Malhotra Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Malhotra Observatory clear sky chart from 2005-11-05 to 2017-09-22.

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
63%
16330
16%
46992
13%
16291
65%
16291
25%
31799

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
55%
716
15%
2327
12%
716
59%
716
21%
1542
January16th to endNight
55%
768
22%
2481
19%
768
63%
768
26%
1514
February1st to 15thNight
54%
702
24%
2078
20%
699
60%
699
31%
1267
February16th to endNight
60%
631
29%
1735
20%
631
66%
631
38%
1022
March1st to 15thNight
58%
720
22%
1980
16%
720
64%
720
33%
1247
March16th to endNight
61%
768
23%
2112
19%
768
64%
768
35%
1284
April1st to 15thNight
74%
718
23%
1970
21%
718
76%
718
44%
1114
April16th to endNight
67%
720
21%
1800
13%
720
71%
720
37%
1143
May1st to 15thNight
76%
719
22%
1799
15%
719
77%
719
46%
1067
May16th to endNight
64%
639
13%
1761
11%
639
64%
639
24%
1250
June1st to 15thNight
59%
540
8%
1620
7%
540
59%
540
14%
1283
June16th to endNight
76%
540
7%
1620
6%
540
76%
540
20%
1152
July1st to 15thNight
70%
510
5%
1530
5%
510
70%
510
17%
1133
July16th to endNight
80%
564
9%
1595
9%
531
80%
531
27%
1055
August1st to 15thNight
75%
634
8%
1704
6%
631
74%
631
24%
1197
August16th to endNight
68%
764
6%
1999
5%
764
68%
764
20%
1501
September1st to 15thNight
67%
720
4%
1980
4%
720
67%
720
15%
1552
September16th to endNight
62%
685
6%
1892
6%
685
62%
685
13%
1540
October1st to 15thNight
61%
660
10%
1929
11%
660
62%
660
17%
1427
October16th to endNight
50%
704
14%
2112
15%
704
52%
704
19%
1510
November1st to 15thNight
58%
700
19%
2101
18%
700
61%
700
23%
1422
November16th to endNight
52%
720
20%
2160
17%
720
57%
720
21%
1507
December1st to 15thNight
54%
720
18%
2211
15%
720
58%
720
20%
1542
December16th to endNight
64%
768
20%
2496
21%
768
67%
768
27%
1528

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
7%5%36%7%47%7%8%11%28%
47872
Night
7%5%26%6%46%6%7%11%35%
47197
TransparencyDay
41%14%17%15%9%2
47574
Night
39%10%17%18%10%2
46999
SeeingDay
9%111%24%30%21%
6133
Night
9%212%29%30%14%
16339

