Observatory on the Ridge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatory on the Ridge clear sky chart from 2005-11-06 to 2024-08-30.

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
30%
23592
4%
92082
3%
23404
31%
23404
4%
79051

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
9%
754
3%
4420
2%
737
11%
737
1%
4009
January11th to 20thNight
11%
759
2%
4169
1%
740
13%
740
1%
3863
January21st to endNight
12%
832
1%
4531
1%
814
14%
814
1%
4269
February1st to 10thNight
10%
760
2%
2470
1%
760
12%
760
1%
2319
February11th to 20thNight
14%
743
3%
2405
1%
740
17%
740
3%
2199
February21st to endNight
14%
628
2%
1965
0%
628
16%
628
3%
1815
March1st to 10thNight
21%
756
13%
3391
3%
743
23%
743
3%
2673
March11th to 20thNight
21%
758
5%
3472
1%
740
24%
740
3%
2844
March21st to endNight
25%
835
5%
3691
2%
814
27%
814
4%
2622
April1st to 10thNight
24%
760
4%
1924
1%
760
25%
760
4%
1794
April11th to 20thNight
29%
742
3%
1866
1%
742
30%
742
6%
1679
April21st to endNight
34%
570
5%
1710
3%
570
36%
570
6%
1495
May1st to 10thNight
39%
565
7%
2786
2%
559
41%
559
3%
2294
May11th to 20thNight
42%
395
3%
2513
2%
389
44%
389
2%
1945
May21st to endNight
48%
404
5%
2713
3%
399
51%
399
3%
1847
June1st to 10thNight
44%
380
4%
1520
5%
380
47%
380
4%
1320
June11th to 20thNight
50%
380
3%
1520
4%
380
52%
380
5%
1298
June21st to endNight
47%
380
4%
1520
4%
380
50%
380
6%
1298
July1st to 10thNight
57%
364
9%
2325
8%
360
59%
360
5%
1660
July11th to 20thNight
51%
362
6%
2183
10%
358
53%
358
4%
1603
July21st to endNight
54%
597
4%
2680
4%
558
53%
558
6%
1960
August1st to 10thNight
61%
567
8%
1690
7%
564
62%
564
10%
1389
August11th to 20thNight
57%
564
6%
1688
4%
564
58%
564
7%
1450
August21st to endNight
55%
737
7%
1985
4%
737
57%
737
10%
1682
September1st to 10thNight
51%
720
6%
1800
3%
720
51%
720
9%
1563
September11th to 20thNight
54%
720
10%
1880
7%
720
55%
720
10%
1594
September21st to endNight
45%
720
8%
2030
7%
720
45%
720
7%
1758
October1st to 10thNight
38%
720
6%
2160
5%
720
39%
720
7%
1878
October11th to 20thNight
25%
720
4%
2160
3%
720
27%
720
5%
1941
October21st to endNight
19%
792
4%
2376
2%
792
22%
792
3%
2174
November1st to 10thNight
29%
740
5%
2416
3%
740
32%
740
4%
2169
November11th to 20thNight
20%
760
4%
2660
1%
760
23%
760
4%
2349
November21st to endNight
16%
760
2%
2660
0%
760
18%
760
2%
2432
December1st to 10thNight
12%
760
2%
2660
1%
760
12%
760
2%
2482
December11th to 20thNight
11%
759
2%
3281
0%
759
14%
759
1%
2974
December21st to endNight
10%
829
1%
4862
0%
817
13%
817
1%
4410

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%11%49%5%4445%7%31%
95737
Night
18%12%49%5%4445%6%29%
93306
TransparencyDay
27%52%7%9%5%
95465
Night
29%52%6%8%4
93131
SeeingDay
20%15%27%22%11%3
14263
Night
23%14%27%24%11%1
23662

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
18%24%7%11%7%5%4345%13%
2517
11th to 20thDay
13%23%7%23%9%5%32348%
2781
21st to endDay
