Bobcat Trail Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bobcat Trail Observatory 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
33%
16170
25%
47385
10%
16126
47%
16126
31%
26097

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%
899
27%
2506
6%
895
37%
895
24%
1293
January16th to endNight
11%
843
30%
2571
4%
843
38%
843
23%
1298
February1st to 15thNight
15%
700
22%
2273
4%
698
34%
698
19%
1211
February16th to endNight
11%
632
26%
1894
3%
632
34%
632
23%
1056
March1st to 15thNight
20%
720
25%
2115
7%
720
38%
720
29%
1161
March16th to endNight
25%
680
22%
2024
9%
680
38%
680
27%
1171
April1st to 15thNight
26%
539
20%
1798
9%
539
42%
539
25%
1023
April16th to endNight
30%
540
20%
1800
11%
540
44%
540
24%
1068
May1st to 15thNight
38%
540
19%
1539
11%
540
46%
540
29%
969
May16th to endNight
46%
563
18%
1498
10%
561
52%
561
32%
940
June1st to 15thNight
49%
540
18%
1440
10%
540
55%
540
40%
832
June16th to endNight
58%
540
28%
1440
17%
540
65%
540
56%
722
July1st to 15thNight
65%
510
18%
1360
13%
510
68%
510
41%
806
July16th to endNight
68%
564
25%
1416
20%
531
70%
531
46%
779
August1st to 15thNight
64%
539
22%
1630
19%
536
69%
536
41%
871
August16th to endNight
67%
573
30%
1910
29%
573
73%
573
42%
978
September1st to 15thNight
60%
540
27%
1800
25%
540
69%
540
38%
950
September16th to endNight
54%
537
35%
1928
29%
537
66%
537
41%
924
October1st to 15thNight
36%
720
26%
2160
13%
720
47%
720
33%
1222
October16th to endNight
29%
816
34%
2352
10%
816
47%
816
36%
1265
November1st to 15thNight
27%
875
29%
2275
8%
875
42%
875
38%
1248
November16th to endNight
17%
900
32%
2448
5%
900
40%
900
34%
1303
December1st to 15thNight
13%
900
20%
2520
2%
900
29%
900
21%
1421
December16th to endNight
14%
960
24%
2688
4%
960
33%
960
20%
1586

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%5%244245%6%8%49%
48385
Night
45%2432445%7%56%
47556
TransparencyDay
31%5%14%25%17%6%
48058
Night
26%5%15%28%18%5%
47385
SeeingDay
12%14%31%24%13%4
6060
Night
8%20%33%25%10%1
16175

