Hawthorne
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hawthorne clear sky chart from 2005-11-06 to 2024-02-20.

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
61%
23612
29%
80001
24%
23522
70%
23522
41%
40076

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
50%
753
25%
4340
18%
736
63%
736
21%
2172
January11th to 20thNight
59%
757
22%
4328
23%
740
68%
740
22%
2252
January21st to endNight
55%
834
18%
4326
23%
814
66%
814
21%
2360
February1st to 10thNight
53%
760
28%
2352
22%
760
63%
760
38%
1264
February11th to 20thNight
53%
738
30%
2212
25%
738
63%
738
40%
1182
February21st to endNight
48%
592
28%
1776
19%
592
62%
592
42%
928
March1st to 10thNight
50%
720
23%
2160
16%
720
62%
720
34%
1217
March11th to 20thNight
56%
720
26%
2101
19%
720
66%
720
42%
1114
March21st to endNight
47%
792
25%
1980
11%
792
58%
792
42%
1163
April1st to 10thNight
52%
720
28%
1800
12%
720
60%
720
42%
1045
April11th to 20thNight
51%
711
30%
1779
12%
711
58%
711
44%
1002
April21st to endNight
54%
720
28%
1800
13%
720
59%
720
47%
1008
May1st to 10thNight
49%
554
30%
1634
18%
554
57%
554
39%
865
May11th to 20thNight
52%
530
28%
1594
20%
530
58%
530
40%
833
May21st to endNight
56%
388
24%
1552
22%
388
65%
388
33%
766
June1st to 10thNight
68%
360
29%
1440
30%
360
77%
360
39%
639
June11th to 20thNight
70%
360
35%
1440
37%
360
82%
360
55%
529
June21st to endNight
71%
360
32%
1440
34%
360
81%
360
55%
540
July1st to 10thNight
79%
350
31%
1400
37%
350
84%
350
57%
520
July11th to 20thNight
78%
348
31%
1392
37%
348
82%
348
48%
579
July21st to endNight
78%
394
33%
1488
38%
372
82%
372
41%
665
August1st to 10thNight
69%
648
32%
1714
20%
646
73%
646
55%
890
August11th to 20thNight
77%
712
35%
1780
21%
712
79%
712
68%
860
August21st to endNight
77%
792
39%
1980
23%
792
79%
792
69%
954
September1st to 10thNight
76%
720
41%
1800
26%
720
80%
720
70%
857
September11th to 20thNight
74%
720
40%
1889
29%
720
79%
720
63%
914
September21st to endNight
72%
720
42%
1980
34%
720
80%
720
64%
921
October1st to 10thNight
70%
720
35%
2020
27%
720
80%
720
57%
984
October11th to 20thNight
73%
720
40%
2160
37%
720
81%
720
63%
934
October21st to endNight
68%
792
42%
2480
37%
792
81%
792
62%
1045
November1st to 10thNight
69%
740
34%
2405
33%
740
77%
740
51%
1095
November11th to 20thNight
65%
760
34%
2470
27%
760
78%
760
51%
1135
November21st to endNight
60%
760
33%
2470
27%
760
69%
760
46%
1179
December1st to 10thNight
55%
760
25%
2579
18%
760
66%
760
40%
1291
December11th to 20thNight
52%
760
23%
3170
22%
758
60%
758
26%
1704
December21st to endNight
45%
827
14%
4770
17%
817
55%
817
16%
2670

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
232342445%7%64%
78453
Night
242442445%7%62%
80761
TransparencyDay
21%6%11%18%24%20%
78157
Night
22%6%11%22%24%15%
80579
SeeingDay
7%15%29%30%16%4
14032
Night
46%25%38%22%5%
23638

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
