Ridgeway
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ridgeway clear sky chart from 2005-11-05 to 2018-08-29.

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
46%
17087
22%
50620
14%
17049
54%
17049
28%
31902

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
28%
778
24%
2522
11%
776
45%
776
24%
1526
January16th to endNight
29%
832
25%
2704
13%
832
45%
832
26%
1611
February1st to 15thNight
28%
761
21%
2482
10%
761
43%
761
24%
1501
February16th to endNight
26%
683
26%
2015
12%
683
41%
683
28%
1255
March1st to 15thNight
31%
780
26%
2145
12%
780
43%
780
29%
1349
March16th to endNight
33%
832
20%
2288
12%
832
41%
832
26%
1520
April1st to 15thNight
33%
778
21%
2027
7%
778
42%
778
31%
1294
April16th to endNight
40%
719
21%
1875
9%
719
47%
719
30%
1237
May1st to 15thNight
44%
585
18%
1755
10%
585
50%
585
25%
1154
May16th to endNight
57%
609
15%
1828
11%
609
59%
609
26%
1199
June1st to 15thNight
66%
585
17%
1755
15%
585
68%
585
32%
1087
June16th to endNight
69%
585
18%
1755
14%
585
71%
585
32%
1083
July1st to 15thNight
70%
555
14%
1665
13%
555
71%
555
29%
1063
July16th to endNight
74%
612
15%
1739
14%
579
74%
579
29%
1121
August1st to 15thNight
66%
575
17%
1715
15%
572
66%
572
24%
1174
August16th to endNight
69%
741
18%
1971
13%
741
70%
741
31%
1302
September1st to 15thNight
65%
720
22%
1875
18%
720
66%
720
32%
1252
September16th to endNight
50%
717
20%
1980
17%
717
53%
717
24%
1397
October1st to 15thNight
50%
720
26%
2155
23%
720
58%
720
30%
1333
October16th to endNight
45%
768
34%
2304
22%
768
62%
768
36%
1297
November1st to 15thNight
48%
760
27%
2291
19%
760
59%
760
33%
1336
November16th to endNight
42%
780
28%
2535
20%
780
55%
780
31%
1437
December1st to 15thNight
36%
780
22%
2535
13%
780
49%
780
23%
1600
December16th to endNight
31%
832
23%
2704
12%
832
45%
832
21%
1774

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
14%5%245%345%5%7%42%
51618
Night
14%5%2442445%7%45%
50813
Cloud CoverDay
14%5%24435%5%5%7%42%
51628
Night
13%5%2442445%7%45%
50817
TransparencyDay
39%6%12%21%16%3
51329
Night
37%6%11%21%18%4
50620
SeeingDay
17%6%21%23%20%10%
6928
Night
16%6%24%30%19%2
17094

By Month

Percentage Cloud Cover NE (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
17%424324445%45%
1746
16th to endDay
16%5%13324336%49%
1872
February1st to 15thDay
15%6%25%423436%45%
1710
16th to endDay
17%6%23424447%42%
1741
March1st to 15thDay
14%5%3332445%7%46%
2134
16th to endDay
18%6%24324446%42%
2288
April1st to 15thDay
11%41441336%7%50%
2251
16th to endDay
15%425%5%24446%42%
2370
May1st to 15thDay
15%5%25%5%36%5%5%6%37%
2526
16th to endDay
12%5%25%6%35%5%6%9%36%
2639
June1st to 15thDay
8%3146%36%6%7%10%40%
2535
16th to endDay
8%425%5%36%6%6%10%40%
2535
July1st to 15thDay
10%5%26%6%36%6%7%8%35%
2535
16th to endDay
8%5%26%7%36%6%7%11%32%
2673
August1st to 15thDay
11%5%26%7%46%6%7%9%31%
2487
16th to endDay
11%5%25%6%36%6%7%9%34%
2513
September1st to 15thDay
12%4244345%5%7%44%
2082
16th to endDay
21%6%15%4235%5%5%37%
1980
October1st to 15thDay
18%313223335%51%
1803
16th to endDay
13%424312325%55%
1920
November1st to 15thDay
16%413323436%50%
1896
16th to endDay
14%31432345%6%50%
1755
December1st to 15thDay
16%6%24434346%44%
1755
16th to endDay
22%5%23314445%40%
1872
January1st to 15thNight
16%5%24323335%48%
2522
16th to endNight
15%5%2431434448%
2704
February1st to 15thNight
16%5%23323445%46%
2480
16th to endNight
13%5%2432445%6%45%
2015
March1st to 15thNight
14%42332345%5%48%
2133
16th to endNight
17%424424445%44%
2288
April1st to 15thNight
13%5%235%24447%46%
2027
16th to endNight
16%41343445%6%45%
1875
May1st to 15thNight
12%6%26%5%34446%42%
1755
16th to endNight
13%6%25%5%2446%9%39%
1826
June1st to 15thNight
9%3243345%7%11%43%
1755
16th to endNight
7%3144345%7%13%44%
1755
July1st to 15thNight
7%4145%36%6%7%10%41%
1755
16th to endNight
6%3145%46%7%9%11%37%
1847
August1st to 15thNight
12%5%25%5%446%7%11%35%
1726
16th to endNight
7%415%5%36%5%8%10%39%
1971
September1st to 15thNight
11%5%15%435%5%6%7%43%
1875
16th to endNight
19%7%25%5%2445%438%
1980
October1st to 15thNight
16%413423335%48%
2155
16th to endNight
12%313323335%57%
2304
November1st to 15thNight
15%423323346%53%
2291
16th to endNight
14%413323345%52%
2535
December1st to 15thNight
16%5%25%424445%44%
2535
16th to endNight
21%5%2443435%6%39%
2704

