Spring Hope Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Spring Hope Observing Site clear sky chart from 2005-11-06 to 2024-03-06.

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
42%
24470
21%
80106
13%
24373
51%
24373
25%
49456

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
23%
754
26%
3990
9%
737
40%
737
16%
2107
January11th to 20thNight
26%
758
26%
3961
11%
740
42%
740
14%
2286
January21st to endNight
25%
827
19%
4449
12%
814
46%
814
16%
2613
February1st to 10thNight
26%
760
20%
2470
11%
760
40%
760
23%
1529
February11th to 20thNight
15%
740
19%
2346
5%
739
31%
739
19%
1510
February21st to endNight
25%
628
27%
1795
12%
628
40%
628
26%
1128
March1st to 10thNight
29%
743
26%
2042
12%
743
43%
743
29%
1267
March11th to 20thNight
25%
720
20%
1980
9%
720
36%
720
24%
1314
March21st to endNight
26%
792
21%
2178
9%
792
37%
792
27%
1419
April1st to 10thNight
30%
720
23%
1832
7%
720
41%
720
30%
1186
April11th to 20thNight
34%
711
25%
1775
8%
711
43%
711
34%
1126
April21st to endNight
38%
720
23%
1800
9%
720
45%
720
33%
1165
May1st to 10thNight
39%
635
18%
1715
8%
635
44%
635
31%
1082
May11th to 20thNight
44%
531
16%
1593
9%
531
49%
531
25%
1058
May21st to endNight
59%
582
16%
1744
11%
582
62%
582
29%
1110
June1st to 10thNight
60%
401
16%
1481
18%
401
63%
401
26%
898
June11th to 20thNight
55%
360
16%
1440
17%
360
59%
360
21%
894
June21st to endNight
65%
499
16%
1579
15%
499
67%
499
25%
1033
July1st to 10thNight
66%
525
13%
1575
12%
525
68%
525
26%
1043
July11th to 20thNight
71%
522
14%
1566
12%
522
72%
522
28%
1004
July21st to endNight
64%
591
17%
1672
13%
558
67%
558
27%
1096
August1st to 10thNight
62%
537
13%
1600
11%
534
62%
534
24%
1089
August11th to 20thNight
62%
623
16%
1687
11%
623
64%
623
23%
1203
August21st to endNight
62%
792
15%
1980
10%
792
63%
792
29%
1384
September1st to 10thNight
66%
720
23%
1800
16%
720
67%
720
34%
1185
September11th to 20thNight
58%
720
24%
1850
18%
720
61%
720
31%
1229
September21st to endNight
47%
720
17%
2053
12%
720
53%
720
22%
1437
October1st to 10thNight
52%
720
24%
2160
21%
720
59%
720
31%
1333
October11th to 20thNight
47%
720
28%
2160
23%
720
58%
720
32%
1273
October21st to endNight
46%
792
31%
2376
21%
792
60%
792
35%
1357
November1st to 10thNight
43%
740
26%
2221
18%
740
53%
740
31%
1333
November11th to 20thNight
40%
760
27%
2322
16%
760
53%
760
29%
1369
November21st to endNight
41%
760
26%
2615
18%
760
54%
760
29%
1476
December1st to 10thNight
29%
760
21%
2660
11%
760
43%
760
20%
1710
December11th to 20thNight
34%
760
24%
3173
16%
758
48%
758
21%
1818
December21st to endNight
30%
827
17%
4466
12%
817
45%
817
15%
2392

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%6%25%5%35%5%6%8%43%
78564
Night
14%6%25%5%3445%7%45%
80935
TransparencyDay
38%6%12%21%18%4
78285
Night
38%6%11%20%20%5%
80733
SeeingDay
17%10%25%25%17%6%
14345
Night
16%8%27%31%16%2
24501

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
18%424423335%51%
2836
