Echo Valley Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Echo Valley Observatory clear sky chart from 2005-11-05 to 2018-03-21.

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
29%
15426
12%
48903
8%
15394
34%
15394
15%
36158

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
13%
782
6%
2719
3%
779
17%
779
6%
2285
January16th to endNight
18%
832
10%
2736
5%
832
24%
832
9%
2214
February1st to 15thNight
16%
762
9%
2482
3%
761
23%
761
8%
2021
February16th to endNight
18%
683
11%
2210
5%
683
26%
683
10%
1732
March1st to 15thNight
18%
780
12%
2146
5%
780
24%
780
14%
1649
March16th to endNight
32%
792
20%
2178
11%
792
40%
792
23%
1492
April1st to 15thNight
23%
718
14%
1802
6%
718
28%
718
18%
1372
April16th to endNight
31%
552
18%
1632
10%
552
38%
552
21%
1136
May1st to 15thNight
37%
438
16%
1518
13%
438
45%
438
20%
1006
May16th to endNight
41%
374
13%
1497
12%
374
50%
374
21%
896
June1st to 15thNight
38%
360
9%
1386
9%
360
44%
360
16%
921
June16th to endNight
47%
360
11%
1260
11%
360
51%
360
20%
815
July1st to 15thNight
53%
340
15%
1223
19%
340
58%
340
30%
689
July16th to endNight
50%
419
15%
1458
16%
394
54%
394
24%
877
August1st to 15thNight
56%
539
15%
1609
12%
536
59%
536
28%
1030
August16th to endNight
51%
618
18%
1764
9%
618
56%
618
30%
1114
September1st to 15thNight
45%
720
14%
1800
7%
720
48%
720
29%
1230
September16th to endNight
46%
717
21%
2006
14%
717
51%
717
29%
1304
October1st to 15thNight
30%
720
15%
2160
10%
720
38%
720
18%
1542
October16th to endNight
19%
768
10%
2304
5%
768
25%
768
10%
1857
November1st to 15thNight
27%
760
14%
2641
12%
760
33%
760
14%
1935
November16th to endNight
19%
780
9%
2730
6%
780
24%
780
8%
2202
December1st to 15thNight
12%
780
5%
2730
2%
780
16%
780
5%
2361
December16th to endNight
11%
832
8%
2912
3%
832
17%
832
5%
2478

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
19%10%47%5%34446%29%
49896
Night
18%12%47%5%34446%29%
49070
Cloud CoverDay
19%10%47%5%34446%29%
49906
Night
18%12%47%5%34445%29%
49075
TransparencyDay
55%5%9%18%9%
49581
Night
56%5%10%17%9%
48903
SeeingDay
25%12%28%20%9%3
6222
Night
24%11%28%24%10%1
15430

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 15thDay
20%17%8%10%6%2333418%
1504
16th to endDay
15%19%8%10%7%43345%17%
1840
February1st to 15thDay
13%18%7%13%8%3443318%
1710
16th to endDay
16%17%7%10%6%2433421%
1548
March1st to 15thDay
16%13%5%8%6%35%446%25%
2131
16th to endDay
13%9%37%5%3435%5%37%
2174
April1st to 15thDay
22%11%45%424345%30%
2145
16th to endDay
20%10%35%422335%37%
2337
May1st to 15thDay
20%8%35%6%3345%6%32%
2433
16th to endDay
16%6%246%2346%7%38%
2618
June1st to 15thDay
22%7%35%5%2445%7%29%
2571
16th to endDay
18%5%25%5%26%5%6%8%32%
2700
July1st to 15thDay
16%5%25%43445%8%37%
2663
16th to endDay
13%6%35%5%36%5%6%9%34%
2609
August1st to 15thDay
13%6%37%6%45%45%6%35%
2340
16th to endDay
15%6%35%6%445%6%6%36%
2426
September1st to 15thDay
19%6%35%5%3435%6%36%
2160
16th to endDay
19%7%23424446%38%
1953
October1st to 15thDay
26%8%36%5%34326%30%
1800
16th to endDay
33%10%36%423345%20%
1920
November1st to 15thDay
21%13%47%6%34445%25%
1545
16th to endDay
24%17%7%9%435%33416%
1560
December1st to 15thDay
20%24%8%9%5%3333414%
1560
16th to endDay
19%22%7%10%5%2424315%
1649
January1st to 15thNight
21%19%7%10%7%3334415%
2719
16th to endNight
14%16%9%11%7%33435%20%
2736
February1st to 15thNight
12%17%6%13%7%44435%19%
2480
16th to endNight
16%16%7%10%6%33335%23%
2210
March1st to 15thNight
17%13%6%8%6%3433428%
2134
16th to endNight
14%8%46%423346%40%
2178
April1st to 15thNight
22%12%35%5%23335%31%
1802
16th to endNight
18%9%25%5%24446%35%
1632
May1st to 15thNight
19%7%25%42345%9%35%
1518
16th to endNight
13%5%245%245%6%8%40%
1495
June1st to 15thNight
16%7%35%43445%8%35%
1386
16th to endNight
14%6%35%435%5%6%7%37%
1260
July1st to 15thNight
11%424424446%50%
1296
16th to endNight
11%4244246%6%7%44%
1557
August1st to 15thNight
12%6%24425%46%6%45%
1620
16th to endNight
12%42442345%7%45%
1764
September1st to 15thNight
14%5%25%43445%8%41%
1800
16th to endNight
16%6%24423346%45%
2006
October1st to 15thNight
21%8%25%434346%34%
2160
16th to endNight
29%11%46%5%2343423%
2304
November1st to 15thNight
22%12%34423346%30%
2641
16th to endNight
24%15%47%6%34335%20%
2730
December1st to 15thNight
21%23%7%10%5%3333313%
2730
16th to endNight
21%19%8%11%6%3333414%
2912

