Mitty Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mitty Observatory clear sky chart from 2005-11-05 to 2017-10-06.

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
50%
15710
24%
47061
18%
15665
56%
15665
30%
28788

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
27%
900
22%
2479
10%
895
37%
895
25%
1637
January16th to endNight
27%
951
22%
2487
10%
951
35%
951
27%
1679
February1st to 15thNight
26%
704
18%
2112
8%
701
35%
701
22%
1429
February16th to endNight
26%
631
23%
1893
10%
631
36%
631
24%
1237
March1st to 15thNight
30%
720
18%
2160
11%
720
37%
720
22%
1448
March16th to endNight
41%
579
20%
1992
17%
579
47%
579
24%
1246
April1st to 15thNight
41%
539
24%
1797
17%
539
54%
539
31%
1034
April16th to endNight
47%
540
24%
1800
21%
540
57%
540
30%
1071
May1st to 15thNight
49%
540
20%
1695
15%
540
55%
540
29%
1043
May16th to endNight
64%
562
22%
1637
18%
561
66%
561
33%
991
June1st to 15thNight
74%
540
24%
1440
19%
540
76%
540
40%
882
June16th to endNight
79%
540
25%
1440
20%
540
80%
540
44%
830
July1st to 15thNight
75%
510
18%
1360
17%
510
76%
510
36%
845
July16th to endNight
82%
564
23%
1521
24%
531
83%
531
44%
836
August1st to 15thNight
79%
539
22%
1788
26%
536
81%
536
36%
971
August16th to endNight
75%
573
25%
1910
31%
573
75%
573
35%
1073
September1st to 15thNight
69%
540
26%
1800
28%
540
71%
540
33%
1026
September16th to endNight
66%
714
31%
1977
25%
714
69%
714
40%
1154
October1st to 15thNight
62%
684
32%
1952
27%
684
65%
684
39%
1104
October16th to endNight
54%
704
31%
2141
25%
704
61%
704
37%
1210
November1st to 15thNight
51%
700
31%
2276
26%
700
59%
700
36%
1234
November16th to endNight
41%
720
25%
2340
20%
720
50%
720
27%
1415
December1st to 15thNight
34%
756
21%
2376
15%
756
42%
756
23%
1553
December16th to endNight
31%
960
20%
2688
11%
960
39%
960
23%
1840

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
12%5%2443445%7%43%
48131
Night
12%5%24424446%48%
47248
TransparencyDay
38%6%11%22%16%3
47821
Night
36%5%10%23%19%5%
47063
SeeingDay
13%317%24%25%15%
5762
Night
15%5%23%31%21%3
15711

By Month

Percentage Cloud Cover SE (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
20%6%34323346%42%
1457
16th to endDay
15%6%35%324336%44%
1734
February1st to 15thDay
18%7%45%433435%40%
1750
16th to endDay
17%8%46%43345%436%
1580
March1st to 15thDay
20%9%35%5%2324438%
1807
16th to endDay
16%6%46%5%345%47%36%
2233
April1st to 15thDay
13%5%25%42445%6%45%
2151
16th to endDay
13%6%35%5%34346%42%
2160
May1st to 15thDay
16%5%245%35%447%39%
2253
16th to endDay
9%5%35%6%36%46%8%39%
2473
June1st to 15thDay
6%425%5%35%6%6%9%44%
2520
16th to endDay
43135%35%6%7%11%47%
2520
July1st to 15thDay
8%425%5%46%6%7%9%38%
2520
16th to endDay
6%315%5%25%7%7%12%42%
2537
August1st to 15thDay
5%414435%6%7%11%42%
2160
16th to endDay
9%4245%35%5%6%11%40%
2292
September1st to 15thDay
11%4245%35%46%8%43%
2151
16th to endDay
11%5%15%424446%49%
1980
October1st to 15thDay
11%42342435%5%52%
1804
16th to endDay
15%41322234356%
1730
November1st to 15thDay
14%5%2322224455%
1582
16th to endDay
18%6%23424335%47%
1620
December1st to 15thDay
21%7%25%412435%39%
1581
16th to endDay
19%9%34323346%38%
1536
January1st to 15thNight
18%7%25%413335%44%
2479
16th to endNight
16%6%25%5%23335%44%
2487
February1st to 15thNight
17%7%35%5%33345%40%
2103
16th to endNight
15%7%25%5%23445%43%
1893
March1st to 15thNight
17%7%25%423436%41%
2160
16th to endNight
14%6%25%434447%42%
1992
April1st to 15thNight
11%42432345%6%49%
1797
16th to endNight
12%414425%35%7%47%
1800
May1st to 15thNight
13%6%25%32335%7%45%
1694
16th to endNight
6%4245%35%46%9%46%
1637
June1st to 15thNight
5%414325%5%6%8%51%
1440
16th to endNight
4212335%6%7%10%52%
1440
July1st to 15thNight
6%3245%35%6%7%9%45%
1440
16th to endNight
4212225%5%6%11%54%
1626
August1st to 15thNight
33135%25%5%6%9%52%
1800
16th to endNight
6%325%4245%6%8%51%
1910
September1st to 15thNight
9%425%424348%50%
1800
16th to endNight
9%423413346%55%
1977
October1st to 15thNight
10%413314346%55%
1952
16th to endNight
14%42331233456%
2141
November1st to 15thNight
11%323312336%56%
2276
16th to endNight
15%5%2432333449%
2340
December1st to 15thNight
20%7%25%313336%41%
2376
16th to endNight
21%7%25%323335%40%
2688

