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 2017-12-01.

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
56%
16034
22%
47834
17%
15995
62%
15995
30%
29481

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
39%
717
21%
2327
12%
716
51%
716
26%
1429
January16th to endNight
37%
768
23%
2430
15%
768
47%
768
26%
1520
February1st to 15thNight
39%
702
25%
2108
14%
700
51%
700
30%
1269
February16th to endNight
41%
631
25%
1893
14%
631
52%
631
30%
1156
March1st to 15thNight
46%
720
27%
1987
16%
720
56%
720
35%
1198
March16th to endNight
50%
768
25%
2112
16%
768
57%
768
37%
1237
April1st to 15thNight
50%
718
24%
1976
16%
718
56%
718
36%
1186
April16th to endNight
57%
615
30%
1767
21%
615
65%
615
41%
984
May1st to 15thNight
64%
539
26%
1619
20%
539
69%
539
40%
895
May16th to endNight
72%
561
22%
1682
18%
561
74%
561
37%
969
June1st to 15thNight
70%
540
15%
1620
13%
540
71%
540
27%
1062
June16th to endNight
76%
540
13%
1620
11%
540
76%
540
28%
1087
July1st to 15thNight
76%
510
9%
1530
9%
510
76%
510
27%
1003
July16th to endNight
74%
564
9%
1595
9%
531
74%
531
23%
1108
August1st to 15thNight
75%
539
10%
1638
9%
536
76%
536
24%
1117
August16th to endNight
65%
645
12%
1982
12%
645
66%
645
20%
1408
September1st to 15thNight
64%
720
12%
1980
12%
720
64%
720
21%
1415
September16th to endNight
59%
717
18%
1980
16%
717
62%
717
24%
1367
October1st to 15thNight
61%
720
28%
2013
24%
720
66%
720
35%
1211
October16th to endNight
61%
768
31%
2304
29%
768
68%
768
37%
1306
November1st to 15thNight
56%
760
31%
2288
27%
760
64%
760
39%
1244
November16th to endNight
51%
780
30%
2535
23%
780
62%
780
35%
1397
December1st to 15thNight
46%
724
26%
2352
22%
724
53%
724
29%
1374
December16th to endNight
48%
768
23%
2496
19%
768
55%
768
26%
1539

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%5%26%6%46%5%6%8%39%
48580
Night
8%5%25%5%345%6%8%45%
48038
TransparencyDay
40%7%12%17%14%7%
48281
Night
34%7%14%19%15%8%
47841
SeeingDay
10%315%22%25%21%
5887
Night
11%420%33%25%5%
16042

By Month

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
13%6%35%5%34448%41%
1611
16th to endDay
13%6%25%424436%44%
1791
February1st to 15thDay
15%7%24323335%46%
1750
16th to endDay
14%6%25%423335%49%
1580
March1st to 15thDay
8%5%1431446%8%50%
1971
16th to endDay
9%5%25%435%45%6%47%
2111
April1st to 15thDay
8%5%35%5%35%45%6%47%
1972
16th to endDay
7%425%33446%7%50%
2202
May1st to 15thDay
4425%325%6%6%8%49%
2331
16th to endDay
6%4246%47%6%6%7%41%
2431
June1st to 15thDay
8%437%8%5%8%7%7%9%28%
2340
16th to endDay
6%5%27%8%5%9%7%8%10%26%
2340
July1st to 15thDay
6%5%27%8%5%10%8%9%10%23%
2340
16th to endDay
6%6%49%9%6%9%8%7%9%22%
2465
August1st to 15thDay
10%6%28%9%6%8%9%7%10%19%
2308
16th to endDay
12%7%47%8%5%6%7%7%8%22%
2208
September1st to 15thDay
9%6%38%9%5%8%7%7%9%24%
1980
16th to endDay
11%7%27%7%5%6%6%7%7%30%
1980
October1st to 15thDay
10%5%26%5%35%45%6%44%
1947
16th to endDay
7%4234245%45%54%
1920
November1st to 15thDay
7%3235%2435%8%55%
1897
16th to endDay
9%423423336%53%
1755
December1st to 15thDay
12%6%35%5%34347%43%
1622
16th to endDay
13%6%36%5%25%46%7%38%
1728
January1st to 15thNight
12%6%25%42445%7%44%
2327
16th to endNight
14%6%345%24345%45%
2430
February1st to 15thNight
13%5%25%323235%51%
2103
16th to endNight
12%6%24423447%47%
1893
March1st to 15thNight
8%5%25%424347%50%
1987
16th to endNight
10%413323345%55%
2112
April1st to 15thNight
9%424334446%51%
1976
16th to endNight
5%4144145%5%7%54%
1767
May1st to 15thNight
5%3133245%5%10%53%
1619
16th to endNight
5%313426%46%10%51%
1682
June1st to 15thNight
8%5%236%36%6%9%12%34%
1620
16th to endNight
6%4245%36%9%8%13%35%
1620
July1st to 15thNight
5%325%6%36%7%10%13%36%
1620
16th to endNight
3436%6%47%7%10%14%30%
1703
August1st to 15thNight
5%315%8%47%6%9%13%32%
1649
16th to endNight
9%5%36%6%46%7%9%10%31%
1982
September1st to 15thNight
10%426%7%45%6%7%12%31%
1980
16th to endNight
8%7%36%6%35%6%8%8%35%
1980
October1st to 15thNight
7%5%25%5%33448%49%
2013
16th to endNight
7%314434445%55%
2304
November1st to 15thNight
6%5%13324347%56%
2288
16th to endNight
8%42432345%7%52%
2535
December1st to 15thNight
11%426%43335%8%46%
2352
16th to endNight
12%5%35%5%2445%7%42%
2496

