Range Land
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Range Land 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
68%
15130
28%
46919
25%
15104
72%
15104
43%
24270

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
63%
716
19%
2506
20%
716
67%
716
29%
1437
January16th to endNight
68%
768
23%
2556
25%
768
71%
768
33%
1443
February1st to 15thNight
64%
697
21%
2231
23%
696
66%
696
33%
1275
February16th to endNight
64%
632
27%
1895
26%
632
69%
632
38%
1049
March1st to 15thNight
62%
720
20%
2133
19%
720
66%
720
38%
1219
March16th to endNight
56%
768
22%
2010
15%
768
60%
768
40%
1176
April1st to 15thNight
54%
719
24%
1799
12%
719
58%
719
37%
1099
April16th to endNight
58%
720
24%
1800
13%
720
61%
720
44%
1051
May1st to 15thNight
60%
525
28%
1605
23%
525
64%
525
47%
792
May16th to endNight
65%
374
22%
1496
25%
374
69%
374
33%
724
June1st to 15thNight
68%
360
26%
1440
32%
360
74%
360
40%
638
June16th to endNight
77%
360
32%
1440
41%
360
83%
360
58%
515
July1st to 15thNight
85%
340
31%
1360
42%
340
88%
340
63%
469
July16th to endNight
83%
381
38%
1421
47%
359
86%
359
59%
509
August1st to 15thNight
81%
611
34%
1684
25%
608
83%
608
63%
801
August16th to endNight
79%
764
43%
1910
27%
764
81%
764
77%
878
September1st to 15thNight
83%
720
40%
1800
27%
720
86%
720
74%
843
September16th to endNight
77%
683
42%
1856
35%
683
82%
683
65%
873
October1st to 15thNight
73%
660
33%
1952
30%
660
78%
660
50%
975
October16th to endNight
73%
704
34%
2157
34%
704
78%
704
51%
1018
November1st to 15thNight
71%
700
27%
2275
27%
700
74%
700
40%
1176
November16th to endNight
65%
720
26%
2385
25%
720
69%
720
39%
1222
December1st to 15thNight
63%
720
19%
2520
18%
720
67%
720
29%
1449
December16th to endNight
54%
768
21%
2688
20%
768
60%
768
25%
1639

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
331332345%7%60%
47981
Night
341432445%7%58%
47093
TransparencyDay
22%49%21%22%18%
47653
Night
23%411%24%20%13%
46920
SeeingDay
6%12%24%28%19%7%
5735
Night
5%414%41%28%5%
15143

