Barking Spider Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Barking Spider Observatory clear sky chart from 2005-11-05 to 2017-09-23.

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
64%
15404
25%
46974
23%
15368
66%
15368
36%
26692

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
62%
716
17%
2386
18%
716
64%
716
28%
1444
January16th to endNight
58%
768
24%
2496
26%
768
60%
768
26%
1555
February1st to 15thNight
56%
697
22%
2288
22%
697
60%
697
24%
1446
February16th to endNight
52%
632
21%
1898
19%
632
57%
632
27%
1226
March1st to 15thNight
52%
720
17%
2007
15%
720
55%
720
27%
1337
March16th to endNight
51%
768
19%
2088
15%
768
55%
768
29%
1374
April1st to 15thNight
52%
719
21%
1799
12%
719
55%
719
33%
1196
April16th to endNight
60%
720
24%
1800
12%
720
63%
720
45%
1057
May1st to 15thNight
66%
614
25%
1694
18%
614
68%
614
47%
910
May16th to endNight
62%
390
23%
1513
24%
390
66%
390
32%
765
June1st to 15thNight
68%
360
23%
1440
27%
360
72%
360
37%
682
June16th to endNight
81%
360
34%
1440
44%
360
84%
360
58%
525
July1st to 15thNight
84%
376
30%
1396
37%
376
84%
376
55%
563
July16th to endNight
71%
564
30%
1593
29%
531
72%
531
47%
782
August1st to 15thNight
68%
556
28%
1629
23%
553
68%
553
44%
836
August16th to endNight
77%
764
33%
1910
22%
764
77%
764
56%
1032
September1st to 15thNight
78%
720
34%
1800
25%
720
78%
720
58%
952
September16th to endNight
77%
688
38%
1880
34%
688
79%
688
56%
939
October1st to 15thNight
71%
660
29%
1980
30%
660
75%
660
43%
1043
October16th to endNight
68%
704
31%
2112
33%
704
71%
704
40%
1160
November1st to 15thNight
68%
700
27%
2186
27%
700
72%
700
38%
1213
November16th to endNight
63%
720
24%
2431
25%
720
66%
720
32%
1365
December1st to 15thNight
56%
720
20%
2520
19%
720
61%
720
23%
1588
December16th to endNight
48%
768
19%
2688
17%
768
54%
768
23%
1702

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
8%5%24313346%56%
47936
Night
10%6%24323347%51%
47161
TransparencyDay
27%49%18%23%16%
47623
Night
31%49%18%20%15%
46975
SeeingDay
9%9%24%34%18%4
6033
Night
11%211%33%32%7%
15417

