Conway
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Conway clear sky chart from 2005-11-05 to 2017-08-12.

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
36%
14632
17%
46463
10%
14601
45%
14601
21%
30757

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
31%
719
18%
2506
9%
716
44%
716
19%
1597
January16th to endNight
24%
768
17%
2688
7%
768
37%
768
15%
1783
February1st to 15thNight
25%
704
15%
2252
6%
701
37%
701
16%
1540
February16th to endNight
27%
631
18%
1893
7%
631
41%
631
19%
1276
March1st to 15thNight
27%
720
16%
2153
8%
720
38%
720
19%
1499
March16th to endNight
32%
768
21%
2035
8%
768
41%
768
24%
1364
April1st to 15thNight
30%
718
17%
1796
6%
718
36%
718
22%
1290
April16th to endNight
31%
567
17%
1647
7%
567
38%
567
22%
1099
May1st to 15thNight
33%
540
14%
1620
9%
540
39%
540
18%
1143
May16th to endNight
40%
377
10%
1499
10%
376
47%
376
15%
1034
June1st to 15thNight
41%
360
10%
1440
10%
360
48%
360
14%
993
June16th to endNight
53%
360
9%
1440
12%
360
58%
360
20%
901
July1st to 15thNight
59%
340
11%
1360
18%
340
61%
340
22%
799
July16th to endNight
59%
376
14%
1418
19%
354
62%
354
23%
847
August1st to 15thNight
52%
468
14%
1517
11%
466
56%
466
23%
970
August16th to endNight
56%
627
18%
1677
12%
627
58%
627
34%
1058
September1st to 15thNight
54%
660
19%
1707
10%
660
58%
660
34%
1075
September16th to endNight
54%
657
24%
1815
16%
657
59%
657
35%
1092
October1st to 15thNight
40%
660
20%
1863
12%
660
49%
660
24%
1246
October16th to endNight
30%
704
14%
2288
8%
704
39%
704
19%
1536
November1st to 15thNight
40%
700
21%
2277
14%
700
50%
700
22%
1470
November16th to endNight
33%
720
19%
2364
11%
720
44%
720
18%
1558
December1st to 15thNight
26%
720
15%
2520
6%
720
37%
720
16%
1713
December16th to endNight
23%
768
16%
2688
7%
768
35%
768
14%
1874

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
16%6%25%5%3445%7%37%
47517
Night
16%6%2442445%6%40%
46633
Cloud CoverDay
17%6%25%5%3445%7%37%
47527
Night
16%6%2442445%6%40%
46638
TransparencyDay
45%6%12%20%12%1
47205
Night
43%6%12%22%12%1
46463
SeeingDay
22%11%26%24%11%4
5670
Night
20%9%26%30%10%1
14633

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
13%7%34446%6%5%6%37%
1432
16th to endDay
11%8%35%5%2445%7%41%
1536
February1st to 15thDay
14%9%36%5%35%5%47%34%
1604
16th to endDay
12%9%46%436%5%46%36%
1580
March1st to 15thDay
15%9%45%5%345%5%7%34%
1796
16th to endDay
13%6%45%5%23436%43%
2187
April1st to 15thDay
17%7%245%34446%39%
2152
16th to endDay
18%5%245%34346%40%
2313
May1st to 15thDay
24%7%35%5%25%45%5%30%
2338
16th to endDay
20%6%245%345%5%6%33%
2618
June1st to 15thDay
25%6%25%434447%31%
2520
16th to endDay
18%6%25%435%5%5%8%32%
2520
July1st to 15thDay
14%425%5%45%6%6%9%35%
2520
16th to endDay
14%425%6%35%7%6%8%35%
2654
August1st to 15thDay
15%5%25%5%46%47%6%36%
2336
16th to endDay
11%325%5%25%5%5%8%43%
2173
September1st to 15thDay
14%41332435%7%47%
1922
16th to endDay
13%313424345%52%
1815
October1st to 15thDay
19%7%24424346%40%
1764
16th to endDay
18%5%245%245%5%5%37%
1584
November1st to 15thDay
17%5%2342345%8%41%
1581
16th to endDay
18%5%3442445%6%40%
1596
December1st to 15thDay
17%8%35%6%35%5%5%6%33%
1440
16th to endDay
19%10%46%42445%5%32%
1536
January1st to 15thNight
11%9%244336%5%8%40%
2506
16th to endNight
12%7%36%6%35%45%6%37%
2688
February1st to 15thNight
10%8%36%6%45%6%6%7%35%
2251
16th to endNight
12%10%34435%45%6%39%
1893
March1st to 15thNight
15%7%35%5%35%5%46%37%
2140
16th to endNight
12%7%34424445%45%
2035
April1st to 15thNight
16%8%246%34445%38%
1796
16th to endNight
21%42342435%6%41%
1647
May1st to 15thNight
20%7%24425%45%5%35%
1620
16th to endNight
21%6%25%43445%8%33%
1497
June1st to 15thNight
25%6%3343346%5%34%
1440
16th to endNight
17%31343446%8%41%
1440
July1st to 15thNight
14%424435%5%5%8%42%
1440
16th to endNight
13%314435%5%6%8%42%
1514
August1st to 15thNight
14%5%244335%5%6%43%
1527
16th to endNight
13%41342335%8%48%
1677
September1st to 15thNight
14%314322436%52%
1707
16th to endNight
14%312313346%54%
1815
October1st to 15thNight
19%5%2443435%5%42%
1863
16th to endNight
20%5%25%5%24346%38%
2288
November1st to 15thNight
15%5%24435%45%6%41%
2277
16th to endNight
16%6%25%424436%42%
2364
December1st to 15thNight
18%9%34424435%38%
2520
16th to endNight
18%8%35%425%5%46%34%
2688

