Mountain Rest Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mountain Rest Observatory clear sky chart from 2005-11-05 to 2017-09-16.

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
49%
15579
22%
46914
15%
15536
57%
15536
27%
29438

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
31%
720
24%
2327
10%
716
47%
716
22%
1419
January16th to endNight
28%
768
25%
2496
12%
768
45%
768
23%
1519
February1st to 15thNight
34%
703
27%
2135
11%
700
51%
700
29%
1242
February16th to endNight
29%
631
26%
1893
11%
631
43%
631
27%
1153
March1st to 15thNight
33%
720
25%
2028
13%
720
44%
720
27%
1276
March16th to endNight
38%
768
19%
2112
10%
768
45%
768
27%
1348
April1st to 15thNight
44%
691
24%
1949
14%
691
53%
691
33%
1158
April16th to endNight
51%
540
23%
1647
15%
540
59%
540
29%
1010
May1st to 15thNight
50%
540
18%
1620
8%
540
57%
540
27%
1042
May16th to endNight
60%
561
18%
1683
13%
561
63%
561
27%
1064
June1st to 15thNight
66%
540
14%
1620
12%
540
67%
540
25%
1076
June16th to endNight
73%
540
15%
1620
12%
540
74%
540
31%
1027
July1st to 15thNight
68%
510
10%
1530
8%
510
68%
510
22%
1081
July16th to endNight
71%
564
13%
1595
11%
531
73%
531
26%
1071
August1st to 15thNight
63%
539
14%
1609
12%
536
64%
536
24%
1118
August16th to endNight
63%
591
17%
1866
17%
591
64%
591
21%
1275
September1st to 15thNight
61%
720
16%
1980
14%
720
62%
720
25%
1357
September16th to endNight
56%
661
20%
1826
15%
661
60%
661
27%
1212
October1st to 15thNight
54%
660
32%
1864
25%
660
62%
660
35%
1112
October16th to endNight
54%
704
33%
2112
25%
704
66%
704
37%
1181
November1st to 15thNight
53%
700
30%
2226
26%
700
62%
700
35%
1216
November16th to endNight
43%
720
27%
2340
19%
720
55%
720
28%
1375
December1st to 15thNight
42%
720
24%
2340
16%
720
54%
720
24%
1450
December16th to endNight
35%
768
23%
2496
15%
768
45%
768
21%
1656

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%424435%5%6%7%42%
47839
Night
14%42442445%7%45%
47113
TransparencyDay
38%7%12%19%16%4
47540
Night
37%6%11%19%18%5%
46916
SeeingDay
16%6%18%23%20%14%
5444
Night
16%6%20%30%21%5%
15582

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
18%5%24313335%47%
1611
16th to endDay
17%413213445%50%
1728
February1st to 15thDay
14%423413347%48%
1723
16th to endDay
16%5%14323335%48%
1580
March1st to 15thDay
18%413324347%46%
1932
16th to endDay
18%42332445%6%42%
2111
April1st to 15thDay
13%223335%5%5%8%45%
2008
16th to endDay
14%3144345%46%47%
2312
May1st to 15thDay
13%5%25%5%35%5%5%7%42%
2331
16th to endDay
12%315%5%36%5%7%10%37%
2431
June1st to 15thDay
9%5%245%47%8%8%10%32%
2340
16th to endDay
6%2136%48%8%8%10%38%
2340
July1st to 15thDay
9%5%26%7%49%8%8%10%27%
2340
16th to endDay
7%325%6%49%8%9%11%30%
2465
August1st to 15thDay
13%4246%37%7%8%10%31%
2340
16th to endDay
12%5%26%5%46%6%7%9%30%
2321
September1st to 15thDay
11%5%25%6%37%5%7%8%34%
1980
16th to endDay
19%41342445%8%39%
1824
October1st to 15thDay
16%312212235%57%
1765
16th to endDay
12%4143222461%
1760
November1st to 15thDay
13%31331224459%
1629
16th to endDay
18%314212346%49%
1620
December1st to 15thDay
19%42432335%6%43%
1620
16th to endDay
27%412312335%42%
1728
January1st to 15thNight
18%31342333449%
2327
16th to endNight
16%5%23423345%47%
2496
February1st to 15thNight
14%313323345%53%
2127
16th to endNight
15%32433435%6%47%
1893
March1st to 15thNight
16%5%13324346%47%
2028
16th to endNight
15%425%423346%46%
2112
April1st to 15thNight
14%313323345%54%
1949
16th to endNight
12%424424446%49%
1647
May1st to 15thNight
13%4245%25%6%47%43%
1619
16th to endNight
10%415%435%46%9%43%
1682
June1st to 15thNight
9%4246%45%6%7%9%38%
1620
16th to endNight
6%3245%25%6%7%11%43%
1620
July1st to 15thNight
9%5%25%7%47%6%7%12%31%
1620
16th to endNight
6%4246%35%7%9%12%36%
1703
August1st to 15thNight
15%5%345%35%6%7%9%33%
1620
16th to endNight
12%5%35%6%45%6%7%10%33%
1866
September1st to 15thNight
13%5%25%5%35%5%6%9%36%
1980
16th to endNight
18%415%424446%42%
1826
October1st to 15thNight
14%313322336%53%
1864
16th to endNight
12%31332333458%
2112
November1st to 15thNight
12%31431223458%
2226
16th to endNight
18%322313445%51%
2340
December1st to 15thNight
17%5%24423345%46%
2340
16th to endNight
23%5%24324345%40%
2496

