Jock River Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Jock River Observatory clear sky chart from 2005-11-05 to 2017-03-15.

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
30%
14138
14%
45219
8%
14107
36%
14107
17%
32067

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
16%
720
7%
2506
4%
716
21%
716
7%
2014
January16th to endNight
20%
768
11%
2641
7%
768
26%
768
11%
1969
February1st to 15thNight
17%
703
10%
2287
4%
701
25%
701
11%
1755
February16th to endNight
23%
631
14%
1946
7%
631
32%
631
14%
1442
March1st to 15thNight
20%
720
14%
2103
7%
720
28%
720
16%
1559
March16th to endNight
32%
704
20%
1862
9%
704
40%
704
22%
1290
April1st to 15thNight
25%
658
16%
1646
5%
658
31%
658
21%
1203
April16th to endNight
31%
597
18%
1587
8%
597
38%
597
24%
1097
May1st to 15thNight
34%
330
19%
1320
14%
330
46%
330
18%
835
May16th to endNight
36%
343
14%
1369
11%
342
48%
342
20%
846
June1st to 15thNight
36%
330
10%
1320
9%
330
45%
330
15%
905
June16th to endNight
41%
330
9%
1320
12%
330
46%
330
20%
830
July1st to 15thNight
54%
310
15%
1240
23%
310
60%
310
29%
665
July16th to endNight
54%
348
13%
1306
15%
326
59%
326
27%
744
August1st to 15thNight
50%
403
15%
1384
13%
401
55%
401
26%
842
August16th to endNight
50%
654
19%
1704
9%
654
55%
654
39%
1044
September1st to 15thNight
46%
660
16%
1650
8%
660
49%
660
30%
1129
September16th to endNight
47%
657
22%
1792
14%
657
51%
657
32%
1138
October1st to 15thNight
35%
660
18%
1980
12%
660
44%
660
21%
1369
October16th to endNight
24%
704
12%
2203
6%
704
32%
704
13%
1661
November1st to 15thNight
26%
700
17%
2325
13%
700
35%
700
17%
1625
November16th to endNight
19%
720
11%
2520
6%
720
25%
720
10%
1919
December1st to 15thNight
18%
720
7%
2520
3%
720
23%
720
9%
2019
December16th to endNight
14%
768
9%
2688
4%
768
21%
768
7%
2167

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%8%36%5%35%45%6%33%
45522
Night
18%9%36%5%34446%32%
45388
Cloud CoverDay
18%8%36%5%34446%33%
45531
Night
18%10%36%5%34445%33%
45394
TransparencyDay
51%412%20%10%1
45209
Night
53%411%20%10%
45219
SeeingDay
21%10%27%23%12%4
4748
Night
23%10%28%26%10%
14139

