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 2017-08-12.

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
25%
14830
17%
46437
7%
14796
37%
14796
17%
31033

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
11%
768
18%
2679
3%
768
30%
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
32%
768
20%
1409
April1st to 15thNight
20%
718
16%
1796
4%
718
27%
718
19%
1286
April16th to endNight
23%
583
17%
1663
4%
583
32%
583
18%
1161
May1st to 15thNight
22%
540
14%
1620
5%
540
29%
540
14%
1166
May16th to endNight
24%
465
10%
1587
5%
464
31%
464
12%
1140
June1st to 15thNight
32%
360
11%
1440
12%
360
39%
360
13%
987
June16th to endNight
41%
360
11%
1440
11%
360
48%
360
18%
891
July1st to 15thNight
37%
340
12%
1360
14%
340
41%
340
17%
852
July16th to endNight
41%
385
13%
1427
14%
363
49%
363
17%
922
August1st to 15thNight
48%
528
15%
1575
10%
524
51%
524
24%
1007
August16th to endNight
51%
651
19%
1701
10%
651
55%
651
29%
1123
September1st to 15thNight
45%
660
20%
1722
11%
660
50%
660
30%
1137
September16th to endNight
43%
657
23%
1815
13%
657
51%
657
27%
1171
October1st to 15thNight
31%
660
21%
1829
10%
660
41%
660
21%
1233
October16th to endNight
25%
704
16%
2280
7%
704
37%
704
18%
1482
November1st to 15thNight
24%
700
16%
2277
9%
700
36%
700
16%
1519
November16th to endNight
20%
720
20%
2340
7%
720
36%
720
16%
1504
December1st to 15thNight
18%
720
17%
2445
5%
720
32%
720
12%
1640
December16th to endNight
12%
768
19%
2688
4%
768
30%
768
11%
1833

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%
47531
Night
17%7%25%424446%39%
46609
Cloud CoverDay
17%6%2442445%7%40%
47541
Night
17%7%25%424446%38%
46614
TransparencyDay
42%6%12%21%14%2
47221
Night
45%5%11%21%14%2
46437
SeeingDay
19%18%28%21%9%2
5841
Night
19%24%26%22%7%
14830

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%6%6%8%42%
2288
16th to endDay
11%425%5%2445%9%44%
2146
September1st to 15thDay
14%5%35%32345%6%45%
1906
16th to endDay
15%5%1331336%5%48%
1815
October1st to 15thDay
20%5%23323346%44%
1801
16th to endDay
16%5%24433446%45%
1591
November1st to 15thDay
24%5%24323335%40%
1581
16th to endDay
16%6%245%33346%41%
1620
December1st to 15thDay
19%6%35%433245%41%
1512
16th to endDay
22%10%24434345%34%
1536
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
9%5%26%5%246%7%8%41%
1587
16th to endNight
13%4245%3346%8%43%
1701
September1st to 15thNight
14%5%2442445%7%44%
1722
16th to endNight
15%6%24424345%47%
1815
October1st to 15thNight
19%6%24423446%41%
1829
16th to endNight
16%6%25%5%23446%41%
2280
November1st to 15thNight
19%6%25%423445%40%
2277
16th to endNight
17%6%26%424347%41%
2340
December1st to 15thNight
20%6%25%5%24346%38%
2445
16th to endNight
19%8%35%434446%37%
2688

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%424435%5%6%9%42%
2288
16th to endDay
11%425%5%235%5%8%46%
2146
September1st to 15thDay
14%5%2432445%6%45%
1906
16th to endDay
15%424323446%47%
1815
October1st to 15thDay
19%5%24423345%43%
1801
16th to endDay
15%4245%24446%44%
1591
November1st to 15thDay
22%6%2442333440%
1581
16th to endDay
17%6%25%424347%40%
1620
December1st to 15thDay
19%6%35%423336%41%
1512
16th to endDay
23%9%33333346%35%
1536
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
9%5%24435%5%8%7%40%
1587
16th to endNight
13%5%25%4245%5%8%43%
1701
September1st to 15thNight
14%435%42346%6%44%
1722
16th to endNight
16%6%24424445%46%
1815
October1st to 15thNight
19%6%24424445%40%
1829
16th to endNight
16%6%25%43445%6%40%
2280
November1st to 15thNight
18%7%25%424445%40%
2277
16th to endNight
17%6%25%423447%39%
2340
December1st to 15thNight
21%5%25%434436%38%
2445
16th to endNight
20%8%345%2335%6%35%
2688

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
35%9%16%22%14%1
2275
16th to endDay
35%7%12%25%17%1
2146
September1st to 15thDay
39%5%12%21%21%
1906
16th to endDay
35%6%9%24%21%3
1815
October1st to 15thDay
41%5%11%22%16%2
1801
16th to endDay
38%5%13%23%15%2
1591
November1st to 15thDay
47%5%12%18%13%2
1581
16th to endDay
43%6%11%24%11%2
1620
December1st to 15thDay
46%5%15%17%14%
1512
16th to endDay
52%5%13%18%9%
1536
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
37%8%13%24%14%1
1575
16th to endNight
37%7%10%27%16%
1701
September1st to 15thNight
38%5%12%23%18%1
1722
16th to endNight
37%6%6%22%25%1
1815
October1st to 15thNight
44%410%22%15%2
1829
16th to endNight
42%6%14%21%13%1
2280
November1st to 15thNight
45%5%11%20%14%2
2277
16th to endNight
44%411%22%13%2
2340
December1st to 15thNight
47%5%12%20%13%
2445
16th to endNight
49%5%12%20%11%
2688

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
12%10%20%37%16%2
297
16th to endDay
13%7%19%28%22%8%
268
September1st to 15thDay
15%7%25%26%19%6%
255
16th to endDay
22%9%24%22%13%8%
254
October1st to 15thDay
21%15%25%19%14%3
252
16th to endDay
15%18%35%20%9%
240
November1st to 15thDay
22%21%25%15%11%2
235
16th to endDay
19%28%26%17%7%
240
December1st to 15thDay
17%24%33%18%6%
132
16th to endDay
35%18%35%6%3
64
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%
528
16th to endNight
15%10%15%34%19%3
651
September1st to 15thNight
15%11%21%33%15%1
660
16th to endNight
19%13%17%25%19%4
657
October1st to 15thNight
22%16%24%24%10%1
660
16th to endNight
19%22%28%21%7%
704
November1st to 15thNight
20%26%23%19%9%1
700
16th to endNight
16%31%28%16%6%
720
December1st to 15thNight
22%29%25%16%5%
720
16th to endNight
23%33%28%12%1
768
Page generated at 2017-08-13 14:16:49. Version ac04

Copyright 2017 A. Danko


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