Carpenter Museum
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Carpenter Museum clear sky chart from 2005-11-05 to 2017-09-17.

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
26%
14948
18%
46812
7%
14916
37%
14916
19%
30970

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
15%
720
19%
2506
6%
716
32%
716
15%
1616
January16th to endNight
13%
768
18%
2688
3%
768
33%
768
13%
1769
February1st to 15thNight
15%
704
17%
2163
4%
701
31%
701
16%
1462
February16th to endNight
14%
631
24%
1893
5%
631
36%
631
18%
1246
March1st to 15thNight
17%
720
17%
2153
5%
720
32%
720
17%
1472
March16th to endNight
19%
768
22%
2037
7%
768
32%
768
19%
1392
April1st to 15thNight
18%
718
16%
1796
3%
718
27%
718
20%
1291
April16th to endNight
20%
594
18%
1674
4%
594
29%
594
20%
1163
May1st to 15thNight
22%
540
14%
1620
5%
540
29%
540
17%
1145
May16th to endNight
24%
439
9%
1561
5%
438
30%
438
15%
1082
June1st to 15thNight
31%
360
11%
1440
9%
360
40%
360
14%
985
June16th to endNight
41%
360
11%
1440
12%
360
48%
360
21%
873
July1st to 15thNight
37%
340
11%
1360
11%
340
44%
340
20%
847
July16th to endNight
45%
376
14%
1418
13%
354
51%
354
19%
899
August1st to 15thNight
41%
524
16%
1595
10%
522
45%
522
27%
1011
August16th to endNight
49%
729
20%
1875
12%
729
52%
729
33%
1223
September1st to 15thNight
39%
720
19%
1866
9%
720
44%
720
30%
1240
September16th to endNight
44%
665
22%
1836
14%
665
51%
665
29%
1167
October1st to 15thNight
33%
660
23%
1826
10%
660
45%
660
24%
1203
October16th to endNight
24%
704
17%
2288
6%
704
38%
704
20%
1488
November1st to 15thNight
27%
700
19%
2277
9%
700
40%
700
20%
1479
November16th to endNight
23%
720
20%
2340
7%
720
39%
720
19%
1480
December1st to 15thNight
19%
720
18%
2472
5%
720
34%
720
15%
1629
December16th to endNight
14%
768
19%
2688
4%
768
32%
768
14%
1808

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%2442445%7%40%
47959
Night
17%6%25%424446%40%
46982
Cloud CoverDay
17%6%2442445%7%40%
47969
Night
17%7%25%424446%40%
46987
TransparencyDay
43%6%12%20%14%2
47648
Night
44%5%11%20%14%2
46812
SeeingDay
22%15%32%18%8%2
5939
Night
21%14%33%22%6%
14948