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
21%17%8%9%6%2423418%
1504
16th to endDay
15%19%8%10%7%4433417%
1840
February1st to 15thDay
13%19%8%14%8%3443318%
1710
16th to endDay
16%17%7%10%6%25%33421%
1548
March1st to 15thDay
16%13%5%8%6%35%446%25%
2142
16th to endDay
13%9%37%5%34345%37%
2173
April1st to 15thDay
22%12%45%423345%30%
2145
16th to endDay
20%10%25%423335%38%
2337
May1st to 15thDay
20%8%35%5%3345%6%32%
2433
16th to endDay
17%6%245%3345%7%38%
2618
June1st to 15thDay
23%7%36%5%3445%7%29%
2571
16th to endDay
18%6%25%5%35%5%5%8%33%
2700
July1st to 15thDay
16%5%25%5%35%45%8%37%
2663
16th to endDay
13%5%25%5%36%5%6%9%34%
2609
August1st to 15thDay
14%7%27%6%35%45%6%36%
2340
16th to endDay
16%5%35%6%35%5%5%7%35%
2426
September1st to 15thDay
21%5%25%5%3335%6%36%
2160
16th to endDay
19%7%24425%35%5%39%
1953
October1st to 15thDay
27%9%25%5%34325%31%
1800
16th to endDay
34%10%36%423445%20%
1920
November1st to 15thDay
21%13%46%6%34445%25%
1545
16th to endDay
24%18%7%8%43434317%
1560
December1st to 15thDay
20%25%8%8%5%2433314%
1560
16th to endDay
20%21%7%10%5%3424415%
1649
January1st to 15thNight
21%19%7%10%7%2334415%
2719
16th to endNight
15%16%9%11%7%34335%19%
2736
February1st to 15thNight
12%17%7%12%7%45%445%19%
2473
16th to endNight
16%15%7%9%6%33335%23%
2210
March1st to 15thNight
18%13%5%8%6%2424428%
2146
16th to endNight
14%8%45%5%23346%40%
2178
April1st to 15thNight
22%12%44433335%31%
1802
16th to endNight
18%9%245%2445%6%35%
1632
May1st to 15thNight
20%7%2442345%8%36%
1518
16th to endNight
14%5%244435%6%8%40%
1495
June1st to 15thNight
17%7%26%4335%5%7%35%
1386
16th to endNight
14%5%26%435%5%6%7%37%
1260
July1st to 15thNight
11%414424447%50%
1296
16th to endNight
11%4244246%6%8%44%
1557
August1st to 15thNight
12%6%24325%45%6%45%
1620
16th to endNight
13%415%42446%8%45%
1764
September1st to 15thNight
15%5%2443345%7%41%
1800
16th to endNight
16%5%24424346%45%
2006
October1st to 15thNight
22%7%35%424346%34%
2160
16th to endNight
29%12%35%6%2333423%
2304
November1st to 15thNight
22%12%35%423346%30%
2641
16th to endNight
25%15%5%7%6%3333420%
2730
December1st to 15thNight
21%22%7%9%5%3343313%
2730
16th to endNight
21%20%8%10%6%3333314%
2912

