Telegraph City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Telegraph City clear sky chart from 2005-11-05 to

2017-09-12
.

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
69%
15299
30%
46825
27%
15262
73%
15262
46%
23854

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
63%
716
19%
2461
21%
716
65%
716
30%
1407
January16th to endNight
62%
768
24%
2496
27%
768
63%
768
29%
1507
February1st to 15thNight
60%
697
25%
2239
26%
697
64%
697
31%
1317
February16th to endNight
58%
632
26%
1895
26%
632
62%
632
33%
1134
March1st to 15thNight
58%
720
19%
2073
19%
720
60%
720
31%
1311
March16th to endNight
57%
768
22%
2046
16%
768
61%
768
36%
1259
April1st to 15thNight
54%
719
22%
1799
12%
719
58%
719
38%
1124
April16th to endNight
62%
720
26%
1800
12%
720
67%
720
50%
1005
May1st to 15thNight
67%
617
31%
1697
21%
617
71%
617
63%
789
May16th to endNight
69%
375
31%
1496
32%
374
76%
374
52%
580
June1st to 15thNight
66%
360
30%
1440
31%
360
77%
360
59%
510
June16th to endNight
83%
360
39%
1440
48%
360
89%
360
76%
438
July1st to 15thNight
87%
340
36%
1360
45%
340
91%
340
76%
411
July16th to endNight
84%
505
39%
1534
36%
472
87%
472
69%
602
August1st to 15thNight
83%
604
39%
1677
28%
601
86%
601
81%
681
August16th to endNight
86%
764
45%
1910
27%
764
88%
764
83%
841
September1st to 15thNight
88%
706
43%
1765
30%
706
91%
706
84%
781
September16th to endNight
82%
656
47%
1770
39%
656
87%
656
77%
758
October1st to 15thNight
76%
660
32%
1980
33%
660
81%
660
56%
925
October16th to endNight
78%
704
38%
2112
40%
704
82%
704
55%
999
November1st to 15thNight
75%
700
31%
2251
34%
700
77%
700
48%
1094
November16th to endNight
67%
720
27%
2376
27%
720
71%
720
38%
1248
December1st to 15thNight
63%
720
21%
2520
22%
720
67%
720
28%
1493
December16th to endNight
53%
768
21%
2688
22%
768
58%
768
25%
1640

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
8%212212335%65%
47832
Night
9%312212235%63%
47014
TransparencyDay
22%38%19%24%22%
47515
Night
23%39%20%23%19%
46830
SeeingDay
8%5%19%33%25%7%
5866
Night
10%213%38%29%6%
15311

By Month

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
16%32342445%7%45%
1474
16th to endDay
18%5%34423436%42%
1728
February1st to 15thDay
18%5%1331345%5%46%
1619
16th to endDay
19%5%24424346%41%
1579
March1st to 15thDay
15%425%33446%8%41%
1884
16th to endDay
13%413424448%46%
2178
April1st to 15thDay
13%5%23324446%48%
2149
16th to endDay
9%312112335%64%
2160
May1st to 15thDay
422212245%72%
2250
16th to endDay
4212212346%66%
2615
June1st to 15thDay
3212212235%72%
2520
16th to endDay
11112386%
2520
July1st to 15thDay
1112386%
2520
16th to endDay
11121383%
2525
August1st to 15thDay
111111287%
2272
16th to endDay
11111386%
2292
September1st to 15thDay
11112386%
2114
16th to endDay
21111112480%
1857
October1st to 15thDay
412213245%70%
1650
16th to endDay
7%22312345%65%
1760
November1st to 15thDay
7%31342336%6%57%
1606
16th to endDay
12%324324347%49%
1584
December1st to 15thDay
16%5%35%6%23335%44%
1440
16th to endDay
20%5%2342435%7%39%
1536
January1st to 15thNight
15%42432235%8%48%
2461
16th to endNight
18%5%13413346%47%
2496
February1st to 15thNight
16%413423337%47%
2232
16th to endNight
20%41221335%6%48%
1895
March1st to 15thNight
16%5%24423236%47%
2073
16th to endNight
15%41322345%7%49%
2046
April1st to 15thNight
12%32332345%8%50%
1799
16th to endNight
7%312213336%63%
1800
May1st to 15thNight
4211211236%73%
1697
16th to endNight
4112212327%70%
1496
June1st to 15thNight
31111235%77%
1440
16th to endNight
111111287%
1440
July1st to 15thNight
11122286%
1440
16th to endNight
11111112282%
1641
August1st to 15thNight
111111385%
1686
16th to endNight
111112286%
1910
September1st to 15thNight
1111387%
1765
16th to endNight
11111112383%
1770
October1st to 15thNight
6%11121324469%
1980
16th to endNight
6%12212335%70%
2112
November1st to 15thNight
9%312212237%63%
2251
16th to endNight
10%322424346%56%
2376
December1st to 15thNight
16%424433346%48%
2520
16th to endNight
21%5%24322245%45%
2688

