Harrington Lodge Silver Star Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Harrington Lodge Silver Star Observatory clear sky chart from 2005-11-05 to 2017-09-22.

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
43%
14864
10%
46630
8%
14837
45%
14837
17%
33613

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
24%
758
4%
2593
4%
755
26%
755
7%
2177
January16th to endNight
30%
768
4%
2688
3%
768
32%
768
8%
2205
February1st to 15thNight
35%
698
6%
2405
6%
698
37%
698
10%
1897
February16th to endNight
44%
632
11%
1959
10%
632
46%
632
17%
1424
March1st to 15thNight
33%
720
6%
2160
4%
720
34%
720
13%
1699
March16th to endNight
36%
768
11%
2007
4%
768
39%
768
18%
1515
April1st to 15thNight
42%
719
8%
1799
4%
719
44%
719
19%
1373
April16th to endNight
43%
492
13%
1572
11%
492
46%
492
18%
1109
May1st to 15thNight
51%
359
12%
1440
19%
359
53%
359
19%
912
May16th to endNight
53%
374
9%
1427
9%
374
54%
374
18%
920
June1st to 15thNight
47%
360
3%
1179
0%
360
47%
360
21%
799
June16th to endNight
50%
360
4%
1080
0%
360
50%
360
23%
719
July1st to 15thNight
66%
340
7%
1131
2%
340
67%
340
38%
595
July16th to endNight
74%
376
13%
1416
20%
354
77%
354
39%
651
August1st to 15thNight
78%
360
22%
1432
33%
358
80%
358
40%
661
August16th to endNight
72%
611
26%
1757
22%
611
74%
611
45%
933
September1st to 15thNight
70%
720
22%
1800
13%
720
71%
720
46%
1063
September16th to endNight
58%
683
21%
1854
15%
683
60%
683
30%
1195
October1st to 15thNight
54%
660
13%
1975
14%
660
55%
660
25%
1307
October16th to endNight
40%
704
10%
2280
8%
704
43%
704
17%
1644
November1st to 15thNight
32%
700
9%
2386
9%
700
34%
700
10%
1877
November16th to endNight
29%
829
5%
2629
3%
829
32%
829
9%
2183
December1st to 15thNight
32%
900
5%
2700
4%
900
33%
900
10%
2239
December16th to endNight
27%
973
4%
2961
2%
973
28%
973
8%
2516

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
14%9%37%6%35%5%5%6%31%
48263
Night
14%11%47%6%3445%6%30%
46787
Cloud CoverDay
15%10%36%6%35%5%5%7%31%
48263
Night
15%12%46%5%3445%6%30%
46790
TransparencyDay
52%415%19%7%1
47924
Night
54%415%17%7%
46630
SeeingDay
19%9%23%26%16%4
6210
Night
22%5%16%32%20%2
14873

By Month

Percentage Cloud Cover NW (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%10%6%45%5%46%11%
1351
16th to endDay
17%12%5%8%7%46%7%5%7%16%
1536
February1st to 15thDay
15%14%5%9%8%35%5%5%5%21%
1457
16th to endDay
13%13%5%8%7%35%6%6%6%24%
1514
March1st to 15thDay
16%14%6%9%7%35%5%5%5%20%
1800
16th to endDay
14%13%5%8%6%46%6%6%7%20%
2215
April1st to 15thDay
13%14%47%7%5%5%5%6%7%22%
2149
16th to endDay
14%11%48%7%46%45%6%25%
2386
May1st to 15thDay
14%8%37%5%35%5%5%7%32%
2511
16th to endDay
18%8%36%6%36%45%7%29%
2683
June1st to 15thDay
19%8%36%7%36%5%5%7%26%
2778
16th to endDay
16%6%36%6%45%5%6%7%31%
2880
July1st to 15thDay
6%4145%35%5%6%7%49%
2754
16th to endDay
5%31342445%8%56%
2657
August1st to 15thDay
5%314435%45%8%53%
2520
16th to endDay
7%4144345%6%7%48%
2443
September1st to 15thDay
8%425%4235%5%7%51%
2160
16th to endDay
15%7%245%35%5%6%8%35%
1918
October1st to 15thDay
14%9%27%6%35%6%5%6%33%
1653
16th to endDay
22%10%47%4345%5%5%26%
1591
November1st to 15thDay
23%12%5%7%5%35%5%5%5%19%
1473
16th to endDay
17%15%6%9%8%47%45%6%14%
1317
December1st to 15thDay
14%15%6%11%10%46%5%5%5%13%
1260
16th to endDay
18%16%5%8%6%5%5%47%417%
1257
January1st to 15thNight
23%19%6%7%6%34346%13%
2593
16th to endNight
16%16%6%10%8%45%5%45%15%
2688
February1st to 15thNight
19%15%49%5%345%5%5%21%
2393
16th to endNight
11%14%5%7%6%35%447%28%
1959
March1st to 15thNight
17%14%5%8%6%25%45%6%23%
2160
16th to endNight
13%12%38%6%35%5%6%7%27%
2003
April1st to 15thNight
12%10%36%7%45%6%6%7%28%
1799
16th to endNight
12%11%5%6%5%45%446%31%
1572
May1st to 15thNight
8%10%37%5%35%46%6%37%
1439
16th to endNight
14%8%35%6%445%5%8%33%
1427
June1st to 15thNight
18%6%26%6%35%5%6%7%32%
1179
16th to endNight
12%6%35%6%36%6%7%6%36%
1080
July1st to 15thNight
431342435%8%56%
1201
16th to endNight
5%2123245%5%6%60%
1512
August1st to 15thNight
5%213314448%59%
1440
16th to endNight
5%41332336%7%58%
1757
September1st to 15thNight
6%31332445%6%56%
1800
16th to endNight
12%6%245%3345%7%44%
1854
October1st to 15thNight
12%6%27%5%35%45%5%40%
1975
16th to endNight
19%8%36%5%44446%30%
2280
November1st to 15thNight
25%12%45%43445%5%23%
2386
16th to endNight
20%15%5%9%7%25%5%5%418%
2629
December1st to 15thNight
17%17%6%10%7%45%445%17%
2700
16th to endNight
16%21%6%9%6%35%5%45%15%
2961

