Ranchita Canyon Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ranchita Canyon Observatory clear sky chart from 2005-11-06 to 2024-01-16.

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
74%
23990
32%
74780
30%
23947
77%
23947
49%
37092

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 10thNight
60%
756
21%
2569
22%
756
63%
756
29%
1496
January11th to 20thNight
68%
744
28%
2416
27%
744
72%
744
38%
1302
January21st to endNight
64%
792
29%
2574
30%
792
68%
792
36%
1405
February1st to 10thNight
65%
720
30%
2284
30%
720
70%
720
37%
1262
February11th to 20thNight
64%
700
32%
2099
30%
700
71%
700
47%
1072
February21st to endNight
61%
592
26%
1776
26%
592
66%
592
39%
984
March1st to 10thNight
58%
720
21%
2111
18%
720
64%
720
35%
1261
March11th to 20thNight
65%
720
25%
1980
23%
720
69%
720
39%
1156
March21st to endNight
60%
792
25%
2078
17%
792
66%
792
44%
1186
April1st to 10thNight
62%
720
30%
1800
18%
720
67%
720
48%
1018
April11th to 20thNight
61%
711
35%
1779
17%
711
67%
711
54%
937
April21st to endNight
61%
720
33%
1800
15%
720
67%
720
57%
947
May1st to 10thNight
69%
720
31%
1800
18%
720
72%
720
62%
912
May11th to 20thNight
71%
581
36%
1644
26%
581
75%
581
66%
739
May21st to endNight
70%
388
33%
1552
31%
388
78%
388
54%
581
June1st to 10thNight
80%
360
34%
1440
38%
360
85%
360
57%
531
June11th to 20thNight
83%
360
42%
1440
47%
360
90%
360
73%
448
June21st to endNight
93%
360
43%
1440
53%
360
94%
360
82%
416
July1st to 10thNight
95%
350
40%
1400
50%
350
96%
350
78%
422
July11th to 20thNight
95%
469
38%
1513
38%
469
95%
469
75%
560
July21st to endNight
92%
591
41%
1674
35%
558
93%
558
71%
685
August1st to 10thNight
92%
625
40%
1690
30%
622
92%
622
76%
732
August11th to 20thNight
94%
712
41%
1780
26%
712
94%
712
83%
790
August21st to endNight
95%
792
45%
1980
30%
792
95%
792
81%
880
September1st to 10thNight
93%
720
46%
1800
35%
720
93%
720
79%
815
September11th to 20thNight
88%
720
48%
1804
39%
720
90%
720
77%
827
September21st to endNight
87%
720
45%
1980
42%
720
90%
720
76%
842
October1st to 10thNight
82%
720
34%
2154
36%
720
85%
720
62%
958
October11th to 20thNight
79%
720
39%
2160
40%
720
84%
720
57%
988
October21st to endNight
80%
792
42%
2376
44%
792
83%
792
58%
1093
November1st to 10thNight
76%
740
37%
2311
38%
740
80%
740
54%
1062
November11th to 20thNight
77%
760
33%
2470
34%
760
81%
760
50%
1158
November21st to endNight
72%
760
31%
2470
31%
760
76%
760
44%
1241
December1st to 10thNight
65%
760
28%
2588
29%
760
70%
760
36%
1371
December11th to 20thNight
62%
759
21%
3230
25%
759
66%
759
20%
2126
December21st to endNight
57%
824
14%
4818
23%
817
63%
817
16%
2889

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
5%313323346%67%
74749
Night
6%323323346%65%
75066
TransparencyDay
19%48%18%28%23%
74468
Night
21%49%19%26%22%
74870
SeeingDay
6%5%16%31%30%13%
14363
Night
6%311%36%36%7%
24012

