Sandstone Trailhead
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sandstone Trailhead clear sky chart from 2005-11-05 to 2017-10-06.

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
75%
15905
33%
47059
28%
15856
79%
15856
50%
23461

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
59%
720
29%
2430
26%
716
68%
716
41%
1198
January16th to endNight
54%
768
34%
2424
26%
768
68%
768
39%
1270
February1st to 15thNight
65%
698
35%
2102
30%
697
75%
697
44%
1099
February16th to endNight
61%
632
27%
1895
29%
632
64%
632
34%
1105
March1st to 15thNight
70%
720
28%
2154
27%
720
76%
720
49%
1071
March16th to endNight
73%
768
29%
1990
23%
768
75%
768
49%
1099
April1st to 15thNight
70%
719
30%
1799
19%
719
74%
719
50%
1008
April16th to endNight
75%
720
31%
1800
17%
720
79%
720
55%
964
May1st to 15thNight
77%
664
26%
1744
18%
664
78%
664
48%
964
May16th to endNight
81%
561
29%
1685
24%
561
83%
561
55%
796
June1st to 15thNight
86%
396
25%
1476
27%
396
86%
396
40%
712
June16th to endNight
93%
360
34%
1440
42%
360
93%
360
54%
553
July1st to 15thNight
91%
340
32%
1360
39%
340
91%
340
53%
521
July16th to endNight
87%
626
30%
1648
24%
586
88%
586
53%
835
August1st to 15thNight
88%
717
33%
1790
22%
713
88%
713
60%
930
August16th to endNight
91%
764
38%
1910
25%
764
91%
764
66%
945
September1st to 15thNight
87%
720
36%
1801
29%
720
87%
720
58%
965
September16th to endNight
91%
716
41%
1980
40%
716
92%
716
66%
904
October1st to 15thNight
82%
684
35%
1939
35%
684
84%
684
58%
931
October16th to endNight
78%
704
40%
2112
41%
704
81%
704
56%
985
November1st to 15thNight
76%
700
36%
2263
34%
700
83%
700
57%
985
November16th to endNight
70%
720
37%
2340
35%
720
77%
720
50%
1081
December1st to 15thNight
63%
720
35%
2340
31%
720
72%
720
40%
1193
December16th to endNight
56%
768
31%
2637
27%
768
67%
768
36%
1347

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
4312212346%66%
48118
Night
5%312212346%66%
47261
TransparencyDay
20%49%18%26%21%
47809
Night
20%37%17%25%24%
47070
SeeingDay
5%6%23%37%20%5%
6063
Night
5%29%29%39%12%
15914

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
6%413322335%62%
1507
16th to endDay
11%423212236%59%
1797
February1st to 15thDay
8%322212336%60%
1751
16th to endDay
11%323423236%55%
1579
March1st to 15thDay
4313324447%59%
1803
16th to endDay
431232435%9%58%
2232
April1st to 15thDay
6%413212347%60%
2149
16th to endDay
421222237%68%
2160
May1st to 15thDay
4413213348%63%
2205
16th to endDay
3312112349%66%
2429
June1st to 15thDay
45%24312348%58%
2480
16th to endDay
122112335%75%
2520
July1st to 15thDay
2212313336%69%
2520
16th to endDay
222212346%70%
2402
August1st to 15thDay
2212212235%74%
2160
16th to endDay
11212236%77%
2292
September1st to 15thDay
112112236%75%
2157
16th to endDay
221112235%76%
1980
October1st to 15thDay
5%212222235%69%
1816
16th to endDay
321321334469%
1760
November1st to 15thDay
3212313235%69%
1595
16th to endDay
4213322237%65%
1620
December1st to 15thDay
6%41332345%7%56%
1620
16th to endDay
10%313323347%57%
1584
January1st to 15thNight
7%5%13313346%59%
2430
16th to endNight
11%422312236%60%
2424
February1st to 15thNight
6%413313245%61%
2101
16th to endNight
13%314323335%54%
1895
March1st to 15thNight
442221345%5%62%
2154
16th to endNight
431332335%7%60%
1990
April1st to 15thNight
6%422212246%65%
1799
16th to endNight
3312213247%69%
1800
May1st to 15thNight
4312212346%65%
1744
16th to endNight
1212212246%70%
1684
June1st to 15thNight
12122235%48%63%
1476
16th to endNight
111112138%74%
1440
July1st to 15thNight
221212247%71%
1440
16th to endNight
22112125%48%66%
1762
August1st to 15thNight
211121245%8%69%
1800
16th to endNight
12212338%73%
1910
September1st to 15thNight
2212212347%69%
1801
16th to endNight
11111346%77%
1980
October1st to 15thNight
3112213235%71%
1939
16th to endNight
432111235%71%
2112
November1st to 15thNight
3212212235%73%
2263
16th to endNight
4213312336%67%
2340
December1st to 15thNight
7%314323245%60%
2340
16th to endNight
11%313212336%59%
2637

