Dexter
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dexter clear sky chart from 2005-11-05 to 2017-10-31.

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%
14934
13%
47380
8%
14903
33%
14903
15%
34691

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
9%
720
5%
2506
3%
716
13%
716
5%
2133
January16th to endNight
16%
768
8%
2601
4%
768
22%
768
8%
2082
February1st to 15thNight
12%
704
7%
2287
3%
701
17%
701
6%
1925
February16th to endNight
19%
631
11%
1940
5%
631
25%
631
10%
1538
March1st to 15thNight
19%
720
13%
2085
6%
720
25%
720
14%
1564
March16th to endNight
25%
768
17%
2043
8%
768
32%
768
19%
1476
April1st to 15thNight
20%
718
14%
1796
4%
718
26%
718
18%
1348
April16th to endNight
31%
693
17%
1773
6%
693
36%
693
25%
1210
May1st to 15thNight
35%
360
17%
1440
15%
360
44%
360
17%
931
May16th to endNight
37%
374
15%
1497
12%
374
48%
374
20%
909
June1st to 15thNight
36%
360
12%
1440
11%
360
46%
360
16%
957
June16th to endNight
37%
360
11%
1440
12%
360
45%
360
21%
872
July1st to 15thNight
53%
340
15%
1360
20%
340
60%
340
26%
746
July16th to endNight
50%
376
14%
1418
15%
354
55%
354
25%
799
August1st to 15thNight
48%
487
14%
1558
11%
485
51%
485
25%
982
August16th to endNight
53%
722
22%
1868
12%
722
57%
722
36%
1176
September1st to 15thNight
47%
720
15%
1800
8%
720
49%
720
31%
1230
September16th to endNight
47%
717
24%
1959
17%
717
53%
717
31%
1265
October1st to 15thNight
30%
720
15%
2160
11%
720
36%
720
18%
1547
October16th to endNight
20%
768
9%
2374
5%
768
26%
768
9%
1891
November1st to 15thNight
25%
700
16%
2307
12%
700
31%
700
15%
1641
November16th to endNight
19%
720
12%
2520
8%
720
25%
720
8%
1993
December1st to 15thNight
12%
720
5%
2520
2%
720
15%
720
5%
2148
December16th to endNight
10%
768
5%
2688
2%
768
14%
768
5%
2328

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
18%9%36%5%34446%33%
48379
Night
19%11%46%5%24446%30%
47549
Cloud CoverDay
19%10%36%5%24446%31%
48388
Night
19%11%46%5%24445%29%
47555
TransparencyDay
53%411%20%9%
48066
Night
56%410%18%9%1
47380
SeeingDay
24%14%27%19%9%3
5692
Night
26%14%26%22%9%1
14935

