Justin's Space Pictures Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Justin's Space Pictures Observatory clear sky chart from 2005-11-06 to 2024-01-12.

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
29%
23259
21%
74585
9%
23215
43%
23215
22%
46330

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
24%
2649
8%
757
37%
757
18%
1568
January11th to 20thNight
21%
727
21%
2514
6%
727
41%
727
16%
1590
January21st to endNight
18%
792
25%
2574
7%
792
40%
792
19%
1556
February1st to 10thNight
16%
720
17%
2340
3%
720
32%
720
17%
1490
February11th to 20thNight
11%
703
21%
2112
4%
699
32%
699
15%
1386
February21st to endNight
16%
592
26%
1776
9%
592
38%
592
17%
1149
March1st to 10thNight
19%
720
24%
2160
9%
720
38%
720
22%
1315
March11th to 20thNight
18%
720
22%
2003
8%
720
33%
720
20%
1311
March21st to endNight
18%
792
23%
2034
5%
792
32%
792
23%
1381
April1st to 10thNight
16%
720
20%
1800
3%
720
27%
720
21%
1223
April11th to 20thNight
23%
711
21%
1775
5%
711
31%
711
26%
1184
April21st to endNight
24%
720
21%
1800
5%
720
33%
720
24%
1218
May1st to 10thNight
23%
590
17%
1670
7%
590
31%
590
20%
1148
May11th to 20thNight
23%
372
19%
1434
8%
372
37%
372
17%
896
May21st to endNight
42%
388
15%
1551
12%
388
48%
388
17%
957
June1st to 10thNight
42%
360
18%
1440
17%
360
53%
360
21%
845
June11th to 20thNight
40%
360
16%
1440
15%
360
50%
360
20%
870
June21st to endNight
46%
360
17%
1440
15%
360
56%
360
26%
792
July1st to 10thNight
47%
350
14%
1400
14%
350
54%
350
21%
861
July11th to 20thNight
56%
348
17%
1392
19%
348
60%
348
27%
765
July21st to endNight
50%
411
20%
1503
16%
389
60%
389
26%
856
August1st to 10thNight
56%
541
18%
1604
13%
538
59%
538
30%
993
August11th to 20thNight
49%
710
17%
1774
9%
710
52%
710
31%
1200
August21st to endNight
51%
792
17%
1980
8%
792
54%
792
32%
1325
September1st to 10thNight
42%
720
22%
1800
9%
720
48%
720
33%
1196
September11th to 20thNight
51%
720
30%
1844
19%
720
57%
720
41%
1091
September21st to endNight
39%
720
25%
1980
16%
720
49%
720
27%
1292
October1st to 10thNight
37%
720
19%
2124
12%
720
46%
720
26%
1345
October11th to 20thNight
37%
720
26%
2160
16%
720
51%
720
30%
1280
October21st to endNight
25%
792
26%
2456
11%
792
43%
792
24%
1517
November1st to 10thNight
32%
740
26%
2407
12%
740
50%
740
28%
1353
November11th to 20thNight
28%
760
26%
2470
12%
760
45%
760
21%
1499
November21st to endNight
24%
760
24%
2553
10%
760
43%
760
22%
1497
December1st to 10thNight
19%
760
20%
2660
6%
760
36%
760
16%
1655
December11th to 20thNight
20%
760
21%
3188
6%
759
39%
759
15%
1906
December21st to endNight
21%
828
15%
4778
8%
817
40%
817
11%
2820

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
15%6%25%5%35%5%5%7%41%
74737
Night
15%6%25%5%3445%7%43%
74965
TransparencyDay
42%311%24%17%3
74444
Night
42%311%24%18%3
74793
SeeingDay
22%16%29%20%10%3
13903
Night
20%15%30%26%9%1
23268

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
14%6%35%5%35%45%6%43%
1517
