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 2017-03-14.

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%
14958
33%
45198
18%
14914
64%
14914
42%
22317

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
40%
720
32%
2327
16%
716
59%
716
37%
1108
January16th to endNight
37%
768
37%
2496
17%
768
61%
768
39%
1142
February1st to 15thNight
38%
703
36%
2115
15%
700
61%
700
46%
968
February16th to endNight
24%
632
40%
1894
11%
632
53%
632
38%
868
March1st to 15thNight
37%
716
36%
2038
14%
716
55%
716
41%
1002
March16th to endNight
34%
646
37%
1878
14%
646
55%
646
47%
878
April1st to 15thNight
28%
494
37%
1648
11%
494
58%
494
35%
747
April16th to endNight
30%
495
38%
1650
15%
495
62%
495
46%
658
May1st to 15thNight
34%
495
32%
1650
15%
495
59%
495
42%
742
May16th to endNight
47%
514
28%
1623
15%
513
65%
513
46%
771
June1st to 15thNight
64%
495
32%
1320
20%
495
73%
495
58%
652
June16th to endNight
69%
495
20%
1334
17%
495
71%
495
43%
774
July1st to 15thNight
75%
465
22%
1395
22%
465
75%
465
38%
794
July16th to endNight
79%
522
19%
1487
19%
489
81%
489
35%
863
August1st to 15thNight
78%
494
21%
1639
25%
491
78%
491
31%
944
August16th to endNight
77%
525
19%
1750
21%
525
78%
525
32%
1006
September1st to 15thNight
71%
495
22%
1650
24%
495
73%
495
31%
975
September16th to endNight
70%
492
32%
1767
31%
492
76%
492
41%
849
October1st to 15thNight
58%
637
36%
1957
23%
637
68%
637
45%
974
October16th to endNight
58%
704
40%
2112
23%
704
70%
704
56%
947
November1st to 15thNight
52%
739
41%
2139
20%
739
67%
739
55%
958
November16th to endNight
44%
900
39%
2340
17%
900
58%
900
46%
1201
December1st to 15thNight
39%
900
39%
2349
14%
900
57%
900
43%
1210
December16th to endNight
32%
912
35%
2640
14%
912
51%
912
37%
1286

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
431342445%7%57%
45487
Night
3212323447%63%
45397
Cloud CoverDay
431342445%7%57%
45485
Night
321232335%7%63%
45397
TransparencyDay
22%5%9%17%25%19%
45187
Night
18%5%9%17%27%20%
45199
SeeingDay
7%15%26%28%16%4
4550
Night
5%15%25%27%20%4
14960

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
1212413445%66%
1611
16th to endDay
5%312323437%62%
1728
February1st to 15thDay
2312222336%68%
1744
16th to endDay
121233326%70%
1580
March1st to 15thDay
23123345%45%62%
1890
16th to endDay
1213313347%66%
1992
April1st to 15thDay
2213214346%67%
1970
16th to endDay
2111112235%75%
1980
May1st to 15thDay
421332445%7%60%
1971
16th to endDay
4113313346%65%
2133
June1st to 15thDay
1123245%6%8%63%
2310
16th to endDay
5%3145%36%6%7%8%46%
2291
July1st to 15thDay
11%426%6%48%6%8%10%31%
2145
16th to endDay
9%5%26%5%47%7%9%11%29%
2263
August1st to 15thDay
10%326%7%48%8%8%8%30%
1980
16th to endDay
8%435%8%46%6%8%9%33%
2100
September1st to 15thDay
14%5%25%6%35%5%6%7%36%
1980
16th to endDay
6%414324446%56%
1862
October1st to 15thDay
5%313223445%64%
1670
16th to endDay
222212235%75%
1760
November1st to 15thDay
211222236%74%
1706
16th to endDay
3211212335%70%
1620
December1st to 15thDay
2222135%5%8%65%
1608
16th to endDay
1312323447%64%
1593
January1st to 15thNight
131331444466%
2327
16th to endNight
4212213337%67%
2496
February1st to 15thNight
1211223347%68%
2105
16th to endNight
221123345%71%
1894
March1st to 15thNight
1212323447%64%
2038
16th to endNight
2112323235%72%
1878
April1st to 15thNight
2212224446%65%
1648
16th to endNight
111212245%75%
1650
May1st to 15thNight
3212213346%68%
1649
16th to endNight
5%22114446%64%
1622
June1st to 15thNight
11222447%7%64%
1320
16th to endNight
22135%37%6%6%9%50%
1334
July1st to 15thNight
8%324425%46%12%45%
1485
16th to endNight
6%314435%6%8%15%40%
1597
August1st to 15thNight
6%3145%346%10%13%40%
1650
16th to endNight
5%314435%5%7%13%44%
1750
September1st to 15thNight
10%4244245%6%10%43%
1650
16th to endNight
7%313313345%62%
1767
October1st to 15thNight
3212322346%66%
1957
16th to endNight
321121223474%
2112
November1st to 15thNight
212212237%72%
2139
16th to endNight
211331332471%
2340
December1st to 15thNight
3212223248%67%
2349
16th to endNight
221232345%6%66%
2640

