Sehgal Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sehgal 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
39%
15019
13%
47657
9%
14991
44%
14991
17%
32698

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
26%
719
7%
2506
4%
716
30%
716
8%
1991
January16th to endNight
27%
768
7%
2688
5%
768
30%
768
10%
2066
February1st to 15thNight
30%
701
7%
2372
5%
700
34%
700
11%
1795
February16th to endNight
35%
632
12%
1951
8%
632
42%
632
16%
1383
March1st to 15thNight
29%
720
9%
2160
5%
720
34%
720
13%
1631
March16th to endNight
30%
768
10%
2003
4%
768
34%
768
15%
1522
April1st to 15thNight
39%
719
11%
1799
5%
719
42%
719
19%
1330
April16th to endNight
39%
531
15%
1611
8%
531
45%
531
20%
1077
May1st to 15thNight
40%
359
16%
1440
15%
359
52%
359
18%
835
May16th to endNight
44%
374
9%
1496
10%
374
51%
374
14%
965
June1st to 15thNight
44%
360
6%
1308
3%
360
46%
360
19%
824
June16th to endNight
46%
360
11%
1141
2%
360
50%
360
25%
678
July1st to 15thNight
57%
340
11%
1315
8%
340
62%
340
35%
583
July16th to endNight
60%
376
20%
1416
23%
354
76%
354
42%
579
August1st to 15thNight
70%
360
25%
1432
32%
358
76%
358
38%
613
August16th to endNight
62%
655
29%
1801
17%
655
69%
655
45%
937
September1st to 15thNight
61%
720
26%
1800
13%
720
65%
720
48%
989
September16th to endNight
56%
716
25%
1938
16%
716
62%
716
33%
1168
October1st to 15thNight
43%
720
15%
2160
13%
720
48%
720
24%
1378
October16th to endNight
42%
768
15%
2468
10%
768
49%
768
17%
1723
November1st to 15thNight
31%
760
9%
2569
8%
760
35%
760
10%
1991
November16th to endNight
25%
798
7%
2748
4%
798
29%
798
8%
2200
December1st to 15thNight
28%
910
8%
2730
4%
910
31%
910
11%
2148
December16th to endNight
21%
885
8%
2805
3%
885
26%
885
8%
2292

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%7%35%5%345%5%7%40%
48790
Night
12%9%35%42445%7%39%
47824
Cloud CoverDay
11%8%36%5%35%5%5%7%37%
48790
Night
12%10%36%42445%6%37%
47828
TransparencyDay
44%9%13%19%10%1
48461
Night
45%8%13%20%9%1
47657
SeeingDay
14%22%27%23%9%2
6029
Night
15%19%18%27%15%2
15025

By Month

Percentage Cloud Cover NW (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
16%14%7%9%6%34437%21%
1432
16th to endDay
14%16%5%9%7%23446%25%
1536
February1st to 15thDay
13%16%47%6%3445%9%25%
1492
16th to endDay
10%13%36%5%445%7%7%31%
1522
March1st to 15thDay
14%11%46%5%36%6%6%8%26%
1800
16th to endDay
11%10%5%8%6%46%5%6%8%26%
2219
April1st to 15thDay
9%7%39%7%47%7%6%6%28%
2149
16th to endDay
8%7%26%5%46%5%7%8%36%
2349
May1st to 15thDay
7%6%35%6%35%46%8%41%
2511
16th to endDay
11%5%35%7%46%6%6%8%33%
2615
June1st to 15thDay
13%5%35%6%345%6%7%37%
2649
16th to endDay
9%5%25%5%35%5%6%8%41%
2808
July1st to 15thDay
32133245%5%6%61%
2559
16th to endDay
321222345%6%64%
2657
August1st to 15thDay
321332345%7%63%
2520
16th to endDay
321332435%8%60%
2398
September1st to 15thDay
3213313345%66%
2160
16th to endDay
7%41343345%7%51%
2019
October1st to 15thDay
9%5%25%425%45%9%45%
1800
16th to endDay
19%9%36%434446%33%
1755
November1st to 15thDay
20%9%46%5%35%5%5%6%27%
1618
16th to endDay
17%15%6%7%5%33447%23%
1527
December1st to 15thDay
14%14%6%7%5%2445%6%27%
1267
16th to endDay
17%18%6%9%6%2434423%
1428
January1st to 15thNight
20%16%7%7%5%33345%22%
2506
16th to endNight
15%19%7%9%424345%23%
2688
February1st to 15thNight
15%16%5%6%424346%29%
2360
16th to endNight
10%10%35%5%25%5%6%8%34%
1951
March1st to 15thNight
13%9%37%5%35%5%7%9%29%
2160
16th to endNight
10%8%47%6%35%6%6%6%33%
1999
April1st to 15thNight
9%6%27%6%36%5%6%8%37%
1799
16th to endNight
5%6%35%425%6%6%9%43%
1611
May1st to 15thNight
6%424435%5%46%50%
1439
16th to endNight
9%6%25%5%36%6%7%9%39%
1496
June1st to 15thNight
10%4345%25%5%7%8%43%
1308
16th to endNight
6%313326%5%5%8%52%
1141
July1st to 15thNight
2212313347%67%
1395
16th to endNight
1111212346%72%
1512
August1st to 15thNight
1212213347%69%
1440
16th to endNight
31221345%8%65%
1801
September1st to 15thNight
222212346%69%
1800
16th to endNight
6%5%1332435%8%55%
1938
October1st to 15thNight
10%6%26%423447%47%
2160
16th to endNight
17%6%24435%46%7%37%
2468
November1st to 15thNight
21%11%35%5%25%45%6%27%
2569
16th to endNight
20%16%5%7%5%34445%23%
2748
December1st to 15thNight
16%14%7%9%5%23445%25%
2730
16th to endNight
18%22%6%7%5%2323422%
2805

