Johnsons Crossing
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Johnsons Crossing clear sky chart from 2005-11-05 to 2017-09-22.

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
41%
14177
4%
46514
4%
14144
42%
14144
10%
37403

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
30%
858
4%
3073
4%
853
31%
853
6%
2651
January16th to endNight
34%
800
7%
3072
7%
800
36%
800
7%
2504
February1st to 15thNight
40%
731
6%
2562
6%
727
41%
727
10%
2044
February16th to endNight
49%
657
10%
2148
8%
657
50%
657
14%
1627
March1st to 15thNight
45%
720
10%
2160
10%
720
46%
720
15%
1670
March16th to endNight
49%
623
5%
2015
6%
623
49%
623
11%
1609
April1st to 15thNight
56%
539
6%
1673
5%
539
56%
539
17%
1228
April16th to endNight
52%
516
2%
1416
2%
516
53%
516
17%
1078
May1st to 15thNight
47%
359
0%
1152
0%
359
47%
359
15%
868
May16th to endNight
60%
374
0%
1020
0%
374
60%
374
26%
682
June1st to 15thNight
57%
207
0%
747
0%
207
57%
207
16%
526
June16th to endNight
56%
180
0%
720
0%
180
56%
180
12%
530
July1st to 15thNight
57%
184
0%
700
0%
184
57%
184
12%
534
July16th to endNight
46%
376
0%
1062
0%
354
47%
354
13%
819
August1st to 15thNight
54%
420
0%
1206
0%
418
54%
418
19%
881
August16th to endNight
37%
573
1%
1542
1%
573
37%
573
11%
1285
September1st to 15thNight
40%
540
6%
1755
5%
540
41%
540
13%
1361
September16th to endNight
36%
641
7%
1861
6%
641
37%
641
12%
1497
October1st to 15thNight
40%
660
8%
2057
7%
660
40%
660
12%
1631
October16th to endNight
37%
721
3%
2409
3%
721
38%
721
8%
1991
November1st to 15thNight
35%
730
3%
2636
2%
730
37%
730
7%
2270
November16th to endNight
34%
846
4%
2976
4%
846
35%
846
7%
2491
December1st to 15thNight
32%
930
4%
3096
3%
930
33%
930
7%
2660
December16th to endNight
33%
992
5%
3456
4%
992
34%
992
6%
2966

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
11%12%6%10%8%46%5%6%7%20%
48457
Night
8%13%6%10%9%5%6%6%6%7%19%
46615
TransparencyDay
61%10%14%11%2
48063
Night
61%9%14%11%2
46514
SeeingDay
16%9%24%26%18%4
7636
Night
15%5%20%31%22%4
14182