1427%6%35%5%6%10%51%
2539
11th to 20thDay
15%37%6%45%5%6%8%50%
2540
21st to endDay
38%35%5%45%6%7%9%45%
3115
February1st to 10thDay
24145%2445%8%61%
1826
11th to 20thDay
24245%3445%10%56%
1841
21st to endDay
12244345%6%8%59%
1480
March1st to 10thDay
15%344346%6%10%55%
1800
11th to 20thDay
14244245%7%11%56%
1855
21st to endDay
2324425%5%6%9%57%
2376
April1st to 10thDay
24244346%5%8%59%
2160
11th to 20thDay
34244345%5%6%61%
2129
21st to endDay
332332445%7%63%
2160
May1st to 10thDay
23134335%47%66%
2326
11th to 20thDay
3313435%447%62%
2301
21st to endDay
5%425%4345%5%8%55%
2721
June1st to 10thDay
3313425%447%63%
2520
11th to 20thDay
2212223346%73%
2520
21st to endDay
2112323335%75%
2520
July1st to 10thDay
3213424435%70%
2520
11th to 20thDay
33235%34346%65%
2520
21st to endDay
4223425%6%5%7%61%
2741
August1st to 10thDay
331332444468%
2213
11th to 20thDay
211222334475%
2122
21st to endDay
211221222380%
2376
September1st to 10thDay
221221223479%
2160
11th to 20thDay
1212212335%78%
2070
21st to endDay
1212212235%80%
1980
October1st to 10thDay
4212223345%73%
1936
11th to 20thDay
1212212245%78%
1800
21st to endDay
2112212345%77%
1874
November1st to 10thDay
221332345%7%67%
1674
11th to 20thDay
321121346%8%70%
1710
21st to endDay
1424323449%65%
1710
December1st to 10thDay
132332346%8%65%
1596
11th to 20thDay
1425%5%47%7%8%11%44%
1928
21st to endDay
17%36%5%36%6%6%10%47%
2794
January1st to 10thNight
17%37%5%345%5%8%54%
4406
11th to 20thNight
16%35%5%36%7%6%9%48%
4420
21st to endNight
47%25%4345%7%9%48%
4548
February1st to 10thNight
16%35%434447%60%
2352
11th to 20thNight
242442445%9%59%
2211
21st to endNight
325%3335%5%8%61%
1776
March1st to 10thNight
25%25%435%5%6%8%55%
2160
11th to 20thNight
2423335%5%6%9%59%
2101
21st to endNight
35%243345%47%60%
1980
April1st to 10thNight
242342445%7%62%
1800
11th to 20thNight
2424324445%66%
1779
21st to endNight
35%23322436%67%
1800
May1st to 10thNight
42244345%5%8%60%
1634
11th to 20thNight
3424433446%62%
1593
21st to endNight
6%42442345%6%60%
1552
June1st to 10thNight
2222434446%66%
1440
11th to 20thNight
2111213245%77%
1440
21st to endNight
111242234475%
1440
July1st to 10thNight
1112323446%73%
1440
11th to 20thNight
1223423447%67%
1440
21st to endNight
33144345%6%7%60%
1576
August1st to 10thNight
3313323446%67%
1722
11th to 20thNight
213222236%75%
1780
21st to endNight
31221234478%
1980
September1st to 10thNight
211221234478%
1800
11th to 20thNight
2112322445%74%
1889
21st to endNight
3212212335%77%
1980
October1st to 10thNight
321231243473%
2020
11th to 20thNight
1212212345%78%
2160
21st to endNight
1212222335%77%
2480
November1st to 10thNight
2313213337%72%
2405
11th to 20thNight
1313324446%72%
2470
21st to endNight
232342445%7%66%
2470
December1st to 10thNight
24144245%5%8%62%
2579
11th to 20thNight
25%36%5%35%6%7%11%49%
3276
21st to endNight
16%36%7%47%7%7%10%42%
