DRAACO
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the DRAACO clear sky chart from 2005-11-06 to 2024-01-10.

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%
22756
14%
74770
9%
22711
41%
22711
17%
52613

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 10thNight
16%
759
10%
2647
4%
757
23%
757
9%
2078
January11th to 20thNight
16%
720
7%
2448
3%
720
21%
720
7%
2010
January21st to endNight
21%
792
10%
2574
4%
792
28%
792
11%
1984
February1st to 10thNight
14%
720
8%
2340
3%
720
20%
720
9%
1859
February11th to 20thNight
18%
700
12%
2275
4%
700
28%
700
12%
1714
February21st to endNight
19%
592
12%
1870
4%
592
30%
592
14%
1365
March1st to 10thNight
23%
720
16%
1997
7%
720
32%
720
18%
1451
March11th to 20thNight
25%
720
16%
1979
8%
720
33%
720
19%
1413
March21st to endNight
32%
792
20%
2174
9%
792
41%
792
24%
1486
April1st to 10thNight
30%
720
15%
1800
5%
720
37%
720
23%
1323
April11th to 20thNight
34%
707
16%
1771
7%
707
38%
707
24%
1270
April21st to endNight
35%
540
16%
1620
8%
540
41%
540
21%
1121
May1st to 10thNight
44%
492
14%
1572
11%
492
48%
492
22%
1052
May11th to 20thNight
47%
354
22%
1416
20%
354
58%
354
23%
827
May21st to endNight
59%
388
17%
1551
20%
388
65%
388
26%
850
June1st to 10thNight
52%
360
14%
1440
13%
360
61%
360
20%
894
June11th to 20thNight
53%
360
16%
1440
20%
360
60%
360
25%
818
June21st to endNight
54%
360
13%
1440
17%
360
59%
360
22%
852
July1st to 10thNight
69%
350
16%
1400
24%
350
73%
350
32%
721
July11th to 20thNight
62%
348
18%
1392
26%
348
65%
348
28%
758
July21st to endNight
66%
485
17%
1572
18%
458
69%
458
32%
903
August1st to 10thNight
64%
537
17%
1600
14%
534
67%
534
33%
954
August11th to 20thNight
67%
534
20%
1598
14%
534
70%
534
34%
946
August21st to endNight
57%
706
21%
1894
11%
706
60%
706
33%
1199
September1st to 10thNight
56%
720
18%
1800
8%
720
59%
720
34%
1190
September11th to 20thNight
59%
720
26%
1843
16%
720
62%
720
38%
1144
September21st to endNight
51%
720
21%
2052
16%
720
55%
720
26%
1360
October1st to 10thNight
40%
720
16%
2160
12%
720
46%
720
22%
1485
October11th to 20thNight
30%
720
13%
2160
10%
720
36%
720
16%
1592
October21st to endNight
27%
792
14%
2376
9%
792
34%
792
16%
1772
November1st to 10thNight
38%
740
17%
2483
15%
740
45%
740
19%
1648
November11th to 20thNight
25%
760
14%
2660
7%
760
35%
760
14%
1897
November21st to endNight
24%
760
9%
2660
6%
760
29%
760
11%
1994
December1st to 10thNight
16%
760
7%
2660
3%
760
22%
760
8%
2133
December11th to 20thNight
19%
759
7%
3244
2%
758
24%
758
7%
2497
December21st to endNight
13%
829
4%
4862
1%
817
19%
817
4%
4053

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
15%9%36%6%35%5%5%7%35%
74657
Night
16%9%36%6%35%5%5%7%35%
75014
TransparencyDay
46%8%14%20%10%1
74368
Night
49%8%13%19%11%1
74837
SeeingDay
18%10%27%28%14%4
13320
Night
19%9%29%28%13%2
22769

