Old Hastings Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Old Hastings Observatory clear sky chart from 2005-11-06 to 2024-10-24.

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
27%
23485
13%
95311
8%
23284
35%
23284
13%
66295

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
11%
754
8%
4408
2%
737
21%
737
4%
3435
January11th to 20thNight
15%
756
7%
4425
4%
740
22%
740
4%
3507
January21st to endNight
19%
829
8%
4547
6%
814
27%
814
6%
3626
February1st to 10thNight
13%
760
10%
2470
3%
760
22%
760
10%
1888
February11th to 20thNight
14%
743
14%
2405
4%
740
27%
740
12%
1765
February21st to endNight
17%
628
13%
1960
4%
628
29%
628
13%
1432
March1st to 10thNight
17%
757
19%
3499
7%
744
28%
744
10%
2435
March11th to 20thNight
20%
755
11%
3468
6%
740
30%
740
10%
2491
March21st to endNight
23%
834
13%
3628
7%
814
33%
814
14%
2257
April1st to 10thNight
20%
760
16%
1900
5%
760
27%
760
20%
1407
April11th to 20thNight
23%
751
18%
1875
6%
751
29%
751
21%
1348
April21st to endNight
29%
589
15%
1729
7%
589
35%
589
18%
1235
May1st to 10thNight
32%
440
18%
2579
11%
435
41%
435
11%
1593
May11th to 20thNight
33%
372
13%
2471
16%
364
50%
364
11%
1510
May21st to endNight
37%
406
12%
2722
12%
399
49%
399
15%
1443
June1st to 10thNight
33%
380
11%
1520
8%
380
45%
380
17%
982
June11th to 20thNight
41%
380
14%
1520
15%
380
50%
380
22%
873
June21st to endNight
39%
380
10%
1520
13%
380
45%
380
19%
940
July1st to 10thNight
46%
366
13%
2390
17%
360
56%
360
16%
1350
July11th to 20thNight
46%
363
12%
2155
18%
358
55%
358
16%
1250
July21st to endNight
48%
408
12%
2366
14%
383
57%
383
18%
1313
August1st to 10thNight
52%
552
17%
2504
11%
541
57%
541
20%
1526
August11th to 20thNight
52%
555
13%
2587
10%
543
59%
543
18%
1623
August21st to endNight
43%
753
15%
3089
8%
743
49%
743
22%
1818
September1st to 10thNight
43%
760
19%
1900
8%
760
48%
760
34%
1246
September11th to 20thNight
51%
760
24%
1900
12%
760
56%
760
39%
1178
September21st to endNight
41%
760
21%
2190
15%
760
47%
760
25%
1453
October1st to 10thNight
32%
760
19%
2280
13%
760
41%
760
21%
1542
October11th to 20thNight
22%
760
11%
2280
5%
760
31%
760
16%
1659
October21st to endNight
20%
805
13%
2457
5%
805
30%
805
13%
1869
November1st to 10thNight
27%
740
16%
2487
12%
740
35%
740
17%
1689
November11th to 20thNight
19%
760
15%
2660
8%
760
29%
760
13%
1914
November21st to endNight
19%
760
10%
2660
5%
760
26%
760
10%
2045
December1st to 10thNight
12%
760
7%
2660
2%
760
18%
760
7%
2154
December11th to 20thNight
13%
760
10%
3253
3%
759
22%
759
7%
2478
December21st to endNight
10%
829
5%
4847
1%
817
16%
817
4%
4021

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
17%11%48%5%4435%7%32%
101461
Night
16%12%48%5%4435%6%31%
97297
TransparencyDay
52%5%11%21%10%1
101218
Night
53%5%11%20%10%1
97159
SeeingDay
23%17%31%18%8%3
14384
Night
22%14%31%23%9%1
23576

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
16%20%6%15%5%4323323%
2517
11th to 20thDay
13%17%11%17%7%6%433416%
