DVHS Espace Academy
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the DVHS Espace Academy clear sky chart from 2005-11-05 to 2017-09-19.

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
66%
15344
30%
46920
25%
15307
72%
15307
45%
23965

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
19%
2410
19%
716
65%
716
30%
1386
January16th to endNight
61%
768
25%
2496
25%
768
64%
768
31%
1451
February1st to 15thNight
57%
697
23%
2285
22%
697
63%
697
28%
1376
February16th to endNight
55%
632
25%
1895
20%
632
63%
632
32%
1126
March1st to 15thNight
54%
720
20%
2022
17%
720
59%
720
31%
1261
March16th to endNight
52%
768
23%
2079
15%
768
59%
768
35%
1268
April1st to 15thNight
49%
719
25%
1799
11%
719
56%
719
36%
1129
April16th to endNight
55%
720
27%
1800
11%
720
61%
720
51%
982
May1st to 15thNight
67%
611
31%
1691
20%
611
72%
611
63%
785
May16th to endNight
65%
374
32%
1496
30%
374
75%
374
56%
547
June1st to 15thNight
66%
360
29%
1440
27%
360
79%
360
52%
549
June16th to endNight
78%
360
39%
1440
45%
360
86%
360
73%
447
July1st to 15thNight
87%
346
36%
1366
41%
346
94%
346
80%
406
July16th to endNight
85%
564
38%
1593
32%
531
90%
531
77%
624
August1st to 15thNight
83%
561
40%
1634
28%
558
87%
558
79%
645
August16th to endNight
86%
764
45%
1910
29%
764
88%
764
85%
834
September1st to 15thNight
85%
720
43%
1800
28%
720
89%
720
80%
810
September16th to endNight
80%
671
44%
1831
38%
671
85%
671
71%
806
October1st to 15thNight
73%
660
33%
1980
30%
660
82%
660
55%
919
October16th to endNight
74%
704
37%
2112
38%
704
79%
704
51%
1039
November1st to 15thNight
71%
700
30%
2206
29%
700
77%
700
45%
1111
November16th to endNight
65%
720
26%
2427
26%
720
69%
720
36%
1302
December1st to 15thNight
58%
720
21%
2520
19%
720
64%
720
25%
1528
December16th to endNight
49%
768
21%
2688
18%
768
57%
768
25%
1634

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
6%312212336%64%
47894
Night
7%212213347%62%
47105
TransparencyDay
21%48%20%25%19%
47578
Night
22%49%20%23%19%
46921
SeeingDay
7%9%25%33%18%5%
5974
Night
8%416%39%27%4
15356

