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 2005-11-06 to 2024-01-13.

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
46%
22699
15%
74781
12%
22659
51%
22659
21%
49149

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 10thNight
25%
758
8%
2646
5%
756
29%
756
9%
2105
January11th to 20thNight
33%
732
11%
2562
8%
732
36%
732
13%
1884
January21st to endNight
36%
792
10%
2772
9%
792
40%
792
14%
2017
February1st to 10thNight
35%
720
10%
2468
6%
720
41%
720
15%
1755
February11th to 20thNight
39%
701
13%
2263
8%
700
47%
700
19%
1556
February21st to endNight
39%
592
15%
1776
10%
592
46%
592
18%
1261
March1st to 10thNight
40%
720
13%
2160
9%
720
45%
720
20%
1509
March11th to 20thNight
41%
720
17%
2090
10%
720
47%
720
20%
1468
March21st to endNight
37%
792
13%
1996
5%
792
41%
792
20%
1464
April1st to 10thNight
44%
720
14%
1800
5%
720
48%
720
25%
1269
April11th to 20thNight
45%
698
16%
1766
7%
698
49%
698
25%
1219
April21st to endNight
47%
455
18%
1535
16%
455
52%
455
22%
976
May1st to 10thNight
51%
360
18%
1440
19%
360
61%
360
23%
829
May11th to 20thNight
57%
354
16%
1416
22%
354
63%
354
24%
807
May21st to endNight
56%
388
9%
1552
13%
388
59%
388
19%
966
June1st to 10thNight
53%
360
8%
1328
7%
360
56%
360
23%
809
June11th to 20thNight
54%
360
8%
1260
4%
360
55%
360
24%
769
June21st to endNight
64%
360
12%
1156
5%
360
66%
360
36%
633
July1st to 10thNight
71%
350
12%
1400
12%
350
73%
350
40%
609
July11th to 20thNight
64%
348
19%
1392
22%
348
74%
348
48%
564
July21st to endNight
77%
394
26%
1488
39%
372
86%
372
56%
543
August1st to 10thNight
75%
358
26%
1424
36%
356
81%
356
45%
608
August11th to 20thNight
80%
370
34%
1438
40%
370
85%
370
54%
561
August21st to endNight
68%
792
30%
1980
18%
792
72%
792
52%
1084
September1st to 10thNight
68%
720
27%
1800
14%
720
72%
720
51%
990
September11th to 20thNight
65%
720
29%
1831
17%
720
68%
720
40%
1096
September21st to endNight
61%
720
25%
1980
19%
720
65%
720
37%
1181
October1st to 10thNight
56%
720
18%
2152
16%
720
60%
720
29%
1321
October11th to 20thNight
50%
720
19%
2211
16%
720
56%
720
26%
1388
October21st to endNight
43%
792
18%
2574
14%
792
51%
792
21%
1694
November1st to 10thNight
37%
740
12%
2443
9%
740
43%
740
16%
1740
November11th to 20thNight
33%
760
12%
2660
8%
760
39%
760
14%
1924
November21st to endNight
34%
792
9%
2692
7%
792
37%
792
14%
1980
December1st to 10thNight
36%
950
13%
2850
8%
950
40%
950
17%
2071
December11th to 20thNight
25%
949
5%
3507
2%
949
28%
949
8%
2859
December21st to endNight
27%
922
8%
4973
7%
909
34%
909
7%
3640

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%8%36%6%35%5%6%7%41%
74695
Night
12%10%46%5%345%5%7%39%
75012
TransparencyDay
45%412%23%14%3
74397
Night
46%413%22%12%2
74828
SeeingDay
16%14%28%26%13%3
13626
Night
16%8%20%34%20%3
22712

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 10thDay
21%18%6%9%6%35%6%45%18%
1519
11th to 20thDay
16%12%6%8%6%45%47%7%26%
1459
21st to endDay
