Keene
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Keene clear sky chart from 2005-11-05 to 2018-03-21.

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
28%
15584
17%
49203
8%
15552
38%
15552
19%
32767

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
17%
780
18%
2716
6%
776
33%
776
13%
1826
January16th to endNight
15%
832
17%
2912
5%
832
31%
832
12%
1955
February1st to 15thNight
13%
764
15%
2405
3%
761
27%
761
13%
1695
February16th to endNight
17%
683
19%
2049
6%
683
34%
683
15%
1427
March1st to 15thNight
17%
780
16%
2340
6%
780
29%
780
15%
1659
March16th to endNight
22%
792
23%
2081
7%
792
35%
792
20%
1405
April1st to 15thNight
22%
718
16%
1796
4%
718
30%
718
20%
1278
April16th to endNight
25%
613
18%
1693
4%
613
34%
613
19%
1160
May1st to 15thNight
23%
523
15%
1603
7%
523
32%
523
17%
1125
May16th to endNight
36%
375
12%
1497
11%
374
43%
374
15%
1011
June1st to 15thNight
35%
360
12%
1440
10%
360
45%
360
15%
956
June16th to endNight
39%
360
11%
1440
13%
360
47%
360
19%
905
July1st to 15thNight
46%
340
13%
1360
16%
340
52%
340
21%
830
July16th to endNight
51%
376
15%
1418
17%
354
57%
354
24%
819
August1st to 15thNight
45%
458
16%
1529
10%
456
51%
456
27%
905
August16th to endNight
51%
753
20%
1899
10%
753
54%
753
35%
1212
September1st to 15thNight
42%
720
20%
1836
8%
720
48%
720
32%
1181
September16th to endNight
46%
717
26%
1980
17%
717
54%
717
34%
1186
October1st to 15thNight
35%
720
19%
2043
11%
720
44%
720
23%
1360
October16th to endNight
24%
768
15%
2478
7%
768
36%
768
17%
1687
November1st to 15thNight
28%
760
19%
2472
9%
760
41%
760
19%
1604
November16th to endNight
24%
780
20%
2574
8%
780
38%
780
17%
1674
December1st to 15thNight
19%
780
15%
2730
4%
780
33%
780
13%
1875
December16th to endNight
15%
832
16%
2912
4%
832
28%
832
11%
2032

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
17%7%35%5%3445%6%35%
49650
Night
16%7%35%43445%6%38%
49373
Cloud CoverDay
17%7%35%5%3445%6%36%
49660
Night
16%7%35%42445%6%38%
49378
TransparencyDay
47%5%11%20%12%1
49338
Night
45%5%12%21%13%1
49203
SeeingDay
22%16%28%19%9%3
6357
Night
20%16%29%24%8%
15584

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
14%7%36%5%45%5%6%7%32%
1552
16th to endDay
13%7%36%5%3446%7%37%
1664
February1st to 15thDay
15%10%37%6%47%5%46%27%
1783
16th to endDay
15%9%47%5%3435%5%33%
1710
March1st to 15thDay
19%9%47%5%34447%30%
1940
16th to endDay
16%7%46%5%23335%39%
2270
April1st to 15thDay
19%7%36%6%33345%35%
2152
16th to endDay
16%7%36%5%34445%38%
2265
May1st to 15thDay
25%8%36%5%34335%31%
2358
16th to endDay
19%6%25%5%24447%37%
2618
June1st to 15thDay
23%6%26%5%2445%7%30%
2520
16th to endDay
17%6%25%7%36%5%6%8%31%
2520
July1st to 15thDay
13%5%36%6%346%6%8%34%
2520
16th to endDay
13%5%25%6%45%6%6%7%36%
2654
August1st to 15thDay
13%5%25%5%36%5%6%8%35%
2408
16th to endDay
10%5%25%5%35%46%7%42%
2300
September1st to 15thDay
16%5%235%246%47%41%
2124
16th to endDay
14%5%24322336%50%
1980
October1st to 15thDay
21%6%25%424345%38%
1914
16th to endDay
18%8%27%5%33446%34%
1745
November1st to 15thDay
17%7%35%323347%40%
1716
16th to endDay
18%6%36%424346%40%
1713
December1st to 15thDay
19%8%36%6%35%34433%
1560
16th to endDay
21%12%35%7%24445%28%
1664
January1st to 15thNight
14%8%36%5%45%5%47%34%
2716
16th to endNight
13%9%46%6%3445%6%34%
2912
February1st to 15thNight
13%9%47%5%36%5%5%6%32%
2404
16th to endNight
14%10%35%5%25%5%5%6%34%
2049
March1st to 15thNight
17%9%26%5%24446%33%
2327
16th to endNight
15%6%2443445%5%41%
2081
April1st to 15thNight
19%7%35%43445%6%36%
1796
16th to endNight
20%6%34423345%39%
1693
May1st to 15thNight
21%8%36%42345%5%34%
1603
16th to endNight
17%6%345%45%45%8%33%
1495
June1st to 15thNight
22%6%244245%47%33%
1440
16th to endNight
14%5%25%435%5%6%8%38%
1440
July1st to 15thNight
11%425%5%35%5%6%7%41%
1440
16th to endNight
11%424425%5%6%8%44%
1514
August1st to 15thNight
10%6%25%4245%5%8%45%
1539
16th to endNight
12%5%25%32445%7%47%
1899
September1st to 15thNight
14%5%1332345%6%48%
1836
16th to endNight
12%41441335%5%53%
1980
October1st to 15thNight
19%7%245%22345%41%
2043
16th to endNight
19%8%25%5%245%5%6%34%
2478
November1st to 15thNight
16%6%36%433335%42%
2472
16th to endNight
16%7%36%42345%5%39%
2574
December1st to 15thNight
20%8%35%43445%6%34%
2730
16th to endNight
20%10%26%43445%7%30%
2912

