This page made possible by the sponsorship of: Walnut Canyon Cabins, C. E. Steuart Dewar.

Old Tunnel State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Old Tunnel State Park clear sky chart from 2005-11-05 to 2019-09-17.

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
50%
18014
26%
54879
18%
17969
58%
17969
34%
31919

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
39%
1047
29%
2717
12%
1045
48%
1045
34%
1702
January16th to endNight
38%
991
30%
2783
13%
991
51%
991
33%
1671
February1st to 15thNight
33%
824
26%
2467
12%
818
45%
818
28%
1477
February16th to endNight
25%
736
26%
2206
8%
736
39%
736
28%
1319
March1st to 15thNight
33%
684
27%
2364
14%
684
47%
684
25%
1401
March16th to endNight
36%
672
23%
2464
16%
672
48%
672
26%
1420
April1st to 15thNight
31%
629
24%
2307
15%
629
46%
629
27%
1289
April16th to endNight
31%
624
26%
2017
15%
624
47%
624
28%
1231
May1st to 15thNight
35%
629
24%
1889
16%
629
46%
629
29%
1167
May16th to endNight
48%
658
23%
1972
19%
657
58%
657
33%
1190
June1st to 15thNight
69%
630
24%
1890
24%
630
75%
630
49%
956
June16th to endNight
68%
630
22%
1890
25%
630
71%
630
40%
1068
July1st to 15thNight
76%
600
19%
1800
21%
600
78%
600
38%
1038
July16th to endNight
83%
660
26%
1882
30%
627
85%
627
48%
966
August1st to 15thNight
88%
620
29%
1980
34%
617
88%
617
52%
928
August16th to endNight
76%
669
20%
2271
24%
669
77%
669
32%
1296
September1st to 15thNight
75%
630
18%
2310
23%
630
75%
630
28%
1351
September16th to endNight
64%
585
22%
2158
24%
585
67%
585
26%
1295
October1st to 15thNight
70%
585
31%
2145
31%
585
73%
585
35%
1116
October16th to endNight
57%
808
36%
2472
23%
808
64%
808
45%
1273
November1st to 15thNight
51%
883
27%
2523
16%
883
57%
883
36%
1493
November16th to endNight
48%
1050
31%
2730
15%
1050
57%
1050
40%
1620
December1st to 15thNight
41%
1050
30%
2730
15%
1050
48%
1050
33%
1726
December16th to endNight
35%
1120
23%
2912
11%
1120
43%
1120
29%
1926

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
12%5%2442445%7%46%
55801
Night
11%5%23323347%52%
55081
Cloud CoverDay
11%5%2442445%7%46%
55799
Night
10%5%23323347%52%
55081
TransparencyDay
37%5%9%19%18%8%
55499
Night
31%5%11%21%18%11%
54886
SeeingDay
13%5%20%30%23%6%
8009
Night
13%6%25%35%17%1
18019

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
14%5%15%32333450%
1881
16th to endDay
13%423223325%54%
2156
February1st to 15thDay
15%6%24322335%48%
2050
16th to endDay
17%6%23223445%47%
1840
March1st to 15thDay
17%7%24413445%45%
2254
16th to endDay
15%5%24423345%47%
2464
April1st to 15thDay
13%5%24423346%47%
2301
16th to endDay
14%5%34424445%46%
2545
May1st to 15thDay
16%6%345%25%5%5%6%37%
2721
16th to endDay
15%6%25%435%45%7%38%
2846
June1st to 15thDay
5%3244345%6%10%47%
2730
16th to endDay
10%425%6%36%5%7%8%37%
2730
July1st to 15thDay
10%425%5%36%5%6%8%41%
2730
16th to endDay
7%2144345%6%9%49%
2882
August1st to 15thDay
3113335%45%10%57%
2549
16th to endDay
7%425%6%45%5%6%9%43%
2634
September1st to 15thDay
12%5%26%6%35%5%5%7%39%
2310
16th to endDay
12%5%25%5%35%5%5%7%40%
2156
October1st to 15thDay
10%5%24434336%49%
2145
16th to endDay
11%313312235%60%
2090
November1st to 15thDay
13%7%25%324346%42%
1991
16th to endDay
13%5%23312235%55%
1890
December1st to 15thDay
18%6%34323335%46%
1890
16th to endDay
16%7%24413345%46%
2016
January1st to 15thNight
16%413323335%51%
2717
16th to endNight
14%6%23322246%52%
2783
February1st to 15thNight
14%7%2422223451%
2462
16th to endNight
15%5%24323346%49%
2206
March1st to 15thNight
14%6%24313345%48%
2364
16th to endNight
14%5%13323446%49%
2464
April1st to 15thNight
10%5%34313347%51%
2307
16th to endNight
13%6%24423235%50%
2017
May1st to 15thNight
12%5%3442345%6%47%
1889
16th to endNight
10%42442435%9%48%
1971
June1st to 15thNight
311221335%9%63%
1890
16th to endNight
7%31332435%10%54%
1890
July1st to 15thNight
6%31242446%11%51%
1890
16th to endNight
331222335%10%61%
1990
August1st to 15thNight
2112213449%66%
1990
16th to endNight
6%3144245%6%10%50%
2271
September1st to 15thNight
8%4245%35%5%5%8%47%
2310
16th to endNight
8%7%25%5%345%5%7%45%
2158
October1st to 15thNight
9%313323346%58%
2145
16th to endNight
11%312212235%63%
2472
November1st to 15thNight
12%424313336%54%
2523
16th to endNight
11%5%13212236%57%
2730
December1st to 15thNight
16%5%14312346%49%
2730
16th to endNight
15%8%24323335%47%
2912