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 10thDay
15%15%6%8%7%4446%7%26%
1509
11th to 20thDay
17%17%6%9%7%45%6%5%5%20%
1510
21st to endDay
13%15%6%11%9%46%445%23%
1782
February1st to 10thDay
16%14%5%12%9%45%5%5%5%21%
1620
11th to 20thDay
13%13%6%11%8%44446%27%
1573
21st to endDay
19%13%7%9%6%34445%27%
1386
March1st to 10thDay
14%10%48%8%445%5%6%30%
1959
11th to 20thDay
14%12%5%7%6%34446%34%
1980
21st to endDay
20%10%46%5%34346%36%
2182
April1st to 10thDay
17%10%49%6%35%5%5%6%31%
2160
11th to 20thDay
20%7%36%6%2445%6%38%
2154
21st to endDay
20%8%36%5%45%5%46%35%
2340
May1st to 10thDay
16%8%37%6%36%5%5%6%34%
2385
11th to 20thDay
15%6%35%5%35%5%5%7%42%
2478
21st to endDay
12%5%25%5%35%5%6%9%43%
2725
June1st to 10thDay
17%5%35%5%45%5%6%8%38%
2520
11th to 20thDay
12%5%25%5%35%5%6%10%41%
2520
21st to endDay
14%5%25%5%36%5%6%8%41%
2520
July1st to 10thDay
8%5%14426%5%7%10%46%
2520
11th to 20thDay
11%4246%36%5%6%9%43%
2520
21st to endDay
8%5%25%5%5%6%7%7%10%40%
2650
August1st to 10thDay
8%6%346%46%6%7%8%42%
2327
11th to 20thDay
9%425%6%36%7%7%9%43%
2303
21st to endDay
11%6%35%436%5%6%9%42%
2444
September1st to 10thDay
13%5%25%5%45%5%5%7%44%
2160
11th to 20thDay
12%5%14425%5%6%9%47%
2115
21st to endDay
13%5%36%5%45%5%5%8%41%
1907
October1st to 10thDay
18%9%26%6%46%5%6%6%34%
1800
11th to 20thDay
20%10%37%6%445%6%6%31%
1800
21st to endDay
23%10%48%7%35%45%5%26%
1980
November1st to 10thDay
15%9%36%5%36%5%5%8%33%
1590
11th to 20thDay
15%11%5%8%6%45%5%8%7%28%
1520
21st to endDay
20%14%46%6%35%45%6%26%
1520
December1st to 10thDay
18%13%6%9%7%46%5%46%21%
1520
11th to 20thDay
18%13%5%8%6%25%5%47%27%
1906
21st to endDay
28%16%6%8%7%4434416%
2772
January1st to 10thNight
18%12%6%9%7%45%5%5%5%26%
2647
11th to 20thNight
19%15%6%9%8%45%5%45%21%
2448
21st to endNight
13%12%5%10%7%46%5%46%28%
2574
February1st to 10thNight
15%15%6%9%7%47%5%5%6%23%
2340
11th to 20thNight
15%11%5%9%7%45%45%6%29%
2273
21st to endNight
16%11%47%6%45%5%5%6%31%
1870
March1st to 10thNight
14%9%48%7%45%45%5%36%
1987
11th to 20thNight
18%9%5%6%5%34445%36%
1979
21st to endNight
16%7%36%6%34446%41%
2174
April1st to 10thNight
20%8%36%435%5%5%6%34%
1800
11th to 20thNight
15%8%36%6%35%5%5%6%38%
1771
21st to endNight
17%8%46%6%35%5%5%7%35%
1620
May1st to 10thNight
18%5%245%35%5%6%7%38%
1572
11th to 20thNight
13%5%25%5%35%5%5%8%45%
1415
21st to endNight
11%43343445%8%50%
1550
June1st to 10thNight
12%5%25%5%46%7%6%8%40%
1440
11th to 20thNight
10%426%5%345%7%8%45%
1440
21st to endNight
12%6%26%5%3446%8%44%
1440
July1st to 10thNight
5%425%4345%5%8%53%
1440
11th to 20thNight
11%5%245%345%5%8%49%
1440
21st to endNight
9%424435%5%6%9%48%
1665
August1st to 10thNight
9%425%4345%7%9%49%
1611
11th to 20thNight
8%425%5%35%5%5%8%50%
1598
21st to endNight
10%5%25%4345%5%8%48%
1894
September1st to 10thNight
12%6%25%436%5%5%6%47%
1800
11th to 20thNight
12%42343345%7%53%
1843
21st to endNight
16%6%245%34447%45%
2052
October1st to 10thNight
16%6%27%5%4445%6%40%
2160
11th to 20thNight
20%8%36%6%35%5%5%7%33%
2160
21st to endNight
22%8%36%7%345%5%6%30%
2376
November1st to 10thNight
17%7%35%5%3445%7%38%
2483
11th to 20thNight
17%9%37%5%45%5%6%8%31%
2660
21st to endNight
20%11%46%5%35%6%5%8%26%
2660
December1st to 10thNight
19%14%5%9%7%35%5%46%23%
2660
11th to 20thNight
17%15%5%7%6%45%5%6%6%25%
3288
21st to endNight
30%14%47%5%35%5%5%6%17%
4884