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
22%15%5%9%7%2434321%
1432
16th to endDay
15%14%6%8%6%36%45%5%24%
1581
February1st to 15thDay
14%14%5%9%7%45%445%23%
1575
16th to endDay
18%13%46%7%3445%5%26%
1527
March1st to 15thDay
17%11%38%6%45%44427%
1843
16th to endDay
16%7%36%42444441%
2010
April1st to 15thDay
23%8%46%5%2334433%
1972
16th to endDay
20%8%25%433345%38%
2052
May1st to 15thDay
18%6%35%5%25%446%35%
2301
16th to endDay
17%5%25%6%3446%6%36%
2394
June1st to 15thDay
21%7%36%436%5%5%6%29%
2310
16th to endDay
17%5%36%5%36%5%5%7%33%
2310
July1st to 15thDay
13%425%5%35%5%5%7%40%
2310
16th to endDay
10%5%35%5%45%5%7%9%37%
2458
August1st to 15thDay
13%6%26%5%35%5%5%6%38%
2233
16th to endDay
10%425%435%46%9%41%
2135
September1st to 15thDay
17%5%25%4235%47%41%
1980
16th to endDay
16%5%245%2345%6%44%
1834
October1st to 15thDay
21%6%35%6%34446%32%
1650
16th to endDay
26%10%37%7%2434425%
1669
November1st to 15thDay
17%8%46%6%35%446%32%
1530
16th to endDay
23%13%37%5%34345%25%
1440
December1st to 15thDay
23%13%48%6%45%34418%
1440
16th to endDay
24%15%5%8%6%3434321%
1536
January1st to 15thNight
18%15%7%10%6%35%44419%
2506
16th to endNight
14%16%6%8%7%34346%25%
2641
February1st to 15thNight
14%13%5%11%7%45%445%23%
2285
16th to endNight
17%12%48%6%3444428%
1946
March1st to 15thNight
20%12%5%6%5%2333431%
2090
16th to endNight
16%6%46%5%3434441%
1862
April1st to 15thNight
22%8%25%5%23335%34%
1646
16th to endNight
19%7%25%424346%38%
1587
May1st to 15thNight
20%6%344345%5%6%37%
1320
16th to endNight
16%7%24424446%40%
1367
June1st to 15thNight
20%7%26%5%25%45%7%31%
1320
16th to endNight
17%425%5%35%5%5%6%38%
1320
July1st to 15thNight
10%224435%45%9%46%
1320
16th to endNight
8%425%435%5%6%8%45%
1402
August1st to 15thNight
11%5%35%5%235%6%10%40%
1394
16th to endNight
10%42442335%7%50%
1704
September1st to 15thNight
16%5%25%5%33346%42%
1650
16th to endNight
16%424332246%48%
1792
October1st to 15thNight
19%8%35%42435%6%35%
1980
16th to endNight
26%9%36%5%34346%26%
2203
November1st to 15thNight
21%9%36%6%24345%33%
2325
16th to endNight
22%11%47%6%33335%25%
2520
December1st to 15thNight
23%15%46%6%35%5%4420%
2520
16th to endNight
25%15%5%8%6%3333419%
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
22%15%6%8%6%2443421%
1432
16th to endDay
14%14%5%8%7%35%5%45%24%
1581
February1st to 15thDay
15%13%5%10%7%45%45%5%22%
1575
16th to endDay
18%13%5%6%7%34445%26%
1527
March1st to 15thDay
17%11%48%6%35%44430%
1853
16th to endDay
16%7%45%32333443%
2009
April1st to 15thDay
24%9%35%5%23335%33%
1972
16th to endDay
20%8%25%434345%37%
2052
May1st to 15thDay
18%6%25%5%24346%39%
2301
16th to endDay
16%425%6%2445%6%41%
2394
June1st to 15thDay
23%5%36%5%35%5%47%29%
2310
16th to endDay
17%5%36%5%36%5%5%7%33%
2310
July1st to 15thDay
14%325%425%5%5%8%40%
2310
16th to endDay
11%5%25%6%35%5%7%8%37%
2458
August1st to 15thDay
19%6%25%5%3445%6%35%
2233
16th to endDay
15%425%43446%8%40%
2135
September1st to 15thDay
17%5%25%5%23447%41%
1980
16th to endDay
16%425%41345%6%44%
1834
October1st to 15thDay
21%7%36%5%24446%33%
1650
16th to endDay
26%10%27%7%2434325%
1669
November1st to 15thDay
16%8%35%6%35%446%32%
1530
16th to endDay
23%13%47%433345%25%
1440
December1st to 15thDay
23%14%48%7%44435%17%
1440
16th to endDay
24%15%5%8%5%3433321%
1536
January1st to 15thNight
19%15%6%10%6%45%44419%
2506
16th to endNight
14%15%6%8%6%34346%25%
2641
February1st to 15thNight
14%13%5%12%7%45%445%23%
2278
16th to endNight
17%13%48%6%3444429%
1946
March1st to 15thNight
20%11%45%5%2333433%
2103
16th to endNight
16%7%35%43323344%
1862
April1st to 15thNight
23%9%345%24335%34%
1646
16th to endNight
19%7%24424346%38%
1587
May1st to 15thNight
19%7%134235%45%40%
1320
16th to endNight
17%6%3342345%7%41%
1367
June1st to 15thNight
21%6%35%5%35%447%30%
1320
16th to endNight
16%5%25%5%35%5%5%7%38%
1320
July1st to 15thNight
10%325%4345%5%9%47%
1320
16th to endNight
8%434425%5%6%7%46%
1402
August1st to 15thNight
14%5%245%2346%9%40%
1394
16th to endNight
13%41432335%7%48%
1704
September1st to 15thNight
16%5%35%5%33436%42%
1650
16th to endNight
16%424422345%48%
1792
October1st to 15thNight
