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 2014-06-16.

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
48%
11303
34%
34131
18%
11259
64%
11259
43%
16576

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%
1116
34%
3614
16%
1112
59%
1112
39%
1660
FebruaryNight
29%
995
38%
2988
12%
992
56%
992
39%
1377
MarchNight
33%
1069
38%
3074
14%
1069
54%
1069
43%
1467
AprilNight
30%
809
39%
2698
14%
809
62%
809
39%
1152
MayNight
41%
823
31%
2669
15%
822
63%
822
45%
1219
JuneNight
64%
765
29%
2050
20%
765
70%
765
50%
1096
JulyNight
76%
708
22%
2039
23%
675
76%
675
36%
1181
AugustNight
78%
743
22%
2469
26%
740
78%
740
34%
1378
SeptemberNight
73%
717
31%
2485
31%
717
77%
717
38%
1274
OctoberNight
57%
975
40%
2959
23%
975
70%
975
54%
1328
NovemberNight
51%
1224
41%
3344
20%
1224
65%
1224
53%
1574
DecemberNight
33%
1359
37%
3742
13%
1359
52%
1359
40%
1870

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
421342445%7%58%
34526
Night
3212323447%64%
34330
Cloud CoverDay
431342445%7%57%
34524
Night
221232435%7%63%
34330
TransparencyDay
21%5%9%17%26%20%
34226
Night
17%5%9%17%29%21%
34132
SeeingDay
7%16%27%28%16%2
1952
Night
417%25%27%19%4
11305

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
3212323446%65%
2502
Night
2312214446%66%
3614
FebruaryDay
1212323327%68%
2476
Night
121122435%7%68%
2978
MarchDay
121232445%7%64%
3060
Night
1212323346%68%
3074
AprilDay
1112223345%71%
3230
Night
1111224345%70%
2698
MayDay
421331335%7%63%
3345
Night
3212213346%67%
2667
JuneDay
3213325%6%6%8%56%
3558
Night
2113326%46%8%58%
2050
JulyDay
12%5%26%6%47%7%8%10%28%
3205
Night
8%323325%5%7%13%42%
2239
AugustDay
9%325%8%47%7%7%9%33%
2976
Night
5%2145%35%5%8%12%45%
2480
SeptemberDay
9%42442445%6%49%
2794
Night
7%31332345%8%56%
2485
OctoberDay
222212335%73%
2495
Night
2112212235%75%
2959
NovemberDay
2112212335%73%
2484
Night
1112213336%72%
3344
DecemberDay
2212213447%66%
2401
Night
2212223347%67%
3742

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
2213224437%64%
2502
Night
221222335%6%65%
3614
FebruaryDay
1213323336%68%
2476
Night
121122435%7%68%
2978
MarchDay
121332345%6%63%
3058
Night
1212323336%68%
3074
AprilDay
1112213345%71%
3230
Night
1112224346%70%
2698
MayDay
421232435%7%62%
3345
Night
32221335%6%66%
2667
JuneDay
2214326%6%6%8%55%
3558
Night
2112436%46%7%58%
2050
JulyDay
12%5%36%7%47%7%8%9%27%
3205
Night
8%323425%6%7%13%41%
2239
AugustDay
8%426%8%48%7%8%8%31%
2976
Night
42245%3448%13%44%
2480
SeptemberDay
8%5%245%3446%6%48%
2794
Night
6%32232346%9%54%
2485
OctoberDay
1112122335%73%
2495
Night
2112212235%75%
2959
NovemberDay
222212236%73%
2484
Night
1112212336%72%
3344
DecemberDay
121222435%7%65%
2401
Night
1212223248%67%
3742

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthOccurrence of each ForecastData
Points
JanuaryDay
17%5%6%16%32%21%
2503
Night
16%48%14%34%21%
3614
FebruaryDay
15%35%16%33%24%
2477
Night
16%26%16%33%25%
2988
MarchDay
17%37%15%31%24%
3060
Night
15%36%14%34%25%
3074
AprilDay
13%36%10%32%33%
3230
Night
14%36%11%33%31%
2698
MayDay
18%5%7%13%25%29%
3348
Night
16%47%14%26%30%
2670
JuneDay
21%49%13%23%28%
3558
Night
18%6%10%13%21%28%
2050
JulyDay
40%11%16%17%10%3
2913
Night
27%9%21%23%14%3
2039
AugustDay
37%10%16%22%9%3
2963
Night
26%9%19%26%14%3
2469
SeptemberDay
28%6%10%19%24%10%
2794
Night
23%7%13%20%24%11%
2485
OctoberDay
13%36%19%31%25%
2495
Night
13%45%19%29%28%
2959
NovemberDay
13%35%21%33%24%
2484
Night
13%3318%34%25%
3344
DecemberDay
16%49%22%37%10%
2401
Night
16%47%21%34%15%
3742

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
MonthOccurrence of each ForecastData
Points
JanuaryNight
326%30%24%12%2
1116
FebruaryNight
428%36%21%8%1
996
MarchDay
9%37%44%8%
225
Night
425%33%26%8%
1069
AprilDay
10%43%36%9%
269
Night
326%36%24%7%
809
MayDay
5%23%41%21%7%
322
Night
414%36%32%11%1
824
JuneDay
36%27%35%23%3
497
Night
2322%41%27%1
765
JulyDay
10%110%42%30%5%
237
Night
7%1425%49%10%
708
AugustDay
10%6%42%30%8%
248
Night
5%319%52%18%
743
SeptemberDay
13%320%43%16%1
154
Night
7%38%31%39%8%
717
OctoberNight
312%25%30%20%7%
975
NovemberNight
316%25%29%17%7%
1224
DecemberNight
7%25%31%24%9%2
1359
Page generated at 2014-06-17 01:07:51. Version ac04

Copyright 2014 A. Danko


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