Moore Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Moore Observatory clear sky chart from 2005-11-05 to 2017-09-17.

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
45%
15613
20%
46753
15%
15569
51%
15569
26%
30344

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
23%
900
15%
2506
7%
895
30%
895
17%
1876
January16th to endNight
23%
793
17%
2513
9%
793
32%
793
17%
1773
February1st to 15thNight
24%
704
15%
2112
5%
701
32%
701
17%
1515
February16th to endNight
22%
631
15%
1893
7%
631
29%
631
18%
1360
March1st to 15thNight
27%
720
17%
2123
10%
720
32%
720
20%
1473
March16th to endNight
36%
753
15%
2097
8%
753
42%
753
21%
1476
April1st to 15thNight
37%
539
22%
1797
14%
539
49%
539
26%
1097
April16th to endNight
42%
540
21%
1694
13%
540
50%
540
25%
1108
May1st to 15thNight
41%
540
16%
1620
10%
540
47%
540
22%
1115
May16th to endNight
63%
561
19%
1684
15%
561
66%
561
30%
1056
June1st to 15thNight
70%
540
21%
1522
17%
540
72%
540
40%
894
June16th to endNight
72%
540
21%
1440
17%
540
74%
540
41%
841
July1st to 15thNight
64%
510
17%
1360
14%
510
65%
510
33%
864
July16th to endNight
75%
564
22%
1554
20%
531
78%
531
40%
884
August1st to 15thNight
79%
539
25%
1611
23%
536
80%
536
39%
907
August16th to endNight
78%
573
24%
1910
27%
573
78%
573
38%
1008
September1st to 15thNight
67%
633
26%
1893
23%
633
70%
633
35%
1113
September16th to endNight
60%
665
27%
1837
22%
665
63%
665
34%
1127
October1st to 15thNight
56%
660
33%
1815
26%
660
62%
660
39%
1057
October16th to endNight
43%
704
26%
2224
20%
704
52%
704
28%
1357
November1st to 15thNight
47%
700
28%
2276
23%
700
56%
700
31%
1316
November16th to endNight
36%
720
22%
2340
17%
720
43%
720
22%
1520
December1st to 15thNight
29%
720
14%
2340
9%
720
35%
720
16%
1678
December16th to endNight
22%
864
15%
2592
8%
864
30%
864
16%
1929

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
14%6%35%5%3445%7%39%
48006
Night
14%6%35%424447%41%
46934
Cloud CoverDay
14%6%35%5%3445%7%39%
48015
Night
14%6%25%424447%41%
46939
TransparencyDay
43%5%10%22%14%2
47705
Night
42%410%22%15%3
46753
SeeingDay
16%418%25%22%11%
5669
Night
18%6%23%30%18%2
15615

By Month

Percentage Cloud Cover NE (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
21%9%5%9%5%23345%30%
1432
16th to endDay
15%10%5%6%424445%34%
1705
February1st to 15thDay
16%10%5%9%413345%34%
1750
16th to endDay
15%11%37%6%35%45%6%31%
1580
March1st to 15thDay
22%8%25%422346%35%
1826
16th to endDay
17%8%35%6%4445%6%32%
2136
April1st to 15thDay
16%7%25%5%35%446%39%
2151
16th to endDay
17%5%35%5%3445%6%39%
2265
May1st to 15thDay
20%7%25%5%35%446%33%
2331
16th to endDay
10%5%26%6%46%6%6%8%35%
2431
June1st to 15thDay
8%425%5%35%5%5%8%44%
2434
16th to endDay
7%425%436%5%7%9%43%
2520
July1st to 15thDay
13%6%35%5%35%5%7%9%34%
2520
16th to endDay
7%4245%36%6%7%10%40%
2505
August1st to 15thDay
6%325%5%45%5%6%10%43%
2335
16th to endDay
7%5%25%5%35%6%6%8%43%
2292
September1st to 15thDay
13%5%25%42445%7%43%
2054
16th to endDay
13%42442335%6%47%
1829
October1st to 15thDay
11%5%24423346%50%
1815
16th to endDay
17%6%24323445%46%
1644
November1st to 15thDay
12%6%24424346%49%
1582
16th to endDay
18%9%24323435%41%
1620
December1st to 15thDay
24%10%46%42334431%
1620
16th to endDay
19%12%46%434345%30%
1629
January1st to 15thNight
18%11%48%5%2444430%
2506
16th to endNight
18%10%47%5%24435%33%
2513
February1st to 15thNight
20%9%36%5%25%445%32%
2110
16th to endNight
17%11%47%424445%32%
1893
March1st to 15thNight
17%9%45%5%33435%36%
2110
16th to endNight
17%8%36%434447%35%
2097
April1st to 15thNight
14%6%34423347%44%
1797
16th to endNight
13%7%35%434446%41%
1694
May1st to 15thNight
15%6%36%6%2446%6%35%
1620
16th to endNight
9%4145%35%6%6%9%41%
1682
June1st to 15thNight
5%325%43445%9%51%
1522
16th to endNight
6%213426%5%8%11%48%
1440
July1st to 15thNight
10%5%15%5%35%448%46%
1440
16th to endNight
6%2244246%6%9%50%
1661
August1st to 15thNight
5%223325%5%7%9%51%
1622
16th to endNight
4314325%5%6%10%49%
1910
September1st to 15thNight
12%32332445%8%49%
1893
16th to endNight
12%5%25%423346%50%
1837
October1st to 15thNight
8%424323447%53%
1815
16th to endNight
16%5%24423335%47%
2224
November1st to 15thNight
12%5%24323346%50%
2276
16th to endNight
19%8%25%434336%39%
2340
December1st to 15thNight
22%10%36%6%24345%31%
2340
16th to endNight
24%10%46%423346%28%
2592

