Tenagra Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tenagra 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
73%
15618
35%
46979
30%
15578
79%
15578
51%
22808

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
73%
719
33%
2327
33%
716
78%
716
50%
1077
January16th to endNight
63%
768
34%
2496
30%
768
73%
768
39%
1286
February1st to 15thNight
70%
698
36%
2185
34%
697
79%
697
51%
1027
February16th to endNight
62%
632
39%
1823
32%
632
72%
632
47%
936
March1st to 15thNight
65%
720
41%
1980
31%
720
74%
720
56%
972
March16th to endNight
70%
768
38%
2112
27%
768
79%
768
58%
1020
April1st to 15thNight
67%
689
36%
1948
24%
689
76%
689
55%
931
April16th to endNight
67%
540
44%
1800
35%
540
79%
540
65%
687
May1st to 15thNight
70%
539
41%
1629
30%
539
81%
539
70%
645
May16th to endNight
75%
561
44%
1684
34%
561
82%
561
75%
654
June1st to 15thNight
80%
540
36%
1620
30%
540
82%
540
69%
673
June16th to endNight
84%
540
30%
1620
26%
540
85%
540
58%
746
July1st to 15thNight
81%
510
17%
1530
15%
510
81%
510
36%
888
July16th to endNight
79%
564
13%
1593
11%
531
79%
531
25%
1051
August1st to 15thNight
84%
539
22%
1611
20%
536
84%
536
36%
920
August16th to endNight
82%
607
27%
1899
26%
607
82%
607
35%
1084
September1st to 15thNight
77%
720
26%
1980
23%
720
78%
720
39%
1183
September16th to endNight
84%
692
42%
1914
32%
692
88%
692
64%
904
October1st to 15thNight
77%
660
40%
1915
32%
660
82%
660
62%
869
October16th to endNight
84%
704
42%
2112
37%
704
88%
704
68%
898
November1st to 15thNight
77%
700
43%
2100
36%
700
83%
700
64%
893
November16th to endNight
68%
720
39%
2265
35%
720
74%
720
49%
1075
December1st to 15thNight
71%
720
37%
2340
38%
720
76%
720
47%
1116
December16th to endNight
64%
768
35%
2496
34%
768
70%
768
41%
1273

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
4213323446%62%
47937
Night
3212223346%66%
47180
TransparencyDay
22%45%11%26%29%
47632
Night
18%46%14%28%28%
46986
SeeingDay
8%11%23%30%19%6%
5451
Night
4312%34%36%7%
15628

