Hines Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hines 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
54%
15654
23%
47018
17%
15612
60%
15612
29%
29147

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
35%
719
23%
2327
11%
716
50%
716
24%
1428
January16th to endNight
36%
768
24%
2427
15%
768
46%
768
25%
1498
February1st to 15thNight
39%
703
24%
2108
13%
700
52%
700
29%
1285
February16th to endNight
36%
631
27%
1893
13%
631
50%
631
31%
1165
March1st to 15thNight
43%
720
28%
2022
15%
720
54%
720
34%
1220
March16th to endNight
45%
768
24%
2112
13%
768
53%
768
35%
1266
April1st to 15thNight
49%
718
25%
1976
17%
718
56%
718
37%
1176
April16th to endNight
55%
543
29%
1707
22%
543
64%
543
38%
926
May1st to 15thNight
59%
539
26%
1619
18%
539
66%
539
37%
938
May16th to endNight
69%
561
22%
1682
18%
561
72%
561
35%
999
June1st to 15thNight
71%
540
13%
1620
12%
540
71%
540
26%
1072
June16th to endNight
72%
540
14%
1620
13%
540
72%
540
24%
1107
July1st to 15thNight
73%
510
12%
1530
10%
510
73%
510
24%
1035
July16th to endNight
76%
564
12%
1595
13%
531
75%
531
25%
1087
August1st to 15thNight
71%
539
12%
1653
13%
536
71%
536
21%
1165
August16th to endNight
64%
606
14%
1943
16%
606
64%
606
19%
1374
September1st to 15thNight
64%
720
15%
1980
13%
720
64%
720
22%
1415
September16th to endNight
59%
693
19%
1914
16%
693
61%
693
25%
1305
October1st to 15thNight
61%
660
31%
1829
27%
660
66%
660
38%
1079
October16th to endNight
58%
704
32%
2112
29%
704
65%
704
39%
1171
November1st to 15thNight
56%
700
31%
2173
27%
700
64%
700
38%
1171
November16th to endNight
46%
720
28%
2340
21%
720
58%
720
34%
1285
December1st to 15thNight
43%
720
24%
2340
18%
720
52%
720
29%
1376
December16th to endNight
41%
768
23%
2496
19%
768
48%
768
23%
1604

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
10%5%25%5%35%5%5%8%41%
47898
Night
9%5%25%5%3445%8%45%
47222
TransparencyDay
39%7%11%17%16%7%
47599
Night
35%6%11%17%17%9%
47025
SeeingDay
12%314%23%25%20%
5531
Night
11%420%32%25%4
15659

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
12%5%35%5%2435%7%43%
1611
16th to endDay
14%5%2442345%6%47%
1794
February1st to 15thDay
13%5%25%4235%46%45%
1750
16th to endDay
13%6%25%323335%49%
1580
March1st to 15thDay
10%5%25%5%23447%48%
1936
16th to endDay
11%5%35%43445%6%46%
2111
April1st to 15thDay
10%4235%35%447%47%
1978
16th to endDay
7%323434448%53%
2256
May1st to 15thDay
7%4245%35%5%5%8%48%
2331
16th to endDay
6%5%26%6%46%5%6%8%41%
2431
June1st to 15thDay
8%5%26%6%46%7%7%11%32%
2340
16th to endDay
5%426%6%5%7%8%8%10%34%
2340
July1st to 15thDay
7%5%36%7%5%8%9%8%9%27%
2340
16th to endDay
8%427%7%5%9%9%8%9%27%
2465
August1st to 15thDay
9%7%38%8%6%8%7%8%11%20%
2292
16th to endDay
12%7%36%7%5%7%7%7%9%26%
2247
September1st to 15thDay
9%7%37%7%46%6%7%9%31%
1980
16th to endDay
13%6%27%5%245%6%7%36%
1905
October1st to 15thDay
13%5%14423335%52%
1801
16th to endDay
8%413313336%58%
1760
November1st to 15thDay
7%42442325%6%56%
1682
16th to endDay
12%5%23422446%52%
1620
December1st to 15thDay
14%5%25%5%33346%44%
1620
16th to endDay
17%8%36%42435%6%37%
1728
January1st to 15thNight
11%6%35%5%35%446%44%
2327
16th to endNight
15%5%35%433345%45%
2427
February1st to 15thNight
13%6%24323446%48%
2103
16th to endNight
12%5%245%24446%47%
1893
March1st to 15thNight
9%4245%23347%51%
2022
16th to endNight
10%5%1432334454%
2112
April1st to 15thNight
10%32442435%6%52%
1976
16th to endNight
7%2134245%6%8%54%
1707
May1st to 15thNight
6%3145%2445%9%51%
1619
16th to endNight
5%325%5%25%47%8%49%
1682
June1st to 15thNight
7%425%5%47%7%7%13%34%
1620
16th to endNight
4436%6%47%7%8%11%34%
1620
July1st to 15thNight
6%5%346%37%7%10%12%33%
1620
16th to endNight
5%436%7%5%6%7%9%12%33%
1703
August1st to 15thNight
7%425%7%45%8%9%14%31%
1664
16th to endNight
8%5%27%6%47%7%8%10%30%
1943
September1st to 15thNight
9%6%36%5%5%5%7%5%10%33%
1980
16th to endNight
9%6%27%6%35%5%6%9%36%
1914
October1st to 15thNight
11%5%23313347%52%
1829
16th to endNight
9%413323345%56%
2112
November1st to 15thNight
8%424323346%57%
2173
16th to endNight
10%423314346%54%
2340
December1st to 15thNight
12%435%42345%7%46%
2340
16th to endNight
14%7%36%5%24347%40%
2496