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
71%28%10%6%
1505
16th to endDay
70%35%9%8%1
1840
February1st to 15thDay
71%46%12%5%
1712
16th to endDay
68%37%12%8%
1548
March1st to 15thDay
59%6%11%14%7%
2142
16th to endDay
48%49%19%15%3
2174
April1st to 15thDay
56%48%17%11%1
2145
16th to endDay
50%47%22%14%2
2337
May1st to 15thDay
52%5%9%19%12%1
2433
16th to endDay
44%7%11%21%13%1
2622
June1st to 15thDay
53%6%8%21%10%
2571
16th to endDay
48%6%12%19%11%1
2700
July1st to 15thDay
41%6%12%25%13%1
2507
16th to endDay
46%6%11%24%10%
2445
August1st to 15thDay
48%7%11%21%10%
2327
16th to endDay
45%8%12%24%8%
2426
September1st to 15thDay
48%5%11%23%9%
2160
16th to endDay
46%5%11%28%7%
1953
October1st to 15thDay
57%310%18%10%
1800
16th to endDay
66%5%9%12%5%
1920
November1st to 15thDay
60%7%10%13%6%
1545
16th to endDay
72%38%10%31
1560
December1st to 15thDay
75%47%8%4
1560
16th to endDay
74%36%10%5%
1649
January1st to 15thNight
74%37%8%5%1
2719
16th to endNight
67%46%11%8%
2736
February1st to 15thNight
68%48%12%5%
2482
16th to endNight
64%47%15%7%
2210
March1st to 15thNight
59%310%15%9%1
2146
16th to endNight
46%48%21%16%2
2178
April1st to 15thNight
56%46%18%12%1
1802
16th to endNight
49%48%18%17%2
1632
May1st to 15thNight
46%5%10%19%15%2
1518
16th to endNight
40%6%14%22%14%1
1497
June1st to 15thNight
47%6%10%19%14%
1386
16th to endNight
44%6%12%24%11%
1260
July1st to 15thNight
32%5%11%30%18%1
1223
16th to endNight
38%6%12%28%13%
1458
August1st to 15thNight
37%7%15%27%11%
1609
16th to endNight
35%7%16%28%10%1
1764
September1st to 15thNight
41%6%16%23%11%
1800
16th to endNight
40%413%31%9%
2006
October1st to 15thNight
50%6%10%20%11%
2160
16th to endNight
65%5%9%13%5%
2304
November1st to 15thNight
54%7%11%18%7%
2641
16th to endNight
68%49%12%4
2730
December1st to 15thNight
75%5%6%8%3
2730
16th to endNight
74%45%8%6%
2912

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
26%24%35%10%3
90
16th to endDay
40%11%35%8%4
137
February1st to 15thDay
29%27%38%4
135
16th to endDay
40%19%33%6%
129
March1st to 15thDay
27%17%31%18%41
330
16th to endDay
21%15%31%21%9%1
311
April1st to 15thDay
25%17%27%19%9%1
270
16th to endDay
28%15%26%15%9%4
270
May1st to 15thDay
31%7%23%23%7%6%
288
16th to endDay
22%13%34%15%10%3
331
June1st to 15thDay
24%12%30%22%9%1
366
16th to endDay
20%12%32%23%8%2
495
July1st to 15thDay
18%7%29%29%11%3
441
16th to endDay
17%8%26%27%12%6%
326
August1st to 15thDay
18%224%32%12%9%
313
16th to endDay
20%7%19%24%17%10%
332
September1st to 15thDay
18%6%25%23%15%9%
315
16th to endDay
18%7%24%26%16%6%
314
October1st to 15thDay
27%12%26%21%10%1
315
16th to endDay
37%15%26%15%4
336
November1st to 15thDay
32%16%31%17%1
102
16th to endDay
41%20%28%7%2
90
December1st to 15thDay
35%18%30%12%3
90
16th to endDay
32%30%28%6%21
96
January1st to 15thNight
32%16%28%17%4
783
16th to endNight
24%12%34%20%6%1
832
February1st to 15thNight
21%18%32%21%5%
764
16th to endNight
27%16%30%20%5%
683
March1st to 15thNight
25%18%30%20%4
780
16th to endNight
20%11%29%26%9%1
792
April1st to 15thNight
28%12%31%21%5%
718
16th to endNight
23%11%28%25%10%
552
May1st to 15thNight
25%5%25%28%13%1
438
16th to endNight
16%5%33%34%9%
375
June1st to 15thNight
21%6%27%32%11%
360
16th to endNight
17%6%21%41%12%
360
July1st to 15thNight
10%324%44%16%
340
16th to endNight
13%225%39%19%
419
August1st to 15thNight
14%317%37%23%3
539
16th to endNight
14%5%23%31%22%3
618
September1st to 15thNight
18%5%25%28%17%4
720
16th to endNight
19%5%23%25%22%2
717
October1st to 15thNight
26%8%27%23%11%1
720
16th to endNight
36%11%27%18%5%
768
November1st to 15thNight
28%12%26%21%9%
760
16th to endNight
35%13%26%17%6%
780
December1st to 15thNight
34%16%29%14%4
780
16th to endNight
32%15%30%16%4
832
Page generated at 2018-03-22 11:34:19. Version ac04

Copyright 2018 A. Danko


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