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
4223322436%64%
1611
16th to endDay
442431335%6%60%
1728
February1st to 15thDay
6%213212235%68%
1670
16th to endDay
5%41432334463%
1649
March1st to 15thDay
3212223346%67%
1980
16th to endDay
2211212335%72%
2112
April1st to 15thDay
2212212346%71%
1999
16th to endDay
111111112381%
2160
May1st to 15thDay
1211213479%
2318
16th to endDay
11222384%
2429
June1st to 15thDay
211112225%78%
2340
16th to endDay
2212323435%68%
2340
July1st to 15thDay
5%326%8%47%7%9%8%34%
2340
16th to endDay
10%5%38%8%5%8%8%8%9%22%
2467
August1st to 15thDay
7%5%36%6%5%7%7%7%7%34%
2340
16th to endDay
4425%6%5%6%6%6%9%42%
2298
September1st to 15thDay
7%5%26%6%45%5%6%7%44%
1980
16th to endDay
321332444464%
1904
October1st to 15thDay
121211325%5%72%
1713
16th to endDay
11212235%77%
1760
November1st to 15thDay
112211235%76%
1759
16th to endDay
3312222235%69%
1692
December1st to 15thDay
6%412223337%62%
1620
16th to endDay
6%413313247%60%
1728
January1st to 15thNight
323313345%67%
2327
16th to endNight
7%3133235%5%5%58%
2496
February1st to 15thNight
3212213245%68%
2179
16th to endNight
2413423436%63%
1823
March1st to 15thNight
2213212246%69%
1980
16th to endNight
2212213335%72%
2112
April1st to 15thNight
1212313335%71%
1948
16th to endNight
1111122381%
1800
May1st to 15thNight
112245%79%
1629
16th to endNight
11112385%
1684
June1st to 15thNight
211111235%79%
1620
16th to endNight
1112212446%70%
1620
July1st to 15thNight
3213436%6%8%13%46%
1620
16th to endNight
4325%5%47%8%10%14%33%
1701
August1st to 15thNight
2212435%7%8%10%51%
1620
16th to endNight
5%223335%6%7%11%48%
1899
September1st to 15thNight
4325%43445%7%53%
1980
16th to endNight
211212335%74%
1914
October1st to 15thNight
11221222477%
1915
16th to endNight
111112225%78%
2112
November1st to 15thNight
1222245%76%
2100
16th to endNight
3313322235%67%
2265
December1st to 15thNight
4312322445%65%
2340
16th to endNight
6%424312336%61%
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
22%3411%27%29%
1612
16th to endDay
24%3216%27%24%
1728
February1st to 15thDay
20%1312%30%32%
1670
16th to endDay
24%2212%30%27%
1649
March1st to 15thDay
19%327%34%32%
1980
16th to endDay
16%228%36%32%
2112
April1st to 15thDay
15%227%39%33%
1999
16th to endDay
11%117%28%49%
2160
May1st to 15thDay
11%216%27%50%
2318
16th to endDay
8%115%32%49%
2432
June1st to 15thDay
10%225%25%54%
2340
16th to endDay
19%337%23%41%
2340
July1st to 15thDay
40%11%13%12%12%8%
2201
16th to endDay
51%15%17%10%4
2312
August1st to 15thDay
44%10%11%14%14%4
2325
16th to endDay
35%11%13%15%13%10%
2298
September1st to 15thDay
38%8%8%15%18%10%
1980
16th to endDay
22%45%12%33%22%
1904
October1st to 15thDay
14%35%12%32%31%
1713
16th to endDay
11%2311%31%40%
1760
November1st to 15thDay
11%2211%36%34%
1759
16th to endDay
18%2412%28%34%
1692
December1st to 15thDay
23%2416%30%22%
1620
16th to endDay
24%26%15%32%18%
1728
January1st to 15thNight
19%3412%31%29%
2327
16th to endNight
26%3415%29%20%
2496
February1st to 15thNight
18%3413%27%33%
2190
16th to endNight
22%3314%31%25%
1823
March1st to 15thNight
17%2211%29%36%
1980
16th to endNight
16%2410%34%32%
2112
April1st to 15thNight
16%2210%39%27%
1948
16th to endNight
9%228%29%47%
1800
May1st to 15thNight
7%229%32%45%
1630
16th to endNight
6%127%35%46%
1685
June1st to 15thNight
10%116%26%53%
1620
16th to endNight
14%449%22%45%
1620
July1st to 15thNight
26%10%19%20%12%10%
1530
16th to endNight
35%13%27%17%41
1593
August1st to 15thNight
24%11%17%22%18%5%
1611
16th to endNight
27%9%16%19%17%8%
1899
September1st to 15thNight
29%7%11%21%20%9%
1980
16th to endNight
12%35%15%40%21%
1914
October1st to 15thNight
13%25%18%30%29%
1915
16th to endNight
11%1412%28%41%
2112
November1st to 15thNight
12%1316%33%32%
2100
16th to endNight
20%2212%28%33%
2265
December1st to 15thNight
20%3315%34%22%
2340
16th to endNight
25%35%17%28%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
16%8%20%42%12%
90
16th to endDay
10%9%20%33%21%4
96
February1st to 15thDay
9%12%23%30%21%2
185
16th to endDay
13%24%28%21%10%1
238
March1st to 15thDay
8%23%27%26%10%4
270
16th to endDay
426%32%21%9%5%
288
April1st to 15thDay
5%20%38%20%11%3
269
16th to endDay
6%23%39%18%10%2
270
May1st to 15thDay
8%20%35%21%11%3
288
16th to endDay
215%37%33%9%2
330
June1st to 15thDay
46%40%33%11%3
315
16th to endDay
4125%40%22%5%
315
July1st to 15thDay
9%110%42%27%7%
305
16th to endDay
14%17%30%32%13%
327
August1st to 15thDay
11%16%31%33%16%
315
16th to endDay
6%8%37%33%14%
332
September1st to 15thDay
13%311%38%24%9%
315
16th to endDay
6%6%25%30%24%6%
288
October1st to 15thDay
310%25%32%20%7%
153
16th to endDay
4219%29%32%12%
96
November1st to 15thDay
8%11%24%27%22%5%
90
16th to endDay
12%16%21%28%21%
90
December1st to 15thDay
8%6%14%30%32%7%
90
16th to endDay
16%16%20%23%21%
96
January1st to 15thNight
5%313%41%29%6%
720
16th to endNight
9%415%39%26%4
768
February1st to 15thNight
5%5%14%42%27%4
704
16th to endNight
5%6%21%43%19%2
632
March1st to 15thNight
47%19%36%27%4
720
16th to endNight
25%16%39%31%4
768
April1st to 15thNight
46%18%46%23%1
689
16th to endNight
25%23%41%23%2
540
May1st to 15thNight
5%21%40%28%3
540
16th to endNight
1416%40%34%2
563
June1st to 15thNight
2210%44%36%3
540
16th to endNight
217%31%52%5%
540
July1st to 15thNight
4419%60%11%
510
16th to endNight
439%61%19%
564
August1st to 15thNight
412%58%23%
539
16th to endNight
6%214%55%20%
607
September1st to 15thNight
6%420%50%16%
720
16th to endNight
38%32%43%11%
692
October1st to 15thNight
2212%37%36%8%
660
16th to endNight
119%35%42%8%
704
November1st to 15thNight
2412%36%36%7%
700
16th to endNight
6%315%35%32%7%
720
December1st to 15thNight
8%311%40%29%6%
720
16th to endNight
10%414%41%23%5%
768
Page generated at 2017-09-25 06:02:29. Version ac04

Copyright 2017 A. Danko


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