11th to 20thDay
14%6%35%5%23445%51%
2840
21st to endDay
18%9%35%433445%42%
3124
February1st to 10thDay
14%6%35%5%3445%6%45%
1710
11th to 20thDay
21%5%33424345%46%
1718
21st to endDay
17%7%36%5%23447%41%
1655
March1st to 10thDay
14%6%24344446%49%
2035
11th to 20thDay
16%6%26%4235%6%8%43%
1980
21st to endDay
16%7%36%5%45%447%39%
2178
April1st to 10thDay
11%42433445%7%54%
2128
11th to 20thDay
11%42443445%9%49%
2134
21st to endDay
14%5%35%5%3445%7%45%
2160
May1st to 10thDay
11%5%245%35%5%7%8%42%
2258
11th to 20thDay
14%6%27%7%35%6%5%7%38%
2301
21st to endDay
12%5%35%6%36%5%6%9%39%
2531
June1st to 10thDay
10%5%25%6%46%7%7%10%39%
2470
11th to 20thDay
9%425%6%36%6%8%10%42%
2520
21st to endDay
8%5%35%6%47%6%8%11%38%
2370
July1st to 10thDay
8%426%6%47%7%9%12%33%
2340
11th to 20thDay
8%5%35%6%5%7%7%8%12%36%
2340
21st to endDay
7%5%36%7%5%6%7%9%12%34%
2547
August1st to 10thDay
10%7%26%7%46%7%8%11%32%
2327
11th to 20thDay
12%6%37%7%5%6%5%7%10%33%
2195
21st to endDay
10%7%36%6%35%6%8%10%36%
2376
September1st to 10thDay
9%5%25%6%46%5%5%10%43%
2160
11th to 20thDay
14%5%25%5%35%46%7%43%
2106
21st to endDay
19%7%46%5%2445%6%38%
1905
October1st to 10thDay
15%6%25%5%23446%48%
1800
11th to 20thDay
13%5%24434445%53%
1800
21st to endDay
11%5%25%43334455%
1980
November1st to 10thDay
14%5%24423346%54%
1857
11th to 20thDay
14%5%23423347%52%
1853
21st to endDay
14%425%42335%6%52%
1563
December1st to 10thDay
18%6%35%6%3445%7%41%
1520
11th to 20thDay
15%5%24323336%55%
1910
21st to endDay
16%6%25%42445%7%43%
3037
January1st to 10thNight
14%6%25%43445%6%47%
4109
11th to 20thNight
14%8%35%5%34445%44%
4120
21st to endNight
18%6%25%5%34345%44%
4532
February1st to 10thNight
17%5%35%43346%6%44%
2470
11th to 20thNight
20%6%35%42445%5%42%
2346
21st to endNight
15%7%244245%6%6%45%
1795
March1st to 10thNight
14%5%24433445%51%
2042
11th to 20thNight
17%6%36%42446%6%42%
1980
21st to endNight
15%6%35%5%3446%7%44%
2178
April1st to 10thNight
14%6%2443345%7%49%
1832
11th to 20thNight
14%5%245%2346%7%49%
1775
21st to endNight
11%5%245%35%6%5%7%48%
1800
May1st to 10thNight
10%7%245%35%5%7%7%46%
1715
11th to 20thNight
15%6%45%6%35%5%5%7%41%
1592
21st to endNight
10%6%35%5%36%5%6%9%43%
1744
June1st to 10thNight
9%5%25%6%46%7%8%10%40%
1481
11th to 20thNight
10%5%36%6%35%7%7%9%39%
1440
21st to endNight
8%5%25%6%37%6%8%11%38%
1579
July1st to 10thNight
6%5%36%7%46%7%8%12%37%
1620
11th to 20thNight
7%5%26%5%46%6%7%13%39%
1620
21st to endNight
6%5%27%6%45%7%8%12%36%
1771
August1st to 10thNight
9%7%36%6%46%6%8%11%35%
1611
11th to 20thNight
8%6%46%7%5%6%7%7%11%34%
1687
21st to endNight
11%7%36%6%35%5%6%11%37%
1980
September1st to 10thNight
10%5%25%6%2446%9%47%
1800
11th to 20thNight
12%6%36%435%45%7%45%
1850
21st to endNight
19%8%36%5%445%5%6%37%
2053
October1st to 10thNight
15%5%25%4335%5%5%49%
2160
11th to 20thNight
14%5%24423345%53%
2160
21st to endNight
12%425%423347%55%
2376
November1st to 10thNight
13%6%25%423435%51%
2221
11th to 20thNight
