Bojarzin Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bojarzin Observatory clear sky chart from 2005-11-05 to 2017-04-30.

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
40%
15470
20%
45649
13%
15426
47%
15426
26%
29343

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
23%
899
18%
2506
7%
895
32%
895
22%
1736
January16th to endNight
21%
960
16%
2541
4%
960
29%
960
19%
1849
February1st to 15thNight
24%
826
13%
2235
4%
824
30%
824
19%
1604
February16th to endNight
26%
631
19%
1893
8%
631
35%
631
23%
1243
March1st to 15thNight
28%
690
17%
2130
9%
690
35%
690
19%
1459
March16th to endNight
32%
576
14%
2013
9%
576
40%
576
18%
1352
April1st to 15thNight
33%
539
21%
1797
12%
539
46%
539
25%
1097
April16th to endNight
35%
537
21%
1791
15%
537
46%
537
24%
1145
May1st to 15thNight
39%
495
18%
1475
12%
495
46%
495
22%
1021
May16th to endNight
51%
515
19%
1369
12%
513
56%
513
33%
896
June1st to 15thNight
62%
495
20%
1320
14%
495
65%
495
39%
796
June16th to endNight
59%
495
19%
1320
14%
495
62%
495
38%
805
July1st to 15thNight
69%
465
19%
1240
16%
465
70%
465
39%
747
July16th to endNight
72%
522
23%
1313
18%
489
74%
489
46%
741
August1st to 15thNight
77%
494
24%
1538
25%
491
79%
491
41%
823
August16th to endNight
74%
525
21%
1750
23%
525
77%
525
35%
969
September1st to 15thNight
64%
495
30%
1650
31%
495
68%
495
34%
910
September16th to endNight
62%
621
31%
1779
23%
621
67%
621
38%
1026
October1st to 15thNight
51%
660
29%
1955
20%
660
59%
660
36%
1129
October16th to endNight
33%
704
24%
2164
15%
704
44%
704
28%
1298
November1st to 15thNight
35%
700
27%
2276
18%
700
49%
700
30%
1288
November16th to endNight
29%
766
22%
2386
12%
766
40%
766
24%
1509
December1st to 15thNight
25%
900
14%
2520
6%
900
32%
900
19%
1843
December16th to endNight
21%
960
13%
2688
5%
960
29%
960
15%
2057

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
12%7%36%5%3445%7%38%
46085
Night
13%7%35%42445%6%42%
45819
Cloud CoverDay
12%7%36%5%3445%7%38%
46093
Night
13%7%35%424446%42%
45824
TransparencyDay
43%5%12%23%13%1
45773
Night
41%411%23%15%2
45650
SeeingDay
14%5%23%28%20%7%
5271
Night
17%7%27%30%14%1
15472

