Spring Gulch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Spring Gulch clear sky chart from 2005-11-06 to 2024-01-10.

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%
24496
22%
74460
17%
24452
61%
24452
33%
43846

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
48%
928
16%
2627
13%
927
51%
927
26%
1737
January11th to 20thNight
48%
720
23%
2340
20%
720
54%
720
27%
1445
January21st to endNight
47%
792
19%
2574
19%
792
50%
792
24%
1677
February1st to 10thNight
43%
720
16%
2340
14%
720
48%
720
24%
1503
February11th to 20thNight
42%
701
17%
2233
13%
700
48%
700
25%
1430
February21st to endNight
37%
592
21%
1776
11%
592
48%
592
25%
1180
March1st to 10thNight
44%
720
20%
2030
13%
720
51%
720
29%
1298
March11th to 20thNight
54%
720
23%
1980
16%
720
59%
720
36%
1200
March21st to endNight
44%
759
18%
2145
10%
759
51%
759
27%
1431
April1st to 10thNight
41%
540
19%
1800
15%
540
48%
540
25%
1096
April11th to 20thNight
45%
533
19%
1777
15%
533
53%
533
24%
1100
April21st to endNight
50%
540
21%
1800
18%
540
55%
540
28%
1075
May1st to 10thNight
50%
540
20%
1656
14%
540
56%
540
28%
1021
May11th to 20thNight
60%
531
21%
1472
17%
531
64%
531
35%
894
May21st to endNight
57%
584
21%
1552
15%
582
62%
582
39%
894
June1st to 10thNight
70%
540
28%
1440
21%
540
73%
540
50%
759
June11th to 20thNight
61%
540
29%
1440
21%
540
66%
540
46%
788
June21st to endNight
75%
540
29%
1440
23%
540
79%
540
61%
703
July1st to 10thNight
75%
525
21%
1400
18%
525
77%
525
43%
802
July11th to 20thNight
83%
522
22%
1448
19%
522
84%
522
46%
786
July21st to endNight
79%
591
17%
1674
16%
558
80%
558
35%
961
August1st to 10thNight
75%
537
18%
1602
17%
534
75%
534
37%
918
August11th to 20thNight
76%
534
29%
1664
26%
534
80%
534
43%
858
August21st to endNight
77%
594
28%
1980
31%
594
79%
594
38%
1040
September1st to 10thNight
74%
540
31%
1800
32%
540
79%
540
41%
917
September11th to 20thNight
74%
540
32%
1800
32%
540
78%
540
42%
912
September21st to endNight
71%
688
32%
2051
25%
688
76%
688
50%
1027
October1st to 10thNight
62%
720
27%
2160
19%
720
68%
720
41%
1201
October11th to 20thNight
59%
720
32%
2160
19%
720
68%
720
47%
1089
October21st to endNight
58%
792
30%
2376
20%
792
64%
792
40%
1314
November1st to 10thNight
54%
824
29%
2304
18%
824
60%
824
45%
1259
November11th to 20thNight
51%
950
27%
2509
17%
950
57%
950
40%
1495
November21st to endNight
54%
950
23%
2660
17%
950
58%
950
36%
1585
December1st to 10thNight
46%
950
16%
2660
11%
950
50%
950
29%
1725
December11th to 20thNight
42%
949
19%
3108
13%
949
45%
949
23%
1955
December21st to endNight
39%
1030
10%
4682
9%
1026
43%
1026
15%
2771

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
35%36%5%35%6%6%8%49%
74688
Night
36%35%5%345%6%7%54%
75008
TransparencyDay
34%8%13%21%18%7%
74403
Night
31%8%14%23%19%6%
74815
SeeingDay
9%14%29%29%15%2
14289
Night
6%6%25%40%21%2
24518