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
9%5%36%7%6%7%6%7%9%31%
1611
16th to endDay
8%5%25%6%37%6%8%9%36%
1740
February1st to 15thDay
8%5%35%6%345%6%9%39%
1776
16th to endDay
6%4146%45%6%7%9%43%
1738
March1st to 15thDay
5%425%6%37%7%9%11%37%
1980
16th to endDay
6%436%6%36%6%7%11%37%
2111
April1st to 15thDay
5%324436%6%8%14%39%
1977
16th to endDay
7%325%6%46%7%8%11%37%
2160
May1st to 15thDay
42245%46%7%7%12%41%
2152
16th to endDay
8%5%37%8%5%8%8%8%11%22%
2359
June1st to 15thDay
10%7%410%9%6%8%8%7%9%15%
2340
16th to endDay
6%5%37%9%6%10%10%10%12%17%
2340
July1st to 15thDay
5%448%8%49%9%9%12%20%
2340
16th to endDay
4327%9%5%9%9%10%12%24%
2465
August1st to 15thDay
5%5%37%8%5%8%8%10%13%22%
2232
16th to endDay
9%427%8%5%9%10%11%13%19%
2199
September1st to 15thDay
7%6%37%10%6%10%8%8%12%17%
1980
16th to endDay
9%9%410%10%5%8%8%9%8%15%
1881
October1st to 15thDay
9%5%37%10%5%8%8%9%11%19%
1700
16th to endDay
14%7%36%6%45%6%8%8%29%
1760
November1st to 15thDay
9%5%36%7%5%7%6%6%8%33%
1757
16th to endDay
11%427%7%37%6%7%9%31%
1800
December1st to 15thDay
11%5%36%7%36%7%7%8%30%
1746
16th to endDay
8%5%26%6%46%7%8%11%32%
1728
January1st to 15thNight
8%6%27%5%46%7%7%10%33%
2327
16th to endNight
5%425%5%36%6%7%11%40%
2481
February1st to 15thNight
8%5%25%42445%9%45%
2075
16th to endNight
4415%4336%7%10%47%
1735
March1st to 15thNight
5%325%5%35%6%7%8%46%
1980
16th to endNight
5%325%5%25%6%7%11%44%
2112
April1st to 15thNight
23134245%7%10%52%
1970
16th to endNight
6%424436%5%8%11%43%
1800
May1st to 15thNight
3214335%5%7%9%53%
1799
16th to endNight
9%6%36%6%46%7%7%12%28%
1760
June1st to 15thNight
12%6%37%8%5%7%8%8%10%21%
1620
16th to endNight
4435%7%46%8%11%14%28%
1620
July1st to 15thNight
45%37%8%48%8%9%10%29%
1620
16th to endNight
3425%5%45%6%8%13%39%
1703
August1st to 15thNight
4426%5%47%6%9%14%33%
1715
16th to endNight
6%5%37%8%5%7%6%9%12%28%
1999
September1st to 15thNight
7%5%36%8%6%8%8%8%12%23%
1980
16th to endNight
8%7%38%8%6%7%8%8%10%20%
1892
October1st to 15thNight
7%7%27%7%5%7%8%8%11%24%
1929
16th to endNight
14%8%38%6%35%5%6%9%29%
2112
November1st to 15thNight
8%6%36%6%36%5%6%9%36%
2101
16th to endNight
11%6%36%7%46%6%6%9%32%
2160
December1st to 15thNight
11%6%36%7%45%6%7%9%31%
2211
16th to endNight
7%5%245%36%6%7%12%38%
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
43%10%14%17%10%3
1612
16th to endDay
37%9%16%17%15%4
1740
February1st to 15thDay
36%7%12%22%16%4
1779
16th to endDay
28%10%15%26%15%4
1738
March1st to 15thDay
33%10%17%21%15%2
1980
16th to endDay
32%11%16%21%13%4
2112
April1st to 15thDay
27%10%21%25%13%1
1977
16th to endDay
32%9%17%20%16%3
2160
May1st to 15thDay
28%11%16%23%14%5%
2152
16th to endDay
46%14%16%18%4
2363
June1st to 15thDay
56%16%14%9%2
2340
16th to endDay
47%21%21%8%1
2340
July1st to 15thDay
44%22%24%8%
2201
16th to endDay
39%21%28%10%
2310
August1st to 15thDay
41%21%22%12%2
2219
16th to endDay
45%20%23%9%
2199
September1st to 15thDay
49%22%20%6%1
1980
16th to endDay
55%18%14%8%2
1881
October1st to 15thDay
48%15%15%13%6%
1700
16th to endDay
45%8%13%15%12%4
1760
November1st to 15thDay
42%8%14%13%16%4
1757
16th to endDay
41%9%13%12%18%4
1800
December1st to 15thDay
44%10%12%16%13%2
1746
16th to endDay
39%10%14%19%14%2
1728
January1st to 15thNight
41%9%16%19%10%2
2327
16th to endNight
35%8%14%22%15%4
2481
February1st to 15thNight
34%6%11%24%16%6%
2083
16th to endNight
27%8%14%25%18%5%
1735
March1st to 15thNight
33%7%12%23%18%4
1980
16th to endNight
30%9%15%24%17%3
2112
April1st to 15thNight
24%7%18%32%15%2
1970
16th to endNight
31%8%17%21%17%3
1800
May1st to 15thNight
24%7%16%32%14%4
1800
16th to endNight
44%8%17%22%6%
1762
June1st to 15thNight
52%15%17%11%3
1620
16th to endNight
39%16%30%12%
1620
July1st to 15thNight
44%16%27%11%
1530
16th to endNight
32%15%34%15%2
1595
August1st to 15thNight
34%18%28%16%2
1704
16th to endNight
43%15%26%13%
1999
September1st to 15thNight
46%19%22%9%1
1980
16th to endNight
53%16%16%8%4
1892
October1st to 15thNight
46%14%17%11%8%1
1929
16th to endNight
50%6%12%16%10%3
2112
November1st to 15thNight
43%7%10%16%17%3
2101
16th to endNight
46%7%9%16%14%5%
2160
December1st to 15thNight
46%8%12%16%13%2
2211
16th to endNight
35%8%14%22%16%2
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
18%8%26%31%14%
90
16th to endDay
9%14%30%32%11%2
96
February1st to 15thDay
5%425%40%22%
118
16th to endDay
10%321%41%23%
239
March1st to 15thDay
9%128%41%17%1
270
16th to endDay
7%326%34%24%3
288
April1st to 15thDay
5%121%38%27%6%
270
16th to endDay
6%114%42%32%2
270
May1st to 15thDay
3113%32%38%11%
288
16th to endDay
5%18%21%41%22%
331
June1st to 15thDay
11%17%19%34%25%
315
16th to endDay
6%28%33%48%
315
July1st to 15thDay
48%39%46%
305
16th to endDay
328%33%51%
326
August1st to 15thDay
6%119%37%43%
313
16th to endDay
11%312%31%40%
332
September1st to 15thDay
11%5%8%30%44%
315
16th to endDay
12%29%32%43%
278
October1st to 15thDay
11%5%30%37%14%
255
16th to endDay
19%213%29%25%9%
272
November1st to 15thDay
10%113%31%31%10%
265
16th to endDay
16%322%32%23%1
270
December1st to 15thDay
18%19%34%22%3
216
16th to endDay
6%312%39%37%1
96
January1st to 15thNight
10%5%19%35%25%3
720
16th to endNight
8%6%23%41%19%1
768
February1st to 15thNight
11%324%39%20%
704
16th to endNight
7%322%43%22%
631
March1st to 15thNight
7%323%41%20%2
720
16th to endNight
6%221%43%24%1
768
April1st to 15thNight
3213%46%32%1
718
16th to endNight
7%115%42%30%1
720
May1st to 15thNight
49%42%39%3
720
16th to endNight
10%28%26%41%11%
641
June1st to 15thNight
14%1317%37%24%
540
16th to endNight
438%41%41%
540
July1st to 15thNight
5%37%40%41%
510
16th to endNight
416%34%52%
564
August1st to 15thNight
7%19%39%41%
634
16th to endNight
10%411%35%37%
764
September1st to 15thNight
12%49%32%40%
720
16th to endNight
13%313%33%34%
685
October1st to 15thNight
13%7%25%38%13%
660
16th to endNight
20%113%27%27%10%
704
November1st to 15thNight
13%214%33%28%7%
700
16th to endNight
13%419%33%26%3
720
December1st to 15thNight
13%417%33%28%2
720
16th to endNight
9%316%35%30%5%
768
Page generated at 2017-09-23 06:43:42. Version ac04

Copyright 2017 A. Danko


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