Fleischmanns Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fleischmanns Observatory 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
24%
22958
14%
74746
7%
22914
33%
22914
14%
52141

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
9%
760
15%
2649
4%
757
23%
757
8%
1861
January11th to 20thNight
13%
744
11%
2602
4%
744
22%
744
8%
1933
January21st to endNight
11%
792
15%
2655
4%
792
24%
792
9%
1863
February1st to 10thNight
7%
720
11%
2340
2%
720
18%
720
7%
1726
February11th to 20thNight
8%
703
12%
2149
2%
700
20%
700
7%
1585
February21st to endNight
11%
592
16%
1776
6%
592
24%
592
10%
1283
March1st to 10thNight
13%
720
14%
2160
5%
720
25%
720
12%
1535
March11th to 20thNight
14%
720
15%
2038
5%
720
24%
720
12%
1488
March21st to endNight
18%
792
19%
2016
5%
792
29%
792
14%
1452
April1st to 10thNight
16%
720
13%
1800
2%
720
23%
720
12%
1386
April11th to 20thNight
20%
711
14%
1775
3%
711
26%
711
18%
1274
April21st to endNight
22%
689
15%
1769
4%
689
28%
689
17%
1299
May1st to 10thNight
26%
486
14%
1566
9%
486
31%
486
14%
1136
May11th to 20thNight
28%
354
18%
1416
11%
354
42%
354
13%
930
May21st to endNight
38%
388
14%
1551
11%
388
48%
388
18%
962
June1st to 10thNight
35%
360
15%
1440
12%
360
47%
360
16%
895
June11th to 20thNight
43%
360
12%
1440
12%
360
51%
360
17%
913
June21st to endNight
43%
360
13%
1440
10%
360
53%
360
21%
851
July1st to 10thNight
48%
350
14%
1400
16%
350
56%
350
21%
824
July11th to 20thNight
48%
348
16%
1392
17%
348
55%
348
23%
814
July21st to endNight
46%
394
16%
1486
15%
372
52%
372
21%
878
August1st to 10thNight
48%
429
15%
1493
11%
427
55%
427
23%
917
August11th to 20thNight
46%
672
14%
1736
8%
672
49%
672
26%
1204
August21st to endNight
48%
792
18%
1980
9%
792
51%
792
30%
1339
September1st to 10thNight
38%
720
17%
1800
6%
720
43%
720
27%
1241
September11th to 20thNight
41%
720
25%
1854
13%
720
48%
720
31%
1184
September21st to endNight
38%
720
22%
1980
14%
720
45%
720
24%
1331
October1st to 10thNight
32%
720
15%
2119
9%
720
39%
720
16%
1510
October11th to 20thNight
27%
720
16%
2160
8%
720
39%
720
17%
1484
October21st to endNight
17%
792
13%
2520
6%
792
26%
792
11%
1851
November1st to 10thNight
24%
740
19%
2407
9%
740
36%
740
15%
1607
November11th to 20thNight
20%
760
16%
2470
9%
760
29%
760
12%
1732
November21st to endNight
18%
760
14%
2636
7%
760
29%
760
11%
1821
December1st to 10thNight
12%
760
9%
2660
4%
760
19%
760
6%
1992
December11th to 20thNight
11%
760
10%
3244
3%
759
19%
759
6%
2400
December21st to endNight
10%
830
7%
4827
3%
817
20%
817
3%
3640

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
14%11%5%8%7%45%5%5%7%30%
74782
Night
14%11%5%9%6%45%5%5%6%31%
75018
TransparencyDay
53%410%20%11%2
74487
Night
52%411%20%11%1
74847
SeeingDay
26%21%28%15%7%3
13711
Night
25%22%24%20%8%1
22965

By Month

Percentage Cloud Cover NE (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
10%11%8%12%9%46%46%6%23%
1517
11th to 20thDay
12%15%6%13%10%46%6%5%420%