13%5%25%42445%6%50%
2322
21st to endNight
13%5%24434446%51%
2615
December1st to 10thNight
18%7%25%5%34446%41%
2660
11th to 20thNight
18%5%25%32345%449%
3285
21st to endNight
16%7%24424346%47%
4614

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
37%37%25%24%5%
2837
11th to 20thDay
36%36%17%32%6%
2840
21st to endDay
44%5%6%18%18%7%
3124
February1st to 10thDay
39%5%11%22%19%5%
1710
11th to 20thDay
42%47%18%23%7%
1727
21st to endDay
43%5%11%15%20%6%
1655
March1st to 10thDay
36%5%10%22%21%6%
2035
11th to 20thDay
40%6%10%22%16%7%
1980
21st to endDay
46%6%10%18%17%4
2178
April1st to 10thDay
30%5%10%25%23%7%
2128
11th to 20thDay
33%6%12%22%21%6%
2134
21st to endDay
38%5%13%22%18%4
2160
May1st to 10thDay
37%8%17%19%16%3
2258
11th to 20thDay
44%7%13%23%12%1
2305
21st to endDay
39%8%16%23%13%1
2531
June1st to 10thDay
39%9%15%21%15%1
2470
11th to 20thDay
34%10%17%24%13%2
2520
21st to endDay
36%10%17%21%14%1
2370
July1st to 10thDay
38%12%16%21%10%3
2275
11th to 20thDay
38%9%22%20%9%2
2271
21st to endDay
38%11%20%20%10%
2405
August1st to 10thDay
43%10%18%20%8%1
2314
11th to 20thDay
44%9%16%20%9%2
2195
21st to endDay
40%11%17%19%10%3
2376
September1st to 10thDay
37%8%16%18%17%4
2160
11th to 20thDay
39%6%11%20%20%3
2106
21st to endDay
46%5%10%20%14%4
1905
October1st to 10thDay
38%5%11%23%20%4
1800
11th to 20thDay
33%5%8%27%21%7%
1800
21st to endDay
33%47%22%25%9%
1980
November1st to 10thDay
33%47%23%27%6%
1857
11th to 20thDay
34%310%20%25%7%
1853
21st to endDay
34%48%23%25%6%
1563
December1st to 10thDay
43%5%10%20%17%4
1520
11th to 20thDay
34%37%27%21%9%
1906
21st to endDay
40%5%10%23%20%2
3037
January1st to 10thNight
37%5%8%21%25%5%
4109
11th to 20thNight
42%47%18%24%5%
4120
21st to endNight
42%46%19%22%7%
4532
February1st to 10thNight
41%49%20%21%5%
2470
11th to 20thNight
44%48%16%20%7%
2348
21st to endNight
37%5%10%20%20%7%
1795
March1st to 10thNight
36%48%21%22%8%
2042
11th to 20thNight
42%5%10%19%18%6%
1980
21st to endNight
40%5%10%21%19%5%
2178
April1st to 10thNight
36%5%9%17%26%7%
1832
11th to 20thNight
33%6%11%22%21%7%
1775
21st to endNight
35%7%10%25%18%5%
1800
May1st to 10thNight
34%7%16%23%17%3
1715
11th to 20thNight
42%7%13%20%16%2
1593
21st to endNight
36%9%17%23%13%1
1745
June1st to 10thNight
35%9%18%21%15%1
1481
11th to 20thNight
39%9%16%18%16%2
1440
21st to endNight
37%12%15%20%14%2
1579
July1st to 10thNight
36%12%18%20%10%3
1575
11th to 20thNight
34%12%21%23%8%2
1566
21st to endNight
36%11%19%23%10%
1672
August1st to 10thNight
40%11%19%23%7%1
1600
11th to 20thNight
42%12%17%20%8%1
1687
21st to endNight
40%9%17%22%9%2
1980
September1st to 10thNight
34%10%15%22%14%5%
1800
11th to 20thNight
38%8%12%19%21%2
1850
21st to endNight
48%6%11%16%16%3
2053
October1st to 10thNight
37%5%9%22%23%5%
2160
11th to 20thNight
34%48%21%25%7%
2160
21st to endNight
31%48%21%26%9%
2376
November1st to 10thNight
36%48%18%27%6%
2221
11th to 20thNight
35%5%9%16%24%11%
2322
21st to endNight
34%5%7%22%26%7%
2615
