StarDust Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the StarDust Ranch clear sky chart from 2005-11-05 to 2017-09-15.

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
59%
16097
20%
46911
15%
16056
64%
16056
30%
29593

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
46%
718
18%
2327
13%
716
55%
716
26%
1442
January16th to endNight
44%
768
25%
2472
18%
768
56%
768
31%
1437
February1st to 15thNight
45%
701
24%
2103
15%
698
55%
698
33%
1241
February16th to endNight
48%
631
28%
1776
15%
631
60%
631
38%
1010
March1st to 15thNight
49%
720
30%
1980
16%
720
61%
720
43%
1087
March16th to endNight
54%
768
27%
2112
19%
768
60%
768
43%
1179
April1st to 15thNight
58%
718
23%
1976
18%
718
63%
718
46%
1064
April16th to endNight
59%
720
26%
1813
15%
720
64%
720
44%
1077
May1st to 15thNight
67%
671
25%
1751
16%
671
71%
671
44%
1019
May16th to endNight
74%
561
21%
1682
16%
561
76%
561
34%
1018
June1st to 15thNight
66%
540
10%
1620
8%
540
66%
540
20%
1166
June16th to endNight
72%
540
10%
1620
9%
540
72%
540
22%
1151
July1st to 15thNight
70%
510
6%
1530
6%
510
70%
510
19%
1136
July16th to endNight
78%
564
8%
1595
8%
531
77%
531
22%
1133
August1st to 15thNight
77%
554
7%
1624
7%
551
77%
551
26%
1117
August16th to endNight
63%
764
6%
2035
5%
764
63%
764
19%
1509
September1st to 15thNight
66%
720
6%
1980
6%
720
66%
720
19%
1482
September16th to endNight
59%
657
9%
1815
9%
657
59%
657
17%
1365
October1st to 15thNight
66%
660
22%
1906
22%
660
70%
660
31%
1207
October16th to endNight
58%
704
23%
2112
21%
704
63%
704
29%
1311
November1st to 15thNight
62%
700
28%
2101
25%
700
69%
700
36%
1219
November16th to endNight
51%
720
29%
2160
23%
720
60%
720
32%
1306
December1st to 15thNight
53%
720
24%
2325
22%
720
59%
720
27%
1455
December16th to endNight
56%
768
22%
2496
20%
768
62%
768
30%
1462

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
8%5%37%7%47%6%7%8%32%
47799
Night
7%425%5%35%5%6%10%42%
47120
TransparencyDay
45%8%14%15%11%4
47500
Night
34%8%17%21%13%4
46923
SeeingDay
9%313%20%25%27%
5921
Night
9%317%31%28%9%
16105

