DaVinci Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the DaVinci Observatory clear sky chart from 2005-11-06 to 2024-01-27.

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
25%
22942
12%
75030
7%
22895
32%
22895
14%
55416

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
8%
757
7%
2649
2%
757
13%
757
4%
2232
January11th to 20thNight
9%
760
4%
2536
2%
760
11%
760
3%
2234
January21st to endNight
13%
820
6%
2664
2%
820
17%
820
5%
2280
February1st to 10thNight
6%
720
6%
2340
1%
720
13%
720
5%
1969
February11th to 20thNight
10%
702
7%
2275
2%
700
18%
700
6%
1860
February21st to endNight
10%
592
7%
1862
2%
592
17%
592
7%
1496
March1st to 10thNight
16%
720
12%
1980
5%
720
23%
720
13%
1543
March11th to 20thNight
18%
720
15%
1980
6%
720
26%
720
14%
1504
March21st to endNight
22%
792
16%
2178
6%
792
30%
792
17%
1624
April1st to 10thNight
18%
720
13%
1805
4%
720
24%
720
16%
1388
April11th to 20thNight
23%
711
15%
1775
6%
711
28%
711
20%
1296
April21st to endNight
26%
551
17%
1631
7%
551
34%
551
20%
1170
May1st to 10thNight
34%
532
14%
1612
9%
532
39%
532
20%
1107
May11th to 20thNight
33%
354
19%
1416
14%
354
44%
354
18%
872
May21st to endNight
42%
388
16%
1551
15%
388
51%
388
23%
896
June1st to 10thNight
35%
360
15%
1440
11%
360
49%
360
18%
932
June11th to 20thNight
40%
360
15%
1440
16%
360
50%
360
20%
860
June21st to endNight
35%
360
14%
1440
11%
360
46%
360
21%
861
July1st to 10thNight
50%
350
17%
1400
19%
350
59%
350
29%
741
July11th to 20thNight
47%
348
17%
1392
19%
348
55%
348
25%
784
July21st to endNight
49%
538
16%
1622
11%
508
55%
508
30%
968
August1st to 10thNight
54%
537
18%
1600
14%
534
57%
534
32%
983
August11th to 20thNight
53%
534
19%
1598
12%
534
57%
534
30%
995
August21st to endNight
49%
716
19%
1904
10%
716
53%
716
32%
1224
September1st to 10thNight
45%
720
17%
1800
8%
720
49%
720
30%
1204
September11th to 20thNight
51%
720
26%
1854
16%
720
56%
720
36%
1173
September21st to endNight
39%
720
19%
2047
14%
720
44%
720
24%
1374
October1st to 10thNight
33%
720
16%
2160
12%
720
39%
720
20%
1487
October11th to 20thNight
21%
720
11%
2160
6%
720
28%
720
14%
1605
October21st to endNight
17%
792
12%
2376
6%
792
25%
792
10%
1861
November1st to 10thNight
27%
740
18%
2429
12%
740
36%
740
17%
1671
November11th to 20thNight
18%
760
13%
2660
7%
760
26%
760
11%
1937
November21st to endNight
14%
760
8%
2660
4%
760
20%
760
8%
2104
December1st to 10thNight
10%
760
5%
2660
2%
760
13%
760
4%
2274
December11th to 20thNight
8%
760
5%
3261
1%
759
13%
759
4%
2714
December21st to endNight
7%
828
3%
4873
0%
817
13%
817
2%
4193

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
17%11%48%6%35%5%5%7%30%
74795
Night
17%11%48%6%45%45%6%29%
75248
TransparencyDay
54%6%12%18%9%1
74509
Night
56%6%11%17%9%1
75068
SeeingDay
25%17%29%18%8%3
13431
Night
25%16%28%22%8%1
22955

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
17%17%8%13%10%47%44413%
1517
11th to 20thDay
18%20%6%15%10%4434412%
