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 2017-04-28.

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
37%
14374
12%
45547
8%
14346
43%
14346
17%
31463

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
5%
716
30%
716
8%
1991
January16th to endNight
29%
768
8%
2688
6%
768
32%
768
10%
2066
February1st to 15thNight
32%
701
7%
2372
5%
700
35%
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
33%
720
13%
1631
March16th to endNight
30%
768
10%
2003
4%
768
34%
768
15%
1522
April1st to 15thNight
37%
719
11%
1799
5%
719
41%
719
19%
1330
April16th to endNight
37%
527
15%
1595
8%
527
43%
527
20%
1066
May1st to 15thNight
38%
329
17%
1320
16%
329
51%
329
18%
750
May16th to endNight
41%
342
8%
1368
8%
342
47%
342
14%
889
June1st to 15thNight
42%
330
6%
1199
3%
330
44%
330
18%
763
June16th to endNight
43%
330
9%
1046
2%
330
46%
330
24%
628
July1st to 15thNight
54%
310
11%
1199
8%
310
59%
310
33%
542
July16th to endNight
59%
348
19%
1304
20%
326
75%
326
40%
547
August1st to 15thNight
66%
330
26%
1312
33%
328
73%
328
36%
576
August16th to endNight
58%
600
26%
1650
15%
600
65%
600
42%
877
September1st to 15thNight
59%
660
27%
1650
13%
660
63%
660
46%
920
September16th to endNight
53%
656
25%
1776
15%
656
59%
656
33%
1066
October1st to 15thNight
42%
660
16%
1980
13%
660
47%
660
23%
1281
October16th to endNight
38%
704
13%
2262
8%
704
46%
704
15%
1613
November1st to 15thNight
32%
700
10%
2366
9%
700
36%
700
11%
1804
November16th to endNight
25%
736
8%
2536
4%
736
30%
736
8%
2013
December1st to 15thNight
28%
900
8%
2700
4%
900
31%
900
11%
2118
December16th to endNight
21%
885
9%
2805
4%
885
27%
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%35%5%5%7%39%
46149
Night
12%9%35%42445%7%38%
45714
Cloud CoverDay
11%8%36%5%35%5%5%7%36%
46149
Night
12%10%46%42445%6%37%
45718
TransparencyDay
45%9%13%19%9%1
45820
Night
46%8%13%20%9%1
45547
SeeingDay
15%24%27%22%8%2
5197
Night
15%20%19%27%15%2
14380