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%14%5%10%7%3445%5%21%
1432
16th to endDay
13%16%5%7%5%2445%5%27%
1536
February1st to 15thDay
15%15%46%6%4345%7%25%
1492
16th to endDay
12%13%26%6%35%5%6%7%28%
1522
March1st to 15thDay
17%13%46%5%37%5%6%8%23%
1800
16th to endDay
13%12%48%7%46%6%5%7%21%
2219
April1st to 15thDay
11%8%6%11%8%5%7%6%5%7%23%
2149
16th to endDay
8%9%47%7%45%47%8%31%
2349
May1st to 15thDay
9%7%36%6%46%5%6%8%36%
2511
16th to endDay
12%7%47%7%46%6%6%8%27%
2615
June1st to 15thDay
15%6%36%6%35%5%6%7%33%
2649
16th to endDay
10%6%36%6%35%5%7%7%37%
2808
July1st to 15thDay
431432445%6%58%
2559
16th to endDay
331332445%6%62%
2657
August1st to 15thDay
321332445%6%60%
2520
16th to endDay
431343446%7%57%
2398
September1st to 15thDay
3312423337%62%
2160
16th to endDay
9%5%145%245%5%7%48%
2019
October1st to 15thDay
12%5%25%5%3345%8%42%
1800
16th to endDay
20%10%35%5%33435%32%
1755
November1st to 15thDay
22%11%45%5%45%45%6%25%
1618
16th to endDay
19%13%7%7%434436%23%
1527
December1st to 15thDay
14%13%6%8%6%35%45%6%26%
1267
16th to endDay
19%16%6%9%5%23345%22%
1428
January1st to 15thNight
21%15%6%9%42345%6%21%
2506
16th to endNight
14%18%5%8%5%24346%24%
2688
February1st to 15thNight
16%14%5%6%424446%29%
2360
16th to endNight
11%12%36%425%5%6%8%32%
1951
March1st to 15thNight
14%11%47%5%35%6%6%8%26%
2160
16th to endNight
12%10%48%7%35%45%6%30%
2003
April1st to 15thNight
10%6%46%6%36%6%6%7%34%
1799
16th to endNight
6%7%26%5%45%5%6%7%41%
1611
May1st to 15thNight
8%5%25%5%45%45%7%47%
1439
16th to endNight
10%6%35%5%35%6%7%9%35%
1496
June1st to 15thNight
10%6%34435%5%8%9%39%
1308
16th to endNight
8%314435%5%6%8%48%
1141
July1st to 15thNight
331222335%7%65%
1395
16th to endNight
121121345%6%69%
1512
August1st to 15thNight
221331335%6%65%
1440
16th to endNight
321232235%8%63%
1801
September1st to 15thNight
3213213347%65%
1800
16th to endNight
7%5%2342336%7%52%
1938
October1st to 15thNight
13%6%26%42345%5%45%
2160
16th to endNight
18%8%25%43445%6%34%
2468
November1st to 15thNight
22%13%45%5%35%346%25%
2569
16th to endNight
20%15%6%8%5%25%34422%
2748
December1st to 15thNight
15%14%6%10%5%24445%25%
2730
16th to endNight
18%21%6%8%5%2233423%
2805

