Skunk Hollow Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Skunk Hollow Observatory clear sky chart from 2005-11-05 to 2017-10-06.

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
36%
15175
16%
47121
10%
15135
43%
15135
20%
31451

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%
717
12%
2419
5%
716
24%
716
10%
1790
January16th to endNight
14%
768
12%
2496
4%
768
24%
768
12%
1786
February1st to 15thNight
15%
704
12%
2287
5%
701
25%
701
12%
1625
February16th to endNight
18%
631
15%
1964
5%
631
31%
631
13%
1376
March1st to 15thNight
24%
720
16%
1980
8%
720
33%
720
17%
1386
March16th to endNight
23%
768
18%
2112
7%
768
32%
768
19%
1414
April1st to 15thNight
23%
718
13%
1801
4%
718
29%
718
19%
1321
April16th to endNight
37%
666
18%
1746
7%
666
43%
666
25%
1179
May1st to 15thNight
42%
531
16%
1611
10%
531
48%
531
21%
1100
May16th to endNight
48%
374
17%
1497
16%
374
54%
374
20%
909
June1st to 15thNight
48%
360
16%
1440
16%
360
55%
360
22%
870
June16th to endNight
55%
360
15%
1440
17%
360
62%
360
25%
806
July1st to 15thNight
54%
340
14%
1360
17%
340
57%
340
22%
817
July16th to endNight
66%
551
16%
1582
14%
518
68%
518
33%
941
August1st to 15thNight
64%
539
18%
1609
13%
536
67%
536
33%
966
August16th to endNight
64%
695
23%
1841
16%
695
65%
695
37%
1126
September1st to 15thNight
53%
720
24%
1800
13%
720
57%
720
32%
1176
September16th to endNight
53%
717
23%
2000
19%
717
57%
717
31%
1256
October1st to 15thNight
44%
684
19%
2051
16%
684
50%
684
26%
1311
October16th to endNight
32%
704
18%
2112
10%
704
43%
704
22%
1394
November1st to 15thNight
39%
700
20%
2245
15%
700
47%
700
24%
1398
November16th to endNight
27%
720
15%
2520
10%
720
37%
720
13%
1699
December1st to 15thNight
24%
720
10%
2520
6%
720
30%
720
10%
1828
December16th to endNight
19%
768
11%
2688
4%
768
28%
768
9%
1977

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%8%37%6%35%5%5%7%31%
48072
Night
13%6%35%5%35%5%5%8%36%
47303
Cloud CoverDay
14%7%37%6%35%5%5%7%31%
48082
Night
13%6%35%5%35%5%5%8%37%
47307
TransparencyDay
49%6%12%19%10%1
47772
Night
44%6%14%21%12%1
47121
SeeingDay
21%13%23%21%14%6%
5611
Night
20%13%24%28%12%1
15179