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 10thDay
12%6%146%346%5%7%46%
1594
11th to 20thDay
8%4234335%5%7%56%
1666
21st to endDay
12%5%235%3445%8%48%
1782
February1st to 10thDay
14%5%23313445%56%
1674
11th to 20thDay
9%425%43445%6%54%
1750
21st to endDay
13%6%35%224447%50%
1480
March1st to 10thDay
10%6%36%5%36%6%6%7%42%
1844
11th to 20thDay
11%6%25%42446%9%46%
1980
21st to endDay
8%5%25%5%245%5%6%54%
2276
April1st to 10thDay
9%5%2432345%8%55%
2160
11th to 20thDay
6%32332445%7%61%
2129
21st to endDay
5%313324347%65%
2160
May1st to 10thDay
3313322336%70%
2160
11th to 20thDay
2212323346%72%
2244
21st to endDay
3213313346%70%
2723
June1st to 10thDay
2212222348%71%
2520
11th to 20thDay
111111122386%
2520
21st to endDay
11111222386%
2520
July1st to 10thDay
1111123485%
2520
11th to 20thDay
111112335%81%
2392
21st to endDay
1111213346%78%
2546
August1st to 10thDay
21211235%81%
2239
11th to 20thDay
111221122485%
2122
21st to endDay
11121222483%
2376
September1st to 10thDay
11111122486%
2160
11th to 20thDay
111211225%83%
2156
21st to endDay
111121234479%
1980
October1st to 10thDay
2212223246%73%
1801
11th to 20thDay
3212323345%73%
1800
21st to endDay
4313212336%71%
1980
November1st to 10thDay
44235%23347%63%
1766
11th to 20thDay
6%32332435%5%63%
1710
21st to endDay
7%42441345%6%61%
1710
December1st to 10thDay
10%5%244235%6%7%52%
1587
11th to 20thDay
23%7%35%42346%6%37%
1928
21st to endDay
14%8%25%435%46%10%38%
2794
January1st to 10thNight
13%5%345%24448%47%
2569
11th to 20thNight
8%42442445%7%54%
2416
21st to endNight
12%42432345%7%55%
2574
February1st to 10thNight
11%5%24324346%56%
2284
11th to 20thNight
7%313323448%60%
2098
21st to endNight
10%6%24424336%56%
1776
March1st to 10thNight
11%6%24425%45%8%49%
2111
11th to 20thNight
9%42442446%8%52%
1980
21st to endNight
9%424323337%60%
2078
April1st to 10thNight
6%42331435%8%60%
1800
11th to 20thNight
4323313335%69%
1779
21st to endNight
3323313336%69%
1800
May1st to 10thNight
3313213347%71%
1800
11th to 20thNight
4212212245%76%
1643
21st to endNight
2212312325%75%
1552
June1st to 10thNight
221221235%5%75%
1440
11th to 20thNight
1111111125%86%
1440
21st to endNight
1111111389%
1440
July1st to 10thNight
111233486%
1440
11th to 20thNight
11211213285%
1563
21st to endNight
2112222245%78%
1773
August1st to 10thNight
11121222385%
1699
11th to 20thNight
11111223484%
1780
21st to endNight
11111122486%
1980
September1st to 10thNight
11111222386%
1800
11th to 20thNight
221211212384%
1804
21st to endNight
121121123384%
1980
October1st to 10thNight
3212222335%74%
2154
11th to 20thNight
3313223345%72%
2160
21st to endNight
4312212335%73%
2376
November1st to 10thNight
3313322346%69%
2311
11th to 20thNight
432332335%7%64%
2470
21st to endNight
5%42442446%7%59%
2470
December1st to 10thNight
11%42332345%8%53%
2588
11th to 20thNight
21%8%2443446%7%37%
3276
21st to endNight
13%7%35%5%35%5%5%8%40%
4862

