Stockton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stockton clear sky chart from 2005-11-05 to 2017-10-31.

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%
15504
30%
47409
27%
15468
75%
15468
47%
23940

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
65%
716
19%
2436
20%
716
67%
716
31%
1392
January16th to endNight
62%
768
24%
2496
25%
768
65%
768
30%
1495
February1st to 15thNight
59%
696
25%
2265
25%
696
64%
696
30%
1349
February16th to endNight
59%
632
26%
1895
23%
632
65%
632
34%
1128
March1st to 15thNight
57%
720
20%
2046
19%
720
60%
720
31%
1282
March16th to endNight
56%
768
23%
2062
17%
768
61%
768
36%
1253
April1st to 15thNight
54%
719
24%
1799
11%
719
60%
719
39%
1116
April16th to endNight
61%
720
27%
1800
12%
720
66%
720
52%
978
May1st to 15thNight
70%
614
31%
1694
21%
614
74%
614
64%
782
May16th to endNight
71%
374
33%
1496
32%
374
80%
374
56%
551
June1st to 15thNight
72%
360
31%
1440
33%
360
81%
360
59%
516
June16th to endNight
86%
360
39%
1440
50%
360
90%
360
75%
437
July1st to 15thNight
94%
340
37%
1360
48%
340
95%
340
80%
396
July16th to endNight
91%
539
39%
1568
36%
506
93%
506
75%
606
August1st to 15thNight
90%
582
40%
1655
30%
579
91%
579
82%
651
August16th to endNight
90%
764
45%
1910
29%
764
91%
764
85%
836
September1st to 15thNight
90%
720
43%
1800
30%
720
92%
720
85%
790
September16th to endNight
84%
716
47%
1944
40%
716
89%
716
77%
833
October1st to 15thNight
76%
720
33%
2160
32%
720
83%
720
59%
976
October16th to endNight
79%
768
40%
2304
42%
768
82%
768
57%
1068
November1st to 15thNight
72%
700
31%
2228
32%
700
76%
700
47%
1092
November16th to endNight
67%
720
26%
2403
28%
720
71%
720
37%
1270
December1st to 15thNight
61%
720
21%
2520
20%
720
66%
720
27%
1510
December16th to endNight
52%
768
21%
2688
19%
768
59%
768
25%
1633

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
6%312212335%65%
48340
Night
8%212212335%65%
47594
TransparencyDay
22%38%19%25%20%
48023
Night
22%39%20%24%19%
47410
SeeingDay
8%5%16%27%28%14%
6105
Night
8%213%37%32%4
15518

