Rattan Creek
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rattan Creek clear sky chart from 2005-11-05 to 2018-01-20.

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
51%
15978
27%
48482
19%
15933
58%
15933
34%
27841

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
38%
972
28%
2522
13%
970
46%
970
34%
1555
January16th to endNight
37%
940
31%
2516
13%
940
48%
940
33%
1564
February1st to 15thNight
34%
704
28%
2106
12%
698
47%
698
30%
1224
February16th to endNight
25%
632
29%
1894
8%
632
41%
632
30%
1101
March1st to 15thNight
33%
543
27%
1983
15%
543
48%
543
24%
1161
March16th to endNight
34%
576
24%
2112
16%
576
45%
576
26%
1195
April1st to 15thNight
31%
539
23%
1977
13%
539
46%
539
25%
1130
April16th to endNight
30%
540
25%
1763
14%
540
46%
540
27%
1072
May1st to 15thNight
37%
539
23%
1620
17%
539
47%
539
30%
988
May16th to endNight
49%
562
25%
1684
20%
561
59%
561
35%
973
June1st to 15thNight
69%
540
23%
1620
25%
540
74%
540
51%
800
June16th to endNight
69%
540
22%
1620
24%
540
73%
540
39%
918
July1st to 15thNight
77%
510
22%
1530
23%
510
81%
510
46%
803
July16th to endNight
81%
564
27%
1594
30%
531
84%
531
47%
825
August1st to 15thNight
89%
539
31%
1627
35%
536
90%
536
57%
759
August16th to endNight
76%
573
21%
1986
25%
573
77%
573
32%
1125
September1st to 15thNight
76%
540
21%
1980
24%
540
78%
540
33%
1088
September16th to endNight
71%
537
27%
1980
30%
537
73%
537
31%
1092
October1st to 15thNight
70%
567
33%
2007
31%
567
74%
567
39%
995
October16th to endNight
59%
768
37%
2304
24%
768
67%
768
48%
1162
November1st to 15thNight
52%
763
27%
2283
18%
763
57%
763
34%
1356
November16th to endNight
47%
975
32%
2535
16%
975
55%
975
39%
1501
December1st to 15thNight
40%
975
28%
2535
15%
975
46%
975
32%
1646
December16th to endNight
37%
1040
24%
2704
11%
1040
43%
1040
28%
1808

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
12%5%2442445%7%47%
49029
Night
11%413323347%52%
48684
TransparencyDay
36%49%20%19%9%
48729
Night
32%411%21%19%11%
48489
SeeingDay
12%417%30%27%7%
5781
Night
14%6%23%35%18%1
15983

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
16%424313335%50%
1746
16th to endDay
16%423323235%51%
1821
February1st to 15thDay
15%6%23322225%52%
1750
16th to endDay
15%7%23213335%50%
1580
March1st to 15thDay
20%6%24323235%44%
1976
16th to endDay
16%6%13323235%49%
2110
April1st to 15thDay
13%5%25%5%2445%6%44%
1971
16th to endDay
14%6%25%434445%44%
2190
May1st to 15thDay
15%6%35%5%3445%6%38%
2331
16th to endDay
14%6%35%5%35%5%6%7%35%
2430
June1st to 15thDay
5%3145%35%7%6%9%46%
2340
16th to endDay
9%5%35%5%25%7%7%10%37%
2340
July1st to 15thDay
8%3245%46%6%6%10%42%
2340
16th to endDay
7%324435%6%5%9%46%
2466
August1st to 15thDay
221231445%9%61%
2320
16th to endDay
7%325%5%35%7%7%10%40%
2214
September1st to 15thDay
9%5%35%6%345%6%8%42%
1980
16th to endDay
9%414445%5%5%7%46%
1980
October1st to 15thDay
9%424323446%54%
1941
16th to endDay
7%312312335%65%
1920
November1st to 15thDay
11%7%25%424446%46%
1901
16th to endDay
13%5%13212335%56%
1755
December1st to 15thDay
17%7%2431335%5%44%
1755
16th to endDay
17%8%34424445%42%
1872
January1st to 15thNight
16%5%23212336%51%
2522
16th to endNight
17%5%13223345%50%
2516
February1st to 15thNight
16%5%2321222455%
2102
16th to endNight
14%5%23313335%52%
1894
March1st to 15thNight
17%6%14314245%48%
1983
16th to endNight
14%5%24323337%49%
2112
April1st to 15thNight
13%424324346%49%
1977
16th to endNight
15%6%34323346%46%
1763
May1st to 15thNight
11%5%25%41446%8%46%
1619
16th to endNight
9%5%1333346%10%48%
1683
June1st to 15thNight
321122335%10%62%
1620
16th to endNight
6%312425%35%10%52%
1620
July1st to 15thNight
5%21321345%13%55%
1620
16th to endNight
421322346%10%56%
1702
August1st to 15thNight
21121336%10%65%
1637
16th to endNight
7%215%5%3447%9%47%
1986
September1st to 15thNight
8%42333445%10%49%
1980
16th to endNight
8%4245%3445%7%49%
1980
October1st to 15thNight
8%313223336%61%
2007
16th to endNight
8%3221233466%
2304
November1st to 15thNight
11%5%24323445%52%
2283
16th to endNight
13%41331233458%
2535
December1st to 15thNight
15%7%34322345%47%
2535
16th to endNight
17%7%2431333446%
2704

