Carpenter Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Carpenter Observatory clear sky chart from 2005-11-05 to 2017-12-04.

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
34%
15393
19%
47838
10%
15358
44%
15358
22%
30685

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
21%
719
19%
2506
8%
716
36%
716
15%
1625
January16th to endNight
18%
768
21%
2505
6%
768
36%
768
19%
1584
February1st to 15thNight
14%
704
17%
2284
4%
701
30%
701
16%
1489
February16th to endNight
16%
631
23%
1893
5%
631
36%
631
18%
1227
March1st to 15thNight
21%
720
19%
2070
7%
720
36%
720
19%
1383
March16th to endNight
21%
768
22%
2046
8%
768
33%
768
25%
1365
April1st to 15thNight
22%
718
17%
1796
4%
718
30%
718
24%
1216
April16th to endNight
32%
720
17%
1800
5%
720
38%
720
27%
1211
May1st to 15thNight
34%
495
16%
1575
8%
495
41%
495
19%
1060
May16th to endNight
46%
374
15%
1497
14%
374
52%
374
18%
949
June1st to 15thNight
46%
360
16%
1440
14%
360
56%
360
20%
887
June16th to endNight
53%
360
15%
1440
18%
360
59%
360
25%
842
July1st to 15thNight
50%
340
12%
1360
14%
340
53%
340
18%
868
July16th to endNight
63%
429
15%
1467
13%
403
68%
403
26%
855
August1st to 15thNight
62%
554
18%
1624
14%
551
63%
551
31%
1022
August16th to endNight
59%
764
18%
1910
10%
764
60%
764
35%
1244
September1st to 15thNight
50%
720
24%
1800
11%
720
55%
720
33%
1176
September16th to endNight
55%
717
26%
1950
19%
717
59%
717
31%
1249
October1st to 15thNight
43%
720
20%
2160
15%
720
51%
720
25%
1370
October16th to endNight
34%
768
26%
2324
14%
768
49%
768
29%
1390
November1st to 15thNight
34%
760
21%
2472
12%
760
47%
760
24%
1514
November16th to endNight
28%
780
21%
2657
10%
780
42%
780
19%
1653
December1st to 15thNight
24%
736
15%
2574
6%
736
35%
736
14%
1746
December16th to endNight
19%
768
17%
2688
5%
768
35%
768
15%
1760

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
14%5%25%5%345%5%7%39%
48655
Night
15%5%25%43445%7%42%
48013
Cloud CoverDay
14%5%25%5%3445%7%39%
48665
Night
14%5%25%42445%7%42%
48018
TransparencyDay
42%6%12%21%14%2
48348
Night
40%6%12%22%15%2
47838
SeeingDay
19%11%27%23%13%4
5956
Night
18%12%29%26%11%
15395

