Table Mountain Star Party at Eden Valley
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Table Mountain Star Party at Eden Valley clear sky chart from 2005-11-05 to 2017-09-22.

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
47%
14735
14%
46829
11%
14708
51%
14708
22%
30981

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
29%
718
8%
2506
6%
716
32%
716
10%
1917
January16th to endNight
36%
768
10%
2688
9%
768
39%
768
13%
1982
February1st to 15thNight
38%
698
8%
2374
6%
697
42%
697
15%
1722
February16th to endNight
43%
632
13%
1948
9%
632
50%
632
20%
1337
March1st to 15thNight
36%
720
10%
2160
6%
720
42%
720
17%
1562
March16th to endNight
36%
768
12%
2003
5%
768
40%
768
18%
1489
April1st to 15thNight
44%
719
13%
1799
5%
719
47%
719
23%
1300
April16th to endNight
48%
534
15%
1614
12%
534
51%
534
24%
1051
May1st to 15thNight
49%
359
17%
1439
19%
359
58%
359
24%
814
May16th to endNight
56%
374
10%
1496
14%
374
60%
374
18%
952
June1st to 15thNight
54%
360
7%
1305
5%
360
55%
360
23%
799
June16th to endNight
59%
360
11%
1191
4%
360
61%
360
32%
674
July1st to 15thNight
68%
340
12%
1360
10%
340
72%
340
42%
576
July16th to endNight
76%
376
21%
1416
31%
354
81%
354
51%
551
August1st to 15thNight
80%
360
27%
1432
38%
358
84%
358
49%
577
August16th to endNight
71%
656
30%
1802
21%
656
74%
656
54%
902
September1st to 15thNight
70%
720
28%
1800
15%
720
73%
720
54%
970
September16th to endNight
65%
683
26%
1851
19%
683
68%
683
37%
1114
October1st to 15thNight
52%
660
17%
1975
16%
660
56%
660
28%
1224
October16th to endNight
45%
704
14%
2265
11%
704
51%
704
19%
1540
November1st to 15thNight
38%
700
10%
2359
9%
700
42%
700
14%
1723
November16th to endNight
31%
740
9%
2540
6%
740
35%
740
11%
1941
December1st to 15thNight
35%
900
9%
2700
6%
900
38%
900
14%
2041
December16th to endNight
27%
886
10%
2806
4%
886
33%
886
10%
2223

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
10%7%36%5%35%45%7%39%
48035
Night
11%9%36%5%2445%7%38%
46997
Cloud CoverDay
11%9%36%5%3445%6%37%
48035
Night
11%10%46%5%3445%6%37%
47001
TransparencyDay
45%5%12%22%11%2
47706
Night
45%5%13%22%10%2
46830
SeeingDay
17%15%27%25%12%3
5706
Night
16%7%17%33%20%4
14745

By Month

Percentage Cloud Cover NW (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
17%13%6%8%5%35%5%46%22%
1432
16th to endDay
14%13%6%8%6%2446%7%25%
1536
February1st to 15thDay
13%13%48%6%35%46%7%26%
1489
16th to endDay
11%11%47%7%36%5%7%7%29%
1526
March1st to 15thDay
15%12%35%6%35%6%7%7%24%
1800
16th to endDay
11%10%5%8%8%45%5%7%8%24%
2218
April1st to 15thDay
10%8%5%10%7%5%7%5%5%7%26%
2149
16th to endDay
8%8%37%7%35%5%6%9%33%
2343
May1st to 15thDay
8%7%26%6%46%5%7%8%38%
2511
16th to endDay
11%7%27%8%46%6%6%8%30%
2615
June1st to 15thDay
13%7%36%5%36%45%8%35%
2652
16th to endDay
9%6%26%5%345%7%8%40%
2741
July1st to 15thDay
231432345%7%61%
2520
16th to endDay
3212323446%65%
2657
August1st to 15thDay
2213323446%63%
2520
16th to endDay
321232445%8%59%
2396
September1st to 15thDay
2313423336%65%
2160
16th to endDay
8%42443445%7%50%
1921
October1st to 15thDay
11%6%25%5%2445%9%42%
1653
16th to endDay
17%9%5%6%5%24346%32%
1606
November1st to 15thDay
19%9%35%5%45%45%6%28%
1497
16th to endDay
15%13%5%7%5%25%47%5%25%
1407
December1st to 15thDay
14%12%5%9%5%35%45%6%27%
1260
16th to endDay
17%16%6%8%7%2345%5%23%
1426
January1st to 15thNight
20%15%6%7%5%2335%6%21%
2506
16th to endNight
13%18%6%9%5%35%35%6%22%
2688
February1st to 15thNight
15%14%5%6%42445%6%29%
2362
16th to endNight
9%11%45%5%346%6%8%34%
1948
March1st to 15thNight
13%10%37%5%35%5%7%8%28%
2160
16th to endNight
10%8%48%8%35%5%6%7%32%
1999
April1st to 15thNight
8%7%46%6%36%5%6%7%36%
1799
16th to endNight
5%7%35%435%7%6%9%40%
1614
May1st to 15thNight
7%5%15%435%5%5%7%47%
1439
16th to endNight
9%7%35%5%35%7%7%8%36%
1496
June1st to 15thNight
11%3245%35%5%7%9%39%
1305
16th to endNight
6%423445%5%5%7%50%
1191
July1st to 15thNight
221231235%7%67%
1440
16th to endNight
1112123346%71%
1512
August1st to 15thNight
211221345%7%69%
1440
16th to endNight
22232445%7%64%
1802
September1st to 15thNight
323222347%67%
1800
16th to endNight
6%5%1342445%7%54%
1851
October1st to 15thNight
11%6%35%42445%7%45%
1975
16th to endNight
16%7%25%6%345%6%8%34%
2265
November1st to 15thNight
20%10%35%5%2446%7%28%
2359
16th to endNight
20%12%6%7%6%35%345%24%
2540
December1st to 15thNight
15%11%6%9%6%34445%26%
2700
16th to endNight
18%18%7%8%5%2333423%
2806