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%
2312
May1st to 15thDay
7%5%35%6%35%46%8%42%
2301
16th to endDay
12%5%36%7%46%6%7%8%32%
2391
June1st to 15thDay
14%5%35%6%3446%7%38%
2428
16th to endDay
9%5%25%6%35%5%6%8%39%
2574
July1st to 15thDay
421332445%6%60%
2346
16th to endDay
321222445%6%62%
2461
August1st to 15thDay
321332345%7%61%
2310
16th to endDay
331332436%9%57%
2197
September1st to 15thDay
3213314345%65%
1980
16th to endDay
8%41343345%7%52%
1851
October1st to 15thDay
10%5%25%425%45%9%44%
1650
16th to endDay
19%9%36%434446%32%
1609
November1st to 15thDay
19%9%36%5%345%6%6%27%
1491
16th to endDay
16%14%6%7%5%3345%8%24%
1410
December1st to 15thDay
14%14%6%7%5%2445%6%27%
1260
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%
1595
May1st to 15thNight
6%423435%5%47%52%
1319
16th to endNight
8%6%25%5%36%6%7%10%38%
1368
June1st to 15thNight
10%4345%25%47%7%42%
1199
16th to endNight
6%323326%6%5%8%51%
1046
July1st to 15thNight
3212313347%67%
1279
16th to endNight
111221335%6%70%
1400
August1st to 15thNight
1213213447%67%
1320
16th to endNight
31221345%8%63%
1650
September1st to 15thNight
333212346%68%
1650
16th to endNight
6%5%13324348%56%
1776
October1st to 15thNight
11%5%26%424447%46%
1980
16th to endNight
17%6%24435%46%8%35%
2262
November1st to 15thNight
20%11%35%5%25%46%7%29%
2366
16th to endNight
20%15%5%7%5%34445%24%
2536
December1st to 15thNight
16%13%7%9%5%23446%26%
2700
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%
2312
May1st to 15thDay
8%7%36%6%35%5%6%7%37%
2301
16th to endDay
13%7%47%7%46%6%6%8%26%
2391
June1st to 15thDay
15%6%36%5%35%5%6%7%33%
2428
16th to endDay
11%6%36%6%35%5%7%7%35%
2574
July1st to 15thDay
432432445%6%57%
2346
16th to endDay
331332445%6%60%
2461
August1st to 15thDay
431342446%6%58%
2310
16th to endDay
431443446%8%54%
2197
September1st to 15thDay
3313423337%61%
1980
16th to endDay
9%5%144245%47%49%
1851
October1st to 15thDay
12%5%25%5%3345%8%41%
1650
16th to endDay
20%11%36%5%33435%31%
1609
November1st to 15thDay
21%11%45%445%5%5%6%25%
1491
16th to endDay
18%12%8%7%4345%46%24%
1410
December1st to 15thDay
15%12%6%8%6%35%45%6%26%
1260
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%
1595
May1st to 15thNight
7%5%245%35%45%7%48%
1319
16th to endNight
10%6%35%5%36%6%7%9%34%
1368
June1st to 15thNight
11%5%34445%5%8%8%39%
1199
16th to endNight
8%315%435%5%6%9%46%
1046
July1st to 15thNight
331222335%7%64%
1279
16th to endNight
121121345%6%68%
1400
August1st to 15thNight
221331346%7%63%
1320
16th to endNight
421232346%8%60%
1650
September1st to 15thNight
3213223347%64%
1650
16th to endNight
7%5%2332335%7%52%
1776
October1st to 15thNight
13%6%26%42345%5%45%
1980
16th to endNight
18%8%26%435%46%6%32%
2262
November1st to 15thNight
21%12%35%5%35%346%26%
2366
16th to endNight
20%14%6%8%5%25%34423%
2536
December1st to 15thNight
15%14%6%10%5%24446%26%
2700
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%13%14%19%4
2312
May1st to 15thDay
41%10%13%22%9%
2301
16th to endDay
51%11%16%14%5%
2395
June1st to 15thDay
47%10%13%17%8%2
2428
16th to endDay
43%10%13%21%11%
2574
July1st to 15thDay
26%7%12%25%20%7%
2197
16th to endDay
23%6%11%27%24%7%
2294
August1st to 15thDay
24%7%12%32%18%3
2293
16th to endDay
25%8%14%28%19%3
2197
September1st to 15thDay
22%6%14%28%23%3
1980
16th to endDay
32%10%14%25%14%2
1851
October1st to 15thDay
39%9%17%24%8%
1650
16th to endDay
53%9%13%18%5%
1609
November1st to 15thDay
56%10%13%14%31
1491
16th to endDay
58%9%11%14%5%
1410
December1st to 15thDay
56%8%14%15%3
1260
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
38%11%15%26%7%
1595
May1st to 15thNight
34%7%13%26%16%1
1320
16th to endNight
41%11%18%22%5%
1368
June1st to 15thNight
38%10%11%26%10%2
1199
16th to endNight
31%9%15%27%14%1
1046
July1st to 15thNight
20%6%14%28%23%8%
1199
16th to endNight
15%6%11%30%27%7%
1304
August1st to 15thNight
18%7%11%35%23%3
1312
16th to endNight
19%7%12%33%24%2
1650
September1st to 15thNight
18%6%14%29%25%5%
1650
16th to endNight
29%8%12%28%17%3
1776
October1st to 15thNight
38%8%15%24%12%1
1980
16th to endNight
48%9%13%23%4
2262
November1st to 15thNight
55%10%14%12%41
2366
16th to endNight
63%7%10%12%5%
2536
December1st to 15thNight
59%8%13%14%3
2700
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%28%15%5%2
259
May1st to 15thDay
14%33%25%21%5%
228
16th to endDay
14%24%26%18%11%4
266
June1st to 15thDay
12%24%24%25%11%1
373
16th to endDay
8%27%29%24%7%1
519
July1st to 15thDay
7%22%28%30%8%2
281
16th to endDay
421%34%26%10%2
271
August1st to 15thDay
8%17%30%29%10%3
255
16th to endDay
8%20%34%25%7%2
268
September1st to 15thDay
7%20%30%24%12%3
255
16th to endDay
13%23%29%20%10%2
255
October1st to 15thDay
18%28%27%19%6%
255
16th to endDay
36%9%21%23%9%
121
November1st to 15thDay
25%18%28%21%6%
75
16th to endDay
25%13%21%18%15%6%
60
December1st to 15thDay
28%6%30%25%6%3
60
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
8%22%24%29%12%2
527
May1st to 15thNight
9%26%20%26%15%1
330
16th to endNight
9%23%17%26%20%2
343
June1st to 15thNight
8%24%20%29%15%1
330
16th to endNight
8%21%21%31%17%
330
July1st to 15thNight
419%19%29%24%3
310
16th to endNight
321%13%33%26%2
348
August1st to 15thNight
313%12%30%37%3
330
16th to endNight
5%13%18%36%24%2
600
September1st to 15thNight
414%17%27%27%8%
660
16th to endNight
11%12%18%30%23%3
656
October1st to 15thNight
17%16%19%26%19%1
660
16th to endNight
22%14%18%29%12%2
704
November1st to 15thNight
24%21%16%29%7%1
700
16th to endNight
25%25%15%20%11%2
736
December1st to 15thNight
21%23%17%32%5%
900
16th to endNight
24%22%22%24%6%
885
Page generated at 2017-04-29 06:44:55. Version ac04

Copyright 2017 A. Danko


Sehgal Observatory Clear Sky Chart | Charts Home