Goat Mountain Astronomical Research Station
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Goat Mountain Astronomical Research Station clear sky chart from 2005-11-05 to

2017-09-12
.

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
74%
16087
40%
46908
31%
16048
82%
16048
66%
20132

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
68%
718
34%
2327
29%
716
78%
716
50%
1048
January16th to endNight
63%
768
40%
2364
29%
768
76%
768
51%
1100
February1st to 15thNight
66%
699
39%
2108
31%
698
78%
698
58%
936
February16th to endNight
61%
632
38%
1895
35%
632
72%
632
54%
889
March1st to 15thNight
63%
720
37%
2142
31%
720
76%
720
61%
927
March16th to endNight
65%
768
40%
2070
27%
768
76%
768
62%
965
April1st to 15thNight
57%
719
39%
1799
17%
719
70%
719
65%
873
April16th to endNight
64%
710
43%
1790
20%
710
74%
710
74%
796
May1st to 15thNight
71%
539
43%
1619
28%
539
78%
539
79%
604
May16th to endNight
69%
561
40%
1685
27%
561
76%
561
77%
644
June1st to 15thNight
79%
540
35%
1620
28%
540
83%
540
81%
607
June16th to endNight
83%
540
37%
1620
32%
540
86%
540
83%
607
July1st to 15thNight
90%
510
32%
1530
29%
510
90%
510
72%
621
July16th to endNight
90%
564
36%
1593
30%
531
90%
531
62%
711
August1st to 15thNight
93%
701
38%
1775
26%
698
93%
698
79%
798
August16th to endNight
92%
764
44%
1910
31%
764
92%
764
79%
867
September1st to 15thNight
92%
706
40%
1849
32%
706
93%
706
78%
814
September16th to endNight
87%
656
48%
1815
42%
656
92%
656
86%
716
October1st to 15thNight
77%
660
45%
1815
35%
660
86%
660
76%
772
October16th to endNight
81%
704
45%
2131
41%
704
88%
704
72%
846
November1st to 15thNight
77%
700
40%
2275
36%
700
88%
700
69%
872
November16th to endNight
76%
720
43%
2340
41%
720
85%
720
64%
933
December1st to 15thNight
70%
720
37%
2340
31%
720
80%
720
52%
1043
December16th to endNight
60%
768
36%
2496
30%
768
72%
768
47%
1143

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
111112235%77%
47745
Night
111112235%78%
47107
TransparencyDay
11%25%14%27%39%
47440
Night
10%25%14%29%37%
46913
SeeingDay
310%24%36%20%4
5796
Night
1416%33%33%10%
16097

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
221221225%6%69%
1611
16th to endDay
2213313346%68%
1858
February1st to 15thDay
111211335%7%71%
1751
16th to endDay
11222435%6%69%
1579
March1st to 15thDay
111235%7%74%
1818
16th to endDay
11112236%75%
2151
April1st to 15thDay
1111212226%76%
2149
16th to endDay
111125%82%
2169
May1st to 15thDay
1111113483%
2331
16th to endDay
1122482%
2429
June1st to 15thDay
112485%
2340
16th to endDay
11111288%
2340
July1st to 15thDay
212212245%73%
2340
16th to endDay
21232445%6%66%
2467
August1st to 15thDay
111121224476%
2172
16th to endDay
21212345%75%
2292
September1st to 15thDay
2121223477%
2028
16th to endDay
121111285%
1815
October1st to 15thDay
1121222479%
1815
16th to endDay
111112483%
1738
November1st to 15thDay
1111223479%
1584
16th to endDay
11113236%75%
1620
December1st to 15thDay
12122223410%67%
1620
16th to endDay
2212223337%68%
1728
January1st to 15thNight
122213447%68%
2327
16th to endNight
222212345%70%
2364
February1st to 15thNight
212212236%74%
2101
16th to endNight
22121246%7%67%
1895
March1st to 15thNight
111211347%74%
2142
16th to endNight
2212245%76%
2070
April1st to 15thNight
1111233478%
1799
16th to endNight
1126%83%
1790
May1st to 15thNight
1225%85%
1619
16th to endNight
1222485%
1684
June1st to 15thNight
113486%
1620
16th to endNight
111290%
1620
July1st to 15thNight
11112235%78%
1620
16th to endNight
112123345%73%
1701
August1st to 15thNight
1111135%81%
1784
16th to endNight
11113482%
1910
September1st to 15thNight
11123482%
1849
16th to endNight
11290%
1815
October1st to 15thNight
111235%81%
1815
16th to endNight
111122483%
2131
November1st to 15thNight
1112235%81%
2275
16th to endNight
211111235%78%
2340
December1st to 15thNight
221213438%68%
2340
16th to endNight
3212212246%69%
2496

