Richfield Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Richfield Observatory clear sky chart from 2005-11-06 to 2024-02-10.

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
34%
24821
17%
80372
10%
24724
42%
24724
21%
54104

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
20%
941
13%
4371
4%
926
29%
926
10%
3067
January11th to 20thNight
16%
947
11%
4369
3%
930
25%
930
8%
3360
January21st to endNight
18%
1038
8%
4827
3%
1023
26%
1023
9%
3672
February1st to 10thNight
20%
948
14%
2464
3%
948
28%
948
18%
1779
February11th to 20thNight
22%
710
20%
2108
7%
709
33%
709
18%
1407
February21st to endNight
16%
592
18%
1776
4%
592
29%
592
17%
1236
March1st to 10thNight
25%
720
15%
2160
7%
720
33%
720
19%
1470
March11th to 20thNight
30%
694
21%
2119
11%
694
40%
694
25%
1320
March21st to endNight
33%
594
18%
1980
14%
594
40%
594
18%
1372
April1st to 10thNight
26%
540
14%
1800
8%
540
36%
540
18%
1221
April11th to 20thNight
30%
533
20%
1775
13%
533
41%
533
19%
1189
April21st to endNight
35%
540
17%
1683
9%
540
43%
540
23%
1115
May1st to 10thNight
34%
540
16%
1603
10%
540
39%
540
23%
1100
May11th to 20thNight
38%
531
19%
1416
9%
531
46%
531
26%
961
May21st to endNight
48%
583
16%
1552
9%
582
53%
582
31%
1022
June1st to 10thNight
52%
540
16%
1440
9%
540
57%
540
36%
892
June11th to 20thNight
48%
540
18%
1440
10%
540
53%
540
34%
917
June21st to endNight
52%
540
18%
1440
10%
540
56%
540
35%
893
July1st to 10thNight
68%
525
18%
1400
12%
525
69%
525
44%
808
July11th to 20thNight
60%
522
21%
1392
14%
522
64%
522
42%
799
July21st to endNight
65%
591
21%
1487
15%
558
69%
558
43%
870
August1st to 10thNight
66%
537
23%
1423
18%
534
68%
534
41%
851
August11th to 20thNight
65%
534
21%
1723
20%
534
70%
534
37%
942
August21st to endNight
61%
594
23%
1980
22%
594
67%
594
34%
1098
September1st to 10thNight
57%
540
24%
1800
23%
540
64%
540
34%
1005
September11th to 20thNight
56%
621
29%
1881
25%
621
62%
621
37%
1076
September21st to endNight
45%
720
24%
1980
15%
720
51%
720
31%
1249
October1st to 10thNight
43%
720
23%
2052
15%
720
48%
720
30%
1291
October11th to 20thNight
29%
720
20%
2182
9%
720
40%
720
23%
1426
October21st to endNight
30%
792
16%
2574
10%
792
38%
792
19%
1731
November1st to 10thNight
31%
740
25%
2406
14%
740
44%
740
25%
1454
November11th to 20thNight
22%
760
18%
2470
8%
760
35%
760
17%
1667
November21st to endNight
21%
898
17%
2608
6%
898
32%
898
20%
1784
December1st to 10thNight
18%
950
14%
2660
4%
950
27%
950
16%
1923
December11th to 20thNight
18%
950
13%
3210
2%
948
26%
948
12%
2373
December21st to endNight
13%
1036
7%
4821
2%
1026
22%
1026
7%
3764

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
13%9%47%6%35%5%5%7%36%
78161
Night
13%9%47%5%345%5%7%37%
80858
TransparencyDay
47%5%12%23%12%1
77862
Night
47%411%23%13%2
80678
SeeingDay
17%11%30%26%13%5%
14804
Night
18%10%31%28%12%1
24852

