Slemon Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Slemon Park clear sky chart from 2005-11-05 to 2018-03-21.

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
25%
15724
12%
49091
5%
15679
31%
15679
15%
36127

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%
825
10%
2871
2%
821
26%
821
9%
2171
January16th to endNight
19%
850
15%
2782
5%
850
31%
850
13%
1985
February1st to 15thNight
18%
764
11%
2481
4%
761
27%
761
14%
1792
February16th to endNight
21%
683
11%
2210
4%
683
30%
683
11%
1671
March1st to 15thNight
22%
779
13%
2170
5%
779
30%
779
15%
1659
March16th to endNight
24%
786
14%
2171
7%
786
31%
786
16%
1651
April1st to 15thNight
25%
539
12%
1793
8%
539
31%
539
12%
1334
April16th to endNight
27%
540
15%
1620
8%
540
34%
540
18%
1164
May1st to 15thNight
30%
540
11%
1482
6%
540
35%
540
19%
1097
May16th to endNight
24%
561
10%
1496
3%
560
30%
560
20%
1107
June1st to 15thNight
29%
432
6%
1332
3%
432
32%
432
16%
997
June16th to endNight
36%
360
7%
1260
4%
360
40%
360
16%
889
July1st to 15thNight
37%
340
10%
1190
7%
340
42%
340
21%
750
July16th to endNight
36%
555
9%
1409
6%
522
38%
522
20%
1032
August1st to 15thNight
41%
539
9%
1603
6%
535
43%
535
20%
1143
August16th to endNight
42%
573
14%
1773
9%
573
47%
573
23%
1169
September1st to 15thNight
34%
540
15%
1800
11%
540
41%
540
24%
1111
September16th to endNight
36%
690
21%
1998
13%
690
44%
690
26%
1279
October1st to 15thNight
31%
720
17%
2160
8%
720
39%
720
22%
1463
October16th to endNight
19%
773
14%
2325
6%
773
26%
773
13%
1760
November1st to 15thNight
22%
805
10%
2660
6%
805
28%
805
12%
2005
November16th to endNight
20%
825
10%
2730
4%
825
27%
825
10%
2130
December1st to 15thNight
12%
825
8%
2730
1%
825
19%
825
7%
2234
December16th to endNight
10%
880
6%
3045
1%
880
16%
880
5%
2534

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%9%46%5%3445%6%30%
49763
Night
19%10%46%6%34446%28%
49252
TransparencyDay
53%5%12%19%8%
49442
Night
56%411%18%8%
49091
SeeingDay
24%10%29%23%9%2
7897
Night
25%11%30%24%7%
15725

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
16%11%6%11%8%3334425%
1394
16th to endDay
13%12%47%6%45%446%29%
1793
February1st to 15thDay
15%12%5%8%5%34445%30%
1710
16th to endDay
14%13%6%7%5%36%45%6%27%
1548
March1st to 15thDay
15%11%5%8%6%34446%28%
2108
16th to endDay
15%12%6%7%5%24445%30%
2181
April1st to 15thDay
17%10%45%5%35%5%5%6%30%
2153
16th to endDay
21%9%35%5%24446%32%
2340
May1st to 15thDay
22%7%36%5%24446%30%
2468
16th to endDay
22%9%35%5%24446%31%
2618
June1st to 15thDay
26%8%26%5%24447%26%
2637
16th to endDay
22%7%35%5%3445%6%32%
2700
July1st to 15thDay
13%6%25%4345%6%9%39%
2697
16th to endDay
15%7%36%5%246%6%9%32%
2653
August1st to 15thDay
15%6%35%5%2445%7%38%
2343
16th to endDay
14%5%144345%5%8%41%
2429
September1st to 15thDay
18%6%25%42345%7%38%
2160
16th to endDay
19%6%25%423345%43%
1960
October1st to 15thDay
18%8%36%5%3445%7%32%
1800
16th to endDay
20%12%47%6%45%446%23%
1899
November1st to 15thDay
21%15%35%6%36%445%22%
1528
16th to endDay
16%14%7%12%6%35%5%6%6%16%
1560
December1st to 15thDay
24%12%6%11%7%44446%13%
1560
16th to endDay
21%14%7%11%9%3444414%
1524
January1st to 15thNight
17%11%5%8%7%36%5%5%6%24%
2871
16th to endNight
16%10%47%6%3435%5%31%
2782
February1st to 15thNight
17%13%47%5%24446%29%
2480
16th to endNight
17%13%5%8%7%25%46%424%
2210
March1st to 15thNight
20%11%47%8%3435%5%26%
2158
16th to endNight
18%13%5%8%5%2433431%
2171
April1st to 15thNight
21%12%46%5%3445%5%26%
1793
16th to endNight
22%11%35%423345%32%
1620
May1st to 15thNight
25%7%25%6%25%445%31%
1482
16th to endNight
19%9%36%5%34348%30%
1494
June1st to 15thNight
24%8%36%6%3445%5%27%
1332
16th to endNight
20%7%445%345%6%6%30%
1260
July1st to 15thNight
12%6%26%5%35%6%6%8%35%
1260
16th to endNight
16%8%36%5%35%5%6%7%29%
1504
August1st to 15thNight
16%7%36%6%36%5%46%32%
1614
16th to endNight
14%5%35%5%25%45%8%38%
1773
September1st to 15thNight
16%7%25%423347%41%
1800
16th to endNight
15%6%24434335%45%
1998
October1st to 15thNight
18%6%26%43345%7%36%
2160
16th to endNight
25%10%36%6%2334427%
2325
November1st to 15thNight
22%13%46%5%34346%26%
2660
16th to endNight
20%12%48%6%35%5%47%21%
2730
December1st to 15thNight
22%13%5%9%7%44446%16%
2730
16th to endNight
24%14%6%8%7%35%445%14%
3045

