The Crystal Spring
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The Crystal Spring clear sky chart from 2005-11-05 to 2017-12-20.

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
26%
15345
17%
47982
7%
15311
37%
15311
17%
32029

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 15thNight
14%
720
18%
2506
5%
716
30%
716
14%
1624
January16th to endNight
12%
768
18%
2679
3%
768
31%
768
11%
1767
February1st to 15thNight
13%
704
16%
2159
3%
701
29%
701
14%
1474
February16th to endNight
13%
631
23%
1893
5%
631
35%
631
17%
1251
March1st to 15thNight
17%
720
17%
2140
6%
720
31%
720
15%
1454
March16th to endNight
20%
768
21%
2055
6%
768
33%
768
20%
1409
April1st to 15thNight
20%
718
16%
1796
4%
718
27%
718
19%
1286
April16th to endNight
24%
583
17%
1663
4%
583
32%
583
18%
1161
May1st to 15thNight
22%
540
14%
1620
5%
540
30%
540
14%
1166
May16th to endNight
23%
465
10%
1587
5%
464
30%
464
12%
1140
June1st to 15thNight
33%
360
11%
1440
12%
360
40%
360
13%
987
June16th to endNight
42%
360
11%
1440
11%
360
49%
360
18%
891
July1st to 15thNight
37%
340
12%
1360
14%
340
42%
340
17%
852
July16th to endNight
41%
385
14%
1427
14%
363
49%
363
17%
922
August1st to 15thNight
47%
539
15%
1608
10%
535
50%
535
24%
1034
August16th to endNight
53%
711
21%
1857
12%
711
57%
711
31%
1209
September1st to 15thNight
44%
720
19%
1879
10%
720
49%
720
30%
1227
September16th to endNight
43%
717
22%
1980
13%
717
51%
717
25%
1308
October1st to 15thNight
34%
720
21%
1995
11%
720
43%
720
22%
1338
October16th to endNight
25%
768
18%
2487
8%
768
39%
768
19%
1606
November1st to 15thNight
25%
760
16%
2472
9%
760
36%
760
16%
1655
November16th to endNight
21%
780
22%
2535
7%
780
38%
780
17%
1602
December1st to 15thNight
18%
780
17%
2649
5%
780
32%
780
12%
1789
December16th to endNight
12%
788
19%
2755
4%
788
30%
788
11%
1877

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%6%24424447%40%
48852
Night
17%7%25%424446%39%
48154
Cloud CoverDay
17%6%2442445%7%40%
48862
Night
17%7%25%424446%39%
48159
TransparencyDay
42%6%12%21%14%2
48542
Night
45%5%11%21%14%2
47982
SeeingDay
19%18%28%22%9%2
6281
Night
19%23%26%22%7%
15345

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 15thDay
17%8%34423436%41%
1432
16th to endDay
15%6%35%424346%42%
1542
February1st to 15thDay
18%7%25%4245%5%6%38%
1699
16th to endDay
16%7%34324445%41%
1580
March1st to 15thDay
19%8%34423347%38%
1808
16th to endDay
17%7%35%324335%42%
2166
April1st to 15thDay
19%7%25%424436%39%
2152
16th to endDay
19%5%3343335%6%41%
2295
May1st to 15thDay
26%7%25%323346%33%
2332
16th to endDay
16%6%245%3445%8%38%
2536
June1st to 15thDay
25%5%245%34447%33%
2520
16th to endDay
13%5%245%25%5%6%9%40%
2520
July1st to 15thDay
14%5%245%345%5%9%39%
2520
16th to endDay
13%5%25%435%6%6%9%38%
2633
August1st to 15thDay
12%414435%5%6%8%42%
2340
16th to endDay
11%4245%2445%9%44%
2342
September1st to 15thDay
14%424423445%47%
2079
16th to endDay
17%5%1331336%5%47%
1980
October1st to 15thDay
19%5%23323346%44%
1964
16th to endDay
17%5%15%423445%45%
1735
November1st to 15thDay
23%5%25%323335%40%
1716
16th to endDay
16%6%245%23346%43%
1755
December1st to 15thDay
19%6%35%434245%40%
1638
16th to endDay
22%10%24434345%35%
1568
January1st to 15thNight
18%7%25%423445%40%
2506
16th to endNight
18%9%34423345%39%
2679
February1st to 15thNight
16%8%36%424345%39%
2158
16th to endNight
15%7%35%5%33335%42%
1893
March1st to 15thNight
18%7%25%423447%38%
2127
16th to endNight
17%7%35%424345%41%
2055
April1st to 15thNight
16%8%36%5%34346%37%
1796
16th to endNight
21%6%25%5%33335%38%
1663
May1st to 15thNight
22%8%26%5%23446%33%
1620
16th to endNight
18%8%46%6%345%5%5%30%
1585
June1st to 15thNight
23%6%35%42445%6%33%
1440
16th to endNight
17%5%13425%45%9%39%
1440
July1st to 15thNight
16%7%24425%448%37%
1440
16th to endNight
13%6%36%5%45%6%7%7%33%
1523
August1st to 15thNight
10%5%26%5%346%7%8%40%
1620
16th to endNight
13%4235%3346%7%45%
1857
September1st to 15thNight
14%5%2442445%7%45%
1879
16th to endNight
16%6%2442435%5%45%
1980
October1st to 15thNight
18%6%24423446%42%
1995
16th to endNight
16%5%25%423447%41%
2487
November1st to 15thNight
18%6%25%42345%5%40%
2472
16th to endNight
16%6%25%324347%42%
2535
December1st to 15thNight
20%6%15%5%24336%38%
2649
16th to endNight
19%9%35%433446%37%
2755

