Critter Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Critter 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
53%
22996
19%
74724
18%
22944
57%
22944
27%
46189

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
32%
756
10%
2646
8%
756
37%
756
13%
1930
January11th to 20thNight
40%
736
17%
2468
14%
736
45%
736
20%
1637
January21st to endNight
45%
792
22%
2574
20%
792
49%
792
22%
1688
February1st to 10thNight
41%
720
16%
2340
14%
720
46%
720
21%
1553
February11th to 20thNight
40%
702
15%
2274
13%
700
44%
700
19%
1573
February21st to endNight
40%
592
15%
1821
11%
592
45%
592
17%
1310
March1st to 10thNight
37%
720
11%
2017
8%
720
41%
720
16%
1478
March11th to 20thNight
41%
720
15%
1980
10%
720
46%
720
19%
1442
March21st to endNight
35%
792
9%
2160
6%
792
37%
792
16%
1655
April1st to 10thNight
39%
720
12%
1800
7%
720
40%
720
19%
1360
April11th to 20thNight
42%
711
14%
1779
7%
711
44%
711
23%
1305
April21st to endNight
50%
611
12%
1691
7%
611
52%
611
25%
1154
May1st to 10thNight
53%
526
15%
1606
12%
526
55%
526
27%
1010
May11th to 20thNight
58%
354
16%
1416
18%
354
60%
354
20%
858
May21st to endNight
53%
389
11%
1552
12%
388
56%
388
20%
968
June1st to 10thNight
63%
360
11%
1440
17%
360
65%
360
22%
857
June11th to 20thNight
63%
360
18%
1440
26%
360
66%
360
29%
748
June21st to endNight
80%
360
26%
1440
39%
360
82%
360
48%
587
July1st to 10thNight
85%
350
26%
1400
41%
350
87%
350
51%
542
July11th to 20thNight
85%
348
35%
1392
49%
348
87%
348
59%
492
July21st to endNight
91%
542
38%
1628
39%
512
92%
512
73%
622
August1st to 10thNight
89%
537
34%
1602
31%
534
90%
534
66%
689
August11th to 20thNight
88%
534
39%
1602
31%
534
90%
534
70%
664
August21st to endNight
79%
760
40%
1948
27%
760
81%
760
73%
906
September1st to 10thNight
80%
720
41%
1800
26%
720
81%
720
74%
846
September11th to 20thNight
75%
720
35%
1818
26%
720
77%
720
56%
972
September21st to endNight
69%
720
29%
2054
26%
720
72%
720
46%
1097
October1st to 10thNight
66%
720
23%
2160
22%
720
70%
720
41%
1178
October11th to 20thNight
64%
720
27%
2160
28%
720
68%
720
38%
1220
October21st to endNight
57%
792
23%
2376
22%
792
61%
792
31%
1443
November1st to 10thNight
45%
740
17%
2357
17%
740
47%
740
20%
1613
November11th to 20thNight
42%
760
13%
2660
12%
760
46%
760
17%
1835
November21st to endNight
43%
760
15%
2660
12%
760
49%
760
21%
1719
December1st to 10thNight
44%
760
19%
2660
16%
760
50%
760
22%
1676
December11th to 20thNight
33%
759
12%
3209
10%
759
38%
759
12%
2271
December21st to endNight
27%
833
9%
4794
10%
817
31%
817
7%
3291

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
9%8%35%5%3445%7%48%
74734
Night
10%9%35%5%3445%7%44%
75050
TransparencyDay
37%412%22%18%7%
74446
Night
40%413%22%15%6%
74859
SeeingDay
17%13%28%27%12%4
13826
Night
16%7%17%32%24%4
23006

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
11%11%6%8%7%46%6%8%8%24%
1519
11th to 20thDay
12%9%36%7%47%6%7%8%33%
1576
21st to endDay