23%19%8%12%7%5%434311%
3124
February1st to 10thDay
17%18%5%14%8%5%5%445%13%
1710
11th to 20thDay
14%18%6%14%8%5%444418%
1663
21st to endDay
21%13%413%9%44445%18%
1485
March1st to 10thDay
19%13%48%5%44346%29%
3432
11th to 20thDay
11%18%5%9%5%45%35%6%29%
3480
21st to endDay
18%11%410%5%4445%6%30%
3815
April1st to 10thDay
18%14%47%45%3445%31%
2255
11th to 20thDay
19%10%26%45%435%6%35%
2279
21st to endDay
20%11%37%5%4444434%
2470
May1st to 10thDay
20%9%37%5%5%5%45%7%31%
4108
11th to 20thDay
13%10%49%6%6%5%5%6%7%30%
4356
21st to endDay
11%7%26%43446%8%45%
4837
June1st to 10thDay
14%8%26%5%45%47%7%38%
2660
11th to 20thDay
12%427%5%5%5%47%9%40%
2660
21st to endDay
14%6%35%44446%7%43%
2660
July1st to 10thDay
9%5%25%445%46%9%45%
4440
11th to 20thDay
12%6%25%445%47%9%42%
4440
21st to endDay
7%5%27%5%5%6%47%9%43%
4474
August1st to 10thDay
10%5%26%445%47%10%42%
2457
11th to 20thDay
10%5%27%5%5%6%47%10%38%
2433
21st to endDay
12%5%25%44447%9%44%
2561
September1st to 10thDay
14%6%26%44446%7%41%
2160
11th to 20thDay
12%5%25%44446%8%46%
2076
21st to endDay
15%7%38%5%6%5%46%8%34%
1929
October1st to 10thDay
20%8%37%5%45%45%6%34%
1800
11th to 20thDay
20%10%410%5%45%45%6%28%
1800
21st to endDay
25%13%5%9%6%44345%21%
1980
November1st to 10thDay
15%10%38%6%5%5%45%6%32%
1657
11th to 20thDay
16%13%48%6%45%35%7%29%
1520
21st to endDay
22%16%310%5%4446%7%20%
1520
December1st to 10thDay
20%20%5%11%6%5%445%6%14%
1520
11th to 20thDay
20%20%6%12%5%45%445%15%
1906
21st to endDay
27%24%6%11%5%4323312%
2772
January1st to 10thNight
20%22%6%11%6%5%434416%
4429
11th to 20thNight
15%20%6%17%8%7%5%35%49%
4175
21st to endNight
25%20%6%13%6%4323312%
4532
February1st to 10thNight
19%18%6%13%6%44345%18%
2470
11th to 20thNight
17%15%5%11%6%5%6%45%6%20%
2403
21st to endNight
20%15%413%7%5%435%5%19%
1965
March1st to 10thNight
21%13%39%5%4433432%
3408
11th to 20thNight
19%16%38%444346%28%
3479
21st to endNight
17%9%27%43435%6%40%
3817
April1st to 10thNight
22%12%38%5%44345%31%
1924
11th to 20thNight
18%9%37%5%5%435%6%35%
1866
21st to endNight
18%9%37%5%46%46%6%34%
1710
May1st to 10thNight
22%10%37%5%44346%31%
2833
11th to 20thNight
13%7%38%5%6%5%47%9%34%
2534
21st to endNight
12%6%26%445%45%9%44%
2738
June1st to 10thNight
13%7%37%5%6%5%5%7%7%36%
1520
11th to 20thNight
11%6%26%6%5%5%46%8%42%
1520
21st to endNight
14%6%35%5%5%5%45%8%39%
1520
July1st to 10thNight
8%6%27%5%45%46%9%44%
2520
11th to 20thNight
12%5%36%44446%9%44%
2520
21st to endNight
10%426%5%5%5%47%8%45%
3075
August1st to 10thNight
8%6%26%446%46%9%44%
1701
11th to 20thNight
10%6%26%445%46%8%44%
1688
21st to endNight
9%5%26%5%5%5%46%9%45%
1985
September1st to 10thNight
14%7%26%43436%7%44%
1800
11th to 20thNight
13%425%33335%6%52%
1880
21st to endNight
16%7%26%5%46%47%6%37%
2030
October1st to 10thNight
19%6%27%45%435%7%38%
2160
11th to 20thNight
22%10%38%45%5%447%29%
2160
21st to endNight
26%9%37%6%5%445%6%25%
2376
November1st to 10thNight
