Mt Bachelor Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mt Bachelor Star Party clear sky chart from 2005-11-05 to 2019-06-10.

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
45%
16970
16%
53908
15%
16943
48%
16943
22%
35921

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
32%
836
10%
2926
9%
836
34%
836
12%
2205
January16th to endNight
37%
896
13%
3017
13%
896
40%
896
16%
2173
February1st to 15thNight
31%
819
7%
2678
7%
817
33%
817
11%
2088
February16th to endNight
28%
736
11%
2283
10%
736
31%
736
13%
1752
March1st to 15thNight
31%
840
9%
2416
8%
840
32%
840
13%
1878
March16th to endNight
28%
896
7%
2402
5%
896
29%
896
13%
1921
April1st to 15thNight
29%
839
7%
2099
4%
839
30%
839
13%
1697
April16th to endNight
42%
773
12%
2021
7%
773
43%
773
23%
1464
May1st to 15thNight
52%
441
19%
1701
20%
441
57%
441
25%
977
May16th to endNight
51%
439
10%
1752
14%
438
53%
438
16%
1183
June1st to 15thNight
54%
408
13%
1632
20%
408
57%
408
22%
971
June16th to endNight
63%
390
19%
1560
30%
390
67%
390
34%
758
July1st to 15thNight
83%
370
24%
1480
38%
370
87%
370
55%
556
July16th to endNight
82%
408
33%
1544
44%
386
85%
386
62%
533
August1st to 15thNight
84%
551
34%
1697
31%
549
86%
549
64%
714
August16th to endNight
76%
764
38%
2006
26%
764
78%
764
66%
951
September1st to 15thNight
77%
780
37%
1950
24%
780
79%
780
69%
939
September16th to endNight
61%
776
27%
2122
22%
776
63%
776
40%
1223
October1st to 15thNight
50%
780
19%
2340
18%
780
54%
780
29%
1464
October16th to endNight
45%
832
17%
2538
18%
832
47%
832
21%
1744
November1st to 15thNight
32%
820
12%
2728
13%
820
35%
820
14%
2041
November16th to endNight
34%
840
8%
2940
9%
840
35%
840
13%
2158
December1st to 15thNight
39%
840
12%
2940
12%
840
41%
840
16%
2111
December16th to endNight
27%
896
9%
3136
8%
896
29%
896
10%
2420

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
10%12%46%424445%39%
54616
Night
9%12%47%5%34445%36%
54076
Cloud CoverDay
5%9%47%6%35%445%40%
54616
Night
48%48%8%46%6%5%6%38%
54080
TransparencyDay
41%7%11%18%15%5%
54287
Night
41%9%12%17%14%4
53909
SeeingDay
13%20%29%22%10%3
7756
Night
9%14%23%29%20%2
16980

By Month

Percentage Cloud Cover NW (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
15%18%5%9%5%25%445%24%
1672
16th to endDay
14%18%5%6%5%24445%28%
1907
February1st to 15thDay
14%19%6%10%6%25%46%5%19%
1846
16th to endDay
9%22%10%11%5%2444419%
1763
March1st to 15thDay
14%22%7%7%6%34345%19%
2201
16th to endDay
13%24%8%8%6%34445%18%
2526
April1st to 15thDay
16%24%7%8%6%2444416%
2509
16th to endDay
8%17%46%5%35%5%47%31%
2541
May1st to 15thDay
10%12%35%4245%5%7%38%
2907
16th to endDay
14%14%46%6%35%45%7%27%
3063
June1st to 15thDay
13%10%36%42345%6%39%
2857
16th to endDay
7%6%25%324347%52%
2730
July1st to 15thDay
3212313335%69%
2730
16th to endDay
32121223375%
2881
August1st to 15thDay
111322235%6%68%
2505
16th to endDay
42221223472%
2548
September1st to 15thDay
2213312335%68%
2340
16th to endDay
9%7%24433446%47%
2165
October1st to 15thDay
13%11%25%5%3433440%
1950
16th to endDay
14%12%36%43335%5%37%
2036
November1st to 15thDay
17%15%37%6%35%5%47%23%
1787
16th to endDay
15%19%5%8%5%4445%5%22%
1680
December1st to 15thDay
14%15%46%6%35%46%7%26%
1680
16th to endDay
14%19%8%9%435%44420%
1792
January1st to 15thNight
11%18%7%7%6%46%445%23%
2926
16th to endNight
11%16%6%8%6%34445%27%
3017
February1st to 15thNight
12%17%8%9%7%36%45%7%19%
2666
16th to endNight
8%18%8%10%7%445%45%22%
2283
March1st to 15thNight
11%20%7%8%7%35%5%35%21%
2416
16th to endNight
9%18%6%11%8%45%45%6%18%
2398
April1st to 15thNight
12%19%7%10%6%46%5%4419%
2099
16th to endNight
7%14%6%8%5%25%6%5%7%30%
2021
May1st to 15thNight
6%9%45%5%25%6%6%6%40%
1701
16th to endNight
9%12%37%5%36%5%6%9%28%
1752
June1st to 15thNight
12%9%35%425%45%7%39%
1632
16th to endNight
6%414325%447%53%
1560
July1st to 15thNight
2211113435%71%
1560
16th to endNight
21211223476%
1640
August1st to 15thNight
123112336%73%
1705
16th to endNight
21221223474%
2006
September1st to 15thNight
211212235%75%
1950
16th to endNight
7%5%15%423447%50%
2122
October1st to 15thNight
9%8%25%5%35%445%46%
2340
16th to endNight
14%13%35%43434437%
2538
November1st to 15thNight
15%15%47%7%36%6%5%5%21%
2728
16th to endNight
13%15%5%8%6%35%45%424%
2940
December1st to 15thNight
14%15%5%7%5%2446%5%27%
2940
16th to endNight
13%21%6%9%7%3444420%
3136