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
1325%43336%9%56%
1432
16th to endDay
132442236%8%58%
1664
February1st to 15thDay
1445%6%3445%8%51%
1589
16th to endDay
7%35%5%1435%8%53%
1580
March1st to 15thDay
35%2442445%9%54%
1842
16th to endDay
5%7%25%5%35%5%5%9%44%
2199
April1st to 15thDay
7%8%3442446%7%47%
2150
16th to endDay
11%9%35%5%245%6%7%37%
2160
May1st to 15thDay
14%9%35%5%3445%6%37%
2411
16th to endDay
10%6%35%6%46%5%7%8%34%
2616
June1st to 15thDay
7%4245%36%5%7%8%44%
2520
16th to endDay
33133146%6%8%56%
2520
July1st to 15thDay
7%4245%35%5%7%8%45%
2520
16th to endDay
5%325%6%36%6%7%9%43%
2656
August1st to 15thDay
6%5%25%6%36%5%7%9%41%
2318
16th to endDay
5%425%5%25%5%5%7%50%
2292
September1st to 15thDay
8%41342445%5%54%
2160
16th to endDay
5%323323347%59%
2028
October1st to 15thDay
7%5%243135%46%54%
1800
16th to endDay
45%2331235%7%59%
1857
November1st to 15thDay
242442445%8%56%
1583
16th to endDay
15%234245%6%9%54%
1512
December1st to 15thDay
2435%42345%8%52%
1440
16th to endDay
15%35%5%3346%6%54%
1536
January1st to 15thNight
32332345%8%61%
2506
16th to endNight
1325%323447%62%
2571
February1st to 15thNight
15%25%434447%58%
2262
16th to endNight
17%34434445%56%
1894
March1st to 15thNight
15%25%325%449%55%
2115
16th to endNight
5%7%134245%5%8%50%
2024
April1st to 15thNight
47%235%245%5%6%50%
1798
16th to endNight
11%8%24314447%47%
1800
May1st to 15thNight
11%7%25%3245%6%8%43%
1538
16th to endNight
8%6%2442446%8%46%
1497
June1st to 15thNight
6%2134245%6%10%52%
1440
16th to endNight
223223246%68%
1440
July1st to 15thNight
6%3144245%5%9%51%
1440
16th to endNight
22144245%7%8%54%
1512
August1st to 15thNight
4314335%45%9%53%
1638
16th to endNight
441332445%7%57%
1910
September1st to 15thNight
8%423323447%56%
1800
16th to endNight
5%313323345%63%
1928
October1st to 15thNight
8%5%2342235%6%55%
2160
16th to endNight
45%23323347%59%
2352
November1st to 15thNight
341332335%8%60%
2275
16th to endNight
132232446%7%60%
2448
December1st to 15thNight
15%25%42345%8%56%
2520
16th to endNight
25%35%42445%8%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
24%422%32%12%3
1433
16th to endDay
22%420%32%15%3
1664
February1st to 15thDay
29%7%23%28%8%3
1589
16th to endDay
28%417%31%14%3
1580
March1st to 15thDay
25%5%17%29%17%3
1842
16th to endDay
34%6%15%28%13%3
2199
April1st to 15thDay
34%5%15%26%12%5%
2150
16th to endDay
44%6%13%21%12%2
2160
May1st to 15thDay
46%6%12%19%14%
2411
16th to endDay
43%7%14%20%11%2
2620
June1st to 15thDay
33%7%15%18%18%6%
2520
16th to endDay
22%5%9%27%21%13%
2520
July1st to 15thDay
33%6%13%17%15%13%
2371
16th to endDay
33%6%10%22%17%9%
2489
August1st to 15thDay
36%6%12%18%14%11%
2302
16th to endDay
31%49%21%24%8%
2292
September1st to 15thDay
29%48%20%25%11%
2160
16th to endDay
24%39%28%29%4
2028
October1st to 15thDay
29%5%10%26%22%6%
1800
16th to endDay
23%311%32%21%6%
1857
November1st to 15thDay
24%6%13%26%21%7%
1583
16th to endDay
23%6%14%32%19%3
1512
December1st to 15thDay
28%6%22%30%10%1
1440
16th to endDay
29%6%17%28%14%3
1536
January1st to 15thNight
20%423%30%16%4
2506
16th to endNight
21%417%31%19%4
2571
February1st to 15thNight
26%6%20%32%12%2
2273
16th to endNight
28%415%29%18%4
1894
March1st to 15thNight
24%6%14%31%19%3
2115
16th to endNight
30%6%14%30%16%2
2024
April1st to 15thNight
32%6%14%28%13%4
1798
16th to endNight
36%411%28%16%1
1800
May1st to 15thNight
36%6%15%26%14%
1539
16th to endNight
34%6%19%23%13%2
1498
June1st to 15thNight
25%7%20%23%16%6%
1440
16th to endNight
16%47%33%22%14%
1440
July1st to 15thNight
28%6%13%23%17%10%
1360
16th to endNight
23%5%14%29%16%10%
1416
August1st to 15thNight
25%5%16%23%18%10%
1630
16th to endNight
24%49%26%23%10%
1910
September1st to 15thNight
27%411%21%21%13%
1800
16th to endNight
23%36%31%30%4
1928
October1st to 15thNight
28%5%11%24%23%6%
2160
16th to endNight
25%410%29%25%5%
2352
November1st to 15thNight
21%414%25%26%7%
2275
16th to endNight
20%413%33%22%4
2448
December1st to 15thNight
26%6%22%29%13%2
2520
16th to endNight
27%8%17%31%13%2
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
14%22%34%14%7%6%
90
16th to endDay
9%32%44%8%32
96
February1st to 15thDay
13%42%34%10%
90
16th to endDay
9%32%39%17%1
81
March1st to 15thDay
15%28%37%12%5%
132
16th to endDay
15%21%47%11%3
288
April1st to 15thDay
15%24%37%17%4
269
16th to endDay
29%22%30%12%4
270
May1st to 15thDay
19%14%31%19%11%3
447
16th to endDay
16%11%29%25%13%3
517
June1st to 15thDay
10%8%30%29%17%4
495
16th to endDay
46%35%29%17%6%
495
July1st to 15thDay
11%421%29%25%7%
475
16th to endDay
5%321%35%26%7%
515
August1st to 15thDay
11%5%30%36%13%2
322
16th to endDay
8%6%25%36%16%5%
332
September1st to 15thDay
9%9%33%31%13%3
315
16th to endDay
12%8%36%22%13%6%
186
October1st to 15thDay
11%10%39%28%6%4
135
16th to endDay
7%24%40%18%8%
144
November1st to 15thDay
413%40%21%12%8%
90
16th to endDay
23%38%27%10%
90
December1st to 15thDay
11%46%32%7%2
90
16th to endDay
344%38%8%5%
96
January1st to 15thNight
9%40%29%13%5%2
900
16th to endNight
8%40%36%9%4
843
February1st to 15thNight
7%37%36%14%4
704
16th to endNight
9%32%41%13%2
632
March1st to 15thNight
5%27%42%18%6%
720
16th to endNight
9%21%40%23%5%
680
April1st to 15thNight
10%18%41%25%4
539
16th to endNight
17%16%33%24%8%
540
May1st to 15thNight
16%10%30%28%13%1
540
16th to endNight
13%7%27%34%16%1
563
June1st to 15thNight
7%7%30%38%13%1
540
16th to endNight
2430%44%16%1
540
July1st to 15thNight
8%115%43%27%3
510
16th to endNight
3117%42%31%3
564
August1st to 15thNight
7%118%48%21%2
539
16th to endNight
5%119%41%28%3
573
September1st to 15thNight
11%320%38%21%5%
540
16th to endNight
7%5%28%37%17%2
537
October1st to 15thNight
10%15%34%27%9%3
720
16th to endNight
7%20%39%22%7%1
816
November1st to 15thNight
8%20%40%22%6%1
875
16th to endNight
6%29%44%15%2
900
December1st to 15thNight
10%36%35%13%3
900
16th to endNight
9%36%35%15%3
960
Page generated at 2017-11-01 15:23:40. Version ac04

Copyright 2017 A. Danko


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