Indian Valley Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Indian Valley Observatory clear sky chart from 2005-11-05 to 2017-12-02.

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
64%
15547
28%
47853
24%
15510
68%
15510
39%
25800

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
56%
717
18%
2401
18%
716
59%
716
24%
1483
January16th to endNight
53%
768
26%
2496
25%
768
58%
768
28%
1514
February1st to 15thNight
52%
697
22%
2288
22%
697
56%
697
23%
1452
February16th to endNight
49%
632
23%
1942
18%
632
56%
632
27%
1204
March1st to 15thNight
47%
720
14%
1987
10%
720
51%
720
23%
1372
March16th to endNight
46%
768
20%
2106
14%
768
51%
768
28%
1363
April1st to 15thNight
42%
719
21%
1799
10%
719
48%
719
30%
1180
April16th to endNight
56%
720
25%
1800
12%
720
61%
720
46%
1023
May1st to 15thNight
63%
544
30%
1624
20%
544
69%
544
52%
785
May16th to endNight
68%
384
28%
1506
28%
384
75%
384
47%
616
June1st to 15thNight
67%
360
26%
1440
30%
360
75%
360
43%
615
June16th to endNight
79%
360
36%
1440
46%
360
84%
360
62%
496
July1st to 15thNight
91%
361
34%
1381
45%
361
93%
361
77%
435
July16th to endNight
93%
564
40%
1593
37%
531
94%
531
83%
592
August1st to 15thNight
93%
538
41%
1611
34%
535
94%
535
80%
617
August16th to endNight
91%
735
45%
1881
30%
735
93%
735
81%
818
September1st to 15thNight
90%
720
43%
1800
30%
720
93%
720
82%
800
September16th to endNight
81%
716
44%
1980
37%
716
87%
716
68%
878
October1st to 15thNight
71%
720
31%
2160
31%
720
78%
720
53%
1029
October16th to endNight
72%
768
35%
2304
36%
768
76%
768
45%
1199
November1st to 15thNight
62%
760
24%
2371
23%
760
67%
760
33%
1392
November16th to endNight
56%
780
22%
2707
23%
780
60%
780
27%
1572
December1st to 15thNight
48%
728
20%
2548
16%
728
55%
728
22%
1602
December16th to endNight
46%
768
20%
2688
19%
768
52%
768
20%
1763

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
9%313313345%61%
48599
Night
10%413313346%58%
48039
TransparencyDay
25%37%20%24%18%
48285
Night
27%38%20%23%16%
47854
SeeingDay
12%9%21%28%20%7%
6243
Night
11%5%12%29%32%9%
15559

