Longs Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Longs Creek Observatory clear sky chart from 2005-11-05 to 2017-09-24.

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
22%
14828
14%
46850
5%
14790
32%
14790
16%
32854

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%
741
13%
2628
2%
737
27%
737
10%
1838
January16th to endNight
14%
768
15%
2622
2%
768
30%
768
12%
1805
February1st to 15thNight
16%
704
12%
2286
3%
701
27%
701
14%
1606
February16th to endNight
16%
631
12%
1964
2%
631
28%
631
11%
1471
March1st to 15thNight
16%
720
16%
2049
5%
720
26%
720
15%
1493
March16th to endNight
19%
768
17%
2112
5%
768
28%
768
17%
1523
April1st to 15thNight
15%
614
15%
1764
4%
614
24%
614
13%
1311
April16th to endNight
19%
540
16%
1620
6%
540
27%
540
17%
1134
May1st to 15thNight
22%
540
12%
1610
5%
540
30%
540
16%
1177
May16th to endNight
19%
496
10%
1431
3%
495
27%
495
14%
1086
June1st to 15thNight
25%
360
7%
1260
4%
360
30%
360
12%
928
June16th to endNight
30%
360
8%
1260
6%
360
34%
360
16%
881
July1st to 15thNight
34%
340
10%
1190
7%
340
42%
340
21%
775
July16th to endNight
34%
430
10%
1426
8%
404
40%
404
17%
988
August1st to 15thNight
38%
539
10%
1608
7%
535
40%
535
20%
1111
August16th to endNight
39%
573
19%
1719
9%
573
46%
573
29%
1074
September1st to 15thNight
31%
633
15%
1873
7%
633
38%
633
23%
1239
September16th to endNight
35%
693
25%
1913
14%
693
46%
693
33%
1148
October1st to 15thNight
29%
660
20%
1950
8%
660
39%
660
23%
1274
October16th to endNight
20%
704
15%
2194
4%
704
31%
704
14%
1563
November1st to 15thNight
22%
714
15%
2361
7%
714
33%
714
16%
1637
November16th to endNight
23%
750
15%
2520
5%
750
35%
750
14%
1764
December1st to 15thNight
13%
750
13%
2610
3%
750
25%
750
10%
1907
December16th to endNight
11%
800
12%
2880
3%
800
23%
800
9%
2121

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
20%8%36%5%34446%32%
48089
Night
19%8%35%5%24446%34%
47016
TransparencyDay
51%5%11%19%10%1
47773
Night
50%5%11%20%10%
46850
SeeingDay
27%15%30%19%7%1
6804
Night
25%14%32%21%5%
14828

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
15%11%5%6%5%24445%33%
1308
16th to endDay
14%11%47%6%33446%31%
1602
February1st to 15thDay
13%10%46%6%45%5%5%6%29%
1575
16th to endDay
15%13%48%6%25%5%5%5%27%
1506
March1st to 15thDay
20%13%36%42433430%
1900
16th to endDay
16%11%5%7%5%24346%32%
2112
April1st to 15thDay
22%11%36%423346%31%
2182
16th to endDay
25%7%2442335%5%33%
2340
May1st to 15thDay
25%7%36%5%24345%29%
2341
16th to endDay
25%7%35%5%2345%7%29%
2693
June1st to 15thDay
27%8%46%5%24345%25%
2700
16th to endDay
24%7%37%5%35%45%6%27%
2700
July1st to 15thDay
14%5%25%5%45%5%6%9%34%
2700
16th to endDay
16%7%36%5%47%5%7%7%29%
2630
August1st to 15thDay
19%6%26%6%35%5%5%6%32%
2340
16th to endDay
14%4246%45%5%5%7%39%
2483
September1st to 15thDay
16%5%25%424345%43%
2083
16th to endDay
16%424422335%49%
1906
October1st to 15thDay
21%6%23323346%40%
1680
16th to endDay
23%8%36%5%33445%31%
1677
November1st to 15thDay
23%8%25%413447%34%
1497
16th to endDay
20%9%36%5%245%36%32%
1440
December1st to 15thDay
25%8%45%425%25%6%29%
1350
16th to endDay
24%12%46%5%23445%26%
1344
January1st to 15thNight
15%9%47%6%35%45%6%31%
2628
16th to endNight
14%10%46%6%35%5%5%7%30%
2622
February1st to 15thNight
12%12%36%6%25%5%6%6%30%
2285
16th to endNight
17%14%36%5%35%44428%
1964
March1st to 15thNight
20%9%45%6%25%435%33%
2037
16th to endNight
18%8%46%6%13445%35%
2112
April1st to 15thNight
22%10%35%6%34435%31%
1764
16th to endNight
25%7%24423345%35%
1620
May1st to 15thNight
22%8%26%5%3445%7%29%
1610
16th to endNight
22%8%36%6%3444430%
1429
June1st to 15thNight
25%6%36%5%35%5%47%26%
1260
16th to endNight
21%6%25%6%25%5%6%7%32%
1260
July1st to 15thNight
13%5%36%436%5%6%10%35%
1260
16th to endNight
18%6%25%6%35%46%8%31%
1525
August1st to 15thNight
18%5%26%5%345%48%36%
1620
16th to endNight
13%5%1443345%7%45%
1719
September1st to 15thNight
17%5%25%434447%41%
1873
16th to endNight
14%413323338%50%
1913
October1st to 15thNight
19%6%24322348%40%
1950
16th to endNight
22%8%35%5%23335%34%
2194
November1st to 15thNight
22%6%25%5%33446%35%
2361
16th to endNight
21%8%25%5%24445%34%
2520
December1st to 15thNight
24%8%46%5%2444430%
2610
16th to endNight
25%10%46%424445%27%
2880

