Musser Hill Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Musser Hill Observatory clear sky chart from 2005-11-05 to 2017-10-31.

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%
15242
25%
47414
22%
15203
66%
15203
36%
26500

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
54%
719
17%
2453
17%
716
59%
716
22%
1585
January16th to endNight
52%
768
24%
2496
24%
768
55%
768
25%
1572
February1st to 15thNight
51%
697
19%
2288
20%
697
55%
697
22%
1531
February16th to endNight
48%
632
20%
1963
15%
632
55%
632
23%
1281
March1st to 15thNight
43%
720
13%
1998
11%
720
46%
720
20%
1427
March16th to endNight
44%
768
18%
2103
11%
768
49%
768
27%
1392
April1st to 15thNight
39%
719
18%
1799
6%
719
46%
719
26%
1231
April16th to endNight
54%
682
23%
1762
12%
682
58%
682
44%
1007
May1st to 15thNight
58%
503
23%
1583
16%
503
64%
503
48%
769
May16th to endNight
61%
374
21%
1496
20%
374
68%
374
34%
722
June1st to 15thNight
62%
360
21%
1440
26%
360
68%
360
36%
688
June16th to endNight
73%
360
32%
1440
41%
360
81%
360
60%
506
July1st to 15thNight
89%
340
31%
1360
42%
340
92%
340
69%
440
July16th to endNight
91%
522
38%
1551
38%
489
93%
489
78%
581
August1st to 15thNight
92%
538
38%
1611
33%
535
93%
535
77%
635
August16th to endNight
88%
708
44%
1854
30%
708
89%
708
80%
806
September1st to 15thNight
87%
720
44%
1800
29%
720
90%
720
87%
770
September16th to endNight
78%
716
39%
1981
33%
716
82%
716
63%
919
October1st to 15thNight
68%
720
29%
2160
28%
720
75%
720
51%
1048
October16th to endNight
69%
768
31%
2304
31%
768
73%
768
41%
1257
November1st to 15thNight
61%
700
21%
2244
20%
700
65%
700
30%
1352
November16th to endNight
53%
720
17%
2520
17%
720
56%
720
24%
1549
December1st to 15thNight
50%
720
18%
2520
16%
720
54%
720
21%
1620
December16th to endNight
43%
768
19%
2688
16%
768
49%
768
18%
1812

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
10%313323346%58%
48342
Night
12%413313346%56%
47598
TransparencyDay
28%48%20%23%14%
48025
Night
30%410%22%21%10%
47415
SeeingDay
14%12%25%28%14%4
6061
Night
14%415%33%27%5%
15252