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
23%16%6%10%5%34335%18%
1432
16th to endDay
16%17%6%11%8%34445%17%
1623
February1st to 15thDay
17%15%7%12%8%35%44417%
1575
16th to endDay
19%17%47%5%3433425%
1533
March1st to 15thDay
18%14%6%8%6%3434425%
1864
16th to endDay
20%8%3442333439%
2181
April1st to 15thDay
23%9%33423335%34%
2152
16th to endDay
19%8%24434445%38%
2193
May1st to 15thDay
19%7%24425%447%35%
2511
16th to endDay
15%5%25%425%45%8%38%
2618
June1st to 15thDay
22%6%1442445%7%33%
2520
16th to endDay
16%5%2443446%8%38%
2520
July1st to 15thDay
12%5%2443445%8%44%
2520
16th to endDay
12%4245%25%5%6%8%41%
2654
August1st to 15thDay
13%5%25%435%5%6%8%39%
2391
16th to endDay
12%42443446%8%44%
2321
September1st to 15thDay
18%5%24324347%42%
2160
16th to endDay
15%5%1442335%7%46%
1999
October1st to 15thDay
22%8%26%424336%33%
1800
16th to endDay
29%8%36%434336%25%
1848
November1st to 15thDay
14%9%36%6%35%46%7%31%
1548
16th to endDay
22%15%6%8%5%3435%5%20%
1440
December1st to 15thDay
23%22%6%8%6%335%35%12%
1440
16th to endDay
26%20%6%8%5%35%43313%
1536
January1st to 15thNight
22%18%6%11%6%3433416%
2506
16th to endNight
16%19%49%7%34345%19%
2601
February1st to 15thNight
18%16%8%13%6%3433318%
2285
16th to endNight
18%13%6%9%6%34335%24%
1940
March1st to 15thNight
21%11%5%6%5%2434428%
2072
16th to endNight
20%9%46%5%23235%36%
2043
April1st to 15thNight
26%8%35%42244432%
1796
16th to endNight
18%6%25%42445%6%38%
1773
May1st to 15thNight
21%6%245%24446%36%
1440
16th to endNight
13%6%245%45%5%5%7%38%
1495
June1st to 15thNight
19%6%26%5%34449%33%
1440
16th to endNight
14%7%14435%5%6%8%38%
1440
July1st to 15thNight
10%324426%46%9%44%
1440
16th to endNight
11%325%5%235%6%8%45%
1514
August1st to 15thNight
11%6%35%5%3446%7%41%
1568
16th to endNight
9%42443345%8%48%
1868
September1st to 15thNight
17%5%244245%36%44%
1800
16th to endNight
15%424423347%46%
1959
October1st to 15thNight
22%7%35%5%34435%34%
2160
16th to endNight
29%9%37%6%24345%22%
2374
November1st to 15thNight
20%8%36%5%2445%6%32%
2307
16th to endNight
24%15%5%7%5%2345%5%20%
2520
December1st to 15thNight
24%21%5%7%5%2434415%
2520
16th to endNight
25%21%6%8%5%23335%13%
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
20%18%6%11%5%3434416%
1432
16th to endDay
14%19%7%10%8%3444415%
1623
February1st to 15thDay
17%16%7%11%9%45%33414%
1575
16th to endDay
18%16%6%8%7%24335%23%
1533
March1st to 15thDay
19%15%5%9%5%25%44423%
1874
16th to endDay
20%10%345%23335%38%
2180
April1st to 15thDay
24%11%34423345%33%
2152
16th to endDay
19%9%24424446%36%
2193
May1st to 15thDay
19%7%34436%447%34%
2511
16th to endDay
17%5%3442446%8%38%
2618
June1st to 15thDay
25%6%25%32445%8%32%
2520
16th to endDay
19%5%24425%46%8%35%
2520
July1st to 15thDay
13%5%15%43445%8%42%
2520
16th to endDay
13%5%245%345%5%9%39%
2654
August1st to 15thDay
14%5%245%35%5%5%9%37%
2391
16th to endDay
13%5%244345%6%7%42%
2321
September1st to 15thDay
19%5%24423347%40%
2160
16th to endDay
16%424323446%46%
1999
October1st to 15thDay
23%7%36%42345%6%32%
1800
16th to endDay
30%10%25%6%24445%23%
1848
November1st to 15thDay
14%11%37%5%345%5%7%30%
1548
16th to endDay
22%16%6%7%6%24345%19%
1440
December1st to 15thDay
23%22%7%9%6%3433412%
1440
16th to endDay
25%23%5%9%6%3323411%
1536
January1st to 15thNight
20%20%7%12%6%2433314%
2506
16th to endNight
15%19%6%9%8%3434419%
2601
February1st to 15thNight
17%17%7%13%8%3433317%
2278
16th to endNight
16%15%7%9%6%3443422%
1940
March1st to 15thNight
21%13%47%6%2424428%
2085
16th to endNight
21%10%46%5%23345%34%
2043
April1st to 15thNight
26%8%34424345%31%
1796
16th to endNight
19%7%2442445%6%39%
1773
May1st to 15thNight
22%6%244235%46%35%
1440
16th to endNight
14%6%25%425%5%6%7%39%
1495
June1st to 15thNight
21%6%25%5%3445%7%33%
1440
16th to endNight
16%5%244345%6%8%37%
1440
July1st to 15thNight
12%424345%46%8%44%
1440
16th to endNight
11%415%3246%5%8%45%
1514
August1st to 15thNight
12%5%246%3445%7%41%
1568
16th to endNight
11%42443446%8%46%
1868
September1st to 15thNight
18%425%3245%45%43%
1800
16th to endNight
16%413424347%46%
1959
October1st to 15thNight
