AstroGeek's Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the AstroGeek's Observatory clear sky chart from 2005-11-06 to 2024-01-15.

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
26%
23011
18%
74581
7%
22967
38%
22967
19%
48884

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
16%
760
21%
2649
6%
757
36%
757
18%
1630
January11th to 20thNight
14%
739
17%
2583
2%
739
31%
739
12%
1777
January21st to endNight
17%
792
20%
2772
6%
792
36%
792
17%
1744
February1st to 10thNight
15%
720
17%
2242
3%
720
31%
720
16%
1508
February11th to 20thNight
11%
703
19%
2100
4%
700
29%
700
15%
1439
February21st to endNight
16%
592
24%
1776
7%
592
36%
592
16%
1184
March1st to 10thNight
18%
720
22%
2160
8%
720
36%
720
20%
1408
March11th to 20thNight
17%
720
18%
2048
5%
720
31%
720
19%
1392
March21st to endNight
18%
792
22%
2083
5%
792
31%
792
20%
1459
April1st to 10thNight
19%
720
18%
1800
4%
720
28%
720
21%
1288
April11th to 20thNight
21%
689
17%
1753
4%
689
29%
689
23%
1229
April21st to endNight
19%
540
19%
1620
5%
540
30%
540
18%
1106
May1st to 10thNight
20%
540
11%
1620
4%
540
26%
540
15%
1177
May11th to 20thNight
19%
532
15%
1594
5%
532
28%
532
18%
1101
May21st to endNight
33%
415
11%
1577
9%
414
39%
414
16%
1056
June1st to 10thNight
35%
360
12%
1440
10%
360
43%
360
15%
939
June11th to 20thNight
35%
360
13%
1440
13%
360
44%
360
18%
932
June21st to endNight
40%
360
12%
1440
10%
360
48%
360
20%
882
July1st to 10thNight
41%
350
13%
1400
15%
350
47%
350
20%
878
July11th to 20thNight
44%
348
14%
1392
15%
348
49%
348
20%
856
July21st to endNight
45%
394
17%
1486
17%
372
51%
372
20%
916
August1st to 10thNight
42%
528
15%
1591
10%
525
45%
525
28%
1012
August11th to 20thNight
46%
545
17%
1609
11%
545
49%
545
26%
1070
August21st to endNight
50%
792
21%
1980
11%
792
53%
792
33%
1296
September1st to 10thNight
41%
720
18%
1821
8%
720
46%
720
30%
1241
September11th to 20thNight
43%
720
23%
1980
13%
720
50%
720
32%
1222
September21st to endNight
38%
720
22%
1980
13%
720
47%
720
26%
1324
October1st to 10thNight
34%
720
17%
1980
10%
720
41%
720
22%
1368
October11th to 20thNight
31%
720
22%
2178
10%
720
45%
720
27%
1344
October21st to endNight
22%
792
16%
2574
6%
792
35%
792
17%
1752
November1st to 10thNight
31%
740
20%
2407
9%
740
44%
740
23%
1492
November11th to 20thNight
21%
760
23%
2470
8%
760
40%
760
19%
1540
November21st to endNight
22%
760
23%
2470
6%
760
41%
760
21%
1504
December1st to 10thNight
17%
760
20%
2569
6%
760
34%
760
15%
1708
December11th to 20thNight
19%
760
18%
3200
4%
759
35%
759
13%
1964
December21st to endNight
15%
828
15%
4797
4%
817
35%
817
9%
3146

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
17%7%35%5%3445%7%40%
74836
Night
17%7%35%5%3445%6%40%
74928
TransparencyDay
43%6%12%22%15%3
74542
Night
44%6%11%22%15%2
74756
SeeingDay
22%18%33%19%7%2
14015
Night
22%14%33%24%7%1
23019

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
15%9%35%5%23445%44%
1517
11th to 20thDay
