Indian Tree Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Indian Tree Observatory clear sky chart from 2005-11-05 to 2017-09-18.

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
51%
15925
27%
46870
17%
15883
60%
15883
40%
25955

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
52%
899
31%
2506
21%
895
61%
895
47%
1316
January16th to endNight
49%
819
33%
2547
24%
819
60%
819
42%
1335
February1st to 15thNight
44%
699
24%
2220
16%
698
54%
698
35%
1242
February16th to endNight
36%
632
34%
1894
15%
632
54%
632
40%
1017
March1st to 15thNight
44%
720
27%
2136
13%
720
56%
720
41%
1168
March16th to endNight
41%
664
27%
2008
14%
664
55%
664
38%
1116
April1st to 15thNight
33%
539
23%
1798
12%
539
49%
539
33%
989
April16th to endNight
38%
540
21%
1800
15%
540
49%
540
28%
1077
May1st to 15thNight
45%
540
19%
1628
14%
540
52%
540
27%
1049
May16th to endNight
44%
562
17%
1498
10%
561
51%
561
33%
930
June1st to 15thNight
57%
540
21%
1440
13%
540
63%
540
46%
781
June16th to endNight
65%
540
25%
1440
19%
540
69%
540
49%
770
July1st to 15thNight
64%
510
16%
1360
13%
510
67%
510
34%
851
July16th to endNight
68%
564
21%
1428
17%
531
70%
531
36%
871
August1st to 15thNight
64%
539
17%
1695
15%
536
67%
536
31%
1005
August16th to endNight
67%
573
25%
1910
25%
573
72%
573
37%
1021
September1st to 15thNight
63%
540
26%
1800
25%
540
69%
540
37%
973
September16th to endNight
66%
501
33%
1815
31%
501
72%
501
45%
842
October1st to 15thNight
50%
624
29%
1944
19%
624
60%
624
40%
1047
October16th to endNight
60%
745
36%
2153
21%
745
69%
745
51%
1096
November1st to 15thNight
55%
875
34%
2275
18%
875
63%
875
53%
1219
November16th to endNight
52%
900
35%
2367
20%
900
60%
900
51%
1272
December1st to 15thNight
47%
900
26%
2520
14%
900
57%
900
43%
1383
December16th to endNight
42%
960
27%
2688
15%
960
53%
960
37%
1585

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
5%42442446%8%52%
47934
Night
45%2432345%7%55%
47044
Cloud CoverDay
5%42442445%8%53%
47932
Night
45%2432345%7%55%
47044
TransparencyDay
28%6%11%23%21%8%
47610
Night
26%5%12%25%21%7%
46870
SeeingDay
9%8%27%28%18%6%
5853
Night
6%431%39%15%2
15932

By Month

Percentage Cloud Cover SW (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
15%25%312347%61%
1432
16th to endDay
25%33323247%61%
1686
February1st to 15thDay
17%36%423337%55%
1640
16th to endDay
26%2442445%7%55%
1580
March1st to 15thDay
35%3433345%7%54%
1821
16th to endDay
6%7%2332445%8%49%
2215
April1st to 15thDay
7%7%1432346%7%50%
2150
16th to endDay
9%7%2343446%6%45%
2160
May1st to 15thDay
9%7%25%4245%7%8%41%
2318
16th to endDay
7%424436%5%7%8%44%
2616
June1st to 15thDay
6%313425%5%7%9%49%
2520
16th to endDay
3213425%5%7%9%55%
2520
July1st to 15thDay
6%414436%6%7%10%45%
2520
16th to endDay
43245%36%7%6%9%45%
2641
August1st to 15thDay
5%4145%35%7%7%9%45%
2255
16th to endDay
5%213435%5%7%9%51%
2292
September1st to 15thDay
7%3134345%5%8%54%
2160
16th to endDay
421332335%5%64%
1868
October1st to 15thDay
6%313223347%60%
1683
16th to endDay
5%41321225%5%66%
1707
November1st to 15thDay
241333345%7%59%
1583
16th to endDay
2423322347%63%
1591
December1st to 15thDay
16%25%42345%7%55%
1440
16th to endDay
35%36%42245%7%53%
1536
January1st to 15thNight
2424422346%61%
2506
16th to endNight
25%25%5%23335%60%
2547
February1st to 15thNight
28%35%424348%52%
2210
16th to endNight
17%34423345%57%
1894
March1st to 15thNight
35%2332345%6%55%
2136
16th to endNight
46%2332435%7%55%
2008
April1st to 15thNight
6%6%2342435%6%53%
1798
16th to endNight
12%7%24323346%47%
1800
May1st to 15thNight
12%7%234345%6%8%42%
1627
16th to endNight
7%5%1442446%9%48%
1497
June1st to 15thNight
421322446%11%55%
1440
16th to endNight
22132235%7%10%58%
1440
July1st to 15thNight
5%325%436%5%8%7%46%
1440
16th to endNight
5%223426%7%8%10%45%
1525
August1st to 15thNight
5%424436%6%5%10%45%
1704
16th to endNight
5%3133145%7%10%51%
1910
September1st to 15thNight
7%41333346%8%52%
1800
16th to endNight
4213323436%65%
1815
October1st to 15thNight
6%5%1332345%5%57%
1944
16th to endNight
4412213347%63%
2153
November1st to 15thNight
2223323347%63%
2275
16th to endNight
35%24313246%63%
2367
December1st to 15thNight
25%25%423347%57%
2520
16th to endNight
28%36%42345%6%53%
2688

