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Lowell Discovery Telescope
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lowell Discovery Telescope clear sky chart from 2005-11-06 to 2024-01-16.

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
49%
23970
33%
74341
20%
23912
64%
23912
40%
36900

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
42%
760
33%
2457
18%
756
61%
756
34%
1260
January11th to 20thNight
34%
740
34%
2405
19%
740
55%
740
33%
1227
January21st to endNight
32%
792
34%
2574
16%
792
55%
792
27%
1391
February1st to 10thNight
38%
720
33%
2331
16%
720
62%
720
38%
1107
February11th to 20thNight
33%
704
32%
2099
16%
700
54%
700
34%
1101
February21st to endNight
33%
592
34%
1750
19%
592
51%
592
31%
958
March1st to 10thNight
29%
720
34%
1980
12%
720
51%
720
33%
1067
March11th to 20thNight
42%
720
34%
1980
18%
720
58%
720
42%
1035
March21st to endNight
36%
792
33%
2178
11%
792
55%
792
38%
1167
April1st to 10thNight
34%
720
31%
1980
11%
720
51%
720
39%
999
April11th to 20thNight
33%
567
37%
1811
14%
567
58%
567
40%
808
April21st to endNight
41%
540
42%
1650
19%
540
64%
540
47%
719
May1st to 10thNight
41%
540
38%
1620
18%
540
59%
540
47%
733
May11th to 20thNight
49%
531
38%
1594
22%
531
62%
531
51%
709
May21st to endNight
44%
582
36%
1746
19%
582
58%
582
56%
724
June1st to 10thNight
51%
540
35%
1620
21%
540
63%
540
60%
696
June11th to 20thNight
53%
540
37%
1620
24%
540
63%
540
66%
647
June21st to endNight
64%
540
32%
1620
24%
540
70%
540
57%
732
July1st to 10thNight
71%
525
24%
1575
18%
525
75%
525
44%
833
July11th to 20thNight
75%
522
21%
1566
16%
522
77%
522
40%
855
July21st to endNight
70%
591
17%
1674
15%
558
72%
558
31%
1018
August1st to 10thNight
76%
537
22%
1602
19%
534
77%
534
41%
863
August11th to 20thNight
77%
534
27%
1602
22%
534
80%
534
39%
882
August21st to endNight
79%
620
30%
1931
29%
620
80%
620
42%
1012
September1st to 10thNight
72%
720
30%
1980
25%
720
76%
720
45%
1087
September11th to 20thNight
72%
720
42%
1980
29%
720
81%
720
62%
941
September21st to endNight
64%
720
37%
1980
24%
720
74%
720
52%
978
October1st to 10thNight
51%
720
37%
2047
20%
720
65%
720
47%
1004
October11th to 20thNight
57%
720
41%
2160
27%
720
70%
720
59%
928
October21st to endNight
51%
792
43%
2376
24%
792
69%
792
49%
1052
November1st to 10thNight
49%
740
39%
2220
21%
740
67%
740
45%
1045
November11th to 20thNight
50%
760
40%
2436
24%
760
69%
760
49%
1052
November21st to endNight
41%
760
36%
2470
21%
760
60%
760
34%
1230
December1st to 10thNight
41%
760
34%
2470
20%
760
60%
760
33%
1269
December11th to 20thNight
37%
759
31%
2924
18%
758
56%
758
24%
1633
December21st to endNight
32%
830
21%
4333
17%
817
50%
817
18%
2138

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
35%2443445%7%59%
74981
Night
242442445%6%63%
74852
TransparencyDay
26%36%17%30%19%
74708
Night
22%36%18%30%21%
74647
SeeingDay
12%19%28%26%12%4
13757
Night
7%15%24%29%20%4
23979