2520
21st to endDay
20%20%7%14%5%4233417%
3097
February1st to 10thDay
13%17%6%15%7%5%435%5%20%
1710
11th to 20thDay
12%16%6%13%5%44435%27%
1663
21st to endDay
18%16%411%6%5%4345%25%
1494
March1st to 10thDay
19%16%49%5%4425%6%27%
3308
11th to 20thDay
11%18%6%10%6%4435%6%27%
3480
21st to endDay
13%10%36%433345%45%
3896
April1st to 10thDay
21%14%48%5%34346%29%
2280
11th to 20thDay
22%11%35%44325%5%36%
2254
21st to endDay
22%12%47%5%44235%33%
2465
May1st to 10thDay
21%8%37%45%435%6%34%
4325
11th to 20thDay
18%9%38%45%5%45%8%31%
4398
21st to endDay
15%6%26%44446%8%41%
4837
June1st to 10thDay
21%8%37%6%5%5%45%8%29%
2660
11th to 20thDay
15%6%26%5%5%5%47%8%36%
2660
21st to endDay
18%7%26%5%5%446%7%34%
2660
July1st to 10thDay
13%6%38%5%6%5%47%9%35%
4440
11th to 20thDay
13%5%26%45%5%46%9%41%
4440
21st to endDay
9%6%27%45%5%5%7%8%42%
4814
August1st to 10thDay
16%8%38%5%45%46%7%34%
4106
11th to 20thDay
17%6%38%45%5%47%9%32%
4044
21st to endDay
11%6%36%5%45%5%7%9%39%
4257
September1st to 10thDay
16%7%26%5%4436%7%40%
2280
11th to 20thDay
12%6%17%5%3435%7%47%
2280
21st to endDay
18%6%27%45%5%36%7%36%
1984
October1st to 10thDay
21%9%38%434346%34%
1900
11th to 20thDay
24%12%38%5%4435%6%26%
1900
21st to endDay
28%12%48%6%43246%23%
1966
November1st to 10thDay
17%10%48%5%45%46%6%33%
1588
11th to 20thDay
16%15%5%9%6%4435%6%27%
1520
21st to endDay
22%18%6%10%6%45%335%20%
1520
December1st to 10thDay
20%22%6%11%7%5%333416%
1520
11th to 20thDay
18%17%6%10%5%44345%24%
1906
21st to endDay
26%21%5%13%43222417%
2772
January1st to 10thNight
18%18%9%12%6%5%3345%17%
4429
11th to 20thNight
13%15%6%15%10%6%6%45%5%15%
4440
21st to endNight
19%16%7%12%6%6%5%34418%
4555
February1st to 10thNight
12%17%5%11%6%5%6%45%7%21%
2470
11th to 20thNight
13%15%6%10%6%5%5%445%29%
2403
21st to endNight
14%15%49%6%4446%6%28%
1960
March1st to 10thNight
18%13%410%443345%30%
3517
11th to 20thNight
13%18%7%8%5%4435%6%27%
3479
21st to endNight
15%9%47%5%4445%6%37%
3736
April1st to 10thNight
20%12%36%5%4435%5%32%
1900
11th to 20thNight
18%10%38%444345%38%
1875
21st to endNight
19%9%47%5%45%45%7%32%
1729
May1st to 10thNight
20%9%36%5%3445%6%35%
2615
11th to 20thNight
18%8%26%5%5%436%7%36%
2495
21st to endNight
13%7%26%5%4425%8%44%
2738
June1st to 10thNight
16%8%37%5%445%7%8%34%
1520
11th to 20thNight
11%6%25%5%5%5%36%8%44%
1520
21st to endNight
16%7%37%5%45%46%7%37%
1520
July1st to 10thNight
9%5%28%6%6%6%46%8%41%
2520
11th to 20thNight
15%5%25%43435%6%48%
2520
21st to endNight
10%6%25%44446%8%48%
2739
August1st to 10thNight
12%5%26%445%46%7%46%
2820
11th to 20thNight
15%8%25%44436%7%43%
2785
21st to endNight
12%5%25%445%46%8%45%
3366
September1st to 10thNight
12%5%26%43445%8%47%
1900
11th to 20thNight
13%424345%45%7%51%
1900
21st to endNight
19%8%25%44435%5%41%
2190
October1st to 10thNight
18%7%36%45%435%6%38%
2280
11th to 20thNight
21%12%38%5%5%4345%30%
2280
21st to endNight
22%13%38%45%436%7%25%
2457
November1st to 10thNight
18%11%37%5%5%435%5%35%
