Granite Gap
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Granite Gap 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
70%
14918
35%
45543
29%
14877
77%
14877
51%
21883

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
66%
718
33%
2327
32%
716
73%
716
49%
1107
January16th to endNight
64%
768
37%
2496
33%
768
74%
768
46%
1206
February1st to 15thNight
67%
699
36%
2277
33%
696
78%
696
57%
983
February16th to endNight
58%
632
44%
1756
31%
632
71%
632
58%
851
March1st to 15thNight
59%
720
41%
1980
27%
720
70%
720
61%
949
March16th to endNight
66%
768
40%
2112
24%
768
78%
768
65%
965
April1st to 15thNight
58%
607
36%
1866
23%
607
73%
607
56%
835
April16th to endNight
60%
534
44%
1780
31%
534
80%
534
66%
675
May1st to 15thNight
60%
494
38%
1600
27%
494
74%
494
63%
640
May16th to endNight
70%
513
38%
1540
31%
513
76%
513
63%
672
June1st to 15thNight
78%
495
36%
1485
32%
495
81%
495
68%
623
June16th to endNight
79%
495
25%
1485
22%
495
80%
495
50%
735
July1st to 15thNight
77%
465
18%
1395
15%
465
78%
465
30%
850
July16th to endNight
78%
522
14%
1467
13%
489
79%
489
25%
965
August1st to 15thNight
80%
494
21%
1506
22%
491
81%
491
31%
908
August16th to endNight
81%
525
22%
1750
25%
525
81%
525
31%
1032
September1st to 15thNight
73%
541
24%
1696
24%
541
74%
541
31%
1041
September16th to endNight
79%
656
37%
1820
28%
656
83%
656
56%
920
October1st to 15thNight
77%
660
37%
1980
30%
660
81%
660
60%
909
October16th to endNight
83%
704
42%
2112
34%
704
88%
704
70%
882
November1st to 15thNight
76%
700
43%
2100
35%
700
83%
700
70%
876
November16th to endNight
68%
720
42%
2177
32%
720
76%
720
55%
1021
December1st to 15thNight
70%
720
39%
2340
36%
720
77%
720
52%
1055
December16th to endNight
62%
768
35%
2496
31%
768
71%
768
48%
1183

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
221332345%7%63%
46140
Night
221232345%6%64%
45750
TransparencyDay
19%36%14%27%27%
45835
Night
18%37%15%28%26%
45556
SeeingDay
5%8%20%31%24%9%
4681
Night
3218%41%29%3
14928