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
15%11%49%7%45%435%27%
1432
16th to endDay
13%12%7%7%6%35%336%30%
1683
February1st to 15thDay
13%10%6%8%5%35%446%30%
1626
16th to endDay
11%11%5%8%6%3445%6%33%
1580
March1st to 15thDay
14%10%5%7%6%33346%33%
1829
16th to endDay
16%10%48%6%34447%29%
2211
April1st to 15thDay
15%7%36%42445%6%37%
2151
16th to endDay
18%6%25%5%35%45%6%35%
2148
May1st to 15thDay
17%8%35%5%35%47%6%31%
2142
16th to endDay
12%6%36%5%35%5%6%8%37%
2393
June1st to 15thDay
9%425%5%35%6%6%9%42%
2310
16th to endDay
8%435%6%45%5%5%8%42%
2310
July1st to 15thDay
8%4245%25%6%8%9%43%
2310
16th to endDay
5%2145%36%6%8%11%43%
2448
August1st to 15thDay
6%425%5%36%5%6%10%42%
2082
16th to endDay
7%425%6%345%6%8%45%
2100
September1st to 15thDay
13%5%24435%446%44%
1980
16th to endDay
8%5%35%42445%7%49%
1839
October1st to 15thDay
14%5%24423346%47%
1673
16th to endDay
15%7%34424345%45%
1708
November1st to 15thDay
15%5%25%314446%46%
1582
16th to endDay
17%8%5%5%5%23335%39%
1572
December1st to 15thDay
18%9%7%6%5%245%5%6%27%
1440
16th to endDay
18%11%5%6%5%245%5%6%27%
1536
January1st to 15thNight
13%8%46%6%34345%38%
2506
16th to endNight
13%11%6%7%5%34335%34%
2541
February1st to 15thNight
14%10%6%7%6%24345%34%
2233
16th to endNight
14%8%36%5%23345%41%
1893
March1st to 15thNight
18%9%25%424445%37%
2117
16th to endNight
17%9%35%5%2445%6%34%
2013
April1st to 15thNight
13%6%25%433447%43%
1797
16th to endNight
16%6%25%424345%41%
1791
May1st to 15thNight
16%7%35%435%5%5%7%35%
1475
16th to endNight
9%5%25%5%2446%9%42%
1368
June1st to 15thNight
8%4233245%6%9%48%
1320
16th to endNight
8%4245%2436%10%46%
1320
July1st to 15thNight
7%3244345%6%9%48%
1320
16th to endNight
32144245%7%11%52%
1409
August1st to 15thNight
6%2133245%6%10%53%
1548
16th to endNight
5%323435%5%6%7%51%
1750
September1st to 15thNight
10%5%24423347%52%
1650
16th to endNight
7%5%1442445%8%52%
1779
October1st to 15thNight
11%424323347%52%
1955
16th to endNight
17%5%15%21335%5%49%
2164
November1st to 15thNight
11%5%24423236%52%
2276
16th to endNight
16%8%23433346%43%
2386
December1st to 15thNight
21%10%45%5%24436%32%
2520
16th to endNight
19%12%47%5%35%44427%
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%11%5%9%7%36%436%27%
1432
16th to endDay
13%12%7%7%6%34346%30%
1683
February1st to 15thDay
13%11%5%8%5%35%346%30%
1626
16th to endDay
11%11%5%7%6%34446%33%
1580
March1st to 15thDay
15%10%5%7%5%33345%33%
1839
16th to endDay
15%10%47%6%24448%29%
2209
April1st to 15thDay
15%7%46%32445%6%37%
2151
16th to endDay
18%6%25%5%35%45%6%35%
2148
May1st to 15thDay
17%8%45%5%345%6%6%31%
2142
16th to endDay
12%6%36%5%35%5%5%8%37%
2393
June1st to 15thDay
9%425%5%35%6%6%8%42%
2310
16th to endDay
8%435%6%45%5%6%8%42%
2310
July1st to 15thDay
8%3245%35%6%8%9%43%
2310
16th to endDay
5%2145%36%6%8%12%42%
2448
August1st to 15thDay
6%425%5%36%5%7%10%42%
2082
16th to endDay
7%425%6%345%6%8%44%
2100
September1st to 15thDay
13%5%24435%447%44%
1980
16th to endDay
8%5%35%424447%49%
1839
October1st to 15thDay
14%5%24423346%47%
1673
16th to endDay
15%7%24324345%45%
1708
November1st to 15thDay
15%5%24313446%46%
1582
16th to endDay
17%8%45%423336%39%
1572
December1st to 15thDay
18%9%7%6%5%25%45%6%27%
1440
16th to endDay
18%11%5%6%5%235%5%6%27%
1536
January1st to 15thNight
13%8%46%6%34445%38%
2506
16th to endNight
13%11%5%7%6%34335%34%
2541
February1st to 15thNight
14%9%6%6%5%25%345%34%
2226
16th to endNight
14%7%36%5%24346%41%
1893
March1st to 15thNight
18%9%25%424445%37%
2130
16th to endNight
18%9%35%5%2446%6%34%
2013
April1st to 15thNight
13%6%25%443447%43%
1797
16th to endNight
16%6%35%5%24445%41%
1791
May1st to 15thNight
16%7%25%435%46%7%35%
1474
16th to endNight
9%5%35%5%245%5%9%42%
1368
June1st to 15thNight
8%5%233245%6%9%48%
1320
16th to endNight
8%425%42436%10%46%
1320
July1st to 15thNight
7%324425%5%6%9%48%
1320
16th to endNight
3214425%47%11%52%
1409
August1st to 15thNight
6%2133245%6%10%53%
1548
16th to endNight
5%314435%5%5%7%52%
1750
September1st to 15thNight
10%5%24413346%52%
1650
16th to endNight
7%41432345%8%52%
1779
October1st to 15thNight
11%423323347%52%
1955