11th to 20thDay
15%7%36%44445%7%42%
1470
21st to endDay
16%8%344345%6%7%42%
1782
February1st to 10thDay
16%8%36%435%5%5%7%38%
1620
11th to 20thDay
17%7%25%425%5%46%41%
1734
21st to endDay
18%9%5%5%434346%39%
1480
March1st to 10thDay
14%7%35%434436%48%
1797
11th to 20thDay
17%6%25%5%345%5%7%40%
1953
21st to endDay
20%6%35%43445%5%40%
2321
April1st to 10thDay
16%8%35%42445%6%42%
2160
11th to 20thDay
15%5%244345%6%7%43%
2134
21st to endDay
16%6%35%5%35%46%7%39%
2160
May1st to 10thDay
20%7%26%5%35%5%5%7%36%
2287
11th to 20thDay
18%5%35%5%35%5%6%8%37%
2475
21st to endDay
14%6%25%5%345%6%9%42%
2725
June1st to 10thDay
13%6%26%5%36%5%7%9%39%
2520
11th to 20thDay
13%6%35%6%46%5%6%9%38%
2520
21st to endDay
11%6%25%6%45%6%6%8%42%
2520
July1st to 10thDay
11%5%35%7%46%6%6%8%39%
2520
11th to 20thDay
7%5%25%6%46%6%7%11%40%
2520
21st to endDay
11%5%36%6%47%6%7%8%37%
2724
August1st to 10thDay
9%5%37%6%5%6%5%7%8%39%
2305
11th to 20thDay
12%5%26%6%46%5%6%9%39%
2126
21st to endDay
13%7%35%6%35%6%6%8%39%
2376
September1st to 10thDay
13%5%26%6%345%6%6%43%
2160
11th to 20thDay
13%6%2342445%8%49%
2115
21st to endDay
17%6%35%6%25%447%40%
1980
October1st to 10thDay
18%6%25%433446%44%
1832
11th to 20thDay
17%5%24424437%49%
1800
21st to endDay
18%5%25%424446%45%
1900
November1st to 10thDay
13%5%145%33346%52%
1671
11th to 20thDay
16%5%25%5%33446%47%
1710
21st to endDay
15%425%434447%47%
1625
December1st to 10thDay
19%7%26%5%3345%8%40%
1520
11th to 20thDay
20%8%3442344445%
1906
21st to endDay
17%6%25%5%46%5%6%7%37%
2772
January1st to 10thNight
17%6%2442445%6%45%
2649
11th to 20thNight
18%6%25%5%3445%7%40%
2514
21st to endNight
14%7%25%5%245%47%44%
2574
February1st to 10thNight
17%8%35%5%3445%6%40%
2340
11th to 20thNight
18%8%35%5%3336%6%41%
2112
21st to endNight
19%7%35%42345%5%43%
1776
March1st to 10thNight
15%5%25%5%3345%6%47%
2150
11th to 20thNight
17%7%35%423346%44%
2002
21st to endNight
17%7%35%5%245%45%43%
2034
April1st to 10thNight
17%7%36%5%245%46%41%
1800
11th to 20thNight
14%7%35%5%34447%44%
1775
21st to endNight
19%6%24435%45%6%43%
1800
May1st to 10thNight
19%6%27%6%34447%36%
1670
11th to 20thNight
18%7%35%5%3446%7%38%
1433
21st to endNight
16%6%36%5%36%5%5%8%39%
1550
June1st to 10thNight
15%5%35%5%345%49%43%
1440
11th to 20thNight
11%6%35%5%46%5%6%8%41%
1440
21st to endNight
9%416%445%5%8%10%43%
1440
July1st to 10thNight
10%6%36%6%36%6%7%9%39%
1440
11th to 20thNight
7%5%25%6%36%7%9%9%43%
1440
21st to endNight
9%426%6%36%6%6%10%43%
1591
August1st to 10thNight
7%6%26%5%36%6%7%10%42%
1615
11th to 20thNight
10%6%36%7%35%5%6%8%40%
1774
21st to endNight
13%6%35%5%35%5%5%8%42%
1980
September1st to 10thNight
15%5%25%6%345%47%45%
1800
11th to 20thNight
11%5%2442435%7%55%
1844
21st to endNight
18%6%25%42445%8%42%
1980
October1st to 10thNight
19%6%25%333447%43%
2124
11th to 20thNight
16%5%24423446%50%
2160
21st to endNight
18%6%25%434346%46%
2456
November1st to 10thNight
12%5%25%43345%6%53%
2407
11th to 20thNight
