Indian Hill Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Indian Hill Observatory clear sky chart from 2005-11-06 to 2024-01-27.

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
30%
23325
13%
75100
9%
23273
35%
23273
15%
55022

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 10thNight
8%
758
8%
2459
2%
757
14%
757
6%
2083
January11th to 20thNight
11%
760
5%
2470
3%
760
14%
760
6%
2092
January21st to endNight
13%
820
6%
2664
3%
820
17%
820
6%
2270
February1st to 10thNight
12%
720
6%
2340
2%
720
16%
720
7%
1947
February11th to 20thNight
12%
702
8%
2256
3%
700
18%
700
8%
1833
February21st to endNight
10%
592
10%
1776
1%
592
19%
592
9%
1431
March1st to 10thNight
19%
720
13%
2011
7%
720
25%
720
14%
1514
March11th to 20thNight
23%
720
16%
1980
8%
720
30%
720
16%
1460
March21st to endNight
22%
792
15%
2178
8%
792
29%
792
16%
1641
April1st to 10thNight
22%
720
11%
1922
5%
720
27%
720
18%
1427
April11th to 20thNight
25%
603
17%
1667
7%
603
32%
603
19%
1176
April21st to endNight
27%
540
16%
1620
6%
540
35%
540
20%
1128
May1st to 10thNight
33%
540
11%
1620
6%
540
37%
540
17%
1154
May11th to 20thNight
38%
531
16%
1592
11%
531
42%
531
22%
1085
May21st to endNight
50%
471
15%
1634
13%
471
56%
471
28%
971
June1st to 10thNight
44%
360
15%
1440
15%
360
52%
360
20%
866
June11th to 20thNight
49%
360
17%
1440
18%
360
58%
360
21%
865
June21st to endNight
50%
360
17%
1440
19%
360
58%
360
22%
842
July1st to 10thNight
62%
439
16%
1489
18%
439
65%
439
30%
865
July11th to 20thNight
58%
522
17%
1566
15%
522
61%
522
33%
945
July21st to endNight
60%
591
17%
1672
14%
558
62%
558
29%
1046
August1st to 10thNight
62%
537
18%
1600
15%
534
63%
534
32%
957
August11th to 20thNight
61%
534
20%
1598
15%
534
65%
534
29%
996
August21st to endNight
56%
632
21%
1820
14%
632
59%
632
32%
1115
September1st to 10thNight
55%
720
19%
1854
12%
720
57%
720
30%
1229
September11th to 20thNight
59%
720
24%
1980
18%
720
61%
720
34%
1225
September21st to endNight
42%
720
19%
1980
15%
720
46%
720
25%
1380
October1st to 10thNight
41%
720
18%
2120
15%
720
45%
720
25%
1385
October11th to 20thNight
28%
720
14%
2160
9%
720
36%
720
17%
1532
October21st to endNight
21%
792
15%
2376
9%
792
29%
792
13%
1807
November1st to 10thNight
30%
740
16%
2388
13%
740
37%
740
19%
1613
November11th to 20thNight
18%
760
13%
2556
7%
760
26%
760
11%
1913
November21st to endNight
15%
760
10%
2660
6%
760
21%
760
9%
2090
December1st to 10thNight
12%
760
4%
2660
3%
760
15%
760
6%
2239
December11th to 20thNight
11%
759
6%
3275
2%
759
17%
759
5%
2654
December21st to endNight
10%
830
3%
4837
1%
817
15%
817
3%
4246

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
15%11%5%8%6%35%5%5%7%30%
74723
Night
15%12%5%8%6%35%45%6%30%
75327
TransparencyDay
53%7%12%17%10%1
74444
Night
54%7%11%17%10%1
75125
SeeingDay
22%17%29%19%10%3
13490
Night
22%15%28%24%10%1
23337

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 10thDay
17%17%9%13%8%345%4416%
1706
11th to 20thDay