1642
21st to endDay
14%19%8%14%12%6%6%44410%
1836
February1st to 10thDay
20%18%6%13%9%46%43414%
1620
11th to 20thDay
14%17%10%15%9%45%43416%
1573
21st to endDay
21%15%6%12%9%45%44416%
1392
March1st to 10thDay
17%11%7%13%8%5%5%43422%
1976
11th to 20thDay
15%16%6%6%6%35%45%6%28%
1980
21st to endDay
20%13%48%6%3445%5%28%
2178
April1st to 10thDay
18%14%5%7%6%3445%6%29%
2155
11th to 20thDay
20%10%36%5%34446%36%
2138
21st to endDay
21%10%37%5%44445%34%
2340
May1st to 10thDay
17%10%36%6%45%5%5%7%33%
2348
11th to 20thDay
18%7%35%5%35%5%6%7%37%
2478
21st to endDay
13%6%35%425%5%6%8%43%
2725
June1st to 10thDay
17%6%25%435%46%9%39%
2520
11th to 20thDay
14%6%25%6%35%5%6%10%39%
2520
21st to endDay
15%6%245%35%46%9%41%
2520
July1st to 10thDay
9%425%435%5%6%8%48%
2520
11th to 20thDay
12%6%26%5%46%6%7%10%36%
2520
21st to endDay
11%5%35%6%46%7%7%10%36%
2596
August1st to 10thDay
10%5%25%6%35%6%7%9%42%
2327
11th to 20thDay
11%5%36%6%45%7%7%9%37%
2303
21st to endDay
13%6%25%5%35%5%6%9%41%
2432
September1st to 10thDay
14%7%35%4345%5%9%40%
2160
11th to 20thDay
14%5%245%35%5%6%7%42%
2103
21st to endDay
15%7%37%5%5%5%5%5%8%34%
1913
October1st to 10thDay
22%6%36%6%4445%7%32%
1800
11th to 20thDay
21%11%5%8%6%345%46%27%
1800
21st to endDay
28%13%5%8%6%34435%21%
1980
November1st to 10thDay
16%12%38%6%45%5%5%7%30%
1645
11th to 20thDay
15%15%5%9%5%35%5%47%26%
1520
21st to endDay
21%18%5%9%7%34446%20%
1520
December1st to 10thDay
20%20%9%11%6%3444414%
1520
11th to 20thDay
20%20%7%13%7%3445%5%13%
1906
21st to endDay
27%23%6%11%7%3433310%
2772
January1st to 10thNight
18%19%7%10%9%5%5%43416%
2649
11th to 20thNight
20%19%8%12%8%5%4445%11%
2536
21st to endNight
16%17%7%12%10%5%5%5%5%414%
2664
February1st to 10thNight
18%18%6%13%8%35%435%17%
2340
11th to 20thNight
16%14%6%11%9%46%5%45%19%
2273
21st to endNight
18%15%7%12%7%35%446%19%
1862
March1st to 10thNight
15%12%5%10%7%5%5%5%45%26%
1970
11th to 20thNight
18%11%5%8%6%35%445%30%
1979
21st to endNight
17%11%5%9%5%33445%33%
2178
April1st to 10thNight
20%11%5%8%6%34445%30%
1805
11th to 20thNight
18%8%36%6%345%5%6%35%
1775
21st to endNight
18%9%47%435%5%5%7%34%
1631
May1st to 10thNight
18%7%36%6%35%5%6%7%34%
1612
11th to 20thNight
13%5%36%6%46%5%7%8%39%
1415
21st to endNight
12%5%25%5%345%6%7%45%
1550
June1st to 10thNight
12%5%36%6%5%6%7%7%8%35%
1440
11th to 20thNight
12%5%25%6%46%5%5%8%43%
1440
21st to endNight
12%6%35%5%35%5%5%8%42%
1440
July1st to 10thNight
7%6%2443445%9%52%
1440
11th to 20thNight
11%5%25%5%35%46%9%45%
1440
21st to endNight
10%5%24435%6%7%8%46%
1718
August1st to 10thNight
9%425%6%35%5%6%8%45%
1611
11th to 20thNight
9%6%26%5%345%6%8%45%
1598
21st to endNight
10%6%25%5%35%5%6%9%44%
1904
September1st to 10thNight
13%7%35%43445%7%44%
1800
11th to 20thNight
14%5%245%2335%7%49%
1854
21st to endNight
17%7%35%5%335%6%8%38%
2047
October1st to 10thNight
17%7%37%6%345%5%7%37%
2160
11th to 20thNight
22%10%38%6%4445%6%29%
2160
21st to endNight