14%14%6%9%6%2346%7%29%
1584
February1st to 10thDay
11%12%49%5%35%5%6%7%31%
1490
11th to 20thDay
10%13%5%8%7%35%5%6%7%32%
1585
21st to endDay
9%11%5%8%8%47%5%7%7%29%
1480
March1st to 10thDay
11%13%46%7%45%6%7%8%29%
1800
11th to 20thDay
12%10%46%6%36%5%7%8%33%
1867
21st to endDay
11%12%5%8%8%45%6%7%8%26%
2359
April1st to 10thDay
11%10%5%9%7%5%7%6%5%8%29%
2160
11th to 20thDay
9%8%38%7%47%6%7%7%33%
2144
21st to endDay
9%9%47%7%35%5%6%9%36%
2421
May1st to 10thDay
9%7%36%6%46%5%7%8%40%
2520
11th to 20thDay
10%8%36%6%36%7%7%9%36%
2477
21st to endDay
12%7%37%7%46%5%7%8%33%
2723
June1st to 10thDay
13%8%36%6%45%5%6%8%35%
2628
11th to 20thDay
12%7%37%6%46%6%8%8%34%
2700
21st to endDay
7%425%5%35%5%6%9%50%
2763
July1st to 10thDay
441443347%8%59%
2520
11th to 20thDay
3424424446%64%
2520
21st to endDay
3211323446%72%
2741
August1st to 10thDay
331342445%7%64%
2507
11th to 20thDay
4313323446%68%
2455
21st to endDay
3324435%5%6%9%55%
2376
September1st to 10thDay
4323424446%64%
2160
11th to 20thDay
7%5%24435%5%5%8%52%
2129
21st to endDay
10%5%2443445%7%52%
1980
October1st to 10thDay
9%6%35%5%35%45%7%48%
1805
11th to 20thDay
11%6%36%5%35%45%7%44%
1747
21st to endDay
17%9%46%5%34447%36%
1782
November1st to 10thDay
18%11%35%6%46%46%7%29%
1632
11th to 20thDay
16%13%47%6%45%45%5%33%
1520
21st to endDay
15%13%6%9%5%25%5%7%7%25%
1466
December1st to 10thDay
14%11%5%8%6%35%5%5%6%31%
1330
11th to 20thDay
17%18%7%10%6%3445%6%21%
1682
21st to endDay
15%17%6%10%9%35%5%6%5%19%
2664
January1st to 10thNight
23%18%6%9%5%3445%6%18%
2646
11th to 20thNight
18%15%6%8%6%2446%7%24%
2562
21st to endNight
13%19%5%9%5%35%46%6%25%
2772
February1st to 10thNight
13%14%5%7%5%35%5%5%8%29%
2468
11th to 20thNight
10%12%47%6%345%7%7%35%
2261
21st to endNight
9%13%5%6%7%45%5%6%7%31%
1776
March1st to 10thNight
12%11%48%5%35%6%6%8%32%
2160
11th to 20thNight
11%9%46%6%36%6%6%7%35%
2090
21st to endNight
11%9%47%8%46%5%6%8%32%
1996
April1st to 10thNight
10%8%37%6%36%5%7%8%38%
1800
11th to 20thNight
7%7%47%6%46%6%6%7%41%
1766
21st to endNight
7%8%46%445%7%6%9%40%
1535
May1st to 10thNight
8%6%25%5%45%6%5%7%47%
1440
11th to 20thNight
7%7%26%5%35%6%8%10%42%
1416
21st to endNight
9%7%46%6%46%7%7%7%38%
1552
June1st to 10thNight
12%4346%45%6%7%9%40%
1328
11th to 20thNight
10%436%5%46%6%6%9%41%
1260
21st to endNight
5%424445%5%6%8%54%
1156
July1st to 10thNight
342332345%8%63%
1440
11th to 20thNight
1212325%447%70%
1440
21st to endNight
112223346%75%
1576
August1st to 10thNight
321332345%7%67%
1432
11th to 20thNight
121331245%8%70%
1438
21st to endNight
43123245%5%9%62%
1980
September1st to 10thNight
431332345%8%63%
1800
11th to 20thNight
7%5%2442336%7%58%
1831
21st to endNight
7%5%25%5%245%5%8%52%
1980
October1st to 10thNight
10%7%35%425%46%7%48%
2152
11th to 20thNight
12%7%36%5%345%6%8%43%
2211
21st to endNight
17%9%25%5%345%5%7%39%
2574
November1st to 10thNight
20%11%35%5%25%46%7%31%
2443
11th to 20thNight
19%11%46%5%345%5%6%31%
2660
