Deer Lodge Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Deer Lodge Site clear sky chart from 2005-11-06 to 2024-02-20.

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
57%
23419
26%
80302
23%
23340
65%
23340
36%
42211

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
44%
749
17%
4349
14%
736
54%
736
16%
2253
January11th to 20thNight
49%
753
15%
4365
16%
740
58%
740
14%
2655
January21st to endNight
49%
830
14%
4440
22%
814
56%
814
15%
2942
February1st to 10thNight
50%
760
23%
2470
20%
760
58%
760
31%
1378
February11th to 20thNight
49%
738
26%
2223
20%
738
59%
738
34%
1240
February21st to endNight
47%
592
26%
1776
20%
592
57%
592
33%
990
March1st to 10thNight
42%
720
19%
2160
13%
720
51%
720
28%
1306
March11th to 20thNight
49%
720
23%
2012
18%
720
55%
720
34%
1171
March21st to endNight
42%
792
18%
2037
8%
792
49%
792
33%
1217
April1st to 10thNight
48%
720
25%
1800
12%
720
53%
720
35%
1111
April11th to 20thNight
48%
711
27%
1779
12%
711
53%
711
40%
1023
April21st to endNight
52%
720
24%
1800
11%
720
57%
720
44%
1027
May1st to 10thNight
50%
599
27%
1679
16%
599
56%
599
43%
890
May11th to 20thNight
58%
372
28%
1434
26%
372
66%
372
38%
670
May21st to endNight
63%
388
21%
1552
23%
388
68%
388
31%
781
June1st to 10thNight
63%
360
26%
1440
29%
360
71%
360
37%
656
June11th to 20thNight
63%
360
33%
1440
35%
360
75%
360
56%
519
June21st to endNight
71%
360
32%
1440
38%
360
80%
360
57%
526
July1st to 10thNight
76%
350
34%
1400
39%
350
85%
350
69%
452
July11th to 20thNight
76%
348
37%
1392
43%
348
82%
348
66%
464
July21st to endNight
80%
430
39%
1522
42%
406
85%
406
59%
567
August1st to 10thNight
78%
545
33%
1610
25%
542
82%
542
58%
756
August11th to 20thNight
73%
712
36%
1780
20%
712
77%
712
71%
852
August21st to endNight
72%
792
43%
1980
25%
792
75%
792
77%
903
September1st to 10thNight
75%
720
44%
1800
26%
720
80%
720
77%
827
September11th to 20thNight
72%
720
43%
1826
29%
720
78%
720
67%
870
September21st to endNight
69%
720
41%
1980
32%
720
78%
720
63%
924
October1st to 10thNight
66%
720
32%
2132
26%
720
76%
720
52%
1022
October11th to 20thNight
71%
720
38%
2160
36%
720
78%
720
58%
956
October21st to endNight
66%
792
37%
2430
35%
792
74%
792
55%
1093
November1st to 10thNight
58%
740
28%
2405
27%
740
64%
740
38%
1241
November11th to 20thNight
57%
760
28%
2470
23%
760
67%
760
41%
1228
November21st to endNight
55%
760
28%
2550
24%
760
63%
760
37%
1310
December1st to 10thNight
51%
760
22%
2660
19%
760
58%
760
28%
1470
December11th to 20thNight
45%
760
19%
3209
18%
759
53%
759
18%
2076
December21st to endNight
39%
826
13%
4800
16%
817
48%
817
13%
2845

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%8%60%
78440
Night
34244345%6%8%58%
80774
TransparencyDay
22%7%12%20%22%17%
78147
Night
23%9%14%22%20%13%
80588
SeeingDay
8%18%29%27%15%4
13985
Night
5%11%22%36%22%4
23458

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
25%35%7%47%7%8%9%43%
