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 2005-11-06 to 2024-03-18.

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
48%
24109
23%
79802
16%
24002
57%
24002
26%
48753

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 10thNight
25%
754
22%
3990
9%
737
43%
737
15%
2273
January11th to 20thNight
33%
757
29%
3907
15%
740
49%
740
17%
2009
January21st to endNight
24%
835
18%
4182
11%
814
40%
814
14%
2618
February1st to 10thNight
32%
760
24%
2280
12%
760
44%
760
26%
1444
February11th to 20thNight
29%
743
23%
2219
9%
740
43%
740
25%
1390
February21st to endNight
27%
628
24%
1884
10%
628
40%
628
25%
1186
March1st to 10thNight
36%
760
27%
2223
15%
760
47%
760
29%
1359
March11th to 20thNight
34%
752
23%
2068
10%
752
44%
752
28%
1321
March21st to endNight
36%
792
24%
2178
11%
792
47%
792
30%
1347
April1st to 10thNight
41%
697
24%
1957
15%
697
49%
697
32%
1184
April11th to 20thNight
43%
533
27%
1775
18%
533
55%
533
31%
995
April21st to endNight
52%
540
32%
1709
23%
540
63%
540
40%
900
May1st to 10thNight
54%
540
27%
1620
17%
540
63%
540
39%
896
May11th to 20thNight
57%
531
18%
1592
13%
531
61%
531
32%
983
May21st to endNight
64%
582
21%
1744
17%
582
67%
582
33%
1062
June1st to 10thNight
62%
540
14%
1620
13%
540
62%
540
23%
1119
June11th to 20thNight
76%
540
19%
1620
17%
540
77%
540
35%
967
June21st to endNight
70%
540
14%
1620
12%
540
70%
540
26%
1079
July1st to 10thNight
72%
525
10%
1575
9%
525
73%
525
21%
1108
July11th to 20thNight
74%
522
10%
1566
10%
522
74%
522
25%
1056
July21st to endNight
76%
591
16%
1672
15%
558
77%
558
30%
1063
August1st to 10thNight
70%
537
12%
1653
13%
534
71%
534
25%
1111
August11th to 20thNight
71%
534
14%
1776
16%
534
71%
534
22%
1168
August21st to endNight
60%
594
15%
1980
17%
594
61%
594
19%
1372
September1st to 10thNight
64%
702
18%
1962
16%
702
65%
702
27%
1314
September11th to 20thNight
60%
720
18%
1980
14%
720
63%
720
27%
1337
September21st to endNight
62%
720
26%
1980
21%
720
66%
720
32%
1258
October1st to 10thNight
55%
720
28%
1980
21%
720
62%
720
37%
1187
October11th to 20thNight
56%
720
34%
2040
27%
720
65%
720
40%
1144
October21st to endNight
51%
792
32%
2376
27%
792
60%
792
35%
1367
November1st to 10thNight
51%
740
29%
2347
23%
740
62%
740
35%
1288
November11th to 20thNight
41%
760
30%
2470
20%
760
56%
760
33%
1365
November21st to endNight
40%
760
26%
2470
18%
760
52%
760
28%
1471
December1st to 10thNight
36%
760
26%
2470
16%
760
51%
760
25%
1509
December11th to 20thNight
34%
759
26%
2901
16%
758
46%
758
21%
1698
December21st to endNight
33%
829
15%
4416
13%
817
44%
817
12%
2805

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
12%6%35%5%35%5%6%8%42%
79111
Night
12%6%25%5%345%6%8%45%
80681
TransparencyDay
39%7%11%18%19%7%
78834
Night
37%6%10%17%20%9%
80477
SeeingDay
14%9%23%25%20%9%
13997
Night
14%8%23%30%21%4
24129

