Carvel Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Carvel Observatory clear sky chart from 2005-11-06 to 2024-02-25.

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
40%
23517
11%
80359
8%
23463
44%
23463
17%
54892

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%
935
10%
4679
5%
926
36%
926
10%
3210
January11th to 20thNight
34%
934
19%
4608
7%
929
41%
929
11%
2986
January21st to endNight
28%
910
10%
4972
7%
900
37%
900
9%
3139
February1st to 10thNight
34%
760
11%
2660
8%
760
39%
760
13%
1915
February11th to 20thNight
36%
740
11%
2484
9%
740
41%
740
15%
1790
February21st to endNight
44%
610
15%
1901
13%
610
49%
610
19%
1345
March1st to 10thNight
39%
720
15%
2160
12%
720
43%
720
18%
1561
March11th to 20thNight
41%
720
16%
2026
10%
720
45%
720
21%
1466
March21st to endNight
40%
792
10%
2116
6%
792
42%
792
18%
1598
April1st to 10thNight
40%
654
12%
1734
5%
654
44%
654
19%
1291
April11th to 20thNight
35%
533
13%
1601
9%
533
40%
533
17%
1165
April21st to endNight
40%
536
11%
1616
10%
536
44%
536
22%
1104
May1st to 10thNight
43%
360
7%
1328
7%
360
47%
360
15%
934
May11th to 20thNight
48%
354
6%
1239
4%
354
50%
354
20%
801
May21st to endNight
42%
388
0%
1358
0%
388
42%
388
18%
948
June1st to 10thNight
40%
360
0%
1260
0%
360
40%
360
15%
895
June11th to 20thNight
43%
360
0%
1098
0%
360
43%
360
13%
853
June21st to endNight
53%
360
0%
1080
0%
360
53%
360
21%
742
July1st to 10thNight
59%
350
0%
1084
0%
350
59%
350
23%
726
July11th to 20thNight
53%
348
0%
1218
0%
348
53%
348
17%
838
July21st to endNight
57%
394
5%
1302
3%
372
58%
372
23%
801
August1st to 10thNight
55%
358
6%
1389
8%
356
57%
356
20%
879
August11th to 20thNight
59%
432
10%
1500
12%
432
62%
432
24%
914
August21st to endNight
54%
594
15%
1782
12%
594
56%
594
26%
1144
September1st to 10thNight
55%
612
14%
1692
10%
612
56%
612
30%
1101
September11th to 20thNight
52%
720
17%
1966
12%
720
55%
720
29%
1274
September21st to endNight
47%
720
19%
1980
12%
720
53%
720
30%
1291
October1st to 10thNight
44%
720
16%
2062
11%
720
48%
720
25%
1406
October11th to 20thNight
38%
720
17%
2340
11%
720
46%
720
22%
1541
October21st to endNight
36%
792
16%
2574
10%
792
45%
792
18%
1776
November1st to 10thNight
31%
900
13%
2565
8%
900
36%
900
16%
1973
November11th to 20thNight
30%
950
13%
2841
6%
950
37%
950
16%
2111
November21st to endNight
32%
950
10%
2850
5%
950
37%
950
18%
2063
December1st to 10thNight
35%
950
15%
2850
9%
950
41%
950
17%
2053
December11th to 20thNight
34%
949
11%
3479
7%
949
38%
949
14%
2535
December21st to endNight
37%
1032
10%
4965
7%
1026
43%
1026
14%
2723

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
10%9%47%7%46%6%6%8%34%
78271
Night
9%10%48%7%45%5%6%8%32%
80974
TransparencyDay
46%7%18%21%7%1
77969
Night
49%7%15%20%9%1
80856
SeeingDay
13%7%24%31%18%6%
14824
Night
14%6%27%35%16%2
23579

