Highland
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Highland clear sky chart from 2005-11-05 to 2018-01-12.

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
60%
16271
22%
48608
19%
16235
63%
16235
33%
29129

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
53%
760
12%
2471
13%
760
54%
760
19%
1732
January16th to endNight
54%
768
14%
2496
16%
768
55%
768
20%
1740
February1st to 15thNight
54%
698
13%
2288
15%
698
55%
698
23%
1516
February16th to endNight
49%
632
19%
1908
18%
632
53%
632
25%
1249
March1st to 15thNight
58%
720
19%
2014
17%
720
60%
720
31%
1292
March16th to endNight
54%
768
19%
2112
15%
768
56%
768
31%
1357
April1st to 15thNight
48%
647
17%
1873
14%
647
51%
647
29%
1187
April16th to endNight
54%
540
24%
1620
17%
540
58%
540
33%
957
May1st to 15thNight
60%
539
23%
1619
19%
539
62%
539
37%
901
May16th to endNight
60%
561
19%
1685
17%
561
62%
561
35%
968
June1st to 15thNight
66%
540
22%
1558
21%
540
69%
540
44%
812
June16th to endNight
73%
540
29%
1598
27%
540
78%
540
63%
704
July1st to 15thNight
69%
510
17%
1530
17%
510
71%
510
40%
840
July16th to endNight
77%
564
23%
1593
22%
531
77%
531
43%
859
August1st to 15thNight
72%
539
26%
1611
21%
536
75%
536
45%
828
August16th to endNight
80%
573
37%
1734
33%
573
81%
573
49%
867
September1st to 15thNight
75%
684
29%
1944
23%
684
79%
684
49%
1011
September16th to endNight
74%
716
36%
1980
30%
716
77%
716
51%
1035
October1st to 15thNight
64%
720
28%
2097
21%
720
68%
720
43%
1146
October16th to endNight
66%
768
32%
2304
28%
768
70%
768
41%
1262
November1st to 15thNight
59%
760
24%
2467
23%
760
62%
760
32%
1422
November16th to endNight
57%
842
23%
2597
21%
842
59%
842
32%
1529
December1st to 15thNight
52%
975
13%
2730
11%
975
53%
975
27%
1841
December16th to endNight
44%
907
12%
2779
11%
907
46%
907
16%
2074

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
7%6%25%42445%7%48%
48681
Night
8%6%2442445%6%48%
48803
TransparencyDay
34%411%19%18%11%
48376
Night
34%412%20%17%9%
48609
SeeingDay
12%5%22%34%20%4
5719
Night
12%316%36%26%4
16284

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
13%9%37%6%35%5%5%6%33%
1710
16th to endDay
12%12%47%4245%5%5%35%
1728
February1st to 15thDay
11%10%47%5%45%45%5%34%
1575
16th to endDay
10%13%45%6%35%46%8%32%
1565
March1st to 15thDay
6%8%45%5%26%7%6%6%40%
1945
16th to endDay
10%11%36%5%246%5%7%35%
2112
April1st to 15thDay
9%7%27%5%25%5%6%6%40%
2071
16th to endDay
7%7%35%5%3446%8%44%
2340
May1st to 15thDay
7%434435%5%6%8%46%
2331
16th to endDay
8%426%5%35%6%7%7%43%
2429
June1st to 15thDay
442442445%7%54%
2381
16th to endDay
32221223474%
2342
July1st to 15thDay
23134245%6%8%57%
2340
16th to endDay
33244345%6%7%54%
2467
August1st to 15thDay
3313325%5%6%8%55%
2340
16th to endDay
3313324447%60%
2468
September1st to 15thDay
43231446%6%62%
2013
16th to endDay
6%22313346%64%
1980
October1st to 15thDay
8%4144335%5%6%52%
1861
16th to endDay
7%5%143235%47%53%
1920
November1st to 15thDay
12%5%345%33445%47%
1719
16th to endDay
10%7%36%5%45%445%42%
1677
December1st to 15thDay
14%9%36%4345%5%7%34%
1560
16th to endDay
16%13%48%5%25%46%6%25%
1807
January1st to 15thNight
12%10%35%4345%6%7%35%
2471
16th to endNight
11%11%36%5%25%45%6%36%
2496
February1st to 15thNight
9%9%26%6%346%5%7%38%
2277
16th to endNight
9%10%35%5%35%5%5%7%38%
1908
March1st to 15thNight
7%7%45%445%5%5%7%42%
2014
16th to endNight
8%7%35%435%6%6%8%40%
2112
April1st to 15thNight
11%9%35%324446%44%
1873
16th to endNight
8%5%245%25%5%5%5%46%
1620
May1st to 15thNight
6%423435%5%47%51%
1619
16th to endNight
9%415%42345%7%49%
1684
June1st to 15thNight
6%313324446%58%
1558
16th to endNight
222212346%71%
1598
July1st to 15thNight
4325%44445%7%53%
1620
16th to endNight
3414425%5%7%7%53%
1701
August1st to 15thNight
32135%245%6%7%56%
1620
16th to endNight
22134235%6%6%59%
1734
September1st to 15thNight
4213324447%61%
1944
16th to endNight
7%313312325%66%
1980
October1st to 15thNight
7%413324446%57%
2097
16th to endNight
6%5%24324436%57%
2304
November1st to 15thNight
10%5%2432335%6%51%
2467
16th to endNight
9%6%25%4145%5%7%47%
2597
December1st to 15thNight
13%7%35%42445%6%42%
2730
16th to endNight
18%11%36%5%34445%30%
2779