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
20%17%6%11%8%445%45%12%
1351
16th to endDay
19%14%5%7%8%45%5%5%8%15%
1536
February1st to 15thDay
16%16%5%8%7%445%45%21%
1457
16th to endDay
12%15%49%6%445%47%22%
1514
March1st to 15thDay
18%16%6%9%5%345%46%19%
1800
16th to endDay
15%14%5%8%6%46%5%7%6%20%
2215
April1st to 15thDay
14%15%48%8%35%45%6%21%
2149
16th to endDay
14%13%48%7%35%5%5%5%25%
2386
May1st to 15thDay
15%9%37%6%345%5%6%32%
2511
16th to endDay
19%8%36%5%35%5%5%7%28%
2683
June1st to 15thDay
21%7%37%6%46%45%6%25%
2778
16th to endDay
17%7%36%5%35%5%5%7%31%
2880
July1st to 15thDay
7%4145%35%5%5%7%49%
2754
16th to endDay
6%3134245%5%7%55%
2657
August1st to 15thDay
5%4144345%5%8%52%
2520
16th to endDay
8%4234346%6%7%48%
2443
September1st to 15thDay
9%5%24424448%51%
2160
16th to endDay
16%7%235%345%6%8%35%
1918
October1st to 15thDay
16%8%26%5%35%5%48%32%
1653
16th to endDay
23%11%36%5%24446%26%
1591
November1st to 15thDay
24%15%48%435%5%45%19%
1473
16th to endDay
18%18%5%8%7%46%5%48%12%
1317
December1st to 15thDay
15%17%5%12%10%46%5%4413%
1260
16th to endDay
19%17%5%9%6%4446%7%14%
1257
January1st to 15thNight
24%19%6%8%6%33345%14%
2592
16th to endNight
16%18%6%10%8%3445%5%15%
2688
February1st to 15thNight
19%18%48%5%33345%22%
2393
16th to endNight
12%16%5%8%5%25%45%7%26%
1959
March1st to 15thNight
19%16%47%5%25%45%6%21%
2160
16th to endNight
14%12%48%5%35%5%6%6%26%
2007
April1st to 15thNight
14%11%46%7%45%5%6%7%26%
1799
16th to endNight
13%12%46%5%35%45%7%30%
1572
May1st to 15thNight
8%11%47%6%3436%6%36%
1439
16th to endNight
15%8%36%5%35%46%8%32%
1427
June1st to 15thNight
18%7%36%6%25%46%8%31%
1179
16th to endNight
13%6%36%5%26%6%7%5%36%
1080
July1st to 15thNight
441343346%7%55%
1201
16th to endNight
5%312325%45%7%59%
1512
August1st to 15thNight
5%21232445%8%58%
1440
16th to endNight
6%31342336%7%57%
1757
September1st to 15thNight
7%31232445%6%55%
1800
16th to endNight
14%6%2443435%7%43%
1854
October1st to 15thNight
14%7%36%5%24446%40%
1975
16th to endNight
21%9%35%5%34446%29%
2280
November1st to 15thNight
26%13%45%5%3435%5%22%
2386
16th to endNight
20%17%6%7%6%345%4417%
2629
December1st to 15thNight
18%17%6%10%7%35%44417%
2700
16th to endNight
17%23%6%8%6%35%435%14%
2961

