Summit Crossing Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Summit Crossing Observatory clear sky chart from 2005-11-05 to 2018-03-11.

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
39%
16037
21%
49133
12%
16001
49%
16001
26%
30824

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
22%
776
23%
2573
8%
776
40%
776
22%
1569
January16th to endNight
24%
832
24%
2704
11%
832
41%
832
22%
1667
February1st to 15thNight
22%
761
20%
2482
7%
761
38%
761
21%
1534
February16th to endNight
20%
683
26%
2074
8%
683
40%
683
23%
1279
March1st to 15thNight
23%
764
23%
2106
9%
764
38%
764
26%
1338
March16th to endNight
25%
768
21%
2099
9%
768
36%
768
25%
1400
April1st to 15thNight
26%
718
21%
1796
4%
718
36%
718
31%
1165
April16th to endNight
38%
720
20%
1800
8%
720
43%
720
32%
1182
May1st to 15thNight
36%
585
16%
1665
7%
585
42%
585
23%
1143
May16th to endNight
53%
396
17%
1519
14%
396
60%
396
24%
912
June1st to 15thNight
60%
360
19%
1440
21%
360
66%
360
24%
834
June16th to endNight
61%
360
17%
1440
18%
360
65%
360
24%
823
July1st to 15thNight
58%
376
13%
1396
15%
376
60%
376
22%
877
July16th to endNight
69%
564
16%
1595
12%
531
73%
531
32%
981
August1st to 15thNight
66%
539
17%
1609
13%
536
67%
536
29%
1039
August16th to endNight
62%
758
18%
1904
12%
758
63%
758
30%
1302
September1st to 15thNight
59%
720
24%
1800
15%
720
62%
720
33%
1201
September16th to endNight
52%
717
21%
1981
17%
717
55%
717
27%
1321
October1st to 15thNight
46%
720
23%
2160
20%
720
53%
720
26%
1394
October16th to endNight
39%
768
31%
2304
20%
768
55%
768
32%
1342
November1st to 15thNight
39%
760
24%
2379
15%
760
51%
760
28%
1422
November16th to endNight
35%
780
24%
2665
14%
780
50%
780
26%
1537
December1st to 15thNight
28%
780
19%
2730
9%
780
42%
780
19%
1730
December16th to endNight
27%
832
22%
2912
11%
832
43%
832
20%
1832

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
14%42442445%7%43%
49484
Night
14%5%2442445%7%44%
49319
Cloud CoverDay
14%5%2442445%7%43%
49494
Night
14%5%2442445%7%44%
49323
TransparencyDay
39%6%11%22%16%3
49188
Night
38%5%11%22%17%3
49133
SeeingDay
18%8%25%25%16%6%
6252
Night
17%9%28%29%14%1
16045

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
16%5%2442345%5%43%
1692
16th to endDay
15%6%24423446%43%
1872
February1st to 15thDay
15%7%26%5%24435%41%
1710
16th to endDay
16%5%25%5%34437%39%
1683
March1st to 15thDay
15%425%423436%46%
2078
16th to endDay
16%7%34424447%40%
2124
April1st to 15thDay
13%42442445%6%47%
2152
16th to endDay
16%6%25%423346%44%
2160
May1st to 15thDay
19%425%424448%39%
2295
16th to endDay
14%3235%25%5%6%8%42%
2596
June1st to 15thDay
11%314425%5%7%9%44%
2520
16th to endDay
7%325%5%36%5%7%11%42%
2520
July1st to 15thDay
10%4246%35%6%6%10%39%
2478
16th to endDay
7%225%5%47%7%7%11%39%
2465
August1st to 15thDay
10%5%26%6%46%5%5%9%35%
2334
16th to endDay
12%425%6%35%6%6%8%40%
2292
September1st to 15thDay
13%314435%446%48%
2160
16th to endDay
17%5%1443445%8%40%
1977
October1st to 15thDay
20%414324245%46%
1800
16th to endDay
14%5%14313335%52%
1920
November1st to 15thDay
16%5%23323345%48%
1808
16th to endDay
15%323323346%50%
1624
December1st to 15thDay
16%6%1342436%6%44%
1560
16th to endDay
18%7%25%423345%41%
1664
January1st to 15thNight
17%5%24423346%45%
2573
16th to endNight
16%5%25%423345%45%
2704
February1st to 15thNight
15%6%24424446%44%
2480
16th to endNight
14%6%2442435%5%46%
2074
March1st to 15thNight
16%424423446%46%
2094
16th to endNight
17%6%24414446%43%
2099
April1st to 15thNight
12%5%25%5%24346%48%
1796
16th to endNight
16%41442345%7%45%
1800
May1st to 15thNight
16%5%25%5%2445%7%38%
1665
16th to endNight
13%3135%246%5%9%42%
1517
June1st to 15thNight
9%4145%35%5%5%9%45%
1440
16th to endNight
9%325%5%35%5%6%10%43%
1440
July1st to 15thNight
7%427%6%35%5%7%9%39%
1479
16th to endNight
6%3145%36%6%8%11%42%
1703
August1st to 15thNight
9%425%5%36%5%6%9%42%
1620
16th to endNight
11%426%6%35%45%10%37%
1904
September1st to 15thNight
12%424425%45%7%45%
1800
16th to endNight
15%5%26%5%24446%41%
1981
October1st to 15thNight
19%5%23323445%44%
2160
16th to endNight
14%313323345%52%
2304
November1st to 15thNight
15%5%24323335%50%
2379
16th to endNight
13%41432445%5%49%
2665
December1st to 15thNight
16%7%35%5%25%345%40%
2730
16th to endNight
16%7%25%42335%7%41%
2912