Percentage Cloud Cover SE (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
17%424324445%45%
1746
16th to endDay
16%5%14324336%48%
1872
February1st to 15thDay
15%6%24423436%45%
1710
16th to endDay
16%5%23434447%42%
1741
March1st to 15thDay
14%5%3332445%7%46%
2145
16th to endDay
18%6%25%324446%42%
2287
April1st to 15thDay
11%41442336%7%50%
2251
16th to endDay
15%435%5%24446%42%
2370
May1st to 15thDay
15%5%25%6%36%5%5%7%36%
2526
16th to endDay
12%5%25%6%36%5%6%9%36%
2639
June1st to 15thDay
8%3246%36%6%7%10%40%
2535
16th to endDay
8%425%5%36%6%6%9%41%
2535
July1st to 15thDay
10%426%6%37%6%7%9%35%
2535
16th to endDay
8%5%26%7%37%6%8%11%31%
2673
August1st to 15thDay
10%5%26%7%46%7%7%10%31%
2487
16th to endDay
11%425%5%46%6%7%10%34%
2513
September1st to 15thDay
12%424435%46%7%44%
2082
16th to endDay
21%6%2442445%6%37%
1980
October1st to 15thDay
17%413313335%51%
1803
16th to endDay
13%424222335%55%
1920
November1st to 15thDay
15%413323436%50%
1896
16th to endDay
14%31432345%6%50%
1755
December1st to 15thDay
16%6%14434445%44%
1755
16th to endDay
22%5%23324446%40%
1872
January1st to 15thNight
15%5%14323336%48%
2522
16th to endNight
15%5%2441434448%
2704
February1st to 15thNight
16%5%23323445%46%
2473
16th to endNight
13%6%2432445%6%45%
2015
March1st to 15thNight
14%5%2432345%5%48%
2145
16th to endNight
17%424424445%43%
2288
April1st to 15thNight
13%5%235%23447%46%
2027
16th to endNight
16%42442445%6%44%
1875
May1st to 15thNight
12%5%35%5%3445%7%42%
1754
16th to endNight
13%6%25%5%3446%9%39%
1826
June1st to 15thNight
9%3244345%7%11%43%
1755
16th to endNight
7%3134345%7%13%44%
1755
July1st to 15thNight
7%4145%26%6%7%10%41%
1755
16th to endNight
6%315%5%46%8%9%12%37%
1847
August1st to 15thNight
11%6%25%5%446%7%11%35%
1726
16th to endNight
7%415%5%35%6%7%11%39%
1971
September1st to 15thNight
11%5%245%25%6%5%8%43%
1875
16th to endNight
19%7%26%43444438%
1980
October1st to 15thNight
16%5%13423335%48%
2155
16th to endNight
12%31332323457%
2304
November1st to 15thNight
15%323313346%53%
2291
16th to endNight
14%413413345%52%
2535
December1st to 15thNight
16%5%25%423445%44%
2535
16th to endNight
20%6%24433446%38%
2704

