FoxStar Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the FoxStar Observatory clear sky chart from 2005-11-05 to 2018-10-27.

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
42%
17363
23%
51357
14%
17316
51%
17316
32%
30543

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
31%
975
22%
2522
9%
970
41%
970
33%
1569
January16th to endNight
27%
1040
25%
2704
9%
1040
38%
1040
32%
1713
February1st to 15thNight
23%
954
16%
2483
5%
950
29%
950
24%
1736
February16th to endNight
26%
728
23%
2094
7%
728
38%
728
28%
1315
March1st to 15thNight
33%
585
23%
2145
14%
585
45%
585
25%
1242
March16th to endNight
26%
624
16%
2288
10%
624
35%
624
18%
1519
April1st to 15thNight
33%
584
22%
1989
14%
584
46%
584
28%
1144
April16th to endNight
35%
579
21%
1860
15%
579
47%
579
25%
1176
May1st to 15thNight
41%
584
20%
1755
15%
584
49%
584
29%
1095
May16th to endNight
49%
611
20%
1739
14%
609
55%
609
35%
1047
June1st to 15thNight
62%
585
23%
1560
14%
585
66%
585
47%
867
June16th to endNight
62%
585
25%
1560
15%
585
67%
585
54%
816
July1st to 15thNight
71%
555
20%
1615
16%
555
73%
555
43%
884
July16th to endNight
75%
612
25%
1738
24%
579
79%
579
47%
892
August1st to 15thNight
78%
575
25%
1717
30%
572
79%
572
48%
881
August16th to endNight
70%
621
27%
1984
31%
621
73%
621
40%
1049
September1st to 15thNight
64%
585
28%
1973
31%
585
68%
585
34%
1080
September16th to endNight
63%
593
29%
2156
26%
593
71%
593
36%
1087
October1st to 15thNight
46%
780
27%
2340
19%
780
51%
780
33%
1377
October16th to endNight
39%
816
30%
2448
16%
816
50%
816
37%
1349
November1st to 15thNight
38%
802
28%
2338
14%
802
50%
802
36%
1316
November16th to endNight
31%
975
26%
2730
10%
975
44%
975
32%
1646
December1st to 15thNight
29%
975
20%
2730
8%
975
39%
975
27%
1754
December16th to endNight
25%
1040
21%
2889
7%
1040
36%
1040
23%
1989

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
12%6%25%42445%7%44%
52184
Night
11%5%24423347%49%
51552
TransparencyDay
39%313%26%14%2
51884
Night
35%312%27%17%3
51357
SeeingDay
13%6%25%29%19%5%
7376
Night
14%7%30%32%13%1
17365

By Month

Percentage Cloud Cover SE (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
12%6%25%5%34345%45%
1746
16th to endDay
13%8%46%434345%42%
1872
February1st to 15thDay
13%9%5%6%5%23346%38%
1710
16th to endDay
13%9%45%5%23346%40%
1675
March1st to 15thDay
11%9%47%5%2445%6%37%
2145
16th to endDay
22%11%45%424335%32%
2286
April1st to 15thDay
16%8%25%5%34346%40%
2289
16th to endDay
20%6%36%5%25%446%33%
2373
May1st to 15thDay
17%6%35%6%24446%37%
2526
16th to endDay
13%6%25%5%345%5%7%39%
2726
June1st to 15thDay
8%4244245%6%9%45%
2730
16th to endDay
6%214435%5%7%10%49%
2730
July1st to 15thDay
7%3244345%7%9%47%
2581
16th to endDay
6%324445%5%7%8%48%
2674
August1st to 15thDay
7%3145%3446%10%47%
2486
16th to endDay
8%4245%2445%9%47%
2568
September1st to 15thDay
12%41432345%7%50%
2314
16th to endDay
8%41442445%7%51%
2119
October1st to 15thDay
16%5%24423246%47%
1950
16th to endDay
12%5%14323246%52%
2033
November1st to 15thDay
11%6%13323346%52%
1847
16th to endDay
15%6%3332333449%
1560
December1st to 15thDay
13%8%36%6%23346%40%
1560
16th to endDay
15%8%46%6%24346%37%
1684
January1st to 15thNight
9%6%25%424446%49%
2522
16th to endNight
9%7%35%424346%47%
2704
February1st to 15thNight
12%9%36%5%34346%38%
2473
16th to endNight
13%7%26%423336%46%
2094
March1st to 15thNight
12%7%24424336%47%
2145
16th to endNight
20%7%25%424447%35%
2288
April1st to 15thNight
12%6%24323347%49%
1989
16th to endNight
17%6%35%423346%43%
1860
May1st to 15thNight
12%5%25%435%5%46%44%
1754
16th to endNight
11%31432445%7%49%
1737
June1st to 15thNight
5%2133245%6%11%52%
1560
16th to endNight
41231346%11%57%
1560
July1st to 15thNight
7%2133235%6%9%53%
1705
16th to endNight
42144245%6%10%55%
1846
August1st to 15thNight
421332445%10%56%
1727
16th to endNight
6%314424446%57%
1984
September1st to 15thNight
11%31432445%7%51%
1973
16th to endNight
7%313434447%55%
2156
October1st to 15thNight
15%42332333452%
2340
16th to endNight
11%42432333457%
2448
November1st to 15thNight
10%423323346%54%
2338
16th to endNight
14%5%24222345%51%
2730
December1st to 15thNight
14%7%34423346%44%
2730
16th to endNight
15%10%37%423345%38%
2889