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%6%26%413346%43%
1525
16th to endDay
16%6%345%23335%44%
1728
February1st to 15thDay
14%6%36%5%14445%43%
1579
16th to endDay
16%4233245%48%43%
1579
March1st to 15thDay
11%6%25%5%3347%9%41%
1935
16th to endDay
9%5%25%5%35%45%7%45%
2145
April1st to 15thDay
12%5%1442445%8%46%
2149
16th to endDay
5%212223336%65%
2160
May1st to 15thDay
31222246%72%
2253
16th to endDay
322212246%70%
2615
June1st to 15thDay
2212112237%70%
2520
16th to endDay
11112484%
2520
July1st to 15thDay
1112486%
2511
16th to endDay
1112485%
2468
August1st to 15thDay
1111485%
2316
16th to endDay
11125%85%
2292
September1st to 15thDay
111225%83%
2160
16th to endDay
211112235%77%
1872
October1st to 15thDay
3212212336%70%
1650
16th to endDay
6%313323336%64%
1760
November1st to 15thDay
7%423413348%54%
1651
16th to endDay
11%5%35%323346%50%
1530
December1st to 15thDay
15%7%35%5%23446%41%
1440
16th to endDay
17%7%4432335%7%41%
1536
January1st to 15thNight
12%42432335%8%48%
2410
16th to endNight
14%42342345%7%49%
2496
February1st to 15thNight
15%423425%446%46%
2273
16th to endNight
14%42331435%7%50%
1895
March1st to 15thNight
12%424423447%47%
2022
16th to endNight
10%423323447%53%
2079
April1st to 15thNight
8%323425%45%8%51%
1799
16th to endNight
6%11223246%66%
1800
May1st to 15thNight
211212147%73%
1691
16th to endNight
211212238%74%
1496
June1st to 15thNight
211212237%74%
1440
16th to endNight
1122485%
1440
July1st to 15thNight
12387%
1446
16th to endNight
111238%79%
1701
August1st to 15thNight
11129%80%
1643
16th to endNight
1136%82%
1910
September1st to 15thNight
11227%81%
1800
16th to endNight
11211136%78%
1831
October1st to 15thNight
411213347%68%
1980
16th to endNight
42231335%8%64%
2112
November1st to 15thNight
7%312213349%61%
2206
16th to endNight
8%313423346%56%
2427
December1st to 15thNight
14%5%24333447%46%
2520
16th to endNight
18%41432335%6%46%
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
40%6%14%16%18%3
1525
16th to endDay
43%5%8%15%20%7%
1728
February1st to 15thDay
42%5%9%20%18%3
1579
16th to endDay
39%6%11%24%13%3
1579
March1st to 15thDay
39%6%13%19%15%5%
1935
16th to endDay
36%8%14%18%18%3
2145
April1st to 15thDay
35%6%13%20%19%3
2149
16th to endDay
20%314%26%26%8%
2160
May1st to 15thDay
13%37%28%35%11%
2253
16th to endDay
16%411%31%26%10%
2619
June1st to 15thDay
15%49%23%26%20%
2520
16th to endDay
6%1315%34%39%
2520
July1st to 15thDay
4129%24%57%
2362
16th to endDay
5%139%25%54%
2313
August1st to 15thDay
5%1212%31%46%
2300
16th to endDay
31113%39%39%
2292
September1st to 15thDay
5%2314%35%38%
2160
16th to endDay
10%35%22%35%23%
1872
October1st to 15thDay
16%48%23%27%20%
1650
16th to endDay
22%310%24%26%13%
1760
November1st to 15thDay
28%6%12%29%17%5%
1651
16th to endDay
36%412%21%20%3
1530
December1st to 15thDay
43%5%9%20%17%3
1440
16th to endDay
42%5%13%19%15%4
1536
January1st to 15thNight
33%5%13%23%16%7%
2410
16th to endNight
34%5%12%17%17%13%
2496
February1st to 15thNight
36%5%10%22%18%7%
2285
16th to endNight
34%413%26%17%3
1895
March1st to 15thNight
35%6%12%22%16%7%
2022
16th to endNight
31%7%12%22%19%7%
2079
April1st to 15thNight
31%6%13%23%18%6%
1799
16th to endNight
19%5%13%25%26%10%
1800
May1st to 15thNight
12%48%25%34%16%
1692
16th to endNight
11%412%33%26%12%
1496
June1st to 15thNight
13%310%21%27%23%
1440
16th to endNight
5%2215%28%44%
1440
July1st to 15thNight
4117%22%62%
1366
16th to endNight
6%238%21%57%
1593
August1st to 15thNight
6%1212%28%48%
1634
16th to endNight
42210%34%46%
1910
September1st to 15thNight
5%2311%29%46%
1800
16th to endNight
8%3321%34%28%
1831
October1st to 15thNight
15%410%22%26%21%
1980
16th to endNight
18%46%24%27%18%
2112
November1st to 15thNight
21%5%12%30%20%9%
2206
16th to endNight
29%49%23%25%7%
2427
December1st to 15thNight
38%6%10%18%19%6%
2520
16th to endNight
39%5%13%16%18%6%
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
21%8%20%26%15%6%
153
16th to endDay
16%8%19%22%21%10%
256
February1st to 15thDay
19%9%21%19%21%7%
237
16th to endDay
18%15%19%22%18%5%
238
March1st to 15thDay
16%11%27%20%16%7%
270
16th to endDay
11%18%30%25%11%3
288
April1st to 15thDay
14%23%27%19%11%3
269
16th to endDay
6%25%30%22%12%2
270
May1st to 15thDay
6%13%38%27%13%1
288
16th to endDay
410%29%34%18%2
330
June1st to 15thDay
415%36%31%10%2
315
16th to endDay
15%28%41%21%1
315
July1st to 15thDay
23%53%19%2
305
16th to endDay
223%50%18%5%
327
August1st to 15thDay
1426%44%20%2
315
16th to endDay
120%45%24%7%
332
September1st to 15thDay
318%45%24%7%
315
16th to endDay
27%21%35%18%13%
268
October1st to 15thDay
5%10%22%32%19%10%
255
16th to endDay
10%8%22%30%18%9%
272
November1st to 15thDay
8%419%21%30%14%
157
16th to endDay
8%12%21%36%22%
75
December1st to 15thDay
25%15%20%28%11%
60
16th to endDay
14%14%23%17%26%4
64
January1st to 15thNight
14%312%31%30%7%
720
16th to endNight
14%5%12%33%25%8%
768
February1st to 15thNight
14%5%14%33%26%5%
704
16th to endNight
13%8%16%33%22%4
632
March1st to 15thNight
14%7%16%31%25%4
720
16th to endNight
11%7%23%35%19%2
768
April1st to 15thNight
9%9%24%35%18%2
719
16th to endNight
7%8%26%34%20%4
720
May1st to 15thNight
3224%45%20%3
612
16th to endNight
2325%45%22%
375
June1st to 15thNight
2325%54%14%
360
16th to endNight
19%57%21%
360
July1st to 15thNight
10%59%28%
346
16th to endNight
18%47%39%2
564
August1st to 15thNight
112%47%34%3
561
16th to endNight
10%49%35%2
764
September1st to 15thNight
110%45%37%4
720
16th to endNight
1213%38%36%8%
671
October1st to 15thNight
4315%39%30%7%
660
16th to endNight
5%312%35%33%10%
704
November1st to 15thNight
6%213%35%33%7%
700
16th to endNight
8%315%33%30%8%
720
December1st to 15thNight
15%5%12%36%22%7%
720
16th to endNight
18%6%17%33%21%2
768
Page generated at 2017-09-20 01:49:53. Version ac04

Copyright 2017 A. Danko


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