By Month

Percentage Cloud Cover SE (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%14%8%11%7%45%445%28%
2527
11th to 20thDay
11%12%6%15%7%35%9%6%6%20%
2530
21st to endDay
18%17%9%11%5%24446%21%
2794
February1st to 10thDay
9%13%6%9%6%35%6%5%7%31%
1701
11th to 20thDay
14%10%48%5%46%447%35%
1737
21st to endDay
11%15%5%10%6%46%5%46%29%
1480
March1st to 10thDay
13%11%6%6%6%35%6%5%6%33%
1800
11th to 20thDay
12%9%37%7%345%5%7%38%
1856
21st to endDay
18%12%47%6%44447%30%
2376
April1st to 10thDay
18%11%5%6%5%445%5%7%29%
2160
11th to 20thDay
16%10%46%6%35%45%6%33%
2134
21st to endDay
18%10%36%5%36%6%5%7%32%
2276
May1st to 10thDay
16%10%37%6%35%5%7%8%31%
2353
11th to 20thDay
17%7%36%6%3445%7%36%
2479
21st to endDay
13%7%36%5%45%5%6%8%38%
2725
June1st to 10thDay
9%5%36%5%35%5%6%9%45%
2520
11th to 20thDay
11%5%25%5%35%5%6%9%43%
2520
21st to endDay
10%5%35%5%45%6%7%9%42%
2520
July1st to 10thDay
7%435%5%35%6%7%10%46%
2520
11th to 20thDay
7%5%25%5%45%5%6%10%45%
2520
21st to endDay
6%5%245%36%6%7%10%47%
2743
August1st to 10thDay
7%425%5%46%8%7%10%42%
2507
11th to 20thDay
11%6%25%6%45%6%7%9%40%
2173
21st to endDay
11%5%36%5%35%6%6%8%43%
2376
September1st to 10thDay
11%6%26%5%35%6%6%6%43%
2160
11th to 20thDay
12%5%24435%36%8%47%
2060
21st to endDay
12%7%26%6%35%5%5%7%42%
1980
October1st to 10thDay
14%7%35%5%34448%43%
1904
11th to 20thDay
20%10%37%6%3446%6%31%
1777
21st to endDay
18%9%47%5%35%5%5%5%35%
1782
November1st to 10thDay
11%9%46%5%35%45%6%43%
1672
11th to 20thDay
11%10%5%8%8%45%5%6%8%31%
1710
21st to endDay
16%12%36%6%34446%36%
1568
December1st to 10thDay
12%13%49%8%36%45%8%28%
1520
11th to 20thDay
11%14%5%8%7%46%5%6%7%28%
1918
21st to endDay
18%19%10%12%5%33445%15%
2783
January1st to 10thNight
13%13%7%10%5%34445%32%
4428
11th to 20thNight
12%13%7%14%7%45%6%7%6%19%
4440
21st to endNight
15%16%8%11%6%35%445%23%
4870
February1st to 10thNight
11%13%5%9%6%445%5%5%34%
2464
11th to 20thNight
12%9%47%6%36%5%46%38%
2107
21st to endNight
16%11%5%7%6%3445%5%34%
1776
March1st to 10thNight
16%9%46%6%35%5%6%6%36%
2160
11th to 20thNight
12%7%36%5%35%5%6%8%42%
2119
21st to endNight
18%9%47%6%445%46%34%
1980
April1st to 10thNight
17%9%47%5%345%6%6%35%
1800
11th to 20thNight
20%9%36%5%3445%5%37%
1775
21st to endNight
17%8%35%435%5%5%7%37%
1683
May1st to 10thNight
15%8%46%5%35%5%6%8%33%
1603
11th to 20thNight
16%7%26%4445%5%7%39%
1416
21st to endNight
11%7%35%5%35%5%6%10%40%
1551
June1st to 10thNight
10%4245%4446%8%48%
1440
11th to 20thNight
10%5%35%435%6%6%8%46%
1440
21st to endNight
9%6%35%5%3445%8%49%
1440
July1st to 10thNight
6%3245%335%6%10%53%
1440
11th to 20thNight
5%325%4345%6%8%55%
1440
21st to endNight
5%4135%36%6%6%9%52%
1575
August1st to 10thNight
6%325%5%35%6%6%9%50%
1432
11th to 20thNight
9%42443445%9%52%
1723
21st to endNight
8%5%245%345%5%7%53%
1980
September1st to 10thNight
9%5%25%43435%7%53%
1800
11th to 20thNight
11%424424447%53%
1881
21st to endNight
11%7%35%444347%48%
1980
October1st to 10thNight
13%7%25%5%3445%5%48%
2052
11th to 20thNight
17%8%36%425%447%40%
