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 2018-02-14.

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%
16106
24%
48800
16%
16061
58%
16061
29%
29841

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
29%
780
23%
2522
10%
776
45%
776
24%
1535
January16th to endNight
31%
832
26%
2592
14%
832
44%
832
25%
1602
February1st to 15thNight
34%
760
25%
2276
12%
755
47%
755
27%
1408
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%
539
14%
1705
17%
536
72%
536
25%
1120
August16th to endNight
64%
573
16%
1910
18%
573
64%
573
21%
1298
September1st to 15thNight
64%
709
17%
1969
16%
709
65%
709
27%
1315
September16th to endNight
59%
717
23%
1980
18%
717
63%
717
28%
1310
October1st to 15thNight
56%
720
30%
1980
23%
720
63%
720
38%
1168
October16th to endNight
54%
768
36%
2285
29%
768
64%
768
39%
1246
November1st to 15thNight
54%
760
30%
2432
24%
760
64%
760
37%
1295
November16th to endNight
44%
780
29%
2535
20%
780
57%
780
32%
1414
December1st to 15thNight
38%
780
25%
2535
16%
780
51%
780
27%
1518
December16th to endNight
36%
832
21%
2704
15%
832
45%
832
20%
1791

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%41%
49261
Night
10%5%2443445%8%46%
49003
TransparencyDay
39%6%10%17%17%6%
48962
Night
35%5%11%18%19%9%
48806
SeeingDay
13%6%19%24%22%14%
5891
Night
12%6%22%29%22%4
16109

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%45%
1746
16th to endDay
16%6%23424345%45%
1983
February1st to 15thDay
16%5%34324446%43%
1883
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%
2240
16th to endDay
13%7%36%7%47%5%7%8%27%
2289
September1st to 15thDay
11%7%36%6%45%6%6%9%33%
1980
16th to endDay
14%6%26%6%35%45%6%38%
1980
October1st to 15thDay
12%6%24424346%49%
1980
16th to endDay
9%314323235%59%
1938
November1st to 15thDay
10%313314435%56%
1753
16th to endDay
13%433323346%51%
1755
December1st to 15thDay
15%5%245%14446%44%
1755
16th to endDay
21%8%36%424335%36%
1872
January1st to 15thNight
14%6%2442335%6%46%
2522
16th to endNight
16%5%2432333447%
2592
February1st to 15thNight
15%5%24433245%46%
2271
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%326%6%46%7%9%13%32%
1716
16th to endNight
11%6%26%5%46%5%7%9%34%
1910
September1st to 15thNight
11%5%25%5%35%5%5%10%39%
1969
16th to endNight
9%6%36%5%35%5%5%8%41%
1980
October1st to 15thNight
10%41332335%7%52%
1980
16th to endNight
9%413323245%59%
2285
November1st to 15thNight
8%413323345%58%
2432
16th to endNight
12%424323345%54%
2535
December1st to 15thNight
14%5%25%324346%46%
2535
16th to endNight
19%7%35%5%24445%37%
2704

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%36%15%25%8%
1747
16th to endDay
40%36%15%22%11%
1983
February1st to 15thDay
42%36%16%21%9%
1885
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%11%18%15%6%
2227
16th to endDay
50%10%13%14%9%1
2289
September1st to 15thDay
43%10%13%14%14%3
1980
16th to endDay
45%6%8%17%17%4
1980
October1st to 15thDay
35%49%19%22%8%
1980
16th to endDay
27%35%15%28%18%
1938
November1st to 15thDay
29%47%17%26%15%
1753
16th to endDay
34%37%15%25%14%
1755
December1st to 15thDay
39%411%15%19%9%
1755
16th to endDay
50%26%19%13%7%
1872
January1st to 15thNight
39%36%16%25%8%
2522
16th to endNight
40%3415%24%11%
2592
February1st to 15thNight
39%25%16%23%13%
2280
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
1705
16th to endNight
42%10%17%16%11%1
1910
September1st to 15thNight
40%8%15%17%14%4
1969
16th to endNight
39%7%12%16%19%4
1980
October1st to 15thNight
31%49%21%19%13%
1980
16th to endNight
28%35%14%31%17%
2285
November1st to 15thNight
28%37%16%28%15%
2432
16th to endNight
32%37%17%23%15%
2535
December1st to 15thNight
38%39%17%21%8%
2535
16th to endNight
47%36%19%15%7%
2704

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
14%22%42%12%34
135
16th to endDay
13%26%40%12%6%
144
February1st to 15thDay
18%23%38%16%3
130
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
12%6%26%30%21%
313
16th to endDay
11%9%22%27%29%
332
September1st to 15thDay
16%111%22%26%21%
315
16th to endDay
18%112%27%28%11%
314
October1st to 15thDay
15%320%27%24%8%
315
16th to endDay
9%9%23%29%22%5%
336
November1st to 15thDay
15%9%26%30%15%3
171
16th to endDay
5%13%38%25%14%3
135
December1st to 15thDay
22%17%31%20%5%2
135
16th to endDay
30%11%29%24%4
144
January1st to 15thNight
17%15%32%25%8%
780
16th to endNight
18%13%31%27%8%
832
February1st to 15thNight
17%12%31%30%8%
760
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%13%
539
16th to endNight
13%8%20%40%15%
573
September1st to 15thNight
13%110%25%38%10%
709
16th to endNight
12%15%36%31%3
717
October1st to 15thNight
13%222%29%27%4
720
16th to endNight
11%8%21%30%25%2
768
November1st to 15thNight
10%6%23%35%20%2
760
16th to endNight
12%9%30%29%16%1
780
December1st to 15thNight
16%8%31%28%13%1
780
16th to endNight
20%9%28%29%10%1
832
Page generated at 2018-02-15 10:58:52. Version ac04

Copyright 2018 A. Danko


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