Velveeta Valley Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Velveeta Valley Observatory clear sky chart from 2005-11-05 to 2017-09-22.

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%
16026
17%
46909
10%
15983
44%
15983
24%
31211

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
23%
900
13%
2506
5%
895
31%
895
19%
1833
January16th to endNight
22%
960
12%
2622
5%
960
29%
960
16%
1975
February1st to 15thNight
22%
850
14%
2262
4%
850
29%
850
20%
1618
February16th to endNight
27%
631
18%
1893
8%
631
37%
631
19%
1305
March1st to 15thNight
30%
717
14%
2157
7%
717
36%
717
20%
1472
March16th to endNight
30%
576
15%
1998
10%
576
37%
576
18%
1377
April1st to 15thNight
28%
539
16%
1797
10%
539
38%
539
19%
1213
April16th to endNight
36%
540
18%
1770
13%
540
45%
540
22%
1182
May1st to 15thNight
36%
540
14%
1527
9%
540
42%
540
22%
1081
May16th to endNight
45%
563
17%
1497
8%
561
52%
561
31%
967
June1st to 15thNight
54%
540
15%
1440
10%
540
57%
540
36%
902
June16th to endNight
50%
540
16%
1440
8%
540
55%
540
31%
940
July1st to 15thNight
66%
510
17%
1360
11%
510
68%
510
43%
798
July16th to endNight
69%
564
21%
1417
16%
531
71%
531
44%
816
August1st to 15thNight
75%
539
22%
1564
22%
536
76%
536
42%
855
August16th to endNight
65%
573
20%
1910
20%
573
69%
573
34%
1073
September1st to 15thNight
63%
540
28%
1800
27%
540
69%
540
37%
951
September16th to endNight
55%
655
25%
1862
17%
655
61%
655
34%
1104
October1st to 15thNight
42%
660
25%
1950
17%
660
50%
660
30%
1202
October16th to endNight
33%
704
18%
2208
9%
704
42%
704
22%
1436
November1st to 15thNight
33%
700
24%
2276
17%
700
43%
700
26%
1370
November16th to endNight
27%
825
16%
2445
8%
825
35%
825
20%
1682
December1st to 15thNight
20%
900
13%
2520
4%
900
27%
900
16%
1903
December16th to endNight
20%
960
11%
2688
3%
960
27%
960
12%
2156

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%36%5%3445%7%36%
47986
Night
14%7%35%5%24446%40%
47078
Cloud CoverDay
14%7%36%5%3445%7%37%
47994
Night
14%7%35%424446%40%
47083
TransparencyDay
45%5%13%22%11%1
47672
Night
43%5%12%22%14%1
46910
SeeingDay
16%7%26%26%17%6%
6032
Night
17%7%29%31%12%1
16029

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
13%11%6%8%5%25%5%5%7%28%
1432
16th to endDay
13%13%5%12%6%24345%26%
1602
February1st to 15thDay
12%13%6%7%5%24446%30%
1600
16th to endDay
14%10%47%6%24336%33%
1580
March1st to 15thDay
15%10%46%5%23348%34%
1803
16th to endDay
18%9%36%6%35%45%6%31%
2226
April1st to 15thDay
18%9%47%5%3445%6%30%
2151
16th to endDay
20%9%26%5%2345%5%33%
2190
May1st to 15thDay
19%8%37%6%3445%7%27%
2422
16th to endDay
13%6%26%5%35%5%6%6%37%
2617
June1st to 15thDay
13%5%245%35%45%8%39%
2520
16th to endDay
9%6%25%5%35%5%6%10%38%
2520
July1st to 15thDay
6%324436%6%7%9%44%
2520
16th to endDay
7%5%25%6%35%5%7%10%41%
2655
August1st to 15thDay
6%425%5%35%6%7%10%41%
2382
16th to endDay
11%5%244345%6%7%44%
2292
September1st to 15thDay
13%413334437%50%
2160
16th to endDay
10%5%25%5%3445%7%45%
1899
October1st to 15thDay
15%7%25%423346%45%
1678
16th to endDay
18%6%25%5%33446%38%
1664
November1st to 15thDay
11%8%35%5%35%35%6%39%
1582
16th to endDay
17%11%45%423236%37%
1515
December1st to 15thDay
18%13%48%434336%29%
1440
16th to endDay
21%14%6%7%6%33445%22%
1536
January1st to 15thNight
15%10%47%5%34345%34%
2506
16th to endNight
12%10%6%10%6%3445%6%28%
2622
February1st to 15thNight
12%11%6%7%5%24345%37%
2260
16th to endNight
15%10%36%5%24445%36%
1893
March1st to 15thNight
16%10%35%5%33345%39%
2144
16th to endNight
18%9%36%5%34446%33%
1998
April1st to 15thNight
18%8%35%424346%37%
1797
16th to endNight
19%7%34424446%38%
1770
May1st to 15thNight
18%5%25%5%25%5%6%8%33%
1527
16th to endNight
10%5%245%245%5%10%43%
1496
June1st to 15thNight
10%4235%245%6%8%47%
1440
16th to endNight
8%4245%35%5%7%8%42%
1440
July1st to 15thNight
6%22332346%9%54%
1440
16th to endNight
6%3234236%7%10%50%
1513
August1st to 15thNight
43145%244410%54%
1573
16th to endNight
9%423424347%52%
1910
September1st to 15thNight
8%413333246%58%
1800
16th to endNight
8%42443446%6%50%
1862
October1st to 15thNight
11%6%24424436%49%
1950
16th to endNight
18%7%24423336%42%
2208
November1st to 15thNight
12%7%35%422335%49%
2276
16th to endNight
18%8%35%424445%37%
2445
December1st to 15thNight
19%11%38%5%34346%29%
2520
16th to endNight
22%12%5%9%5%25%44423%
2688

