FoxStar II Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the FoxStar II Observatory clear sky chart from 2005-11-05 to 2018-01-20.

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
35%
16377
23%
48543
13%
16330
45%
16330
29%
29324

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
18%
975
21%
2522
5%
970
30%
970
25%
1636
January16th to endNight
20%
985
25%
2561
7%
985
33%
985
26%
1665
February1st to 15thNight
17%
880
18%
2288
4%
876
25%
876
22%
1529
February16th to endNight
17%
655
23%
1917
5%
655
30%
655
23%
1200
March1st to 15thNight
21%
540
21%
1980
10%
540
35%
540
19%
1243
March16th to endNight
22%
576
14%
2112
8%
576
32%
576
16%
1409
April1st to 15thNight
26%
539
22%
1811
12%
539
42%
539
27%
1012
April16th to endNight
27%
540
20%
1800
11%
540
42%
540
23%
1142
May1st to 15thNight
35%
540
20%
1632
13%
540
45%
540
26%
1045
May16th to endNight
39%
563
20%
1586
13%
561
47%
561
28%
1029
June1st to 15thNight
57%
540
20%
1440
13%
540
63%
540
44%
820
June16th to endNight
52%
540
27%
1440
15%
540
60%
540
51%
781
July1st to 15thNight
59%
510
18%
1473
13%
510
63%
510
39%
838
July16th to endNight
71%
564
26%
1594
26%
531
76%
531
47%
830
August1st to 15thNight
73%
539
26%
1610
29%
536
75%
536
42%
858
August16th to endNight
69%
573
28%
1881
31%
573
73%
573
42%
964
September1st to 15thNight
60%
540
27%
1800
27%
540
65%
540
35%
985
September16th to endNight
57%
576
31%
1992
25%
576
66%
576
37%
1037
October1st to 15thNight
43%
720
28%
2160
17%
720
52%
720
37%
1198
October16th to endNight
32%
768
31%
2304
14%
768
47%
768
34%
1293
November1st to 15thNight
31%
760
30%
2319
14%
760
46%
760
31%
1325
November16th to endNight
23%
939
25%
2694
9%
939
38%
939
26%
1683
December1st to 15thNight
22%
975
19%
2730
6%
975
34%
975
23%
1793
December16th to endNight
18%
1040
20%
2897
5%
1040
29%
1040
19%
2009

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%35%43445%7%42%
48974
Night
12%6%24423347%48%
48738
TransparencyDay
40%412%25%15%2
48674
Night
36%311%26%18%3
48543
SeeingDay
16%9%27%27%14%3
6233
Night
16%12%31%26%12%1
16377

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
13%6%35%424336%46%
1746
16th to endDay
12%8%35%433346%43%
1767
February1st to 15thDay
12%9%37%6%34326%38%
1575
16th to endDay
13%10%45%4335%45%38%
1566
March1st to 15thDay
16%9%46%424435%37%
1980
16th to endDay
21%10%46%423445%32%
2110
April1st to 15thDay
16%8%25%5%24445%42%
2136
16th to endDay
20%7%36%5%34346%33%
2160
May1st to 15thDay
19%5%35%4345%5%6%37%
2317
16th to endDay
14%6%35%6%35%5%47%37%
2526
June1st to 15thDay
8%425%435%5%5%9%43%
2520
16th to endDay
5%2135%35%5%6%10%49%
2520
July1st to 15thDay
10%5%245%36%6%5%10%40%
2394
16th to endDay
6%425%5%36%6%8%9%40%
2466
August1st to 15thDay
7%4245%35%6%6%10%42%
2340
16th to endDay
7%5%245%35%45%6%47%
2321
September1st to 15thDay
12%5%245%25%45%7%44%
2160
16th to endDay
9%5%244345%5%7%47%
1953
October1st to 15thDay
14%5%24323335%51%
1800
16th to endDay
13%5%24322335%53%
1920
November1st to 15thDay
13%6%23322346%51%
1868
16th to endDay
17%5%24423337%45%
1592
December1st to 15thDay
15%7%445%235%47%40%
1560
16th to endDay
15%11%47%324336%37%
1677
January1st to 15thNight
13%6%25%5%23445%45%
2522
16th to endNight
10%7%35%5%33445%47%
2561
February1st to 15thNight
12%10%46%31335%7%40%
2278
16th to endNight
12%7%45%423337%44%
1917
March1st to 15thNight
16%7%35%423335%42%
1980
16th to endNight
20%6%345%24345%36%
2112
April1st to 15thNight
10%6%24323246%51%
1811
16th to endNight
16%6%34434437%42%
1800
May1st to 15thNight
15%5%25%425%447%43%
1631
16th to endNight
12%5%36%424438%44%
1584
June1st to 15thNight
431343447%9%51%
1440
16th to endNight
32123235%7%10%57%
1440
July1st to 15thNight
7%31342447%10%48%
1563
16th to endNight
5%21242446%10%55%
1702
August1st to 15thNight
432442445%8%55%
1620
16th to endNight
431442446%7%56%
1881
September1st to 15thNight
12%31331345%8%51%
1800
16th to endNight
7%314413448%55%
1992
October1st to 15thNight
13%412223346%55%
2160
16th to endNight
12%413322336%56%
2304
November1st to 15thNight
12%6%23322345%53%
2319
16th to endNight
14%8%24322335%49%
2694
December1st to 15thNight
17%7%24423346%42%
2730
16th to endNight
16%10%46%423345%38%
2897