December1st to 10thNight
45%5%9%18%19%4
2660
11th to 20thNight
38%48%20%23%7%
3288
21st to endNight
38%48%25%22%3
4614

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
23%23%34%17%3
270
11th to 20thDay
25%25%33%13%4
270
21st to endDay
21%22%41%13%2
297
February1st to 10thDay
20%20%41%16%4
270
11th to 20thDay
35%19%33%12%1
325
21st to endDay
25%20%32%17%4
382
March1st to 10thDay
20%18%36%20%5%1
440
11th to 20thDay
24%18%36%15%6%1
420
21st to endDay
22%16%36%18%6%2
462
April1st to 10thDay
20%16%33%24%6%1
420
11th to 20thDay
14%19%28%25%11%3
412
21st to endDay
19%12%29%26%13%1
420
May1st to 10thDay
15%13%33%24%12%2
423
11th to 20thDay
19%6%25%28%19%4
447
21st to endDay
18%5%20%23%25%9%
485
June1st to 10thDay
13%419%34%22%7%
450
11th to 20thDay
11%5%19%31%25%10%
450
21st to endDay
10%420%33%27%7%
450
July1st to 10thDay
10%29%31%34%14%
445
11th to 20thDay
9%110%28%38%13%
444
21st to endDay
8%115%34%33%10%
488
August1st to 10thDay
14%413%30%27%12%
446
11th to 20thDay
12%214%26%30%16%
439
21st to endDay
11%311%30%26%18%
495
September1st to 10thDay
14%213%25%27%18%
450
11th to 20thDay
14%6%12%34%21%14%
450
21st to endDay
23%7%25%23%18%5%
450
October1st to 10thDay
18%6%23%22%22%9%
450
11th to 20thDay
14%8%27%28%19%4
450
21st to endDay
14%11%25%31%15%4
495
November1st to 10thDay
19%9%29%25%14%4
455
11th to 20thDay
18%13%31%27%10%1
438
21st to endDay
21%15%25%23%14%3
223
December1st to 10thDay
22%21%37%12%7%1
180
11th to 20thDay
18%17%34%23%7%1
180
21st to endDay
25%17%29%17%12%
274
January1st to 10thNight
20%16%36%22%6%1
760
11th to 20thNight
22%12%36%25%5%
760
21st to endNight
20%12%39%25%3
836
February1st to 10thNight
21%12%38%26%4
760
11th to 20thNight
24%18%40%16%1
743
21st to endNight
18%16%38%25%3
628
March1st to 10thNight
17%14%36%27%6%
743
11th to 20thNight
21%11%37%22%8%
720
21st to endNight
18%12%40%24%6%
792
April1st to 10thNight
18%16%34%27%6%
720
11th to 20thNight
16%13%34%27%10%
711
21st to endNight
14%8%36%34%8%
720
May1st to 10thNight
11%12%34%33%10%
635
11th to 20thNight
17%5%26%37%15%1
531
21st to endNight
12%218%37%28%2
584
June1st to 10thNight
9%222%41%25%
401
11th to 20thNight
12%219%42%22%4
360
21st to endNight
9%214%44%27%3
499
July1st to 10thNight
9%112%38%37%4
525
11th to 20thNight
8%29%39%36%5%
522
21st to endNight
7%214%40%33%3
591
August1st to 10thNight
11%310%40%32%4
537
11th to 20thNight
12%310%33%37%5%
623
21st to endNight
13%311%32%33%7%
792
September1st to 10thNight
13%210%34%34%6%
720
11th to 20thNight
15%414%34%29%4
720
21st to endNight
23%418%32%22%1
720
October1st to 10thNight
17%321%30%25%5%
720
11th to 20thNight
17%7%24%31%19%2
720
21st to endNight
15%6%28%30%19%2
792
November1st to 10thNight
17%7%29%30%15%3
740
11th to 20thNight
16%11%30%31%12%
760
21st to endNight
14%10%31%30%14%1
760
December1st to 10thNight
21%11%33%27%8%
760
11th to 20thNight
19%10%32%32%7%
760
21st to endNight
20%12%31%29%8%1
836
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