Red Buttes Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Red Buttes Observatory clear sky chart from 2005-11-06 to 2024-02-25.

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
29%
24835
25%
80032
10%
24731
44%
24731
26%
43392

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 10thNight
14%
944
25%
4349
5%
926
32%
926
13%
2280
January11th to 20thNight
12%
950
23%
4367
4%
930
33%
930
11%
2312
January21st to endNight
11%
828
18%
4309
3%
814
37%
814
12%
1993
February1st to 10thNight
9%
760
22%
2470
3%
760
30%
760
14%
1399
February11th to 20thNight
11%
741
22%
2302
2%
740
32%
740
16%
1311
February21st to endNight
8%
610
27%
1830
2%
610
33%
610
18%
1013
March1st to 10thNight
17%
720
25%
2160
6%
720
37%
720
25%
1179
March11th to 20thNight
24%
720
26%
1980
9%
720
38%
720
29%
1127
March21st to endNight
19%
676
22%
2062
5%
676
36%
676
23%
1222
April1st to 10thNight
20%
540
20%
1800
5%
540
40%
540
23%
1001
April11th to 20thNight
19%
533
22%
1777
8%
533
38%
533
21%
1052
April21st to endNight
31%
540
22%
1800
12%
540
46%
540
24%
1060
May1st to 10thNight
32%
540
19%
1584
11%
540
41%
540
25%
1004
May11th to 20thNight
39%
531
17%
1418
12%
531
43%
531
30%
910
May21st to endNight
44%
584
18%
1552
10%
582
51%
582
33%
946
June1st to 10thNight
52%
540
20%
1440
12%
540
58%
540
43%
785
June11th to 20thNight
41%
540
26%
1440
12%
540
51%
540
45%
776
June21st to endNight
54%
540
27%
1440
17%
540
60%
540
49%
757
July1st to 10thNight
65%
525
22%
1400
17%
525
68%
525
44%
786
July11th to 20thNight
66%
522
27%
1392
20%
522
70%
522
50%
744
July21st to endNight
67%
591
27%
1501
20%
558
71%
558
45%
838
August1st to 10thNight
62%
537
21%
1602
19%
534
64%
534
40%
869
August11th to 20thNight
65%
534
29%
1713
25%
534
73%
534
46%
841
August21st to endNight
63%
594
31%
1980
29%
594
70%
594
42%
991
September1st to 10thNight
56%
540
31%
1800
25%
540
67%
540
40%
900
September11th to 20thNight
58%
540
36%
1800
30%
540
69%
540
45%
853
September21st to endNight
48%
566
33%
2001
24%
566
62%
566
40%
960
October1st to 10thNight
37%
720
28%
2160
13%
720
48%
720
33%
1195
October11th to 20thNight
29%
720
33%
2160
10%
720
47%
720
34%
1104
October21st to endNight
20%
846
28%
2430
6%
846
38%
846
30%
1353
November1st to 10thNight
20%
925
29%
2405
6%
925
36%
925
34%
1309
November11th to 20thNight
12%
950
31%
2473
3%
950
33%
950
25%
1387
November21st to endNight
14%
950
27%
2660
4%
950
35%
950
25%
1471
December1st to 10thNight
11%
950
23%
2660
3%
950
30%
950
19%
1481
December11th to 20thNight
11%
950
26%
3109
3%
949
31%
949
15%
1668
December21st to endNight
10%
1038
16%
4706
3%
1026
29%
1026
9%
2515

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
46%36%6%35%5%6%8%48%
78483
Night
35%35%5%345%6%8%54%
80887
TransparencyDay
32%7%13%24%19%6%
78187
Night
27%6%14%29%19%5%
80705
SeeingDay
12%25%32%20%9%2
14643
Night
8%28%32%23%9%1
24859