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%5%25%31433450%
1881
16th to endDay
13%423323335%54%
2156
February1st to 15thDay
14%6%24313346%48%
2050
16th to endDay
16%6%2432345%5%47%
1840
March1st to 15thDay
17%7%24423436%45%
2254
16th to endDay
15%5%24423445%47%
2462
April1st to 15thDay
12%6%24323346%47%
2301
16th to endDay
13%6%25%424346%46%
2545
May1st to 15thDay
15%7%35%5%25%5%46%37%
2721
16th to endDay
14%6%35%5%35%45%7%38%
2846
June1st to 15thDay
44245%345%7%10%47%
2730
16th to endDay
9%436%6%36%6%6%9%36%
2730
July1st to 15thDay
8%435%5%46%5%6%8%41%
2730
16th to endDay
7%214425%5%6%10%48%
2882
August1st to 15thDay
221343445%10%57%
2549
16th to endDay
7%425%6%45%5%6%9%42%
2634
September1st to 15thDay
12%5%36%5%35%5%5%7%38%
2310
16th to endDay
11%5%25%5%45%5%5%6%40%
2156
October1st to 15thDay
10%5%24434346%49%
2145
16th to endDay
11%313322235%60%
2090
November1st to 15thDay
13%7%25%434347%42%
1991
16th to endDay
11%6%24312335%55%
1890
December1st to 15thDay
17%8%24323235%46%
1890
16th to endDay
15%7%24323345%46%
2016
January1st to 15thNight
16%413323335%51%
2717
16th to endNight
13%5%23323245%52%
2783
February1st to 15thNight
14%7%2331323452%
2462
16th to endNight
14%6%24313346%49%
2206
March1st to 15thNight
14%6%25%323346%48%
2364
16th to endNight
13%5%23323446%50%
2464
April1st to 15thNight
9%6%24323346%51%
2307
16th to endNight
12%6%24324235%50%
2017
May1st to 15thNight
11%6%34423447%46%
1889
16th to endNight
9%5%25%32435%9%49%
1971
June1st to 15thNight
311321436%9%63%
1890
16th to endNight
6%31332445%10%54%
1890
July1st to 15thNight
6%31242446%11%51%
1890
16th to endNight
321322335%9%60%
1990
August1st to 15thNight
211221345%9%66%
1990
16th to endNight
6%4145%245%6%9%50%
2271
September1st to 15thNight
7%5%235%35%46%8%46%
2310
16th to endNight
8%7%25%5%245%5%7%44%
2158
October1st to 15thNight
9%313323347%58%
2145
16th to endNight
10%312213235%63%
2472
November1st to 15thNight
11%5%24323246%54%
2523
16th to endNight
10%6%23222236%57%
2730
December1st to 15thNight
14%7%23323246%49%
2730
16th to endNight
15%8%2432333447%
2912

