Great Basin College
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Great Basin College clear sky chart from 2005-11-06 to 2024-03-08.

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
62%
23354
21%
80627
20%
23284
65%
23284
29%
48237

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 10thNight
50%
748
10%
4371
11%
736
53%
736
10%
2984
January11th to 20thNight
52%
754
7%
4417
12%
740
55%
740
9%
3405
January21st to endNight
52%
825
9%
4759
17%
814
55%
814
10%
3625
February1st to 10thNight
54%
760
14%
2352
12%
760
57%
760
24%
1556
February11th to 20thNight
56%
741
18%
2219
18%
740
60%
740
28%
1419
February21st to endNight
50%
628
17%
1884
16%
628
55%
628
26%
1234
March1st to 10thNight
51%
750
15%
2249
13%
750
56%
750
24%
1500
March11th to 20thNight
60%
720
18%
2034
16%
720
63%
720
32%
1270
March21st to endNight
52%
792
14%
2120
9%
792
55%
792
27%
1449
April1st to 10thNight
55%
720
18%
1800
10%
720
58%
720
31%
1218
April11th to 20thNight
55%
697
23%
1765
13%
697
58%
697
36%
1101
April21st to endNight
57%
540
24%
1620
17%
540
60%
540
35%
945
May1st to 10thNight
55%
540
25%
1620
19%
540
59%
540
39%
891
May11th to 20thNight
58%
531
20%
1594
17%
531
60%
531
33%
939
May21st to endNight
57%
492
15%
1656
13%
492
61%
492
26%
1014
June1st to 10thNight
65%
360
24%
1440
28%
360
72%
360
39%
652
June11th to 20thNight
62%
360
27%
1440
30%
360
73%
360
42%
626
June21st to endNight
73%
360
30%
1440
39%
360
82%
360
52%
547
July1st to 10thNight
78%
350
26%
1400
35%
350
80%
350
42%
606
July11th to 20thNight
78%
348
31%
1392
40%
348
82%
348
47%
573
July21st to endNight
77%
452
31%
1543
34%
427
80%
427
43%
733
August1st to 10thNight
72%
537
29%
1602
23%
534
74%
534
45%
823
August11th to 20thNight
80%
566
34%
1634
25%
566
82%
566
58%
757
August21st to endNight
81%
792
36%
1980
23%
792
82%
792
64%
1010
September1st to 10thNight
80%
720
36%
1822
24%
720
83%
720
64%
909
September11th to 20thNight
77%
720
36%
1980
29%
720
79%
720
56%
993
September21st to endNight
78%
720
38%
1980
33%
720
82%
720
59%
969
October1st to 10thNight
68%
720
30%
1980
24%
720
73%
720
47%
1074
October11th to 20thNight
70%
720
34%
2128
30%
720
75%
720
47%
1108
October21st to endNight
69%
792
33%
2574
33%
792
75%
792
49%
1219
November1st to 10thNight
64%
740
24%
2405
24%
740
66%
740
30%
1394
November11th to 20thNight
64%
760
25%
2470
24%
760
69%
760
36%
1357
November21st to endNight
60%
760
20%
2470
19%
760
65%
760
31%
1452
December1st to 10thNight
51%
760
17%
2481
16%
760
55%
760
24%
1592
December11th to 20thNight
52%
759
13%
3199
13%
758
55%
758
15%
2139
December21st to endNight
41%
820
8%
4807
12%
817
45%
817
10%
3154

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
45%36%6%35%5%6%8%50%
78592
Night
5%7%36%6%45%6%6%8%45%
80990
TransparencyDay
30%8%12%18%18%14%
78300
Night
32%9%13%18%16%11%
80804
SeeingDay
6%9%22%31%23%9%
13761
Night
7%418%41%26%3
23405