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
16%5%245%2345%5%43%
1692
16th to endDay
16%6%24423446%43%
1872
February1st to 15thDay
15%7%26%5%34446%40%
1710
16th to endDay
15%6%35%5%34347%39%
1683
March1st to 15thDay
15%425%424446%45%
2089
16th to endDay
16%7%34424447%40%
2123
April1st to 15thDay
13%42442345%7%47%
2152
16th to endDay
16%6%24333346%44%
2160
May1st to 15thDay
18%42442445%7%39%
2295
16th to endDay
14%3145%246%6%8%41%
2596
June1st to 15thDay
11%323435%5%7%9%43%
2520
16th to endDay
6%3246%46%5%7%11%42%
2520
July1st to 15thDay
10%425%5%36%6%6%10%38%
2478
16th to endDay
6%325%5%37%8%7%11%38%
2465
August1st to 15thDay
10%6%26%7%35%6%6%9%35%
2334
16th to endDay
12%415%5%35%5%6%8%40%
2292
September1st to 15thDay
13%314435%447%47%
2160
16th to endDay
17%5%15%43445%6%40%
1977
October1st to 15thDay
20%423314345%46%
1800
16th to endDay
14%5%14223235%52%
1920
November1st to 15thDay
16%423324345%48%
1808
16th to endDay
15%423324336%51%
1624
December1st to 15thDay
16%6%1342435%6%44%
1560
16th to endDay
18%8%25%423345%40%
1664
January1st to 15thNight
17%5%24423347%45%
2573
16th to endNight
16%5%25%423445%45%
2704
February1st to 15thNight
14%7%24424446%44%
2473
16th to endNight
14%6%24424346%46%
2074
March1st to 15thNight
16%42432335%6%46%
2106
16th to endNight
17%5%3441445%6%42%
2099
April1st to 15thNight
12%425%5%2335%6%48%
1796
16th to endNight
15%5%2432335%7%45%
1800
May1st to 15thNight
16%6%246%2446%7%38%
1664
16th to endNight
12%4145%345%6%9%42%
1517
June1st to 15thNight
8%415%5%35%5%5%9%45%
1440
16th to endNight
8%425%6%25%6%5%10%42%
1440
July1st to 15thNight
7%5%27%6%35%6%6%9%39%
1479
16th to endNight
6%3145%36%6%7%10%42%
1703
August1st to 15thNight
8%415%6%36%5%6%9%41%
1620
16th to endNight
11%426%6%26%5%5%10%37%
1904
September1st to 15thNight
11%5%24425%5%5%7%45%
1800
16th to endNight
15%5%26%4245%46%41%
1981
October1st to 15thNight
19%5%14324446%44%
2160
16th to endNight
13%414413345%52%
2304
November1st to 15thNight
15%5%24323336%50%
2379
16th to endNight
14%42432445%5%49%
2665
December1st to 15thNight
16%7%35%424345%40%
2730
16th to endNight
16%7%25%42335%6%41%
2912