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
37%35%18%19%15%
1882
16th to endDay
33%35%14%26%15%
2156
February1st to 15thDay
38%46%13%20%16%
2051
16th to endDay
38%45%17%20%13%
1840
March1st to 15thDay
40%47%14%18%13%
2254
16th to endDay
38%48%18%19%10%
2464
April1st to 15thDay
38%47%17%20%12%
2301
16th to endDay
39%46%18%19%10%
2545
May1st to 15thDay
45%6%8%14%18%5%
2721
16th to endDay
44%7%9%19%16%3
2850
June1st to 15thDay
30%7%13%24%20%4
2730
16th to endDay
42%7%11%22%14%3
2730
July1st to 15thDay
37%8%14%25%11%2
2591
16th to endDay
26%8%16%32%13%1
2727
August1st to 15thDay
21%7%15%37%16%1
2535
16th to endDay
35%9%15%26%10%2
2634
September1st to 15thDay
44%6%10%18%16%3
2310
16th to endDay
41%7%9%16%16%7%
2156
October1st to 15thDay
35%5%11%18%20%9%
2145
16th to endDay
28%35%15%26%20%
2090
November1st to 15thDay
41%48%18%16%9%
1991
16th to endDay
33%35%15%22%19%
1890
December1st to 15thDay
42%35%16%21%11%
1890
16th to endDay
41%37%13%23%10%
2016
January1st to 15thNight
35%3417%20%18%
2717
16th to endNight
35%2415%24%16%
2783
February1st to 15thNight
37%36%12%20%19%
2472
16th to endNight
37%36%14%21%15%
2206
March1st to 15thNight
37%48%15%19%14%
2364
16th to endNight
35%6%9%17%19%11%
2464
April1st to 15thNight
34%48%17%18%16%
2307
16th to endNight
37%48%18%17%12%
2017
May1st to 15thNight
36%6%10%21%16%9%
1890
16th to endNight
33%6%13%28%14%4
1973
June1st to 15thNight
18%7%15%31%23%4
1890
16th to endNight
26%7%17%30%15%3
1890
July1st to 15thNight
25%10%20%30%12%
1800
16th to endNight
18%7%24%34%13%1
1882
August1st to 15thNight
15%6%20%40%16%1
1980
16th to endNight
28%10%21%27%10%2
2271
September1st to 15thNight
34%7%16%21%15%4
2310
16th to endNight
37%6%14%17%16%7%
2158
October1st to 15thNight
26%6%13%24%18%10%
2145
16th to endNight
24%26%17%27%21%
2472
November1st to 15thNight
32%48%22%19%12%
2523
16th to endNight
30%37%16%21%20%
2730
December1st to 15thNight
36%47%17%22%12%
2730
16th to endNight
40%35%13%21%13%
2912

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
18%12%37%23%6%1
180
16th to endDay
16%13%35%25%9%
192
February1st to 15thDay
21%15%34%23%31
180
16th to endDay
30%11%37%18%1
159
March1st to 15thDay
22%15%40%15%6%
180
16th to endDay
10%12%38%28%8%1
192
April1st to 15thDay
17%11%41%25%4
180
16th to endDay
14%15%37%26%7%
437
May1st to 15thDay
18%8%35%28%8%
618
16th to endDay
18%7%28%29%15%1
677
June1st to 15thDay
5%116%46%26%3
645
16th to endDay
10%114%38%28%6%
645
July1st to 15thDay
8%9%36%36%9%
625
16th to endDay
5%330%48%11%
675
August1st to 15thDay
4331%44%15%
494
16th to endDay
7%7%29%35%18%
418
September1st to 15thDay
10%422%36%25%
225
16th to endDay
14%15%22%43%13%
183
October1st to 15thDay
7%14%26%36%14%
180
16th to endDay
22%418%31%20%2
192
November1st to 15thDay
25%7%26%25%10%3
180
16th to endDay
20%10%30%22%12%5%
180
December1st to 15thDay
23%11%26%22%12%2
180
16th to endDay
26%13%32%23%4
192
January1st to 15thNight
18%9%28%33%8%
1050
16th to endNight
18%8%30%33%9%
991
February1st to 15thNight
20%12%30%30%6%
824
16th to endNight
19%10%42%24%2
736
March1st to 15thNight
18%8%35%32%5%
684
16th to endNight
15%9%36%33%4
672
April1st to 15thNight
12%10%42%31%2
629
16th to endNight
14%9%41%27%7%
624
May1st to 15thNight
13%10%38%32%5%
630
16th to endNight
10%5%31%38%12%
659
June1st to 15thNight
222%51%21%
630
16th to endNight
5%20%48%22%1
630
July1st to 15thNight
6%18%44%35%3
600
16th to endNight
45%46%39%2
660
August1st to 15thNight
2342%45%5%
620
16th to endNight
7%5%40%40%5%
669
September1st to 15thNight
10%6%34%41%6%
630
16th to endNight
11%211%36%33%4
585
October1st to 15thNight
11%212%41%28%4
585
16th to endNight
12%422%31%25%3
808
November1st to 15thNight
12%6%23%36%18%2
883
16th to endNight
15%6%26%35%14%1
1050
December1st to 15thNight
19%8%27%33%9%1
1050
16th to endNight
20%9%29%31%8%
1120
Page generated at 2019-09-17 20:12:18. Version ac04

Copyright 2019 A. Danko


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