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
62%6%10%11%8%
1395
16th to endDay
55%5%9%17%12%
1793
February1st to 15thDay
55%411%19%8%1
1713
16th to endDay
57%410%16%8%1
1548
March1st to 15thDay
56%410%18%8%
2119
16th to endDay
55%5%9%18%10%
2181
April1st to 15thDay
53%48%18%12%2
2153
16th to endDay
52%411%17%12%1
2340
May1st to 15thDay
54%5%9%19%8%1
2468
16th to endDay
53%6%12%20%6%
2622
June1st to 15thDay
57%5%11%18%7%
2637
16th to endDay
51%5%14%20%7%
2700
July1st to 15thDay
38%7%16%26%10%
2538
16th to endDay
47%6%19%19%6%
2486
August1st to 15thDay
42%6%15%27%6%
2329
16th to endDay
40%6%18%26%7%
2429
September1st to 15thDay
44%6%15%23%10%
2160
16th to endDay
43%411%26%12%
1960
October1st to 15thDay
49%5%12%23%8%
1800
16th to endDay
60%5%10%17%6%
1899
November1st to 15thDay
62%5%13%12%7%
1528
16th to endDay
67%6%13%9%3
1560
December1st to 15thDay
72%5%10%8%3
1560
16th to endDay
73%47%9%4
1524
January1st to 15thNight
59%6%11%14%7%
2871
16th to endNight
54%410%20%8%
2782
February1st to 15thNight
56%311%17%10%
2481
16th to endNight
61%49%14%8%1
2210
March1st to 15thNight
59%39%17%8%1
2170
16th to endNight
58%36%18%11%1
2171
April1st to 15thNight
59%49%13%10%2
1793
16th to endNight
54%39%16%14%1
1620
May1st to 15thNight
54%410%21%7%1
1482
16th to endNight
53%414%19%7%
1496
June1st to 15thNight
57%5%13%15%7%
1332
16th to endNight
52%5%14%19%7%
1260
July1st to 15thNight
41%7%17%25%7%
1190
16th to endNight
50%6%17%16%8%
1409
August1st to 15thNight
49%6%15%21%6%
1603
16th to endNight
43%6%18%24%6%
1773
September1st to 15thNight
41%413%28%11%
1800
16th to endNight
41%412%28%12%
1998
October1st to 15thNight
46%414%25%8%
2160
16th to endNight
58%48%19%8%
2325
November1st to 15thNight
60%313%15%5%
2660
16th to endNight
61%6%13%13%4
2730
December1st to 15thNight
68%5%10%12%3
2730
16th to endNight
72%48%10%4
3045

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%26%40%8%7%
126
16th to endDay
20%14%40%21%2
304
February1st to 15thDay
24%9%37%21%6%
281
16th to endDay
25%11%31%23%6%1
251
March1st to 15thDay
23%13%34%22%4
324
16th to endDay
22%13%31%20%8%2
311
April1st to 15thDay
26%13%31%19%9%
270
16th to endDay
21%14%30%18%12%1
270
May1st to 15thDay
32%11%24%18%9%3
424
16th to endDay
30%8%28%24%7%
519
June1st to 15thDay
32%9%24%22%9%1
495
16th to endDay
25%5%27%28%11%2
495
July1st to 15thDay
16%333%29%13%2
475
16th to endDay
23%5%21%33%14%2
514
August1st to 15thDay
18%5%24%29%17%5%
316
16th to endDay
15%5%25%30%17%5%
332
September1st to 15thDay
21%7%29%27%12%1
315
16th to endDay
25%7%24%29%9%3
303
October1st to 15thDay
19%12%26%23%13%4
270
16th to endDay
26%20%27%17%7%
288
November1st to 15thDay
27%15%28%16%10%2
280
16th to endDay
24%18%34%17%41
285
December1st to 15thDay
34%17%28%16%2
285
16th to endDay
23%15%41%17%2
164
January1st to 15thNight
22%17%34%20%4
825
16th to endNight
22%15%34%21%41
850
February1st to 15thNight
26%10%35%21%4
764
16th to endNight
25%10%32%22%7%1
683
March1st to 15thNight
24%11%32%25%5%
780
16th to endNight
25%13%27%21%10%1
786
April1st to 15thNight
30%9%28%23%7%
539
16th to endNight
26%9%28%25%9%
540
May1st to 15thNight
29%6%28%23%10%2
540
16th to endNight
23%7%35%25%6%
561
June1st to 15thNight
27%429%29%8%
432
16th to endNight
22%329%32%8%1
360
July1st to 15thNight
15%335%31%12%
340
16th to endNight
19%5%31%31%10%1
555
August1st to 15thNight
18%426%32%16%
539
16th to endNight
16%430%34%13%1
573
September1st to 15thNight
20%6%33%30%8%
540
16th to endNight
18%10%30%28%11%
690
October1st to 15thNight
21%9%31%25%10%
720
16th to endNight
31%16%26%18%6%
773
November1st to 15thNight
30%14%25%22%5%1
805
16th to endNight
27%18%25%21%6%
825
December1st to 15thNight
31%18%31%15%3
825
16th to endNight
32%19%26%16%31
880
Page generated at 2018-03-22 12:34:23. Version ac04

Copyright 2018 A. Danko


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