Randolph State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Randolph State Park clear sky chart from 2005-11-05 to 2017-09-22.

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
42%
15930
24%
47083
14%
15885
51%
15885
34%
27343

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
33%
900
23%
2327
9%
895
43%
895
34%
1456
January16th to endNight
32%
960
27%
2496
10%
960
43%
960
37%
1510
February1st to 15thNight
28%
879
16%
2288
5%
875
35%
875
25%
1579
February16th to endNight
29%
635
26%
1897
8%
635
43%
635
30%
1127
March1st to 15thNight
35%
567
23%
2007
14%
567
47%
567
29%
1112
March16th to endNight
27%
576
17%
2112
10%
576
38%
576
21%
1322
April1st to 15thNight
29%
539
20%
1896
11%
539
43%
539
28%
1064
April16th to endNight
32%
540
23%
1620
15%
540
44%
540
26%
1028
May1st to 15thNight
37%
539
18%
1620
14%
539
45%
539
26%
1045
May16th to endNight
46%
561
17%
1684
11%
561
52%
561
32%
1016
June1st to 15thNight
53%
540
18%
1620
11%
540
58%
540
41%
877
June16th to endNight
60%
540
23%
1620
13%
540
65%
540
51%
789
July1st to 15thNight
67%
510
17%
1530
13%
510
69%
510
43%
820
July16th to endNight
73%
564
24%
1594
23%
531
75%
531
43%
853
August1st to 15thNight
73%
539
23%
1610
24%
536
76%
536
44%
838
August16th to endNight
68%
573
29%
1745
30%
573
73%
573
42%
937
September1st to 15thNight
56%
540
24%
1950
23%
540
65%
540
34%
1026
September16th to endNight
54%
513
30%
1891
26%
513
65%
513
37%
934
October1st to 15thNight
41%
601
28%
1921
20%
601
49%
601
31%
1103
October16th to endNight
42%
704
30%
2112
16%
704
52%
704
40%
1123
November1st to 15thNight
43%
850
31%
2250
13%
850
53%
850
44%
1230
November16th to endNight
37%
900
28%
2340
11%
900
48%
900
38%
1381
December1st to 15thNight
31%
900
20%
2457
8%
900
40%
900
30%
1545
December16th to endNight
32%
960
26%
2496
11%
960
43%
960
30%
1628

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
10%5%2442445%7%47%
47781
Night
9%5%2442345%7%51%
47279
Cloud CoverDay
10%5%2442445%7%47%
47779
Night
9%5%2442335%7%51%
47279
TransparencyDay
36%5%13%26%16%2
47479
Night
32%413%27%18%3
47084
SeeingDay
12%6%27%32%16%3
5937
Night
12%8%32%34%11%
15934

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
9%5%145%34447%49%
1611
16th to endDay
9%7%36%42345%6%46%
1728
February1st to 15thDay
10%9%37%42345%7%40%
1582
16th to endDay
7%7%35%434447%47%
1580
March1st to 15thDay
10%8%25%5%2445%6%43%
1953
16th to endDay
18%8%35%5%13445%39%
2112
April1st to 15thDay
13%6%26%424346%44%
2049
16th to endDay
18%7%35%5%24446%38%
2340
May1st to 15thDay
14%6%35%5%3445%6%41%
2331
16th to endDay
13%6%25%435%5%6%6%40%
2430
June1st to 15thDay
9%3244245%36%51%
2340
16th to endDay
5%213235%46%8%55%
2340
July1st to 15thDay
7%324436%5%7%8%45%
2340
16th to endDay
5%313435%6%6%9%49%
2466
August1st to 15thDay
7%31442446%9%50%
2340
16th to endDay
7%42343336%7%53%
2456
September1st to 15thDay
11%42432345%7%49%
2007
16th to endDay
8%314423447%55%
1881
October1st to 15thDay
13%5%14322346%52%
1697
16th to endDay
9%41441333457%
1760
November1st to 15thDay
7%31332345%6%59%
1605
16th to endDay
12%5%23323246%53%
1620
December1st to 15thDay
11%8%25%7%2445%5%41%
1485
16th to endDay
12%8%47%42445%7%38%
1728
January1st to 15thNight
6%6%35%425%35%6%50%
2327
16th to endNight
8%5%24423236%54%
2496
February1st to 15thNight
9%8%36%5%44446%41%
2278
16th to endNight
7%6%245%2445%6%49%
1897
March1st to 15thNight
8%6%2432345%7%50%
2007
16th to endNight
16%7%25%42335%6%41%
2112
April1st to 15thNight
11%5%2442335%6%49%
1896
16th to endNight
16%6%2442445%7%43%
1620
May1st to 15thNight
13%6%26%4145%45%44%
1619
16th to endNight
12%32342346%9%47%
1683
June1st to 15thNight
5%31332445%9%54%
1620
16th to endNight
41222446%10%60%
1620
July1st to 15thNight
5%213425%5%5%9%55%
1620
16th to endNight
3213335%5%7%9%53%
1702
August1st to 15thNight
421332446%10%55%
1620
16th to endNight
6%31332345%6%58%
1745
September1st to 15thNight
9%42432345%7%53%
1950
16th to endNight
8%223422346%58%
1891
October1st to 15thNight
13%414423345%52%
1921
16th to endNight
9%413212236%60%
2112
November1st to 15thNight
6%413313347%60%
2250
16th to endNight
10%5%13213445%56%
2340
December1st to 15thNight
11%5%25%42345%6%47%
2457
16th to endNight
12%8%35%313246%46%
2496

