2
1945
March1st to 15thNight
51%411%15%13%2
1980
16th to endNight
45%413%20%14%2
2112
April1st to 15thNight
43%415%21%12%2
1807
16th to endNight
28%314%30%18%4
1779
May1st to 15thNight
23%28%29%27%8%
1620
16th to endNight
23%311%38%16%6%
1534
June1st to 15thNight
24%310%25%24%11%
1440
16th to endNight
11%26%19%37%22%
1440
July1st to 15thNight
6%1212%38%38%
1410
16th to endNight
8%239%24%51%
1593
August1st to 15thNight
7%1218%33%35%
1611
16th to endNight
7%2318%33%34%
1863
September1st to 15thNight
8%1214%35%37%
1800
16th to endNight
15%16%22%31%22%
1990
October1st to 15thNight
22%26%20%28%19%
2160
16th to endNight
31%26%21%22%15%
2304
November1st to 15thNight
38%5%14%21%11%8%
2162
16th to endNight
40%39%19%18%7%
2520
December1st to 15thNight
49%36%17%17%5%
2520
16th to endNight
52%28%13%16%6%
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
31%10%20%18%16%2
189
16th to endDay
30%9%21%15%16%6%
256
February1st to 15thDay
30%10%22%17%17%
236
16th to endDay
28%20%17%23%8%
227
March1st to 15thDay
35%15%24%11%8%3
270
16th to endDay
26%22%30%14%41
288
April1st to 15thDay
27%19%27%15%7%2
269
16th to endDay
23%21%29%19%32
270
May1st to 15thDay
13%23%31%20%7%3
288
16th to endDay
16%12%24%22%16%7%
330
June1st to 15thDay
12%11%38%25%9%3
315
16th to endDay
5%8%36%33%10%5%
315
July1st to 15thDay
25%21%43%20%7%
305
16th to endDay
1222%45%19%8%
327
August1st to 15thDay
2329%36%21%6%
315
16th to endDay
325%38%20%11%
332
September1st to 15thDay
4325%40%18%8%
315
16th to endDay
6%8%27%29%18%9%
315
October1st to 15thDay
10%11%26%27%15%8%
315
16th to endDay
13%10%21%28%18%6%
336
November1st to 15thDay
12%9%20%25%26%4
201
16th to endDay
20%15%31%18%8%6%
60
December1st to 15thDay
43%10%21%21%11
60
16th to endDay
25%14%14%20%15%10%
64
January1st to 15thNight
20%310%33%23%8%
720
16th to endNight
24%412%27%23%8%
768
February1st to 15thNight
23%5%13%29%22%5%
704
16th to endNight
23%5%18%28%18%4
632
March1st to 15thNight
25%6%14%29%19%4
720
16th to endNight
23%7%18%30%16%3
768
April1st to 15thNight
21%11%18%27%16%5%
719
16th to endNight
11%10%21%29%20%5%
699
May1st to 15thNight
6%5%24%31%26%5%
540
16th to endNight
7%424%30%26%6%
412
June1st to 15thNight
7%424%35%25%3
360
16th to endNight
3120%43%26%3
360
July1st to 15thNight
112%34%40%11%
390
16th to endNight
16%30%42%18%
564
August1st to 15thNight
15%35%42%15%
538
16th to endNight
27%31%45%12%
717
September1st to 15thNight
217%32%40%15%
720
16th to endNight
4311%33%31%14%
716
October1st to 15thNight
7%313%34%30%11%
720
16th to endNight
12%310%27%31%14%
768
November1st to 15thNight
17%312%31%26%9%
700
16th to endNight
18%6%11%30%24%8%
720
December1st to 15thNight
27%411%28%19%8%
720
16th to endNight
27%6%15%27%18%4
768
Page generated at 2017-11-01 14:23:39. Version ac04

Copyright 2017 A. Danko


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