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

2017-09-12
.

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
38%
15489
15%
46768
10%
15453
43%
15453
22%
31896

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
18%
895
10%
2506
4%
895
23%
895
13%
1969
January16th to endNight
21%
825
10%
2553
5%
825
28%
825
13%
1953
February1st to 15thNight
17%
701
10%
2281
2%
701
25%
701
12%
1728
February16th to endNight
25%
631
15%
1893
6%
631
33%
631
16%
1371
March1st to 15thNight
26%
720
15%
2061
9%
720
31%
720
18%
1489
March16th to endNight
35%
768
18%
2112
10%
768
41%
768
23%
1465
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%
671
23%
1896
17%
671
62%
671
35%
1139
September16th to endNight
61%
657
22%
1815
17%
657
64%
657
35%
1105
October1st to 15thNight
47%
660
19%
1914
16%
660
53%
660
29%
1224
October16th to endNight
25%
704
14%
2186
8%
704
35%
704
17%
1547
November1st to 15thNight
38%
700
21%
2276
16%
700
46%
700
23%
1455
November16th to endNight
26%
720
14%
2451
9%
720
33%
720
15%
1729
December1st to 15thNight
16%
720
8%
2520
3%
720
23%
720
11%
1905
December16th to endNight
16%
947
8%
2801
2%
947
22%
947
10%
2279

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%46%6%35%5%5%7%33%
47872
Night
14%8%36%5%3445%6%36%
46948
Cloud CoverDay
13%8%47%6%35%5%5%7%33%
47882
Night
14%8%36%5%3445%6%36%
46952
TransparencyDay
48%5%12%21%10%1
47571
Night
47%5%12%21%11%1
46768
SeeingDay
16%6%26%26%17%7%
5776
Night
18%6%28%30%13%1
15499

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
17%14%6%9%8%35%45%5%19%
1432
16th to endDay
14%17%7%10%9%45%45%415%
1670
February1st to 15thDay
15%13%6%10%8%45%45%6%19%
1578
16th to endDay
13%14%6%9%8%35%45%5%23%
1580
March1st to 15thDay
17%12%6%8%5%34436%27%
1888
16th to endDay
18%11%48%6%35%345%29%
2112
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%
1969
16th to endDay
13%5%35%435%5%6%8%39%
1815
October1st to 15thDay
12%7%35%5%3345%7%40%
1716
16th to endDay
20%10%37%5%34335%32%
1684
November1st to 15thDay
13%7%37%5%25%446%38%
1582
16th to endDay
18%9%5%7%6%35%45%5%28%
1509
December1st to 15thDay
16%12%7%10%6%44445%22%
1440
16th to endDay
20%16%7%8%6%34445%19%
1416
January1st to 15thNight
21%11%5%7%7%35%345%24%
2506
16th to endNight
13%13%7%10%7%35%5%45%24%
2553
February1st to 15thNight
14%13%49%7%35%44426%
2279
16th to endNight
16%10%48%6%44445%29%
1893
March1st to 15thNight
16%10%5%6%434446%32%
2049
16th to endNight
16%7%25%5%35%5%5%7%36%
2112
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
10%434423447%50%
1896
16th to endNight
11%425%424447%48%
1815
October1st to 15thNight
15%5%2443345%7%43%
1914
16th to endNight
20%8%37%5%345%5%5%31%
2186
November1st to 15thNight
13%7%345%2446%7%39%
2276
16th to endNight
20%9%36%5%25%45%6%29%
2451
December1st to 15thNight
20%12%5%7%5%2445%5%24%
2520
16th to endNight
22%14%7%8%6%3434419%
2801

