Two Goats Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Two Goats Observatory clear sky chart from 2005-11-05 to 2017-09-24.

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
70%
15799
36%
46905
28%
15750
77%
15750
59%
21394

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
55%
720
29%
2479
24%
716
66%
716
41%
1200
January16th to endNight
52%
768
34%
2391
24%
768
66%
768
42%
1218
February1st to 15thNight
59%
700
34%
2108
27%
698
70%
698
47%
1063
February16th to endNight
55%
632
30%
1895
26%
632
64%
632
42%
1021
March1st to 15thNight
59%
720
28%
2160
24%
720
69%
720
51%
1052
March16th to endNight
62%
768
32%
2001
21%
768
70%
768
56%
1037
April1st to 15thNight
54%
719
32%
1799
15%
719
63%
719
56%
957
April16th to endNight
60%
720
35%
1800
16%
720
67%
720
68%
865
May1st to 15thNight
67%
616
33%
1696
21%
616
71%
616
71%
743
May16th to endNight
62%
561
35%
1685
23%
561
69%
561
67%
695
June1st to 15thNight
77%
423
36%
1503
33%
423
83%
423
74%
511
June16th to endNight
92%
360
42%
1440
49%
360
94%
360
82%
412
July1st to 15thNight
92%
340
36%
1360
43%
340
92%
340
68%
445
July16th to endNight
91%
587
36%
1610
31%
548
91%
548
68%
698
August1st to 15thNight
92%
717
38%
1790
25%
713
92%
713
84%
777
August16th to endNight
95%
764
46%
1910
31%
764
95%
764
84%
844
September1st to 15thNight
91%
720
43%
1821
34%
720
92%
720
81%
812
September16th to endNight
86%
692
48%
1914
43%
692
91%
692
84%
768
October1st to 15thNight
74%
660
38%
1842
33%
660
81%
660
64%
850
October16th to endNight
73%
704
43%
2136
40%
704
82%
704
63%
919
November1st to 15thNight
72%
700
37%
2275
34%
700
82%
700
59%
952
November16th to endNight
69%
720
37%
2340
35%
720
77%
720
54%
1043
December1st to 15thNight
58%
720
33%
2340
26%
720
70%
720
43%
1163
December16th to endNight
52%
768
30%
2610
24%
768
64%
768
36%
1349

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
1112212336%72%
48012
Night
1112213346%71%
47100
TransparencyDay
14%27%16%27%31%
47702
Night
14%37%17%28%28%
46910
SeeingDay
311%30%34%15%4
5937
Night
2319%39%29%4
15806

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
433334337%61%
1456
16th to endDay
6%5%25%323246%57%
1830
February1st to 15thDay
231333335%7%62%
1751
16th to endDay
4324423447%56%
1579
March1st to 15thDay
221142446%9%60%
1800
16th to endDay
121332445%9%58%
2220
April1st to 15thDay
2313313336%66%
2149
16th to endDay
111213238%72%
2160
May1st to 15thDay
112212347%72%
2253
16th to endDay
1112212336%74%
2429
June1st to 15thDay
1212235%79%
2454
16th to endDay
1111288%
2520
July1st to 15thDay
1121223379%
2520
16th to endDay
21112225%77%
2441
August1st to 15thDay
111112385%
2160
16th to endDay
111122484%
2292
September1st to 15thDay
111122483%
2139
16th to endDay
111222383%
1904
October1st to 15thDay
11221324474%
1785
16th to endDay
12222345%74%
1735
November1st to 15thDay
1112122345%72%
1584
16th to endDay
121232235%8%63%
1620
December1st to 15thDay
22134345%6%9%56%
1620
16th to endDay
6%31442445%6%57%
1611
January1st to 15thNight
332431335%8%59%
2479
16th to endNight
4414424347%58%
2391
February1st to 15thNight
232332335%7%62%
2101
16th to endNight
32244345%46%57%
1895
March1st to 15thNight
1213225%5%5%8%61%
2160
16th to endNight
111332345%9%63%
2001
April1st to 15thNight
1222313346%67%
1799
16th to endNight
11213346%73%
1800
May1st to 15thNight
111436%8%71%
1696
16th to endNight
1211235%79%
1684
June1st to 15thNight
12335%81%
1503
16th to endNight
111290%
1440
July1st to 15thNight
1121123381%
1440
16th to endNight
12213335%75%
1723
August1st to 15thNight
111112386%
1800
16th to endNight
1122385%
1910
September1st to 15thNight
11113483%
1821
16th to endNight
11122485%
1914
October1st to 15thNight
332334473%
1842
16th to endNight
112213335%75%
2136
November1st to 15thNight
1211313345%72%
2275
16th to endNight
111331335%7%66%
2340
December1st to 15thNight
33135%14447%61%
2340
16th to endNight
4323424447%57%
2610

