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Discovery Channel Telescope
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Discovery Channel Telescope clear sky chart from 2005-11-05 to 2018-02-14.

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
50%
16173
33%
48778
20%
16128
64%
16128
42%
24339

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
39%
780
30%
2522
17%
776
57%
776
32%
1312
January16th to endNight
36%
832
35%
2704
18%
832
59%
832
32%
1409
February1st to 15thNight
42%
760
31%
2403
18%
756
61%
756
39%
1173
February16th to endNight
33%
632
35%
1877
18%
632
55%
632
32%
995
March1st to 15thNight
39%
720
36%
1980
17%
720
57%
720
41%
1023
March16th to endNight
42%
768
35%
2112
15%
768
60%
768
45%
1072
April1st to 15thNight
33%
680
29%
1939
10%
680
50%
680
36%
995
April16th to endNight
40%
540
41%
1699
18%
540
63%
540
47%
716
May1st to 15thNight
44%
540
35%
1619
18%
539
59%
539
49%
732
May16th to endNight
45%
561
35%
1684
19%
561
59%
561
52%
732
June1st to 15thNight
48%
540
32%
1620
19%
540
59%
540
61%
692
June16th to endNight
66%
540
33%
1620
26%
540
71%
540
63%
690
July1st to 15thNight
72%
510
19%
1530
15%
510
75%
510
39%
850
July16th to endNight
72%
564
17%
1593
14%
531
73%
531
33%
947
August1st to 15thNight
74%
539
25%
1611
20%
536
75%
536
37%
891
August16th to endNight
79%
591
30%
1820
27%
591
81%
591
41%
978
September1st to 15thNight
73%
720
29%
1980
22%
720
77%
720
45%
1107
September16th to endNight
65%
716
43%
1980
26%
716
77%
716
60%
915
October1st to 15thNight
51%
720
38%
2085
21%
720
66%
720
51%
966
October16th to endNight
57%
768
43%
2304
26%
768
72%
768
52%
1046
November1st to 15thNight
47%
760
35%
2322
19%
760
64%
760
44%
1107
November16th to endNight
45%
780
39%
2535
25%
780
64%
780
41%
1165
December1st to 15thNight
43%
780
32%
2535
19%
780
60%
780
32%
1314
December16th to endNight
35%
832
31%
2704
19%
832
52%
832
27%
1512

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
4413323446%59%
49293
Night
3413323346%63%
48974
TransparencyDay
25%36%18%29%16%
48988
Night
21%36%19%29%18%
48780
SeeingDay
11%18%29%26%10%2
5867
Night
6%14%23%28%21%4
16175

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
47%13313336%61%
1746
16th to endDay
6%7%13213336%59%
1872
February1st to 15thDay
38%33213337%58%
1756
16th to endDay
38%24423347%55%
1597
March1st to 15thDay
36%1231345%6%60%
1980
16th to endDay
45%12323337%62%
2112
April1st to 15thDay
3214323446%61%
2006
16th to endDay
3413212345%67%
2259
May1st to 15thDay
3312212346%65%
2331
16th to endDay
431232334466%
2429
June1st to 15thDay
11111223478%
2340
16th to endDay
111222334473%
2340
July1st to 15thDay
7%3246%46%5%8%7%44%
2340
16th to endDay
10%5%26%7%47%7%7%9%30%
2467
August1st to 15thDay
8%5%25%7%45%6%6%7%39%
2340
16th to endDay
6%425%5%45%5%6%8%43%
2378
September1st to 15thDay
7%5%25%6%45%5%5%6%46%
1980
16th to endDay
3212213225%70%
1980
October1st to 15thDay
321331333470%
1875
16th to endDay
3312212336%70%
1920
November1st to 15thDay
222231344467%
1863
16th to endDay
441221323468%
1755
December1st to 15thDay
5%7%23313347%57%
1755
16th to endDay
49%46%422345%52%
1872
January1st to 15thNight
36%14313446%58%
2522
16th to endNight
5%7%2332333460%
2704
February1st to 15thNight
26%2321234464%
2392
16th to endNight
37%13313446%58%
1877
March1st to 15thNight
35%23212346%64%
1980
16th to endNight
321221335%6%66%
2112
April1st to 15thNight
242432335%5%62%
1939
16th to endNight
11121224475%
1699
May1st to 15thNight
2111313236%71%
1619
16th to endNight
21121233475%
1684
June1st to 15thNight
21111123477%
1620
16th to endNight
11221222378%
1620
July1st to 15thNight
3313445%5%8%9%49%
1620
16th to endNight
5%325%6%46%7%9%10%39%
1701
August1st to 15thNight
32146%25%5%5%9%51%
1620
16th to endNight
2214435%5%6%10%52%
1820
September1st to 15thNight
3224425%36%7%57%
1980
16th to endNight
31111233476%
1980
October1st to 15thNight
2112212245%72%
2085
16th to endNight
221321224473%
2304
November1st to 15thNight
3212223445%66%
2322
16th to endNight
35%12222235%68%
2535
December1st to 15thNight
36%14223346%59%
2535
16th to endNight
5%7%35%423345%53%
2704

