Telescope Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Telescope Park clear sky chart from 2005-11-05 to 2017-12-02.

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
32%
15140
17%
47856
8%
15109
42%
15109
20%
31878

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
19%
720
19%
2506
6%
716
35%
716
16%
1604
January16th to endNight
16%
768
17%
2685
4%
768
32%
768
15%
1741
February1st to 15thNight
17%
702
15%
2246
5%
701
30%
701
15%
1553
February16th to endNight
21%
631
19%
1893
6%
631
37%
631
20%
1284
March1st to 15thNight
21%
720
16%
2112
6%
720
33%
720
17%
1500
March16th to endNight
27%
768
20%
2096
8%
768
37%
768
24%
1391
April1st to 15thNight
23%
700
18%
1778
5%
700
32%
700
23%
1269
April16th to endNight
32%
540
16%
1620
6%
540
39%
540
21%
1126
May1st to 15thNight
32%
540
14%
1620
9%
540
38%
540
19%
1146
May16th to endNight
33%
443
11%
1565
11%
442
38%
442
14%
1147
June1st to 15thNight
39%
360
9%
1338
8%
360
45%
360
12%
980
June16th to endNight
50%
360
9%
1352
13%
360
52%
360
19%
895
July1st to 15thNight
55%
340
10%
1360
16%
340
57%
340
19%
864
July16th to endNight
53%
376
12%
1418
16%
354
56%
354
19%
900
August1st to 15thNight
54%
537
13%
1607
10%
534
55%
534
23%
1077
August16th to endNight
59%
618
21%
1764
13%
618
62%
618
32%
1102
September1st to 15thNight
50%
720
18%
1902
10%
720
54%
720
33%
1229
September16th to endNight
49%
717
26%
1980
17%
717
57%
717
35%
1190
October1st to 15thNight
38%
720
20%
2046
11%
720
47%
720
25%
1343
October16th to endNight
26%
768
18%
2466
8%
768
38%
768
21%
1615
November1st to 15thNight
31%
760
19%
2472
11%
760
42%
760
21%
1601
November16th to endNight
27%
792
20%
2587
8%
792
42%
792
19%
1669
December1st to 15thNight
18%
759
16%
2680
4%
759
33%
759
16%
1803
December16th to endNight
16%
781
17%
2763
4%
781
33%
781
15%
1849

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
18%6%2442445%6%39%
48576
Night
18%7%24424446%38%
48027
TransparencyDay
44%5%12%22%13%1
48266
Night
46%411%22%13%1
47856
SeeingDay
23%9%30%24%10%2
6357
Night
22%9%29%25%10%1
15142

By Month

Percentage Cloud Cover NE (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%5%336%3345%6%40%
1432
16th to endDay
17%7%35%424345%42%
1537
February1st to 15thDay
17%9%26%5%25%45%6%35%
1615
16th to endDay
14%11%35%435%45%6%36%
1580
March1st to 15thDay
20%8%34414336%36%
1838
16th to endDay
17%7%345%34335%42%
2127
April1st to 15thDay
20%7%24324446%39%
2169
16th to endDay
20%5%2442445%6%39%
2340
May1st to 15thDay
26%6%26%6%2345%6%31%
2332
16th to endDay
22%6%2442445%7%33%
2560
June1st to 15thDay
26%6%3442335%7%30%
2616
16th to endDay
20%5%25%5%24448%35%
2600
July1st to 15thDay
14%5%24425%5%7%9%37%
2520
16th to endDay
14%425%5%35%6%6%8%37%
2642
August1st to 15thDay
13%5%25%425%6%7%8%39%
2340
16th to endDay
11%4134345%6%7%47%
2435
September1st to 15thDay
13%414423446%49%
2058
16th to endDay
14%5%13313236%52%
1980
October1st to 15thDay
19%5%24424325%43%
1912
16th to endDay
20%6%24423445%42%
1758
November1st to 15thDay
19%6%24412446%42%
1716
16th to endDay
21%5%24312235%44%
1700
December1st to 15thDay
22%7%34423345%38%
1314
16th to endDay
23%9%35%323435%34%
1455
January1st to 15thNight
15%8%2432445%7%39%
2506
16th to endNight
15%11%34424445%39%
2685
February1st to 15thNight
14%8%35%7%45%445%35%
2245
16th to endNight
15%10%35%323446%38%
1893
March1st to 15thNight
20%10%35%5%24345%35%
2099
16th to endNight
17%6%24424346%42%
2096
April1st to 15thNight
20%7%25%425%345%36%
1778
16th to endNight
22%6%35%425%446%34%
1620
May1st to 15thNight
22%8%25%5%246%5%6%31%
1620
16th to endNight
23%9%35%5%24446%28%
1563
June1st to 15thNight
26%8%24436%5%45%28%
1338
16th to endNight
21%6%25%425%448%34%
1352
July1st to 15thNight
17%5%345%35%46%9%34%
1440
16th to endNight
15%6%25%5%35%47%9%33%
1514
August1st to 15thNight
14%7%25%435%5%5%7%38%
1618
16th to endNight
13%4144245%48%46%
1764
September1st to 15thNight
14%5%23324346%48%
1902
16th to endNight
12%413323346%53%
1980
October1st to 15thNight
18%6%2342445%6%42%
2046
16th to endNight
21%6%24424345%40%
2466
November1st to 15thNight
18%6%25%424445%42%
2472
16th to endNight
17%6%24424446%42%
2587
December1st to 15thNight
23%8%24423335%38%
2680
16th to endNight
22%9%24323346%37%
2763