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
16%47%19%32%20%
1612
16th to endDay
17%45%21%28%22%
1858
February1st to 15thDay
14%46%18%30%25%
1751
16th to endDay
15%5%8%19%34%17%
1579
March1st to 15thDay
9%35%20%33%28%
1818
16th to endDay
10%27%23%32%24%
2151
April1st to 15thDay
13%1415%36%27%
2149
16th to endDay
6%1417%33%37%
2169
May1st to 15thDay
7%1310%35%41%
2331
16th to endDay
7%1411%31%43%
2432
June1st to 15thDay
5%128%18%62%
2340
16th to endDay
6%139%77%
2340
July1st to 15thDay
12%249%18%52%
2201
16th to endDay
16%5%7%14%21%35%
2312
August1st to 15thDay
10%239%21%52%
2157
16th to endDay
10%3410%23%47%
2292
September1st to 15thDay
11%349%20%50%
2028
16th to endDay
7%115%26%56%
1815
October1st to 15thDay
9%2410%31%41%
1815
16th to endDay
8%2310%29%45%
1738
November1st to 15thDay
10%2414%34%33%
1584
16th to endDay
11%25%16%32%30%
1620
December1st to 15thDay
16%49%22%27%20%
1620
16th to endDay
18%5%9%25%24%16%
1728
January1st to 15thNight
16%47%18%29%24%
2327
16th to endNight
16%46%19%26%25%
2364
February1st to 15thNight
14%26%19%30%27%
2112
16th to endNight
15%5%7%20%31%20%
1895
March1st to 15thNight
11%35%20%32%27%
2142
16th to endNight
11%36%19%37%22%
2070
April1st to 15thNight
10%35%17%35%27%
1799
16th to endNight
5%2315%37%36%
1790
May1st to 15thNight
41315%36%38%
1620
16th to endNight
5%2315%36%36%
1685
June1st to 15thNight
41310%19%60%
1620
16th to endNight
415%12%74%
1620
July1st to 15thNight
9%147%17%58%
1530
16th to endNight
12%46%15%25%35%
1593
August1st to 15thNight
6%2310%22%54%
1775
16th to endNight
6%238%27%50%
1910
September1st to 15thNight
7%26%10%21%53%
1849
16th to endNight
416%27%60%
1815
October1st to 15thNight
7%2411%34%39%
1815
16th to endNight
7%25%9%26%48%
2131
November1st to 15thNight
8%2413%36%33%
2275
16th to endNight
11%15%18%30%32%
2340
December1st to 15thNight
15%5%8%18%28%24%
2340
16th to endNight
17%312%19%27%19%
2496

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
10%7%28%43%10%
90
16th to endDay
419%33%29%10%3
226
February1st to 15thDay
414%31%30%15%3
266
16th to endDay
7%22%29%26%14%
238
March1st to 15thDay
419%25%32%17%2
270
16th to endDay
5%16%30%31%13%2
288
April1st to 15thDay
7%23%26%26%13%3
269
16th to endDay
427%29%25%11%2
270
May1st to 15thDay
314%26%38%12%4
288
16th to endDay
110%30%36%15%4
330
June1st to 15thDay
16%27%37%22%3
315
16th to endDay
1324%37%22%10%
315
July1st to 15thDay
14%47%27%8%
305
16th to endDay
315%41%27%11%
327
August1st to 15thDay
2118%45%23%8%
315
16th to endDay
1113%41%30%12%
332
September1st to 15thDay
2220%50%23%3
300
16th to endDay
37%22%35%28%2
255
October1st to 15thDay
210%28%41%15%1
255
16th to endDay
27%21%34%30%2
176
November1st to 15thDay
113%16%23%36%8%
90
16th to endDay
411%33%26%23%1
90
December1st to 15thDay
7%8%18%28%34%1
90
16th to endDay
8%11%27%34%18%
96
January1st to 15thNight
25%20%36%23%11%
720
16th to endNight
35%23%33%26%7%
768
February1st to 15thNight
25%22%34%27%7%
704
16th to endNight
35%28%35%20%7%
632
March1st to 15thNight
27%23%33%25%7%
720
16th to endNight
8%21%34%25%8%
768
April1st to 15thNight
17%29%31%23%5%
719
16th to endNight
9%24%31%26%7%
710
May1st to 15thNight
421%39%27%5%
540
16th to endNight
423%36%28%5%
563
June1st to 15thNight
117%44%32%2
540
16th to endNight
13%42%39%3
540
July1st to 15thNight
1433%50%8%
510
16th to endNight
2332%54%7%
564
August1st to 15thNight
227%52%15%
701
16th to endNight
2219%51%23%
764
September1st to 15thNight
228%49%17%
706
16th to endNight
18%30%44%15%
656
October1st to 15thNight
1117%33%37%8%
660
16th to endNight
311%31%35%16%
704
November1st to 15thNight
1218%31%35%11%
700
16th to endNight
3414%31%32%13%
720
December1st to 15thNight
3419%37%27%8%
720
16th to endNight
5%8%21%34%22%7%
768
Page generated at 2017-09-13 04:39:06. Version ac04

Copyright 2017 A. Danko


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