Conway Summit
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Conway Summit clear sky chart from 2005-11-05 to 2017-09-19.

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
64%
15300
30%
46878
24%
15273
71%
15273
50%
22299

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
61%
716
25%
2506
21%
716
70%
716
43%
1183
January16th to endNight
57%
768
27%
2529
25%
768
64%
768
42%
1257
February1st to 15thNight
56%
698
27%
2174
24%
698
64%
698
44%
1091
February16th to endNight
52%
632
26%
1895
22%
632
62%
632
44%
972
March1st to 15thNight
53%
720
23%
2151
19%
720
61%
720
46%
1079
March16th to endNight
50%
768
23%
1996
13%
768
57%
768
45%
1111
April1st to 15thNight
50%
719
24%
1799
10%
719
57%
719
42%
1034
April16th to endNight
55%
720
24%
1800
11%
720
60%
720
49%
987
May1st to 15thNight
60%
580
28%
1660
19%
580
64%
580
50%
835
May16th to endNight
62%
414
25%
1537
24%
414
68%
414
40%
704
June1st to 15thNight
69%
360
27%
1440
30%
360
77%
360
46%
593
June16th to endNight
79%
360
36%
1440
42%
360
87%
360
68%
471
July1st to 15thNight
89%
340
32%
1360
43%
340
90%
340
63%
469
July16th to endNight
82%
409
36%
1447
39%
385
84%
385
52%
601
August1st to 15thNight
82%
669
35%
1743
23%
666
84%
666
71%
798
August16th to endNight
84%
764
42%
1910
26%
764
85%
764
75%
894
September1st to 15thNight
83%
720
41%
1800
27%
720
85%
720
75%
830
September16th to endNight
75%
671
42%
1839
34%
671
82%
671
68%
830
October1st to 15thNight
67%
660
34%
1918
28%
660
76%
660
56%
905
October16th to endNight
70%
704
37%
2150
35%
704
79%
704
59%
937
November1st to 15thNight
68%
700
32%
2275
31%
700
75%
700
51%
1042
November16th to endNight
59%
720
33%
2340
26%
720
71%
720
52%
1040
December1st to 15thNight
54%
720
21%
2481
16%
720
63%
720
38%
1227
December16th to endNight
48%
768
25%
2688
19%
768
59%
768
34%
1409

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
121332335%7%65%
47947
Night
1212213347%69%
47054
TransparencyDay
18%7%12%21%23%16%
47622
Night
14%7%14%24%26%13%
46880
SeeingDay
5%16%31%27%14%4
5778
Night
25%23%33%26%7%
15312