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 10thDay
410%6%15%9%5%6%6%7%9%23%
2539
11th to 20thDay
411%5%10%10%6%9%8%7%7%23%
2540
21st to endDay
5%10%412%17%8%7%8%7%7%15%
2891
February1st to 10thDay
46%5%9%8%47%8%8%11%31%
1824
11th to 20thDay
37%38%8%5%6%8%9%8%34%
1850
21st to endDay
26%38%7%47%7%8%10%39%
1570
March1st to 10thDay
39%5%8%7%5%6%7%7%10%33%
1871
11th to 20thDay
37%37%6%47%6%7%10%39%
1926
21st to endDay
5%8%38%8%5%6%6%6%8%36%
2233
April1st to 10thDay
5%8%37%6%46%5%7%9%39%
2160
11th to 20thDay
5%5%36%6%46%6%6%8%45%
2142
21st to endDay
6%6%25%5%3445%8%50%
2340
May1st to 10thDay
5%5%245%345%6%8%53%
2340
11th to 20thDay
6%6%246%35%6%7%9%46%
2301
21st to endDay
6%7%35%7%46%6%7%8%43%
2614
June1st to 10thDay
43245%35%6%6%7%56%
2520
11th to 20thDay
331332345%6%66%
2520
21st to endDay
2212222335%75%
2520
July1st to 10thDay
221332435%6%69%
2520
11th to 20thDay
2212312446%72%
2520
21st to endDay
33244345%5%7%60%
2683
August1st to 10thDay
4314423447%63%
2328
11th to 20thDay
223323436%73%
2263
21st to endDay
122223346%74%
2376
September1st to 10thDay
2112223345%76%
2138
11th to 20thDay
3213324345%70%
1980
21st to endDay
331432323471%
1980
October1st to 10thDay
4425%4235%46%61%
1980
11th to 20thDay
35%2342345%6%63%
1829
21st to endDay
431333446%7%63%
1782
November1st to 10thDay
45%47%6%36%5%7%8%46%
1674
11th to 20thDay
6%6%345%26%5%8%8%46%
1710
21st to endDay
5%6%38%6%45%5%6%8%43%
1710
December1st to 10thDay
5%7%37%9%5%5%5%6%8%39%
1696
11th to 20thDay
5%9%5%8%8%47%7%9%11%29%
1928
21st to endDay
5%8%49%8%6%8%8%8%9%29%
2794
January1st to 10thNight
411%411%9%5%9%7%8%9%23%
4406
11th to 20thNight
415%5%11%11%6%7%7%6%7%22%
4420
21st to endNight
6%13%5%12%13%5%8%7%5%7%19%
4765
February1st to 10thNight
47%38%8%46%6%8%11%35%
2352
11th to 20thNight
37%47%6%46%7%8%10%38%
2218
21st to endNight
28%5%8%8%6%8%7%7%8%34%
1884
March1st to 10thNight
5%7%47%8%46%7%8%10%34%
2249
11th to 20thNight
37%36%6%36%6%8%11%41%
2034
21st to endNight
7%8%37%6%45%6%7%8%40%
2120
April1st to 10thNight
5%6%36%6%36%7%7%9%42%
1800
11th to 20thNight
5%7%245%45%6%6%6%50%
1765
21st to endNight
7%8%25%4245%5%5%53%
1620
May1st to 10thNight
6%5%246%345%5%8%54%
1620
11th to 20thNight
6%5%36%6%25%6%6%9%45%
1594
21st to endNight
7%6%36%5%36%6%6%7%45%
1656
June1st to 10thNight
3324435%45%8%61%
1440
11th to 20thNight
5%41342345%5%65%
1440
21st to endNight
221342335%6%70%
1440
July1st to 10thNight
42235%345%6%7%60%
1440
11th to 20thNight
322442445%7%64%
1440
21st to endNight
4334435%5%6%6%58%
1634
August1st to 10thNight
4324435%6%7%7%56%
1611
11th to 20thNight
222432345%6%68%
1634
21st to endNight
2213323447%69%
1980
September1st to 10thNight
411232235%5%72%
1822
11th to 20thNight
4322323346%69%
1980
21st to endNight
431232233473%
1980
October1st to 10thNight
45%23324346%63%
1980
11th to 20thNight
4414433445%64%
2128
21st to endNight
4413323447%66%
2574
November1st to 10thNight
7%6%35%435%5%6%7%50%
2405
11th to 20thNight
45%25%5%35%5%7%8%52%
2470
21st to endNight
36%36%7%46%6%7%11%43%
2470
December1st to 10thNight
5%8%37%7%35%6%6%9%40%
2481
11th to 20thNight
7%9%48%8%5%7%8%7%12%26%
3276
21st to endNight
6%9%410%10%6%7%8%10%9%23%
4862