2487
11th to 20thNight
18%13%48%6%4445%6%28%
2660
21st to endNight
20%15%49%5%5%5%446%22%
2660
December1st to 10thNight
20%19%6%10%5%5%445%5%16%
2660
11th to 20thNight
18%19%6%10%5%43335%24%
3288
21st to endNight
27%20%5%13%5%4333414%
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
67%310%12%6%1
2518
11th to 20thDay
71%411%8%6%1
2520
21st to endDay
73%46%11%5%2
3097
February1st to 10thDay
65%5%9%14%5%1
1710
11th to 20thDay
61%5%8%14%11%1
1672
21st to endDay
62%410%13%11%1
1494
March1st to 10thDay
59%412%14%10%1
3311
11th to 20thDay
57%412%16%9%2
3480
21st to endDay
42%38%26%17%4
3896
April1st to 10thDay
57%46%19%11%3
2280
11th to 20thDay
51%48%22%15%1
2254
21st to endDay
56%47%17%13%3
2465
May1st to 10thDay
50%5%8%24%11%2
4338
11th to 20thDay
50%7%11%21%10%1
4402
21st to endDay
41%6%13%22%16%3
4837
June1st to 10thDay
53%5%10%19%12%1
2660
11th to 20thDay
43%6%12%24%13%2
2660
21st to endDay
47%7%12%21%12%1
2660
July1st to 10thDay
44%5%14%23%13%1
4370
11th to 20thDay
38%5%14%32%10%
4365
21st to endDay
38%7%11%32%12%
4661
August1st to 10thDay
49%5%13%22%11%
4092
11th to 20thDay
47%6%14%26%8%
4083
21st to endDay
40%5%12%32%10%1
4257
September1st to 10thDay
42%7%11%27%12%1
2280
11th to 20thDay
36%5%13%30%16%1
2280
21st to endDay
46%6%13%24%11%
1984
October1st to 10thDay
52%5%11%20%11%1
1900
11th to 20thDay
58%5%14%15%7%1
1900
21st to endDay
64%410%15%7%
1966
November1st to 10thDay
51%5%14%21%7%1
1588
11th to 20thDay
57%414%15%9%1
1520
21st to endDay
67%5%10%11%7%1
1520
December1st to 10thDay
72%49%10%4
1520
11th to 20thDay
62%7%11%11%8%
1906
21st to endDay
73%26%14%4
2772
January1st to 10thNight
70%310%13%4
4429
11th to 20thNight
69%5%11%10%5%1
4440
21st to endNight
69%410%10%7%1
4555
February1st to 10thNight
61%5%12%15%7%1
2470
11th to 20thNight
57%49%20%9%
2405
21st to endNight
55%5%10%19%10%1
1960
March1st to 10thNight
56%49%20%11%1
3527
11th to 20thNight
57%5%12%17%7%1
3480
21st to endNight
45%5%9%24%16%2
3736
April1st to 10thNight
53%38%21%12%3
1900
11th to 20thNight
48%5%7%23%15%1
1875
21st to endNight
51%6%9%17%15%3
1729
May1st to 10thNight
48%5%11%20%14%2
2621
11th to 20thNight
46%7%12%24%10%2
2496
21st to endNight
39%5%13%23%19%2
2739
June1st to 10thNight
46%7%12%22%13%1
1520
11th to 20thNight
37%6%13%25%18%2
1520
21st to endNight
44%5%15%22%12%2
1520
July1st to 10thNight
40%6%14%23%16%2
2480
11th to 20thNight
38%5%12%33%13%
2472
21st to endNight
33%7%16%30%14%
2651
August1st to 10thNight
37%6%14%27%15%2
2810
11th to 20thNight
40%6%16%26%10%1
2812
21st to endNight
36%6%13%32%11%2
3366
September1st to 10thNight
35%7%15%28%14%1
1900
11th to 20thNight
32%5%15%33%14%1
1900
21st to endNight
42%6%12%28%11%
2190
October1st to 10thNight
46%5%11%23%15%
2280
11th to 20thNight
54%5%13%20%8%
2280
21st to endNight
58%6%12%14%9%
2457
November1st to 10thNight
50%5%13%23%9%
2487
11th to 20thNight
55%5%12%18%9%1
2660
21st to endNight
62%6%13%16%4
2660
December1st to 10thNight
68%6%10%13%3
2660
11th to 20thNight
