Highlands Wilderness Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Highlands Wilderness Observatory clear sky chart from 2005-11-05 to 2018-04-23.

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
29%
15578
14%
49431
8%
15546
35%
15546
16%
35222

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
12%
779
7%
2716
3%
776
17%
776
6%
2205
January16th to endNight
18%
832
10%
2737
6%
832
24%
832
10%
2157
February1st to 15thNight
14%
761
11%
2482
3%
761
23%
761
9%
1962
February16th to endNight
19%
683
13%
2191
3%
683
30%
683
12%
1630
March1st to 15thNight
18%
780
13%
2161
5%
780
25%
780
14%
1619
March16th to endNight
28%
832
21%
2285
10%
832
37%
832
23%
1531
April1st to 15thNight
22%
778
15%
1946
6%
778
27%
778
18%
1479
April16th to endNight
29%
599
20%
1713
9%
599
37%
599
23%
1162
May1st to 15thNight
36%
432
17%
1512
12%
432
45%
432
20%
976
May16th to endNight
39%
375
15%
1497
11%
374
51%
374
22%
872
June1st to 15thNight
38%
360
10%
1440
9%
360
48%
360
18%
896
June16th to endNight
45%
360
11%
1323
12%
360
50%
360
22%
831
July1st to 15thNight
53%
340
15%
1327
20%
340
58%
340
31%
704
July16th to endNight
54%
415
16%
1454
16%
390
60%
390
29%
826
August1st to 15thNight
58%
539
15%
1609
11%
536
61%
536
33%
957
August16th to endNight
53%
636
19%
1782
10%
636
58%
636
35%
1082
September1st to 15thNight
45%
720
17%
1800
8%
720
49%
720
32%
1196
September16th to endNight
49%
717
23%
1999
16%
717
54%
717
30%
1286
October1st to 15thNight
35%
720
15%
2160
11%
720
41%
720
19%
1528
October16th to endNight
19%
768
13%
2304
5%
768
28%
768
12%
1769
November1st to 15thNight
28%
760
16%
2621
13%
760
36%
760
16%
1827
November16th to endNight
20%
780
10%
2730
5%
780
26%
780
10%
2094
December1st to 15thNight
12%
780
6%
2730
2%
780
16%
780
6%
2245
December16th to endNight
11%
832
9%
2912
3%
832
18%
832
7%
2388

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%10%47%5%34446%30%
50074
Night
17%10%47%5%34446%31%
49605
Cloud CoverDay
17%10%47%5%34446%30%
50084
Night
16%10%47%5%34446%31%
49610
TransparencyDay
53%410%19%10%1
49766
Night
53%411%19%10%
49431
SeeingDay
23%12%28%20%9%4
6154
Night
23%11%28%23%10%1
15582

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
20%15%7%9%6%3434420%
1552
16th to endDay
13%17%9%12%7%3343419%
1836
February1st to 15thDay
14%15%6%14%9%3433320%
1710
16th to endDay
16%16%6%9%6%4434422%
1567
March1st to 15thDay
15%15%5%6%6%45%445%26%
2118
16th to endDay
14%10%35%5%34445%37%
2291
April1st to 15thDay
23%11%45%43434430%
2332
16th to endDay
21%8%3442334439%
2371
May1st to 15thDay
19%7%37%5%35%446%32%
2437
16th to endDay
15%5%25%445%45%8%36%
2618
June1st to 15thDay
21%6%36%5%34448%29%
2520
16th to endDay
17%6%35%5%35%5%6%8%32%
2628
July1st to 15thDay
13%5%245%35%5%5%9%37%
2547
16th to endDay
11%6%36%6%46%6%5%8%34%
2612
August1st to 15thDay
13%6%26%6%35%5%6%7%35%
2340
16th to endDay
13%5%26%5%35%5%6%8%37%
2407
September1st to 15thDay
18%6%25%433447%39%
2160
16th to endDay
16%6%34434336%41%
1959
October1st to 15thDay
24%8%27%5%34446%29%
1800
16th to endDay
30%11%26%5%33445%22%
1920
November1st to 15thDay
19%10%36%6%44345%30%
1565
16th to endDay
24%15%5%8%5%3344418%
1560
December1st to 15thDay
18%23%7%9%5%2344415%
1560
16th to endDay
20%19%8%9%5%3433318%
1664
January1st to 15thNight
20%17%6%9%7%3433418%
2716
16th to endNight
14%15%7%11%7%34345%21%
2737
February1st to 15thNight
12%14%7%12%7%45%5%45%20%
2480
16th to endNight
16%13%5%8%6%35%445%26%
2191
March1st to 15thNight
17%13%46%6%3344430%
2149
16th to endNight
14%8%46%5%23345%41%
2285
April1st to 15thNight
21%11%36%434345%31%
1946
16th to endNight
17%8%25%423446%38%
1713
May1st to 15thNight
18%5%25%5%25%446%37%
1512
16th to endNight
12%4345%35%46%7%42%
1495
June1st to 15thNight
16%7%14435%46%7%36%
1440
16th to endNight
13%5%25%445%46%8%39%
1323
July1st to 15thNight
8%41443446%7%49%
1407
16th to endNight
10%5%13425%45%8%46%
1553
August1st to 15thNight
9%424435%47%8%45%
1620
16th to endNight
9%5%145%25%45%7%49%
1782
September1st to 15thNight
15%5%25%5%1345%6%44%
1800
16th to endNight
15%5%245%33345%46%
1999
October1st to 15thNight
19%8%36%5%2335%6%33%
2160
16th to endNight
25%11%47%5%23345%25%
2304
November1st to 15thNight
20%8%35%5%34446%32%
2621
16th to endNight
23%12%46%6%35%446%22%
2730
December1st to 15thNight
21%20%6%9%6%24345%15%
2730
16th to endNight
21%18%7%10%5%3333416%
2912