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
6%11%5%11%8%6%7%6%45%25%
1672
16th to endDay
6%12%6%9%7%35%5%5%5%30%
1907
February1st to 15thDay
6%12%6%11%10%5%7%6%5%5%20%
1846
16th to endDay
312%9%14%11%5%7%5%3420%
1763
March1st to 15thDay
416%8%12%11%46%45%420%
2201
16th to endDay
6%16%8%11%9%46%5%46%19%
2526
April1st to 15thDay
9%16%10%11%8%36%5%45%17%
2509
16th to endDay
412%5%8%7%35%5%5%7%32%
2541
May1st to 15thDay
6%11%46%5%345%5%6%40%
2907
16th to endDay
11%12%48%7%345%5%7%27%
3063
June1st to 15thDay
10%8%36%5%25%5%46%40%
2857
16th to endDay
5%5%25%424446%53%
2730
July1st to 15thDay
2113223435%68%
2730
16th to endDay
321111223474%
2881
August1st to 15thDay
111231335%7%68%
2505
16th to endDay
22221332473%
2548
September1st to 15thDay
1313313345%69%
2340
16th to endDay
6%7%25%5%3445%6%48%
2165
October1st to 15thDay
7%11%37%7%4444439%
1950
16th to endDay
7%8%5%8%7%36%5%5%5%38%
2036
November1st to 15thDay
5%10%6%10%10%47%6%5%6%26%
1787
16th to endDay
310%7%12%11%5%7%6%6%6%22%
1680
December1st to 15thDay
6%10%5%11%8%47%5%6%7%27%
1680
16th to endDay
410%9%12%11%5%7%5%6%421%
1792
January1st to 15thNight
411%410%12%5%8%7%5%6%23%
2926
16th to endNight
311%5%10%12%5%6%6%5%5%28%
3017
February1st to 15thNight
410%6%10%11%5%8%8%5%6%21%
2666
16th to endNight
47%6%12%11%5%7%7%5%6%24%
2283
March1st to 15thNight
49%5%12%11%5%9%8%45%22%
2416
16th to endNight
310%5%12%11%6%8%7%5%7%20%
2402
April1st to 15thNight
5%12%6%11%10%49%6%5%5%22%
2099
16th to endNight
48%47%8%47%5%5%7%35%
2021
May1st to 15thNight
48%36%5%245%6%8%44%
1701
16th to endNight
6%8%5%6%7%46%6%5%8%33%
1752
June1st to 15thNight
8%7%35%43446%7%42%
1632
16th to endNight
5%424423446%56%
1560
July1st to 15thNight
1211112436%73%
1560
16th to endNight
2221223477%
1640
August1st to 15thNight
1212211236%74%
1705
16th to endNight
11221223475%
2006
September1st to 15thNight
121212235%76%
1950
16th to endNight
4325%4345%47%53%
2122
October1st to 15thNight
48%26%6%45%445%46%
2340
16th to endNight
6%8%37%8%45%6%5%438%
2538
November1st to 15thNight
49%5%10%12%6%7%6%5%6%25%
2728
16th to endNight
38%5%11%11%6%8%7%6%5%25%
2940
December1st to 15thNight
5%10%5%9%9%6%7%6%5%7%27%
2940
16th to endNight
211%6%12%13%5%8%7%45%21%
3136

