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

2017-09-12
.

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
25%
14885
11%
46623
5%
14840
32%
14840
15%
34311

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%
750
10%
2649
2%
746
27%
746
9%
1985
January16th to endNight
18%
780
14%
2568
4%
780
31%
780
13%
1837
February1st to 15thNight
17%
704
11%
2286
4%
701
27%
701
14%
1656
February16th to endNight
22%
631
10%
2042
3%
631
30%
631
11%
1556
March1st to 15thNight
23%
719
14%
2003
5%
719
31%
719
15%
1522
March16th to endNight
24%
762
14%
2106
7%
762
30%
762
16%
1599
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
33%
531
15%
1768
10%
531
40%
531
24%
1098
September16th to endNight
36%
632
20%
1831
13%
632
43%
632
26%
1166
October1st to 15thNight
31%
660
17%
1980
8%
660
39%
660
21%
1364
October16th to endNight
17%
707
12%
2131
4%
707
24%
707
12%
1636
November1st to 15thNight
22%
730
10%
2450
5%
730
28%
730
12%
1848
November16th to endNight
20%
750
9%
2520
4%
750
27%
750
10%
1959
December1st to 15thNight
12%
750
8%
2520
1%
750
20%
750
6%
2058
December16th to endNight
10%
800
6%
2811
0%
800
16%
800
5%
2345

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%
48042
Night
19%10%46%6%34446%28%
46784
TransparencyDay
53%5%12%19%8%
47721
Night
56%412%18%7%
46623
SeeingDay
24%10%29%23%9%2
7314
Night
25%11%30%24%7%1
14886

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%12%6%11%8%3334424%
1286
16th to endDay
13%12%47%7%45%45%6%29%
1655
February1st to 15thDay
14%12%5%8%5%35%446%30%
1575
16th to endDay
14%14%6%7%5%26%45%6%25%
1430
March1st to 15thDay
15%10%5%8%6%34446%30%
1945
16th to endDay
16%12%6%7%5%24445%30%
2118
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
19%7%25%42345%7%36%
2112
16th to endDay
18%5%24423346%44%
1797
October1st to 15thDay
19%8%36%5%2445%7%31%
1650
16th to endDay
22%13%48%6%45%445%21%
1741
November1st to 15thDay
22%15%35%6%36%445%22%
1408
16th to endDay
16%14%7%12%7%35%5%6%5%15%
1440
December1st to 15thDay
23%11%6%11%7%445%5%6%12%
1440
16th to endDay
22%14%8%11%8%3444314%
1407
January1st to 15thNight
18%11%5%7%7%35%5%5%6%25%
2649
16th to endNight
15%10%5%7%6%3445%5%31%
2568
February1st to 15thNight
16%13%47%5%24446%28%
2285
16th to endNight
16%14%5%8%7%35%46%5%23%
2042
March1st to 15thNight
20%10%36%8%2435%5%27%
1991
16th to endNight
19%13%5%8%41433431%
2106
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
17%7%25%423347%41%
1768
16th to endNight
15%6%24424345%45%
1831
October1st to 15thNight
19%7%26%43345%8%34%
1980
16th to endNight
27%11%36%6%2334425%
2131
November1st to 15thNight
23%12%46%5%34346%26%
2450
16th to endNight
21%12%48%6%35%447%21%
2520
December1st to 15thNight
22%12%5%9%7%45%445%16%
2520
16th to endNight
25%15%7%7%7%35%44414%
2811

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
63%5%10%11%8%
1287
16th to endDay
54%5%9%17%12%
1655
February1st to 15thDay
54%411%19%7%1
1578
16th to endDay
58%410%16%8%1
1430
March1st to 15thDay
55%411%19%8%1
1956
16th to endDay
55%5%9%17%10%
2118
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
45%6%15%22%10%
2112
16th to endDay
42%311%28%12%1
1797
October1st to 15thDay
50%5%11%23%8%
1650
16th to endDay
63%5%10%15%5%
1741
November1st to 15thDay
62%413%11%6%
1408
16th to endDay
68%6%12%9%2
1440
December1st to 15thDay
72%5%11%8%2
1440
16th to endDay
74%47%9%3
1407
January1st to 15thNight
59%5%11%15%6%
2649
16th to endNight
54%410%20%8%
2568
February1st to 15thNight
56%311%17%10%
2286
16th to endNight
61%410%14%7%1
2042
March1st to 15thNight
58%39%18%8%1
2003
16th to endNight
58%37%18%10%1
2106
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%10%
1768
16th to endNight
40%413%29%11%
1831
October1st to 15thNight
48%413%24%8%
1980
16th to endNight
60%38%18%8%
2131
November1st to 15thNight
60%314%15%5%
2450
16th to endNight
62%5%13%13%4
2520
December1st to 15thNight
68%5%10%12%2
2520
16th to endNight
72%48%10%3
2811

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
17%26%39%8%7%
93
16th to endDay
19%14%38%23%2
256
February1st to 15thDay
22%8%38%22%7%
236
16th to endDay
27%10%29%22%7%1
212
March1st to 15thDay
22%14%33%24%41
266
16th to endDay
23%13%31%20%7%3
288
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
22%7%31%26%11%1
299
16th to endDay
23%8%27%28%9%3
247
October1st to 15thDay
21%12%24%23%14%4
225
16th to endDay
30%18%28%15%6%
240
November1st to 15thDay
30%15%25%16%10%1
235
16th to endDay
25%17%33%18%41
240
December1st to 15thDay
32%18%29%15%2
240
16th to endDay
24%13%41%17%3
127
January1st to 15thNight
23%16%33%20%4
750
16th to endNight
22%15%35%20%5%1
780
February1st to 15thNight
26%10%36%20%4
704
16th to endNight
25%10%32%22%7%1
631
March1st to 15thNight
24%11%31%26%5%
720
16th to endNight
26%13%27%20%10%1
762
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%29%8%
531
16th to endNight
18%10%30%28%10%
632
October1st to 15thNight
23%9%30%25%10%1
660
16th to endNight
33%16%26%17%6%
707
November1st to 15thNight
30%13%26%21%5%2
730
16th to endNight
28%17%24%21%6%1
750
December1st to 15thNight
30%19%31%14%3
750
16th to endNight
32%19%26%16%31
800
Page generated at 2017-09-13 08:39:23. Version ac04

Copyright 2017 A. Danko


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