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%35%5%35%45%7%36%
1432
16th to endDay
13%6%45%5%25%5%5%7%37%
1716
February1st to 15thDay
14%6%45%6%245%5%7%36%
1578
16th to endDay
13%7%47%5%3435%7%38%
1580
March1st to 15thDay
15%6%25%7%35%45%7%37%
1879
16th to endDay
18%7%24433446%40%
2176
April1st to 15thDay
17%5%25%42345%7%40%
2152
16th to endDay
15%42443445%7%43%
2160
May1st to 15thDay
18%6%25%5%25%5%5%7%34%
2385
16th to endDay
16%5%245%35%5%7%7%36%
2618
June1st to 15thDay
13%5%245%347%7%10%36%
2520
16th to endDay
12%4245%45%5%7%9%38%
2520
July1st to 15thDay
10%426%6%36%6%7%9%36%
2520
16th to endDay
7%425%7%46%7%7%9%37%
2598
August1st to 15thDay
12%5%25%5%35%6%7%8%36%
2312
16th to endDay
13%4235%3446%7%43%
2292
September1st to 15thDay
15%4244235%47%44%
2160
16th to endDay
14%426%424346%45%
2007
October1st to 15thDay
18%6%2432345%7%43%
1800
16th to endDay
17%5%1442335%8%42%
1899
November1st to 15thDay
16%7%24423446%44%
1716
16th to endDay
17%5%24324447%43%
1631
December1st to 15thDay
16%6%25%5%3446%7%36%
1468
16th to endDay
18%7%45%42426%7%36%
1536
January1st to 15thNight
16%6%35%435%447%37%
2506
16th to endNight
14%8%3443335%6%41%
2505
February1st to 15thNight
14%7%25%6%35%35%5%39%
2282
16th to endNight
15%5%25%334446%43%
1893
March1st to 15thNight
16%6%24435%446%41%
2058
16th to endNight
17%5%23423346%44%
2046
April1st to 15thNight
16%5%2443435%8%40%
1796
16th to endNight
16%42443345%6%44%
1800
May1st to 15thNight
18%5%26%434447%38%
1575
16th to endNight
14%5%35%42446%7%40%
1495
June1st to 15thNight
16%42443436%7%41%
1440
16th to endNight
11%3144445%7%10%42%
1440
July1st to 15thNight
9%426%7%36%5%6%9%39%
1440
16th to endNight
8%4245%36%5%6%10%42%
1567
August1st to 15thNight
9%425%5%2446%7%44%
1635
16th to endNight
11%4145%245%5%8%45%
1910
September1st to 15thNight
14%42432345%6%47%
1800
16th to endNight
13%324425%45%7%46%
1950
October1st to 15thNight
17%6%24323337%45%
2160
16th to endNight
17%414222446%49%
2324
November1st to 15thNight
14%5%24423447%45%
2472
16th to endNight
16%425%42435%7%41%
2657
December1st to 15thNight
18%6%27%5%35%45%6%33%
2574
16th to endNight
17%6%25%5%25%45%7%36%
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
14%7%346%45%45%7%36%
1432
16th to endDay
14%7%36%5%25%45%7%37%
1716
February1st to 15thDay
15%7%36%5%335%6%7%36%
1578
16th to endDay
14%7%46%6%34446%37%
1580
March1st to 15thDay
15%5%35%6%4445%7%37%
1890
16th to endDay
18%7%35%424345%40%
2175
April1st to 15thDay
17%6%35%323447%40%
2152
16th to endDay
15%425%42335%7%44%
2160
May1st to 15thDay
18%6%25%5%345%6%6%34%
2385
16th to endDay
16%5%25%5%245%6%8%36%
2618
June1st to 15thDay
13%6%25%435%5%6%10%36%
2520
16th to endDay
11%5%245%36%6%6%9%38%
2520
July1st to 15thDay
10%5%26%6%45%6%7%9%36%
2520
16th to endDay
8%425%6%46%7%7%8%38%
2598
August1st to 15thDay
12%5%26%5%45%5%6%9%37%
2312
16th to endDay
13%42443446%7%43%
2292
September1st to 15thDay
15%41442445%7%44%
2160
16th to endDay
13%5%26%424346%45%
2007
October1st to 15thDay
17%6%2441345%7%43%
1800
16th to endDay
18%5%2442335%7%43%
1899
November1st to 15thDay
15%8%2441335%6%44%
1716
16th to endDay
16%5%24324437%44%
1631
December1st to 15thDay
16%7%26%5%3445%7%36%
1468
16th to endDay
17%6%46%5%2426%7%36%
1536
January1st to 15thNight
15%6%36%43445%7%37%
2506
16th to endNight
14%7%35%433347%41%
2505
February1st to 15thNight
14%8%25%5%35%45%6%39%
2275
16th to endNight
15%6%3433445%5%42%
1893
March1st to 15thNight
16%6%245%34346%41%
2070
16th to endNight
17%6%24424336%44%
2046
April1st to 15thNight
15%6%24434448%40%
1796
16th to endNight
16%5%25%424446%44%
1800
May1st to 15thNight
17%5%25%435%447%38%
1575
16th to endNight
14%6%36%3245%5%7%41%
1495
June1st to 15thNight
16%42443445%8%40%
1440
16th to endNight
10%3245%35%5%6%10%42%
1440
July1st to 15thNight
9%5%26%5%36%5%6%8%39%
1440
16th to endNight
8%4245%35%6%7%10%42%
1567
August1st to 15thNight
8%5%25%5%3446%7%45%
1635
16th to endNight
11%4145%24448%46%
1910
September1st to 15thNight
13%42432345%6%47%
1800
16th to endNight
13%4145%24446%47%
1950
October1st to 15thNight
17%6%24422336%45%
2160
16th to endNight
16%5%13323346%50%
2324
