McElmo Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the McElmo Creek Observatory clear sky chart from 2005-11-05 to 2018-01-12.

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
61%
16235
29%
48458
23%
16197
67%
16197
39%
26703

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
62%
760
29%
2471
27%
760
68%
760
41%
1274
January16th to endNight
57%
768
32%
2496
30%
768
65%
768
37%
1330
February1st to 15thNight
55%
700
27%
2288
23%
699
64%
699
37%
1218
February16th to endNight
48%
632
32%
1902
22%
632
59%
632
36%
1074
March1st to 15thNight
54%
720
30%
1980
20%
720
63%
720
40%
1133
March16th to endNight
53%
768
27%
2112
17%
768
60%
768
36%
1253
April1st to 15thNight
46%
566
25%
1825
16%
566
58%
566
30%
1031
April16th to endNight
45%
540
30%
1800
21%
540
60%
540
34%
932
May1st to 15thNight
53%
539
27%
1623
19%
539
60%
539
37%
897
May16th to endNight
54%
562
25%
1646
18%
561
60%
561
37%
918
June1st to 15thNight
68%
540
31%
1440
24%
540
72%
540
55%
724
June16th to endNight
77%
540
31%
1455
26%
540
81%
540
58%
729
July1st to 15thNight
69%
510
15%
1530
12%
510
70%
510
28%
958
July16th to endNight
72%
564
17%
1593
16%
531
72%
531
25%
1052
August1st to 15thNight
76%
539
19%
1611
19%
536
76%
536
32%
990
August16th to endNight
76%
573
26%
1875
28%
573
77%
573
35%
1057
September1st to 15thNight
70%
540
25%
1800
27%
540
73%
540
30%
1063
September16th to endNight
73%
710
38%
2001
29%
710
78%
710
52%
1011
October1st to 15thNight
64%
720
32%
2160
24%
720
70%
720
49%
1078
October16th to endNight
67%
768
40%
2304
29%
768
76%
768
51%
1112
November1st to 15thNight
68%
760
35%
2280
28%
760
73%
760
47%
1155
November16th to endNight
60%
956
36%
2679
25%
956
68%
956
48%
1370
December1st to 15thNight
55%
975
25%
2730
19%
975
60%
975
38%
1573
December16th to endNight
50%
985
24%
2857
19%
985
54%
985
30%
1771

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
5%5%2442445%7%54%
48866
Night
5%5%24323446%57%
48653
TransparencyDay
28%49%19%24%12%
48561
Night
27%48%21%24%13%
48459
SeeingDay
10%12%26%32%14%3
5867
Night
9%5%18%35%26%4
16245

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
7%7%1332334457%
1710
16th to endDay
7%11%24313235%54%
1728
February1st to 15thDay
410%25%5%24326%52%
1575
16th to endDay
6%10%25%5%3443448%
1569
March1st to 15thDay
6%7%2432435%6%52%
1980
16th to endDay
5%5%35%424447%51%
2112
April1st to 15thDay
5%6%35%5%24446%50%
2123
16th to endDay
45%1442445%7%54%
2160
May1st to 15thDay
44245%35%45%7%51%
2325
16th to endDay
431342345%7%58%
2465
June1st to 15thDay
3213222346%66%
2520
16th to endDay
11222335%6%71%
2500
July1st to 15thDay
32145%36%6%7%9%47%
2340
16th to endDay
6%425%6%46%7%8%10%35%
2467
August1st to 15thDay
5%5%15%6%37%7%6%8%41%
2340
16th to endDay
32246%35%7%7%10%45%
2325
September1st to 15thDay
6%3245%36%46%7%48%
2160
16th to endDay
433423335%66%
1956
October1st to 15thDay
6%313323346%62%
1800
16th to endDay
3313313235%68%
1920
November1st to 15thDay
4313322337%64%
1909
16th to endDay
441231333367%
1593
December1st to 15thDay
8%8%14313345%54%
1560
16th to endDay
8%9%46%423346%46%
1729
January1st to 15thNight
6%7%23213235%61%
2471
16th to endNight
8%6%2332323459%
2496
February1st to 15thNight
48%33313335%58%
2277
16th to endNight
6%6%24414336%54%
1902
March1st to 15thNight
5%5%24423446%56%
1980
16th to endNight
6%6%24423446%52%
2112
April1st to 15thNight
8%5%23425%448%49%
1825
16th to endNight
5%42343334459%
1800
May1st to 15thNight
45%25%32335%8%55%
1623
16th to endNight
7%324414346%57%
1645
June1st to 15thNight
3212213335%69%
1440
16th to endNight
2122225%5%6%67%
1455
July1st to 15thNight
2226%6%47%7%7%9%43%
1620
16th to endNight
3336%7%48%8%7%10%34%
1701
August1st to 15thNight
3326%5%45%7%7%8%46%
1620
16th to endNight
3314445%6%8%9%47%
1875
September1st to 15thNight
4326%6%45%6%6%8%46%
1800
16th to endNight
421232232469%
2001
October1st to 15thNight
5%21232335%5%65%
2160
16th to endNight
3313312335%69%
2304
November1st to 15thNight
5%422213346%63%
2280
16th to endNight
6%5%12212325%66%
2679
December1st to 15thNight
7%7%24323335%57%
2730
16th to endNight
8%10%35%313335%49%
2857

