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 2017-08-12.

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%
14770
18%
46457
7%
14738
39%
14738
20%
30340

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%
720
19%
2506
6%
716
33%
716
16%
1617
January16th to endNight
15%
768
19%
2688
4%
768
34%
768
15%
1708
February1st to 15thNight
17%
704
17%
2186
5%
701
32%
701
17%
1473
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
21%
768
23%
2034
7%
768
34%
768
22%
1395
April1st to 15thNight
21%
718
18%
1796
4%
718
30%
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
29%
540
17%
1129
May16th to endNight
26%
422
11%
1544
7%
421
33%
421
16%
1018
June1st to 15thNight
28%
360
11%
1440
7%
360
39%
360
15%
964
June16th to endNight
35%
360
12%
1440
11%
360
45%
360
21%
875
July1st to 15thNight
41%
340
12%
1360
13%
340
48%
340
23%
806
July16th to endNight
43%
376
15%
1418
12%
354
51%
354
20%
882
August1st to 15thNight
43%
501
16%
1550
10%
499
47%
499
27%
957
August16th to endNight
52%
662
18%
1712
10%
662
55%
662
34%
1095
September1st to 15thNight
40%
660
20%
1708
8%
660
47%
660
31%
1126
September16th to endNight
45%
657
25%
1815
16%
657
52%
657
35%
1106
October1st to 15thNight
33%
660
23%
1836
11%
660
44%
660
25%
1190
October16th to endNight
25%
704
16%
2288
5%
704
40%
704
20%
1482
November1st to 15thNight
29%
700
20%
2277
10%
700
42%
700
21%
1451
November16th to endNight
25%
720
20%
2340
8%
720
39%
720
18%
1494
December1st to 15thNight
20%
720
17%
2493
5%
720
35%
720
16%
1620
December16th to endNight
15%
768
19%
2688
5%
768
32%
768
15%
1793

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%39%
47533
Night
17%6%25%424446%41%
46627
Cloud CoverDay
17%6%25%42445%7%39%
47543
Night
16%7%25%424446%40%
46632
TransparencyDay
43%5%11%21%14%2
47221
Night
44%5%12%21%15%2
46457
SeeingDay
22%13%31%21%8%2
5763
Night
21%13%33%24%6%
14770

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%2432445%5%41%
1432
16th to endDay
15%6%25%43335%7%42%
1536
February1st to 15thDay
17%6%345%245%5%6%35%
1674
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%7%7%39%
2303
16th to endDay
12%4245%35%5%5%7%42%
2137
September1st to 15thDay
14%425%234446%46%
1922
16th to endDay
15%5%2432335%5%51%
1815
October1st to 15thDay
21%423423236%43%
1793
16th to endDay
17%6%24424347%42%
1584
November1st to 15thDay
21%6%2332333344%
1581
16th to endDay
17%5%2432445%5%43%
1620
December1st to 15thDay
17%6%25%433445%40%
1467
16th to endDay
23%8%23325%345%35%
1536
January1st to 15thNight
17%8%25%423245%40%
2506
16th to endNight
15%9%35%423345%40%
2688
February1st to 15thNight
15%8%26%5%3445%6%38%
2185
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%345%7%7%45%
1560
16th to endNight
12%414335%45%9%45%
1712
September1st to 15thNight
14%4245%245%47%45%
1708
16th to endNight
14%5%13323345%51%
1815
October1st to 15thNight
20%5%23323335%45%
1836
16th to endNight
19%6%24434346%40%
2288
November1st to 15thNight
17%6%25%324335%44%
2277
16th to endNight
18%5%35%423345%42%
2340
December1st to 15thNight
19%6%25%5%24345%40%
2493
16th to endNight
18%9%35%423346%37%
2688

