Gas Line Road
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gas Line Road clear sky chart from 2005-11-05 to 2017-12-04.

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
68%
15452
28%
47817
25%
15428
72%
15428
44%
24581

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%
2506
20%
716
69%
716
31%
1403
January16th to endNight
69%
768
22%
2566
25%
768
71%
768
32%
1446
February1st to 15thNight
68%
697
22%
2204
23%
697
70%
697
34%
1259
February16th to endNight
61%
632
27%
1895
27%
632
67%
632
39%
1056
March1st to 15thNight
60%
720
20%
2154
18%
720
65%
720
38%
1205
March16th to endNight
55%
768
23%
1995
15%
768
61%
768
42%
1161
April1st to 15thNight
54%
719
25%
1799
11%
719
59%
719
39%
1092
April16th to endNight
56%
720
26%
1800
13%
720
60%
720
45%
1040
May1st to 15thNight
59%
545
29%
1625
21%
545
64%
545
48%
796
May16th to endNight
63%
374
23%
1496
25%
374
68%
374
33%
736
June1st to 15thNight
65%
360
26%
1440
31%
360
72%
360
42%
636
June16th to endNight
73%
360
33%
1440
39%
360
82%
360
61%
497
July1st to 15thNight
81%
340
31%
1360
39%
340
86%
340
57%
500
July16th to endNight
78%
376
37%
1416
42%
354
83%
354
55%
529
August1st to 15thNight
76%
625
34%
1700
23%
623
81%
623
65%
806
August16th to endNight
80%
764
42%
1910
26%
764
82%
764
76%
885
September1st to 15thNight
84%
720
40%
1800
26%
720
86%
720
72%
858
September16th to endNight
77%
716
43%
1959
37%
716
82%
716
67%
890
October1st to 15thNight
70%
720
32%
2103
29%
720
77%
720
51%
1050
October16th to endNight
78%
768
38%
2367
40%
768
83%
768
56%
1069
November1st to 15thNight
75%
760
28%
2470
30%
760
78%
760
43%
1252
November16th to endNight
67%
780
27%
2548
27%
780
72%
780
41%
1316
December1st to 15thNight
62%
736
18%
2576
18%
736
67%
736
31%
1462
December16th to endNight
56%
768
21%
2688
20%
768
61%
768
26%
1637

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
3313323346%62%
48687
Night
3313323346%61%
47991
TransparencyDay
21%410%20%22%20%
48358
Night
22%5%11%23%21%15%
47819
SeeingDay
5%12%21%29%23%7%
5971
Night
4317%39%28%5%
15465