18%10%36%44435%6%38%
2416
11th to 20thNight
16%12%48%6%5%5%35%7%29%
2660
21st to endNight
20%13%410%5%5%5%45%7%22%
2660
December1st to 10thNight
22%20%5%9%6%45%45%5%16%
2660
11th to 20thNight
18%21%6%11%6%44445%18%
3288
21st to endNight
30%17%5%10%5%4435%5%11%
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
48%40%6%43
2518
11th to 20thDay
53%40%431
2781
21st to endDay
49%42%6%2
3124
February1st to 10thDay
26%67%43
1710
11th to 20thDay
24%65%36%1
1672
21st to endDay
19%66%6%6%3
1485
March1st to 10thDay
32%42%6%14%5%
3435
11th to 20thDay
33%43%13%9%3
3480
21st to endDay
33%43%6%14%41
3815
April1st to 10thDay
22%66%36%2
2255
11th to 20thDay
19%66%37%41
2279
21st to endDay
20%66%45%41
2470
May1st to 10thDay
32%42%9%11%6%1
4120
11th to 20thDay
33%45%9%12%1
4360
21st to endDay
23%41%7%17%10%2
4837
June1st to 10thDay
16%67%47%6%1
2660
11th to 20thDay
14%66%6%7%6%
2660
21st to endDay
15%64%410%7%
2660
July1st to 10thDay
25%36%8%18%12%1
4370
11th to 20thDay
23%37%9%20%11%
4365
21st to endDay
22%37%12%13%14%1
4331
August1st to 10thDay
13%62%8%11%5%1
2444
11th to 20thDay
17%64%7%10%2
2433
21st to endDay
13%63%7%12%5%1
2561
September1st to 10thDay
14%65%6%10%4
2160
11th to 20thDay
11%64%5%10%8%1
2076
21st to endDay
15%64%6%11%4
1929
October1st to 10thDay
19%64%6%6%41
1800
11th to 20thDay
20%64%6%6%41
1800
21st to endDay
27%62%442
1980
November1st to 10thDay
26%60%7%5%11
1657
11th to 20thDay
24%62%6%7%2
1520
21st to endDay
27%61%7%41
1520
December1st to 10thDay
30%62%6%3
1520
11th to 20thDay
40%50%6%31
1906
21st to endDay
50%40%6%4
2772
January1st to 10thNight
47%42%6%41
4429
11th to 20thNight
51%40%5%31
4175
21st to endNight
51%41%421
4532
February1st to 10thNight
25%67%44
2470
11th to 20thNight
23%65%46%2
2405
21st to endNight
23%66%45%2
1965
March1st to 10thNight
34%41%5%15%4
3418
11th to 20thNight
37%41%10%7%31
3480
21st to endNight
25%40%8%16%10%
3817
April1st to 10thNight
23%65%36%2
1924
11th to 20thNight
17%66%46%5%1
1866
21st to endNight
16%65%5%8%5%1
1710
May1st to 10thNight
35%43%6%10%5%2
2840
11th to 20thNight
30%45%12%13%1
2535
21st to endNight
23%42%5%16%13%1
2739
June1st to 10thNight
16%66%37%7%1
1520
11th to 20thNight
15%65%49%6%1
1520
21st to endNight
16%64%48%7%1
1520
July1st to 10thNight
27%37%8%15%12%2
2480
11th to 20thNight
25%37%10%20%8%
2472
21st to endNight
24%38%11%14%12%1
2977
August1st to 10thNight
12%61%8%13%5%1
1690
11th to 20thNight
17%62%7%11%3
1688
21st to endNight
14%62%7%11%5%1
1985
September1st to 10thNight
13%65%8%9%5%1
1800
11th to 20thNight
12%64%6%10%7%1
1880
21st to endNight
15%65%5%10%5%
2030
October1st to 10thNight
18%63%5%8%6%
2160
11th to 20thNight
20%65%6%5%4
2160
21st to endNight
24%64%5%5%3
2376
November1st to 10thNight
25%60%5%5%4
2416
11th to 20thNight
22%61%5%8%2
2660
21st to endNight
26%62%6%5%1
2660
December1st to 10thNight
29%61%6%31
2660
11th to 20thNight
36%52%7%41
3288
21st to endNight