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
26%24213347%61%
1432
16th to endDay
25%24323347%61%
1686
February1st to 15thDay
17%36%433446%55%
1640
16th to endDay
27%2342335%7%56%
1580
March1st to 15thDay
35%3442435%7%55%
1821
16th to endDay
6%7%2332445%7%49%
2213
April1st to 15thDay
8%6%1442346%8%51%
2150
16th to endDay
10%7%23425%5%6%6%45%
2160
May1st to 15thDay
10%7%25%4345%6%8%42%
2318
16th to endDay
8%424436%6%6%8%45%
2616
June1st to 15thDay
7%313425%5%7%9%49%
2520
16th to endDay
3113325%5%7%10%55%
2520
July1st to 15thDay
7%313435%5%8%10%46%
2520
16th to endDay
5%3145%36%6%6%10%46%
2641
August1st to 15thDay
5%324426%6%6%9%47%
2255
16th to endDay
5%213335%5%6%9%52%
2292
September1st to 15thDay
7%31342346%8%54%
2160
16th to endDay
4213223346%65%
1868
October1st to 15thDay
6%313313347%61%
1683
16th to endDay
5%31321125%5%66%
1707
November1st to 15thDay
25%1342445%6%60%
1583
16th to endDay
25%23313336%62%
1591
December1st to 15thDay
27%26%32445%7%55%
1440
16th to endDay
45%46%323447%53%
1536
January1st to 15thNight
1424323347%61%
2506
16th to endNight
25%35%5%23235%60%
2547
February1st to 15thNight
28%35%324347%52%
2210
16th to endNight
17%35%423346%57%
1894
March1st to 15thNight
46%2432345%6%56%
2136
16th to endNight
5%7%2331335%7%55%
2008
April1st to 15thNight
6%7%2342435%6%53%
1798
16th to endNight
14%7%34323346%48%
1800
May1st to 15thNight
13%6%1343446%7%43%
1627
16th to endNight
8%425%42445%7%50%
1497
June1st to 15thNight
421332336%11%56%
1440
16th to endNight
22133245%6%9%59%
1440
July1st to 15thNight
6%324446%6%7%8%46%
1440
16th to endNight
5%214436%6%8%10%45%
1525
August1st to 15thNight
5%424436%5%7%8%47%
1704
16th to endNight
6%3133135%7%9%53%
1910
September1st to 15thNight
7%41332446%8%53%
1800
16th to endNight
5%213312445%65%
1815
October1st to 15thNight
6%5%1331345%5%58%
1944
16th to endNight
4412212347%63%
2153
November1st to 15thNight
3213323346%63%
2275
16th to endNight
35%23223237%62%
2367
December1st to 15thNight
26%35%32245%7%57%
2520
16th to endNight
28%45%42345%6%52%
2688

