Hard Labor Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hard Labor Creek Observatory 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
49%
16308
24%
49201
16%
16264
57%
16264
29%
30145

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
28%
780
23%
2522
10%
776
44%
776
21%
1538
January16th to endNight
28%
832
26%
2678
13%
832
45%
832
22%
1647
February1st to 15thNight
31%
764
25%
2291
11%
760
46%
760
25%
1420
February16th to endNight
28%
683
26%
2049
10%
683
43%
683
25%
1272
March1st to 15thNight
33%
780
26%
2207
12%
780
46%
780
29%
1358
March16th to endNight
38%
792
23%
2178
12%
792
48%
792
31%
1331
April1st to 15thNight
41%
682
25%
1940
16%
682
51%
682
35%
1126
April16th to endNight
49%
540
26%
1680
16%
540
59%
540
32%
972
May1st to 15thNight
50%
540
21%
1620
11%
540
57%
540
30%
989
May16th to endNight
63%
561
22%
1682
15%
561
67%
561
33%
1017
June1st to 15thNight
67%
540
17%
1620
14%
540
68%
540
32%
1009
June16th to endNight
74%
540
17%
1620
15%
540
75%
540
34%
973
July1st to 15thNight
71%
510
13%
1530
11%
510
72%
510
28%
1002
July16th to endNight
76%
564
16%
1595
13%
531
78%
531
29%
1028
August1st to 15thNight
69%
539
18%
1609
17%
536
70%
536
25%
1088
August16th to endNight
65%
584
17%
1916
18%
584
65%
584
22%
1290
September1st to 15thNight
65%
720
19%
1980
18%
720
66%
720
28%
1304
September16th to endNight
60%
717
26%
1980
20%
717
64%
717
32%
1260
October1st to 15thNight
54%
720
30%
2010
23%
720
62%
720
35%
1208
October16th to endNight
54%
768
36%
2304
27%
768
67%
768
39%
1249
November1st to 15thNight
52%
760
31%
2416
25%
760
62%
760
37%
1299
November16th to endNight
43%
780
29%
2535
20%
780
57%
780
30%
1425
December1st to 15thNight
39%
780
24%
2535
14%
780
52%
780
24%
1553
December16th to endNight
33%
832
22%
2704
14%
832
43%
832
20%
1787

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
12%5%245%345%5%7%42%
49641
Night
12%42442445%7%46%
49401
TransparencyDay
38%6%11%20%18%5%
49342
Night
36%5%10%20%20%7%
49204
SeeingDay
16%6%18%23%22%12%
6058
Night
14%7%21%29%22%4
16310

By Month

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
16%7%34323346%45%
1746
16th to endDay
18%5%14322446%46%
1895
February1st to 15thDay
17%6%24424445%43%
1900
16th to endDay
17%5%2432445%5%44%
1710
March1st to 15thDay
15%4245%23337%46%
2080
16th to endDay
16%5%24424446%44%
2173
April1st to 15thDay
11%435%423447%47%
2017
16th to endDay
9%325%5%2445%7%50%
2280
May1st to 15thDay
10%5%25%5%2435%7%45%
2331
16th to endDay
10%425%5%36%6%6%9%40%
2431
June1st to 15thDay
8%415%6%46%7%7%10%35%
2340
16th to endDay
43145%46%7%8%10%44%
2340
July1st to 15thDay
8%5%26%6%46%7%9%10%31%
2340
16th to endDay
6%426%7%47%7%10%12%30%
2465
August1st to 15thDay
10%5%26%6%5%7%6%8%11%29%
2340
16th to endDay
14%6%26%6%45%6%8%9%28%
2270
September1st to 15thDay
13%5%25%6%46%5%6%7%37%
1980
16th to endDay
16%6%24434346%45%
1980
October1st to 15thDay
14%413323335%54%
1950
16th to endDay
10%313322345%59%
1920
November1st to 15thDay
11%423323445%54%
1771
16th to endDay
13%423423346%50%
1755
December1st to 15thDay
16%8%245%23445%42%
1755
16th to endDay
23%8%25%423445%35%
1872
January1st to 15thNight
17%6%24423345%46%
2522
16th to endNight
16%6%24423335%46%
2678
February1st to 15thNight
16%5%14423336%47%
2283
16th to endNight
14%4245%24345%48%
2049
March1st to 15thNight
13%424423345%50%
2207
16th to endNight
12%414324447%49%
2178
April1st to 15thNight
13%413213449%51%
1940
16th to endNight
8%41442445%8%49%
1680
May1st to 15thNight
8%4335%35%45%7%46%
1619
16th to endNight
7%324435%6%6%9%46%
1682
June1st to 15thNight
7%415%5%36%6%6%14%39%
1620
16th to endNight
43235%46%6%8%11%43%
1620
July1st to 15thNight
8%4245%45%6%7%13%36%
1620
16th to endNight
43145%47%8%10%14%35%
1703
August1st to 15thNight
7%425%6%46%6%8%12%34%
1620
16th to endNight
12%5%26%6%45%6%5%10%35%
1916
September1st to 15thNight
9%5%25%5%35%5%6%10%39%
1980
16th to endNight
12%5%15%42345%8%46%
1980
October1st to 15thNight
13%5%23423345%52%
2010
16th to endNight
10%213323335%59%
2304
November1st to 15thNight
11%313212236%57%
2416
16th to endNight
12%423424336%52%
2535
December1st to 15thNight
15%6%24423445%46%
2535
16th to endNight
19%7%35%424446%38%
2704