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
40%48%15%19%10%
1612
16th to endDay
38%36%17%21%11%
1794
February1st to 15thDay
39%46%14%23%11%
1752
16th to endDay
38%35%16%24%11%
1580
March1st to 15thDay
35%5%8%18%22%9%
1936
16th to endDay
37%5%10%16%22%7%
2112
April1st to 15thDay
36%5%7%19%21%9%
1978
16th to endDay
30%5%9%23%23%8%
2256
May1st to 15thDay
33%6%10%21%21%7%
2331
16th to endDay
37%6%15%22%14%3
2435
June1st to 15thDay
41%11%16%19%10%
2340
16th to endDay
39%11%18%17%11%1
2340
July1st to 15thDay
44%14%19%15%5%
2201
16th to endDay
45%13%18%17%4
2310
August1st to 15thDay
52%12%17%13%3
2279
16th to endDay
49%13%14%13%7%1
2247
September1st to 15thDay
45%12%13%12%12%2
1980
16th to endDay
43%8%11%15%16%4
1905
October1st to 15thDay
34%38%18%22%12%
1801
16th to endDay
28%35%15%29%16%
1760
November1st to 15thDay
29%37%18%25%16%
1682
16th to endDay
33%37%16%23%15%
1620
December1st to 15thDay
40%48%18%17%9%
1620
16th to endDay
47%39%19%12%8%
1728
January1st to 15thNight
40%47%15%22%10%
2327
16th to endNight
40%36%13%24%11%
2427
February1st to 15thNight
37%36%14%22%15%
2112
16th to endNight
36%46%16%20%16%
1893
March1st to 15thNight
32%5%8%20%21%11%
2022
16th to endNight
32%310%17%24%10%
2112
April1st to 15thNight
31%48%19%22%12%
1976
16th to endNight
27%5%12%21%22%10%
1707
May1st to 15thNight
29%6%13%19%21%10%
1620
16th to endNight
30%7%15%24%16%5%
1684
June1st to 15thNight
37%10%21%18%10%1
1620
16th to endNight
38%13%17%19%9%2
1620
July1st to 15thNight
36%14%23%18%6%1
1530
16th to endNight
37%12%23%19%5%
1595
August1st to 15thNight
38%17%22%16%5%
1653
16th to endNight
43%13%17%15%7%2
1943
September1st to 15thNight
43%11%14%14%13%2
1980
16th to endNight
41%9%14%14%15%5%
1914
October1st to 15thNight
31%49%21%19%14%
1829
16th to endNight
29%37%13%25%19%
2112
November1st to 15thNight
28%37%17%25%17%
2173
16th to endNight
30%38%16%22%17%
2340
December1st to 15thNight
36%312%17%20%8%
2340
16th to endNight
43%47%21%14%8%
2496

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%13%31%20%10%8%
90
16th to endDay
15%15%41%16%7%3
96
February1st to 15thDay
10%24%31%22%12%
90
16th to endDay
11%11%34%34%8%
81
March1st to 15thDay
11%7%31%35%12%1
226
16th to endDay
13%5%25%33%21%1
288
April1st to 15thDay
14%9%21%28%22%3
270
16th to endDay
10%218%30%25%11%
270
May1st to 15thDay
7%6%20%31%20%13%
288
16th to endDay
7%19%25%29%25%
331
June1st to 15thDay
11%9%16%33%29%
315
16th to endDay
10%314%32%38%
315
July1st to 15thDay
8%214%29%45%
305
16th to endDay
8%39%29%47%
326
August1st to 15thDay
12%416%31%34%
313
16th to endDay
13%1314%25%42%
332
September1st to 15thDay
16%17%18%30%25%
315
16th to endDay
16%8%21%35%17%
287
October1st to 15thDay
14%115%31%29%7%
255
16th to endDay
9%418%30%30%6%
272
November1st to 15thDay
14%225%29%21%7%
190
16th to endDay
310%31%28%15%11%
90
December1st to 15thDay
18%8%28%23%12%7%
90
16th to endDay
26%8%18%33%10%3
96
January1st to 15thNight
15%10%33%31%8%1
720
16th to endNight
17%9%32%32%7%
768
February1st to 15thNight
14%10%29%35%9%
704
16th to endNight
15%7%36%34%6%
631
March1st to 15thNight
11%8%31%37%10%
720
16th to endNight
12%7%29%32%16%1
768
April1st to 15thNight
12%6%28%37%15%
718
16th to endNight
7%328%34%23%1
543
May1st to 15thNight
7%223%37%24%3
540
16th to endNight
7%113%35%36%5%
563
June1st to 15thNight
9%17%33%38%9%
540
16th to endNight
7%430%44%12%
540
July1st to 15thNight
9%424%44%16%
510
16th to endNight
6%222%54%13%
564
August1st to 15thNight
9%420%55%10%
539
16th to endNight
11%16%21%44%15%
606
September1st to 15thNight
11%18%27%38%12%
720
16th to endNight
12%110%33%37%2
693
October1st to 15thNight
14%115%35%30%2
660
16th to endNight
10%322%34%27%2
704
November1st to 15thNight
10%5%20%37%23%2
700
16th to endNight
10%7%31%30%18%1
720
December1st to 15thNight
15%5%29%31%15%1
720
16th to endNight
18%7%24%34%14%
768
Page generated at 2017-09-25 09:02:24. Version ac04

Copyright 2017 A. Danko


Hines Observatory Clear Sky Chart | Charts Home