64%410%15%7%1
3288
21st to endNight
75%37%11%4
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
25%25%31%14%41
180
11th to 20thDay
27%20%34%16%21
180
21st to endDay
29%19%35%14%3
291
February1st to 10thDay
29%27%33%9%3
270
11th to 20thDay
30%27%36%6%1
270
21st to endDay
35%21%34%9%1
306
March1st to 10thDay
24%22%37%14%3
460
11th to 20thDay
26%23%32%14%41
460
21st to endDay
32%20%28%13%5%1
506
April1st to 10thDay
29%19%34%13%5%
460
11th to 20thDay
35%22%22%12%8%2
452
21st to endDay
30%19%31%13%42
460
May1st to 10thDay
26%17%31%17%5%3
463
11th to 20thDay
22%16%35%19%6%3
487
21st to endDay
18%19%31%20%9%3
529
June1st to 10thDay
24%13%34%21%7%1
490
11th to 20thDay
16%16%35%21%10%2
490
21st to endDay
22%13%34%19%9%2
490
July1st to 10thDay
13%9%34%28%13%2
485
11th to 20thDay
13%13%33%24%13%4
484
21st to endDay
13%11%35%26%12%3
532
August1st to 10thDay
15%8%34%27%11%5%
486
11th to 20thDay
15%8%26%32%13%7%
479
21st to endDay
15%11%31%24%13%6%
539
September1st to 10thDay
16%12%33%19%13%6%
490
11th to 20thDay
11%12%27%20%19%11%
490
21st to endDay
19%15%25%24%12%5%
490
October1st to 10thDay
27%16%24%17%13%3
490
11th to 20thDay
26%23%30%14%6%1
490
21st to endDay
34%18%29%15%4
485
November1st to 10thDay
27%18%33%17%6%
282
11th to 20thDay
32%23%29%9%6%1
180
21st to endDay
29%20%38%8%31
180
December1st to 10thDay
31%21%32%14%2
180
11th to 20thDay
34%26%27%10%21
180
21st to endDay
36%21%28%12%31
198
January1st to 10thNight
27%20%33%16%4
760
11th to 20thNight
29%17%30%19%5%
760
21st to endNight
21%15%34%23%6%1
836
February1st to 10thNight
23%21%36%19%1
760
11th to 20thNight
22%20%38%17%3
743
21st to endNight
24%21%34%18%3
628
March1st to 10thNight
24%19%35%19%3
760
11th to 20thNight
23%19%33%19%41
760
21st to endNight
21%16%34%21%8%1
836
April1st to 10thNight
26%15%34%21%5%
760
11th to 20thNight
24%19%30%18%8%1
751
21st to endNight
24%12%31%23%10%
589
May1st to 10thNight
22%11%28%27%11%1
442
11th to 20thNight
16%13%32%30%9%
374
21st to endNight
14%9%36%29%12%1
411
June1st to 10thNight
18%8%34%31%9%
380
11th to 20thNight
14%12%29%33%12%1
380
21st to endNight
19%8%28%34%10%
380
July1st to 10thNight
6%7%31%40%14%1
370
11th to 20thNight
11%6%30%36%16%1
368
21st to endNight
10%430%41%14%1
416
August1st to 10thNight
12%5%23%35%24%2
562
11th to 20thNight
12%5%23%35%23%3
564
21st to endNight
13%7%31%28%19%2
765
September1st to 10thNight
13%7%32%29%16%3
760
11th to 20thNight
13%6%26%28%22%5%
760
21st to endNight
22%11%21%26%17%3
760
October1st to 10thNight
22%12%29%22%14%2
760
11th to 20thNight
28%15%29%20%8%1
760
21st to endNight
30%16%30%19%5%
805
November1st to 10thNight
24%13%30%25%7%
740
11th to 20thNight
25%18%32%17%7%1
760
21st to endNight
31%16%28%20%5%1
760
December1st to 10thNight
32%19%31%15%4
760
11th to 20thNight
27%19%35%16%31
760
21st to endNight
33%15%33%16%2
836
Page generated at 2024-10-21 02:20:03. Version ac07

Copyright © 2024 Attilla Danko.


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