Morris Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Morris Observatory clear sky chart from 2005-11-05 to 2017-12-02.

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
38%
16175
17%
47735
11%
16132
44%
16132
23%
32294

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
17%
900
11%
2506
5%
895
23%
895
14%
1953
January16th to endNight
19%
927
11%
2655
5%
927
25%
927
13%
2060
February1st to 15thNight
21%
702
10%
2151
4%
701
27%
701
15%
1580
February16th to endNight
21%
631
15%
1893
6%
631
30%
631
16%
1371
March1st to 15thNight
27%
720
13%
2136
9%
720
31%
720
17%
1537
March16th to endNight
28%
729
16%
2073
7%
729
36%
729
20%
1464
April1st to 15thNight
31%
539
14%
1797
9%
539
40%
539
20%
1204
April16th to endNight
33%
540
22%
1668
11%
540
44%
540
25%
1073
May1st to 15thNight
36%
540
14%
1620
9%
540
42%
540
21%
1141
May16th to endNight
52%
562
16%
1618
12%
561
55%
561
28%
1031
June1st to 15thNight
54%
540
16%
1440
10%
540
59%
540
37%
879
June16th to endNight
57%
540
18%
1440
12%
540
62%
540
35%
911
July1st to 15thNight
64%
510
17%
1360
13%
510
66%
510
38%
833
July16th to endNight
70%
564
21%
1448
17%
531
72%
531
41%
838
August1st to 15thNight
70%
539
22%
1609
19%
536
72%
536
40%
879
August16th to endNight
69%
573
20%
1868
19%
573
72%
573
33%
1059
September1st to 15thNight
64%
614
27%
1874
24%
614
68%
614
36%
1067
September16th to endNight
60%
717
28%
1980
22%
717
64%
717
37%
1180
October1st to 15thNight
50%
720
26%
1993
19%
720
55%
720
32%
1221
October16th to endNight
30%
768
19%
2475
13%
768
39%
768
20%
1634
November1st to 15thNight
35%
760
23%
2471
16%
760
46%
760
25%
1529
November16th to endNight
27%
780
18%
2535
12%
780
36%
780
16%
1787
December1st to 15thNight
22%
800
9%
2437
4%
800
27%
800
13%
1864
December16th to endNight
14%
960
9%
2688
2%
960
20%
960
11%
2199

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%8%36%5%3445%7%34%
48713
Night
15%8%36%5%3445%6%37%
47907
Cloud CoverDay
15%8%36%5%35%45%7%35%
48722
Night
15%8%36%5%24446%37%
47912
TransparencyDay
47%5%12%20%12%1
48403
Night
46%411%21%13%1
47735
SeeingDay
16%6%25%24%18%8%
6139
Night
19%8%27%29%14%1
16178

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%16%48%6%3434421%
1432
16th to endDay
13%18%8%9%6%35%447%18%
1567
February1st to 15thDay
15%14%6%10%7%35%346%21%
1708
16th to endDay
16%13%6%9%5%34445%25%
1580
March1st to 15thDay
20%11%49%7%33446%23%
1814
16th to endDay
19%9%36%7%25%346%30%
2160
April1st to 15thDay
20%9%35%5%34446%31%
2151
16th to endDay
17%8%36%5%34446%35%
2292
May1st to 15thDay
20%7%37%5%36%446%29%
2331
16th to endDay
13%6%25%5%45%46%6%38%
2494
June1st to 15thDay
11%425%5%35%6%6%8%41%
2520
16th to endDay
9%425%6%35%6%7%10%38%
2520
July1st to 15thDay
8%5%25%5%35%5%6%8%43%
2520
16th to endDay
6%325%5%35%7%7%10%40%
2622
August1st to 15thDay
7%425%436%47%9%44%
2340
16th to endDay
9%4245%35%5%7%10%41%
2333
September1st to 15thDay
12%5%25%5%3445%6%44%
2073
16th to endDay
10%5%25%434448%46%
1980
October1st to 15thDay
15%6%26%5%2445%5%41%
1965
16th to endDay
20%7%26%5%2445%6%32%
1746
November1st to 15thDay
15%7%34424346%43%
1717
16th to endDay
19%11%5%7%5%23446%29%
1755
December1st to 15thDay
19%13%6%9%5%34345%23%
1557
16th to endDay
22%19%6%9%43433417%
1536
January1st to 15thNight
21%13%6%8%6%33435%24%
2506
16th to endNight
16%13%6%9%6%34445%24%
2655
February1st to 15thNight
16%13%6%7%5%23446%29%
2149
16th to endNight
16%11%5%7%6%34345%29%
1893
March1st to 15thNight
17%9%46%5%35%35%5%32%
2123
16th to endNight
15%8%47%5%35%447%34%
2073
April1st to 15thNight
18%6%25%435%5%5%7%33%
1797
16th to endNight
17%7%3442346%6%40%
1668
May1st to 15thNight
20%7%26%5%2436%6%31%
1620
16th to endNight
13%5%235%346%5%7%42%
1616
June1st to 15thNight
8%424425%447%50%
1440
16th to endNight
8%424435%5%7%9%44%
1440
July1st to 15thNight
6%4345%35%45%7%50%
1440
16th to endNight
5%324425%46%9%50%
1546
August1st to 15thNight
5%3244345%6%9%50%
1620
16th to endNight
8%3233345%6%7%50%
1868
September1st to 15thNight
10%3135%2435%6%53%
1874
16th to endNight
11%5%24324345%52%
1980
October1st to 15thNight
12%5%25%423346%48%
1993
16th to endNight
18%7%25%5%24445%38%
2475
November1st to 15thNight
14%7%35%43335%6%43%
2471
16th to endNight
19%11%36%5%33446%30%
2535
December1st to 15thNight
20%13%7%5%5%24345%25%
2437
16th to endNight
25%13%5%9%6%3434419%
2688