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 10thDay
53%12%16%16%3
2539
11th to 20thDay
52%15%15%10%6%1
2540
21st to endDay
48%21%16%10%41
2891
February1st to 10thDay
42%12%18%20%6%2
1824
11th to 20thDay
39%11%17%20%11%2
1860
21st to endDay
34%11%21%24%9%2
1570
March1st to 10thDay
42%11%17%21%7%2
1871
11th to 20thDay
37%8%19%22%11%3
1926
21st to endDay
43%11%20%16%6%3
2233
April1st to 10thDay
39%9%15%20%13%3
2160
11th to 20thDay
34%9%14%22%19%3
2145
21st to endDay
32%7%14%26%18%4
2340
May1st to 10thDay
27%8%12%24%25%5%
2340
11th to 20thDay
31%9%12%24%19%6%
2304
21st to endDay
35%10%15%20%18%4
2614
June1st to 10thDay
25%6%12%20%28%9%
2520
11th to 20thDay
19%5%8%18%29%21%
2520
21st to endDay
12%35%15%29%36%
2520
July1st to 10thDay
15%46%12%23%40%
2451
11th to 20thDay
13%35%9%21%48%
2445
21st to endDay
21%5%6%10%21%37%
2534
August1st to 10thDay
20%46%11%18%41%
2313
11th to 20thDay
13%35%11%29%39%
2263
21st to endDay
11%35%14%29%38%
2376
September1st to 10thDay
12%26%10%28%42%
2138
11th to 20thDay
16%5%7%16%29%27%
1980
21st to endDay
18%36%16%32%25%
1980
October1st to 10thDay
25%5%9%19%27%15%
1980
11th to 20thDay
21%5%9%24%31%10%
1829
21st to endDay
20%5%14%32%23%6%
1782
November1st to 10thDay
34%9%11%23%19%5%
1674
11th to 20thDay
31%9%12%31%15%2
1710
21st to endDay
38%6%15%22%15%3
1710
December1st to 10thDay
40%11%16%21%8%3
1696
11th to 20thDay
43%14%17%16%10%1
1928
21st to endDay
43%14%15%16%12%
2794
January1st to 10thNight
47%13%20%15%5%1
4406
11th to 20thNight
54%15%14%8%6%2
4420
21st to endNight
46%22%15%11%5%2
4765
February1st to 10thNight
38%11%20%22%7%2
2352
11th to 20thNight
36%10%17%23%13%2
2219
21st to endNight
38%10%20%22%9%2
1884
March1st to 10thNight
40%10%18%21%8%2
2249
11th to 20thNight
32%10%19%24%13%2
2034
21st to endNight
37%12%18%22%8%3
2120
April1st to 10thNight
36%10%15%22%14%3
1800
11th to 20thNight
31%8%13%27%18%4
1765
21st to endNight
30%7%14%23%23%3
1620
May1st to 10thNight
27%6%12%24%26%5%
1620
11th to 20thNight
31%8%13%22%21%6%
1595
21st to endNight
35%10%14%19%19%4
1656
June1st to 10thNight
21%6%14%21%31%8%
1440
11th to 20thNight
20%5%7%19%29%21%
1440
21st to endNight
14%47%12%30%33%
1440
July1st to 10thNight
20%5%7%11%21%36%
1400
11th to 20thNight
17%5%6%10%19%44%
1392
21st to endNight
22%5%6%10%18%39%
1543
August1st to 10thNight
22%6%7%13%19%33%
1602
11th to 20thNight
15%38%11%26%36%
1634
21st to endNight
15%37%11%23%41%
1980
September1st to 10thNight
14%36%10%25%41%
1822
11th to 20thNight
18%46%14%26%32%
1980
21st to endNight
16%35%14%32%29%
1980
October1st to 10thNight
22%6%8%18%28%17%
1980
11th to 20thNight
22%5%6%21%33%13%
2128
21st to endNight
19%5%11%30%27%8%
2574
November1st to 10thNight
32%8%12%20%20%8%
2405
11th to 20thNight
27%7%14%25%23%3
2470
21st to endNight
32%8%15%26%15%3
2470
December1st to 10thNight
38%10%16%23%9%4
2481
11th to 20thNight
44%11%18%18%8%1
3276
21st to endNight
42%16%20%15%6%1
4862