27%11%36%7%3445%5%24%
2376
November1st to 10thNight
16%10%47%5%34446%37%
2429
11th to 20thNight
16%11%5%8%7%45%46%7%27%
2660
21st to endNight
18%15%6%8%6%36%5%5%7%21%
2660
December1st to 10thNight
21%19%8%9%7%34445%15%
2660
11th to 20thNight
17%21%7%11%6%34445%17%
3288
21st to endNight
30%16%6%9%6%45%45%5%10%
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
76%5%7%9%2
1518
11th to 20thDay
78%5%7%8%2
1642
21st to endDay
79%5%8%6%1
1836
February1st to 10thDay
76%410%9%1
1620
11th to 20thDay
73%6%7%11%3
1582
21st to endDay
73%5%8%10%5%
1392
March1st to 10thDay
66%5%10%14%41
1979
11th to 20thDay
58%6%10%15%9%1
1980
21st to endDay
58%48%19%9%2
2178
April1st to 10thDay
57%5%9%18%9%1
2155
11th to 20thDay
50%410%20%13%2
2138
21st to endDay
54%49%19%13%2
2340
May1st to 10thDay
51%5%10%21%11%2
2348
11th to 20thDay
46%7%11%22%12%2
2482
21st to endDay
38%7%16%23%14%2
2725
June1st to 10thDay
43%6%13%21%15%2
2520
11th to 20thDay
41%6%14%24%14%1
2520
21st to endDay
40%7%15%23%15%1
2520
July1st to 10thDay
33%7%12%28%17%2
2450
11th to 20thDay
40%8%16%24%11%
2445
21st to endDay
42%9%15%22%11%1
2451
August1st to 10thDay
36%8%17%25%12%1
2314
11th to 20thDay
41%8%17%24%9%1
2303
21st to endDay
40%6%14%27%11%2
2432
September1st to 10thDay
41%7%14%26%11%1
2160
11th to 20thDay
38%8%13%26%14%1
2103
21st to endDay
48%6%14%22%10%1
1913
October1st to 10thDay
51%6%14%17%12%1
1800
11th to 20thDay
57%6%14%16%6%1
1800
21st to endDay
67%5%10%11%6%1
1980
November1st to 10thDay
54%7%11%18%9%1
1645
11th to 20thDay
59%6%14%14%6%1
1520
21st to endDay
68%5%12%11%4
1520
December1st to 10thDay
75%5%10%9%1
1520
11th to 20thDay
73%8%9%7%2
1906
21st to endDay
80%5%8%6%1
2772
January1st to 10thNight
73%5%8%9%4
2649
11th to 20thNight
77%6%8%7%2
2536
21st to endNight
74%6%8%9%3
2664
February1st to 10thNight
72%5%9%10%4
2340
11th to 20thNight
68%6%10%12%4
2275
21st to endNight
67%5%11%13%5%
1862
March1st to 10thNight
59%6%12%17%7%
1980
11th to 20thNight
57%5%10%18%9%1
1980
21st to endNight
55%47%18%13%2
2178
April1st to 10thNight
56%5%9%19%10%1
1805
11th to 20thNight
49%7%9%20%13%2
1775
21st to endNight
50%6%9%19%14%2
1631
May1st to 10thNight
48%5%11%20%14%2
1612
11th to 20thNight
43%6%13%23%13%2
1416
21st to endNight
36%7%14%23%17%3
1551
June1st to 10thNight
44%8%10%21%16%1
1440
11th to 20thNight
40%6%12%20%19%2
1440
21st to endNight
40%6%14%22%16%1
1440
July1st to 10thNight
32%5%14%28%18%3
1400
11th to 20thNight
35%7%14%27%15%2
1392
21st to endNight
34%7%16%24%16%2
1622
August1st to 10thNight
34%8%17%28%13%1
1600
11th to 20thNight
37%6%16%28%12%
1598
21st to endNight
36%7%14%28%13%2
1904
September1st to 10thNight
38%7%14%27%13%1
1800
11th to 20thNight
35%5%12%30%17%1
1854
21st to endNight
43%7%14%23%13%1
2047
October1st to 10thNight
47%6%11%20%14%1
2160
11th to 20thNight
55%6%13%18%8%
2160
21st to endNight
62%6%10%14%7%1
2376
November1st to 10thNight
49%5%11%22%11%2
2429
11th to 20thNight
56%6%13%16%8%1
2660
21st to endNight