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
19%15%6%9%6%34345%20%
1552
16th to endDay
14%17%9%12%7%3343419%
1836
February1st to 15thDay
14%15%7%13%9%3433320%
1710
16th to endDay
16%16%6%9%6%4434422%
1567
March1st to 15thDay
16%14%5%8%5%45%445%26%
2129
16th to endDay
15%10%35%5%25%345%37%
2290
April1st to 15thDay
23%11%35%42444430%
2332
16th to endDay
21%8%34423345%39%
2371
May1st to 15thDay
19%8%36%5%34446%32%
2437
16th to endDay
15%6%25%5%35%45%8%37%
2618
June1st to 15thDay
21%6%36%5%3445%8%29%
2520
16th to endDay
16%6%35%5%35%5%6%9%32%
2628
July1st to 15thDay
12%5%25%5%35%5%6%9%37%
2547
16th to endDay
11%6%35%7%46%6%5%8%34%
2612
August1st to 15thDay
12%6%36%6%35%5%6%7%35%
2340
16th to endDay
12%6%26%435%5%6%9%36%
2407
September1st to 15thDay
17%5%35%5%23447%39%
2160
16th to endDay
15%7%25%434337%41%
1959
October1st to 15thDay
23%8%36%6%33445%30%
1800
16th to endDay
29%11%36%5%34445%22%
1920
November1st to 15thDay
19%10%26%7%34445%30%
1565
16th to endDay
23%16%5%8%6%3445%5%18%
1560
December1st to 15thDay
19%22%7%10%5%2343415%
1560
16th to endDay
20%19%8%9%6%2433317%
1664
January1st to 15thNight
20%17%6%9%8%4333418%
2716
16th to endNight
14%14%7%11%7%34345%21%
2737
February1st to 15thNight
12%14%6%11%7%45%5%45%20%
2473
16th to endNight
16%13%48%7%35%45%5%26%
2191
March1st to 15thNight
17%12%5%6%6%33435%30%
2161
16th to endNight
14%7%46%5%23345%41%
2285
April1st to 15thNight
21%11%46%434345%30%
1946
16th to endNight
16%8%26%423446%39%
1713
May1st to 15thNight
17%6%35%5%25%346%38%
1512
16th to endNight
11%5%34445%5%5%7%42%
1495
June1st to 15thNight
16%7%24435%46%7%36%
1440
16th to endNight
12%5%25%5%35%46%8%40%
1323
July1st to 15thNight
8%4235%3446%6%49%
1407
16th to endNight
10%423336%46%8%46%
1553
August1st to 15thNight
8%4245%25%46%9%45%
1620
16th to endNight
8%424435%5%5%7%49%
1782
September1st to 15thNight
15%5%26%42345%7%43%
1800
16th to endNight
15%5%24423445%46%
1999
October1st to 15thNight
18%9%26%5%33446%33%
2160
16th to endNight
25%11%37%5%33445%25%
2304
November1st to 15thNight
20%8%35%5%3445%6%32%
2621
16th to endNight
23%12%46%6%45%45%5%22%
2730
December1st to 15thNight
21%19%6%9%5%24445%15%
2730
16th to endNight
21%17%7%10%5%33345%16%
2912