2539
11th to 20thDay
37%37%6%46%6%7%9%41%
2576
21st to endDay
5%10%48%8%5%6%6%7%9%32%
3146
February1st to 10thDay
45%25%6%35%6%6%10%48%
1710
11th to 20thDay
25%45%6%345%6%10%49%
1827
21st to endDay
15%24435%6%7%11%53%
1480
March1st to 10thDay
37%36%6%45%7%7%10%44%
1800
11th to 20thDay
36%36%435%6%6%11%46%
1944
21st to endDay
15%25%5%45%6%6%11%51%
2317
April1st to 10thDay
3425%6%35%5%7%8%51%
2160
11th to 20thDay
3423435%46%8%57%
2129
21st to endDay
35%24424447%61%
2160
May1st to 10thDay
242442345%8%61%
2278
11th to 20thDay
44245%2445%7%60%
2456
21st to endDay
45%36%5%35%5%6%6%51%
2723
June1st to 10thDay
33144245%5%9%60%
2520
11th to 20thDay
1212223335%75%
2520
21st to endDay
2212222335%75%
2520
July1st to 10thDay
1111213345%78%
2520
11th to 20thDay
111213335%79%
2520
21st to endDay
221332344472%
2702
August1st to 10thDay
221332345%5%72%
2320
11th to 20thDay
111222223479%
2122
21st to endDay
11111223484%
2376
September1st to 10thDay
111121123483%
2160
11th to 20thDay
2212313345%75%
2134
21st to endDay
3212212345%75%
1980
October1st to 10thDay
4324322336%68%
1826
11th to 20thDay
221332235%7%72%
1800
21st to endDay
231332335%8%66%
1924
November1st to 10thDay
34234245%6%8%59%
1674
11th to 20thDay
3323425%7%7%10%55%
1710
21st to endDay
2323435%6%6%10%55%
1625
December1st to 10thDay
45%35%5%345%6%9%50%
1520
11th to 20thDay
6%10%48%7%35%5%8%11%33%
1928
21st to endDay
26%47%6%47%6%7%14%37%
2794
January1st to 10thNight
25%25%7%46%6%8%11%45%
4406
11th to 20thNight
27%49%7%46%7%8%9%38%
4384
21st to endNight
5%10%48%7%46%7%7%9%35%
4521
February1st to 10thNight
25%35%5%35%5%6%9%53%
2470
11th to 20thNight
25%35%435%5%7%11%51%
2222
21st to endNight
25%25%4445%6%10%56%
1776
March1st to 10thNight
26%35%5%36%6%7%10%48%
2160
11th to 20thNight
26%24435%5%7%10%53%
2012
21st to endNight
34244345%6%8%56%
2037
April1st to 10thNight
2423435%6%8%10%52%
1800
11th to 20thNight
2324325%5%5%8%62%
1779
21st to endNight
441342335%8%63%
1800
May1st to 10thNight
5%42342345%6%62%
1679
11th to 20thNight
341333446%7%61%
1434
21st to endNight
43244345%6%7%57%
1552
June1st to 10thNight
442332435%7%64%
1440
11th to 20thNight
1312212336%77%
1440
21st to endNight
211222433377%
1440
July1st to 10thNight
1111212345%80%
1440
11th to 20thNight
111121332481%
1440
21st to endNight
3212212245%75%
1612
August1st to 10thNight
3213323445%70%
1619
11th to 20thNight
211222234478%
1780
21st to endNight
221211122483%
1980
September1st to 10thNight
211211123484%
1800
11th to 20thNight
3312212235%77%
1826
21st to endNight
1212222335%75%
1980
October1st to 10thNight
4323313435%70%
2132
11th to 20thNight
2212222346%75%
2160
21st to endNight
2313212348%70%
2430
November1st to 10thNight
34145%3346%8%60%
2405
11th to 20thNight
23233245%6%9%61%
2470
21st to endNight
2325%4345%6%8%58%
2550
December1st to 10thNight
45%35%4245%6%10%53%
2660
11th to 20thNight
7%7%37%6%35%6%7%13%36%
3276
21st to endNight