17%5%35%423445%48%
2470
21st to endNight
13%5%245%35%5%5%6%46%
2553
December1st to 10thNight
20%7%35%42445%7%40%
2660
11th to 20thNight
17%6%35%5%3435%7%42%
3288
21st to endNight
17%7%36%5%35%5%6%7%38%
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%312%23%15%5%
1518
11th to 20thDay
43%313%24%14%3
1470
21st to endDay
43%39%26%16%3
1782
February1st to 10thDay
47%311%26%11%2
1620
11th to 20thDay
44%49%25%15%3
1743
21st to endDay
49%27%22%15%5%
1480
March1st to 10thDay
40%211%28%15%3
1800
11th to 20thDay
44%29%24%17%4
1953
21st to endDay
47%36%22%18%4
2321
April1st to 10thDay
44%39%22%17%5%
2160
11th to 20thDay
40%311%24%18%4
2134
21st to endDay
44%39%21%19%4
2160
May1st to 10thDay
48%39%21%17%3
2287
11th to 20thDay
46%312%23%14%2
2479
21st to endDay
40%415%25%14%2
2725
June1st to 10thDay
41%5%11%25%16%2
2520
11th to 20thDay
43%412%25%13%2
2520
21st to endDay
40%413%24%18%1
2520
July1st to 10thDay
43%5%12%22%16%2
2450
11th to 20thDay
36%5%13%27%16%2
2445
21st to endDay
42%5%11%23%17%2
2572
August1st to 10thDay
43%412%26%15%1
2292
11th to 20thDay
41%415%21%17%2
2126
21st to endDay
41%5%12%22%17%4
2376
September1st to 10thDay
41%311%21%21%3
2160
11th to 20thDay
34%38%25%26%4
2115
21st to endDay
46%38%19%22%2
1980
October1st to 10thDay
43%310%24%19%2
1832
11th to 20thDay
38%29%26%23%3
1800
21st to endDay
43%28%25%21%2
1900
November1st to 10thDay
35%211%28%21%3
1671
11th to 20thDay
39%38%24%23%3
1710
21st to endDay
39%311%31%14%3
1625
December1st to 10thDay
45%314%23%15%1
1520
11th to 20thDay
44%211%28%12%3
1906
21st to endDay
48%212%24%14%1
2772
January1st to 10thNight
41%210%25%18%4
2649
11th to 20thNight
45%313%24%13%2
2514
21st to endNight
41%29%27%19%3
2574
February1st to 10thNight
45%213%24%13%2
2340
11th to 20thNight
45%38%21%17%5%
2114
21st to endNight
45%27%24%17%5%
1776
March1st to 10thNight
39%211%26%19%4
2160
11th to 20thNight
43%29%22%19%4
2003
21st to endNight
45%28%19%19%6%
2034
April1st to 10thNight
45%29%20%19%5%
1800
11th to 20thNight
42%39%22%20%4
1775
21st to endNight
43%48%20%20%5%
1800
May1st to 10thNight
49%39%19%18%2
1670
11th to 20thNight
46%412%17%18%3
1434
21st to endNight
44%5%15%20%13%2
1551
June1st to 10thNight
40%5%11%22%19%2
1440
11th to 20thNight
41%6%13%25%13%2
1440
21st to endNight
36%415%28%15%2
1440
July1st to 10thNight
42%6%15%21%13%2
1400
11th to 20thNight
35%415%28%15%2
1392
21st to endNight
36%6%14%27%16%2
1503
August1st to 10thNight
37%5%16%24%16%1
1604
11th to 20thNight
42%415%21%17%2
1774
21st to endNight
41%413%20%19%3
1980
September1st to 10thNight
40%313%21%19%3
1800
11th to 20thNight
31%310%26%26%4
1844
21st to endNight
42%36%24%21%2
1980
October1st to 10thNight
42%311%24%18%3
2124
11th to 20thNight
36%210%29%19%3
2160
21st to endNight
41%28%26%20%2
2456
November1st to 10thNight
34%311%25%21%5%
2407
11th to 20thNight
40%38%23%20%6%
2470
21st to endNight
38%311%28%18%2
2553
December1st to 10thNight
46%212%24%15%2
2660
11th to 20thNight
