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 2017-10-31.

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
30%
14837
14%
47376
9%
14806
37%
14806
17%
33486

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%
768
21%
2031
10%
768
40%
768
22%
1406
April1st to 15thNight
26%
718
16%
1796
6%
718
31%
718
21%
1311
April16th to endNight
31%
651
18%
1731
8%
651
37%
651
23%
1207
May1st to 15thNight
33%
360
17%
1440
13%
360
44%
360
17%
939
May16th to endNight
35%
375
14%
1497
10%
374
47%
374
19%
935
June1st to 15thNight
36%
360
9%
1440
9%
360
45%
360
16%
971
June16th to endNight
40%
360
9%
1440
12%
360
46%
360
19%
916
July1st to 15thNight
53%
340
15%
1360
21%
340
59%
340
28%
744
July16th to endNight
55%
376
14%
1418
17%
354
60%
354
27%
805
August1st to 15thNight
51%
440
15%
1511
13%
438
56%
438
25%
924
August16th to endNight
51%
714
20%
1860
10%
714
56%
714
39%
1137
September1st to 15thNight
47%
720
16%
1800
8%
720
50%
720
31%
1226
September16th to endNight
49%
717
24%
1955
16%
717
53%
717
33%
1229
October1st to 15thNight
36%
720
18%
2160
11%
720
45%
720
22%
1471
October16th to endNight
24%
768
13%
2401
7%
768
33%
768
14%
1796
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%3445%6%33%
48381
Night
18%9%36%5%34446%33%
47545
Cloud CoverDay
18%8%36%5%34446%33%
48390
Night
18%9%36%5%34445%33%
47551
TransparencyDay
51%412%20%9%1
48068
Night
52%411%20%10%1
47376
SeeingDay
22%10%27%22%12%4
5653
Night
23%10%28%26%10%
14838

