Sommers-Bausch Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sommers-Bausch 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
53%
15840
28%
46502
17%
15797
64%
15797
39%
24755

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
37%
899
32%
2506
15%
895
53%
895
39%
1279
January16th to endNight
35%
807
34%
2535
15%
807
55%
807
35%
1252
February1st to 15thNight
32%
699
26%
2258
10%
698
51%
698
29%
1205
February16th to endNight
37%
632
33%
1894
13%
632
57%
632
35%
1024
March1st to 15thNight
45%
720
29%
2109
14%
720
59%
720
40%
1122
March16th to endNight
46%
684
28%
2028
16%
684
58%
684
37%
1108
April1st to 15thNight
44%
539
25%
1798
17%
539
57%
539
34%
943
April16th to endNight
44%
540
24%
1800
18%
540
56%
540
30%
1018
May1st to 15thNight
51%
540
19%
1592
16%
540
56%
540
29%
1002
May16th to endNight
64%
563
18%
1498
14%
561
68%
561
38%
886
June1st to 15thNight
73%
540
22%
1440
18%
540
74%
540
49%
769
June16th to endNight
81%
540
29%
1440
24%
540
83%
540
60%
711
July1st to 15thNight
77%
510
19%
1360
16%
510
78%
510
39%
801
July16th to endNight
83%
564
26%
1444
25%
531
84%
531
47%
783
August1st to 15thNight
82%
527
22%
1619
24%
524
83%
524
44%
833
August16th to endNight
79%
525
28%
1750
33%
525
80%
525
41%
887
September1st to 15thNight
73%
495
30%
1650
31%
495
78%
495
39%
852
September16th to endNight
75%
492
37%
1766
36%
492
82%
492
48%
778
October1st to 15thNight
59%
658
28%
1978
19%
658
66%
658
42%
1058
October16th to endNight
54%
731
33%
2139
17%
731
65%
731
41%
1121
November1st to 15thNight
52%
875
34%
2275
17%
875
61%
875
48%
1195
November16th to endNight
48%
900
35%
2415
16%
900
61%
900
50%
1234
December1st to 15thNight
38%
900
27%
2520
9%
900
53%
900
35%
1363
December16th to endNight
40%
960
27%
2688
11%
960
54%
960
32%
1531

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
5%4233245%6%8%53%
47483
Night
442332335%7%59%
46677
TransparencyDay
27%6%12%24%21%7%
47160
Night
24%5%11%26%23%8%
46502
SeeingDay
9%8%27%31%17%5%
5720
Night
6%10%23%37%18%3
15846