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
14%11%6%7%5%35%5%5%6%27%
1432
16th to endDay
13%14%6%11%6%3435%5%26%
1602
February1st to 15thDay
12%13%6%6%6%24436%30%
1600
16th to endDay
14%11%36%7%24336%34%
1580
March1st to 15thDay
16%9%37%423349%34%
1813
16th to endDay
19%9%36%5%35%45%6%31%
2224
April1st to 15thDay
18%9%47%5%35%45%6%30%
2151
16th to endDay
21%9%35%5%24346%33%
2190
May1st to 15thDay
20%7%37%6%345%6%6%28%
2422
16th to endDay
13%6%25%6%35%5%6%7%37%
2617
June1st to 15thDay
14%425%5%35%5%6%7%40%
2520
16th to endDay
10%5%25%5%35%5%6%9%39%
2520
July1st to 15thDay
7%424436%5%7%9%44%
2520
16th to endDay
8%5%26%5%35%5%7%9%41%
2655
August1st to 15thDay
6%315%6%36%6%7%10%41%
2382
16th to endDay
12%5%245%2446%7%45%
2292
September1st to 15thDay
13%413424447%50%
2160
16th to endDay
10%5%25%425%45%8%44%
1899
October1st to 15thDay
17%6%15%423336%45%
1678
16th to endDay
19%7%246%3345%6%37%
1664
November1st to 15thDay
12%7%45%5%2435%6%40%
1582
16th to endDay
17%11%45%423336%37%
1515
December1st to 15thDay
19%12%48%434336%29%
1440
16th to endDay
21%14%6%7%6%24345%22%
1536
January1st to 15thNight
15%10%5%7%5%3434434%
2506
16th to endNight
13%10%6%9%6%35%45%6%29%
2622
February1st to 15thNight
13%12%6%6%5%23235%37%
2253
16th to endNight
16%10%46%5%24346%35%
1893
March1st to 15thNight
16%9%35%5%3435%5%38%
2157
16th to endNight
18%9%35%5%24447%33%
1998
April1st to 15thNight
18%8%35%424446%37%
1797
16th to endNight
19%7%25%42435%6%38%
1770
May1st to 15thNight
17%6%25%5%25%5%6%8%33%
1526
16th to endNight
10%5%24425%45%10%43%
1496
June1st to 15thNight
11%42342346%9%47%
1440
16th to endNight
9%425%445%5%6%9%42%
1440
July1st to 15thNight
5%21332346%9%55%
1440
16th to endNight
6%3233235%7%11%50%
1513
August1st to 15thNight
5%31342445%9%55%
1573
16th to endNight
9%324423447%51%
1910
September1st to 15thNight
8%5%13323245%58%
1800
16th to endNight
8%42443445%6%50%
1862
October1st to 15thNight
12%5%245%24345%49%
1950
16th to endNight
19%7%14424346%42%
2208
November1st to 15thNight
12%7%25%313345%49%
2276
16th to endNight
19%8%35%424446%37%
2445
December1st to 15thNight
19%11%47%5%34345%29%
2520
16th to endNight
22%13%48%5%3444423%
2688