37%36%7%5%7%7%8%10%37%
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
31%14%21%25%8%1
2539
11th to 20thDay
36%12%18%22%9%3
2576
21st to endDay
43%13%14%20%9%1
3146
February1st to 10thDay
29%9%17%25%15%5%
1710
11th to 20thDay
28%7%18%27%16%4
1837
21st to endDay
24%9%21%27%16%3
1480
March1st to 10thDay
32%10%19%23%14%2
1800
11th to 20thDay
31%11%15%21%19%4
1944
21st to endDay
25%12%24%24%11%3
2317
April1st to 10thDay
28%8%17%24%17%5%
2160
11th to 20thDay
23%10%13%28%21%6%
2132
21st to endDay
22%7%15%29%24%4
2160
May1st to 10thDay
20%7%11%28%29%6%
2278
11th to 20thDay
23%6%11%25%27%8%
2459
21st to endDay
30%8%13%21%23%4
2724
June1st to 10thDay
20%6%11%21%30%12%
2520
11th to 20thDay
12%47%20%33%23%
2520
21st to endDay
12%3414%31%37%
2520
July1st to 10thDay
9%349%24%51%
2451
11th to 20thDay
9%249%25%51%
2445
21st to endDay
14%35%9%22%47%
2552
August1st to 10thDay
15%4411%22%44%
2304
11th to 20thDay
9%248%28%48%
2122
21st to endDay
7%138%32%48%
2376
September1st to 10thDay
7%2310%27%50%
2160
11th to 20thDay
13%46%16%34%27%
2134
21st to endDay
13%36%18%34%25%
1980
October1st to 10thDay
18%48%19%31%19%
1826
11th to 20thDay
13%5%10%24%31%18%
1800
21st to endDay
16%5%11%27%27%13%
1924
November1st to 10thDay
22%8%14%24%24%8%
1674
11th to 20thDay
20%10%18%27%23%3
1710
21st to endDay
24%9%11%28%25%4
1625
December1st to 10thDay
28%10%15%27%16%4
1520
11th to 20thDay
40%14%13%22%10%2
1928
21st to endDay
33%13%22%22%10%1
2794
January1st to 10thNight
28%13%24%25%9%1
4406
11th to 20thNight
36%15%20%18%8%4
4384
21st to endNight
41%13%14%19%11%1
4521
February1st to 10thNight
26%10%15%27%17%5%
2470
11th to 20thNight
24%9%16%30%19%2
2223
21st to endNight
24%10%17%30%14%4
1776
March1st to 10thNight
29%11%17%24%15%3
2160
11th to 20thNight
24%11%16%26%20%4
2012
21st to endNight
23%11%24%26%13%3
2037
April1st to 10thNight
24%12%17%28%16%4
1800
11th to 20thNight
21%9%17%29%19%6%
1779
21st to endNight
20%9%16%31%20%4
1800
May1st to 10thNight
21%6%13%26%29%6%
1679
11th to 20thNight
21%7%14%27%22%8%
1434
21st to endNight
23%10%15%27%21%4
1552
June1st to 10thNight
21%7%10%24%28%11%
1440
11th to 20thNight
11%39%21%33%22%
1440
21st to endNight
12%45%15%31%34%
1440
July1st to 10thNight
7%25%9%29%48%
1400
11th to 20thNight
7%449%26%50%
1392
21st to endNight
12%36%8%24%48%
1522
August1st to 10thNight
15%5%7%11%24%38%
1610
11th to 20thNight
10%35%9%27%46%
1780
21st to endNight
8%239%33%46%
1980
September1st to 10thNight
7%347%31%49%
1800
11th to 20thNight
11%47%17%36%26%
1826
21st to endNight
12%36%19%33%26%
1980
October1st to 10thNight
17%49%20%28%21%
2132
11th to 20thNight
12%410%23%32%19%
2160
21st to endNight
14%410%27%31%13%
2430
November1st to 10thNight
21%8%14%25%21%10%
2405
11th to 20thNight
19%8%16%28%25%4
2470
21st to endNight
23%7%14%26%23%6%
2550
December1st to 10thNight
28%10%14%25%20%4
2660
11th to 20thNight
36%14%13%21%13%2
3276
21st to endNight
35%14%19%19%12%2
