Stargate Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stargate Observatory clear sky chart from 2005-11-05 to 2018-03-21.

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%
16285
16%
49195
10%
16249
43%
16249
22%
33574

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
19%
970
10%
2716
4%
970
24%
970
14%
2110
January16th to endNight
21%
894
10%
2766
4%
894
27%
894
13%
2116
February1st to 15thNight
17%
761
10%
2475
2%
761
25%
761
12%
1887
February16th to endNight
24%
683
15%
2049
6%
683
32%
683
15%
1494
March1st to 15thNight
26%
780
15%
2233
10%
780
31%
780
18%
1605
March16th to endNight
35%
792
20%
2178
10%
792
42%
792
24%
1502
April1st to 15thNight
30%
611
15%
1815
8%
611
37%
611
21%
1257
April16th to endNight
39%
540
20%
1620
8%
540
48%
540
27%
1045
May1st to 15thNight
41%
540
14%
1620
9%
540
47%
540
25%
1098
May16th to endNight
49%
558
16%
1681
12%
558
55%
558
30%
1045
June1st to 15thNight
56%
360
17%
1281
18%
360
63%
360
28%
753
June16th to endNight
60%
375
19%
1275
20%
375
65%
375
31%
738
July1st to 15thNight
66%
510
17%
1360
15%
510
68%
510
41%
803
July16th to endNight
70%
564
17%
1523
15%
531
72%
531
41%
864
August1st to 15thNight
67%
539
19%
1609
15%
536
69%
536
37%
932
August16th to endNight
63%
573
24%
1719
18%
573
68%
573
35%
1003
September1st to 15thNight
58%
684
23%
1932
17%
684
61%
684
34%
1165
September16th to endNight
62%
717
24%
1980
18%
717
65%
717
36%
1194
October1st to 15thNight
47%
720
18%
2088
15%
720
52%
720
28%
1351
October16th to endNight
26%
768
16%
2385
9%
768
36%
768
18%
1665
November1st to 15thNight
38%
760
20%
2471
16%
760
45%
760
23%
1598
November16th to endNight
26%
780
15%
2655
9%
780
34%
780
16%
1847
December1st to 15thNight
17%
780
8%
2730
3%
780
24%
780
11%
2046
December16th to endNight
16%
1026
8%
3034
2%
1026
22%
1026
10%
2456

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
13%8%36%6%35%5%5%7%33%
49632
Night
14%8%36%5%3445%6%36%
49375
Cloud CoverDay
13%8%37%6%35%5%5%7%33%
49642
Night
14%8%36%5%3445%6%36%
49379
TransparencyDay
48%5%12%21%10%1
49331
Night
47%5%12%21%11%1
49195
SeeingDay
16%6%26%25%17%7%
6369
Night
18%6%28%30%13%1
16295

By Month

Percentage Cloud Cover NE (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%5%9%8%35%45%5%20%
1552
16th to endDay
14%16%7%10%9%35%35%417%
1809
February1st to 15thDay
16%14%6%10%8%4445%6%19%
1713
16th to endDay
13%14%6%9%7%35%45%5%24%
1710
March1st to 15thDay
16%12%6%7%5%34437%27%
2046
16th to endDay
17%11%47%6%35%345%30%
2174
April1st to 15thDay
18%10%46%5%35%447%31%
2142
16th to endDay
17%8%25%5%23447%37%
2340
May1st to 15thDay
18%7%37%5%35%446%33%
2331
16th to endDay
13%6%25%6%25%5%48%39%
2431
June1st to 15thDay
10%435%5%45%5%6%9%40%
2676
16th to endDay
8%5%25%6%37%6%6%10%36%
2681
July1st to 15thDay
7%425%5%35%6%5%8%45%
2520
16th to endDay
8%425%6%36%6%8%10%38%
2537
August1st to 15thDay
8%5%25%6%36%6%6%9%37%
2340
16th to endDay
11%425%5%35%46%8%40%
2483
September1st to 15thDay
12%5%35%4345%6%9%39%
2013
16th to endDay
12%5%25%425%5%6%8%41%
1980
October1st to 15thDay
13%7%35%5%3445%6%40%
1872
16th to endDay
19%9%37%5%34435%32%
1837
November1st to 15thDay
14%7%37%5%25%446%38%
1717
16th to endDay
17%9%47%6%35%45%5%29%
1634
December1st to 15thDay
16%12%7%10%6%4445%6%23%
1560
16th to endDay
20%15%7%7%6%24445%18%
1534
January1st to 15thNight
21%10%5%7%7%34346%25%
2716
16th to endNight
13%12%7%10%7%35%5%4424%
2766
February1st to 15thNight
14%13%49%7%35%44426%
2473
16th to endNight
16%11%48%6%34445%29%
2049
March1st to 15thNight
16%10%5%6%5%34446%33%
2221
16th to endNight
16%7%25%5%35%5%5%7%36%
2178
April1st to 15thNight
19%8%35%42446%6%34%
1815
16th to endNight
14%6%345%2445%7%41%
1620
May1st to 15thNight
16%6%16%5%345%5%8%35%
1620
16th to endNight
11%435%5%2435%7%46%
1679
June1st to 15thNight
7%4345%25%5%6%8%45%
1281
16th to endNight
8%5%245%3446%9%45%
1275
July1st to 15thNight
7%32442435%8%53%
1440
16th to endNight
5%3233345%7%9%51%
1628
August1st to 15thNight
5%225%436%47%8%48%
1620
16th to endNight
9%423434347%52%
1719
September1st to 15thNight
9%434423446%50%
1932
16th to endNight
10%425%4235%48%49%
1980
October1st to 15thNight
15%6%2443345%7%42%
2088
16th to endNight
19%7%36%5%345%5%5%33%
2385
November1st to 15thNight
14%8%345%2446%6%38%
2471
16th to endNight
19%9%36%5%25%45%6%30%
2655
December1st to 15thNight
19%12%5%7%5%2445%6%25%
2730
16th to endNight
21%14%7%8%6%3434420%
3034