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
40%49%17%17%11%
1612
16th to endDay
40%46%18%19%11%
1791
February1st to 15thDay
40%36%14%19%15%
1752
16th to endDay
38%37%15%22%13%
1580
March1st to 15thDay
30%410%21%23%9%
1971
16th to endDay
34%410%18%19%11%
2112
April1st to 15thDay
36%5%8%18%22%9%
1972
16th to endDay
31%5%10%22%20%9%
2202
May1st to 15thDay
28%6%12%22%21%8%
2331
16th to endDay
37%8%14%21%14%4
2435
June1st to 15thDay
48%10%16%15%8%
2340
16th to endDay
46%11%19%16%5%
2340
July1st to 15thDay
46%12%24%14%1
2201
16th to endDay
51%12%19%12%3
2310
August1st to 15thDay
53%12%21%11%2
2295
16th to endDay
55%12%16%12%3
2208
September1st to 15thDay
52%10%15%12%7%1
1980
16th to endDay
49%8%12%15%10%3
1980
October1st to 15thDay
39%410%17%17%11%
1947
16th to endDay
30%5%6%16%23%17%
1920
November1st to 15thDay
27%49%23%23%12%
1897
16th to endDay
32%39%18%23%14%
1755
December1st to 15thDay
40%48%21%18%7%
1622
16th to endDay
41%5%10%20%13%8%
1728
January1st to 15thNight
39%49%17%18%10%
2327
16th to endNight
40%47%13%22%12%
2430
February1st to 15thNight
37%37%14%20%16%
2112
16th to endNight
36%48%17%18%14%
1893
March1st to 15thNight
32%410%22%19%10%
1987
16th to endNight
30%410%20%21%12%
2112
April1st to 15thNight
32%410%18%24%9%
1976
16th to endNight
26%5%12%24%21%9%
1767
May1st to 15thNight
24%7%14%24%18%9%
1620
16th to endNight
27%8%17%25%16%4
1684
June1st to 15thNight
36%10%21%23%6%
1620
16th to endNight
34%13%22%21%6%
1620
July1st to 15thNight
33%13%30%19%2
1530
16th to endNight
36%16%28%14%4
1595
August1st to 15thNight
35%15%30%15%2
1638
16th to endNight
42%13%22%15%4
1982
September1st to 15thNight
42%13%20%14%7%1
1980
16th to endNight
40%11%15%18%10%3
1980
October1st to 15thNight
32%6%11%19%19%11%
2013
16th to endNight
30%47%17%23%17%
2304
November1st to 15thNight
27%48%23%24%11%
2288
16th to endNight
30%49%19%20%15%
2535
December1st to 15thNight
36%312%23%16%7%
2352
16th to endNight
39%5%10%22%13%8%
2496

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
14%14%37%15%8%8%
90
16th to endDay
15%17%33%23%9%
96
February1st to 15thDay
11%23%28%22%12%2
90
16th to endDay
6%14%41%27%8%1
81
March1st to 15thDay
13%6%30%31%16%1
261
16th to endDay
8%5%28%31%21%4
288
April1st to 15thDay
10%7%26%25%24%4
270
16th to endDay
8%318%27%28%13%
270
May1st to 15thDay
7%6%18%28%20%17%
288
16th to endDay
6%18%17%35%29%
331
June1st to 15thDay
13%6%15%28%34%
315
16th to endDay
11%113%29%42%
315
July1st to 15thDay
7%110%25%55%
305
16th to endDay
6%411%31%44%
326
August1st to 15thDay
15%213%26%40%
313
16th to endDay
9%6%12%29%41%
332
September1st to 15thDay
13%16%18%32%27%
315
16th to endDay
18%16%18%35%20%
314
October1st to 15thDay
14%115%29%28%9%
315
16th to endDay
9%420%34%25%5%
336
November1st to 15thDay
9%320%38%21%7%
315
16th to endDay
6%5%29%30%22%5%
135
December1st to 15thDay
11%7%38%22%15%4
90
16th to endDay
14%8%22%37%10%6%
96
January1st to 15thNight
15%9%31%29%13%
720
16th to endNight
16%9%31%34%8%
768
February1st to 15thNight
15%8%31%34%9%
704
16th to endNight
15%7%31%40%4
631
March1st to 15thNight
10%7%29%40%11%
720
16th to endNight
12%5%26%37%16%
768
April1st to 15thNight
10%5%28%38%16%
718
16th to endNight
8%326%37%22%1
615
May1st to 15thNight
6%122%44%21%3
540
16th to endNight
7%210%35%39%4
563
June1st to 15thNight
11%15%31%40%8%
540
16th to endNight
7%6%22%47%15%
540
July1st to 15thNight
6%321%45%22%
510
16th to endNight
5%1320%50%19%
564
August1st to 15thNight
7%116%56%18%
539
16th to endNight
11%16%21%41%17%
645
September1st to 15thNight
12%16%25%40%13%
720
16th to endNight
13%110%32%37%4
717
October1st to 15thNight
11%18%36%30%2
720
16th to endNight
8%222%38%25%2
768
November1st to 15thNight
9%324%41%19%1
760
16th to endNight
10%329%37%17%1
780
December1st to 15thNight
13%5%26%35%17%1
724
16th to endNight
14%6%24%35%19%
768
Page generated at 2017-12-02 09:14:14. Version ac04

Copyright 2017 A. Danko


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