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
17%38%7%46%6%5%9%44%
1542
11th to 20thDay
18%5%7%6%345%6%7%47%
1620
21st to endDay
19%5%8%7%45%5%6%7%44%
1782
February1st to 10thDay
29%5%10%8%45%5%5%6%41%
1620
11th to 20thDay
110%6%8%7%46%6%5%7%40%
1615
21st to endDay
18%7%9%7%46%6%7%6%39%
1480
March1st to 10thDay
39%48%5%35%5%5%6%46%
1928
11th to 20thDay
27%37%6%45%6%7%8%46%
1980
21st to endDay
210%48%6%5%6%7%5%8%37%
2209
April1st to 10thDay
48%46%6%45%6%6%8%45%
2160
11th to 20thDay
49%37%7%36%7%6%8%39%
2131
21st to endDay
47%37%7%46%7%7%8%43%
2160
May1st to 10thDay
5%7%37%6%36%6%6%9%40%
2302
11th to 20thDay
6%6%26%5%46%6%7%9%43%
2423
21st to endDay
5%425%6%47%7%7%8%46%
2724
June1st to 10thDay
3313335%5%7%9%58%
2520
11th to 20thDay
32134345%6%7%62%
2520
21st to endDay
2212335%5%7%8%62%
2520
July1st to 10thDay
42235%37%7%7%9%51%
2520
11th to 20thDay
3325%6%47%6%8%10%47%
2460
21st to endDay
5%436%7%5%6%7%7%10%40%
2545
August1st to 10thDay
6%5%25%7%5%7%7%7%9%39%
2328
11th to 20thDay
43245%45%6%7%8%53%
2235
21st to endDay
3325%6%35%7%8%10%48%
2376
September1st to 10thDay
5%215%4345%5%7%58%
2160
11th to 20thDay
5%2135%445%6%8%57%
2160
21st to endDay
6%32432445%6%62%
1905
October1st to 10thDay
6%425%435%5%5%6%55%
1800
11th to 20thDay
5%5%24223447%64%
1800
21st to endDay
5%7%343235%45%58%
1980
November1st to 10thDay
25%2432346%7%63%
1755
11th to 20thDay
37%35%42345%5%59%
1668
21st to endDay
26%48%5%33445%56%
1520
December1st to 10thDay
28%49%9%46%445%46%
1520
11th to 20thDay
27%48%6%345%5%7%47%
1926
21st to endDay
17%49%7%46%6%5%6%44%
2794
January1st to 10thNight
18%49%6%45%5%5%7%47%
2627
11th to 20thNight
17%46%7%45%446%51%
2340
21st to endNight
29%6%8%6%4445%6%45%
2574
February1st to 10thNight
16%47%6%45%6%6%7%48%
2340
11th to 20thNight
17%5%7%6%36%6%6%8%45%
2232
21st to endNight
210%5%8%5%45%5%5%7%44%
1776
March1st to 10thNight
17%47%5%35%6%6%8%49%
2030
11th to 20thNight
27%35%445%45%6%55%
1980
21st to endNight
39%35%5%46%6%6%9%45%
2145
April1st to 10thNight
46%35%6%46%6%6%6%48%
1800
11th to 20thNight
49%36%5%35%6%5%9%46%
1777
21st to endNight
5%6%35%5%3446%7%51%
1800
May1st to 10thNight
5%5%35%435%5%7%9%48%
1656
11th to 20thNight
5%425%4345%7%9%52%
1471
21st to endNight
4323435%5%6%8%58%
1552
June1st to 10thNight
221232447%8%65%
1440
11th to 20thNight
421333345%7%64%
1440
21st to endNight
1122235%6%9%69%
1440
July1st to 10thNight
42225%35%5%7%10%57%
1440
11th to 20thNight
2213435%5%8%10%57%
1496
21st to endNight
43136%36%7%9%11%47%
1773
August1st to 10thNight
43145%347%8%10%51%
1611
11th to 20thNight
332343446%8%59%
1664
21st to endNight
32244345%6%9%58%
1980
September1st to 10thNight
432443445%6%62%
1800
11th to 20thNight
32134245%6%9%61%
1800
21st to endNight
4213323446%68%
2051
October1st to 10thNight
441343345%8%60%
2160
11th to 20thNight
431332345%6%66%
2160
21st to endNight
5%7%24323345%61%
2376
November1st to 10thNight
25%2331446%7%64%
2304
11th to 20thNight
37%244245%46%59%
2509
21st to endNight
26%35%4345%5%6%57%
2660
December1st to 10thNight
18%47%7%45%5%45%50%
2660
11th to 20thNight
37%36%6%35%5%6%9%45%
3271
21st to endNight
17%48%8%46%5%5%6%46%
4873