14%11%36%44445%8%37%
1782
February1st to 10thDay
7%11%48%7%47%8%6%7%31%
1620
11th to 20thDay
10%11%47%7%445%5%7%36%
1575
21st to endDay
12%16%49%7%4446%6%29%
1435
March1st to 10thDay
12%14%411%7%46%5%5%8%25%
1939
11th to 20thDay
11%12%48%7%5%6%5%6%7%29%
1980
21st to endDay
13%13%5%9%7%36%5%6%8%24%
2194
April1st to 10thDay
12%13%6%10%8%445%5%6%27%
2160
11th to 20thDay
14%13%5%7%6%45%45%7%31%
2129
21st to endDay
12%10%37%5%2446%9%38%
2267
May1st to 10thDay
10%8%35%5%3345%7%46%
2353
11th to 20thDay
11%9%35%6%245%5%8%42%
2477
21st to endDay
16%10%35%5%35%45%8%37%
2723
June1st to 10thDay
11%7%35%5%3446%8%44%
2520
11th to 20thDay
8%6%25%434347%54%
2520
21st to endDay
4313223335%70%
2520
July1st to 10thDay
2312212235%78%
2520
11th to 20thDay
321222223378%
2520
21st to endDay
221221233381%
2590
August1st to 10thDay
2212213346%75%
2328
11th to 20thDay
1212112235%79%
2298
21st to endDay
321221123478%
2406
September1st to 10thDay
3211212335%78%
2160
11th to 20thDay
44233245%5%6%62%
2138
21st to endDay
7%32432345%7%61%
1905
October1st to 10thDay
8%5%2442435%6%57%
1800
11th to 20thDay
7%6%35%5%3445%8%52%
1800
21st to endDay
10%7%36%6%34447%47%
1980
November1st to 10thDay
14%8%47%7%35%5%6%8%33%
1718
11th to 20thDay
13%8%38%7%36%5%8%9%29%
1520
21st to endDay
11%12%45%6%46%5%5%7%35%
1520
December1st to 10thDay
9%9%26%5%35%5%7%8%38%
1520
11th to 20thDay
13%12%5%7%7%45%5%6%8%26%
1928
21st to endDay
13%14%48%8%5%6%6%7%8%21%
2794
January1st to 10thNight
13%10%37%7%47%8%7%8%25%
2646
11th to 20thNight
10%11%47%6%35%5%6%8%35%
2468
21st to endNight
12%11%36%5%35%5%6%7%37%
2574
February1st to 10thNight
9%13%36%6%35%5%6%8%35%
2340
11th to 20thNight
11%14%5%7%5%35%5%6%6%34%
2272
21st to endNight
9%14%5%7%6%35%6%6%7%30%
1821
March1st to 10thNight
12%15%5%6%6%46%6%6%7%28%
2017
11th to 20thNight
9%12%49%7%46%6%5%8%30%
1980
21st to endNight
13%14%5%8%7%46%5%5%7%26%
2160
April1st to 10thNight
12%15%5%7%6%35%5%6%7%29%
1800
11th to 20thNight
11%13%5%7%6%345%6%6%34%
1779
21st to endNight
15%10%35%42446%10%37%
1691
May1st to 10thNight
10%9%36%6%3345%7%45%
1606
11th to 20thNight
11%7%36%5%46%5%5%6%41%
1416
21st to endNight
15%8%35%5%3445%7%40%
1552
June1st to 10thNight
12%6%34436%47%7%45%
1440
11th to 20thNight
10%6%25%42325%7%54%
1440
21st to endNight
5%312313235%72%
1440
July1st to 10thNight
2212324335%74%
1440
11th to 20thNight
3212322215%79%
1440
21st to endNight
211111122385%
1724
August1st to 10thNight
2211312335%77%
1611
11th to 20thNight
211212335%80%
1602
21st to endNight
2211212335%80%
1948
September1st to 10thNight
321111114480%
1800
11th to 20thNight
431332246%7%64%
1818
21st to endNight
8%414323346%62%
2054
October1st to 10thNight
7%5%24423345%60%
2160
11th to 20thNight
8%5%25%42435%6%55%
2160
21st to endNight
10%7%25%43445%7%47%
2376
November1st to 10thNight
14%11%46%6%35%5%6%6%34%
2357
11th to 20thNight
14%9%36%7%5%6%6%7%8%30%
2660
21st to endNight
14%10%46%5%35%45%8%38%
2660
December1st to 10thNight