23%7%26%5%24345%33%
2160
16th to endNight
31%9%37%6%3444422%
2374
November1st to 15thNight
20%10%25%4245%46%31%
2307
16th to endNight
22%17%47%42345%5%21%
2520
December1st to 15thNight
24%22%5%8%6%2434314%
2520
16th to endNight
24%23%7%8%5%2323412%
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
72%37%12%3
1433
16th to endDay
71%47%11%5%
1623
February1st to 15thDay
73%36%13%2
1577
16th to endDay
65%39%13%7%
1533
March1st to 15thDay
65%210%15%5%
1874
16th to endDay
51%28%19%15%2
2181
April1st to 15thDay
54%38%20%11%1
2152
16th to endDay
49%29%21%13%3
2193
May1st to 15thDay
48%5%9%21%13%1
2511
16th to endDay
43%5%14%22%12%1
2622
June1st to 15thDay
50%412%21%9%
2520
16th to endDay
45%414%23%11%
2520
July1st to 15thDay
38%5%13%29%12%
2371
16th to endDay
41%5%17%25%10%
2487
August1st to 15thDay
42%5%16%25%9%
2377
16th to endDay
39%5%15%29%10%
2321
September1st to 15thDay
43%311%27%13%1
2160
16th to endDay
38%411%30%14%
1999
October1st to 15thDay
52%49%23%9%
1800
16th to endDay
62%412%14%5%
1848
November1st to 15thDay
52%6%14%16%7%2
1548
16th to endDay
66%410%11%7%
1440
December1st to 15thDay
76%5%7%8%1
1440
16th to endDay
77%37%8%2
1536
January1st to 15thNight
74%5%7%9%2
2506
16th to endNight
68%37%13%6%
2601
February1st to 15thNight
72%47%11%3
2287
16th to endNight
65%38%15%6%
1940
March1st to 15thNight
59%310%18%7%
2085
16th to endNight
53%29%18%13%2
2043
April1st to 15thNight
54%48%19%12%1
1796
16th to endNight
45%311%20%16%2
1773
May1st to 15thNight
48%49%19%15%3
1440
16th to endNight
43%413%23%12%2
1497
June1st to 15thNight
50%412%22%9%
1440
16th to endNight
41%5%15%23%13%
1440
July1st to 15thNight
34%412%30%15%1
1360
16th to endNight
35%5%15%27%14%1
1418
August1st to 15thNight
40%6%15%25%11%
1558
16th to endNight
34%412%35%11%
1868
September1st to 15thNight
41%5%12%26%12%1
1800
16th to endNight
38%410%30%15%
1959
October1st to 15thNight
53%49%21%10%
2160
16th to endNight
65%5%10%13%4
2374
November1st to 15thNight
53%5%11%17%8%2
2307
16th to endNight
65%5%8%14%5%1
2520
December1st to 15thNight
74%48%9%1
2520
16th to endNight
76%48%7%3
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%26%16%25%5%
60
16th to endDay
40%24%21%11%2
79
February1st to 15thDay
34%32%26%6%
90
16th to endDay
27%27%28%13%2
192
March1st to 15thDay
30%20%25%16%5%
270
16th to endDay
29%19%29%12%7%1
288
April1st to 15thDay
33%23%21%12%7%
270
16th to endDay
28%18%24%16%5%6%
270
May1st to 15thDay
30%11%26%19%9%2
288
16th to endDay
19%16%33%18%10%2
331
June1st to 15thDay
32%9%31%17%7%1
315
16th to endDay
21%12%33%23%6%1
315
July1st to 15thDay
16%8%29%27%13%4
305
16th to endDay
15%11%30%29%10%3
326
August1st to 15thDay
16%7%29%26%14%6%
313
16th to endDay
14%9%24%26%14%10%
332
September1st to 15thDay
19%7%23%25%15%8%
315
16th to endDay
14%9%24%22%18%8%
314
October1st to 15thDay
26%13%23%18%13%5%
315
16th to endDay
37%16%25%15%5%
318
November1st to 15thDay
21%16%31%18%9%1
202
16th to endDay
30%21%25%20%3
60
December1st to 15thDay
41%18%23%13%3
60
16th to endDay
45%31%21%1
64
January1st to 15thNight
32%21%28%13%3
720
16th to endNight
28%20%27%19%4
768
February1st to 15thNight
27%22%29%18%2
704
16th to endNight
27%16%29%20%4
631
March1st to 15thNight
30%17%28%19%3
720
16th to endNight
26%17%26%20%7%
768
April1st to 15thNight
29%17%27%22%2
718
16th to endNight
26%13%26%23%8%1
693
May1st to 15thNight
25%6%29%29%8%
360
16th to endNight
17%8%31%31%11%
375
June1st to 15thNight
23%6%26%30%11%
360
16th to endNight
15%5%36%32%9%
360
July1st to 15thNight
10%425%40%18%1
340
16th to endNight
13%5%24%38%17%
376
August1st to 15thNight
16%422%34%19%2
487
16th to endNight
12%6%21%33%22%2
722
September1st to 15thNight
20%6%20%31%18%2
720
16th to endNight
16%10%22%25%21%4
717
October1st to 15thNight
27%12%23%17%15%2
720
16th to endNight
34%15%24%21%4
768
November1st to 15thNight
27%12%30%20%9%1
700
16th to endNight
35%18%23%15%7%
720
December1st to 15thNight
40%20%21%13%3
720
16th to endNight
37%20%26%13%1
768
Page generated at 2017-11-01 17:23:29. Version ac04

Copyright 2017 A. Danko


Dexter Clear Sky Chart |Charts Home