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
44%38%23%17%2
1458
16th to endDay
41%410%25%14%2
1734
February1st to 15thDay
46%49%22%14%2
1752
16th to endDay
48%5%9%19%14%2
1580
March1st to 15thDay
50%39%18%13%3
1807
16th to endDay
47%5%12%21%12%
2235
April1st to 15thDay
38%5%9%22%20%3
2151
16th to endDay
42%48%24%17%1
2160
May1st to 15thDay
44%6%12%18%15%1
2253
16th to endDay
40%9%14%21%11%2
2477
June1st to 15thDay
32%9%13%23%18%2
2520
16th to endDay
27%9%14%25%19%3
2520
July1st to 15thDay
38%9%15%21%11%4
2371
16th to endDay
30%10%17%25%13%1
2379
August1st to 15thDay
31%10%16%23%16%2
2148
16th to endDay
36%7%14%22%16%3
2292
September1st to 15thDay
37%8%11%23%14%4
2151
16th to endDay
34%6%9%21%23%5%
1980
October1st to 15thDay
32%5%10%21%23%6%
1804
16th to endDay
31%36%23%28%6%
1730
November1st to 15thDay
33%37%20%27%8%
1582
16th to endDay
39%47%24%20%3
1620
December1st to 15thDay
46%5%9%20%14%3
1581
16th to endDay
46%411%20%13%2
1536
January1st to 15thNight
43%37%21%20%3
2479
16th to endNight
43%48%21%18%3
2487
February1st to 15thNight
46%410%18%16%3
2112
16th to endNight
43%48%23%15%3
1893
March1st to 15thNight
45%5%8%17%17%6%
2160
16th to endNight
40%5%12%23%15%1
1992
April1st to 15thNight
34%410%24%19%6%
1797
16th to endNight
35%5%8%25%20%4
1800
May1st to 15thNight
38%412%23%18%3
1695
16th to endNight
32%7%15%26%14%4
1639
June1st to 15thNight
28%7%13%24%22%2
1440
16th to endNight
23%7%17%25%18%5%
1440
July1st to 15thNight
30%9%14%26%14%5%
1360
16th to endNight
21%8%21%29%16%1
1521
August1st to 15thNight
25%9%16%25%20%3
1788
16th to endNight
29%7%13%27%17%5%
1910
September1st to 15thNight
33%5%12%24%18%6%
1800
16th to endNight
29%5%9%23%24%7%
1977
October1st to 15thNight
29%410%21%24%9%
1952
16th to endNight
31%36%20%28%9%
2141
November1st to 15thNight
30%36%23%26%10%
2276
16th to endNight
38%47%21%22%5%
2340
December1st to 15thNight
44%48%20%17%4
2376
16th to endNight
46%410%18%17%2
2688

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
28%10%37%14%7%1
90
16th to endDay
21%7%48%16%41
96
February1st to 15thDay
23%12%37%18%7%
90
16th to endDay
28%340%16%11%
81
March1st to 15thDay
34%8%31%21%4
90
16th to endDay
18%10%29%26%13%
219
April1st to 15thDay
16%9%28%31%11%2
270
16th to endDay
17%6%27%28%15%4
270
May1st to 15thDay
19%7%21%28%14%8%
288
16th to endDay
14%218%28%20%15%
373
June1st to 15thDay
7%114%25%29%21%
495
16th to endDay
6%112%29%33%17%
495
July1st to 15thDay
10%11%28%31%18%
475
16th to endDay
6%419%35%33%
489
August1st to 15thDay
7%5%21%39%25%
313
16th to endDay
17%417%38%22%
332
September1st to 15thDay
11%6%20%35%24%
315
16th to endDay
13%28%22%33%19%
314
October1st to 15thDay
10%15%37%27%9%
205
16th to endDay
17%317%27%29%5%
96
November1st to 15thDay
12%224%28%24%7%
90
16th to endDay
27%8%31%16%11%4
90
December1st to 15thDay
24%435%22%12%1
90
16th to endDay
20%12%42%19%4
96
January1st to 15thNight
21%13%33%25%5%
900
16th to endNight
20%9%38%29%2
951
February1st to 15thNight
20%10%38%27%3
704
16th to endNight
19%12%39%27%2
631
March1st to 15thNight
20%10%35%30%3
720
16th to endNight
15%7%30%31%14%1
579
April1st to 15thNight
12%7%33%33%12%
539
16th to endNight
12%5%28%36%15%
540
May1st to 15thNight
16%225%36%16%2
540
16th to endNight
7%116%36%32%4
563
June1st to 15thNight
6%19%41%36%4
540
16th to endNight
5%8%35%43%6%
540
July1st to 15thNight
7%6%33%44%7%
510
16th to endNight
5%5%23%50%15%
564
August1st to 15thNight
4428%53%8%
539
16th to endNight
8%432%45%8%
573
September1st to 15thNight
10%18%29%40%9%
540
16th to endNight
11%112%30%39%5%
714
October1st to 15thNight
11%316%33%30%4
684
16th to endNight
17%5%21%34%19%2
704
November1st to 15thNight
12%5%27%32%20%1
700
16th to endNight
18%6%28%33%11%1
720
December1st to 15thNight
25%7%27%29%10%
756
16th to endNight
23%9%30%30%4
960
Page generated at 2017-10-07 13:07:46. Version ac04

Copyright 2017 A. Danko


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