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
17%14%6%9%8%44445%20%
1552
16th to endDay
14%16%8%10%9%35%44417%
1809
February1st to 15thDay
16%14%5%10%9%35%446%19%
1713
16th to endDay
13%13%6%9%7%35%445%24%
1710
March1st to 15thDay
17%12%5%8%5%34446%27%
2057
16th to endDay
17%12%38%6%34345%29%
2173
April1st to 15thDay
18%10%36%5%34446%31%
2142
16th to endDay
17%7%36%5%23447%36%
2340
May1st to 15thDay
18%6%37%5%3445%6%33%
2331
16th to endDay
13%5%26%5%345%48%39%
2431
June1st to 15thDay
9%5%26%5%35%5%6%9%40%
2676
16th to endDay
8%5%25%5%37%6%7%10%36%
2681
July1st to 15thDay
6%425%5%35%6%5%9%44%
2520
16th to endDay
7%425%6%46%6%8%10%37%
2537
August1st to 15thDay
8%426%6%46%6%7%9%37%
2340
16th to endDay
11%426%5%35%5%5%8%40%
2483
September1st to 15thDay
11%5%35%5%345%6%9%39%
2013
16th to endDay
11%6%34435%5%6%8%40%
1980
October1st to 15thDay
12%8%35%5%2445%7%39%
1872
16th to endDay
19%9%48%5%3434432%
1837
November1st to 15thDay
14%8%36%5%2445%7%37%
1717
16th to endDay
17%10%47%6%35%45%5%29%
1634
December1st to 15thDay
16%12%7%10%5%4445%6%23%
1560
16th to endDay
21%15%6%9%5%33436%19%
1534
January1st to 15thNight
21%11%47%6%44345%24%
2716
16th to endNight
13%12%7%10%6%45%5%4424%
2766
February1st to 15thNight
14%13%5%10%7%35%44425%
2466
16th to endNight
16%11%5%8%6%3434429%
2049
March1st to 15thNight
17%10%5%6%5%34436%32%
2233
16th to endNight
16%6%35%5%35%447%36%
2178
April1st to 15thNight
19%7%345%3445%7%34%
1815
16th to endNight
14%6%25%4245%5%7%41%
1620
May1st to 15thNight
16%6%25%6%345%5%7%36%
1619
16th to endNight
10%5%25%6%23447%45%
1679
June1st to 15thNight
7%335%5%346%6%9%45%
1281
16th to endNight
8%4246%245%6%10%45%
1275
July1st to 15thNight
7%32342435%8%53%
1440
16th to endNight
5%3233345%7%9%52%
1628
August1st to 15thNight
5%3245%35%47%8%48%
1620
16th to endNight
9%4235%24346%52%
1719
September1st to 15thNight
9%425%434346%50%
1932
16th to endNight
10%425%42345%8%48%
1980
October1st to 15thNight
15%6%245%2445%6%42%
2088
16th to endNight
19%8%35%5%345%46%32%
2385
November1st to 15thNight
14%8%344345%6%6%38%
2471
16th to endNight
18%10%37%43445%7%29%
2655
December1st to 15thNight
19%12%5%8%5%2445%5%25%
2730
16th to endNight
21%14%6%8%6%3434420%
3034

