Chechaquo Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chechaquo Ranch clear sky chart from 2005-11-06 to 2024-03-08.

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
30%
22434
13%
80359
8%
22347
38%
22347
17%
53568

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
19%
756
8%
4376
4%
736
26%
736
5%
3323
January11th to 20thNight
20%
755
16%
4336
6%
740
28%
740
7%
2940
January21st to endNight
25%
828
7%
4862
7%
814
33%
814
7%
3920
February1st to 10thNight
17%
760
10%
2542
5%
760
24%
760
11%
1874
February11th to 20thNight
24%
741
13%
2404
6%
740
34%
740
17%
1629
February21st to endNight
25%
628
13%
1915
7%
628
32%
628
12%
1421
March1st to 10thNight
25%
750
12%
2249
7%
750
32%
750
14%
1649
March11th to 20thNight
27%
720
13%
2034
6%
720
33%
720
18%
1445
March21st to endNight
23%
792
10%
2036
3%
792
27%
792
16%
1547
April1st to 10thNight
27%
720
11%
1800
3%
720
31%
720
20%
1282
April11th to 20thNight
28%
711
14%
1779
4%
711
34%
711
23%
1229
April21st to endNight
29%
445
15%
1525
7%
445
39%
445
21%
935
May1st to 10thNight
33%
360
14%
1440
9%
360
47%
360
20%
809
May11th to 20thNight
43%
354
12%
1416
12%
354
52%
354
21%
830
May21st to endNight
38%
388
8%
1552
9%
388
43%
388
19%
949
June1st to 10thNight
34%
360
7%
1440
5%
360
38%
360
20%
867
June11th to 20thNight
32%
360
7%
1310
2%
360
37%
360
22%
760
June21st to endNight
42%
360
11%
1260
4%
360
47%
360
34%
646
July1st to 10thNight
46%
350
12%
1255
7%
350
54%
350
38%
608
July11th to 20thNight
41%
348
17%
1392
14%
348
58%
348
39%
591
July21st to endNight
54%
394
25%
1488
23%
372
75%
372
57%
519
August1st to 10thNight
57%
358
24%
1424
26%
356
68%
356
44%
590
August11th to 20thNight
56%
439
30%
1507
23%
439
67%
439
52%
653
August21st to endNight
47%
756
26%
1944
13%
756
55%
756
45%
1067
September1st to 10thNight
42%
720
25%
1800
9%
720
50%
720
46%
1005
September11th to 20thNight
52%
720
28%
1800
14%
720
58%
720
39%
1080
September21st to endNight
44%
720
22%
2021
13%
720
51%
720
32%
1216
October1st to 10thNight
40%
720
17%
2160
11%
720
48%
720
27%
1338
October11th to 20thNight
31%
720
17%
2164
10%
720
40%
720
21%
1436
October21st to endNight
28%
792
16%
2574
9%
792
39%
792
19%
1726
November1st to 10thNight
20%
740
11%
2489
5%
740
29%
740
13%
1814
November11th to 20thNight
22%
760
12%
2660
6%
760
29%
760
12%
1917
November21st to endNight
21%
760
9%
2660
2%
760
29%
760
12%
1955
December1st to 10thNight
24%
760
13%
2660
6%
760
33%
760
14%
1872
December11th to 20thNight
17%
760
6%
3260
2%
759
23%
759
7%
2507
December21st to endNight
15%
829
8%
4825
3%
817
27%
817
6%
3619

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
7%10%47%6%45%5%6%8%39%
78840
Night
7%11%47%6%35%5%6%8%39%
80669
TransparencyDay
41%11%15%18%12%3
78563
Night
42%11%16%20%10%2
80526
SeeingDay
14%24%34%20%7%1
13767
Night
12%14%38%26%9%1
22462

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 10thDay
9%18%8%11%8%45%5%5%6%22%
2539
11th to 20thDay
8%15%5%10%6%3435%7%34%