21st to endNight
19%13%6%8%5%35%45%6%26%
2692
December1st to 10thNight
15%13%6%8%7%3445%5%29%
2850
11th to 20thNight
17%22%7%10%6%24445%19%
3510
21st to endNight
17%21%6%8%5%34445%23%
5019

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 10thDay
69%49%12%5%
1519
11th to 20thDay
57%5%14%18%42
1459
21st to endDay
54%315%20%8%
1584
February1st to 10thDay
54%5%17%16%7%1
1490
11th to 20thDay
54%5%14%18%9%
1594
21st to endDay
55%6%11%17%9%1
1480
March1st to 10thDay
54%5%14%16%9%2
1800
11th to 20thDay
52%5%13%22%8%
1867
21st to endDay
60%5%13%17%5%1
2359
April1st to 10thDay
58%5%12%17%7%1
2160
11th to 20thDay
52%6%11%17%12%2
2144
21st to endDay
49%5%10%22%12%2
2421
May1st to 10thDay
45%413%26%11%1
2520
11th to 20thDay
48%5%12%25%10%1
2480
21st to endDay
53%411%23%8%1
2724
June1st to 10thDay
51%49%20%12%4
2628
11th to 20thDay
51%411%23%11%1
2700
21st to endDay
35%412%28%19%2
2763
July1st to 10thDay
27%410%27%24%9%
2451
11th to 20thDay
23%37%24%29%13%
2445
21st to endDay
17%2427%36%13%
2589
August1st to 10thDay
23%38%29%27%11%
2490
11th to 20thDay
21%39%31%29%7%
2455
21st to endDay
28%410%34%21%3
2376
September1st to 10thDay
24%312%34%22%5%
2160
11th to 20thDay
35%410%28%19%4
2129
21st to endDay
35%315%28%16%2
1980
October1st to 10thDay
38%5%14%30%13%
1805
11th to 20thDay
41%5%17%25%12%
1747
21st to endDay
50%413%25%8%
1782
November1st to 10thDay
54%6%14%17%8%
1632
11th to 20thDay
56%5%14%18%6%1
1520
21st to endDay
56%5%15%17%6%1
1466
December1st to 10thDay
52%6%16%18%7%
1330
11th to 20thDay
65%414%12%5%
1684
21st to endDay
66%311%15%5%
2664
January1st to 10thNight
67%411%12%5%1
2646
11th to 20thNight
59%414%16%5%1
2562
21st to endNight
58%414%17%7%1
2772
February1st to 10thNight
53%6%17%16%7%2
2468
11th to 20thNight
50%5%16%21%8%
2263
21st to endNight
51%5%15%18%10%1
1776
March1st to 10thNight
50%5%15%19%10%1
2160
11th to 20thNight
50%5%11%25%9%
2091
21st to endNight
52%5%16%19%7%
1996
April1st to 10thNight
47%414%24%9%2
1800
11th to 20thNight
46%412%22%14%2
1766
21st to endNight
43%5%11%28%12%1
1535
May1st to 10thNight
40%411%30%14%1
1440
11th to 20thNight
39%316%28%12%1
1416
21st to endNight
45%5%12%27%10%1
1552
June1st to 10thNight
41%5%10%27%14%3
1328
11th to 20thNight
41%413%29%13%
1260
21st to endNight
30%415%28%20%3
1156
July1st to 10thNight
23%38%33%25%9%
1400
11th to 20thNight
18%311%28%28%13%
1392
21st to endNight
13%25%29%36%16%
1488
August1st to 10thNight
19%49%27%31%11%
1424
11th to 20thNight
15%210%34%33%5%
1438
21st to endNight
21%310%36%26%4
1980
September1st to 10thNight
22%311%33%25%5%
1800
11th to 20thNight
30%410%27%24%5%
1831
21st to endNight
33%414%31%14%4
1980
October1st to 10thNight
38%414%28%16%1
2152
11th to 20thNight
41%415%26%13%1
2211
21st to endNight
46%5%11%28%10%1
2574
November1st to 10thNight
52%6%16%16%8%2
2443
11th to 20thNight
55%6%15%16%6%2
2660
21st to endNight
59%415%15%6%1
2692
December1st to 10thNight
55%414%21%5%
2850
11th to 20thNight