19%10%35%43445%6%39%
1472
21st to endDay
14%7%45%43345%7%43%
1584
February1st to 10thDay
21%7%35%4346%5%6%35%
1712
11th to 20thDay
15%8%35%4345%47%42%
1748
21st to endDay
18%9%46%434445%38%
1480
March1st to 10thDay
17%8%345%345%5%7%40%
1797
11th to 20thDay
16%7%36%5%25%5%5%7%39%
1911
21st to endDay
18%10%35%5%24346%41%
2271
April1st to 10thDay
21%8%25%424447%38%
2160
11th to 20thDay
18%5%25%435%46%7%40%
2155
21st to endDay
21%6%25%6%45%446%38%
2340
May1st to 10thDay
25%8%35%43445%7%32%
2340
11th to 20thDay
19%7%34434447%41%
2301
21st to endDay
16%5%25%4345%48%44%
2712
June1st to 10thDay
20%7%25%5%35%5%6%9%34%
2520
11th to 20thDay
17%6%25%6%35%6%6%9%36%
2520
21st to endDay
16%6%245%45%5%6%9%37%
2520
July1st to 10thDay
13%5%35%5%36%6%7%9%39%
2520
11th to 20thDay
14%6%35%5%46%5%6%10%37%
2520
21st to endDay
13%425%6%36%6%6%9%39%
2735
August1st to 10thDay
11%6%36%6%45%6%7%10%38%
2327
11th to 20thDay
13%6%35%5%46%6%6%8%39%
2287
21st to endDay
14%6%25%5%35%46%9%42%
2376
September1st to 10thDay
14%5%25%5%345%5%6%45%
2138
11th to 20thDay
14%6%24433346%51%
1980
21st to endDay
19%5%24433347%44%
1980
October1st to 10thDay
24%6%15%423345%42%
1980
11th to 20thDay
15%6%25%42445%7%46%
1776
21st to endDay
19%6%35%43445%7%40%
1782
November1st to 10thDay
18%7%24333345%48%
1671
11th to 20thDay
19%6%24423445%46%
1710
21st to endDay
17%7%3442445%6%44%
1710
December1st to 10thDay
20%7%35%434446%40%
1606
11th to 20thDay
21%6%24434326%44%
1906
21st to endDay
22%11%37%5%3345%5%33%
2772
January1st to 10thNight
17%7%35%433446%44%
2649
11th to 20thNight
20%10%36%434446%36%
2583
21st to endNight
15%9%45%5%3445%6%42%
2772
February1st to 10thNight
17%9%46%43445%6%39%
2242
11th to 20thNight
18%8%37%5%3445%5%39%
2098
21st to endNight
18%8%35%5%3445%5%41%
1776
March1st to 10thNight
16%7%35%435%5%5%7%41%
2150
11th to 20thNight
15%9%46%5%34446%39%
2047
21st to endNight
19%8%36%5%33335%41%
2083
April1st to 10thNight
19%8%36%5%345%5%5%38%
1800
11th to 20thNight
19%7%245%3446%6%39%
1753
21st to endNight
21%8%345%3445%6%38%
1620
May1st to 10thNight
24%9%36%43445%7%31%
1620
11th to 20thNight
19%7%35%5%35%5%6%7%35%
1593
21st to endNight
18%7%36%6%4445%7%37%
1576
June1st to 10thNight
18%6%35%6%35%5%5%7%36%
1440
11th to 20thNight
19%6%46%5%4445%8%36%
1440
21st to endNight
17%8%35%4245%5%9%40%
1440
July1st to 10thNight
13%7%36%5%25%6%6%9%39%
1440
11th to 20thNight
14%6%35%7%35%46%10%36%
1440
21st to endNight
12%6%36%5%36%6%6%8%39%
1574
August1st to 10thNight
9%7%25%6%35%6%8%9%41%
1602
11th to 20thNight
10%7%27%5%45%6%6%9%39%
1609
21st to endNight
14%435%43446%7%46%
1980
September1st to 10thNight
14%6%36%5%445%5%6%42%
1821
11th to 20thNight
14%6%24333446%51%
1980
21st to endNight
18%6%25%4335%5%6%44%
1980
October1st to 10thNight
21%7%35%433436%42%
1980
11th to 20thNight
15%6%345%235%5%7%45%
2178
21st to endNight
21%8%35%5%34446%38%
2574
November1st to 10thNight
16%4345%3445%6%46%
2407
11th to 20thNight
18%7%25%424445%46%
2470