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
51%5%14%18%8%1
1309
16th to endDay
52%48%21%11%
1602
February1st to 15thDay
53%6%11%19%8%1
1578
16th to endDay
57%5%10%17%7%1
1506
March1st to 15thDay
57%49%16%10%1
1911
16th to endDay
52%49%19%12%2
2112
April1st to 15thDay
55%38%17%13%2
2182
16th to endDay
52%49%17%12%4
2340
May1st to 15thDay
56%48%18%9%2
2341
16th to endDay
54%6%11%20%6%
2697
June1st to 15thDay
60%5%10%14%8%1
2700
16th to endDay
55%6%12%16%8%
2700
July1st to 15thDay
42%9%15%19%12%
2541
16th to endDay
50%7%16%18%6%
2467
August1st to 15thDay
50%7%13%22%6%
2327
16th to endDay
42%7%14%25%10%
2483
September1st to 15thDay
42%5%12%26%13%
2083
16th to endDay
37%38%29%18%1
1906
October1st to 15thDay
45%413%26%11%
1680
16th to endDay
54%311%21%8%
1677
November1st to 15thDay
50%6%13%15%13%
1497
16th to endDay
52%5%13%17%9%
1440
December1st to 15thDay
55%6%11%20%6%
1350
16th to endDay
59%5%9%16%8%
1344
January1st to 15thNight
50%7%12%18%9%
2628
16th to endNight
50%5%10%22%9%
2622
February1st to 15thNight
51%5%13%19%8%
2286
16th to endNight
57%49%15%10%2
1964
March1st to 15thNight
53%49%19%10%2
2049
16th to endNight
50%5%9%20%12%1
2112
April1st to 15thNight
56%48%15%12%3
1764
16th to endNight
51%48%18%14%2
1620
May1st to 15thNight
53%6%10%18%9%1
1610
16th to endNight
57%6%11%16%8%
1431
June1st to 15thNight
56%6%12%17%5%1
1260
16th to endNight
51%6%12%20%8%
1260
July1st to 15thNight
41%8%18%22%8%
1190
16th to endNight
50%6%13%20%8%
1426
August1st to 15thNight
45%8%15%22%8%
1608
16th to endNight
37%6%17%29%9%
1719
September1st to 15thNight
43%5%11%25%12%1
1873
16th to endNight
33%313%31%16%
1913
October1st to 15thNight
43%412%25%13%
1950
16th to endNight
52%49%22%9%
2194
November1st to 15thNight
50%5%14%19%9%1
2361
16th to endNight
51%6%13%19%9%
2520
December1st to 15thNight
56%5%10%21%5%
2610
16th to endNight
58%410%18%8%
2880

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
28%18%38%13%1
60
16th to endDay
21%24%32%17%3
130
February1st to 15thDay
22%16%38%19%4
236
16th to endDay
23%23%27%20%4
226
March1st to 15thDay
30%22%31%11%3
270
16th to endDay
28%18%29%15%5%3
288
April1st to 15thDay
34%21%25%14%3
270
16th to endDay
31%16%32%12%5%2
270
May1st to 15thDay
36%16%26%15%41
297
16th to endDay
30%16%31%14%7%
519
June1st to 15thDay
33%15%26%18%5%
495
16th to endDay
26%10%34%20%7%1
495
July1st to 15thDay
21%9%32%24%11%1
475
16th to endDay
22%6%33%27%8%1
367
August1st to 15thDay
22%7%31%25%10%2
313
16th to endDay
19%11%28%25%13%3
332
September1st to 15thDay
19%13%32%24%6%3
315
16th to endDay
18%12%31%21%10%6%
287
October1st to 15thDay
28%13%22%20%9%5%
230
16th to endDay
30%21%27%12%6%
240
November1st to 15thDay
28%15%28%19%7%1
235
16th to endDay
29%20%26%17%5%
240
December1st to 15thDay
35%19%22%19%3
150
16th to endDay
43%21%26%7%
64
January1st to 15thNight
25%19%34%18%2
741
16th to endNight
22%21%35%17%3
768
February1st to 15thNight
21%19%36%17%4
704
16th to endNight
29%19%30%17%2
631
March1st to 15thNight
26%18%34%19%1
720
16th to endNight
24%17%33%19%5%
768
April1st to 15thNight
30%17%32%14%4
614
16th to endNight
29%13%35%17%5%
540
May1st to 15thNight
27%13%32%21%4
540
16th to endNight
25%12%37%19%4
496
June1st to 15thNight
28%9%31%25%5%
360
16th to endNight
23%8%33%28%5%
360
July1st to 15thNight
15%439%30%9%
340
16th to endNight
20%5%32%32%8%
430
August1st to 15thNight
20%5%28%33%12%
539
16th to endNight
15%6%33%31%12%
573
September1st to 15thNight
21%9%34%25%8%
633
16th to endNight
17%10%32%27%10%1
693
October1st to 15thNight
23%10%31%24%8%
660
16th to endNight
28%17%29%18%5%
704
November1st to 15thNight
25%14%32%19%6%
714
16th to endNight
26%18%27%20%6%
750
December1st to 15thNight
31%18%29%16%3
750
16th to endNight
34%19%28%13%3
800
Page generated at 2017-09-25 10:02:26. Version ac04

Copyright 2017 A. Danko


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