2516
21st to endDay
13%24%6%9%5%3445%6%21%
2794
February1st to 10thDay
5%13%6%8%7%46%7%7%9%28%
1634
11th to 20thDay
5%12%5%9%6%36%6%6%10%34%
1665
21st to endDay
311%7%12%9%5%7%5%7%9%25%
1538
March1st to 10thDay
6%13%5%8%7%46%6%6%7%31%
1871
11th to 20thDay
6%15%6%7%7%5%6%7%7%8%26%
1922
21st to endDay
7%15%6%9%6%47%7%7%8%24%
2319
April1st to 10thDay
8%12%48%9%5%7%6%6%9%25%
2160
11th to 20thDay
6%10%5%9%7%47%7%7%8%30%
2132
21st to endDay
5%10%46%6%5%7%7%7%10%33%
2430
May1st to 10thDay
7%8%36%6%47%7%8%9%36%
2520
11th to 20thDay
10%9%47%7%46%7%6%8%34%
2477
21st to endDay
13%8%38%7%5%6%6%6%8%31%
2723
June1st to 10thDay
11%7%37%6%5%7%6%6%7%35%
2520
11th to 20thDay
9%6%46%7%47%7%8%8%34%
2645
21st to endDay
6%5%25%6%45%5%6%8%47%
2700
July1st to 10thDay
4425%5%345%5%8%53%
2665
11th to 20thDay
432442445%6%60%
2520
21st to endDay
2213323445%70%
2741
August1st to 10thDay
332443435%7%62%
2507
11th to 20thDay
321343345%7%63%
2389
21st to endDay
45%25%5%36%5%6%7%53%
2412
September1st to 10thDay
5%42342345%8%59%
2160
11th to 20thDay
6%5%35%6%45%5%5%7%48%
2160
21st to endDay
10%8%245%3445%6%49%
1935
October1st to 10thDay
10%6%36%6%345%5%7%44%
1800
11th to 20thDay
10%7%36%6%345%7%8%40%
1796
21st to endDay
11%12%36%5%35%5%5%7%37%
1782
November1st to 10thDay
11%15%46%6%35%6%7%9%28%
1589
11th to 20thDay
8%15%5%8%6%45%5%5%7%32%
1520
21st to endDay
5%12%5%10%8%5%6%5%5%8%30%
1520
December1st to 10thDay
6%12%6%7%7%35%6%6%8%35%
1520
11th to 20thDay
7%16%6%8%5%3446%7%34%
1925
21st to endDay
8%18%8%11%6%45%5%5%6%25%
2794
January1st to 10thNight
8%17%7%12%7%45%5%5%7%22%
4406
11th to 20thNight
7%16%6%9%6%345%5%8%30%
4382
21st to endNight
11%26%6%8%6%35%446%21%
4862
February1st to 10thNight
8%13%47%7%5%6%6%6%9%29%
2542
11th to 20thNight
410%46%6%35%5%7%10%39%
2402
21st to endNight
413%5%9%6%46%7%9%10%27%
1915
March1st to 10thNight
6%13%6%8%6%46%6%7%8%31%
2249
11th to 20thNight
6%11%46%6%47%6%6%8%35%
2033
21st to endNight
6%11%48%7%46%7%6%9%33%
2036
April1st to 10thNight
6%9%37%6%46%7%8%10%35%
1800
11th to 20thNight
5%7%46%7%36%6%7%8%42%
1779
21st to endNight
5%7%25%5%46%5%6%9%45%
1525
May1st to 10thNight
45%25%5%47%5%7%8%48%
1440
11th to 20thNight
8%6%246%35%5%6%11%44%
1416
21st to endNight
8%6%25%5%35%5%8%10%42%
1552
June1st to 10thNight
8%5%345%47%6%8%9%40%
1440
11th to 20thNight
5%4245%46%6%7%10%47%
1310
21st to endNight
43135%25%5%7%9%57%
1260
July1st to 10thNight
331332447%10%61%
1291
11th to 20thNight
131342445%8%66%
1440
21st to endNight
111212436%77%
1576
August1st to 10thNight
2212424347%70%
1432
11th to 20thNight
2211312448%71%
1507
21st to endNight
3313435%46%8%61%
1944
September1st to 10thNight
421442445%6%65%
1800
11th to 20thNight
6%4244345%5%7%57%
1800
21st to endNight
7%5%244245%6%10%48%
2021
October1st to 10thNight
9%6%25%5%245%6%8%48%
2160
11th to 20thNight
9%7%35%6%35%5%6%8%43%
2164
21st to endNight
12%10%25%5%45%5%7%8%39%
2574
November1st to 10thNight
13%15%46%435%5%7%7%30%
2489
11th to 20thNight