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
21%9%49%43334431%
1432
16th to endDay
16%10%47%434446%33%
1705
February1st to 15thDay
16%10%5%9%5%13345%34%
1750
16th to endDay
15%11%47%6%35%35%5%31%
1580
March1st to 15thDay
23%8%25%422345%35%
1836
16th to endDay
17%8%36%6%35%46%6%32%
2135
April1st to 15thDay
16%7%245%34436%39%
2151
16th to endDay
17%5%35%5%2445%6%39%
2265
May1st to 15thDay
20%7%245%35%447%33%
2331
16th to endDay
10%5%26%6%46%6%6%8%35%
2431
June1st to 15thDay
9%425%6%35%5%5%8%44%
2434
16th to endDay
7%4245%35%6%7%9%43%
2520
July1st to 15thDay
13%6%345%35%5%6%10%34%
2520
16th to endDay
7%425%5%36%6%7%10%40%
2505
August1st to 15thDay
6%425%5%45%5%6%9%43%
2335
16th to endDay
7%5%25%5%35%6%6%8%43%
2292
September1st to 15thDay
13%5%25%42445%7%43%
2054
16th to endDay
14%43442335%6%47%
1829
October1st to 15thDay
11%424424346%50%
1815
16th to endDay
17%6%24323345%45%
1644
November1st to 15thDay
13%5%24324346%49%
1582
16th to endDay
18%9%24324336%41%
1620
December1st to 15thDay
24%9%47%5%2333431%
1620
16th to endDay
19%12%5%6%434335%30%
1629
January1st to 15thNight
18%11%5%8%5%2434430%
2506
16th to endNight
18%10%47%5%24345%33%
2513
February1st to 15thNight
20%8%36%5%25%445%32%
2103
16th to endNight
17%12%37%5%24445%32%
1893
March1st to 15thNight
17%9%36%5%34445%36%
2123
16th to endNight
17%8%36%435%446%35%
2097
April1st to 15thNight
15%6%35%323347%44%
1797
16th to endNight
14%6%35%434446%41%
1694
May1st to 15thNight
16%5%35%6%35%46%7%36%
1619
16th to endNight
9%315%5%35%6%7%9%42%
1682
June1st to 15thNight
5%325%43445%9%51%
1522
16th to endNight
6%313425%5%7%12%48%
1440
July1st to 15thNight
10%415%435%448%46%
1440
16th to endNight
6%3244245%6%9%50%
1661
August1st to 15thNight
5%323325%5%7%9%51%
1622
16th to endNight
4314435%47%10%50%
1910
September1st to 15thNight
12%3233245%5%8%49%
1893
16th to endNight
12%424323446%50%
1837
October1st to 15thNight
8%5%14423447%53%
1815
16th to endNight
16%6%24423345%47%
2224
November1st to 15thNight
13%5%24323346%50%
2276
16th to endNight
19%7%25%424336%39%
2340
December1st to 15thNight
22%10%36%5%34345%31%
2340
16th to endNight
24%10%46%423346%28%
2592