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 10thDay
16%6%35%5%2345%7%44%
2836
11th to 20thDay
13%6%23323346%55%
2840
21st to endDay
20%8%35%434335%41%
3389
February1st to 10thDay
15%8%36%5%35%45%7%40%
1900
11th to 20thDay
18%6%35%42445%7%44%
1848
21st to endDay
16%7%35%5%3445%7%42%
1570
March1st to 10thDay
13%5%35%4345%5%6%47%
1954
11th to 20thDay
13%6%46%4345%5%7%42%
2058
21st to endDay
13%6%35%5%3445%6%46%
2178
April1st to 10thDay
11%6%35%5%35%5%5%6%46%
2017
11th to 20thDay
13%5%2443445%7%49%
2134
21st to endDay
7%42443445%7%56%
2250
May1st to 10thDay
8%3245%35%46%8%52%
2340
11th to 20thDay
8%6%27%6%46%6%6%8%42%
2301
21st to endDay
9%5%25%6%45%6%6%9%42%
2531
June1st to 10thDay
11%6%36%7%5%7%8%8%10%30%
2340
11th to 20thDay
6%425%6%47%7%7%12%40%
2340
21st to endDay
6%5%36%8%6%8%8%9%9%33%
2340
July1st to 10thDay
9%6%37%9%6%8%8%10%10%25%
2340
11th to 20thDay
9%5%37%9%5%8%7%8%10%29%
2340
21st to endDay
6%5%37%8%5%7%8%8%11%31%
2547
August1st to 10thDay
9%5%37%8%5%7%8%8%12%28%
2269
11th to 20thDay
11%6%37%8%5%7%7%8%11%26%
2125
21st to endDay
13%8%36%7%5%7%6%7%8%29%
2373
September1st to 10thDay
9%7%36%7%46%6%7%9%36%
1980
11th to 20thDay
13%6%26%6%446%6%8%39%
1980
21st to endDay
12%6%36%6%3445%6%45%
1980
October1st to 10thDay
11%6%25%423446%53%
1980
11th to 20thDay
11%42432435%7%54%
1918
21st to endDay
11%5%25%433446%54%
1980
November1st to 10thDay
11%5%24424445%56%
1726
11th to 20thDay
13%5%24323446%55%
1710
21st to endDay
15%5%34434447%47%
1710
December1st to 10thDay
16%5%25%6%36%45%7%42%
1710
11th to 20thDay
17%8%35%5%24445%44%
2153
21st to endDay
19%8%36%424335%42%
3124
January1st to 10thNight
17%7%24435%46%7%41%
4109
11th to 20thNight
10%5%25%5%345%5%8%49%
4120
21st to endNight
21%9%35%423345%41%
4264
February1st to 10thNight
15%6%36%5%3445%6%43%
2280
11th to 20thNight
19%6%24433346%46%
2218
21st to endNight
16%7%25%4345%5%7%43%
1884
March1st to 10thNight
12%7%25%5%34346%50%
2223
11th to 20thNight
13%6%35%5%3445%7%46%
2068
21st to endNight
11%5%244345%6%6%49%
2178
April1st to 10thNight
10%5%24435%47%7%48%
1957
11th to 20thNight
12%5%2442445%8%50%
1775
21st to endNight
7%42442445%8%57%
1709
May1st to 10thNight
6%315%4345%5%9%54%
1620
11th to 20thNight
7%5%26%6%345%8%10%45%
1592
21st to endNight
9%425%6%45%5%6%9%46%
1744
June1st to 10thNight
8%6%36%7%5%6%7%7%12%33%
1620
11th to 20thNight
3335%5%47%7%8%14%43%
1620
21st to endNight
5%436%8%5%7%7%9%12%36%
1620
July1st to 10thNight
6%436%6%5%7%9%10%14%30%
1620
11th to 20thNight
6%427%7%5%7%6%9%13%34%
1620
21st to endNight
4426%7%46%7%9%12%39%
1771
August1st to 10thNight
6%5%27%6%5%7%7%10%13%32%
1664
11th to 20thNight
9%5%26%6%46%7%9%13%34%
1776
21st to endNight
11%8%36%7%46%6%8%8%33%
1980
September1st to 10thNight
10%6%35%6%45%6%5%12%38%
1962
11th to 20thNight
12%7%35%5%346%5%8%41%
1980
21st to endNight
8%5%27%5%445%6%8%45%
1980
October1st to 10thNight
10%5%25%43345%8%52%
1980
11th to 20thNight
11%42342335%5%57%
2040
21st to endNight
10%5%25%334345%55%
2376
November1st to 10thNight
10%5%2433445%5%57%
2347
11th to 20thNight
14%424323345%56%
2470
21st to endNight
14%6%35%424446%48%
2470
December1st to 10thNight
15%6%2442445%7%46%
2470
11th to 20thNight
16%5%35%5%24446%47%
3042
21st to endNight
20%8%36%5%3445%6%37%
4532