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
1213323436%66%
1611
16th to endDay
4412224337%62%
1728
February1st to 15thDay
1313222336%68%
1744
16th to endDay
1212313335%71%
1580
March1st to 15thDay
23123345%46%61%
1890
16th to endDay
121332335%7%66%
1990
April1st to 15thDay
2212224446%67%
1970
16th to endDay
1111112235%75%
1980
May1st to 15thDay
331332435%7%60%
1971
16th to endDay
4112223346%64%
2133
June1st to 15thDay
11123245%6%8%62%
2310
16th to endDay
4324437%7%7%9%45%
2291
July1st to 15thDay
10%426%7%47%6%7%10%30%
2145
16th to endDay
9%5%35%6%47%8%9%9%28%
2263
August1st to 15thDay
9%5%26%8%5%8%7%8%8%29%
1980
16th to endDay
8%426%9%47%7%8%9%32%
2100
September1st to 15thDay
14%6%35%6%35%5%6%7%35%
1980
16th to endDay
6%41442435%6%56%
1862
October1st to 15thDay
5%213223345%64%
1670
16th to endDay
1212212325%75%
1760
November1st to 15thDay
211213235%75%
1706
16th to endDay
322212336%70%
1620
December1st to 15thDay
22232235%8%64%
1608
16th to endDay
1313224347%64%
1593
January1st to 15thNight
131322435%466%
2327
16th to endNight
3212222347%66%
2496
February1st to 15thNight
211214347%68%
2105
16th to endNight
2211113246%71%
1894
March1st to 15thNight
1312323447%65%
2038
16th to endNight
2211223325%72%
1878
April1st to 15thNight
2211224447%65%
1648
16th to endNight
1112213245%75%
1650
May1st to 15thNight
3312213346%67%
1649
16th to endNight
5%2122345%6%65%
1622
June1st to 15thNight
111232447%8%63%
1320
16th to endNight
22235%48%5%6%8%50%
1334
July1st to 15thNight
8%3235%25%46%11%45%
1485
16th to endNight
6%213435%7%9%15%40%
1597
August1st to 15thNight
5%2246%346%10%14%38%
1650
16th to endNight
43245%4448%13%44%
1750
September1st to 15thNight
9%5%234345%7%10%42%
1650
16th to endNight
6%31221335%6%61%
1767
October1st to 15thNight
3212323346%66%
1957
16th to endNight
32221213474%
2112
November1st to 15thNight
2112212337%72%
2139
16th to endNight
221332332471%
2340
December1st to 15thNight
2212223348%66%
2349
16th to endNight
1312323447%66%
2640

