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 2019-07-16.

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%
18053
23%
54240
17%
18011
60%
18011
29%
33594

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%
839
24%
2717
13%
836
51%
836
25%
1647
January16th to endNight
36%
896
25%
2831
15%
896
47%
896
26%
1734
February1st to 15thNight
39%
823
24%
2468
13%
820
50%
820
29%
1526
February16th to endNight
39%
735
27%
2205
15%
735
51%
735
31%
1355
March1st to 15thNight
42%
840
28%
2360
15%
840
52%
840
34%
1423
March16th to endNight
44%
896
23%
2464
12%
896
52%
896
35%
1483
April1st to 15thNight
49%
838
25%
2306
17%
838
56%
838
35%
1391
April16th to endNight
57%
628
30%
1970
22%
628
66%
628
40%
1045
May1st to 15thNight
61%
629
27%
1889
19%
629
67%
629
38%
1083
May16th to endNight
68%
657
21%
1970
17%
657
71%
657
34%
1188
June1st to 15thNight
71%
630
14%
1890
12%
630
72%
630
26%
1254
June16th to endNight
74%
630
13%
1890
11%
630
74%
630
26%
1276
July1st to 15thNight
74%
600
12%
1800
10%
600
74%
600
24%
1225
July16th to endNight
75%
615
12%
1748
12%
582
75%
582
25%
1191
August1st to 15thNight
72%
575
13%
1762
14%
572
72%
572
22%
1236
August16th to endNight
64%
657
13%
2106
15%
657
64%
657
19%
1493
September1st to 15thNight
65%
780
14%
2145
13%
780
65%
780
23%
1523
September16th to endNight
62%
777
20%
2145
18%
777
64%
777
28%
1418
October1st to 15thNight
61%
780
31%
2161
26%
780
66%
780
38%
1276
October16th to endNight
57%
832
32%
2496
28%
832
65%
832
39%
1384
November1st to 15thNight
55%
820
29%
2545
26%
820
63%
820
35%
1416
November16th to endNight
47%
840
27%
2730
21%
840
59%
840
34%
1499
December1st to 15thNight
41%
840
24%
2730
17%
840
52%
840
28%
1638
December16th to endNight
41%
896
22%
2912
18%
896
48%
896
22%
1890

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%6%8%41%
55062
Night
9%5%25%5%345%5%8%45%
54444
TransparencyDay
39%7%11%17%16%6%
54763
Night
35%7%12%18%17%9%
54247
SeeingDay
12%416%23%24%19%
7915
Night
11%421%32%25%4
18058

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
11%6%36%5%2435%7%44%
1881
16th to endDay
13%5%2442445%6%47%
2094
February1st to 15thDay
14%6%25%5%245%5%6%41%
2050
16th to endDay
13%6%25%424435%46%
1840
March1st to 15thDay
9%5%25%5%23447%48%
2258
16th to endDay
10%5%35%43445%6%46%
2463
April1st to 15thDay
11%5%235%35%5%47%46%
2308
16th to endDay
7%323434447%54%
2599
May1st to 15thDay
7%3235%245%5%8%49%
2721
16th to endDay
6%5%25%6%46%5%6%8%41%
2847
June1st to 15thDay
8%5%26%6%47%7%7%11%32%
2730
16th to endDay
5%425%6%5%7%8%8%11%34%
2730
July1st to 15thDay
7%5%36%7%5%8%9%8%10%27%
2730
16th to endDay
8%5%27%7%5%9%9%8%9%27%
2676
August1st to 15thDay
9%7%37%8%5%8%7%8%11%21%
2436
16th to endDay
12%7%26%8%5%7%7%7%9%25%
2435
September1st to 15thDay
9%6%37%7%46%6%7%9%31%
2145
16th to endDay
12%5%26%5%345%6%8%38%
2145
October1st to 15thDay
12%5%14423446%51%
2128
16th to endDay
8%313313346%59%
2080
November1st to 15thDay
8%5%2442335%6%53%
1970
16th to endDay
11%5%23322446%51%
1890
December1st to 15thDay
15%6%25%5%33346%43%
1890
16th to endDay
17%8%36%424346%37%
2016
January1st to 15thNight
11%5%35%5%25%446%45%
2717
16th to endNight
14%5%34433345%45%
2831
February1st to 15thNight
13%6%24423447%46%
2463
16th to endNight
11%5%245%34446%47%
2205
March1st to 15thNight
9%4145%23446%51%
2360
16th to endNight
9%5%14324445%53%
2464
April1st to 15thNight
10%42442445%6%51%
2306
16th to endNight
6%21342446%8%56%
1970
May1st to 15thNight
6%3145%2446%9%52%
1889
16th to endNight
6%325%5%25%46%8%47%
1970
June1st to 15thNight
6%426%5%37%7%7%12%35%
1890
16th to endNight
4425%6%47%7%8%11%35%
1890
July1st to 15thNight
5%5%346%36%7%9%13%32%
1890
16th to endNight
5%435%6%5%6%7%9%12%33%
1856
August1st to 15thNight
7%425%7%45%8%8%13%32%
1773
16th to endNight
8%6%27%6%47%7%8%10%30%
2106
September1st to 15thNight
8%6%36%5%5%5%7%6%10%33%
2145
16th to endNight
8%5%26%6%35%5%6%9%40%
2145
October1st to 15thNight
10%424313447%52%
2161
16th to endNight
8%414423345%57%
2496
November1st to 15thNight
9%5%24423346%54%
2545
16th to endNight
10%423314346%54%
2730
December1st to 15thNight
14%5%35%423446%46%
2730
16th to endNight
14%7%26%5%24347%40%
2912

