Cottontail Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cottontail Observatory clear sky chart from 2005-11-06 to 2024-03-08.

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
54%
23671
31%
80098
22%
23580
65%
23580
41%
38670

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
40%
752
28%
4318
16%
736
58%
736
21%
1971
January11th to 20thNight
49%
755
25%
4264
20%
740
62%
740
22%
2026
January21st to endNight
44%
833
20%
4268
20%
814
58%
814
21%
2273
February1st to 10thNight
43%
760
29%
2413
21%
760
55%
760
34%
1274
February11th to 20thNight
43%
741
31%
2219
22%
740
57%
740
38%
1151
February21st to endNight
43%
628
28%
1884
18%
628
57%
628
37%
985
March1st to 10thNight
36%
750
25%
2249
13%
750
52%
750
31%
1252
March11th to 20thNight
44%
720
26%
2041
18%
720
54%
720
36%
1092
March21st to endNight
37%
792
26%
2016
10%
792
49%
792
38%
1144
April1st to 10thNight
44%
720
25%
1800
10%
720
52%
720
41%
1050
April11th to 20thNight
45%
711
27%
1779
11%
711
51%
711
41%
1003
April21st to endNight
48%
720
27%
1800
11%
720
54%
720
47%
970
May1st to 10thNight
49%
604
29%
1684
16%
604
56%
604
44%
873
May11th to 20thNight
55%
462
31%
1524
23%
462
62%
462
42%
735
May21st to endNight
59%
388
27%
1552
25%
388
68%
388
36%
722
June1st to 10thNight
60%
360
29%
1440
27%
360
74%
360
43%
601
June11th to 20thNight
62%
360
35%
1440
33%
360
78%
360
61%
480
June21st to endNight
69%
360
35%
1440
37%
360
80%
360
57%
514
July1st to 10thNight
74%
350
36%
1400
38%
350
85%
350
69%
449
July11th to 20thNight
68%
348
34%
1392
34%
348
77%
348
54%
527
July21st to endNight
75%
444
38%
1536
36%
420
81%
420
50%
663
August1st to 10thNight
71%
609
35%
1674
21%
606
78%
606
64%
783
August11th to 20thNight
71%
712
37%
1780
19%
712
77%
712
69%
852
August21st to endNight
72%
792
42%
1980
23%
792
76%
792
74%
915
September1st to 10thNight
72%
720
44%
1800
24%
720
80%
720
78%
806
September11th to 20thNight
68%
720
44%
1851
28%
720
76%
720
66%
859
September21st to endNight
64%
720
42%
1980
30%
720
76%
720
59%
932
October1st to 10thNight
65%
720
35%
2083
28%
720
75%
720
54%
985
October11th to 20thNight
68%
720
40%
2160
36%
720
77%
720
58%
955
October21st to endNight
63%
792
42%
2434
35%
792
76%
792
61%
1026
November1st to 10thNight
58%
740
34%
2405
29%
740
70%
740
46%
1098
November11th to 20thNight
52%
760
35%
2470
24%
760
69%
760
47%
1112
November21st to endNight
49%
760
35%
2470
24%
760
65%
760
44%
1169
December1st to 10thNight
47%
760
26%
2645
19%
760
59%
760
38%
1274
December11th to 20thNight
41%
759
26%
3157
20%
758
52%
758
24%
1670
December21st to endNight
36%
829
17%
4750
17%
817
50%
817
16%
2479

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
242443445%7%59%
78637
Night
242442445%7%62%
80946
TransparencyDay
24%5%8%20%25%17%
78345
Night
21%410%24%26%14%
80760
SeeingDay
9%22%30%25%12%3
14144
Night
412%26%34%19%5%
23699