11%9%46%5%35%46%9%38%
2660
11th to 20thNight
11%12%48%8%5%7%6%7%8%25%
3276
21st to endNight
13%14%48%7%46%5%6%7%25%
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
55%5%17%14%6%3
1519
11th to 20thDay
47%5%13%16%11%8%
1576
21st to endDay
47%411%20%12%6%
1782
February1st to 10thDay
50%5%17%16%10%2
1620
11th to 20thDay
48%415%21%9%2
1584
21st to endDay
57%49%17%10%2
1435
March1st to 10thDay
58%5%14%16%7%
1939
11th to 20thDay
54%413%18%10%1
1980
21st to endDay
59%6%15%15%5%
2194
April1st to 10thDay
59%5%12%15%8%2
2160
11th to 20thDay
53%5%16%14%8%4
2132
21st to endDay
45%5%16%22%11%1
2267
May1st to 10thDay
39%5%15%28%12%1
2353
11th to 20thDay
43%415%27%10%2
2480
21st to endDay
46%5%19%23%7%
2724
June1st to 10thDay
41%416%29%10%
2520
11th to 20thDay
31%413%35%15%2
2520
21st to endDay
19%211%35%25%8%
2520
July1st to 10thDay
12%39%29%30%17%
2451
11th to 20thDay
14%2423%35%21%
2445
21st to endDay
10%2222%46%19%
2446
August1st to 10thDay
12%39%32%31%13%
2312
11th to 20thDay
10%27%26%43%12%
2298
21st to endDay
11%37%27%38%13%
2406
September1st to 10thDay
12%2424%35%23%
2160
11th to 20thDay
23%410%27%27%11%
2138
21st to endDay
23%311%25%23%15%
1905
October1st to 10thDay
29%412%20%22%13%
1800
11th to 20thDay
32%414%21%21%8%
1800
21st to endDay
39%412%19%16%10%
1980
November1st to 10thDay
50%313%19%13%3
1718
11th to 20thDay
49%6%15%17%10%4
1520
21st to endDay
48%5%11%17%12%7%
1520
December1st to 10thDay
42%414%21%16%3
1520
11th to 20thDay
57%317%13%8%1
1928
21st to endDay
59%315%17%5%2
2794
January1st to 10thNight
55%6%16%13%7%3
2646
11th to 20thNight
48%412%17%11%8%
2468
21st to endNight
46%411%18%16%6%
2574
February1st to 10thNight
47%415%19%13%2
2340
11th to 20thNight
51%412%21%10%2
2274
21st to endNight
52%7%15%16%9%2
1821
March1st to 10thNight
55%5%14%18%8%
2017
11th to 20thNight
52%6%12%19%10%1
1980
21st to endNight
58%5%17%16%4
2160
April1st to 10thNight
55%5%16%17%6%1
1800
11th to 20thNight
49%7%17%16%8%3
1779
21st to endNight
43%8%20%22%6%1
1691
May1st to 10thNight
40%5%17%26%10%2
1606
11th to 20thNight
43%5%17%28%43
1416
21st to endNight
44%5%22%24%5%
1552
June1st to 10thNight
40%6%19%31%5%
1440
11th to 20thNight
32%5%16%36%11%1
1440
21st to endNight
19%212%41%21%4
1440
July1st to 10thNight
14%49%33%25%15%
1400
11th to 20thNight
13%25%28%37%16%
1392
21st to endNight
9%2325%49%13%
1628
August1st to 10thNight
11%38%37%32%8%
1602
11th to 20thNight
10%27%34%37%10%
1602
21st to endNight
9%28%33%35%11%
1948
September1st to 10thNight
10%15%28%36%20%
1800
11th to 20thNight
20%311%31%27%8%
1818
21st to endNight
26%212%26%18%16%
2054
October1st to 10thNight
28%411%22%25%11%
2160
11th to 20thNight
32%313%22%20%10%
2160
21st to endNight
36%5%15%18%15%11%
2376
November1st to 10thNight
50%413%16%12%5%
2357
11th to 20thNight
51%5%14%15%10%5%
2660
21st to endNight
46%413%13%16%8%
2660
December1st to 10thNight
43%5%11%22%15%3
2660
11th to 20thNight
56%413%15%11%1
3276
21st to endNight