By Month

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
221441245%8%63%
1611
16th to endDay
442421335%7%60%
1728
February1st to 15thDay
2212223436%69%
1575
16th to endDay
321231245%5%66%
1713
March1st to 15thDay
1212323436%68%
1980
16th to endDay
2212212245%73%
2112
April1st to 15thDay
122112247%72%
2081
16th to endDay
11111112482%
2127
May1st to 15thDay
11213336%73%
2018
16th to endDay
11121324476%
2221
June1st to 15thDay
1111122247%73%
2145
16th to endDay
221242445%8%61%
2145
July1st to 15thDay
43235%37%6%8%11%43%
2145
16th to endDay
6%325%6%47%8%8%11%34%
2285
August1st to 15thDay
5%425%5%47%7%8%11%37%
2114
16th to endDay
43245%36%6%8%11%43%
2100
September1st to 15thDay
6%425%5%35%6%8%8%43%
1931
16th to endDay
32232345%6%65%
1810
October1st to 15thDay
111232235%5%70%
1650
16th to endDay
11212325%76%
1760
November1st to 15thDay
12212236%76%
1759
16th to endDay
223323335%69%
1782
December1st to 15thDay
32332335%6%65%
1620
16th to endDay
3413323346%62%
1728
January1st to 15thNight
3323312346%65%
2327
16th to endNight
4323323446%61%
2496
February1st to 15thNight
1212213346%69%
2277
16th to endNight
1213323235%69%
1756
March1st to 15thNight
2211213346%69%
1980
16th to endNight
21211333376%
2112
April1st to 15thNight
11231444469%
1866
16th to endNight
111223382%
1780
May1st to 15thNight
112112345%75%
1600
16th to endNight
11121324475%
1540
June1st to 15thNight
211112245%75%
1485
16th to endNight
1112425%5%6%7%60%
1485
July1st to 15thNight
22146%48%8%9%12%37%
1485
16th to endNight
23246%410%9%11%14%29%
1575
August1st to 15thNight
32145%46%8%10%13%39%
1515
16th to endNight
33245%36%7%9%11%42%
1750
September1st to 15thNight
5%425%5%46%7%8%10%40%
1696
16th to endNight
323213345%69%
1820
October1st to 15thNight
1112312346%70%
1980
16th to endNight
111111335%77%
2112
November1st to 15thNight
11212336%76%
2100
16th to endNight
3312312235%70%
2177
December1st to 15thNight
321222235%6%66%
2340
16th to endNight
3313423345%63%
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
19%36%19%32%18%
1612
16th to endDay
24%1416%33%18%
1728
February1st to 15thDay
16%2414%30%31%
1575
16th to endDay
18%1315%34%26%
1713
March1st to 15thDay
16%1311%34%32%
1980
16th to endDay
14%1310%33%35%
2112
April1st to 15thDay
12%139%37%35%
2081
16th to endDay
9%117%25%54%
2127
May1st to 15thDay
11%249%26%46%
2018
16th to endDay
12%149%25%47%
2224
June1st to 15thDay
12%125%22%55%
2145
16th to endDay
19%45%9%22%39%
2145
July1st to 15thDay
29%8%15%18%15%12%
2006
16th to endDay
36%11%19%21%10%1
2130
August1st to 15thDay
34%9%14%19%16%4
2099
16th to endDay
31%9%14%17%16%10%
2100
September1st to 15thDay
34%7%10%18%17%11%
1931
16th to endDay
18%3415%35%22%
1810
October1st to 15thDay
15%27%15%28%31%
1650
16th to endDay
12%1416%32%33%
1760
November1st to 15thDay
10%1417%36%29%
1759
16th to endDay
18%2315%34%25%
1782
December1st to 15thDay
18%25%23%32%16%
1620
16th to endDay
22%28%22%32%11%
1728
January1st to 15thNight
20%35%17%33%19%
2327
16th to endNight
22%2419%33%17%
2496
February1st to 15thNight
15%1416%31%29%
2288
16th to endNight
17%1315%35%26%
1756
March1st to 15thNight
15%1314%32%32%
1980
16th to endNight
12%1410%36%33%
2112
April1st to 15thNight
16%1311%34%32%
1866
16th to endNight
9%128%30%48%
1780
May1st to 15thNight
11%138%27%46%
1601
16th to endNight
12%2312%25%43%
1541
June1st to 15thNight
11%136%23%53%
1485
16th to endNight
20%45%12%19%37%
1485
July1st to 15thNight
29%12%15%19%13%9%
1395
16th to endNight
34%14%22%20%6%1
1467
August1st to 15thNight
30%11%18%20%14%4
1506
16th to endNight
30%10%17%18%14%9%
1750
September1st to 15thNight
32%9%14%17%15%10%
1696
16th to endNight
17%4415%36%21%
1820
October1st to 15thNight
15%27%16%26%31%
1980
16th to endNight
10%2414%29%38%
2112
November1st to 15thNight
9%2318%36%29%
2100
16th to endNight
18%1313%31%30%
2177
December1st to 15thNight
18%26%22%32%17%
2340
16th to endNight
21%210%21%32%12%
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
6%432%37%14%4
90
16th to endDay
5%6%19%40%18%9%
96
February1st to 15thDay
8%411%28%38%7%
90
16th to endDay
8%18%33%24%12%2
219
March1st to 15thDay
416%30%25%16%7%
270
16th to endDay
6%19%25%29%11%6%
288
April1st to 15thDay
320%28%27%15%4
269
16th to endDay
320%32%26%14%2
259
May1st to 15thDay
417%40%27%8%2
228
16th to endDay
310%30%34%20%1
266
June1st to 15thDay
45%25%38%17%9%
255
16th to endDay
5%114%43%26%8%
255
July1st to 15thDay
7%9%37%35%8%
245
16th to endDay
5%8%31%33%20%
271
August1st to 15thDay
6%1429%36%21%
255
16th to endDay
32428%47%14%
268
September1st to 15thDay
11%9%32%36%8%
255
16th to endDay
5%419%30%30%10%
250
October1st to 15thDay
1116%25%31%24%
90
16th to endDay
310%33%33%19%
96
November1st to 15thDay
47%26%25%22%13%
90
16th to endDay
415%28%35%13%2
90
December1st to 15thDay
25%21%24%32%14%
90
16th to endDay
13%11%26%35%13%
96
January1st to 15thNight
4320%46%23%1
720
16th to endNight
6%5%19%44%22%2
768
February1st to 15thNight
3320%43%25%2
704
16th to endNight
25%31%45%14%
632
March1st to 15thNight
4429%40%18%2
720
16th to endNight
2424%44%23%1
768
April1st to 15thNight
26%28%46%14%1
607
16th to endNight
15%31%42%17%1
534
May1st to 15thNight
1430%45%16%1
495
16th to endNight
2220%49%24%
515
June1st to 15thNight
2113%51%28%1
495
16th to endNight
119%52%34%1
495
July1st to 15thNight
39%35%47%4
465
16th to endNight
3330%54%7%
522
August1st to 15thNight
4221%57%13%
494
16th to endNight
4427%56%7%
525
September1st to 15thNight
6%19%28%51%4
541
16th to endNight
4110%39%39%4
656
October1st to 15thNight
216%45%31%3
660
16th to endNight
2110%44%35%6%
704
November1st to 15thNight
1118%43%30%5%
700
16th to endNight
5%319%40%27%3
720
December1st to 15thNight
5%218%44%25%2
720
16th to endNight
4424%44%18%4
768
Page generated at 2017-04-29 07:45:09. Version ac04

Copyright 2017 A. Danko


Granite Gap Clear Sky Chart | Charts Home