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
16%24435%6%7%10%52%
2539
11th to 20thDay
15%25%5%45%7%8%10%48%
2604
21st to endDay
39%46%5%45%5%7%9%43%
3146
February1st to 10thDay
15%36%42445%10%57%
1765
11th to 20thDay
1447%5%345%6%11%52%
1850
21st to endDay
1427%5%25%45%8%56%
1570
March1st to 10thDay
27%48%5%35%6%7%9%45%
1871
11th to 20thDay
145%45%36%6%6%11%49%
1916
21st to endDay
16%35%325%7%7%8%52%
2340
April1st to 10thDay
35%26%5%3446%8%54%
2160
11th to 20thDay
25%3443446%7%58%
2129
21st to endDay
36%244235%5%7%60%
2160
May1st to 10thDay
5%6%2443345%7%58%
2273
11th to 20thDay
5%6%35%4335%5%7%55%
2366
21st to endDay
7%8%25%5%35%45%7%49%
2723
June1st to 10thDay
43245%3445%7%58%
2520
11th to 20thDay
221232235%5%73%
2520
21st to endDay
332332444469%
2520
July1st to 10thDay
222323435%6%68%
2520
11th to 20thDay
3324433445%65%
2520
21st to endDay
43245%35%45%6%59%
2687
August1st to 10thDay
3324434445%62%
2253
11th to 20thDay
32145%3334468%
2122
21st to endDay
231331333474%
2376
September1st to 10thDay
221332333472%
2160
11th to 20thDay
3314323345%69%
2107
21st to endDay
2312222235%75%
1980
October1st to 10thDay
46%2422233468%
1872
11th to 20thDay
2323213335%73%
1800
21st to endDay
1312213347%72%
1922
November1st to 10thDay
14343245%5%7%63%
1674
11th to 20thDay
221323446%8%65%
1710
21st to endDay
132432446%11%61%
1710
December1st to 10thDay
14233345%5%9%60%
1530
11th to 20thDay
35%48%6%5%7%6%7%9%41%
1928
21st to endDay
16%37%425%7%7%12%45%
2794
January1st to 10thNight
1447%5%3446%8%52%
4406
11th to 20thNight
16%37%6%35%6%8%10%47%
4354
21st to endNight
28%36%5%35%6%7%8%46%
4521
February1st to 10thNight
1436%5%346%6%7%55%
2413
11th to 20thNight
15%35%5%2447%11%56%
2218
21st to endNight
1425%42446%8%59%
1884
March1st to 10thNight
16%36%4346%7%8%52%
2249
11th to 20thNight
1424325%5%7%11%56%
2041
21st to endNight
5%35%42345%8%60%
2016
April1st to 10thNight
34343245%6%9%56%
1800
11th to 20thNight
15%3342435%6%63%
1779
21st to endNight
35%32324446%65%
1800
May1st to 10thNight
45%2432345%7%62%
1684
11th to 20thNight
5%6%34322348%63%
1524
21st to endNight
6%5%1442435%6%61%
1552
June1st to 10thNight
5%31232345%6%68%
1440
11th to 20thNight
1112212245%80%
1440
21st to endNight
311221233379%
1440
July1st to 10thNight
1111212235%81%
1440
11th to 20thNight
2212323335%74%
1440
21st to endNight
3313324445%68%
1626
August1st to 10thNight
311322334474%
1683
11th to 20thNight
1111223435%77%
1780
21st to endNight
211111223482%
1980
September1st to 10thNight
111121222484%
1800
11th to 20thNight
121221223479%
1851
21st to endNight
221231334475%
1980
October1st to 10thNight
4412213345%72%
2083
11th to 20thNight
1223212245%76%
2160
21st to endNight
1212222346%75%
2434
November1st to 10thNight
1313323448%67%
2405
11th to 20thNight
131232445%9%66%
2470
21st to endNight
232432335%8%64%
2470
December1st to 10thNight
23244245%6%9%60%
2645
11th to 20thNight
25%36%5%35%5%9%11%47%
3276
21st to endNight
16%48%6%36%6%8%10%41%
4862