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
35%26%5%45%47%11%41%
1432
16th to endDay
6%6%25%5%36%5%6%9%41%
1667
February1st to 15thDay
5%426%5%25%5%6%10%44%
1631
16th to endDay
26%36%43448%9%45%
1579
March1st to 15thDay
35%25%436%6%6%10%46%
1824
16th to endDay
25%25%5%35%5%7%9%49%
2214
April1st to 15thDay
35%36%4236%5%8%48%
2149
16th to endDay
4423323346%59%
2160
May1st to 15thDay
3313312347%63%
2341
16th to endDay
5%5%25%424447%52%
2615
June1st to 15thDay
3414323447%60%
2520
16th to endDay
21211122479%
2520
July1st to 15thDay
121334476%
2520
16th to endDay
111121233476%
2651
August1st to 15thDay
21121233474%
2265
16th to endDay
1111122481%
2292
September1st to 15thDay
1121235%79%
2160
16th to endDay
321212225%73%
1915
October1st to 15thDay
3213223435%66%
1678
16th to endDay
43332245%7%61%
1713
November1st to 15thDay
5%4123145%7%7%55%
1584
16th to endDay
243432446%9%53%
1575
December1st to 15thDay
5%6%25%5%35%47%10%41%
1440
16th to endDay
5%8%47%7%35%7%7%8%35%
1536
January1st to 15thNight
45%36%5%35%5%6%10%44%
2506
16th to endNight
46%25%4345%6%8%48%
2556
February1st to 15thNight
25%35%5%36%5%8%9%45%
2220
16th to endNight
25%3443436%10%52%
1895
March1st to 15thNight
2425%426%5%6%9%49%
2133
16th to endNight
26%2443445%9%53%
2010
April1st to 15thNight
4424435%5%8%9%47%
1799
16th to endNight
5%42332345%6%58%
1800
May1st to 15thNight
431231335%6%63%
1605
16th to endNight
5%41442445%8%53%
1496
June1st to 15thNight
4313314245%63%
1440
16th to endNight
2211213279%
1440
July1st to 15thNight
112212235%76%
1440
16th to endNight
21211322377%
1517
August1st to 15thNight
312212335%71%
1693
16th to endNight
11111113481%
1910
September1st to 15thNight
111111235%78%
1800
16th to endNight
222212237%72%
1856
October1st to 15thNight
4213413345%64%
1952
16th to endNight
4312212346%66%
2157
November1st to 15thNight
441332446%8%55%
2275
16th to endNight
342432345%8%56%
2385
December1st to 15thNight
45%35%325%6%6%10%46%
2520
16th to endNight
6%7%26%5%25%6%7%8%40%
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
33%9%18%28%9%
1432
16th to endDay
35%8%15%24%14%1
1667
February1st to 15thDay
31%6%18%27%13%2
1631
16th to endDay
29%6%15%32%12%2
1579
March1st to 15thDay
30%6%18%26%15%2
1824
16th to endDay
28%6%21%26%12%3
2214
April1st to 15thDay
31%6%12%28%18%3
2149
16th to endDay
23%411%31%23%5%
2160
May1st to 15thDay
20%38%27%32%7%
2341
16th to endDay
30%49%23%26%6%
2619
June1st to 15thDay
22%47%18%27%18%
2520
16th to endDay
11%1112%33%38%
2520
July1st to 15thDay
10%228%22%53%
2371
16th to endDay
12%228%22%52%
2484
August1st to 15thDay
12%2210%22%48%
2249
16th to endDay
8%117%32%48%
2292
September1st to 15thDay
9%2212%30%42%
2160
16th to endDay
13%3319%34%24%
1915
October1st to 15thDay
19%37%27%33%9%
1678
16th to endDay
21%310%28%26%8%
1713
November1st to 15thDay
24%5%16%31%16%5%
1584
16th to endDay
27%5%13%30%21%2
1575
December1st to 15thDay
34%8%18%27%10%
1440
16th to endDay
41%7%16%23%9%
1536
January1st to 15thNight
32%7%17%29%11%1
2506
16th to endNight
31%5%15%25%18%3
2556
February1st to 15thNight
30%7%16%28%13%3
2231
16th to endNight
26%6%15%34%14%2
1895
March1st to 15thNight
28%5%18%27%15%4
2133
16th to endNight
25%7%20%27%14%4
2010
April1st to 15thNight
29%6%16%29%15%3
1799
16th to endNight
25%5%12%31%18%6%
1800
May1st to 15thNight
20%39%29%28%8%
1606
16th to endNight
27%412%27%20%6%
1496
June1st to 15thNight
21%49%21%23%19%
1440
16th to endNight
12%2414%31%35%
1440
July1st to 15thNight
10%128%24%51%
1360
16th to endNight
12%239%21%51%
1421
August1st to 15thNight
14%2312%24%42%
1684
16th to endNight
8%129%34%43%
1910
September1st to 15thNight
9%1410%32%40%
1800
16th to endNight
13%2421%32%26%
1856
October1st to 15thNight
21%27%29%30%9%
1952
16th to endNight
18%38%30%30%8%
2157
November1st to 15thNight
24%6%14%32%15%6%
2275
16th to endNight
25%414%29%21%4
2385
December1st to 15thNight
31%9%17%27%13%
2520
16th to endNight
36%8%14%26%12%1
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
11%10%11%46%13%6%
60
16th to endDay
12%313%35%26%9%
195
February1st to 15thDay
8%8%15%34%30%3
246
16th to endDay
7%15%18%34%21%2
238
March1st to 15thDay
6%13%24%31%15%9%
270
16th to endDay
11%15%26%27%14%4
288
April1st to 15thDay
9%25%23%17%16%7%
269
16th to endDay
12%24%23%20%12%5%
270
May1st to 15thDay
9%20%25%25%14%3
288
16th to endDay
11%13%21%23%17%11%
330
June1st to 15thDay
9%16%29%20%20%4
315
16th to endDay
413%29%24%19%8%
315
July1st to 15thDay
29%24%33%19%10%
305
16th to endDay
15%32%31%19%10%
327
August1st to 15thDay
310%29%29%16%10%
315
16th to endDay
28%30%27%19%12%
332
September1st to 15thDay
26%24%33%23%10%
315
16th to endDay
6%12%25%23%25%6%
280
October1st to 15thDay
6%14%27%25%17%8%
255
16th to endDay
10%11%23%32%20%2
225
November1st to 15thDay
448%24%33%24%
90
16th to endDay
46%28%31%25%3
83
December1st to 15thDay
6%16%13%50%11%1
60
16th to endDay
7%412%37%32%4
64
January1st to 15thNight
7%310%44%27%6%
720
16th to endNight
6%310%46%26%7%
768
February1st to 15thNight
4413%46%27%3
704
16th to endNight
6%6%14%46%21%4
632
March1st to 15thNight
5%419%42%23%5%
720
16th to endNight
5%7%24%37%23%2
768
April1st to 15thNight
5%11%20%37%23%1
719
16th to endNight
6%8%22%33%24%5%
720
May1st to 15thNight
5%8%20%38%23%3
526
16th to endNight
6%416%40%27%5%
375
June1st to 15thNight
7%216%43%27%2
360
16th to endNight
3113%51%28%2
360
July1st to 15thNight
27%50%37%2
340
16th to endNight
318%45%40%1
381
August1st to 15thNight
49%45%36%3
611
16th to endNight
1114%41%37%4
764
September1st to 15thNight
1110%32%43%9%
720
16th to endNight
3411%34%32%12%
683
October1st to 15thNight
5%5%10%40%29%8%
660
16th to endNight
6%310%38%30%11%
704
November1st to 15thNight
6%211%43%28%7%
700
16th to endNight
5%5%16%43%22%6%
720
December1st to 15thNight
6%414%47%20%5%
720
16th to endNight
9%5%17%44%21%1
768
Page generated at 2017-09-23 03:43:37. Version ac04

Copyright 2017 A. Danko


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