16%20%9%14%7%44445%14%
1710
21st to endDay
15%19%11%17%9%4444411%
1836
February1st to 10thDay
16%18%9%13%9%4433417%
1620
11th to 20thDay
14%15%9%13%9%5%5%445%17%
1591
21st to endDay
17%17%6%13%6%25%6%45%21%
1480
March1st to 10thDay
17%13%7%9%6%335%6%6%25%
1948
11th to 20thDay
17%14%5%9%6%34436%29%
1980
21st to endDay
20%13%6%8%5%33445%28%
2178
April1st to 10thDay
14%13%6%7%5%3445%6%32%
2038
11th to 20thDay
19%12%37%6%35%445%32%
2258
21st to endDay
20%12%47%5%34345%34%
2340
May1st to 10thDay
16%9%5%7%6%46%6%5%6%30%
2340
11th to 20thDay
19%8%36%5%35%46%7%34%
2301
21st to endDay
11%6%36%6%45%6%7%8%39%
2640
June1st to 10thDay
14%6%36%6%36%6%6%8%36%
2520
11th to 20thDay
13%7%36%6%345%6%8%38%
2520
21st to endDay
12%5%35%5%35%5%6%10%40%
2520
July1st to 10thDay
9%5%35%6%35%5%6%9%42%
2421
11th to 20thDay
11%6%36%6%35%6%6%10%39%
2340
21st to endDay
10%5%26%5%46%6%7%10%39%
2547
August1st to 10thDay
8%6%36%6%46%6%6%10%39%
2327
11th to 20thDay
10%6%27%7%5%7%6%9%8%34%
2303
21st to endDay
12%6%35%6%45%6%7%10%37%
2517
September1st to 10thDay
16%6%26%5%35%6%5%7%39%
2102
11th to 20thDay
11%6%26%6%35%6%6%8%41%
1980
21st to endDay
18%8%36%4345%5%7%37%
1980
October1st to 10thDay
17%6%37%6%35%5%6%6%36%
1838
11th to 20thDay
22%9%38%6%45%446%30%
1800
21st to endDay
23%12%38%6%45%45%6%24%
1980
November1st to 10thDay
12%11%5%8%6%35%5%5%7%34%
1688
11th to 20thDay
16%18%49%5%34447%24%
1620
21st to endDay
18%18%8%9%8%45%35%6%17%
1520
December1st to 10thDay
15%22%11%12%7%4444414%
1520
11th to 20thDay
16%19%8%15%6%345%5%5%14%
1910
21st to endDay
23%25%8%11%7%334339%
2804
January1st to 10thNight
17%18%9%13%8%45%445%15%
2459
11th to 20thNight
18%17%9%14%8%3433415%
2470
21st to endNight
15%19%8%13%10%45%33415%
2664
February1st to 10thNight
19%16%6%12%9%45%445%17%
2340
11th to 20thNight
16%15%6%13%8%46%5%45%19%
2254
21st to endNight
19%13%6%11%8%45%34423%
1776
March1st to 10thNight
15%12%6%9%7%445%5%5%29%
2011
11th to 20thNight
17%11%48%6%34446%32%
1980
21st to endNight
17%12%5%8%6%345%5%430%
2178
April1st to 10thNight
16%12%6%7%5%44446%32%
1922
11th to 20thNight
15%11%36%5%35%5%5%7%35%
1667
21st to endNight
15%10%37%7%35%5%5%6%35%
1620
May1st to 10thNight
17%9%37%5%36%6%5%7%32%
1620
11th to 20thNight
13%9%46%5%45%5%6%8%36%
1592
21st to endNight
12%415%5%35%47%11%43%
1633
June1st to 10thNight
9%7%27%5%45%6%5%8%42%
1440
11th to 20thNight
9%5%37%7%36%5%5%9%42%
1440
21st to endNight
10%5%36%435%5%7%10%42%
1440
July1st to 10thNight
7%435%6%346%5%7%51%
1534
11th to 20thNight
8%5%246%345%6%11%46%
1620
21st to endNight
7%5%35%5%46%6%6%9%44%
1771
August1st to 10thNight
6%5%16%6%346%7%8%47%
1611
11th to 20thNight
8%5%26%6%45%5%6%8%44%
1598
21st to endNight
9%5%35%5%35%5%6%10%45%
1820
September1st to 10thNight
14%6%245%346%6%8%44%
1854
11th to 20thNight
11%425%5%3346%7%50%
1980
21st to endNight
15%7%36%6%35%45%6%39%
1980
October1st to 10thNight
14%7%26%4345%5%8%41%
2120
11th to 20thNight
17%9%37%7%345%5%8%32%
2160
21st to endNight
