Penitentiary Glen Reservation
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Penitentiary Glen Reservation clear sky chart from 2005-11-05 to 2018-03-11.

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
31%
15822
12%
49186
9%
15781
36%
15781
15%
36347

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
7%
778
7%
2522
3%
776
12%
776
6%
2149
January16th to endNight
9%
832
6%
2704
1%
832
15%
832
6%
2311
February1st to 15thNight
14%
764
6%
2482
2%
761
18%
761
6%
2090
February16th to endNight
15%
683
8%
2090
3%
683
22%
683
9%
1685
March1st to 15thNight
20%
764
12%
2131
7%
764
25%
764
13%
1684
March16th to endNight
28%
768
15%
2112
9%
768
32%
768
18%
1561
April1st to 15thNight
25%
692
11%
1857
4%
692
30%
692
18%
1368
April16th to endNight
33%
540
18%
1620
8%
540
42%
540
24%
1095
May1st to 15thNight
40%
540
13%
1620
9%
540
44%
540
18%
1160
May16th to endNight
51%
501
14%
1624
13%
501
53%
501
26%
1035
June1st to 15thNight
48%
360
15%
1440
16%
360
55%
360
20%
884
June16th to endNight
53%
360
15%
1440
16%
360
60%
360
23%
863
July1st to 15thNight
59%
469
15%
1489
15%
469
63%
469
31%
888
July16th to endNight
61%
564
15%
1595
14%
531
63%
531
31%
964
August1st to 15thNight
64%
539
18%
1609
15%
536
65%
536
31%
973
August16th to endNight
62%
591
22%
1737
16%
591
65%
591
32%
1052
September1st to 15thNight
54%
720
20%
1908
13%
720
57%
720
30%
1259
September16th to endNight
51%
717
22%
1980
17%
717
55%
717
27%
1320
October1st to 15thNight
43%
720
17%
2127
15%
720
46%
720
23%
1430
October16th to endNight
19%
768
13%
2304
7%
768
27%
768
13%
1748
November1st to 15thNight
27%
760
15%
2471
12%
760
34%
760
16%
1776
November16th to endNight
14%
780
10%
2711
7%
780
19%
780
8%
2160
December1st to 15thNight
12%
780
4%
2730
3%
780
14%
780
5%
2341
December16th to endNight
7%
832
3%
2883
0%
832
11%
832
3%
2551

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
16%10%47%5%2445%6%30%
49426
Night
17%12%47%5%34446%29%
49379
Cloud CoverDay
17%11%46%5%24446%30%
49436
Night
17%11%5%7%5%34445%29%
49383
TransparencyDay
53%6%11%17%9%1
49137
Night
55%5%10%16%9%1
49186
SeeingDay
21%12%26%22%13%4
5868
Night
22%14%26%23%11%1
15826

By Month

Percentage Cloud Cover NE (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
19%18%8%9%8%2434414%
1746
16th to endDay
16%19%10%13%8%4324311%
1872
February1st to 15thDay
17%19%7%12%10%4323414%
1710
16th to endDay
17%15%7%10%7%2434420%
1669
March1st to 15thDay
19%16%6%9%423335%23%
2053
16th to endDay
19%11%5%6%5%24445%30%
2112
April1st to 15thDay
21%11%36%5%2445%6%29%
2101
16th to endDay
18%10%35%423345%38%
2340
May1st to 15thDay
18%7%36%5%45%45%6%32%
2331
16th to endDay
12%5%35%5%245%5%8%40%
2491
June1st to 15thDay
15%6%25%42446%7%39%
2520
16th to endDay
14%4245%25%5%6%10%38%
2520
July1st to 15thDay
11%5%24435%5%6%10%41%
2377
16th to endDay
11%4244245%7%10%41%
2465
August1st to 15thDay
8%425%6%36%6%7%10%38%
2340
16th to endDay
11%425%5%35%5%7%9%40%
2453
September1st to 15thDay
16%6%35%42445%8%36%
2049
16th to endDay
17%7%25%42446%6%38%
1980
October1st to 15thDay
21%6%26%5%34446%34%
1833
16th to endDay
27%10%35%424345%26%
1920
November1st to 15thDay
16%15%36%5%34436%30%
1717
16th to endDay
21%21%5%8%5%24335%18%
1577
December1st to 15thDay
18%23%10%11%5%2432312%
1560
16th to endDay
20%25%9%14%6%222239%
1690
January1st to 15thNight
20%20%9%12%6%3332315%
2522
16th to endNight
16%20%8%12%9%3333315%
2704
February1st to 15thNight
19%16%7%12%7%4433317%
2480
16th to endNight
19%13%6%11%7%3434322%
2090
March1st to 15thNight
18%14%6%8%5%3444425%
2119
16th to endNight
16%12%5%6%424345%32%
2112
April1st to 15thNight
20%12%46%42345%6%30%
1857
16th to endNight
13%7%36%5%345%5%7%37%
1620
May1st to 15thNight
19%7%36%5%35%46%7%30%
1620
16th to endNight
11%5%35%5%345%6%8%40%
1622
June1st to 15thNight
10%5%26%5%45%446%43%
1440
16th to endNight
9%435%5%35%7%5%9%41%
1440
July1st to 15thNight
8%425%4235%6%8%48%
1579
16th to endNight
8%4245%2445%8%46%
1703
August1st to 15thNight
8%414435%6%6%9%45%
1620
16th to endNight
11%424335%45%8%46%
1737
September1st to 15thNight
13%5%244245%5%6%43%
1908
16th to endNight
16%5%245%3446%6%41%
1980
October1st to 15thNight
17%6%2443345%7%39%
2127
16th to endNight
27%8%26%5%3335%6%26%
2304
November1st to 15thNight
19%13%35%423346%31%
2471
16th to endNight
22%19%47%5%2434419%
2711
December1st to 15thNight
21%22%8%9%5%2333314%
2730
16th to endNight
22%21%8%10%7%343449%
2883