69%5%12%9%5%
3507
21st to endNight
64%312%14%7%
5019

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 10thDay
26%15%18%25%13%3
180
11th to 20thDay
29%7%18%30%13%3
165
21st to endDay
24%8%26%27%13%2
176
February1st to 10thDay
15%16%36%26%6%1
210
11th to 20thDay
23%17%29%21%9%1
340
21st to endDay
14%14%32%27%10%1
346
March1st to 10thDay
22%20%34%14%8%2
420
11th to 20thDay
21%18%24%22%14%
420
21st to endDay
23%20%28%18%11%2
462
April1st to 10thDay
26%17%31%17%8%2
420
11th to 20thDay
22%22%25%18%8%4
412
21st to endDay
19%20%26%23%10%3
420
May1st to 10thDay
16%19%28%24%10%2
423
11th to 20thDay
22%10%24%29%10%4
448
21st to endDay
17%11%25%27%15%5%
485
June1st to 10thDay
17%14%26%28%12%3
558
11th to 20thDay
16%12%30%26%14%3
630
21st to endDay
8%11%27%30%18%5%
693
July1st to 10thDay
9%10%30%37%12%2
446
11th to 20thDay
6%16%35%28%12%4
444
21st to endDay
310%31%32%17%6%
487
August1st to 10thDay
6%8%26%37%17%6%
447
11th to 20thDay
6%8%27%31%20%8%
437
21st to endDay
9%13%28%30%13%7%
495
September1st to 10thDay
8%15%30%25%17%5%
450
11th to 20thDay
15%11%24%30%16%4
450
21st to endDay
17%14%30%24%12%4
450
October1st to 10thDay
16%16%26%26%14%2
450
11th to 20thDay
18%12%28%24%14%3
397
21st to endDay
23%14%28%24%10%1
297
November1st to 10thDay
20%14%25%29%12%
250
11th to 20thDay
23%17%28%19%14%
180
21st to endDay
19%16%26%22%12%5%
180
December1st to 10thDay
21%10%16%30%16%7%
180
11th to 20thDay
21%10%34%22%11%3
180
21st to endDay
21%12%18%36%11%3
198
January1st to 10thNight
27%9%23%29%11%2
760
11th to 20thNight
21%7%20%35%14%2
732
21st to endNight
18%6%21%38%15%2
792
February1st to 10thNight
20%10%23%32%12%3
720
11th to 20thNight
16%8%24%32%17%3
704
21st to endNight
15%8%24%32%17%3
592
March1st to 10thNight
18%8%23%30%18%3
720
11th to 20thNight
15%12%23%30%18%1
720
21st to endNight
16%12%22%32%15%2
792
April1st to 10thNight
15%8%21%32%20%4
720
11th to 20thNight
11%11%25%31%18%3
698
21st to endNight
13%12%22%34%17%2
455
May1st to 10thNight
10%8%23%37%19%3
360
11th to 20thNight
12%5%18%29%31%5%
354
21st to endNight
13%5%15%31%29%7%
389
June1st to 10thNight
13%6%19%37%21%3
360
11th to 20thNight
13%7%18%36%24%3
360
21st to endNight
9%5%16%36%30%4
360
July1st to 10thNight
45%14%40%34%4
350
11th to 20thNight
35%23%39%27%3
348
21st to endNight
15%12%43%36%4
394
August1st to 10thNight
4313%34%37%9%
358
11th to 20thNight
2311%35%42%7%
370
21st to endNight
6%6%17%38%29%4
792
September1st to 10thNight
6%6%15%39%26%8%
720
11th to 20thNight
11%5%12%31%31%10%
720
21st to endNight
11%6%15%42%21%5%
720
October1st to 10thNight
17%7%14%30%29%3
720
11th to 20thNight
16%7%20%32%23%3
720
21st to endNight
22%8%20%33%15%2
792
November1st to 10thNight
26%8%22%34%9%1
740
11th to 20thNight
24%12%21%28%13%2
760
21st to endNight
26%7%19%32%15%2
792
December1st to 10thNight
21%7%20%35%15%2
950
11th to 20thNight
26%7%21%34%11%1
950
21st to endNight
26%8%23%33%9%1
928
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