1486
21st to endDay
8%12%9%13%9%46%6%4326%
1696
February1st to 10thDay
12%13%8%12%11%5%5%5%45%19%
1620
11th to 20thDay
9%11%7%12%9%36%5%5%6%26%
1699
21st to endDay
15%14%411%8%45%45%5%25%
1480
March1st to 10thDay
11%12%6%11%8%35%446%29%
1797
11th to 20thDay
13%14%7%9%7%35%445%29%
1919
21st to endDay
17%12%6%8%6%34446%31%
2340
April1st to 10thDay
14%15%6%8%6%35%446%30%
2160
11th to 20thDay
14%12%46%6%35%5%5%6%34%
2134
21st to endDay
18%15%5%7%5%35%346%31%
2191
May1st to 10thDay
21%13%47%6%35%446%28%
2407
11th to 20thDay
18%8%46%4446%6%7%33%
2478
21st to endDay
13%7%36%7%46%5%6%7%35%
2725
June1st to 10thDay
17%8%47%7%45%6%6%8%29%
2520
11th to 20thDay
16%8%37%6%46%7%5%10%29%
2520
21st to endDay
17%8%37%6%446%6%8%30%
2520
July1st to 10thDay
12%6%48%7%46%6%6%8%32%
2520
11th to 20thDay
10%6%27%6%46%6%8%9%34%
2520
21st to endDay
13%7%46%7%46%6%7%8%32%
2744
August1st to 10thDay
10%7%48%7%46%6%7%9%31%
2432
11th to 20thDay
13%8%37%7%5%7%7%7%9%28%
2145
21st to endDay
14%7%36%5%45%6%7%9%34%
2376
September1st to 10thDay
16%6%37%6%35%5%6%8%36%
2160
11th to 20thDay
13%8%36%5%345%47%42%
2106
21st to endDay
15%7%36%6%35%6%5%7%38%
1980
October1st to 10thDay
17%11%48%7%3445%7%31%
1837
11th to 20thDay
13%13%36%6%45%5%6%5%35%
1800
21st to endDay
19%17%48%6%3345%5%25%
1835
November1st to 10thDay
12%13%47%43446%6%38%
1671
11th to 20thDay
14%15%6%9%8%3444429%
1710
21st to endDay
14%15%6%9%7%34446%27%
1539
December1st to 10thDay
12%18%8%14%7%45%445%19%
1520
11th to 20thDay
15%14%9%12%7%33345%25%
1906
21st to endDay
15%17%7%14%8%4446%6%16%
2772
January1st to 10thNight
11%12%7%12%9%46%5%5%6%24%
2649
11th to 20thNight
12%13%8%13%8%46%5%5%5%21%
2602
21st to endNight
8%11%8%11%9%5%7%5%5%6%24%
2655
February1st to 10thNight
12%12%6%12%9%5%6%6%5%6%21%
2340
11th to 20thNight
9%12%7%13%9%6%5%6%5%5%22%
2147
21st to endNight
16%11%5%11%8%35%5%6%6%25%
1776
March1st to 10thNight
13%11%6%11%8%35%45%6%27%
2150
11th to 20thNight
12%11%7%12%9%44446%27%
2037
21st to endNight
15%13%5%7%5%345%5%6%34%
2016
April1st to 10thNight
13%14%6%9%7%45%5%5%6%27%
1800
11th to 20thNight
16%11%5%6%5%3445%6%35%
1775
21st to endNight
18%12%5%6%5%35%445%33%
1769
May1st to 10thNight
19%14%47%5%34446%30%
1566
11th to 20thNight
13%10%47%5%35%5%5%8%35%
1415
21st to endNight
12%8%36%5%35%5%6%8%40%
1550
June1st to 10thNight
15%8%36%5%35%46%7%38%
1440
11th to 20thNight
17%8%35%5%3437%9%37%
1440
21st to endNight
11%6%25%5%45%6%5%9%42%
1440
July1st to 10thNight
12%6%35%5%35%5%6%9%42%
1440
11th to 20thNight
12%5%35%435%6%6%10%41%
1440
21st to endNight
11%6%25%6%445%6%8%41%
1574
August1st to 10thNight
11%7%26%6%45%6%6%8%40%
1503
11th to 20thNight
12%7%39%6%35%5%6%6%38%
1736
21st to endNight
15%7%35%5%3446%8%42%
1980
September1st to 10thNight
14%7%26%5%25%5%5%7%41%
1800
11th to 20thNight
14%7%24423447%48%
1854
21st to endNight
15%8%26%6%345%5%5%41%
1980
October1st to 10thNight
17%11%47%6%3445%6%34%
2119
11th to 20thNight
15%11%37%5%35%5%47%36%
2160