25%10%36%6%35%5%5%5%27%
2376
November1st to 10thNight
14%9%47%7%3445%6%36%
2388
11th to 20thNight
15%15%5%10%7%35%45%6%25%
2556
21st to endNight
18%17%6%9%7%35%5%5%6%21%
2660
December1st to 10thNight
19%19%9%9%7%4444416%
2660
11th to 20thNight
16%19%8%13%6%45%345%17%
3285
21st to endNight
23%22%8%10%7%4444410%
4848

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 10thDay
72%6%11%8%4
1707
11th to 20thDay
74%5%11%8%2
1710
21st to endDay
78%5%7%8%3
1836
February1st to 10thDay
72%5%8%10%4
1620
11th to 20thDay
70%6%9%10%6%
1600
21st to endDay
64%7%10%11%6%2
1480
March1st to 10thDay
58%6%13%18%5%
1948
11th to 20thDay
58%6%10%15%9%2
1980
21st to endDay
59%48%18%9%2
2178
April1st to 10thDay
51%7%13%16%13%1
2038
11th to 20thDay
53%6%11%16%12%2
2258
21st to endDay
53%5%10%19%10%2
2340
May1st to 10thDay
52%9%10%19%9%2
2340
11th to 20thDay
49%8%11%17%13%2
2305
21st to endDay
41%10%14%22%12%2
2640
June1st to 10thDay
44%8%12%23%12%1
2520
11th to 20thDay
41%9%14%21%13%1
2520
21st to endDay
39%7%13%25%15%1
2520
July1st to 10thDay
38%8%12%24%16%2
2356
11th to 20thDay
38%8%14%24%14%1
2271
21st to endDay
37%10%15%22%15%2
2405
August1st to 10thDay
37%10%15%25%13%
2314
11th to 20thDay
42%12%14%20%10%2
2303
21st to endDay
39%9%15%20%14%2
2517
September1st to 10thDay
42%8%14%20%13%3
2102
11th to 20thDay
39%8%14%23%15%1
1980
21st to endDay
46%7%11%24%12%1
1980
October1st to 10thDay
45%8%14%19%12%1
1838
11th to 20thDay
54%7%11%19%8%1
1800
21st to endDay
61%6%12%13%8%1
1980
November1st to 10thDay
48%7%13%18%13%1
1688
11th to 20thDay
60%5%12%14%7%3
1620
21st to endDay
67%7%8%13%5%
1520
December1st to 10thDay
74%6%8%10%2
1520
11th to 20thDay
71%8%9%10%2
1906
21st to endDay
80%6%7%6%1
2804
January1st to 10thNight
71%6%8%10%4
2459
11th to 20thNight
73%410%9%21
2470
21st to endNight
73%5%8%10%31
2664
February1st to 10thNight
70%6%10%11%3
2340
11th to 20thNight
67%6%9%13%5%
2256
21st to endNight
65%6%8%14%7%1
1776
March1st to 10thNight
55%7%11%19%8%
2011
11th to 20thNight
53%6%11%18%11%2
1980
21st to endNight
56%5%7%18%11%2
2178
April1st to 10thNight
53%6%11%17%11%2
1922
11th to 20thNight
49%6%11%19%13%2
1667
21st to endNight
48%6%13%18%12%3
1620
May1st to 10thNight
50%7%12%16%12%3
1620
11th to 20thNight
46%6%11%18%14%4
1593
21st to endNight
35%8%16%25%15%1
1634
June1st to 10thNight
40%8%12%24%15%2
1440
11th to 20thNight
38%8%13%21%18%2
1440
21st to endNight
35%10%12%25%17%1
1440
July1st to 10thNight
33%7%12%25%19%4
1489
11th to 20thNight
31%9%14%23%20%3
1566
21st to endNight
34%10%14%22%17%3
1672
August1st to 10thNight
31%9%15%29%16%1
1600
11th to 20thNight
37%7%16%26%13%1
1598
21st to endNight
33%8%13%26%17%3
1820
September1st to 10thNight
37%8%13%24%15%3
1854
11th to 20thNight
32%8%15%24%19%2
1980
21st to endNight
44%7%11%21%16%1
1980
October1st to 10thNight
40%8%14%20%17%1
2120
11th to 20thNight
49%8%12%20%10%1
2160
21st to endNight
56%7%11%15%9%1
2376
November1st to 10thNight
46%8%14%19%11%3
2388
11th to 20thNight
59%6%11%15%6%3
