Old Man on His Back Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Old Man on His Back Ranch clear sky chart from 2005-11-05 to 2018-01-20.

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
42%
16118
15%
48448
10%
16086
48%
16086
26%
31255

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
32%
970
10%
2910
6%
970
37%
970
17%
2099
January16th to endNight
31%
937
16%
2833
8%
937
39%
937
20%
1934
February1st to 15thNight
41%
698
12%
2288
10%
697
46%
697
21%
1519
February16th to endNight
37%
632
13%
2052
11%
632
43%
632
19%
1407
March1st to 15thNight
41%
720
11%
2043
7%
720
45%
720
24%
1415
March16th to endNight
36%
756
11%
2100
6%
756
41%
756
20%
1531
April1st to 15thNight
38%
539
14%
1760
9%
539
44%
539
21%
1166
April16th to endNight
40%
540
17%
1616
12%
540
44%
540
23%
1090
May1st to 15thNight
49%
539
14%
1440
11%
539
51%
539
33%
921
May16th to endNight
43%
481
9%
1416
6%
479
45%
479
21%
999
June1st to 15thNight
43%
360
5%
1260
4%
360
46%
360
23%
773
June16th to endNight
52%
360
8%
1260
7%
360
55%
360
32%
673
July1st to 15thNight
62%
340
9%
1190
7%
340
66%
340
38%
592
July16th to endNight
64%
429
20%
1288
17%
403
69%
403
51%
607
August1st to 15thNight
63%
539
17%
1543
14%
536
68%
536
43%
855
August16th to endNight
63%
573
27%
1730
21%
573
67%
573
43%
915
September1st to 15thNight
55%
540
20%
1800
18%
540
60%
540
35%
991
September16th to endNight
54%
692
26%
1988
20%
692
61%
692
38%
1142
October1st to 15thNight
45%
720
20%
2160
11%
720
53%
720
29%
1340
October16th to endNight
42%
813
22%
2403
12%
813
51%
813
27%
1527
November1st to 15thNight
35%
950
17%
2660
9%
950
42%
950
27%
1729
November16th to endNight
33%
975
15%
2730
8%
975
38%
975
25%
1831
December1st to 15thNight
33%
975
11%
2858
6%
975
38%
975
19%
2052
December16th to endNight
34%
1040
15%
3120
6%
1040
41%
1040
20%
2147

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
9%6%35%5%35%5%5%8%41%
49112
Night
7%6%36%5%35%5%6%8%41%
48599
Cloud CoverDay
8%7%36%5%35%5%5%8%41%
49113
Night
7%6%36%5%35%5%6%8%41%
48601
TransparencyDay
39%8%16%23%10%1
48767
Night
38%8%17%22%11%1
48448
SeeingDay
12%7%27%30%18%4
6425
Night
10%6%31%34%14%1
16130

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
6%10%48%8%5%5%6%6%6%30%
1358
16th to endDay
310%5%7%6%47%7%7%10%29%
1503
February1st to 15thDay
8%10%48%7%36%6%6%6%31%
1575
16th to endDay
6%11%5%12%9%36%5%6%7%25%
1422
March1st to 15thDay
45%47%7%36%6%7%11%35%
1914
16th to endDay
9%9%5%8%6%45%6%6%9%28%
2123
April1st to 15thDay
10%8%35%5%35%6%6%9%34%
2186
16th to endDay
13%9%36%424447%37%
2343
May1st to 15thDay
12%7%25%5%35%45%8%39%
2511
16th to endDay
22%7%35%5%3445%7%29%
2697
June1st to 15thDay
16%5%25%5%35%5%6%7%34%
2700
16th to endDay
9%3244245%5%9%47%
2700
July1st to 15thDay
5%31342445%8%55%
2700
16th to endDay
5%21231345%7%62%
2792
August1st to 15thDay
6%3145%2445%8%53%
2409
16th to endDay
7%213313347%60%
2471
September1st to 15thDay
10%413425%346%53%
2160
16th to endDay
13%312324447%52%
1968
October1st to 15thDay
11%8%36%5%245%6%7%40%
1800
16th to endDay
6%7%36%5%2445%9%42%
1806
November1st to 15thDay
6%9%46%5%445%6%8%38%
1528
16th to endDay
6%8%5%5%5%35%6%6%7%40%
1560
December1st to 15thDay
5%11%6%11%8%5%5%6%47%27%
1430
16th to endDay
5%13%5%7%7%5%7%6%5%8%27%
1456
January1st to 15thNight
6%7%47%8%47%7%7%8%29%
2910
16th to endNight
5%7%39%6%345%6%10%35%
2833
February1st to 15thNight
6%6%47%7%36%5%6%8%36%
2277
16th to endNight
5%9%410%6%445%7%8%33%
2052
March1st to 15thNight
47%37%8%45%5%6%10%36%
2043
16th to endNight
8%9%5%8%5%45%6%7%8%31%
2097
April1st to 15thNight
9%8%36%5%35%5%5%8%38%
1760
16th to endNight
13%7%36%5%3445%7%37%
1616
May1st to 15thNight
11%5%244345%6%7%44%
1439
16th to endNight
19%6%26%335%5%5%6%35%
1416
June1st to 15thNight
14%6%24424447%43%
1260
16th to endNight
6%413325%46%9%52%
1260
July1st to 15thNight
5%41332345%8%58%
1260
16th to endNight
5%11212345%8%63%
1376
August1st to 15thNight
7%313323448%57%
1551
16th to endNight
8%31322345%6%58%
1730
September1st to 15thNight
9%5%24423335%56%
1800
16th to endNight
9%41332445%7%53%
1988
October1st to 15thNight
9%5%25%5%245%5%9%45%
2160
16th to endNight
7%7%26%5%2446%7%44%
2403
November1st to 15thNight
6%7%35%5%35%5%6%8%42%
2660
16th to endNight
5%8%48%6%3446%7%39%
2730
December1st to 15thNight
48%5%10%7%35%5%6%8%33%
2858
16th to endNight
6%8%48%7%35%5%6%9%33%
3120