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
9%5%145%34347%48%
1611
16th to endDay
9%6%36%433446%46%
1728
February1st to 15thDay
10%9%37%5%2345%7%40%
1582
16th to endDay
7%7%35%425%347%46%
1580
March1st to 15thDay
11%7%25%5%3446%6%43%
1953
16th to endDay
18%8%35%5%23346%38%
2110
April1st to 15thDay
13%6%36%42435%6%43%
2049
16th to endDay
18%6%35%5%34346%37%
2340
May1st to 15thDay
14%6%35%5%3345%6%40%
2331
16th to endDay
13%6%34435%5%6%7%40%
2430
June1st to 15thDay
9%324425%5%37%51%
2340
16th to endDay
5%213325%5%6%8%55%
2340
July1st to 15thDay
7%424435%6%6%8%46%
2340
16th to endDay
5%323426%6%6%9%49%
2466
August1st to 15thDay
7%32443446%9%50%
2340
16th to endDay
8%32342336%7%53%
2456
September1st to 15thDay
11%42342345%7%49%
2007
16th to endDay
8%314424447%55%
1881
October1st to 15thDay
13%423323345%53%
1697
16th to endDay
9%5%2432333457%
1760
November1st to 15thDay
7%213324446%59%
1605
16th to endDay
12%6%23323346%53%
1620
December1st to 15thDay
11%8%25%7%3445%6%40%
1485
16th to endDay
12%8%47%42435%7%38%
1728
January1st to 15thNight
6%6%35%435%346%50%
2327
16th to endNight
8%6%24423246%54%
2496
February1st to 15thNight
10%8%46%5%34446%40%
2278
16th to endNight
7%5%25%424447%49%
1897
March1st to 15thNight
8%6%2432345%7%50%
2007
16th to endNight
17%6%35%42335%6%41%
2112
April1st to 15thNight
11%5%15%42335%6%50%
1896
16th to endNight
16%6%2442345%7%42%
1620
May1st to 15thNight
13%6%26%424446%43%
1619
16th to endNight
12%42332345%9%47%
1683
June1st to 15thNight
5%31342345%9%55%
1620
16th to endNight
41222346%10%60%
1620
July1st to 15thNight
5%213425%5%5%9%54%
1620
16th to endNight
32134345%6%9%53%
1702
August1st to 15thNight
421431446%10%54%
1620
16th to endNight
6%41342335%6%58%
1745
September1st to 15thNight
9%32432435%7%53%
1950
16th to endNight
8%224413346%58%
1891
October1st to 15thNight
13%414313346%52%
1921
16th to endNight
9%5%13212235%60%
2112
November1st to 15thNight
6%413313347%59%
2250
16th to endNight
10%5%23223345%56%
2340
December1st to 15thNight
11%5%25%423446%47%
2457
16th to endNight
12%9%34413247%45%
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
35%416%28%13%2
1612
16th to endDay
37%416%26%13%1
1728
February1st to 15thDay
44%415%23%9%2
1583
16th to endDay
37%413%25%15%2
1580
March1st to 15thDay
40%412%23%16%2
1953
16th to endDay
46%5%12%22%10%2
2112
April1st to 15thDay
41%412%24%16%
2049
16th to endDay
47%411%22%12%
2340
May1st to 15thDay
43%5%11%24%13%1
2331
16th to endDay
41%5%17%23%10%1
2434
June1st to 15thDay
33%6%13%29%15%2
2340
16th to endDay
23%6%16%30%20%2
2340
July1st to 15thDay
33%6%12%27%16%3
2201
16th to endDay
26%6%14%31%18%2
2311
August1st to 15thDay
29%6%17%27%16%2
2326
16th to endDay
29%5%11%27%19%6%
2456
September1st to 15thDay
33%412%24%19%5%
2007
16th to endDay
29%412%30%22%1
1881
October1st to 15thDay
33%310%24%25%3
1697
16th to endDay
30%311%28%21%4
1760
November1st to 15thDay
24%411%27%26%4
1605
16th to endDay
33%311%30%19%1
1620
December1st to 15thDay
44%416%23%11%