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%15%48%6%3434421%
1432
16th to endDay
13%18%9%8%6%26%45%6%19%
1567
February1st to 15thDay
15%14%7%10%6%35%346%21%
1708
16th to endDay
16%14%5%9%5%34445%25%
1580
March1st to 15thDay
21%11%48%7%34446%24%
1824
16th to endDay
19%9%36%7%24346%30%
2159
April1st to 15thDay
20%9%35%425%446%32%
2151
16th to endDay
18%8%36%433446%36%
2292
May1st to 15thDay
20%7%36%5%36%446%30%
2331
16th to endDay
14%5%25%5%45%5%5%6%39%
2494
June1st to 15thDay
11%424435%6%6%8%42%
2520
16th to endDay
9%425%6%36%5%7%9%38%
2520
July1st to 15thDay
8%5%25%5%35%5%6%8%43%
2520
16th to endDay
6%325%5%45%6%7%10%40%
2622
August1st to 15thDay
7%415%436%5%6%9%45%
2340
16th to endDay
9%4245%35%5%7%9%42%
2333
September1st to 15thDay
12%5%25%5%25%446%45%
2073
16th to endDay
11%425%434448%46%
1980
October1st to 15thDay
15%6%26%5%2445%6%41%
1965
16th to endDay
20%7%26%6%3445%6%32%
1746
November1st to 15thDay
15%7%24424346%42%
1717
16th to endDay
19%11%5%6%5%24446%29%
1755
December1st to 15thDay
19%14%6%9%6%34345%23%
1557
16th to endDay
22%19%6%9%5%2434417%
1536
January1st to 15thNight
21%12%6%8%6%33445%24%
2506
16th to endNight
16%13%6%9%6%34345%25%
2655
February1st to 15thNight
16%13%6%7%5%23436%29%
2142
16th to endNight
16%11%5%8%5%44345%29%
1893
March1st to 15thNight
18%10%47%5%35%34432%
2136
16th to endNight
15%8%37%5%34447%34%
2073
April1st to 15thNight
18%6%25%5%35%5%6%7%34%
1797
16th to endNight
17%7%2442345%6%40%
1668
May1st to 15thNight
21%6%36%5%3436%6%32%
1619
16th to endNight
13%4235%346%5%8%42%
1616
June1st to 15thNight
8%5%25%425%446%50%
1440
16th to endNight
9%425%5%25%5%7%9%44%
1440
July1st to 15thNight
7%425%425%447%50%
1440
16th to endNight
5%324425%46%9%51%
1546
August1st to 15thNight
6%3234245%6%9%50%
1620
16th to endNight
8%32343446%7%51%
1868
September1st to 15thNight
10%3135%24347%53%
1874
16th to endNight
11%424323445%52%
1980
October1st to 15thNight
12%5%15%43335%6%48%
1993
16th to endNight
19%6%25%5%24345%38%
2475
November1st to 15thNight
15%7%3442335%6%43%
2471
16th to endNight
19%10%36%5%23447%30%
2535
December1st to 15thNight
20%13%6%5%6%34345%25%
2437
16th to endNight
25%13%6%8%6%34345%19%
2688

