Deer Run Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Deer Run Observatory clear sky chart from 2005-11-05 to 2017-08-12.

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
50%
15379
23%
46565
16%
15334
58%
15334
29%
28526

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
30%
720
23%
2327
10%
716
46%
716
24%
1422
January16th to endNight
30%
768
25%
2393
13%
768
44%
768
24%
1488
February1st to 15thNight
35%
704
27%
2108
12%
699
49%
699
29%
1279
February16th to endNight
29%
631
27%
1893
10%
631
44%
631
28%
1148
March1st to 15thNight
37%
720
26%
2064
13%
720
48%
720
31%
1234
March16th to endNight
42%
768
24%
2112
11%
768
51%
768
32%
1281
April1st to 15thNight
46%
643
26%
1901
18%
643
54%
643
35%
1097
April16th to endNight
51%
540
29%
1738
20%
540
62%
540
38%
932
May1st to 15thNight
55%
539
24%
1620
16%
539
62%
539
36%
939
May16th to endNight
64%
561
22%
1682
16%
561
68%
561
35%
1005
June1st to 15thNight
67%
540
15%
1620
14%
540
68%
540
27%
1075
June16th to endNight
74%
540
17%
1620
16%
540
75%
540
29%
1044
July1st to 15thNight
75%
510
10%
1530
10%
510
75%
510
26%
1015
July16th to endNight
74%
564
15%
1595
14%
531
74%
531
27%
1051
August1st to 15thNight
71%
527
15%
1667
17%
524
71%
524
25%
1097
August16th to endNight
64%
525
15%
1750
17%
525
64%
525
20%
1201
September1st to 15thNight
64%
650
18%
1805
17%
650
65%
650
27%
1217
September16th to endNight
56%
657
21%
1815
16%
657
60%
657
26%
1228
October1st to 15thNight
58%
660
32%
1815
24%
660
65%
660
39%
1064
October16th to endNight
54%
704
34%
2094
28%
704
64%
704
38%
1155
November1st to 15thNight
52%
700
31%
2240
25%
700
63%
700
37%
1197
November16th to endNight
42%
720
28%
2340
19%
720
55%
720
31%
1318
December1st to 15thNight
39%
720
25%
2340
17%
720
50%
720
27%
1397
December16th to endNight
36%
768
21%
2496
15%
768
45%
768
21%
1642

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
11%5%25%5%35%5%5%7%40%
47392
Night
10%5%2443445%8%45%
46768
TransparencyDay
40%6%10%17%17%6%
47093
Night
36%5%11%18%19%9%
46571
SeeingDay
13%6%17%24%23%14%
5248
Night
12%6%22%30%22%4
15382