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
27%9%20%30%13%1
2539
11th to 20thDay
31%9%14%23%18%4
2540
21st to endDay
33%9%17%22%16%3
3115
February1st to 10thDay
23%7%14%25%22%9%
1826
11th to 20thDay
25%6%12%24%25%8%
1851
21st to endDay
22%7%16%25%24%6%
1480
March1st to 10thDay
25%9%13%27%21%5%
1800
11th to 20thDay
23%7%15%23%25%7%
1855
21st to endDay
23%9%18%27%18%5%
2376
April1st to 10thDay
25%7%12%24%22%9%
2160
11th to 20thDay
23%6%11%21%26%12%
2132
21st to endDay
21%7%12%26%27%8%
2160
May1st to 10thDay
20%6%9%22%32%11%
2326
11th to 20thDay
23%6%10%22%29%10%
2304
21st to endDay
29%8%9%21%25%9%
2722
June1st to 10thDay
22%6%9%16%29%18%
2520
11th to 20thDay
13%48%15%30%30%
2520
21st to endDay
14%36%9%26%42%
2520
July1st to 10thDay
17%46%8%18%47%
2451
11th to 20thDay
20%46%9%18%43%
2445
21st to endDay
22%5%7%10%20%36%
2589
August1st to 10thDay
19%37%9%16%45%
2196
11th to 20thDay
13%35%7%23%48%
2122
21st to endDay
12%25%6%25%50%
2376
September1st to 10thDay
12%35%6%24%49%
2160
11th to 20thDay
11%37%12%33%34%
2070
21st to endDay
11%36%13%34%34%
1980
October1st to 10thDay
16%48%14%32%26%
1936
11th to 20thDay
12%35%19%37%24%
1800
21st to endDay
11%47%22%37%18%
1874
November1st to 10thDay
18%5%11%21%32%12%
1674
11th to 20thDay
13%7%12%24%35%9%
1710
21st to endDay
20%5%12%25%29%9%
1710
December1st to 10thDay
18%8%15%26%26%7%
1596
11th to 20thDay
31%13%14%22%15%5%
1928
21st to endDay
30%12%21%21%15%3
2794
January1st to 10thNight
29%9%15%29%16%2
4406
11th to 20thNight
31%8%16%26%15%4
4420
21st to endNight
30%10%15%27%14%3
4548
February1st to 10thNight
26%6%12%27%21%7%
2352
11th to 20thNight
23%7%12%26%25%7%
2212
21st to endNight
22%6%16%27%22%6%
1776
March1st to 10thNight
27%7%13%23%23%6%
2160
11th to 20thNight
22%6%14%25%25%8%
2101
21st to endNight
23%8%17%28%19%5%
1980
April1st to 10thNight
24%7%12%29%19%9%
1800
11th to 20thNight
21%7%10%27%25%11%
1779
21st to endNight
21%6%11%31%26%5%
1800
May1st to 10thNight
23%6%9%20%34%8%
1634
11th to 20thNight
24%6%9%22%31%9%
1594
21st to endNight
25%8%11%24%26%7%
1552
June1st to 10thNight
19%7%8%22%28%16%
1440
11th to 20thNight
11%5%5%17%35%28%
1440
21st to endNight
13%36%13%26%38%
1440
July1st to 10thNight
12%48%11%23%43%
1400
11th to 20thNight
17%47%11%22%39%
1392
21st to endNight
21%5%8%11%20%35%
1488
August1st to 10thNight
19%36%12%18%42%
1714
11th to 20thNight
12%25%12%27%42%
1780
21st to endNight
12%25%9%27%44%
1980
September1st to 10thNight
10%36%9%26%47%
1800
11th to 20thNight
13%47%14%28%34%
1889
21st to endNight
13%3413%33%34%
1980
October1st to 10thNight
17%38%16%30%26%
2020
11th to 20thNight
11%37%21%34%24%
2160
21st to endNight
11%46%23%38%18%
2480
November1st to 10thNight
15%6%9%28%29%13%
2405
11th to 20thNight
15%7%11%26%33%8%
2470
21st to endNight
20%5%12%25%30%9%
2470
December1st to 10thNight
22%7%14%26%25%6%
2579
11th to 20thNight
28%9%17%23%17%6%
3276
21st to endNight
34%11%16%19%17%3