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
40%5%7%16%23%6%
1612
16th to endDay
35%37%22%21%9%
1728
February1st to 15thDay
35%49%21%23%5%
1725
16th to endDay
38%39%21%18%7%
1580
March1st to 15thDay
38%5%7%21%20%7%
1932
16th to endDay
41%6%11%20%16%3
2112
April1st to 15thDay
34%5%10%22%20%5%
2008
16th to endDay
36%6%10%20%20%5%
2312
May1st to 15thDay
39%7%13%18%17%2
2331
16th to endDay
39%9%16%20%12%1
2435
June1st to 15thDay
39%13%18%21%5%1
2340
16th to endDay
33%12%17%20%12%2
2340
July1st to 15thDay
42%13%16%17%7%1
2201
16th to endDay
38%14%20%17%6%1
2310
August1st to 15thDay
42%11%16%20%7%1
2327
16th to endDay
45%11%17%17%7%1
2321
September1st to 15thDay
42%11%12%16%15%2
1980
16th to endDay
41%5%13%18%17%4
1824
October1st to 15thDay
30%411%19%26%7%
1765
16th to endDay
29%26%19%28%12%
1760
November1st to 15thDay
29%37%18%30%11%
1629
16th to endDay
36%36%18%25%8%
1620
December1st to 15thDay
41%48%18%18%7%
1620
16th to endDay
45%38%18%17%7%
1728
January1st to 15thNight
39%48%15%25%7%
2327
16th to endNight
40%35%18%23%8%
2496
February1st to 15thNight
33%38%21%24%7%
2136
16th to endNight
36%39%22%21%5%
1893
March1st to 15thNight
37%5%8%19%20%9%
2028
16th to endNight
39%411%19%19%5%
2112
April1st to 15thNight
32%48%24%23%6%
1949
16th to endNight
36%5%10%20%20%6%
1647
May1st to 15thNight
38%7%13%21%16%2
1620
16th to endNight
35%10%14%26%10%2
1684
June1st to 15thNight
38%11%19%22%8%1
1620
16th to endNight
31%11%19%20%14%3
1620
July1st to 15thNight
41%13%19%18%6%
1530
16th to endNight
34%14%23%17%7%2
1595
August1st to 15thNight
43%9%18%17%10%
1609
16th to endNight
42%10%16%20%7%1
1866
September1st to 15thNight
41%9%15%19%12%2
1980
16th to endNight
40%6%12%19%15%5%
1826
October1st to 15thNight
32%5%10%19%24%6%
1864
16th to endNight
29%35%19%28%12%
2112
November1st to 15thNight
31%35%17%30%12%
2226
16th to endNight
35%45%18%26%9%
2340
December1st to 15thNight
40%48%18%19%8%
2340
16th to endNight
46%48%15%17%7%
2496

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
26%11%38%18%4
90
16th to endDay
16%36%29%15%2
96
February1st to 15thDay
14%22%55%7%
90
16th to endDay
24%14%45%12%2
81
March1st to 15thDay
19%18%27%23%9%1
222
16th to endDay
21%11%26%27%11%2
288
April1st to 15thDay
16%9%25%27%17%3
270
16th to endDay
16%6%23%26%20%7%
270
May1st to 15thDay
14%9%26%19%16%14%
288
16th to endDay
16%415%23%21%18%
331
June1st to 15thDay
12%39%26%25%22%
315
16th to endDay
9%115%26%19%27%
315
July1st to 15thDay
7%213%23%26%26%
305
16th to endDay
5%7%20%32%33%
326
August1st to 15thDay
21%9%19%23%25%
313
16th to endDay
15%28%21%28%23%
332
September1st to 15thDay
15%113%21%31%17%
315
16th to endDay
25%28%24%25%12%
257
October1st to 15thDay
21%116%29%21%8%
255
16th to endDay
15%5%18%31%23%5%
272
November1st to 15thDay
24%8%18%29%14%4
137
16th to endDay
18%6%27%31%14%1
90
December1st to 15thDay
22%15%33%23%41
90
16th to endDay
35%13%32%16%11
96
January1st to 15thNight
20%13%30%27%7%
720
16th to endNight
19%12%34%29%3
768
February1st to 15thNight
16%14%31%34%3
704
16th to endNight
16%15%35%28%5%
631
March1st to 15thNight
18%11%31%30%7%
720
16th to endNight
17%10%27%31%12%
768
April1st to 15thNight
15%10%25%32%14%1
691
16th to endNight
14%5%21%36%19%2
540
May1st to 15thNight
13%5%21%34%21%3
540
16th to endNight
13%113%28%33%9%
563
June1st to 15thNight
10%110%28%36%12%
540
16th to endNight
8%11%27%40%12%
540
July1st to 15thNight
11%15%25%43%12%
510
16th to endNight
7%17%24%42%17%
564
August1st to 15thNight
16%15%23%40%12%
539
16th to endNight
13%26%23%40%13%
591
September1st to 15thNight
15%110%24%36%10%
720
16th to endNight
19%113%32%28%4
661
October1st to 15thNight
15%5%20%27%25%6%
660
16th to endNight
13%5%20%34%21%4
704
November1st to 15thNight
13%6%20%33%21%4
700
16th to endNight
19%8%23%31%15%1
720
December1st to 15thNight
20%8%22%35%11%1
720
16th to endNight
26%7%27%30%7%
768
Page generated at 2017-09-17 12:05:47. Version ac04

Copyright 2017 A. Danko


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