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
39%5%8%21%19%4
1747
16th to endDay
38%38%24%19%6%
1872
February1st to 15thDay
40%310%23%18%4
1712
16th to endDay
40%5%12%21%17%3
1741
March1st to 15thDay
37%49%23%18%6%
2145
16th to endDay
42%5%9%22%15%4
2288
April1st to 15thDay
31%412%26%16%7%
2251
16th to endDay
42%49%18%16%7%
2370
May1st to 15thDay
44%7%14%18%11%2
2526
16th to endDay
41%8%14%24%9%1
2643
June1st to 15thDay
35%9%18%22%12%1
2535
16th to endDay
35%10%14%20%15%2
2535
July1st to 15thDay
41%10%15%17%12%3
2396
16th to endDay
41%9%18%19%10%
2518
August1st to 15thDay
43%9%17%19%9%
2474
16th to endDay
41%9%16%19%10%1
2513
September1st to 15thDay
36%6%14%20%18%3
2082
16th to endDay
46%410%17%19%1
1980
October1st to 15thDay
35%310%26%19%5%
1803
16th to endDay
31%36%28%22%7%
1920
November1st to 15thDay
35%49%17%24%8%
1896
16th to endDay
34%38%23%24%4
1755
December1st to 15thDay
39%5%9%22%17%4
1755
16th to endDay
44%412%19%16%3
1872
January1st to 15thNight
38%49%16%23%7%
2522
16th to endNight
38%38%23%20%5%
2704
February1st to 15thNight
38%49%23%19%5%
2482
16th to endNight
36%410%24%19%3
2015
March1st to 15thNight
36%5%8%22%22%5%
2145
16th to endNight
41%5%9%22%17%3
2288
April1st to 15thNight
37%310%23%18%5%
2027
16th to endNight
39%5%10%18%18%7%
1875
May1st to 15thNight
40%7%13%20%15%2
1755
16th to endNight
39%8%16%24%9%1
1828
June1st to 15thNight
32%9%18%24%13%1
1755
16th to endNight
30%11%16%21%16%3
1755
July1st to 15thNight
33%11%17%20%13%3
1665
16th to endNight
33%11%19%22%11%1
1739
August1st to 15thNight
40%10%15%18%12%1
1715
16th to endNight
35%9%17%24%9%2
1971
September1st to 15thNight
37%7%12%20%16%4
1875
16th to endNight
47%5%9%16%19%1
1980
October1st to 15thNight
37%47%25%20%4
2155
16th to endNight
30%36%25%24%8%
2304
November1st to 15thNight
33%47%19%24%10%
2291
16th to endNight
33%36%23%25%6%
2535
December1st to 15thNight
41%49%21%17%5%
2535
16th to endNight
45%49%18%17%3
2704

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
18%17%42%17%3
135
16th to endDay
23%20%34%14%6%
144
February1st to 15thDay
25%21%41%9%2
135
16th to endDay
23%12%37%21%4
185
March1st to 15thDay
20%13%33%23%7%
330
16th to endDay
21%11%32%25%8%
352
April1st to 15thDay
17%13%30%24%11%2
330
16th to endDay
20%7%24%24%16%6%
319
May1st to 15thDay
17%9%27%22%15%8%
348
16th to endDay
18%216%22%26%12%
395
June1st to 15thDay
10%215%27%27%16%
375
16th to endDay
11%416%25%25%16%
375
July1st to 15thDay
13%9%27%36%13%
365
16th to endDay
10%18%25%32%20%
390
August1st to 15thDay
15%29%23%28%20%
358
16th to endDay
11%18%24%26%27%
384
September1st to 15thDay
15%115%18%24%23%
315
16th to endDay
29%212%21%22%12%
314
October1st to 15thDay
20%416%26%23%6%
315
16th to endDay
14%6%23%30%21%4
336
November1st to 15thDay
23%6%21%27%19%2
314
16th to endDay
10%16%21%23%24%3
135
December1st to 15thDay
17%12%39%21%7%1
135
16th to endDay
35%13%30%19%1
144
January1st to 15thNight
17%13%35%27%5%
780
16th to endNight
18%11%37%29%3
832
February1st to 15thNight
21%11%35%28%2
764
16th to endNight
15%13%38%28%3
683
March1st to 15thNight
17%12%34%29%5%
780
16th to endNight
20%7%33%30%7%
832
April1st to 15thNight
16%12%34%26%9%
778
16th to endNight
19%6%28%29%15%
719
May1st to 15thNight
15%5%25%36%16%
585
16th to endNight
14%114%31%34%3
611
June1st to 15thNight
10%212%34%34%4
585
16th to endNight
8%111%32%41%3
585
July1st to 15thNight
10%17%30%45%5%
555
16th to endNight
7%18%32%44%6%
612
August1st to 15thNight
13%16%32%38%6%
575
16th to endNight
10%7%28%43%8%
741
September1st to 15thNight
13%19%31%36%6%
720
16th to endNight
22%212%28%31%3
717
October1st to 15thNight
19%419%28%24%4
720
16th to endNight
13%6%29%31%17%1
768
November1st to 15thNight
16%5%24%35%15%2
760
16th to endNight
16%8%27%31%15%
780
December1st to 15thNight
20%8%28%33%8%
780
16th to endNight
24%9%29%32%4
832
Page generated at 2018-08-30 05:34:20. Version ac04

Copyright 2018 A. Danko


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