16th to endNight
17%5%24223345%49%
2164
November1st to 15thNight
11%5%24423235%52%
2276
16th to endNight
15%8%23423346%43%
2386
December1st to 15thNight
21%10%45%5%24435%32%
2520
16th to endNight
19%12%47%5%35%34428%
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
58%38%18%10%
1433
16th to endDay
55%314%19%7%
1683
February1st to 15thDay
53%412%21%6%
1628
16th to endDay
51%313%21%9%
1580
March1st to 15thDay
52%413%22%7%
1839
16th to endDay
53%5%13%20%7%
2211
April1st to 15thDay
45%411%24%12%1
2151
16th to endDay
47%5%11%20%12%1
2148
May1st to 15thDay
49%5%14%20%8%
2142
16th to endDay
43%6%13%18%15%2
2397
June1st to 15thDay
35%7%14%26%14%1
2310
16th to endDay
37%6%12%22%17%3
2310
July1st to 15thDay
35%6%12%27%14%3
2161
16th to endDay
30%7%17%29%14%
2282
August1st to 15thDay
33%7%14%27%16%1
2068
16th to endDay
34%6%12%24%16%6%
2100
September1st to 15thDay
39%5%6%24%18%5%
1980
16th to endDay
33%48%31%19%2
1839
October1st to 15thDay
36%310%26%19%2
1673
16th to endDay
39%410%26%16%2
1708
November1st to 15thDay
37%411%22%19%4
1582
16th to endDay
47%311%26%10%1
1572
December1st to 15thDay
55%5%13%17%8%
1440
16th to endDay
55%410%19%7%1
1536
January1st to 15thNight
47%411%22%13%
2506
16th to endNight
52%412%21%9%
2541
February1st to 15thNight
52%311%19%11%1
2235
16th to endNight
45%313%25%11%
1893
March1st to 15thNight
49%410%22%11%1
2130
16th to endNight
49%412%21%9%1
2013
April1st to 15thNight
40%39%27%16%2
1797
16th to endNight
44%39%22%16%3
1791
May1st to 15thNight
47%5%10%21%14%
1475
16th to endNight
36%6%15%17%19%3
1370
June1st to 15thNight
30%5%13%30%17%2
1320
16th to endNight
31%5%13%24%19%5%
1320
July1st to 15thNight
30%5%12%28%18%4
1240
16th to endNight
24%6%18%31%18%1
1313
August1st to 15thNight
24%6%14%28%22%2
1538
16th to endNight
28%6%12%25%20%6%
1750
September1st to 15thNight
32%38%24%23%8%
1650
16th to endNight
29%49%26%25%5%
1779
October1st to 15thNight
31%48%26%22%5%
1955
16th to endNight
37%39%26%19%3
2164
November1st to 15thNight
34%310%24%21%6%
2276
16th to endNight
42%310%27%16%
2386
December1st to 15thNight
54%312%18%10%
2520
16th to endNight
58%410%16%8%1
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
32%8%36%13%8%
90
16th to endDay
11%21%38%23%4
96
February1st to 15thDay
18%17%36%22%4
90
16th to endDay
13%18%32%30%31
81
March1st to 15thDay
28%10%37%18%4
90
16th to endDay
22%13%33%22%7%
195
April1st to 15thDay
18%11%31%26%11%
270
16th to endDay
19%5%31%27%13%3
266
May1st to 15thDay
19%9%29%29%8%4
264
16th to endDay
15%6%27%29%15%6%
437
June1st to 15thDay
12%322%32%23%6%
420
16th to endDay
11%324%32%21%7%
420
July1st to 15thDay
12%216%29%27%12%
400
16th to endDay
7%111%31%33%14%
445
August1st to 15thDay
7%11%32%31%16%
355
16th to endDay
9%113%24%35%16%
268
September1st to 15thDay
16%28%31%30%11%
255
16th to endDay
10%414%27%30%12%
254
October1st to 15thDay
8%8%21%30%25%5%
113
16th to endDay
19%5%32%30%11%1
96
November1st to 15thDay
6%5%23%26%23%14%
90
16th to endDay
34%12%33%15%4
90
December1st to 15thDay
13%13%37%25%6%3
90
16th to endDay
29%13%43%13%
96
January1st to 15thNight
18%13%38%24%5%
900
16th to endNight
18%14%36%26%4
960
February1st to 15thNight
20%12%35%28%3
827
16th to endNight
20%10%36%29%2
631
March1st to 15thNight
24%9%33%27%5%
690
16th to endNight
22%8%30%28%10%
576
April1st to 15thNight
17%13%33%28%8%
539
16th to endNight
21%433%29%10%
537
May1st to 15thNight
20%429%33%10%1
495
16th to endNight
10%126%36%21%2
515
June1st to 15thNight
10%319%47%18%1
495
16th to endNight
10%219%42%24%1
495
July1st to 15thNight
10%10%41%32%3
465
16th to endNight
4112%38%38%4
522
August1st to 15thNight
7%16%41%36%6%
494
16th to endNight
5%111%37%39%5%
525
September1st to 15thNight
10%312%37%30%5%
495
16th to endNight
9%416%33%31%5%
621
October1st to 15thNight
13%425%31%23%2
660
16th to endNight
20%8%33%27%9%
704
November1st to 15thNight
15%8%36%27%11%1
700
16th to endNight
21%10%34%24%8%
766
December1st to 15thNight
27%10%31%23%6%
900
16th to endNight
26%11%31%24%4
960
Page generated at 2017-04-30 19:40:12. Version ac04

Copyright 2017 A. Danko


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