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
19%18%7%9%8%3443415%
1746
16th to endDay
16%20%10%13%8%3323311%
1872
February1st to 15thDay
18%19%9%11%9%4232415%
1710
16th to endDay
17%15%7%11%7%2344420%
1669
March1st to 15thDay
20%16%7%8%422336%23%
2064
16th to endDay
19%12%5%6%424336%30%
2111
April1st to 15thDay
21%12%45%424446%29%
2101
16th to endDay
19%10%35%423335%38%
2340
May1st to 15thDay
18%8%26%6%46%446%32%
2331
16th to endDay
13%5%25%5%345%5%8%40%
2491
June1st to 15thDay
17%5%2442436%7%39%
2520
16th to endDay
14%5%24425%5%6%10%38%
2520
July1st to 15thDay
12%425%4345%6%9%41%
2377
16th to endDay
11%5%244246%6%10%41%
2465
August1st to 15thDay
9%5%25%5%36%6%7%9%38%
2340
16th to endDay
12%5%25%435%6%5%9%39%
2453
September1st to 15thDay
17%6%245%2445%8%36%
2049
16th to endDay
17%7%25%42445%6%38%
1980
October1st to 15thDay
22%6%25%434446%34%
1833
16th to endDay
28%9%35%423345%27%
1920
November1st to 15thDay
16%15%35%5%24446%30%
1717
16th to endDay
21%22%5%7%5%23336%18%
1577
December1st to 15thDay
19%22%11%10%6%2432313%
1560
16th to endDay
19%24%11%13%6%1222310%
1690
January1st to 15thNight
20%19%9%11%7%2332315%
2522
16th to endNight
16%19%9%12%9%3332315%
2704
February1st to 15thNight
19%16%7%12%6%4433317%
2473
16th to endNight
19%14%6%11%7%3433322%
2090
March1st to 15thNight
18%14%6%8%5%2444425%
2131
16th to endNight
16%12%6%6%423345%32%
2112
April1st to 15thNight
20%12%46%42345%5%30%
1857
16th to endNight
13%7%36%5%35%5%5%6%38%
1620
May1st to 15thNight
19%7%36%5%35%46%7%30%
1619
16th to endNight
12%5%35%5%335%6%8%40%
1622
June1st to 15thNight
11%5%27%5%44447%42%
1440
16th to endNight
9%5%25%5%35%6%6%9%41%
1440
July1st to 15thNight
9%4244235%6%8%48%
1579
16th to endNight
8%5%24425%5%5%8%46%
1703
August1st to 15thNight
9%3145%35%5%7%8%45%
1620
16th to endNight
11%424425%45%8%46%
1737
September1st to 15thNight
14%5%244345%5%6%44%
1908
16th to endNight
16%425%5%35%35%6%41%
1980
October1st to 15thNight
17%6%24433447%39%
2127
16th to endNight
28%8%35%42345%5%26%
2304
November1st to 15thNight
19%13%35%5%24346%31%
2471
16th to endNight
22%20%47%5%23445%19%
2711
December1st to 15thNight
21%22%9%8%43433314%
2730
16th to endNight
22%20%8%10%6%433449%
2883