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
41%311%25%16%1
1747
16th to endDay
44%215%24%11%1
1872
February1st to 15thDay
47%316%23%9%
1711
16th to endDay
45%212%22%14%1
1675
March1st to 15thDay
46%311%25%10%2
2145
16th to endDay
55%312%18%8%1
2288
April1st to 15thDay
44%312%24%13%
2289
16th to endDay
51%311%22%10%
2373
May1st to 15thDay
47%412%23%10%
2526
16th to endDay
41%5%15%23%11%1
2730
June1st to 15thDay
33%314%31%14%1
2730
16th to endDay
27%418%31%15%2
2730
July1st to 15thDay
31%416%29%13%3
2442
16th to endDay
29%5%14%34%15%1
2519
August1st to 15thDay
30%5%16%30%16%1
2472
16th to endDay
32%414%26%16%5%
2568
September1st to 15thDay
33%412%24%20%5%
2314
16th to endDay
32%410%31%19%2
2119
October1st to 15thDay
38%29%26%18%4
1950
16th to endDay
33%210%27%21%4
2033
November1st to 15thDay
33%213%25%20%4
1847
16th to endDay
39%19%29%18%
1560
December1st to 15thDay
45%314%25%11%
1560
16th to endDay
47%314%20%10%2
1684
January1st to 15thNight
35%315%27%17%1
2522
16th to endNight
37%214%27%15%1
2704
February1st to 15thNight
47%312%22%11%2
2483
16th to endNight
40%211%22%19%2
2094
March1st to 15thNight
39%211%26%16%4
2145
16th to endNight
49%312%23%9%1
2288
April1st to 15thNight
36%29%28%19%2
1989
16th to endNight
42%29%26%16%1
1860
May1st to 15thNight
39%415%24%15%
1755
16th to endNight
33%5%16%28%14%1
1739
June1st to 15thNight
24%415%35%17%2
1560
16th to endNight
18%415%35%22%2
1560
July1st to 15thNight
25%5%13%34%17%4
1615
16th to endNight
21%414%37%18%1
1738
August1st to 15thNight
22%317%34%19%2
1717
16th to endNight
27%49%27%24%6%
1984
September1st to 15thNight
31%410%23%23%6%
1973
16th to endNight
28%39%31%22%4
2156
October1st to 15thNight
36%28%26%20%6%
2340
16th to endNight
30%28%28%24%5%
2448
November1st to 15thNight
31%212%24%22%7%
2338
16th to endNight
36%28%30%19%2
2730
December1st to 15thNight
41%314%26%13%
2730
16th to endNight
48%211%21%12%3
2889

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
25%13%32%22%5%
135
16th to endDay
16%8%50%19%4
144
February1st to 15thDay
18%18%40%18%4
135
16th to endDay
21%21%34%13%7%1
120
March1st to 15thDay
22%12%48%13%2
135
16th to endDay
31%13%31%21%2
144
April1st to 15thDay
19%13%34%21%9%
288
16th to endDay
23%9%31%21%11%2
385
May1st to 15thDay
16%8%35%25%11%1
543
16th to endDay
17%427%28%16%5%
597
June1st to 15thDay
8%5%22%33%24%6%
570
16th to endDay
7%228%37%20%3
570
July1st to 15thDay
10%115%31%27%12%
550
16th to endDay
6%110%35%37%7%
595
August1st to 15thDay
6%111%37%35%8%
549
16th to endDay
10%215%34%28%9%
480
September1st to 15thDay
10%211%34%31%8%
349
16th to endDay
10%322%33%18%12%
180
October1st to 15thDay
19%6%32%26%10%4
180
16th to endDay
11%7%37%35%7%
178
November1st to 15thDay
14%6%28%30%11%8%
135
16th to endDay
27%13%29%19%9%
135
December1st to 15thDay
13%15%40%20%5%3
135
16th to endDay
19%22%38%16%2
144
January1st to 15thNight
13%12%39%26%7%
975
16th to endNight
12%12%43%27%4
1040
February1st to 15thNight
16%10%43%26%3
955
16th to endNight
19%10%40%23%5%
728
March1st to 15thNight
16%11%34%29%7%
585
16th to endNight
24%8%35%26%4
624
April1st to 15thNight
15%10%37%28%8%
584
16th to endNight
22%7%30%30%8%
579
May1st to 15thNight
14%6%32%33%11%
585
16th to endNight
12%427%35%17%2
611
June1st to 15thNight
6%220%45%21%2
585
16th to endNight
4126%46%18%2
585
July1st to 15thNight
8%111%41%32%4
555
16th to endNight
5%110%43%37%2
612
August1st to 15thNight
5%6%45%39%2
575
16th to endNight
7%112%39%34%4
621
September1st to 15thNight
11%115%39%25%5%
585
16th to endNight
8%218%38%25%5%
593
October1st to 15thNight
17%427%33%15%2
780
16th to endNight
14%7%35%31%11%
816
November1st to 15thNight
12%10%34%30%12%
802
16th to endNight
17%10%38%26%7%
975
December1st to 15thNight
19%11%35%27%5%
975
16th to endNight
19%10%37%26%5%
1040
Page generated at 2018-10-28 07:41:06. Version ac04

Copyright 2018 A. Danko


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