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
17%6%345%23335%43%
1536
16th to endDay
18%6%35%413445%43%
1728
February1st to 15thDay
19%6%1443325%6%41%
1576
16th to endDay
21%6%1342446%7%37%
1532
March1st to 15thDay
20%7%37%5%24445%33%
1971
16th to endDay
18%5%25%434447%37%
2118
April1st to 15thDay
15%7%3442445%7%40%
2149
16th to endDay
6%423423348%56%
2160
May1st to 15thDay
431221435%8%62%
2325
16th to endDay
5%314323447%60%
2604
June1st to 15thDay
4313223346%64%
2520
16th to endDay
2111122480%
2520
July1st to 15thDay
1112286%
2495
16th to endDay
1111387%
2468
August1st to 15thDay
11112384%
2340
16th to endDay
11289%
2321
September1st to 15thDay
11222483%
2160
16th to endDay
211212236%75%
1977
October1st to 15thDay
7%32212345%67%
1800
16th to endDay
10%312323236%59%
1920
November1st to 15thDay
10%3135%2446%7%49%
1816
16th to endDay
15%5%3442434446%
1579
December1st to 15thDay
19%7%26%323335%41%
1448
16th to endDay
24%6%3332345%6%37%
1536
January1st to 15thNight
16%5%14434447%42%
2401
16th to endNight
19%7%22213235%48%
2496
February1st to 15thNight
17%6%25%5%24446%39%
2276
16th to endNight
17%5%2442335%6%43%
1942
March1st to 15thNight
16%7%36%5%3445%7%36%
1987
16th to endNight
16%7%1432335%6%44%
2106
April1st to 15thNight
11%6%35%5%2335%7%45%
1799
16th to endNight
6%313324338%59%
1800
May1st to 15thNight
3312312346%66%
1624
16th to endNight
3213213346%67%
1506
June1st to 15thNight
3312213336%66%
1440
16th to endNight
31111112281%
1440
July1st to 15thNight
11112287%
1462
16th to endNight
11388%
1701
August1st to 15thNight
11112287%
1620
16th to endNight
11221385%
1881
September1st to 15thNight
11122485%
1800
16th to endNight
211112236%77%
1980
October1st to 15thNight
5%212312335%69%
2160
16th to endNight
9%212223345%61%
2304
November1st to 15thNight
10%4133245%7%8%46%
2371
16th to endNight
14%5%3442335%6%47%
2707
December1st to 15thNight
21%6%23413346%40%
2548
16th to endNight
22%5%24423346%38%
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
44%48%18%13%11%
1536
16th to endDay
42%46%12%20%13%
1728
February1st to 15thDay
43%28%19%20%5%
1576
16th to endDay
44%410%23%13%3
1532
March1st to 15thDay
51%48%14%13%6%
1971
16th to endDay
44%5%13%17%15%3
2118
April1st to 15thDay
41%413%21%15%2
2149
16th to endDay
26%413%27%20%7%
2160
May1st to 15thDay
19%39%31%28%7%
2325
16th to endDay
23%312%32%21%6%
2608
June1st to 15thDay
21%49%24%25%14%
2520
16th to endDay
9%1418%38%27%
2520
July1st to 15thDay
5%1212%36%41%
2348
16th to endDay
5%1310%27%50%
2313
August1st to 15thDay
6%1117%36%36%
2324
16th to endDay
41216%37%37%
2321
September1st to 15thDay
6%2216%34%37%
2160
16th to endDay
11%26%23%33%23%
1977
October1st to 15thDay
19%36%21%27%21%
1800
16th to endDay
26%26%21%27%15%
1920
November1st to 15thDay
32%49%29%14%9%
1816
16th to endDay
40%38%20%18%8%
1579
December1st to 15thDay
45%47%15%21%5%
1448
16th to endDay
46%5%8%15%16%8%
1536
January1st to 15thNight
41%410%17%16%9%
2401
16th to endNight
39%36%17%18%14%
2496
February1st to 15thNight
43%49%17%17%7%
2288
16th to endNight
40%311%25%15%3
1942
March1st to 15thNight
46%5%13%15%14%5%
1987
16th to endNight
39%5%13%20%16%4
2106
April1st to 15thNight
37%5%15%21%15%4
1799
16th to endNight
24%412%30%22%6%
1800
May1st to 15thNight
18%37%29%32%9%
1625
16th to endNight
16%315%35%20%7%
1506
June1st to 15thNight
19%311%25%25%13%
1440
16th to endNight
10%1420%36%26%
1440
July1st to 15thNight
6%1212%35%43%
1381
16th to endNight
41311%24%54%
1593
August1st to 15thNight
6%1117%34%38%
1611
16th to endNight
6%1216%36%36%
1881
September1st to 15thNight
5%1213%35%40%
1800
16th to endNight
9%3424%32%26%
1980
October1st to 15thNight
19%26%21%28%21%
2160
16th to endNight
24%36%23%23%19%
2304
November1st to 15thNight
31%7%13%25%14%8%
2371
16th to endNight
37%39%20%20%8%
2707
December1st to 15thNight
44%38%16%20%6%
2548
16th to endNight
46%47%15%18%7%
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
33%10%21%15%16%1
164
16th to endDay
22%10%20%25%13%8%
256
February1st to 15thDay
25%11%19%23%18%1
236
16th to endDay
22%16%20%25%13%1
230
March1st to 15thDay
31%13%20%18%11%4
270
16th to endDay
20%17%32%19%9%1
288
April1st to 15thDay
22%20%21%19%12%4
269
16th to endDay
14%21%28%21%12%1
270
May1st to 15thDay
7%19%30%21%15%4
288
16th to endDay
9%12%20%26%21%8%
330
June1st to 15thDay
7%13%27%33%14%4
315
16th to endDay
36%29%32%20%7%
315
July1st to 15thDay
2217%40%26%10%
305
16th to endDay
112%49%21%14%
327
August1st to 15thDay
219%39%25%11%
315
16th to endDay
1116%31%32%15%
332
September1st to 15thDay
215%39%32%9%
315
16th to endDay
5%6%20%29%27%10%
315
October1st to 15thDay
8%8%25%29%19%9%
315
16th to endDay
13%8%18%28%25%6%
336
November1st to 15thDay
13%6%18%22%28%9%
232
16th to endDay
19%430%28%11%5%
94
December1st to 15thDay
37%8%24%24%41
62
16th to endDay
23%7%15%25%20%7%
64
January1st to 15thNight
17%5%8%34%25%7%
720
16th to endNight
21%413%29%22%8%
768
February1st to 15thNight
20%5%10%33%25%4
704
16th to endNight
19%7%16%28%21%5%
632
March1st to 15thNight
19%7%15%28%24%4
720
16th to endNight
18%9%18%29%20%4
768
April1st to 15thNight
14%11%21%27%20%4
719
16th to endNight
9%9%21%28%25%6%
720
May1st to 15thNight
4421%30%30%8%
545
16th to endNight
45%16%31%35%6%
385
June1st to 15thNight
45%18%31%37%4
360
16th to endNight
3112%37%38%5%
360
July1st to 15thNight
1425%55%12%
361
16th to endNight
1320%53%21%
564
August1st to 15thNight
1225%52%18%
538
16th to endNight
5%23%53%15%
735
September1st to 15thNight
5%25%50%16%
720
16th to endNight
329%27%37%18%
716
October1st to 15thNight
6%312%30%32%14%
720
16th to endNight
10%39%24%36%14%
768
November1st to 15thNight
11%5%11%31%30%8%
760
16th to endNight
15%7%10%32%25%8%
780
December1st to 15thNight
23%7%11%28%20%8%
728
16th to endNight
23%7%14%31%19%2
768
Page generated at 2017-12-03 08:16:41. Version ac04

Copyright 2017 A. Danko


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