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
40%210%26%18%
1747
16th to endDay
41%211%28%12%2
1767
February1st to 15thDay
47%313%23%10%
1576
16th to endDay
46%310%23%13%2
1566
March1st to 15thDay
48%39%21%13%2
1980
16th to endDay
53%412%18%10%
2112
April1st to 15thDay
44%311%23%15%1
2136
16th to endDay
51%311%19%11%1
2160
May1st to 15thDay
46%5%12%22%12%
2317
16th to endDay
46%5%13%21%12%1
2530
June1st to 15thDay
36%5%15%25%16%1
2520
16th to endDay
28%5%17%30%15%2
2520
July1st to 15thDay
37%6%14%26%12%2
2255
16th to endDay
33%7%14%29%13%1
2311
August1st to 15thDay
34%5%17%25%16%
2326
16th to endDay
34%5%10%25%17%6%
2321
September1st to 15thDay
37%410%24%17%4
2160
16th to endDay
34%5%9%30%17%3
1953
October1st to 15thDay
36%28%25%21%5%
1800
16th to endDay
34%27%29%20%5%
1920
November1st to 15thDay
34%310%26%19%5%
1868
16th to endDay
39%38%25%22%1
1592
December1st to 15thDay
43%312%25%14%
1560
16th to endDay
49%312%21%10%2
1677
January1st to 15thNight
40%312%26%16%
2522
16th to endNight
39%312%27%15%1
2561
February1st to 15thNight
43%311%26%13%1
2288
16th to endNight
40%212%25%17%2
1917
March1st to 15thNight
45%38%23%16%3
1980
16th to endNight
49%411%21%12%
2112
April1st to 15thNight
33%312%26%19%3
1811
16th to endNight
42%410%25%14%1
1800
May1st to 15thNight
40%5%12%23%18%
1632
16th to endNight
39%6%14%24%11%2
1586
June1st to 15thNight
25%5%18%28%19%2
1440
16th to endNight
20%5%15%31%23%3
1440
July1st to 15thNight
28%5%15%29%16%4
1473
16th to endNight
22%5%13%38%19%
1594
August1st to 15thNight
25%5%14%35%18%1
1610
16th to endNight
25%413%26%23%6%
1881
September1st to 15thNight
30%410%27%20%6%
1800
16th to endNight
28%310%31%22%3
1992
October1st to 15thNight
30%210%25%23%7%
2160
16th to endNight
30%37%29%22%6%
2304
November1st to 15thNight
33%29%26%20%7%
2319
16th to endNight
38%27%27%20%2
2694
December1st to 15thNight
43%312%23%15%
2730
16th to endNight
49%312%18%12%3
2897

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
30%21%35%11%1
135
16th to endDay
23%27%31%14%2
109
February1st to 15thDay
24%23%40%10%2
90
16th to endDay
23%25%35%12%2
81
March1st to 15thDay
38%18%33%8%
90
16th to endDay
29%20%32%15%2
96
April1st to 15thDay
25%13%34%19%6%
255
16th to endDay
28%12%34%15%8%
270
May1st to 15thDay
22%14%32%22%7%1
454
16th to endDay
19%8%37%24%8%1
517
June1st to 15thDay
9%7%27%33%17%4
495
16th to endDay
6%435%34%15%3
495
July1st to 15thDay
14%220%39%18%4
475
16th to endDay
7%114%37%33%5%
515
August1st to 15thDay
10%116%36%29%5%
493
16th to endDay
11%315%37%26%6%
361
September1st to 15thDay
13%416%34%24%6%
315
16th to endDay
11%429%33%15%5%
159
October1st to 15thDay
14%12%36%26%5%3
135
16th to endDay
18%13%39%22%4
144
November1st to 15thDay
23%9%37%19%7%2
135
16th to endDay
33%12%32%17%3
135
December1st to 15thDay
20%28%31%11%5%2
135
16th to endDay
28%28%31%9%1
144
January1st to 15thNight
21%20%36%17%4
975
16th to endNight
16%23%36%20%3
985
February1st to 15thNight
20%22%36%17%2
880
16th to endNight
21%19%38%16%3
655
March1st to 15thNight
22%16%36%21%3
540
16th to endNight
24%13%35%20%6%
576
April1st to 15thNight
17%16%38%22%5%
539
16th to endNight
20%10%38%23%6%
540
May1st to 15thNight
16%8%34%31%9%
540
16th to endNight
14%7%30%32%13%1
563
June1st to 15thNight
6%325%42%21%1
540
16th to endNight
5%233%37%20%1
540
July1st to 15thNight
10%21%39%23%3
510
16th to endNight
6%113%40%35%3
564
August1st to 15thNight
7%11%43%33%3
539
16th to endNight
5%116%39%32%4
573
September1st to 15thNight
13%216%34%30%3
540
16th to endNight
11%320%34%24%4
576
October1st to 15thNight
15%7%30%24%18%3
720
16th to endNight
16%12%37%23%9%
768
November1st to 15thNight
17%14%33%23%10%
760
16th to endNight
22%17%34%18%6%
939
December1st to 15thNight
23%18%32%19%5%
975
16th to endNight
24%18%35%19%2
1040
Page generated at 2018-01-21 11:19:30. Version ac04

Copyright 2018 A. Danko


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