21st to endNight
20%14%47%6%35%5%5%6%26%
2520
November1st to 10thNight
11%14%5%8%5%34445%38%
2407
11th to 20thNight
15%15%6%8%6%3445%6%28%
2470
21st to endNight
11%13%7%8%7%46%45%6%29%
2636
December1st to 10thNight
14%16%8%12%8%45%5%5%6%19%
2660
11th to 20thNight
15%15%7%12%7%3445%423%
3288
21st to endNight
17%16%7%14%7%44445%18%
4884

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
57%310%18%11%1
1518
11th to 20thDay
63%410%12%8%3
1486
21st to endDay
57%38%19%11%3
1696
February1st to 10thDay
63%49%16%7%1
1620
11th to 20thDay
53%38%21%13%2
1708
21st to endDay
58%39%18%10%1
1480
March1st to 10thDay
54%311%18%11%3
1800
11th to 20thDay
57%37%19%12%2
1919
21st to endDay
55%37%16%15%4
2340
April1st to 10thDay
56%37%20%11%2
2160
11th to 20thDay
52%310%20%13%2
2134
21st to endDay
58%38%18%11%3
2191
May1st to 10thDay
60%36%19%10%2
2407
11th to 20thDay
51%48%24%12%1
2482
21st to endDay
48%5%15%21%9%2
2725
June1st to 10thDay
53%5%13%19%11%
2520
11th to 20thDay
52%5%13%20%9%1
2520
21st to endDay
51%5%11%23%9%
2520
July1st to 10thDay
49%5%12%21%12%1
2450
11th to 20thDay
44%6%15%25%10%
2445
21st to endDay
48%5%12%22%12%1
2591
August1st to 10thDay
48%5%13%23%11%1
2418
11th to 20thDay
51%5%13%24%7%
2145
21st to endDay
45%411%25%13%1
2376
September1st to 10thDay
47%410%25%12%1
2160
11th to 20thDay
42%49%23%21%2
2106
21st to endDay
46%410%21%16%2
1980
October1st to 10thDay
54%38%20%13%2
1837
11th to 20thDay
49%411%23%12%1
1800
21st to endDay
60%310%14%9%3
1835
November1st to 10thDay
45%312%22%15%3
1671
11th to 20thDay
56%28%17%13%3
1710
21st to endDay
57%312%20%7%1
1539
December1st to 10thDay
64%39%15%7%1
1520
11th to 20thDay
59%312%18%7%1
1906
21st to endDay
67%37%13%9%
2772
January1st to 10thNight
56%39%17%13%2
2649
11th to 20thNight
60%411%15%7%3
2602
21st to endNight
55%38%20%12%2
2655
February1st to 10thNight
58%412%16%9%1
2340
11th to 20thNight
57%410%16%12%1
2149
21st to endNight
55%39%21%9%2
1776
March1st to 10thNight
53%312%19%11%2
2160
11th to 20thNight
56%39%20%11%2
2038
21st to endNight
51%38%19%15%3
2016
April1st to 10thNight
58%49%18%10%2
1800
11th to 20thNight
50%411%21%14%
1775
21st to endNight
53%39%21%12%2
1769
May1st to 10thNight
58%29%17%12%2
1566
11th to 20thNight
49%5%9%23%13%2
1416
21st to endNight
43%6%16%24%10%1
1551
June1st to 10thNight
46%412%26%12%
1440
11th to 20thNight
46%5%15%24%9%
1440
21st to endNight
38%7%17%27%11%1
1440
July1st to 10thNight
39%6%15%27%12%2
1400
11th to 20thNight
38%6%16%31%9%
1392
21st to endNight
42%416%23%14%2
1486
August1st to 10thNight
42%5%15%28%9%1
1493
11th to 20thNight
45%417%24%9%
1736
21st to endNight
42%413%27%14%1
1980
September1st to 10thNight
43%6%12%26%13%1
1800
11th to 20thNight
38%310%24%24%1
1854
21st to endNight
46%29%24%17%1
1980
October1st to 10thNight
52%49%20%13%1
2119
11th to 20thNight
49%412%23%11%2
2160
21st to endNight
58%311%18%9%1
2520
November1st to 10thNight
48%49%20%16%3
2407
11th to 20thNight
54%310%18%12%3
2470