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
17%37%17%31%21%
1612
16th to endDay
19%5%6%15%31%21%
1728
February1st to 15thDay
16%36%16%28%28%
1745
16th to endDay
15%25%14%36%26%
1580
March1st to 15thDay
19%5%7%16%29%21%
1890
16th to endDay
17%35%14%32%26%
1992
April1st to 15thDay
17%36%13%34%24%
1970
16th to endDay
10%35%10%33%36%
1980
May1st to 15thDay
20%5%8%11%26%27%
1971
16th to endDay
17%47%15%25%29%
2136
June1st to 15thDay
14%5%9%14%25%30%
2310
16th to endDay
27%6%11%16%18%19%
2291
July1st to 15thDay
37%11%15%16%11%7%
2006
16th to endDay
37%12%18%19%11%
2110
August1st to 15thDay
38%11%17%21%8%2
1967
16th to endDay
39%10%15%20%11%2
2100
September1st to 15thDay
38%9%13%18%15%5%
1980
16th to endDay
24%5%9%21%26%12%
1862
October1st to 15thDay
20%48%17%26%22%
1670
16th to endDay
12%2419%34%26%
1760
November1st to 15thDay
12%35%21%33%23%
1706
16th to endDay
15%35%17%31%26%
1620
December1st to 15thDay
17%38%22%36%12%
1608
16th to endDay
17%5%11%19%32%13%
1593
January1st to 15thNight
19%48%14%30%21%
2327
16th to endNight
16%46%15%34%21%
2496
February1st to 15thNight
15%28%15%26%30%
2115
16th to endNight
15%2314%36%26%
1894
March1st to 15thNight
16%47%16%31%23%
2038
16th to endNight
14%35%13%35%26%
1878
April1st to 15thNight
17%46%11%36%23%
1648
16th to endNight
10%36%10%33%34%
1650
May1st to 15thNight
17%36%13%29%29%
1650
16th to endNight
17%47%15%24%28%
1624
June1st to 15thNight
13%5%9%15%22%32%
1320
16th to endNight
23%9%14%16%16%19%
1334
July1st to 15thNight
27%7%18%23%16%6%
1395
16th to endNight
26%10%25%21%13%1
1487
August1st to 15thNight
28%10%20%25%12%2
1639
16th to endNight
28%10%20%22%15%2
1750
September1st to 15thNight
31%9%18%20%13%6%
1650
16th to endNight
23%410%20%28%11%
1767
October1st to 15thNight
18%6%6%17%29%21%
1957
16th to endNight
13%2418%28%31%
2112
November1st to 15thNight
12%3419%34%25%
2139
16th to endNight
17%3415%30%29%
2340
December1st to 15thNight
17%46%20%32%19%
2349
16th to endNight
16%49%22%32%14%
2640

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
7%30%33%18%7%2
90
16th to endDay
8%39%19%21%9%1
96
February1st to 15thDay
8%14%30%32%14%
90
16th to endDay
6%29%33%19%7%3
81
March1st to 15thDay
7%29%45%14%2
192
16th to endDay
7%34%42%13%2
224
April1st to 15thDay
11%39%33%14%
209
16th to endDay
7%45%35%9%
210
May1st to 15thDay
5%33%44%14%1
228
16th to endDay
6%21%37%24%9%
326
June1st to 15thDay
26%30%35%22%2
420
16th to endDay
6%219%36%28%6%
401
July1st to 15thDay
8%11%48%23%6%
245
16th to endDay
228%30%41%14%
271
August1st to 15thDay
6%18%32%36%13%
255
16th to endDay
12%28%40%26%8%
268
September1st to 15thDay
15%215%42%18%5%
255
16th to endDay
4324%44%18%5%
137
October1st to 15thDay
17%6%26%28%13%6%
90
16th to endDay
5%6%28%31%18%10%
96
November1st to 15thDay
14%17%27%20%15%4
90
16th to endDay
11%30%34%15%6%2
90
December1st to 15thDay
7%21%38%23%6%2
90
16th to endDay
14%27%39%15%3
96
January1st to 15thNight
422%28%26%14%3
720
16th to endNight
5%26%29%24%11%2
768
February1st to 15thNight
320%35%25%10%4
704
16th to endNight
6%30%37%19%5%1
632
March1st to 15thNight
5%26%29%27%10%1
716
16th to endNight
421%38%28%7%
646
April1st to 15thNight
5%27%37%22%6%
494
16th to endNight
224%38%26%6%
495
May1st to 15thNight
5%17%40%30%5%
495
16th to endNight
5%10%33%31%16%2
515
June1st to 15thNight
2326%43%23%
495
16th to endNight
3216%38%35%3
495
July1st to 15thNight
7%16%33%45%6%
465
16th to endNight
5%1222%54%13%
522
August1st to 15thNight
6%1315%50%21%
494
16th to endNight
4424%50%15%
525
September1st to 15thNight
10%26%28%43%7%
495
16th to endNight
10%311%34%34%6%
492
October1st to 15thNight
5%7%24%33%22%6%
637
16th to endNight
5%11%22%30%22%8%
704
November1st to 15thNight
216%25%29%18%7%
739
16th to endNight
5%19%26%27%15%5%
900
December1st to 15thNight
7%21%29%26%12%2
900
16th to endNight
6%27%30%23%8%2
912
Page generated at 2017-03-15 09:32:36. Version ac04

Copyright 2017 A. Danko


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