D'Auria Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the D'Auria Observatory clear sky chart from 2005-11-05 to 2017-10-16.

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
68%
16382
19%
47282
16%
16343
70%
16343
30%
30183

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
62%
717
17%
2327
16%
716
67%
716
27%
1428
January16th to endNight
60%
768
26%
2445
23%
768
66%
768
33%
1397
February1st to 15thNight
58%
701
27%
2095
23%
699
63%
699
35%
1230
February16th to endNight
67%
631
31%
1735
23%
631
73%
631
42%
981
March1st to 15thNight
64%
720
26%
1980
19%
720
69%
720
39%
1161
March16th to endNight
66%
768
26%
2112
22%
768
69%
768
42%
1206
April1st to 15thNight
74%
718
25%
1976
22%
718
76%
718
49%
1063
April16th to endNight
68%
720
25%
1818
16%
720
72%
720
42%
1094
May1st to 15thNight
76%
719
25%
1799
17%
719
77%
719
50%
1006
May16th to endNight
73%
615
16%
1737
13%
615
73%
615
28%
1159
June1st to 15thNight
64%
540
8%
1620
7%
540
64%
540
16%
1232
June16th to endNight
80%
540
7%
1620
6%
540
80%
540
23%
1137
July1st to 15thNight
75%
510
5%
1530
5%
510
75%
510
22%
1065
July16th to endNight
83%
564
10%
1595
10%
531
83%
531
31%
997
August1st to 15thNight
76%
614
9%
1684
8%
611
76%
611
28%
1134
August16th to endNight
70%
764
6%
2054
6%
764
70%
764
21%
1509
September1st to 15thNight
70%
720
5%
1980
5%
720
70%
720
17%
1509
September16th to endNight
63%
717
6%
1980
6%
717
63%
717
16%
1513
October1st to 15thNight
69%
720
14%
2084
16%
720
70%
720
22%
1464
October16th to endNight
59%
708
18%
2123
19%
708
61%
708
23%
1447
November1st to 15thNight
66%
700
25%
2101
24%
700
70%
700
31%
1291
November16th to endNight
63%
720
27%
2160
25%
720
68%
720
30%
1354
December1st to 15thNight
65%
720
23%
2231
21%
720
69%
720
28%
1396
December16th to endNight
69%
768
25%
2496
26%
768
72%
768
34%
1410

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
7%5%38%8%5%7%7%7%9%26%
48115
Night
5%425%5%36%6%7%11%41%
47488
TransparencyDay
48%10%13%15%10%2
47816
Night
35%9%18%21%12%2
47291
SeeingDay
8%111%22%27%28%
6192
Night
7%111%30%33%15%
16391

By Month

Percentage Cloud Cover SE (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
9%6%38%6%45%6%7%9%30%
1611
16th to endDay
7%5%36%6%37%5%7%10%36%
1776
February1st to 15thDay
8%5%26%6%46%5%5%10%39%
1757
16th to endDay
5%425%5%35%6%7%10%43%
1738
March1st to 15thDay
5%426%5%47%6%9%9%37%
1980
16th to endDay
5%436%7%46%6%6%9%38%
2111
April1st to 15thDay
4326%6%37%6%8%12%37%
1972
16th to endDay
7%426%8%47%6%7%11%34%
2140
May1st to 15thDay
4326%6%5%7%7%7%9%39%
2152
16th to endDay
9%5%38%10%5%8%8%8%9%20%
2384
June1st to 15thDay
12%8%5%11%11%6%10%7%5%6%13%
2340
16th to endDay
7%7%411%13%7%11%8%7%7%13%
2340
July1st to 15thDay
6%6%410%11%7%9%9%7%10%16%
2340
16th to endDay
6%5%38%11%8%10%9%9%9%17%
2465
August1st to 15thDay
6%6%310%10%6%8%9%8%9%19%
2251
16th to endDay
8%6%39%11%8%10%9%8%9%14%
2143
September1st to 15thDay
8%6%312%12%7%8%9%9%8%12%
1980
16th to endDay
12%10%5%11%9%6%8%8%7%6%12%
1980
October1st to 15thDay
8%5%410%9%6%7%7%8%10%19%
1875
16th to endDay
14%7%27%8%46%6%6%9%27%
1770
November1st to 15thDay
7%5%35%7%47%7%6%8%35%
1757
16th to endDay
9%5%27%7%45%5%7%7%37%
1800
December1st to 15thDay
9%6%35%7%46%6%6%10%33%
1725
16th to endDay
6%435%6%5%6%7%8%10%34%
1728
January1st to 15thNight
7%4245%35%6%9%11%38%
2327
16th to endNight
4434435%5%7%9%47%
2445
February1st to 15thNight
7%42442446%8%48%
2093
16th to endNight
42145%2435%9%55%
1735
March1st to 15thNight
5%224435%5%5%8%51%
1980
16th to endNight
3314335%5%6%9%52%
2112
April1st to 15thNight
221342346%9%59%
1976
16th to endNight
6%213325%5%6%10%50%
1818
May1st to 15thNight
22133235%6%11%58%
1799
16th to endNight
6%4346%36%6%8%11%36%
1736
June1st to 15thNight
10%6%36%8%47%8%7%11%23%
1620
16th to endNight
44246%49%9%10%15%29%
1620
July1st to 15thNight
35%25%6%36%7%9%15%33%
1620
16th to endNight
2314446%6%10%14%39%
1703
August1st to 15thNight
3325%6%45%6%8%15%36%
1695
16th to endNight
5%427%7%47%8%8%13%29%
2054
September1st to 15thNight
5%426%8%5%9%8%8%12%27%
1980
16th to endNight
7%6%38%8%5%7%7%9%11%25%
1980
October1st to 15thNight
5%427%6%47%7%9%13%30%
2084
16th to endNight
10%6%36%6%35%5%7%8%34%
2123
November1st to 15thNight
6%425%5%35%6%6%8%44%
2101
16th to endNight
7%435%6%35%5%5%8%44%
2160
December1st to 15thNight
7%425%5%36%5%7%9%41%
2231
16th to endNight
5%224436%6%6%9%47%
2496