21st to endNight
53%313%23%8%1
2636
December1st to 10thNight
61%311%18%6%
2660
11th to 20thNight
61%310%14%11%1
3288
21st to endNight
66%28%16%8%
4884

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
36%25%28%8%21
180
11th to 20thDay
40%27%23%8%11
172
21st to endDay
28%36%25%8%3
226
February1st to 10thDay
44%35%18%3
240
11th to 20thDay
39%34%19%7%1
367
21st to endDay
40%28%23%7%1
346
March1st to 10thDay
32%28%30%9%2
420
11th to 20thDay
35%28%23%10%41
420
21st to endDay
36%28%20%8%43
462
April1st to 10thDay
34%29%19%12%5%1
420
11th to 20thDay
31%25%25%11%6%2
412
21st to endDay
34%26%27%8%42
420
May1st to 10thDay
36%22%26%8%6%3
423
11th to 20thDay
24%22%34%14%5%2
447
21st to endDay
18%13%35%19%11%3
485
June1st to 10thDay
22%20%31%18%7%2
450
11th to 20thDay
18%20%31%22%6%2
450
21st to endDay
21%19%34%18%8%1
450
July1st to 10thDay
16%12%35%22%13%3
445
11th to 20thDay
11%11%39%28%9%2
444
21st to endDay
16%14%40%19%8%3
488
August1st to 10thDay
9%17%32%25%13%5%
446
11th to 20thDay
16%13%32%22%11%6%
439
21st to endDay
15%15%29%22%12%7%
495
September1st to 10thDay
22%12%24%23%13%6%
450
11th to 20thDay
16%16%27%20%11%10%
450
21st to endDay
22%16%28%20%8%6%
450
October1st to 10thDay
26%16%26%19%10%4
450
11th to 20thDay
27%20%28%17%7%1
450
21st to endDay
29%25%28%13%41
422
November1st to 10thDay
27%21%26%16%8%1
365
11th to 20thDay
36%24%24%11%5%1
370
21st to endDay
34%27%27%12%1
199
December1st to 10thDay
38%32%18%8%31
180
11th to 20thDay
41%29%22%6%2
180
21st to endDay
36%30%25%7%21
198
January1st to 10thNight
29%31%27%10%2
760
11th to 20thNight
29%27%25%17%2
744
21st to endNight
24%32%27%15%3
792
February1st to 10thNight
31%29%28%11%1
720
11th to 20thNight
29%33%25%12%1
703
21st to endNight
35%26%25%13%2
592
March1st to 10thNight
32%27%25%13%3
720
11th to 20thNight
31%27%23%15%3
720
21st to endNight
27%26%24%16%5%1
792
April1st to 10thNight
27%27%26%16%4
720
11th to 20thNight
27%24%25%17%6%1
711
21st to endNight
28%22%24%18%8%
689
May1st to 10thNight
30%17%23%20%8%1
486
11th to 20thNight
19%22%26%28%41
354
21st to endNight
18%11%27%28%15%1
389
June1st to 10thNight
18%14%26%29%14%
360
11th to 20thNight
21%11%21%33%14%1
360
21st to endNight
14%9%27%36%13%1
360
July1st to 10thNight
15%10%23%35%16%2
350
11th to 20thNight
14%8%24%34%18%1
348
21st to endNight
13%9%25%36%16%1
394
August1st to 10thNight
10%5%28%32%22%2
429
11th to 20thNight
17%7%20%32%20%3
672
21st to endNight
16%10%21%30%21%2
792
September1st to 10thNight
16%10%28%27%17%3
720
11th to 20thNight
19%12%23%22%17%7%
720
21st to endNight
19%13%25%24%16%3
720
October1st to 10thNight
26%17%19%21%14%2
720
11th to 20thNight
25%18%25%22%9%1
720
21st to endNight
30%27%22%17%41
792
November1st to 10thNight
23%23%26%20%8%1
740
11th to 20thNight
30%25%23%14%7%2
760
21st to endNight
26%28%25%16%5%1
760
December1st to 10thNight
32%29%22%12%5%
760
11th to 20thNight
32%26%26%14%3
760
21st to endNight
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