Whitin Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Whitin Observatory clear sky chart from 2005-11-05 to 2018-02-14.

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
27%
15510
18%
48771
8%
15478
39%
15478
21%
31774

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
19%
2716
6%
776
33%
776
17%
1734
January16th to endNight
15%
832
19%
2912
4%
832
33%
832
15%
1860
February1st to 15thNight
17%
760
17%
2358
5%
757
32%
757
17%
1604
February16th to endNight
17%
631
23%
1893
6%
631
37%
631
19%
1249
March1st to 15thNight
17%
720
17%
2154
6%
720
31%
720
17%
1495
March16th to endNight
20%
768
23%
2034
7%
768
34%
768
22%
1395
April1st to 15thNight
20%
718
18%
1796
4%
718
29%
718
21%
1275
April16th to endNight
23%
591
18%
1671
4%
591
32%
591
19%
1140
May1st to 15thNight
22%
540
15%
1620
7%
540
30%
540
17%
1129
May16th to endNight
25%
422
11%
1544
7%
421
33%
421
16%
1018
June1st to 15thNight
27%
360
11%
1440
7%
360
38%
360
15%
964
June16th to endNight
35%
360
12%
1440
11%
360
45%
360
21%
875
July1st to 15thNight
40%
340
12%
1360
13%
340
47%
340
23%
806
July16th to endNight
43%
376
15%
1418
12%
354
51%
354
20%
882
August1st to 15thNight
42%
512
16%
1583
10%
510
46%
510
27%
979
August16th to endNight
53%
723
21%
1869
11%
723
56%
723
35%
1185
September1st to 15thNight
39%
720
19%
1863
8%
720
45%
720
31%
1219
September16th to endNight
45%
717
25%
1980
17%
717
52%
717
34%
1214
October1st to 15thNight
35%
720
23%
2004
11%
720
45%
720
26%
1285
October16th to endNight
25%
768
18%
2496
7%
768
41%
768
21%
1605
November1st to 15thNight
29%
760
19%
2472
10%
760
42%
760
21%
1582
November16th to endNight
25%
780
22%
2535
8%
780
41%
780
19%
1590
December1st to 15thNight
20%
780
17%
2701
5%
780
35%
780
16%
1762
December16th to endNight
15%
832
19%
2912
5%
832
32%
832
15%
1927

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%6%2443445%6%40%
49321
Night
17%6%25%424446%41%
48941
Cloud CoverDay
17%6%25%42445%6%39%
49331
Night
16%7%25%424446%40%
48946
TransparencyDay
43%5%11%21%14%2
49009
Night
43%5%11%21%15%2
48771
SeeingDay
22%13%32%20%8%2
6334
Night
21%12%33%24%7%
15510