21st to endNight
16%6%25%42445%7%45%
2470
December1st to 10thNight
21%7%35%5%34446%39%
2569
11th to 20thNight
20%8%2442445%6%41%
3288
21st to endNight
19%12%47%5%23345%35%
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
42%49%26%16%3
1518
11th to 20thDay
46%7%12%20%12%3
1472
21st to endDay
40%5%11%26%17%2
1584
February1st to 10thDay
48%6%12%17%14%3
1712
11th to 20thDay
42%6%11%22%15%3
1757
21st to endDay
49%49%21%14%3
1480
March1st to 10thDay
44%412%22%14%4
1800
11th to 20thDay
44%5%10%23%15%4
1911
21st to endDay
47%5%9%17%17%6%
2271
April1st to 10thDay
47%5%9%20%16%4
2160
11th to 20thDay
44%6%9%22%17%3
2155
21st to endDay
48%49%19%15%4
2340
May1st to 10thDay
51%5%10%19%13%2
2340
11th to 20thDay
44%6%11%18%18%3
2305
21st to endDay
39%7%15%23%14%2
2712
June1st to 10thDay
48%7%13%22%11%1
2520
11th to 20thDay
44%7%13%21%14%2
2520
21st to endDay
41%9%15%22%13%1
2520
July1st to 10thDay
39%9%11%24%14%3
2450
11th to 20thDay
42%6%13%24%12%2
2445
21st to endDay
37%10%14%23%13%3
2582
August1st to 10thDay
40%8%16%23%13%1
2314
11th to 20thDay
41%9%13%23%13%1
2287
21st to endDay
38%7%12%21%19%2
2376
September1st to 10thDay
38%6%11%24%19%1
2138
11th to 20thDay
36%5%10%24%23%3
1980
21st to endDay
41%5%9%20%23%2
1980
October1st to 10thDay
45%5%9%22%15%3
1980
11th to 20thDay
37%5%10%30%16%1
1776
21st to endDay
43%5%13%19%15%4
1782
November1st to 10thDay
41%413%22%17%2
1671
11th to 20thDay
40%5%10%23%19%3
1710
21st to endDay
42%6%11%26%13%2
1710
December1st to 10thDay
47%413%17%17%2
1606
11th to 20thDay
44%413%16%16%5%
1906
21st to endDay
52%411%21%10%1
2772
January1st to 10thNight
42%411%23%17%3
2649
11th to 20thNight
51%5%12%19%10%2
2583
21st to endNight
44%410%20%19%3
2772
February1st to 10thNight
47%5%12%21%13%2
2242
11th to 20thNight
48%49%20%15%4
2100
21st to endNight
45%5%8%23%16%4
1776
March1st to 10thNight
43%5%10%22%16%4
2160
11th to 20thNight
46%411%17%17%4
2048
21st to endNight
48%47%18%18%6%
2083
April1st to 10thNight
48%5%9%18%17%4
1800
11th to 20thNight
44%6%9%20%18%3
1753
21st to endNight
48%5%10%19%14%4
1620
May1st to 10thNight
55%5%10%16%11%3
1620
11th to 20thNight
46%8%13%18%12%4
1594
21st to endNight
47%8%13%19%12%1
1577
June1st to 10thNight
47%8%13%20%12%
1440
11th to 20thNight
47%5%11%22%13%1
1440
21st to endNight
40%8%15%23%13%1
1440
July1st to 10thNight
41%8%12%23%15%1
1400
11th to 20thNight
42%7%14%27%10%1
1392
21st to endNight
41%7%14%25%10%2
1486
August1st to 10thNight
37%8%15%25%13%2
1591
11th to 20thNight
40%9%17%23%12%
1609
21st to endNight
36%7%11%26%19%1
1980
September1st to 10thNight
41%6%12%23%17%2
1821
11th to 20thNight
36%5%10%23%25%2
1980
21st to endNight
41%7%8%22%20%3
1980
October1st to 10thNight
46%6%10%20%14%3
1980
11th to 20thNight
37%6%13%28%15%1
2178
21st to endNight
48%6%11%19%14%2
2574
November1st to 10thNight
39%6%12%22%17%3
2407
11th to 20thNight
42%410%22%19%4
2470
21st to endNight
39%414%27%13%3
2470
December1st to 10thNight
47%5%12%20%14%1
2569