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
24%6%15%29%21%4
2539
11th to 20thDay
29%415%24%20%8%
2604
21st to endDay
38%5%9%24%20%4
3146
February1st to 10thDay
23%6%11%24%25%10%
1765
11th to 20thDay
27%410%24%26%8%
1860
21st to endDay
27%6%10%25%25%6%
1570
March1st to 10thDay
34%7%11%23%18%6%
1871
11th to 20thDay
28%8%13%22%23%7%
1916
21st to endDay
26%8%17%28%16%4
2340
April1st to 10thDay
28%6%12%25%20%8%
2160
11th to 20thDay
25%6%11%26%23%9%
2132
21st to endDay
24%6%13%29%22%5%
2160
May1st to 10thDay
26%411%27%25%7%
2273
11th to 20thDay
28%6%9%27%25%6%
2369
21st to endDay
35%5%8%24%23%5%
2724
June1st to 10thDay
26%5%9%21%29%11%
2520
11th to 20thDay
15%35%22%35%21%
2520
21st to endDay
19%3311%33%30%
2520
July1st to 10thDay
16%3310%25%44%
2451
11th to 20thDay
21%4313%20%40%
2445
21st to endDay
24%4411%22%35%
2538
August1st to 10thDay
23%4411%18%40%
2237
11th to 20thDay
20%428%28%38%
2122
21st to endDay
16%328%32%41%
2376
September1st to 10thDay
16%339%31%38%
2160
11th to 20thDay
18%3318%33%25%
2107
21st to endDay
15%3218%36%26%
1980
October1st to 10thDay
22%35%17%29%24%
1872
11th to 20thDay
15%35%22%34%21%
1800
21st to endDay
13%46%25%35%18%
1922
November1st to 10thDay
20%6%9%22%28%14%
1674
11th to 20thDay
15%413%23%32%12%
1710
21st to endDay
18%5%10%26%27%14%
1710
December1st to 10thDay
20%6%13%26%25%9%
1530
11th to 20thDay
37%6%12%21%17%7%
1928
21st to endDay
30%5%16%21%22%5%
2794
January1st to 10thNight
29%413%29%20%4
4406
11th to 20thNight
30%416%25%18%6%
4354
21st to endNight
34%5%12%26%19%6%
4521
February1st to 10thNight
25%6%11%25%21%12%
2413
11th to 20thNight
24%410%27%26%10%
2219
21st to endNight
22%6%12%28%24%7%
1884
March1st to 10thNight
28%6%13%23%22%7%
2249
11th to 20thNight
22%7%15%26%24%6%
2041
21st to endNight
24%5%18%29%19%5%
2016
April1st to 10thNight
24%7%15%30%18%8%
1800
11th to 20thNight
22%5%14%26%23%10%
1779
21st to endNight
20%416%34%24%3
1800
May1st to 10thNight
21%5%11%28%31%5%
1684
11th to 20thNight
23%38%31%29%5%
1524
21st to endNight
24%411%31%24%5%
1552
June1st to 10thNight
18%411%26%32%9%
1440
11th to 20thNight
9%29%21%38%22%
1440
21st to endNight
12%3317%32%33%
1440
July1st to 10thNight
7%2312%33%43%
1400
11th to 20thNight
14%3312%29%38%
1392
21st to endNight
18%3314%27%34%
1536
August1st to 10thNight
14%25%16%24%39%
1674
11th to 20thNight
11%3216%32%37%
1780
21st to endNight
8%2212%36%38%
1980
September1st to 10thNight
7%2114%37%39%
1800
11th to 20thNight
11%25%21%36%25%
1851
21st to endNight
14%3320%36%24%
1980
October1st to 10thNight
18%27%21%33%20%
2083
11th to 20thNight
13%35%24%34%21%
2160
21st to endNight
12%27%25%37%17%
2434
November1st to 10thNight
16%5%8%28%28%14%
2405
11th to 20thNight
16%5%9%27%32%11%
2470
21st to endNight
19%411%24%29%12%
2470
December1st to 10thNight
20%7%14%23%25%10%
2645
11th to 20thNight
29%6%13%25%20%6%
3276
21st to endNight
35%6%12%20%20%8%
4862