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
73%8%11%6%1
1351
16th to endDay
65%6%17%7%11
1536
February1st to 15thDay
64%7%16%9%1
1457
16th to endDay
59%418%13%3
1514
March1st to 15thDay
65%5%14%12%1
1800
16th to endDay
61%317%13%3
2215
April1st to 15thDay
61%5%14%16%2
2149
16th to endDay
59%414%17%3
2386
May1st to 15thDay
50%314%20%9%
2511
16th to endDay
55%217%19%4
2687
June1st to 15thDay
58%312%16%7%
2778
16th to endDay
51%312%20%10%
2880
July1st to 15thDay
33%313%26%17%4
2595
16th to endDay
26%316%30%20%2
2490
August1st to 15thDay
28%416%33%14%2
2503
16th to endDay
32%416%30%13%1
2443
September1st to 15thDay
32%315%32%15%1
2160
16th to endDay
45%5%18%22%7%1
1918
October1st to 15thDay
49%5%20%20%4
1653
16th to endDay
58%420%14%1
1591
November1st to 15thDay
66%5%14%10%2
1473
16th to endDay
69%8%12%8%1
1317
December1st to 15thDay
71%7%11%8%
1260
16th to endDay
68%6%16%7%1
1257
January1st to 15thNight
72%413%6%2
2593
16th to endNight
68%6%15%7%1
2688
February1st to 15thNight
65%414%11%3
2405
16th to endNight
56%318%16%4
1959
March1st to 15thNight
62%5%16%12%2
2160
16th to endNight
56%417%17%4
2007
April1st to 15thNight
54%5%17%16%5%
1799
16th to endNight
52%414%22%5%
1572
May1st to 15thNight
47%313%22%12%
1440
16th to endNight
46%5%16%23%7%
1427
June1st to 15thNight
49%212%22%9%1
1179
16th to endNight
45%5%15%22%10%
1080
July1st to 15thNight
27%413%27%20%6%
1131
16th to endNight
24%313%32%23%2
1416
August1st to 15thNight
23%312%33%20%5%
1432
16th to endNight
25%314%35%19%2
1757
September1st to 15thNight
28%315%29%20%3
1800
16th to endNight
40%313%29%9%3
1854
October1st to 15thNight
44%418%23%8%
1975
16th to endNight
55%318%19%2
2280
November1st to 15thNight
63%6%13%12%3
2386
16th to endNight
69%413%9%2
2629
December1st to 15thNight
69%415%9%1
2700
16th to endNight
71%5%13%8%
2961

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
16%5%6%28%25%18%
60
16th to endDay
29%315%31%14%6%
64
February1st to 15thDay
28%12%15%27%12%3
117
16th to endDay
18%12%20%30%14%2
227
March1st to 15thDay
34%17%25%16%5%
270
16th to endDay
28%12%30%21%6%
288
April1st to 15thDay
30%12%25%19%9%2
269
16th to endDay
20%16%28%20%9%3
270
May1st to 15thDay
21%12%30%26%6%3
288
16th to endDay
22%8%18%23%19%8%
398
June1st to 15thDay
21%10%19%27%18%3
573
16th to endDay
18%8%23%27%20%2
675
July1st to 15thDay
8%8%19%32%25%5%
529
16th to endDay
6%11%29%33%15%4
327
August1st to 15thDay
9%6%20%32%21%9%
315
16th to endDay
9%9%22%37%13%6%
332
September1st to 15thDay
12%9%26%27%19%4
315
16th to endDay
22%8%28%21%16%3
280
October1st to 15thDay
24%8%26%24%13%2
255
16th to endDay
26%19%27%21%4
103
November1st to 15thDay
33%7%22%22%12%1
71
16th to endDay
30%316%23%13%13%
60
December1st to 15thDay
26%11%11%21%20%8%
60
16th to endDay
23%115%40%12%6%
64
January1st to 15thNight
35%7%17%24%11%2
759
16th to endNight
25%6%18%31%15%2
768
February1st to 15thNight
29%6%12%32%17%1
704
16th to endNight
20%5%16%32%22%2
632
March1st to 15thNight
28%7%19%30%12%1
720
16th to endNight
21%7%24%31%13%2
768
April1st to 15thNight
20%8%17%32%19%1
719
16th to endNight
20%6%18%38%16%
492
May1st to 15thNight
14%6%14%40%22%1
360
16th to endNight
19%312%33%28%3
375
June1st to 15thNight
19%6%16%32%22%2
360
16th to endNight
16%415%38%22%2
360
July1st to 15thNight
6%214%33%38%3
340
16th to endNight
6%210%37%39%2
376
August1st to 15thNight
6%26%27%49%7%
360
16th to endNight
8%29%39%36%3
611
September1st to 15thNight
9%211%30%37%8%
720
16th to endNight
18%412%32%28%3
683
October1st to 15thNight
16%314%37%24%3
660
16th to endNight
26%5%15%31%17%2
704
November1st to 15thNight
33%6%18%33%7%1
700
16th to endNight
29%7%17%29%12%4
829
December1st to 15thNight
26%6%16%33%14%2
900
16th to endNight
31%420%32%9%
973
Page generated at 2017-09-23 03:43:45. Version ac04

Copyright 2017 A. Danko


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