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
36%35%434446%59%
1708
11th to 20thDay
37%35%423346%61%
1665
21st to endDay
5%8%36%424446%55%
1782
February1st to 10thDay
28%44413347%60%
1624
11th to 20thDay
28%4432446%7%56%
1750
21st to endDay
37%46%5%33336%56%
1506
March1st to 10thDay
37%233336%5%7%56%
1980
11th to 20thDay
26%45%334446%58%
1980
21st to endDay
35%2443435%7%60%
2178
April1st to 10thDay
23244345%5%7%62%
1980
11th to 20thDay
142332235%6%68%
2095
21st to endDay
3423323446%67%
2307
May1st to 10thDay
342332335%7%66%
2340
11th to 20thDay
23233245%5%6%65%
2301
21st to endDay
3412322346%71%
2530
June1st to 10thDay
1112313336%74%
2340
11th to 20thDay
111121222483%
2340
21st to endDay
2214334445%68%
2340
July1st to 10thDay
4325%6%46%6%6%6%52%
2340
11th to 20thDay
6%426%7%5%8%8%9%9%36%
2340
21st to endDay
8%6%27%8%5%7%9%9%10%29%
2545
August1st to 10thDay
6%5%26%7%47%5%7%8%44%
2328
11th to 20thDay
4426%7%48%7%8%9%40%
2299
21st to endDay
5%5%36%6%45%6%7%8%45%
2417
September1st to 10thDay
6%5%25%7%5%6%5%6%6%47%
1980
11th to 20thDay
4213424445%65%
1980
21st to endDay
3313323446%67%
1980
October1st to 10thDay
3324324445%65%
1913
11th to 20thDay
3213312225%76%
1800
21st to endDay
2412223345%73%
1980
November1st to 10thDay
2322223446%71%
1859
11th to 20thDay
1313223445%70%
1739
21st to endDay
36%33323346%65%
1710
December1st to 10thDay
5%6%3442435%7%57%
1710
11th to 20thDay
49%46%5%345%7%8%46%
2169
21st to endDay
49%48%5%33446%51%
3146
January1st to 10thNight
26%25%4245%5%6%58%
2457
11th to 20thNight
28%35%31335%6%60%
2405
21st to endNight
5%7%37%423445%57%
2574
February1st to 10thNight
16%3332335%5%66%
2331
11th to 20thNight
27%35%324446%60%
2098
21st to endNight
38%35%42345%6%58%
1750
March1st to 10thNight
35%3443346%7%60%
1980
11th to 20thNight
37%34323347%63%
1980
21st to endNight
3323425%45%6%63%
2178
April1st to 10thNight
1423424446%65%
1980
11th to 20thNight
141432334470%
1811
21st to endNight
1112323247%74%
1650
May1st to 10thNight
2213325%345%71%
1620
11th to 20thNight
2212313346%74%
1594
21st to endNight
2211222335%77%
1746
June1st to 10thNight
221221235%6%75%
1620
11th to 20thNight
11221222385%
1620
21st to endNight
221232334474%
1620
July1st to 10thNight
2324435%6%7%9%55%
1620
11th to 20thNight
33245%47%6%8%10%50%
1620
21st to endNight
6%5%35%7%47%7%8%12%38%
1773
August1st to 10thNight
33145%36%5%6%9%54%
1611
11th to 20thNight
3315%5%36%7%7%11%49%
1602
21st to endNight
2324436%5%7%10%53%
1931
September1st to 10thNight
3424435%47%7%57%
1980
11th to 20thNight
221232234475%
1980
21st to endNight
2213333346%71%
1980
October1st to 10thNight
3312323445%69%
2047
11th to 20thNight
221221223478%
2160
21st to endNight
231332234474%
2376
November1st to 10thNight
3312224445%69%
2220
11th to 20thNight
1213324345%72%
2436
21st to endNight
35%34423345%63%
2470
December1st to 10thNight
46%35%32445%7%58%
2470
11th to 20thNight
37%37%5%245%5%8%49%
3041
21st to endNight
37%37%5%4444455%
4521