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 15thDay
18%7%25%324446%41%
1432
16th to endDay
15%6%34433346%42%
1542
February1st to 15thDay
17%6%25%33445%7%38%
1699
16th to endDay
15%8%245%24447%40%
1580
March1st to 15thDay
19%7%25%424347%37%
1818
16th to endDay
16%6%35%323346%42%
2166
April1st to 15thDay
19%6%2442445%6%39%
2152
16th to endDay
18%5%235%34447%40%
2295
May1st to 15thDay
24%7%25%424347%32%
2332
16th to endDay
17%6%25%5%35%45%7%37%
2536
June1st to 15thDay
23%6%245%3445%8%32%
2520
16th to endDay
13%5%244245%7%9%40%
2520
July1st to 15thDay
13%5%246%245%6%7%40%
2520
16th to endDay
12%5%26%436%5%6%9%37%
2633
August1st to 15thDay
11%5%245%345%6%9%42%
2340
16th to endDay
11%425%5%235%5%8%46%
2342
September1st to 15thDay
14%5%2432435%6%46%
2079
16th to endDay
17%5%24313446%46%
1980
October1st to 15thDay
19%5%24423445%43%
1964
16th to endDay
15%424424446%45%
1735
November1st to 15thDay
21%6%3442333440%
1716
16th to endDay
17%5%25%423347%42%
1755
December1st to 15thDay
20%6%35%423336%40%
1638
16th to endDay
22%9%33333346%35%
1568
January1st to 15thNight
18%7%24424446%39%
2506
16th to endNight
18%10%35%323345%38%
2679
February1st to 15thNight
16%8%35%434446%38%
2151
16th to endNight
15%7%35%5%33336%41%
1893
March1st to 15thNight
18%7%26%424447%37%
2140
16th to endNight
16%7%35%5%24435%41%
2054
April1st to 15thNight
17%8%36%5%24447%36%
1796
16th to endNight
21%6%36%423335%38%
1663
May1st to 15thNight
22%9%35%5%23346%32%
1620
16th to endNight
18%10%36%5%25%5%47%30%
1585
June1st to 15thNight
23%10%24413447%32%
1440
16th to endNight
17%6%2342345%9%38%
1440
July1st to 15thNight
16%8%25%5%2345%7%37%
1440
16th to endNight
13%7%35%6%36%5%7%8%32%
1523
August1st to 15thNight
10%5%25%435%5%8%7%40%
1620
16th to endNight
13%5%1442445%8%45%
1857
September1st to 15thNight
14%425%32346%6%45%
1879
16th to endNight
17%6%24424445%44%
1980
October1st to 15thNight
18%6%24424445%41%
1995
16th to endNight
16%6%25%434447%41%
2487
November1st to 15thNight
18%7%25%434445%39%
2472
16th to endNight
16%6%35%323447%41%
2535
December1st to 15thNight
21%5%25%5%34436%37%
2649
16th to endNight
20%8%345%2335%6%35%
2755