By Month

Percentage Cloud Cover NW (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
414%6%12%10%45%5%6%9%27%
2219
11th to 20thDay
6%10%5%7%7%35%8%7%9%33%
2199
21st to endDay
7%13%5%7%6%5%5%5%6%7%34%
2674
February1st to 10thDay
10%12%6%11%8%5%6%6%7%8%22%
1520
11th to 20thDay
6%11%6%11%8%47%5%6%7%28%
1584
21st to endDay
411%7%9%10%5%7%7%8%7%26%
1446
March1st to 10thDay
7%14%6%9%10%5%5%5%6%7%25%
1800
11th to 20thDay
8%11%48%5%36%6%7%8%34%
1933
21st to endDay
9%13%6%9%7%46%6%8%7%25%
2238
April1st to 10thDay
8%12%48%7%45%6%7%9%30%
2225
11th to 20thDay
12%10%5%7%7%46%5%7%8%30%
2310
21st to endDay
11%9%37%6%5%5%5%7%8%33%
2343
May1st to 10thDay
13%8%38%6%5%6%6%6%8%29%
2632
11th to 20thDay
9%6%35%6%46%5%7%8%41%
2654
21st to endDay
19%6%36%5%36%5%6%8%34%
2917
June1st to 10thDay
18%7%36%7%36%5%6%8%31%
2700
11th to 20thDay
19%7%48%7%5%7%6%6%7%24%
2857
21st to endDay
11%5%25%6%46%5%7%11%39%
2880
July1st to 10thDay
11%6%27%5%45%6%7%9%39%
2841
11th to 20thDay
11%6%26%6%47%7%7%9%36%
2700
21st to endDay
10%325%5%35%5%7%9%45%
2938
August1st to 10thDay
11%5%25%6%46%6%7%10%38%
2540
11th to 20thDay
8%5%25%6%35%5%7%10%44%
2400
21st to endDay
11%6%25%5%35%6%7%9%41%
2574
September1st to 10thDay
13%7%36%5%3446%8%42%
2265
11th to 20thDay
15%6%25%43445%9%42%
1994
21st to endDay
9%6%37%6%445%6%9%41%
1980
October1st to 10thDay
11%10%48%6%44436%40%
1893
11th to 20thDay
10%10%47%5%35%6%6%7%37%
1620
21st to endDay
9%12%48%7%5%6%6%6%6%30%
1782
November1st to 10thDay
11%16%5%9%7%35%6%6%7%25%
1494
11th to 20thDay
7%12%5%10%8%45%447%33%
1335
21st to endDay
6%10%6%12%8%5%6%5%5%8%29%
1330
December1st to 10thDay
6%12%6%11%8%5%8%5%6%7%26%
1330
11th to 20thDay
6%12%5%11%9%5%6%5%5%9%28%
1682
21st to endDay
48%47%7%45%5%6%11%39%
2442
January1st to 10thNight
413%6%12%10%5%5%5%6%7%28%
4726
11th to 20thNight
5%8%5%9%10%5%6%6%7%7%32%
4699
21st to endNight
6%13%5%9%8%45%5%5%8%32%
5013
February1st to 10thNight
7%12%6%12%9%5%5%5%6%7%27%
2660
11th to 20thNight
6%12%5%10%9%5%6%7%6%6%28%
2482
21st to endNight
6%12%6%8%8%5%6%5%5%9%30%
1901
March1st to 10thNight
6%11%6%10%9%5%5%5%6%8%29%
2160
11th to 20thNight
8%9%5%8%8%5%6%6%6%8%30%
2026
21st to endNight
9%14%6%9%7%46%6%6%7%26%
2116
April1st to 10thNight
9%9%49%9%5%8%5%7%7%28%
1734
11th to 20thNight
9%12%410%9%46%5%6%8%28%
1601
21st to endNight
13%9%47%5%25%5%6%9%34%
1616
May1st to 10thNight
12%9%49%7%5%6%7%7%7%27%
1328
11th to 20thNight
9%7%47%7%35%6%6%8%37%
1239
21st to endNight
17%9%48%5%35%5%5%8%31%
1358
June1st to 10thNight
18%7%48%6%35%7%5%7%30%
1260
11th to 20thNight
17%9%48%7%5%7%7%8%8%20%
1098
21st to endNight
12%5%26%7%5%6%7%8%10%33%
1080
July1st to 10thNight
14%5%35%6%446%6%8%39%
1116
11th to 20thNight
11%6%25%6%5%8%6%7%11%32%
1260
21st to endNight
11%435%6%35%5%7%10%41%
1379
August1st to 10thNight
11%6%35%7%47%6%6%8%38%
1396
11th to 20thNight
10%6%26%5%36%6%6%10%41%
1500
21st to endNight
12%6%35%5%35%5%6%9%40%
1782
September1st to 10thNight
13%6%26%6%345%5%7%43%
1692
11th to 20thNight
12%6%345%346%6%8%43%
1966
21st to endNight
11%7%35%5%35%5%6%8%42%
1980
October1st to 10thNight
12%8%47%6%45%5%5%7%38%
2062
11th to 20thNight
9%9%38%6%346%6%7%38%
2340
21st to endNight
8%10%49%8%45%5%6%7%33%
2574
November1st to 10thNight
14%15%6%9%7%45%45%7%25%
2565
11th to 20thNight
8%13%6%10%7%46%5%6%7%28%
2841
21st to endNight
7%10%6%10%9%5%6%5%6%7%29%
2850
December1st to 10thNight
9%13%5%9%7%45%6%5%8%29%
2850
11th to 20thNight
8%14%6%9%7%45%5%5%7%28%
3510
21st to endNight
39%38%7%45%5%5%8%42%
5214