8%14%47%6%46%6%6%8%32%
2660
21st to endNight
6%15%5%9%7%35%6%6%8%30%
2660
December1st to 10thNight
7%12%6%8%5%35%5%6%9%33%
2660
11th to 20thNight
8%17%7%10%7%45%6%5%8%24%
3280
21st to endNight
9%20%6%10%6%35%5%46%25%
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
59%12%12%11%5%1
2539
11th to 20thDay
52%8%14%17%6%3
2540
21st to endDay
64%9%11%10%5%
2794
February1st to 10thDay
49%15%18%13%41
1634
11th to 20thDay
43%15%18%15%8%1
1674
21st to endDay
50%15%14%14%7%
1538
March1st to 10thDay
47%14%14%14%8%2
1871
11th to 20thDay
49%15%14%16%5%
1922
21st to endDay
53%15%16%12%3
2319
April1st to 10thDay
51%14%18%14%4
2160
11th to 20thDay
48%14%15%14%8%1
2132
21st to endDay
42%14%18%17%8%1
2430
May1st to 10thDay
39%15%20%18%7%1
2520
11th to 20thDay
46%12%17%19%6%
2480
21st to endDay
48%13%16%18%4
2724
June1st to 10thDay
45%10%15%17%10%3
2520
11th to 20thDay
42%13%19%17%9%1
2645
21st to endDay
31%11%17%24%14%2
2700
July1st to 10thDay
28%9%15%22%20%5%
2592
11th to 20thDay
23%7%12%22%25%10%
2445
21st to endDay
16%6%11%25%30%12%
2589
August1st to 10thDay
22%8%12%26%23%9%
2490
11th to 20thDay
19%8%13%27%26%6%
2389
21st to endDay
26%10%14%28%18%3
2412
September1st to 10thDay
22%8%15%29%21%5%
2160
11th to 20thDay
33%9%12%20%21%5%
2160
21st to endDay
35%8%17%21%17%3
1935
October1st to 10thDay
38%9%15%26%12%1
1800
11th to 20thDay
38%13%15%21%12%1
1796
21st to endDay
44%13%13%21%10%
1782
November1st to 10thDay
49%13%15%15%8%1
1589
11th to 20thDay
51%12%15%13%7%1
1520
21st to endDay
50%12%15%13%7%3
1520
December1st to 10thDay
46%13%14%16%10%
1520
11th to 20thDay
50%11%19%14%6%
1928
21st to endDay
59%11%11%12%7%
2794
January1st to 10thNight
59%11%12%12%5%1
4406
11th to 20thNight
49%12%13%15%9%3
4420
21st to endNight
65%8%11%10%5%1
4862
February1st to 10thNight
49%13%16%14%6%1
2542
11th to 20thNight
40%14%18%19%9%1
2404
21st to endNight
47%15%14%15%8%
1915
March1st to 10thNight
47%13%16%14%9%2
2249
11th to 20thNight
41%14%18%20%6%
2034
21st to endNight
46%15%20%15%41
2036
April1st to 10thNight
39%14%20%20%6%1
1800
11th to 20thNight
36%13%19%20%11%1
1779
21st to endNight
34%12%20%25%10%
1525
May1st to 10thNight
30%12%23%25%10%1
1440
11th to 20thNight
33%12%24%24%7%
1416
21st to endNight
35%13%21%25%6%
1552
June1st to 10thNight
36%11%19%21%12%2
1440
11th to 20thNight
29%12%23%24%11%
1310
21st to endNight
21%12%23%29%14%2
1260
July1st to 10thNight
19%9%17%31%17%6%
1255
11th to 20thNight
16%7%16%32%22%7%
1392
21st to endNight
8%5%13%33%31%10%
1488
August1st to 10thNight
15%7%16%29%24%9%
1424
11th to 20thNight
13%7%17%33%26%5%
1507
21st to endNight
18%9%17%33%21%3
1944
September1st to 10thNight
19%8%15%32%22%4
1800
11th to 20thNight
25%9%13%27%23%3
1800
21st to endNight
29%9%18%27%13%3
2021
October1st to 10thNight
34%9%13%29%13%1
2160
11th to 20thNight
38%11%15%23%12%1
2164
21st to endNight
42%10%15%22%12%
2574
November1st to 10thNight
48%13%16%14%8%1
2489
11th to 20thNight
47%14%15%16%6%2
2660
21st to endNight