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
17%14%6%8%6%44345%24%
1432
16th to endDay
13%16%47%5%2345%8%27%
1536
February1st to 15thDay
14%15%5%7%6%35%36%6%25%
1489
16th to endDay
12%12%5%8%5%35%6%5%6%27%
1526
March1st to 15thDay
15%15%46%7%35%5%5%6%24%
1800
16th to endDay
13%12%6%9%8%45%45%7%20%
2218
April1st to 15thDay
10%13%6%10%8%45%5%6%5%23%
2149
16th to endDay
9%11%5%8%7%35%46%7%29%
2343
May1st to 15thDay
9%9%36%6%36%5%5%6%35%
2511
16th to endDay
13%8%48%7%46%5%6%8%26%
2615
June1st to 15thDay
16%7%47%6%36%5%5%7%31%
2652
16th to endDay
11%8%35%5%35%5%5%8%37%
2741
July1st to 15thDay
3414324447%57%
2520
16th to endDay
3213424445%63%
2657
August1st to 15thDay
3324423446%60%
2520
16th to endDay
4313435%45%6%58%
2396
September1st to 15thDay
3414313246%62%
2160
16th to endDay
10%6%2442345%7%48%
1921
October1st to 15thDay
13%7%26%43345%6%41%
1653
16th to endDay
18%11%46%5%34435%31%
1606
November1st to 15thDay
18%12%36%5%3445%6%28%
1497
16th to endDay
15%14%6%7%5%2445%6%26%
1407
December1st to 15thDay
13%11%7%6%6%445%46%27%
1260
16th to endDay
17%17%6%7%6%23345%23%
1426
January1st to 15thNight
20%14%6%9%5%24345%22%
2506
16th to endNight
12%17%6%9%6%34346%24%
2688
February1st to 15thNight
15%14%5%6%5%34446%30%
2362
16th to endNight
10%12%5%5%425%5%5%7%34%
1948
March1st to 15thNight
13%12%38%5%35%6%6%8%27%
2160
16th to endNight
11%11%48%8%345%5%6%29%
2003
April1st to 15thNight
9%9%46%7%36%6%5%6%34%
1799
16th to endNight
6%9%46%6%46%5%5%7%38%
1614
May1st to 15thNight
8%6%35%5%26%45%6%45%
1439
16th to endNight
11%7%36%5%5%5%6%6%7%34%
1496
June1st to 15thNight
11%425%6%45%5%7%7%38%
1305
16th to endNight
7%5%25%435%5%5%7%46%
1191
July1st to 15thNight
232231325%7%65%
1440
16th to endNight
1111223347%69%
1512
August1st to 15thNight
22231335%8%66%
1440
16th to endNight
311232346%7%63%
1802
September1st to 15thNight
4213223347%64%
1800
16th to endNight
8%5%1443445%7%50%
1851
October1st to 15thNight
12%7%24424446%43%
1975
16th to endNight
16%9%35%6%35%46%7%32%
2265
November1st to 15thNight
20%10%46%5%345%5%7%26%
2359
16th to endNight
18%14%6%8%6%34345%24%
2540
December1st to 15thNight
14%12%6%10%6%35%35%6%26%
2700
16th to endNight
17%19%7%8%5%2333423%
2806