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
16%8%25%324445%42%
1552
16th to endDay
16%6%2443335%6%42%
1664
February1st to 15thDay
18%6%345%245%5%6%35%
1802
16th to endDay
14%8%245%35%345%41%
1580
March1st to 15thDay
21%7%25%434447%35%
1796
16th to endDay
18%6%35%433346%41%
2190
April1st to 15thDay
19%6%26%5%33345%38%
2152
16th to endDay
19%41443445%7%40%
2289
May1st to 15thDay
24%8%25%424335%32%
2332
16th to endDay
17%5%245%2445%8%38%
2580
June1st to 15thDay
25%5%2442445%7%32%
2520
16th to endDay
15%5%25%5%35%6%6%8%35%
2520
July1st to 15thDay
12%425%5%36%6%5%8%37%
2520
16th to endDay
12%435%6%35%5%5%8%38%
2654
August1st to 15thDay
12%5%25%5%36%5%6%6%39%
2355
16th to endDay
11%4245%35%46%8%43%
2332
September1st to 15thDay
14%425%334446%46%
2096
16th to endDay
16%5%2432325%5%50%
1980
October1st to 15thDay
21%5%135%23236%44%
1955
16th to endDay
17%6%24424346%43%
1728
November1st to 15thDay
21%7%2432334343%
1716
16th to endDay
17%5%2432445%5%44%
1755
December1st to 15thDay
17%7%25%433445%40%
1589
16th to endDay
22%8%24335%345%36%
1664
January1st to 15thNight
16%8%25%424245%41%
2716
16th to endNight
15%9%35%5%23345%40%
2912
February1st to 15thNight
16%8%25%5%3445%5%37%
2357
16th to endNight
16%9%34323346%41%
1893
March1st to 15thNight
18%7%25%43445%5%37%
2141
16th to endNight
15%8%35%42433444%
2034
April1st to 15thNight
17%7%26%434446%37%
1796
16th to endNight
22%5%245%23335%40%
1671
May1st to 15thNight
22%6%43424446%36%
1620
16th to endNight
19%6%35%5%325%48%35%
1542
June1st to 15thNight
23%5%35%424347%34%
1440
16th to endNight
15%424435%5%5%8%41%
1440
July1st to 15thNight
11%5%25%5%345%7%8%40%
1440
16th to endNight
11%5%35%5%45%5%5%9%38%
1514
August1st to 15thNight
9%4145%35%5%7%7%44%
1593
16th to endNight
12%413325%45%9%46%
1869
September1st to 15thNight
14%4245%24446%46%
1863
16th to endNight
14%5%23322345%51%
1980
October1st to 15thNight
18%5%23323335%46%
2004
16th to endNight
19%5%24433346%40%
2496
November1st to 15thNight
17%6%25%324435%44%
2472
16th to endNight
17%5%35%323345%44%
2535
December1st to 15thNight
19%7%25%5%23346%39%
2701
16th to endNight
18%9%35%423346%38%
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
15%8%3432445%5%42%
1552
16th to endDay
16%6%25%42335%6%42%
1664
February1st to 15thDay
17%7%25%5%3445%6%36%
1802
16th to endDay
14%8%25%5%35%445%41%
1580
March1st to 15thDay
20%8%25%4235%47%35%
1806
16th to endDay
18%6%35%424345%41%
2190
April1st to 15thDay
18%7%36%5%24346%37%
2152
16th to endDay
18%4245%2445%7%40%
2289
May1st to 15thDay
23%8%35%5%24435%33%
2332
16th to endDay
17%5%25%434448%38%
2580
June1st to 15thDay
25%5%24424447%32%
2520
16th to endDay
14%5%25%6%36%5%7%8%35%
2520
July1st to 15thDay
11%5%245%37%5%6%8%36%
2520
16th to endDay
11%5%35%5%36%6%6%8%37%
2654
August1st to 15thDay
12%6%25%5%35%6%5%9%37%
2355
16th to endDay
11%5%25%435%45%8%43%
2332
September1st to 15thDay
13%425%42345%6%46%
2096
16th to endDay
16%5%24323345%49%
1980
October1st to 15thDay
21%424423336%43%
1955
16th to endDay
16%6%24424446%43%
1728
November1st to 15thDay
20%7%2332424443%
1716
16th to endDay
16%5%2433445%5%43%
1755
December1st to 15thDay
18%6%35%43435%5%39%
1589
16th to endDay
22%8%23425%436%36%
1664
January1st to 15thNight
16%8%35%424345%41%
2716
16th to endNight
15%10%35%423445%40%
2912
February1st to 15thNight
16%8%35%5%34346%37%
2350
16th to endNight
16%8%34334346%41%
1893
March1st to 15thNight
18%8%35%5%2445%6%36%
2154
16th to endNight
15%8%35%42333443%
2033
April1st to 15thNight
16%8%36%44345%6%36%
1796
16th to endNight
21%5%245%24245%39%
1671
May1st to 15thNight
21%8%25%43435%6%35%
1620
16th to endNight
18%6%3443445%8%35%
1542
June1st to 15thNight
23%5%25%42445%7%34%
1440
16th to endNight
15%4245%245%5%8%40%
1440
July1st to 15thNight
10%5%35%4245%6%9%39%
1440
16th to endNight
11%5%35%6%45%5%6%9%36%
1514
August1st to 15thNight
9%4246%35%5%6%8%42%
1593
16th to endNight
12%413425%45%9%45%
1869
September1st to 15thNight
13%4235%2445%6%45%
1863
16th to endNight
14%5%23313435%51%
1980
October1st to 15thNight
19%5%14323345%45%
2004
16th to endNight
19%5%25%433446%40%