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%26%21%30%15%
1709
11th to 20thDay
26%35%21%32%13%
1665
21st to endDay
30%35%16%33%13%
1782
February1st to 10thDay
25%27%17%28%21%
1624
11th to 20thDay
29%4421%24%19%
1760
21st to endDay
31%2317%27%20%
1506
March1st to 10thDay
26%4418%33%16%
1980
11th to 20thDay
28%3418%34%13%
1980
21st to endDay
25%3423%34%11%
2178
April1st to 10thDay
22%3422%35%13%
1980
11th to 20thDay
19%2218%39%20%
2098
21st to endDay
19%2418%41%15%
2307
May1st to 10thDay
18%35%18%37%19%
2340
11th to 20thDay
19%35%19%37%18%
2304
21st to endDay
17%2315%39%24%
2530
June1st to 10thDay
13%2214%35%33%
2340
11th to 20thDay
8%218%31%50%
2340
21st to endDay
19%229%32%35%
2340
July1st to 10thDay
30%5%7%15%18%25%
2276
11th to 20thDay
38%7%16%19%12%8%
2271
21st to endDay
46%8%18%15%11%3
2404
August1st to 10thDay
38%5%10%14%19%14%
2313
11th to 20thDay
38%5%12%18%17%10%
2299
21st to endDay
35%5%10%18%25%6%
2417
September1st to 10thDay
36%5%8%14%20%18%
1980
11th to 20thDay
22%2416%35%22%
1980
21st to endDay
21%3316%34%24%
1980
October1st to 10thDay
23%35%18%26%25%
1913
11th to 20thDay
14%1311%38%32%
1800
21st to endDay
16%2417%41%20%
1980
November1st to 10thDay
17%3324%34%19%
1859
11th to 20thDay
16%35%18%37%22%
1739
21st to endDay
23%2317%35%19%
1710
December1st to 10thDay
27%36%19%26%19%
1710
11th to 20thDay
37%26%21%21%13%
2168
21st to endDay
37%2319%27%12%
3146
January1st to 10thNight
26%35%22%31%13%
2457
11th to 20thNight
27%3321%33%14%
2405
21st to endNight
30%3415%34%14%
2574
February1st to 10thNight
21%27%19%27%24%
2331
11th to 20thNight
26%25%22%23%21%
2099
21st to endNight
28%4215%30%22%
1750
March1st to 10thNight
24%3418%36%16%
1980
11th to 20thNight
23%2323%35%15%
1980
21st to endNight
23%36%24%32%12%
2178
April1st to 10thNight
20%26%21%35%16%
1980
11th to 20thNight
17%2317%37%24%
1811
21st to endNight
14%2423%40%18%
1650
May1st to 10thNight
15%26%22%35%20%
1620
11th to 20thNight
15%2421%38%20%
1595
21st to endNight
11%2417%39%28%
1746
June1st to 10thNight
13%2112%35%37%
1620
11th to 20thNight
9%116%30%53%
1620
21st to endNight
16%229%28%44%
1620
July1st to 10thNight
23%6%9%15%20%27%
1575
11th to 20thNight
26%6%18%25%16%9%
1566
21st to endNight
35%7%22%20%12%5%
1674
August1st to 10thNight
25%7%16%16%19%18%
1602
11th to 20thNight
27%6%16%20%19%12%
1602
21st to endNight
25%6%13%26%22%9%
1931
September1st to 10thNight
24%5%12%18%24%17%
1980
11th to 20thNight
14%35%20%31%27%
1980
21st to endNight
16%4415%34%27%
1980
October1st to 10thNight
18%35%21%24%28%
2047
11th to 20thNight
13%2413%36%33%
2160
21st to endNight
14%2415%38%26%
2376
November1st to 10thNight
18%3322%35%19%
2220
11th to 20thNight
16%25%17%37%23%
2436
21st to endNight
25%3216%32%22%
2470
December1st to 10thNight
27%35%19%26%20%
2470
11th to 20thNight
34%35%17%26%14%
3041
21st to endNight
34%2417%23%19%
4521