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
36%25%5%35%7%7%10%41%
1432
16th to endDay
45%25%5%345%6%10%44%
1656
February1st to 15thDay
25%335%2447%10%50%
1658
16th to endDay
34144335%5%9%52%
1579
March1st to 15thDay
24245%345%5%9%52%
1803
16th to endDay
34245%345%5%8%52%
2228
April1st to 15thDay
44245%25%46%9%49%
2149
16th to endDay
5%313323345%64%
2160
May1st to 15thDay
3222212247%66%
2320
16th to endDay
5%425%5%24445%55%
2615
June1st to 15thDay
3213324346%63%
2520
16th to endDay
111111223479%
2520
July1st to 15thDay
11221333474%
2520
16th to endDay
211131334473%
2657
August1st to 15thDay
11221323475%
2249
16th to endDay
21121123381%
2292
September1st to 15thDay
1112222381%
2160
16th to endDay
211212235%76%
1999
October1st to 15thDay
323222235%70%
1854
16th to endDay
312323347%66%
1857
November1st to 15thDay
431232435%8%59%
1719
16th to endDay
241442345%9%57%
1739
December1st to 15thDay
35%26%5%45%45%10%45%
1465
16th to endDay
5%6%37%5%45%5%8%9%38%
1536
January1st to 15thNight
36%25%5%2436%8%50%
2506
16th to endNight
45%345%2445%8%49%
2566
February1st to 15thNight
35%23435%5%7%10%48%
2194
16th to endNight
26%2443445%8%55%
1895
March1st to 15thNight
342432445%8%55%
2154
16th to endNight
34243345%5%7%55%
1995
April1st to 15thNight
34135%35%47%8%53%
1799
16th to endNight
5%5%13323246%61%
1800
May1st to 15thNight
5%212222447%65%
1625
16th to endNight
6%3245%23446%56%
1496
June1st to 15thNight
433313326%65%
1440
16th to endNight
11111213380%
1440
July1st to 15thNight
2221333474%
1440
16th to endNight
21221223474%
1512
August1st to 15thNight
212223335%72%
1708
16th to endNight
11111235%79%
1910
September1st to 15thNight
11211223478%
1800
16th to endNight
3111223476%
1959
October1st to 15thNight
5%22322335%67%
2103
16th to endNight
322212246%70%
2367
November1st to 15thNight
3413313347%62%
2470
16th to endNight
3414424447%58%
2548
December1st to 15thNight
35%25%5%2446%9%50%
2576
16th to endNight
5%6%35%5%35%5%5%7%45%
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
31%10%23%25%8%
1432
16th to endDay
34%9%16%25%12%1
1656
February1st to 15thDay
28%7%18%27%15%2
1658
16th to endDay
27%5%15%34%13%3
1579
March1st to 15thDay
27%7%17%26%18%3
1803
16th to endDay
27%7%16%26%16%4
2228
April1st to 15thDay
30%6%11%24%21%6%
2149
16th to endDay
22%5%9%27%28%7%
2160
May1st to 15thDay
17%49%24%34%9%
2320
16th to endDay
30%47%20%25%10%
2619
June1st to 15thDay
20%5%8%15%28%21%
2520
16th to endDay
11%1310%27%46%
2520
July1st to 15thDay
12%247%17%56%
2371
16th to endDay
14%237%18%53%
2490
August1st to 15thDay
13%338%19%51%
2232
16th to endDay
9%127%25%52%
2292
September1st to 15thDay
9%238%28%46%
2160
16th to endDay
12%25%19%33%26%
1999
October1st to 15thDay
18%27%23%34%12%
1854
16th to endDay
17%310%29%29%8%
1857
November1st to 15thDay
22%6%17%30%19%2
1719
16th to endDay
23%6%15%32%20%2
1739
December1st to 15thDay
33%8%20%26%10%
1465
16th to endDay
38%8%20%23%8%
1536
January1st to 15thNight
30%7%18%31%12%
2506
16th to endNight
31%6%16%25%17%3
2566
February1st to 15thNight
28%8%16%29%13%4
2205
16th to endNight
26%6%13%34%15%2
1895
March1st to 15thNight
26%7%17%25%17%6%
2154
16th to endNight
24%7%19%27%15%5%
1995
April1st to 15thNight
28%6%14%28%18%4
1799
16th to endNight
24%5%12%26%22%7%
1800
May1st to 15thNight
19%47%24%32%11%
1626
16th to endNight
27%412%22%23%9%
1496
June1st to 15thNight
20%47%17%25%24%
1440
16th to endNight
10%2312%28%42%
1440
July1st to 15thNight
12%237%20%53%
1360
16th to endNight
14%238%19%51%
1416
August1st to 15thNight
13%2311%20%47%
1700
16th to endNight
8%138%28%49%
1910
September1st to 15thNight
10%2410%27%45%
1800
16th to endNight
12%15%16%32%32%
1959
October1st to 15thNight
20%36%21%33%14%
2103
16th to endNight
15%38%27%31%13%
2367
November1st to 15thNight
22%6%14%32%18%6%
2470
16th to endNight
24%5%14%28%22%4
2548
December1st to 15thNight
31%7%18%27%14%
2576
16th to endNight
36%8%15%25%13%
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
8%10%23%35%21%1
60
16th to endDay
10%414%35%23%10%
184
February1st to 15thDay
5%11%17%32%26%5%
251
16th to endDay
9%18%21%26%20%3
238
March1st to 15thDay
5%24%23%22%17%7%
270
16th to endDay
7%25%24%24%15%2
288
April1st to 15thDay
7%26%24%23%13%5%
269
16th to endDay
10%20%28%22%14%4
270
May1st to 15thDay
7%20%25%26%14%4
288
16th to endDay
7%13%20%25%22%11%
330
June1st to 15thDay
6%17%23%24%22%5%
315
16th to endDay
29%26%32%21%8%
315
July1st to 15thDay
16%19%33%29%10%
305
16th to endDay
2319%39%25%9%
327
August1st to 15thDay
27%24%32%23%9%
315
16th to endDay
3320%30%28%14%
332
September1st to 15thDay
16%18%35%27%10%
315
16th to endDay
29%20%26%33%6%
315
October1st to 15thDay
310%23%30%22%9%
315
16th to endDay
6%6%17%27%32%9%
273
November1st to 15thDay
5%217%32%28%14%
135
16th to endDay
39%22%37%22%4
131
December1st to 15thDay
6%9%22%45%12%4
66
16th to endDay
6%423%31%29%4
64
January1st to 15thNight
6%214%39%28%8%
720
16th to endNight
6%211%43%27%7%
768
February1st to 15thNight
4215%44%26%5%
704
16th to endNight
4422%41%21%5%
632
March1st to 15thNight
5%422%39%23%4
720
16th to endNight
48%26%36%20%2
768
April1st to 15thNight
310%25%36%21%2
719
16th to endNight
7%9%23%31%22%6%
720
May1st to 15thNight
5%7%24%38%20%2
546
16th to endNight
8%318%38%27%3
375
June1st to 15thNight
6%420%40%26%1
360
16th to endNight
2118%50%24%1
360
July1st to 15thNight
310%50%32%1
340
16th to endNight
213%46%36%1
376
August1st to 15thNight
214%44%34%2
625
16th to endNight
113%40%39%3
764
September1st to 15thNight
119%32%46%8%
720
16th to endNight
3213%31%37%10%
716
October1st to 15thNight
6%116%37%28%9%
720
16th to endNight
4310%34%35%12%
768
November1st to 15thNight
5%112%41%30%8%
760
16th to endNight
6%315%40%27%7%
780
December1st to 15thNight
5%218%45%22%5%
736
16th to endNight
6%5%20%43%21%2
768
Page generated at 2017-12-05 07:19:03. Version ac04

Copyright 2017 A. Danko


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