1485
16th to endDay
45%315%22%11%
1728
January1st to 15thNight
35%316%25%18%
2327
16th to endNight
32%316%28%16%3
2496
February1st to 15thNight
44%5%13%23%11%2
2288
16th to endNight
34%412%26%17%4
1897
March1st to 15thNight
33%313%24%19%4
2007
16th to endNight
43%413%22%12%3
2112
April1st to 15thNight
34%312%26%20%2
1896
16th to endNight
40%5%10%26%16%1
1620
May1st to 15thNight
41%5%12%21%17%1
1620
16th to endNight
33%6%20%23%14%1
1685
June1st to 15thNight
25%5%17%30%16%4
1620
16th to endNight
17%5%15%35%21%4
1620
July1st to 15thNight
24%6%16%30%18%4
1530
16th to endNight
24%6%13%32%21%2
1594
August1st to 15thNight
23%5%19%30%18%3
1610
16th to endNight
25%410%28%23%7%
1745
September1st to 15thNight
29%5%12%27%17%8%
1950
16th to endNight
26%310%28%25%4
1891
October1st to 15thNight
34%38%24%23%5%
1921
16th to endNight
26%310%30%24%5%
2112
November1st to 15thNight
24%311%26%25%8%
2250
16th to endNight
30%310%31%20%3
2340
December1st to 15thNight
36%5%15%28%13%
2457
16th to endNight
39%315%23%15%2
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
16%14%45%15%7%
90
16th to endDay
12%11%37%32%6%
96
February1st to 15thDay
10%17%47%17%6%
90
16th to endDay
11%17%37%23%8%2
81
March1st to 15thDay
16%16%42%20%22
90
16th to endDay
21%11%42%20%3
96
April1st to 15thDay
19%13%35%23%8%
168
16th to endDay
21%15%34%20%6%1
450
May1st to 15thDay
17%11%30%26%11%2
468
16th to endDay
16%6%34%28%11%1
517
June1st to 15thDay
8%426%36%20%3
495
16th to endDay
5%335%36%16%3
495
July1st to 15thDay
10%217%39%25%4
475
16th to endDay
7%112%44%30%4
515
August1st to 15thDay
7%113%45%28%3
493
16th to endDay
10%219%36%25%6%
496
September1st to 15thDay
7%425%38%18%4
162
16th to endDay
7%231%37%16%4
108
October1st to 15thDay
13%5%26%36%11%6%
90
16th to endDay
8%7%43%29%10%1
96
November1st to 15thDay
7%6%30%35%13%6%
90
16th to endDay
35%11%40%11%2
90
December1st to 15thDay
13%17%45%13%6%3
90
16th to endDay
17%17%38%22%3
96
January1st to 15thNight
9%11%39%30%7%
900
16th to endNight
11%10%40%30%5%
960
February1st to 15thNight
14%11%39%30%3
880
16th to endNight
11%13%41%26%6%
635
March1st to 15thNight
13%12%35%31%7%
567
16th to endNight
18%12%37%24%5%
576
April1st to 15thNight
15%10%40%28%4
539
16th to endNight
20%10%35%26%6%
540
May1st to 15thNight
15%9%32%31%10%1
540
16th to endNight
14%431%35%12%1
563
June1st to 15thNight
6%431%39%18%
540
16th to endNight
4229%47%15%
540
July1st to 15thNight
5%19%50%21%
510
16th to endNight
4113%51%27%1
564
August1st to 15thNight
5%12%51%27%1
539
16th to endNight
7%315%42%26%4
573
September1st to 15thNight
10%423%38%21%2
540
16th to endNight
9%228%38%20%1
513
October1st to 15thNight
15%7%30%30%14%1
601
16th to endNight
11%8%33%35%9%
704
November1st to 15thNight
9%10%33%35%10%
850
16th to endNight
13%12%34%30%8%
900
December1st to 15thNight
15%11%38%29%5%
900
16th to endNight
17%10%33%32%5%
960
Page generated at 2017-09-23 05:43:46. Version ac04

Copyright 2017 A. Danko


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