Galaxy Quest Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Galaxy Quest Observatory clear sky chart from 2005-11-05 to 2017-09-21.

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
32%
14844
17%
46889
8%
14813
42%
14813
20%
31125

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
20%
720
19%
2506
7%
716
37%
716
17%
1588
January16th to endNight
15%
768
17%
2673
3%
768
32%
768
15%
1754
February1st to 15thNight
18%
702
15%
2268
5%
701
31%
701
15%
1558
February16th to endNight
21%
631
19%
1893
5%
631
38%
631
20%
1273
March1st to 15thNight
20%
720
16%
2099
5%
720
33%
720
18%
1486
March16th to endNight
28%
768
20%
2112
7%
768
38%
768
23%
1417
April1st to 15thNight
23%
682
18%
1763
4%
682
32%
682
22%
1263
April16th to endNight
32%
540
15%
1620
7%
540
39%
540
20%
1125
May1st to 15thNight
34%
540
12%
1620
8%
540
39%
540
20%
1160
May16th to endNight
34%
452
11%
1557
10%
452
39%
452
15%
1109
June1st to 15thNight
40%
360
9%
1260
9%
360
45%
360
14%
909
June16th to endNight
50%
360
10%
1260
11%
360
53%
360
19%
851
July1st to 15thNight
55%
340
10%
1348
16%
340
57%
340
20%
848
July16th to endNight
52%
385
12%
1427
14%
363
56%
363
19%
923
August1st to 15thNight
55%
539
12%
1608
9%
535
56%
535
24%
1061
August16th to endNight
57%
591
22%
1737
14%
591
60%
591
32%
1050
September1st to 15thNight
50%
720
18%
1914
10%
720
55%
720
34%
1207
September16th to endNight
48%
681
27%
1880
15%
681
56%
681
36%
1112
October1st to 15thNight
36%
660
21%
1892
10%
660
46%
660
25%
1248
October16th to endNight
26%
704
18%
2246
7%
704
39%
704
21%
1462
November1st to 15thNight
34%
700
21%
2277
12%
700
45%
700
22%
1447
November16th to endNight
27%
739
19%
2451
8%
739
41%
739
18%
1586
December1st to 15thNight
17%
750
17%
2646
4%
750
33%
750
16%
1772
December16th to endNight
16%
792
17%
2832
3%
792
33%
792
14%
1916

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
18%6%25%43445%7%37%
47968
Night
18%7%25%424446%38%
47061
TransparencyDay
45%411%22%13%1
47658
Night
47%311%22%13%1
46889
SeeingDay
23%6%27%27%12%2
6344
Night
22%8%28%26%11%1
14847

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
15%6%35%43445%7%40%
1432
16th to endDay
16%7%35%423446%39%
1551
February1st to 15thDay
16%10%25%5%35%5%46%36%
1591
16th to endDay
12%10%36%436%5%5%6%34%
1580
March1st to 15thDay
20%8%34434446%35%
1850
16th to endDay
16%8%24434345%41%
2112
April1st to 15thDay
19%6%36%433346%37%
2183
16th to endDay
20%7%25%424347%36%
2340
May1st to 15thDay
24%8%25%5%24447%31%
2332
16th to endDay
22%6%2442445%8%33%
2563
June1st to 15thDay
25%8%345%3445%7%28%
2700
16th to endDay
21%5%36%5%246%6%7%32%
2700
July1st to 15thDay
14%5%245%25%5%6%9%38%
2528
16th to endDay
14%6%25%5%36%5%6%10%33%
2632
August1st to 15thDay
14%5%34435%5%7%9%36%
2340
16th to endDay
12%41443447%9%44%
2464
September1st to 15thDay
11%424434447%48%
2046
16th to endDay
15%414313346%50%
1873
October1st to 15thDay
18%5%35%423445%42%
1738
16th to endDay
21%5%23424445%40%
1625
November1st to 15thDay
20%6%24324448%39%
1581
16th to endDay
19%8%34332335%42%
1507
December1st to 15thDay
21%8%34423437%36%
1311
16th to endDay
22%11%345%3333434%
1389
January1st to 15thNight
15%8%345%1445%7%40%
2506
16th to endNight
14%10%26%5%24446%37%
2673
February1st to 15thNight
14%8%36%5%46%446%34%
2267
16th to endNight
15%9%35%434346%39%
1893
March1st to 15thNight
19%10%35%434345%34%
2086
16th to endNight
16%6%25%5%24446%40%
2112
April1st to 15thNight
19%9%35%5%34346%33%
1763
16th to endNight
22%8%244235%47%33%
1620
May1st to 15thNight
23%7%35%434446%31%
1620
16th to endNight
21%8%37%5%25%45%7%28%
1555
June1st to 15thNight
25%8%25%5%35%5%5%6%25%
1260
16th to endNight
19%6%25%5%26%446%35%
1260
July1st to 15thNight
16%5%35%435%5%5%8%35%
1428
16th to endNight
16%6%36%435%5%5%7%34%
1523
August1st to 15thNight
14%7%245%35%5%5%7%38%
1620
16th to endNight
13%42441445%8%46%
1737
September1st to 15thNight
14%5%2432345%6%48%
1914
16th to endNight
13%413223346%52%
1880
October1st to 15thNight
20%5%25%423346%42%
1892
16th to endNight
20%6%25%423346%40%
2246
November1st to 15thNight
19%6%25%323346%41%
2277
16th to endNight
19%5%24424345%41%
2451
December1st to 15thNight
21%8%245%33345%37%
2646
16th to endNight
22%10%34423345%36%
2832