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
13%29%28%21%9%1
180
11th to 20thDay
10%25%28%22%12%2
218
21st to endDay
7%21%31%28%9%3
407
February1st to 10thDay
8%28%31%21%10%2
397
11th to 20thDay
9%29%31%21%9%1
455
21st to endDay
13%26%33%23%6%
382
March1st to 10thDay
16%29%31%18%5%1
449
11th to 20thDay
10%33%28%18%10%
420
21st to endDay
11%30%33%20%5%
462
April1st to 10thDay
11%31%31%20%7%
420
11th to 20thDay
17%30%28%18%7%1
412
21st to endDay
13%29%29%19%9%1
420
May1st to 10thDay
14%27%27%21%8%3
423
11th to 20thDay
13%27%28%20%10%3
448
21st to endDay
15%19%25%23%13%5%
485
June1st to 10thDay
9%22%31%20%14%5%
450
11th to 20thDay
9%23%32%21%12%4
450
21st to endDay
5%17%33%27%13%6%
450
July1st to 10thDay
317%32%29%15%4
446
11th to 20thDay
5%14%25%32%18%6%
444
21st to endDay
6%11%31%30%16%7%
487
August1st to 10thDay
417%28%27%19%4
447
11th to 20thDay
5%15%27%29%19%5%
437
21st to endDay
314%34%30%16%3
495
September1st to 10thDay
413%30%32%16%5%
450
11th to 20thDay
7%21%26%29%13%3
450
21st to endDay
6%15%36%30%11%2
450
October1st to 10thDay
7%20%28%28%15%1
450
11th to 20thDay
6%16%28%35%12%4
450
21st to endDay
6%17%31%27%15%4
437
November1st to 10thDay
9%18%25%23%19%6%
270
11th to 20thDay
320%27%30%14%7%
270
21st to endDay
320%29%30%15%3
270
December1st to 10thDay
10%23%23%23%16%5%
185
11th to 20thDay
5%25%31%24%11%3
180
21st to endDay
15%19%27%27%10%3
198
January1st to 10thNight
6%16%32%24%15%8%
760
11th to 20thNight
415%28%33%15%5%
760
21st to endNight
5%12%32%30%15%5%
836
February1st to 10thNight
315%31%31%16%3
760
11th to 20thNight
5%15%31%29%15%6%
744
21st to endNight
5%20%27%34%11%3
628
March1st to 10thNight
7%18%33%27%11%3
750
11th to 20thNight
322%26%28%17%5%
720
21st to endNight
422%32%28%13%1
792
April1st to 10thNight
6%14%31%32%14%2
720
11th to 20thNight
6%19%27%28%15%5%
711
21st to endNight
6%15%26%31%17%5%
720
May1st to 10thNight
8%11%29%31%16%5%
604
11th to 20thNight
8%10%23%40%17%2
462
21st to endNight
8%5%22%38%25%2
389
June1st to 10thNight
6%8%23%39%20%3
360
11th to 20thNight
27%27%40%21%3
360
21st to endNight
35%19%46%23%4
360
July1st to 10thNight
1319%48%25%3
350
11th to 20thNight
2123%47%24%2
348
21st to endNight
2315%42%32%5%
444
August1st to 10thNight
2219%40%31%6%
609
11th to 20thNight
1321%43%27%5%
712
21st to endNight
2319%45%26%5%
792
September1st to 10thNight
1321%38%32%6%
720
11th to 20thNight
27%19%37%28%7%
720
21st to endNight
28%23%31%29%7%
720
October1st to 10thNight
5%8%18%39%23%7%
720
11th to 20thNight
39%17%40%24%7%
720
21st to endNight
38%23%31%23%11%
792
November1st to 10thNight
313%23%31%22%8%
740
11th to 20thNight
411%30%34%15%6%
760
21st to endNight
413%28%32%18%6%
760
December1st to 10thNight
5%14%29%33%14%5%
760
11th to 20thNight
5%18%31%28%14%4
760
21st to endNight
6%16%35%29%11%3
836
Page generated at 2024-03-05 04:24:05. Version ac07

Copyright © 2024 Attilla Danko.


Cottontail Observatory Clear Sky Chart |Charts Home