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
14%8%45%5%45%5%5%7%33%
1552
16th to endDay
13%7%35%5%3445%7%38%
1664
February1st to 15thDay
15%10%47%6%46%6%5%6%27%
1783
16th to endDay
15%9%47%5%35%345%34%
1710
March1st to 15thDay
19%10%46%5%34446%30%
1950
16th to endDay
16%7%46%5%23345%40%
2270
April1st to 15thDay
19%8%36%6%23346%35%
2152
16th to endDay
16%7%36%5%25%445%38%
2265
May1st to 15thDay
24%9%35%5%34435%30%
2358
16th to endDay
19%6%35%434347%37%
2618
June1st to 15thDay
23%6%35%6%25%45%7%30%
2520
16th to endDay
17%6%26%6%35%5%5%9%30%
2520
July1st to 15thDay
13%6%35%6%26%6%7%8%34%
2520
16th to endDay
14%5%25%6%36%5%6%7%36%
2654
August1st to 15thDay
13%5%25%6%35%5%6%8%36%
2408
16th to endDay
10%5%245%45%45%8%42%
2300
September1st to 15thDay
15%5%245%25%45%7%41%
2124
16th to endDay
14%5%24323237%50%
1980
October1st to 15thDay
20%6%25%5%2433439%
1914
16th to endDay
18%8%36%5%24346%35%
1745
November1st to 15thDay
16%8%25%32435%6%40%
1716
16th to endDay
18%6%26%424345%41%
1713
December1st to 15thDay
19%8%46%5%35%435%33%
1560
16th to endDay
21%11%35%6%34445%28%
1664
January1st to 15thNight
13%8%35%5%35%5%5%7%35%
2716
16th to endNight
13%9%46%5%35%45%7%34%
2912
February1st to 15thNight
13%9%36%6%35%5%5%6%33%
2397
16th to endNight
14%10%35%5%25%45%7%34%
2049
March1st to 15thNight
18%9%26%5%25%45%5%34%
2340
16th to endNight
15%6%3442445%5%41%
2080
April1st to 15thNight
18%7%35%42445%6%36%
1796
16th to endNight
20%6%35%324445%39%
1693
May1st to 15thNight
19%9%45%5%2345%5%34%
1603
16th to endNight
17%6%35%6%3446%7%33%
1495
June1st to 15thNight
22%7%25%41445%7%34%
1440
16th to endNight
15%6%244335%6%8%38%
1440
July1st to 15thNight
11%426%425%6%6%7%41%
1440
16th to endNight
11%425%4335%5%8%44%
1514
August1st to 15thNight
10%5%245%245%5%8%44%
1539
16th to endNight
13%5%2442445%8%46%
1899
September1st to 15thNight
14%5%1332345%6%48%
1836
16th to endNight
12%423423346%52%
1980
October1st to 15thNight
18%7%25%423345%42%
2043
16th to endNight
20%6%35%4335%5%6%35%
2478
November1st to 15thNight
16%7%26%433335%42%
2472
16th to endNight
16%7%35%42345%5%40%
2574
December1st to 15thNight
20%7%35%42445%6%34%
2730
16th to endNight
20%10%26%42445%6%31%
2912