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%
1845
16th to endDay
17%7%36%42444441%
2193
April1st to 15thDay
24%8%36%423345%33%
2152
16th to endDay
20%8%25%423445%37%
2239
May1st to 15thDay
20%7%35%5%25%45%6%33%
2511
16th to endDay
18%5%26%5%3445%6%35%
2618
June1st to 15thDay
21%7%36%436%5%5%6%30%
2520
16th to endDay
18%5%36%5%36%6%5%7%32%
2520
July1st to 15thDay
14%425%5%35%5%5%7%40%
2520
16th to endDay
11%5%35%5%45%5%7%9%37%
2654
August1st to 15thDay
13%6%26%5%45%6%5%6%38%
2436
16th to endDay
11%425%435%46%8%42%
2330
September1st to 15thDay
17%425%423447%42%
2160
16th to endDay
14%4245%23446%46%
2001
October1st to 15thDay
21%6%35%6%34446%33%
1800
16th to endDay
25%9%37%7%24345%26%
1821
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
17%6%45%5%2334341%
2031
April1st to 15thNight
23%8%25%5%23335%35%
1796
16th to endNight
19%7%25%424346%37%
1731
May1st to 15thNight
22%7%34424446%35%
1440
16th to endNight
17%7%244245%5%6%39%
1495
June1st to 15thNight
19%6%26%5%25%45%8%31%
1440
16th to endNight
18%425%5%35%5%5%6%37%
1440
July1st to 15thNight
10%324435%45%9%46%
1440
16th to endNight
9%425%435%5%6%8%46%
1514
August1st to 15thNight
10%5%35%5%235%6%10%40%
1521
16th to endNight
10%42443345%7%50%
1860
September1st to 15thNight
15%5%25%5%34346%43%
1800
16th to endNight
16%424332246%48%
1955
October1st to 15thNight
18%8%35%42335%6%37%
2160
16th to endNight
25%9%36%5%34346%27%
2401
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%
1855
16th to endDay
16%7%44323335%43%
2192
April1st to 15thDay
24%9%35%5%13335%33%
2152
16th to endDay
20%8%25%433345%37%
2239
May1st to 15thDay
20%7%25%5%24346%37%
2511
16th to endDay
17%5%25%5%2445%6%39%
2618
June1st to 15thDay
22%6%35%5%35%5%47%30%
2520
16th to endDay
18%5%36%5%36%5%5%7%32%
2520
July1st to 15thDay
14%425%435%5%5%8%39%
2520
16th to endDay
12%5%25%5%35%5%7%8%37%
2654
August1st to 15thDay
18%6%25%5%35%5%5%7%35%
2436
16th to endDay
15%425%43445%8%40%
2330
September1st to 15thDay
17%5%25%5%23447%42%
2160
16th to endDay
15%425%413446%46%
2001
October1st to 15thDay
21%7%36%6%24446%33%
1800
16th to endDay
25%10%27%7%2434426%
1821
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
17%7%35%43323344%
2031
April1st to 15thNight
23%8%34424335%35%
1796
16th to endNight
19%7%25%434346%37%
1731
May1st to 15thNight
21%8%244235%45%38%
1440
16th to endNight
17%6%3342345%7%40%
1495
June1st to 15thNight
20%6%35%5%35%45%8%31%
1440
16th to endNight
17%5%25%5%35%5%6%7%36%
1440
July1st to 15thNight
10%3244345%5%9%46%
1440
16th to endNight
9%434425%5%6%7%46%
1514
August1st to 15thNight
13%6%25%5%2346%9%40%
1521
16th to endNight
13%415%32435%7%48%
1860
September1st to 15thNight
16%5%35%5%33446%43%
1800
16th to endNight
16%424422345%49%
1955
October1st to 15thNight
18%8%35%5%2335%6%37%
2160
16th to endNight
25%10%36%5%23446%26%
2401
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
59%412%15%7%
1855
16th to endDay
45%49%20%14%5%
2193
April1st to 15thDay
53%36%21%12%2
2152
16th to endDay
49%37%20%15%3
2239
May1st to 15thDay
50%48%20%13%2
2511
16th to endDay
47%5%11%20%11%1
2622
June1st to 15thDay
53%5%10%21%9%
2520
16th to endDay
48%6%13%20%10%
2520
July1st to 15thDay
38%5%14%27%12%
2371
16th to endDay
42%7%16%23%10%
2487
August1st to 15thDay
44%6%15%22%10%
2422
16th to endDay
37%5%15%29%11%
2330
September1st to 15thDay
41%5%12%28%11%
2160
16th to endDay
38%5%12%33%10%
2001
October1st to 15thDay
51%413%21%8%
1800
16th to endDay
60%412%14%6%
1821
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%38%19%16%4
2031
April1st to 15thNight
52%28%20%15%1
1796
16th to endNight
47%47%19%17%3
1731
May1st to 15thNight
50%36%20%14%4
1440
16th to endNight
44%5%12%22%13%2
1497
June1st to 15thNight
49%5%11%20%10%1
1440
16th to endNight
45%5%12%20%15%
1440
July1st to 15thNight
32%5%13%31%14%1
1360
16th to endNight
35%6%14%27%15%
1418
August1st to 15thNight
37%7%18%23%12%
1511
16th to endNight
32%317%33%11%
1860
September1st to 15thNight
42%311%29%11%
1800
16th to endNight
36%311%35%11%
1955
October1st to 15thNight
46%410%25%12%
2160
16th to endNight
58%413%18%5%
2401
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%22%5%
270
16th to endDay
22%15%27%20%10%2
288
April1st to 15thDay
29%17%26%17%7%1
270
16th to endDay
25%16%24%17%11%4
270
May1st to 15thDay
27%11%27%21%7%4
288
16th to endDay
19%13%33%19%12%1
331
June1st to 15thDay
27%6%32%21%9%2
315
16th to endDay
20%7%30%25%13%2
315
July1st to 15thDay
16%329%28%16%5%
305
16th to endDay
12%327%31%17%6%
326
August1st to 15thDay
13%7%25%28%19%6%
313
16th to endDay
12%326%28%16%12%
332
September1st to 15thDay
21%422%20%19%12%
315
16th to endDay
15%6%27%18%21%11%
314
October1st to 15thDay
23%10%23%25%12%4
315
16th to endDay
31%14%26%20%7%
311
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%15%25%26%9%
768
April1st to 15thNight
27%12%29%25%5%
718
16th to endNight
24%12%28%25%8%
651
May1st to 15thNight
26%6%27%27%9%1
360
16th to endNight
18%5%33%28%13%
375
June1st to 15thNight
22%6%25%35%9%
360
16th to endNight
19%430%31%13%
360
July1st to 15thNight
10%327%43%14%
340
16th to endNight
9%126%42%17%1
376
August1st to 15thNight
15%220%37%21%1
440
16th to endNight
11%425%33%23%2
714
September1st to 15thNight
19%5%22%32%18%1
720
16th to endNight
17%7%22%25%24%2
717
October1st to 15thNight
23%7%26%26%13%1
720
16th to endNight
30%12%24%24%7%
768
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 2017-11-01 17:23:28. Version ac04

Copyright 2017 A. Danko


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