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
65%411%12%5%
1433
16th to endDay
64%413%11%5%
1567
February1st to 15thDay
63%310%14%6%
1710
16th to endDay
60%5%11%18%4
1580
March1st to 15thDay
61%411%14%6%
1824
16th to endDay
54%314%20%5%1
2160
April1st to 15thDay
52%410%21%11%
2151
16th to endDay
48%412%18%11%4
2292
May1st to 15thDay
54%411%19%8%
2331
16th to endDay
43%6%11%22%14%2
2498
June1st to 15thDay
38%5%11%24%17%1
2520
16th to endDay
39%6%15%20%16%1
2520
July1st to 15thDay
37%5%11%23%18%3
2371
16th to endDay
33%8%15%24%14%2
2457
August1st to 15thDay
33%7%15%26%15%2
2327
16th to endDay
35%6%13%23%16%4
2333
September1st to 15thDay
39%5%10%22%17%3
2073
16th to endDay
36%310%27%20%1
1980
October1st to 15thDay
43%410%23%16%1
1965
16th to endDay
50%313%21%10%
1746
November1st to 15thDay
41%410%23%17%1
1717
16th to endDay
55%412%20%6%
1755
December1st to 15thDay
64%311%16%3
1557
16th to endDay
71%310%11%3
1536
January1st to 15thNight
61%310%15%8%
2506
16th to endNight
61%312%16%5%
2655
February1st to 15thNight
56%413%16%7%
2151
16th to endNight
55%312%19%8%
1893
March1st to 15thNight
54%312%18%9%1
2136
16th to endNight
50%5%11%22%8%1
2073
April1st to 15thNight
46%5%11%20%14%1
1797
16th to endNight
43%410%22%16%4
1668
May1st to 15thNight
51%312%21%9%1
1620
16th to endNight
38%6%13%22%15%3
1618
June1st to 15thNight
33%413%26%20%1
1440
16th to endNight
33%7%16%23%16%3
1440
July1st to 15thNight
32%413%24%20%4
1360
16th to endNight
27%6%15%25%19%4
1448
August1st to 15thNight
27%415%28%21%2
1609
16th to endNight
30%7%12%22%22%5%
1868
September1st to 15thNight
30%410%27%20%5%
1874
16th to endNight
33%38%27%24%2
1980
October1st to 15thNight
36%48%27%21%1
1993
16th to endNight
46%39%25%12%1
2475
November1st to 15thNight
41%39%23%18%2
2471
16th to endNight
53%312%22%8%
2535
December1st to 15thNight
60%411%16%7%
2437
16th to endNight
68%310%12%4
2688

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
27%13%40%11%5%2
90
16th to endDay
23%13%39%19%3
96
February1st to 15thDay
18%23%38%17%1
90
16th to endDay
18%14%35%19%8%2
81
March1st to 15thDay
35%14%28%18%4
114
16th to endDay
28%8%30%20%9%2
288
April1st to 15thDay
22%9%34%19%13%
270
16th to endDay
21%9%28%22%12%5%
270
May1st to 15thDay
26%8%26%23%11%3
288
16th to endDay
17%5%27%22%18%8%
394
June1st to 15thDay
13%426%30%17%7%
495
16th to endDay
12%6%32%23%18%7%
495
July1st to 15thDay
11%226%27%20%12%
475
16th to endDay
7%214%30%27%17%
482
August1st to 15thDay
9%27%30%29%20%
313
16th to endDay
12%313%23%28%18%
332
September1st to 15thDay
13%314%23%30%14%
315
16th to endDay
12%412%21%36%12%
314
October1st to 15thDay
17%5%21%29%19%6%
315
16th to endDay
25%6%31%30%5%
162
November1st to 15thDay
19%8%26%22%18%5%
135
16th to endDay
23%16%38%16%5%
135
December1st to 15thDay
23%11%37%15%11%
94
16th to endDay
28%20%43%5%2
96
January1st to 15thNight
27%14%32%20%3
900
16th to endNight
20%14%35%24%4
927
February1st to 15thNight
24%10%37%24%4
704
16th to endNight
21%12%37%23%4
631
March1st to 15thNight
22%10%32%27%6%
720
16th to endNight
19%9%36%26%7%
729
April1st to 15thNight
20%10%34%27%5%
539
16th to endNight
21%6%33%26%9%1
540
May1st to 15thNight
24%428%31%11%
540
16th to endNight
15%321%40%17%1
563
June1st to 15thNight
10%224%43%18%
540
16th to endNight
11%222%38%24%1
540
July1st to 15thNight
10%215%44%25%2
510
16th to endNight
6%112%39%36%3
564
August1st to 15thNight
7%12%42%30%5%
539
16th to endNight
9%112%32%38%4
573
September1st to 15thNight
11%314%35%31%3
614
16th to endNight
13%216%31%31%3
717
October1st to 15thNight
15%5%23%31%19%3
720
16th to endNight
23%10%31%24%9%
768
November1st to 15thNight
18%10%32%26%12%
760
16th to endNight
25%11%28%25%8%
780
December1st to 15thNight
27%13%30%21%6%
800
16th to endNight
31%12%33%18%4
960
Page generated at 2017-12-03 11:16:44. Version ac04

Copyright 2017 A. Danko


Morris Observatory Clear Sky Chart |Charts Home