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
66%49%11%6%
1553
16th to endDay
68%37%9%8%1
1836
February1st to 15thDay
70%37%14%4
1712
16th to endDay
64%29%11%10%
1567
March1st to 15thDay
59%311%15%7%1
2129
16th to endDay
48%47%20%15%3
2291
April1st to 15thDay
57%37%17%12%1
2332
16th to endDay
47%37%23%15%2
2371
May1st to 15thDay
52%39%19%13%1
2437
16th to endDay
44%6%11%21%14%1
2622
June1st to 15thDay
52%49%22%10%
2520
16th to endDay
47%5%13%20%11%
2628
July1st to 15thDay
39%5%12%28%13%1
2398
16th to endDay
45%6%12%24%9%
2448
August1st to 15thDay
46%6%13%21%11%1
2327
16th to endDay
42%6%11%28%10%
2407
September1st to 15thDay
45%412%26%10%
2160
16th to endDay
44%411%29%9%
1959
October1st to 15thDay
55%49%20%9%
1800
16th to endDay
63%411%13%6%
1920
November1st to 15thDay
54%5%12%17%8%1
1565
16th to endDay
66%5%10%10%41
1560
December1st to 15thDay
72%49%10%3
1560
16th to endDay
71%36%12%5%
1664
January1st to 15thNight
70%37%10%5%1
2716
16th to endNight
65%48%13%7%
2737
February1st to 15thNight
65%48%15%5%
2482
16th to endNight
58%410%18%8%
2191
March1st to 15thNight
56%410%17%9%1
2161
16th to endNight
45%29%23%16%2
2285
April1st to 15thNight
56%36%19%12%1
1946
16th to endNight
45%48%19%19%1
1713
May1st to 15thNight
46%310%19%15%3
1512
16th to endNight
39%5%12%25%15%1
1497
June1st to 15thNight
44%5%11%22%15%
1440
16th to endNight
41%6%13%23%14%
1323
July1st to 15thNight
30%5%11%30%21%
1327
16th to endNight
35%413%30%15%
1454
August1st to 15thNight
32%6%20%26%13%
1609
16th to endNight
33%5%16%29%14%
1782
September1st to 15thNight
39%416%26%11%1
1800
16th to endNight
39%411%33%11%
1999
October1st to 15thNight
51%410%20%12%
2160
16th to endNight
61%411%15%7%
2304
November1st to 15thNight
51%5%13%19%8%
2621
16th to endNight
62%5%13%13%4
2730
December1st to 15thNight
71%49%10%3
2730
16th to endNight
70%38%10%6%
2912

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
27%20%36%10%5%
90
16th to endDay
33%14%37%11%2
136
February1st to 15thDay
31%26%36%5%
135
16th to endDay
36%16%34%11%
148
March1st to 15thDay
28%15%30%21%3
330
16th to endDay
24%16%32%18%6%1
352
April1st to 15thDay
30%18%24%17%6%1
330
16th to endDay
26%13%28%15%12%3
289
May1st to 15thDay
32%8%22%21%8%6%
288
16th to endDay
19%13%33%18%10%3
331
June1st to 15thDay
26%9%30%24%6%2
315
16th to endDay
19%9%32%25%10%2
423
July1st to 15thDay
13%7%30%25%13%8%
332
16th to endDay
9%9%31%28%15%7%
326
August1st to 15thDay
15%427%26%15%10%
313
16th to endDay
17%8%21%26%15%11%
332
September1st to 15thDay
15%7%24%23%16%11%
315
16th to endDay
17%9%20%22%19%10%
314
October1st to 15thDay
24%12%27%19%12%3
315
16th to endDay
36%15%25%18%4
336
November1st to 15thDay
25%15%28%25%31
128
16th to endDay
38%11%40%8%1
90
December1st to 15thDay
33%21%26%14%4
90
16th to endDay
37%25%29%6%2
96
January1st to 15thNight
31%17%30%14%5%
780
16th to endNight
23%14%32%22%6%1
832
February1st to 15thNight
22%19%35%18%3
764
16th to endNight
25%16%32%19%5%
683
March1st to 15thNight
27%17%31%20%3
780
16th to endNight
21%12%32%22%10%
832
April1st to 15thNight
29%13%30%20%5%
778
16th to endNight
23%12%31%21%10%1
599
May1st to 15thNight
22%428%26%15%2
432
16th to endNight
15%333%34%12%
375
June1st to 15thNight
20%8%25%35%10%
360
16th to endNight
15%5%26%38%13%
360
July1st to 15thNight
8%326%39%21%
340
16th to endNight
11%325%39%21%
415
August1st to 15thNight
10%317%37%25%4
539
16th to endNight
11%424%29%26%2
636
September1st to 15thNight
17%5%26%26%19%5%
720
16th to endNight
18%5%19%30%21%4
717
October1st to 15thNight
24%10%25%25%13%1
720
16th to endNight
31%13%27%21%5%
768
November1st to 15thNight
26%10%28%22%9%1
760
16th to endNight
31%11%29%19%6%
780
December1st to 15thNight
33%19%29%14%3
780
16th to endNight
32%14%33%17%2
832
Page generated at 2018-04-24 10:03:02. Version ac04

Copyright 2018 A. Danko


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