11th to 20thNight
44%414%18%17%2
3288
21st to endNight
51%5%8%24%11%1
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
25%29%28%16%2
180
11th to 20thDay
25%30%33%8%31
168
21st to endDay
23%28%37%9%21
176
February1st to 10thDay
32%23%32%12%2
374
11th to 20thDay
27%30%34%7%2
416
21st to endDay
26%29%32%11%2
346
March1st to 10thDay
26%24%35%12%3
420
11th to 20thDay
24%28%34%10%41
420
21st to endDay
26%23%34%11%5%2
462
April1st to 10thDay
29%25%28%12%5%1
420
11th to 20thDay
24%27%32%14%3
412
21st to endDay
28%19%33%15%32
420
May1st to 10thDay
31%24%29%12%31
423
11th to 20thDay
22%17%42%13%6%1
447
21st to endDay
19%13%35%24%8%1
485
June1st to 10thDay
20%16%32%23%8%1
450
11th to 20thDay
16%18%40%19%6%2
450
21st to endDay
16%13%37%26%6%2
450
July1st to 10thDay
15%9%31%32%11%2
445
11th to 20thDay
14%8%31%32%13%2
444
21st to endDay
12%12%35%30%11%1
488
August1st to 10thDay
13%9%35%31%11%2
446
11th to 20thDay
14%11%31%28%13%3
439
21st to endDay
15%9%32%26%12%5%
495
September1st to 10thDay
19%9%31%24%14%3
450
11th to 20thDay
18%13%30%24%10%6%
450
21st to endDay
24%12%29%23%7%5%
450
October1st to 10thDay
27%13%26%20%8%5%
450
11th to 20thDay
19%16%34%20%11%1
394
21st to endDay
25%19%29%19%6%3
396
November1st to 10thDay
19%18%34%18%9%2
365
11th to 20thDay
27%22%31%15%5%1
370
21st to endDay
22%23%30%16%9%
370
December1st to 10thDay
20%26%36%14%4
266
11th to 20thDay
30%28%32%8%2
180
21st to endDay
26%25%35%9%42
198
January1st to 10thNight
22%20%37%18%3
760
11th to 20thNight
29%20%34%14%3
739
21st to endNight
22%20%35%19%3
792
February1st to 10thNight
26%18%38%18%1
720
11th to 20thNight
26%21%39%13%1
703
21st to endNight
24%22%34%17%2
592
March1st to 10thNight
24%19%35%19%3
720
11th to 20thNight
21%20%39%17%4
720
21st to endNight
24%19%35%18%3
792
April1st to 10thNight
24%18%35%19%4
720
11th to 20thNight
23%18%36%20%3
689
21st to endNight
24%16%36%20%4
540
May1st to 10thNight
29%14%33%19%4
540
11th to 20thNight
22%14%40%19%4
532
21st to endNight
22%7%32%32%7%
415
June1st to 10thNight
19%8%30%33%9%1
360
11th to 20thNight
21%6%33%32%8%
360
21st to endNight
20%6%29%38%7%
360
July1st to 10thNight
15%430%40%10%1
350
11th to 20thNight
16%5%26%43%10%
348
21st to endNight
14%428%44%10%
394
August1st to 10thNight
12%6%34%40%9%
528
11th to 20thNight
15%6%27%41%11%
545
21st to endNight
14%5%24%39%16%2
792
September1st to 10thNight
15%5%31%35%13%1
720
11th to 20thNight
17%8%26%30%17%3
720
21st to endNight
22%6%28%29%13%2
720
October1st to 10thNight
25%9%27%26%12%2
720
11th to 20thNight
18%11%34%24%12%1
720
21st to endNight
25%13%35%19%7%1
792
November1st to 10thNight
18%14%32%25%10%1
740
11th to 20thNight
21%22%33%18%7%1
760
21st to endNight
20%21%34%21%41
760
December1st to 10thNight
25%18%34%18%4
760
11th to 20thNight
24%20%33%20%3
760
21st to endNight
26%19%34%19%2
836
Page generated at 2024-01-12 07:31:47. Version ac07

Copyright 2024 Attilla Danko


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