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
12%9%5%13%8%25%446%25%
1519
16th to endDay
13%13%7%10%8%46%5%5%420%
1728
February1st to 15thDay
14%14%5%8%7%36%35%7%22%
1575
16th to endDay
13%11%5%10%8%45%445%26%
1506
March1st to 15thDay
15%10%47%7%35%45%6%28%
1969
16th to endDay
16%10%36%6%2445%8%30%
2112
April1st to 15thDay
15%9%5%7%6%44446%31%
2146
16th to endDay
18%8%36%42435%6%35%
2223
May1st to 15thDay
19%8%37%5%35%5%5%6%29%
2340
16th to endDay
15%6%25%6%45%5%5%8%34%
2618
June1st to 15thDay
13%5%26%6%45%5%6%8%34%
2520
16th to endDay
13%5%26%6%445%7%9%34%
2520
July1st to 15thDay
9%6%46%7%37%6%6%8%32%
2520
16th to endDay
8%5%36%6%47%7%7%9%33%
2476
August1st to 15thDay
10%6%36%7%5%6%7%8%9%28%
2340
16th to endDay
14%425%5%45%5%6%8%37%
2348
September1st to 15thDay
18%6%345%3445%6%38%
2160
16th to endDay
15%6%25%42445%7%41%
1959
October1st to 15thDay
17%8%34434446%36%
1707
16th to endDay
16%8%36%6%25%446%33%
1760
November1st to 15thDay
10%6%36%6%35%45%8%39%
1610
16th to endDay
19%8%37%6%25%5%45%29%
1440
December1st to 15thDay
17%10%5%9%5%46%6%5%6%23%
1440
16th to endDay
19%11%5%9%6%36%45%6%20%
1536
January1st to 15thNight
15%9%48%7%46%5%6%6%25%
2419
16th to endNight
13%9%48%8%35%6%5%8%26%
2496
February1st to 15thNight
13%9%5%6%6%25%5%6%8%28%
2285
16th to endNight
10%8%47%7%38%6%5%6%31%
1964
March1st to 15thNight
15%8%35%435%5%6%8%34%
1968
16th to endNight
16%7%2442445%7%40%
2112
April1st to 15thNight
14%10%46%6%345%36%34%
1801
16th to endNight
15%6%35%42345%6%41%
1746
May1st to 15thNight
18%5%25%435%5%5%7%36%
1611
16th to endNight
13%5%344245%6%7%41%
1495
June1st to 15thNight
12%425%425%5%5%9%42%
1440
16th to endNight
9%414335%5%7%10%43%
1440
July1st to 15thNight
9%425%5%25%45%9%44%
1440
16th to endNight
6%3146%345%7%10%45%
1689
August1st to 15thNight
8%425%4345%6%10%46%
1620
16th to endNight
10%5%1332446%8%49%
1841
September1st to 15thNight
13%5%25%423446%47%
1800
16th to endNight
13%42442445%7%46%
2000
October1st to 15thNight
16%5%24423446%43%
2051
16th to endNight
17%6%25%4345%5%7%37%
2112
November1st to 15thNight
12%6%35%42445%7%43%
2245
16th to endNight
18%7%35%435%5%6%8%31%
2520
December1st to 15thNight
16%7%37%7%36%6%7%8%24%
2520
16th to endNight
15%10%47%6%35%6%5%10%23%
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
12%9%5%13%8%35%45%6%25%
1519
16th to endDay
13%13%7%10%8%46%5%5%420%
1728
February1st to 15thDay
14%14%6%8%6%46%45%7%21%
1575
16th to endDay
13%11%5%11%8%36%45%426%
1506
March1st to 15thDay
15%10%47%7%45%45%6%28%
1980
16th to endDay
17%9%45%6%2445%8%30%
2111
April1st to 15thDay
15%9%5%6%6%34446%32%
2146
16th to endDay
18%8%36%43435%6%35%
2223
May1st to 15thDay
19%7%37%6%35%5%5%7%28%
2340
16th to endDay
15%5%25%5%45%5%5%8%34%
2618
June1st to 15thDay
13%5%36%6%45%6%6%8%34%
2520
16th to endDay
13%436%6%45%6%7%9%34%
2520
July1st to 15thDay
9%6%37%6%38%6%6%8%32%
2520
16th to endDay
8%5%35%6%47%7%7%9%33%
2476
August1st to 15thDay
10%5%36%7%5%6%7%8%9%29%
2340
16th to endDay
13%4245%35%5%7%8%37%
2348
September1st to 15thDay
17%6%235%35%5%46%39%
2160
16th to endDay
15%6%25%42445%7%41%
1959
October1st to 15thDay
17%8%35%434447%36%
1707
16th to endDay
16%7%37%5%35%45%6%34%
1760
November1st to 15thDay
10%6%36%6%35%46%8%39%
1610
16th to endDay
19%8%46%6%35%5%5%5%29%
1440
December1st to 15thDay
17%10%5%9%5%46%5%6%5%23%
1440
16th to endDay
19%11%5%9%6%36%5%5%6%19%
1536
January1st to 15thNight
15%9%48%8%36%5%6%6%25%
2419
16th to endNight
13%9%47%8%35%5%6%7%26%
2496
February1st to 15thNight
13%9%5%7%6%35%5%6%8%28%
2278
16th to endNight
10%8%46%7%47%6%5%5%31%
1964
March1st to 15thNight
15%8%35%435%5%6%7%34%
1980
16th to endNight
16%7%24425%45%7%40%
2112
April1st to 15thNight
14%9%46%5%345%46%34%
1801
16th to endNight
15%6%25%424446%41%
1746
May1st to 15thNight
18%5%25%435%46%7%36%
1610
16th to endNight
13%6%3343446%7%42%
1495
June1st to 15thNight
12%424425%5%5%9%43%
1440
16th to endNight
9%423425%5%8%10%43%
1440
July1st to 15thNight
9%425%425%45%9%44%
1440
16th to endNight
6%315%5%345%6%11%45%
1689
August1st to 15thNight
7%425%33447%11%45%
1620
16th to endNight
10%4134135%6%8%49%
1841
September1st to 15thNight
13%434424446%47%
1800
16th to endNight
13%42442445%8%46%
2000
October1st to 15thNight