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
40%8%19%23%9%2
1543
11th to 20thDay
40%7%18%21%14%1
1620
21st to endDay
43%7%18%21%9%3
1782
February1st to 10thDay
47%7%16%17%10%2
1620
11th to 20thDay
48%6%10%21%13%2
1624
21st to endDay
48%8%13%18%11%3
1480
March1st to 10thDay
41%6%13%23%17%
1928
11th to 20thDay
36%10%15%24%12%3
1980
21st to endDay
46%10%13%21%9%2
2209
April1st to 10thDay
40%8%14%17%16%6%
2160
11th to 20thDay
44%9%12%18%16%2
2134
21st to endDay
39%8%14%23%14%2
2160
May1st to 10thDay
41%9%11%20%16%2
2302
11th to 20thDay
37%10%13%24%13%3
2427
21st to endDay
34%9%11%21%20%5%
2724
June1st to 10thDay
23%7%12%22%26%11%
2520
11th to 20thDay
22%7%8%15%26%22%
2520
21st to endDay
20%6%8%19%26%21%
2520
July1st to 10thDay
30%6%11%15%20%18%
2451
11th to 20thDay
30%9%16%18%16%11%
2385
21st to endDay
37%11%18%17%12%6%
2404
August1st to 10thDay
39%9%14%15%15%8%
2313
11th to 20thDay
30%8%14%16%21%11%
2235
21st to endDay
31%9%14%18%20%8%
2376
September1st to 10thDay
27%7%9%16%22%19%
2160
11th to 20thDay
27%7%12%18%25%11%
2160
21st to endDay
26%5%7%23%31%9%
1905
October1st to 10thDay
32%7%11%22%21%6%
1800
11th to 20thDay
26%48%29%27%7%
1800
21st to endDay
28%7%14%28%19%4
1980
November1st to 10thDay
24%7%14%25%27%3
1755
11th to 20thDay
28%6%16%28%19%3
1668
21st to endDay
34%5%12%30%15%4
1520
December1st to 10thDay
43%8%16%20%10%3
1520
11th to 20thDay
39%8%12%27%13%
1924
21st to endDay
39%11%11%18%18%3
2794
January1st to 10thNight
39%9%17%23%10%2
2627
11th to 20thNight
38%7%16%24%15%1
2340
21st to endNight
43%6%17%21%9%4
2574
February1st to 10thNight
39%9%16%23%11%1
2340
11th to 20thNight
40%7%14%24%12%2
2233
21st to endNight
42%7%13%23%12%3
1776
March1st to 10thNight
36%8%13%27%16%
2030
11th to 20thNight
29%8%15%30%14%4
1980
21st to endNight
37%11%14%25%12%2
2145
April1st to 10thNight
37%7%13%20%19%4
1800
11th to 20thNight
36%10%13%22%16%3
1777
21st to endNight
34%8%13%24%19%2
1800
May1st to 10thNight
35%8%13%25%17%2
1656
11th to 20thNight
28%11%16%28%14%3
1472
21st to endNight
25%9%15%22%23%7%
1552
June1st to 10thNight
18%7%12%24%28%12%
1440
11th to 20thNight
21%7%7%15%24%26%
1440
21st to endNight
13%5%12%17%27%25%
1440
July1st to 10thNight
23%10%12%15%19%21%
1400
11th to 20thNight
19%10%17%22%17%15%
1448
21st to endNight
26%11%24%19%13%7%
1674
August1st to 10thNight
26%10%19%20%15%10%
1602
11th to 20thNight
21%8%15%19%23%14%
1664
21st to endNight
24%8%13%20%21%15%
1980
September1st to 10thNight
24%6%11%15%23%22%
1800
11th to 20thNight
22%7%13%18%25%15%
1800
21st to endNight
19%6%8%23%35%10%
2051
October1st to 10thNight
25%8%11%25%21%11%
2160
11th to 20thNight
21%5%11%28%29%7%
2160
21st to endNight
27%6%13%29%21%5%
2376
November1st to 10thNight
22%7%14%26%27%4
2304
11th to 20thNight
28%7%13%29%20%3
2509
21st to endNight
31%6%11%29%19%4
2660
December1st to 10thNight
39%6%17%21%15%2
2660
11th to 20thNight
37%9%15%25%15%1
3272
21st to endNight
39%9%13%17%21%1
4873