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
54%6%15%14%8%
1433
16th to endDay
60%412%14%7%
1602
February1st to 15thDay
55%5%11%18%7%
1602
16th to endDay
52%5%11%21%8%1
1580
March1st to 15thDay
48%5%15%19%9%
1813
16th to endDay
52%6%13%20%6%
2226
April1st to 15thDay
54%411%20%8%
2151
16th to endDay
51%5%11%18%11%2
2190
May1st to 15thDay
54%6%12%19%5%
2422
16th to endDay
45%7%12%20%13%1
2621
June1st to 15thDay
41%7%12%23%14%
2520
16th to endDay
38%7%14%23%14%1
2520
July1st to 15thDay
33%7%16%25%14%1
2371
16th to endDay
36%6%18%22%13%3
2488
August1st to 15thDay
34%6%15%28%13%1
2367
16th to endDay
37%5%13%26%15%2
2292
September1st to 15thDay
33%5%8%29%20%1
2160
16th to endDay
36%5%13%28%15%1
1899
October1st to 15thDay
41%411%27%15%
1678
16th to endDay
47%5%12%23%10%1
1664
November1st to 15thDay
43%411%24%13%1
1582
16th to endDay
50%416%22%6%
1515
December1st to 15thDay
58%414%15%6%
1440
16th to endDay
64%5%11%10%7%
1536
January1st to 15thNight
52%411%19%11%
2506
16th to endNight
56%413%15%9%
2622
February1st to 15thNight
51%312%20%11%1
2262
16th to endNight
49%413%21%8%2
1893
March1st to 15thNight
47%5%14%18%12%1
2157
16th to endNight
50%5%13%20%9%
1998
April1st to 15thNight
47%49%21%14%1
1797
16th to endNight
46%410%23%11%3
1770
May1st to 15thNight
46%7%13%20%11%
1527
16th to endNight
35%8%14%22%16%2
1498
June1st to 15thNight
33%6%13%25%20%1
1440
16th to endNight
36%8%11%21%19%3
1440
July1st to 15thNight
26%6%14%29%20%2
1360
16th to endNight
24%7%17%28%18%3
1417
August1st to 15thNight
25%5%14%32%19%2
1564
16th to endNight
31%5%14%26%18%3
1910
September1st to 15thNight
28%410%27%27%2
1800
16th to endNight
32%5%10%31%17%1
1862
October1st to 15thNight
36%5%9%25%21%1
1950
16th to endNight
44%412%25%12%1
2208
November1st to 15thNight
37%411%24%18%3
2276
16th to endNight
48%413%22%10%
2445
December1st to 15thNight
57%310%20%7%
2520
16th to endNight
63%5%10%13%6%
2688

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%12%33%27%4
90
16th to endDay
23%8%29%23%13%1
96
February1st to 15thDay
24%14%38%15%6%
90
16th to endDay
27%16%23%25%7%
81
March1st to 15thDay
28%16%33%17%21
90
16th to endDay
31%7%27%18%13%1
210
April1st to 15thDay
25%9%32%22%10%
270
16th to endDay
22%11%25%24%11%4
270
May1st to 15thDay
24%11%27%24%8%3
379
16th to endDay
17%11%29%23%13%5%
517
June1st to 15thDay
13%429%31%17%3
495
16th to endDay
13%6%30%29%13%6%
495
July1st to 15thDay
9%224%32%21%10%
475
16th to endDay
9%321%31%24%9%
515
August1st to 15thDay
6%319%31%28%10%
454
16th to endDay
13%415%27%26%12%
332
September1st to 15thDay
12%217%27%29%10%
315
16th to endDay
10%6%19%30%25%7%
278
October1st to 15thDay
10%9%27%28%21%3
118
16th to endDay
21%13%28%29%7%
96
November1st to 15thDay
5%11%32%25%17%7%
90
16th to endDay
40%8%34%8%7%
90
December1st to 15thDay
24%14%33%23%22
90
16th to endDay
32%13%46%5%2
96
January1st to 15thNight
20%12%37%23%6%
900
16th to endNight
18%11%36%29%4
960
February1st to 15thNight
20%10%37%25%6%
853
16th to endNight
20%11%33%26%6%
631
March1st to 15thNight
20%10%33%28%7%
717
16th to endNight
20%8%34%25%10%1
576
April1st to 15thNight
21%10%33%28%5%
539
16th to endNight
22%7%30%30%8%
540
May1st to 15thNight
21%5%31%29%11%
540
16th to endNight
12%331%37%14%
563
June1st to 15thNight
12%225%44%14%
540
16th to endNight
8%331%37%17%
540
July1st to 15thNight
7%219%41%27%2
510
16th to endNight
7%115%45%27%2
564
August1st to 15thNight
5%9%47%31%4
539
16th to endNight
10%213%39%29%4
573
September1st to 15thNight
9%219%35%28%5%
540
16th to endNight
9%5%21%34%27%2
655
October1st to 15thNight
14%6%30%29%17%1
660
16th to endNight
22%9%31%26%9%
704
November1st to 15thNight
15%8%37%27%11%
700
16th to endNight
22%10%32%25%7%
825
December1st to 15thNight
25%9%35%23%5%
900
16th to endNight
26%11%32%25%3
960
Page generated at 2017-09-23 05:43:34. Version ac04

Copyright 2017 A. Danko


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