By Month

Percentage Cloud Cover NW (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
8%18%8%16%12%46%46%411%
878
16th to endDay
6%15%8%12%8%5%6%5%8%10%12%
1152
February1st to 15thDay
6%13%6%12%7%46%7%5%9%19%
1301
16th to endDay
310%8%9%8%5%8%7%5%10%22%
1323
March1st to 15thDay
312%6%10%9%6%8%6%7%7%20%
1800
16th to endDay
311%8%14%9%37%5%5%8%21%
2208
April1st to 15thDay
5%15%7%11%8%46%5%6%7%20%
2273
16th to endDay
413%6%11%10%5%7%5%5%7%21%
2544
May1st to 15thDay
11%17%6%9%7%45%45%5%22%
2799
16th to endDay
9%9%48%7%46%5%6%6%29%
3093
June1st to 15thDay
14%9%5%9%9%46%6%5%6%22%
3212
16th to endDay
14%9%49%9%47%5%6%7%19%
3240
July1st to 15thDay
16%9%49%8%48%7%7%7%17%
3219
16th to endDay
15%8%49%7%5%6%5%6%7%21%
3035
August1st to 15thDay
11%8%49%6%45%5%6%8%28%
2746
16th to endDay
23%11%5%8%6%5%5%5%5%5%18%
2660
September1st to 15thDay
18%11%410%7%36%5%5%6%19%
2203
16th to endDay
16%11%5%11%9%35%5%6%419%
1911
October1st to 15thDay
13%15%5%9%6%5%5%446%22%
1573
16th to endDay
9%14%5%12%10%46%46%6%18%
1463
November1st to 15thDay
8%16%8%13%9%5%46%5%7%13%
1220
16th to endDay
5%12%8%14%11%6%5%7%8%7%11%
972
December1st to 15thDay
8%15%7%14%11%5%7%6%7%7%9%
864
16th to endDay
5%17%6%13%10%7%5%8%10%7%7%
768
January1st to 15thNight
8%18%9%13%9%46%5%5%5%12%
3073
16th to endNight
7%15%7%12%9%5%6%6%7%8%13%
3072
February1st to 15thNight
5%13%6%11%9%5%7%7%7%9%16%
2550
16th to endNight
310%7%11%9%5%6%6%6%8%24%
2148
March1st to 15thNight
411%8%10%8%5%8%6%5%6%25%
2160
16th to endNight
211%8%12%10%6%8%6%5%6%20%
2010
April1st to 15thNight
410%410%7%5%6%5%7%7%29%
1673
16th to endNight
410%5%7%7%6%8%6%8%7%26%
1416
May1st to 15thNight
9%11%47%7%46%5%6%7%29%
1151
16th to endNight
7%6%36%6%36%6%8%9%36%
1020
June1st to 15thNight
10%6%348%45%6%8%10%31%
747
16th to endNight
10%7%26%7%47%8%7%8%27%
720
July1st to 15thNight
12%6%38%6%6%8%7%8%12%20%
741
16th to endNight
14%8%36%7%5%6%6%6%10%24%
1134
August1st to 15thNight
9%6%37%7%35%7%7%9%32%
1212
16th to endNight
20%10%5%8%8%35%5%46%20%
1542
September1st to 15thNight
16%9%47%6%35%5%6%6%27%
1755
16th to endNight
14%13%49%7%45%45%5%23%
1861
October1st to 15thNight
14%14%48%6%35%45%6%27%
2057
16th to endNight
9%19%5%9%9%45%45%5%20%
2409
November1st to 15thNight
8%15%8%11%10%5%8%6%7%6%12%
2636
16th to endNight
6%14%7%14%10%46%6%5%8%12%
2976
December1st to 15thNight
7%18%9%11%10%5%5%5%6%7%10%
3096
16th to endNight
7%17%6%12%11%6%8%6%5%6%10%
3456

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
75%6%8%5%2
878
16th to endDay
62%10%14%9%2
1152
February1st to 15thDay
59%7%14%13%3
1301
16th to endDay
55%9%16%13%4
1323
March1st to 15thDay
60%8%11%13%41
1800
16th to endDay
60%8%12%10%6%
2208
April1st to 15thDay
60%9%16%11%2
2273
16th to endDay
59%10%16%11%1
2544
May1st to 15thDay
61%9%14%11%3
2799
16th to endDay
50%10%16%19%3
3097
June1st to 15thDay
61%9%13%13%3
3212
16th to endDay
61%10%15%10%1
3240
July1st to 15thDay
62%12%14%8%1
3031
16th to endDay
60%12%16%9%
2844
August1st to 15thDay
52%10%20%13%2
2727
16th to endDay
68%9%15%5%
2660
September1st to 15thDay
64%10%12%9%2
2203
16th to endDay
65%10%13%9%1
1911
October1st to 15thDay
63%8%15%11%1
1573
16th to endDay
65%11%14%8%
1463
November1st to 15thDay
69%10%11%7%
1220
16th to endDay
65%11%10%9%2
972
December1st to 15thDay
70%9%11%8%
864
16th to endDay
69%10%9%7%3
768
January1st to 15thNight
72%8%8%7%2
3073
16th to endNight
65%9%11%11%2
3072
February1st to 15thNight
63%7%12%13%3
2562
16th to endNight
53%10%16%13%6%
2148
March1st to 15thNight
57%8%11%14%6%1
2160
16th to endNight
63%7%12%8%7%
2015
April1st to 15thNight
50%10%17%18%3
1673
16th to endNight
51%11%17%17%2
1416
May1st to 15thNight
51%11%18%14%3
1152
16th to endNight
41%6%21%24%4
1020
June1st to 15thNight
48%10%21%16%2
747
16th to endNight
50%13%19%14%1
720
July1st to 15thNight
52%14%20%10%2
700
16th to endNight
53%13%20%12%
1062
August1st to 15thNight
44%14%22%15%2
1206
16th to endNight
63%10%15%10%
1542
September1st to 15thNight
56%10%17%14%
1755
16th to endNight
60%9%15%12%1
1861
October1st to 15thNight
57%11%16%12%1
2057
16th to endNight
64%10%15%8%
2409
November1st to 15thNight
68%11%12%7%
2636
16th to endNight
67%9%11%9%1
2976
December1st to 15thNight
70%8%11%8%1
3096
16th to endNight
71%8%9%7%3
3456