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
63%7%12%12%4
1432
16th to endDay
57%7%14%15%41
1536
February1st to 15thDay
57%9%16%12%2
1492
16th to endDay
51%12%14%13%7%
1522
March1st to 15thDay
55%12%14%13%3
1800
16th to endDay
57%12%14%12%2
2219
April1st to 15thDay
56%10%13%14%4
2149
16th to endDay
47%12%14%19%5%
2349
May1st to 15thDay
42%11%13%21%9%1
2511
16th to endDay
50%11%16%16%5%
2619
June1st to 15thDay
47%10%13%17%7%2
2649
16th to endDay
42%9%12%21%13%
2808
July1st to 15thDay
24%7%12%25%21%8%
2410
16th to endDay
21%6%11%26%27%7%
2490
August1st to 15thDay
22%7%12%30%20%5%
2503
16th to endDay
23%8%14%30%19%3
2398
September1st to 15thDay
21%6%14%28%25%3
2160
16th to endDay
32%10%15%25%14%2
2019
October1st to 15thDay
38%10%17%24%9%
1800
16th to endDay
52%8%13%19%5%
1755
November1st to 15thDay
57%10%13%13%31
1618
16th to endDay
60%9%10%13%5%
1527
December1st to 15thDay
57%8%14%15%3
1267
16th to endDay
64%7%10%13%4
1428
January1st to 15thNight
62%8%12%11%4
2506
16th to endNight
61%6%13%13%31
2688
February1st to 15thNight
56%8%15%14%31
2372
16th to endNight
47%10%17%19%5%
1951
March1st to 15thNight
51%11%16%16%4
2160
16th to endNight
51%10%15%17%5%
2003
April1st to 15thNight
44%11%14%20%7%1
1799
16th to endNight
39%10%15%26%7%
1611
May1st to 15thNight
35%8%13%25%15%1
1440
16th to endNight
41%11%17%23%5%
1496
June1st to 15thNight
38%9%12%27%9%1
1308
16th to endNight
30%9%14%27%15%1
1141
July1st to 15thNight
18%6%13%27%24%9%
1315
16th to endNight
14%6%11%29%29%8%
1416
August1st to 15thNight
17%6%11%33%25%5%
1432
16th to endNight
18%6%12%33%25%3
1801
September1st to 15thNight
17%6%13%28%28%5%
1800
16th to endNight
29%7%13%28%16%3
1938
October1st to 15thNight
37%7%15%24%13%
2160
16th to endNight
47%9%13%24%4
2468
November1st to 15thNight
57%10%13%12%41
2569
16th to endNight
64%7%10%12%5%
2748
December1st to 15thNight
59%8%13%14%3
2730
16th to endNight
65%7%8%12%5%
2805

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
15%8%15%33%20%8%
60
16th to endDay
40%417%28%44
64
February1st to 15thDay
22%22%27%20%5%1
152
16th to endDay
21%20%21%25%9%
229
March1st to 15thDay
30%34%24%10%1
270
16th to endDay
25%33%24%13%3
288
April1st to 15thDay
20%28%27%16%5%1
269
16th to endDay
12%35%29%14%5%2
270
May1st to 15thDay
14%32%26%20%5%
288
16th to endDay
13%22%25%20%12%5%
330
June1st to 15thDay
12%22%25%26%12%1
444
16th to endDay
9%25%29%24%8%1
603
July1st to 15thDay
5%19%29%32%10%1
344
16th to endDay
320%34%27%10%2
327
August1st to 15thDay
6%14%28%31%13%5%
315
16th to endDay
7%17%31%29%10%4
332
September1st to 15thDay
6%19%29%26%13%4
315
16th to endDay
13%19%28%24%12%2
315
October1st to 15thDay
15%26%28%20%8%
315
16th to endDay
32%8%24%22%11%
171
November1st to 15thDay
28%16%24%23%8%
112
16th to endDay
32%13%21%17%11%4
90
December1st to 15thDay
29%6%30%24%6%3
62
16th to endDay
20%10%26%23%15%3
64
January1st to 15thNight
22%22%17%24%10%2
720
16th to endNight
20%19%18%25%14%1
768
February1st to 15thNight
20%21%16%26%13%2
704
16th to endNight
16%21%19%24%15%2
632
March1st to 15thNight
16%25%21%23%10%1
720
16th to endNight
15%23%24%26%8%1
768
April1st to 15thNight
10%22%20%28%15%1
719
16th to endNight
9%22%24%29%12%2
531
May1st to 15thNight
8%25%20%28%15%1
360
16th to endNight
11%21%16%26%20%2
375
June1st to 15thNight
8%23%19%31%16%1
360
16th to endNight
8%20%22%30%18%
360
July1st to 15thNight
317%17%31%25%2
340
16th to endNight
219%13%32%28%1
376
August1st to 15thNight
212%11%30%38%4
360
16th to endNight
5%11%17%34%27%3
655
September1st to 15thNight
413%17%28%28%7%
720
16th to endNight
11%11%17%30%24%4
716
October1st to 15thNight
17%14%20%26%19%1
720
16th to endNight
21%13%17%30%13%2
768
November1st to 15thNight
26%19%16%28%8%1
760
16th to endNight
26%23%16%20%10%2
798
December1st to 15thNight
21%23%16%31%5%
910
16th to endNight
24%22%22%24%6%
885
Page generated at 2017-12-03 08:16:48. Version ac04

Copyright 2017 A. Danko


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