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
22%312%30%25%5%
1433
16th to endDay
22%310%31%22%8%
1686
February1st to 15thDay
29%312%34%14%4
1641
16th to endDay
26%5%7%29%24%7%
1580
March1st to 15thDay
28%411%24%23%8%
1821
16th to endDay
31%412%24%20%5%
2215
April1st to 15thDay
31%5%11%24%20%7%
2150
16th to endDay
36%7%12%21%17%4
2160
May1st to 15thDay
39%7%11%22%15%2
2318
16th to endDay
34%8%13%23%13%6%
2620
June1st to 15thDay
27%7%14%20%19%11%
2520
16th to endDay
22%6%10%20%27%12%
2520
July1st to 15thDay
31%9%12%18%16%11%
2371
16th to endDay
31%9%12%23%16%6%
2475
August1st to 15thDay
31%10%13%19%15%9%
2240
16th to endDay
27%6%11%22%25%6%
2292
September1st to 15thDay
26%5%10%21%20%13%
2160
16th to endDay
20%47%23%35%8%
1868
October1st to 15thDay
23%411%22%30%8%
1683
16th to endDay
20%37%27%30%10%
1707
November1st to 15thDay
21%311%23%25%14%
1583
16th to endDay
20%27%23%32%12%
1591
December1st to 15thDay
27%5%12%29%20%4
1440
16th to endDay
30%5%14%24%19%6%
1536
January1st to 15thNight
22%412%29%25%6%
2506
16th to endNight
25%39%27%24%9%
2547
February1st to 15thNight
30%412%30%17%4
2220
16th to endNight
27%37%30%23%8%
1894
March1st to 15thNight
25%5%10%25%25%7%
2136
16th to endNight
28%411%24%25%5%
2008
April1st to 15thNight
29%6%11%26%19%7%
1798
16th to endNight
37%5%11%25%16%4
1800
May1st to 15thNight
38%8%13%22%13%4
1628
16th to endNight
31%9%19%22%11%6%
1498
June1st to 15thNight
21%6%19%26%13%11%
1440
16th to endNight
19%7%12%24%25%9%
1440
July1st to 15thNight
32%8%16%20%13%8%
1360
16th to endNight
28%9%16%23%18%2
1428
August1st to 15thNight
31%9%15%22%13%6%
1695
16th to endNight
25%7%12%29%18%5%
1910
September1st to 15thNight
27%6%12%22%20%10%
1800
16th to endNight
19%5%10%27%29%7%
1815
October1st to 15thNight
25%5%13%20%26%8%
1944
16th to endNight
20%38%27%29%10%
2153
November1st to 15thNight
20%310%24%26%14%
2275
16th to endNight
22%38%24%31%10%
2367
December1st to 15thNight
25%414%30%20%5%
2520
16th to endNight
30%5%13%24%21%4
2688

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
12%7%14%38%24%2
90
16th to endDay
6%7%27%41%16%1
96
February1st to 15thDay
311%47%31%6%
90
16th to endDay
413%38%24%18%
81
March1st to 15thDay
213%36%36%7%2
111
16th to endDay
16%22%35%19%5%1
288
April1st to 15thDay
14%19%34%21%7%2
269
16th to endDay
17%26%30%20%41
270
May1st to 15thDay
14%10%32%27%12%2
435
16th to endDay
14%11%25%24%17%5%
517
June1st to 15thDay
10%7%25%28%20%7%
495
16th to endDay
45%25%32%23%7%
495
July1st to 15thDay
9%318%28%29%10%
475
16th to endDay
8%217%28%32%11%
500
August1st to 15thDay
9%5%23%33%20%8%
315
16th to endDay
6%225%37%21%6%
332
September1st to 15thDay
7%6%33%27%15%10%
315
16th to endDay
3329%27%19%15%
127
October1st to 15thDay
2426%30%21%15%
90
16th to endDay
10%328%29%20%8%
96
November1st to 15thDay
2418%40%25%8%
90
16th to endDay
7%8%43%28%10%1
90
December1st to 15thDay
6%12%48%23%8%
90
16th to endDay
37%39%40%8%1
96
January1st to 15thNight
4434%41%13%3
900
16th to endNight
3435%44%10%1
819
February1st to 15thNight
5%5%38%42%7%
704
16th to endNight
5%6%45%34%7%
632
March1st to 15thNight
5%440%38%10%1
720
16th to endNight
7%8%38%36%8%
664
April1st to 15thNight
9%9%43%30%6%
539
16th to endNight
17%7%32%31%10%
540
May1st to 15thNight
15%429%37%11%
540
16th to endNight
10%433%33%14%1
563
June1st to 15thNight
5%328%41%18%1
540
16th to endNight
3123%46%23%1
540
July1st to 15thNight
6%117%39%29%4
510
16th to endNight
6%114%40%35%3
564
August1st to 15thNight
7%216%42%29%2
539
16th to endNight
6%18%44%25%4
573
September1st to 15thNight
8%219%42%22%4
540
16th to endNight
5%120%43%24%3
501
October1st to 15thNight
8%5%31%36%14%4
624
16th to endNight
6%225%38%21%4
745
November1st to 15thNight
35%30%42%16%1
875
16th to endNight
5%433%38%15%2
900
December1st to 15thNight
45%37%41%10%
900
16th to endNight
6%5%39%37%10%1
960
Page generated at 2017-09-19 05:32:32. Version ac04

Copyright 2017 A. Danko


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