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
47%5%10%22%11%2
1553
16th to endDay
44%5%15%21%12%1
1664
February1st to 15thDay
55%6%10%17%9%
1786
16th to endDay
51%49%18%13%2
1710
March1st to 15thDay
54%311%16%11%1
1950
16th to endDay
47%39%18%16%4
2270
April1st to 15thDay
50%49%19%13%2
2152
16th to endDay
46%48%20%16%3
2265
May1st to 15thDay
55%46%18%12%2
2358
16th to endDay
46%6%13%19%12%1
2622
June1st to 15thDay
52%6%12%18%9%
2520
16th to endDay
48%7%12%18%11%
2520
July1st to 15thDay
43%8%13%21%12%1
2371
16th to endDay
42%8%14%22%11%
2487
August1st to 15thDay
43%8%13%23%10%1
2394
16th to endDay
38%6%11%27%14%1
2300
September1st to 15thDay
41%5%10%22%17%1
2124
16th to endDay
36%47%25%23%2
1980
October1st to 15thDay
48%48%24%11%2
1914
16th to endDay
49%412%21%10%1
1745
November1st to 15thDay
43%5%14%22%12%1
1716
16th to endDay
45%412%21%13%1
1713
December1st to 15thDay
52%5%13%16%10%
1560
16th to endDay
57%5%10%15%9%
1664
January1st to 15thNight
47%6%11%20%12%2
2716
16th to endNight
48%5%11%19%12%2
2912
February1st to 15thNight
50%5%13%18%10%1
2405
16th to endNight
48%5%10%21%10%3
2049
March1st to 15thNight
51%5%10%20%10%2
2340
16th to endNight
42%410%17%19%4
2081
April1st to 15thNight
47%411%18%17%1
1796
16th to endNight
46%5%8%18%17%3
1693
May1st to 15thNight
50%49%17%15%2
1603
16th to endNight
48%7%12%19%10%1
1497
June1st to 15thNight
49%5%13%22%8%
1440
16th to endNight
41%8%14%22%13%
1440
July1st to 15thNight
37%9%12%27%12%
1360
16th to endNight
35%8%15%28%11%1
1418
August1st to 15thNight
35%6%17%25%13%
1529
16th to endNight
35%413%30%15%
1899
September1st to 15thNight
35%6%12%26%18%1
1836
16th to endNight
32%49%29%22%1
1980
October1st to 15thNight
44%312%22%13%2
2043
16th to endNight
48%5%12%23%9%
2478
November1st to 15thNight
44%411%21%15%1
2472
16th to endNight
44%5%13%22%12%1
2574
December1st to 15thNight
49%6%14%20%9%
2730
16th to endNight
52%5%12%18%10%
2912

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
23%27%33%10%5%
90
16th to endDay
20%27%39%10%2
96
February1st to 15thDay
27%29%27%13%2
229
16th to endDay
23%25%29%17%3
291
March1st to 15thDay
31%20%32%12%3
330
16th to endDay
23%26%28%11%7%3
311
April1st to 15thDay
28%20%27%14%7%2
270
16th to endDay
20%19%30%17%8%3
270
May1st to 15thDay
32%18%22%14%9%2
288
16th to endDay
21%12%34%23%7%1
331
June1st to 15thDay
24%13%29%22%8%1
315
16th to endDay
17%16%31%23%8%2
315
July1st to 15thDay
17%8%30%27%13%2
305
16th to endDay
16%9%25%32%11%4
326
August1st to 15thDay
13%11%26%28%14%6%
313
16th to endDay
12%8%24%25%19%10%
332
September1st to 15thDay
17%11%25%21%15%8%
315
16th to endDay
15%10%27%16%14%14%
314
October1st to 15thDay
22%12%23%22%14%5%
315
16th to endDay
26%15%28%21%6%1
292
November1st to 15thDay
21%16%28%22%10%1
280
16th to endDay
26%18%26%19%6%2
243
December1st to 15thDay
24%26%30%12%5%1
90
16th to endDay
37%28%27%6%1
96
January1st to 15thNight
19%24%35%18%2
780
16th to endNight
21%21%34%20%2
832
February1st to 15thNight
20%24%36%17%1
764
16th to endNight
24%22%31%19%2
683
March1st to 15thNight
24%22%32%18%2
780
16th to endNight
21%21%29%20%6%
792
April1st to 15thNight
23%19%30%22%4
718
16th to endNight
26%16%27%21%7%
613
May1st to 15thNight
24%13%33%22%6%
523
16th to endNight
18%10%27%33%9%1
375
June1st to 15thNight
23%10%23%30%10%
360
16th to endNight
17%5%30%38%7%
360
July1st to 15thNight
13%430%40%11%1
340
16th to endNight
11%327%37%18%
376
August1st to 15thNight
12%5%27%36%15%1
458
16th to endNight
15%421%33%22%2
753
September1st to 15thNight
17%7%27%29%16%1
720
16th to endNight
14%7%25%27%20%3
717
October1st to 15thNight
23%12%22%25%13%2
720
16th to endNight
25%16%29%22%6%
768
November1st to 15thNight
19%18%26%24%9%
760
16th to endNight
21%18%30%19%8%
780
December1st to 15thNight
25%21%29%19%4
780
16th to endNight
26%21%33%15%2
832
Page generated at 2018-03-22 11:34:20. Version ac04

Copyright 2018 A. Danko


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