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%7%35%324445%43%
1432
16th to endDay
16%6%35%413445%43%
1536
February1st to 15thDay
18%7%24435%5%47%37%
1693
16th to endDay
16%8%24424445%42%
1580
March1st to 15thDay
21%8%2332435%6%38%
1796
16th to endDay
17%8%24423345%42%
2185
April1st to 15thDay
19%7%25%424447%37%
2152
16th to endDay
19%5%24424446%42%
2285
May1st to 15thDay
26%8%24323346%34%
2332
16th to endDay
17%5%2442445%7%40%
2562
June1st to 15thDay
25%5%2442445%7%32%
2520
16th to endDay
13%5%24435%5%6%10%37%
2520
July1st to 15thDay
13%5%36%5%25%5%6%9%36%
2520
16th to endDay
13%5%25%5%36%5%7%8%36%
2654
August1st to 15thDay
13%6%346%35%5%5%7%38%
2340
16th to endDay
11%5%25%445%5%47%43%
2325
September1st to 15thDay
14%5%2443445%5%46%
2092
16th to endDay
15%413323346%50%
1830
October1st to 15thDay
21%5%24323335%44%
1799
16th to endDay
16%5%235%2445%6%43%
1584
November1st to 15thDay
22%7%23323335%42%
1581
16th to endDay
16%5%24424347%42%
1620
December1st to 15thDay
20%7%24414346%41%
1485
16th to endDay
23%8%25%424345%35%
1536
January1st to 15thNight
19%7%25%434335%41%
2506
16th to endNight
18%10%2443333440%
2688
February1st to 15thNight
15%8%36%42445%5%38%
2162
16th to endNight
17%8%34424435%42%
1893
March1st to 15thNight
18%7%25%5%245%46%37%
2140
16th to endNight
17%8%35%42333442%
2037
April1st to 15thNight
18%8%245%25%45%5%36%
1796
16th to endNight
21%5%35%43333440%
1674
May1st to 15thNight
22%7%25%434345%35%
1620
16th to endNight
19%5%36%42446%8%33%
1559
June1st to 15thNight
22%6%35%5%24346%34%
1440
16th to endNight
16%5%24425%46%9%40%
1440
July1st to 15thNight
13%5%25%5%25%5%5%8%38%
1440
16th to endNight
12%5%35%5%35%6%6%8%36%
1514
August1st to 15thNight
9%5%35%435%46%8%41%
1605
16th to endNight
12%4244335%5%6%46%
1875
September1st to 15thNight
15%4244335%46%45%
1866
16th to endNight
15%5%24324345%48%
1836
October1st to 15thNight
19%5%23423335%45%
1826
16th to endNight
18%6%23423446%41%
2288
November1st to 15thNight
19%5%25%413345%43%
2277
16th to endNight
18%5%3432435%6%42%
2340
December1st to 15thNight
21%7%24424345%40%
2472
16th to endNight
19%9%35%42435%6%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
16%7%25%324445%42%
1432
16th to endDay
15%6%35%423445%43%
1536
February1st to 15thDay
18%7%23435%5%47%37%
1693
16th to endDay
16%7%25%424445%41%
1580
March1st to 15thDay
21%7%3342435%6%38%
1806
16th to endDay
17%7%34423346%42%
2185
April1st to 15thDay
19%7%34424446%37%
2152
16th to endDay
18%6%24424447%41%
2285
May1st to 15thDay
26%7%35%31335%5%34%
2332
16th to endDay
17%5%2442445%9%38%
2562
June1st to 15thDay
24%5%3442445%7%33%
2520
16th to endDay
13%5%24426%5%6%10%37%
2520
July1st to 15thDay
13%5%25%6%35%5%6%9%36%
2520
16th to endDay
13%5%25%435%5%7%9%36%
2654
August1st to 15thDay
12%5%25%5%35%5%5%8%39%
2340
16th to endDay
11%5%245%35%5%5%7%43%
2325
September1st to 15thDay
13%5%25%42445%5%46%
2092
16th to endDay
14%5%13324345%49%
1830
October1st to 15thDay
20%6%23323335%44%
1799
16th to endDay
15%5%15%43345%6%43%
1584
November1st to 15thDay
22%7%24223335%41%
1581
16th to endDay
16%5%335%24347%42%
1620
December1st to 15thDay
20%7%25%323346%41%
1485
16th to endDay
23%7%34434345%35%
1536
January1st to 15thNight
19%7%25%424335%41%
2506
16th to endNight
18%10%25%42433440%
2688
February1st to 15thNight
15%8%36%5%24445%39%
2155
16th to endNight
17%7%35%324435%42%
1893
March1st to 15thNight
18%7%25%4245%46%37%
2153
16th to endNight
16%8%36%423335%42%
2036
April1st to 15thNight
18%8%35%4345%5%5%36%
1796
16th to endNight
22%5%35%42433440%
1674
May1st to 15thNight
22%7%25%423445%35%
1620
16th to endNight
19%6%36%5%345%5%8%32%
1559
June1st to 15thNight
22%6%44424347%35%
1440
16th to endNight
15%5%243245%5%9%39%
1440
July1st to 15thNight
14%5%245%26%5%5%9%37%
1440
16th to endNight
11%5%36%5%36%5%7%9%34%
1514
August1st to 15thNight
9%6%345%35%6%6%8%41%
1605
16th to endNight
12%415%4335%5%7%45%
1875
September1st to 15thNight
15%325%4235%46%45%
1866
16th to endNight
15%5%24324345%47%
1836
October1st to 15thNight
19%5%24423326%44%
1826
16th to endNight
18%7%23423446%41%
2288