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
23%49%30%20%11%
43
16th to endDay
18%9%18%26%21%4
64
February1st to 15thDay
13%6%28%28%19%4
214
16th to endDay
7%428%30%18%10%
211
March1st to 15thDay
7%13%31%28%13%5%
240
16th to endDay
7%9%23%32%22%4
280
April1st to 15thDay
9%13%27%26%17%4
304
16th to endDay
10%14%28%27%18%2
450
May1st to 15thDay
17%13%28%23%12%4
468
16th to endDay
11%9%24%26%21%5%
620
June1st to 15thDay
16%7%24%28%20%2
675
16th to endDay
16%6%20%29%22%4
675
July1st to 15thDay
20%5%19%25%23%5%
639
16th to endDay
20%11%21%26%16%2
515
August1st to 15thDay
16%8%22%25%19%7%
494
16th to endDay
27%11%24%23%9%2
509
September1st to 15thDay
27%14%21%19%11%4
315
16th to endDay
23%13%28%15%13%5%
277
October1st to 15thDay
20%16%27%22%10%3
225
16th to endDay
17%5%27%25%18%4
212
November1st to 15thDay
23%5%30%31%6%3
60
16th to endDay
6%6%15%31%16%23%
60
December1st to 15thDay
5%111%29%29%22%
54
16th to endDay
6%18%37%31%6%
32
January1st to 15thNight
17%423%33%17%2
858
16th to endNight
14%7%26%34%15%1
800
February1st to 15thNight
12%5%24%37%18%2
734
16th to endNight
7%321%39%22%5%
657
March1st to 15thNight
8%7%24%33%24%2
720
16th to endNight
8%215%30%34%9%
623
April1st to 15thNight
7%415%31%34%5%
539
16th to endNight
8%321%29%31%5%
516
May1st to 15thNight
14%5%18%28%27%6%
360
16th to endNight
10%216%28%36%5%
375
June1st to 15thNight
13%118%31%31%2
207
16th to endNight
17%115%30%33%2
180
July1st to 15thNight
14%214%28%35%3
184
16th to endNight
17%419%28%24%5%
376
August1st to 15thNight
12%319%27%30%6%
420
16th to endNight
26%419%25%20%4
573
September1st to 15thNight
22%419%28%19%4
540
16th to endNight
24%7%22%24%17%4
641
October1st to 15thNight
22%6%21%31%16%2
660
16th to endNight
21%7%18%29%17%5%
721
November1st to 15thNight
17%322%34%17%4
730
16th to endNight
15%5%19%31%23%3
846
December1st to 15thNight
15%7%20%32%21%2
930
16th to endNight
15%422%32%20%5%
992
Page generated at 2017-09-23 03:43:42. Version ac04

Copyright 2017 A. Danko


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