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 10thDay
35%7%11%22%18%7%
1594
11th to 20thDay
28%411%22%21%15%
1666
21st to endDay
34%5%13%16%21%11%
1782
February1st to 10thDay
31%38%20%23%15%
1674
11th to 20thDay
30%5%8%21%27%10%
1760
21st to endDay
32%5%12%22%24%6%
1480
March1st to 10thDay
38%7%11%17%18%8%
1844
11th to 20thDay
34%7%12%19%20%7%
1980
21st to endDay
29%5%13%27%18%7%
2276
April1st to 10thDay
28%5%11%25%21%10%
2160
11th to 20thDay
22%6%11%27%25%9%
2132
21st to endDay
19%5%11%28%29%9%
2160
May1st to 10thDay
16%411%20%37%12%
2160
11th to 20thDay
14%38%26%37%12%
2247
21st to endDay
16%410%30%34%7%
2724
June1st to 10thDay
13%410%20%35%18%
2520
11th to 20thDay
7%25%13%41%32%
2520
21st to endDay
6%2410%34%44%
2520
July1st to 10thDay
5%228%29%55%
2451
11th to 20thDay
8%249%30%47%
2320
21st to endDay
10%35%12%26%44%
2405
August1st to 10thDay
9%2310%28%49%
2223
11th to 20thDay
7%1310%33%46%
2122
21st to endDay
9%129%36%43%
2376
September1st to 10thDay
6%2310%30%49%
2160
11th to 20thDay
8%2318%40%29%
2156
21st to endDay
10%2418%38%28%
1980
October1st to 10thDay
14%36%21%24%33%
1801
11th to 20thDay
15%37%18%29%28%
1800
21st to endDay
17%35%17%30%28%
1980
November1st to 10thDay
21%39%19%30%18%
1766
11th to 20thDay
23%410%22%26%15%
1710
21st to endDay
25%48%18%26%19%
1710
December1st to 10thDay
31%6%9%19%20%15%
1587
11th to 20thDay
46%7%8%17%14%8%
1928
21st to endDay
39%8%13%22%13%4
2794
January1st to 10thNight
36%5%12%20%21%6%
2569
11th to 20thNight
28%5%11%23%18%15%
2416
21st to endNight
29%5%13%18%22%12%
2574
February1st to 10thNight
31%47%19%26%14%
2284
11th to 20thNight
23%310%24%29%11%
2099
21st to endNight
30%310%24%25%7%
1776
March1st to 10thNight
33%6%12%23%18%8%
2111
11th to 20thNight
29%6%13%21%23%8%
1980
21st to endNight
26%415%25%22%7%
2078
April1st to 10thNight
23%5%15%27%18%12%
1800
11th to 20thNight
20%312%29%27%10%
1779
21st to endNight
17%49%29%33%8%
1800
May1st to 10thNight
14%410%24%32%15%
1800
11th to 20thNight
12%28%27%39%12%
1644
21st to endNight
13%312%28%33%10%
1552
June1st to 10thNight
11%412%20%34%19%
1440
11th to 20thNight
7%1417%39%32%
1440
21st to endNight
41210%37%47%
1440
July1st to 10thNight
4228%26%58%
1400
11th to 20thNight
7%239%28%52%
1513
21st to endNight
9%239%27%48%
1674
August1st to 10thNight
9%129%27%52%
1690
11th to 20thNight
5%228%32%51%
1780
21st to endNight
7%129%31%50%
1980
September1st to 10thNight
7%238%26%54%
1800
11th to 20thNight
8%2316%34%37%
1804
21st to endNight
8%2317%40%31%
1980
October1st to 10thNight
14%37%18%25%33%
2154
11th to 20thNight
16%38%17%30%27%
2160
21st to endNight
16%3417%32%28%
2376
November1st to 10thNight
18%37%21%31%20%
2311
11th to 20thNight
19%412%20%26%19%
2470
21st to endNight
24%412%16%26%18%
2470
December1st to 10thNight
29%5%11%18%22%15%
2588
11th to 20thNight
44%7%10%16%15%8%
3276
21st to endNight
41%9%14%20%12%5%
4862