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 10thDay
40%35%19%23%10%
2837
11th to 20thDay
31%3417%31%13%
2840
21st to endDay
46%45%13%21%12%
3389
February1st to 10thDay
45%47%16%19%9%
1900
11th to 20thDay
42%5%5%15%25%9%
1858
21st to endDay
43%46%17%19%11%
1570
March1st to 10thDay
37%5%7%18%21%12%
1954
11th to 20thDay
41%5%12%14%19%9%
2058
21st to endDay
38%5%10%19%21%6%
2178
April1st to 10thDay
38%6%8%20%18%10%
2017
11th to 20thDay
35%48%20%24%10%
2134
21st to endDay
27%48%26%26%8%
2250
May1st to 10thDay
29%5%11%22%26%6%
2340
11th to 20thDay
38%7%15%21%15%4
2305
21st to endDay
37%7%10%24%18%3
2531
June1st to 10thDay
45%9%15%19%10%1
2340
11th to 20thDay
33%10%17%23%14%1
2340
21st to endDay
40%14%16%18%10%2
2340
July1st to 10thDay
45%13%21%13%6%1
2275
11th to 20thDay
44%12%22%14%6%1
2271
21st to endDay
41%11%22%19%6%
2405
August1st to 10thDay
44%11%21%20%4
2256
11th to 20thDay
48%12%18%13%7%1
2125
21st to endDay
50%11%14%15%8%2
2373
September1st to 10thDay
42%10%15%15%15%4
1980
11th to 20thDay
41%9%9%19%18%4
1980
21st to endDay
41%5%8%18%21%6%
1980
October1st to 10thDay
33%410%19%24%10%
1980
11th to 20thDay
29%5%7%24%26%9%
1918
21st to endDay
32%35%13%30%17%
1980
November1st to 10thDay
32%47%15%27%16%
1726
11th to 20thDay
32%36%16%28%14%
1710
21st to endDay
37%47%19%22%11%
1710
December1st to 10thDay
41%5%12%15%19%9%
1710
11th to 20thDay
42%35%15%25%9%
2150
21st to endDay
47%35%17%24%5%
3124
January1st to 10thNight
40%46%14%24%11%
4109
11th to 20thNight
34%45%20%25%11%
4120
21st to endNight
47%3412%25%8%
4264
February1st to 10thNight
42%37%16%20%12%
2280
11th to 20thNight
41%35%15%22%14%
2219
21st to endNight
39%5%8%16%17%15%
1884
March1st to 10thNight
36%46%18%22%13%
2223
11th to 20thNight
38%6%11%16%20%10%
2068
21st to endNight
35%5%10%18%24%8%
2178
April1st to 10thNight
33%5%11%18%19%13%
1957
11th to 20thNight
33%48%21%23%11%
1775
21st to endNight
26%5%10%27%24%9%
1709
May1st to 10thNight
27%6%12%22%25%9%
1620
11th to 20thNight
33%9%19%17%17%6%
1593
21st to endNight
33%7%14%21%19%5%
1745
June1st to 10thNight
42%10%15%19%13%1
1620
11th to 20thNight
28%10%20%28%12%2
1620
21st to endNight
36%12%20%17%11%3
1620
July1st to 10thNight
39%16%23%14%6%1
1575
11th to 20thNight
38%13%27%15%7%1
1566
21st to endNight
33%12%25%23%7%1
1672
August1st to 10thNight
37%13%24%21%41
1653
11th to 20thNight
38%13%22%18%8%1
1776
21st to endNight
45%11%16%16%10%2
1980
September1st to 10thNight
39%9%17%16%14%5%
1962
11th to 20thNight
41%8%13%16%18%5%
1980
21st to endNight
35%8%11%17%22%7%
1980
October1st to 10thNight
31%6%9%20%22%13%
1980
11th to 20thNight
29%48%19%29%11%
2040
21st to endNight
31%5%5%15%28%17%
2376
November1st to 10thNight
30%47%15%28%16%
2347
11th to 20thNight
33%35%15%28%16%
2470
21st to endNight
38%47%18%22%11%
2470
December1st to 10thNight
39%49%18%22%7%
2470
11th to 20thNight
39%35%15%28%9%
3044
21st to endNight
49%45%17%20%4
4532