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
16%42432445%7%43%
1549
16th to endDay
17%6%25%424336%42%
1728
February1st to 15thDay
17%8%25%314346%41%
1576
16th to endDay
18%7%34422346%39%
1576
March1st to 15thDay
15%5%36%5%25%35%9%36%
1950
16th to endDay
13%6%25%425%5%5%7%40%
2136
April1st to 15thDay
15%7%25%42345%5%42%
2149
16th to endDay
8%423323347%57%
2160
May1st to 15thDay
4413213348%62%
2253
16th to endDay
7%7%24312347%55%
2599
June1st to 15thDay
5%6%13323346%59%
2520
16th to endDay
2312112225%73%
2520
July1st to 15thDay
1422212236%71%
2478
16th to endDay
1312212236%72%
2468
August1st to 15thDay
15%13212225%69%
2322
16th to endDay
323212235%72%
2292
September1st to 15thDay
2412212235%71%
2160
16th to endDay
4412112236%69%
1915
October1st to 15thDay
5%313313337%63%
1650
16th to endDay
8%5%13323336%59%
1760
November1st to 15thDay
9%5%2422445%6%51%
1672
16th to endDay
13%7%35%332445%47%
1527
December1st to 15thDay
18%7%35%32344442%
1440
16th to endDay
19%7%24423347%40%
1536
January1st to 15thNight
14%6%2442345%8%43%
2386
16th to endNight
17%6%34313445%45%
2496
February1st to 15thNight
16%5%3443435%5%42%
2276
16th to endNight
16%6%35%324437%42%
1898
March1st to 15thNight
17%6%25%424346%41%
2007
16th to endNight
14%6%35%424345%44%
2088
April1st to 15thNight
13%5%2442446%7%44%
1799
16th to endNight
8%313323347%57%
1800
May1st to 15thNight
36%25%313248%57%
1694
16th to endNight
6%10%24322337%51%
1512
June1st to 15thNight
5%6%15%313348%55%
1440
16th to endNight
2412212335%71%
1440
July1st to 15thNight
1413213249%63%
1479
16th to endNight
17%45%42335%8%52%
1701
August1st to 15thNight
29%35%5%2345%9%48%
1638
16th to endNight
6%25%32335%9%55%
1910
September1st to 15thNight
25%24323337%62%
1800
16th to endNight
3423213346%65%
1880
October1st to 15thNight
7%314322436%59%
1980
16th to endNight
7%5%2442335%5%55%
2112
November1st to 15thNight
9%5%2322335%7%53%
2186
16th to endNight
10%5%24323346%52%
2431
December1st to 15thNight
17%6%25%424345%43%
2520
16th to endNight
19%6%24323335%43%
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
38%6%12%18%16%7%
1549
16th to endDay
43%5%8%12%18%10%
1728
February1st to 15thDay
42%5%9%17%21%3
1576
16th to endDay
44%5%9%23%12%3
1576
March1st to 15thDay
44%412%18%14%5%
1950
16th to endDay
41%8%12%18%16%2
2136
April1st to 15thDay
41%5%14%17%18%2
2149
16th to endDay
26%414%24%22%7%
2160
May1st to 15thDay
19%39%28%29%8%
2253
16th to endDay
27%411%26%23%5%
2603
June1st to 15thDay
24%410%20%23%16%
2520
16th to endDay
12%2417%33%29%
2520
July1st to 15thDay
13%239%23%47%
2332
16th to endDay
12%249%25%44%
2313
August1st to 15thDay
17%2312%29%34%
2306
16th to endDay
12%2415%36%28%
2292
September1st to 15thDay
14%25%14%31%31%
2160
16th to endDay
17%26%24%29%19%
1915
October1st to 15thDay
22%49%20%26%17%
1650
16th to endDay
26%410%22%22%13%
1760
November1st to 15thDay
31%5%12%26%16%7%
1672
16th to endDay
37%5%10%17%24%4
1527
December1st to 15thDay
44%5%10%16%18%4
1440
16th to endDay
43%5%12%17%15%4
1536
January1st to 15thNight
37%5%12%19%16%8%
2386
16th to endNight
40%5%9%13%16%15%
2496
February1st to 15thNight
41%5%10%18%17%7%
2288
16th to endNight
41%5%13%23%14%2
1898
March1st to 15thNight
43%412%19%14%5%
2007
16th to endNight
40%5%13%18%17%5%
2088
April1st to 15thNight
36%7%14%20%17%3
1799
16th to endNight
25%5%13%26%20%8%
1800
May1st to 15thNight
23%410%21%28%11%
1695
16th to endNight
29%412%24%22%6%
1513
June1st to 15thNight
24%410%20%21%17%
1440
16th to endNight
13%1416%31%32%
1440
July1st to 15thNight
16%138%20%48%
1396
16th to endNight
23%25%10%20%37%
1593
August1st to 15thNight
27%311%24%31%
1629
16th to endNight
20%2413%28%30%
1910
September1st to 15thNight
20%25%10%26%35%
1800
16th to endNight
18%26%22%27%22%
1880
October1st to 15thNight
25%38%21%22%17%
1980
16th to endNight
28%47%22%23%14%
2112
November1st to 15thNight
28%5%13%27%16%8%
2186
16th to endNight
32%5%10%22%21%8%
2431
December1st to 15thNight
41%5%9%16%19%6%
2520
16th to endNight
42%5%12%15%17%6%
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
21%7%24%29%14%2
177
16th to endDay
20%8%18%27%21%3
256
February1st to 15thDay
20%8%22%24%22%1
236
16th to endDay
19%13%27%25%13%1
237
March1st to 15thDay
18%11%29%21%15%2
270
16th to endDay
14%17%35%21%10%1
288
April1st to 15thDay
18%20%29%21%9%
269
16th to endDay
10%23%29%28%6%2
270
May1st to 15thDay
7%13%38%30%8%1
288
16th to endDay
9%12%24%37%12%3
330
June1st to 15thDay
5%13%33%34%11%1
315
16th to endDay
2324%40%23%5%
315
July1st to 15thDay
1118%53%20%4
305
16th to endDay
118%45%24%8%
327
August1st to 15thDay
2218%48%22%6%
315
16th to endDay
116%46%27%7%
332
September1st to 15thDay
3216%44%26%6%
315
16th to endDay
37%22%36%22%8%
284
October1st to 15thDay
7%8%21%38%19%5%
255
16th to endDay
12%7%27%30%19%2
272
November1st to 15thDay
11%223%25%29%6%
178
16th to endDay
9%16%20%33%21%
75
December1st to 15thDay
18%15%26%28%11%
60
16th to endDay
18%10%18%26%20%4
64
January1st to 15thNight
15%310%33%28%8%
720
16th to endNight
18%211%33%24%9%
768
February1st to 15thNight
17%411%34%26%6%
704
16th to endNight
17%5%15%34%21%5%
632
March1st to 15thNight
17%6%14%27%28%5%
720
16th to endNight
14%5%18%35%22%3
768
April1st to 15thNight
11%6%20%36%21%3
719
16th to endNight
8%420%35%25%5%
720
May1st to 15thNight
6%113%41%31%4
615
16th to endNight
9%211%39%31%4
391
June1st to 15thNight
5%111%48%29%2
360
16th to endNight
48%44%40%2
360
July1st to 15thNight
3132%56%6%
376
16th to endNight
4227%51%14%
564
August1st to 15thNight
6%5%31%46%9%
556
16th to endNight
25%33%48%9%
764
September1st to 15thNight
5%5%28%48%12%
720
16th to endNight
5%8%29%42%12%
688
October1st to 15thNight
8%28%34%35%10%
660
16th to endNight
9%28%31%33%13%
704
November1st to 15thNight
9%112%33%33%9%
700
16th to endNight
11%213%31%30%9%
720
December1st to 15thNight
19%411%33%23%6%
720
16th to endNight
20%418%33%20%3
768
Page generated at 2017-09-24 06:15:51. Version ac04

Copyright 2017 A. Danko


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