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 10thDay
15%7%23%34%17%4
255
11th to 20thDay
13%6%21%33%22%6%
356
21st to endDay
11%321%34%24%7%
374
February1st to 10thDay
12%7%21%28%24%7%
364
11th to 20thDay
10%11%20%35%19%4
415
21st to endDay
11%11%22%35%18%3
346
March1st to 10thDay
14%10%24%33%18%1
420
11th to 20thDay
15%8%24%29%20%4
420
21st to endDay
11%12%25%32%18%3
462
April1st to 10thDay
13%8%25%28%20%7%
420
11th to 20thDay
7%11%24%33%19%6%
412
21st to endDay
310%24%31%20%12%
420
May1st to 10thDay
7%7%25%31%23%7%
423
11th to 20thDay
37%22%34%25%10%
448
21st to endDay
5%10%17%34%23%11%
485
June1st to 10thDay
26%16%31%30%16%
450
11th to 20thDay
1318%32%30%16%
450
21st to endDay
1113%30%33%23%
450
July1st to 10thDay
6%37%34%22%
446
11th to 20thDay
2328%39%27%
444
21st to endDay
1430%39%26%
487
August1st to 10thDay
219%31%37%20%
447
11th to 20thDay
16%25%40%27%
437
21st to endDay
2423%43%27%
495
September1st to 10thDay
29%25%39%25%
450
11th to 20thDay
2110%29%42%15%
450
21st to endDay
139%25%45%17%
450
October1st to 10thDay
3415%34%33%11%
450
11th to 20thDay
3317%30%36%11%
450
21st to endDay
4413%28%39%11%
495
November1st to 10thDay
48%12%28%41%7%
362
11th to 20thDay
6%5%12%34%34%10%
270
21st to endDay
6%418%36%30%6%
270
December1st to 10thDay
14%6%17%33%28%2
212
11th to 20thDay
9%10%16%31%25%9%
180
21st to endDay
17%7%17%31%22%5%
198
January1st to 10thNight
14%214%43%22%5%
760
11th to 20thNight
10%213%44%27%4
744
21st to endNight
13%214%43%25%3
792
February1st to 10thNight
12%312%40%28%5%
720
11th to 20thNight
8%318%41%25%5%
704
21st to endNight
12%5%15%46%19%3
592
March1st to 10thNight
12%317%43%21%3
720
11th to 20thNight
10%415%37%29%5%
720
21st to endNight
10%5%18%37%26%3
792
April1st to 10thNight
6%7%18%39%27%3
720
11th to 20thNight
5%6%21%34%29%5%
711
21st to endNight
4424%31%28%8%
720
May1st to 10thNight
3418%40%29%7%
720
11th to 20thNight
4218%37%34%6%
581
21st to endNight
3417%37%33%6%
389
June1st to 10thNight
2210%42%41%4
360
11th to 20thNight
1111%39%43%5%
360
21st to endNight
1439%48%8%
360
July1st to 10thNight
1327%62%8%
350
11th to 20thNight
1113%64%21%
469
21st to endNight
11112%62%23%
591
August1st to 10thNight
1325%56%14%
625
11th to 20thNight
222%62%14%
712
21st to endNight
1118%64%16%
792
September1st to 10thNight
11322%58%15%
720
11th to 20thNight
215%34%47%11%
720
21st to endNight
117%28%53%10%
720
October1st to 10thNight
418%37%41%8%
720
11th to 20thNight
339%37%40%7%
720
21st to endNight
5%27%37%38%11%
792
November1st to 10thNight
4212%38%38%6%
740
11th to 20thNight
5%28%47%33%5%
760
21st to endNight
5%212%46%30%5%
760
December1st to 10thNight
11%313%42%28%3
760
11th to 20thNight
14%312%46%22%3
760
21st to endNight
12%5%17%44%20%3
836
Page generated at 2024-01-13 06:37:58. Version ac07

Copyright 2024 Attilla Danko


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