2182
21st to endNight
18%10%35%5%35%45%7%35%
2574
November1st to 10thNight
12%7%35%5%3345%7%46%
2406
11th to 20thNight
13%10%47%6%45%5%5%7%34%
2470
21st to endNight
16%8%46%5%3445%6%38%
2608
December1st to 10thNight
14%11%48%7%4445%7%32%
2660
11th to 20thNight
14%13%5%9%7%45%5%46%29%
3279
21st to endNight
20%18%6%9%6%45%5%45%20%
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
59%413%17%7%
2528
11th to 20thDay
62%411%19%5%
2530
21st to endDay
66%39%17%5%
2794
February1st to 10thDay
52%412%21%10%1
1701
11th to 20thDay
50%410%22%12%2
1747
21st to endDay
58%39%17%11%2
1480
March1st to 10thDay
52%5%11%22%8%2
1800
11th to 20thDay
46%5%11%21%14%2
1856
21st to endDay
56%413%19%7%1
2376
April1st to 10thDay
54%5%11%19%11%
2160
11th to 20thDay
51%5%10%20%13%3
2134
21st to endDay
50%6%13%18%12%1
2276
May1st to 10thDay
49%5%12%24%9%1
2353
11th to 20thDay
47%5%13%23%12%1
2483
21st to endDay
43%6%12%23%14%2
2725
June1st to 10thDay
35%6%13%28%15%2
2520
11th to 20thDay
37%5%14%25%17%1
2520
21st to endDay
37%7%15%24%16%1
2520
July1st to 10thDay
32%6%14%32%14%3
2451
11th to 20thDay
33%6%14%28%16%2
2445
21st to endDay
30%7%16%27%16%4
2591
August1st to 10thDay
35%7%17%27%13%2
2492
11th to 20thDay
38%6%15%27%13%1
2173
21st to endDay
37%6%12%26%18%2
2376
September1st to 10thDay
40%6%10%27%16%1
2160
11th to 20thDay
36%5%11%32%15%1
2060
21st to endDay
42%411%30%13%
1980
October1st to 10thDay
42%49%29%15%1
1904
11th to 20thDay
53%411%21%11%1
1777
21st to endDay
50%412%21%11%1
1782
November1st to 10thDay
42%413%25%15%2
1672
11th to 20thDay
51%413%22%9%1
1710
21st to endDay
50%213%25%8%1
1568
December1st to 10thDay
54%316%19%7%1
1520
11th to 20thDay
55%314%18%8%2
1915
21st to endDay
71%39%11%5%
2783
January1st to 10thNight
57%39%20%10%1
4428
11th to 20thNight
64%310%13%8%
4440
21st to endNight
64%311%15%6%
4870
February1st to 10thNight
52%310%19%13%2
2464
11th to 20thNight
47%410%22%16%2
2108
21st to endNight
52%311%20%13%3
1776
March1st to 10thNight
48%5%14%20%11%2
2160
11th to 20thNight
40%413%24%16%3
2119
21st to endNight
52%49%23%10%2
1980
April1st to 10thNight
48%5%9%20%16%1
1800
11th to 20thNight
49%37%19%18%3
1775
21st to endNight
45%412%22%14%2
1683
May1st to 10thNight
46%6%12%23%12%1
1603
11th to 20thNight
43%6%12%24%14%2
1417
21st to endNight
39%5%14%24%14%3
1552
June1st to 10thNight
33%5%14%28%18%2
1440
11th to 20thNight
35%6%9%27%20%2
1440
21st to endNight
34%5%16%25%18%2
1440
July1st to 10thNight
26%6%15%31%19%4
1400
11th to 20thNight
27%5%13%31%19%4
1392
21st to endNight
26%7%16%27%18%5%
1487
August1st to 10thNight
30%5%17%29%16%3
1423
11th to 20thNight
29%5%17%32%16%1
1723
21st to endNight
31%411%30%20%3
1980
September1st to 10thNight
31%6%12%26%24%2
1800
11th to 20thNight
32%410%35%17%1
1881
21st to endNight
38%49%31%16%1
1980
October1st to 10thNight
38%49%30%17%2
2052
11th to 20thNight
44%412%23%16%1
2182
21st to endNight
49%5%12%23%11%1
2574
November1st to 10thNight
39%410%27%17%2
2406
11th to 20thNight
48%5%12%22%11%2
2470
21st to endNight
48%414%23%9%1
2608