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
57%38%19%10%
1433
16th to endDay
50%410%26%7%1
1705
February1st to 15thDay
53%39%24%8%1
1752
16th to endDay
53%411%21%8%
1580
March1st to 15thDay
51%311%19%12%1
1836
16th to endDay
50%5%11%22%8%
2136
April1st to 15thDay
45%48%24%15%1
2151
16th to endDay
44%49%23%13%4
2265
May1st to 15thDay
50%6%11%19%11%
2331
16th to endDay
42%7%15%18%13%2
2435
June1st to 15thDay
36%6%12%24%17%2
2434
16th to endDay
33%7%12%22%19%3
2520
July1st to 15thDay
43%5%12%18%14%4
2371
16th to endDay
34%8%15%25%13%2
2349
August1st to 15thDay
35%7%12%23%19%2
2322
16th to endDay
34%6%12%23%17%4
2292
September1st to 15thDay
40%410%20%18%6%
2054
16th to endDay
38%38%21%25%2
1829
October1st to 15thDay
34%36%27%23%3
1815
16th to endDay
40%39%27%16%3
1644
November1st to 15thDay
36%27%26%19%7%
1582
16th to endDay
45%36%24%18%1
1620
December1st to 15thDay
57%39%19%8%1
1620
16th to endDay
56%310%20%7%
1629
January1st to 15thNight
56%48%17%12%1
2506
16th to endNight
53%39%22%9%1
2513
February1st to 15thNight
53%49%23%7%1
2112
16th to endNight
53%411%19%10%
1893
March1st to 15thNight
50%38%21%13%2
2123
16th to endNight
48%5%13%22%8%1
2097
April1st to 15thNight
39%49%22%20%3
1797
16th to endNight
43%48%23%13%6%
1694
May1st to 15thNight
46%6%11%22%11%1
1620
16th to endNight
35%7%13%22%15%4
1684
June1st to 15thNight
29%5%12%26%21%4
1522
16th to endNight
27%6%18%20%19%6%
1440
July1st to 15thNight
36%5%11%23%17%5%
1360
16th to endNight
26%6%15%28%18%2
1554
August1st to 15thNight
25%8%15%25%19%4
1611
16th to endNight
27%5%15%26%20%4
1910
September1st to 15thNight
31%6%10%23%20%6%
1893
16th to endNight
35%37%22%25%5%
1837
October1st to 15thNight
30%48%26%25%5%
1815
16th to endNight
39%36%27%18%4
2224
November1st to 15thNight
35%37%22%23%6%
2276
16th to endNight
46%37%22%17%1
2340
December1st to 15thNight
55%310%19%9%1
2340
16th to endNight
57%410%18%8%1
2592

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
32%8%35%15%6%1
90
16th to endDay
19%12%51%14%2
96
February1st to 15thDay
20%20%40%12%7%
90
16th to endDay
24%13%32%20%8%
81
March1st to 15thDay
23%11%36%20%7%
126
16th to endDay
21%8%32%26%9%2
288
April1st to 15thDay
22%10%22%27%14%2
270
16th to endDay
20%7%22%29%14%5%
270
May1st to 15thDay
25%6%22%22%15%7%
288
16th to endDay
16%219%26%20%14%
331
June1st to 15thDay
11%212%28%31%14%
409
16th to endDay
9%417%32%25%10%
495
July1st to 15thDay
19%211%27%26%12%
475
16th to endDay
8%6%22%35%26%
365
August1st to 15thDay
8%7%22%32%28%
313
16th to endDay
11%17%25%33%20%
332
September1st to 15thDay
16%211%22%30%16%
315
16th to endDay
17%211%20%30%16%
259
October1st to 15thDay
13%220%29%23%10%
255
16th to endDay
19%324%31%19%1
155
November1st to 15thDay
8%8%22%30%18%11%
90
16th to endDay
25%7%34%23%7%1
90
December1st to 15thDay
17%10%33%26%8%3
90
16th to endDay
31%13%41%10%3
96
January1st to 15thNight
24%12%33%25%5%
900
16th to endNight
25%10%35%25%2
793
February1st to 15thNight
26%8%32%30%1
704
16th to endNight
22%10%37%26%2
631
March1st to 15thNight
23%10%31%26%6%
720
16th to endNight
21%6%28%31%10%1
753
April1st to 15thNight
18%7%33%28%11%
539
16th to endNight
16%5%27%34%12%2
540
May1st to 15thNight
19%425%31%17%1
540
16th to endNight
12%112%40%25%6%
563
June1st to 15thNight
7%112%41%32%4
540
16th to endNight
6%11%42%34%4
540
July1st to 15thNight
13%19%31%40%4
510
16th to endNight
8%16%30%42%11%
564
August1st to 15thNight
6%15%35%43%8%
539
16th to endNight
6%15%35%44%6%
573
September1st to 15thNight
13%110%30%37%6%
633
16th to endNight
14%312%29%34%5%
665
October1st to 15thNight
12%320%33%23%6%
660
16th to endNight
19%5%26%33%14%
704
November1st to 15thNight
15%6%27%28%20%2
700
16th to endNight
22%10%25%30%10%
720
December1st to 15thNight
27%8%29%25%7%1
720
16th to endNight
31%9%30%23%3
864
Page generated at 2017-09-18 08:38:29. Version ac04

Copyright 2017 A. Danko


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