49%40%7%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
27%27%28%11%6%2
180
11th to 20thDay
27%29%28%11%31
255
21st to endDay
24%26%29%16%4
297
February1st to 10thDay
29%26%31%11%2
270
11th to 20thDay
26%29%35%10%
270
21st to endDay
29%24%35%11%1
272
March1st to 10thDay
23%20%35%17%32
460
11th to 20thDay
24%20%34%17%5%1
460
21st to endDay
28%14%32%19%6%1
506
April1st to 10thDay
23%22%31%18%6%1
460
11th to 20thDay
26%21%25%17%9%3
452
21st to endDay
25%15%31%21%7%2
460
May1st to 10thDay
26%13%27%21%10%3
463
11th to 20thDay
16%11%28%27%14%3
487
21st to endDay
14%8%30%28%15%5%
529
June1st to 10thDay
17%16%27%29%11%1
490
11th to 20thDay
12%13%23%31%17%3
490
21st to endDay
16%10%31%29%11%3
490
July1st to 10thDay
9%8%21%34%23%5%
485
11th to 20thDay
13%9%25%29%19%5%
484
21st to endDay
9%8%28%32%17%6%
532
August1st to 10thDay
12%6%22%31%21%8%
486
11th to 20thDay
14%6%23%29%21%8%
479
21st to endDay
11%7%25%30%19%8%
532
September1st to 10thDay
14%9%24%28%18%7%
450
11th to 20thDay
11%6%21%28%24%10%
450
21st to endDay
16%14%26%21%16%6%
450
October1st to 10thDay
21%13%25%17%17%6%
450
11th to 20thDay
25%19%30%19%5%2
450
21st to endDay
34%21%22%17%5%
495
November1st to 10thDay
24%18%31%18%7%2
311
11th to 20thDay
32%27%23%14%32
180
21st to endDay
33%26%29%11%1
180
December1st to 10thDay
32%26%28%9%5%
180
11th to 20thDay
32%25%26%16%2
180
21st to endDay
31%32%25%11%2
198
January1st to 10thNight
31%24%27%13%5%
760
11th to 20thNight
32%23%27%14%3
760
21st to endNight
24%17%36%18%5%
836
February1st to 10thNight
28%24%29%16%3
760
11th to 20thNight
26%21%32%18%3
743
21st to endNight
28%20%32%18%2
628
March1st to 10thNight
23%17%33%22%5%
760
11th to 20thNight
26%17%30%20%6%1
760
21st to endNight
24%12%34%20%9%1
836
April1st to 10thNight
26%15%30%24%4
760
11th to 20thNight
24%14%29%22%9%1
742
21st to endNight
23%9%27%30%9%1
570
May1st to 10thNight
21%9%23%32%13%2
570
11th to 20thNight
14%9%26%41%10%1
400
21st to endNight
13%6%27%31%21%2
411
June1st to 10thNight
14%6%30%35%15%1
380
11th to 20thNight
14%7%24%37%17%1
380
21st to endNight
14%8%25%38%14%
380
July1st to 10thNight
8%422%42%21%2
370
11th to 20thNight
12%426%36%20%2
368
21st to endNight
11%324%36%23%2
612
August1st to 10thNight
11%417%39%25%3
567
11th to 20thNight
10%6%18%33%30%3
564
21st to endNight
12%5%21%34%25%3
737
September1st to 10thNight
16%7%19%33%21%4
720
11th to 20thNight
15%6%20%28%27%5%
720
21st to endNight
19%10%22%29%18%4
720
October1st to 10thNight
21%8%28%23%18%2
720
11th to 20thNight
26%19%25%23%7%1
720
21st to endNight
32%16%28%19%4
792
November1st to 10thNight
24%15%30%23%8%1
740
11th to 20thNight
24%22%30%16%8%1
760
21st to endNight
27%22%30%16%5%
760
December1st to 10thNight
36%24%24%13%4
760
11th to 20thNight
31%25%27%15%3
760
21st to endNight
35%19%28%16%2
836
Page generated at 2024-08-27 09:49:37. Version ac07

Copyright © 2024 Attilla Danko.


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