58%413%17%6%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
33%12%27%20%5%2
180
11th to 20thDay
24%14%29%18%11%4
272
21st to endDay
25%15%23%21%16%1
374
February1st to 10thDay
19%16%31%24%9%1
340
11th to 20thDay
25%20%27%20%7%1
335
21st to endDay
28%18%29%21%3
326
March1st to 10thDay
29%19%26%19%7%
420
11th to 20thDay
25%15%28%22%9%1
420
21st to endDay
29%18%28%18%6%
462
April1st to 10thDay
25%20%28%19%7%1
420
11th to 20thDay
28%20%25%19%5%2
412
21st to endDay
24%18%27%21%9%2
420
May1st to 10thDay
20%15%33%20%10%3
423
11th to 20thDay
24%15%26%24%7%4
448
21st to endDay
22%11%24%27%9%6%
485
June1st to 10thDay
19%15%26%23%12%5%
450
11th to 20thDay
14%17%30%26%10%3
450
21st to endDay
410%35%33%11%7%
450
July1st to 10thDay
7%11%35%28%14%6%
446
11th to 20thDay
310%38%28%13%8%
444
21st to endDay
36%34%33%14%10%
487
August1st to 10thDay
37%32%34%15%8%
447
11th to 20thDay
39%25%37%16%9%
437
21st to endDay
5%9%27%38%15%5%
495
September1st to 10thDay
5%9%27%39%16%4
450
11th to 20thDay
9%10%27%36%16%2
450
21st to endDay
11%10%29%33%15%2
450
October1st to 10thDay
14%10%26%32%15%1
450
11th to 20thDay
15%8%27%30%18%2
450
21st to endDay
18%12%28%26%13%3
495
November1st to 10thDay
21%10%25%28%14%2
320
11th to 20thDay
17%8%27%27%16%4
180
21st to endDay
19%9%31%24%16%1
180
December1st to 10thDay
22%10%28%23%13%4
180
11th to 20thDay
28%9%22%28%9%4
180
21st to endDay
34%6%23%23%12%2
198
January1st to 10thNight
23%10%27%26%11%3
760
11th to 20thNight
19%10%26%28%12%4
736
21st to endNight
19%7%22%33%17%3
792
February1st to 10thNight
18%9%22%35%14%1
720
11th to 20thNight
22%9%22%31%14%2
704
21st to endNight
18%13%22%32%14%1
592
March1st to 10thNight
24%12%19%29%12%3
720
11th to 20thNight
20%9%20%31%18%3
720
21st to endNight
21%15%18%29%15%1
792
April1st to 10thNight
23%9%20%30%16%2
720
11th to 20thNight
21%9%21%29%16%5%
711
21st to endNight
23%6%14%31%23%3
611
May1st to 10thNight
18%6%13%34%24%5%
526
11th to 20thNight
16%413%33%31%3
354
21st to endNight
18%5%13%30%30%5%
389
June1st to 10thNight
15%6%9%33%34%4
360
11th to 20thNight
15%411%39%27%3
360
21st to endNight
6%46%37%44%4
360
July1st to 10thNight
316%30%56%3
350
11th to 20thNight
5%15%37%48%3
348
21st to endNight
31326%58%10%
542
August1st to 10thNight
3327%56%10%
537
11th to 20thNight
2430%53%10%
534
21st to endNight
3214%33%41%7%
760
September1st to 10thNight
4311%32%43%7%
720
11th to 20thNight
6%211%33%38%9%
720
21st to endNight
12%310%34%31%9%
720
October1st to 10thNight
9%314%39%29%5%
720
11th to 20thNight
11%5%14%37%28%6%
720
21st to endNight
15%5%16%36%21%8%
792
November1st to 10thNight
21%5%19%34%16%4
740
11th to 20thNight
20%7%24%35%13%2
760
21st to endNight
20%8%21%33%16%1
760
December1st to 10thNight
20%10%21%32%15%2
760
11th to 20thNight
22%11%27%26%12%3
760
21st to endNight
28%12%25%26%8%1
836
Page generated at 2024-01-11 19:33:45. Version ac07

Copyright 2024 Attilla Danko


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