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
44%8%12%18%11%5%
1612
16th to endDay
40%7%11%19%16%5%
1776
February1st to 15thDay
37%6%8%21%19%5%
1759
16th to endDay
32%6%12%27%16%4
1738
March1st to 15thDay
36%8%11%22%17%3
1980
16th to endDay
37%7%11%22%16%5%
2112
April1st to 15thDay
32%8%14%25%16%2
1972
16th to endDay
37%8%12%20%16%4
2140
May1st to 15thDay
38%7%11%21%14%5%
2152
16th to endDay
52%11%13%16%5%
2388
June1st to 15thDay
68%9%10%8%2
2340
16th to endDay
62%12%16%7%1
2340
July1st to 15thDay
56%15%19%8%
2201
16th to endDay
53%15%21%9%
2310
August1st to 15thDay
52%14%18%12%1
2238
16th to endDay
58%14%17%9%
2143
September1st to 15thDay
61%14%16%6%
1980
16th to endDay
66%12%11%7%2
1980
October1st to 15thDay
54%11%13%10%8%1
1875
16th to endDay
51%9%9%13%12%4
1770
November1st to 15thDay
42%7%11%14%19%4
1757
16th to endDay
43%6%9%13%20%6%
1800
December1st to 15thDay
44%7%11%16%17%2
1725
16th to endDay
39%6%12%21%16%3
1728
January1st to 15thNight
36%7%17%22%12%3
2327
16th to endNight
31%6%12%27%17%4
2445
February1st to 15thNight
32%5%10%24%20%7%
2102
16th to endNight
26%6%13%26%21%6%
1735
March1st to 15thNight
30%412%28%19%4
1980
16th to endNight
25%6%16%26%19%4
2112
April1st to 15thNight
21%6%16%34%17%3
1976
16th to endNight
27%7%15%24%21%3
1818
May1st to 15thNight
20%6%15%34%17%4
1800
16th to endNight
36%10%17%25%9%
1738
June1st to 15thNight
50%12%19%13%3
1620
16th to endNight
38%15%32%12%1
1620
July1st to 15thNight
37%16%34%11%
1530
16th to endNight
28%13%38%16%1
1595
August1st to 15thNight
33%14%30%20%1
1684
16th to endNight
44%13%28%12%
2054
September1st to 15thNight
45%17%24%11%1
1980
16th to endNight
48%14%22%11%3
1980
October1st to 15thNight
43%10%17%16%9%1
2084
16th to endNight
45%6%11%18%13%4
2123
November1st to 15thNight
36%5%11%19%22%4
2101
16th to endNight
37%6%10%18%20%6%
2160
December1st to 15thNight
37%6%14%19%18%2
2231
16th to endNight
31%5%13%27%19%2
2496

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
21%434%27%12%
90
16th to endDay
13%11%25%37%9%3
96
February1st to 15thDay
6%435%35%14%4
98
16th to endDay
7%225%35%26%1
239
March1st to 15thDay
6%126%35%26%3
270
16th to endDay
7%222%32%25%9%
288
April1st to 15thDay
4317%32%27%15%
270
16th to endDay
8%115%30%28%16%
270
May1st to 15thDay
2113%24%32%25%
288
16th to endDay
5%16%19%33%32%
331
June1st to 15thDay
14%16%20%24%32%
315
16th to endDay
4313%24%54%
315
July1st to 15thDay
5%111%27%54%
305
16th to endDay
6%28%24%56%
326
August1st to 15thDay
7%35%27%54%
313
16th to endDay
11%1310%25%47%
332
September1st to 15thDay
9%311%24%50%
315
16th to endDay
13%48%25%48%
314
October1st to 15thDay
8%19%27%33%19%
315
16th to endDay
15%117%26%26%14%
276
November1st to 15thDay
8%111%32%34%12%
265
16th to endDay
10%224%31%26%4
270
December1st to 15thDay
15%414%32%27%5%
195
16th to endDay
6%412%40%33%3
96
January1st to 15thNight
9%317%36%29%3
720
16th to endNight
6%223%43%21%1
768
February1st to 15thNight
9%122%41%23%1
704
16th to endNight
4319%47%24%1
631
March1st to 15thNight
7%120%42%24%2
720
16th to endNight
6%119%44%26%2
768
April1st to 15thNight
3114%47%30%3
718
16th to endNight
7%115%44%29%2
720
May1st to 15thNight
312%39%39%4
720
16th to endNight
9%15%25%43%13%
617
June1st to 15thNight
14%416%40%23%
540
16th to endNight
429%40%43%
540
July1st to 15thNight
6%17%41%43%
510
16th to endNight
415%36%51%
564
August1st to 15thNight
6%17%44%40%
614
16th to endNight
8%310%41%36%
764
September1st to 15thNight
8%49%34%42%
720
16th to endNight
9%411%39%35%
717
October1st to 15thNight
9%5%28%41%14%
720
16th to endNight
15%12%25%32%12%
708
November1st to 15thNight
8%15%36%34%5%
700
16th to endNight
10%114%39%28%5%
720
December1st to 15thNight
10%212%40%30%3
720
16th to endNight
7%113%37%34%5%
768
Page generated at 2017-10-17 16:35:30. Version ac04

Copyright 2017 A. Danko


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