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
6%10%48%8%5%6%6%6%8%30%
1358
16th to endDay
29%5%7%6%48%7%7%10%29%
1503
February1st to 15thDay
7%11%47%7%46%6%6%6%30%
1575
16th to endDay
6%11%5%11%10%5%6%5%5%7%24%
1422
March1st to 15thDay
35%37%7%46%6%8%9%35%
1914
16th to endDay
9%8%5%9%7%45%6%6%9%28%
2124
April1st to 15thDay
9%9%25%5%35%6%7%9%35%
2186
16th to endDay
12%10%35%5%2445%8%37%
2343
May1st to 15thDay
12%8%26%5%35%45%7%38%
2511
16th to endDay
21%7%36%5%35%45%7%29%
2697
June1st to 15thDay
15%6%25%5%45%5%6%8%34%
2700
16th to endDay
8%3244245%5%10%47%
2700
July1st to 15thDay
5%31342445%9%54%
2700
16th to endDay
421231345%8%61%
2792
August1st to 15thDay
5%324435%5%5%7%53%
2409
16th to endDay
6%213323348%60%
2471
September1st to 15thDay
10%413434446%53%
2160
16th to endDay
12%422324447%51%
1968
October1st to 15thDay
9%9%36%4245%6%7%40%
1800
16th to endDay
6%8%27%43445%8%43%
1806
November1st to 15thDay
6%8%36%5%35%5%7%9%38%
1528
16th to endDay
5%8%5%6%6%35%6%6%7%39%
1560
December1st to 15thDay
5%10%5%12%8%47%5%5%6%27%
1430
16th to endDay
5%13%5%9%7%46%7%5%8%28%
1456
January1st to 15thNight
5%8%47%8%47%6%8%8%30%
2910
16th to endNight
47%49%7%45%5%6%10%34%
2833
February1st to 15thNight
6%6%47%7%45%5%6%8%36%
2277
16th to endNight
49%49%7%35%5%7%8%33%
2052
March1st to 15thNight
47%37%6%46%5%7%9%36%
2043
16th to endNight
8%8%5%8%6%36%7%6%9%30%
2100
April1st to 15thNight
8%8%46%5%26%6%6%8%38%
1760
16th to endNight
12%7%46%43445%7%37%
1616
May1st to 15thNight
10%5%244345%5%8%44%
1439
16th to endNight
18%7%34425%5%47%35%
1415
June1st to 15thNight
12%7%3443345%8%42%
1260
16th to endNight
5%324325%36%9%52%
1260
July1st to 15thNight
441331435%9%57%
1260
16th to endNight
411221346%8%63%
1376
August1st to 15thNight
7%21242345%8%57%
1551
16th to endNight
7%31322335%7%58%
1730
September1st to 15thNight
9%5%24423335%56%
1800
16th to endNight
8%4134245%5%8%52%
1988
October1st to 15thNight
8%6%345%245%5%8%46%
2160
16th to endNight
6%7%36%5%335%5%8%44%
2403
November1st to 15thNight
5%7%26%6%345%7%8%42%
2660
16th to endNight
5%8%48%6%25%45%7%39%
2730
December1st to 15thNight
48%5%10%6%35%5%6%7%33%
2858
16th to endNight
6%9%5%8%6%35%5%6%9%33%
3120