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
14%6%35%424345%46%
1611
16th to endDay
16%6%23424445%44%
1830
February1st to 15thDay
14%5%34324446%44%
1750
16th to endDay
15%5%25%423336%46%
1580
March1st to 15thDay
12%6%35%32345%6%45%
1893
16th to endDay
13%5%25%433346%47%
2111
April1st to 15thDay
11%5%2442345%6%47%
2056
16th to endDay
9%424434447%53%
2220
May1st to 15thDay
9%425%5%25%46%8%45%
2331
16th to endDay
7%5%15%6%45%6%5%9%42%
2431
June1st to 15thDay
9%5%25%6%48%8%7%10%30%
2340
16th to endDay
5%325%7%5%7%7%9%10%36%
2340
July1st to 15thDay
10%6%26%8%5%8%8%8%9%25%
2340
16th to endDay
7%5%37%8%5%7%7%8%9%28%
2465
August1st to 15thDay
10%5%37%7%47%8%8%12%23%
2192
16th to endDay
14%7%36%7%47%6%7%8%26%
2097
September1st to 15thDay
10%7%36%6%45%6%6%9%32%
1815
16th to endDay
15%6%26%6%35%45%6%36%
1815
October1st to 15thDay
12%6%23313346%50%
1815
16th to endDay
10%314323345%58%
1777
November1st to 15thDay
10%413314435%55%
1615
16th to endDay
14%423323346%50%
1620
December1st to 15thDay
14%5%245%1445%6%44%
1620
16th to endDay
22%7%36%423335%36%
1728
January1st to 15thNight
14%6%2442335%6%45%
2327
16th to endNight
16%5%2432334446%
2393
February1st to 15thNight
14%5%24433246%48%
2103
16th to endNight
13%5%2432345%6%48%
1893
March1st to 15thNight
10%424433346%50%
2064
16th to endNight
11%5%24333446%50%
2112
April1st to 15thNight
11%32332436%7%50%
1901
16th to endNight
8%31332345%8%54%
1738
May1st to 15thNight
7%4145%245%5%8%50%
1619
16th to endNight
6%425%5%345%5%8%48%
1682
June1st to 15thNight
6%435%5%46%5%7%14%34%
1620
16th to endNight
4425%6%37%6%8%12%38%
1620
July1st to 15thNight
4326%6%5%7%6%9%13%34%
1620
16th to endNight
5%426%6%37%6%8%13%35%
1703
August1st to 15thNight
7%426%6%46%7%9%13%32%
1678
16th to endNight
11%7%26%6%46%5%6%9%33%
1750
September1st to 15thNight
10%6%25%5%35%5%411%38%
1805
16th to endNight
10%6%37%5%345%5%8%38%
1815
October1st to 15thNight
10%41332336%7%52%
1815
16th to endNight
9%41332334458%
2094
November1st to 15thNight
8%423323345%57%
2240
16th to endNight
13%423323345%52%
2340
December1st to 15thNight
13%5%25%42435%6%46%
2340
16th to endNight
19%6%345%24345%38%
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
39%47%14%25%8%
1612
16th to endDay
41%36%16%22%10%
1830
February1st to 15thDay
40%35%16%22%10%
1752
16th to endDay
39%3417%25%9%
1580
March1st to 15thDay
38%48%18%21%8%
1893
16th to endDay
38%410%18%22%6%
2112
April1st to 15thDay
37%46%20%21%9%
2056
16th to endDay
30%310%24%23%8%
2220
May1st to 15thDay
36%5%12%19%21%5%
2331
16th to endDay
36%6%11%25%14%4
2435
June1st to 15thDay
44%9%15%19%10%1
2340
16th to endDay
36%12%16%19%13%1
2340
July1st to 15thDay
46%11%20%13%5%1
2201
16th to endDay
45%10%18%17%7%
2310
August1st to 15thDay
48%10%18%15%7%
2179
16th to endDay
52%10%13%13%10%1
2097
September1st to 15thDay
44%10%13%14%14%2
1815
16th to endDay
47%6%7%16%17%4
1815
October1st to 15thDay
35%38%19%23%9%
1815
16th to endDay
28%35%16%27%18%
1777
November1st to 15thDay
30%46%16%26%16%
1615
16th to endDay
34%37%15%24%14%
1620
December1st to 15thDay
38%411%16%19%9%
1620
16th to endDay
50%26%17%14%7%
1728
January1st to 15thNight
39%36%16%25%8%
2327
16th to endNight
40%3415%24%11%
2393
February1st to 15thNight
37%25%17%23%13%
2112
16th to endNight
37%35%15%22%14%
1893
March1st to 15thNight
34%47%20%22%10%
2064
16th to endNight
34%410%17%24%8%
2112
April1st to 15thNight
31%49%20%21%12%
1901
16th to endNight
27%410%25%20%10%
1738
May1st to 15thNight
29%6%13%18%22%8%
1620
16th to endNight
31%6%16%22%15%7%
1684
June1st to 15thNight
37%10%16%24%11%
1620
16th to endNight
34%10%18%19%13%3
1620
July1st to 15thNight
36%11%27%16%6%1
1530
16th to endNight
36%10%21%22%7%1
1595
August1st to 15thNight
36%12%22%19%7%1
1667
16th to endNight
43%10%16%15%10%2
1750
September1st to 15thNight
40%8%15%17%14%3
1805
16th to endNight
42%7%10%15%19%5%
1815
October1st to 15thNight
30%48%22%19%14%
1815
16th to endNight
28%35%14%29%18%
2094
November1st to 15thNight
28%36%15%29%16%
2240
16th to endNight
33%36%16%23%16%
2340
December1st to 15thNight
38%38%19%21%8%
2340
16th to endNight
46%36%18%16%8%
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
17%17%35%16%5%6%
90
16th to endDay
13%26%44%9%5%1
96
February1st to 15thDay
7%28%38%21%3
90
16th to endDay
16%14%46%20%1
81
March1st to 15thDay
12%16%35%22%12%1
183
16th to endDay
13%7%35%26%15%1
288
April1st to 15thDay
17%13%20%27%19%2
270
16th to endDay
11%425%28%24%6%
270
May1st to 15thDay
10%10%23%25%19%11%
288
16th to endDay
12%212%27%27%17%
331
June1st to 15thDay
13%8%23%29%24%
315
16th to endDay
9%7%23%30%28%
315
July1st to 15thDay
8%1419%33%33%
305
16th to endDay
6%15%20%32%33%
326
August1st to 15thDay
13%16%27%31%20%
297
16th to endDay
13%7%21%26%31%
268
September1st to 15thDay
16%19%20%28%24%
255
16th to endDay
22%112%27%27%7%
254
October1st to 15thDay
16%317%30%26%6%
255
16th to endDay
10%7%22%27%25%7%
272
November1st to 15thDay
19%12%22%27%15%2
123
16th to endDay
5%14%38%23%12%5%
90
December1st to 15thDay
17%18%34%20%5%3
90
16th to endDay
35%8%23%26%5%1
96
January1st to 15thNight
17%15%32%26%8%
720
16th to endNight
18%13%32%27%7%
768
February1st to 15thNight
15%12%31%31%8%
704
16th to endNight
15%12%39%27%4
631
March1st to 15thNight
13%12%32%32%8%
720
16th to endNight
13%11%29%28%16%1
768
April1st to 15thNight
14%7%28%33%16%
643
16th to endNight
9%5%29%33%21%1
540
May1st to 15thNight
8%6%25%33%22%5%
540
16th to endNight
7%17%36%32%4
563
June1st to 15thNight
7%110%35%36%9%
540
16th to endNight
5%16%30%44%13%
540
July1st to 15thNight
6%429%40%17%
510
16th to endNight
6%1424%49%13%
564
August1st to 15thNight
8%6%25%45%12%
527
16th to endNight
14%7%21%40%15%
525
September1st to 15thNight
13%19%24%40%11%
650
16th to endNight
13%16%37%28%2
657
October1st to 15thNight
13%320%30%28%3
660
16th to endNight
12%7%20%31%25%2
704
November1st to 15thNight
10%7%24%34%19%2
700
16th to endNight
13%9%31%29%14%1
720
December1st to 15thNight
15%9%31%29%13%1
720
16th to endNight
20%9%27%29%10%1
768
Page generated at 2017-08-13 14:16:49. Version ac04

Copyright 2017 A. Danko


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