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
18%5%223245%5%6%41%
1483
16th to endDay
20%6%24323336%44%
1728
February1st to 15thDay
21%6%14425%46%5%38%
1576
16th to endDay
17%7%24434438%38%
1509
March1st to 15thDay
23%8%25%334437%31%
1959
16th to endDay
19%6%2442445%7%38%
2121
April1st to 15thDay
18%6%24425%5%5%8%36%
2149
16th to endDay
7%424423446%54%
2196
May1st to 15thDay
5%31232445%8%59%
2367
16th to endDay
10%414334446%52%
2615
June1st to 15thDay
6%31332435%5%60%
2520
16th to endDay
41111222476%
2520
July1st to 15thDay
1111223480%
2520
16th to endDay
1111112383%
2509
August1st to 15thDay
111223482%
2340
16th to endDay
1111113384%
2348
September1st to 15thDay
111123481%
2160
16th to endDay
311212236%72%
1974
October1st to 15thDay
9%212212335%65%
1800
16th to endDay
11%413322347%54%
1918
November1st to 15thDay
11%42442445%9%45%
1614
16th to endDay
16%5%24335%5%46%43%
1440
December1st to 15thDay
20%7%144245%5%8%36%
1440
16th to endDay
26%6%1442435%7%33%
1536
January1st to 15thNight
16%7%2443345%6%41%
2453
16th to endNight
20%6%23223446%44%
2496
February1st to 15thNight
21%7%2432445%5%37%
2276
16th to endNight
16%6%144245%5%9%39%
1963
March1st to 15thNight
22%6%24424448%34%
1998
16th to endNight
18%5%2341435%8%41%
2103
April1st to 15thNight
14%6%34423448%42%
1799
16th to endNight
7%5%12213447%60%
1762
May1st to 15thNight
5%112213347%65%
1583
16th to endNight
7%21331345%5%60%
1496
June1st to 15thNight
6%22322345%6%60%
1440
16th to endNight
3111112379%
1440
July1st to 15thNight
111233382%
1440
16th to endNight
111112287%
1658
August1st to 15thNight
11122384%
1620
16th to endNight
111112386%
1854
September1st to 15thNight
2488%
1800
16th to endNight
211213246%73%
1981
October1st to 15thNight
7%212212235%68%
2160
16th to endNight
10%312313347%58%
2304
November1st to 15thNight
12%4233345%6%8%46%
2244
16th to endNight
16%5%1442445%8%41%
2520
December1st to 15thNight
24%5%23313246%41%
2520
16th to endNight
25%5%14425%346%36%
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
42%6%9%20%13%7%
1483
16th to endDay
42%5%7%16%16%10%
1728
February1st to 15thDay
46%5%9%20%15%2
1576
16th to endDay
45%412%24%11%1
1509
March1st to 15thDay
52%5%10%13%14%2
1959
16th to endDay
46%5%15%18%10%3
2121
April1st to 15thDay
45%6%12%22%13%
2149
16th to endDay
29%413%28%18%4
2196
May1st to 15thDay
22%5%11%28%24%7%
2367
16th to endDay
32%410%28%20%3
2619
June1st to 15thDay
25%5%8%23%25%11%
2520
16th to endDay
14%35%20%37%18%
2520
July1st to 15thDay
8%25%17%34%31%
2371
16th to endDay
8%2211%31%43%
2353
August1st to 15thDay
7%2421%33%31%
2324
16th to endDay
7%2316%36%34%
2348
September1st to 15thDay
7%2313%33%38%
2160
16th to endDay
14%37%23%32%17%
1974
October1st to 15thDay
22%47%23%26%16%
1800
16th to endDay
29%48%25%17%13%
1918
November1st to 15thDay
35%5%15%23%12%7%
1614
16th to endDay
42%411%17%16%7%
1440
December1st to 15thDay
47%47%18%16%4
1440
16th to endDay
49%5%8%16%14%4
1536
January1st to 15thNight
43%6%10%18%14%6%
2453
16th to endNight
42%48%19%14%10%
2496
February1st to 15thNight
47%410%17%16%4
2288
16th to endNight
41%6%12%24%13%2
1963
March1st to 15thNight
48%7%10%16%15%1
1998
16th to endNight
41%5%15%22%11%2
2103
April1st to 15thNight
41%6%15%20%14%2
1799
16th to endNight
24%6%16%32%17%2
1762
May1st to 15thNight
19%5%15%31%23%4
1584
16th to endNight
25%5%16%34%15%2
1496
June1st to 15thNight
24%5%15%26%22%5%
1440
16th to endNight
12%15%31%39%10%
1440
July1st to 15thNight
6%2425%36%24%
1360
16th to endNight
7%1415%35%36%
1551
August1st to 15thNight
7%15%26%37%21%
1611
16th to endNight
6%2323%40%24%
1854
September1st to 15thNight
31420%34%35%
1800
16th to endNight
13%38%26%28%20%
1981
October1st to 15thNight
19%38%23%30%14%
2160
16th to endNight
27%410%24%21%12%
2304
November1st to 15thNight
35%6%16%23%12%5%
2244
16th to endNight
40%5%12%19%16%6%
2520
December1st to 15thNight
46%39%16%20%3
2520
16th to endNight
48%5%8%16%16%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
34%9%23%18%11%2
111
16th to endDay
25%11%21%18%16%5%
256
February1st to 15thDay
28%9%26%20%12%2
236
16th to endDay
25%15%28%18%11%1
227
March1st to 15thDay
32%15%24%18%5%2
270
16th to endDay
28%20%27%17%5%1
288
April1st to 15thDay
28%17%25%18%7%1
269
16th to endDay
17%24%28%21%7%1
270
May1st to 15thDay
10%22%29%25%7%3
288
16th to endDay
13%18%20%26%13%6%
330
June1st to 15thDay
9%20%28%25%13%3
315
16th to endDay
6%11%33%31%14%3
315
July1st to 15thDay
25%23%42%19%6%
305
16th to endDay
16%19%46%17%8%
327
August1st to 15thDay
16%25%41%17%8%
315
16th to endDay
2427%31%25%8%
332
September1st to 15thDay
26%23%38%21%7%
315
16th to endDay
6%10%26%33%18%5%
315
October1st to 15thDay
12%12%28%25%15%5%
315
16th to endDay
16%7%22%28%19%4
336
November1st to 15thDay
13%7%21%33%20%2
142
16th to endDay
21%15%35%21%5%1
60
December1st to 15thDay
33%13%31%20%1
60
16th to endDay
18%431%20%21%3
64
January1st to 15thNight
18%414%38%18%5%
720
16th to endNight
23%315%27%23%7%
768
February1st to 15thNight
23%313%31%23%3
704
16th to endNight
20%7%15%35%16%3
632
March1st to 15thNight
25%7%14%28%18%4
720
16th to endNight
20%8%20%33%15%1
768
April1st to 15thNight
18%8%26%27%16%2
719
16th to endNight
10%7%24%34%19%3
682
May1st to 15thNight
6%228%37%21%2
504
16th to endNight
7%420%36%29%2
375
June1st to 15thNight
7%5%21%34%30%1
360
16th to endNight
3218%45%29%
360
July1st to 15thNight
17%37%49%3
340
16th to endNight
1439%47%6%
522
August1st to 15thNight
1337%48%8%
538
16th to endNight
28%35%46%7%
708
September1st to 15thNight
118%31%47%8%
720
16th to endNight
4210%35%39%6%
716
October1st to 15thNight
9%215%35%31%5%
720
16th to endNight
12%310%32%31%9%
768
November1st to 15thNight
14%215%40%20%6%
700
16th to endNight
19%5%16%30%22%5%
720
December1st to 15thNight
27%312%31%16%7%
720
16th to endNight
27%418%32%13%3
768
Page generated at 2017-11-01 14:23:33. Version ac04

Copyright 2017 A. Danko


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