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
49%10%14%20%4
1358
16th to endDay
45%10%19%18%4
1503
February1st to 15thDay
50%9%16%17%5%
1575
16th to endDay
57%7%16%12%5%
1422
March1st to 15thDay
40%13%23%17%4
1914
16th to endDay
49%10%18%17%3
2124
April1st to 15thDay
43%9%18%21%7%
2186
16th to endDay
45%7%14%23%7%1
2343
May1st to 15thDay
43%6%15%24%9%
2511
16th to endDay
53%7%14%17%6%
2701
June1st to 15thDay
45%8%15%20%9%
2700
16th to endDay
30%7%18%31%10%
2700
July1st to 15thDay
26%6%16%28%19%2
2541
16th to endDay
19%5%14%31%22%6%
2617
August1st to 15thDay
27%7%15%28%16%3
2393
16th to endDay
23%411%30%24%5%
2471
September1st to 15thDay
31%5%13%27%17%5%
2160
16th to endDay
32%6%12%30%16%2
1968
October1st to 15thDay
40%7%19%23%7%
1800
16th to endDay
37%7%20%24%9%
1806
November1st to 15thDay
40%9%18%23%7%
1528
16th to endDay
40%9%20%19%8%
1560
December1st to 15thDay
55%7%15%17%3
1430
16th to endDay
51%9%18%15%5%
1456
January1st to 15thNight
46%11%19%16%4
2910
16th to endNight
43%9%17%20%7%1
2833
February1st to 15thNight
43%7%19%21%7%1
2288
16th to endNight
45%8%15%20%8%
2052
March1st to 15thNight
41%10%21%18%8%
2043
16th to endNight
47%9%17%19%6%
2100
April1st to 15thNight
41%9%16%22%9%
1760
16th to endNight
44%6%13%22%11%2
1616
May1st to 15thNight
36%6%14%28%13%1
1440
16th to endNight
47%7%15%18%10%
1416
June1st to 15thNight
39%6%17%22%11%1
1260
16th to endNight
27%7%16%33%13%1
1260
July1st to 15thNight
22%7%12%29%22%5%
1190
16th to endNight
17%5%14%31%26%5%
1288
August1st to 15thNight
24%6%14%31%17%5%
1543
16th to endNight
24%410%26%25%8%
1730
September1st to 15thNight
30%5%10%25%19%8%
1800
16th to endNight
28%5%13%29%17%4
1988
October1st to 15thNight
34%7%17%25%12%1
2160
16th to endNight
36%8%15%26%12%
2403
November1st to 15thNight
37%8%20%22%10%1
2660
16th to endNight
41%7%24%18%8%
2730
December1st to 15thNight
47%9%19%19%4
2858
16th to endNight
45%8%19%20%6%
3120

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%16%26%26%14%
90
16th to endDay
13%438%27%9%7%
84
February1st to 15thDay
14%8%32%30%10%4
90
16th to endDay
16%324%41%11%2
81
March1st to 15thDay
7%8%42%28%10%2
222
16th to endDay
8%9%38%25%15%2
288
April1st to 15thDay
12%15%30%30%10%
269
16th to endDay
20%10%24%27%12%3
273
May1st to 15thDay
14%7%26%27%19%4
468
16th to endDay
20%7%24%22%19%5%
517
June1st to 15thDay
14%9%27%26%19%1
495
16th to endDay
8%8%28%28%20%4
495
July1st to 15thDay
7%221%39%24%3
475
16th to endDay
5%326%39%20%5%
515
August1st to 15thDay
7%422%36%21%7%
384
16th to endDay
6%6%18%37%25%5%
332
September1st to 15thDay
16%428%30%15%4
315
16th to endDay
14%7%23%30%17%6%
282
October1st to 15thDay
26%323%32%11%1
135
16th to endDay
11%9%31%32%10%3
144
November1st to 15thDay
10%8%34%23%19%2
135
16th to endDay
5%11%42%27%10%2
135
December1st to 15thDay
10%8%41%27%6%4
105
16th to endDay
19%6%33%25%12%3
96
January1st to 15thNight
9%9%36%28%12%2
975
16th to endNight
7%11%39%27%12%1
937
February1st to 15thNight
9%8%28%33%16%3
704
16th to endNight
7%7%34%34%14%2
632
March1st to 15thNight
7%7%35%35%13%1
720
16th to endNight
13%5%34%32%11%2
756
April1st to 15thNight
12%8%34%32%11%1
539
16th to endNight
17%6%28%33%13%1
540
May1st to 15thNight
11%5%26%37%17%1
540
16th to endNight
19%5%23%31%17%2
481
June1st to 15thNight
16%430%30%16%1
360
16th to endNight
8%5%31%35%18%
360
July1st to 15thNight
7%321%50%16%
340
16th to endNight
4224%48%18%
429
August1st to 15thNight
8%122%44%21%1
539
16th to endNight
8%320%42%24%
573
September1st to 15thNight
11%325%33%22%3
540
16th to endNight
9%426%37%19%2
692
October1st to 15thNight
11%6%29%34%16%1
720
16th to endNight
11%8%30%36%12%
813
November1st to 15thNight
10%9%37%29%11%1
950
16th to endNight
9%7%40%34%8%
975
December1st to 15thNight
8%7%36%31%14%2
975
16th to endNight
10%7%35%32%12%2
1040
Page generated at 2018-01-21 11:19:26. Version ac04

Copyright 2018 A. Danko


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