November1st to 15thNight
14%425%42335%6%46%
2472
16th to endNight
16%5%245%24448%41%
2657
December1st to 15thNight
18%6%26%5%35%45%6%34%
2574
16th to endNight
16%7%25%5%25%35%8%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
47%5%12%21%9%2
1433
16th to endDay
45%6%14%20%11%1
1716
February1st to 15thDay
45%7%12%21%10%1
1580
16th to endDay
47%5%12%23%10%1
1580
March1st to 15thDay
46%6%13%21%11%1
1890
16th to endDay
46%410%19%16%1
2176
April1st to 15thDay
43%5%10%23%13%4
2152
16th to endDay
39%5%10%20%18%5%
2160
May1st to 15thDay
47%7%9%18%14%2
2385
16th to endDay
44%9%12%19%13%1
2622
June1st to 15thDay
41%9%14%22%10%1
2520
16th to endDay
39%9%14%23%11%1
2520
July1st to 15thDay
42%8%12%20%14%2
2371
16th to endDay
38%8%13%23%13%1
2435
August1st to 15thDay
42%7%13%19%15%
2299
16th to endDay
37%6%11%22%18%2
2292
September1st to 15thDay
38%6%11%19%21%2
2160
16th to endDay
39%49%21%22%2
2007
October1st to 15thDay
40%414%21%16%1
1800
16th to endDay
40%411%25%15%1
1899
November1st to 15thDay
40%5%14%20%15%3
1716
16th to endDay
40%5%10%28%13%1
1631
December1st to 15thDay
46%7%16%19%9%1
1468
16th to endDay
47%5%16%20%9%
1536
January1st to 15thNight
45%5%13%20%13%2
2506
16th to endNight
42%413%24%13%1
2505
February1st to 15thNight
45%413%22%12%1
2284
16th to endNight
41%5%11%23%16%2
1893
March1st to 15thNight
43%5%12%23%14%1
2070
16th to endNight
41%411%23%16%2
2046
April1st to 15thNight
41%5%12%21%16%3
1796
16th to endNight
39%6%11%18%19%4
1800
May1st to 15thNight
44%8%10%18%15%2
1575
16th to endNight
41%9%14%15%16%3
1497
June1st to 15thNight
40%8%11%22%16%
1440
16th to endNight
35%8%14%26%14%1
1440
July1st to 15thNight
42%8%12%19%12%2
1360
16th to endNight
33%9%17%23%13%2
1467
August1st to 15thNight
35%7%14%21%19%1
1624
16th to endNight
35%6%13%21%20%2
1910
September1st to 15thNight
35%7%11%21%21%2
1800
16th to endNight
37%5%7%20%25%3
1950
October1st to 15thNight
40%412%24%15%2
2160
16th to endNight
35%411%29%17%1
2324
November1st to 15thNight
38%5%12%22%15%5%
2472
16th to endNight
41%411%24%15%1
2657
December1st to 15thNight
49%5%13%19%10%
2574
16th to endNight
45%6%15%21%9%
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
33%21%36%5%3
60
16th to endDay
22%25%37%12%2
94
February1st to 15thDay
23%30%35%10%
93
16th to endDay
20%23%34%18%2
239
March1st to 15thDay
20%21%31%21%4
270
16th to endDay
22%21%28%19%42
288
April1st to 15thDay
24%17%29%18%7%2
270
16th to endDay
21%11%31%20%8%5%
270
May1st to 15thDay
34%13%22%16%10%3
288
16th to endDay
23%6%24%24%17%3
331
June1st to 15thDay
17%10%29%25%15%2
315
16th to endDay
15%9%32%28%11%2
315
July1st to 15thDay
14%327%31%19%3
305
16th to endDay
7%425%34%21%7%
326
August1st to 15thDay
14%321%29%20%10%
313
16th to endDay
12%118%31%21%13%
332
September1st to 15thDay
17%8%22%22%18%10%
315
16th to endDay
17%5%20%22%20%14%
314
October1st to 15thDay
23%6%19%25%20%5%
315
16th to endDay
16%15%32%20%12%1
331
November1st to 15thDay
18%12%28%27%11%2
280
16th to endDay
15%22%35%19%5%
161
December1st to 15thDay
20%25%25%13%11%2
67
16th to endDay
29%26%32%9%1
64
January1st to 15thNight
20%19%34%21%3
720
16th to endNight
22%18%37%20%1
768
February1st to 15thNight
21%18%39%18%1
704
16th to endNight
21%22%36%17%2
631
March1st to 15thNight
22%18%33%21%4
720
16th to endNight
21%15%37%18%6%
768
April1st to 15thNight
19%20%33%22%4
718
16th to endNight
19%12%32%25%9%
720
May1st to 15thNight
23%8%30%27%9%
495
16th to endNight
14%6%25%38%13%1
375
June1st to 15thNight
15%7%24%38%14%
360
16th to endNight
10%127%47%11%
360
July1st to 15thNight
12%224%42%17%
340
16th to endNight
10%217%41%25%2
429
August1st to 15thNight
12%217%41%24%2
554
16th to endNight
14%117%35%27%2
764
September1st to 15thNight
14%424%33%20%2
720
16th to endNight
16%418%28%28%4
717
October1st to 15thNight
21%7%22%27%17%2
720
16th to endNight
20%12%29%26%9%
768
November1st to 15thNight
16%11%31%26%11%1
760
16th to endNight
19%17%30%23%8%
780
December1st to 15thNight
23%16%30%22%7%
736
16th to endNight
22%17%36%20%2
768
Page generated at 2017-12-05 10:18:58. Version ac04

Copyright 2017 A. Danko


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