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
39%5%12%19%18%3
1474
16th to endDay
44%6%9%17%16%6%
1728
February1st to 15thDay
38%6%11%25%14%3
1619
16th to endDay
41%412%24%15%1
1579
March1st to 15thDay
36%6%13%22%18%3
1884
16th to endDay
35%6%16%21%17%3
2178
April1st to 15thDay
33%6%12%25%15%6%
2149
16th to endDay
21%312%26%26%7%
2160
May1st to 15thDay
14%28%27%34%12%
2250
16th to endDay
17%311%28%28%11%
2619
June1st to 15thDay
15%28%23%25%24%
2520
16th to endDay
6%213%32%44%
2520
July1st to 15thDay
4127%22%61%
2371
16th to endDay
8%127%21%57%
2369
August1st to 15thDay
6%18%27%54%
2256
16th to endDay
6%128%34%47%
2292
September1st to 15thDay
6%210%32%46%
2114
16th to endDay
10%1321%36%26%
1857
October1st to 15thDay
15%27%25%26%22%
1650
16th to endDay
20%38%24%27%14%
1760
November1st to 15thDay
25%313%30%22%4
1606
16th to endDay
34%5%11%24%21%2
1584
December1st to 15thDay
44%412%19%15%3
1440
16th to endDay
44%5%14%17%14%3
1536
January1st to 15thNight
34%413%21%19%6%
2461
16th to endNight
38%410%17%16%12%
2496
February1st to 15thNight
35%410%25%17%7%
2243
16th to endNight
35%412%27%18%2
1895
March1st to 15thNight
37%5%11%19%18%6%
2073
16th to endNight
32%5%12%22%18%7%
2046
April1st to 15thNight
31%5%15%25%17%5%
1799
16th to endNight
21%413%22%27%10%
1800
May1st to 15thNight
13%29%25%33%16%
1698
16th to endNight
15%311%32%26%11%
1496
June1st to 15thNight
11%210%23%27%24%
1440
16th to endNight
6%212%31%46%
1440
July1st to 15thNight
5%127%18%64%
1360
16th to endNight
9%235%21%57%
1534
August1st to 15thNight
7%211%25%52%
1677
16th to endNight
5%119%31%50%
1910
September1st to 15thNight
6%39%32%47%
1765
16th to endNight
8%1219%39%28%
1770
October1st to 15thNight
17%28%22%27%20%
1980
16th to endNight
17%37%23%29%19%
2112
November1st to 15thNight
22%211%26%26%10%
2251
16th to endNight
27%410%25%25%6%
2376
December1st to 15thNight
37%5%11%20%18%6%
2520
16th to endNight
40%413%20%15%5%
2688

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
27%318%30%11%7%
102
16th to endDay
22%217%23%21%12%
256
February1st to 15thDay
20%5%16%20%24%12%
244
16th to endDay
18%6%23%24%19%7%
238
March1st to 15thDay
17%9%20%25%18%8%
270
16th to endDay
14%9%24%28%15%6%
288
April1st to 15thDay
17%8%33%19%14%7%
269
16th to endDay
11%12%28%25%15%5%
270
May1st to 15thDay
7%8%28%33%17%4
288
16th to endDay
49%20%33%27%3
330
June1st to 15thDay
5%7%28%36%19%2
315
16th to endDay
1122%39%30%5%
315
July1st to 15thDay
13%37%43%5%
305
16th to endDay
8%45%37%7%
327
August1st to 15thDay
315%45%29%5%
315
16th to endDay
13%44%33%7%
332
September1st to 15thDay
1112%45%32%7%
300
16th to endDay
4416%36%28%9%
255
October1st to 15thDay
5%8%22%31%23%9%
255
16th to endDay
11%419%27%28%9%
272
November1st to 15thDay
8%28%17%39%22%
112
16th to endDay
7%8%16%35%29%2
84
December1st to 15thDay
25%323%33%15%
60
16th to endDay
17%118%25%29%7%
64
January1st to 15thNight
15%110%32%29%9%
720
16th to endNight
19%37%30%28%10%
768
February1st to 15thNight
17%312%32%28%6%
704
16th to endNight
21%312%34%22%5%
632
March1st to 15thNight
18%312%33%27%5%
720
16th to endNight
16%318%34%24%2
768
April1st to 15thNight
13%421%34%22%2
719
16th to endNight
7%320%39%23%5%
720
May1st to 15thNight
4222%41%24%3
618
16th to endNight
4221%42%28%1
375
June1st to 15thNight
4125%46%21%
360
16th to endNight
113%53%29%1
360
July1st to 15thNight
9%58%30%
340
16th to endNight
119%44%38%4
505
August1st to 15thNight
111%48%35%3
604
16th to endNight
110%46%37%3
764
September1st to 15thNight
18%45%39%5%
706
16th to endNight
1112%36%38%9%
656
October1st to 15thNight
6%110%39%32%7%
660
16th to endNight
6%19%35%32%13%
704
November1st to 15thNight
10%18%38%30%10%
700
16th to endNight
11%111%35%31%8%
720
December1st to 15thNight
18%10%37%25%7%
720
16th to endNight
21%313%33%23%4
768
Page generated at 2017-09-13 04:39:25. Version ac04

Copyright 2017 A. Danko


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