2556
21st to endNight
64%6%12%14%4
2660
December1st to 10thNight
71%7%10%8%4
2660
11th to 20thNight
68%7%12%11%2
3288
21st to endNight
76%8%9%6%1
4848

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 10thDay
34%26%29%7%3
270
11th to 20thDay
30%33%26%8%2
270
21st to endDay
29%36%26%7%2
282
February1st to 10thDay
38%23%34%5%
240
11th to 20thDay
35%34%26%5%
240
21st to endDay
37%32%28%4
198
March1st to 10thDay
29%24%31%13%3
388
11th to 20thDay
28%23%31%14%31
420
21st to endDay
36%21%26%14%4
462
April1st to 10thDay
26%27%26%14%6%1
420
11th to 20thDay
30%19%26%15%9%1
412
21st to endDay
30%20%30%15%5%1
420
May1st to 10thDay
26%22%28%17%42
423
11th to 20thDay
22%15%31%22%8%2
447
21st to endDay
14%12%32%23%15%5%
485
June1st to 10thDay
16%12%37%23%9%2
450
11th to 20thDay
15%13%31%25%14%2
450
21st to endDay
14%11%36%26%10%3
450
July1st to 10thDay
10%8%23%29%23%7%
445
11th to 20thDay
14%9%29%25%18%6%
444
21st to endDay
10%7%33%29%15%6%
488
August1st to 10thDay
8%9%27%28%21%8%
446
11th to 20thDay
11%10%28%26%15%9%
439
21st to endDay
11%9%27%26%18%8%
495
September1st to 10thDay
16%8%24%27%20%5%
450
11th to 20thDay
10%8%24%28%21%10%
450
21st to endDay
20%14%27%20%13%5%
450
October1st to 10thDay
16%14%30%21%16%4
450
11th to 20thDay
25%22%32%16%41
450
21st to endDay
34%18%29%15%3
495
November1st to 10thDay
24%23%26%17%8%2
286
11th to 20thDay
37%20%26%13%4
228
21st to endDay
27%25%39%9%
180
December1st to 10thDay
28%29%28%11%31
180
11th to 20thDay
29%28%33%8%1
180
21st to endDay
35%29%28%7%1
207
January1st to 10thNight
29%26%32%11%3
760
11th to 20thNight
32%23%29%13%2
760
21st to endNight
25%24%32%17%2
820
February1st to 10thNight
32%21%30%16%1
720
11th to 20thNight
29%23%32%15%2
703
21st to endNight
31%22%32%13%1
592
March1st to 10thNight
24%21%32%20%3
720
11th to 20thNight
26%22%27%20%5%1
720
21st to endNight
25%17%30%22%5%1
792
April1st to 10thNight
25%15%34%22%5%
720
11th to 20thNight
22%16%34%20%6%1
603
21st to endNight
18%13%37%26%6%
540
May1st to 10thNight
22%11%29%29%10%1
540
11th to 20thNight
18%10%28%33%10%2
531
21st to endNight
12%5%28%34%19%1
473
June1st to 10thNight
11%433%38%13%1
360
11th to 20thNight
11%8%26%39%16%1
360
21st to endNight
11%9%24%40%16%
360
July1st to 10thNight
6%419%39%26%5%
439
11th to 20thNight
10%422%36%24%4
522
21st to endNight
9%5%20%41%24%2
591
August1st to 10thNight
9%417%41%26%3
537
11th to 20thNight
9%5%15%39%28%3
534
21st to endNight
11%6%22%30%28%3
632
September1st to 10thNight
15%7%17%32%25%4
720
11th to 20thNight
13%417%37%25%5%
720
21st to endNight
18%9%24%28%17%4
720
October1st to 10thNight
18%11%26%25%18%3
720
11th to 20thNight
22%16%29%25%7%1
720
21st to endNight
30%16%30%20%4
792
November1st to 10thNight
20%17%29%26%8%1
740
11th to 20thNight
27%21%29%17%5%1
760
21st to endNight
30%22%29%15%4
760
December1st to 10thNight
33%22%29%13%4
760
11th to 20thNight
28%25%30%14%2
760
21st to endNight
32%21%31%14%1
836
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