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 10thDay
337%9%45%45%6%53%
2538
11th to 20thDay
6%5%9%9%5%7%5%6%8%41%
2571
21st to endDay
1436%5%3445%8%57%
3146
February1st to 10thDay
16%49%8%45%5%5%7%46%
1710
11th to 20thDay
15%37%7%46%5%7%8%47%
1765
21st to endDay
16%46%6%3446%10%51%
1520
March1st to 10thDay
37%35%5%346%5%9%51%
1800
11th to 20thDay
39%37%6%35%5%6%9%46%
1976
21st to endDay
39%38%7%36%6%6%8%40%
2294
April1st to 10thDay
49%36%6%35%5%6%8%45%
2160
11th to 20thDay
5%12%38%7%45%5%6%8%37%
2131
21st to endDay
7%11%47%7%35%5%5%7%38%
2160
May1st to 10thDay
9%11%47%6%45%5%6%7%36%
2371
11th to 20thDay
11%9%36%6%46%7%6%7%35%
2478
21st to endDay
7%6%36%7%47%8%8%9%36%
2724
June1st to 10thDay
5%425%5%46%7%8%10%45%
2520
11th to 20thDay
6%425%5%25%5%7%8%51%
2520
21st to endDay
33145%35%7%8%9%52%
2520
July1st to 10thDay
5%425%6%47%6%7%9%44%
2520
11th to 20thDay
34245%36%6%7%10%50%
2520
21st to endDay
6%5%25%6%46%7%8%9%42%
2725
August1st to 10thDay
5%5%26%6%47%7%8%10%41%
2328
11th to 20thDay
5%426%5%35%6%5%7%49%
2188
21st to endDay
4425%6%46%6%6%8%49%
2376
September1st to 10thDay
4424425%5%48%58%
2160
11th to 20thDay
44244245%5%7%58%
2160
21st to endDay
5%5%25%324336%62%
1955
October1st to 10thDay
6%5%26%5%3445%7%54%
1800
11th to 20thDay
45%234245%46%60%
1800
21st to endDay
47%35%42345%6%58%
1908
November1st to 10thDay
242443345%9%60%
1673
11th to 20thDay
26%35%32346%8%57%
1706
21st to endDay
15%37%6%35%45%7%54%
1520
December1st to 10thDay
15%37%6%35%6%6%8%51%
1520
11th to 20thDay
25%35%43446%12%52%
1926
21st to endDay
15%49%8%35%45%7%49%
2794
January1st to 10thNight
5%39%8%3445%8%51%
4417
11th to 20thNight
5%48%6%35%5%5%8%50%
4430
21st to endNight
15%36%5%35%45%7%56%
4521
February1st to 10thNight
16%38%6%35%45%8%53%
2470
11th to 20thNight
16%36%6%46%6%5%6%50%
2301
21st to endNight
17%37%5%3435%7%56%
1830
March1st to 10thNight
16%26%43446%9%55%
2160
11th to 20thNight
37%4432345%8%56%
1980
21st to endNight
49%36%4245%5%8%48%
2062
April1st to 10thNight
46%35%6%35%46%7%52%
1800
11th to 20thNight
5%10%36%5%3445%7%47%
1777
21st to endNight
7%9%46%5%2346%6%48%
1800
May1st to 10thNight
7%8%35%5%445%6%7%43%
1584
11th to 20thNight
9%6%27%5%46%5%6%8%43%
1417
21st to endNight
45%245%47%6%8%9%47%
1552
June1st to 10thNight
4213335%6%7%11%55%
1440
11th to 20thNight
4313415%5%6%7%60%
1440
21st to endNight
332343435%9%61%
1440
July1st to 10thNight
43135%35%6%7%9%54%
1440
11th to 20thNight
2223435%5%7%9%58%
1440
21st to endNight
3215%436%7%8%9%52%
1589
August1st to 10thNight
3325%5%45%5%7%10%51%
1611
11th to 20thNight
332432446%9%60%
1713
21st to endNight
33244345%7%8%58%
1980
September1st to 10thNight
5%42442445%8%59%
1800
11th to 20thNight
4414324446%64%
1800
21st to endNight
5%32342445%6%63%
2001
October1st to 10thNight
5%5%244346%6%7%54%
2160
11th to 20thNight
4424324346%64%
2160
21st to endNight
48%34333446%57%
2430
November1st to 10thNight
35%13324448%62%
2405
11th to 20thNight
25%244345%48%59%
2473
21st to endNight
25%46%42446%8%55%
2660
December1st to 10thNight
1435%5%35%45%8%57%
2660
11th to 20thNight
15%35%5%345%5%10%54%
3271
21st to endNight
27%37%6%35%5%6%8%49%
4873