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
41%411%21%16%4
1693
16th to endDay
40%410%21%17%4
1872
February1st to 15thDay
44%49%22%14%3
1712
16th to endDay
44%410%20%17%1
1683
March1st to 15thDay
39%5%9%23%17%5%
2089
16th to endDay
43%410%19%17%4
2124
April1st to 15thDay
35%410%23%19%5%
2152
16th to endDay
41%49%19%17%7%
2160
May1st to 15thDay
44%6%12%20%15%1
2295
16th to endDay
37%8%15%25%12%1
2600
June1st to 15thDay
34%7%16%25%14%1
2520
16th to endDay
34%9%15%22%16%1
2520
July1st to 15thDay
39%8%14%20%14%3
2332
16th to endDay
34%11%14%22%15%1
2310
August1st to 15thDay
42%8%13%20%13%1
2321
16th to endDay
38%8%14%22%14%1
2292
September1st to 15thDay
35%8%12%20%19%3
2160
16th to endDay
43%6%7%22%18%1
1977
October1st to 15thDay
39%5%8%25%17%3
1800
16th to endDay
35%37%25%23%4
1920
November1st to 15thDay
38%49%22%18%6%
1808
16th to endDay
34%39%24%23%3
1624
December1st to 15thDay
39%5%11%24%14%4
1560
16th to endDay
45%49%23%14%1
1664
January1st to 15thNight
40%310%19%18%7%
2573
16th to endNight
41%39%24%17%3
2704
February1st to 15thNight
41%38%24%17%3
2482
16th to endNight
39%38%24%18%4
2074
March1st to 15thNight
38%410%26%16%3
2106
16th to endNight
40%6%10%22%17%3
2099
April1st to 15thNight
36%5%8%22%22%4
1796
16th to endNight
38%411%20%17%7%
1800
May1st to 15thNight
43%8%12%19%13%2
1665
16th to endNight
36%8%16%23%13%1
1519
June1st to 15thNight
34%8%13%25%15%1
1440
16th to endNight
35%7%15%18%20%2
1440
July1st to 15thNight
39%8%15%18%13%4
1396
16th to endNight
31%9%17%24%15%1
1595
August1st to 15thNight
36%9%13%21%17%1
1609
16th to endNight
39%8%13%23%14%1
1904
September1st to 15thNight
36%7%12%20%18%4
1800
16th to endNight
42%5%10%17%20%3
1981
October1st to 15thNight
41%5%8%21%18%4
2160
16th to endNight
33%38%26%23%5%
2304
November1st to 15thNight
37%39%21%21%6%
2379
16th to endNight
35%48%24%22%4
2665
December1st to 15thNight
44%410%20%15%3
2730
16th to endNight
42%5%11%22%14%3
2912

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
21%25%33%15%4
122
16th to endDay
24%24%31%15%3
144
February1st to 15thDay
28%25%36%8%1
135
16th to endDay
23%17%32%24%2
264
March1st to 15thDay
19%20%31%22%5%
312
16th to endDay
20%15%35%19%5%2
288
April1st to 15thDay
17%12%30%26%12%1
270
16th to endDay
23%6%27%28%10%4
270
May1st to 15thDay
29%11%28%13%12%3
288
16th to endDay
20%222%29%20%4
331
June1st to 15thDay
13%6%22%27%21%8%
315
16th to endDay
9%5%23%36%20%4
315
July1st to 15thDay
12%220%33%24%6%
305
16th to endDay
6%114%34%27%15%
326
August1st to 15thDay
14%216%25%28%12%
313
16th to endDay
13%12%29%27%15%
332
September1st to 15thDay
13%121%26%20%16%
315
16th to endDay
24%216%26%15%14%
314
October1st to 15thDay
24%319%22%21%7%
315
16th to endDay
12%10%32%22%19%3
336
November1st to 15thDay
21%6%26%26%17%2
302
16th to endDay
14%11%37%20%14%1
154
December1st to 15thDay
26%10%34%14%13%1
90
16th to endDay
30%19%28%16%5%
96
January1st to 15thNight
19%17%36%21%5%
780
16th to endNight
20%13%37%26%2
832
February1st to 15thNight
20%13%40%23%1
764
16th to endNight
20%19%36%21%2
683
March1st to 15thNight
19%15%36%24%3
764
16th to endNight
20%12%37%22%6%
768
April1st to 15thNight
14%16%40%23%5%
718
16th to endNight
19%8%28%31%11%
720
May1st to 15thNight
19%6%31%28%12%1
585
16th to endNight
15%320%39%21%
397
June1st to 15thNight
9%319%41%24%1
360
16th to endNight
8%121%47%20%
360
July1st to 15thNight
9%118%39%29%1
376
16th to endNight
6%14%38%33%6%
564
August1st to 15thNight
10%12%42%30%2
539
16th to endNight
13%12%36%30%5%
758
September1st to 15thNight
15%115%35%30%2
720
16th to endNight
17%316%30%27%3
717
October1st to 15thNight
22%6%19%27%21%2
720
16th to endNight
15%10%31%26%14%1
768
November1st to 15thNight
18%9%28%27%14%1
760
16th to endNight
15%12%32%26%11%
780
December1st to 15thNight
20%10%34%23%10%
780
16th to endNight
20%12%36%26%4
832
Page generated at 2018-03-12 13:28:06. Version ac04

Copyright 2018 A. Danko


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