By Month

Percentage Cloud Cover SW (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
5%23423248%59%
1432
16th to endDay
15%2432235%6%62%
1698
February1st to 15thDay
15%17%32445%8%56%
1603
16th to endDay
15%25%32345%7%58%
1580
March1st to 15thDay
2435%42345%9%54%
1850
16th to endDay
5%7%2432245%10%50%
2196
April1st to 15thDay
7%6%2222335%9%53%
2150
16th to endDay
12%7%243245%5%7%44%
2160
May1st to 15thDay
11%7%245%25%5%6%7%40%
2355
16th to endDay
11%5%23426%5%7%9%41%
2616
June1st to 15thDay
6%313425%6%6%9%50%
2520
16th to endDay
2212325%6%8%9%54%
2520
July1st to 15thDay
7%4135%35%6%7%9%45%
2520
16th to endDay
5%213436%6%8%9%47%
2623
August1st to 15thDay
6%3245%46%6%8%9%43%
2245
16th to endDay
6%313425%5%7%9%50%
2100
September1st to 15thDay
8%31232345%7%55%
1980
16th to endDay
5%312213335%66%
1862
October1st to 15thDay
5%413413446%60%
1650
16th to endDay
5%5%12312236%65%
1722
November1st to 15thDay
241332245%7%63%
1583
16th to endDay
223321245%7%61%
1542
December1st to 15thDay
15%24423448%57%
1440
16th to endDay
35%24313447%58%
1536
January1st to 15thNight
1324322348%64%
2506
16th to endNight
15%2431325%5%63%
2535
February1st to 15thNight
17%345%23345%59%
2248
16th to endNight
16%34323446%58%
1894
March1st to 15thNight
25%2332335%8%58%
2109
16th to endNight
5%5%13312347%59%
2028
April1st to 15thNight
5%6%13223446%58%
1798
16th to endNight
12%7%13313336%51%
1800
May1st to 15thNight
14%5%23423448%45%
1591
16th to endNight
9%41242345%8%54%
1497
June1st to 15thNight
5%2222346%8%61%
1440
16th to endNight
12121335%9%67%
1440
July1st to 15thNight
6%212325%47%10%52%
1440
16th to endNight
42133245%7%8%56%
1542
August1st to 15thNight
311332445%9%58%
1628
16th to endNight
5%21432345%8%57%
1750
September1st to 15thNight
9%21322345%7%58%
1650
16th to endNight
411221225%5%69%
1766
October1st to 15thNight
6%5%3322445%61%
1978
16th to endNight
6%5%23312346%61%
2139
November1st to 15thNight
131321325%6%66%
2275
16th to endNight
232221235%5%66%
2415
December1st to 15thNight
26%24312349%58%
2520
16th to endNight
27%2442345%7%54%
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
23%5%12%33%21%5%
1433
16th to endDay
22%310%34%22%7%
1698
February1st to 15thDay
26%5%14%34%14%4
1604
16th to endDay
23%49%28%27%5%
1580
March1st to 15thDay
26%5%10%28%23%5%
1850
16th to endDay
29%5%13%25%21%5%
2196
April1st to 15thDay
28%6%11%26%19%7%
2150
16th to endDay
36%7%12%21%17%3
2160
May1st to 15thDay
40%8%12%21%13%2
2355
16th to endDay
36%9%15%21%11%5%
2620
June1st to 15thDay
27%10%13%19%18%10%
2520
16th to endDay
21%7%12%20%27%10%
2520
July1st to 15thDay
32%9%11%19%15%12%
2371
16th to endDay
28%10%13%23%16%7%
2458
August1st to 15thDay
32%11%13%17%15%9%
2230
16th to endDay
27%8%11%22%23%6%
2100
September1st to 15thDay
27%6%8%22%20%14%
1980
16th to endDay
20%47%24%36%7%
1862
October1st to 15thDay
25%6%12%20%28%8%
1650
16th to endDay
20%48%27%30%9%
1722
November1st to 15thDay
20%411%26%26%11%
1583
16th to endDay
20%38%26%31%9%
1542
December1st to 15thDay
24%5%12%33%19%3
1440
16th to endDay
25%6%15%25%21%5%
1536
January1st to 15thNight
19%412%31%27%5%
2506
16th to endNight
23%210%28%25%8%
2535
February1st to 15thNight
28%311%32%19%4
2258
16th to endNight
26%46%28%25%8%
1894
March1st to 15thNight
24%47%28%28%7%
2109
16th to endNight
26%411%27%25%4
2028
April1st to 15thNight
27%410%25%22%9%
1798
16th to endNight
34%411%25%19%4
1800
May1st to 15thNight
36%6%14%20%16%4
1592
16th to endNight
28%7%19%24%14%5%
1498
June1st to 15thNight
19%6%16%28%15%13%
1440
16th to endNight
13%6%11%22%31%15%
1440
July1st to 15thNight
26%9%13%21%18%10%
1360
16th to endNight
20%8%14%29%18%9%
1444
August1st to 15thNight
21%6%16%25%19%10%
1619
16th to endNight
23%5%11%26%23%9%
1750
September1st to 15thNight
25%5%11%22%19%15%
1650
16th to endNight
17%47%26%35%9%
1766
October1st to 15thNight
24%5%14%18%27%10%
1978
16th to endNight
24%38%23%31%9%
2139
November1st to 15thNight
19%39%26%27%13%
2275
16th to endNight
18%39%26%32%9%
2415
December1st to 15thNight
23%414%30%21%5%
2520
16th to endNight
27%6%15%27%20%4
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
313%23%36%13%10%
90
16th to endDay
7%9%33%31%17%1
96
February1st to 15thDay
426%40%27%1
90
16th to endDay
319%28%38%7%2
81
March1st to 15thDay
423%32%33%42
140
16th to endDay
14%20%39%20%4
288
April1st to 15thDay
13%21%36%18%7%2
269
16th to endDay
18%19%35%20%5%1
270
May1st to 15thDay
15%7%30%32%12%2
420
16th to endDay
16%6%25%27%17%6%
517
June1st to 15thDay
6%323%34%24%7%
495
16th to endDay
2327%33%23%9%
495
July1st to 15thDay
11%117%30%27%11%
475
16th to endDay
7%214%32%32%11%
482
August1st to 15thDay
8%5%30%34%18%4
300
16th to endDay
8%424%40%16%4
268
September1st to 15thDay
9%435%36%12%1
255
16th to endDay
4326%30%27%8%
137
October1st to 15thDay
46%28%24%25%10%
90
16th to endDay
8%8%22%40%14%5%
96
November1st to 15thDay
2422%31%31%8%
90
16th to endDay
10%12%36%36%4
90
December1st to 15thDay
6%25%36%25%5%
90
16th to endDay
39%36%44%6%
96
January1st to 15thNight
223%31%28%10%2
900
16th to endNight
421%34%30%7%2
807
February1st to 15thNight
420%34%32%6%
704
16th to endNight
317%35%36%6%
632
March1st to 15thNight
412%32%39%9%2
720
16th to endNight
8%11%28%43%7%1
684
April1st to 15thNight
8%10%30%39%9%
539
16th to endNight
16%6%26%35%13%1
540
May1st to 15thNight
16%321%40%15%2
540
16th to endNight
11%215%41%24%4
563
June1st to 15thNight
7%112%49%24%3
540
16th to endNight
211%42%40%2
540
July1st to 15thNight
6%8%31%45%7%
510
16th to endNight
4429%52%8%
564
August1st to 15thNight
46%38%44%5%
527
16th to endNight
6%7%37%37%11%
525
September1st to 15thNight
8%111%41%30%7%
495
16th to endNight
4312%42%26%10%
492
October1st to 15thNight
10%5%22%39%17%5%
658
16th to endNight
8%10%22%37%16%4
731
November1st to 15thNight
313%26%38%14%2
875
16th to endNight
411%32%40%9%1
900
December1st to 15thNight
5%19%30%36%7%1
900
16th to endNight
5%18%30%34%9%2
960
Page generated at 2017-08-13 12:16:34. Version ac04

Copyright 2017 A. Danko


Sommers-Bausch Observatory Clear Sky Chart | Charts Home