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 15thDay
43%6%12%23%12%3
1433
16th to endDay
41%5%10%26%13%1
1542
February1st to 15thDay
44%6%14%19%13%2
1702
16th to endDay
43%412%22%13%2
1580
March1st to 15thDay
47%414%21%9%2
1818
16th to endDay
42%411%20%15%4
2166
April1st to 15thDay
45%5%9%20%16%2
2152
16th to endDay
42%6%10%21%16%3
2295
May1st to 15thDay
51%6%8%16%14%2
2332
16th to endDay
44%6%14%21%10%1
2540
June1st to 15thDay
50%6%12%19%10%
2520
16th to endDay
39%8%14%22%14%
2520
July1st to 15thDay
40%8%14%20%14%1
2371
16th to endDay
38%9%15%22%11%3
2467
August1st to 15thDay
36%9%15%22%14%1
2327
16th to endDay
34%7%12%25%17%1
2342
September1st to 15thDay
38%5%11%21%21%1
2079
16th to endDay
37%6%8%23%21%3
1980
October1st to 15thDay
41%5%11%23%15%2
1964
16th to endDay
38%5%12%24%16%2
1735
November1st to 15thDay
47%5%12%18%13%2
1716
16th to endDay
41%6%11%25%12%2
1755
December1st to 15thDay
47%5%14%16%14%1
1638
16th to endDay
51%5%14%18%9%
1568
January1st to 15thNight
45%5%13%21%12%1
2506
16th to endNight
48%410%20%15%2
2679
February1st to 15thNight
47%5%11%22%11%1
2159
16th to endNight
44%310%22%16%2
1893
March1st to 15thNight
46%412%19%13%3
2140
16th to endNight
44%49%17%18%4
2055
April1st to 15thNight
47%5%9%18%15%2
1796
16th to endNight
47%5%8%19%14%4
1663
May1st to 15thNight
52%5%10%15%12%3
1620
16th to endNight
52%7%12%17%7%2
1587
June1st to 15thNight
51%6%11%17%12%
1440
16th to endNight
41%7%12%22%14%1
1440
July1st to 15thNight
44%6%11%23%13%
1360
16th to endNight
44%8%14%23%7%2
1427
August1st to 15thNight
38%8%13%24%14%1
1608
16th to endNight
36%7%10%27%17%
1857
September1st to 15thNight
37%5%12%24%18%1
1879
16th to endNight
40%5%7%20%24%1
1980
October1st to 15thNight
44%410%22%15%2
1995
16th to endNight
41%6%13%22%13%1
2487
November1st to 15thNight
45%5%11%19%13%2
2472
16th to endNight
42%411%24%14%2
2535
December1st to 15thNight
47%5%13%20%12%
2649
16th to endNight
49%5%12%20%11%
2755

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 15thDay
18%28%31%20%1
60
16th to endDay
20%21%38%20%
70
February1st to 15thDay
22%24%36%13%1
257
16th to endDay
14%29%35%15%4
239
March1st to 15thDay
24%30%24%17%2
270
16th to endDay
17%29%31%15%5%
288
April1st to 15thDay
21%22%32%17%4
270
16th to endDay
20%21%31%17%5%2
270
May1st to 15thDay
31%22%22%14%6%1
288
16th to endDay
20%16%29%25%7%
331
June1st to 15thDay
21%17%25%24%10%
315
16th to endDay
13%15%35%23%10%1
315
July1st to 15thDay
17%10%22%31%16%2
305
16th to endDay
11%13%24%33%14%2
326
August1st to 15thDay
14%10%21%36%15%2
313
16th to endDay
12%6%22%29%20%7%
332
September1st to 15thDay
15%8%28%25%17%5%
315
16th to endDay
25%8%22%20%13%9%
314
October1st to 15thDay
20%13%24%22%14%4
310
16th to endDay
16%17%32%20%10%1
288
November1st to 15thDay
22%20%30%15%10%2
280
16th to endDay
18%29%25%17%8%
285
December1st to 15thDay
19%22%32%20%5%
168
16th to endDay
34%20%36%5%2
72
January1st to 15thNight
18%31%33%13%2
720
16th to endNight
22%33%28%13%2
768
February1st to 15thNight
17%31%32%17%
704
16th to endNight
18%31%34%14%2
631
March1st to 15thNight
21%27%29%17%3
720
16th to endNight
17%27%29%19%5%
768
April1st to 15thNight
18%25%31%20%3
718
16th to endNight
18%25%27%21%7%
583
May1st to 15thNight
21%24%26%19%7%
540
16th to endNight
21%23%24%23%7%
465
June1st to 15thNight
23%19%19%27%10%
360
16th to endNight
17%18%17%36%9%
360
July1st to 15thNight
18%14%22%31%12%
340
16th to endNight
14%17%19%36%10%
385
August1st to 15thNight
11%11%21%41%13%
539
16th to endNight
15%9%15%35%19%3
711
September1st to 15thNight
15%11%23%33%14%1
720
16th to endNight
20%12%17%24%20%4
717
October1st to 15thNight
21%15%23%25%12%1
720
16th to endNight
19%22%28%20%8%
768
November1st to 15thNight
20%24%24%20%9%1
760
16th to endNight
15%30%29%16%6%
780
December1st to 15thNight
22%28%25%16%5%
780
16th to endNight
23%33%28%12%1
788
Page generated at 2017-12-21 07:04:45. Version ac04

Copyright 2017 A. Danko


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