63%8%13%13%3
2660
December1st to 10thNight
72%8%10%9%2
2660
11th to 20thNight
71%6%9%11%3
3288
21st to endNight
76%6%10%6%1
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
37%24%24%9%41
180
11th to 20thDay
33%31%24%10%21
238
21st to endDay
32%26%28%13%2
282
February1st to 10thDay
37%33%26%4
240
11th to 20thDay
35%35%27%3
240
21st to endDay
41%27%24%8%
258
March1st to 10thDay
31%23%30%12%3
420
11th to 20thDay
31%22%32%12%21
420
21st to endDay
33%21%27%14%42
462
April1st to 10thDay
30%20%32%12%5%1
420
11th to 20thDay
33%20%23%17%6%2
412
21st to endDay
30%20%31%13%6%1
420
May1st to 10thDay
28%15%31%17%6%4
423
11th to 20thDay
24%14%30%21%8%2
447
21st to endDay
19%14%31%22%10%4
485
June1st to 10thDay
20%16%39%18%6%1
450
11th to 20thDay
20%12%33%24%9%2
450
21st to endDay
20%14%36%21%7%2
450
July1st to 10thDay
11%9%31%28%18%4
445
11th to 20thDay
15%10%30%27%14%4
444
21st to endDay
14%10%35%28%10%3
488
August1st to 10thDay
12%10%27%29%16%6%
446
11th to 20thDay
12%8%31%28%16%6%
439
21st to endDay
16%9%29%26%11%8%
495
September1st to 10thDay
16%11%28%26%12%7%
450
11th to 20thDay
14%7%26%25%19%9%
450
21st to endDay
19%17%27%19%12%6%
450
October1st to 10thDay
26%13%25%20%12%4
450
11th to 20thDay
31%20%26%16%41
450
21st to endDay
39%16%28%12%5%
495
November1st to 10thDay
32%17%30%13%6%1
314
11th to 20thDay
36%23%28%9%22
180
21st to endDay
37%23%29%11%1
180
December1st to 10thDay
39%22%27%8%31
180
11th to 20thDay
41%23%25%10%1
180
21st to endDay
41%27%24%7%11
198
January1st to 10thNight
34%24%26%12%4
760
11th to 20thNight
34%25%26%13%2
760
21st to endNight
27%22%30%17%4
820
February1st to 10thNight
33%28%27%11%1
720
11th to 20thNight
28%27%28%14%2
703
21st to endNight
30%26%29%13%2
592
March1st to 10thNight
26%20%33%17%4
720
11th to 20thNight
28%19%29%19%41
720
21st to endNight
25%14%34%19%7%1
792
April1st to 10thNight
27%19%31%21%2
720
11th to 20thNight
26%16%31%20%7%1
711
21st to endNight
23%12%33%24%8%
551
May1st to 10thNight
22%10%28%26%12%2
532
11th to 20thNight
15%11%34%33%7%
354
21st to endNight
14%10%29%33%14%1
389
June1st to 10thNight
14%8%36%33%9%
360
11th to 20thNight
14%9%30%36%11%
360
21st to endNight
13%8%37%36%5%1
360
July1st to 10thNight
10%6%28%40%16%1
350
11th to 20thNight
12%6%30%36%14%2
348
21st to endNight
12%431%36%16%2
538
August1st to 10thNight
11%423%41%19%2
537
11th to 20thNight
12%422%36%24%2
534
21st to endNight
13%428%33%20%2
716
September1st to 10thNight
17%8%24%33%15%2
720
11th to 20thNight
15%7%23%29%22%4
720
21st to endNight
19%11%26%27%14%4
720
October1st to 10thNight
20%11%29%24%14%2
720
11th to 20thNight
30%16%26%21%6%1
720
21st to endNight
36%15%27%18%3
792
November1st to 10thNight
26%15%28%23%7%1
740
11th to 20thNight
27%18%30%17%8%1
760
21st to endNight
31%21%27%16%5%
760
December1st to 10thNight
37%23%23%13%4
760
11th to 20thNight
33%24%28%13%3
760
21st to endNight
38%22%26%13%2
836
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