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

2017-09-12
.

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
60%
15712
28%
46924
22%
15674
67%
15674
38%
25979

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%
716
30%
2327
28%
716
67%
716
41%
1197
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%
530
25%
1766
27%
530
73%
530
30%
1050
September16th to endNight
74%
650
37%
1834
28%
650
79%
650
54%
914
October1st to 15thNight
64%
660
33%
1980
24%
660
70%
660
46%
1016
October16th to endNight
67%
704
38%
2112
27%
704
76%
704
51%
1025
November1st to 15thNight
68%
700
36%
2100
28%
700
73%
700
46%
1064
November16th to endNight
59%
882
34%
2472
23%
882
67%
882
47%
1277
December1st to 15thNight
53%
900
25%
2520
18%
900
59%
900
37%
1477
December16th to endNight
48%
909
23%
2637
18%
909
53%
909
28%
1663

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%
47722
Night
5%5%24424446%56%
47119
TransparencyDay
28%49%19%24%12%
47417
Night
28%48%20%24%13%
46925
SeeingDay
10%12%26%32%14%3
5485
Night
9%5%18%35%26%5%
15722

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%1332334458%
1611
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%5%6%7%48%
2113
16th to endDay
433423335%66%
1793
October1st to 15thDay
7%313323346%59%
1650
16th to endDay
3323313235%67%
1760
November1st to 15thDay
4313322336%64%
1759
16th to endDay
45%1231333367%
1471
December1st to 15thDay
8%8%15%323335%52%
1440
16th to endDay
9%10%46%413346%46%
1596
January1st to 15thNight
6%7%23212235%62%
2327
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%45%
1766
16th to endNight
331232232469%
1834
October1st to 15thNight
5%21232335%5%63%
1980
16th to endNight
331331233469%
2112
November1st to 15thNight
4423213346%63%
2100
16th to endNight
5%6%12212325%65%
2472
December1st to 15thNight
8%7%24323335%55%
2520
16th to endNight
9%11%35%323335%48%
2637

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%415%33%16%1
1612
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%14%20%16%
2113
16th to endDay
20%46%14%32%21%
1793
October1st to 15thDay
24%37%20%32%11%
1650
16th to endDay
20%36%21%38%10%
1760
November1st to 15thDay
20%38%24%34%8%
1759
16th to endDay
22%27%31%27%7%
1471
December1st to 15thDay
34%413%30%15%1
1440
16th to endDay
40%5%16%23%12%1
1596
January1st to 15thNight
26%311%32%24%3
2327
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
34%7%8%14%15%19%
1766
16th to endNight
20%26%13%31%26%
1834
October1st to 15thNight
23%36%19%28%18%
1980
16th to endNight
18%35%17%39%14%
2112
November1st to 15thNight
22%36%21%33%12%
2100
16th to endNight
22%26%26%30%11%
2472
December1st to 15thNight
30%411%29%20%3
2520
16th to endNight
39%412%26%15%1
2637

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
40%324%23%7%1
90
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%432%39%12%3
300
16th to endDay
8%8%27%36%11%7%
230
October1st to 15thDay
310%31%25%20%10%
90
16th to endDay
7%10%40%23%14%3
96
November1st to 15thDay
7%12%13%36%28%1
90
16th to endDay
20%20%31%18%10%
90
December1st to 15thDay
15%14%26%37%5%
90
16th to endDay
25%10%18%31%13%1
96
January1st to 15thNight
11%417%37%24%5%
720
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%39%36%5%
530
16th to endNight
6%212%33%33%11%
650
October1st to 15thNight
7%419%39%22%5%
660
16th to endNight
45%16%36%30%7%
704
November1st to 15thNight
8%414%38%27%6%
700
16th to endNight
10%7%19%31%23%6%
882
December1st to 15thNight
12%6%21%38%18%2
900
16th to endNight
16%7%19%35%18%2
909
Page generated at 2017-09-13 05:39:05. Version ac04

Copyright 2017 A. Danko


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