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 10thDay
20%23%43%10%4
270
11th to 20thDay
19%21%38%15%6%1
270
21st to endDay
23%28%38%8%2
297
February1st to 10thDay
20%26%39%11%4
270
11th to 20thDay
28%18%39%14%1
270
21st to endDay
23%22%44%9%2
225
March1st to 10thDay
18%20%32%23%6%1
324
11th to 20thDay
17%16%41%17%9%1
449
21st to endDay
18%16%37%21%8%1
462
April1st to 10thDay
17%17%28%26%11%1
420
11th to 20thDay
16%14%32%23%13%2
412
21st to endDay
10%10%30%30%16%4
420
May1st to 10thDay
8%13%25%30%20%5%
423
11th to 20thDay
9%321%32%24%11%
447
21st to endDay
12%414%31%28%12%
485
June1st to 10thDay
12%214%32%26%13%
450
11th to 20thDay
8%313%27%28%21%
450
21st to endDay
6%116%30%30%17%
450
July1st to 10thDay
8%27%25%33%26%
445
11th to 20thDay
7%15%20%35%30%
444
21st to endDay
5%27%24%36%25%
488
August1st to 10thDay
11%19%28%32%20%
446
11th to 20thDay
9%16%25%34%24%
439
21st to endDay
13%38%28%30%17%
495
September1st to 10thDay
8%313%26%34%15%
450
11th to 20thDay
14%214%34%26%9%
450
21st to endDay
15%314%27%29%11%
450
October1st to 10thDay
14%428%28%19%6%
450
11th to 20thDay
12%7%20%33%20%7%
450
21st to endDay
15%9%27%27%19%3
495
November1st to 10thDay
17%8%26%32%13%4
324
11th to 20thDay
14%17%39%23%6%2
270
21st to endDay
14%13%39%24%9%1
270
December1st to 10thDay
23%18%32%22%41
270
11th to 20thDay
25%19%34%16%6%
270
21st to endDay
26%14%32%23%5%1
297
January1st to 10thNight
19%16%35%24%5%
760
11th to 20thNight
19%14%28%29%9%
760
21st to endNight
21%16%37%23%4
836
February1st to 10thNight
18%11%33%30%8%
760
11th to 20thNight
22%13%33%27%5%
743
21st to endNight
18%14%39%27%3
628
March1st to 10thNight
15%14%31%32%7%
760
11th to 20thNight
15%13%33%27%11%1
752
21st to endNight
14%14%32%29%11%
792
April1st to 10thNight
13%10%32%33%12%
697
11th to 20thNight
15%10%29%29%16%1
533
21st to endNight
7%7%29%36%21%1
540
May1st to 10thNight
8%8%26%36%20%2
540
11th to 20thNight
9%224%35%24%6%
531
21st to endNight
10%115%34%36%5%
584
June1st to 10thNight
9%214%36%34%5%
540
11th to 20thNight
429%33%39%14%
540
21st to endNight
6%28%36%39%10%
540
July1st to 10thNight
8%25%27%41%17%
525
11th to 20thNight
9%1323%47%17%
522
21st to endNight
425%28%49%13%
591
August1st to 10thNight
8%17%27%42%14%
537
11th to 20thNight
11%15%25%46%13%
534
21st to endNight
14%211%23%36%14%
594
September1st to 10thNight
10%211%27%39%10%
702
11th to 20thNight
13%214%34%31%6%
720
21st to endNight
10%116%33%35%4
720
October1st to 10thNight
12%323%34%23%5%
720
11th to 20thNight
13%422%31%27%3
720
21st to endNight
14%9%22%31%23%2
792
November1st to 10thNight
12%8%24%34%20%2
740
11th to 20thNight
15%10%31%31%12%1
760
21st to endNight
16%10%29%31%13%1
760
December1st to 10thNight
17%10%32%29%11%1
760
11th to 20thNight
19%10%32%29%9%1
760
21st to endNight
25%12%26%28%8%
836
Page generated at 2024-03-15 14:01:46. Version ac07

Copyright © 2024 Attilla Danko.


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