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
13%8%33436%6%5%6%38%
1432
16th to endDay
12%9%26%424448%41%
1536
February1st to 15thDay
14%9%35%5%36%5%47%35%
1604
16th to endDay
12%9%45%5%35%5%46%36%
1580
March1st to 15thDay
17%9%45%4345%5%6%33%
1806
16th to endDay
14%7%35%5%34345%43%
2187
April1st to 15thDay
17%6%25%5%24446%39%
2152
16th to endDay
18%5%15%5%34446%39%
2313
May1st to 15thDay
24%7%35%5%25%446%30%
2338
16th to endDay
20%6%245%35%447%33%
2618
June1st to 15thDay
25%6%25%424446%31%
2520
16th to endDay
18%6%26%435%5%5%8%32%
2520
July1st to 15thDay
13%5%25%6%35%5%7%9%34%
2520
16th to endDay
14%425%6%36%6%6%8%35%
2654
August1st to 15thDay
14%6%25%6%45%5%6%7%36%
2336
16th to endDay
11%3245%35%5%6%8%43%
2173
September1st to 15thDay
15%41332435%7%47%
1922
16th to endDay
14%32332435%5%53%
1815
October1st to 15thDay
20%6%34424336%40%
1764
16th to endDay
19%6%244245%5%6%38%
1584
November1st to 15thDay
17%6%2332345%7%41%
1581
16th to endDay
18%5%2442345%5%41%
1596
December1st to 15thDay
18%7%36%5%3445%5%33%
1440
16th to endDay
19%11%36%42445%432%
1536
January1st to 15thNight
12%9%2442446%7%41%
2506
16th to endNight
13%8%46%5%35%5%46%36%
2688
February1st to 15thNight
11%8%36%6%36%5%6%6%35%
2244
16th to endNight
13%10%2443445%6%39%
1893
March1st to 15thNight
16%8%35%435%45%5%36%
2153
16th to endNight
13%7%34424345%44%
2034
April1st to 15thNight
16%8%35%5%3445%5%37%
1796
16th to endNight
21%5%24424346%41%
1647
May1st to 15thNight
20%6%25%5%35%45%5%35%
1620
16th to endNight
21%6%26%5%3445%8%32%
1497
June1st to 15thNight
25%6%2442435%6%33%
1440
16th to endNight
17%41343446%8%41%
1440
July1st to 15thNight
14%4234345%5%8%41%
1440
16th to endNight
12%414435%5%6%9%42%
1514
August1st to 15thNight
14%6%244245%5%7%42%
1527
16th to endNight
13%41432345%9%47%
1677
September1st to 15thNight
14%423413347%51%
1707
16th to endNight
14%312323336%54%
1815
October1st to 15thNight
19%42443335%6%41%
1863
16th to endNight
20%6%245%34346%38%
2288
November1st to 15thNight
15%6%2443445%6%42%
2277
16th to endNight
16%6%35%424435%42%
2364
December1st to 15thNight
19%9%24424335%38%
2520
16th to endNight
18%8%45%5%25%446%34%
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
43%6%13%23%12%1
1433
16th to endDay
43%5%12%24%13%1
1536
February1st to 15thDay
49%6%13%19%9%1
1607
16th to endDay
49%5%11%16%13%3
1580
March1st to 15thDay
49%6%12%16%11%3
1806
16th to endDay
44%5%10%17%17%5%
2187
April1st to 15thDay
45%5%10%20%15%3
2152
16th to endDay
45%5%10%20%14%2
2313
May1st to 15thDay
54%5%7%17%12%1
2338
16th to endDay
49%6%12%18%10%2
2622
June1st to 15thDay
53%413%18%8%
2520
16th to endDay
49%8%11%19%10%1
2520
July1st to 15thDay
42%8%14%22%10%
2371
16th to endDay
42%9%14%21%10%
2487
August1st to 15thDay
45%7%14%22%9%
2322
16th to endDay
36%6%15%26%13%1
2173
September1st to 15thDay
36%6%11%29%15%
1922
16th to endDay
33%410%26%22%1
1815
October1st to 15thDay
46%5%10%23%12%1
1764
16th to endDay
45%6%14%21%11%1
1584
November1st to 15thDay
40%6%15%22%12%2
1581
16th to endDay
44%6%14%19%14%1
1596
December1st to 15thDay