16%5%15%424446%43%
2051
16th to endNight
17%6%25%4345%5%7%37%
2112
November1st to 15thNight
12%6%35%42445%7%43%
2245
16th to endNight
17%7%45%5%35%5%5%8%32%
2520
December1st to 15thNight
16%7%36%7%36%5%7%8%25%
2520
16th to endNight
16%10%46%6%45%6%6%9%24%
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
57%415%13%7%
1520
16th to endDay
63%413%13%3
1728
February1st to 15thDay
61%5%14%13%4
1577
16th to endDay
58%414%15%6%
1506
March1st to 15thDay
55%6%12%17%6%
1980
16th to endDay
50%5%12%21%8%1
2112
April1st to 15thDay
52%5%9%18%12%1
2146
16th to endDay
48%48%18%16%3
2223
May1st to 15thDay
53%6%10%18%10%1
2340
16th to endDay
46%7%15%17%11%2
2622
June1st to 15thDay
44%7%11%21%13%
2520
16th to endDay
42%7%14%23%11%
2520
July1st to 15thDay
46%8%12%17%12%2
2371
16th to endDay
40%9%13%21%13%1
2320
August1st to 15thDay
45%8%14%21%9%
2327
16th to endDay
41%6%12%23%13%2
2348
September1st to 15thDay
43%5%10%22%16%1
2160
16th to endDay
40%5%10%23%17%2
1959
October1st to 15thDay
45%6%12%20%14%1
1707
16th to endDay
48%6%13%21%9%
1760
November1st to 15thDay
41%5%16%19%12%4
1610
16th to endDay
54%5%12%19%8%
1440
December1st to 15thDay
59%7%15%12%4
1440
16th to endDay
61%6%12%14%4
1536
January1st to 15thNight
56%6%13%15%7%1
2419
16th to endNight
53%418%16%6%
2496
February1st to 15thNight
51%6%15%18%6%
2287
16th to endNight
49%6%12%21%10%
1964
March1st to 15thNight
46%6%15%21%9%
1980
16th to endNight
43%5%16%20%12%1
2112
April1st to 15thNight
50%5%10%18%13%
1801
16th to endNight
42%410%22%15%4
1746
May1st to 15thNight
45%6%11%20%13%1
1611
16th to endNight
39%7%15%20%14%2
1497
June1st to 15thNight
37%8%12%28%12%
1440
16th to endNight
32%8%16%25%15%1
1440
July1st to 15thNight
37%8%13%22%14%3
1360
16th to endNight
30%8%17%23%17%2
1582
August1st to 15thNight
31%8%16%25%16%
1609
16th to endNight
31%6%12%27%17%3
1841
September1st to 15thNight
37%5%10%25%19%2
1800
16th to endNight
36%5%11%26%18%1
2000
October1st to 15thNight
40%5%14%23%15%1
2051
16th to endNight
43%5%15%24%11%
2112
November1st to 15thNight
39%415%21%14%4
2245
16th to endNight
49%5%13%19%10%1
2520
December1st to 15thNight
53%8%15%15%6%
2520
16th to endNight
54%7%18%15%3
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
30%28%26%8%5%1
75
16th to endDay
36%22%31%9%
96
February1st to 15thDay
30%35%26%7%
90
16th to endDay
25%26%32%14%
156
March1st to 15thDay
25%18%24%24%5%
270
16th to endDay
27%17%28%17%6%3
288
April1st to 15thDay
27%17%23%20%9%1
270
16th to endDay
21%15%21%19%15%5%
270
May1st to 15thDay
33%14%20%16%9%5%
288
16th to endDay
20%13%25%18%14%7%
331
June1st to 15thDay
17%13%26%26%13%3
315
16th to endDay
17%11%26%25%14%4
315
July1st to 15thDay
12%10%30%22%16%6%
305
16th to endDay
10%5%22%30%22%9%
326
August1st to 15thDay
12%6%22%24%21%12%
313
16th to endDay
14%418%24%19%19%
332
September1st to 15thDay
19%7%17%20%23%11%
315
16th to endDay
18%7%13%22%23%15%
314
October1st to 15thDay
25%5%16%24%21%6%
278
16th to endDay
20%20%26%23%7%
272
November1st to 15thDay
17%12%21%27%20%
208
16th to endDay
23%21%30%16%8%
60
December1st to 15thDay
33%21%18%10%13%3
60
16th to endDay
37%15%34%12%
64
January1st to 15thNight
26%20%30%18%3
720
16th to endNight
24%21%32%20%1
768
February1st to 15thNight
25%20%32%19%2
704
16th to endNight
21%22%31%22%1
631
March1st to 15thNight
25%17%28%25%3
720
16th to endNight
20%20%28%20%8%
768
April1st to 15thNight
23%18%29%22%5%
718
16th to endNight
19%12%23%32%12%
666
May1st to 15thNight
21%7%21%35%11%1
531
16th to endNight
15%8%20%32%20%2
375
June1st to 15thNight
14%6%24%34%20%
360
16th to endNight
11%324%43%17%
360
July1st to 15thNight
13%318%42%19%1
340
16th to endNight
7%313%44%28%2
551
August1st to 15thNight
11%15%42%27%2
539
16th to endNight
12%311%36%31%4
695
September1st to 15thNight
16%6%16%29%26%3
720
16th to endNight
13%6%18%23%29%7%
717
October1st to 15thNight
19%9%20%27%20%2
684
16th to endNight
23%15%24%29%6%
704
November1st to 15thNight
17%13%24%32%10%1
700
16th to endNight
27%19%21%22%7%1
720
December1st to 15thNight
27%17%25%24%5%
720
16th to endNight
24%22%29%22%1
768
Page generated at 2017-10-07 14:07:49. Version ac04

Copyright 2017 A. Danko


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