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
41%38%16%24%4
1747
16th to endDay
38%35%20%21%8%
1895
February1st to 15thDay
42%37%20%21%4
1902
16th to endDay
40%37%21%20%6%
1710
March1st to 15thDay
38%38%20%20%8%
2080
16th to endDay
39%411%22%17%4
2174
April1st to 15thDay
37%39%20%22%6%
2017
16th to endDay
33%5%10%20%24%5%
2280
May1st to 15thDay
37%412%22%18%4
2331
16th to endDay
37%8%12%25%13%2
2435
June1st to 15thDay
38%10%18%22%8%1
2340
16th to endDay
29%9%17%24%15%2
2340
July1st to 15thDay
39%11%19%19%7%2
2201
16th to endDay
39%12%17%22%7%1
2310
August1st to 15thDay
45%9%16%19%8%
2327
16th to endDay
48%9%14%15%11%1
2270
September1st to 15thDay
44%7%10%18%16%2
1980
16th to endDay
39%410%22%18%4
1980
October1st to 15thDay
33%310%21%25%6%
1950
16th to endDay
27%35%17%32%12%
1920
November1st to 15thDay
31%47%17%28%10%
1771
16th to endDay
34%46%17%28%8%
1755
December1st to 15thDay
43%37%20%16%7%
1755
16th to endDay
50%37%18%12%6%
1872
January1st to 15thNight
40%37%18%24%6%
2522
16th to endNight
40%3418%22%10%
2678
February1st to 15thNight
39%25%19%21%10%
2292
16th to endNight
38%45%20%23%7%
2049
March1st to 15thNight
35%48%18%22%10%
2207
16th to endNight
33%5%10%22%22%5%
2178
April1st to 15thNight
30%49%24%22%8%
1940
16th to endNight
31%5%9%21%22%9%
1680
May1st to 15thNight
35%6%12%20%20%4
1620
16th to endNight
30%8%14%27%14%3
1684
June1st to 15thNight
34%7%19%26%10%1
1620
16th to endNight
30%8%19%23%15%2
1620
July1st to 15thNight
36%10%22%20%7%2
1530
16th to endNight
32%13%24%18%9%2
1595
August1st to 15thNight
39%10%15%22%9%
1609
16th to endNight
42%9%17%18%11%
1916
September1st to 15thNight
37%9%13%17%16%4
1980
16th to endNight
37%5%12%20%19%5%
1980
October1st to 15thNight
33%48%19%26%7%
2010
16th to endNight
28%35%16%31%15%
2304
November1st to 15thNight
28%37%18%28%13%
2416
16th to endNight
33%36%16%27%12%
2535
December1st to 15thNight
38%48%20%18%8%
2535
16th to endNight
47%38%17%17%5%
2704

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
20%17%39%20%2
135
16th to endDay
18%26%32%17%4
144
February1st to 15thDay
26%18%37%16%
135
16th to endDay
31%7%39%18%3
120
March1st to 15thDay
17%18%29%26%7%
265
16th to endDay
17%9%29%25%16%1
311
April1st to 15thDay
18%8%26%21%20%4
270
16th to endDay
12%5%24%26%25%5%
270
May1st to 15thDay
14%11%29%17%15%13%
288
16th to endDay
14%5%15%22%25%17%
331
June1st to 15thDay
10%111%23%30%23%
315
16th to endDay
7%113%25%26%24%
315
July1st to 15thDay
8%15%24%33%25%
305
16th to endDay
7%1419%36%30%
326
August1st to 15thDay
18%5%23%29%22%
313
16th to endDay
18%16%18%30%23%
332
September1st to 15thDay
15%212%19%32%17%
315
16th to endDay
18%211%27%28%11%
314
October1st to 15thDay
21%120%25%20%10%
315
16th to endDay
11%7%19%28%28%4
336
November1st to 15thDay
24%6%19%29%17%2
189
16th to endDay
9%11%23%33%17%4
135
December1st to 15thDay
30%11%29%20%7%
135
16th to endDay
36%16%26%16%3
144
January1st to 15thNight
21%16%26%27%7%
780
16th to endNight
20%15%30%27%5%
832
February1st to 15thNight
22%13%26%32%4
764
16th to endNight
17%14%35%28%4
683
March1st to 15thNight
16%12%33%31%6%
780
16th to endNight
14%11%30%28%13%
792
April1st to 15thNight
15%11%29%26%16%
682
16th to endNight
11%7%23%33%22%2
540
May1st to 15thNight
11%326%30%22%4
540
16th to endNight
10%214%31%34%6%
563
June1st to 15thNight
9%210%31%35%9%
540
16th to endNight
5%8%30%43%11%
540
July1st to 15thNight
9%16%24%44%13%
510
16th to endNight
5%6%28%49%10%
564
August1st to 15thNight
10%2426%46%10%
539
16th to endNight
13%16%23%43%10%
584
September1st to 15thNight
12%19%24%42%9%
720
16th to endNight
16%111%29%35%5%
717
October1st to 15thNight
15%320%30%25%5%
720
16th to endNight
11%7%21%30%25%3
768
November1st to 15thNight
11%7%23%31%23%2
760
16th to endNight
15%10%24%30%17%1
780
December1st to 15thNight
18%12%24%30%12%1
780
16th to endNight
23%11%26%30%8%
832
Page generated at 2018-03-22 11:34:22. Version ac04

Copyright 2018 A. Danko


Hard Labor Creek Observatory Clear Sky Chart |Charts Home