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%8%3332445%5%42%
1432
16th to endDay
15%6%25%5%2335%6%43%
1536
February1st to 15thDay
17%7%25%5%3445%6%36%
1674
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%5%25%5%35%7%5%9%37%
2303
16th to endDay
11%5%25%5%35%45%8%42%
2137
September1st to 15thDay
14%425%32345%6%46%
1922
16th to endDay
14%5%24323345%50%
1815
October1st to 15thDay
21%5%24423336%43%
1793
16th to endDay
16%6%24424446%42%
1584
November1st to 15thDay
21%7%2332424444%
1581
16th to endDay
16%5%2443445%5%42%
1620
December1st to 15thDay
18%6%35%424345%40%
1467
16th to endDay
22%8%23425%435%35%
1536
January1st to 15thNight
17%8%35%424345%40%
2506
16th to endNight
15%10%35%433345%40%
2688
February1st to 15thNight
15%8%35%5%3435%6%37%
2178
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%425%6%35%5%6%8%43%
1560
16th to endNight
12%5%23325%45%9%44%
1712
September1st to 15thNight
13%5%235%25%5%5%6%43%
1708
16th to endNight
13%5%24313435%51%
1815
October1st to 15thNight
21%5%14323345%44%
1836
16th to endNight
19%5%25%433447%40%
2288
November1st to 15thNight
17%6%25%423345%44%
2277
16th to endNight
18%6%35%423445%42%
2340
December1st to 15thNight
18%7%26%424345%40%
2493
16th to endNight
18%9%35%424347%36%
2688

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
43%6%10%23%12%3
1433
16th to endDay
41%411%27%14%1
1536
February1st to 15thDay
46%5%13%19%13%1
1677
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
2289
16th to endDay
38%6%10%25%16%2
2137
September1st to 15thDay
36%6%11%22%20%1
1922
16th to endDay
36%37%25%24%2
1815
October1st to 15thDay
43%49%25%15%3
1793
16th to endDay
41%5%12%22%15%2
1584
November1st to 15thDay
45%311%23%14%1
1581
16th to endDay
41%5%12%24%14%1
1620
December1st to 15thDay
45%315%17%17%
1467
16th to endDay
51%5%13%18%10%1
1536
January1st to 15thNight
46%312%21%14%1
2506
16th to endNight
46%311%20%15%2
2688
February1st to 15thNight
46%412%21%11%2
2186
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%15%2
1550
16th to endNight
35%6%14%26%16%
1712
September1st to 15thNight
38%5%12%23%19%
1708
16th to endNight
34%38%23%27%2
1815
October1st to 15thNight
42%311%22%16%3
1836
16th to endNight
43%413%22%14%
2288
November1st to 15thNight
42%411%22%16%3
2277
16th to endNight
44%312%22%14%2
2340
December1st to 15thNight
46%414%21%12%
2493
16th to endNight
48%412%21%12%
2688

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
26%16%31%21%3
60
16th to endDay
31%17%35%15%
64
February1st to 15thDay
28%17%34%16%3
228
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%8%29%31%13%2
297
16th to endDay
14%6%24%27%21%5%
268
September1st to 15thDay
18%5%27%27%16%5%
255
16th to endDay
19%5%27%22%12%12%
254
October1st to 15thDay
25%9%22%22%12%7%
254
16th to endDay
20%14%32%23%7%
240
November1st to 15thDay
27%11%30%17%8%4
235
16th to endDay
21%17%31%17%9%1
240
December1st to 15thDay
25%26%31%14%2
87
16th to endDay
28%26%31%12%1
64
January1st to 15thNight
24%16%37%19%2
720
16th to endNight
23%17%36%18%2
768
February1st to 15thNight
21%16%38%22%1
704
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%41%9%
501
16th to endNight
15%224%40%15%2
662
September1st to 15thNight
16%5%30%32%13%
660
16th to endNight
17%5%26%27%19%2
657
October1st to 15thNight
24%10%26%25%10%2
660
16th to endNight
23%14%33%21%6%
704
November1st to 15thNight
20%14%30%23%10%1
700
16th to endNight
22%17%29%21%7%
720
December1st to 15thNight
22%16%35%20%4
720
16th to endNight
26%16%36%17%2
768
Page generated at 2017-08-13 14:16:31. Version ac04

Copyright 2017 A. Danko


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