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
23%48%19%26%18%
1456
16th to endDay
28%38%18%20%20%
1830
February1st to 15thDay
21%46%21%27%18%
1751
16th to endDay
27%47%20%29%9%
1579
March1st to 15thDay
18%312%22%24%17%
1800
16th to endDay
21%410%26%23%13%
2220
April1st to 15thDay
19%311%23%28%14%
2149
16th to endDay
10%311%22%32%18%
2160
May1st to 15thDay
11%29%20%31%24%
2253
16th to endDay
11%28%20%39%16%
2432
June1st to 15thDay
8%26%14%28%40%
2454
16th to endDay
5%125%21%63%
2520
July1st to 15thDay
9%137%19%57%
2371
16th to endDay
10%25%14%27%39%
2291
August1st to 15thDay
7%17%26%55%
2146
16th to endDay
6%28%30%50%
2292
September1st to 15thDay
6%1410%27%48%
2139
16th to endDay
7%128%35%44%
1904
October1st to 15thDay
13%2417%30%30%
1785
16th to endDay
11%35%13%28%37%
1735
November1st to 15thDay
14%37%17%35%22%
1584
16th to endDay
18%38%18%26%24%
1620
December1st to 15thDay
20%5%11%20%25%14%
1620
16th to endDay
27%5%9%24%20%11%
1611
January1st to 15thNight
22%5%8%18%28%17%
2479
16th to endNight
24%310%16%21%22%
2391
February1st to 15thNight
20%5%8%18%25%22%
2112
16th to endNight
25%5%9%19%29%10%
1895
March1st to 15thNight
17%5%12%22%23%18%
2160
16th to endNight
16%412%25%26%12%
2001
April1st to 15thNight
17%411%29%23%12%
1799
16th to endNight
10%211%25%32%17%
1800
May1st to 15thNight
7%311%23%34%18%
1697
16th to endNight
8%39%24%39%15%
1685
June1st to 15thNight
5%27%19%28%35%
1503
16th to endNight
4136%25%59%
1440
July1st to 15thNight
8%239%21%55%
1360
16th to endNight
10%25%13%26%40%
1610
August1st to 15thNight
5%28%27%54%
1790
16th to endNight
5%128%34%48%
1910
September1st to 15thNight
6%139%30%47%
1821
16th to endNight
41210%39%41%
1914
October1st to 15thNight
13%25%14%34%29%
1842
16th to endNight
12%2413%28%37%
2136
November1st to 15thNight
13%26%17%33%26%
2275
16th to endNight
16%38%18%26%26%
2340
December1st to 15thNight
22%49%17%27%17%
2340
16th to endNight
25%5%10%21%22%14%
2610

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
9%21%33%27%7%1
84
16th to endDay
8%18%33%24%13%1
273
February1st to 15thDay
320%32%27%14%1
266
16th to endDay
5%24%33%21%13%1
238
March1st to 15thDay
5%21%30%23%16%2
270
16th to endDay
5%18%35%25%13%2
288
April1st to 15thDay
6%21%37%21%10%3
269
16th to endDay
327%38%21%7%2
270
May1st to 15thDay
314%39%26%13%2
288
16th to endDay
313%38%31%9%4
330
June1st to 15thDay
18%36%34%11%6%
315
16th to endDay
1331%39%16%8%
315
July1st to 15thDay
123%47%18%8%
305
16th to endDay
217%50%19%9%
327
August1st to 15thDay
1127%46%15%7%
315
16th to endDay
18%53%16%10%
332
September1st to 15thDay
227%46%17%4
315
16th to endDay
6%27%40%21%2
288
October1st to 15thDay
112%35%32%15%1
255
16th to endDay
210%29%32%23%2
247
November1st to 15thDay
18%14%33%26%15%
90
16th to endDay
312%37%33%13%
90
December1st to 15thDay
28%25%37%23%2
90
16th to endDay
11%22%18%38%9%
77
January1st to 15thNight
47%27%38%18%3
720
16th to endNight
6%6%28%36%18%2
768
February1st to 15thNight
35%26%39%21%4
704
16th to endNight
5%6%30%38%16%3
632
March1st to 15thNight
2429%39%20%3
720
16th to endNight
25%26%41%21%2
768
April1st to 15thNight
26%30%36%20%2
719
16th to endNight
15%29%38%20%3
720
May1st to 15thNight
326%43%22%2
617
16th to endNight
6%27%39%24%1
563
June1st to 15thNight
218%51%26%1
423
16th to endNight
6%52%39%1
360
July1st to 15thNight
1136%57%3
340
16th to endNight
1135%54%6%
587
August1st to 15thNight
338%48%7%
717
16th to endNight
129%54%13%
764
September1st to 15thNight
15%32%50%10%
720
16th to endNight
10%37%41%9%
692
October1st to 15thNight
1217%44%30%4
660
16th to endNight
2217%37%31%9%
704
November1st to 15thNight
2219%41%28%6%
700
16th to endNight
2220%40%27%5%
720
December1st to 15thNight
45%23%41%21%2
720
16th to endNight
6%8%28%37%16%1
768
Page generated at 2017-09-25 06:02:23. Version ac04

Copyright 2017 A. Danko


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