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 10thDay
56%10%15%13%5%
1510
11th to 20thDay
66%10%9%8%6%
1510
21st to endDay
64%8%10%11%6%1
1782
February1st to 10thDay
65%8%11%11%31
1620
11th to 20thDay
58%8%10%14%9%1
1582
21st to endDay
59%5%12%17%6%
1386
March1st to 10thDay
52%7%15%15%10%1
1962
11th to 20thDay
51%6%11%18%13%2
1980
21st to endDay
49%5%9%18%16%3
2182
April1st to 10thDay
51%6%12%18%10%2
2160
11th to 20thDay
47%6%10%21%15%1
2154
21st to endDay
48%7%11%19%12%2
2340
May1st to 10thDay
46%8%12%18%14%3
2385
11th to 20thDay
40%8%11%25%14%2
2482
21st to endDay
36%8%17%24%13%2
2725
June1st to 10thDay
41%9%14%21%14%1
2520
11th to 20thDay
36%8%15%25%15%2
2520
21st to endDay
37%9%17%23%13%1
2520
July1st to 10thDay
29%9%15%27%18%2
2450
11th to 20thDay
34%9%17%29%10%1
2445
21st to endDay
34%11%18%24%12%1
2502
August1st to 10thDay
34%10%17%25%12%1
2314
11th to 20thDay
32%10%17%27%12%
2303
21st to endDay
34%9%17%27%11%1
2444
September1st to 10thDay
36%9%15%28%11%1
2160
11th to 20thDay
32%7%16%29%15%1
2115
21st to endDay
39%10%15%26%10%1
1907
October1st to 10thDay
48%9%13%19%10%1
1800
11th to 20thDay
51%9%15%18%6%1
1800
21st to endDay
58%7%14%14%6%1
1980
November1st to 10thDay
46%10%14%19%9%1
1590
11th to 20thDay
52%10%16%14%7%1
1520
21st to endDay
57%9%14%16%5%
1520
December1st to 10thDay
64%9%13%11%2
1520
11th to 20thDay
57%11%14%11%6%
1906
21st to endDay
70%11%8%9%2
2772
January1st to 10thNight
61%9%11%13%5%
2647
11th to 20thNight
65%10%10%9%5%1
2448
21st to endNight
58%9%11%14%8%1
2574
February1st to 10thNight
62%8%12%13%41
2340
11th to 20thNight
58%6%11%16%8%
2275
21st to endNight
53%8%14%18%7%1
1870
March1st to 10thNight
50%7%13%19%9%2
1997
11th to 20thNight
49%6%11%21%11%1
1980
21st to endNight
44%6%9%22%15%3
2174
April1st to 10thNight
49%6%11%20%13%2
1800
11th to 20thNight
46%7%10%18%18%2
1771
21st to endNight
47%6%12%18%14%2
1620
May1st to 10thNight
44%8%11%19%16%3
1572
11th to 20thNight
37%7%11%25%16%4
1416
21st to endNight
32%7%14%24%19%4
1551
June1st to 10thNight
40%9%10%22%16%3
1440
11th to 20thNight
34%8%13%21%22%3
1440
21st to endNight
38%8%13%24%15%1
1440
July1st to 10thNight
27%8%14%24%24%3
1400
11th to 20thNight
33%5%13%29%18%1
1392
21st to endNight
31%8%15%29%16%2
1572
August1st to 10thNight
31%8%19%27%14%1
1600
11th to 20thNight
32%7%16%30%14%1
1598
21st to endNight
34%8%14%29%15%1
1894
September1st to 10thNight
36%7%16%25%14%2
1800
11th to 20thNight
31%7%14%30%17%1
1843
21st to endNight
40%8%11%28%13%1
2052
October1st to 10thNight
45%8%12%20%14%1
2160
11th to 20thNight
51%10%12%20%7%
2160
21st to endNight
53%9%14%14%10%1
2376
November1st to 10thNight
43%9%14%21%12%1
2483
11th to 20thNight
50%10%14%16%10%1
2660
21st to endNight
56%10%17%13%4
2660
December1st to 10thNight
63%9%12%12%4
2660
11th to 20thNight
59%10%13%14%4
3288
21st to endNight
68%10%11%8%3
4884

