Dry Creek View Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dry Creek View Observatory clear sky chart from 2005-11-05 to 2017-09-23.

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
59%
15565
24%
46990
21%
15529
63%
15529
35%
27266

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
58%
716
17%
2327
18%
716
60%
716
26%
1477
January16th to endNight
56%
768
21%
2496
21%
768
59%
768
25%
1592
February1st to 15thNight
56%
699
15%
2267
17%
699
58%
699
25%
1446
February16th to endNight
50%
632
21%
1895
20%
632
54%
632
28%
1203
March1st to 15thNight
58%
720
25%
2025
22%
720
62%
720
36%
1212
March16th to endNight
52%
768
23%
2112
17%
768
57%
768
33%
1325
April1st to 15thNight
45%
672
18%
1888
13%
672
48%
672
29%
1202
April16th to endNight
48%
540
25%
1620
17%
540
54%
540
30%
968
May1st to 15thNight
52%
539
22%
1620
17%
539
55%
539
33%
952
May16th to endNight
56%
561
21%
1685
19%
561
59%
561
36%
950
June1st to 15thNight
60%
540
25%
1620
22%
540
65%
540
47%
797
June16th to endNight
63%
540
28%
1620
23%
540
71%
540
58%
736
July1st to 15thNight
64%
510
19%
1530
18%
510
68%
510
38%
849
July16th to endNight
64%
564
20%
1593
17%
531
65%
531
33%
932
August1st to 15thNight
63%
539
28%
1611
19%
536
69%
536
42%
850
August16th to endNight
72%
577
35%
1731
29%
577
75%
577
46%
883
September1st to 15thNight
75%
720
31%
1980
23%
720
81%
720
54%
1023
September16th to endNight
73%
688
38%
1903
30%
688
77%
688
55%
954
October1st to 15thNight
66%
660
30%
1904
24%
660
70%
660
43%
1047
October16th to endNight
64%
704
32%
2112
27%
704
70%
704
43%
1110
November1st to 15thNight
63%
700
28%
2275
28%
700
66%
700
36%
1246
November16th to endNight
62%
720
28%
2340
29%
720
64%
720
36%
1275
December1st to 15thNight
59%
720
18%
2340
18%
720
60%
720
27%
1449
December16th to endNight
46%
768
15%
2496
15%
768
48%
768
17%
1788

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%6%24424446%52%
47918
Night
7%7%24423446%51%
47184
TransparencyDay
31%49%19%20%14%
47613
Night
32%49%21%19%12%
46990
SeeingDay
8%10%24%32%19%4
5382
Night
10%417%37%26%3
15577