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
15%27%33%17%8%
270
11th to 20thDay
15%24%31%21%7%2
255
21st to endDay
12%31%30%17%9%2
264
February1st to 10thDay
17%25%29%21%8%1
244
11th to 20thDay
24%28%28%15%4
415
21st to endDay
27%29%27%14%2
346
March1st to 10thDay
24%31%26%16%3
420
11th to 20thDay
20%23%27%20%7%3
420
21st to endDay
24%30%28%12%41
462
April1st to 10thDay
12%30%33%17%6%2
420
11th to 20thDay
19%32%31%11%5%1
412
21st to endDay
16%30%27%17%7%2
420
May1st to 10thDay
11%27%37%18%5%1
423
11th to 20thDay
9%20%34%24%10%3
448
21st to endDay
13%22%34%22%7%1
485
June1st to 10thDay
5%17%38%29%10%1
450
11th to 20thDay
6%17%41%22%11%3
450
21st to endDay
312%34%38%10%3
450
July1st to 10thDay
5%431%39%17%4
446
11th to 20thDay
7%320%37%25%8%
444
21st to endDay
8%411%38%29%10%
487
August1st to 10thDay
6%420%42%20%8%
447
11th to 20thDay
6%6%15%44%21%7%
437
21st to endDay
5%317%38%26%10%
495
September1st to 10thDay
7%7%22%37%20%7%
450
11th to 20thDay
5%11%31%34%12%6%
450
21st to endDay
10%11%27%32%16%4
450
October1st to 10thDay
10%23%26%25%14%3
383
11th to 20thDay
9%18%27%25%16%6%
270
21st to endDay
14%17%29%24%13%3
297
November1st to 10thDay
15%21%26%22%11%4
270
11th to 20thDay
11%19%27%24%13%5%
270
21st to endDay
20%17%29%20%11%3
270
December1st to 10thDay
14%24%27%24%10%1
270
11th to 20thDay
14%21%33%23%7%3
270
21st to endDay
23%23%30%18%6%2
297
January1st to 10thNight
9%19%26%28%14%4
760
11th to 20thNight
11%20%31%22%14%2
740
21st to endNight
12%25%26%26%10%2
792
February1st to 10thNight
10%19%29%29%12%2
720
11th to 20thNight
10%22%32%25%9%2
704
21st to endNight
13%24%27%24%9%2
592
March1st to 10thNight
14%27%27%23%8%1
720
11th to 20thNight
11%16%28%27%16%3
720
21st to endNight
9%22%29%27%11%1
792
April1st to 10thNight
7%24%30%26%12%1
720
11th to 20thNight
10%20%32%28%9%1
567
21st to endNight
6%22%29%27%13%3
540
May1st to 10thNight
5%18%33%32%11%1
540
11th to 20thNight
5%13%27%31%21%3
531
21st to endNight
6%16%31%29%15%2
584
June1st to 10thNight
310%33%36%16%1
540
11th to 20thNight
310%32%36%19%1
540
21st to endNight
35%23%42%24%3
540
July1st to 10thNight
2117%43%33%4
525
11th to 20thNight
49%36%43%8%
522
21st to endNight
6%37%27%44%13%
591
August1st to 10thNight
429%31%41%12%
537
11th to 20thNight
427%34%42%11%
534
21st to endNight
326%28%48%13%
620
September1st to 10thNight
4411%28%44%9%
720
11th to 20thNight
3417%33%38%5%
720
21st to endNight
5%11%16%28%32%8%
720
October1st to 10thNight
6%15%23%31%21%3
720
11th to 20thNight
411%25%36%20%5%
720
21st to endNight
5%18%22%28%21%7%
792
November1st to 10thNight
7%16%25%28%19%5%
740
11th to 20thNight
6%17%24%30%18%5%
760
21st to endNight
12%18%26%26%15%3
760
December1st to 10thNight
13%17%25%29%16%1
760
11th to 20thNight
10%20%28%28%13%2
760
21st to endNight
13%21%28%28%8%2
836
Page generated at 2024-01-12 23:38:09. Version ac07

Copyright 2024 Attilla Danko


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