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
29%414%32%16%1
1711
16th to endDay
34%311%26%21%3
1728
February1st to 15thDay
34%413%24%18%4
1575
16th to endDay
39%36%20%28%2
1569
March1st to 15thDay
30%37%27%25%4
1980
16th to endDay
32%28%21%28%6%
2112
April1st to 15thDay
33%37%18%24%11%
2123
16th to endDay
28%46%21%26%11%
2160
May1st to 15thDay
30%48%17%29%9%
2325
16th to endDay
24%48%15%32%15%
2468
June1st to 15thDay
19%25%10%27%34%
2520
16th to endDay
13%25%10%23%44%
2500
July1st to 15thDay
27%8%14%13%15%20%
2201
16th to endDay
34%10%16%18%11%8%
2312
August1st to 15thDay
34%8%12%14%16%13%
2325
16th to endDay
29%7%12%18%20%11%
2325
September1st to 15thDay
32%6%9%15%20%16%
2160
16th to endDay
20%47%14%31%21%
1956
October1st to 15thDay
23%37%19%33%13%
1800
16th to endDay
20%36%21%37%11%
1920
November1st to 15thDay
20%38%25%34%7%
1909
16th to endDay
21%37%31%28%7%
1593
December1st to 15thDay
32%413%29%16%3
1560
16th to endDay
39%5%16%23%14%1
1729
January1st to 15thNight
26%311%31%24%3
2471
16th to endNight
29%27%31%24%4
2496
February1st to 15thNight
29%312%27%19%7%
2288
16th to endNight
31%37%20%33%4
1902
March1st to 15thNight
29%25%28%27%6%
1980
16th to endNight
31%36%19%29%8%
2112
April1st to 15thNight
32%36%19%23%13%
1825
16th to endNight
27%3419%29%14%
1800
May1st to 15thNight
28%47%17%31%10%
1624
16th to endNight
28%48%15%26%16%
1646
June1st to 15thNight
17%349%26%38%
1440
16th to endNight
15%45%9%20%44%
1455
July1st to 15thNight
34%9%12%11%10%21%
1530
16th to endNight
40%8%14%15%11%9%
1593
August1st to 15thNight
31%10%13%12%14%17%
1611
16th to endNight
29%6%12%19%18%13%
1875
September1st to 15thNight
33%6%8%15%15%19%
1800
16th to endNight
20%26%13%30%25%
2001
October1st to 15thNight
21%26%19%29%20%
2160
16th to endNight
18%35%17%39%16%
2304
November1st to 15thNight
22%36%22%33%11%
2280
16th to endNight
22%25%27%31%11%
2679
December1st to 15thNight
29%410%28%20%6%
2730
16th to endNight
38%312%26%17%1
2857

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
30%5%27%24%9%1
123
16th to endDay
20%7%25%27%15%4
96
February1st to 15thDay
13%8%23%36%17%
90
16th to endDay
14%22%29%23%9%
127
March1st to 15thDay
14%22%29%24%8%
270
16th to endDay
11%31%32%17%6%
288
April1st to 15thDay
13%27%31%17%7%1
269
16th to endDay
19%30%31%14%3
270
May1st to 15thDay
13%19%39%20%6%
288
16th to endDay
10%17%29%27%11%2
366
June1st to 15thDay
6%9%22%35%21%4
495
16th to endDay
2423%42%19%7%
475
July1st to 15thDay
5%418%50%19%2
305
16th to endDay
6%217%46%22%5%
327
August1st to 15thDay
9%317%46%20%3
315
16th to endDay
5%326%40%20%2
332
September1st to 15thDay
8%431%38%13%3
315
16th to endDay
9%11%28%34%10%6%
288
October1st to 15thDay
7%15%28%21%18%8%
135
16th to endDay
6%11%32%27%18%3
144
November1st to 15thDay
8%12%20%36%22%
135
16th to endDay
14%14%29%26%12%1
135
December1st to 15thDay
11%12%25%40%9%1
135
16th to endDay
17%9%21%34%15%1
144
January1st to 15thNight
10%417%38%24%5%
764
16th to endNight
13%5%19%34%20%6%
768
February1st to 15thNight
9%5%24%38%19%2
704
16th to endNight
13%6%26%36%14%1
632
March1st to 15thNight
9%5%24%34%22%3
720
16th to endNight
10%9%21%35%19%2
768
April1st to 15thNight
12%13%22%34%15%1
566
16th to endNight
10%13%25%31%17%1
540
May1st to 15thNight
8%7%25%37%18%2
540
16th to endNight
11%6%23%31%23%3
563
June1st to 15thNight
46%18%37%31%2
540
16th to endNight
2114%38%37%4
540
July1st to 15thNight
6%10%35%40%7%
510
16th to endNight
6%17%30%45%8%
564
August1st to 15thNight
46%29%47%11%
539
16th to endNight
4110%30%44%9%
573
September1st to 15thNight
5%112%38%36%6%
540
16th to endNight
6%213%34%31%10%
710
October1st to 15thNight
7%420%40%22%5%
720
16th to endNight
45%16%35%30%7%
768
November1st to 15thNight
8%415%39%26%6%
760
16th to endNight
10%7%18%33%24%6%
956
December1st to 15thNight
11%6%20%38%19%2
975
16th to endNight
15%7%19%37%19%2
985
Page generated at 2018-01-12 20:01:24. Version ac04

Copyright 2018 A. Danko


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