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
49%10%18%16%4
1711
16th to endDay
50%8%14%15%8%1
1728
February1st to 15thDay
50%9%13%16%9%
1575
16th to endDay
47%5%18%19%8%
1565
March1st to 15thDay
38%7%19%20%12%1
1945
16th to endDay
45%416%19%8%4
2112
April1st to 15thDay
42%5%13%20%15%3
2071
16th to endDay
36%312%24%18%3
2340
May1st to 15thDay
32%310%24%21%6%
2331
16th to endDay
35%411%21%21%4
2432
June1st to 15thDay
27%28%18%30%12%
2381
16th to endDay
15%1310%27%42%
2342
July1st to 15thDay
23%37%13%21%30%
2201
16th to endDay
25%38%11%21%29%
2312
August1st to 15thDay
24%37%17%19%27%
2325
16th to endDay
21%35%18%29%21%
2468
September1st to 15thDay
20%47%16%27%23%
2013
16th to endDay
20%27%23%29%16%
1980
October1st to 15thDay
31%410%24%23%5%
1861
16th to endDay
27%5%12%29%21%2
1920
November1st to 15thDay
39%5%12%22%16%3
1719
16th to endDay
42%5%14%24%11%1
1677
December1st to 15thDay
49%8%17%18%6%
1560
16th to endDay
57%6%14%15%4
1807
January1st to 15thNight
46%9%18%18%5%1
2471
16th to endNight
46%9%16%16%9%1
2496
February1st to 15thNight
44%6%17%20%10%
2288
16th to endNight
42%5%14%25%10%
1908
March1st to 15thNight
38%5%16%25%12%1
2014
16th to endNight
37%6%16%23%13%3
2112
April1st to 15thNight
40%313%20%17%4
1873
16th to endNight
35%313%23%21%2
1620
May1st to 15thNight
30%411%25%22%6%
1620
16th to endNight
33%311%27%19%4
1685
June1st to 15thNight
24%28%19%30%13%
1558
16th to endNight
14%1410%28%40%
1598
July1st to 15thNight
29%37%12%16%31%
1530
16th to endNight
27%39%13%18%28%
1593
August1st to 15thNight
23%310%18%16%26%
1611
16th to endNight
21%37%13%30%23%
1734
September1st to 15thNight
22%37%15%25%24%
1944
16th to endNight
22%26%18%29%21%
1980
October1st to 15thNight
27%310%25%24%8%
2097
16th to endNight
28%39%26%28%4
2304
November1st to 15thNight
33%411%25%18%5%
2467
16th to endNight
35%316%27%14%2
2597
December1st to 15thNight
42%6%19%22%8%
2730
16th to endNight
56%5%15%16%5%
2779

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
34%48%27%18%6%
123
16th to endDay
21%215%31%23%5%
96
February1st to 15thDay
18%5%14%28%25%6%
90
16th to endDay
15%436%30%10%3
224
March1st to 15thDay
13%6%29%32%16%2
270
16th to endDay
21%7%33%23%12%
288
April1st to 15thDay
14%13%28%23%14%5%
269
16th to endDay
17%15%28%24%12%1
270
May1st to 15thDay
10%11%30%29%14%3
288
16th to endDay
10%6%23%29%24%5%
330
June1st to 15thDay
10%7%20%35%22%4
356
16th to endDay
3324%38%23%5%
317
July1st to 15thDay
3416%39%28%7%
305
16th to endDay
417%51%21%3
327
August1st to 15thDay
7%122%42%20%5%
315
16th to endDay
6%215%41%26%7%
332
September1st to 15thDay
7%222%35%23%7%
315
16th to endDay
10%416%35%26%6%
315
October1st to 15thDay
10%8%27%27%20%6%
196
16th to endDay
14%419%34%19%7%
144
November1st to 15thDay
16%321%30%18%9%
135
16th to endDay
20%5%19%32%19%2
135
December1st to 15thDay
17%123%33%17%5%
135
16th to endDay
20%217%40%18%
144
January1st to 15thNight
18%216%34%22%4
764
16th to endNight
16%415%32%23%6%
768
February1st to 15thNight
16%215%41%20%2
704
16th to endNight
14%325%37%17%2
632
March1st to 15thNight
13%418%41%18%3
720
16th to endNight
12%5%22%38%17%2
768
April1st to 15thNight
18%6%21%34%17%2
647
16th to endNight
12%5%22%36%21%2
540
May1st to 15thNight
9%321%40%23%1
540
16th to endNight
12%414%34%30%4
563
June1st to 15thNight
8%5%15%42%26%1
540
16th to endNight
5%16%40%34%3
540
July1st to 15thNight
7%110%29%43%6%
510
16th to endNight
7%6%34%47%3
564
August1st to 15thNight
5%11%43%36%1
539
16th to endNight
47%38%45%4
573
September1st to 15thNight
5%11%37%37%6%
684
16th to endNight
8%211%28%38%10%
716
October1st to 15thNight
10%120%33%28%6%
720
16th to endNight
10%314%36%29%5%
768
November1st to 15thNight
13%318%34%25%4
760
16th to endNight
13%319%38%20%5%
842
December1st to 15thNight
18%319%39%16%2
975
16th to endNight
21%6%17%37%15%1
907
Page generated at 2018-01-12 20:01:26. Version ac04

Copyright 2018 A. Danko


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