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
8%12%46%5%33237%41%
1611
16th to endDay
10%11%35%5%2336%9%39%
1728
February1st to 15thDay
8%10%37%5%25%5%5%8%37%
1594
16th to endDay
9%10%45%324447%42%
1579
March1st to 15thDay
6%9%46%423446%48%
1935
16th to endDay
8%11%45%5%34446%41%
2112
April1st to 15thDay
6%8%25%4245%46%48%
2056
16th to endDay
8%8%25%424345%50%
2340
May1st to 15thDay
7%5%25%4245%5%5%51%
2331
16th to endDay
6%5%1443445%6%51%
2429
June1st to 15thDay
4323323345%62%
2340
16th to endDay
21221223378%
2340
July1st to 15thDay
321342446%7%58%
2340
16th to endDay
44235%246%6%8%51%
2467
August1st to 15thDay
33134245%5%7%58%
2340
16th to endDay
321243335%6%62%
2468
September1st to 15thDay
3212324345%65%
1980
16th to endDay
321221233471%
1893
October1st to 15thDay
6%4235%24437%55%
1724
16th to endDay
6%5%23222445%59%
1759
November1st to 15thDay
9%6%34323345%51%
1584
16th to endDay
6%7%25%413447%50%
1620
December1st to 15thDay
9%12%36%42445%6%40%
1620
16th to endDay
13%14%5%7%5%2445%6%30%
1728
January1st to 15thNight
9%9%46%5%23346%44%
2327
16th to endNight
10%9%45%423446%43%
2496
February1st to 15thNight
9%9%46%43445%6%41%
2256
16th to endNight
6%10%46%5%25%35%6%43%
1895
March1st to 15thNight
7%8%3441435%7%48%
2025
16th to endNight
8%9%3443435%7%45%
2112
April1st to 15thNight
9%9%35%424445%45%
1888
16th to endNight
9%8%24424447%47%
1620
May1st to 15thNight
9%6%245%24345%50%
1619
16th to endNight
7%5%2443445%7%51%
1684
June1st to 15thNight
5%312323345%63%
1620
16th to endNight
221211233373%
1620
July1st to 15thNight
4325%4245%6%7%52%
1620
16th to endNight
44246%36%6%7%7%44%
1701
August1st to 15thNight
44144235%5%7%54%
1620
16th to endNight
3334245%6%6%58%
1731
September1st to 15thNight
322323445%65%
1980
16th to endNight
5%22312235%69%
1903
October1st to 15thNight
7%42341345%5%57%
1904
16th to endNight
5%5%14323446%58%
2112
November1st to 15thNight
6%8%24223345%55%
2275
16th to endNight
6%8%34323345%55%
2340
December1st to 15thNight
11%10%35%323436%44%
2340
16th to endNight
13%14%6%7%5%24435%33%
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%5%21%20%7%
1612
16th to endDay
41%7%16%24%8%1
1728
February1st to 15thDay
45%5%17%21%9%
1594
16th to endDay
41%5%9%26%15%1
1579
March1st to 15thDay
36%48%29%16%3
1935
16th to endDay
42%38%25%14%4
2112
April1st to 15thDay
35%5%8%23%20%6%
2056
16th to endDay
35%47%20%24%6%
2340
May1st to 15thDay
33%46%17%27%9%
2331
16th to endDay
30%47%18%27%10%
2432
June1st to 15thDay
22%25%11%31%25%
2340
16th to endDay
12%126%22%54%
2340
July1st to 15thDay
23%47%12%15%35%
2201
16th to endDay
28%5%8%13%18%25%
2312
August1st to 15thDay
23%46%15%20%29%
2325
16th to endDay
21%26%14%26%28%
2468
September1st to 15thDay
21%37%11%24%31%
1980
16th to endDay
17%3418%30%24%
1893
October1st to 15thDay
28%38%22%29%6%
1724
16th to endDay
25%38%26%29%5%
1759
November1st to 15thDay
35%310%22%20%7%
1584
16th to endDay
32%312%29%17%3
1620
December1st to 15thDay
44%5%17%24%8%
1620
16th to endDay
53%6%16%18%6%
1728
January1st to 15thNight
40%6%18%24%9%1
2327
16th to endNight
42%413%23%12%2
2496
February1st to 15thNight
42%5%15%22%12%2
2267
16th to endNight
41%311%25%17%
1895
March1st to 15thNight
33%39%32%18%2
2025
16th to endNight
36%49%26%18%5%
2112
April1st to 15thNight
39%39%20%19%7%
1888
16th to endNight
36%39%22%23%5%
1620
May1st to 15thNight
33%46%17%27%10%
1620
16th to endNight
29%48%21%25%9%
1685
June1st to 15thNight
21%26%13%29%25%
1620
16th to endNight
16%125%20%53%
1620
July1st to 15thNight
27%6%6%9%15%34%
1530
16th to endNight
32%6%10%11%15%23%
1593
August1st to 15thNight
24%5%9%19%15%25%
1611
16th to endNight
22%47%13%23%28%
1731
September1st to 15thNight
19%37%13%20%34%
1980
16th to endNight
18%2417%28%28%
1903
October1st to 15thNight
27%37%21%31%8%
1904
16th to endNight
25%38%22%34%6%
2112
November1st to 15thNight
30%37%25%23%8%
2275
16th to endNight
31%29%31%20%3
2340
December1st to 15thNight
41%314%28%10%1
2340
16th to endNight
53%414%19%6%
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
34%318%23%15%4
90
16th to endDay
17%412%28%30%7%
96
February1st to 15thDay
8%9%14%33%27%7%
109
16th to endDay
13%13%32%26%11%2
238
March1st to 15thDay
9%13%27%31%15%2
270
16th to endDay
19%13%31%23%10%
288
April1st to 15thDay
10%25%23%23%14%2
269
16th to endDay
16%22%26%21%12%
270
May1st to 15thDay
6%16%32%29%11%2
288
16th to endDay
7%12%26%27%23%3
330
June1st to 15thDay
6%12%31%32%13%4
315
16th to endDay
36%25%38%19%6%
315
July1st to 15thDay
25%24%39%21%6%
305
16th to endDay
7%221%41%23%3
327
August1st to 15thDay
3427%40%18%5%
315
16th to endDay
5%219%35%29%6%
332
September1st to 15thDay
36%24%38%20%6%
315
16th to endDay
311%18%32%27%6%
284
October1st to 15thDay
410%26%31%15%10%
164
16th to endDay
13%6%21%33%21%3
96
November1st to 15thDay
5%6%11%32%31%13%
90
16th to endDay
12%11%23%37%14%1
90
December1st to 15thDay
21%223%37%13%2
90
16th to endDay
14%415%36%28%1
96
January1st to 15thNight
12%414%37%25%5%
720
16th to endNight
14%412%36%26%5%
768
February1st to 15thNight
12%315%45%18%4
704
16th to endNight
12%5%23%40%17%1
632
March1st to 15thNight
10%6%17%41%21%1
720
16th to endNight
11%8%21%38%19%1
768
April1st to 15thNight
13%9%23%32%18%2
672
16th to endNight
13%10%20%33%20%2
540
May1st to 15thNight
12%5%20%36%21%2
540
16th to endNight
9%7%19%35%24%3
563
June1st to 15thNight
6%7%20%40%24%1
540
16th to endNight
3325%38%28%1
540
July1st to 15thNight
5%113%35%39%3
510
16th to endNight
7%115%32%40%2
564
August1st to 15thNight
6%117%45%27%2
539
16th to endNight
5%111%36%40%4
577
September1st to 15thNight
4112%34%39%7%
720
16th to endNight
5%412%30%38%8%
688
October1st to 15thNight
8%415%36%28%4
660
16th to endNight
8%415%32%33%5%
704
November1st to 15thNight
8%416%35%30%4
700
16th to endNight
9%5%15%40%22%7%
720
December1st to 15thNight
15%313%45%19%2
720
16th to endNight
16%5%17%37%21%1
768
Page generated at 2017-09-24 07:15:44. Version ac04

Copyright 2017 A. Danko


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