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%4445%5%19%
1432
16th to endDay
14%17%8%10%9%45%44415%
1670
February1st to 15thDay
15%14%6%10%9%35%45%6%19%
1578
16th to endDay
12%13%6%9%7%35%5%45%24%
1580
March1st to 15thDay
17%12%5%8%434446%27%
1899
16th to endDay
17%12%38%6%35%345%28%
2111
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%5%9%39%
1969
16th to endDay
12%6%34435%5%6%8%39%
1815
October1st to 15thDay
12%7%36%5%3445%7%39%
1716
16th to endDay
20%9%48%43434432%
1684
November1st to 15thDay
13%7%36%5%245%5%7%38%
1582
16th to endDay
18%10%47%6%3445%5%28%
1509
December1st to 15thDay
16%12%7%11%5%4445%6%22%
1440
16th to endDay
21%16%7%9%6%33436%19%
1416
January1st to 15thNight
22%11%48%6%44345%23%
2506
16th to endNight
14%12%8%10%6%35%5%4424%
2553
February1st to 15thNight
13%13%5%10%7%35%445%26%
2272
16th to endNight
15%11%5%8%6%45%445%29%
1893
March1st to 15thNight
18%10%46%5%34436%32%
2061
16th to endNight
17%6%35%5%35%5%47%36%
2112
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
10%425%434346%50%
1896
16th to endNight
10%425%424448%48%
1815
October1st to 15thNight
14%5%245%2445%7%43%
1914
16th to endNight
19%9%36%5%345%46%31%
2186
November1st to 15thNight
13%7%344345%6%6%39%
2276
16th to endNight
19%10%37%5%3445%7%28%
2451
December1st to 15thNight
20%11%5%8%5%2445%5%24%
2520
16th to endNight
21%14%6%8%6%3435%419%
2801

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%12%4
1433
16th to endDay
70%49%10%4
1670
February1st to 15thDay
65%5%8%15%5%
1580
16th to endDay
61%411%16%5%1
1580
March1st to 15thDay
58%5%12%16%6%
1899
16th to endDay
57%49%20%7%1
2112
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
39%6%13%27%12%
1969
16th to endDay
40%5%12%29%11%
1815
October1st to 15thDay
42%414%24%13%1
1716
16th to endDay
54%5%14%18%7%
1684
November1st to 15thDay
44%6%13%23%10%1
1582
16th to endDay
56%5%14%16%6%
1509
December1st to 15thDay
63%413%14%4
1440
16th to endDay
67%412%11%3
1416
January1st to 15thNight
61%410%15%6%
2506
16th to endNight
61%413%16%4
2553
February1st to 15thNight
59%6%10%15%7%
2281
16th to endNight
56%312%20%7%
1893
March1st to 15thNight
53%411%20%9%1
2061
16th to endNight
47%412%24%10%1
2112
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
33%413%28%17%1
1896
16th to endNight
34%414%31%14%
1815
October1st to 15thNight
39%5%12%23%18%
1914
16th to endNight
51%413%22%6%
2186
November1st to 15thNight
42%5%13%25%11%1
2276
16th to endNight
54%315%19%6%
2451
December1st to 15thNight
60%5%14%14%5%
2520
16th to endNight
66%5%11%11%4
2801

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%43%16%5%1
90
16th to endDay
30%12%37%15%31
96
February1st to 15thDay
16%15%48%17%1
90
16th to endDay
16%16%43%19%4
81
March1st to 15thDay
28%13%28%21%7%
189
16th to endDay
26%6%26%28%9%2
288
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
11%5%19%18%29%16%
299
16th to endDay
16%313%24%29%12%
254
October1st to 15thDay
13%6%25%25%21%7%
255
16th to endDay
26%9%35%22%5%1
196
November1st to 15thDay
12%12%25%32%15%2
90
16th to endDay
21%22%35%15%5%
71
December1st to 15thDay
23%13%43%16%3
60
16th to endDay
32%20%34%13%
75
January1st to 15thNight
27%10%36%20%41
900
16th to endNight
20%10%35%28%6%
825
February1st to 15thNight
20%10%41%23%3
704
16th to endNight
21%9%34%28%5%
631
March1st to 15thNight
22%9%35%26%6%
720
16th to endNight
19%6%31%30%10%1
768
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%
671
16th to endNight
13%315%35%27%5%
657
October1st to 15thNight
19%422%30%19%2
660
16th to endNight
24%10%33%26%4
704
November1st to 15thNight
18%8%29%27%14%1
700
16th to endNight
25%12%28%23%8%
720
December1st to 15thNight
28%9%37%18%5%
720
16th to endNight
27%9%35%23%3
947
Page generated at 2017-09-13 07:39:07. Version ac04

Copyright 2017 A. Danko


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