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
44%412%23%13%2
1433
16th to endDay
45%112%26%13%1
1551
February1st to 15thDay
48%313%20%13%
1594
16th to endDay
48%311%19%13%2
1580
March1st to 15thDay
49%311%19%13%2
1860
16th to endDay
42%310%19%19%4
2112
April1st to 15thDay
47%27%21%17%2
2183
16th to endDay
47%310%19%14%4
2340
May1st to 15thDay
52%28%20%13%2
2332
16th to endDay
49%413%20%10%1
2567
June1st to 15thDay
54%410%20%8%1
2700
16th to endDay
50%6%9%19%12%
2700
July1st to 15thDay
39%5%15%26%11%
2379
16th to endDay
44%5%15%23%9%1
2466
August1st to 15thDay
41%6%15%27%9%
2327
16th to endDay
34%5%14%26%18%
2464
September1st to 15thDay
35%412%27%18%1
2046
16th to endDay
36%39%27%21%1
1873
October1st to 15thDay
43%39%26%14%1
1738
16th to endDay
45%212%24%13%
1625
November1st to 15thDay
45%312%23%14%1
1581
16th to endDay
46%313%18%16%1
1507
December1st to 15thDay
48%311%24%10%
1311
16th to endDay
54%39%17%14%
1389
January1st to 15thNight
44%412%24%12%2
2506
16th to endNight
48%310%21%14%1
2673
February1st to 15thNight
51%311%20%11%1
2268
16th to endNight
46%310%22%14%2
1893
March1st to 15thNight
52%28%19%13%2
2099
16th to endNight
44%39%18%19%4
2112
April1st to 15thNight
50%37%17%17%2
1763
16th to endNight
51%39%18%14%3
1620
May1st to 15thNight
52%410%16%14%1
1620
16th to endNight
56%310%17%10%1
1557
June1st to 15thNight
56%5%12%17%6%2
1260
16th to endNight
50%311%21%11%1
1260
July1st to 15thNight
45%5%14%22%12%
1348
16th to endNight
47%414%23%8%1
1427
August1st to 15thNight
45%415%23%10%
1608
16th to endNight
36%413%28%16%
1737
September1st to 15thNight
37%313%28%16%1
1914
16th to endNight
34%29%31%20%1
1880
October1st to 15thNight
44%39%25%14%1
1892
16th to endNight
45%311%25%13%1
2246
November1st to 15thNight
43%312%23%15%1
2277
16th to endNight
46%311%22%15%1
2451
December1st to 15thNight
50%210%23%12%
2646
16th to endNight
51%310%21%12%
2832

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
13%25%23%28%10%
60
16th to endDay
20%8%39%29%2
79
February1st to 15thDay
27%10%38%17%5%
239
16th to endDay
18%12%34%27%6%
239
March1st to 15thDay
26%12%37%18%4
270
16th to endDay
22%13%33%22%6%2
288
April1st to 15thDay
27%8%33%21%8%1
270
16th to endDay
23%5%37%21%9%2
270
May1st to 15thDay
32%5%25%26%6%3
288
16th to endDay
25%6%27%28%11%1
346
June1st to 15thDay
27%324%28%14%1
495
16th to endDay
25%222%32%14%3
495
July1st to 15thDay
18%120%38%15%3
313
16th to endDay
19%19%34%20%5%
326
August1st to 15thDay
16%321%33%22%3
313
16th to endDay
18%317%32%24%4
332
September1st to 15thDay
15%323%31%20%5%
315
16th to endDay
19%223%29%16%9%
275
October1st to 15thDay
19%9%24%21%18%5%
241
16th to endDay
25%9%31%26%6%
240
November1st to 15thDay
22%10%26%28%7%4
235
16th to endDay
27%14%27%25%5%1
240
December1st to 15thDay
27%11%35%16%9%
111
16th to endDay
34%20%26%17%1
64
January1st to 15thNight
20%18%35%22%3
720
16th to endNight
22%17%36%19%3
768
February1st to 15thNight
21%16%37%22%2
704
16th to endNight
21%12%35%22%6%
631
March1st to 15thNight
26%10%35%22%4
720
16th to endNight
20%11%32%25%9%1
768
April1st to 15thNight
25%6%36%24%7%
682
16th to endNight
27%7%25%28%10%1
540
May1st to 15thNight
27%226%28%12%2
540
16th to endNight
26%322%32%13%2
453
June1st to 15thNight
30%215%34%15%1
360
16th to endNight
23%115%41%17%
360
July1st to 15thNight
21%13%40%21%2
340
16th to endNight
19%13%36%28%
385
August1st to 15thNight
16%211%42%23%2
539
16th to endNight
16%216%36%25%4
591
September1st to 15thNight
16%221%34%21%3
720
16th to endNight
17%325%27%19%6%
681
October1st to 15thNight
24%5%25%27%14%2
660
16th to endNight
24%11%33%23%7%
704
November1st to 15thNight
22%8%28%27%11%1
700
16th to endNight
21%14%31%23%8%1
739
December1st to 15thNight
29%13%34%18%4
750
16th to endNight
29%15%33%17%3
792
Page generated at 2017-09-22 07:35:33. Version ac04

Copyright 2017 A. Danko


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