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
11122335%10%66%
1432
16th to endDay
5%1332347%8%57%
1692
February1st to 15thDay
21221446%9%63%
1687
16th to endDay
213325%47%9%58%
1579
March1st to 15thDay
21332347%12%58%
1806
16th to endDay
112225%6%7%10%58%
2227
April1st to 15thDay
12143245%7%11%54%
2149
16th to endDay
1212423447%65%
2160
May1st to 15thDay
1412424347%63%
2289
16th to endDay
46%2442435%6%53%
2573
June1st to 15thDay
321232345%5%63%
2520
16th to endDay
21121222477%
2520
July1st to 15thDay
3313224335%66%
2520
16th to endDay
4313324435%62%
2621
August1st to 15thDay
12332333470%
2208
16th to endDay
22322222473%
2292
September1st to 15thDay
221332223470%
2160
16th to endDay
112312335%74%
1864
October1st to 15thDay
3312323335%67%
1711
16th to endDay
1212212247%71%
1721
November1st to 15thDay
111222325%7%68%
1584
16th to endDay
211345%9%69%
1620
December1st to 15thDay
21322345%8%65%
1476
16th to endDay
1342449%11%57%
1536
January1st to 15thNight
12122134410%64%
2506
16th to endNight
131231347%9%60%
2529
February1st to 15thNight
21332446%10%61%
2164
16th to endNight
31322346%9%62%
1895
March1st to 15thNight
11232346%9%64%
2151
16th to endNight
21322435%9%63%
1996
April1st to 15thNight
213325%5%5%8%61%
1799
16th to endNight
1312222345%70%
1800
May1st to 15thNight
1212213348%68%
1660
16th to endNight
342212336%66%
1536
June1st to 15thNight
321211335%5%69%
1440
16th to endNight
111111385%
1440
July1st to 15thNight
111112335%77%
1440
16th to endNight
2212313335%71%
1545
August1st to 15thNight
2121211480%
1752
16th to endNight
111223480%
1910
September1st to 15thNight
1111213481%
1800
16th to endNight
121111225%78%
1839
October1st to 15thNight
2212211235%72%
1918
16th to endNight
112212245%74%
2150
November1st to 15thNight
111113337%72%
2275
16th to endNight
21212248%72%
2340
December1st to 15thNight
11321346%10%63%
2481
16th to endNight
1144146%6%12%57%
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
14%9%19%29%19%7%
1432
16th to endDay
21%11%16%22%17%10%
1692
February1st to 15thDay
16%9%19%26%19%8%
1687
16th to endDay
18%11%19%28%19%2
1579
March1st to 15thDay
15%10%24%22%19%7%
1806
16th to endDay
16%12%25%26%13%4
2227
April1st to 15thDay
21%12%18%25%16%5%
2149
16th to endDay
18%9%19%27%19%5%
2160
May1st to 15thDay
20%8%14%30%23%4
2289
16th to endDay
28%6%14%22%22%5%
2577
June1st to 15thDay
20%7%10%20%28%13%
2520
16th to endDay
11%2411%37%31%
2520
July1st to 15thDay
19%349%20%42%
2371
16th to endDay
22%45%10%15%41%
2457
August1st to 15thDay
16%3412%19%43%
2192
16th to endDay
16%2310%33%34%
2292
September1st to 15thDay
18%35%11%30%31%
2160
16th to endDay
13%35%24%32%21%
1864
October1st to 15thDay
18%39%24%29%14%
1711
16th to endDay
13%49%25%33%12%
1721
November1st to 15thDay
15%6%15%28%24%9%
1584
16th to endDay
11%7%16%28%29%6%
1620
December1st to 15thDay
17%12%19%28%17%4
1476
16th to endDay
19%15%19%22%18%5%
1536
January1st to 15thNight
16%9%18%26%22%6%
2506
16th to endNight
18%9%17%23%20%10%
2529
February1st to 15thNight
17%8%17%28%18%9%
2175
16th to endNight
17%8%19%29%20%3
1895
March1st to 15thNight
15%9%22%23%19%9%
2151
16th to endNight
16%11%23%26%18%3
1996
April1st to 15thNight
19%9%17%29%18%4
1799
16th to endNight
17%8%19%30%20%4
1800
May1st to 15thNight
15%7%14%32%25%4
1661
16th to endNight
20%6%14%27%25%6%
1537
June1st to 15thNight
15%5%11%24%31%11%
1440
16th to endNight
7%2416%39%30%
1440
July1st to 15thNight
9%35%11%30%39%
1360
16th to endNight
16%35%12%24%37%
1447
August1st to 15thNight
10%26%15%24%42%
1743
16th to endNight
8%2414%38%30%
1910
September1st to 15thNight
8%26%15%38%28%
1800
16th to endNight
10%27%23%36%19%
1839
October1st to 15thNight
15%49%28%33%8%
1918
16th to endNight
11%411%25%36%10%
2150
November1st to 15thNight
12%9%13%29%24%10%
2275
16th to endNight
12%6%16%27%30%7%
2340
December1st to 15thNight
16%12%22%24%20%3
2481
16th to endNight
18%14%18%22%19%6%
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%36%21%6%6%
60
16th to endDay
315%26%30%16%7%
220
February1st to 15thDay
415%27%25%22%5%
255
16th to endDay
214%35%30%15%2
238
March1st to 15thDay
117%32%25%15%7%
270
16th to endDay
324%36%22%12%
288
April1st to 15thDay
7%28%31%19%10%1
269
16th to endDay
330%38%19%5%1
270
May1st to 15thDay
6%22%36%22%7%4
288
16th to endDay
11%19%25%23%14%5%
330
June1st to 15thDay
8%21%34%20%10%4
315
16th to endDay
413%30%31%12%7%
315
July1st to 15thDay
5%5%28%33%20%5%
305
16th to endDay
7%5%28%38%13%6%
327
August1st to 15thDay
311%35%28%16%4
315
16th to endDay
37%31%32%18%6%
332
September1st to 15thDay
7%7%31%33%16%2
315
16th to endDay
413%25%32%20%2
268
October1st to 15thDay
7%21%30%24%11%4
255
16th to endDay
315%37%26%16%
233
November1st to 15thDay
110%14%22%30%22%
90
16th to endDay
325%14%32%21%3
90
December1st to 15thDay
6%18%37%27%9%1
66
16th to endDay
310%23%32%21%7%
64
January1st to 15thNight
25%26%31%22%10%
720
16th to endNight
25%29%34%17%10%
768
February1st to 15thNight
16%30%30%22%7%
704
16th to endNight
110%30%32%17%6%
632
March1st to 15thNight
16%33%30%19%7%
720
16th to endNight
110%33%29%19%4
768
April1st to 15thNight
211%30%32%19%3
719
16th to endNight
39%28%31%18%8%
720
May1st to 15thNight
36%26%33%24%4
581
16th to endNight
5%5%21%29%31%5%
415
June1st to 15thNight
4220%36%32%2
360
16th to endNight
115%46%30%4
360
July1st to 15thNight
25%45%43%3
340
16th to endNight
26%39%43%6%
409
August1st to 15thNight
210%38%40%7%
669
16th to endNight
210%36%42%7%
764
September1st to 15thNight
210%35%42%8%
720
16th to endNight
2415%30%35%11%
671
October1st to 15thNight
35%19%33%26%10%
660
16th to endNight
36%17%32%27%13%
704
November1st to 15thNight
1324%34%26%9%
700
16th to endNight
29%25%30%23%7%
720
December1st to 15thNight
27%31%35%15%7%
720
16th to endNight
8%37%30%17%4
768
Page generated at 2017-09-20 01:49:45. Version ac04

Copyright 2017 A. Danko


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