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 10thDay
24%17%31%19%8%1
178
11th to 20thDay
25%21%34%14%5%1
192
21st to endDay
20%21%32%22%4
264
February1st to 10thDay
25%25%35%13%3
240
11th to 20thDay
22%20%41%16%1
240
21st to endDay
30%21%31%17%1
252
March1st to 10thDay
21%14%38%21%5%
420
11th to 20thDay
20%18%34%22%5%1
420
21st to endDay
27%10%33%20%9%1
462
April1st to 10thDay
19%14%34%25%8%1
420
11th to 20thDay
24%10%31%22%9%4
412
21st to endDay
23%9%33%25%8%2
420
May1st to 10thDay
20%9%26%28%13%4
423
11th to 20thDay
17%5%24%34%16%4
447
21st to endDay
12%322%36%22%6%
485
June1st to 10thDay
16%427%36%16%2
450
11th to 20thDay
14%6%21%34%21%4
450
21st to endDay
16%5%20%37%18%5%
450
July1st to 10thDay
8%218%36%28%7%
445
11th to 20thDay
13%318%35%24%8%
444
21st to endDay
8%323%43%18%5%
488
August1st to 10thDay
9%217%37%26%9%
446
11th to 20thDay
10%318%33%28%8%
439
21st to endDay
11%422%35%21%7%
495
September1st to 10thDay
11%5%23%29%23%9%
450
11th to 20thDay
11%420%32%21%13%
450
21st to endDay
14%7%27%28%17%6%
450
October1st to 10thDay
22%8%24%24%16%6%
450
11th to 20thDay
19%16%31%25%8%1
450
21st to endDay
27%15%28%22%8%
495
November1st to 10thDay
21%16%27%26%9%1
275
11th to 20thDay
19%19%36%20%42
180
21st to endDay
27%12%36%19%5%
180
December1st to 10thDay
22%18%34%20%6%1
180
11th to 20thDay
23%24%32%17%31
180
21st to endDay
29%17%36%17%1
198
January1st to 10thNight
24%17%37%16%6%
760
11th to 20thNight
27%14%33%21%5%
720
21st to endNight
20%13%36%25%5%1
792
February1st to 10thNight
23%17%41%18%2
720
11th to 20thNight
21%16%37%22%4
703
21st to endNight
22%15%39%21%4
592
March1st to 10thNight
20%13%37%26%5%
720
11th to 20thNight
21%13%34%26%5%1
720
21st to endNight
19%8%33%27%11%1
792
April1st to 10thNight
22%9%32%29%7%
720
11th to 20thNight
18%9%33%27%12%1
707
21st to endNight
20%7%29%31%13%1
540
May1st to 10thNight
21%324%34%15%3
492
11th to 20thNight
15%328%38%15%1
354
21st to endNight
11%319%40%25%2
389
June1st to 10thNight
13%223%42%18%2
360
11th to 20thNight
10%324%42%20%2
360
21st to endNight
12%220%44%21%1
360
July1st to 10thNight
5%315%51%24%3
350
11th to 20thNight
12%217%37%29%2
348
21st to endNight
11%115%46%24%3
485
August1st to 10thNight
10%214%38%31%4
537
11th to 20thNight
10%213%37%33%5%
534
21st to endNight
12%419%35%27%3
706
September1st to 10thNight
13%419%34%25%5%
720
11th to 20thNight
13%418%32%26%7%
720
21st to endNight
17%6%20%27%24%5%
720
October1st to 10thNight
20%5%28%26%20%2
720
11th to 20thNight
23%11%29%26%10%1
720
21st to endNight
23%11%31%27%6%
792
November1st to 10thNight
22%10%25%31%11%1
740
11th to 20thNight
21%14%32%24%7%2
760
21st to endNight
25%11%34%23%7%
760
December1st to 10thNight
27%14%35%20%4
760
11th to 20thNight
23%14%37%22%41
760
21st to endNight
31%14%35%17%2
836
Page generated at 2024-01-07 10:06:52. Version ac07

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