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
73%5%9%8%3
1747
16th to endDay
78%39%6%1
1872
February1st to 15thDay
75%46%10%3
1712
16th to endDay
66%5%10%11%5%1
1669
March1st to 15thDay
63%5%10%14%5%
2064
16th to endDay
55%5%8%20%8%1
2112
April1st to 15thDay
54%5%12%16%10%
2101
16th to endDay
48%5%10%18%12%4
2340
May1st to 15thDay
51%7%9%19%10%1
2331
16th to endDay
40%7%14%23%12%1
2495
June1st to 15thDay
42%6%12%24%11%1
2520
16th to endDay
39%8%13%22%15%1
2520
July1st to 15thDay
38%7%10%23%18%1
2238
16th to endDay
35%8%15%24%15%1
2310
August1st to 15thDay
37%9%14%24%13%
2327
16th to endDay
38%8%14%21%13%2
2453
September1st to 15thDay
44%7%12%21%11%1
2049
16th to endDay
44%5%11%22%15%1
1980
October1st to 15thDay
50%6%11%17%12%
1833
16th to endDay
58%414%15%6%
1920
November1st to 15thDay
54%6%9%17%9%2
1717
16th to endDay
68%411%10%5%
1577
December1st to 15thDay
77%48%7%1
1560
16th to endDay
82%38%41
1690
January1st to 15thNight
75%37%9%4
2522
16th to endNight
75%39%9%2
2704
February1st to 15thNight
72%5%8%10%3
2482
16th to endNight
66%5%9%14%5%
2090
March1st to 15thNight
61%5%8%15%8%
2131
16th to endNight
53%5%9%19%9%1
2112
April1st to 15thNight
54%412%16%12%
1857
16th to endNight
44%6%10%19%14%4
1620
May1st to 15thNight
50%6%11%18%10%2
1620
16th to endNight
38%7%13%23%13%2
1624
June1st to 15thNight
41%6%9%24%16%1
1440
16th to endNight
37%8%12%22%15%2
1440
July1st to 15thNight
32%7%11%25%19%3
1489
16th to endNight
33%7%14%21%18%3
1595
August1st to 15thNight
32%8%13%27%15%1
1609
16th to endNight
34%6%12%26%16%3
1737
September1st to 15thNight
39%6%13%23%15%2
1908
16th to endNight
42%5%10%21%18%1
1980
October1st to 15thNight
44%6%13%18%17%1
2127
16th to endNight
58%5%12%16%6%
2304
November1st to 15thNight
54%411%15%9%3
2471
16th to endNight
67%49%13%5%
2711
December1st to 15thNight
74%5%8%8%3
2730
16th to endNight
79%49%6%
2883

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
20%33%31%11%4
135
16th to endDay
33%25%33%6%
144
February1st to 15thDay
32%28%33%5%
135
16th to endDay
30%25%39%5%
120
March1st to 15thDay
26%21%32%15%3
280
16th to endDay
27%16%30%17%7%1
288
April1st to 15thDay
26%18%27%19%7%1
270
16th to endDay
21%13%31%21%9%3
270
May1st to 15thDay
22%10%30%25%9%1
288
16th to endDay
16%6%31%26%15%4
331
June1st to 15thDay
20%328%30%14%2
315
16th to endDay
18%6%29%29%13%2
315
July1st to 15thDay
17%325%28%19%5%
305
16th to endDay
12%221%32%23%7%
326
August1st to 15thDay
12%220%33%21%8%
313
16th to endDay
15%416%29%21%12%
332
September1st to 15thDay
18%5%16%25%25%8%
315
16th to endDay
18%7%16%20%24%12%
314
October1st to 15thDay
21%11%20%25%18%3
315
16th to endDay
32%15%29%19%3
336
November1st to 15thDay
23%19%20%23%10%2
135
16th to endDay
31%25%25%13%3
94
December1st to 15thDay
23%32%25%14%22
90
16th to endDay
31%40%27%
102
January1st to 15thNight
28%25%31%11%2
780
16th to endNight
25%24%33%14%2
832
February1st to 15thNight
27%23%28%16%2
764
16th to endNight
25%20%32%18%2
683
March1st to 15thNight
23%18%33%20%3
764
16th to endNight
22%14%30%22%9%1
768
April1st to 15thNight
24%17%27%24%6%
692
16th to endNight
16%9%36%26%10%1
540
May1st to 15thNight
21%7%23%34%12%
540
16th to endNight
14%421%36%18%3
503
June1st to 15thNight
11%328%37%18%1
360
16th to endNight
10%327%39%18%
360
July1st to 15thNight
8%321%35%26%4
469
16th to endNight
10%316%37%27%3
564
August1st to 15thNight
11%214%39%27%5%
539
16th to endNight
12%315%31%33%4
591
September1st to 15thNight
16%5%17%29%27%3
720
16th to endNight
17%6%18%25%24%6%
717
October1st to 15thNight
20%9%22%27%18%1
720
16th to endNight
33%15%28%17%4
768
November1st to 15thNight
26%12%29%20%8%1
760
16th to endNight
34%22%24%11%5%
780
December1st to 15thNight
33%23%25%13%3
780
16th to endNight
32%24%30%11%1
832
Page generated at 2018-03-12 13:28:10. Version ac04

Copyright 2018 A. Danko


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