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
56%10%12%10%8%1
1672
16th to endDay
51%8%11%15%8%4
1907
February1st to 15thDay
56%11%12%13%5%
1846
16th to endDay
61%10%10%13%4
1763
March1st to 15thDay
61%7%11%12%5%
2201
16th to endDay
61%9%12%12%4
2526
April1st to 15thDay
64%7%11%12%4
2509
16th to endDay
45%8%16%17%9%1
2541
May1st to 15thDay
40%7%14%25%11%
2907
16th to endDay
53%7%15%17%6%
3067
June1st to 15thDay
41%7%13%24%10%2
2857
16th to endDay
29%5%13%30%17%3
2730
July1st to 15thDay
16%410%19%31%16%
2581
16th to endDay
13%35%15%35%27%
2714
August1st to 15thDay
15%410%26%27%15%
2488
16th to endDay
15%36%24%39%10%
2548
September1st to 15thDay
15%38%23%35%13%
2340
16th to endDay
33%5%11%24%17%7%
2165
October1st to 15thDay
43%7%9%15%18%5%
1950
16th to endDay
43%8%11%15%19%1
2036
November1st to 15thDay
51%10%12%14%9%1
1787
16th to endDay
55%10%12%10%10%1
1680
December1st to 15thDay
49%11%12%17%8%
1680
16th to endDay
57%11%11%12%5%1
1792
January1st to 15thNight
54%11%12%11%8%1
2926
16th to endNight
52%7%11%13%8%5%
3017
February1st to 15thNight
54%14%13%9%7%
2678
16th to endNight
53%12%12%13%6%1
2283
March1st to 15thNight
54%11%11%13%7%
2416
16th to endNight
55%12%14%13%2
2402
April1st to 15thNight
56%12%13%10%6%
2099
16th to endNight
43%10%17%18%8%1
2021
May1st to 15thNight
33%8%16%28%10%1
1702
16th to endNight
44%11%16%19%7%
1752
June1st to 15thNight
37%8%14%26%10%2
1632
16th to endNight
25%5%14%33%17%3
1560
July1st to 15thNight
11%410%27%28%16%
1480
16th to endNight
11%16%17%36%26%
1544
August1st to 15thNight
12%27%28%35%13%
1697
16th to endNight
11%37%26%37%12%
2006
September1st to 15thNight
10%38%26%38%12%
1950
16th to endNight
26%7%12%23%21%9%
2122
October1st to 15thNight
34%8%12%19%18%6%
2340
16th to endNight
42%10%12%12%20%2
2538
November1st to 15thNight
51%12%12%12%9%1
2728
16th to endNight
50%12%13%10%9%3
2940
December1st to 15thNight
49%10%12%16%10%1
2940
16th to endNight
56%11%12%12%6%1
3136

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
17%12%27%26%13%2
120
16th to endDay
17%25%20%21%11%3
243
February1st to 15thDay
18%29%25%19%6%
326
16th to endDay
16%37%24%17%4
320
March1st to 15thDay
19%30%25%20%4
390
16th to endDay
22%27%30%15%4
416
April1st to 15thDay
28%27%25%10%6%2
389
16th to endDay
13%29%30%17%6%2
378
May1st to 15thDay
15%22%29%19%9%3
408
16th to endDay
19%14%29%20%12%3
458
June1st to 15thDay
11%22%27%23%12%2
412
16th to endDay
10%16%32%25%13%1
375
July1st to 15thDay
412%38%27%13%3
365
16th to endDay
111%40%28%13%4
391
August1st to 15thDay
29%35%31%13%7%
359
16th to endDay
411%26%33%15%8%
396
September1st to 15thDay
38%33%33%16%4
375
16th to endDay
10%17%24%30%16%1
375
October1st to 15thDay
15%22%29%19%12%
375
16th to endDay
15%19%22%19%16%5%
356
November1st to 15thDay
11%21%33%24%6%2
161
16th to endDay
13%36%20%18%7%4
120
December1st to 15thDay
12%21%31%18%10%5%
120
16th to endDay
9%27%35%17%9%1
128
January1st to 15thNight
14%18%27%21%16%2
840
16th to endNight
13%16%24%24%16%5%
896
February1st to 15thNight
12%18%25%29%12%1
824
16th to endNight
10%21%32%25%9%
736
March1st to 15thNight
10%25%24%26%11%1
840
16th to endNight
9%23%29%23%12%
896
April1st to 15thNight
11%23%29%23%11%1
839
16th to endNight
8%14%27%27%18%3
773
May1st to 15thNight
7%11%22%32%24%1
442
16th to endNight
10%7%20%31%27%2
439
June1st to 15thNight
10%8%20%37%21%2
408
16th to endNight
6%420%46%21%
390
July1st to 15thNight
110%52%32%1
370
16th to endNight
211%52%32%1
408
August1st to 15thNight
37%38%45%5%
551
16th to endNight
2313%39%37%3
764
September1st to 15thNight
2214%36%38%5%
780
16th to endNight
6%6%20%32%30%4
776
October1st to 15thNight
7%8%26%30%22%3
780
16th to endNight
12%12%22%24%20%7%
832
November1st to 15thNight
10%17%32%27%10%1
820
16th to endNight
10%25%22%23%14%3
840
December1st to 15thNight
12%16%24%29%15%2
840
16th to endNight
11%28%25%23%10%1
896
Page generated at 2019-06-10 16:29:46. Version ac04

Copyright 2019 A. Danko


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