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
7%19%34%31%8%1
180
11th to 20thDay
5%16%33%28%15%3
180
21st to endDay
7%11%28%32%19%3
389
February1st to 10thDay
6%18%33%26%11%6%
426
11th to 20thDay
10%15%34%28%13%1
452
21st to endDay
12%18%33%27%9%1
346
March1st to 10thDay
10%16%36%28%8%2
420
11th to 20thDay
8%20%36%21%11%3
420
21st to endDay
12%22%35%25%6%
462
April1st to 10thDay
10%25%32%22%9%2
420
11th to 20thDay
14%22%33%20%9%3
412
21st to endDay
14%19%29%24%11%3
420
May1st to 10thDay
11%24%31%21%10%3
423
11th to 20thDay
10%22%27%24%13%3
448
21st to endDay
15%15%24%24%17%5%
485
June1st to 10thDay
9%16%27%28%15%5%
450
11th to 20thDay
8%19%30%24%15%4
450
21st to endDay
315%30%31%17%4
450
July1st to 10thDay
410%25%33%21%6%
446
11th to 20thDay
47%22%36%26%4
444
21st to endDay
46%26%36%21%7%
487
August1st to 10thDay
6%10%29%32%19%4
447
11th to 20thDay
5%11%26%28%24%5%
437
21st to endDay
37%28%38%19%6%
495
September1st to 10thDay
39%25%37%21%4
450
11th to 20thDay
412%29%36%16%3
450
21st to endDay
411%25%40%18%1
450
October1st to 10thDay
5%16%29%31%18%1
450
11th to 20thDay
5%10%28%34%18%3
450
21st to endDay
7%13%26%28%22%5%
389
November1st to 10thDay
6%10%26%30%24%4
270
11th to 20thDay
5%12%24%32%19%8%
270
21st to endDay
6%6%31%37%19%2
270
December1st to 10thDay
9%10%25%33%17%6%
216
11th to 20thDay
6%11%39%24%17%4
180
21st to endDay
6%20%26%36%9%3
198
January1st to 10thNight
46%34%30%17%9%
760
11th to 20thNight
26%29%38%19%7%
760
21st to endNight
5%6%28%36%17%6%
836
February1st to 10thNight
5%7%31%35%18%5%
760
11th to 20thNight
49%27%37%17%5%
742
21st to endNight
38%36%37%12%3
592
March1st to 10thNight
411%31%35%16%4
720
11th to 20thNight
310%28%33%20%5%
720
21st to endNight
5%11%33%33%16%2
792
April1st to 10thNight
6%11%28%37%15%3
720
11th to 20thNight
5%14%28%32%16%5%
711
21st to endNight
5%11%28%34%19%4
720
May1st to 10thNight
6%12%29%34%16%3
554
11th to 20thNight
5%10%29%35%20%2
530
21st to endNight
8%5%27%36%22%2
389
June1st to 10thNight
35%20%46%25%2
360
11th to 20thNight
35%21%46%23%2
360
21st to endNight
1418%50%25%2
360
July1st to 10thNight
2114%49%32%2
350
11th to 20thNight
3111%56%28%1
348
21st to endNight
2211%52%33%1
394
August1st to 10thNight
4219%43%28%3
648
11th to 20thNight
3214%48%29%4
712
21st to endNight
4215%40%36%3
792
September1st to 10thNight
2316%40%32%7%
720
11th to 20thNight
3416%42%29%6%
720
21st to endNight
4417%36%33%7%
720
October1st to 10thNight
4418%47%21%7%
720
11th to 20thNight
35%18%42%27%6%
720
21st to endNight
3423%32%27%11%
792
November1st to 10thNight
45%20%37%26%8%
740
11th to 20thNight
2427%41%20%6%
760
21st to endNight
35%27%37%23%5%
760
December1st to 10thNight
46%29%36%19%6%
760
11th to 20thNight
5%7%31%37%16%5%
760
21st to endNight
410%34%33%16%3
836
Page generated at 2024-02-17 03:28:41. Version ac07

Copyright 2024 Attilla Danko


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