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 10thDay
27%12%15%23%22%2
2539
11th to 20thDay
33%14%19%18%13%2
2571
21st to endDay
23%6%21%31%15%3
3146
February1st to 10thDay
36%6%18%22%15%2
1710
11th to 20thDay
31%7%13%29%16%4
1774
21st to endDay
28%7%16%28%18%3
1520
March1st to 10thDay
30%5%16%31%18%2
1800
11th to 20thDay
35%5%14%28%15%3
1976
21st to endDay
39%7%14%26%12%2
2294
April1st to 10thDay
34%8%15%23%15%5%
2160
11th to 20thDay
44%7%11%21%14%2
2134
21st to endDay
43%6%8%27%14%1
2160
May1st to 10thDay
46%6%11%22%13%1
2371
11th to 20thDay
46%6%13%24%10%1
2482
21st to endDay
41%8%14%22%12%3
2724
June1st to 10thDay
31%7%17%22%17%6%
2520
11th to 20thDay
29%7%10%19%23%12%
2520
21st to endDay
24%7%9%24%22%13%
2520
July1st to 10thDay
33%8%10%17%23%9%
2451
11th to 20thDay
27%7%10%21%22%13%
2445
21st to endDay
35%7%11%22%17%8%
2573
August1st to 10thDay
35%8%13%21%15%8%
2313
11th to 20thDay
32%6%10%18%23%11%
2188
21st to endDay
31%6%8%18%28%9%
2376
September1st to 10thDay
25%47%18%30%15%
2160
11th to 20thDay
23%5%8%25%26%12%
2160
21st to endDay
26%36%25%35%5%
1955
October1st to 10thDay
30%5%8%27%23%7%
1800
11th to 20thDay
25%5%9%31%23%7%
1800
21st to endDay
27%411%31%21%5%
1908
November1st to 10thDay
22%5%13%29%28%3
1673
11th to 20thDay
23%6%15%32%21%4
1706
21st to endDay
28%5%11%32%21%4
1520
December1st to 10thDay
28%8%21%25%16%3
1520
11th to 20thDay
26%7%16%36%14%1
1924
21st to endDay
32%9%12%25%17%6%
2794
January1st to 10thNight
29%8%14%32%14%3
4417
11th to 20thNight
27%10%21%21%15%5%
4430
21st to endNight
26%6%21%30%13%4
4521
February1st to 10thNight
30%6%18%28%15%2
2470
11th to 20thNight
30%6%13%31%16%3
2302
21st to endNight
28%415%26%22%5%
1830
March1st to 10thNight
26%5%15%33%19%2
2160
11th to 20thNight
27%5%13%30%22%4
1980
21st to endNight
33%6%14%32%13%1
2062
April1st to 10thNight
30%7%15%27%16%6%
1800
11th to 20thNight
36%6%11%29%15%3
1777
21st to endNight
36%5%10%30%18%1
1800
May1st to 10thNight
38%6%13%28%13%1
1584
11th to 20thNight
39%5%18%27%11%
1418
21st to endNight
31%7%17%27%16%3
1552
June1st to 10thNight
21%8%23%28%15%5%
1440
11th to 20thNight
21%5%11%25%24%13%
1440
21st to endNight
20%5%8%29%24%14%
1440
July1st to 10thNight
24%7%11%27%22%9%
1400
11th to 20thNight
21%5%12%25%22%14%
1392
21st to endNight
23%7%15%30%17%8%
1501
August1st to 10thNight
27%5%17%27%17%8%
1602
11th to 20thNight
21%5%11%27%24%12%
1713
21st to endNight
22%6%10%24%28%10%
1980
September1st to 10thNight
24%48%21%26%16%
1800
11th to 20thNight
21%49%28%25%13%
1800
21st to endNight
22%47%28%32%7%
2001
October1st to 10thNight
26%6%9%27%25%7%
2160
11th to 20thNight
22%49%33%23%9%
2160
21st to endNight
27%5%13%30%20%5%
2430
November1st to 10thNight
20%6%14%29%26%5%
2405
11th to 20thNight
23%5%15%32%19%5%
2473
21st to endNight
26%5%11%34%20%4
2660
December1st to 10thNight
24%7%20%28%17%3
2660
11th to 20thNight
25%7%15%37%15%1
3272
21st to endNight
30%9%11%27%18%4
4873