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
25%38%13%22%26%
1507
16th to endDay
27%27%17%18%25%
1797
February1st to 15thDay
25%26%16%27%21%
1751
16th to endDay
30%48%19%27%9%
1579
March1st to 15thDay
22%410%20%22%19%
1803
16th to endDay
21%6%14%23%19%13%
2232
April1st to 15thDay
22%412%26%23%10%
2149
16th to endDay
18%312%22%27%16%
2160
May1st to 15thDay
21%5%11%21%24%16%
2205
16th to endDay
17%5%13%27%27%8%
2432
June1st to 15thDay
26%5%9%16%29%13%
2480
16th to endDay
14%28%12%31%29%
2520
July1st to 15thDay
18%46%14%26%29%
2371
16th to endDay
17%410%21%27%18%
2253
August1st to 15thDay
16%26%17%32%24%
2146
16th to endDay
11%36%14%38%25%
2292
September1st to 15thDay
12%47%17%27%29%
2157
16th to endDay
15%25%18%30%27%
1980
October1st to 15thDay
17%39%21%23%25%
1816
16th to endDay
18%37%16%22%31%
1760
November1st to 15thDay
19%25%15%23%32%
1595
16th to endDay
20%39%15%21%30%
1620
December1st to 15thDay
25%5%9%16%23%20%
1620
16th to endDay
27%48%19%20%19%
1584
January1st to 15thNight
25%27%14%23%26%
2430
16th to endNight
27%26%15%16%31%
2424
February1st to 15thNight
24%36%15%24%25%
2112
16th to endNight
33%46%16%24%15%
1895
March1st to 15thNight
20%310%20%25%18%
2154
16th to endNight
22%413%21%23%14%
1990
April1st to 15thNight
23%38%27%24%12%
1799
16th to endNight
19%39%24%24%18%
1800
May1st to 15thNight
22%5%10%21%24%14%
1745
16th to endNight
16%310%28%30%10%
1685
June1st to 15thNight
21%7%11%17%29%12%
1476
16th to endNight
13%36%14%31%30%
1440
July1st to 15thNight
13%46%13%26%36%
1360
16th to endNight
17%6%7%24%22%20%
1648
August1st to 15thNight
16%36%13%32%27%
1790
16th to endNight
11%46%12%38%26%
1910
September1st to 15thNight
17%45%12%28%31%
1801
16th to endNight
13%1414%32%32%
1980
October1st to 15thNight
16%36%19%26%27%
1939
16th to endNight
16%35%15%23%35%
2112
November1st to 15thNight
15%26%15%22%36%
2263
16th to endNight
19%36%18%20%32%
2340
December1st to 15thNight
26%28%16%20%25%
2340
16th to endNight
26%48%16%23%20%
2637

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
12%6%47%28%4
135
16th to endDay
14%13%34%29%6%1
267
February1st to 15thDay
11%8%34%32%10%3
266
16th to endDay
15%11%28%29%13%
238
March1st to 15thDay
5%12%32%30%14%3
270
16th to endDay
6%6%32%38%13%2
288
April1st to 15thDay
7%10%34%28%12%5%
269
16th to endDay
312%38%33%9%2
270
May1st to 15thDay
6%9%26%35%17%3
288
16th to endDay
37%30%33%19%5%
330
June1st to 15thDay
8%423%37%20%5%
315
16th to endDay
110%42%33%11%
315
July1st to 15thDay
27%43%35%9%
305
16th to endDay
27%36%38%14%
327
August1st to 15thDay
37%51%29%7%
315
16th to endDay
8%41%37%10%
332
September1st to 15thDay
319%47%22%6%
315
16th to endDay
1318%45%22%7%
315
October1st to 15thDay
38%29%38%17%1
278
16th to endDay
37%24%41%20%2
272
November1st to 15thDay
26%22%32%13%20%
101
16th to endDay
413%32%28%17%3
90
December1st to 15thDay
7%8%20%38%22%2
90
16th to endDay
8%16%36%26%11%1
72
January1st to 15thNight
9%319%40%21%5%
720
16th to endNight
12%5%18%35%23%3
768
February1st to 15thNight
7%314%39%27%7%
704
16th to endNight
14%312%38%25%5%
632
March1st to 15thNight
5%412%41%29%6%
720
16th to endNight
6%211%35%37%6%
768
April1st to 15thNight
6%411%36%35%5%
719
16th to endNight
4410%33%37%9%
720
May1st to 15thNight
5%29%33%39%9%
665
16th to endNight
119%32%44%10%
563
June1st to 15thNight
11428%50%13%
396
16th to endNight
117%65%14%
360
July1st to 15thNight
31462%28%
340
16th to endNight
325%51%36%
626
August1st to 15thNight
2211%58%24%
717
16th to endNight
119%53%34%
764
September1st to 15thNight
31216%51%24%
720
16th to endNight
1221%54%18%
716
October1st to 15thNight
46%33%44%10%
684
16th to endNight
5%9%31%39%12%
704
November1st to 15thNight
4212%39%31%11%
700
16th to endNight
4215%35%33%9%
720
December1st to 15thNight
8%415%38%28%6%
720
16th to endNight
14%5%17%35%23%3
768
Page generated at 2017-10-07 11:07:52. Version ac04

Copyright 2017 A. Danko


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