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
43%5%11%23%13%1
1433
16th to endDay
45%412%24%12%1
1537
February1st to 15thDay
49%413%19%11%
1618
16th to endDay
47%411%19%12%2
1580
March1st to 15thDay
49%312%18%12%2
1848
16th to endDay
43%39%19%19%4
2127
April1st to 15thDay
45%39%21%16%3
2169
16th to endDay
45%5%9%21%14%3
2340
May1st to 15thDay
53%38%17%13%2
2332
16th to endDay
48%6%12%18%11%1
2564
June1st to 15thDay
52%5%12%20%8%1
2616
16th to endDay
47%7%10%21%11%1
2600
July1st to 15thDay
39%7%14%26%11%
2371
16th to endDay
40%8%16%22%10%1
2476
August1st to 15thDay
39%7%17%25%9%
2327
16th to endDay
32%5%16%25%17%1
2435
September1st to 15thDay
34%6%11%27%19%1
2058
16th to endDay
35%6%7%27%22%1
1980
October1st to 15thDay
43%310%25%14%2
1912
16th to endDay
43%412%25%13%
1758
November1st to 15thDay
43%413%23%14%1
1716
16th to endDay
43%314%20%16%1
1700
December1st to 15thDay
49%412%21%12%
1314
16th to endDay
52%5%9%18%13%1
1455
January1st to 15thNight
44%412%24%12%1
2506
16th to endNight
47%310%21%14%2
2685
February1st to 15thNight
50%411%20%12%1
2246
16th to endNight
47%410%22%13%2
1893
March1st to 15thNight
53%28%19%13%2
2112
16th to endNight
42%410%18%19%5%
2096
April1st to 15thNight
49%37%18%18%3
1778
16th to endNight
49%49%19%13%3
1620
May1st to 15thNight
50%5%9%16%14%2
1620
16th to endNight
56%5%8%16%10%1
1565
June1st to 15thNight
57%5%10%16%7%1
1338
16th to endNight
48%413%20%12%
1352
July1st to 15thNight
44%7%13%23%11%
1360
16th to endNight
44%6%15%22%9%
1418
August1st to 15thNight
43%7%13%23%10%1
1607
16th to endNight
34%7%12%28%16%
1764
September1st to 15thNight
36%5%10%28%16%1
1902
16th to endNight
33%48%31%20%1
1980
October1st to 15thNight
43%49%25%15%2
2046
16th to endNight
45%311%24%12%1
2466
November1st to 15thNight
44%5%12%21%14%1
2472
16th to endNight
43%5%12%21%15%1
2587
December1st to 15thNight
50%311%23%12%
2680
16th to endNight
49%312%20%12%
2763

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
20%26%33%15%5%
60
16th to endDay
20%21%30%27%
65
February1st to 15thDay
24%16%35%20%2
243
16th to endDay
19%13%38%22%6%
239
March1st to 15thDay
26%15%38%15%3
270
16th to endDay
23%17%34%15%6%2
288
April1st to 15thDay
27%11%34%17%7%1
270
16th to endDay
25%8%39%18%5%2
270
May1st to 15thDay
35%7%29%17%9%1
288
16th to endDay
25%8%33%23%6%1
331
June1st to 15thDay
26%427%27%12%
411
16th to endDay
24%5%25%31%10%2
395
July1st to 15thDay
18%328%31%14%2
305
16th to endDay
17%426%31%16%3
326
August1st to 15thDay
15%328%31%16%3
313
16th to endDay
13%423%31%19%6%
332
September1st to 15thDay
18%424%32%14%5%
315
16th to endDay
18%7%29%19%15%9%
314
October1st to 15thDay
23%10%22%26%13%5%
298
16th to endDay
25%11%31%22%7%
288
November1st to 15thDay
25%10%29%22%9%3
280
16th to endDay
25%15%28%19%9%1
285
December1st to 15thDay
28%14%35%19%2
107
16th to endDay
37%20%28%12%1
64
January1st to 15thNight
21%18%36%19%4
720
16th to endNight
23%20%34%17%3
768
February1st to 15thNight
21%17%36%20%3
704
16th to endNight
21%14%38%19%6%
631
March1st to 15thNight
26%14%33%21%4
720
16th to endNight
21%12%32%23%8%1
768
April1st to 15thNight
25%9%36%21%6%
700
16th to endNight
27%5%28%27%9%1
540
May1st to 15thNight
27%328%27%11%1
540
16th to endNight
31%223%30%11%1
443
June1st to 15thNight
28%317%34%14%1
360
16th to endNight
24%215%41%13%1
360
July1st to 15thNight
20%213%40%22%1
340
16th to endNight
18%115%39%23%
376
August1st to 15thNight
16%316%40%21%1
537
16th to endNight
14%117%37%25%3
618
September1st to 15thNight
17%223%32%22%2
720
16th to endNight
15%423%28%22%4
717
October1st to 15thNight
22%6%25%28%14%2
720
16th to endNight
24%11%33%22%7%
768
November1st to 15thNight
22%9%30%26%9%1
760
16th to endNight
21%15%31%22%8%
792
December1st to 15thNight
28%11%36%18%5%
759
16th to endNight
29%13%36%16%3
781
Page generated at 2017-12-03 11:16:36. Version ac04

Copyright 2017 A. Danko


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