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 10thDay
16%33%29%14%6%2
270
11th to 20thDay
16%47%24%12%1
270
21st to endDay
10%45%34%8%3
297
February1st to 10thDay
20%52%23%5%1
270
11th to 20thDay
19%41%32%8%
270
21st to endDay
20%43%28%9%
210
March1st to 10thDay
13%44%33%8%2
240
11th to 20thDay
16%32%37%13%2
416
21st to endDay
17%36%33%11%2
462
April1st to 10thDay
20%36%34%9%2
420
11th to 20thDay
23%39%26%9%3
412
21st to endDay
17%32%32%14%41
420
May1st to 10thDay
19%26%32%16%7%1
549
11th to 20thDay
17%19%32%20%9%2
625
21st to endDay
12%20%28%26%12%2
679
June1st to 10thDay
6%16%30%28%17%3
630
11th to 20thDay
8%18%40%24%9%2
630
21st to endDay
415%36%27%17%2
630
July1st to 10thDay
7%5%28%34%23%3
621
11th to 20thDay
47%32%33%20%3
618
21st to endDay
6%6%27%34%23%3
667
August1st to 10thDay
9%7%41%32%9%2
447
11th to 20thDay
7%8%35%35%12%4
437
21st to endDay
7%11%37%30%13%3
495
September1st to 10thDay
9%15%32%30%12%2
450
11th to 20thDay
418%41%23%12%2
450
21st to endDay
8%22%32%20%14%4
274
October1st to 10thDay
10%22%31%20%12%5%
270
11th to 20thDay
17%30%32%14%42
270
21st to endDay
12%38%35%11%31
297
November1st to 10thDay
15%35%32%11%6%1
270
11th to 20thDay
16%41%34%7%2
270
21st to endDay
13%44%30%11%2
270
December1st to 10thDay
18%45%28%5%4
270
11th to 20thDay
16%52%25%7%
270
21st to endDay
20%46%23%8%21
297
January1st to 10thNight
10%42%30%13%5%1
950
11th to 20thNight
8%53%25%10%4
950
21st to endNight
5%47%32%12%4
836
February1st to 10thNight
10%48%30%8%4
760
11th to 20thNight
7%42%33%16%1
744
21st to endNight
9%45%35%10%1
610
March1st to 10thNight
7%36%39%16%3
720
11th to 20thNight
8%28%36%23%5%
720
21st to endNight
10%29%38%17%5%1
676
April1st to 10thNight
11%27%40%19%3
540
11th to 20thNight
12%26%39%18%5%
533
21st to endNight
14%20%32%26%8%1
540
May1st to 10thNight
12%17%35%26%9%1
540
11th to 20thNight
13%12%32%30%13%1
531
21st to endNight
6%14%33%30%16%1
584
June1st to 10thNight
410%30%37%16%2
540
11th to 20thNight
6%10%39%35%9%
540
21st to endNight
5%7%29%42%16%1
540
July1st to 10thNight
4223%47%22%1
525
11th to 20thNight
3123%48%23%2
522
21st to endNight
5%219%46%26%2
591
August1st to 10thNight
4223%49%21%1
537
11th to 20thNight
4322%50%20%2
534
21st to endNight
4324%41%27%2
594
September1st to 10thNight
8%5%25%43%17%2
540
11th to 20thNight
5%7%27%42%17%2
540
21st to endNight
7%12%30%35%15%1
566
October1st to 10thNight
8%20%33%28%12%1
720
11th to 20thNight
9%27%34%22%8%1
720
21st to endNight
11%26%41%16%5%1
846
November1st to 10thNight
8%32%39%16%5%1
925
11th to 20thNight
12%40%35%12%1
950
21st to endNight
6%39%39%14%2
950
December1st to 10thNight
11%45%31%11%2
950
11th to 20thNight
8%48%30%12%2
950
21st to endNight
12%48%26%10%4
1045
Page generated at 2024-02-22 04:05:42. Version ac07

Copyright 2024 Attilla Danko


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