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
65%5%11%11%5%
1553
16th to endDay
69%410%10%4
1809
February1st to 15thDay
65%5%8%15%5%
1715
16th to endDay
61%311%16%6%1
1710
March1st to 15thDay
57%5%11%16%7%
2057
16th to endDay
55%49%21%7%1
2174
April1st to 15thDay
52%410%20%11%
2142
16th to endDay
46%414%17%14%2
2340
May1st to 15thDay
50%410%20%10%2
2331
16th to endDay
42%5%12%23%14%1
2435
June1st to 15thDay
39%5%14%25%13%1
2676
16th to endDay
39%8%13%22%14%1
2681
July1st to 15thDay
35%7%9%27%19%1
2371
16th to endDay
36%7%16%23%13%2
2380
August1st to 15thDay
38%7%14%25%13%1
2327
16th to endDay
38%7%11%27%13%2
2483
September1st to 15thDay
38%6%14%27%12%
2013
16th to endDay
38%5%12%30%11%
1980
October1st to 15thDay
43%413%24%13%1
1872
16th to endDay
53%5%14%18%8%
1837
November1st to 15thDay
45%6%13%23%10%1
1717
16th to endDay
55%5%14%17%6%
1634
December1st to 15thDay
61%413%14%5%
1560
16th to endDay
66%412%11%4
1534
January1st to 15thNight
60%411%15%7%
2716
16th to endNight
61%414%15%4
2766
February1st to 15thNight
60%6%10%15%7%
2475
16th to endNight
56%311%20%7%
2049
March1st to 15thNight
52%410%20%10%1
2233
16th to endNight
46%411%25%10%1
2178
April1st to 15thNight
48%5%11%20%13%
1815
16th to endNight
40%5%11%20%17%4
1620
May1st to 15thNight
45%412%21%13%2
1620
16th to endNight
37%5%12%24%16%3
1681
June1st to 15thNight
34%7%12%28%16%1
1281
16th to endNight
33%5%14%24%20%1
1275
July1st to 15thNight
29%49%32%21%2
1360
16th to endNight
26%7%18%26%18%3
1523
August1st to 15thNight
30%5%15%32%14%2
1609
16th to endNight
31%5%11%30%18%2
1719
September1st to 15thNight
34%413%28%17%1
1932
16th to endNight
33%414%31%15%
1980
October1st to 15thNight
41%411%23%17%1
2088
16th to endNight
50%413%23%7%
2385
November1st to 15thNight
43%5%13%24%11%1
2471
16th to endNight
53%315%20%6%
2655
December1st to 15thNight
59%5%14%14%6%
2730
16th to endNight
66%5%11%12%5%
3034

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
22%11%42%16%5%
135
16th to endDay
28%11%41%14%3
144
February1st to 15thDay
25%13%43%16%1
135
16th to endDay
22%15%43%15%3
120
March1st to 15thDay
26%11%33%20%8%
242
16th to endDay
25%6%25%31%9%2
311
April1st to 15thDay
21%9%30%23%12%2
270
16th to endDay
22%5%30%19%14%7%
270
May1st to 15thDay
24%425%24%16%4
288
16th to endDay
16%425%25%18%8%
331
June1st to 15thDay
11%430%31%17%4
471
16th to endDay
10%431%28%19%5%
495
July1st to 15thDay
8%221%34%21%11%
475
16th to endDay
7%320%32%24%11%
397
August1st to 15thDay
9%214%30%23%19%
313
16th to endDay
13%414%24%24%19%
332
September1st to 15thDay
10%418%18%30%17%
315
16th to endDay
15%313%21%30%15%
314
October1st to 15thDay
15%6%26%23%20%7%
315
16th to endDay
24%10%34%23%5%1
253
November1st to 15thDay
19%10%26%26%14%2
135
16th to endDay
18%16%41%16%5%
106
December1st to 15thDay
23%14%41%13%7%
90
16th to endDay
28%17%37%13%2
112
January1st to 15thNight
26%9%36%21%41
975
16th to endNight
19%9%36%28%5%
894
February1st to 15thNight
20%9%42%23%3
764
16th to endNight
22%9%34%27%5%
683
March1st to 15thNight
22%8%35%27%6%
780
16th to endNight
19%6%31%31%10%1
792
April1st to 15thNight
23%9%30%30%5%
611
16th to endNight
17%6%33%30%10%1
540
May1st to 15thNight
18%427%34%13%1
540
16th to endNight
12%225%36%20%2
560
June1st to 15thNight
8%126%48%14%
360
16th to endNight
12%119%45%21%
375
July1st to 15thNight
9%115%39%30%3
510
16th to endNight
5%215%48%25%3
564
August1st to 15thNight
7%15%38%33%4
539
16th to endNight
11%14%34%34%4
573
September1st to 15thNight
12%418%32%26%5%
684
16th to endNight
12%315%33%28%6%
717
October1st to 15thNight
20%422%31%18%3
720
16th to endNight
24%9%33%26%5%
768
November1st to 15thNight
19%8%28%28%13%1
760
16th to endNight
24%12%30%23%8%
780
December1st to 15thNight
27%10%37%19%5%
780
16th to endNight
27%9%36%23%3
1026
Page generated at 2018-03-22 11:34:20. Version ac04

Copyright 2018 A. Danko


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