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
39%38%17%20%9%
1882
16th to endDay
37%36%18%21%11%
2094
February1st to 15thDay
41%5%8%14%21%9%
2052
16th to endDay
39%45%16%23%9%
1840
March1st to 15thDay
34%5%9%17%22%11%
2258
16th to endDay
37%5%10%16%21%8%
2464
April1st to 15thDay
37%5%8%20%19%8%
2308
16th to endDay
29%5%8%23%23%9%
2599
May1st to 15thDay
31%6%10%20%23%7%
2721
16th to endDay
37%7%13%21%15%3
2851
June1st to 15thDay
42%11%15%18%11%
2730
16th to endDay
37%12%20%18%10%1
2730
July1st to 15thDay
43%14%21%14%5%
2591
16th to endDay
45%13%18%16%4
2521
August1st to 15thDay
51%12%18%13%3
2423
16th to endDay
50%13%14%13%6%
2435
September1st to 15thDay
46%11%14%13%11%2
2145
16th to endDay
40%8%12%17%16%4
2145
October1st to 15thDay
34%410%18%21%10%
2128
16th to endDay
26%36%16%29%16%
2080
November1st to 15thDay
31%38%19%23%13%
1970
16th to endDay
32%47%17%24%13%
1890
December1st to 15thDay
41%49%17%17%9%
1890
16th to endDay
47%38%20%11%7%
2016
January1st to 15thNight
39%47%17%22%9%
2717
16th to endNight
40%35%14%24%11%
2831
February1st to 15thNight
38%38%14%20%13%
2472
16th to endNight
35%5%6%17%19%14%
2205
March1st to 15thNight
32%5%9%19%20%12%
2360
16th to endNight
33%410%17%23%11%
2464
April1st to 15thNight
32%5%8%20%22%11%
2306
16th to endNight
25%5%11%22%23%11%
1970
May1st to 15thNight
28%6%13%20%21%10%
1890
16th to endNight
31%7%14%22%17%6%
1972
June1st to 15thNight
36%11%20%18%10%1
1890
16th to endNight
36%13%20%19%8%1
1890
July1st to 15thNight
35%15%24%16%5%1
1800
16th to endNight
37%13%24%18%5%
1748
August1st to 15thNight
37%16%23%16%4
1762
16th to endNight
43%13%17%16%6%1
2106
September1st to 15thNight
42%12%17%13%12%2
2145
16th to endNight
38%9%15%16%15%5%
2145
October1st to 15thNight
30%5%10%22%18%12%
2161
16th to endNight
29%37%13%26%18%
2496
November1st to 15thNight
30%47%17%24%15%
2545
16th to endNight
30%48%17%22%16%
2730
December1st to 15thNight
38%312%16%20%8%
2730
16th to endNight
44%47%20%14%8%
2912

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
13%12%36%23%8%5%
180
16th to endDay
15%14%38%20%8%2
192
February1st to 15thDay
17%17%32%21%11%
180
16th to endDay
13%11%35%28%9%
159
March1st to 15thDay
12%8%36%31%10%
338
16th to endDay
13%6%30%29%17%1
416
April1st to 15thDay
16%8%24%27%21%2
390
16th to endDay
9%418%30%26%11%
379
May1st to 15thDay
8%5%17%28%25%14%
408
16th to endDay
9%18%23%26%30%
459
June1st to 15thDay
11%9%18%31%28%
435
16th to endDay
8%317%30%40%
435
July1st to 15thDay
8%213%29%46%
425
16th to endDay
8%410%30%45%
391
August1st to 15thDay
13%415%30%36%
358
16th to endDay
14%1314%25%40%
396
September1st to 15thDay
14%16%19%31%26%
375
16th to endDay
13%6%21%35%22%
374
October1st to 15thDay
12%117%28%27%13%
375
16th to endDay
9%6%18%32%26%6%
400
November1st to 15thDay
17%323%27%22%6%
298
16th to endDay
7%9%25%30%20%7%
180
December1st to 15thDay
23%7%28%23%12%3
180
16th to endDay
24%6%28%29%9%1
192
January1st to 15thNight
14%10%34%31%8%1
840
16th to endNight
16%9%32%32%8%
896
February1st to 15thNight
15%9%30%34%9%
824
16th to endNight
14%7%35%36%5%
735
March1st to 15thNight
11%7%33%36%10%
840
16th to endNight
11%8%31%32%15%
896
April1st to 15thNight
11%6%28%37%15%
838
16th to endNight
7%426%35%24%1
628
May1st to 15thNight
6%222%39%25%3
630
16th to endNight
9%12%33%37%6%
659
June1st to 15thNight
8%6%34%38%9%
630
16th to endNight
6%329%44%13%
630
July1st to 15thNight
9%423%45%18%
600
16th to endNight
7%320%53%14%
615
August1st to 15thNight
9%419%54%12%
575
16th to endNight
10%16%22%43%15%
657
September1st to 15thNight
10%18%27%40%12%
780
16th to endNight
11%110%32%40%3
777
October1st to 15thNight
13%116%33%30%4
780
16th to endNight
9%323%33%26%2
832
November1st to 15thNight
12%420%37%22%1
820
16th to endNight
11%6%30%31%18%1
840
December1st to 15thNight
17%5%30%30%15%1
840
16th to endNight
19%7%24%33%14%
896
Page generated at 2019-07-17 08:53:10. Version ac04

Copyright 2019 A. Danko


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