This page made possible by the sponsorship of: Chris Traher.

Sacramento Mountains Astronomy Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sacramento Mountains Astronomy Park clear sky chart from 2005-11-05 to 2013-06-30.

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%
9994
35%
30149
19%
9947
65%
9947
43%
14629

By Month

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
JanuaryNight
37%
992
34%
3211
16%
988
59%
988
37%
1499
FebruaryNight
30%
883
40%
2652
13%
880
58%
880
39%
1208
MarchNight
34%
950
39%
2732
15%
950
54%
950
43%
1303
AprilNight
31%
719
39%
2398
14%
719
63%
719
40%
1024
MayNight
42%
724
33%
2351
17%
723
65%
723
45%
1082
JuneNight
65%
687
30%
1842
21%
687
71%
687
47%
1005
JulyNight
77%
615
23%
1758
23%
582
78%
582
38%
996
AugustNight
79%
650
23%
2150
27%
644
80%
644
35%
1194
SeptemberNight
75%
627
32%
2174
33%
627
78%
627
40%
1098
OctoberNight
58%
853
41%
2589
24%
853
70%
853
54%
1159
NovemberNight
52%
1086
42%
2966
21%
1086
66%
1086
55%
1381
DecemberNight
32%
1208
37%
3326
13%
1208
52%
1208
40%
1680

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
5%5%7%58%
30512
Night
7%64%
30357
Cloud CoverDay
5%7%57%
29965
Night
5%7%63%
29539
TransparencyDay
6%9%18%28%21%
28430
Night
5%9%18%30%23%
28527
SeeingDay
16%27%29%16%
1693
Night
17%25%27%20%5%
9881

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
MonthOccurrence of each ForecastData
Points
JanuaryDay
5%6%63%
2223
Night
6%65%
3211
FebruaryDay
6%68%
2196
Night
6%70%
2642
MarchDay
5%7%63%
2720
Night
6%68%
2732
AprilDay
6%70%
2870
Night
5%70%
2398
MayDay
5%7%62%
2940
Night
7%66%
2349
JuneDay
5%6%6%7%54%
3189
Night
7%5%6%7%57%
1842
JulyDay
12%5%6%7%7%7%10%29%
2804
Night
8%6%8%14%42%
1958
AugustDay
8%5%8%7%8%8%9%33%
2604
Night
5%5%5%5%8%12%45%
2170
SeptemberDay
8%5%5%7%49%
2445
Night
6%5%8%57%
2174
OctoberDay
5%72%
2183
Night
5%74%
2589
NovemberDay
5%74%
2204
Night
6%72%
2966
DecemberDay
5%5%7%64%
2134
Night
7%66%
3326

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
MonthOccurrence of each ForecastData
Points
JanuaryDay
7%63%
1944
Night
6%66%
2808
FebruaryDay
6%68%
2196
Night
6%70%
2642
MarchDay
5%6%62%
2718
Night
6%68%
2732
AprilDay
5%70%
2870
Night
5%70%
2398
MayDay
5%7%61%
2940
Night
5%7%66%
2349
JuneDay
6%6%6%7%53%
3189
Night
7%6%7%56%
1842
JulyDay
12%5%6%7%7%7%8%9%28%
2804
Night
8%5%6%8%13%42%
1958
AugustDay
8%6%8%8%7%8%8%31%
2604
Night
5%8%13%44%
2170
SeptemberDay
7%5%5%6%7%48%
2445
Night
6%6%9%55%
2174
OctoberDay
5%72%
2183
Night
5%74%
2589
NovemberDay
6%74%
2204
Night
6%72%
2966
DecemberDay
6%8%62%
1868
Night
8%65%
2911

Transparency (when cloud cover <= 30%)
Color Meanings:
Poor Below Average Average Above average Transparent
MonthOccurrence of each ForecastData
Points
JanuaryDay
5%7%18%32%21%
2108
Night
5%9%15%33%23%
3011
FebruaryDay
5%15%35%27%
2089
Night
6%15%35%28%
2538
MarchDay
8%15%33%26%
2537
Night
6%14%36%28%
2547
AprilDay
6%10%33%36%
2724
Night
6%10%34%34%
2279
MayDay
5%8%15%24%33%
2742
Night
5%8%15%25%34%
2191
JuneDay
5%10%13%24%30%
2919
Night
7%11%13%22%31%
1680
JulyDay
12%16%20%13%
2286
Night
10%22%25%17%
1608
AugustDay
11%18%25%11%
2340
Night
10%21%28%15%
1973
SeptemberDay
6%11%21%26%9%
2346
Night
7%13%22%26%10%
2102
OctoberDay
6%19%33%25%
2117
Night
6%20%30%28%
2512
NovemberDay
5%21%33%25%
2167
Night
18%36%27%
2890
DecemberDay
5%9%24%36%10%
2055
Night
8%22%34%15%
3196

Seeing (when cloud cover <= 80%)
Color Meanings:
Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthOccurrence of each ForecastData
Points
JanuaryNight
27%30%23%13%
979
FebruaryNight
30%34%21%9%
868
MarchDay
37%45%10%
191
Night
25%34%27%9%
927
AprilDay
44%38%10%
229
Night
26%36%25%7%
712
MayDay
23%41%21%7%
280
Night
14%36%31%12%
716
JuneDay
6%24%35%25%
441
Night
20%40%29%
685
JulyDay
10%43%27%6%
204
Night
27%50%11%
607
AugustDay
6%41%32%8%
216
Night
19%53%18%
644
SeptemberDay
23%42%18%
132
Night
8%33%39%9%
619
OctoberNight
12%24%30%22%7%
847
NovemberNight
16%25%30%18%7%
1075
DecemberNight
25%32%25%8%
1202
Page generated at 2013-07-02 09:07:46. Version ac01


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