49%13%14%13%7%2
2660
December1st to 10thNight
48%11%16%17%8%
2660
11th to 20thNight
57%12%14%11%5%1
3276
21st to endNight
58%10%11%13%7%1
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
22%23%26%18%9%3
180
11th to 20thDay
17%18%32%21%9%3
180
21st to endDay
21%19%35%16%9%
198
February1st to 10thDay
18%31%37%10%4
294
11th to 20thDay
21%24%37%14%41
365
21st to endDay
13%28%38%18%3
368
March1st to 10thDay
18%30%33%15%41
449
11th to 20thDay
18%30%28%17%7%
420
21st to endDay
21%29%32%15%2
462
April1st to 10thDay
22%29%31%13%5%
420
11th to 20thDay
17%34%26%16%41
412
21st to endDay
15%30%33%15%6%2
420
May1st to 10thDay
12%26%37%20%41
423
11th to 20thDay
20%19%28%22%9%2
448
21st to endDay
16%23%31%21%7%2
485
June1st to 10thDay
16%23%37%18%6%
450
11th to 20thDay
17%27%36%16%31
575
21st to endDay
10%24%38%21%7%1
630
July1st to 10thDay
7%23%35%28%6%1
587
11th to 20thDay
9%18%37%27%7%1
444
21st to endDay
5%17%37%30%10%2
487
August1st to 10thDay
8%14%39%27%11%1
447
11th to 20thDay
414%35%33%12%2
437
21st to endDay
7%23%37%25%7%1
495
September1st to 10thDay
9%22%40%21%7%1
450
11th to 20thDay
13%21%34%22%10%1
450
21st to endDay
17%24%32%20%6%1
450
October1st to 10thDay
13%23%33%21%9%1
450
11th to 20thDay
17%28%26%20%7%2
446
21st to endDay
22%22%33%15%6%2
297
November1st to 10thDay
17%28%33%16%5%
230
11th to 20thDay
18%23%31%16%9%3
180
21st to endDay
21%12%38%17%9%4
180
December1st to 10thDay
18%16%28%19%15%4
180
11th to 20thDay
11%22%38%23%6%1
180
21st to endDay
9%21%40%22%9%1
198
January1st to 10thNight
17%18%36%20%8%1
760
11th to 20thNight
16%15%41%19%8%1
760
21st to endNight
15%13%38%26%8%
836
February1st to 10thNight
15%19%42%19%5%1
760
11th to 20thNight
11%16%41%25%7%
744
21st to endNight
15%15%38%22%10%
628
March1st to 10thNight
11%17%37%27%8%1
750
11th to 20thNight
12%16%39%22%10%
720
21st to endNight
13%14%44%24%5%1
792
April1st to 10thNight
9%16%40%26%8%1
720
11th to 20thNight
7%20%40%24%7%2
711
21st to endNight
9%17%43%23%7%1
445
May1st to 10thNight
9%14%39%32%6%
360
11th to 20thNight
11%10%32%34%12%
354
21st to endNight
11%12%35%31%10%
389
June1st to 10thNight
12%12%40%28%9%
360
11th to 20thNight
8%18%39%30%5%
360
21st to endNight
6%9%39%35%11%
360
July1st to 10thNight
49%38%37%11%
350
11th to 20thNight
312%42%35%9%
348
21st to endNight
19%34%42%13%
394
August1st to 10thNight
47%30%42%18%
358
11th to 20thNight
37%32%38%18%2
439
21st to endNight
5%12%33%35%14%1
756
September1st to 10thNight
5%11%38%27%16%3
720
11th to 20thNight
7%11%26%30%21%5%
720
21st to endNight
11%11%31%30%14%3
720
October1st to 10thNight
13%11%32%31%12%1
720
11th to 20thNight
13%14%37%22%13%1
720
21st to endNight
18%18%34%21%7%2
792
November1st to 10thNight
20%16%39%20%4
740
11th to 20thNight
20%15%38%18%8%1
760
21st to endNight
16%13%39%20%9%3
760
December1st to 10thNight
15%12%40%24%8%2
760
11th to 20thNight
16%15%43%23%21
760
21st to endNight
15%16%43%21%4
836
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