December1st to 10thNight
53%412%21%9%1
2660
11th to 20thNight
56%5%11%18%9%1
3281
21st to endNight
66%410%14%5%
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
18%15%39%21%6%1
270
11th to 20thDay
18%19%34%23%6%1
270
21st to endDay
24%13%38%20%41
297
February1st to 10thDay
12%19%45%17%5%1
267
11th to 20thDay
20%25%35%14%5%
240
21st to endDay
20%25%41%14%1
198
March1st to 10thDay
19%23%40%15%3
240
11th to 20thDay
23%19%28%21%7%2
253
21st to endDay
27%13%29%22%7%2
462
April1st to 10thDay
27%11%36%21%6%
420
11th to 20thDay
23%19%25%22%9%3
412
21st to endDay
24%10%29%23%13%1
420
May1st to 10thDay
22%10%35%22%8%3
436
11th to 20thDay
21%11%32%24%9%3
625
21st to endDay
17%8%29%27%13%6%
679
June1st to 10thDay
9%9%32%31%15%5%
630
11th to 20thDay
13%9%28%31%14%5%
630
21st to endDay
12%7%31%31%15%4
630
July1st to 10thDay
9%220%32%25%11%
621
11th to 20thDay
9%6%27%33%20%6%
618
21st to endDay
6%429%37%18%7%
684
August1st to 10thDay
8%323%36%19%11%
626
11th to 20thDay
11%416%30%25%14%
443
21st to endDay
13%6%20%30%21%10%
495
September1st to 10thDay
15%6%24%28%20%8%
450
11th to 20thDay
13%322%30%22%10%
450
21st to endDay
16%12%23%26%17%6%
450
October1st to 10thDay
21%9%24%28%13%6%
374
11th to 20thDay
24%18%32%16%9%
270
21st to endDay
28%13%38%15%41
297
November1st to 10thDay
17%17%33%22%9%1
270
11th to 20thDay
16%21%36%20%7%
270
21st to endDay
24%11%42%19%5%
270
December1st to 10thDay
21%18%41%13%6%1
270
11th to 20thDay
19%19%37%17%8%1
270
21st to endDay
24%21%35%16%4
297
January1st to 10thNight
18%18%35%22%6%
950
11th to 20thNight
21%15%37%20%7%1
950
21st to endNight
20%11%37%25%6%
1045
February1st to 10thNight
18%15%36%25%5%
948
11th to 20thNight
18%17%35%25%5%
712
21st to endNight
25%15%38%18%5%1
592
March1st to 10thNight
20%13%34%24%8%1
720
11th to 20thNight
17%13%36%27%7%1
694
21st to endNight
22%7%29%32%7%2
594
April1st to 10thNight
23%11%34%25%7%
540
11th to 20thNight
26%9%32%25%7%1
533
21st to endNight
21%8%31%29%10%1
540
May1st to 10thNight
19%7%33%34%7%1
540
11th to 20thNight
20%6%29%31%14%1
531
21st to endNight
13%325%38%19%2
584
June1st to 10thNight
11%427%41%17%1
540
11th to 20thNight
14%330%36%15%1
540
21st to endNight
11%425%42%18%1
540
July1st to 10thNight
8%217%40%30%4
525
11th to 20thNight
6%223%43%24%2
522
21st to endNight
8%121%46%24%2
591
August1st to 10thNight
7%216%45%27%3
537
11th to 20thNight
11%115%38%29%5%
534
21st to endNight
11%317%40%26%3
594
September1st to 10thNight
10%322%35%25%5%
540
11th to 20thNight
13%322%31%26%5%
621
21st to endNight
15%8%24%27%22%4
720
October1st to 10thNight
16%8%26%30%17%2
720
11th to 20thNight
21%11%33%25%8%1
720
21st to endNight
23%10%31%27%8%1
792
November1st to 10thNight
16%12%38%23%11%1
740
11th to 20thNight
19%17%35%22%7%
760
21st to endNight
21%13%37%21%7%
898
December1st to 10thNight
23%15%37%21%4
950
11th to 20thNight
22%13%37%21%6%1
950
21st to endNight
29%14%35%18%3
1045
Page generated at 2024-02-07 05:11:54. Version ac07

Copyright 2024 Attilla Danko


Richfield Observatory Clear Sky Chart |Charts Home