2496
November1st to 15thNight
17%6%25%423345%43%
2472
16th to endNight
17%6%34423445%44%
2535
December1st to 15thNight
19%7%25%424345%39%
2701
16th to endNight
18%9%35%423347%37%
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
42%6%9%23%13%3
1553
16th to endDay
41%411%26%14%1
1664
February1st to 15thDay
47%5%13%19%12%1
1805
16th to endDay
44%5%11%21%14%3
1580
March1st to 15thDay
48%412%21%10%3
1806
16th to endDay
44%49%20%14%5%
2190
April1st to 15thDay
47%410%19%15%3
2152
16th to endDay
43%49%20%17%3
2289
May1st to 15thDay
53%48%17%14%2
2332
16th to endDay
42%6%13%21%13%2
2584
June1st to 15thDay
50%5%12%19%9%1
2520
16th to endDay
43%8%12%19%14%1
2520
July1st to 15thDay
41%8%11%21%14%2
2371
16th to endDay
41%7%13%21%12%3
2487
August1st to 15thDay
40%7%14%22%13%1
2341
16th to endDay
37%6%10%25%17%1
2332
September1st to 15thDay
36%6%11%23%20%2
2096
16th to endDay
37%37%25%24%2
1980
October1st to 15thDay
42%49%25%14%3
1955
16th to endDay
40%5%11%23%16%2
1728
November1st to 15thDay
45%312%22%14%1
1716
16th to endDay
40%411%25%15%2
1755
December1st to 15thDay
46%315%16%17%
1589
16th to endDay
50%5%12%18%11%1
1664
January1st to 15thNight
45%312%21%14%1
2716
16th to endNight
46%312%19%15%2
2912
February1st to 15thNight
47%412%20%12%2
2358
16th to endNight
44%39%22%16%2
1893
March1st to 15thNight
48%5%9%19%13%3
2154
16th to endNight
44%37%18%19%5%
2034
April1st to 15thNight
46%49%19%16%2
1796
16th to endNight
46%5%8%19%16%4
1671
May1st to 15thNight
49%5%10%17%14%3
1620
16th to endNight
46%6%15%18%9%2
1544
June1st to 15thNight
48%6%13%19%10%1
1440
16th to endNight
39%7%12%23%14%1
1440
July1st to 15thNight
37%7%14%26%13%
1360
16th to endNight
41%7%13%26%9%2
1418
August1st to 15thNight
36%8%16%22%14%2
1583
16th to endNight
34%5%13%26%18%
1869
September1st to 15thNight
38%5%11%24%19%1
1863
16th to endNight
35%48%23%27%2
1980
October1st to 15thNight
40%311%23%16%3
2004
16th to endNight
43%413%23%14%
2496
November1st to 15thNight
43%410%22%15%3
2472
16th to endNight
42%312%23%15%2
2535
December1st to 15thNight
47%414%20%12%
2701
16th to endNight
47%411%20%13%1
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%24%31%16%4
90
16th to endDay
30%21%32%15%
96
February1st to 15thDay
28%18%35%14%2
276
16th to endDay
19%17%38%18%4
239
March1st to 15thDay
33%17%30%14%4
270
16th to endDay
22%21%34%10%10%1
288
April1st to 15thDay
25%17%31%17%7%1
270
16th to endDay
22%16%34%19%42
270
May1st to 15thDay
37%14%23%14%6%1
288
16th to endDay
21%13%36%21%6%
331
June1st to 15thDay
27%10%35%18%6%
315
16th to endDay
14%14%38%24%5%2
315
July1st to 15thDay
19%7%34%27%9%
305
16th to endDay
13%6%34%31%10%3
326
August1st to 15thDay
14%9%30%30%13%2
313
16th to endDay
13%6%29%26%18%4
332
September1st to 15thDay
18%7%31%23%14%4
315
16th to endDay
23%5%25%20%13%12%
314
October1st to 15thDay
23%9%25%22%12%6%
313
16th to endDay
21%13%32%21%9%
288
November1st to 15thDay
25%12%31%17%8%3
280
16th to endDay
22%17%30%18%9%1
285
December1st to 15thDay
26%22%32%13%5%
119
16th to endDay
25%30%33%10%1
96
January1st to 15thNight
23%16%38%18%2
780
16th to endNight
23%17%37%18%2
832
February1st to 15thNight
22%16%38%21%1
760
16th to endNight
23%17%37%18%3
631
March1st to 15thNight
23%17%38%17%3
720
16th to endNight
20%17%35%19%5%
768
April1st to 15thNight
21%18%35%20%4
718
16th to endNight
23%17%32%20%5%
591
May1st to 15thNight
26%14%33%21%4
540
16th to endNight
21%11%36%25%4
422
June1st to 15thNight
24%6%35%26%7%
360
16th to endNight
15%440%33%6%
360
July1st to 15thNight
12%335%38%10%
340
16th to endNight
11%332%40%10%
376
August1st to 15thNight
11%433%40%9%
512
16th to endNight
15%223%40%15%2
723
September1st to 15thNight
16%6%32%31%12%
720
16th to endNight
19%5%24%26%20%2
717
October1st to 15thNight
22%9%27%26%12%2
720
16th to endNight
22%14%33%20%8%
768
November1st to 15thNight
20%13%30%23%10%1
760
16th to endNight
21%17%30%21%7%
780
December1st to 15thNight
23%16%34%20%4
780
16th to endNight
25%16%37%18%2
832
Page generated at 2018-02-15 10:58:43. Version ac04

Copyright 2018 A. Danko


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