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
10%6%35%436%6%6%9%35%
1611
16th to endDay
10%415%5%35%5%7%7%43%
1749
February1st to 15thDay
10%5%245%35%46%7%44%
1750
16th to endDay
7%425%5%45%5%5%10%43%
1696
March1st to 15thDay
43246%45%5%7%8%46%
1980
16th to endDay
6%4245%46%5%6%8%44%
2111
April1st to 15thDay
6%325%5%46%5%7%9%41%
1972
16th to endDay
7%426%6%46%6%6%9%39%
2145
May1st to 15thDay
5%3247%47%5%6%9%43%
2208
16th to endDay
7%5%38%7%5%8%7%7%8%30%
2431
June1st to 15thDay
10%8%49%9%6%7%7%8%10%18%
2340
16th to endDay
7%6%48%10%6%9%8%7%8%21%
2340
July1st to 15thDay
10%6%49%10%5%8%7%9%8%17%
2340
16th to endDay
6%7%410%10%5%9%8%8%9%18%
2465
August1st to 15thDay
6%6%39%8%6%7%9%8%11%22%
2313
16th to endDay
9%7%5%9%10%5%9%7%7%7%19%
2163
September1st to 15thDay
7%6%410%10%7%9%6%8%9%19%
1969
16th to endDay
11%8%49%9%6%8%8%7%7%17%
1815
October1st to 15thDay
7%5%28%7%5%7%7%7%8%31%
1724
16th to endDay
8%7%35%7%35%6%6%8%37%
1760
November1st to 15thDay
6%426%6%45%7%6%8%40%
1757
16th to endDay
8%6%36%6%37%5%5%8%39%
1800
December1st to 15thDay
10%6%47%6%35%6%6%6%37%
1632
16th to endDay
6%325%437%5%7%10%42%
1728
January1st to 15thNight
8%6%345%345%7%9%40%
2327
16th to endNight
10%5%23425%46%8%46%
2472
February1st to 15thNight
11%5%15%33445%6%48%
2103
16th to endNight
6%4144245%6%9%52%
1776
March1st to 15thNight
3413425%349%56%
1980
16th to endNight
43134135%6%7%56%
2112
April1st to 15thNight
33134245%6%9%56%
1976
16th to endNight
6%213435%46%8%53%
1813
May1st to 15thNight
4323335%5%5%8%55%
1751
16th to endNight
5%324435%6%9%12%42%
1682
June1st to 15thNight
8%8%36%7%5%6%6%8%11%27%
1620
16th to endNight
6%5%26%7%5%6%7%8%11%32%
1620
July1st to 15thNight
9%5%36%7%35%6%7%11%31%
1620
16th to endNight
3436%7%48%8%8%11%32%
1703
August1st to 15thNight
3436%5%35%8%9%14%33%
1635
16th to endNight
11%6%36%6%35%6%8%13%28%
2035
September1st to 15thNight
7%5%36%7%48%7%8%13%27%
1980
16th to endNight
9%6%47%7%47%7%6%11%26%
1815
October1st to 15thNight
6%5%25%5%35%5%7%10%41%
1906
16th to endNight
9%6%2442445%9%43%
2112
November1st to 15thNight
43245%35%47%9%48%
2101
16th to endNight
7%5%25%5%3445%8%46%
2160
December1st to 15thNight
9%5%35%5%36%5%5%7%43%
2325
16th to endNight
45%35%436%5%7%8%46%
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
43%8%8%18%16%5%
1612
16th to endDay
37%5%7%21%18%9%
1749
February1st to 15thDay
36%5%8%18%21%10%
1752
16th to endDay
35%5%11%19%17%9%
1696
March1st to 15thDay
33%6%11%23%18%6%
1980
16th to endDay
36%6%11%20%18%7%
2112
April1st to 15thDay
35%7%13%20%18%4
1972
16th to endDay
39%6%9%17%21%6%
2145
May1st to 15thDay
34%7%12%20%18%6%
2208
16th to endDay
48%7%13%18%10%1
2435
June1st to 15thDay
55%9%16%14%3
2340
16th to endDay
56%11%18%11%2
2340
July1st to 15thDay
56%14%20%7%1
2201
16th to endDay
54%14%20%10%
2310
August1st to 15thDay
50%12%28%8%
2300
16th to endDay
57%13%21%6%
2163
September1st to 15thDay
54%13%19%9%1
1969
16th to endDay
59%11%16%9%2
1815
October1st to 15thDay
45%9%11%14%14%4
1724
16th to endDay
43%6%7%14%20%7%
1760
November1st to 15thDay
38%6%8%21%16%8%
1757
16th to endDay
41%6%7%17%15%11%
1800
December1st to 15thDay
45%7%9%17%14%5%
1632
16th to endDay
35%6%13%23%15%6%
1728
January1st to 15thNight
38%6%14%21%14%5%
2327
16th to endNight
34%410%25%17%7%
2472
February1st to 15thNight
33%48%20%21%11%
2112
16th to endNight
27%5%13%24%21%7%
1776
March1st to 15thNight
24%5%13%30%20%6%
1980
16th to endNight
25%5%14%25%20%8%
2112
April1st to 15thNight
23%419%27%18%6%
1976
16th to endNight
26%6%14%24%23%5%
1813
May1st to 15thNight
26%5%13%30%16%7%
1752
16th to endNight
31%8%18%27%14%
1684
June1st to 15thNight
47%10%21%16%4
1620
16th to endNight
40%14%24%18%2
1620
July1st to 15thNight
43%15%25%13%1
1530
16th to endNight
36%18%28%15%1
1595
August1st to 15thNight
34%16%37%11%
1624
16th to endNight
43%15%28%11%
2035
September1st to 15thNight
44%16%24%13%2
1980
16th to endNight
48%13%18%14%3
1815
October1st to 15thNight
35%8%16%17%19%3
1906
16th to endNight
37%6%10%16%21%8%
2112
November1st to 15thNight
31%5%10%23%20%7%
2101
16th to endNight
35%5%9%22%17%10%
2160
December1st to 15thNight
38%6%11%23%13%6%
2325
16th to endNight
33%6%15%22%16%5%
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
17%10%36%20%10%5%
90
16th to endDay
16%16%33%13%16%3
96
February1st to 15thDay
10%10%30%33%10%6%
90
16th to endDay
12%7%30%31%17%
197
March1st to 15thDay
47%30%31%21%4
270
16th to endDay
6%6%24%28%25%7%
288
April1st to 15thDay
45%26%29%23%11%
270
16th to endDay
7%315%26%29%17%
270
May1st to 15thDay
5%211%28%34%17%
288
16th to endDay
8%29%17%35%26%
331
June1st to 15thDay
14%8%13%28%34%
315
16th to endDay
7%138%27%51%
315
July1st to 15thDay
7%16%26%58%
305
16th to endDay
10%210%21%54%
326
August1st to 15thDay
7%210%22%55%
313
16th to endDay
12%15%10%22%47%
332
September1st to 15thDay
8%5%12%24%48%
311
16th to endDay
11%311%26%46%
254
October1st to 15thDay
10%19%27%35%16%
255
16th to endDay
11%123%24%26%12%
272
November1st to 15thDay
9%213%28%33%12%
265
16th to endDay
7%424%36%24%3
270
December1st to 15thDay
12%5%37%27%15%
102
16th to endDay
45%14%41%29%5%
96
January1st to 15thNight
11%7%26%32%19%1
720
16th to endNight
11%8%30%35%13%
768
February1st to 15thNight
12%5%31%37%12%
704
16th to endNight
8%6%30%42%11%
631
March1st to 15thNight
5%6%35%38%13%1
720
16th to endNight
7%427%41%19%
768
April1st to 15thNight
4427%43%19%
718
16th to endNight
7%422%45%18%1
720
May1st to 15thNight
6%117%47%24%2
672
16th to endNight
5%18%34%40%9%
563
June1st to 15thNight
12%2323%44%13%
540
16th to endNight
8%215%45%27%
540
July1st to 15thNight
9%1111%44%31%
510
16th to endNight
41111%46%35%
564
August1st to 15thNight
5%111%46%34%
554
16th to endNight
12%15%15%41%24%
764
September1st to 15thNight
11%1313%47%23%
720
16th to endNight
14%2320%39%19%
657
October1st to 15thNight
10%18%36%34%9%
660
16th to endNight
14%216%31%30%5%
704
November1st to 15thNight
6%319%40%26%3
700
16th to endNight
9%5%24%37%21%1
720
December1st to 15thNight
11%422%38%21%1
720
16th to endNight
5%5%23%36%24%2
768
Page generated at 2017-09-16 00:58:32. Version ac04

Copyright 2017 A. Danko


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