43%212%20%18%4
3288
21st to endNight
47%212%26%12%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
28%24%31%13%41
180
11th to 20thDay
35%28%24%12%1
172
21st to endDay
30%33%24%10%22
264
February1st to 10thDay
33%31%25%9%2
240
11th to 20thDay
32%26%32%8%1
402
21st to endDay
33%27%29%10%1
346
March1st to 10thDay
29%24%28%17%3
420
11th to 20thDay
28%24%31%13%22
420
21st to endDay
29%24%30%12%41
462
April1st to 10thDay
27%29%28%10%5%1
420
11th to 20thDay
22%22%34%15%6%1
412
21st to endDay
30%20%33%11%5%1
420
May1st to 10thDay
32%20%27%15%6%1
423
11th to 20thDay
24%16%34%18%6%2
447
21st to endDay
19%11%24%29%13%4
485
June1st to 10thDay
16%14%30%25%12%3
450
11th to 20thDay
18%13%32%25%11%2
450
21st to endDay
13%11%30%30%12%4
450
July1st to 10thDay
13%5%26%31%19%6%
445
11th to 20thDay
7%5%29%33%21%5%
444
21st to endDay
13%6%29%32%15%5%
488
August1st to 10thDay
12%430%32%15%6%
446
11th to 20thDay
15%422%36%18%5%
439
21st to endDay
14%7%30%24%16%8%
495
September1st to 10thDay
16%9%27%23%16%8%
450
11th to 20thDay
16%7%27%28%13%8%
450
21st to endDay
26%12%26%20%10%5%
450
October1st to 10thDay
26%10%26%20%13%5%
450
11th to 20thDay
21%17%26%21%12%2
450
21st to endDay
21%19%34%16%9%1
455
November1st to 10thDay
19%16%33%18%13%2
365
11th to 20thDay
25%21%29%18%7%
370
21st to endDay
22%19%32%19%6%1
285
December1st to 10thDay
28%30%28%8%6%
180
11th to 20thDay
35%18%33%12%21
180
21st to endDay
32%17%29%16%6%1
198
January1st to 10thNight
22%24%33%17%3
760
11th to 20thNight
25%20%29%22%3
727
21st to endNight
19%24%34%21%2
792
February1st to 10thNight
22%22%34%20%1
720
11th to 20thNight
26%28%31%13%1
703
21st to endNight
26%24%30%18%2
592
March1st to 10thNight
22%23%33%17%4
720
11th to 20thNight
25%23%29%17%7%
720
21st to endNight
21%19%38%16%5%
792
April1st to 10thNight
22%24%33%16%4
720
11th to 20thNight
20%16%37%22%5%
711
21st to endNight
23%16%34%22%4
720
May1st to 10thNight
22%15%35%22%6%
590
11th to 20thNight
19%14%38%25%5%
372
21st to endNight
18%7%24%39%10%2
389
June1st to 10thNight
18%6%30%36%9%1
360
11th to 20thNight
12%5%33%38%11%1
360
21st to endNight
11%331%44%11%
360
July1st to 10thNight
9%232%41%14%2
350
11th to 20thNight
8%324%46%18%1
348
21st to endNight
11%428%39%18%
411
August1st to 10thNight
11%320%43%22%2
541
11th to 20thNight
14%420%40%19%3
710
21st to endNight
15%321%39%20%3
792
September1st to 10thNight
17%5%26%33%15%3
720
11th to 20thNight
13%6%23%34%21%4
720
21st to endNight
22%7%26%28%16%1
720
October1st to 10thNight
23%8%26%25%15%3
720
11th to 20thNight
18%13%28%29%12%1
720
21st to endNight
21%14%36%21%8%
792
November1st to 10thNight
16%13%34%25%11%1
740
11th to 20thNight
20%17%29%25%9%
760
21st to endNight
19%17%34%21%8%1
760
December1st to 10thNight
27%18%30%18%6%1
760
11th to 20thNight
20%20%32%22%5%
760
21st to endNight
22%19%32%25%2
836
Page generated at 2024-01-09 07:14:39. Version ac07

Copyright 2024 Attilla Danko


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