Allan & Kay Poage Memorial Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Allan & Kay Poage Memorial Observatory clear sky chart from 2005-11-05 to 2018-03-11.

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%
16330
29%
49067
19%
16286
58%
16286
38%
26921

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
38%
972
30%
2522
12%
970
49%
970
39%
1476
January16th to endNight
36%
1040
34%
2704
13%
1040
49%
1040
39%
1577
February1st to 15thNight
33%
832
26%
2359
11%
828
44%
828
32%
1392
February16th to endNight
23%
661
28%
2027
9%
661
39%
661
29%
1175
March1st to 15thNight
32%
573
27%
2101
15%
573
46%
573
26%
1199
March16th to endNight
32%
576
25%
2112
14%
576
47%
576
28%
1161
April1st to 15thNight
31%
539
26%
1971
14%
539
50%
539
31%
1017
April16th to endNight
34%
540
27%
1719
16%
540
50%
540
34%
958
May1st to 15thNight
35%
540
23%
1620
14%
540
49%
540
31%
965
May16th to endNight
47%
563
26%
1684
21%
561
58%
561
39%
944
June1st to 15thNight
67%
540
25%
1620
24%
540
75%
540
53%
780
June16th to endNight
69%
540
26%
1620
27%
540
73%
540
46%
830
July1st to 15thNight
73%
510
25%
1530
26%
510
78%
510
48%
784
July16th to endNight
85%
564
31%
1594
36%
531
88%
531
57%
750
August1st to 15thNight
88%
539
37%
1610
44%
536
88%
536
61%
731
August16th to endNight
77%
573
28%
1883
32%
573
80%
573
40%
995
September1st to 15thNight
71%
540
23%
1980
27%
540
72%
540
35%
1028
September16th to endNight
71%
537
35%
1980
35%
537
76%
537
40%
963
October1st to 15thNight
59%
623
34%
2063
26%
623
66%
623
43%
1026
October16th to endNight
51%
768
38%
2304
22%
768
63%
768
47%
1150
November1st to 15thNight
48%
770
30%
2290
17%
770
58%
770
40%
1253
November16th to endNight
41%
975
35%
2535
16%
975
52%
975
40%
1477
December1st to 15thNight
36%
975
31%
2535
13%
975
47%
975
36%
1561
December16th to endNight
34%
1040
27%
2704
12%
1040
43%
1040
32%
1729

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%424323447%50%
49553
Night
10%413313347%56%
49264
TransparencyDay
33%49%23%21%7%
49253
Night
28%39%23%23%10%
49069
SeeingDay
11%6%21%29%24%7%
6104
Night
12%7%28%34%16%1
16333