19%8%35%5%2335%6%36%
1980
16th to endNight
26%10%36%5%33346%26%
2203
November1st to 15thNight
21%9%35%5%24345%33%
2325
16th to endNight
23%11%48%6%33335%26%
2520
December1st to 15thNight
23%15%47%5%35%44420%
2520
16th to endNight
25%15%5%8%6%2433420%
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
67%38%14%5%
1433
16th to endDay
60%412%12%7%
1581
February1st to 15thDay
62%410%17%3
1577
16th to endDay
59%311%15%9%1
1527
March1st to 15thDay
58%412%15%7%
1853
16th to endDay
45%310%20%13%5%
2010
April1st to 15thDay
53%36%20%12%2
1972
16th to endDay
49%27%19%17%4
2052
May1st to 15thDay
48%48%20%14%2
2301
16th to endDay
47%5%11%21%12%2
2398
June1st to 15thDay
53%5%10%20%9%
2310
16th to endDay
47%5%13%21%10%1
2310
July1st to 15thDay
37%5%14%28%12%
2161
16th to endDay
42%7%16%23%10%
2291
August1st to 15thDay
44%6%15%22%10%
2219
16th to endDay
37%5%16%28%11%
2135
September1st to 15thDay
42%5%13%27%11%
1980
16th to endDay
40%412%32%9%
1834
October1st to 15thDay
51%413%20%8%
1650
16th to endDay
62%411%14%6%
1669
November1st to 15thDay
51%414%20%8%
1530
16th to endDay
61%313%14%5%1
1440
December1st to 15thDay
68%6%11%12%2
1440
16th to endDay
68%5%10%10%5%
1536
January1st to 15thNight
68%49%11%5%
2506
16th to endNight
60%39%17%8%
2641
February1st to 15thNight
63%310%16%5%
2287
16th to endNight
58%310%18%9%
1946
March1st to 15thNight
57%210%19%8%1
2103
16th to endNight
47%39%20%16%3
1862
April1st to 15thNight
53%28%19%15%1
1646
16th to endNight
46%37%19%18%3
1587
May1st to 15thNight
47%37%21%15%5%
1320
16th to endNight
43%411%22%14%2
1369
June1st to 15thNight
51%6%11%19%10%1
1320
16th to endNight
44%5%12%20%16%
1320
July1st to 15thNight
31%5%14%33%14%
1240
16th to endNight
35%6%15%27%15%
1306
August1st to 15thNight
37%7%17%24%13%
1384
16th to endNight
33%317%32%12%
1704
September1st to 15thNight
43%311%29%11%
1650
16th to endNight
38%311%34%10%
1792
October1st to 15thNight
48%410%23%12%
1980
16th to endNight
59%412%17%6%
2203
November1st to 15thNight
53%313%17%10%1
2325
16th to endNight
62%311%16%4
2520
December1st to 15thNight
66%5%11%13%3
2520
16th to endNight
68%48%12%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
33%16%18%26%5%
60
16th to endDay
35%15%28%16%4
71
February1st to 15thDay
36%18%32%12%
90
16th to endDay
32%17%24%20%4
186
March1st to 15thDay
25%13%32%23%5%
269
16th to endDay
20%16%24%20%12%3
224
April1st to 15thDay
26%18%26%20%8%1
210
16th to endDay
20%14%25%20%13%5%
210
May1st to 15thDay
22%10%29%23%8%5%
228
16th to endDay
16%12%34%20%13%1
267
June1st to 15thDay
29%6%29%20%11%3
255
16th to endDay
17%431%27%16%2
255
July1st to 15thDay
15%328%29%18%5%
245
16th to endDay
10%329%32%17%6%
270
August1st to 15thDay
14%7%23%28%19%6%
253
16th to endDay
12%127%29%17%11%
268
September1st to 15thDay
20%421%20%21%12%
255
16th to endDay
17%5%31%19%15%10%
254
October1st to 15thDay
23%10%23%25%14%3
255
16th to endDay
34%13%25%19%7%
255
November1st to 15thDay
19%11%30%23%13%2
184
16th to endDay
31%13%26%25%3
60
December1st to 15thDay
21%20%40%13%5%
60
16th to endDay
40%18%34%6%
64
January1st to 15thNight
25%16%31%20%5%
720
16th to endNight
23%11%34%24%5%
768
February1st to 15thNight
22%13%36%22%4
704
16th to endNight
25%13%32%23%5%
631
March1st to 15thNight
27%12%34%23%2
720
16th to endNight
20%16%25%26%10%
704
April1st to 15thNight
26%12%30%25%4
658
16th to endNight
23%11%28%26%8%
597
May1st to 15thNight
24%6%29%27%10%1
330
16th to endNight
18%5%32%29%13%
343
June1st to 15thNight
23%7%24%36%8%
330
16th to endNight
18%429%31%14%
330
July1st to 15thNight
10%326%43%15%
310
16th to endNight
8%228%41%17%1
348
August1st to 15thNight
15%221%38%20%1
403
16th to endNight
11%325%34%22%1
654
September1st to 15thNight
20%5%22%31%18%1
660
16th to endNight
18%7%23%26%21%1
657
October1st to 15thNight
24%8%26%27%12%1
660
16th to endNight
31%11%24%24%7%
704
November1st to 15thNight
27%10%30%20%11%
700
16th to endNight
29%15%25%20%8%
720
December1st to 15thNight
31%13%29%20%4
720
16th to endNight
34%11%30%18%41
768
Page generated at 2017-03-16 11:05:28. Version ac04

Copyright 2017 A. Danko


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