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%27%27%23%9%2
180
11th to 20thDay
8%27%24%24%15%2
203
21st to endDay
7%15%35%26%13%3
407
February1st to 10thDay
8%26%29%23%12%1
370
11th to 20thDay
8%27%27%27%10%1
446
21st to endDay
10%23%30%29%7%1
346
March1st to 10thDay
12%29%30%20%8%1
420
11th to 20thDay
12%28%28%19%12%2
420
21st to endDay
12%28%29%24%6%
462
April1st to 10thDay
12%28%29%22%7%2
420
11th to 20thDay
14%29%28%18%9%2
412
21st to endDay
15%23%24%25%10%3
420
May1st to 10thDay
12%23%30%23%10%2
423
11th to 20thDay
14%23%29%19%10%5%
448
21st to endDay
12%19%24%23%15%7%
485
June1st to 10thDay
8%18%29%23%16%5%
450
11th to 20thDay
9%19%33%24%12%2
450
21st to endDay
313%31%30%18%6%
450
July1st to 10thDay
210%37%30%17%5%
446
11th to 20thDay
29%33%31%20%5%
444
21st to endDay
27%30%34%21%7%
487
August1st to 10thDay
410%31%27%21%7%
447
11th to 20thDay
39%29%31%20%9%
437
21st to endDay
29%33%33%19%4
495
September1st to 10thDay
39%31%30%22%6%
450
11th to 20thDay
6%12%28%31%21%2
450
21st to endDay
415%28%36%14%2
450
October1st to 10thDay
6%18%25%27%19%4
450
11th to 20thDay
7%17%20%30%21%5%
450
21st to endDay
8%17%24%30%19%3
439
November1st to 10thDay
11%14%21%27%20%7%
270
11th to 20thDay
416%23%32%17%8%
270
21st to endDay
6%19%25%25%20%5%
230
December1st to 10thDay
11%19%23%24%16%6%
180
11th to 20thDay
7%18%35%17%16%7%
180
21st to endDay
14%19%23%30%12%2
198
January1st to 10thNight
5%16%27%28%18%7%
760
11th to 20thNight
5%16%22%36%19%3
760
21st to endNight
6%9%28%34%19%5%
836
February1st to 10thNight
5%13%26%34%18%3
760
11th to 20thNight
414%26%34%17%4
742
21st to endNight
6%19%22%38%13%2
592
March1st to 10thNight
5%19%30%27%15%3
720
11th to 20thNight
6%18%24%29%21%4
720
21st to endNight
423%27%30%15%1
792
April1st to 10thNight
5%18%26%33%17%1
720
11th to 20thNight
6%18%26%30%16%4
711
21st to endNight
6%15%24%32%20%3
720
May1st to 10thNight
8%14%25%34%17%2
599
11th to 20thNight
39%24%40%22%2
372
21st to endNight
6%7%20%37%26%3
389
June1st to 10thNight
6%6%21%40%24%3
360
11th to 20thNight
26%26%38%27%1
360
21st to endNight
2322%45%27%3
360
July1st to 10thNight
1218%48%29%3
350
11th to 20thNight
1120%51%27%
348
21st to endNight
3111%49%32%4
430
August1st to 10thNight
413%46%34%3
545
11th to 20thNight
2319%41%31%4
712
21st to endNight
2321%45%26%3
792
September1st to 10thNight
1317%40%33%5%
720
11th to 20thNight
36%16%34%34%6%
720
21st to endNight
27%19%36%27%9%
720
October1st to 10thNight
5%7%18%39%24%7%
720
11th to 20thNight
48%14%38%29%6%
720
21st to endNight
5%9%17%32%26%11%
792
November1st to 10thNight
5%13%20%29%26%7%
740
11th to 20thNight
5%11%25%36%19%5%
760
21st to endNight
413%24%31%24%4
760
December1st to 10thNight
7%13%23%36%16%5%
760
11th to 20thNight
7%15%24%33%16%5%
760
21st to endNight
8%17%28%33%13%2
836
Page generated at 2024-02-17 03:28:41. Version ac07

Copyright 2024 Attilla Danko


Deer Lodge Site Clear Sky Chart |Charts Home