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 10thDay
12%9%22%31%21%5%
180
11th to 20thDay
9%8%13%34%25%11%
180
21st to endDay
7%8%17%30%25%15%
226
February1st to 10thDay
7%7%32%28%20%6%
384
11th to 20thDay
6%10%27%33%18%5%
455
21st to endDay
311%30%34%19%3
382
March1st to 10thDay
7%9%25%34%22%3
449
11th to 20thDay
310%24%32%25%6%
420
21st to endDay
8%11%25%37%16%3
462
April1st to 10thDay
11%13%22%28%21%6%
420
11th to 20thDay
6%13%27%36%12%5%
412
21st to endDay
10%10%22%30%21%6%
420
May1st to 10thDay
5%12%24%33%17%9%
423
11th to 20thDay
11%8%27%30%16%9%
448
21st to endDay
11%12%20%25%22%10%
485
June1st to 10thDay
6%12%21%25%26%10%
450
11th to 20thDay
7%14%26%29%18%6%
450
21st to endDay
37%24%34%20%13%
450
July1st to 10thDay
35%23%34%26%8%
446
11th to 20thDay
2423%35%26%10%
444
21st to endDay
3318%31%33%12%
487
August1st to 10thDay
6%421%30%29%11%
447
11th to 20thDay
3320%28%30%16%
437
21st to endDay
1421%30%29%14%
495
September1st to 10thDay
26%18%29%26%18%
450
11th to 20thDay
410%19%27%25%15%
450
21st to endDay
6%7%20%30%27%11%
450
October1st to 10thDay
310%24%23%27%14%
450
11th to 20thDay
5%11%20%23%28%14%
360
21st to endDay
7%8%18%32%26%8%
297
November1st to 10thDay
6%11%21%28%26%7%
270
11th to 20thDay
9%5%20%34%24%9%
270
21st to endDay
9%9%14%33%26%8%
270
December1st to 10thDay
7%9%19%33%22%11%
264
11th to 20thDay
48%21%28%29%9%
180
21st to endDay
11%10%18%33%23%6%
198
January1st to 10thNight
9%7%19%35%25%5%
760
11th to 20thNight
6%7%22%36%25%4
760
21st to endNight
10%5%17%39%24%6%
836
February1st to 10thNight
6%7%21%42%21%3
760
11th to 20thNight
6%322%48%18%2
744
21st to endNight
5%6%26%43%19%2
628
March1st to 10thNight
7%5%24%42%19%3
750
11th to 20thNight
6%420%43%25%2
720
21st to endNight
11%6%22%43%17%1
792
April1st to 10thNight
8%6%24%40%20%2
720
11th to 20thNight
8%7%23%40%19%3
697
21st to endNight
11%422%35%25%3
540
May1st to 10thNight
6%7%25%40%20%3
540
11th to 20thNight
10%421%34%28%4
531
21st to endNight
10%5%19%34%28%3
494
June1st to 10thNight
4323%38%29%4
360
11th to 20thNight
6%321%42%27%1
360
21st to endNight
3216%51%27%1
360
July1st to 10thNight
419%51%33%1
350
11th to 20thNight
3113%54%29%
348
21st to endNight
418%50%37%1
452
August1st to 10thNight
5%214%47%31%1
537
11th to 20thNight
3110%51%33%2
566
21st to endNight
2210%45%38%3
792
September1st to 10thNight
5%28%43%38%5%
720
11th to 20thNight
5%212%37%38%7%
720
21st to endNight
5%211%37%36%9%
720
October1st to 10thNight
7%217%38%32%4
720
11th to 20thNight
5%5%15%39%33%4
720
21st to endNight
6%318%39%28%6%
792
November1st to 10thNight
10%316%38%29%4
740
11th to 20thNight
7%419%46%21%4
760
21st to endNight
5%421%39%26%5%
760
December1st to 10thNight
8%6%22%40%20%4
760
11th to 20thNight
11%6%18%41%21%2
760
21st to endNight
13%9%23%38%15%2
836
Page generated at 2024-03-05 04:24:05. Version ac07

Copyright © 2024 Attilla Danko.


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