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
36%26%19%22%12%
1747
16th to endDay
36%25%14%25%15%
1821
February1st to 15thDay
37%25%15%23%15%
1751
16th to endDay
38%2419%20%13%
1580
March1st to 15thDay
43%27%12%22%11%
1976
16th to endDay
38%38%17%22%9%
2112
April1st to 15thDay
40%47%17%17%12%
1971
16th to endDay
42%36%18%18%10%
2190
May1st to 15thDay
45%5%8%14%17%7%
2331
16th to endDay
45%6%10%17%16%3
2434
June1st to 15thDay
31%7%10%23%21%5%
2340
16th to endDay
39%7%13%21%15%2
2340
July1st to 15thDay
33%7%16%27%13%1
2201
16th to endDay
30%7%18%28%13%
2311
August1st to 15thDay
18%5%18%37%19%1
2306
16th to endDay
35%8%16%25%11%3
2214
September1st to 15thDay
38%6%11%21%15%6%
1980
16th to endDay
36%6%10%19%18%8%
1980
October1st to 15thDay
31%310%21%18%14%
1941
16th to endDay
23%25%15%31%21%
1920
November1st to 15thDay
40%37%21%16%10%
1901
16th to endDay
33%25%16%22%19%
1755
December1st to 15thDay
42%37%16%20%9%
1755
16th to endDay
44%38%15%18%9%
1872
January1st to 15thNight
35%25%17%21%16%
2522
16th to endNight
37%2415%23%17%
2516
February1st to 15thNight
35%25%14%22%20%
2112
16th to endNight
35%36%17%21%16%
1894
March1st to 15thNight
39%48%12%22%13%
1983
16th to endNight
36%310%15%22%10%
2112
April1st to 15thNight
36%48%16%18%15%
1977
16th to endNight
39%410%17%17%11%
1763
May1st to 15thNight
35%5%11%20%17%8%
1620
16th to endNight
30%5%16%27%16%3
1685
June1st to 15thNight
18%5%15%27%28%4
1620
16th to endNight
27%6%16%29%17%3
1620
July1st to 15thNight
20%7%23%33%13%1
1530
16th to endNight
20%6%25%35%11%
1594
August1st to 15thNight
13%6%22%37%18%1
1627
16th to endNight
30%7%20%26%10%3
1986
September1st to 15thNight
29%6%17%24%14%6%
1980
16th to endNight
32%5%13%22%17%9%
1980
October1st to 15thNight
25%311%25%18%14%
2007
16th to endNight
22%25%17%26%24%
2304
November1st to 15thNight
33%49%20%18%12%
2283
16th to endNight
31%25%16%22%20%
2535
December1st to 15thNight
39%37%18%19%10%
2535
16th to endNight
42%35%15%21%11%
2704

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%8%35%27%8%2
135
16th to endDay
20%10%32%25%11%
109
February1st to 15thDay
11%14%37%26%8%1
90
16th to endDay
17%12%38%27%4
81
March1st to 15thDay
28%11%30%17%11%1
90
16th to endDay
15%8%32%31%11%1
96
April1st to 15thDay
12%14%36%30%6%
90
16th to endDay
18%14%32%23%11%
300
May1st to 15thDay
16%8%37%26%10%
468
16th to endDay
22%423%32%14%3
517
June1st to 15thDay
6%110%45%28%6%
495
16th to endDay
10%19%36%31%9%
495
July1st to 15thDay
6%18%38%35%8%
475
16th to endDay
6%330%49%10%
515
August1st to 15thDay
3227%52%13%
473
16th to endDay
14%1433%32%13%
254
September1st to 15thDay
2222%54%17%
135
16th to endDay
12%122%43%19%
135
October1st to 15thDay
29%25%41%20%
135
16th to endDay
13%6%15%27%27%8%
144
November1st to 15thDay
25%320%31%15%2
135
16th to endDay
21%6%22%31%13%5%
135
December1st to 15thDay
22%5%29%22%14%5%
135
16th to endDay
30%17%25%20%41
144
January1st to 15thNight
20%9%26%32%10%
975
16th to endNight
19%9%29%33%8%
940
February1st to 15thNight
19%13%29%30%7%
704
16th to endNight
18%11%42%24%2
632
March1st to 15thNight
21%7%34%31%5%
543
16th to endNight
14%11%37%30%5%
576
April1st to 15thNight
15%8%41%32%2
539
16th to endNight
17%7%41%24%7%
540
May1st to 15thNight
14%8%36%34%6%
540
16th to endNight
11%430%36%16%
563
June1st to 15thNight
5%120%48%22%1
540
16th to endNight
6%115%47%26%2
540
July1st to 15thNight
5%19%47%31%4
510
16th to endNight
5%5%47%37%4
564
August1st to 15thNight
2349%38%6%
539
16th to endNight
8%342%40%4
573
September1st to 15thNight
10%1336%41%6%
540
16th to endNight
10%7%34%42%5%
537
October1st to 15thNight
9%112%40%28%6%
567
16th to endNight
9%422%33%26%2
768
November1st to 15thNight
14%423%35%20%1
763
16th to endNight
15%7%25%32%16%1
975
December1st to 15thNight
21%6%27%33%10%
975
16th to endNight
22%8%26%32%9%
1040
Page generated at 2018-01-21 11:19:33. Version ac04

Copyright 2018 A. Danko


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