50%6%13%19%9%
1440
16th to endDay
53%6%10%17%10%1
1536
January1st to 15thNight
42%6%14%22%12%1
2506
16th to endNight
46%6%11%18%14%2
2688
February1st to 15thNight
47%6%13%18%12%1
2252
16th to endNight
45%5%11%21%12%3
1893
March1st to 15thNight
47%5%10%21%11%2
2153
16th to endNight
40%5%11%17%19%5%
2035
April1st to 15thNight
47%5%9%20%15%2
1796
16th to endNight
44%5%11%21%13%3
1647
May1st to 15thNight
49%6%8%18%13%3
1620
16th to endNight
49%8%14%18%8%1
1499
June1st to 15thNight
51%6%12%19%8%
1440
16th to endNight
39%9%14%22%11%1
1440
July1st to 15thNight
37%8%17%25%12%
1360
16th to endNight
38%7%16%24%12%
1418
August1st to 15thNight
40%7%14%24%12%
1517
16th to endNight
33%7%16%27%14%
1677
September1st to 15thNight
33%7%13%32%14%
1707
16th to endNight
32%5%11%31%17%1
1815
October1st to 15thNight
42%5%12%22%14%2
1863
16th to endNight
46%5%13%22%10%1
2288
November1st to 15thNight
42%6%13%22%13%1
2277
16th to endNight
44%5%13%22%12%1
2364
December1st to 15thNight
49%6%12%22%9%
2520
16th to endNight
50%6%11%18%11%
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
23%21%15%33%6%
60
16th to endDay
20%21%29%23%4
64
February1st to 15thDay
25%13%29%25%5%
190
16th to endDay
18%17%29%26%6%1
239
March1st to 15thDay
26%17%24%25%6%
270
16th to endDay
19%16%27%20%11%3
288
April1st to 15thDay
27%12%25%21%8%3
270
16th to endDay
22%14%34%14%11%2
270
May1st to 15thDay
37%10%26%14%7%3
288
16th to endDay
25%12%31%21%6%2
331
June1st to 15thDay
26%11%31%20%9%1
315
16th to endDay
21%10%30%23%12%1
315
July1st to 15thDay
16%8%31%24%14%4
305
16th to endDay
14%8%26%31%15%4
326
August1st to 15thDay
15%8%21%30%16%7%
297
16th to endDay
13%418%29%21%12%
268
September1st to 15thDay
18%5%19%23%21%11%
255
16th to endDay
18%7%21%23%15%14%
254
October1st to 15thDay
24%11%15%21%19%7%
250
16th to endDay
23%10%27%27%10%
240
November1st to 15thDay
21%13%20%32%10%2
235
16th to endDay
25%13%24%21%12%1
216
December1st to 15thDay
21%20%31%18%8%
60
16th to endDay
34%14%32%18%
64
January1st to 15thNight
17%13%31%32%5%
720
16th to endNight
19%14%33%27%5%
768
February1st to 15thNight
16%13%36%31%2
704
16th to endNight
19%13%34%25%6%
631
March1st to 15thNight
22%12%32%28%3
720
16th to endNight
18%13%29%27%10%1
768
April1st to 15thNight
21%12%30%29%5%
718
16th to endNight
24%13%25%26%8%
567
May1st to 15thNight
24%9%26%27%10%1
540
16th to endNight
22%6%23%34%11%1
377
June1st to 15thNight
27%5%21%34%11%
360
16th to endNight
20%120%41%15%
360
July1st to 15thNight
16%115%41%23%1
340
16th to endNight
13%117%43%22%1
376
August1st to 15thNight
18%220%38%19%1
468
16th to endNight
15%317%36%23%3
627
September1st to 15thNight
16%319%36%21%2
660
16th to endNight
16%5%20%29%22%5%
657
October1st to 15thNight
23%8%21%29%15%1
660
16th to endNight
25%10%28%27%7%
704
November1st to 15thNight
19%9%25%33%10%1
700
16th to endNight
22%14%23%28%10%1
720
December1st to 15thNight
26%10%31%26%5%
720
16th to endNight
23%12%33%27%3
768
Page generated at 2017-08-13 14:16:14. Version ac04

Copyright 2017 A. Danko


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