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
54%5%15%19%6%1
2219
11th to 20thDay
46%6%11%14%22%2
2220
21st to endDay
48%7%19%21%5%
2674
February1st to 10thDay
58%5%15%14%7%1
1520
11th to 20thDay
53%7%13%17%8%
1592
21st to endDay
53%7%13%19%7%
1446
March1st to 10thDay
58%7%14%17%5%1
1800
11th to 20thDay
44%8%14%23%11%1
1934
21st to endDay
55%7%15%17%5%
2238
April1st to 10thDay
48%10%15%19%7%1
2225
11th to 20thDay
50%7%14%21%7%
2310
21st to endDay
48%6%15%22%7%2
2343
May1st to 10thDay
52%6%15%18%9%1
2632
11th to 20thDay
38%7%15%29%11%
2658
21st to endDay
48%7%14%21%10%
2918
June1st to 10thDay
49%6%16%22%6%
2700
11th to 20thDay
57%8%15%14%5%
2857
21st to endDay
38%9%24%24%5%1
2880
July1st to 10thDay
41%9%20%24%5%1
2764
11th to 20thDay
42%9%27%20%2
2619
21st to endDay
34%9%28%25%4
2775
August1st to 10thDay
38%10%27%21%3
2522
11th to 20thDay
33%9%27%25%6%
2400
21st to endDay
37%8%24%24%7%
2574
September1st to 10thDay
40%7%21%24%7%2
2265
11th to 20thDay
40%6%19%28%7%
1994
21st to endDay
39%7%17%26%9%2
1980
October1st to 10thDay
47%6%16%22%9%1
1893
11th to 20thDay
43%8%16%23%9%
1620
21st to endDay
50%7%13%22%7%1
1782
November1st to 10thDay
58%6%14%15%6%1
1494
11th to 20thDay
51%6%17%19%8%
1335
21st to endDay
52%8%16%18%6%1
1330
December1st to 10thDay
55%8%11%16%9%1
1330
11th to 20thDay
54%6%15%17%7%
1684
21st to endDay
38%6%13%25%15%3
2442
January1st to 10thNight
55%6%15%16%7%2
4726
11th to 20thNight
49%6%12%14%17%2
4740
21st to endNight
51%5%18%18%8%1
5013
February1st to 10thNight
56%5%12%18%8%1
2660
11th to 20thNight
53%7%14%15%10%1
2484
21st to endNight
50%6%11%21%9%1
1901
March1st to 10thNight
51%7%14%21%6%1
2160
11th to 20thNight
50%6%11%20%12%1
2026
21st to endNight
53%8%14%18%6%1
2116
April1st to 10thNight
52%7%12%19%9%1
1734
11th to 20thNight
53%7%11%18%9%2
1601
21st to endNight
45%7%13%22%11%1
1616
May1st to 10thNight
52%7%12%19%9%1
1328
11th to 20thNight
43%8%12%23%13%1
1239
21st to endNight
50%6%14%17%10%2
1358
June1st to 10thNight
52%8%13%20%7%
1260
11th to 20thNight
58%9%16%13%3
1098
21st to endNight
42%11%21%21%41
1080
July1st to 10thNight
41%10%20%22%6%1
1084
11th to 20thNight
45%11%23%17%4
1218
21st to endNight
37%10%23%26%4
1302
August1st to 10thNight
41%9%25%23%2
1389
11th to 20thNight
36%9%23%25%6%1
1500
21st to endNight
39%8%18%25%9%1
1782
September1st to 10thNight
38%7%19%24%10%2
1692
11th to 20thNight
39%6%16%28%9%2
1966
21st to endNight
38%7%15%25%13%2
1980
October1st to 10thNight
45%6%14%25%10%
2062
11th to 20thNight
43%7%14%26%9%1
2340
21st to endNight
47%8%15%22%8%1
2574
November1st to 10thNight
58%6%11%18%7%
2565
11th to 20thNight
54%7%12%19%7%1
2841
21st to endNight
52%6%16%18%6%1
2850
December1st to 10thNight
52%6%12%19%9%2
2850
11th to 20thNight
54%7%16%17%6%
3507
21st to endNight
40%416%23%14%3
5214