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
61%412%15%4
1432
16th to endDay
55%415%18%5%1
1536
February1st to 15thDay
57%5%18%14%2
1489
16th to endDay
53%6%14%17%7%
1526
March1st to 15thDay
58%5%14%16%4
1800
16th to endDay
61%6%12%15%3
2218
April1st to 15thDay
58%6%13%15%5%
2149
16th to endDay
50%7%12%22%6%1
2343
May1st to 15thDay
46%411%26%9%1
2511
16th to endDay
53%5%13%20%5%
2619
June1st to 15thDay
51%49%21%9%2
2652
16th to endDay
43%310%25%14%
2741
July1st to 15thDay
25%48%26%24%9%
2371
16th to endDay
22%36%28%28%10%
2490
August1st to 15thDay
24%38%31%25%6%
2503
16th to endDay
24%311%33%21%4
2396
September1st to 15thDay
23%311%33%24%4
2160
16th to endDay
34%413%29%14%2
1921
October1st to 15thDay
40%5%16%27%10%
1653
16th to endDay
52%5%14%21%5%
1606
November1st to 15thDay
54%6%14%16%5%1
1497
16th to endDay
56%5%14%17%5%
1407
December1st to 15thDay
54%7%15%17%4
1260
16th to endDay
61%5%12%15%4
1426
January1st to 15thNight
62%413%14%4
2506
16th to endNight
59%314%15%5%1
2688
February1st to 15thNight
54%6%17%16%41
2374
16th to endNight
48%5%17%22%6%
1948
March1st to 15thNight
51%6%16%20%4
2160
16th to endNight
53%5%14%20%5%
2003
April1st to 15thNight
48%5%13%23%7%1
1799
16th to endNight
41%5%14%28%7%1
1614
May1st to 15thNight
37%411%29%15%1
1440
16th to endNight
45%5%15%24%7%
1496
June1st to 15thNight
40%5%10%29%11%2
1305
16th to endNight
32%413%30%17%1
1191
July1st to 15thNight
20%39%30%25%10%
1360
16th to endNight
15%29%28%30%12%
1416
August1st to 15thNight
15%410%34%28%6%
1432
16th to endNight
19%211%34%27%4
1802
September1st to 15thNight
19%310%31%29%6%
1800
16th to endNight
31%5%11%30%15%5%
1851
October1st to 15thNight
39%316%25%12%1
1975
16th to endNight
47%6%14%25%5%
2265
November1st to 15thNight
54%6%16%14%5%2
2359
16th to endNight
62%412%15%5%
2540
December1st to 15thNight
57%6%15%16%4
2700
16th to endNight
64%5%10%14%5%
2806

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
15%10%5%40%20%10%
60
16th to endDay
34%318%26%12%4
64
February1st to 15thDay
20%18%26%22%9%2
149
16th to endDay
20%16%24%26%10%1
229
March1st to 15thDay
31%22%31%10%3
270
16th to endDay
30%23%27%14%4
288
April1st to 15thDay
25%18%30%17%7%2
269
16th to endDay
17%25%27%17%8%2
270
May1st to 15thDay
19%23%29%19%6%1
288
16th to endDay
19%10%21%26%15%5%
330
June1st to 15thDay
18%11%21%28%17%2
447
16th to endDay
13%12%26%28%15%3
536
July1st to 15thDay
7%10%31%36%10%2
305
16th to endDay
413%37%26%12%4
327
August1st to 15thDay
6%7%26%35%16%6%
315
16th to endDay
7%12%29%31%14%4
332
September1st to 15thDay
7%15%27%27%18%4
315
16th to endDay
13%15%30%25%13%2
280
October1st to 15thDay
23%17%27%21%9%1
255
16th to endDay
33%7%20%27%9%1
118
November1st to 15thDay
24%16%21%29%9%
75
16th to endDay
23%13%25%13%16%8%
60
December1st to 15thDay
23%11%23%25%13%3
60
16th to endDay
23%10%20%29%10%4
64
January1st to 15thNight
23%10%19%30%14%1
720
16th to endNight
19%419%36%16%2
768
February1st to 15thNight
22%6%18%30%17%4
704
16th to endNight
16%7%21%30%20%3
632
March1st to 15thNight
20%10%22%29%14%3
720
16th to endNight
16%13%21%33%13%2
768
April1st to 15thNight
13%9%19%31%21%4
719
16th to endNight
10%11%20%35%18%3
534
May1st to 15thNight
11%8%21%34%19%3
360
16th to endNight
14%5%12%28%32%7%
375
June1st to 15thNight
12%5%15%35%27%3
360
16th to endNight
10%416%37%26%4
360
July1st to 15thNight
37%14%32%36%5%
340
16th to endNight
2313%39%36%4
376
August1st to 15thNight
328%28%46%10%
360
16th to endNight
5%315%35%33%6%
656
September1st to 15thNight
5%5%12%30%31%14%
720
16th to endNight
11%411%39%26%6%
683
October1st to 15thNight
18%6%14%29%27%2
660
16th to endNight
22%5%14%33%20%2
704
November1st to 15thNight
24%10%18%35%9%2
700
16th to endNight
27%10%16%25%17%2
740
December1st to 15thNight
23%7%17%37%12%1
900
16th to endNight
26%7%21%35%8%
886
Page generated at 2017-09-23 03:43:38. Version ac04

Copyright 2017 A. Danko


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