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
25%35%21%32%10%
1747
16th to endDay
26%26%19%33%11%
1872
February1st to 15thDay
26%16%23%24%16%
1756
16th to endDay
29%3422%28%11%
1597
March1st to 15thDay
23%3319%36%13%
1980
16th to endDay
23%2425%31%12%
2112
April1st to 15thDay
23%2322%34%12%
2006
16th to endDay
19%2419%39%15%
2259
May1st to 15thDay
18%2421%35%17%
2331
16th to endDay
20%2415%40%16%
2432
June1st to 15thDay
11%1211%33%39%
2340
16th to endDay
15%228%29%42%
2340
July1st to 15thDay
34%6%10%15%13%18%
2201
16th to endDay
45%8%18%15%11%1
2312
August1st to 15thDay
41%5%8%16%17%9%
2325
16th to endDay
37%5%12%16%21%6%
2378
September1st to 15thDay
37%5%8%15%20%13%
1980
16th to endDay
18%2117%37%22%
1980
October1st to 15thDay
18%2416%33%24%
1875
16th to endDay
16%2416%42%17%
1920
November1st to 15thDay
19%3424%32%17%
1863
16th to endDay
19%2419%34%20%
1755
December1st to 15thDay
26%38%23%25%12%
1755
16th to endDay
34%27%21%25%8%
1872
January1st to 15thNight
26%4422%31%11%
2522
16th to endNight
27%2418%32%14%
2704
February1st to 15thNight
22%27%22%25%18%
2403
16th to endNight
25%3424%28%14%
1877
March1st to 15thNight
21%2321%38%13%
1980
16th to endNight
19%26%25%33%12%
2112
April1st to 15thNight
22%25%20%34%14%
1939
16th to endNight
13%2423%37%19%
1699
May1st to 15thNight
15%25%25%31%20%
1620
16th to endNight
13%1417%43%18%
1685
June1st to 15thNight
12%119%32%42%
1620
16th to endNight
12%216%24%52%
1620
July1st to 15thNight
26%6%14%15%17%19%
1530
16th to endNight
32%7%22%22%12%3
1593
August1st to 15thNight
27%6%13%20%20%11%
1611
16th to endNight
24%6%15%22%22%8%
1820
September1st to 15thNight
24%5%13%21%22%14%
1980
16th to endNight
11%3217%37%26%
1980
October1st to 15thNight
14%3420%28%28%
2085
16th to endNight
15%25%13%38%24%
2304
November1st to 15thNight
19%35%22%32%16%
2322
16th to endNight
19%2317%33%23%
2535
December1st to 15thNight
26%36%21%26%15%
2535
16th to endNight
32%36%21%25%9%
2704

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
17%25%30%20%6%
135
16th to endDay
13%24%28%19%12%2
144
February1st to 15thDay
12%25%30%15%13%2
193
16th to endDay
23%31%26%15%2
238
March1st to 15thDay
15%27%29%19%5%2
270
16th to endDay
16%23%33%18%43
288
April1st to 15thDay
17%28%33%11%6%2
269
16th to endDay
17%32%31%11%5%
270
May1st to 15thDay
12%27%36%18%31
288
16th to endDay
10%25%32%24%6%
330
June1st to 15thDay
421%42%20%8%1
315
16th to endDay
17%37%40%10%2
315
July1st to 15thDay
7%7%31%37%13%1
305
16th to endDay
12%319%40%17%6%
327
August1st to 15thDay
9%219%47%16%4
315
16th to endDay
8%418%40%22%6%
332
September1st to 15thDay
9%11%23%37%12%4
315
16th to endDay
10%12%30%32%10%3
315
October1st to 15thDay
6%28%32%22%6%2
210
16th to endDay
8%15%25%27%19%3
144
November1st to 15thDay
11%16%32%25%10%3
135
16th to endDay
14%22%28%20%11%2
135
December1st to 15thDay
11%24%29%21%11%2
135
16th to endDay
15%15%33%21%9%4
144
January1st to 15thNight
8%20%26%25%13%4
780
16th to endNight
9%21%27%25%13%2
832
February1st to 15thNight
7%18%28%29%13%2
760
16th to endNight
9%25%28%24%9%2
632
March1st to 15thNight
9%20%27%25%13%2
720
16th to endNight
6%17%29%28%14%2
768
April1st to 15thNight
8%23%29%25%11%1
680
16th to endNight
5%22%30%25%12%3
540
May1st to 15thNight
416%32%32%14%
540
16th to endNight
5%15%28%26%19%3
563
June1st to 15thNight
39%36%31%17%1
540
16th to endNight
2422%41%26%3
540
July1st to 15thNight
313%40%36%4
510
16th to endNight
427%30%43%10%
564
August1st to 15thNight
5%16%28%45%12%
539
16th to endNight
216%30%43%14%
591
September1st to 15thNight
4310%28%44%8%
720
16th to endNight
48%19%25%33%8%
716
October1st to 15thNight
415%26%31%18%4
720
16th to endNight
312%23%30%22%8%
768
November1st to 15thNight
5%16%27%28%15%6%
760
16th to endNight
8%17%25%25%17%5%
780
December1st to 15thNight
9%18%23%31%15%1
780
16th to endNight
11%18%28%25%12%3
832
Page generated at 2018-02-15 08:58:43. Version ac04

Copyright 2018 A. Danko


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