The Bishop's Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The Bishop's Ranch clear sky chart from 2005-11-05 to 2017-09-20.

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
62%
15318
26%
46945
23%
15281
66%
15281
35%
26408

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
58%
716
18%
2374
17%
716
62%
716
26%
1471
January16th to endNight
56%
768
26%
2496
26%
768
60%
768
28%
1518
February1st to 15thNight
54%
699
22%
2288
22%
698
59%
698
23%
1464
February16th to endNight
47%
632
21%
1936
16%
632
55%
632
25%
1238
March1st to 15thNight
49%
720
15%
1980
11%
720
52%
720
24%
1367
March16th to endNight
47%
768
21%
2109
15%
768
52%
768
29%
1361
April1st to 15thNight
44%
719
23%
1799
11%
719
50%
719
30%
1166
April16th to endNight
53%
720
27%
1800
12%
720
58%
720
41%
1058
May1st to 15thNight
60%
551
28%
1631
19%
551
66%
551
45%
835
May16th to endNight
64%
408
27%
1531
25%
408
72%
408
38%
710
June1st to 15thNight
62%
360
26%
1440
26%
360
70%
360
37%
658
June16th to endNight
78%
360
34%
1440
42%
360
83%
360
57%
526
July1st to 15thNight
86%
390
30%
1410
35%
390
88%
390
61%
536
July16th to endNight
80%
564
34%
1593
32%
531
80%
531
51%
742
August1st to 15thNight
79%
538
33%
1611
27%
535
80%
535
50%
754
August16th to endNight
79%
738
36%
1884
24%
738
81%
738
56%
989
September1st to 15thNight
82%
720
37%
1800
25%
720
84%
720
62%
920
September16th to endNight
78%
675
39%
1867
34%
675
82%
675
59%
911
October1st to 15thNight
68%
660
29%
1980
29%
660
74%
660
42%
1032
October16th to endNight
68%
704
31%
2112
32%
704
72%
704
38%
1189
November1st to 15thNight
65%
700
25%
2166
24%
700
69%
700
37%
1213
November16th to endNight
58%
720
23%
2490
24%
720
62%
720
29%
1423
December1st to 15thNight
52%
720
19%
2520
18%
720
58%
720
21%
1627
December16th to endNight
48%
768
21%
2688
19%
768
54%
768
22%
1700

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%413323335%59%
47888
Night
10%423323346%56%
47133
TransparencyDay
29%38%20%23%14%
47576
Night
31%38%19%22%14%
46946
SeeingDay
13%10%24%30%16%4
6037
Night
13%413%29%31%7%
15329