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
10%13%24%36%16%1
267
11th to 20thDay
8%12%37%32%11%
240
21st to endDay
7%13%35%34%10%1
264
February1st to 10thDay
15%16%37%26%5%1
240
11th to 20thDay
14%19%33%27%6%1
240
21st to endDay
20%19%36%19%6%1
198
March1st to 10thDay
19%24%31%21%5%
368
11th to 20thDay
13%22%32%26%7%
420
21st to endDay
16%31%37%13%4
462
April1st to 10thDay
17%28%30%16%7%1
420
11th to 20thDay
20%29%27%17%5%1
412
21st to endDay
14%28%32%20%6%1
420
May1st to 10thDay
14%24%38%17%6%1
423
11th to 20thDay
11%14%28%30%14%2
570
21st to endDay
8%15%28%30%17%2
679
June1st to 10thDay
5%13%28%30%22%2
630
11th to 20thDay
5%14%32%32%16%1
630
21st to endDay
311%31%31%22%2
630
July1st to 10thDay
5%422%35%30%4
621
11th to 20thDay
2324%38%28%4
558
21st to endDay
5%5%23%39%23%6%
487
August1st to 10thDay
7%7%27%35%19%5%
447
11th to 20thDay
35%29%38%22%5%
437
21st to endDay
36%23%39%23%5%
495
September1st to 10thDay
6%9%26%31%22%5%
450
11th to 20thDay
6%11%33%32%15%4
450
21st to endDay
12%12%24%29%16%6%
347
October1st to 10thDay
11%13%21%30%17%8%
270
11th to 20thDay
10%17%25%29%17%4
270
21st to endDay
12%12%33%28%13%2
297
November1st to 10thDay
14%18%29%25%14%1
270
11th to 20thDay
8%14%28%34%14%2
270
21st to endDay
9%13%30%30%15%2
270
December1st to 10thDay
10%13%34%28%13%2
270
11th to 20thDay
10%10%30%35%14%
270
21st to endDay
12%14%36%28%9%
297
January1st to 10thNight
5%9%29%39%16%2
931
11th to 20thNight
6%6%32%39%16%2
720
21st to endNight
8%5%29%44%12%2
792
February1st to 10thNight
6%7%36%43%8%
720
11th to 20thNight
7%8%35%40%11%
704
21st to endNight
8%9%39%39%5%
592
March1st to 10thNight
6%9%36%38%10%1
720
11th to 20thNight
6%7%26%45%16%
720
21st to endNight
8%9%32%40%11%
759
April1st to 10thNight
8%12%35%36%9%
540
11th to 20thNight
9%11%33%35%12%1
533
21st to endNight
10%9%27%36%16%2
540
May1st to 10thNight
9%7%31%40%13%1
540
11th to 20thNight
8%422%40%24%2
531
21st to endNight
8%7%21%37%24%3
584
June1st to 10thNight
4417%44%30%1
540
11th to 20thNight
6%6%23%44%20%1
540
21st to endNight
1119%44%33%1
540
July1st to 10thNight
4112%39%42%3
525
11th to 20thNight
217%44%43%4
522
21st to endNight
315%34%55%3
591
August1st to 10thNight
7%18%39%43%2
537
11th to 20thNight
4111%42%39%3
534
21st to endNight
2111%39%44%4
594
September1st to 10thNight
4213%47%34%1
540
11th to 20thNight
4314%45%33%2
540
21st to endNight
4318%38%33%4
688
October1st to 10thNight
6%423%42%23%2
720
11th to 20thNight
5%427%39%22%3
720
21st to endNight
9%7%23%39%20%3
792
November1st to 10thNight
5%7%31%37%20%1
824
11th to 20thNight
8%9%28%38%15%2
950
21st to endNight
7%9%26%39%18%1
950
December1st to 10thNight
7%7%33%40%12%1
950
11th to 20thNight
9%10%31%35%14%1
950
21st to endNight
9%9%33%37%10%1
1045
Page generated at 2024-01-07 08:06:54. Version ac07

Copyright 2024 Attilla Danko


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