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
16%7%35%424336%42%
1501
16th to endDay
15%8%46%324335%40%
1728
February1st to 15thDay
17%5%45%435%43442%
1597
16th to endDay
17%425%42335%6%44%
1579
March1st to 15thDay
12%5%235%246%6%9%40%
1911
16th to endDay
10%5%245%245%5%7%45%
2160
April1st to 15thDay
11%6%2432346%7%47%
2149
16th to endDay
7%212213336%65%
2160
May1st to 15thDay
211222235%74%
2250
16th to endDay
3212212347%69%
2615
June1st to 15thDay
222212235%73%
2520
16th to endDay
1112387%
2520
July1st to 15thDay
11389%
2520
16th to endDay
1111386%
2491
August1st to 15thDay
111111287%
2295
16th to endDay
11112386%
2292
September1st to 15thDay
1112386%
2160
16th to endDay
2112123378%
2013
October1st to 15thDay
312212346%72%
1800
16th to endDay
5%31231334465%
1918
November1st to 15thDay
7%4234235%47%54%
1628
16th to endDay
12%7%34413346%46%
1557
December1st to 15thDay
15%9%27%5%23337%40%
1440
16th to endDay
18%6%36%423336%41%
1536
January1st to 15thNight
13%42332435%7%49%
2436
16th to endNight
14%5%14314446%48%
2496
February1st to 15thNight
16%424323448%46%
2254
16th to endNight
15%31332335%6%50%
1895
March1st to 15thNight
13%424423347%48%
2046
16th to endNight
10%5%22234446%53%
2062
April1st to 15thNight
10%31443445%6%52%
1799
16th to endNight
6%212212337%65%
1800
May1st to 15thNight
2113112245%74%
1694
16th to endNight
212112225%76%
1496
June1st to 15thNight
21111223479%
1440
16th to endNight
11111387%
1440
July1st to 15thNight
111289%
1440
16th to endNight
111112284%
1675
August1st to 15thNight
1111287%
1664
16th to endNight
1111387%
1910
September1st to 15thNight
22288%
1800
16th to endNight
111112483%
1944
October1st to 15thNight
4111212235%72%
2160
16th to endNight
4211212345%71%
2304
November1st to 15thNight
7%313211247%64%
2228
16th to endNight
9%313413346%57%
2403
December1st to 15thNight
15%424413447%47%
2520
16th to endNight
18%5%24213346%47%
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
42%7%13%16%18%2
1501
16th to endDay
47%6%7%16%17%5%
1728
February1st to 15thDay
45%410%22%13%3
1597
16th to endDay
40%411%25%14%2
1579
March1st to 15thDay
37%8%12%21%16%3
1911
16th to endDay
36%7%15%19%17%3
2160
April1st to 15thDay
34%6%12%24%17%4
2149
16th to endDay
20%412%27%27%7%
2160
May1st to 15thDay
13%28%27%36%11%
2250
16th to endDay
16%312%29%27%10%
2619
June1st to 15thDay
14%49%23%25%22%
2520
16th to endDay
5%1215%35%40%
2520
July1st to 15thDay
427%24%59%
2371
16th to endDay
6%228%26%54%
2335
August1st to 15thDay
6%1110%31%48%
2279
16th to endDay
5%1212%36%41%
2292
September1st to 15thDay
5%1315%34%40%
2160
16th to endDay
10%2422%37%22%
2013
October1st to 15thDay
13%39%22%25%25%
1800
16th to endDay
21%49%22%28%13%
1918
November1st to 15thDay
28%5%12%30%19%2
1628
16th to endDay
38%5%12%23%17%2
1557
December1st to 15thDay
46%5%11%18%15%3
1440
16th to endDay
45%6%12%18%13%4
1536
January1st to 15thNight
33%5%13%23%17%6%
2436
16th to endNight
35%6%11%17%16%12%
2496
February1st to 15thNight
36%411%23%18%6%
2265
16th to endNight
34%412%25%19%3
1895
March1st to 15thNight
37%5%11%20%17%7%
2046
16th to endNight
32%6%11%23%19%7%
2062
April1st to 15thNight
31%5%14%23%18%7%
1799
16th to endNight
19%5%15%22%27%10%
1800
May1st to 15thNight
13%38%24%32%18%
1695
16th to endNight
12%210%33%27%12%
1496
June1st to 15thNight
10%39%24%27%23%
1440
16th to endNight
5%1115%29%46%
1440
July1st to 15thNight
4117%22%62%
1360
16th to endNight
7%228%22%56%
1568
August1st to 15thNight
6%213%26%50%
1655
16th to endNight
5%1211%34%45%
1910
September1st to 15thNight
41412%31%44%
1800
16th to endNight
7%1421%37%27%
1944
October1st to 15thNight
14%28%20%26%26%
2160
16th to endNight
15%38%22%28%21%
2304
November1st to 15thNight
22%311%28%25%8%
2228
16th to endNight
27%49%24%25%6%
2403
December1st to 15thNight
37%6%11%19%19%5%
2520
16th to endNight
38%5%13%18%17%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
27%315%24%14%13%
129
16th to endDay
17%7%16%20%17%19%
256
February1st to 15thDay
19%7%15%17%25%16%
240
16th to endDay
20%7%18%20%21%11%
238
March1st to 15thDay
15%8%20%21%20%13%
270
16th to endDay
12%11%22%25%19%8%
288
April1st to 15thDay
15%12%26%22%14%8%
269
16th to endDay
10%12%24%25%18%9%
270
May1st to 15thDay
5%6%28%30%21%7%
288
16th to endDay
45%21%26%26%15%
330
June1st to 15thDay
6%6%24%34%21%6%
315
16th to endDay
214%37%34%11%
315
July1st to 15thDay
10%33%43%10%
305
16th to endDay
7%35%39%16%
327
August1st to 15thDay
2112%34%40%7%
315
16th to endDay
8%34%36%19%
332
September1st to 15thDay
19%32%40%14%
315
16th to endDay
3315%28%30%19%
315
October1st to 15thDay
4419%27%23%20%
315
16th to endDay
9%411%21%29%24%
336
November1st to 15thDay
8%314%14%27%32%
134
16th to endDay
12%312%37%29%3
79
December1st to 15thDay
25%6%21%21%23%1
60
16th to endDay
15%315%21%35%7%
64
January1st to 15thNight
15%210%33%31%6%
720
16th to endNight
15%312%33%27%7%
768
February1st to 15thNight
17%312%33%29%4
704
16th to endNight
16%316%37%21%4
632
March1st to 15thNight
15%414%34%27%3
720
16th to endNight
13%419%36%23%2
768
April1st to 15thNight
10%5%23%37%21%1
719
16th to endNight
6%423%35%26%4
720
May1st to 15thNight
2120%43%26%4
615
16th to endNight
4218%40%33%
375
June1st to 15thNight
3119%47%26%
360
16th to endNight
10%50%35%2
360
July1st to 15thNight
349%45%1
340
16th to endNight
5%38%51%4
539
August1st to 15thNight
16%41%46%3
582
16th to endNight
7%42%46%2
764
September1st to 15thNight
16%40%46%4
720
16th to endNight
1111%37%39%8%
716
October1st to 15thNight
5%312%38%32%7%
720
16th to endNight
5%29%31%40%11%
768
November1st to 15thNight
7%211%37%35%6%
700
16th to endNight
9%112%38%31%6%
720
December1st to 15thNight
14%411%37%25%6%
720
16th to endNight
18%5%16%33%22%2
768
Page generated at 2017-11-01 14:23:40. Version ac04

Copyright 2017 A. Danko


Stockton Clear Sky Chart |Charts Home