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
7%6%29%32%22%5%
180
11th to 20thDay
12%6%28%29%17%8%
180
21st to endDay
13%9%27%29%16%6%
198
February1st to 10thDay
16%8%31%33%11%2
180
11th to 20thDay
13%437%30%14%3
230
21st to endDay
8%7%32%32%15%7%
288
March1st to 10thDay
14%9%27%31%18%2
420
11th to 20thDay
11%5%30%34%14%5%
420
21st to endDay
14%7%28%31%17%4
462
April1st to 10thDay
9%14%32%30%11%3
420
11th to 20thDay
16%8%22%30%18%7%
412
21st to endDay
15%9%27%28%15%5%
420
May1st to 10thDay
14%9%24%33%18%4
535
11th to 20thDay
11%6%21%38%18%6%
625
21st to endDay
18%5%19%32%19%7%
679
June1st to 10thDay
17%10%23%32%14%4
630
11th to 20thDay
21%7%20%25%22%5%
787
21st to endDay
13%419%31%25%8%
810
July1st to 10thDay
12%319%35%22%9%
759
11th to 20thDay
11%421%32%24%8%
618
21st to endDay
10%5%16%30%26%12%
684
August1st to 10thDay
11%416%31%23%15%
480
11th to 20thDay
9%5%24%33%22%7%
437
21st to endDay
15%6%15%30%24%9%
495
September1st to 10thDay
18%6%26%28%15%7%
450
11th to 20thDay
18%6%21%29%19%7%
450
21st to endDay
11%11%27%29%15%6%
450
October1st to 10thDay
15%6%23%33%16%6%
367
11th to 20thDay
16%9%28%27%14%6%
270
21st to endDay
14%13%34%25%12%2
297
November1st to 10thDay
19%433%29%12%3
270
11th to 20thDay
14%5%37%28%14%3
183
21st to endDay
7%8%31%39%9%6%
180
December1st to 10thDay
13%7%28%34%12%6%
180
11th to 20thDay
11%11%31%28%16%3
180
21st to endDay
7%424%35%23%7%
198
January1st to 10thNight
12%6%32%33%14%2
950
11th to 20thNight
12%9%30%35%13%2
950
21st to endNight
15%10%32%29%12%1
922
February1st to 10thNight
10%9%26%33%18%3
760
11th to 20thNight
11%6%32%35%15%1
744
21st to endNight
9%5%26%37%19%4
610
March1st to 10thNight
10%5%30%35%18%2
720
11th to 20thNight
13%429%36%16%2
720
21st to endNight
15%424%38%15%3
792
April1st to 10thNight
12%8%26%37%15%2
654
11th to 20thNight
15%7%29%33%15%1
533
21st to endNight
17%6%27%35%15%1
536
May1st to 10thNight
16%423%39%15%3
360
11th to 20thNight
13%424%39%19%1
354
21st to endNight
21%5%20%37%15%2
389
June1st to 10thNight
20%6%24%34%14%1
360
11th to 20thNight
21%5%20%33%19%2
360
21st to endNight
14%418%37%26%2
360
July1st to 10thNight
15%413%44%23%1
350
11th to 20thNight
14%418%43%19%3
348
21st to endNight
13%218%38%26%3
394
August1st to 10thNight
13%5%15%32%30%5%
358
11th to 20thNight
13%316%36%28%3
432
21st to endNight
13%319%40%24%1
594
September1st to 10thNight
17%218%39%22%2
612
11th to 20thNight
15%420%41%19%1
720
21st to endNight
14%5%26%36%17%2
720
October1st to 10thNight
17%325%37%17%1
720
11th to 20thNight
13%5%32%33%15%2
720
21st to endNight
13%7%32%34%13%1
792
November1st to 10thNight
22%7%27%32%11%2
900
11th to 20thNight
14%8%35%29%12%2
950
21st to endNight
11%5%37%36%10%1
950
December1st to 10thNight
14%7%30%33%14%2
950
11th to 20thNight
13%6%32%33%14%1
950
21st to endNight
11%6%28%35%17%3
1045
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