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%5%13312225%55%
1746
16th to endDay
14%413213235%55%
1872
February1st to 15thDay
15%6%25%31322451%
1843
16th to endDay
20%5%13321235%49%
1731
March1st to 15thDay
19%424423435%46%
2095
16th to endDay
14%6%34333335%48%
2110
April1st to 15thDay
12%425%32335%7%48%
1977
16th to endDay
14%5%2332445%7%46%
2238
May1st to 15thDay
15%5%34424446%42%
2331
16th to endDay
11%5%345%35%5%6%8%40%
2430
June1st to 15thDay
5%3145%245%5%7%53%
2340
16th to endDay
7%3145%2445%8%51%
2340
July1st to 15thDay
6%324435%5%6%9%47%
2340
16th to endDay
3313436%6%6%11%50%
2466
August1st to 15thDay
31133245%7%8%59%
2340
16th to endDay
6%4145%36%7%7%10%41%
2313
September1st to 15thDay
11%31342446%6%50%
1980
16th to endDay
8%314323447%54%
1980
October1st to 15thDay
10%313224346%57%
1884
16th to endDay
9%3221222466%
1920
November1st to 15thDay
10%324323436%54%
1895
16th to endDay
12%42321233459%
1755
December1st to 15thDay
17%5%2431233450%
1755
16th to endDay
19%6%24312346%46%
1872
January1st to 15thNight
12%413312235%58%
2522
16th to endNight
13%42221324459%
2704
February1st to 15thNight
14%42331323456%
2350
16th to endNight
16%5%24312135%53%
2027
March1st to 15thNight
16%5%1421335%6%48%
2101
16th to endNight
11%414314346%54%
2112
April1st to 15thNight
9%323314448%54%
1971
16th to endNight
12%423223346%54%
1719
May1st to 15thNight
10%42441445%7%49%
1619
16th to endNight
7%414325%26%9%51%
1683
June1st to 15thNight
421132235%9%64%
1620
16th to endNight
321342445%10%57%
1620
July1st to 15thNight
421232445%11%56%
1620
16th to endNight
21222346%11%61%
1702
August1st to 15thNight
121222349%68%
1620
16th to endNight
5%3143245%6%11%50%
1883
September1st to 15thNight
10%41332345%7%53%
1980
16th to endNight
7%412323448%58%
1980
October1st to 15thNight
9%313313246%61%
2063
16th to endNight
9%31211222368%
2304
November1st to 15thNight
7%41432323460%
2290
16th to endNight
11%323212335%58%
2535
December1st to 15thNight
14%5%24313336%52%
2535
16th to endNight
15%6%24322346%48%
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
32%27%21%28%7%
1747
16th to endDay
32%25%19%30%10%
1872
February1st to 15thDay
38%25%22%22%8%
1844
16th to endDay
39%26%20%20%11%
1731
March1st to 15thDay
41%26%18%22%8%
2095
16th to endDay
39%39%19%21%6%
2112
April1st to 15thDay
35%49%22%17%10%
1977
16th to endDay
37%48%19%24%6%
2238
May1st to 15thDay
41%48%17%20%7%
2331
16th to endDay
40%5%12%20%17%2
2434
June1st to 15thDay
28%5%13%29%19%3
2340
16th to endDay
30%411%28%20%4
2340
July1st to 15thDay
29%6%14%32%15%1
2201
16th to endDay
25%7%18%32%15%
2311
August1st to 15thDay
20%5%13%33%23%2
2326
16th to endDay
32%8%16%27%12%2
2313
September1st to 15thDay
32%411%25%19%7%
1980
16th to endDay
29%47%24%25%8%
1980
October1st to 15thDay
28%310%22%19%15%
1884
16th to endDay
23%26%18%30%18%
1920
November1st to 15thDay
31%310%23%22%8%
1895
16th to endDay
29%2420%30%11%
1755
December1st to 15thDay
38%26%20%25%6%
1755
16th to endDay
40%26%22%20%6%
1872
January1st to 15thNight
30%17%18%28%11%
2522
16th to endNight
30%25%18%29%14%
2704
February1st to 15thNight
33%37%17%24%13%
2360
16th to endNight
34%38%19%21%13%
2027
March1st to 15thNight
36%48%16%21%12%
2101
16th to endNight
32%410%20%25%6%
2112
April1st to 15thNight
28%410%23%18%14%
1971
16th to endNight
31%39%21%23%10%
1719
May1st to 15thNight
33%5%11%19%20%9%
1620
16th to endNight
28%417%26%18%4
1685
June1st to 15thNight
17%413%35%23%6%
1620
16th to endNight
22%413%28%25%6%
1620
July1st to 15thNight
21%414%37%18%4
1530
16th to endNight
14%5%19%37%20%2
1594
August1st to 15thNight
14%312%33%30%6%
1610
16th to endNight
25%5%14%31%18%4
1883
September1st to 15thNight
29%411%23%21%10%
1980
16th to endNight
24%38%23%26%11%
1980
October1st to 15thNight
24%310%24%20%17%
2063
16th to endNight
22%2317%30%23%
2304
November1st to 15thNight
28%27%23%24%12%
2290
16th to endNight
29%35%15%32%13%
2535
December1st to 15thNight
35%28%19%22%10%
2535
16th to endNight
38%27%21%20%9%
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
17%11%41%22%7%
135
16th to endDay
11%13%43%20%8%2
144
February1st to 15thDay
11%18%44%21%3
135
16th to endDay
32%15%36%12%2
120
March1st to 15thDay
23%19%35%16%3
121
16th to endDay
10%17%37%22%10%1
96
April1st to 15thDay
12%17%30%27%12%
96
16th to endDay
18%14%31%26%8%
348
May1st to 15thDay
14%12%37%25%7%2
468
16th to endDay
15%6%32%26%16%2
517
June1st to 15thDay
6%214%43%24%8%
495
16th to endDay
6%213%37%28%10%
495
July1st to 15thDay
7%12%36%33%9%
475
16th to endDay
21325%50%15%
515
August1st to 15thDay
4335%44%12%
493
16th to endDay
11%17%32%34%12%
353
September1st to 15thDay
2225%48%20%
135
16th to endDay
8%428%42%15%
135
October1st to 15thDay
1221%31%33%9%
135
16th to endDay
11%8%17%39%20%3
144
November1st to 15thDay
21%230%28%12%4
135
16th to endDay
17%14%30%25%9%2
135
December1st to 15thDay
23%5%31%22%11%4
135
16th to endDay
24%15%35%20%3
144
January1st to 15thNight
14%11%31%33%9%
975
16th to endNight
15%11%34%31%6%
1040
February1st to 15thNight
17%11%34%30%5%
832
16th to endNight
17%14%40%22%3
661
March1st to 15thNight
19%9%35%30%5%
573
16th to endNight
11%12%42%27%6%
576
April1st to 15thNight
9%13%42%28%5%
539
16th to endNight
14%8%39%28%8%
540
May1st to 15thNight
10%6%42%30%7%1
540
16th to endNight
8%5%32%36%16%1
563
June1st to 15thNight
5%120%46%24%2
540
16th to endNight
3117%45%28%3
540
July1st to 15thNight
414%45%31%3
510
16th to endNight
26%46%38%4
564
August1st to 15thNight
2447%39%6%
539
16th to endNight
7%6%38%39%6%
573
September1st to 15thNight
11%18%38%35%4
540
16th to endNight
8%112%37%35%4
537
October1st to 15thNight
10%224%32%27%3
623
16th to endNight
11%6%28%33%19%1
768
November1st to 15thNight
9%5%31%34%16%1
770
16th to endNight
14%9%31%30%12%1
975
December1st to 15thNight
17%8%34%32%7%
975
16th to endNight
19%9%32%31%6%
1040
Page generated at 2018-03-12 12:28:03. Version ac04

Copyright 2018 A. Danko


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