November1st to 15thNight
19%6%25%423335%43%
2277
16th to endNight
18%6%25%32335%7%41%
2340
December1st to 15thNight
21%7%24424345%40%
2472
16th to endNight
19%9%35%324346%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%5%11%23%12%3
1433
16th to endDay
41%5%10%26%15%1
1536
February1st to 15thDay
45%5%13%18%13%2
1696
16th to endDay
44%412%22%14%2
1580
March1st to 15thDay
46%5%12%21%9%3
1806
16th to endDay
43%5%10%19%15%5%
2185
April1st to 15thDay
46%410%19%16%2
2152
16th to endDay
42%5%10%19%17%4
2285
May1st to 15thDay
51%5%9%16%13%2
2332
16th to endDay
42%8%14%19%12%2
2566
June1st to 15thDay
50%7%12%19%10%
2520
16th to endDay
39%9%14%21%13%1
2520
July1st to 15thDay
42%8%12%19%13%2
2371
16th to endDay
41%9%15%19%11%3
2487
August1st to 15thDay
40%9%14%19%14%1
2327
16th to endDay
37%8%10%23%17%2
2325
September1st to 15thDay
37%6%12%19%21%1
2092
16th to endDay
35%5%8%22%25%2
1830
October1st to 15thDay
42%410%23%16%3
1799
16th to endDay
39%5%12%22%16%2
1584
November1st to 15thDay
45%413%19%15%2
1581
16th to endDay
42%412%22%14%2
1620
December1st to 15thDay
44%5%15%17%16%
1485
16th to endDay
51%5%13%18%10%1
1536
January1st to 15thNight
46%412%21%13%1
2506
16th to endNight
47%410%19%14%2
2688
February1st to 15thNight
47%412%21%12%2
2163
16th to endNight
44%410%20%17%2
1893
March1st to 15thNight
46%5%11%19%13%3
2153
16th to endNight
44%48%18%18%5%
2037
April1st to 15thNight
47%5%10%18%14%2
1796
16th to endNight
47%5%8%18%15%4
1674
May1st to 15thNight
49%6%11%16%13%3
1620
16th to endNight
48%9%16%15%8%2
1561
June1st to 15thNight
50%7%10%17%12%
1440
16th to endNight
39%7%14%22%14%1
1440
July1st to 15thNight
41%7%13%22%14%
1360
16th to endNight
41%9%14%22%9%2
1418
August1st to 15thNight
38%7%14%23%14%2
1595
16th to endNight
35%7%11%27%17%
1875
September1st to 15thNight
38%7%12%22%18%1
1866
16th to endNight
38%47%21%25%1
1836
October1st to 15thNight
42%410%22%15%3
1826
16th to endNight
42%6%13%21%14%1
2288
November1st to 15thNight
43%5%12%19%16%2
2277
16th to endNight
42%412%23%14%2
2340
December1st to 15thNight
47%5%13%19%13%
2472
16th to endNight
48%5%12%20%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
23%30%33%11%1
60
16th to endDay
18%32%37%10%
64
February1st to 15thDay
29%21%34%12%1
241
16th to endDay
17%29%33%14%4
239
March1st to 15thDay
30%22%27%14%3
270
16th to endDay
21%25%33%10%6%1
288
April1st to 15thDay
25%18%37%11%6%
270
16th to endDay
21%18%34%18%23
270
May1st to 15thDay
35%19%23%15%31
288
16th to endDay
20%12%39%20%6%
331
June1st to 15thDay
26%15%33%17%6%
315
16th to endDay
15%15%39%21%5%2
315
July1st to 15thDay
20%7%35%25%8%1
305
16th to endDay
14%8%34%27%12%2
326
August1st to 15thDay
14%8%31%29%13%1
313
16th to endDay
14%8%30%25%15%6%
332
September1st to 15thDay
18%10%27%25%13%4
315
16th to endDay
20%5%33%18%9%12%
259
October1st to 15thDay
24%11%25%20%12%4
254
16th to endDay
19%19%30%20%8%1
240
November1st to 15thDay
28%11%32%12%10%3
235
16th to endDay
22%18%33%15%9%1
240
December1st to 15thDay
21%30%30%12%3
105
16th to endDay
35%29%26%43
64
January1st to 15thNight
24%20%35%15%3
720
16th to endNight
24%23%34%15%1
768
February1st to 15thNight
21%21%37%17%1
704
16th to endNight
22%22%35%16%2
631
March1st to 15thNight
23%20%36%16%3
720
16th to endNight
23%21%32%18%4
768
April1st to 15thNight
21%20%37%17%3
718
16th to endNight
23%17%34%19%4
594
May1st to 15thNight
26%14%33%21%4
540
16th to endNight
23%9%38%24%5%
439
June1st to 15thNight
23%7%30%32%7%
360
16th to endNight
16%433%36%7%
360
July1st to 15thNight
15%337%33%9%
340
16th to endNight
14%230%43%8%
376
August1st to 15thNight
12%435%38%9%
524
16th to endNight
14%324%38%16%1
729
September1st to 15thNight
17%433%30%11%
720
16th to endNight
19%6%24%26%18%3
665
October1st to 15thNight
22%10%29%25%10%1
660
16th to endNight
23%15%33%20%7%
704
November1st to 15thNight
21%14%32%19%10%1
700
16th to endNight
22%18%31%20%6%
720
December1st to 15thNight
25%18%33%17%4
720
16th to endNight
26%22%33%15%1
768
Page generated at 2017-09-18 08:38:22. Version ac04

Copyright 2017 A. Danko


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