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%4245%12345%46%
1561
16th to endDay
17%5%24424336%44%
1728
February1st to 15thDay
18%425%324346%44%
1576
16th to endDay
19%6%24423446%40%
1535
March1st to 15thDay
19%6%35%5%2345%6%36%
1980
16th to endDay
18%425%5%24446%42%
2114
April1st to 15thDay
15%5%345%24446%42%
2149
16th to endDay
8%413313347%57%
2160
May1st to 15thDay
6%412212346%64%
2316
16th to endDay
6%5%13313347%59%
2580
June1st to 15thDay
6%412213236%63%
2520
16th to endDay
31111123477%
2520
July1st to 15thDay
121221212377%
2462
16th to endDay
131121222475%
2468
August1st to 15thDay
1312222235%73%
2340
16th to endDay
1411222135%73%
2315
September1st to 15thDay
1211212235%73%
2160
16th to endDay
421112235%73%
1859
October1st to 15thDay
10%212213335%63%
1650
16th to endDay
11%314313345%57%
1760
November1st to 15thDay
8%32343345%5%54%
1692
16th to endDay
14%5%2433333450%
1467
December1st to 15thDay
21%6%24333335%42%
1440
16th to endDay
22%5%24413335%40%
1536
January1st to 15thNight
16%423425%448%44%
2374
16th to endNight
19%5%13313336%49%
2496
February1st to 15thNight
18%5%24324446%43%
2276
16th to endNight
16%6%23224347%44%
1936
March1st to 15thNight
17%4345%25%45%5%40%
1980
16th to endNight
16%5%24323247%47%
2109
April1st to 15thNight
11%5%24434347%49%
1799
16th to endNight
7%413324336%60%
1800
May1st to 15thNight
4323323236%64%
1631
16th to endNight
4212323446%64%
1530
June1st to 15thNight
35%13223338%62%
1440
16th to endNight
32111122477%
1440
July1st to 15thNight
22122122477%
1494
16th to endNight
15%12211246%69%
1701
August1st to 15thNight
1413322245%68%
1620
16th to endNight
5%13212337%67%
1884
September1st to 15thNight
1313212238%70%
1800
16th to endNight
3312112245%72%
1867
October1st to 15thNight
6%423313345%63%
1980
16th to endNight
9%313324246%56%
2112
November1st to 15thNight
10%42232335%9%54%
2166
16th to endNight
14%424323345%52%
2490
December1st to 15thNight
23%5%23314435%42%
2520
16th to endNight
22%5%13323246%44%
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
42%311%18%13%10%
1561
16th to endDay
43%46%13%18%12%
1728
February1st to 15thDay
43%48%19%20%4
1576
16th to endDay
45%5%10%23%11%3
1535
March1st to 15thDay
48%6%10%16%13%4
1980
16th to endDay
44%6%11%20%14%3
2114
April1st to 15thDay
43%5%12%20%15%2
2149
16th to endDay
27%5%15%26%20%5%
2160
May1st to 15thDay
21%39%31%26%7%
2316
16th to endDay
26%413%28%21%5%
2584
June1st to 15thDay
24%410%24%24%12%
2520
16th to endDay
13%15%17%38%22%
2520
July1st to 15thDay
14%1312%31%36%
2317
16th to endDay
16%2311%28%38%
2313
August1st to 15thDay
16%1317%33%27%
2324
16th to endDay
17%1417%36%23%
2315
September1st to 15thDay
15%15%16%32%27%
2160
16th to endDay
16%26%25%30%18%
1859
October1st to 15thDay
24%38%21%27%14%
1650
16th to endDay
29%38%24%23%9%
1760
November1st to 15thDay
32%5%10%30%12%7%
1692
16th to endDay
40%49%19%18%7%
1467
December1st to 15thDay
46%5%9%14%19%4
1440
16th to endDay
46%5%8%17%14%7%
1536
January1st to 15thNight
40%5%12%18%13%9%
2374
16th to endNight
39%38%16%18%14%
2496
February1st to 15thNight
43%48%18%16%7%
2288
16th to endNight
41%5%12%21%16%3
1936
March1st to 15thNight
45%6%13%14%16%4
1980
16th to endNight
39%410%22%18%5%
2109
April1st to 15thNight
36%5%13%21%18%4
1799
16th to endNight
27%39%28%22%8%
1800
May1st to 15thNight
23%37%23%30%11%
1632
16th to endNight
21%5%10%30%23%7%
1531
June1st to 15thNight
22%48%23%23%16%
1440
16th to endNight
14%15%15%35%28%
1440
July1st to 15thNight
13%38%34%39%
1410
16th to endNight
21%15%10%22%38%
1593
August1st to 15thNight
21%1314%28%30%
1611
16th to endNight
20%1414%30%27%
1884
September1st to 15thNight
17%1412%31%31%
1800
16th to endNight
17%1421%31%22%
1867
October1st to 15thNight
25%37%19%25%18%
1980
16th to endNight
30%36%21%24%12%
2112
November1st to 15thNight
30%414%28%14%7%
2166
16th to endNight
35%38%22%20%8%
2490
December1st to 15thNight
45%47%16%19%5%
2520
16th to endNight
43%5%9%15%19%7%
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
28%10%27%16%14%2
189
16th to endDay
21%12%21%25%16%1
256
February1st to 15thDay
23%11%24%22%15%1
236
16th to endDay
22%17%22%23%12%
231
March1st to 15thDay
27%17%22%19%9%3
270
16th to endDay
19%19%34%18%6%1
288
April1st to 15thDay
22%25%24%19%7%
269
16th to endDay
19%22%28%21%5%2
270
May1st to 15thDay
15%19%32%23%7%1
288
16th to endDay
13%11%21%30%17%6%
330
June1st to 15thDay
10%13%31%31%10%2
315
16th to endDay
5%5%26%39%18%5%
315
July1st to 15thDay
4117%47%23%5%
305
16th to endDay
2116%51%21%7%
327
August1st to 15thDay
4322%46%18%4
315
16th to endDay
4123%40%24%6%
332
September1st to 15thDay
5%420%40%20%7%
315
16th to endDay
6%8%19%33%25%7%
272
October1st to 15thDay
10%9%28%27%16%8%
255
16th to endDay
18%8%24%26%21%1
272
November1st to 15thDay
10%11%17%28%27%5%
198
16th to endDay
15%12%33%15%18%4
65
December1st to 15thDay
40%13%20%15%11%
60
16th to endDay
28%9%15%25%15%6%
64
January1st to 15thNight
18%312%33%26%6%
720
16th to endNight
23%312%28%25%6%
768
February1st to 15thNight
21%5%10%32%26%3
704
16th to endNight
21%6%18%28%19%4
632
March1st to 15thNight
19%7%15%27%25%5%
720
16th to endNight
19%6%21%29%19%3
768
April1st to 15thNight
15%10%21%28%19%4
719
16th to endNight
10%12%19%27%23%6%
720
May1st to 15thNight
7%420%30%32%4
552
16th to endNight
6%6%16%31%32%6%
409
June1st to 15thNight
6%5%20%36%30%1
360
16th to endNight
5%212%36%39%3
360
July1st to 15thNight
26%26%54%8%
390
16th to endNight
5%329%48%13%
564
August1st to 15thNight
5%5%28%50%10%
538
16th to endNight
46%28%52%7%
738
September1st to 15thNight
36%25%51%12%
720
16th to endNight
6%18%29%38%14%
675
October1st to 15thNight
9%311%30%32%11%
660
16th to endNight
12%112%24%36%12%
704
November1st to 15thNight
13%113%29%33%8%
700
16th to endNight
16%413%28%28%8%
720
December1st to 15thNight
27%311%26%24%6%
720
16th to endNight
25%5%15%31%18%2
768
Page generated at 2017-09-21 04:18:19. Version ac04

Copyright 2017 A. Danko


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